JP2025035710A - Clamping device, injection molding machine equipped with same, and method for controlling clamping device - Google Patents

Abstract

To provide a mold clamping device capable of controlling a speed of a movable platen.SOLUTION: A mold clamping device 2 has: a movable platen 23 for attaching a movable mold M2; a fixed platen 22 for attaching a fixed mold M1; a link mechanism 27 for moving the movable platen 23 in a forward and backward direction relative to the fixed platen 22; a motor 29 for driving the link mechanism 27; a control device 4 for the motor 29; and a detection device 29A connected to the control device 4 and for detecting a position of the movable platen 23. The control device 4 has an input part 42 for a target moving speed of the movable platen 23, and controls the motor 29 so as to control a speed of the movable platen 23 based on the target moving speed inputted from the input part 42 and the position of the movable platen 23 detected by the detection device 29A.SELECTED DRAWING: Figure 3

Description

The present invention relates to a mold clamping device, an injection molding machine equipped with the same, and a method for controlling the mold clamping device.

An injection molding machine is mainly composed of an injection unit and a mold clamping unit. The mold clamping unit is equipped with a movement mechanism that moves the movable platen forward and backward relative to the fixed platen. A motor-driven link mechanism is widely used as the movement mechanism. Patent Document 1 describes a method for controlling the speed of a movable platen based on the acceleration pattern of the movable platen.

Patent No. 5325808

The clamping device of an injection molding machine is sometimes required to work in conjunction with peripheral devices such as a device for removing the molded product and the core inside the mold. To effectively achieve this coordination, it is desirable to directly control the speed of the movable platen. Conventionally, it has been difficult to control the speed of the movable platen due to the configuration of the link mechanism. The object of the present invention is to provide a clamping device that can control the speed of the movable platen.

The mold clamping device has a motor that drives a link mechanism that moves the movable platen in the forward and backward directions relative to the fixed platen, and a control device for the motor. The control device controls the motor so as to control the speed of the movable platen based on the input target moving speed and the detected position of the movable platen.

The present invention provides a mold clamping device that can control the speed of a movable platen.

1 is a schematic front view of an injection molding machine according to an embodiment of the present invention. FIG. 2 is a diagram showing a state of the mold clamping unit shown in FIG. 1 in a fully open position. FIG. 2 is a diagram showing a state of the mold clamping unit shown in FIG. 1 at an intermediate position. FIG. 2 is a diagram showing a state of the mold clamping unit shown in FIG. 1 in a fully closed position. FIG. 13 is a diagram showing the relationship between the position and the moving speed of a movable platen. FIG. 4 is a diagram showing an example of the relationship shown in FIG. 3 in a table format. FIG. FIG. 11 is a flowchart showing a method for controlling the movable platen.

<Overall configuration of injection molding machine 1>
An embodiment of the mold clamping device of the present invention will be described with reference to the drawings. Fig. 1 shows a schematic front view of an injection molding machine 1 including a mold clamping device 2 according to this embodiment. The injection molding machine 1 is generally composed of a mold clamping device 2 that clamps a mold, an injection device 3 that heats, melts, and injects the material to be injected, and a control device 4. The control device 4 is provided to control the overall operation of the injection molding machine 1. In the following description, the direction in which the movable platen 23 advances and retreats relative to the fixed platen 22 or the mold opening and closing direction is referred to as the X direction. The X direction is a horizontal direction and coincides with the direction in which the screw 33 of the injection device 3 extends.

<Clamping device 2>
The mold clamping device 2 includes a fixed platen 22 fixed on a bed 21 and having a fixed mold M1 attached thereto, a mold clamping housing 24 slidable on the bed 21, and a movable platen 23 slidable on the bed 21 and having a movable mold M2 attached thereto. The fixed mold M1 and the movable mold M2 may be collectively referred to as a mold M. The fixed platen 22 and the mold clamping housing 24 are connected by a plurality of tie bars 25. A mold clamping mechanism 26 for opening and closing the mold M is provided between the movable platen 23 and the mold clamping housing 24. The mold clamping mechanism 26 includes a link mechanism 27 also called a toggle mechanism, a ball screw 28 connected to the link mechanism 27, and a motor 29 for driving the link mechanism 27 via the ball screw 28. It is preferable to use a servo motor as the motor 29.

<Link mechanism 27>
Figures 2A to 2C show the movement of the link mechanism 27. Figure 2A shows the position where the movable platen 23 is farthest from the fixed platen 22 (hereinafter referred to as the fully open position), Figure 2C shows the position where the movable mold M2 attached to the movable platen 23 and the fixed mold M1 attached to the fixed platen 22 are in close contact (hereinafter referred to as the fully closed position), and Figure 2B shows an intermediate position between the fully open position and the fully closed position. The configuration and operation of the link mechanism 27 will be described with reference to Figure 1 and Figures 2A to 2C.

The link mechanism 27 has an upper link portion 27A, a lower link portion 27B, and a crosshead 27C connecting the upper link portion 27A and the lower link portion 27B. The upper link portion 27A has a movable platen connecting portion 271 pin-connected to the movable platen 23, a housing connecting portion 272 pin-connected to the mold clamping housing 24, and an intermediate member 273 pin-connected to the housing connecting portion 272 and the crosshead 27C. The movable platen connecting portion 271 and the housing connecting portion 272 are pin-connected. The lower link portion 27B has a movable platen connecting portion 274 pin-connected to the movable platen 23, a housing connecting portion 275 pin-connected to the mold clamping housing 24, and an intermediate member 276 pin-connected to the housing connecting portion 275 and the crosshead 27C. The movable platen connecting portion 274 and the housing connecting portion 275 are pin-connected. The crosshead 27C has a receiving portion 277 with which the ball screw 28 meshes.

The ball screw 28 is rotated by the motor 29, causing the crosshead 27C to move in the X direction. As the crosshead 27C moves in the X direction, the fixed platen connection part 271 and the housing connection part 272 of the upper link part 27A, and the fixed platen connection part 274 and the housing connection part 275 of the lower link part 27B bend and extend as a whole, causing the movable platen 23 to move in the X direction.

<Detection device 29A>
The mold clamping unit 2 has a detection device 29A that detects the position of the movable platen 23. The detection device 29A is connected to the control device 4. The detection device 29A has an encoder (not shown) that detects the rotation angle of the motor 29, and the detection device 29A can calculate the X-direction position of the crosshead 27C based on the rotation angle of the motor 29 measured by the encoder. The position of the movable platen 23 and the position of the crosshead 27C have a one-to-one correspondence. Therefore, the X-direction position of the movable platen 23 can be calculated from the X-direction position of the crosshead 27C, and conversely, the X-direction position of the crosshead 27C can be calculated from the X-direction position of the movable platen 23.

<Injection device 3>
The injection device 3 is provided on a base 31. The injection device 3 includes a cylinder 32, a screw 33 housed in the cylinder 32, and a drive mechanism 34 for driving the screw 33. The screw 33 is driven to rotate and in the X direction by the drive mechanism 34. A hopper 35 for supplying the material to be injected is provided near the rear end of the cylinder 32 in the material injection direction (parallel to the X direction). An injection nozzle 36 for supplying the injection material to the inside of the mold M when it hits the fixed mold M1 is provided at the front end of the cylinder 32 in the material injection direction.

The injection device 3 is equipped with a nozzle touch device 37. The nozzle touch device 37 advances the injection device 3, so that the injection nozzle 36 touches the sprue bush M3 of the mold M. The nozzle touch device 37 connects the drive mechanism 34 and the fixed platen 22. The nozzle touch device 37 can be configured as a link mechanism using a ball screw.

<Speed Control of Movable Platen 23>
3 shows the relationship between the position and the moving speed of the movable platen 23. The crosshead 27C moves at a constant speed by driving the motor 29 at a constant output (hereinafter, such control is referred to as constant motor output control). However, since the movable platen 23 is driven in the X direction via the link mechanism 27, the moving speed of the movable platen 23 differs depending on the position of the movable platen 23. Therefore, the movable platen 23 cannot be moved at a constant speed by the constant motor output control.

Figure 3 shows the relationship between the position and moving speed of the movable platen 23, with the output of the motor 29 (hereinafter referred to as motor output) as a parameter. The relationship between the position, moving speed and motor output of the movable platen 23 is stored in advance in the memory unit 41 (see Figure 1) of the control device 4. This relationship can be stored in the form of multiple approximation formulas, but it is preferable to store it in the table format shown in Figure 4. This allows for rapid control of the motor output, which will be described later.

The moving speed of the crosshead 27C is proportional to the motor output, and the moving speed of the movable platen 23 is proportional to the motor output because the moving speed of the crosshead 27C is proportional to the moving speed of the movable platen 23. Therefore, the graphs shown in FIG. 3 differ only in the ratio of the vertical axis. For example, when the relationship between the position and moving speed of the movable platen 23 is actually measured for a motor output of 100%, the above relationship for other motor outputs can be calculated by multiplying the actual measured value of the moving speed by the ratio of the motor output. However, the relationship shown in FIG. 3 may be obtained by actually measuring the position and moving speed of the movable platen 23 for each motor output. The relationship between the position and moving speed of the movable platen 23 was actually measured when the movable platen 23 was moved from the fully open position to the fully closed position and when it was moved from the fully closed position to the fully open position, but there was no significant difference between the two.

Conventionally, motor output is controlled to drive the movable platen 23. Because it is cumbersome to continuously adjust the motor output, the range from the fully open position to the fully closed position is often divided into several sections, and the motor output is set for each section. However, constant motor output control is performed in each section, so the speed of the movable platen 23 fluctuates. For this reason, it was difficult to predict when the movable platen 23 would pass through which position, and when it would reach the fully closed position.

On the other hand, there is a demand to adjust the timing of other processes in accordance with the movement of the movable platen 23, leading to the streamlining of the entire manufacturing process. For example, if it were possible to predict in advance when the movable platen 23 would reach the fully open position, it would be possible to optimize the timing of removing the molded product and moving the mold core. To achieve this, it is preferable to directly control the speed of the movable platen 23 (speed control) rather than controlling it with the motor output, and it is even more preferable to move it at a constant speed as much as possible.

<Method of controlling the speed of the movable platen 23>
FIG. 5 shows a target speed diagram of the movable platen 23. The movable platen 23 moves from the fully open position through the acceleration section K1, the intermediate section K2, and the deceleration section K3 in this order to reach the fully closed position. The intermediate section K2 is between the acceleration section K1 and the deceleration section K3. The movable platen 23 gradually increases its speed from a stationary state in the acceleration section K1, moves at a substantially constant speed in the intermediate section K2, and gradually decelerates in the deceleration section K3 to stop at the fully closed position. A method for realizing the target speed shown in FIG. 5 will be described with reference to the flow chart shown in FIG. 6 and FIG. 3. Note that the control device 4 actually refers to the table shown in FIG. 4 instead of the graph shown in FIG. 3, but for convenience of explanation, the description will be made with reference to FIG. 3. The thick line in FIG. 3 indicates the line of the moving speed that the movable platen 23 actually follows in one example of control described below.

6, first, the following information is input to the control device 4 (step S1). The control device 4 has an input unit 42 for this information (see FIG. 1).
Reference positions P0 to Pn of the movable platen 23
- Fully closed position of the movable platen 23 - Target moving speed in the intermediate section K2 The reference positions P0 to Pn and the fully closed position of the movable platen 23 are set, for example, based on the fully open position. The reason why the fully closed position of the movable platen 23 is input is because the fully closed position of the movable platen 23 differs depending on the shape and size of the mold. The reference positions P0 to Pn will be described later.

In the acceleration section K1, the motor output is controlled so that the speed of the movable platen 23 reaches the target moving speed at the boundary between the acceleration section K1 and the intermediate section K2 (hereinafter referred to as the reference position P0) (step S2). As long as the speed of the movable platen 23 reaches the target moving speed at the reference position P0, the method of controlling the motor 29 in the acceleration section K1 is not limited. As an example, the motor constant output control can be performed in the acceleration section K1. That is, the control device 4 refers to FIG. 3 and calculates the motor output (80% in the example of FIG. 3) at which the speed of the movable platen 23 becomes the target moving speed at the reference position P0, and controls the motor 29 with the calculated motor output. The detection device 29A monitors the position of the movable platen 23, and when it detects that the movable platen 23 has reached the reference position P0 (step S3), the control device 4 ends the motor constant output control.

Next, the control device 4 performs constant speed control of the movable platen 23. A number of reference positions are set in the intermediate section K2, and the motor output is updated at each reference position. First, the movable platen 23 is driven at 80% motor output from the reference position P0 (step S4). Referring to FIG. 3, the speed of the movable platen 23 gradually increases. When the detection device 29A detects that the movable platen 23 has reached the reference position P1 (step S5), the control device 4 reads the target moving speed of the movable platen 23 at the reference position P1 from FIG. 3. In order to achieve the target moving speed at the reference position P1, the motor output needs to be 70%. The control device 4 sets the motor output to 70% and drives the movable platen 23 at 70% motor output (step S6). The speed of the movable platen 23 changes along the graph of the motor output of 70%.

When the detector 29A detects that the movable platen 23 has reached the reference position P2 (step S7), the controller 4 reads the target movement speed of the movable platen 23 at the reference position P2 from FIG. 3. To achieve the target movement speed at the reference position P2, the motor output needs to be about 65%. The controller 4 sets the motor output to 65% and drives the movable platen 23 at the motor output of 65% (step S8). The speed of the movable platen 23 changes along the graph of the motor output of 65%. The controller 4 actually refers to the table in FIG. 4, but the motor output corresponding to the target movement speed at the reference position P2 can be easily determined by interpolation.

The detection device 29A detects that the movable platen 23 has reached the reference position P3 (step S9), and the above process is repeated thereafter. Each time the reference position is reached, the motor output for achieving the target moving speed at that reference position is calculated, and the movable platen 23 is controlled with the calculated motor output. In section A (see FIG. 3) where the graph of the moving speed of the movable platen 23 slopes downward to the right, the motor output may be increased, but the movable platen 23 moves at least a part of the intermediate section K2 in the moving range of the movable platen 23 at a speed of a sawtooth pattern along the target moving speed. Since the sawtooth pattern depends on the relationship between the position and moving speed of the movable platen 23 shown in FIG. 3 and the positions of the reference positions P1 to Pn, it may not appear in some sections, or may be partially reversed. The movable platen 23 is driven with a motor output corresponding to the target moving speed at the reference position Pn-1 (step 10), and when the detection device 29A detects that the movable platen 23 has reached the last reference position Pn of the intermediate section K2 (step S11), the control device 4 ends the constant speed control. It is preferable to set the reference position Pn at the boundary between the intermediate section K2 and the deceleration section K3.

In the control described above, the motor output is adjusted intermittently, so the movable platen 23 is not driven at a constant speed strictly speaking; however, by increasing the number of reference positions, the deviation from the target moving speed is reduced, making it possible to control at a substantially constant speed. Also, since the area where the rate of change of the moving speed of the movable platen 23 is large (in the example of FIG. 3, near the reference positions P0 to P2) is known in advance, the interval between the reference positions may be made smaller in the area where the rate of change is large than in the area where the rate of change is small.

Next, the control device 4 performs deceleration control (step S12). The control device 4 gradually reduces the motor output so that the speed of the movable platen 23 becomes zero at the fully closed position. Since it is desirable to sufficiently reduce the speed of the movable platen 23 near the fully closed position, it is preferable to reduce the motor output as soon as the movable platen 23 enters the deceleration section K3.

Here, we have shown a control method when the movable platen 23 moves from the fully open position to the fully closed position, but the control method when the movable platen 23 moves from the fully closed position to the fully open position is basically the same. It is preferable that the target speed diagram of the movable platen 23 shown in Figure 5 has the shape indicated by the dashed lines in the acceleration section K1 and the deceleration section K3, but the intermediate section K2 has the same shape regardless of the moving direction of the movable platen 23. Therefore, the control flow shown in Figure 6 can also be applied when the movable platen 23 moves from the fully closed position to the fully open position.

In this embodiment, the motor output is updated at multiple reference positions, so that the movable platen 23 in the intermediate section K2 can be moved at an almost constant speed. This embodiment does not require a speed sensor, so it is possible to suppress an increase in the cost of the mold clamping unit 2. In addition, since feedback control using the output of the speed sensor is not performed, the response is good and fluctuations in the moving speed can be suppressed. However, it is also possible to perform control in which the speed of the movable platen is measured by a speed sensor and feedback control is combined.

In this embodiment, the motor output is updated based on the relationship between the motor output, the position of the movable platen, and the moving speed of the movable platen, but the position of the crosshead can also be used instead of the position of the movable platen. As mentioned above, the position of the movable platen and the position of the crosshead have a one-to-one correspondence, so the same control can be achieved whether either is used.

(Additional Note) This specification includes the following disclosure.
[Configuration 1]
a movable platen to which a movable mold is attached, a fixed platen to which a fixed mold is attached, a link mechanism for moving the movable platen in a forward and backward direction relative to the fixed platen, a motor for driving the link mechanism, a control device for the motor, and a detection device connected to the control device and detecting a position of the movable platen,
The control device has an input unit for a target moving speed of the movable platen, and controls the motor to control the speed of the movable platen, based on the target moving speed input from the input unit and the position of the movable platen detected by the detection device.
[Configuration 2]
The control device has a memory unit which stores a relationship between an output of the motor, a position of the movable platen, and a moving speed of the movable platen, calculates the output of the motor from the target moving speed input from the input unit and the position of the movable platen detected by the detection device and the relationship, and controls the motor with the calculated output.
[Configuration 3]
3. The mold clamping apparatus according to claim 2, wherein the storage unit stores the relationship in a table format.
[Configuration 4]
4. The clamping device according to any one of configurations 1 to 3, wherein a movement range of the movable platen has an acceleration section, a deceleration section, and an intermediate section between the acceleration section and the deceleration section, and the control device controls the motor to control a speed of the movable platen when the movable platen is in the intermediate section.
[Configuration 5]
The mold clamping device according to configuration 4, wherein the control device controls the motor so that the movable platen moves in the intermediate section at a substantially constant speed.
[Configuration 6]
The mold clamping device according to configuration 4, wherein the control device controls the motor so that the movable platen moves through at least a portion of the intermediate section at a sawtooth pattern speed along the target moving speed.
[Configuration 7]
The mold clamping device according to any one of configurations 4 to 6, wherein the control device updates the output of the motor at a plurality of reference positions in the intermediate section and controls the motor with the updated output.
[Configuration 8]
The mold clamping device includes an injection device that injects a material and a mold clamping device that clamps a mold.
the mold clamping device includes a movable platen to which a movable mold is attached, a fixed platen to which a fixed mold is attached, a link mechanism for moving the movable platen in an advance/retract direction relative to the fixed platen, a motor for driving the link mechanism, a control device for the motor, and a detection device connected to the control device and detecting a position of the movable platen,
The control device has an input unit for a target moving speed of the movable platen, and controls the motor to control a speed of the movable platen, based on the target moving speed input from the input unit and the position of the movable platen detected by the detection device.
[Method 1]
A control method for a mold clamping unit having a movable platen to which a movable mold is attached, a fixed platen to which a fixed mold is attached, a link mechanism for moving the movable platen in an advancing/retreating direction relative to the fixed platen, a motor for driving the link mechanism, a control device for the motor, and a detection device connected to the control device and detecting a position of the movable platen, comprising:
the control device controls the motor to control a velocity of the movable platen, based on the target moving speed input from an input unit for a target moving speed of the movable platen and the position of the movable platen detected by the detection device.

REFERENCE SIGNS LIST 1 injection molding machine 2 mold clamping device 3 injection device 4 control device 22 fixed platen 23 movable platen 27 link mechanism 29 motor 29A detection device 41 memory unit 42 input unit K2 intermediate section M1 fixed mold M2 movable mold

Claims (9)

a movable platen to which a movable mold is attached, a fixed platen to which a fixed mold is attached, a link mechanism for moving the movable platen in a forward and backward direction relative to the fixed platen, a motor for driving the link mechanism, a control device for the motor, and a detection device connected to the control device and detecting a position of the movable platen,
The control device has an input unit for a target moving speed of the movable platen, and controls the motor to control the speed of the movable platen, based on the target moving speed input from the input unit and the position of the movable platen detected by the detection device. The mold clamping device according to claim 1, wherein the control device has a memory unit that stores the relationship between the output of the motor, the position of the movable platen, and the moving speed of the movable platen, calculates the output of the motor from the target moving speed input from the input unit and the position of the movable platen detected by the detection device and the relationship, and controls the motor with the calculated output. The clamping device according to claim 2, wherein the memory unit stores the relationship in the form of a table. The clamping device according to claim 1, wherein the moving range of the movable platen has an acceleration section, a deceleration section, and an intermediate section between the acceleration section and the deceleration section, and the control device controls the motor to control the speed of the movable platen when the movable platen is in the intermediate section. The clamping device according to claim 4, wherein the control device controls the motor so that the movable platen moves through the intermediate section at a substantially constant speed. The mold clamping device according to claim 4, wherein the control device controls the motor so that the movable platen moves at least a portion of the intermediate section at a sawtooth pattern speed that is aligned with the target moving speed. The mold clamping device according to any one of claims 4 to 6, wherein the control device updates the output of the motor at multiple reference positions in the intermediate section and controls the motor with the updated output. The mold clamping device includes an injection device that injects a material and a mold clamping device that clamps a mold.
the mold clamping device includes a movable platen to which a movable mold is attached, a fixed platen to which a fixed mold is attached, a link mechanism for moving the movable platen in an advance/retract direction relative to the fixed platen, a motor for driving the link mechanism, a control device for the motor, and a detection device connected to the control device and detecting a position of the movable platen,
The control device has an input unit for a target moving speed of the movable platen, and controls the motor to control a speed of the movable platen, based on the target moving speed input from the input unit and the position of the movable platen detected by the detection device. A control method for a mold clamping unit having a movable platen to which a movable mold is attached, a fixed platen to which a fixed mold is attached, a link mechanism for moving the movable platen in an advancing/retreating direction relative to the fixed platen, a motor for driving the link mechanism, a control device for the motor, and a detection device connected to the control device and detecting a position of the movable platen, comprising:
the control device controls the motor to control a velocity of the movable platen, based on the target moving speed input from an input unit for a target moving speed of the movable platen and the position of the movable platen detected by the detection device.