Injection device

Abstract

To provide an injection apparatus of a metal injection molding machine capable of adjusting the holding pressure.SOLUTION: An injection hydraulic cylinder 9 drives an injection piston 10 in the axial direction by pressure of hydraulic oil. The injection piston is connected to a screw 2 and drives the screw provided in a heating barrel 1. Inside of the injection hydraulic cylinder is partitioned into a front chamber 11A in which pressure oil is supplied to and a rear chamber 11B from which hydraulic oil is discharged. An oil discharge port 18 is provided in the injection hydraulic cylinder 9 and discharges the hydraulic oil from the rear chamber 11B. A flow control valve 16 is inserted in a path for discharging the hydraulic oil discharged via the oil discharge port 18 from the rear chamber 11B. A relief valve 20 opens when a part of the hydraulic oil supplied to the front chamber 11A is provided and the pressure of the provided oil is higher than a first threshold value. The flow control valve 16 closes when the pressure of the hydraulic oil supplied through the relief valve 20 is applied to the flow control valve.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an injection device, and more particularly to an injection device of an injection molding machine that injection molds metals such as magnesium alloys and aluminum alloys. [Background technology]

[0002] Metal injection molding machines are widely used to mold products by filling a cavity in a mold with molten metal material (so-called molten metal).As an example of injection molding used in such metal injection molding machines, an injection device of a metal injection molding machine having a configuration in which the speed of an injection piston is suddenly decelerated to transition from an injection process to a pressure holding process has been proposed (Patent Document 1).

[0003] In this injection device, the rear chamber is provided with an oil discharge port with a large opening and an oil discharge port with a small opening, and when the injection piston advances to the pressure holding switching position, the oil discharge port with the large opening is blocked by the injection piston, which significantly reduces the amount of hydraulic oil discharged, so that the injection piston is suddenly braked, and the hydraulic oil during the pressure holding process can be discharged through the oil discharge port with the small opening. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-216285 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned injection device, although the piston can be rapidly decelerated, the pressure of the molten metal drops rapidly, which causes a problem that a sufficient dwell pressure cannot be secured in the dwelling step after the filling of the molten metal is completed.

[0006] Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0007] An injection device according to one embodiment includes an injection piston connected to a screw arranged in the axial direction within a heating cylinder to drive the screw in the axial direction, an injection hydraulic cylinder that drives the injection piston in the axial direction by hydraulic pressure and is divided into a first chamber to which pressurized hydraulic oil is supplied to drive the injection piston and a second chamber from which the hydraulic oil is discharged, an oil discharge port that discharges the hydraulic oil from the second chamber, a first valve inserted in a path for discharging the hydraulic oil from the second chamber, and a second valve that opens when the pressure of the hydraulic oil supplied to the first chamber is higher than a first threshold value, and the first valve closes when pressure of the hydraulic oil supplied via the second valve is applied. Effect of the Invention

[0008] According to one embodiment, it is possible to provide an injection device of a metal injection molding machine that is capable of adjusting the dwell pressure. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing a schematic configuration of an injection device of a metal injection molding machine according to a first embodiment. [Diagram 2] FIG. 2 is an enlarged view of the injection device according to the first embodiment. [Diagram 3] FIG. 2 is a diagram showing a more detailed configuration of an injection device of the metal injection molding machine according to the first embodiment. [Figure 4] FIG. 4 is a diagram showing the pressure of hydraulic oil and the pressure of molten metal in an injection process and a pressure holding process. [Diagram 5] FIG. 13 is a diagram showing the oil pressure and the molten metal pressure when the opening pressure of the relief valve is set to a lower value. [Figure 6] FIG. 1 is a diagram showing a schematic configuration of an injection device of a general metal injection molding machine. [Figure 7]FIG. 1 is a diagram showing the pressure of hydraulic oil and the pressure of molten metal in a typical injection device. [Figure 8] FIG. 13 is a diagram showing the pressure of molten metal in another typical injection device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Specific embodiments will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments. In addition, the following description and drawings are appropriately simplified for clarity. In addition, the same elements are given the same reference numerals, and duplicated descriptions are omitted.

[0011] 1 to 3 and 6, the direction from the rear chamber to the front chamber along the central axis of the injection piston 10 is the X direction, the vertical direction from bottom to top of the paper is the Z direction, and the normal direction from the front to the back of the paper, which is perpendicular to the X and Z directions, is the Y direction.

[0012] First embodiment As a premise for understanding the injection device of the metal injection molding machine according to the present embodiment, the injection device of a general metal injection molding machine according to Patent Document 1 will be described. FIG. 6 shows a schematic configuration of an injection device 100 of a general metal injection molding machine. The injection device 100 has a heating barrel 101 and a screw 102 that is provided in the heating barrel 101 so as to be freely driven in the axial and rotational directions. A molding material is charged into the heating barrel 101 from a hopper 103, and the charged material is melted by frictional heat and shear heat generated with the rotation of the screw 102 and heat applied from a heater 104 provided on the outer periphery of the heating barrel 101. The molten material (molten metal) is kneaded by the rotation of the screw 102 and sent to the front of the heating barrel 101. A nozzle 105 is attached to the tip of the heating barrel 101. When injecting the material, the molten metal stored at the tip of the heating barrel 101 is injected through a nozzle 105 into a cavity 107 of a closed mold 106 .

[0013] The screw 102 is rotationally driven by a motor 108 and is driven axially by an injection piston 110 provided inside an injection hydraulic cylinder 109 .

[0014] The inside of the injection hydraulic cylinder 109 is divided into two chambers by the injection piston 110, and a rear chamber 111B is provided on the -X side, and a front chamber 111A is provided on the +X side. Pressure oil accumulated in an accumulator 113 by a hydraulic pump 112 is supplied to the front chamber 111A via a flow control valve 114. The rear chamber 111B is provided with a first oil discharge port 115A that is completely or mostly blocked by the injection piston 110 at a desired pressure holding switching position of the injection piston 110, and a second oil discharge port 115B that is not blocked by the injection piston 110 even at the most forward position of the injection piston 110. The first oil discharge port 115A is formed on a side surface of the injection hydraulic cylinder 109, and the second oil discharge port 115B is formed on an end surface of the injection hydraulic cylinder 109.

[0015] The first oil discharge port 115A is connected to the oil tank 117 via a flow control valve 116, and has an opening area large enough to discharge the hydraulic oil stored in the rear chamber 111B to the oil tank 117 during the injection process. The second oil discharge port 115B is connected to the oil tank 117 via a flow control valve 118, and discharges the hydraulic oil in the rear chamber 111B to the oil tank 117 during the pressure holding process. However, the second oil discharge port 115B only needs to be able to flow hydraulic oil at a flow rate required for the pressure holding process and for the retreat (movement in the +X direction) of the injection piston 110 during the metering process, so the opening area may be smaller than that of the first oil discharge port 115A.

[0016] Injection molding mainly consists of a metering process, an injection process, and a pressure holding process. In the metering process, solid molding material is put into the heating cylinder 101 from the hopper 103, and the screw 102 is rotated by the motor 108 while being driven axially backward (+X direction) by the injection hydraulic cylinder 109, so that the material is melted in the heating cylinder 101 and sent forward (-X direction) to be measured. In the injection process, when the measured value reaches a predetermined size, pressure oil is supplied to the injection hydraulic cylinder 109 to drive the screw 102 axially forward (-X direction), and the measured molten material is injected from the nozzle 105 into the cavity 107 of the mold 106. In the pressure holding process, pressure is applied to the material in the mold 106 through the material remaining in the heating cylinder 101 to compensate for the shrinkage of the material caused by the cooling of the material after the injection is completed. These steps allow the material to be molded into the desired shape that cavity 107 has.

[0017] In the above-mentioned injection device, although it is possible to rapidly decelerate the piston, the pressure of the molten metal also drops rapidly, which causes a problem that sufficient pressure holding cannot be ensured in the pressure holding step.

[0018] FIG. 7 shows the hydraulic oil pressure and the molten metal pressure in the injection device 100 described above. When the process starts, the hydraulic oil is supplied to the front chamber 111A, and the hydraulic pressure rises rapidly. After that, the plug comes out, and the hydraulic pressure drops, and the injection piston 110 starts to advance. After that, when the filling of the molten metal into the mold is completed, the hydraulic pressure in the front chamber 111A and the rear chamber 111B rises rapidly due to a reaction. At this time, the hydraulic pressure rises rapidly and reaches a peak due to the inertia of the hydraulic oil supplied to the injection piston 110 and the front chamber 111A. The effect of inertia is alleviated, and the hydraulic pressure steeply processes, and then gradually drops until solidification is completed.

[0019] The pressure of the molten metal at this time is calculated by subtracting the hydraulic pressure in the front chamber 111A x the pressure-receiving area of ​​the injection piston 110 on the rear chamber 111B x the pressure-receiving area of ​​the injection piston 110 on the rear chamber 111B from the hydraulic pressure in the front chamber 111A x the pressure-receiving area of ​​the injection piston 110 on the rear chamber 111B, and dividing the result by the cross-sectional area of ​​the cylinder. Therefore, the pressure of the molten metal after filling is completed drops to zero, and then gradually rises according to the difference between the hydraulic pressure in the rear chamber 111B and the hydraulic pressure in the front chamber 111A.

[0020] However, in the dwelling process, there is a pressure (hereinafter referred to as a target dwelling pressure) that must be maintained in order to mold the material in the cavity 107 of the mold into a desired shape. In this case, when the dwelling process is started after the filling of the molten metal is completed, the pressure of the molten metal becomes zero, so the pressure of the molten metal becomes significantly lower than the target dwelling pressure. Although the pressure of the molten metal increases thereafter, the pressure of the molten metal remains lower than the target dwelling pressure. Therefore, in the above-mentioned injection device 100, a problem occurs in that a sufficient molten metal pressure, i.e., a dwelling pressure, cannot be secured in the dwelling operation.

[0021] On the other hand, in other general injection devices that do not perform rapid deceleration of the injection piston like the above-mentioned injection device 100, a problem occurs in that the dwell pressure increases excessively. Figure 8 shows the pressure of the molten metal in another general injection device. In this example, the hydraulic oil in the rear chamber continues to be discharged even after the filling is completed, and the hydraulic pressure in the rear chamber is kept low during the dwell process. As a result, the pressure of the molten metal increases rapidly with the start of the dwell process, and the pressure of the molten metal remains high even after it reaches its peak. In this case, the time during which the pressure of the molten metal is excessively higher than the target dwell pressure is long, which causes problems such as the generation of burrs on the product, the ejection of the molten metal from the mold, and an increased load on the mold.

[0022] In the following, in this embodiment, an injection device of a metal injection molding machine that is configured so that the dwell pressure can be adjusted will be described.

[0023] An injection device according to the first embodiment will be described. FIG. 1 is a diagram showing a schematic configuration of an injection device of a metal injection molding machine according to the first embodiment. The injection device 100 shown in FIG. 1 has a heating barrel 1 and a screw 2 provided inside the heating barrel 1 so as to be freely driven in the axial and rotational directions. A molding material is charged from a hopper 3 into the heating barrel 1, and the charged material is melted by frictional heat and shear heat generated by the rotation of the screw 2 and heat applied from a heater 4 provided on the outer periphery of the heating barrel 1. The molten material (i.e., molten metal) is kneaded by the rotation of the screw 2 and sent to the front (-X direction) of the heating barrel 1. A nozzle 5 is attached to the tip of the heating barrel 1. When the material is injected, the molten molding material stored at the tip of the heating barrel 1 is injected into a cavity 7 of a closed mold 6 through the nozzle 5.

[0024] The screw 2 is rotationally driven by a motor 8 and is driven axially by an injection piston 10 provided inside an injection hydraulic cylinder 9 .

[0025] The inside of the injection hydraulic cylinder 9 is divided into two chambers by the injection piston 10, with a front chamber 11A (also referred to as a first chamber) being provided on the +X side and a rear chamber 11B (also referred to as a second chamber) being provided on the -X side. An oil supply port 15 is provided in the front chamber 11A. After pressure oil accumulated in an accumulator 13 by a hydraulic pump 12 has its flow rate controlled by a flow control valve 14, the oil is supplied to the front chamber 11A through the oil supply port 15. In this embodiment, in order to supply pressure oil to the front chamber 11A, it is desirable that the flow control valve 14 is configured as, for example, a servo valve, more specifically, a cartridge servo valve.

[0026] The configuration of the injection device 100 will be described in detail below. Fig. 2 shows an enlarged view of the injection device 100. The rear chamber 11B is provided with an oil discharge port 18 that is provided at a position that is not completely blocked by the injection piston 10 when the injection piston 10 is at a desired pressure holding switching position.

[0027] In Fig. 2, sealing members 19A to 19C such as guard rings and oil seals are provided to prevent leakage of hydraulic oil. Sealing member 19A is provided to seal between the inner surface of the opening on the -X side of housing 9A of injection hydraulic cylinder 9 and the shaft connected to injection piston 10. Sealing member 19B is provided to seal between the inner surface of housing 9A and injection piston 10. Sealing member 19C is provided to seal between the inner surface of the opening on the +X side of housing 9A and the shaft connected to injection piston 10.

[0028] In the rear chamber 11B, an oil discharge port 18 is provided so as to penetrate the injection hydraulic cylinder 9 in the radial direction. The oil discharge port 18 is connected to an oil tank 17 via a flow control valve 16 (also referred to as a first valve), and has an opening area large enough to discharge the hydraulic oil stored in the rear chamber 11B to the oil tank 17 in an injection process described below. In this embodiment, the flow control valve 16 is configured as an external pilot type valve, and a part of the pressure oil supplied into the front chamber 11A is supplied as operating pressure oil via a relief valve 20 (also referred to as a second valve) described below.

[0029] In this configuration, a relief valve 20 is provided to prevent an excessive increase in brake pressure. A portion of the pressure oil supplied to the front chamber 11A is supplied to the relief valve 20. The relief valve 20 is configured as an internal pilot type valve that opens when the pressure of the supplied pressure oil becomes greater than a predetermined value.

[0030] When the relief valve 20 is opened, a portion of the pressure oil supplied to the front chamber 11A is supplied as operating pressure oil to the flow control valve 16. In this configuration, the flow control valve 16 is configured as an external pilot type valve, which opens when the pressure of the operating pressure oil supplied is equal to or higher than a predetermined value, and closes when it is lower than the predetermined value.

[0031] In this configuration, in order to prevent malfunction of relief valve 20, it is desirable to insert a valve in a path that supplies pressure oil to relief valve 20. FIG. 3 shows a more detailed configuration of the injection device of the metal injection molding machine according to the first embodiment. As shown in FIG. 3, a solenoid valve 21 (also referred to as a third valve) is inserted in the path between front chamber 11A and relief valve 20. Also, a control unit 30 configured to be able to monitor the pressure of the hydraulic oil in front chamber 11A is provided, and control unit 30 controls the opening and closing of solenoid valve 21 based on the monitoring result.

[0032] Next, a description will be given of injection molding using the injection device 100. Injection molding mainly consists of a metering process, an injection process, and a pressure holding process. Each process will be described below.

[0033] The metering process is a process of metering the material to be filled into the cavity. In this process, solid molding material is poured from the hopper 3 into the inside of the heating barrel 1, and the screw 2 is driven axially backward (+X direction) by the injection hydraulic cylinder 9 while being rotated by the motor 8. As a result, the material is sent in a molten state to the front of the screw 2 inside the heating barrel 1. Here, by measuring the amount of movement of the screw 2, the material introduced into the heating barrel 1 can be metered.

[0034] The injection process is a process for filling the cavity 7 with material. In the injection process, when the measured value reaches a predetermined value, the screw 2 is driven forward in the axial direction by supplying pressure oil to the injection hydraulic cylinder 9, and the measured molten material (molten metal) is injected from the nozzle 5 into the cavity 7 of the mold 6. When injection molding an alloy material, if the material is not injected at a relatively high speed, the molten metal will be cooled rapidly and will not be sufficiently filled into the cavity 7. Therefore, in general injection molding of metal materials, an accumulator 13 is used as a pressure oil supply source for the injection hydraulic cylinder 9, and the screw 2 is driven in the axial direction at a high speed (for example, 1 to 5 m / s) to inject the molten material.

[0035] The dwelling process is a process in which pressure is applied to the material filled in the cavity 7 by maintaining the pressure applied to the molten metal remaining in the heating barrel 1 in order to compensate for the shrinkage that occurs as the material cools after the injection of the material is completed. After that, the material in the cavity 7 is cooled while applying the dwelling pressure. This allows the material to be molded into the desired shape that the cavity 7 has.

[0036] The operation in the injection process and the pressure holding process in this embodiment will be specifically described below. Fig. 4 shows the pressure of the hydraulic oil and the pressure of the molten metal in the injection process and the pressure holding process. The upper side of Fig. 4 shows the pressure of the hydraulic oil in the front chamber 11A and the pressure of the hydraulic oil in the rear chamber 11B. The lower side of Fig. 4 shows the pressure of the molten metal.

[0037] In this embodiment, when hydraulic oil is supplied from the accumulator 13 to the front chamber 11A of the injection hydraulic cylinder 9 in the injection process, the pressure of the hydraulic oil in the front chamber 11A starts to rise (timing T0).

[0038] When the hydraulic oil in the front chamber 11A reaches a certain pressure (pressure P1 in FIG. 4), a so-called plug (also called cold plug) leak occurs, the pressure of the hydraulic oil in the front chamber 11A starts to drop, and the injection piston 10 starts to move forward in the injection direction (-X direction). Thereafter, the pressure of the hydraulic oil in the front chamber 11A is maintained at a predetermined pressure (pressure P2 in FIG. 4) (after timing T1) by supplying pressurized hydraulic oil via the flow control valve (servo valve) 14. On the other hand, the hydraulic oil in the rear chamber 11B is discharged from the oil discharge port 18 as the injection piston 10 moves forward, so that the hydraulic oil in the rear chamber 11B becomes low pressure.

[0039] As described above, the pressure of the molten metal is calculated by subtracting the hydraulic pressure in the front chamber 11A and the pressure-receiving area of ​​the injection piston 10 on the front chamber 11A side from the hydraulic pressure in the rear chamber 11B and the pressure-receiving area of ​​the injection piston 10 on the rear chamber 11B side, and dividing the result by the cross-sectional area of ​​the cylinder. Therefore, the pressure of the molten metal rises sharply after the start of the injection stroke, drops when the plug comes out (timing T0 to T1), and remains at a constant pressure during filling (timing T1 and after).

[0040] Thereafter, after the pressure of the hydraulic oil in the front chamber 11A becomes smaller than a predetermined value, the solenoid valve 21, which was closed beforehand, opens (timing T2). Here, the solenoid valve 21 is closed in the initial state and opened after the plug removal occurs in order to prevent the relief valve 20 from opening prematurely. As described later, the relief valve 20 is opened and closed to adjust the holding pressure, and is therefore required to open and close from the latter half of the injection process to the holding pressure process. However, after the start of the injection process, the pressure of the hydraulic oil in the front chamber 11A becomes high once before the plug removal occurs, and then becomes low after the plug removal. At this time, if the pressure of the hydraulic oil in the front chamber 11A becomes higher than the opening set pressure PS (also referred to as the first threshold value) of the relief valve 20 before the plug removal occurs, the relief valve 20 opens at an undesired timing. Therefore, in this configuration, a solenoid valve 21 is provided between the front chamber 11A and the relief valve 20, and the solenoid valve 21 is closed from the start of operation of the injection device through plug removal until the pressure of the hydraulic oil in the front chamber 11A drops, thereby preventing the relief valve 20 from opening prematurely and undesirably. Also, by opening the solenoid valve 21 after the pressure of the hydraulic oil in the front chamber 11A drops, it is possible to open and close the relief valve 20 at a desired time.

[0041] After that, when the filling of the inside of the mold with the molten metal is completed, the reaction brakes the injection piston 10. As a result, the pressure of the hydraulic oil in the front chamber 11A rises suddenly temporarily (timing T3) due to the inertia caused by the forward movement of the injection piston 10. However, the hydraulic oil in the rear chamber 11B is discharged from the oil discharge port 18 via the flow control valve 16, so the hydraulic oil in the rear chamber 11B remains at a low pressure.

[0042] When the pressure of the hydraulic oil in the front chamber 11A increases and becomes higher than the opening set pressure PS (first) of the relief valve 20, the relief valve 20 opens. When the relief valve 20 opens, the pressure of the hydraulic oil in the front chamber 11A is applied to the flow control valve 16, which closes the flow control valve 16. This stops the discharge of the hydraulic oil in the rear chamber 11B from the oil discharge port 18, and the pressure of the hydraulic oil in the rear chamber 11B begins to increase (timing T4). Note that since the effect of the inertia of the injection piston 10 is temporary, the pressure of the hydraulic oil in the front chamber 11A begins to decrease after reaching a peak. As a result, the pressure of the molten metal decreases and is maintained in the vicinity of the target holding pressure PT.

[0043] Thereafter, when the pressure of the hydraulic oil in the front chamber 11A falls below the set opening pressure PS (first threshold) of the relief valve 20, the relief valve 20 closes (timing T5). When the relief valve 20 closes, the pressure of the hydraulic oil in the front chamber 11A is no longer applied to the flow control valve 16, and the flow control valve 16 opens. As a result, the hydraulic oil in the rear chamber 11B is discharged from the oil discharge port 18, and the pressure of the hydraulic oil in the rear chamber 11B drops. As a result, the pressure of the molten metal continues to be maintained near the target holding pressure PT.

[0044] As described above, although the pressure of the molten metal rises sharply after time T3, resulting in a temporary surplus to the holding pressure, it can then be maintained at approximately the target holding pressure PT until the completion of the holding process (time T6), although there is a slight deficiency or surplus relative to the release set pressure PS.

[0045] As described above, according to this configuration, the pressure of the molten metal in the pressure holding process can be adjusted by the timing of opening and closing the relief valve, and as a result, an excessive increase in the pressure of the molten metal can be suppressed.

[0046] By appropriately setting the relief valve's opening pressure, it is possible to control the behavior of the molten metal pressure during the pressure holding process. Figure 5 shows the oil pressure and molten metal pressure when the relief valve's opening pressure is set to a lower value.

[0047] The process from the start of the process (timing T0) to the completion of filling of the molten metal (timing T3) is the same as in the case of FIG. 4, so the process after the completion of filling will be described.

[0048] In this example, the set opening pressure PS of the relief valve 20 is lower than that in FIG. 4. Therefore, the relief valve opens earlier than that in FIG. 4 (timing T7). When the relief valve 20 opens, the pressure of the hydraulic oil in the front chamber 11A is applied to the flow control valve 16, and the flow control valve 16 closes earlier. This stops the hydraulic oil in the rear chamber 11B from being discharged from the oil outlet 18, and the pressure of the hydraulic oil in the rear chamber 11B starts to rise. As a result, the pressure of the molten metal starts to drop earlier than that in FIG. 4. Therefore, the peak value of the pressure of the molten metal is also lower than that in FIG. 4. This further suppresses the rise in the pressure of the molten metal.

[0049] After that, although the pressure of the hydraulic oil in the front chamber 11A drops, it is still higher than the set open pressure PS of the relief valve 20, so the relief valve 20 remains open and solidification is completed (timing T8). In this example, it can be seen that the surplus region, which indicates a state in which the pressure of the molten metal is higher than the target holding pressure PT, is smaller than in Fig. 4, and the rise in the pressure of the molten metal is further suppressed. Also, it can be seen that the deficiency region, where the pressure of the molten metal is lower than the target holding pressure PT, has significantly increased, and therefore the period during which the target holding pressure PT is insufficient has increased.

[0050] In this way, when the opening setting value of the relief valve 20 is set to a low value, the period during which the target holding pressure PT is insufficient increases, but this is suitable for materials with a small shrinkage rate after filling or materials that take a short time to harden. In this case, it is also possible to further suppress the occurrence of flash and the load on the mold.

[0051] In this manner, in this configuration, by appropriately setting the opening setting value of the relief valve depending on the material of the molten metal to be filled into the mold, the dwelling pressure can be adjusted and the desired dwelling process can be realized.

[0052] Other embodiments The present invention is not limited to the above embodiment, and can be modified as appropriate without departing from the spirit of the present invention. For example, the end of the path for supplying hydraulic oil to the relief valve 20 and the solenoid valve 21 is connected between the oil supply port 15 and the flow control valve 14, but this is merely an example. A separate opening may be provided in the housing 9A, and the hydraulic oil in the front chamber 11A may be supplied to the relief valve 20 and the solenoid valve 21 through the separate opening.

[0053] It goes without saying that various types of valves can be used for the flow control valve 16, the relief valve 20, and the solenoid valve 21 as long as they can perform similar functions.

[0054] In the above-described embodiment, an example has been described in which metal is used as the injected material. However, this is merely an example, and it goes without saying that the configuration according to the above-described embodiment may also be applied to an injection molding machine that injects other materials, such as resin. [Explanation of symbols]

[0055] 1, 101 heating tube 2, 102 screw 3, 103 Hopper 4, 104 Heater 5, 105 nozzle 6, 106 Mold 7, 107 Cavity 8, 108 Motor 9, 109 Hydraulic cylinder for injection 9A, 109A Housing 10, 110 Injection piston 11A, 111A Anterior chamber 11B, 111B rear chamber 12, 112 Hydraulic pump 13, 113 Accumulator 14, 114 Flow control valve 15 Oil supply port 16, 116 Flow control valve 17, 117 Oil tank 18 Oil drain 19A~19C Sealing member 20 Relief valve 21 Solenoid valve 30 Control section 100 Injection device 119A~119C Sealing member

Claims

1. an injection piston that is drivable along the axial direction of the heating barrel, is rotatably connected to a screw provided in the heating barrel, and drives the screw along the axial direction to inject molding material into a mold; an injection hydraulic cylinder which drives the housed injection piston in the axial direction by hydraulic pressure, and which is divided into a first chamber to which pressurized hydraulic oil is supplied for driving the injection piston, and a second chamber from which the hydraulic oil is discharged; an oil discharge port provided in the injection hydraulic cylinder for discharging hydraulic oil from the second chamber; a first valve that is inserted in a path that discharges the hydraulic oil discharged from the second chamber through the oil discharge port and that closes when operating pressure oil is supplied; a second valve that receives a portion of the hydraulic oil supplied to the first chamber, and opens when the filling of the molding material into the mold is completed and the pressure of the portion of the hydraulic oil becomes higher than a first threshold value, thereby supplying the portion of the hydraulic oil to the first valve as the operating pressure oil, and closes when the pressure of the portion of the hydraulic oil becomes lower than the first threshold value, thereby stopping the supply of the operating pressure oil to the first valve. Injection device.

2. The hydraulic cylinder further includes an oil supply port for supplying hydraulic oil to the first chamber, The second valve is provided between the oil supply port and the first valve. The injection device according to claim 1 .

3. a third valve that is inserted in a path for supplying hydraulic oil to the second valve and opens after a predetermined period of time has elapsed since the start of supplying hydraulic oil to the first chamber; 3. An injection device according to claim 1 or 2.

4. The third valve is configured to open after a plug removal occurs after starting the supply of hydraulic oil to the first chamber.

4. The injection device according to claim 3.

5. The first threshold value can be set according to the material to be put into the heating barrel. An injection device according to any one of claims 1 to 4.

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