Injection device and injection molding machine

Abstract

To provide a screw of an injection molding machine which has high extrusion efficiency and is equipped with a step part flight.SOLUTION: A step part flight (28) is formed on a screw (18) of an injection molding machine (1). The step part flight (28) is a flight (21) in which a step-shaped step part is formed on a top part (29) thereof. The top part (29) of the flight (21) consists of a large-diameter part (31) on an upstream side and a land part (32) on a downstream side. Regarding a clearance H1 between the land part (32) and a bore (35) of a heating cylinder (17) and a clearance H2 between the large-diameter part (31) and the bore (35), a clearance ratio m=H1 / H2 is considered. In the present invention, the clearance ratio m is selected as 2.3≤m≤6.4.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a screw for an injection molding machine in which a stepped portion, i.e., a land portion, is formed at the top of the flight, an injection device provided with the screw, and an injection molding machine.

Background Art

[0002] The injection device of an injection molding machine is composed of a heating cylinder and a screw inserted into the bore of this heating cylinder. The screw is formed with flights for melting and metering an injection material, and the flights have various shapes.

[0003] For example, the screw described in Patent Document 1 is a stepped flight in which a stepped portion is formed at the top of the flight. The stepped flight has a large-diameter portion on the upstream side, i.e., the hopper side, and a land portion on the downstream side, i.e., the injection nozzle side, at the top of the flight.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, the inventors found that in an injection molding apparatus equipped with a screw described in Patent Document 1, there is a problem in that the screw equipped with a stepped flight needs to have a higher plasticizing capacity. A screw equipped with a stepped flight has a smaller amount of extrusion of injection material compared to a so-called conventional screw of the same diameter, in which a stepped portion is not formed at the top of the flight. This is because the gap between the top of the flight and the bore of the heating cylinder is small only in the large diameter portion, and the gap is larger in the land portion. This is because the sealing effect at the top of the flight is smaller compared to a conventional screw.

[0006] Therefore, the present invention provides a screw with high plasticizing ability, an injection device, and an injection molding machine.

[0007] Other challenges and novel features will become apparent from the description and accompanying drawings in this specification. [Means for solving the problem]

[0008] This disclosure comprises the following components injection device That is to say. Injection device A stepped flight is formed on the screw. The stepped flight is a flight with a stepped section formed at the top of the flight, creating a large diameter section on the upstream side and a land section on the downstream side. Let the gaps between the land section and the large diameter section be H1 and H2, respectively, and the gap ratio m = H1 / H2, then select 2.33 ≤ m ≤ 6.33. [Effects of the Invention]

[0009] According to this disclosure, for a screw with stepped flights, the gap ratio m is 2.33~6.33 When selected, it results in an increased extrusion rate, which in turn enhances the plasticizing ability. [Brief explanation of the drawing]

[0010] [Figure 1] This is a front view showing the injection molding machine according to this embodiment. [Figure 2] This is a front cross-sectional view showing the injection device according to this embodiment. [Figure 3] This is a front view showing a part of the screw according to this embodiment. [Figure 4] This is a cross-sectional view showing the stepped flight provided on the screw according to this embodiment. [Figure 5] This figure shows a cross-sectional view of a stepped flight provided on a screw according to this embodiment, and a graph showing the lubrication pressure generated at the top of the stepped flight by the injection material flowing between the stepped flight and the bore of the heating cylinder. [Figure 6] This diagram schematically illustrates the behavior of a viscous fluid flowing through the gap between a moving piece and a stationary piece. [Figure 7] This graph shows the change in the load capacity coefficient related to the lubrication pressure at the top of a stepped flight when the shape factor β is changed. [Figure 8] This graph shows the change in the load capacity coefficient related to the lubrication pressure at the top of a stepped flight when the gap ratio m is changed. [Figure 9] When a screw is rotated inside a heating cylinder, the screw vibrates and its axis of rotation becomes eccentric with respect to the central axis of the heating cylinder. The figure shows graphs illustrating the degree of screw vibration at various screw positions for three screws with stepped flights having different clearance ratios m, and for a conventional screw. [Figure 10] This is a cross-sectional view showing the stepped flight of the screw according to this embodiment, which is provided in the heating cylinder. [Figure 11] This graph shows the relationship between the gap ratio m and the load capacity coefficient. [Figure 12] This is a cross-sectional view showing the upper half of the central axis of the screw, specifically the stepped flight of the screw according to this embodiment, which is provided on the heating cylinder. [Modes for carrying out the invention]

[0011] 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 the sake of clarity, the following description and drawings are appropriately simplified. In each drawing, the same elements are denoted by the same reference numerals, and duplicate descriptions are omitted as necessary. Also, in order not to complicate the drawings, there are parts where hatching is omitted.

[0012] This embodiment will be described. <Injection molding machine> As shown in FIG. 1, the injection molding machine 1 according to this embodiment is schematically composed of a mold clamping device 2 provided on a bed B and an injection device 3 according to this embodiment described below. The mold clamping device 2 is composed of a fixed platen 7, a movable platen 8, a mold clamping housing 9, tie bars 10, 10,... connecting the mold clamping housing 9 and the fixed platen 7, and a mold clamping mechanism 11 composed of a toggle mechanism. The molds 13, 14 are provided on the fixed platen 7 and the movable platen 8. When the mold clamping mechanism 11 is driven, the molds 13, 14 are clamped.

[0013] <Injection device> The injection device 3 according to this embodiment is provided so as to be able to move forward and backward with respect to the mold clamping device 2, and injects an injection material into the molds 13, 14 clamped by the mold clamping device 2. As shown in FIG. 2, the injection device 3 is composed of a heating cylinder 17 and a screw 18 according to this embodiment. A hopper 19 is provided near the rear end portion of the heating cylinder 17, and an injection nozzle 20 is provided at the front end portion. When the injection material is put into the hopper 19 and the screw 18 is rotated, the injection material is melted and sent forward and metered. That is, in the injection device 3, the hopper 19 side is the upstream side and the injection nozzle 20 side is the downstream side.

[0014] <Screw> The screw 18 according to this embodiment has a characteristic in part of the shape of its flight 21, which will be described below. As a whole, it is as follows. In the screw 18, the grooves formed by the flight 21 have a depth that changes in each part of the screw 18, and the inside of the heating cylinder 17 is divided. That is, the upstream side of the screw 18 has deep grooves formed, and it serves as a supply part 23 where the injection material is sent downstream while being heated. And in the middle stream, the groove depth gradually becomes shallower, and it becomes a compression part 24 where the injection material is compressed while being melted. In the downstream, the groove is formed shallowly and it becomes a metering part 25 where the injection material is metered.

[0015] Part of the screw 18 according to this embodiment is enlarged and shown in FIG. 3. It is characterized in that a part of the flight 21 is a stepped flight 28. The cross-section of the stepped flight 28 cut along A - A in FIG. 3 is shown in FIG. 4, and it is characterized by its top 29. That is, the stepped flight 28 has its top 29 formed as a stepped part, and is composed of a large-diameter part 31 on the upstream side and a land part 32 on the downstream side. Since the land part 32 has a smaller diameter than the large-diameter part 31 by a step 33, the gap H1 between the land part 32 and the bore 35 of the heating cylinder 17 is larger than the gap H2 between the large-diameter part 31. Because it is formed in this way, the stepped flight 28 allows the molten injection material to enter and generate an appropriate lubricating pressure at the top 29, preventing contact between the heating cylinder 17 and the screw 18.

[0016] In this embodiment, the stepped flight 28 is provided in the compression part 24 and the metering part 25. When the screw 18 rotates, the screw 18 may vibrate and its rotation axis may be eccentric from the axis of the heating cylinder 17. The degree of this vibration is relatively large in the compression part 24 and the metering part 25 is large next to it. Therefore, although the stepped flight 28 is provided in these sections, even if the stepped flight 28 is provided only in the compression part 24 where the degree of vibration is large, the effect of preventing contact between the heating cylinder 17 and the screw 18 can be obtained.

[0017] When the screw 18 rotates and feeds the injection material forward, the stepped flight 28 has a land portion 32 formed on it, and the gap H1 is larger than that of a conventional screw, allowing the injection material to flow more easily, resulting in a lower plasticizing capacity compared to a conventional screw. However, the screw 18 according to this embodiment is characterized by the numerical range of the gap ratio m, and despite having a stepped flight 28, it has a high plasticizing capacity. The gap ratio m is the ratio of the gap H1 to the gap H2, i.e., m = H1 / H2, and is specifically selected within the following numerical range. 2.3 ≤ m ≤ 6.4 (Numerical range A)

[0018] When the gap ratio m is selected in this way, the plasticizing ability increases. This fact was confirmed by experiments, which will be explained later. However, according to theoretical considerations based on the model to be explained next, the ideal range for the gap ratio m is 1.65 to 2.15. This is because high lubrication pressure can be obtained in this range. The numerical range A of the gap ratio m selected in this embodiment is larger than this range.

[0019] Two questions arise here. The first question is why the plasticizing capacity is higher than that of a screw in the ideal range, even though the numerical range A is larger than the ideal range. It should be that as the gap ratio m increases, the gap H1 in the land portion 32 increases, making it easier for the resin material to flow and thus reducing the plasticizing capacity. However, this expectation is contradicted. The second question is whether the necessary lubrication pressure is generated even when the gap ratio m is outside the ideal range. As mentioned above, experiments have shown that the screw 18 in this embodiment has a higher plasticizing capacity than a screw in the ideal range for a gap ratio m. Experiments have also confirmed that the necessary lubrication pressure can be obtained for the second question. These points will now be explained.

[0020] First, we will theoretically consider the behavior of the injection material in the stepped flight 28 using a model.

[0021] <Mechanism of lubrication pressure generation and lubrication load capacity W> First, the mechanism by which lubrication pressure is generated in the stepped flight 28 will be explained, and the repulsive force that prevents contact between the top 29 of the stepped flight 28 and the bore of the heating cylinder 17, i.e., the lubrication load capacity W, will be shown by mathematical formula.

[0022] When the screw 18 rotates within the heating cylinder 17, the stepped flight 28 is driven at a predetermined speed relative to the bore of the heating cylinder 17, and this speed can be divided into a component parallel to the stepped flight 28 and a component perpendicular to it. Considering the component perpendicular to the stepped flight 28, the stepped flight 28 appears to be moving to the left with velocity U' relative to the heating cylinder 17, as shown in Figure 5. If we consider the stepped flight 28 to be fixed, we can consider the heating cylinder 17 to be moving to the right with velocity U. Velocity U is equal in magnitude to velocity U' but in the opposite direction.

[0023] The molten injection material enters gap H1 and is discharged from gap H2. This generates lubrication pressure. The distribution of the velocity v of the injection material in gaps H1 and H2 is schematically shown in Figure 5. The lubrication pressure p reaches its maximum value Ps at the boundary between the large diameter section 31 and the land section 32, that is, near the stepped section, and becomes virtually zero at both ends of the stepped section flight 28. The lubrication pressure p changes linearly in both the large diameter section 31 and the land section 32. The reason why the lubrication pressure p changes linearly is that the flow of molten resin with high viscosity becomes laminar flow, and in laminar flow, pressure is lost in proportion to the distance traveled.

[0024] Here, we consider the general behavior of a viscous fluid between two relatively moving planes. Figure 6 shows a model consisting of a fixed piece 37 and a moving piece 38 that slides relative to the fixed piece 37 at velocity V, with a Newtonian fluid filling the space between the fixed piece 37 and the moving piece 38. Considering the balance of forces acting on a small element 39 of the fluid, we obtain equation 1 from the balance of forces in the x-axis direction. Here, p is the pressure and τ is the shear force. TIFF0007837669000001.tif15143

[0025] The shear force τ is given by two equations, where μ is the viscosity of the fluid and v is the flow velocity in the x-direction. From equations 1 and 2, equation 3 can be obtained in TIFF0007837669000002.tif141441. Equation TIFF0007837669000003.tif141433 can also be derived from the so-called Navier-Stokes equations, and it represents the steady flow of an incompressible fluid.

[0026] If the gap between the fixed piece 37 and the moving piece 38 in the y-direction is h, then the fluid velocity v=0 at y=h. Also, the fluid velocity v=V at y=0. Solving equation 3 with these as boundary conditions yields equation 4, which is the relationship between the flow velocity v and the pressure distribution. TIFF0007837669000004.tif14144 Considering a unit width perpendicular to the plane of the paper, the flow rate Q of the fluid flowing through the gap h is given by equation 5, which is obtained by integrating equation 4. TIFF0007837669000005.tif16144

[0027] Equation 5 is used to calculate the flow rate Qx of molten resin flowing through gaps H1 and H2 in the model shown in Figure 5. The flow rate Qx is equal in both gaps H1 and H2. Here, if the flight width of the stepped flight 28 is B1 and the width of the land section 32 is B2, then the pressure gradient dp / dx is given by Ps / B2 in gap H1 and by (0-Ps) / (B1-B2) in gap H2. Then the flow rate Qx is given by Equation 6. TIFF0007837669000006.tif16144

[0028] Solving these six equations for the maximum lubrication pressure Ps yields equation seven. TIFF0007837669000007.tif16144

[0029] The lubrication load capacity W per unit length in the stepped flight 28 is obtained by integrating the lubrication pressure p with respect to the width of the stepped flight 28. Incidentally, as shown in Figure 5, the lubrication pressure p changes like a triangle with base length B1 and height Ps. In this case, the load capacity W is given as the area of ​​this triangle. The load capacity W calculated in this way is shown in Equation 8. TIFF0007837669000008.tif34143 Note that Kw is the load capacity coefficient, m is the gap ratio, i.e., the ratio of gaps H1 and H2, and β is the shape factor, i.e., the ratio of the flight width B1 to the width B2 of the land section 32.

[0030] The stepped flight 28, due to the lubrication load capacity W shown in equation 8, generates a repulsive force between the top 29 and the bore of the heating cylinder 17, thereby preventing contact.

[0031] The lubrication load capacity W is proportional to the load capacity coefficient Kw, which changes depending on the gap ratio m, which is the ratio of gaps H1 and H2, and the shape factor β, which is the ratio of the flight width B1 to the width B2 of the land section 32. Therefore, Figure 7 shows the change in the load capacity coefficient Kw given by equation 8 when the shape factor β is changed for various gap ratios m. Furthermore, Figure 8 shows the change in the load capacity coefficient Kw when the gap ratio m is changed for various shape factors β.

[0032] The load capacity coefficient Kw becomes 0.2 or higher when the gap ratio m and shape factor β meet the following conditions. 1.65 ≤ m ≤ 2.15 0.63 ≤ β ≤ 0.79 At this time, the load capacity W is greatest, and the high lubrication pressure ensures that the top 29 of the stepped flight 28 does not come into contact with the bore 35 of the heating cylinder 17. The above is a theoretical consideration based on the model.

[0033] As described above, in the stepped flight 28 of the screw 18 according to this embodiment, the gap ratio m is selected to be within the numerical range A. This selection is based on the following experiment. The first experiment will be described below.

[0034] <Experiment 1> Objective of the experiment: In a screw 18 equipped with stepped flight 28, the relationship between the gap ratio m and the plasticizing ability is clarified. Preparation for the experiment: A heating cylinder 17 with an inner diameter of 91.8 mm and five screws X, Y, A, B, and C with the same screw diameter and flight groove depth were prepared. Screw X was a conventional screw with a flat flight top, while screws Y, A to C were screws 18 according to this embodiment, with stepped flights 28 formed in the compression section 24 and metering section 25. The gap ratio m = H1 / H2 was changed for screws Y, A, B, and C. Specifically, it was set to 2.00, 2.33, 4.33, and 6.33, respectively.

[0035] Experimental method: Screws X, Y, A, B, and C were sequentially set in the heating cylinder 17, and polypropylene (PP) and polyethylene (PE) were supplied as resin materials, and the extrusion amount was measured. This extrusion amount serves as an indicator of the plasticizing capacity when the screw rotation speed is the same. In other words, the higher the extrusion amount, the higher the plasticizing capacity. The extrusion amount was measured according to the following conditions 1 and 2. "Condition 1" The weight of the resin material extruded was measured after rotating the screw for 90 seconds. "Condition 2" The screw was rotated for 10 seconds, then stopped for 10 seconds, rotated for 10 seconds, stopped for 10 seconds, and so on. This was repeated 10 times, and the weight pushed out was measured. The experimental results are shown in Table 1.

[0036] [Table 1]

[0037] Experimental findings: The clearance ratio m of screw Y falls within the ideal numerical range obtained through theoretical considerations using a model, but its extrusion volume is smaller compared to conventional screw X. In contrast, screws A, B, and C have clearance ratios m that are larger than the ideal numerical range, but their extrusion volumes are larger compared to screw Y.

[0038] By the way, if we consider the flow rate Q1 of the injection material flowing through the gap H1 in the land portion 32 based on equation 5, we obtain the following equation 9. TIFF0007837669000010.tif17143 Normally, as the gap ratio m increases, the gap H1 will inevitably increase, so from the first term of equation 9, the flow rate Q1 should increase. Since the flow rate Q1 is considered to be the leakage of the injection material at the top 29 of flight 21, the extrusion amount should decrease as the gap ratio m increases. However, the results of this experiment show the opposite effect to this expectation.

[0039] This is discussed in Figure 10. When the gap ratio m is large, that is, when the gap H1 is larger than the gap H2, it is thought that the injection material accumulates in the region indicated by symbol 41 near the step 33. This accumulation has the effect of pushing back the injection material, and the thickness of the injection material flow in the land portion 32 becomes thinner. As a result, the apparent gap H1' becomes smaller than the actual gap H1. Therefore, it is thought that the flow rate Q1 shown in equation 9 becomes smaller. It is thought that the larger the gap ratio m, the larger the accumulating region 41 becomes, the smaller the apparent gap H1' becomes compared to the actual gap H1, and as a result the flow rate Q1 becomes smaller and the extrusion amount becomes larger.

[0040] Summary of the experiment: In a screw 18 equipped with stepped flight 28, it was found that screws A, B, and C, with gap ratios m of 2.33, 4.33, and 6.33, all had higher plasticizing ability compared to screw Y with a gap ratio m of 2.00. From the viewpoint of plasticizing ability, the aforementioned numerical range A for the gap ratio m is preferable.

[0041] Next, a second experiment was conducted to confirm whether the necessary lubrication pressure was generated for the screw 18 having a gap ratio m within the numerical range A.

[0042] <Experiment 2> Objective of the experiment: For a screw 18 with a clearance ratio m within the numerical range A, when it is rotated in the heated cylinder 17 to measure the injection material, it is confirmed whether the lubrication pressure is generated appropriately and whether the top 29 of the flight 21 is reliably prevented from contacting the bore 35.

[0043] Preparation for the experiment: In the injection apparatus 3 according to this embodiment shown in Figure 2, sensors for detecting the distance to the screw are embedded at multiple locations G7, G8, ..., G12 in the heating cylinder 17. Locations G7 to G9 correspond to the compression section 24, and locations G10 to G12 correspond to the metering section 25. Screws X, A, B, and C, which were used in Experiment 1, were prepared.

[0044] Experimental procedure and results: In the heating cylinder 17, screws X, A, B, and C were sequentially installed and rotated to measure the injection material. At this time, the screw amplitude ratio at each location was obtained from the distance to the screw detected at each location G7, G8, ..., G12. The results are shown in the graph in Figure 9. Reference numerals 46, 47, and 48 represent the graphs for screws A, B, and C, respectively, i.e., the graphs for clearance ratios m of 2.33, 4.33, and 6.33. Reference numeral 49 represents the graph for screw X, i.e., the conventional screw. The screw amplitude ratio is 0.0 when the central axis of screw 18 coincides with the central axis of the heating cylinder 17, and 1.0 when screw 18 and the bore of the heating cylinder 17 are in contact.

[0045] Consideration: For screw C with a clearance ratio m of 6.4, the screw amplitude ratio was found to be sufficiently smaller compared to the conventional screw, and it was confirmed that the required lubrication pressure could be obtained. However, for screw C, the shape factor β is 0.94, and from the theoretical formula 8, the load capacity coefficient Kw is 0.056, so theoretically, it is expected that sufficient lubrication pressure cannot necessarily be obtained. However, in reality, it has been confirmed by experiment that the required lubrication pressure is obtained. One possible reason for this is that, as considered in Figure 10 in the first experiment, when the clearance ratio m is large, the apparent gap H1' is thinner compared to the gap H1 in the land portion 32. In that case, for example, the graph showing the relationship between the clearance ratio m and the load capacity coefficient Kw when the shape factor β is 0.9, as shown in Figure 8, actually looks like the dotted line graph 50, as schematically shown in Figure 11.

[0046] Summary of the experiment: In the screw 18 equipped with stepped flight 28, it was confirmed that screws A, B, and C with clearance ratios m of 2.33, 4.33, and 6.33 all provided the necessary lubrication pressure, and contact with the bore 35 of the heated cylinder 17 was adequately prevented. It was found that selecting the clearance ratio m from the numerical range A poses no problem in terms of obtaining the necessary lubrication pressure.

[0047] This second experiment showed that sufficient lubrication pressure can be obtained even when the shape factor β is 0.94. From the graph in Figure 8, it can be seen that when the shape factor β is 0.5, the theoretical load capacity coefficient Kw is 0.056 or higher when the clearance ratio m is 4.6 or less, and when the shape factor β is 0.6, the theoretical load capacity coefficient Kw is 0.056 or higher when the clearance ratio m is 5.2 or less. Furthermore, when the shape factor β is 0.95, the theoretical load capacity coefficient Kw is 0.056 or higher when the clearance ratio m is 6.5 or less. It is known that when the clearance ratio m is large, the actual load capacity coefficient Kw is larger than the theoretical value and the required lubrication pressure is obtained. Therefore, it can be said that the range of the shape factor β is preferably 0.5 to 0.95.

[0048] Next, we will consider the favorable conditions for the diameter of the screw 18. In the compression section 24, as shown in Figure 12, solid injection material 51 and molten injection material 52 are mixed inside the heating cylinder 17. The solid injection material 51 is layered on the back side of the flight 21, i.e., the upstream side, thereby forming a solid bed 54. A melt film 55 made of molten injection material is formed between this solid bed 54 and the bore 35 of the heating cylinder 17, and a melt pool 57 made of molten injection material is formed upstream of the solid bed 54.

[0049] As the screw 18 rotates, lubrication pressure is generated at the top 29 of the stepped flight 28, as already explained, but negative pressure is generated in the melt film 55. This negative pressure causes the screw 18 to vibrate when it rotates, and its magnitude increases as the thickness H3 of the melt film 55 decreases. In other words, if the thickness H3 of the melt film 55 is thin, there is a risk that the screw 18 will come into contact with the bore 35 of the heating cylinder 17.

[0050] Incidentally, the thickness H3 of the melt film 55 increases as the diameter of the screw 18 increases. In other words, as the injection device 3 becomes larger, the thickness H3 of the melt film 55 increases. This is because larger machines require more efficient melting of the injection material, and therefore the heating cylinder 17 needs to be heated more efficiently. Also, as the machine becomes larger, the rotation speed of the screw 18 decreases, and the time for the injection material to melt increases. In the industry, it is common to consider a machine with a screw 18 diameter of 70 mm or more as a large machine, and for screws 18 with a diameter of 70 mm or more, the thickness H3 of the melt film 55 becomes sufficiently large, and the effect of negative pressure from the melt film 55 does not need to be considered. Therefore, a screw 18 diameter of 70 mm or more is preferable.

[0051] 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 appropriate combinations. [Explanation of Symbols]

[0052] 1 Injection molding machine 2 Mold clamping device 3 Injection device 13 Mold 14 Mold 17 Heating cylinder 18 Screw 21 Flight 23 Supply section 24 Compression section 25 Weighing section 28 Stage section flight 29 Top 31 Large diameter section 32 Land section 33 Step

Claims

1. It consists of a heating cylinder and a screw placed in the bore of the heating cylinder, The aforementioned screw has a stepped flight with a stepped portion formed at the top of the flight, which consists of a large diameter portion on the upstream side and a land portion on the downstream side. The gap H between the large diameter portion and the bore ２ and the gap H between the land portion and the bore １ The gap ratio m = H is the ratio of the two values. １ / H ２ However, the injection device has a ratio of 2.33 to 6.

33.

2. The injection device according to claim 1, wherein the diameter of the large-diameter portion is 70 mm or more.

3. In the aforementioned stepped flight, the flight width B is in the direction perpendicular to the lead angle. １ and the width B of the land portion ２ is width B ２ is width B １ The injection device according to claim 1 or 2, wherein the amount is 0.5 to 0.95 times the amount of the original.

4. When the screw rotates within the heating cylinder, the heating cylinder is divided into an upstream supply section where the injection material is supplied, a compression section where the injection material is compressed while being melted, and a metering section where the molten injection material is metered. The injection apparatus according to any one of claims 1 to 3, wherein the stepped flight is formed in the compression section.

5. The injection device according to claim 4, wherein the stepped flight is formed in the metering section.

6. It consists of a mold clamping device for clamping the mold and an injection device for injecting injection material into the mold. The injection device consists of a heating cylinder and a screw placed in the bore of the heating cylinder. The aforementioned screw has a stepped flight with a stepped portion formed at the top of the flight, which consists of a large diameter portion on the upstream side and a land portion on the downstream side. The clearance H between the large-diameter portion and the bore ２ and the clearance H between the land portion and the bore １ The clearance ratio m = H １ / H ２ of an injection molding machine is 2.33 to 6.

33.

7. The injection molding machine according to claim 6, wherein the diameter of the large-diameter portion is 70 mm or more.

8. In the aforementioned stepped flight, the flight width B is in the direction perpendicular to the lead angle. １ and the width B of the land portion ２ is width B ２ is width B １ The injection molding machine according to claim 6 or 7, wherein the ratio is 0.5 to 0.95 times.

9. When the screw rotates within the heating cylinder, the heating cylinder is divided into an upstream supply section where the injection material is supplied, a compression section where the injection material is compressed while being melted, and a metering section where the molten injection material is metered. The injection molding machine according to any one of claims 6 to 8, wherein the stepped flight is formed in the compression section.

10. The injection molding machine according to claim 9, wherein the stepped flight is formed in the metering section.

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