Clamping device and injection molding machine
The control device ensures uniform clamping forces by independently setting and restricting axial force values for ball screw mechanisms, addressing premature deterioration issues in mold clamping devices.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- THE JAPAN STEEL WORKS LTD
- Filing Date
- 2022-06-24
- Publication Date
- 2026-05-11
Smart Images
Figure 0007856505000001 
Figure 0007856505000002 
Figure 0007856505000003
Abstract
Description
Technical Field
[0001] The present invention relates to a mold clamping device including two mold plates and a plurality of ball screw mechanisms connecting these mold plates, and an injection molding machine.
Background Art
[0002] An injection molding machine or a press machine is provided with a mold clamping device for clamping a mold. There are various types of mold clamping devices, and Patent Document 1 describes a mold clamping device including two mold plates. That is, the mold plates consist of a fixed mold plate and a movable mold plate. The fixed mold plate and the movable mold plate are connected by four sets of ball screw mechanisms, and each of the four ball screw mechanisms is provided with a servo motor. Therefore, when the four servo motors are driven, the four sets of ball screw mechanisms are driven, and the movable mold plate slides relative to the fixed mold plate. That is, the mold opens and closes.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] The mold clamping device described in Patent Document 1 can drive four servo motors independently, and can independently control the axial forces acting on each of the four ball screw mechanisms. Therefore, even when the molds are attached to the mold plates at positions where their centers are displaced from each other, the mold clamping force can be uniformly applied to the molds by adjusting the axial forces acting on the four ball screw mechanisms during mold clamping. However, problems to be solved can also be found. Specifically, there is no restriction on the settable axial force, and it is possible to set an axial force that places a burden on some of the ball screw mechanisms, which may cause premature deterioration of the ball screw mechanisms.
[0005] This disclosure provides a clamping device that suppresses the premature deterioration of a ball screw mechanism.
[0006] Other challenges and novel features will become apparent from the description and accompanying drawings in this specification. [Means for solving the problem]
[0007] This disclosure relates to a mold clamping device comprising two mold plates, a plurality of ball screw mechanisms connecting the mold plates, a plurality of servo motors for driving the ball screw mechanisms, and a control device. The control device independently controls the servo motors based on a plurality of axial force setting values set for each of the plurality of ball screw mechanisms, and the plurality of axial force setting values are configured to be set in the control device based on constraints that define a mutually settable tolerance range. The constraints are that the maximum value among the multiple axial force settings set for each of the multiple ball screw mechanisms is set as the maximum axial force setting, and the difference between the other axial force setting values and the maximum axial force setting value is less than or equal to the allowable difference amount, and the allowable difference amount decreases as the maximum axial force setting value increases. [Effects of the Invention]
[0008] This disclosure makes it possible to suppress the premature deterioration of the ball screw mechanism. [Brief explanation of the drawing]
[0009] [Figure 1] This is a front view showing the injection molding machine according to this embodiment. [Figure 2] This is a perspective view showing the clamping device according to this embodiment. [Figure 3] This is a plan view of the movable platen according to this embodiment. [Figure 4] This is a front view of the clamping device according to this embodiment. [Figure 5] This is a flowchart showing the method for inspecting the axial force setting value according to this embodiment. [Figure 6] This graph shows the constraints applied in the inspection method for axial force setting values according to this embodiment. [Figure 7A] This graph shows the constraints related to Modification Example 1. [Figure 7B] This graph shows the constraints related to Modification Example 2. [Modes for carrying out the invention]
[0010] The following describes specific embodiments in detail with reference to the drawings. However, the embodiments are not limited to those described below. For clarity, the following descriptions and drawings have been simplified as appropriate. In each drawing, the same elements are denoted by the same reference numerals, and redundant explanations have been omitted where necessary. Also, hatching has been omitted in some parts of the drawings to avoid clutter.
[0011] <Injection molding machine according to this embodiment> As shown in Figure 1, the injection molding machine 1 according to this embodiment consists of a clamping device 2 provided on the bed B, an injection device 4, and a control device 5 that controls these.
[0012] <Injection device> The injection device 4 consists of a heating cylinder 6, a screw 7 placed inside the heating cylinder 6, and a screw drive device 8 that drives the screw 7. The heating cylinder 6 is equipped with a hopper 10, and an injection nozzle 11 is provided at its tip. Injection material is fed from the hopper 10, and when the screw 7 is rotated and the injection material is melted, it is metered at the tip of the screw 7. When the screw 7 is driven in the axial direction, the injection material is injected.
[0013] <Mold clamping device> The mold clamping device 2 according to this embodiment is composed of a so-called two-platen mold clamping device. That is, as shown in FIG. 2, the mold clamping device 2 includes two mold plates 13 and 14, namely a fixed mold plate 13 and a movable mold plate 14. The fixed mold plate 13 is fixed on the bed B, and the movable mold plate 14 is placed on linear guides 15 and 15 provided on the bed B. That is, the movable mold plate 14 is slidable in the direction of approaching and separating from the fixed mold plate 13. As shown in FIG. 1, a fixed-side mold 16 is attached to the fixed mold plate 13, and a movable-side mold 17 is attached to the movable mold plate 14. It is preferable that the fixed-side mold 16 and the movable-side mold 17 are provided at the center of the mold plate on the fixed mold plate 13 and the movable mold plate 14 respectively, but there may be cases where they have to be arranged at positions deviated from the center. FIG. 1 shows a state where these molds 16 and 17 are arranged at positions deviated above the center of the mold plate.
[0014] The mold clamping device 2 according to the first embodiment is such that two mold plates 13 and 14, namely a fixed mold plate 13 and a movable mold plate 14, are connected by four rod-shaped members, namely four ball screw mechanisms 18, 18,.... Each ball screw mechanism 18, 18,... includes ball screws 19, 19,... and ball nuts 20, 20,... attached to the ball screws 19, 19,....
[0015] Although not shown in FIG. 2, through holes are formed in the movable mold plate 14, and the ball nuts 20, 20,... are fixed to these through holes. That is, one end side of the ball screws 19, 19,... is connected to the movable mold plate 14 via the ball nuts 20, 20,.... The other end of the ball screws 19, 19,... penetrates the fixed mold plate 13 and is rotatably supported with respect to the fixed mold plate 13. Servo motors 22, 22,... are provided on the fixed mold plate 13 and are connected to the ball screws 19, 19,.... Therefore, when the servo motors 22, 22,... are driven, the ball screws 19, 19,... rotate, and the movable mold plate 14 slides. That is, the molds 16, 17 (see FIG. 1) are opened and closed.
[0016] <When the axial force setting value is constant> In the injection molding machine 1 according to this embodiment, the control device 5 (see FIG. 1) is configured to independently control a plurality of servo motors 22, 22,.... And the set value of the axial force acting on the plurality of ball screw mechanisms 18, 18,... that is, the axial force set value can be set for each of the ball screw mechanisms 18, 18,.... For example, the axial force set value may be set as a torque set value for each of the servo motors 22, 22,.... In any case, the reason for enabling independent setting of the axial force is to apply a substantially uniform clamping force to the molds 16 and 17. Here, consider a control different from this embodiment. That is, consider what happens when only the same axial force set value can be set for the ball screw mechanisms 18, 18,.... In FIGS. 3 and 4, different reference numerals 18a, 18b, 18c, 18d are arbitrarily assigned to each of the ball screw mechanisms 18a, 18b, 18c, 18d for convenience of explanation.
[0017] As shown in FIG. 3, the mold 17 is arranged offset above the center C on the movable platen 14. That is, the mold 17 is close to the ball screw mechanisms 18a and 18b and is spaced apart from the ball screw mechanisms 18c and 18d. In this state, a substantially same axial force is applied to all of the ball screw mechanisms 18a, 18b, 18c, 18d. Then, as shown in FIG. 4, the axial force F2 acting on the movable platen 14 from the ball screw mechanisms 18a and 18b and the axial force F3 acting on the movable platen 14 from the ball screw mechanisms 18c and 18d are substantially the same magnitude. On the other hand, a force F1 acts on the movable platen 14 from the mold 17. Since the distance between the action point of the force F1 and the action point of the axial force F3 is farther than the distance between the action point of the force F1 and the action point of the axial force F2, a stronger bending moment acts on the lower side than on the upper side of the movable platen 14. Therefore, the movable platen 14 is slightly deformed as shown by the dotted line, and the degree of deformation is larger on the lower side.
[0018] Similarly, the fixed platen 13 is subjected to axial forces F2 and F7, as well as force F5 from the mold 16, causing it to deform slightly as shown by the dotted line. When the movable platen 14 and the fixed platen 13 deform in this way, the distance between the movable platen 14 and the fixed platen 13 narrows slightly downwards. As a result, stronger forces act on the molds 17 and 16 at the locations indicated by symbols p2 and p4 than at the locations indicated by symbols p1 and p3, respectively. This causes the clamping force acting on the molds 16 and 17 to become uneven.
[0019] <Setting different axial force values> The control device 5 (see Figure 1) of the injection molding machine 1 according to this embodiment allows for setting different axial force values for each of the four ball screw mechanisms 18, 18, ... For example, as explained in Figure 3, a slightly larger axial force value can be set for ball screw mechanisms 18a and 18b, and a slightly smaller axial force value can be set for ball screw mechanisms 18c and 18d. In this way, deformation as shown by the dotted line in Figure 4 hardly occurs, and a uniform clamping force can be generated in the molds 16 and 17.
[0020] Incidentally, if there are no restrictions or protections on the axial force settings that can be set for each ball screw mechanism 18a, 18b, 18c, and 18d, dangerous settings become possible. For example, due to an operational error in the control device 5 (see Figure 1), it is possible to set excessively high axial force settings for ball screw mechanisms 18a and 18b, and set axial force settings for ball screw mechanisms 18c and 18d to be virtually zero. In that case, excessive loads would be placed on ball screw mechanisms 18a and 18b, causing them to deteriorate prematurely. Not limited to operational errors, even if large differences in axial force settings are intentionally set for each ball screw mechanism 18a, 18b, 18c, and 18d, the load on some of the ball screw mechanisms 18a, 18b, 18c, and 18d will increase, potentially causing premature deterioration.
[0021] The injection molding machine 1 according to this embodiment (see Figure 1) restricts the range in which each ball screw mechanism 18a, 18b, 18c, and 18d can be set by imposing constraints on the axial force setting values. This protects each ball screw mechanism 18a, 18b, 18c, and 18d. The inspection method for the axial force setting values according to this embodiment, which is implemented in the control device 5, and the constraints applied in this inspection method will be described below.
[0022] <Inspection method for axial force setting value> The operator sets axial force setting values for each of the four ball screw mechanisms 18a, 18b, 18c, and 18d (see Figure 3) in the control device 5 (see Figure 1). The control device 5 then checks whether each axial force setting value is appropriate. As shown in Figure 5, the control device 5 executes step S01 to identify the maximum axial force setting value. That is, it identifies the maximum axial force setting value, which is the maximum value among the axial force setting values set for each of the four ball screw mechanisms 18a, 18b, 18c, and 18d. At this time, it also identifies the ball screw mechanism to which the maximum axial force setting value is set. For example, if the ball screw mechanism 18b has the maximum axial force setting value set, then this ball screw mechanism 18b is identified.
[0023] Next, step S02 is performed. That is, it is checked whether the constraints are met for the other ball screw mechanisms 18a, 18c, and 18d. The constraints are conditions that define the allowable range that can be set for each other when setting the axial force setting value for the ball screw mechanisms 18a, 18b, 18c, and 18d. In this embodiment, the condition is that the difference between the axial force setting value set for the other ball screw mechanisms 18a, 18c, and 18d and the maximum axial force setting value is less than or equal to the allowable difference amount. This will be explained with reference to Figure 6.
[0024] In Figure 6, the horizontal axis represents the maximum axial force setting value, and the vertical axis represents the settable axial force setting value. Graph 30 shows the maximum axial force setting value. Graph 31 shows the lower limit of the settable axial force. For example, when the maximum axial force setting value set for the ball screw mechanism 18b is 50kN, the value in graph 30 (symbol 32) is naturally 50kN. On the other hand, the value in graph 31 (symbol 33) is 15kN. This means that the lower limit of the settable axial force is 15kN. Therefore, when the maximum axial force setting value is 50kN, the allowable difference is 35kN (50kN - 15kN). In step S02, it is checked whether the axial force setting values set for the other ball screw mechanisms 18a, 18c, and 18d are less than or equal to the allowable difference of 35kN relative to the maximum axial force setting value of 50kN.
[0025] If the constraints are not met (NO), step S03 shown in Figure 5 is executed. In step S03, the control device 5 outputs a warning that the axial force set value set by the operator cannot be set. It then shows the magnitude of the deviation in axial force for the ball screw mechanisms 18a, 18c, and 18d whose difference from the maximum axial force set value exceeds the allowable difference amount. Seeing this warning, the operator can understand the appropriate range of axial force set values and set the axial force set values again for each of the ball screw mechanisms 18a, 18b, 18c, and 18d. The control device 5 performs step S04 to determine whether the operator has reset the axial force set values. If they have been reset (YES), it returns to step S01. On the other hand, if they have not been reset (NO), it returns to step S03.
[0026] If it is determined in step S02 that the constraints are met (YES), then step S05 is executed. That is, the axial force setting values that the operator has set for each of the four ball screw mechanisms 18a, 18b, 18c, and 18d (see Figure 3) are finalized and saved to the control device 5. The inspection is then completed.
[0027] As is clear from graphs 30 and 31 in Figure 6, the constraints in this embodiment are such that the allowable difference amount changes depending on the maximum axial force setting value. In other words, as the maximum axial force setting value increases, the allowable difference amount decreases.
[0028] <Example 1> The constraints can be modified in various ways. Figure 7A is a graph showing the constraints related to Modification 1. In Figure 7A, which shows the constraints related to Modification 1, graph 36, which shows the lower limit of the settable axial force, is a graph that is shifted downward in the vertical axis direction relative to graph 35, which shows the maximum axial force setting value. Under these constraints, the difference between graph 35 and graph 36 is fixed at 20kN. That is, the allowable difference is a constant 20kN. The injection molding machine 1 and clamping device 2 to which these constraints related to Modification 1 are adopted have the same configuration as shown in Figures 1 and 2, and their explanation is omitted.
[0029] When adopting the constraints related to Modification 1, the following applies. In step S02, when adopting the constraints related to Modification 1, the method for inspecting the axial force setting value according to this embodiment, as explained in Figure 5, is as follows. That is, the inspection will be conducted to determine whether the difference between the axial force setting values set in the other ball screw mechanisms 18a, 18c, and 18d (see Figure 3) and the maximum axial force setting value set in the ball screw mechanism 18b is within 20kN.
[0030] <Modification 2> Figure 7B shows a graph illustrating the constraints related to Modification 2. The injection molding machine 1 and clamping device 2, which employ the constraints related to Modification 2, have the same configuration as shown in Figures 1 and 2, and their explanation is omitted. In the constraints related to Modification 2, the slope of graph 39, which shows the lower limit of the configurable axial force, is smaller than that of graph 38, which shows the maximum axial force setting value. Under these constraints, the allowable difference amount changes with the maximum axial force setting value, and increases as the maximum axial force setting value increases.
[0031] The present invention has been described in detail above based on embodiments, but it goes without saying that the present invention is not limited to the embodiments already described, and various modifications are possible without departing from the spirit of the invention. The multiple examples described above can also be implemented in combination as appropriate. [Explanation of Symbols]
[0032] 1 Injection molding machine 2 Mold clamping device 4. Injection device 5. Control unit 6 Heating cylinder 7 Screw 8 Screw drive mechanism 10 Hopper 11 Injection nozzle 13 Fixing plate 14. Movable plate 15. Linear guide 16 Fixed mold 17 Movable mold 18 Ball screw mechanism 19 Ball screw 20 Ball nuts 22 Servo motors B Bed C center
Claims
1. Two molds, Multiple ball screw mechanisms connecting the aforementioned panel boards, Multiple servo motors are provided on each of the multiple ball screw mechanisms to drive the ball screw mechanisms, A control device is provided, The control device is configured to independently control the servo motor based on multiple axial force setting values set for each of the multiple ball screw mechanisms. Multiple axial force setting values are set in the control device based on constraints that define the allowable ranges within which they can be set mutually. A clamping device in which, when the maximum value among the multiple axial force setting values set for each of the multiple ball screw mechanisms is set as the maximum axial force setting value, the constraint condition is that the difference between the other axial force setting values and the maximum axial force setting value is less than or equal to an allowable difference amount, and the allowable difference amount decreases as the maximum axial force setting value increases.
2. A mold clamping device for clamping the mold, It consists of an injection device for injecting injection material, The clamping device comprises two mold plates, Multiple ball screw mechanisms connecting the aforementioned panel boards, Multiple servo motors are provided on each of the multiple ball screw mechanisms to drive the ball screw mechanisms, A control device is provided, The control device is configured to independently control the servo motor based on multiple axial force setting values set for each of the multiple ball screw mechanisms. Multiple axial force setting values are set in the control device based on constraints that define the allowable ranges within which they can be set mutually. An injection molding machine in which, when the maximum value among the multiple axial force setting values set for each of the multiple ball screw mechanisms is set as the maximum axial force setting value, the constraint condition is that the difference between the other axial force setting values and the maximum axial force setting value is less than or equal to an allowable difference amount, and the allowable difference amount decreases as the maximum axial force setting value increases.