Drive control device and drive control method for hydraulic injection molding machine

Abstract

The drive system is constructed inexpensively, and the advantages of a gear pump are enjoyed, while stable discharge flow rate and discharge pressure are ensured, and highly accurate discharge pressure control and discharge flow rate control are realized. [Solution] A gear pump 3 is provided to drive and control hydraulic actuators 2a, 2b, etc., and a flow rate detection means 5 for detecting a discharge flow rate Fo and a pressure detection means 6 for detecting a discharge pressure Po are connected to a hydraulic circuit 4 that supplies pressurized oil discharged from this gear pump 3. The rotation speed of a drive motor 7 that drives and rotates the gear pump 3 is variably controlled based on the detected discharge flow rate Fo, thereby performing feedback control on the discharge flow rate Fo, and the rotation speed of the drive motor 7 is variably controlled based on the detected discharge pressure Po, thereby performing feedback control on the discharge pressure Po.

Description

[Technical Field]

[0001] The present invention relates to a drive control device and a drive control method for a hydraulic injection molding machine that is equipped with a plurality of hydraulic actuators that drive and control at least an injection unit and a mold clamping unit. [Background technology]

[0002] BACKGROUND ART Conventionally, as a drive control device (drive control method) for a hydraulic injection molding machine, a drive control device and its control method provided for an injection molding machine, which are described in Patent Document 1 proposed by the present applicant, are known.

[0003] The control method for an injection molding machine described in the document 1 aims to improve the flexibility of control capability and expand the control range by combining control conditions, and to perform appropriate control for various molding modes. Specifically, the pump body is driven to rotate by a first drive motor, and the rotation speed of the first drive motor in a hydraulic pump that can vary at least the discharge flow rate by varying the rotation speed of the first drive motor is variably controlled to control each operating process in a molding cycle. In addition, the angle of the swash plate (swash plate angle) in a swash plate-type piston pump that can vary at least the discharge flow rate is varied by the rotation amount of the second drive motor in a swash plate angle variable mechanism that uses a second drive motor, and the operating process is controlled based on a combination of a first control condition that is preset for the rotation speed of the first drive motor and a second control condition that is preset for the rotation amount of the second drive motor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2009-269325 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional drive control devices, including the drive control device provided in the hydraulic injection molding machine described above, have the following problems to be solved.

[0006] That is, a hydraulic injection molding machine is equipped with multiple hydraulic actuators that drive and control the injection device and the mold clamping device, and the molding cycle includes a mold clamping process that requires highly accurate pressure control and an injection process that requires highly accurate speed control (flow control). Therefore, the hydraulic pump used in the drive control device of a hydraulic injection molding machine is almost always a swash plate type piston pump (variable displacement type) described in Patent Document 1, which is a hydraulic pump that is highly efficient, has excellent responsiveness, and is capable of a wide variety of control methods.

[0007] However, this type of piston pump has the drawback of being expensive and complex in structure due to the incorporation of a swash plate mechanism. On the other hand, fixed-displacement gear pumps, which are not variable displacement but have a simple and compact structure, are also known. This type of gear pump is primarily used in machine tools and construction machinery, which do not require high precision, and is not suitable for hydraulic injection molding machines, which require high precision. However, if it can be used effectively as a drive control device for a hydraulic injection molding machine, it can contribute to cost reduction and other benefits of a gear pump.

[0008] SUMMARY OF THE INVENTION An object of the present invention is to provide a drive control device and a drive control method for a hydraulic injection molding machine that solves the problems present in the background art. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the drive control device 1 of the hydraulic injection molding machine M according to the present invention is configured to drive and control a plurality of hydraulic actuators (2a, 2b, 2c...) including the injection cylinder 2a and metering motor 2b of the injection unit Mi, and the clamping cylinder 2c and ejection cylinder 2d of the clamping unit Mc, and is characterized by comprising: a single gear pump 3 for driving and controlling each of the hydraulic actuators (2a, 2b, 2c...); flow rate detecting means 5 connected to a hydraulic circuit 4 that supplies pressure oil discharged from the gear pump 3 and detecting a discharge flow rate Fo; pressure detecting means 6 connected to the hydraulic circuit 4 and detecting a discharge pressure Po; and a molding machine controller 8 that variably controls the rotation speed of a drive motor 7 using a servo motor 12 connected to a servo circuit 11 that rotates and drives the gear pump 3 based on the detected discharge flow rate Fo during the injection process, thereby performing feedback control of the discharge flow rate Fo, and that variably controls the rotation speed of the drive motor 7 based on the detected discharge pressure Po during the clamping process, thereby performing feedback control of the discharge pressure Po.

[0010] On the other hand, in order to solve the above-mentioned problems, the drive control method for a hydraulic injection molding machine M according to the present invention is characterized in that, when drive controlling a plurality of hydraulic actuators (2a, 2b, 2c...) including the injection cylinder 2a and metering motor 2b of the injection unit Mi and the clamping cylinder 2c and ejection cylinder 2d of the clamping unit Mc, a single gear pump 3 is provided to drive and control each hydraulic actuator (2a, 2b, 2c...), and a flow rate detection means 5 and a pressure detection means 6 are connected to a hydraulic circuit 4 that supplies pressure oil discharged from the gear pump 3 and detect a discharge flow rate Fo and a discharge pressure Po, respectively, and feedback control of the discharge flow rate Fo is performed by variably controlling the rotation speed of a drive motor 7 using a servo motor 12 connected to a servo circuit 11 that drives the gear pump 3, based on the discharge flow rate Fo detected during the injection process, and also by variably controlling the rotation speed of the drive motor 7 based on the discharge pressure Po detected during the clamping process,

[0011] Furthermore, according to a preferred embodiment of the present invention, the hydraulic actuator (2a, 2b, 2c, ...) can include an injection unit moving cylinder 2e that moves the injection unit Mi back and forth to bring the nozzle into contact with the mold 23 or release it. [Effects of the Invention]

[0012] The drive control device 1 and the drive control method for the hydraulic injection molding machine M according to the present invention have the following significant effects.

[0013] (1) The drive control device 1 (drive control method) includes a single gear pump 3 that drives and controls each of the hydraulic actuators 2 a, 2 b, 2 c, etc., a flow rate detection means 5 connected to a hydraulic circuit 4 that supplies pressurized oil discharged from the gear pump 3 and detects a discharge flow rate Fo, a pressure detection means 6 connected to the hydraulic circuit 4 and detects a discharge pressure Po, and a molding machine controller 8 that variably controls the rotation speed of a drive motor 7 that rotates and drives the gear pump 3 based on the discharge flow rate Fo detected during the injection process, thereby performing feedback control of the discharge flow rate Fo, and variably controls the rotation speed of the drive motor 7 based on the discharge pressure Po detected during the mold clamping process, thereby enabling the gear pump 3, which has a simple and compact structure, to be used in a hydraulic injection molding machine M. This allows the drive system to be constructed inexpensively, and thereby provides the advantages of the gear pump 3, and also makes it possible to ensure stable discharge flow rate Fo and discharge pressure Po in the hydraulic injection molding machine M, thereby achieving highly accurate discharge pressure control and discharge flow rate control.

[0014] (2) Since the hydraulic actuators 2a, 2b, etc. include the injection cylinder 2a and the metering motor 2b of the injection unit Mi, it is possible to achieve high precision and good balance in the overall control processing on the injection unit Mi side, including the metering process, injection process, and pressure holding process, etc., in one molding cycle of the hydraulic injection molding machine M.

[0015] (3) Since the hydraulic actuators 2a, 2b, etc. include the clamping cylinder 2c and the ejection cylinder 2d of the clamping device Mc, the entire control process on the clamping device Mc side, including the ejection process and the clamping process in one molding cycle of the hydraulic injection molding machine M, can be realized with high precision and in a good balance.

[0016] (4) Since the servo motor 12 connected to the servo circuit 11 is used as the drive motor 7, the drive control device 1 and the drive control method according to the present invention can be implemented in an optimal manner. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a block circuit diagram of a drive control device provided in a hydraulic injection molding machine according to a preferred embodiment of the present invention; [Figure 2] An overall configuration diagram including the drive control device of the hydraulic injection molding machine. [Figure 3] A diagram showing the principle of the cap pump used in the drive control device. [Figure 4] An operating characteristic diagram of a cap pump used in the drive control device; [Figure 5] A flowchart for explaining the processing procedure during production of a hydraulic injection molding machine including the drive control device. DETAILED DESCRIPTION OF THE INVENTION

[0018] Next, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[0019] First, the overall configuration of a hydraulic injection molding machine M including a drive control device 1 according to this embodiment will be described with reference to FIGS. 1 to 4. FIG.

[0020] 2, M denotes a hydraulic injection molding machine, and is equipped with an injection unit Mi and a mold clamping unit Mc. The injection unit Mi and the mold clamping unit Mc incorporate various hydraulic actuators 2a.... Specifically, the machine is equipped with an injection cylinder 2a that advances and retreats or applies pressure to a screw 22 incorporated in a heating barrel 21 of the injection unit Mi, a metering motor (oil motor) 2b that rotates the screw 22 forward or backward, a mold clamping cylinder 2c that opens, closes, and clamps a mold 23 in the mold clamping unit Mc, an ejection cylinder 2d that ejects (ejects) a molded product from the mold 23, and an injection unit moving cylinder 2e that moves the injection unit Mi forward or backward to bring the nozzle into contact with the mold 23 or release it.

[0021] In this way, if the hydraulic actuators 2a, 2b... include at least the injection cylinder 2a and metering motor 2b provided in the injection device Mi, the overall control processing on the mold clamping device Mc side, including the ejection process and mold clamping process in one molding cycle of the hydraulic injection molding machine M, can be realized with high precision and in a balanced manner, and if the hydraulic actuators 2a, 2b... include at least the mold clamping cylinder 2c and ejection cylinder 2d provided in the mold clamping device Mc, the overall control processing on the mold clamping device Mc side, including the ejection process and mold clamping process in one molding cycle of the hydraulic injection molding machine M, can be realized with high precision and in a balanced manner.

[0022] On the other hand, reference numeral 1 denotes a drive control device, which includes a gear pump 3 serving as a hydraulic drive source and a hydraulic circuit 4, with this hydraulic circuit 4 including a valve circuit group 20. FIG. 3 shows the basic configuration of the gear pump 3. The gear pump 3 has a basic configuration in which a drive gear 32 and a driven gear 33 are arranged inside a housing 31, and is a fixed-displacement hydraulic pump. The drive gear 32 and driven gear 33 mesh with each other, and the drive gear 32 is connected to a servo motor 12 via a rotation transmission mechanism 34. This servo motor 12 constitutes the drive motor 7. As a result, the rotational output of the servo motor 12 is transmitted to the drive gear 32 via the rotation transmission mechanism 34, and the drive gear 32 and driven gear 33 rotate in the direction of arrow Fr in FIG. 3.

[0023] A discharge port 31o is provided on one side of the housing 31 facing the meshing portion of the drive gear 32 and the driven gear 33, and a suction port 31i is provided on the other side. A discharge line 30o is connected to the discharge port 31o, and a suction line 30i is connected to the suction port 31i.

[0024] As a result, when the servo motor 12 is operated, the drive gear 32 and the driven gear 33 rotate in the direction of the arrow Fr, and on the side where the meshing portion of the drive gear 32 and the driven gear 33 separates, oil is sucked in from the suction port 31i, and the sucked oil is guided along the inner surface of the housing 31 to the discharge port 31o and discharged from the discharge port 31o. The suction port 31i side and the discharge port 31o side are blocked by the meshing portion of the drive gear 32 and the driven gear 33. In Figure 3, the arrow indicated by (Fo) indicates the discharge direction and discharge flow rate of the pressure oil, and (Po) indicates the discharge pressure of the pressure oil at the discharge port 31o.

[0025] 4 shows the operating characteristics of the cap pump 3, i.e., the relationship between the discharge pressure Po (MPa) and the discharge flow rate Fo (L / min) and the shaft power D (kW). The cap pump 3 basically controls the rotation speed of the servo motor 12, i.e., the discharge flow rate Fo can be variably controlled by providing a rotation speed command value to the servo motor 12.

[0026] 2, the suction line 30i connected to the suction port 31i of the cap pump 3 is connected to the oil tank 25, and the discharge port 31o is connected to the hydraulic circuit 4 including the discharge line 30o. The hydraulic circuit 4 includes a valve circuit group 20 to which pressure oil is supplied from the discharge line 30o, and the pressure oil output section (secondary side) of this valve circuit group 20 is connected to each of the hydraulic actuators 2a..., i.e., the injection cylinder 2a, the metering motor 2b, the clamping cylinder 2c, the ejection cylinder 2d, and the injection unit moving cylinder 2e, which serve as main valves. More specifically, as shown in FIG. 1, the hydraulic circuit 4 includes a switching valve circuit 20a connected to the injection cylinder 2a, a switching valve circuit 20b connected to the metering motor 2b, a switching valve circuit 20c connected to the clamping cylinder 2c, a switching valve circuit 20d connected to the ejection cylinder 2d, and a switching valve circuit 20e connected to the injection unit moving cylinder 2e.

[0027] Each switching valve circuit 20a... is composed of one or more valve components as well as necessary auxiliary hydraulic components, etc., and has a switching function related to the supply, stop, and discharge of hydraulic oil to at least the injection cylinder 2a, metering motor 2b, mold clamping cylinder 2c, ejection cylinder 2d, and injection unit moving cylinder 2e. Each switching valve circuit 20a... is connected to the molding machine controller 8 constituting the control means, and the valve components and auxiliary hydraulic components constituted by electromagnetic components, etc. to be controlled are switched or variably controlled.

[0028] Furthermore, a flow rate sensor (flow rate detecting means) 5 that detects the discharge flow rate Fo of the pressure oil discharged from the gear pump 3 is connected to a discharge line 30o that is connected to the discharge port 31o of the gear pump 3, and a pressure sensor (pressure detecting means) 6 that detects the discharge pressure Po of the pressure oil discharged from the gear pump 3 is also connected to the discharge line 30o. The discharge flow rate Fo (discharge flow rate value) detected by the flow rate sensor 5 and the discharge pressure Po (discharge pressure value) detected by the pressure sensor 6 are then provided to a molding machine controller 8 that constitutes a control means.

[0029] Furthermore, as shown in FIG. 1, the servo motor 12 that rotates the drive gear 32 of the gear pump 3 is connected to the output side of the servo circuit 11, and a rotary encoder 26 that detects the number of rotations per unit time is attached to the servo motor 12. In this way, by using the servo motor 12 connected to the servo circuit 11 as the drive motor 7 that rotates the gear pump 3, the drive control device 1 and drive control method according to the present invention can be implemented in an optimal manner. The rotation speed (detected value) of the rotary encoder 26 is applied to this servo circuit 11, and feedback control of the rotation speed is performed. The molding machine controller 8 also applies various control command values ​​for various control processes to the servo circuit 11. Note that the servo circuit 11 is omitted from FIG. 2.

[0030] This provides a drive control device 1 for a hydraulic injection molding machine M that can perform feedback control of the discharge flow rate Fo by variably controlling the rotation speed of the servo motor 12 that rotates and drives the gear pump 3 based on the detected discharge flow rate Fo, and can also perform feedback control of the discharge pressure Po by variably controlling the rotation speed of the drive motor 7 based on the detected discharge pressure Po.

[0031] Next, the processing procedure during production of the hydraulic injection molding machine M, including the operation of the drive control device 1 according to this embodiment, will be described according to the flowchart shown in FIG. 5 with reference to the various drawings. For ease of understanding, the illustrated processing procedure is a typical processing procedure in a hydraulic injection molding machine M as an example.

[0032] First, the operation of the injection molding machine M is started (Step S1). In this case, the injection molding machine M is in automatic operation mode, the mold clamping unit Mc is in the mold open state, and the screw 22 of the injection unit Mi is in the plasticization start position (metering start position). In addition, the servo motor 12 starts rotating, and the gear pump 3 is put into operation (Step S2).

[0033] First, a metering process (plasticization process) is performed (step S3). In the metering process, the screw 22 of the injection unit Mi rotates, and the plasticized resin is metered and accumulated in front of the screw 22. Meanwhile, the mold clamping unit Mc performs a mold clamping process (step S4). In this case, the control mode is switched to the pressure control mode (step S41). At this time, the discharge pressure Po detected by the pressure sensor 6 is provided to the molding machine controller 8 (step S42). Then, the mold is closed at a predetermined mold closing speed, and a set value related to the mold clamping force is provided to the servo circuit 11. In addition, the rotation speed of the servo motor 12 is detected by the rotary encoder 26, and this rotation speed (detected value) is provided to the servo circuit 11.

[0034] The above-described pressure feedback control system variably controls the rotation speed of the servo motor 12 so that the discharge pressure Po becomes the set value. Then, when the discharge pressure Po reaches the set value, the discharge pressure Po is controlled (or locked) to maintain the set value (steps S43, S44). Note that this control example is just one example, and various control modes are not excluded, such as controlling the discharge pressure Po to be constant and performing pressure feedback control so that the set clamping force is achieved based on the detected value of a separate pressure sensor attached to the mold clamping unit Mc.

[0035] Next, the injection process is performed by the injection unit Mi (step S5). In this case, the control mode is switched to the flow rate control mode (step S51). At this time, the discharge flow rate Fo detected by the flow rate sensor 5 is provided to the molding machine controller 8 (step S52). Then, the screw 22 moves forward at the set injection speed, and the plasticized molten resin is injected and filled into the cavity of the mold 23. Meanwhile, a set value related to the injection speed is provided to the servo circuit 11. In addition, the rotation speed of the servo motor 12 is detected by the rotary encoder 26, and this rotation speed (detected value) is provided to the servo circuit 11.

[0036] The speed feedback control system described above variably controls the rotation speed of the servo motor 12 so that the discharge flow rate Po, i.e., the injection speed, becomes a set value. When the screw 22 reaches the set injection end position, the forward movement of the screw 22 is stopped (steps S53 and S54). Note that this control example is merely an example, and various control modes are not excluded, such as controlling the discharge flow rate Fo to be constant and performing flow rate feedback control so that the set injection speed is achieved based on the detected value of a separate position sensor or the like attached to the injection unit Mi.

[0037] Upon completion of the injection process, a cooling process of the filled resin in the cavity of the mold 23 is carried out (step S6). Upon completion of the cooling process, a removal process is carried out (step S7). In the removal process, the movable mold in a clamped state moves backward from the fixed mold to the mold open position, the mold is opened relative to the mold 23, and the ejection cylinder 2d attached to the mold 23 is operated to remove the molded product.

[0038] This completes the molding process (molding cycle) for one shot of the injection molding machine M. After this, the same molding process is repeated (steps S8, S3, ...) until production (production plan) is completed. Furthermore, once the planned production is completed, the operation of the injection molding machine M is stopped (step S8).

[0039] Therefore, according to the drive control device 1 (drive control method) of the hydraulic injection molding machine M of this embodiment, as a basic configuration, it comprises a gear pump 3 that drives and controls the hydraulic actuators 2a, 2b, 2c..., a flow rate detection means 5 connected to a hydraulic circuit 4 that supplies pressure oil discharged from the gear pump 3 and detects a discharge flow rate Fo, a pressure detection means 6 connected to the hydraulic circuit 4 and detects a discharge pressure Po, and a molding machine controller 8 that variably controls the rotation speed of a drive motor 7 that rotates and drives the gear pump 3 based on the detected discharge flow rate Fo to perform feedback control of the discharge flow rate Fo, and variably controls the rotation speed of the drive motor 7 based on the detected discharge pressure Po. Therefore, the gear pump 3, which can be configured simply and compactly, can be used in the hydraulic injection molding machine M, and therefore the drive system can be configured inexpensively, and the advantages of the gear pump 3 can be enjoyed. In addition, it is possible to ensure stable discharge flow rate Fo and discharge pressure Po in the hydraulic injection molding machine M, and highly accurate discharge pressure control and discharge flow rate control can be realized.

[0040] Although the preferred embodiment has been described in detail above, the present invention is not limited to such an embodiment, and the detailed configuration, shape, material, quantity, numerical values, method (procedure), etc. can be arbitrarily changed, added, or deleted without departing from the gist of the present invention.

[0041] For example, the injection cylinder 2a and metering motor 2b provided in the injection unit Mi, the clamping cylinder 2c and ejector cylinder 2d provided in the clamping unit Mc, and the injection unit moving cylinder 2e have been exemplified as the multiple hydraulic actuators 2a, 2b, 2c..., but various other hydraulic actuators can also be applied. Also, a flow sensor is used as the flow rate detection means 5 and a pressure sensor is used as the pressure detection means 6, but various other detection means having similar detection functions can be used. [Industrial Applicability]

[0042] The drive control device (drive control method) according to the present invention can be used in various hydraulic injection molding machines that are equipped with a plurality of hydraulic actuators that drive and control at least the injection device and the mold clamping device. [Explanation of symbols]

[0043] 1: Drive control device, 2a: Injection cylinder (hydraulic actuator), 2b: Metering motor (hydraulic actuator), 2c: Clamping cylinder (hydraulic actuator), 2d: Ejector cylinder (hydraulic actuator), 3: Gear pump, 4: Hydraulic circuit, 5: Flow rate detection means, 6: Pressure detection means, 7: Drive motor, 8: Molding machine controller, 11: Servo circuit, 12: Servo motor, M: Hydraulic injection molding machine, Mi: Injection unit, Mc: Clamping unit, Fo: Discharge flow rate, Po: Discharge pressure

Claims

1. a hydraulic motor connected to a servo circuit that rotates the gear pump, to variably control the rotation speed of a drive motor using a servo motor connected to a servo circuit that rotates the gear pump, based on the detected discharge flow rate, thereby performing feedback control of the discharge flow rate; and a molding machine controller that variably controls the rotation speed of the drive motor, based on the detected discharge pressure, thereby performing feedback control of the discharge pressure.

2. 2. A drive control device for a hydraulic injection molding machine according to claim 1, wherein the hydraulic actuator includes an injection unit moving cylinder that moves the injection unit back and forth to bring the nozzle into contact with the mold or release the nozzle from the contact.

3. A drive control method for a hydraulic injection molding machine that drive controls a plurality of hydraulic actuators including an injection cylinder and a metering motor of an injection unit, and a clamping cylinder and an ejector cylinder of a clamping unit, comprising: a single gear pump that drive controls each of the hydraulic actuators; flow rate detecting means that detects a discharge flow rate and a pressure detecting means that detects a discharge pressure, connected to a hydraulic circuit that supplies pressure oil discharged from the gear pump; feedback control of the discharge flow rate by variably controlling the rotation speed of a drive motor using a servo motor connected to a servo circuit that rotates the gear pump, based on the discharge flow rate detected during the injection process; and feedback control of the discharge pressure by variably controlling the rotation speed of the drive motor, based on the discharge pressure detected during the clamping process.

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