WO2024009513A1

WO2024009513A1 - Control device for injection molding machine and control method for injection molding machine

Info

Publication number: WO2024009513A1
Application number: PCT/JP2022/027151
Authority: WO
Inventors: 市原稔章
Original assignee: ファナック株式会社
Priority date: 2022-07-08
Filing date: 2022-07-08
Publication date: 2024-01-11

Abstract

A control device (12) for an injection molding machine (10) is provided with: a first motor control unit (90) that moves an injection member (24) in each of a first direction and a second direction while reducing a torque of an injection motor (62); a torque setting unit (91) that sets a second prescribed torque on the basis of a control result of the first motor control unit (90); a second motor control unit (92) that controls the injection motor (62) on the basis of a second prescribed torque; and a zero-point correction unit (94) that corrects zero point on the basis of a detection value output by a pressure sensor (48) during control of the second motor control unit (92).

Description

Injection molding machine control device and injection molding machine control method

The present disclosure relates to an injection molding machine control device and an injection molding machine control method.

The injection molding machine includes an injection cylinder, a screw, and a pressure sensor. Resin is supplied to the injection cylinder. The screw is inserted into the injection cylinder. The pressure sensor is used to detect the pressure that the screw applies to the resin in the injection cylinder.

A method of correcting the zero point of a pressure sensor has been proposed (Japanese Patent Application Laid-Open No. 9-117946).

Recently, there has been a long-awaited technology that can more efficiently correct the zero point of a pressure sensor.

A first aspect of the present disclosure includes an injection member that is inserted into an injection cylinder and movable within the injection cylinder, an injection motor that moves the injection member, and a resin pressure inside the injection cylinder. A control device for an injection molding machine, comprising: a pressure sensor for detecting a pressure sensor; and controlling the injection motor so that the torque gradually decreases from the first predetermined torque when the movement of the injection member is stopped in the first control, so that the injection motor is controlled in the first direction. a first motor control unit that performs a second control to move the injection member in an opposite second direction; a torque of the injection motor when the injection member stops in the first control; and a torque of the injection motor when the injection member is stopped in the first control; a torque setting unit that sets the smaller of the torque of the injection motor when the injection member stops as a second predetermined torque; A third control is performed in which the injection member is controlled to move in one of the first direction and the second direction, and the movement of the injection member is stopped in the third control. a fourth direction, the injection motor is controlled so that the torque becomes the second predetermined torque, and the injection member is moved in the other direction of the first direction and the second direction; A second motor control unit that performs control, and a zero point of the pressure sensor based on a detection value output by the pressure sensor during the third control and a detection value output by the pressure sensor during the fourth control. This is a control device for an injection molding machine, including a zero point correction section that corrects the.

A second aspect of the present disclosure includes an injection member inserted into an injection cylinder and movable within the injection cylinder, an injection motor that moves the injection member, and a pressure of resin within the injection cylinder. A method for controlling an injection molding machine, comprising: a pressure sensor for detecting a pressure sensor; and controlling the injection motor so that the torque gradually decreases from a first predetermined torque to move the injection member in a first direction and a second control that controls the injection motor so that the torque gradually decreases from the first predetermined torque and moves the injection member in a second direction opposite to the first direction. a first motor control step to be performed; a torque of the injection motor when the injection member stops in the first control; and a torque of the injection motor when the injection member stops in the second control; a torque setting step of setting the smaller of the two as a second predetermined torque; and controlling the injection motor so that the torque becomes the second predetermined torque, the smaller one of the first direction and the second direction. a third control that controls the injection member to move in one direction; and a third control that controls the injection motor so that the torque becomes the second predetermined torque to move the injection member in the first direction and the second direction. a second motor control step of performing a fourth control to control the injection member to move in the other direction; a detection value output by the pressure sensor during the third control; The method of controlling an injection molding machine includes a zero point correction step of correcting the zero point of the pressure sensor based on a detected value outputted during the injection molding machine.

FIG. 1 is an overall configuration diagram of an injection molding system according to an embodiment. FIG. 2 is a schematic diagram showing the configuration of the injection device. FIG. 3 is a block diagram of the control device. FIG. 4A is a graph illustrating the time course of the torque of the injection motor during the first control. FIG. 4B is a graph illustrating the time course of the torque of the injection motor during the second control. FIG. 5 is a flowchart illustrating a method for controlling an injection molding machine.

If the zero point of the pressure sensor that detects the resin pressure is off, it will adversely affect the quality of the molded products produced by the injection molding machine. Therefore, it is preferable that the shift in the zero point of the pressure sensor is corrected. Further, it is preferable that the time required to correct the zero point of the pressure sensor be as short as possible.

[One embodiment]
An injection molding machine control device and an injection molding machine control method according to one embodiment will be described with reference to the drawings. In addition, in the following description, the same code|symbol is attached to the structure which has the same or similar function. Redundant explanations of these configurations may be omitted.

FIG. 1 is an overall configuration diagram of an injection molding system SYS according to this embodiment. The direction from the right side of the paper in FIG. 1 to the left side of the paper in FIG. 1 is defined as a first direction D1. The direction from the left side of the paper in FIG. 1 to the right side of the paper in FIG. 1 is defined as a second direction D2. For convenience of explanation, the left side in FIG. 1 may be referred to as the front side, and the right side in FIG. 1 may be referred to as the rear side.

The "injection member" referred to in this application is inserted into the injection cylinder 22 (see FIG. 2) of the injection molding machine 10, and is inserted into the injection cylinder 22 in order to inject resin into the cavity 20c of the mold 20. means a moving member. In this embodiment, an example will be described in which the injection member 24 is configured by the screw 24A, but the invention is not limited to this. For example, the injection member 24 may be configured by a plunger (not shown).

In the present application, "automatic purge" refers to a predetermined operation automatically performed by the injection molding machine 10 to discharge resin from within the injection cylinder 22. The predetermined motion is, for example, one or more reciprocating motions of the injection member 24 along the axis LA of the injection cylinder 22 (see FIG. 2).

The injection molding system SYS includes an injection molding machine 10 and a control device 12.

The injection molding machine 10 includes a mold clamping device 14, an injection device 16, and a machine stand 18.

The mold clamping device 14 is a device that applies mold clamping force to the mold 20. The mold clamping device 14 is supported by a machine stand 18. The mold clamping device 14 opens and closes the mold 20. The mold clamping device 14 applies clamping force to the mold 20 so that the mold 20 does not open. The mold 20 forms a cavity 20c in the closed state. FIG. 1 shows the mold 20 in a closed state. A more detailed explanation of the mold clamping device 14 will be omitted.

The injection device 16 is a device that plasticizes the resin and injects the plasticized resin into the cavity 20c of the mold 20. The injection device 16 is supported by a machine stand 18. The injection molding machine 10 produces a molded product by solidifying the resin filled into the cavity 20c by the injection device 16.

FIG. 2 is a schematic diagram showing the configuration of the injection device 16.

The injection device 16 includes an injection cylinder 22, an injection member 24, a front plate 26, a rear plate 28, a pusher plate 30, and a slide mechanism 32.

The injection cylinder 22 is a cylindrical member. The axis LA of the injection cylinder 22 is parallel to the first direction D1 and the second direction D2.

A nozzle 34 is provided at the front end (tip part) of the injection cylinder 22. The nozzle 34 has an injection port 34p. The injection port 34p is an opening for injecting the resin in the injection cylinder 22 into the cavity 20c.

A hopper 36 is provided at the rear end of the injection cylinder 22. Hopper 36 stores resin. Further, the hopper 36 supplies the stored resin into the injection cylinder 22.

In this embodiment, the injection member 24 is constituted by the screw 24A. The screw 24A has a screw head 24a, a flight portion 24b, and a base end portion 24c. The screw head 24a is located at the front end (tip part) of the screw 24A. The flight portion 24b is a spiral portion formed in the body of the screw 24A. The flight portion 24b shears the resin within the injection cylinder 22 in response to the rotation of the screw 24A by a first drive device 50, which will be described later. The base end portion 24c is located at the rear end of the screw 24A. The axis LA of the injection cylinder 22 coincides with the axis of the injection member 24.

The front plate 26 is located on the rear side of the injection cylinder 22. The front plate 26 supports the injection cylinder 22. The injection member 24 passes through the front plate 26. The base end portion 24c of the injection member 24 is located further back than the front plate 26.

The rear plate 28 is located behind the front plate 26. A predetermined space is left between the rear plate 28 and the front plate 26.

The pusher plate 30 is provided between the front plate 26 and the rear plate 28.

The slide mechanism 32 includes a rail 38 and a slider 40. The rail 38 extends in the direction along the axis LA. Slider 40 is movable along rail 38. Slider 40 supports pusher plate 30. Therefore, the pusher plate 30 is movable along the rail 38.

The front plate 26, the rear plate 28, and the slide mechanism 32 are provided on a flat base 42. The front plate 26, the rear plate 28, and the base 42 may be integrally molded.

The injection device 16 includes a spline bush 44, a screw sleeve 46, a pressure sensor 48, a first drive device 50, and a second drive device 52.

The spline bush 44 supports the base end 24c of the injection member 24. For example, the base end 24c of the injection member 24 has a male spline (not shown). On the other hand, the spline bushing 44 has a female spline (not shown). The male spline of the base end 24c and the female spline of the spline bush 44 fit together, so that the spline bush 44 supports the base end 24c of the injection member 24.

A screw sleeve 46 is provided between the pusher plate 30 and the spline bushing 44. The screw sleeve 46 rotatably supports the spline bushing 44. Further, the screw sleeve 46 restricts relative movement of the spline bushing 44 with respect to the screw sleeve 46 in the direction along the axis LA. The screw sleeve 46 includes, for example, a bearing member (not shown). The bearing member rotatably supports the screw sleeve 46 while restricting relative movement of the spline bushing 44 in the direction along the axis LA.

The pressure sensor 48 detects the pressure inside the injection cylinder 22. The pressure sensor 48 is, for example, a load cell. The pressure sensor 48 is provided inside the screw sleeve 46, for example. However, the installation location of the pressure sensor 48 may be changed as appropriate.

The first drive device 50 is a device that rotates the injection member 24 around the axis LA. The first drive device 50 includes a rotation motor 54, a first drive pulley 56, a first belt 58, and a first driven pulley 60.

The rotation motor 54 is, for example, a servo motor. The rotation motor 54 includes a shaft 54a. The shaft 54a rotates when current is supplied to the rotation motor 54. The shaft 54a is connected to a first drive pulley 56.

The first drive pulley 56 rotates in accordance with the rotation of the shaft 54a. The first belt 58 spans the first driving pulley 56 and the first driven pulley 60. The first belt 58 transmits the rotation of the first drive pulley 56 to the first driven pulley 60.

The first driven pulley 60 rotates as a result of the rotation of the first driving pulley 56 transmitted via the first belt 58. That is, the first driven pulley 60 rotates in accordance with the rotation of the shaft 54a. The first driven pulley 60 is provided inside the pusher plate 30, for example. The first driven pulley 60 is connected to the spline bushing 44 . The first driven pulley 60 and the spline bushing 44 rotate integrally.

As described above, the rotation of the shaft 54a causes the spline bushing 44 to rotate. The rotation of the spline bushing 44 causes the injection member 24 to rotate. In this way, the first drive device 50 can rotate the injection member 24 about the axis LA.

The second drive device 52 is a device that moves the injection member 24 along the axis LA. The second drive device 52 includes an injection motor 62, a second drive pulley 64, a second belt 66, a second driven pulley 68, a ball screw 70, and a nut 72.

The injection motor 62 is, for example, a servo motor. The injection motor 62 includes a shaft 62a and a rotational position sensor 62b. The shaft 62a rotates when current is supplied to the injection motor 62. The shaft 62a is connected to a second drive pulley 64. The rotational position sensor 62b detects the rotational position of the shaft 62a.

The second drive pulley 64 rotates in accordance with the rotation of the shaft 62a. The second belt 66 spans the second drive pulley 64 and the second driven pulley 68. The second belt 66 transmits the rotation of the second drive pulley 64 to the second driven pulley 68.

The second driven pulley 68 rotates as a result of the rotation of the second driving pulley 64 transmitted via the second belt 66. That is, the second driven pulley 68 rotates in accordance with the rotation of the shaft 62a.

The direction of the axis of the ball screw 70 is parallel to the direction of the axis LA of the injection cylinder 22. The ball screw 70 passes through the rear plate 28. The rear plate 28 rotatably supports the ball screw 70 while restricting movement of the ball screw 70 in the direction along the axis LA. For example, the rear plate 28 has a bearing member 74. The bearing member 74 rotatably supports the ball screw 70 and restricts movement of the ball screw 70 in the direction along the axis LA.

The ball screw 70 is connected to the second driven pulley 68. The ball screw 70 rotates together with the second driven pulley 68. Therefore, the ball screw 70 rotates in accordance with the rotation of the shaft 62a.

The nut 72 is provided on the rear side of the pusher plate 30. Pusher plate 30 rotatably supports nut 72. More specifically, the pusher plate 30 rotatably supports the nut 72 using a bearing member (not shown) provided on the pusher plate 30 .

The nut 72 is screwed onto the ball screw 70. The nut 72 moves in the direction of the axis of the ball screw 70 as the ball screw 70 rotates. That is, the nut 72 moves in the first direction D1 or the second direction D2 according to the rotation of the shaft 62a. When the nut 72 moves in the first direction D1, the pusher plate 30 moves in the first direction D1 together with the nut 72. When the nut 72 moves in the second direction D2, the pusher plate 30 moves in the second direction D2 together with the nut 72. Since the slide mechanism 32 supports the pusher plate 30, the pusher plate 30 can move smoothly in the first direction D1 or the second direction D2.

When the pusher plate 30 moves in the first direction D1, the pusher plate 30 pushes the injection member 24 in the first direction D1 via the screw sleeve 46 and the spline bushing 44. When the pusher plate 30 moves in the second direction D2, the pusher plate 30 pulls the injection member 24 in the second direction D2 via the screw sleeve 46 and the spline bushing 44.

The injection member 24 moves within the injection cylinder 22 in the first direction D1 or the second direction D2 depending on the force received from the pusher plate 30. That is, the injection member 24 can move along the axis LA of the injection cylinder 22.

The position of a predetermined portion of the injection member 24 is defined as the position of the injection member 24. For example, the position of the tip of the screw head 24a can be the position of the injection member 24. In this case, the movable range of the tip of the screw head 24a is the movable range of the injection member 24. The position of the front end of the movable range of the injection member 24 may be referred to as a first end position PE1. The position of the rear end of the movable range of the injection member 24 may be referred to as a second end position PE2. The first end position PE1 is the frontmost position that can be reached by the tip of the screw head 24a. The second end position PE2 is the rearmost position that can be reached by the tip of the screw head 24a.

The rotation direction of the shaft 62a when the injection member 24 is moved in the first direction D1 and the rotation direction of the shaft 62a when the injection member 24 is moved in the second direction D2 are opposite to each other. The rotational direction of the shaft 62a when the injection member 24 is moved in the first direction D1 is also referred to as a first rotational direction in the following description. The rotational direction of the shaft 62a when the injection member 24 is moved in the second direction D2 is also referred to as a second rotational direction in the following description.

The amount of movement of the injection member 24 correlates with the amount of rotation of the shaft 62a. For example, the amount of movement of the injection member 24 in the first direction D1 correlates with the amount of rotation of the shaft 62a in the first rotation direction. Similarly, the amount of movement of the injection member 24 in the second direction D2 correlates with the amount of rotation of the shaft 62a in the second rotational direction. Since the amount of movement of the injection member 24 is correlated to the amount of rotation of the shaft 62a, the rotational position of the shaft 62a detected by the rotational position sensor 62b substantially indicates the position of the injection member 24 in the direction along the axis LA.

FIG. 3 is a block diagram of the control device 12.

The control device 12 is an electronic device (computer) that controls the injection molding machine 10. The control device 12 is, for example, a numerical control device. The control device 12 includes a display section 76, an operation section 78, a storage section 80, and a calculation section 82.

The display unit 76 is a display device including a display screen 76d. The display unit 76 is, for example, a liquid crystal display or an OEL (Organic Electro-Luminescence) display.

The operation unit 78 is an input device that accepts information input to the control device 12. The operation unit 78 includes, for example, an operation panel 78a and a touch panel 78b. The touch panel 78b is provided on the display screen 76d. The operation panel 78a may include a keyboard, a mouse, and the like. The operator can use the operation unit 78 to instruct the control device 12 to execute automatic purge, for example.

The storage unit 80 may include a volatile memory (not shown) and a nonvolatile memory (not shown). Examples of volatile memory include RAM (Random Access Memory). Examples of nonvolatile memory include ROM (Read Only Memory), flash memory, and the like. Data etc. are stored in volatile memory, for example. Programs, data tables, maps, etc. are stored in, for example, non-volatile memory. At least a portion of the storage unit 80 may be included in a processor, an integrated circuit, or the like, which will be described later. The storage unit 80 stores a control program 84, first torque information 86, and second torque information 88.

The control program 84 is a program for causing the control device 12 to execute the control method of this embodiment. A more detailed explanation of the control method will be given later.

The first torque information 86 is information indicating the magnitude of the first predetermined torque TC. The first predetermined torque TC is an initial target torque value of the injection motor 62 when the first motor control unit 90, which will be described later, controls the injection motor 62.

The first torque information 86 is provided to the user, for example, by the manufacturer of the injection molding system SYS. More specifically, the manufacturer of the injection molding system SYS provides the user with the first predetermined torque TC, which is determined based on, for example, an experiment. The user can input the first predetermined torque TC using the operating section 78.

The second torque information 88 is information indicating the magnitude of the second predetermined torque. The second predetermined torque is a target torque value of the injection motor 62 when the second motor control section 92, which will be described later, controls the injection motor 62. The second torque information 88 is set by a torque setting section 91, which will be described later.

The calculation unit 82 is configured by, for example, a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). That is, the calculation unit 82 may be configured by a processing circuit. The calculation section 82 includes a first motor control section 90 , a torque setting section 91 , a second motor control section 92 , and a zero point correction section 94 .

The first motor control section 90, the torque setting section 91, the second motor control section 92, and the zero point correction section 94 are realized by the calculation section 82 executing the control program 84. Note that at least a part of the first motor control section 90, torque setting section 91, second motor control section 92, and zero point correction section 94 is implemented using an ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), etc. It may also be realized by an integrated circuit. Further, at least a portion of the first motor control section 90, the torque setting section 91, the second motor control section 92, and the zero point correction section 94 may be configured by an electronic circuit including a discrete device.

The first motor control section 90 performs first control described below. In the first control, the first motor control section 90 controls the injection motor 62 so that the magnitude of the torque in the first rotational direction gradually decreases from the first predetermined torque TC, and moves the injection member 24 in the first direction. Move to D1. As described above, the first rotation direction is the rotation direction of the shaft 62a when the injection member 24 is moved in the first direction D1. Note that the torque of the injection motor 62 correlates with the amount of current supplied to the injection motor 62. Therefore, the first motor control unit 90 can gradually lower the torque of the injection motor 62 by controlling the injection motor 62 so that the amount of current supplied to the injection motor 62 gradually decreases.

The injection member 24 presses the resin within the injection cylinder 22 in the first direction D1 by moving in the first direction D1. When the torque is relatively large, the force with which the pusher plate 30 pushes the injection member 24 is relatively large. That is, the force that moves the injection member 24 in the first direction D1 is relatively large. Therefore, the injection member 24 can move in the first direction D1. That is, although a resistance force that inhibits the movement of the injection member 24 in the first direction D1 is generated by the resin, the force that moves the injection member 24 in the first direction D1 is sufficiently large, so that the injection member 24 moves in the first direction D1. It can move in one direction D1.

As the torque of the injection motor 62 is gradually lowered, the force with which the pusher plate 30 presses the injection member 24 gradually decreases. That is, the force that moves the injection member 24 in the first direction D1 gradually decreases. Therefore, when the torque of the injection motor 62 decreases to a certain level, the injection member 24 cannot be moved in the first direction D1. That is, movement of the injection member 24 in the first direction D1 is stopped by the resin. In this case, even before the injection member 24 reaches the first end position PE1 and the torque of the injection motor 62 in the first rotational direction is greater than zero, the movement of the injection member 24 in the first direction D1 stops.

The first motor control unit 90 causes the storage unit 80 to store information indicating the torque of the injection motor 62 when the movement of the injection member 24 is stopped in the first control. For example, the first motor control unit 90 causes the storage unit 80 to store information indicating the amount of current that was being supplied to the injection motor 62 when the movement of the injection member 24 stopped in the first control. Note that the first motor control unit 90 determines whether the injection member 24 has stopped based on the rotational position of the shaft 62a detected by the rotational position sensor 62b.

FIG. 4A is a graph illustrating the time course of the torque of the injection motor 62 during the first control. The vertical axis in FIG. 4A indicates the torque of the injection motor 62 in the first rotational direction. The horizontal axis in FIG. 4A indicates time.

Time t1 in FIG. 4A is the time when the injection member 24 stops moving in the first direction D1. Torque TA in FIG. 4A is the torque in the first rotational direction of the injection motor 62 at time t1. In this case, the first motor control section 90 causes the storage section 80 to store information indicating the torque TA. In the following description, the torque TA is also referred to as the first acquired torque TA.

When the movement of the injection member 24 is stopped in the first control, the first motor control section 90 further performs the second control described below. In the second control, the first motor control section 90 controls the injection motor 62 so that the magnitude of the torque in the second rotational direction gradually decreases from the first predetermined torque TC, and moves the injection member 24 in the second direction. Move to D2. As described above, the second rotation direction is the rotation direction of the shaft 62a when the injection member 24 is moved in the second direction D2.

When the torque is relatively large, the force with which the pusher plate 30 pulls the injection member 24 is relatively large. That is, the force that moves the injection member 24 in the second direction D2 is relatively large. Therefore, the injection member 24 can move in the second direction D2. That is, although a resistance force that inhibits movement of the injection member 24 in the second direction D2 is generated by the resin, the force that moves the injection member 24 in the second direction D2 is sufficiently large, so that the injection member 24 moves in the second direction D2. It can move in two directions D2.

As the torque of the injection motor 62 is gradually lowered, the force with which the pusher plate 30 pulls the injection member 24 gradually becomes smaller. That is, the force that moves the injection member 24 in the second direction D2 gradually decreases. Therefore, when the torque of the injection motor 62 decreases to a certain level, the injection member 24 cannot be moved in the second direction D2. That is, movement of the injection member 24 in the second direction D2 is stopped by the resin. In this case, even before the injection member 24 reaches the second end position PE2 and the torque of the injection motor 62 in the second rotational direction is greater than zero, the injection member 24 cannot be moved in the second direction D2. stops.

The first motor control unit 90 causes the storage unit 80 to store information indicating the torque of the injection motor 62 when the movement of the injection member 24 is stopped in the second control. For example, the first motor control unit 90 causes the storage unit 80 to store information indicating the amount of current that was being supplied to the injection motor 62 when the movement of the injection member 24 stopped in the second control.

FIG. 4B is a graph illustrating the time course of the torque of the injection motor 62 during the second control. The format of the graph in FIG. 4B is similar to the format of the graph in FIG. 4A.

Time t2 in FIG. 4B is the time when the injection member 24 stops moving in the second direction D2. Torque TB in FIG. 4B is the torque in the second rotational direction of the injection motor 62 at time t2. In this case, the first motor control section 90 causes the storage section 80 to store information indicating the torque TB. In the following description, the torque TB is also referred to as the second acquired torque TB.

The torque setting unit 91 determines the magnitude of the second predetermined torque described above using information indicating the first acquired torque TA and information indicating the second acquired torque TB. That is, the torque setting unit 91 creates the second torque information 88 using the information indicating the first acquired torque TA and the information indicating the second acquired torque TB.

More specifically, the torque setting unit 91 compares the magnitude of the first acquired torque TA and the magnitude of the second acquired torque TB. The torque setting unit 91 sets the smaller of the first acquired torque TA and the second acquired torque TB as the second predetermined torque. When the magnitude of the first acquired torque TA and the magnitude of the second acquired torque TB are equal, the torque setting unit 91 sets the second predetermined torque based on the magnitude.

The second motor control unit 92 performs the third control described below based on the second predetermined torque. In the third control, the second motor control section 92 controls the injection motor 62 so that the magnitude of the torque in the first rotational direction becomes the second predetermined torque. Thereby, the injection member 24 is controlled to move in the first direction D1. The second motor control unit 92 appropriately adjusts the amount of current supplied to the injection motor 62 to maintain the torque of the injection motor 62 at a second predetermined torque.

As described above, the second predetermined torque is the torque TA when the injection member 24 stops moving in the first direction D1, and the torque TB when the injection member 24 stops moving in the second direction D2. This is the smaller one. Therefore, when the second motor control section 92 controls the injection motor 62 so that the magnitude of the torque in the first rotational direction becomes the second predetermined torque, the injection member 24 also rotates in the first direction D1. It does not move in the second direction D2 either.

In the third control, the injection member 24 does not move, but an axial force in a direction parallel to the axis LA acts on the injection member 24. The detection value of the pressure sensor 48 when the axial force acts on the injection member 24 is acquired by the calculation unit 82. When the calculation unit 82 acquires the detection value of the pressure sensor 48 when the axial force acts on the injection member 24, the second motor control unit 92 ends the third control.

After the third control is completed, the second motor control section 92 further performs the fourth control described below. In the fourth control, the second motor control section 92 controls the injection motor 62 so that the magnitude of the torque in the second rotational direction becomes the second predetermined torque. Thereby, the injection member 24 is controlled to move in the second direction D2.

As described above, the second predetermined torque is the torque TA when the injection member 24 stops moving in the first direction D1, and the torque TB when the injection member 24 stops moving in the second direction D2. This is the smaller one. Therefore, when the second motor control section 92 controls the injection motor 62 so that the magnitude of the torque in the second rotational direction becomes the second predetermined torque, the injection member 24 does not move.

Even in the fourth control, the injection member 24 does not move, but an axial force in a direction parallel to the axis LA acts on the injection member 24. The detection value of the pressure sensor 48 when the axial force acts on the injection member 24 is acquired by the calculation unit 82. When the calculation unit 82 acquires the detected value of the pressure sensor 48 when the axial force acts on the injection member 24, the second motor control unit 92 ends the fourth control.

The magnitude of the axial force acting on the injection member 24 in the third control is correlated to the second predetermined torque. The magnitude of the axial force acting on the injection member 24 in the fourth control also correlates with the second predetermined torque. Therefore, the magnitude of the axial force acting on the injection member 24 in the third control is equal to the magnitude of the axial force acting on the injection member 24 in the fourth control. Therefore, the magnitude of the detection value output by the pressure sensor 48 in the third control should be equal to the magnitude of the detection value output by the pressure sensor 48 in the fourth control. However, if the zero point of the pressure sensor 48 is not set correctly, the magnitude of the detection value output by the pressure sensor 48 in the third control and the magnitude of the detection value output by the pressure sensor 48 in the fourth control may differ. not equal.

The zero point correction unit 94 can correct the zero point P0 of the pressure sensor 48. That is, the zero point correction unit 94 corrects the zero point of the pressure sensor 48 based on the detection value output by the pressure sensor 48 during the third control and the detection value output by the pressure sensor 48 during the fourth control. . More specifically, the zero point correction unit 94 determines that the absolute value of the detection value output by the pressure sensor 48 during the third control is equal to the absolute value of the detection value output by the pressure sensor 48 during the fourth control. The zero point of the pressure sensor 48 is corrected so that That is, the zero point correction unit 94 calculates the difference value between the detected value outputted by the pressure sensor 48 during the third control and the corrected zero point, and the detected value outputted by the pressure sensor 48 during the fourth control and the corrected zero point. The zero point of the pressure sensor 48 is corrected so that the difference value from the zero point of the pressure sensor 48 is equal to the difference value. Thereby, an error in the zero point of the pressure sensor 48 can be corrected.

FIG. 5 is a flowchart illustrating a method of controlling the injection molding machine 10.

The control device 12 can execute the control method shown in FIG. 5, for example. This control method includes a first motor control step S1, a torque setting step S2, a second motor control step S3, and a zero point correction step S4.

The first motor control step S1 includes a first control step S11 and a second control step S12.

In the first control step S11, the first motor control section 90 executes the first control. More specifically, in the first control step S11, the injection motor 62 is controlled so that the torque in the first rotational direction gradually decreases from the first predetermined torque TC. As a result, the injection member 24 moves in the first direction D1, but when the torque decreases to a certain level, the movement of the injection member 24 in the first direction D1 is stopped due to inhibition by the resin.

The first motor control unit 90 causes the storage unit 80 to store the first acquired torque TA when the injection member 24 stops in the first control. This ends the first control step S11.

Note that the injection member 24 may be at the first end position PE1 at the start of the first motor control step S1. In that case, the first motor control unit 90 cannot move the injection member 24 in the first direction D1.

In order to cause the injection member 24 to stop before the injection member 24 reaches the first end position PE1, the injection member 24 may be moved in the second direction D2 before starting the first motor control step S1. good.

In the second control step S12, the first motor control section 90 executes the second control. More specifically, in the second control step S12, the injection motor 62 is controlled so that the torque in the second rotational direction gradually decreases from the first predetermined torque TC. As a result, the injection member 24 moves in the second direction D2, but when the torque decreases to a certain level, the movement of the injection member 24 in the second direction D2 is stopped by the resin.

The first motor control unit 90 causes the storage unit 80 to store the second acquired torque TB when the injection member 24 stops in the second control. This ends the second control step S12. When the second control step S12 is completed, the control device 12 starts the torque setting step S2.

In the torque setting step S2, the torque setting section 91 sets a second predetermined torque. The torque setting unit 91 sets the smaller of the first acquired torque TA and the second acquired torque TB as the second predetermined torque.

The torque setting section 91 causes the storage section 80 to store second torque information 88 indicating the second predetermined torque. This completes the torque setting step S2. When the torque setting step S2 is completed, the control device 12 starts the second motor control step S3.

The second motor control step S3 includes a third control step S31 and a fourth control step S32.

In the third control step S31, the second motor control section 92 executes the third control. More specifically, in the third control step S31, the second motor control unit 92 controls the injection motor 62 so that the torque in the first rotational direction becomes the second predetermined torque. As described above, the second predetermined torque is the smaller of the first acquired torque TA and the second acquired torque TB. Therefore, the injection member 24 does not move in the first direction D1. When the detected value of the pressure sensor 48 is acquired, the control device 12 ends the third control step S31.

In the fourth control step S32, the second motor control section 92 executes the fourth control. More specifically, in the fourth control step S32, the second motor control unit 92 controls the injection motor 62 so that the torque in the second rotational direction becomes the second predetermined torque. As described above, the second predetermined torque is the smaller of the first acquired torque TA and the second acquired torque TB. Therefore, the injection member 24 does not move in the second direction D2. When the detected value of the pressure sensor 48 is acquired, the control device 12 ends the fourth control step S32.

In the zero point correction step S4, the zero point correction section 94 corrects the zero point of the pressure sensor 48. The zero point correction unit 94 adjusts the zero point of the pressure sensor 48 based on the detection value output by the pressure sensor 48 during the third control step S31 and the detection value output by the pressure sensor 48 during the fourth control step S32. Correct. The control method of FIG. 5 ends when the zero point correction section 94 corrects the zero point of the pressure sensor 48.

According to the control device 12, the zero point error of the pressure sensor 48 is corrected. Moreover, the number of times the injection member 24 moves in order to correct the zero point of the pressure sensor 48 is the number of times the injection member 24 moves in the first direction D1 when the first control is executed and the number of times the injection member 24 moves in the first direction D1 when the second control is executed. It may be necessary to move at least twice in two directions D2. In other words, the control device 12 can correct the zero point of the pressure sensor 48 while suppressing the number of times the injection member 24 moves.

By suppressing the number of times the injection member 24 moves, for example, the risk of air being drawn into the injection cylinder 22 from the injection port 34p due to the injection member 24 moving many times is reduced. By reducing the risk of air being drawn into the injection cylinder 22, the risk of the air drawn into the injection cylinder 22 causing resin burn on the resin within the injection cylinder 22 is also reduced.

According to the control device 12, the time required to execute the control method of FIG. 5 can also be reduced. In other words, according to the control device 12, the time required to correct the zero point of the pressure sensor 48 can also be suppressed.

The timing at which the control device 12 executes the control method of FIG. 5 is not particularly limited as long as it is within the period when the resin that imparts viscous resistance to the injection member 24 remains in the injection cylinder 22. However, it is preferable that the control device 12 performs the first motor control step S1 and the second motor control step S3 during automatic purge. In other words, it is preferable that the control device 12 also automatically starts the control method of FIG. 5 when starting automatic purge. This eliminates the need to delay the start of the molding cycle just to correct the zero point of the pressure sensor 48. Furthermore, there is no need to interrupt the molding cycle just to correct the zero point of the pressure sensor 48. Note that the control device 12 appropriately controls the rotation motor 54 and the injection motor 62 to execute automatic purging.

[Modified example]
The control device 12 may be applied to a pre-plastic injection molding machine.

In a pre-plastic injection molding machine, the injection member 24 is configured by a plunger (not shown). The plunger is inserted into the injection cylinder 22. The plunger moves in the first direction D1 and the second direction D2 according to the drive of the injection motor 62.

Also in this modification, the first motor control section 90 can perform the first control and the second control similarly to the above embodiment. Thereby, the first acquired torque TA when the plunger stops moving in the first direction D1 and the second acquired torque TB when the plunger stops moving in the second direction D2 are acquired. Therefore, the torque setting unit 91 can set the second predetermined torque based on the first acquired torque TA and the second acquired torque TB, similarly to the above embodiment.

Also in this modification, the second motor control section 92 can perform the third control and the fourth control similarly to the above embodiment. Further, similarly to the above embodiment, the zero point correction unit 94 detects the pressure sensor based on the detected value outputted by the pressure sensor 48 during the third control and the detected value outputted by the pressure sensor 48 during the fourth control. 48 zero points can be corrected. Furthermore, the zero point correction section 94 can correct the zero point P0 of the pressure sensor 48 while minimizing the number of times the plunger moves.

[Additional notes]
Regarding the above embodiments and modifications, the following additional notes are disclosed.

(Additional note 1)
An injection member (24) inserted into the injection cylinder (22) and movable within the injection cylinder, an injection motor (62) that moves the injection member, and the pressure of the resin within the injection cylinder. The control device (12) of the injection molding machine (10), which includes a pressure sensor (48) for detecting to perform first control to move the injection member in a first direction, and control the injection control so that the torque gradually decreases from the first predetermined torque when the movement of the injection member is stopped in the first control. a first motor control unit (90) that performs second control to control a motor to move the injection member in a second direction opposite to the first direction, and when the injection member stops in the first control; and a torque of the injection motor when the injection member stops in the second control, the smaller of which is set as a second predetermined torque. , a third control for controlling the injection motor so that the torque becomes the second predetermined torque, and controlling the injection member to move in one of the first direction and the second direction; At the same time, when the movement of the injection member is stopped in the third control, the injection motor is controlled so that the torque becomes the second predetermined torque. a second motor control unit (92) that performs fourth control to control the injection member to move in the other direction; a detected value that the pressure sensor outputs during the third control; and a detection value that the pressure sensor outputs during the third control; and a zero point correction section (94) that corrects the zero point of the pressure sensor based on the detected value output during the fourth control. Thereby, the zero point of the pressure sensor can be corrected while suppressing the number of times the injection member is moved.

(Additional note 2)
The control device for an injection molding machine according to Supplementary Note 1, wherein the zero point correction unit is configured to output an absolute value of a detection value outputted by the pressure sensor during the third control, and an absolute value of the detected value outputted by the pressure sensor during the fourth control. The control device for the injection molding machine may correct the zero point so that the absolute value of the detected value outputted to the zero point becomes equal to the absolute value of the detected value. Thereby, the zero point of the pressure sensor can be corrected while suppressing the number of times the injection member is moved.

(Additional note 3)
The control device for an injection molding machine according to Supplementary Note 1 or 2, wherein the first motor control section and the second motor control section are configured to control the injection molding machine while the injection molding machine executes automatic purge. It may also be a control device for an injection molding machine that controls a motor. This eliminates the need to delay the start of the molding cycle just to correct the zero point of the pressure sensor. Furthermore, there is no need to interrupt the molding cycle just to correct the zero point of the pressure sensor.

(Additional note 4)
An injection member (24) inserted into the injection cylinder (22) and movable within the injection cylinder, an injection motor (62) that moves the injection member, and the pressure of the resin within the injection cylinder. A method for controlling an injection molding machine (10), comprising: a pressure sensor (48) for detecting a pressure sensor (48); a first control for moving the injection member in a first direction; and controlling the injection motor so that the torque gradually decreases from the first predetermined torque to inject the injection in a second direction opposite to the first direction. a first motor control step (S1) that performs a second control for moving the member, a torque of the injection motor when the injection member stops in the first control, and a torque of the injection motor when the injection member stops in the second control; a torque setting step (S2) of setting the smaller of the torque of the injection motor when stopped as a second predetermined torque; and controlling the injection motor so that the torque becomes the second predetermined torque. a third control for controlling the injection member to move in one of the first direction and the second direction; and controlling the injection motor so that the torque becomes the second predetermined torque. a second motor control step (S3) for controlling the injection member to move in the other direction of the first direction and the second direction; and a zero point correction step (S4) of correcting the zero point of the pressure sensor based on the detected value output during the third control and the detected value output by the pressure sensor during the fourth control. Thereby, the zero point of the pressure sensor can be corrected while suppressing the number of times the injection member is moved.

Although the embodiments of the present disclosure have been described in detail, the present disclosure is not limited to the individual embodiments described above. These embodiments may include various additions, substitutions, changes, and parts without departing from the gist of the invention or the spirit and spirit derived from the content stated in the claims and equivalents thereof. It is possible to delete etc. For example, in the embodiments described above, the order of each operation or the order of each process is shown as an example, and the order is not limited thereto. Further, the same applies when numerical values or formulas are used in the description of the above-described embodiments.

DESCRIPTION OF SYMBOLS 10... Injection molding machine 12... Control device 22... Injection cylinder 24... Injection member 48... Pressure sensor 62... Injection motor 90... First motor control section 91... Torque setting section 92... Second motor control section 94... Zero point Correction section

Claims

An injection member (24) that is inserted into an injection cylinder (22) and movable within the injection cylinder, an injection motor (62) that moves the injection member, and a resin pressure inside the injection cylinder. A control device (12) for an injection molding machine (10), comprising a pressure sensor (48) for detecting the
Performing first control to move the injection member in a first direction by controlling the injection motor so that the torque gradually decreases from a first predetermined torque (TC), and moving the injection member in the first control. When the injection motor stops, a second control is performed to move the injection member in a second direction opposite to the first direction by controlling the injection motor so that the torque gradually decreases from the first predetermined torque. a first motor control section (90);
The smaller of the torque of the injection motor when the injection member stops in the first control and the torque of the injection motor when the injection member stops in the second control is determined as the second control. a torque setting section (91) that sets a predetermined torque;
performing a third control of controlling the injection motor so that the torque becomes the second predetermined torque, and controlling the injection member to move in one of the first direction and the second direction; At the same time, when the movement of the injection member is stopped in the third control, the injection motor is controlled so that the torque becomes the second predetermined torque, and the injection motor is controlled in the first direction and the second direction. a second motor control unit (92) that performs fourth control to control the injection member to move in the other direction;
a zero point correction unit (94) that corrects the zero point of the pressure sensor based on a detection value output by the pressure sensor during the third control and a detection value output by the pressure sensor during the fourth control; and,
A control device for an injection molding machine.
A control device for an injection molding machine according to claim 1,
The zero point correction unit adjusts the zero point correction unit so that the absolute value of the detected value outputted by the pressure sensor during the third control is equal to the absolute value of the detected value outputted by the pressure sensor during the fourth control. An injection molding machine control device that corrects the zero point.
A control device for an injection molding machine according to claim 1 or 2,
The first motor control unit and the second motor control unit are control devices for an injection molding machine that control the injection motor while the injection molding machine is performing automatic purge.
An injection member (24) inserted into the injection cylinder (22) and movable within the injection cylinder, an injection motor (62) that moves the injection member, and the pressure of the resin within the injection cylinder. A method for controlling an injection molding machine (10), comprising: a pressure sensor (48) for detecting
a first control for moving the injection member in a first direction by controlling the injection motor so that the torque gradually decreases from a first predetermined torque (TC); and a first control for moving the injection member in a first direction so that the torque gradually decreases from the first predetermined torque a first motor control step (S1) of controlling the injection motor to move the injection member in a second direction opposite to the first direction;
The smaller of the torque of the injection motor when the injection member stops in the first control and the torque of the injection motor when the injection member stops in the second control is determined as the second control. a torque setting step (S2) of setting a predetermined torque;
a third control that controls the injection motor so that the torque becomes the second predetermined torque, and controls the injection member to move in one of the first direction and the second direction; a fourth control that controls the injection motor so that the torque becomes the second predetermined torque, and controls the injection member to move in the other direction of the first direction and the second direction; a second motor control step (S3) to perform;
a zero point correction step (S4) of correcting the zero point of the pressure sensor based on the detection value output by the pressure sensor during the third control and the detection value output by the pressure sensor during the fourth control; and,
A method of controlling an injection molding machine, including: