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

Abstract

In the present invention, a gear pump 3 that controls driving of hydraulic actuators 2a, 2b, … is provided. A flow rate detection means 5 that detects a discharge flow rate Fo and a pressure detection means 6 that detects a discharge pressure Po are connected to a hydraulic circuit 4 that supplies pressure oil discharged from this gear pump 3. On the basis of the detected discharge flow rate Fo, the rotational rate of a drive motor 7 that rotates and drives the gear pump 3 is variably controlled so as to apply feedback control to the discharge flow rate Fo, and, on the basis of the detected discharge pressure Po, the rate of rotation of the drive motor 7 is variably controlled to apply feedback control to the discharge pressure Po.

Description

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

[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.

[0002] 2. Description of the Related Art Conventionally, as a drive control device (drive control method) for a hydraulic injection molding machine, a drive control device and a control method thereof disclosed 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 rotationally driven 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 operation process in a molding cycle, and 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 operation 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.

[0004] Japanese Patent Application Laid-Open No. 2009-269325

[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 a plurality of 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 rate control). Therefore, the hydraulic pump used in the drive control device of a hydraulic injection molding machine is in most cases 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.

[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 as a drive control device having a plurality of hydraulic actuators 2a, 2b, 2c... that drive and control at least the injection device Mi and the mold clamping device Mc, and is characterized by comprising: a gear pump 3 that drives and controls the hydraulic actuators 2a, 2b, 2c...; 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; 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 that variably controls the rotation speed of the drive motor 7 based on the detected discharge pressure Po to perform 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 carrying out the drive control method equipped with a plurality of hydraulic actuators 2a, 2b, 2c... that drive and control at least the injection unit Mi and the mold clamping unit Mc, a gear pump 3 that drives and controls the hydraulic actuators 2a, 2b, 2c... is provided, and a flow rate detection means 5 that detects a discharge flow rate Fo and a pressure detection means 6 that detects a discharge pressure Po are connected to a hydraulic circuit 4 that supplies pressure oil discharged from the gear pump 3, and the rotation speed of a drive motor 7 that rotates and drives the gear pump 3 is variably controlled based on the detected discharge flow rate Fo to perform feedback control of the discharge flow rate Fo, and the rotation speed of the drive motor 7 is variably controlled based on the detected discharge pressure Po to perform feedback control of the discharge pressure Po.

[0011] In addition, according to a preferred embodiment of the present invention, the hydraulic actuators 2 a, 2 b can include at least the injection cylinder 2 a and the metering motor 2 b provided in the injection unit Mi, and can also include at least the clamping cylinder 2 c and the ejection cylinder 2 d provided in the clamping unit Mc. On the other hand, a servo motor 12 connected to a servo circuit 11 can be used as the drive motor 7.

[0012] The drive control device 1 and 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 gear pump 3 that drives and controls the hydraulic actuators 2 a, 2 b, 2 c, etc., 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 that variably controls the rotation speed of the drive motor 7 based on the detected discharge pressure Po. Therefore, the gear pump 3, which has a simple and compact structure, can be used in a hydraulic injection molding machine M. This allows the drive system to be inexpensively configured, and other advantages of the gear pump 3 can be enjoyed. In addition, a stable discharge flow rate Fo and discharge pressure Po can be ensured in the hydraulic injection molding machine M, enabling highly accurate discharge pressure control and discharge flow rate control to be realized.

[0014] (2) In a preferred embodiment, if the hydraulic actuators 2 a, 2 b, etc. include at least the injection cylinder 2 a and the metering motor 2 b provided in 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) In a preferred embodiment, if the hydraulic actuators 2 a, 2 b, etc. include at least the clamping cylinder 2 c and the ejection cylinder 2 d provided in the clamping device Mc, it is possible to achieve high precision and good balance in the overall control processing 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.

[0016] (4) In a preferred embodiment, if the drive motor 7 is a servo motor 12 connected to a servo circuit 11, the drive control device 1 and the drive control method according to the present invention can be implemented in an optimal manner.

[0017] 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, an overall configuration diagram including the drive control device of the hydraulic injection molding machine, a principle configuration diagram of a cap pump used in the drive control device, an operating characteristic diagram of a cap pump used in the drive control device, and a flowchart for explaining the processing procedure during production of a hydraulic injection molding machine including the drive control device.

[0018] 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

[0019] Next, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

[0020] 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.

[0021] 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 the nozzle touch.

[0022] 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 well-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 well-balanced manner.

[0023] 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 the hydraulic circuit 4 including a valve circuit group 20. Figure 3 shows the basic configuration of the gear pump 3. The gear pump 3 is a fixed-displacement hydraulic pump, having a basic configuration in which a drive gear 32 and a driven gear 33 are disposed inside a housing 31. 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 Figure 3.

[0024] 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.

[0025] 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 portions of the drive gear 32 and the driven gear 33 separate, 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.

[0026] 4 shows the operating characteristics of the cap pump 3, i.e., the relationship between the discharge flow rate Fo (L / min) and the shaft power D (kW) with respect to the discharge pressure Po (MPa). 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.

[0027] 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 main valves, that is, the injection cylinder 2a, the metering motor 2b, the clamping cylinder 2c, the ejection cylinder 2d, and the injection unit moving cylinder 2e. 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.

[0028] Each switching valve circuit 20a is configured with one or more valve components and 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, the metering motor 2b, the mold clamping cylinder 2c, the ejection cylinder 2d, and the injection unit moving cylinder 2e. Each switching valve circuit 20a is connected to the molding machine controller 8, which constitutes the control means, and the valve components and auxiliary hydraulic components, which are composed of electromagnetic components, etc., to be controlled, are switched or variably controlled.

[0029] Furthermore, a flow rate sensor (flow rate detection means) 5 that detects the discharge flow rate Fo of the pressure oil discharged from the gear pump 3 is connected to the discharge line 30o that is connected to the discharge port 31o of the gear pump 3, and a pressure sensor (pressure detection 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 that is connected to the discharge port 31o of the gear pump 3. 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 control means.

[0030] 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.

[0031] 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.

[0032] 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 figures.

[0033] For ease of understanding, the illustrated processing procedure is a typical processing procedure in a hydraulic injection molding machine M as an example.

[0034] 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 in an operating state (Step S2).

[0035] First, a metering process (plasticization process) is performed (step S3). During 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 a pressure control mode (step S41). At this time, the discharge pressure Po detected by the pressure sensor 6 is applied 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 applied to the servo circuit 11. The rotation speed of the servo motor 12 is detected by the rotary encoder 26, and this rotation speed (detected value) is applied to the servo circuit 11.

[0036] 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 and 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.

[0037] 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, the 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.

[0038] 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.

[0039] After the injection process is completed, the resin filled in the cavity of the mold 23 is cooled (Step S6). After the cooling process is completed, the ejection process is performed (Step S7). In the ejection process, the movable mold, which is in a clamped state, moves back from the fixed mold to the mold open position, opening the mold 23, and the ejection cylinder 2d attached to the mold 23 is activated to eject the molded product.

[0040] 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).

[0041]

[0013] Therefore, the drive control device 1 (drive control method) for the hydraulic injection molding machine M according to this embodiment basically comprises the gear pump 3 for controlling the drive of the hydraulic actuators 2a, 2b, 2c..., flow rate detection means 5 connected to the hydraulic circuit 4 that supplies pressure oil discharged from the gear pump 3 and detects a discharge flow rate Fo, 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 the gear pump 3 based on the detected discharge flow rate Fo to perform 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. Therefore, the gear pump 3, which has a simple and compact structure, can be used in the hydraulic injection molding machine M, and therefore the drive system can be inexpensively configured, and other advantages of the gear pump 3 can be enjoyed. In addition, a stable discharge flow rate Fo and discharge pressure Po can be ensured in the hydraulic injection molding machine M, thereby achieving highly accurate discharge pressure control and discharge flow rate control.

[0042] Although the best mode has been described in detail above, the present invention is not limited to such mode, and various changes, additions, and deletions can be made to the detailed configuration, shape, materials, quantities, values, methods (procedures), etc., without departing from the spirit of the present invention.

[0043] 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, etc., but various other hydraulic actuators can be applied. Also, although a flow sensor is used as the flow rate detection means 5 and a pressure sensor is used as the pressure detection means 6, various detection means having similar detection functions can be used. Meanwhile, although the example has been given in which the servo motor 12 connected to the servo circuit 11 is used as the drive motor 7 that rotates and drives the gear pump 3, this does not exclude the use of various drive motors having similar functions.

[0044] 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.

Claims

1. A drive control device for a hydraulic injection molding machine equipped with a plurality of hydraulic actuators that drive and control at least an injection unit and a mold clamping unit, comprising: a gear pump that drives and controls the hydraulic actuators; flow rate detection means connected to a hydraulic circuit that supplies pressurized oil discharged from the gear pump and that detects a discharge flow rate; pressure detection means connected to the hydraulic circuit and that detects a discharge pressure; and a molding machine controller that variably controls the rotation speed of a drive motor that rotates and drives the gear pump based on the detected discharge flow rate, thereby performing feedback control of the discharge flow rate, and 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. A drive control device for a hydraulic injection molding machine according to claim 1, wherein said hydraulic actuator includes at least an injection cylinder and a metering motor provided in said injection unit.

3. A drive control device for a hydraulic injection molding machine according to claim 1, wherein said hydraulic actuator includes at least a clamping cylinder and an ejection cylinder provided in said clamping device.

4. A drive control device for a hydraulic injection molding machine according to claim 1, wherein the drive motor is a servo motor connected to a servo circuit.

5. A method for controlling a hydraulic injection molding machine having a plurality of hydraulic actuators that drive and control at least an injection unit and a mold clamping unit, comprising providing a gear pump that drives and controls the hydraulic actuators, connecting a flow rate detection means that detects the discharge flow rate and a pressure detection means that detects the discharge pressure to a hydraulic circuit that supplies pressure oil discharged from the gear pump, and performing feedback control of the discharge flow rate by variably controlling the rotation speed of a drive motor that rotates and drives the gear pump based on the detected discharge flow rate, and performing feedback control of the discharge pressure by variably controlling the rotation speed of the drive motor based on the detected discharge pressure.

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