JP6560628B2 - Injection device and molding machine - Google Patents

Description

  The present invention relates to an injection device and a molding machine having the injection device. The molding machine is, for example, a die casting machine.

  In the molding machine, for example, the molding material in the sleeve is extruded by a plunger to fill the molding material into the mold. At this time, the speed of the plunger is made relatively high in order to quickly fill the mold with the molding material without delaying the solidification of the molding material. In order to realize this high injection speed, a die casting machine often employs a configuration including an injection cylinder coupled to a plunger and an accumulator that supplies hydraulic fluid to the injection cylinder (for example, Patent Document 1). Or 2).

  When the pressure of the molding material is relatively high, the molding material is ejected into the gaps between the molds to generate burrs, and the quality of the molded product is degraded. A main factor that causes this burr is a temporary and relatively rapid pressure increase (generation of surge pressure) that occurs when filling of the molding material into the mold is completed. This pressure increase is mainly caused by the inertial force of the molding material or the like pushed out toward the mold, and the amount of the increase generally increases in proportion to the square of the injection speed.

  When reducing the surge pressure, it is generally performed to set the injection speed so that the plunger is decelerated immediately before the surge pressure is generated. Patent Document 1 discloses a technique for providing an accumulator or a spring for absorbing a surge pressure (background art column) and a technique for providing a reverse inertia force generator for canceling the surge pressure. Although Patent Document 2 does not intend to reduce burr or surge pressure, a configuration in which a speed accumulator used in high-speed injection and a pressure increase accumulator used in subsequent pressure increase are provided (to an injection cylinder). A configuration in which the accumulator for supplying the hydraulic fluid is divided into two is disclosed.

JP 2009-183964 A Japanese Patent Laid-Open No. 2001-300715

  If the speed is reduced before the surge pressure is generated as is generally done, for example, it becomes impossible to quickly fill the mold with the molding material. As a result, for example, the quality of the molded product may be deteriorated. Moreover, in the technique disclosed in Patent Document 1, a special configuration must be provided for absorbing or canceling surge pressure.

  Therefore, it is desirable to provide an injection apparatus and a molding machine that can suitably reduce the risk of burrs.

  An injection device according to an aspect of the present invention is set via a drive unit that drives a plunger that pushes a molding material in a sleeve into a mold, an input device that receives an operation for setting molding conditions, and the input device. A control device that controls the drive unit based on molding conditions, and the drive unit is an injection cylinder coupled to the plunger, and a speed accumulator capable of supplying hydraulic fluid to the injection cylinder And a pressure-increasing drive source that generates a driving force transmitted to the plunger, and the control device supplies high-speed injection by supplying hydraulic fluid from the speed accumulator to the injection cylinder in a molding cycle. After that, an injection control unit that controls the drive unit to perform pressure increase by the driving force of the pressure increase drive source, and is set via the input device. Based on the high-speed injection speed as molding conditions, wherein the pressure rate accumulator has a pressure calculation unit for calculating a minimum necessary pressure to achieve the high-speed injection speed.

  Preferably, the injection device further includes a pressure increasing / decreasing unit capable of pressurizing and depressurizing the speed accumulator, and an ACC pressure sensor capable of detecting the pressure of the speed accumulator, and the control device includes a molding cycle. The pressure control unit further controls the pressure increasing / decreasing unit so that the pressure detected by the ACC pressure sensor becomes a target pressure based on the necessary minimum pressure before injection.

  Preferably, the injection device further includes a display device capable of displaying an image, and the control device includes at least one of the calculated minimum necessary pressure and a target pressure based on the minimum necessary pressure. Is further displayed on the display device.

Preferably, the pressure calculation unit calculates the minimum necessary pressure by calculating a predetermined calculation formula, and the calculation formula is a first formula that converts an injection speed into a flow rate of a molding material, P− The second equation for calculating the P intercept of the machine line when Q ^{2 at} the intersection of the die line and the machine line in the Q ² diagram is the square of the flow rate calculated by the first equation, and the second equation Including the third equation for converting the P-intercept calculated by the above equation into the pressure of the velocity accumulator, or at least the substitution of the first equation into the second equation and the substitution of the second equation into the third equation The pressure calculation unit substantially includes the above three formulas arranged in one, and the pressure calculation unit substitutes the set high-speed injection speed into the calculation formula as the injection speed of the first formula. The speed value calculated by equation (3) It calculates a pressure of Yumureta as the minimum necessary pressure.

  Preferably, the injection device further includes an injection pressure sensor capable of detecting an injection pressure, and the pressure calculation unit performs the high-speed injection of the molding cycle performed previously for each one or a plurality of molding cycles. A gate outflow coefficient is calculated based on the injection pressure detected by the injection pressure sensor, and the calculated gate outflow coefficient is used in the second equation.

  A molding machine according to one aspect of the present embodiment includes the above-described injection device.

  According to the present invention, the pressure of the accumulator for injection can be easily adjusted.

The schematic diagram which shows the principal part structure of the injection apparatus of the die-casting machine which concerns on embodiment of this invention. The block diagram which shows the structure of the control system of the injection device of FIG. The schematic diagram which shows the definition of the symbol which concerns on the speed, pressure, and area in the injection device of FIG. Schematic diagram illustrating an example of a P-Q ² line view. The figure which shows an example of the actual value of a gate outflow coefficient. The flowchart which shows an example of the procedure of the process which the injection device of FIG. 1 performs. The flowchart which shows an example of the detail of the cycle process of step ST3 of FIG. The schematic diagram for demonstrating the time-dependent change of the injection speed and injection pressure in the injection device of FIG. FIG. 9A to FIG. 9C are diagrams showing the results of an experiment for confirming the operation of the injection device of FIG.

<Configuration of injection device>
FIG. 1 is a schematic diagram showing a main configuration of an injection apparatus 1 of a die casting machine DC1 according to an embodiment of the present invention. In the following, the left-right direction of the paper (the forward / backward direction of the plunger 5 described later) may be referred to as the front-back direction.

  The die casting machine DC1 manufactures a die cast product (molded product) by injecting a molten metal (a molten metal material) into the mold 101 (cavity 107) and solidifying the molten metal in the mold 101. is there. The mold 101 includes, for example, a fixed mold 103 and a moving mold 105.

  Specifically, the die casting machine DC1 includes, for example, a mold clamping device (not shown) that opens and closes the mold 101, an injection apparatus 1 that injects a molten metal into the mold 101, and a die casting. It has an unillustrated extruding device for extruding a product from the fixed mold 103 or the moving mold 105, and a control device for controlling them. The configuration other than the injection device 1 may be basically the same as various conventional configurations, and a description thereof will be omitted.

  The injection device 1 includes, for example, a sleeve 3 communicating with the cavity 107, a plunger 5 that pushes the molten metal in the sleeve 3 to the cavity 107, a drive unit 10 that drives the plunger 5, and a control device 11 that controls the drive unit 10. have. These configurations are, for example, as follows.

  The sleeve 3 is, for example, a cylindrical member inserted through the fixed mold 103. The plunger 5 has a plunger tip 5a that can slide in the front-rear direction within the sleeve 3, and a plunger rod 5b fixed to the plunger tip 5a. The molten metal is supplied into the sleeve 3 from a hot water supply port 3 a formed on the upper surface of the sleeve 3, and the plunger tip 5 a slides (moves forward) toward the cavity 107 in the sleeve 3, whereby the molten metal is injected into the cavity 107. Is done.

  The drive unit 10 includes an injection cylinder 7 connected to the plunger 5 and a hydraulic device 9 that supplies hydraulic fluid (for example, oil) to the injection cylinder 7.

  The injection cylinder 7 is constituted by, for example, a so-called direct connection type pressure increasing cylinder. Specifically, for example, the injection cylinder 7 is fixed to the cylinder portion 13, the injection piston 15 and the pressure increasing piston 17 slidable inside the cylinder portion 13, and the injection piston 15, and extends from the cylinder portion 13. And a piston rod 19.

  The cylinder part 13 has, for example, an injection cylinder part 13a and a pressure increasing cylinder part 13b connected to the rear end of the injection cylinder part 13a (the side opposite to the side from which the piston rod 19 extends). The injection cylinder part 13a and the pressure increasing cylinder part 13b are, for example, cylindrical bodies having a circular cross section. The injection cylinder portion 13a has a constant diameter in the longitudinal direction, for example. The pressure-increasing cylinder portion 13b includes, for example, a small-diameter cylinder portion 13ba on the injection cylinder portion 13a side, and a large-diameter cylinder portion 13bb located on the opposite side and having a larger diameter than the small-diameter cylinder portion 13ba. The small diameter cylinder part 13ba has a smaller diameter than the injection cylinder part 13a, for example, and the large diameter cylinder part 13bb has a larger diameter than the injection cylinder part 13a, for example.

  The injection piston 15 is disposed in the injection cylinder portion 13a. The inside of the injection cylinder portion 13a is partitioned by the injection piston 15 into a rod side chamber 13r on the side where the piston rod 19 extends and a head side chamber 13h on the opposite side. When the hydraulic fluid is selectively supplied to the rod side chamber 13r and the head side chamber 13h, the injection piston 15 slides in the injection cylinder portion 13a in the front-rear direction.

  The pressure increasing piston 17 has a small-diameter piston portion 17a that can slide the small-diameter cylinder portion 13ba, and a large-diameter piston portion 17b that can slide the large-diameter cylinder portion 13bb. The inside of the large diameter cylinder portion 13bb is partitioned by a large diameter piston portion 17b into a front chamber 13f on the small diameter cylinder portion 13ba side and a rear chamber 13g on the opposite side.

  Therefore, when the pressure in the front chamber 13f is released, the pressure increasing piston 17 is caused by the difference between the pressure receiving area in the head side chamber 13h of the small diameter piston portion 17a and the pressure receiving area in the rear chamber 13g of the large diameter piston portion 17b. A pressure higher than the pressure received from the hydraulic fluid in the rear chamber 13g can be applied to the hydraulic fluid in the head side chamber 13h. Thereby, the injection cylinder 7 exhibits a pressure increasing function.

  The injection cylinder 7 is disposed coaxially with the plunger 5. The piston rod 19 is connected to the plunger 5 via a coupling (reference numeral omitted). The cylinder portion 13 is fixedly provided to a mold clamping device (not shown). Therefore, the plunger 5 moves forward or backward in the sleeve 3 by the movement of the injection piston 15 relative to the cylinder portion 13.

  The hydraulic device 9 includes, for example, a tank 21 that stores hydraulic fluid, a pump 23 that can deliver hydraulic fluid in the tank 21, a speed accumulator 25A and a pressure increase accumulator 25B (hereinafter referred to as pressure accumulator 25B that can discharge accumulated hydraulic fluid). Without distinguishing the two, it may be simply referred to as an accumulator 25.), a plurality of flow paths (first flow path 27A to sixth flow path 27F) that connect these and the injection cylinder 7 to each other, and the plurality of flow paths. And a plurality of valves (first valve 29A to fifth valve 29E) for controlling the flow of hydraulic fluid in the passage.

  In FIG. 1, for convenience of illustration, tanks 21 and pumps 23 are shown at a plurality of locations. In practice, the plurality of tanks 21 and pumps 23 may be integrated into one tank 21 and one pump 23.

  The tank 21 is an open tank, for example, and holds the working fluid under atmospheric pressure. The tank 21 supplies the working fluid to the injection cylinder 7 via the pump 23 and the accumulator 25 and stores the working fluid discharged from the injection cylinder 7.

  The pump 23 is driven by an electric motor (not shown) and delivers hydraulic fluid. The pump may be of an appropriate type such as a rotary pump, a plunger pump, a constant displacement pump, a variable displacement pump, a one-way pump, a bidirectional (two-way) pump, or the like. The electric motor that drives the pump 23 may be of an appropriate system such as a DC motor, an AC motor, an induction motor, a synchronous motor, or a servo motor. The pump 23 (electric motor) may be always driven during operation of the die casting machine DC1, or may be driven as necessary. The pump 23 contributes to supply of hydraulic fluid to the accumulator 25 (accumulation pressure in the accumulator 25) and supply of hydraulic fluid to the injection cylinder 7.

  The accumulator 25 may have an appropriate configuration as long as the pressure (hereinafter sometimes referred to as ACC pressure) can be adjusted. For example, the accumulator 25 is of a weight type, a spring type, a gas pressure type (including a pneumatic type), a cylinder type or a prada type. In the illustrated example, the accumulator 25 is of a cylinder type and includes a cylinder part 31 and a piston 33 that partitions the cylinder part 31 into a liquid chamber 31a and a gas chamber 31b. The liquid chamber 31a can store hydraulic fluid, and the gas chamber 31b is filled with gas (for example, air or nitrogen). When the hydraulic fluid is supplied to the liquid chamber 31a and the piston 33 moves to the gas chamber 31b side, the gas in the gas chamber 31b is compressed, and the accumulator 25 is accumulated. Further, the working fluid is discharged from the liquid chamber 31a using the pressure of the gas.

  The velocity accumulator 25A and the pressure increasing accumulator 25B may have different configurations, may have the same configuration, or may have a configuration (capacity) that can accumulate pressure at a higher pressure. Preferably, the pressure increasing accumulator 25B is configured to be capable of accumulating at a higher pressure than the speed accumulator 25A. Moreover, before discharge | release of hydraulic fluid of a shaping | molding cycle (in operation | use of the accumulator 25), either may accumulate pressure higher than the other. Preferably, in the molding cycle, the pressure increasing accumulator 25B is accumulated at a higher pressure than the speed accumulator 25A.

The pressure-increasing accumulator 25B only needs to be able to apply a larger force (pressure x cross-sectional area) to the plunger 5 (piston 15) than the speed accumulator 25A. For example, when the injection cylinder 7 is of the pressure increasing type as in the present embodiment, the pressure applied by the pressure increasing accumulator 25B to the head side chamber 13h via the rear side chamber 13g and the pressure increasing piston 17 is the speed accumulator 25A. Is higher than the pressure applied to the head side chamber 13h. Specifically, when for example, prior to the pressure side chamber 13f and 0, _{which A 1} a pressure receiving area in the head side chamber 13h of the small-diameter piston portion 17a, a pressure receiving area in the side chamber 13g after the large-diameter piston portion 17b and the _{A 2,} The pressure of the pressure increasing accumulator 25B only needs to be larger than A ₁ / A ₂ times the pressure of the speed accumulator 25A.

  The first flow path 27A connects the pump 23 and the speed accumulator 25A (its liquid chamber 31a). Thereby, for example, hydraulic fluid can be supplied from the pump 23 to the speed accumulator 25A to accumulate the pressure accumulator 25A.

  The second flow path 27B connects the pump 23 and the pressure increasing accumulator 25B (its liquid chamber 31a). Thereby, for example, the hydraulic fluid can be supplied from the pump 23 to the pressure increasing accumulator 25B to accumulate the pressure increasing accumulator 25B.

  The third flow path 27C connects the speed accumulator 25A (its liquid chamber 31a) and the head side chamber 13h. Thereby, for example, the hydraulic fluid can be supplied from the speed accumulator 25A to the head side chamber 13h, and the injection piston 15 can be advanced.

  The fourth flow path 27D connects the pressure increasing accumulator 25B (its liquid chamber 31a) and the rear chamber 13g. Thereby, for example, the hydraulic fluid can be supplied from the pressure increasing accumulator 25B to the rear chamber 13g, and the hydraulic fluid in the head side chamber 13h can be pressurized by the pressure increasing piston 17.

  The fifth flow path 27E connects the rod side chamber 13r and the tank 21. Thereby, for example, the hydraulic fluid discharged from the rod side chamber 13r as the injection piston 15 moves forward can be stored in the tank 21.

  The sixth flow path 27F connects the front chamber 13f and the tank 21. Thereby, for example, the front side chamber 13f can be depressurized and the pressure increasing action by the pressure increasing piston 17 can be obtained.

  FIG. 1 illustrates a typical flow path that the hydraulic device 9 has, and the hydraulic device 9 actually has another flow path (not shown). For example, the hydraulic device 9 has a flow path for supplying hydraulic fluid from the pump 23 to the rod side chamber 13r in order to retract the injection piston 15.

  The plurality of flow paths illustrated or not illustrated is configured by, for example, a steel pipe, a flexible hose, or a metal block. Some of the plurality of flow paths may be shared as appropriate. For example, in the example of FIG. 1, the first flow path 27A and the third flow path 27C are partially shared on the speed accumulator 25A side, and the second flow path 27B and the fourth flow path 27D are the pressure increase accumulator 25B. A part on the side is made common, and a part on the tank 21 side is made common to the fifth flow path 27E and the sixth flow path 27F.

  The first valve 29A is provided in the first flow path 27A, and for example, permits and prohibits the supply of hydraulic fluid from the pump 23 to the speed accumulator 25A, and discharges the hydraulic fluid from the speed accumulator 25A to the tank 21. Contributes to tolerance and prohibition. The first valve 29A is configured by, for example, a direction control valve, and more specifically, is configured by, for example, a 4-port 3-position switching valve driven by a spring and an electromagnet. For example, the first valve 29A prohibits the flow between the speed accumulator 25A and the tank 21 and the pump 23 at one position (for example, neutral position), and from the pump 23 to the speed accumulator 25A at the other position. The flow from the speed accumulator 25A to the tank 21 is prohibited, and at the other position, the flow from the pump 23 to the speed accumulator 25A is prohibited and the flow from the speed accumulator 25A to the tank 21 is prohibited. Is acceptable.

  The pump 23, the tank 21, and the first valve 29A constitute a pressure increasing / decreasing unit 30 that adjusts the pressure by increasing / decreasing the pressure accumulator 25A.

  The second valve 29B is provided in the second flow path 27B. For example, the supply and the prohibition of the supply of the hydraulic fluid from the pump 23 to the pressure increasing accumulator 25B and the operation fluid from the pressure increasing accumulator 25B to the tank 21 are provided. Contributes to permitting and prohibiting emissions. For example, the configuration may be the same as that of the first valve 29A described above, and the description of the first valve 29A is the description of the second valve 29B by replacing the speed accumulator 25A with the pressure increasing accumulator 25B. It's okay.

  The third valve 29C is provided in the third flow path 27C, and contributes to, for example, permitting and prohibiting the supply of hydraulic fluid from the speed accumulator 25A to the head side chamber 13h. The third valve 29C is constituted by, for example, a pilot type check valve. When the pilot pressure is not introduced, the third valve 29C allows the flow of the hydraulic fluid from the speed accumulator 25A to the head side chamber 13h and vice versa. Flow in the direction is prohibited, and when the pilot pressure is introduced, both flows are prohibited.

  The fourth valve 29D is provided in the fourth flow path 27D, and contributes to, for example, permitting and prohibiting the supply of hydraulic fluid from the pressure increasing accumulator 25B to the rear chamber 13g. The fourth valve 29D is constituted by, for example, a logic valve, and is closed when the pilot pressure is introduced, and is opened when the pilot pressure is not introduced.

  The fifth valve 29E is provided in the fifth flow path 27E and contributes to, for example, control of the flow rate of the hydraulic fluid from the rod side chamber 13r to the tank 21. The forward speed of the injection piston 15 is controlled by controlling the flow rate. That is, the fifth valve 29E constitutes a so-called meter-out circuit. The fifth valve 29E is configured by, for example, a pressure compensation flow regulating valve that can keep the flow rate constant even when there is a pressure fluctuation. The fifth valve 29E is used in a servo mechanism, for example, and is configured by a servo valve that can modulate the flow rate in a stepless manner in accordance with an input signal.

  Note that a meter-in circuit may be provided instead of or in addition to the meter-out circuit. For example, a flow rate control valve having the same configuration as the fifth valve 29E may be provided between the speed accumulator 25A and the head side chamber 13h.

  In FIG. 1, the typical valve | bulb which the hydraulic apparatus 9 has is illustrated, and actually the hydraulic apparatus 9 has another valve | bulb not shown. For example, the hydraulic device 9 has a valve for allowing and prohibiting the supply of hydraulic fluid from the pump 23 to the rod side chamber 13r.

  For example, the control device 11 includes a CPU, a ROM, a RAM, an external storage device, and the like, although not particularly illustrated. The control device 11 outputs a control signal (control command) for controlling each part based on the input signal according to a program stored in advance. The control device 11 may be configured as a control device for the injection device 1, and controls not only the operation of the injection device 1 but also the operation of a mold clamping device (not shown) and an extrusion device (not shown). You may be comprised as a control apparatus of machine DC1. Further, the hardware may be distributed in a plurality of positions (a plurality of housings) or may be grouped.

  A signal is input to the control device 11, for example, an input device 35 that receives an operator's input operation, a speed ACC pressure sensor 37 </ b> A that detects the pressure of the speed accumulator 25 </ b> A, and a pressure increase ACC pressure that detects the pressure of the pressure increase accumulator 25 </ b> B. A sensor 37B, a head side pressure sensor 39H that detects the pressure in the head side chamber 13h, a rod side pressure sensor 39R that detects the pressure in the rod side chamber 13r, and a position sensor 41 that detects the position of the plunger 5 (piston rod 19). The control device 11 outputs a signal, for example, a display device 43 that displays information to an operator, an electric motor (not shown) that drives the pump 23, and various valves (the illustrated valve or the illustrated one). Valve for controlling the pilot pressure for the valve).

  The input device 35 and the display device 43 may be appropriately configured, and a part or all of them may be integrally configured. For example, the input device 35 and the display device 43 may include a touch panel and a mechanical switch. The input device 35 receives, for example, an operation for setting molding conditions such as a low injection speed, a high injection speed, and a casting pressure, and an operation for instructing the injection device 1 to start a molding cycle.

  The speed ACC pressure sensor 37A and the pressure-increasing ACC pressure sensor 37B may detect the pressure in the gas chamber 31b or may detect the pressure in the liquid chamber 31a. In FIG. Is illustrated. These pressure sensors may be of an appropriate type such as a resistance type, a capacitance type, and a vibration type.

  The head side pressure sensor 39H and the rod side pressure sensor 39R indirectly detect the pressure applied by the plunger 5 to the molten metal, such as the pressure (injection pressure) applied to the molten metal by the plunger 5 when the molten metal is injected into the cavity 107. is there. A formula for converting the pressure of the hydraulic fluid detected by these pressure sensors into the pressure of the molten metal will be described later. These pressure sensors may be of an appropriate type such as a resistance type, a capacitance type, and a vibration type.

  For example, the position sensor 41 detects the position of the piston rod 19 with respect to the cylinder portion 13 and indirectly detects the position of the plunger 5. The configuration of the position sensor 41 may be appropriate. For example, the position sensor 41 may be fixed to the piston rod 19, and may constitute a magnetic or optical linear encoder together with a scale portion (not shown) extending in the axial direction of the piston rod 19. You may comprise by the laser length measuring device which measures the distance with the member fixed to the piston rod 19. FIG. The position sensor 41 or the control device 11 can also acquire (detect) the speed of the plunger 5 that is a differential value of the detected position.

  FIG. 2 is a block diagram showing the configuration of the control system of the injection apparatus 1.

  When the CPU of the control device 11 executes a program stored in the ROM and / or the external storage device, the control device 11 includes a plurality of functional units (11a to 11d) that perform various operations. The operation of the plurality of functional units is, for example, as follows.

  The injection controller 11a controls the hydraulic device 9 based on signals from the input device 35 and a sensor (for example, the position sensor 41) in order to realize operations related to injection such as low-speed injection, high-speed injection, and pressure increase. Output a signal.

  The pressure calculation unit 11b calculates the pressure that the speed accumulator 25A should hold based on the signal from the input device 35. Further, the pressure calculation unit 11b calculates a coefficient necessary for calculating the pressure (for example, a gate outflow coefficient described later) based on the detection value of the injection pressure sensor (39H, 39R).

  The pressure control unit 11c outputs a control signal to the hydraulic device 9 so that the pressure of the speed accumulator 25A (detected pressure of the speed ACC pressure sensor 37A) becomes the pressure calculated by the pressure calculation unit 11b.

  The display control unit 11 d outputs a control signal to the display device 43 in order to cause the display device 43 to display the pressure calculated by the pressure calculation unit 11 b.

<Outline of basic operation of injection device>
An outline of an example of the basic operation of the injection apparatus 1 having the above configuration will be described.

(Low speed injection)
First, when the clamping of the stationary mold 103 and the movable mold 105 is completed by a mold clamping device (not shown) and the molten metal is supplied to the sleeve 3, the control device 11 advances the plunger 5 at a relatively low speed. Thereby, the molten metal in the sleeve 3 is pushed out toward the cavity 107 while suppressing the air from being entrained by the molten metal. The injection speed (low speed injection speed) at this time may be set as appropriate, but is, for example, less than 1 m / s.

  Specifically, for example, the control device 11 controls the hydraulic device 9 so as to supply the working fluid from the pump 23 to the head side chamber 13h or to supply the working fluid from the speed accumulator 25A to the head side chamber 13h. . The hydraulic fluid in the rod side chamber 13r is discharged, for example, to the tank 21 or returned to the head side chamber 13h via a flow path (not shown). The speed of the plunger 5 is determined based on, for example, the rotation value of the pump 23 (when supplying the working fluid from the pump 23 to the head side chamber 13h), meter-in circuit (not shown), and / or meter-out based on the detection value of the position sensor 41. Feedback control is performed by a circuit (fifth valve 29E).

(High speed injection)
When the position sensor 41 detects that the plunger 5 has reached a predetermined high-speed switching position, the control device 11 advances the plunger 5 at a relatively high speed. Thereby, for example, the molten metal is quickly filled into the cavity 107 without delaying the solidification of the molten metal. The injection speed (high-speed injection speed) at this time may be set as appropriate, but is, for example, 1 m / s or more.

  Specifically, for example, when the hydraulic fluid is not supplied from the speed accumulator 25A to the head side chamber 13h in the low speed injection, the control device 11 opens the third valve 29C and operates from the accumulator 25 to the head side chamber 13h. Allow supply of liquid. Further, for example, when the hydraulic fluid has already been supplied from the speed accumulator 25A to the head side chamber 13h in the low speed injection, the valve (not shown) constituting the meter-in circuit and / or the fifth valve 25E constituting the meter-out circuit is opened. Increase the degree. The hydraulic fluid in the rod side chamber 13r is discharged, for example, to the tank 21 or returned to the head side chamber 13h via a flow path (not shown). The speed of the plunger 5 is feedback-controlled by a meter-in circuit (not shown) and / or a meter-out circuit (fifth valve 29E) based on, for example, a detection value of the position sensor 41.

(Deceleration, pressure increase and holding pressure)
As a result of the high-speed injection, when the molten metal is filled in the cavity 107, the pressure of the molten metal increases and the plunger 5 decelerates. At this time, the pressure of the molten metal temporarily and relatively rapidly rises due to an inertial force of the molten metal or the like, and a so-called surge pressure is generated. Note that deceleration control may be performed by a meter-in circuit (not shown) and / or a meter-out circuit (fifth valve 29E) at an appropriate time before the surge pressure is generated.

  At substantially the same time as the deceleration of the plunger 5, the control device 11 opens the fourth valve 29D. As a result, the hydraulic fluid is supplied from the pressure increasing accumulator 25B to the rear chamber 13g, and the pressure increasing action by the pressure increasing piston 17 occurs. As a result, the pressure of the molten metal in the cavity 107 increases. The rod side chamber 13r and the front side chamber 13f are allowed to discharge the hydraulic fluid to the tank 21, for example. And the pressure of the molten metal converges to a certain magnitude (final pressure, narrowly defined casting pressure). In another viewpoint, the force that the plunger 5 receives from the molten metal is balanced with the force that the pressure increasing accumulator 25B applies to the plunger 5 through the working fluid.

  The timing at which the hydraulic fluid in the head side chamber 13h starts to be pressurized by the pressure increasing piston 17 is preferably after the generation of the surge pressure, and it is preferable that the deviation from the generation of the surge pressure does not become large. The timing at which the control device 11 outputs a control signal for opening the fourth valve 29D may be appropriately set in consideration of a time delay from the timing until the actual pressure increase starts. For example, the output timing is such that when the speed of the plunger 5 detected by the position sensor 41 falls below a predetermined threshold, or the injection pressure detected by the rod side pressure sensor 39R and the head side pressure sensor 39H exceeds the predetermined threshold. May be timed. The threshold value may be set by the manufacturer of the injection apparatus 1 or may be set by an operator.

  The third valve 29C is self-closed as the pressure in the head side chamber 13h increases. However, the third valve 29C may be closed by introducing pilot pressure. The closing timing in this case may be set as appropriate within a range in which unintended deceleration does not occur, and may be before the generation of surge pressure or after the generation of surge pressure.

  After the pressure of the molten metal reaches the final pressure, the pressure of the molten metal is kept constant by continuously applying pressure from the pressure increasing accumulator 25B to the rear chamber 13g. That is, the pressure is maintained.

  When the molten metal is solidified, the mold 5 is opened by a mold clamping device (not shown), the die-cast product is pushed out from the mold by an extrusion device (not shown), and the plunger 5 is retracted by supplying hydraulic fluid to the rod side chamber 13r. Etc. are performed.

<Outline of burr suppression method>
As described above, the generation of surge pressure is one of the main factors that generate burrs. Specifically, the burrs are caused by the surge pressure exceeding the mold clamping force or exceeding the burr blowing limit pressure determined by the gap of the mold 101 and the solidified thickness of the molten metal surface at the time of occurrence of the surge pressure. Occur. Surge pressure is generated by the inertial force of the molten metal and the amount of pressure increase when the surge pressure is generated generally increases in proportion to the square of the (high speed) injection speed. Has been reduced by doing

  In short, in this embodiment, the surge pressure is lowered by lowering the pressure of the speed accumulator 25A. Even in the conventional configuration, the pressure of the accumulator can be adjusted by an operator or the like. However, few operators understand that even if the injection speed is the same, the surge pressure can be lowered by lowering the pressure of the speed accumulator 25A.

  When both high-speed injection and pressure increase are performed by one accumulator (when both the hydraulic fluid is supplied to the head side chamber 13h and the hydraulic fluid to the rear chamber 13g by one accumulator), when the accumulator pressure is reduced, Changes in the pressure of the molten metal from the end of high-speed injection to the final pressure (pressure increase curve, where surge pressure is excluded) are also affected. Therefore, if the pressure of one such accumulator is lowered, the desired quality may not be obtained. However, in the present embodiment, the speed accumulator 25A and the pressure increase accumulator 25B are provided, and the pressure increase is performed by the pressure increase accumulator 25B. Therefore, the setting of the pressure of the speed accumulator 25A has little or no effect on the pressure increase curve.

Further, if the pressure of the speed accumulator 25A is too low, a desired high speed injection speed cannot be realized. Therefore, in the present embodiment, a minimum necessary pressure for realizing a desired high-speed injection speed is calculated using a PQ ² diagram or the like, and the pressure of the speed accumulator 25A is set to the minimum necessary pressure. Set. Note that the PQ ² diagram is generally used to confirm that the mold conditions do not exceed the machine (injection apparatus 1) conditions. do not do.

<Calculation method of minimum necessary pressure>
A method of calculating the minimum necessary pressure for realizing the desired (high speed) injection speed as described above will be described.

(Definition of symbols)
FIG. 3 shows definitions of symbols necessary for explaining the calculation method of the minimum necessary pressure. Specifically, it is as follows.
A _g: the gate area of the mold 101 P _g: pressure of the molten metal in the gate of the mold 101 V _g: velocity of the molten metal in the gate of the mold 101 A _p: tip area P of the plunger tip 5a: pressure of the molten metal in the sleeve 3 V: Speed of the molten metal in the sleeve 3 Q: Flow rate of the molten metal in the sleeve 3 or gate P _t : P when Q = 0
A _r : pressure receiving area in the rod side chamber 13r of the injection piston 15 P _r : pressure in the rod side chamber 13r A _h : pressure receiving area in the head side chamber 13h of the injection piston 15 P _h : pressure in the head side chamber 13h

The gate of the mold 101 is a portion where the cross-sectional area is the smallest between the cavity 107 (product part) and the sleeve 3. A _p, A _r and A _h is the fluid in the moving direction of the plunger 5, or injection piston 15 area to receive a pressure from the (molten or hydraulic fluid) (projected area) is not affected by the unevenness of the basic member surface. V is equivalent to the speed of the plunger 5 and may be referred to as an injection speed V. Q is common to both because of the continuity between the sleeve 3 and the gate. Pressure rate accumulator 25A, in a state where the speed accumulator 25A and the head side chamber 13h is connected, can be regarded as _{P h.}

(Summary of PQ ² diagram)
Figure 4 is a schematic diagram showing an example of a P-Q ² line view.

In the PQ ² diagram, the square Q ² of the flow rate of the molten metal is taken on the horizontal axis, and the pressure P of the molten metal is taken on the vertical axis. Then, the die lines L _D showing the relationship between Q ² and P which satisfies respect mold 101, and machine lines L _M showing the relationship between Q ² and P which satisfies respect injection device 1 is pulled.

Die line L _D, for example, passes through the origin, the slope is positive linear function. The inclination is determined by the shape (dimension) of the mold 101 and the like.

Furthermore, the machine line L _M is, for example, a linear function slope is negative with a section. The inclination and intercept are determined by the conditions of the injection apparatus 1. When the pressure of the rate accumulator 25A decreases, as shown by line L _{M 'of} the two-dot chain line, the machine line L _M is moved to the origin side.

Unlike the present embodiment, generally, the PQ ² diagram is used as follows. First, the pressure of the accumulator is set to a sufficiently large value, the machine line L _M is obtained under these conditions. Further, mold conditions are set, die lines L _D is determined. Then, since the the injection speed V and the like are set flow rate of the squared ^Q 2 _{(and Q} ^{1 2)} is obtained, a point corresponding to _Q ^{1 2} on die line _{L D} Pn1 is obtained. If the origin side than the sought point Pn1 the machine line L _M, the injection speed V is determined to be implemented.

In this embodiment, contrary to the above, obtaining later machine line L _M. Specifically, first, set the injection speed V, determine the point Pn1 on die line L _D corresponding to the injection speed V. Then, a machine line L _M (line L _M ′) passing through the point Pn1 is obtained. When the pressure of the speed accumulator 25A becomes smaller than the pressure corresponding to the calculated machine line L _M (line L _M ′), the machine line L _M moves to the origin side and falls below the point Pn1, and the set injection speed V Cannot be realized. Therefore, by obtaining the machine line L _M passing through the point Pn1, the pressure of the rate accumulator 25A, it will be required minimum required pressure to realize the injection speed V that has been set.

  A specific calculation formula for obtaining the minimum necessary pressure in this way is as follows.

(Basic formula of die line)
When the pressure and speed of the molten metal are applied to Bernoulli's equation, the following equation is established.
P _g / (ρg) + V _g ² / (2 g) + Z _g
= P / (ρg) + V ² / (2 g) + Z _p
= C (const) (1)
Note that ρ is the density of the molten metal, and g is the acceleration of gravity. Z _g and Z _p are vertical heights of the gate and sleeve 3.

Here, in general, since Z _g −Z _p ≈0, V << V _g , and P _g ≈0, Z _g , Z _p , V, and P _g can be omitted, and the following formula can be obtained.
^{_{P = ρV g 2/2 (}} 2)
This formula (2) is the basic formula of the die line.

(Basic formula of machine line)
Since Z _p can be omitted in the equation (1) as described above, the following equation is obtained from the portion (second row and third row) related to the sleeve 3 of the equation (1).
^{P = C'-ρV 2/2} (3)
However, C ′ = ρgC.

  Here, boundary conditions are considered. When the filling of the molten metal into the cavity 107 is completed, since the plunger 5 stops, Q = 0 (V = 0). On the other hand, the pressure of the molten metal becomes the casting pressure Pt. However, the casting pressure Pt referred to here is a case where injection is performed only by supplying hydraulic fluid from the speed accumulator 25A to the head side chamber 13h without providing the pressure increasing cylinder portion 13b, the pressure increasing piston 17 and the pressure increasing accumulator 25B. Of casting pressure. That is, the casting pressure by a single dynamic pressure.

Substituting the above boundary condition Q = 0 and P = Pt into equation (3) yields C ′ = Pt. Substituting this into equation (3) gives the following equation:
^{P = Pt-ρV 2/2} (4)
This equation (4) is the basic equation of the machine line.

(Formula in PQ ² diagram)
The continuous equation between the sleeve 3 and the gate is as follows.
_{Q = C g A g V g} = A p V (5)
Here, C _g is a gate outflow coefficient, and in short, corresponds to a flow coefficient in fluid dynamics using a gate cross-sectional area as a square value of a representative length.

Theoretically, Q = A _g V _g , but since the gate is a portion where the cross-sectional area rapidly decreases, the difference between the theoretical value and the actual value is relatively large. Therefore, in Equation (5), A _g V _g is multiplied by the gate outflow coefficient C _g which is a correction coefficient. The value of the gate discharge coefficient C _g, in general, an average value irrespective of the shape of the mold 101 such as (e.g., about 0.6) is used.

From the above equation (5), the following equation is obtained.
V _g = Q / (C _g A _g ) (6)
V = Q / A _p (7)

When the above equation (6) is substituted into the basic equation (2) of the die line, the die line equation in the PQ ² diagram shown below is obtained.
P = ρQ ² / (2C _g ² A _g ² ) (8)

Further, when the above equation (7) is substituted into the basic equation (4) of the machine line, the following equation of the machine line in the PQ ² diagram is obtained.
P = Pt−ρQ ² / (2A _p ² ) (9)

As shown in the above equation (8), in the die line equation, P is a linear function passing through the origin with Q ² as an independent variable, and its slope is determined by ρ, C _g, and _Ag . Is done. As shown in the above equation (9), in the machine line equation, P is a linear function of negative slope with Q ² as an independent variable and the value of P intercept as Pt, and the slope is ρ and by the _{A p.} In addition, the value Q ₀ ² (FIG. 4) of the Q ² intercept corresponds to the square of the flow rate at the time of idling.

(Calculation formula to calculate the minimum required pressure)
Since Pt in the above equation (9) is a casting pressure at a single dynamic pressure, it is basically proportional to the pressure of the speed accumulator 25A (pressure P _{h of the} head side chamber 13h). Thus, reducing the pressure of the speed accumulator 25A, the value of P slices machine line becomes small, as described with reference to FIG. 4, the machine line L _M is moved to the home side.

On the other hand, as can be understood from Bernoulli's equation, in the PQ ² diagram, the origin side is the side where the mechanical energy is low. Accordingly, the flow rate Q is determined by the desired injection speed V, die line L when the point on the _D has been determined, this point exceeds the side opposite to the origin machine line L _M, the injection speed V This is impossible to realize in the injection apparatus 1. Conversely, if the desired injection points corresponding to the velocity V machine line L _M to the origin side, the injection speed V will be referred to as feasible in the injection device 1.

Therefore, when the points on the die line L _D by the desired injection speed V (coordinates (Qc 2, ^Pc) to) is determined, Pt is a P slice machine line L _M passing through this point, the rate accumulator This is the pressure of the molten metal when the pressure at 25A is the minimum pressure necessary to achieve the desired injection speed V. Then, by converting the Pt to P _h, it can be determined minimal pressure required in the rate accumulator 25A. The specific calculation formula is, for example, as follows.

First, the injection speed V is converted into the flow rate Q. Although the conversion formula overlaps with the formula (5), it is as follows.
Q = A _p V (10)

Next, the casting pressure Pt of single dynamic pressure is calculated from the flow rate Q by the following formula. The following equations are obtained by modifying these equations so as to solve for Pt while eliminating P in equations (8) and (9).
Pt = ρQ ² / (2C _g ² A _g ² ) + ρQ ² / (2A _p ² ) (11)

Next, the casting pressure Pt in terms of the pressure _{P h} of the head side chamber 13h, thereby to obtain the minimum pressure _{P min} of the speed accumulator 25A. The conversion formula is as follows.
P _min = Pt · A _p / A _h (12)

In the above (1), the calculation is performed with P _r = 0. However, in the case where deceleration is performed by the meter-out circuit when filling is completed, the following equation may be used.
P _min = (Pt · A _p + P _{r Ar} ) / A _h (13)
_{Pr in} this case may be set appropriately.

Thus, the calculation formula for calculating the minimum pressure P _min includes three formulas (10) to (12), and the control device 11 (pressure calculation section 11b) calculate. In addition, the calculation formula should just contain these three formulas substantially. That is, the calculation formula is arranged by performing at least one of the substitution of the formula (10) into the formula (11) and the substitution of the formula (11) into the formula (12) (or the formula (13)). It may be a shape.

For example, the calculation formulas may be arranged as follows.
^{_{P min = ρV 2/2 ×}} (1 + A p 2 / (C g 2 A g 2)) (14)
In the above equation (14), the flow rate Q and the casting pressure Pt which is the P intercept of the machine line do not appear, but substantially include the equations (10) to (12).

(Gate runoff coefficient)
As understood from the above equation (11) (or equation (14)), the gate outflow coefficient _Cg is required for the calculation of the minimum pressure _Pmin .

  FIG. 5 is a diagram illustrating an example of an actual measurement value of the gate outflow coefficient. In FIG. 5, the horizontal axis indicates the injection speed V (m / s), and the vertical axis indicates the gate outflow coefficient (dimensionless amount). The plotted marks are shown in different shapes for each gate thickness (Tg (mm)).

  As shown in this figure, the gate outflow coefficient varies depending on the shape and size of the mold 101. In addition, the gate outflow coefficient should be constant regardless of the injection speed V in view of the correction coefficient when the injection speed V is converted into the flow rate Q. Change.

  In general, an average value is used for the gate outflow coefficient regardless of the shape of the mold 101 or the like. In the present embodiment, such an average value may be used, but preferably, a value corresponding to the mold 101 and the injection speed is obtained by actual measurement, and the gate outflow coefficient is preferably used.

Specifically, by substituting the injection speed V and the molten metal pressure P in the following formula obtained from the formulas (7) and (8), an actual measurement value of the gate outflow coefficient is obtained.
C _g = √ ((ρA _p ² V ² ) / (2PA _g ² )) (15)

  As the value of the injection speed V, for example, a target value of the injection speed or a measured value of the injection speed measured by the position sensor 41 may be used. In general, the injection speed is feedback-controlled, and the difference between the target value of the injection speed and the measured value is relatively small.

  Further, the pressure P of the molten metal is indirectly measured by detecting the pressure of the working fluid in the injection cylinder 7 by the head side pressure sensor 39H and the rod side pressure sensor 39R.

Specifically, the meter-out circuit is not provided, or when not in use, using a pressure P _h in the head side chamber 13h which is detected by the head-side pressure sensor 39H, pressure P of the molten metal by the following formula Is obtained.
P = _Ph * _Ah / _Ap (16)

Further, when the meter-out circuit is used, the pressure P _h of the head side chamber 13h which is detected by the head-side pressure sensor 39H, the pressure P _r of the rod side chamber 13r detected by the rod-side pressure sensor 39R The actual measured value of the pressure P of the molten metal is obtained by the following formula.
_{P = (P h A h -P} r A r) / A p (17)

  The injection speed V and the pressure P that are substituted into the above equation (15) are, for example, during high-speed injection. In the case where measured values are used as the injection speed V and the pressure P, measured values at a predetermined time point during high-speed injection may be used, or average values during a predetermined period during high-speed injection may be used. Ideally, both are the same.

The gate outflow coefficient C _g is obtained as an actual measurement value in a trial run, and a constant value may be used for calculating P _min in all subsequent molding cycles, or an actual measurement value is obtained for each molding cycle. The value may be used to calculate P _min in the next molding cycle. Further, an actual measurement value of the gate outflow coefficient may be obtained for every two or more predetermined number of molding cycles, and the actual measurement value may be used for the subsequent predetermined number of molding cycles. In addition, the gate outflow coefficient C _g (and thus the minimum pressure P _min ) may be calculated at an appropriate time. The actual measurement value (and hence the minimum pressure P _min ) of the gate outflow coefficient may be obtained based on the measurement result in one molding cycle, or may be obtained based on the average value of the measurement results in a plurality of molding cycles. Alternatively, when an actual measurement value is obtained for each one or a predetermined number of molding cycles, it may be obtained based on a moving average of measurement results.

(Minimum pressure correction or target pressure calculation based on minimum pressure)
Bernoulli's equation is an equation that is established under various assumptions such as non-viscosity and non-compression. Also, various assumptions are made when the above-described various equations are obtained based on Bernoulli's equation. Therefore, there is a difference between the theoretical minimum pressure P _min calculated based on the above formula and the actual minimum pressure P _min . Correction for eliminating such a deviation may be performed, and the pressure of the speed accumulator 25A may be adjusted so that the minimum pressure P _min after the correction is realized.

Further, minimal pressure P _min of the calculated theoretical falls below the actual minimum pressure P _min, will not be achieved the desired injection speed. Accordingly, the minimum pressure P _min after the correction in consideration of a predetermined margin amount with respect to the theoretical minimum pressure P _min (in another concept, a speed accumulator based on the minimum pressure P _min is used. 25A target pressure).

  The correction (including the addition of the margin) may be performed by, for example, multiplying an appropriate correction coefficient and / or adding an appropriate correction constant. Such a correction coefficient and / or correction constant may be set by the manufacturer of the injection apparatus 1, may be set by an operator, or may be set to an injection speed and an injection pressure detected in a test run or a molding cycle. The control device 11 may calculate and set based on this.

Further, the pressure of the speed accumulator 25A decreases as the hydraulic fluid is released. You may consider the fall amount. For example, assuming that the minimum pressure P _min before correction obtained from the equation (14) is the pressure after injection of the hydraulic fluid, and the target value of pressure before injection is the minimum pressure P _min to be finally obtained. For example, the following correction may be performed.

When the speed accumulator 25 </ b> A is a cylinder type as illustrated in FIG. 1, the product of the pressure and the volume of the gas chamber 31 b can be regarded as substantially constant before and after the movement of the piston 33. Therefore, for example, the pressure and volume when the piston 33 is located at the drive source on the liquid chamber 31a side are P ₀ and V ₀ , the pressure and volume before injection are P ₁ and V ₁ , and the pressure and volume after injection are P When ₂ and _{V 2,} is established the following equation.
P ₀ × V ₀ = P ₁ × V ₁ = P ₂ × V ₂ (18)

V ₀ is determined by the configuration of the speed accumulator 25A. P ₀ can be obtained, for example, by detecting the pressure in the gas chamber 31b when the hydraulic fluid in the liquid chamber 31a is completely discharged by the speed ACC pressure sensor 37A. Accordingly, when the minimum pressure P _min before correction is used as the post-injection pressure P ₂ , the post-injection volume V ₂ (= V ₀ × P ₀ / P ₂ ) is obtained.

The difference V _d (= V ₂ −V ₁ ) between the volume before injection and the volume after injection corresponds to the amount of hydraulic fluid supplied to the head side chamber 13h in low speed injection and high speed injection. This amount is determined by the advance distance of the plunger 5 in the low speed injection and the high speed injection, and the pressure receiving area A _h of the injection piston 15, and ideally fixed for a molding cycle repeated for one mold 101. Value. Therefore, the volume V ₁ (= V ₂ −V _d ) before injection is obtained from the amount of the hydraulic fluid and the volume V ₂ after injection.

Since P ₀ and V ₀ are obtained as described above, the pre-injection pressure P ₁ (= P ₀ × V ₀ / V ₁ ) is obtained as the minimum pressure P _min after correction.

  Note that the pressure change before and after the injection in the speed accumulator 25A may be taken into consideration in consideration of the above-described margin amount without performing such calculation.

(Accumulator pressure adjustment method)
The method for adjusting the pressure of the speed accumulator 25A is performed, for example, by supplying and discharging the hydraulic fluid in the liquid chamber 31a. However, the pressure of the speed accumulator 25A may be adjusted by adjusting the gas amount (mass) of the gas chamber 31b.

(Example of processing procedure)
FIG. 6 is a flowchart illustrating an example of a procedure of processing executed by the injection device 1 (control device 11) in order to realize the operation as described above. This process is started, for example, when the injection apparatus 1 is turned on.

  In step ST1, the control device 11 sets various molding conditions based on an operation on the input device 35 by the operator. The molding conditions set at this time include, for example, the injection speed V (low speed injection speed and high speed injection speed), the switching position from low speed injection to high speed injection, and the final pressure when the pressure is increased by the pressure increasing accumulator 25B. It is.

  In step ST2, the control device 11 determines whether or not an operation for instructing the input device 35 to start a molding cycle has been performed. And the control apparatus 11 progresses to step ST3 at the time of affirmation determination, and waits at the time of negative determination.

  In step ST3, the control device 11 performs a process for performing one molding cycle.

  In step ST4, the control device 11 determines whether a condition for ending the repetition of the molding cycle is satisfied. For example, it is determined whether or not the number of cycles set in step ST1 has been reached, or whether or not the input device 35 has been operated to end the molding cycle. When the determination is affirmative, the control device 11 proceeds to step ST4. When the determination is negative, the control device 11 returns to step ST3 and repeats the molding cycle.

  FIG. 7 is a flowchart showing an example of details of the cycle process in step ST3. However, in this drawing, only the part related to the injection and the part related to the feature of the present embodiment in the molding cycle is shown.

  In step ST11, the control device 11 determines whether or not the molding cycle is the first time. And the control apparatus 11 progresses to step ST12 at the time of affirmation determination, and progresses to step ST13 at the time of negative determination.

In step ST12, the control unit 11, as the value of the gate discharge coefficient C _g, (value eg the injection device 1 manufacturer were recorded in the control unit 11) the initial value in advance controller 11 holds, or steps In ST1, an initial value set by the operator is set. Without molding cycle is from that you can not determine the actual value of the gate discharge coefficient C _g.

In step ST13, the control device 11 uses the value of the injection speed V (the target value set in step ST1 or the actual measurement value in the previous molding cycle) and the actual measurement value of the molten metal pressure P in the previous molding cycle. (15) the calculated formula, and calculates the measured value of the gate discharge coefficient C _g. And the control apparatus 11 sets the calculated actual value as a value of the gate outflow coefficient _Cg . Incidentally, in (15), [rho, the value of _{A P} and _{A g} are, for example, is recorded in advance in the control unit 11 by the operator in step ST1, and the like.

In step ST14, the control unit 11, (target value set, for example, step ST1) injection speed values of V, and using the values of the gate discharge coefficient _{C g} set in step ST12 or ST13, (10) to Expression Equation (12) (or Equation (14)) is calculated, and the minimum pressure P _min is calculated. Incidentally, in these formulas, [rho, the value of A _P and A _g are as described above, it is recorded in advance in the control device 11. As described above, the minimum pressure P _min may be corrected as appropriate.

Although not particularly illustrated, after step ST14, the control device 11 may cause the display device 43 to display the calculated minimum pressure _Pmin .

In step ST15, the control device 11 determines whether or not the pressure P _ACC of the speed accumulator 25A is equal to the minimum pressure P _min . Specifically, the determination of whether or not they are equal is, for example, a determination of whether or not the difference between the pressure P _ACC and the pressure P _min is within a predetermined range. The predetermined range may be set by the manufacturer of the injection apparatus 1 or may be set by the operator. And the control apparatus 11 progresses to step ST19 at the time of affirmation determination, and progresses to step ST16 at the time of negative determination.

In step ST16, the control device 11 determines whether or not the pressure P _ACC of the speed accumulator 25A is lower than the minimum pressure P _min . When the determination is affirmative, the control device 11 proceeds to step ST17, and when the determination is negative, the control device 11 proceeds to step ST18.

In step ST17, the control device 11 pressurizes the speed accumulator 25A to increase the pressure P _ACC . Specifically, for example, the hydraulic fluid is supplied from the pump 23 to the liquid chamber 31a of the speed accumulator 25A.

In step ST18, the control device 11 reduces the pressure P _ACC by reducing the pressure accumulator 25A. Specifically, for example, the hydraulic fluid in the liquid chamber 31a of the speed accumulator 25A is discharged to the tank 21.

After step ST17 or step ST18, the control device 11 returns to step ST15. Therefore, the pressure accumulator 25A is repeatedly pressurized or depressurized until the pressure P _ACC reaches the minimum pressure P _min .

When the molding cycle is repeated and the injection operation becomes stable, the minimum pressure _Pmin is equal between the previous molding cycle and the current molding cycle. On the other hand, the pressure P _ACC of the speed accumulator 25A is lowered by the discharge of the working fluid for injection. Therefore, when the injection operation is stabilized, steps ST15 to ST18 are operations for recovering the pressure reduced by the injection.

In the control for repeating the determination as to whether or not the pressure P _ACC has become the pressure P _min and the pressurization or depressurization, the pressurization amount or the depressurization amount in steps ST17 and ST18 may be a constant value. Further, instead of or in addition to the control of repeating the determination and pressurization or depressurization, pressure adjustment may be performed with a pressurization amount or a depressurization amount corresponding to the difference between the pressure _PACC and the minimum pressure _Pmin. Good.

  In step ST19, the control device 11 performs control for performing low-speed injection. Specifically, for example, the control device 11 supplies the hydraulic fluid from the pump 23 or the speed accumulator 25A to the head side chamber 13h, and the hydraulic device so that the speed of the plunger 5 becomes the low speed injection speed set in step ST1. 9 is controlled.

  In step ST20, the control device 11 determines whether or not the position of the plunger 5 detected by the position sensor 41 has reached a predetermined switching position. And the control apparatus 11 progresses to step ST21 at the time of affirmation determination, and continues low speed injection at the time of negative determination.

  In step ST21, the control device 11 performs control for performing high-speed injection. Specifically, for example, the control device 11 supplies the hydraulic fluid from the speed accumulator 25A to the head side chamber 13h and controls the hydraulic device 9 so that the speed of the plunger 5 becomes the high speed injection speed set in step ST1. To do.

The pressure P _ACC of the speed accumulator 25A is the minimum pressure P _min that can realize the high-speed injection speed set in step ST1, and theoretically, a meter-out circuit and / or a meter-in circuit, etc. Even if the speed control is not performed, the injection speed becomes the set high speed injection speed. However, since there is a difference between the theoretical value and the actual value, in practice, speed control is required.

  In step ST22, the control device 11 determines whether or not the pressure increase start condition is satisfied. And the control apparatus 11 progresses to step ST23 at the time of affirmation determination, and continues high-speed injection at the time of negative determination.

  In step ST23, the control device 11 performs control for increasing pressure. Specifically, for example, the control device 11 controls the hydraulic device 9 so as to supply the working fluid from the pressure increasing accumulator 25B to the rear chamber 13g.

  Steps ST19 to ST23 correspond to the operation of the injection control unit 11a, steps ST11 to ST14 correspond to the operation of the pressure calculation unit 11b, and steps ST15 to ST18 correspond to the operation of the pressure control unit 11c.

(Example of injection speed and injection pressure)
FIG. 8 is a schematic diagram for explaining temporal changes in the injection speed V and the injection pressure P in the injection apparatus 1 of the present embodiment.

  The horizontal axis represents time t, and the vertical axis represents injection speed V and injection pressure P. A line Ln1 indicates a change with time of the injection speed V in the present embodiment and the comparative example. A line Ln2 indicates a change with time of the injection pressure P in the comparative example. A line Ln3 indicates a change with time of the injection pressure P in the present embodiment. However, the line Ln3 partially overlaps the line Ln2, and only the line Ln2 is shown in the overlap. The comparative example here is the same as the present embodiment except for the method of setting the pressure of the speed accumulator 25A.

The injection speed V in the comparative example and the present embodiment is set to the low speed injection speed V _{L at} the initial stage of injection, and then to the high speed injection speed V _H. When the molten metal is filled into the cavity 107 to some extent (time point t1), the injection speed V decreases rapidly, and when the molten metal is substantially filled, the plunger 5 is substantially stopped (time point t2).

Injection pressure P in the comparative example is relatively low pressure P _L in the low-speed injection, then a relatively higher pressure P _H in comparison to the pressure P _L in accordance with the start of high-speed injection. When the melt 107 is filled to some extent (time t1), the injection pressure P increases rapidly, and when the melt is almost filled, a surge pressure (P _S ) is generated (time t2). Thereafter, the injection pressure P increases as the pressure is increased, and reaches a constant value (final pressure).

  The injection pressure P in the present embodiment is substantially the same as that in the comparative example in the low-speed injection and the high-speed injection. The pressure during injection greatly depends on the injection speed V as understood from the equation (3), and the injection speed V is controlled by feedback control so that the set injection speed is achieved. This is because the form and the comparative example are equivalent.

Thereafter, also in the present embodiment, when the molten metal is filled into the cavity 107 to some extent (time t1), the injection pressure P rapidly increases, and when the molten metal is substantially filled, a surge pressure is generated (time t2). However, its size is smaller than the surge pressure (P _S) in the comparative example. This is because the surge pressure (here, the pressure is 0 as a reference) includes the dynamic pressure of the molten metal and the static pressure applied to the molten metal, and because the pressure of the speed accumulator 25A is set low, This is because the static pressure applied to is reduced.

  On the other hand, in the present embodiment, as in the comparative example, the pressure is increased by the pressure increasing accumulator 25B. Therefore, the boosting curve after the surge pressure is generated is almost the same as in the comparative example. That is, setting the pressure of the speed accumulator 25A low does not have a great effect on the boost curve.

(Example of experimental results)
Experiments have confirmed that the theory described above is correct. Specifically, injection was performed without using the pressure-increasing accumulator 25B, and the injection speed V and injection pressure P at that time were measured. Then, the pressure of the speed accumulator 25A was set variously, and the influence of the pressure of the speed accumulator 25A on the injection speed V and the injection pressure P (surge pressure) was confirmed.

Fig.9 (a)-FIG.9 (c) are the figures which show the result of experiment. These horizontal and vertical axes are the same as those in FIG. In each figure, a line Ln11 indicates a change with time in the injection speed V, and a line Ln12 indicates a change with time in the injection pressure P. The pressure before injection of the speed accumulator 25A in each figure is as follows.
FIG. 9 (a): 7.5 MPa
FIG. 9B: 10.0 MPa
FIG. 9C: 13.5 MPa

  From these figures, it can be confirmed that the pressure of the speed accumulator 25A does not significantly affect the injection speed V and the injection pressure P in the low speed injection and the high speed injection. On the other hand, it can be confirmed that the surge pressure can be reduced by reducing the pressure of the speed accumulator 25A.

  In these figures, the pressures after the surge pressure is reduced are different from each other. This is because the pressure increase by the pressure increase accumulator 25B is not performed as described above. Therefore, if the pressure is increased by the pressure increasing accumulator 25B, the pressure after the surge pressure is reduced is higher than the illustrated pressure, and is equivalent to each other in the drawings.

As described above, the injection device 1 according to this embodiment includes the drive unit 10 that drives the plunger 5 that pushes the molding material in the sleeve 3 into the mold 101, the input device 35 that receives an operation for setting molding conditions, And a control device 11 that controls the drive unit 10 based on molding conditions set via the input device 35. The drive unit 10 includes an injection cylinder 7 connected to the plunger 5, a speed accumulator 25 </ b> A capable of supplying hydraulic fluid to the injection cylinder, and a pressure increasing drive source that generates a driving force transmitted to the plunger 5 (in this embodiment). Pressure increasing accumulator 25B). The control device 11 includes an injection control unit 11a and a pressure calculation unit 11b. In the molding cycle, the injection control unit 11a performs high-speed injection by supplying hydraulic fluid from the speed accumulator 25A to the injection cylinder 7, and then increases pressure by the driving force of the pressure-increasing drive source (pressure-increasing accumulator 25B). Thus, the drive unit 10 is controlled. Based on the high-speed injection speed as the molding condition set via the input device 35, the pressure calculation unit 11b calculates the minimum necessary pressure P _min for realizing the high-speed injection speed for the pressure of the speed accumulator 25A.

Therefore, as described above, the pressure increase characteristic can be maintained by the driving force generated by the pressure increasing accumulator 25B while the pressure of the speed accumulator 25A is set low to lower the surge pressure. Since the control device 11 calculates the necessary minimum pressure P _min , the calculation result is automatically used by the control device 11 or manually through an operator, and is set via the input device 35. The ACC pressure for realizing the high injection speed can be set without excess or deficiency. It is expected that there is a difference between the calculated minimum necessary pressure _Pmin and the actual minimum necessary pressure _Pmin . However, a sufficient effect is expected compared to the current situation where the ACC pressure is set to be relatively high.

Further, in the present embodiment, the injection device 1 has a pressure adjusting / depressurizing unit 30 (tank 21, pump 23 and first valve 29A) capable of pressurizing and depressurizing the speed accumulator 25A, and a speed capable of detecting the pressure of the speed accumulator 25A. And an ACC pressure sensor 37A. In the molding cycle, the control device 11 makes the pressure detected by the speed ACC pressure sensor 37A become a target pressure (including the necessary minimum pressure _Pmin itself) based on the minimum required pressure _Pmin before the injection. A pressure control unit 11c that controls the pressure increasing / decreasing unit 30 is further provided.

Therefore, the minimum necessary pressure P _min calculated by the pressure calculation unit 11b is automatically reflected in the pressure of the speed accumulator 25A. As a result, the burden on the operator is reduced. Further, when an actual measurement value of the gate outflow coefficient is obtained in the molding cycle and the obtained actual measurement value is used as the minimum necessary pressure _Pmin , the actual measurement value is quickly reflected in the adjustment of the pressure of the speed accumulator 25A. Can do.

In the above embodiment, the die casting machine DC1 is an example of a molding machine, the molten metal is an example of a molding material, the pressure-increasing accumulator 25B is an example of a pressure-increasing drive source, and the head-side pressure sensor 39H or the head-side pressure The combination of the sensor 39H and the rod side pressure sensor 39R is an example of an injection pressure sensor. The necessary minimum pressure P _min is the necessary minimum pressure itself, but is also an example of a target pressure based on the necessary minimum pressure.

  The present invention is not limited to the above embodiment, and may be implemented in various aspects.

  The molding machine is not limited to a die casting machine. For example, the molding machine may be another metal molding machine, a plastic injection molding machine, or a molding machine that molds a material obtained by mixing wood powder with a thermoplastic resin or the like. Good. In addition, the injection device is not limited to horizontal mold clamping horizontal injection, and may be vertical mold clamping vertical injection, horizontal mold clamping vertical injection, vertical mold clamping horizontal injection, for example. The hydraulic fluid is not limited to oil and may be water, for example.

  The injection device is not limited to one that performs all processes including injection and pressure increase by hydraulic pressure. That is, the injection device may be a so-called hybrid type instead of the total hydraulic type. For example, the low speed injection may be performed by transmitting the driving force of the electric motor to the plunger without passing through the hydraulic fluid. Further, for example, the pressure increase may be performed by transmitting the driving force of the electric motor to the plunger without passing through the hydraulic fluid, or the driving force of the electric motor is transmitted to the pressure increasing piston 17 without passing through the hydraulic fluid. May be performed.

  As understood from the above description, the pressure increasing drive source is not limited to the pressure increasing accumulator 25B, and may be, for example, an electric motor. This is because as long as the pressure-increasing drive source is provided separately from the speed accumulator 25A, the influence of the adjustment of the pressure of the speed accumulator on the boost curve can be reduced. As mentioned in the embodiment, the pressure-increasing drive source only needs to be able to apply a force larger than the force (pressure × cross-sectional area) applied to the plunger by the speed accumulator via the injection cylinder.

  The injection cylinder is not limited to the pressure increasing type, and may be a single acting type (single cylinder type). That is, the injection cylinder may have only the injection cylinder portion 13a and the injection piston 15 in the injection cylinder 7 of the embodiment. However, in this case, it is necessary to increase the driving force of the pressure-increasing driving source. For example, when the pressure increasing drive source is a pressure increasing accumulator that supplies hydraulic fluid to the head side chamber 13h of the single-acting injection cylinder, the pressure increasing accumulator needs to be accumulated at a higher pressure than the speed accumulator. Further, in the directly-coupled pressure-increasing injection cylinder, even if the small-diameter cylinder portion 13ba of the pressure-increasing cylinder portion 13b has the same diameter as the injection cylinder portion 13a (the small-diameter cylinder portion 13ba is not provided from another viewpoint). Good. Further, the pressure increasing type injection cylinder is not limited to a direct connection type, and the injection cylinder portion 13a and the pressure increasing cylinder portion 13b may be separated from each other and connected by a flow path. Further, in the pressure increasing type injection cylinder, the rod side chamber and the front side chamber may not be connected.

  In the embodiment, the control device 11 adjusts the pressure of the speed accumulator 25A by supplying and discharging the hydraulic fluid in the liquid chamber 31a. However, the pressure of the speed accumulator 25A may be adjusted by supplying / discharging the gas in the gas chamber 31b or by an operator.

In an aspect in which the operator adjusts the pressure of the speed accumulator 25A, for example, the control device 11 (display control unit 11d) calculates the calculated minimum pressure P _min or a target pressure (minimum pressure) based on the minimum pressure P _min. P _min itself may be the target pressure) is displayed on the display device 43, and an operator who sees it displays the pressure to adjust the pressure on the injection device 1. This operation may be performed on the input device 35, or may be such that the valve is directly operated.

In the embodiment, the measured value of the gate outflow coefficient is basically obtained except for the first molding cycle. However, the gate outflow coefficient may be an average value (for example, about 0.6) that does not depend on the shape of the mold or the like in all molding cycles. In this case, the target pressure (minimum pressure P _min ) of the speed accumulator 25A may be calculated only once before the molding cycle. As described above, the calculation of the measured value of the gate outflow coefficient (and hence the calculation of the target pressure of the speed accumulator 25A) does not have to be performed for each molding cycle.

The method for calculating the minimum necessary pressure for realizing the set injection speed (high-speed injection speed) is not limited to the one using the concept of the PQ ² diagram. For example, the concept of the mold limit speed may be used. The mold limit speed (Vpc) is the upper limit of the injection speed that can be realized by the molding system in a mold having a certain gate cross-sectional area, and is expressed by the following formula using the pressure (P _ACC ) of the speed accumulator.
^{_{Vpc = 17.4 × √ (A g}} 2 A h P ACC / A p 3)
In the above equation, the minimum necessary pressure can be obtained by back-calculating P _ACC using Vcc as the Vpc. This formula is also based on Bernoulli's theorem.

  In the embodiment, the minimum necessary pressure is calculated by calculating the calculation formula, but the minimum necessary pressure may be calculated (specified) based on the database. For example, the gate cross-sectional area may be divided into a plurality of sections, and a map in which the injection speed is associated with the minimum necessary pressure may be prepared for each section. Such a map can be created by comprehensively considering theory and experiment.

DESCRIPTION OF SYMBOLS 1 ... Injection apparatus, 3 ... Sleeve, 5 ... Plunger, 7 ... Injection cylinder, 10 ... Drive part, 11 ... Control apparatus, 11a ... Injection control part, 11b ... Pressure calculation part, 25A ... Speed accumulator, 25B ... Pressure increase accumulator (Pressure increasing drive source), 35... Input device, 101.

Claims (6)

A drive unit that drives a plunger that pushes the molding material in the sleeve into the mold;
An input device for accepting an operation for setting molding conditions;
A control device for controlling the drive unit based on molding conditions set via the input device;
Have
The drive unit is
An injection cylinder coupled to the plunger;
A speed accumulator capable of supplying hydraulic fluid to the injection cylinder;
A pressure increasing drive source for generating a driving force transmitted to the plunger,
The control device includes:
An injection control unit that controls the drive unit to perform high-speed injection by supplying hydraulic fluid from the speed accumulator to the injection cylinder in a molding cycle, and then increase pressure by the driving force of the pressure increase drive source. When,
A pressure calculation unit that calculates a minimum necessary pressure for realizing the high-speed injection speed with respect to the pressure of the speed accumulator based on a high-speed injection speed as a molding condition set through the input device. The injection device. A pressurizing / depressurizing unit capable of pressurizing and depressurizing the speed accumulator;
An accumulator pressure sensor capable of detecting the pressure of the speed accumulator;
Further comprising
The control device further includes a pressure control unit that controls the pressure increasing / decreasing unit so that a pressure detected by the accumulator pressure sensor becomes a target pressure based on the minimum necessary pressure before injection in a molding cycle. The injection device according to claim 1. A display device capable of displaying images;
The control device further includes an image control unit that causes the display device to display at least one of the calculated minimum necessary pressure and a target pressure based on the minimum necessary pressure. The injection device according to. The pressure calculation unit calculates the minimum necessary pressure by calculating a predetermined calculation formula,
The calculation formula is
The first equation for converting the injection speed into the flow rate of the molding material,
A second equation for calculating the P intercept of the machine line when Q ^{2 at} the intersection of the die line and the machine line in the PQ ² diagram is the square of the flow rate calculated by the first equation; Including a third equation for converting the P-intercept calculated by equation (2) into the pressure of the velocity accumulator, or substituting the first equation into the second equation and substituting the second equation into the third equation Substantially comprising the above three formulas in an organized form by at least one of
The pressure calculation unit substitutes the pressure of the speed accumulator calculated by the third formula by substituting the set high-speed injection speed as the injection speed of the first formula into the calculation formula. The injection device according to any one of claims 1 to 3. An injection pressure sensor capable of detecting the injection pressure;
The pressure calculation unit calculates a gate outflow coefficient based on the injection pressure detected by the injection pressure sensor in the high-speed injection of the molding cycle performed previously for one or a plurality of molding cycles, and calculates the calculated gate The injection device according to claim 4, wherein an outflow coefficient is used in the second equation.   The molding machine which has the injection apparatus of any one of Claims 1-5.

Images