Injection device

Abstract

An injection device 10 comprises: a feed cylinder 18 having a built-in feed screw 19; a hopper 23 for supplying a resin material 22 to the feed cylinder 18; a connection pipe 17 for connecting a heating cylinder 12 and the feed cylinder 18, and guiding the resin material 22 to a drop port 12a of the heating cylinder 12; an imaging mechanism 24 for imaging the drop port 12a from the outside; and a computation / control unit 25 for performing control to increase / decrease the number of rotations of the feed screw 19 on the basis of image information obtained by the imaging mechanism 24, wherein the imaging mechanism 24 is disposed above the drop port 12a and is disposed in the vicinity of the drop port 12a, and the computation / control unit 25 acquires a measurement time determined on the basis of the retreat of the injection screw when the supply of the resin material is excessive, and further performs control to stop the rotation of the feed screw when the measurement time is greater than or equal to a measurement threshold value.

Description

Injection device

[0001] The present invention relates to an injection device for injecting a resin material into a mold.

[0002] Many metal products and wood products have been replaced by plastic products. Many plastic products are manufactured by injection molding devices. An injection molding device consists of a mold, a mold clamping device for clamping this mold, and an injection device for injecting a molten resin material into the mold.

[0003] The injection device mainly includes a heating cylinder having a nozzle at its tip, a screw rotatably and axially movably housed in this heating cylinder, and a hopper for supplying a resin material to the heating cylinder. The resin material dropped from the hopper into the heating cylinder is stirred by the screw in the heating cylinder and plasticized by shear heat while moving toward the nozzle. Molten resin accumulates at the front part (nozzle side) of the heating cylinder. Receiving the reaction force of this molten resin, the screw gradually retreats. When the retreat distance reaches a predetermined value, the screw is advanced to inject the molten resin into the mold.

[0004] In this process, it is important that the resin material is supplied to the heating cylinder without excess or deficiency. Therefore, various techniques for supplying an appropriate amount of resin material have been proposed (for example, refer to Patent Document 1 (FIG. 1, FIG. 3)).

[0005] Patent Document 1 will be described based on the following figures. FIG. 11(a) is a cross-sectional view of a conventional injection device, and FIG. 11(b) is a cross-sectional view taken along line b-b of FIG. 11(a). As shown in FIG. 11(a), the injection device 100 mainly includes a heating cylinder 102 having a nozzle 101 at its tip, an injection screw 103 rotatably and axially movably housed in this heating cylinder 102, and a material feeder 105 for supplying a resin material to the heating cylinder 102.

[0006] The material feeder 105 consists of a vertical cylinder 106 extending upward from the heating cylinder 102 at a position sufficiently far from the nozzle 101, a horizontal cylinder 107 extending horizontally from the upper part of this vertical cylinder 106, a feed screw 108 rotatably housed in this horizontal cylinder 107, and a hopper 109 for supplying a resin material to the horizontal cylinder 107.

[0007] The resin material falls from the hopper 109 into the horizontal cylinder 107. The resin material is pushed forward inside the horizontal cylinder 107 by the feed screw 108. Next, it falls into the heating cylinder 102 through the vertical cylinder 106. The fallen resin material is plasticized while rotating by the heating cylinder 102 and the injection screw 103, and moves forward towards the front of the heating cylinder 102 (towards the nozzle 101).

[0008] The heating cylinder 102 is provided with a vent hole 111 located closer to the nozzle 101 than the axial center, for discharging gases and water vapor generated from the resin material. An imaging mechanism 112 is placed above this vent hole 111. The imaging mechanism 112 photographs the inside of the heating cylinder 102 through the vent hole 111. The obtained images are processed to calculate the filling status of the resin material.

[0009] When the filling is insufficient, the controller 113 increases the rotational speed of the feed screw 108 to increase the amount of resin material supplied to the heating cylinder 102. Conversely, when the filling is excessive, the controller 113 decreases the rotational speed of the feed screw 108 to reduce the amount of resin material supplied to the heating cylinder 102.

[0010] As a result, the amount of resin material can be optimized. However, in the heating cylinder 102, the area near the vertical cylinder 106, that is, near the drop-off port, is at a low temperature, while the area near the vent hole 111, where the plasticization of the resin material has progressed sufficiently, is at a high temperature. High-temperature gas and water vapor are then discharged upward from the vent hole 111. If the imaging mechanism 112 is placed directly above the vent hole 111, then heat-resistant measures will need to be taken for the imaging mechanism 112.

[0011] Therefore, Patent Document 1 recommends a mounting structure in which a mirror 114 is placed above the vent hole 111, the upward-facing light rays are changed to a horizontal direction, and the imaging mechanism 112 is not placed directly above the vent hole 111, as shown in Figure 11(b).

[0012] However, the image is distorted because the mirror 114 fogs up with water vapor. The image is also distorted by rising heat. Accurate information cannot be obtained from a distorted image. If the image is corrected as a countermeasure, the cost of image processing will increase. In addition, the imaging mechanism 112, which includes the mirror 114, becomes structurally complex, increasing the cost of the equipment.

[0013] The inventors focused on the fact that the area near the drop-off point is sufficiently cold and considered moving the imaging mechanism 112 to the vicinity of the drop-off point, that is, to the vicinity of the vertical cylinder 106. With this measure, the area around the imaging mechanism 112 is sufficiently cold, eliminating the need for special heat-resistant measures for the imaging mechanism 112, and is expected to have the advantage of preventing image distortion due to water vapor or hot air.

[0014] Therefore, the inventors moved the imaging mechanism 112 to the vicinity of the drop opening and conducted repeated injection experiments. Favorable results were obtained in many experiments. However, molding defects occurred, albeit infrequently. Since countermeasures could not be taken in this state, a technology was needed that would allow the imaging mechanism 112 to be moved to the vicinity of the drop opening while preventing molding defects, that is, maintaining good molding.

[0015] Special Publication No. 6-39119

[0016] The object of this invention is to provide an injection molding device that maintains good molding even when the imaging mechanism is located near the drop-off port.

[0017] The inventors discovered that molding defects were caused by clogging of the resin material inside the heating cylinder 102. Clogging was more likely to occur inside the heating cylinder 102 near the drop-off port. This is thought to be because the resin material was still at a low temperature, making it less fluid and more prone to clogging. Therefore, countermeasures were taken to prevent clogging. As a result, good molding performance could be maintained. Based on the above findings, the completed invention is as follows.

[0018] The invention according to claim 1 is an injection device comprising: a heating cylinder having a nozzle at its tip; an injection screw rotatably and axially movable housed in the heating cylinder; a feed cylinder containing a feed screw; a hopper for supplying resin material to the feed cylinder; a connecting pipe connecting a portion of the heating cylinder far from the nozzle and a portion of the feed cylinder far from the hopper, guiding the resin material to a discharge port of the heating cylinder; an imaging mechanism for photographing the discharge port from the outside; and a calculation / control unit that controls the feed screw to increase its rotation speed when the supply of resin material is insufficient and to decrease its rotation speed when the supply of resin material is excessive, wherein the imaging mechanism is positioned above and near the discharge port, and the calculation / control unit further implements control to obtain a metering time determined based on the retraction of the injection screw when the supply of resin material is excessive, and to stop the rotation of the feed screw when this metering time is greater than or equal to a metering threshold.

[0019] The invention according to claim 2 is preferably the injection apparatus according to claim 1, wherein the connecting tube includes a straight tube portion extending linearly outward from the heating cylinder, and the imaging mechanism photographs the drop opening through the straight tube portion.

[0020] The invention according to claim 3 is preferably the injection apparatus according to claim 1, wherein the heating cylinder has an opening that leads to the outside near the drop-off port and in a place that does not interfere with the connecting tube, and the imaging mechanism photographs the drop-off port through the opening.

[0021] In the invention according to claim 1, the imaging mechanism is positioned near the drop-off point. The drop-off point is sufficiently cold. Therefore, the imaging mechanism can acquire distortion-free images, and there is no need to provide the imaging mechanism with any special cooling mechanism.

[0022] In addition, the present invention uses a calculation and control unit to control the supply of resin material based on images acquired by the imaging mechanism. Furthermore, if a problem such as clogging occurs in the heating cylinder, the supply of resin material is stopped to promptly resolve the problem and correct any defects during molding. Therefore, the present invention provides an injection molding device that maintains good molding even when the imaging mechanism is located near the vertical cylinder.

[0023] In the invention according to claim 2, the connecting pipe includes a straight pipe section that extends linearly outward from the heating cylinder, and the imaging mechanism photographs the drop-off port through the straight pipe section. In claim 2, the imaging mechanism can be positioned at a distance from the heating cylinder equal to the length of the straight pipe section. Although the area near the drop-off port is sufficiently cold, the imaging mechanism is positioned even further away from this area, thus improving the thermal environment of the imaging mechanism.

[0024] In the invention according to claim 3, the heating cylinder has an opening that leads to the outside near the drop-off port and in a location that does not interfere with the connecting pipe, and the imaging mechanism photographs the drop-off port through the opening. In claim 3, it is necessary to provide an opening in the heating cylinder separately from the connecting pipe, but the position of the opening can be set relatively freely near the drop-off port. As a result, the degree of freedom in the arrangement of the imaging mechanism is greatly increased.

[0025] This is an overall diagram of the injection device according to the present invention. (a) is an enlarged view of part 2a in Figure 1, (b) is a diagram showing a modified example, and (c) is a diagram of operation. This is a control flow diagram by the calculation / control unit according to the present invention. This is a diagram showing an example of Map A. (a) is a diagram illustrating the injection screw groove, and (b) is a diagram illustrating the area of ​​the resin material. (a) to (e) are diagrams illustrating the supply form of the resin material. This is a diagram showing an example of modification of the injection device. This is a diagram showing a further modification of the injection device. (a) is a diagram showing a further modification of the injection device, and (b) is a cross-sectional view taken along the line b-b in (a). This is a diagram showing a further modification of the injection device. (a) is a cross-sectional view of a conventional injection device, and (b) is a cross-sectional view taken along the line b-b in (a).

[0026] Embodiments of the present invention will be described below with reference to the attached drawings.

[0027] [Injection device] As shown in Figure 1, the injection device 10 includes a heating cylinder 12 equipped with a nozzle 11 at its tip, an injection screw 13 housed in the heating cylinder 12 so as to be rotatable and axially movable, a screw rotation motor 14 for rotating the injection screw 13, an injection cylinder 15 for advancing the injection screw 13, a metering sensor 16 for detecting the axial position of the injection cylinder 15, a feed cylinder 18 containing a feed screw 19, a feed rotation motor 21 for rotating the feed screw 19, and a feed cylinder 18 for supplying resin The system includes a hopper 23 for supplying material 22, a connecting pipe 17 that connects the part of the heating cylinder 12 furthest from the nozzle 11 and the part of the feed cylinder 18 furthest from the hopper 23, guiding the resin material 22 to the drop-off port 12a of the heating cylinder 12, an imaging mechanism 24 that photographs the drop-off port 12a from the outside, and a calculation / control unit 25 that controls the feed screw 19 to increase its rotation speed when the supply of resin material 22 is low and to decrease its rotation speed when the supply of resin material 22 is high, based on the image information obtained by the imaging mechanism 24.

[0028] [Feed Screw Posture] The feed screw 19 may be positioned horizontally, but in this embodiment, it is positioned with the hopper 23 side at a lower position and the front rising as it moves away from the hopper 23. This is preferable because gravity causes the resin material 22 to always accumulate in the feed cylinder 18, eliminating variations in the supply amount.

[0029] [Imaging mechanism] The imaging mechanism 24 is, for example, a CCD camera.

[0030] [Plasticization] The resin material 22 in the hopper 23 is extruded by the feed screw 19, falls through the connecting pipe 17 to the drop-off port 12a of the heating cylinder 12, and is pushed by the injection screw 13 toward the nozzle 11.

[0031] During this time, the resin material 22 inside the heating cylinder 12 is compressed between the heating cylinder 12 and the injection screw 13, sheared by the rotation of the injection screw 13, and heated by the heating cylinder 12, resulting in plasticization through a combined action.

[0032] The area near the drop-off port 12a is significantly cooler than the nozzle 11 side. The imaging mechanism 24 is positioned above this drop-off port 12a. There is no need to take any special thermal countermeasures for the imaging mechanism 24. In addition, the amount of water vapor and hot air rising inside the connecting pipe 17 is tolerable. Therefore, no image distortion caused by water vapor or hot air occurs, and a clear image can be easily obtained.

[0033] [Measuring] The plasticized resin material 22 accumulates on the nozzle 11 side of the injection screw 13. As the amount of this accumulation increases, the injection screw 13 retracts. The measured value of the resin material 22 is calculated using the formula: (internal cross-sectional area of ​​heating cylinder 12) × (retraction distance of injection screw 13) = measured value. The (retraction distance of injection screw 13) is detected by the measuring sensor 16.

[0034] [Injection] A measurement value is determined corresponding to the volume of the mold cavity. When the measurement value calculated based on the information from the measurement sensor 16 matches the determined measurement value, the injection cylinder 15 advances the injection screw 13. This advancement injects the molten resin material into the mold.

[0035] [Structure of the tip of the feed screw] Figure 2(a) is an enlarged view of part 2a in Figure 1. As shown in Figure 2(a), a bearing part 27 is provided in the connecting pipe 17. The tip of the feed screw 19 and the part that protrudes from the feed cylinder 18 is a small-diameter shaft part 28, which is sufficiently smaller in diameter than the central axis 19a of the feed screw 19. The tip of this small-diameter shaft part 28 is inserted into the bearing part 27. Because it is supported by the bearing part 27, good rotation of the feed screw 19 is maintained. In addition, because the small-diameter shaft part 28 is small in diameter, the influence on imaging of the imaging mechanism 24 is mitigated.

[0036] Figure 2(b) shows a modified example. As shown in Figure 2(b), the small-diameter shaft portion 28 may be omitted from the feed screw 19. Since the small-diameter shaft portion 28 is omitted, the field of view of the imaging mechanism 24 is not obstructed. As a result, a higher quality image can be obtained. Another advantage is that the structure of the connecting tube 17 becomes simpler because the bearing portion 27 is not required. Therefore, it is arbitrary to adopt either the structure in Figure 2(a) or Figure 2(b).

[0037] Figure 2(c) is an operation diagram of the structure shown in Figure 2(b). Since the feed cylinder 18 slopes upward at the front, the extruded resin material 22 mainly spills from the lower end 29 at the tip of the feed cylinder 18 into the connecting pipe 17. Then, the resin material 22 flows down along the wall 17b farther from the nozzle (reference numeral 11 in Figure 1) of the connecting pipe 17. Therefore, a better image can be obtained by the imaging mechanism 24.

[0038] Next, the control to be implemented by the arithmetic and control unit 25 will be described based on Figure 3. In Figure 3, at ST (indicating the step number; the same applies hereinafter) 01, the rotational speeds rl, rm, rh, and rhh related to the feed screw are set. However, 0 < rl < rm < rx < rh < rhh.

[0039] Prepare a map A as shown in Figure 4. The map A lists the resin material names to be used, and for each resin material, the transportation efficiency j, the plasticization efficiency ε, the solid density ρ, and the melt density ρ'.

[0040] At ST02 in Figure 3, the resin material name is set. At ST03, based on map A (see Figure 4), the transportation efficiency j, the plasticization efficiency ε, the solid density ρ, and the melt density ρ' corresponding to the set resin material are set.

[0041] [Starvation rate] When there are requirements such as increasing the purity of resin products, it is necessary to remove gas or the like from the resin material during plasticization before injection. At this time, if the resin material is porous, the escape of gas or the like is improved. The porosity of the resin material is expressed by the starvation rate.

[0042] That is, a large starvation rate indicates porosity. Conversely, a small starvation rate indicates density. Therefore, the starvation rate is determined based on the type of resin material, product quality, required specifications, etc. Note that the starvation rate is not set to 100%.

[0043] At ST04, the starvation rate x is set. At ST05, the rotational command value rx related to the feed screw is calculated by the following formula (1).

[0044]

[0045] In formula (1), rmax, Qmax, Rmax, and Gmax are fixed values determined for each piece of equipment. R is the rotational speed of the injection screw determined during operation. ε, j, and ρ are preset values determined by map A. ρGGPS is the solid density of the resin material of general-purpose polystyrene. x is the value set in ST04. Therefore, according to formula (1), the rotational command value rx (rpm) of the feed screw when the starvation rate is x can be calculated. rpm is the number of rotations per minute.

[0046] In FIG. 3, a metering operation is performed in ST06, a still image at the dropping port is acquired (ST07), and the coating rate y of the injection screw groove part is calculated based on the acquired still image (ST08). In this calculation, as shown in FIG. 5(a), the screw groove part 31 marked with oblique lines ( / / / ) is the calculation target, and the flight 13a is excluded from the calculation target.

[0047] In the case of the model shown in FIG. 5(b), the arithmetic and control unit (in FIG. 1, reference numeral 25) calculates the area of the resin material 22 in the screw groove part 31 (in this example, the areas of M1 to M6). At the same time, the area of the visible part (in this example, the areas of S1 to S3) in the screw groove part 31 is calculated.

[0048] Then, the coating rate y (%) of the injection screw groove part is calculated by the formula 100×Σ(M1 to M6)÷{Σ(S1 to S3)+Σ(M1 to M6)}. Hereinafter, the coating rate y of the injection screw groove part may be abbreviated as the coating rate y.

[0049] FIGS. 6(a) to (e) show the forms of the supply state of the resin material. In FIG. 6(a), only the resin material 22 is visible, so the supply is excessive. The coating rate y is, for example, 110% or more. In FIG. 6(b), the resin material 22 and the flight 13a are visible. The resin material 22 is still relatively large. The coating rate y is, for example, 90 to 109%.

[0050] Figure 6(c) shows the resin material 22 and the screw groove portion 31. The resin material 22 is supplied appropriately. The coverage rate y is, for example, 50 to 89%. Figure 6(d) shows that there are many screw groove portions 31 and few resin materials 22. In other words, there is less resin material 22. The coverage rate y is, for example, 10 to 49%.

[0051] Figure 6(e) shows an even smaller amount of resin material 22. In other words, there is a shortage of resin material 22. The coverage rate y will be, for example, 9% or less. That is, the magnitude of the coverage rate y allows us to determine whether the supply is "appropriate" or not, and if not, whether it is "excessive," "too much," "too little," or "insufficient."

[0052] Therefore, in Figure 3, ST09 checks whether the coverage rate y is "appropriately supplied," and if YES, the rotation command value rx of the feed screw is maintained without change (ST10).

[0053] If the answer to ST09 is NO, then in ST11, it is necessary to check whether y is "excessive supply," and if it is YES, the supply of resin material by the feed screw must be suppressed. However, if the answer to ST11 is YES, several patterns are possible.

[0054] For example, in Figure 1, the resin material 22 may clog at the location indicated by arrow A. In this case, the resin material 22 may not be supplied to the nozzle 11, or the amount supplied may be reduced. This will cause the retraction of the injection screw 13 to be delayed, and the metering time will be longer than the expected time (expected metering time). When there is "excessive supply," it is necessary to suspect a clog of the resin material, and therefore it is effective to check the metering time at that time based on the expected metering time.

[0055] The expected metering time tx is calculated using the following formula (2).

[0056]

[0057] In equation (2), D, S, Qmax, and Rmax are fixed values ​​determined for each piece of equipment. R is the rotational speed of the injection screw determined during operation. ρ' and ε are default values ​​determined by map A. x is the value set in ST04. Therefore, equation (2) allows us to calculate the expected metering time tx (seconds) when the starvation rate is x.

[0058] In Figure 3, when the coverage rate y at ST11 is in excess supply, the starvation rate x becomes 0. Therefore, we set x to 0 in equation (2). As a result, equation (3) below is derived, and the expected metering time t0 is determined by this equation.

[0059]

[0060] In ST13, it is checked whether the measurement time t obtained based on the measurement information from the measurement sensor (Figure 1, reference numeral 16) is greater than or equal to the expected measurement time t0.

[0061] [Measurement threshold] The predicted measurement time t0 described above is defined as the measurement threshold.

[0062] If the answer to ST13 is YES, a blockage is suspected, so replace rx with "0" and stop the rotation of the feed screw (ST14). By stopping the supply of resin material, it is expected that the blockage around the injection screw will gradually be cleared.

[0063] If the result in ST13 is NO, a blockage is not suspected, so it is recognized as simply an oversupply, and in ST15, rx is replaced with "rl". Since rl is sufficiently small, it is expected that the oversupply will be resolved.

[0064] If the answer in ST11 is NO, then in ST16, check whether y is "too much". If the answer is YES, then in ST17, replace rx with "rm". Since rm is small, it is expected that the excess will be resolved.

[0065] If the answer in ST16 is NO, then in ST18, check whether y is "slightly low". If the answer is YES, then in ST19, replace rx with "rh". Since rh is large, it is expected that the supply of resin material will increase and the "slightly low" issue will be resolved.

[0066] If the result in ST18 is NO, there is a supply shortage, and in ST20, replace rx with "rhh". Since rhh is even larger, it is expected that the supply of resin material will increase further, and the supply shortage will be resolved.

[0067] After ST10, ST14, ST15, ST17, ST19, or ST20, the status is recorded and graphed in ST21. Then, in ST22, it is checked whether there is a termination command. If YES, this control flow is terminated; if NO, it returns to ST06 and the next metering operation is performed.

[0068] By repeating the control flow, it is expected that "excessive supply" will shift to "slightly above average," and then from "slightly above average" to "appropriate supply." Furthermore, by repeating the control flow, it is expected that "shortage supply" will shift to "slightly below average," and then from "slightly below average" to "appropriate supply."

[0069] Furthermore, in Figures 6(a) to (e), if the appearance rate of Figure 6(e) is small, in Figure 3, ST18 and ST20 may be omitted, and the NO branch of ST16 may be directly connected to ST19. Therefore, the classifications and y values ​​explained in Figures 6(a) to (e) are merely preferred examples and can be modified as appropriate.

[0070] Next, examples of modifications to the injection apparatus 10 according to the present invention will be described in order with reference to Figures 7 to 10.

[0071] [Example of modification of injection device (1)] As shown in Figure 7, the injection device 10 according to modification example (1) differs from the injection device 10 shown in Figure 1 in the structure of the connecting pipe 17, but otherwise remains unchanged. For parts that remain unchanged, the reference numerals from Figure 1 are reused, and detailed explanations are omitted. The same applies to Figures 8 to 10 described later.

[0072] In other words, the connecting pipe 17 consists of a straight pipe section 17a that extends linearly outward from the heating cylinder 12, a slanted pipe section 17b that extends diagonally upward from the height of the straight pipe section 17a and partway up, and a second straight pipe section 17c that extends upward from the slanted pipe section 17b and connects to the feed cylinder 18. The imaging mechanism 24 is positioned directly above the straight pipe section 17a and photographs the drop-off port 12a through the straight pipe section 17a.

[0073] According to this modification example (1), the straight pipe section 17a extends along the vertical line. Furthermore, the presence of the angled pipe section 17b and the second straight pipe section 17c leaves the area above the straight pipe section 17a open. Therefore, a large imaging mechanism 24 can be easily positioned. This also has the advantage of allowing easy inspection of the imaging mechanism 24 from above or the side.

[0074] The present invention is suitable for horizontal injection molding machines where the injection axis is horizontal, as shown in Figures 1 and 7, but it can also be applied to vertical injection molding machines where the injection axis is vertical. A specific example will be explained based on Figure 8.

[0075] [Example of modification of injection device (2)] As shown in Figure 8, the injection device 10 according to modification example (2) is a vertical injection device in which the injection axis is vertical. That is, the part of the heating cylinder 12 furthest from the nozzle 11 and the part of the feed cylinder 18 furthest from the hopper 23 are connected by a connecting pipe 17.

[0076] The connecting pipe 17 consists of a straight pipe section 17a extending diagonally upward from the drop-off opening 12a, and a second straight pipe section 17c extending upward from the middle of the straight pipe section 17a and connecting to the feed cylinder 18. The imaging mechanism 24 is positioned above the drop-off opening 12a and next to the straight pipe section 17a, and photographs the drop-off opening 12a through the straight pipe section 17a.

[0077] In the injection device 10 shown in Figures 1, 7, and 8, the connecting tube 17 includes a straight tube section 17a that extends linearly outward from the heating cylinder 12, and the imaging mechanism 24 photographs the drop-off port 12a through the straight tube section 17a. The imaging mechanism 24 can be positioned at a distance from the heating cylinder 12 equal to the length of the straight tube section 17a. The area near the drop-off port 12a is sufficiently cold, but by positioning the imaging mechanism 24 at an even greater distance from the drop-off port 12a, the thermal environment of the imaging mechanism 24 becomes even better.

[0078] Furthermore, if the imaging mechanism 24 is positioned sufficiently far from the drop-off opening 12a, there is concern about the influence of external light. In this regard, the straight tube section 17a acts as the tube of the telescope, that is, it blocks external light, thus suppressing the influence of external light.

[0079] [Example of modification of the injection device (3)] The injection device 10 shown in Figure 9(a) differs from that in Figure 1 in that the imaging mechanism (Figure 1, reference numeral 24) is located at the back of the connecting pipe 17. Figure 9(b) is a cross-sectional view taken along the line b-b in Figure 9(a).

[0080] As shown in Figure 9(b), the heating cylinder 12 has an opening 33 that leads to the outside near the drop-off port 12a and in a location that does not interfere with the connecting pipe 17, and the imaging mechanism 24 photographs the drop-off port 12a through the opening 33. In this modified example (3), although the structure of the heating cylinder 12 becomes more complex because the opening 33 and the connecting pipe 17 are provided separately, it has the advantage that the imaging mechanism 24 can be brought closer to the drop-off port 12a.

[0081] [Example of modification of the injection device (4)] As shown in Figure 10, the heating cylinder 12 has an opening 33 that leads outwards near the drop port 12a and in a place that does not interfere with the connecting pipe 17, and the imaging mechanism 24 photographs the drop port 12a through the opening 33. In other words, in this modification example (4), the imaging mechanism 24 is positioned above the heating cylinder 12, below the feed cylinder 18, and behind the connecting pipe 17.

[0082] In this modified example (4), although the structure of the heating cylinder 12 becomes more complex because the opening 33 and the connecting pipe 17 are provided separately, it has the advantage of allowing the imaging mechanism 24 to be brought closer to the drop-off port 12a. In addition, it has the advantage that the imaging mechanism 24 is protected by the feed cylinder 18 and the connecting pipe 17.

[0083] In the ejection device 10 shown in Figures 9(a), (b) and 10, the heating cylinder 12 has an opening 33 that leads to the outside, located near the drop-off port 12a and in a place that does not interfere with the connecting pipe 17, and the imaging mechanism 24 photographs the drop-off port 12a through the opening 33. Although it is necessary to provide the opening 33 in the heating cylinder 12 separately from the connecting pipe 17, which has the disadvantage of making the structure of the heating cylinder 12 more complex, it has the advantage that the position of the opening 33 can be set relatively freely near the drop-off port 12a, greatly increasing the degree of freedom in the placement of the imaging mechanism 24.

[0084] Based on the above description, the present invention can be summarized as follows. As shown in Figures 1, 7 to 10, the injection device 10 comprises a heating cylinder 12 equipped with a nozzle 11 at its tip, an injection screw 13 housed in the heating cylinder 12 so as to be rotatable and axially movable, a feed cylinder 18 containing a feed screw 19, a hopper 23 for supplying resin material 22 to the feed cylinder 18, a connecting pipe 17 connecting the part of the heating cylinder 12 far from the nozzle 11 and the part of the feed cylinder 18 far from the hopper 23, and guiding the resin material 22 to the drop port 12a of the heating cylinder 12, an imaging mechanism 24 for photographing the drop port 12a from the outside, and a calculation / control unit 25 that controls the feed screw 19 to increase its rotation speed when the supply of resin material 22 is low and to decrease its rotation speed when the supply of resin material 22 is high, based on the image information obtained by the imaging mechanism 24. The imaging mechanism 24 is positioned above the drop opening 12a and in the vicinity of the drop opening 12a.

[0085] Then, as shown in Figure 3, the calculation and control unit 25, when the supply of resin material 22 is excessive, acquires a metering time t determined based on the retraction of the injection screw 13, and further performs control (ST14) to stop the rotation of the feed screw when this metering time t is equal to the metering threshold t0.

[0086] If the supply of resin material 22 is excessive, simply reducing the rotation speed of the feed screw 19 will cause some problems when the resin material 22 clogs the heating cylinder 12. In other words, if the supply of resin material continues despite the clog, the clog will never be cleared.

[0087] In this regard, the present invention detects clogging based on the metering time and stops the supply of resin material. This stopping the supply resolves the clogging. Therefore, the present invention maintains better injection molding performance.

[0088] Furthermore, in Figure 2(a), the central axis of the imaging mechanism 24 may be offset towards the front or back of the drawing relative to the small-diameter shaft portion 28 of the feed screw 19. This offset eliminates interference between the small-diameter shaft portion 28 and the central axis of the imaging mechanism 24, which is preferable.

[0089] Furthermore, in Figure 1, the feed screw 19 may be positioned horizontally, but preferably it is inclined upwards toward the connecting pipe 17. This inclination allows the feed cylinder 18 to be filled completely with resin material 22.

[0090] This invention is suitable for injection molding equipment that injects resin material into a mold.

[0091] 10...Injection device, 11...Nozzle, 12...Heating cylinder, 12a...Discharge port, 13...Injection screw, 17...Connecting tube, 17a...Straight tube section, 18...Feed cylinder, 19...Feed screw, 22...Resin material, 23...Hopper, 24...Imaging mechanism, 25...Calculation / control unit, 33...Opening.

Claims

1. An injection device comprising: a heating cylinder equipped with a nozzle at its tip; an injection screw rotatably and axially movable within the heating cylinder; a feed cylinder containing a feed screw; a hopper for supplying resin material to the feed cylinder; a connecting pipe connecting the portion of the heating cylinder furthest from the nozzle and the portion of the feed cylinder furthest from the hopper, guiding the resin material to the discharge port of the heating cylinder; an imaging mechanism for photographing the discharge port from the outside; and a calculation / control unit that controls the feed screw to increase its rotation speed when the supply of resin material is insufficient and to decrease its rotation speed when the supply of resin material is excessive, wherein the imaging mechanism is positioned above and near the discharge port, and the calculation / control unit further controls the feed screw to stop rotating when the supply of resin material is excessive, by acquiring a metering time determined based on the retraction of the injection screw, and stopping the rotation of the feed screw when this metering time is greater than or equal to a metering threshold.

2. An injection device according to claim 1, wherein the connecting tube includes a straight tube portion extending linearly outward from the heating cylinder, and the imaging mechanism photographs the drop opening through the straight tube portion.

3. An injection device according to claim 1, wherein the heating cylinder has an opening that leads to the outside near the drop-off port and in a location that does not interfere with the connecting tube, and the imaging mechanism photographs the drop-off port through the opening.

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