Needle Valve Wear Diagnosis Method for Shut-off Nozzle, Injection Device, and Injection Molding Machine

Abstract

To provide a needle valve wear inspection method of a shut-off nozzle capable of determining whether it should be replaced or not.SOLUTION: A subject shut-off nozzle (5) comprises a nozzle portion (25), a needle valve (26) and a needle valve driving means (28). A needle hole (36) is formed obliquely from an outer peripheral surface of the nozzle portion (25) so as to reach an injection flow path (34) inside. The needle valve (26) is inserted in this needle hole (36). With such a shut-off nozzle (5) as a target, based on an initial gap about a gap of the needle valve (26) and the needle hole (36), a friction constant, and an allowable gap of an allowable amount of the gap, an expected maximum number of shots that is an expected number of operable shot number is predicted.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a needle valve wear diagnosis method for diagnosing wear of a needle valve of a shut-off nozzle, an injection device provided with a shut-off nozzle, and an injection molding machine provided with a shut-off nozzle.

Background Art

[0002] The shut-off nozzle provided in the injection device of an injection molding machine can open and close the flow path through which the injection material of the injection nozzle flows to prevent so-called drooling. There are various types of shut-off nozzles, and the type targeted by the present invention is, for example, the type described in Patent Document 1. That is, the shut-off nozzle includes a nozzle portion and a needle valve provided obliquely with respect to this nozzle portion. In this type of shut-off nozzle, an oblique hole, that is, a needle hole, reaching from the outer peripheral surface of the nozzle portion to the injection flow path inside the nozzle portion is formed. A needle valve is inserted into this needle hole so as to be able to advance and retreat. When the needle valve is advanced, the injection flow path is closed, and when it is retreated, the injection flow path is opened.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When performing a molding cycle, the needle valve is advanced and retracted for each molding cycle, that is, for each shot. A slight gap is formed between the needle valve and the needle hole, and injection material may leak little by little from this gap. The leaked injection material gradually grows and may eventually come into contact with the heater wound around the shut-off nozzle, causing smoke. Conventionally, the shut-off nozzle was cleaned by observing the degree of injection material leakage or the generation of smoke. By the way, the needle valve and the needle hole gradually wear, and these gaps expand due to long-term operation. When the gap expands, injection material leakage recurs immediately even after cleaning. That is, the cleaning becomes useless, and the shut-off nozzle must be replaced. Conventionally, there has been a problem that it is impossible to determine whether to replace the shut-off nozzle or clean it.

[0005] In the present disclosure, a method for diagnosing wear of a needle valve of a shut-off nozzle that can determine whether or not to replace the shut-off nozzle is provided.

[0006] Other problems and novel features will become apparent from the description of this specification and the accompanying drawings.

Means for Solving the Problems

[0007] The present disclosure targets a shut-off nozzle including a nozzle portion and a needle valve inserted into a needle hole formed obliquely with respect to the axial direction reaching the internal injection flow path from its outer peripheral surface. The expected maximum number of operable shots, which is the expected number of operable shots, is predicted from the initial gap regarding the gap between the needle valve and the needle hole, the wear constant, and the allowable gap that is the allowable amount of the gap. The shut-off nozzle also includes a camera. The image of the shut-off nozzle obtained by the camera is used to detect leakage of the injection material from the needle hole. When leakage of the injection material is detected, if the number of shots at the shut-off nozzle has not reached the maximum possible number of shots before the number of shots reaches the maximum possible number of shots during operation, a message prompting cleaning of the shut-off nozzle is output.

Effects of the Invention

[0008] The present disclosure can determine whether or not the shut-off nozzle should be replaced.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0010] Hereinafter, specific embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. For clarity of explanation, the following description and drawings are appropriately simplified. In each drawing, the same elements are denoted by the same reference numerals, and redundant explanations are omitted as necessary. Also, there are parts where hatching is omitted so that the drawings do not become complicated.

[0011] The present embodiment will be described. <Injection Molding Machine> As shown in Fig. 1, the injection molding machine 1 according to this embodiment includes a toggle type mold clamping device 2 and an injection device 3. The injection device 3 according to this embodiment is provided with a shut-off nozzle 5, and a camera 6 is provided in the vicinity of the shut-off nozzle 5. The injection molding machine 1 is provided with a control device 4, and the mold clamping device 2, the injection device 3, the shut-off nozzle 5, the camera 6, etc. are connected to the control device 4 and are controlled by the control device 4.

[0012] <Mold clamping device> The mold clamping device 2 includes a fixed platen 7 fixed to the bed B, a movable platen 8 slidably provided on the bed B, and a mold clamping housing 9. The fixed platen 7 and the mold clamping housing 9 are connected by a plurality of tie bars 11, 11,... The movable platen 8 is slidable between the fixed platen 7 and the mold clamping housing 9. A mold clamping mechanism, that is, a toggle mechanism 13 in this embodiment, is provided between the mold clamping housing 9 and the movable platen 8. Fixed-side molds 15 and movable-side molds 16 are provided on the fixed platen 7 and the movable platen 8, respectively. Therefore, when the toggle mechanism 13 is driven, the molds 15 and 16 are opened and closed.

[0013] <Injection device> The injection device 3 includes a heating cylinder 19, a screw 20 provided in the heating cylinder 19, and a screw driving device 22. The heating cylinder 19 is supported by the screw driving device 22, and the screw 20 is driven in the rotational direction and the axial direction by the screw driving device 22. The heating cylinder 19 is provided with a hopper 23 and the shut-off nozzle 5 according to this embodiment described below. When the heating cylinder 19 is heated, the injection material is supplied from the hopper 23 and the screw 20 is rotated, the injection material is melted and metered. When the screw 20 is driven in the axial direction by the screw driving device 22, the injection material can be injected into the molds 15 and 16.

[0014] <Shut-off nozzle according to this embodiment> As shown in Fig. 2, the shut-off nozzle 5 according to this embodiment includes a nozzle portion 25, a needle valve 26, a needle valve driving means 28 for driving the needle valve 26, and a support structure 30 for supporting the needle valve driving means 28. The nozzle portion 25 is provided to the heating cylinder 19 via an adapter 32.

[0015] In the nozzle portion 25, a flow path through which the injection material flows, that is, an injection flow path 34, is formed inside. The injection flow path 34 is formed on the axial center of the nozzle portion 25. In this specification, the axial direction means the direction of the axis of the nozzle portion 25. That is, the injection flow path 34 is formed axially inside the nozzle portion 25. The nozzle portion 25 is also formed with a hole that reaches the injection flow path 34 from its outer peripheral surface, that is, a needle hole 36. The needle hole 36 is opened obliquely with respect to the axial direction. The needle valve 26 is inserted into the needle hole 36 so as to be able to advance and retreat.

[0016] In this embodiment, the needle valve 26 is formed of a large-diameter shaft portion 38 having a large shaft diameter, a small-diameter shaft portion 39 having a small shaft diameter provided at the tip of the large-diameter shaft portion 38, and a hemispherical head portion 40 formed at the tip of the small-diameter shaft portion 39. A part of the small-diameter shaft portion 39 is slidably inserted into the needle hole 36 with the head portion 40 at the front. The needle valve driving means 28 for driving the needle valve 26 consists of a piston cylinder unit and is supported by the support structure 30. When the needle valve driving means 28 is driven according to a command from the control device 4 (see Fig. 1), the needle valve 26 moves forward and backward, and the head portion 40 closes and opens the injection flow path 34.

[0017] Near the shut-off nozzle 5 configured as described above, the camera 6 is provided as described above. More specifically, the camera 6 is configured to photograph the vicinity of the outlet of the needle hole 36 of the nozzle portion 25 and the small-diameter shaft portion 39 of the needle valve 26.

[0018] The inner diameter of the needle hole 36 is slightly larger than the shaft diameter of the small-diameter shaft portion 39 of the needle valve 26. That is, there is a slight gap between the small-diameter shaft portion 39 of the needle valve 26 and the needle hole 36. Therefore, the needle valve 26 can be driven smoothly. Since the gap is slight, the amount of injection material in the injection flow path 34 leaking to the outside through this gap is almost zero. However, when the molding cycle is carried out for a long time, as shown in FIG. 3, the injection material leaks and adheres to the outer peripheral surface of the nozzle portion 25. That is, an injection material leak 44 is formed. Alternatively, when the gap expands due to wear of the needle hole 36 and the small-diameter shaft portion 39 of the needle valve 26, the injection material leak 44 is formed relatively early.

[0019] The camera 6 is adapted to detect such an injection material leak 44. More specifically, the control device 4 (FIG. 1) inspects the image captured by the camera 6. Then, by comparing the image when it was normal with the newly captured image, a portion where the luminance has changed is searched for. If there is a changing portion and its size is equal to or greater than a specified size, it is determined that an injection material leak 44 has occurred.

[0020] <Needle Valve Wear Diagnosis Method According to the Present Embodiment> When the molding cycle is repeated in the shut-off nozzle 5 according to the present embodiment, the gap between the needle hole 36 and the small-diameter shaft portion 39 of the needle valve 26 gradually expands due to wear. The needle valve wear diagnosis method according to the present embodiment is adapted to predict how this gap expands depending on the number of shots in the molding cycle. Therefore, when an injection material leak occurs in the shut-off nozzle 5, it is possible to determine whether the shut-off nozzle 5 can be restored by cleaning or whether it needs to be replaced. Hereinafter, the needle valve wear diagnosis method according to the present embodiment will be described.

[0021] <Wear Constant> The needle valve wear diagnosis method according to this embodiment is implemented in the control device 4. It is necessary to set a wear constant in advance in the control device 4. The wear constant is a constant indicating the relationship between the wear that expands the gap between the needle hole 36 and the small-diameter shaft portion 39 of the needle valve 26 and the number of shots. The wear constant is a fixed constant for the model of the shut-off nozzle 5 and can be determined by experiment as follows. First, for a new experimental shut-off nozzle 5, measure the inner diameter of the needle hole 36 and the shaft diameter of the small-diameter shaft portion 39 of the needle valve 26. Then obtain the difference between these, that is, the gap, as the initial gap. The initial gap varies slightly from product to product due to manufacturing variations even for shut-off nozzles 5 of the same model. For example, an initial gap of 0.005 mm is obtained.

[0022] Next, attach this experimental shut-off nozzle 5 to the injection device 3 (see FIG. 2), repeat the shots, and move the needle valve 26 forward and backward. Repeat a predetermined number of times, for example, 10,000 shots. This is taken as the measured number of shots. Remove the shut-off nozzle 5 from the injection device 3, measure the inner diameter of the needle hole 36 and the shaft diameter of the small-diameter shaft portion 39 of the needle valve 26 again, and obtain the difference between these as the measured gap. FIG. 4 shows the initial gap, the measured gap, and the measured number of shots, and shows how the gap 51 increases with the increase in the number of shots. The gap 51 increases monotonically but does not necessarily increase at a constant rate. However, assume that it increases at a constant rate and obtain the slope, which is taken as the friction constant. It can be obtained by the following formula. Friction constant = (Measured gap - Initial gap) / Measured number of shots Set the obtained friction constant in the control device 4 (see FIG. 1).

[0023] <Allowable gap> The control device 4 also needs to set the allowable clearance. The allowable clearance is the clearance that can be tolerated in the clearance between the needle hole 36 (see Fig. 2) and the small-diameter shaft portion 39 of the needle valve 26. If the clearance becomes greater than or equal to the allowable clearance, it is determined that wear has progressed and the shut-off nozzle 5 will be replaced. For example, 0.03 mm can be selected as the allowable clearance. Set the allowable clearance in the control device 4.

[0024] <Preparation process> When attaching the new shut-off nozzle 5 to the injection device 3 (see Fig. 2), first perform the preparation process. First, as shown as step S01 in Fig. 5, reset the counter of the number of shots stored in the control device 4 to zero. The counter of the number of shots is the cumulative number of shots for the shut-off nozzle 5 and increases each time a shot is made. Next, measure the inner diameter of the needle hole 36 and the shaft diameter of the small-diameter shaft portion 39 of the needle valve 26 for the shut-off nozzle 5, and take the difference to obtain the initial clearance. As described above, the initial clearance is a unique value that varies for each product of the shut-off nozzle 5. Set the initial clearance related to the shut-off nozzle 5 in the control device 4 (step S02).

[0025] After resetting the counter and setting the initial clearance, the control device 4 calculates the maximum expected number of operable shots for the shut-off nozzle 5. The maximum expected number of operable shots is the expected maximum number of shots that can be operated by the shut-off nozzle 5. More specifically, as shown in Fig. 6, when shots are repeated using the shut-off nozzle 5 with a predetermined initial clearance, the clearance between the inner diameter of the needle hole 36 and the small-diameter shaft portion 39 of the needle valve 26 is expected to increase as shown in the graph 54. The number of shots when the increasing clearance is expected to reach the allowable clearance is the maximum expected number of operable shots. Based on this number of shots, consideration will be given to replacing the shut-off nozzle 5.

[0026] The control device 4 calculates the maximum expected number of operable shots by the following formula. Maximum expected number of shots for operation = (Allowable clearance - Initial clearance) / Wear constant The calculated maximum expected number of shots for operation is stored in the control device 4 (step S04). At this time, the control device 4 may display the maximum expected number of shots for operation on an attached display device. The preparation process is completed.

[0027] <Processing in the molding cycle> The molding cycle is executed using the shut-off nozzle 5. When executing the molding cycle, as shown in FIG. 7, the control device 4 (see FIG. 1) first updates the shot number counter (step S11). That is, 1 is added to the counter. When the molding cycle is completed, the shut-off nozzle 5 is photographed by the camera 6 (see FIG. 2), and the control device 4 processes the image file to check whether injection material leakage 44 has occurred (step S12). If there is no leakage, the next molding cycle is executed and the process returns to step S11. On the other hand, if injection material leakage 44 has occurred, the process proceeds to step S13.

[0028] The control device 4 compares the current shot number counter with the specified minimum number of shot times (step S14). The specified minimum number of shot times is the number of shot times for determining the initial defect of the shut-off nozzle 5, and for example, 30 times or the like is set. If the shot number counter is less than the specified minimum number of shot times, it is determined that there is an initial defect. In this case, the control device 4 transfers to step S14 and stops the injection molding machine 1 (see FIG. 1). Then, a message prompting the replacement of the shut-off nozzle 5 is output to the monitor attached to the control device 4. On the other hand, if the shot number counter is equal to or greater than the specified minimum number of shot times, the process proceeds to the next step S15.

[0029] The control device 4 compares the counter of the current number of shots with the maximum expected number of operable shots calculated and set in the preparation process (step S15). If the counter of the current number of shots is equal to or greater than the maximum expected number of operable shots, the process proceeds to step S14. That is, the control device 4 determines that the shut-off nozzle 5 has reached the end of its life and stops the injection molding machine 1 (see FIG. 1). Next, a message prompting the replacement of the shut-off nozzle 5 is output to the monitor attached to the control device 4. On the other hand, if the counter of the current number of shots is less than the maximum expected number of operable shots, step S16 is executed. That is, the injection molding machine 1 (see FIG. 1) is stopped, and a message prompting the cleaning of the shut-off nozzle 5 is output to the monitor attached to the control device 4. The operator cleans the shut-off nozzle 5. After the cleaning is completed, the operation is restarted as shown in step S17. The molding cycle is repeated.

[0030] Incidentally, the maximum expected number of operable shots is the number of shots at which the gap between the needle hole 36 (see FIG. 2) and the small-diameter shaft portion 39 of the needle valve 26 is expected to reach the allowable gap as described above. Then, even if the actual number of shots reaches this maximum expected number of operable shots, the gap may not reach the allowable gap. Or even if it reaches, there may be cases where the injection material leakage 44 (see FIG. 2) does not occur. Or conversely, there may be cases where the gap exceeds the allowable gap and the injection material leakage 44 occurs before reaching the maximum expected number of operable shots. In FIG. 6, the range of the number of shots at which the shut-off nozzle 5 should be replaced is indicated by reference numeral 56, but there is a certain width before and after including the maximum expected number of operable shots. The needle valve wear diagnosis method according to the present embodiment described above prompts the replacement of the shut-off nozzle 5, but whether to actually replace it can also be appropriately determined by the operator after checking the wear state.

[0031] <Modification Example of the Present Embodiment> This embodiment can be variously modified. For example, in the needle valve wear diagnosis method according to this embodiment, it has been described that in each molding cycle, the camera 6 takes a photograph and the control device 4 detects the injection material leakage 44. However, it may be configured to take a photograph every time a predetermined number of molding cycles are completed. Furthermore, there is also a method that does not use the camera 6. When the camera 6 is not used, the control device 4 can monitor the shot number counter and output a message that replacement is required when the maximum possible operating shot number is reached. Alternatively, a message may be output when the shot number reaches a number that is a specified number less than the maximum possible operating shot number.

[0032] In this embodiment, it has been described that the friction constant is obtained by experiments. However, the friction coefficient may be obtained from the past operation results. For example, assume that as a result of actually operating the shut-off nozzle 5, there was an example where it was determined that the life had been reached due to wear and it was replaced when a predetermined shot number was reached. At that time, the wear constant can be obtained from the shot number at that time, the gap at the time of replacement between the needle hole 36 (see FIG. 2) and the small-diameter shaft portion 39 of the needle valve 26, and the initial gap. Regarding the gap at the time of replacement, it may be measured actually, or 0.03 mm which is generally considered to cause leakage may be adopted. Also, regarding the initial gap, if it has not been measured in advance in the shut-off nozzle 5, an average value for the model of the shut-off nozzle 5 can be adopted.

[0033] As described above, the invention made by the present inventor has been specifically described based on the embodiment. However, it goes without saying that the present invention is not limited to the embodiment already described, and various modifications are possible without departing from the gist thereof. The plurality of examples described above can also be implemented in appropriate combinations.

Explanation of Reference Numerals

[0034] 1 Injection molding machine 2 Mold clamping device 3 Injection device 4 Control device 5 Shut-off nozzle 6 Camera 7 Fixed plate 8 Movable plate 9 Clamping housing 11 Tie bar 13 Toggle mechanism 15 Fixed-side mold 16 Movable-side mold 19 Heating cylinder 20 Screw 22 Screw drive device 23 Hopper 25 Nozzle part 26 Needle valve 28 Needle valve drive means 30 Support structure 32 Adapter 34 Injection flow path 36 Needle hole 38 Large-diameter shaft part 39 Small-diameter shaft part 40 Head B Bed

Claims

1. A nozzle part in which an injection flow path for flowing an injection material is formed in the axial direction, a needle valve, a camera, and is provided with, In the shut-off nozzle in which the needle valve is inserted through a gap with respect to a needle hole that is obliquely opened with respect to the axial direction reaching the injection flow path from the outer peripheral surface of the nozzle part and advances and retreats to open and close the injection flow path, an initial gap which is the gap before the start of use peculiar to the shut-off nozzle, a wear constant showing the relationship between the wear of the needle valve and the needle hole that expands the gap, the number of shots, and the number of shots, a permissible gap which is the allowable amount of the gap, so as to predict the maximum possible number of shots that can be operated from, Detecting injection material leakage from the needle hole from an image of the shut-off nozzle obtained by the camera, and when the injection material leakage is detected, if the number of shots in the shut-off nozzle reaches before the maximum possible number of shots that can be operated, output a message prompting cleaning of the shut-off nozzle. A method for diagnosing needle valve wear of a shut-off nozzle.

2. The wear constant is obtained by obtaining the initial gap for other shut-off nozzles of the same model, repeating the shots a measured number of shots which is a specified number of times, then obtaining a measured gap which is the measured value of the gap, and obtaining from the initial gap, the measured gap, and the measured number of shots. The method for diagnosing needle valve wear of a shut-off nozzle according to Claim 1.

3. The maximum possible number of shots that can be operated is obtained by dividing the difference between the permissible gap and the initial gap by the wear constant. The method for diagnosing needle valve wear of a shut-off nozzle according to Claim 1 or 2.

4. When detecting the injection material leakage from the image, if the number of shots in the shut-off nozzle is less than or equal to a specified minimum number of shots, output a message indicating that the shut-off nozzle is initially defective. The method for diagnosing needle valve wear of a shut-off nozzle according to any one of Claims 1 to 3.

5. The detection of the injection material leakage from the image is determined by a change in the brightness of the image. The method for diagnosing needle valve wear of a shut-off nozzle according to any one of Claims 1 to 3.

6. A control device, a heating cylinder, a screw placed in the heating cylinder, a shut-off nozzle provided in the heating cylinder, A camera provided near the shut-off nozzle, and the shut-off nozzle includes a nozzle portion in which an injection flow path for flowing an injection material is formed in the axial direction, and a needle valve, and the needle valve is inserted through a gap with respect to a needle hole that is obliquely opened with respect to the axial direction reaching the injection flow path from the outer peripheral surface of the nozzle portion, and advances and retreats to open and close the injection flow path, the control device includes an initial gap that is the gap before use specific to the shut-off nozzle, a wear constant indicating the relationship between the wear of the needle valve and the needle hole that expands the gap, the number of shots, and a permissible gap that is the allowable amount of the gap, and predicts a maximum possible number of shots that can be operated, the control device is configured to detect leakage of the injection material from the needle hole from an image of the shut-off nozzle obtained by the camera, and when the control device detects the leakage of the injection material, if the number of shots at the shut-off nozzle reaches the maximum possible number of shots before the number of shots reaches the maximum possible number of shots, an injection device that outputs a message prompting cleaning of the shut-off nozzle.

7. The wear constant is obtained from the initial gap for other shut-off nozzles of the same model, after repeating the shots a measured number of shots which is a specified number of times, obtaining a measured gap which is the measured value of the gap, and from the initial gap, the measured gap, and the measured number of shots. The injection device according to claim 6.

8. The maximum possible number of shots that can be operated is obtained by dividing the difference between the permissible gap and the initial gap by the wear constant. The injection device according to claim 6 or 7.

9. When the control device detects the leakage of the injection material, if the number of shots at the shut-off nozzle is less than or equal to a specified minimum number of shots, a message indicating that the shut-off nozzle is initially defective is output. The injection device according to any one of claims 6 to 8.

10. The detection of the leakage of the injection material from the image is determined by a change in the brightness of the image. The injection device according to any one of claims 6 to 8.

11. A control device, a mold clamping device for clamping a mold, an injection molding machine including an injection device for injecting an injection material, wherein the injection device includes a heating cylinder, A screw placed in the heating cylinder, A shut-off nozzle provided in the heating cylinder, A camera provided near the shut-off nozzle, and The shut-off nozzle includes a nozzle portion in which an injection flow path for flowing an injection material is formed in the axial direction, A needle valve, The needle valve is inserted through a gap with respect to a needle hole that is obliquely opened with respect to the axial direction reaching the injection flow path from the outer peripheral surface of the nozzle portion, and advances and retreats to open and close the injection flow path, The control device includes an initial gap that is the gap before the start of use specific to the shut-off nozzle, A wear constant indicating the relationship between the wear of the needle valve and the needle hole for expanding the gap, the number of shots, and A permissible gap that is the allowable amount of the gap, and predicts an expected maximum number of operable shots that is the expected number of operable shots, The control device is configured to detect leakage of the injection material from the needle hole from an image of the shut-off nozzle obtained by the camera. When the control device detects the leakage of the injection material, if the number of shots at the shut-off nozzle reaches the expected maximum number of operable shots before the number of shots reaches the expected maximum number of operable shots, a message prompting cleaning of the shut-off nozzle is output. An injection molding machine.

12. The wear constant is obtained by obtaining the initial gap for other shut-off nozzles of the same model, repeating the shots a measured number of shots that is a specified number of times, then obtaining a measured gap that is the measured value of the gap, and obtaining from the initial gap, the measured gap, and the measured number of shots. The injection molding machine according to claim 11.

13. The expected maximum number of operable shots is obtained by dividing the difference between the permissible gap and the initial gap by the wear constant. The injection molding machine according to claim 11 or 12.

14. When the control device detects the leakage of the injection material, if the number of shots at the shut-off nozzle is less than or equal to a specified minimum number of shots, a message indicating that the shut-off nozzle has an initial defect is output. The injection molding machine according to any one of claims 11 to 13.

15. The detection of the leakage of the injection material from the image is determined based on a change in the luminance of the image. The injection molding machine according to any one of claims 11 to 13.

Images