JP2006289461A - Die-casting machine and control method for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a die-casting machine which can manufacture castings of high quality with a stable casting process, and a control method for the same. <P>SOLUTION: The invented die-casting machine is equipped with an injection cylinder 16 which injects molten metal into the cavity of a mold 10, and a control section 22 which controls the pressure of the molten metal to be injected by the injection cylinder 16. The die-casting machine is also equipped with a sleeve 12 which is a passage for feeding the molten metal to the cavity of the mold 10, and a temperature sensor placed near the sleeve 12. The control section 22 estimates the temperature of the overflow section of the mold 10 on the basis of a sleeve temperature detected by means of the temperature sensor and controls the injection pressure of the injection cylinder 16 on the basis of the estimated temperature of the overflow section of the mold 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a die casting apparatus and a method for controlling the die casting apparatus. More specifically, the present invention relates to a die casting apparatus that controls injection pressure based on the temperature of a molten metal and a method for controlling the die casting apparatus.

  In the die casting apparatus, in order to perform casting stably and safely, injection control of molten metal is performed to automate the casting process.

  Die casting equipment that measures the mold temperature, changes the conditions affecting the mold temperature among the casting conditions if the mold temperature is different from the target temperature, and optimizes the conditions affecting the quality of the cast product A control method is disclosed (Patent Document 1).

  In addition, the injection speed and injection time of the molten metal are corrected using the die casting equipment specifications, product parameters, mold parameters, hydraulic accumulator filling pressure as fixed conditions, and mold temperature, hydraulic oil temperature, hydraulic pressure, etc. as variable conditions. A method for controlling a die casting apparatus for setting casting conditions is disclosed (Patent Document 2).

Japanese Patent Laid-Open No. 2001-246452 Japanese Patent Publication 8-13410

  However, in the above prior art, since the position of the temperature sensor for measuring the mold temperature is not optimized, the temperature of the injected molten metal cannot be accurately measured to the required level. Since the viscosity of the molten metal changes depending on the temperature, the molten metal cannot be accurately grasped. Therefore, the injection pressure is too high and the molten metal is ejected from the mold mating surface, or the injection pressure is too low. There has been a problem that the product has become insufficient and the product has become defective.

  An object of the present invention is to provide a die casting apparatus and a method for controlling the die casting apparatus that solve the above-described problems of the prior art.

  The present invention relates to a die casting apparatus comprising an injection cylinder for injecting molten metal into a mold cavity, and a control unit for controlling conditions when die casting is performed using the mold. And a temperature sensor disposed in the sleeve.

  More specifically, the present invention is a die casting apparatus comprising an injection cylinder that injects molten metal into a cavity of a mold, and a control unit that controls conditions when performing die casting using the mold, The control unit obtains a first temperature when the molten metal is supplied to the vicinity of the supply unit from a first temperature sensor disposed in the vicinity of the supply unit of the molten metal to the cavity of the mold, and the first temperature sensor An estimated value of the temperature of the endmost part of the mold is estimated based on the temperature of 1, and a condition for performing the die casting is controlled based on the estimated value.

  In this die casting apparatus, the step of measuring the temperature in the vicinity of the molten metal supply part to the mold cavity as the first temperature, and the estimated value of the temperature at the extreme end of the mold based on the first temperature And a step of estimating, and a condition for performing the die casting can be controlled based on the estimated value.

  In casting, it is particularly important to consider the supply state of the molten metal to the extreme end part such as the overflow part of the mold in order to avoid the injection of the molten metal and the shortage of the molten metal. In the present invention, the temperature in the vicinity of the molten metal supply part to the cavity of the mold is measured as the first temperature, and the first temperature is used as a value directly indicating the temperature of the molten metal. Then, the temperature at the extreme end of the mold that directly indicates molten metal jetting or lack of hot water is estimated based on the first temperature, the viscosity of the molten metal is obtained from the estimated temperature, and the die casting corresponding to the viscosity is performed. Optimize conditions when doing. Therefore, it is possible to avoid the problem that the molten metal is ejected from the mating surfaces of the molds, or the hot water is insufficient and the product becomes defective.

  Furthermore, the control unit obtains a second temperature when the molten metal is filled into the cavity of the mold from a second temperature sensor disposed in the vicinity of the endmost part, and the estimated value is obtained as the first value. It is preferable to correct based on the temperature of 2. Accordingly, when the molten metal is filled in the cavity of the mold, the step of measuring the temperature in the vicinity of the endmost portion as the second temperature, and the estimated value based on the first temperature is set as the second temperature. And a step of correcting based on.

  Thereby, the estimated value of the temperature at the extreme end is compared with the measured temperature (second temperature) in the vicinity of the extreme end, the validity of the estimated value is evaluated, and based on the measured value (second temperature). The estimated value can be corrected. By using the corrected estimated value, the conditions for performing die casting can be made more appropriate.

  For example, it is preferable that the control unit controls an injection pressure of the injection cylinder based on the estimated value. The injection pressure of the injection cylinder can be calculated by a predetermined arithmetic expression. Specifically, the control unit executes a step of estimating the viscosity μ of the molten metal based on the estimated value, and a step of calculating the optimum injection pressure P as the optimum injection pressure P = viscosity μ × coefficient a. It is preferable to control the injection pressure of the injection cylinder as the optimum injection pressure P.

  Thus, in order to obtain the optimum injection pressure, it is preferable that the optimum injection pressure P = viscosity μ × coefficient a by using the Hagen-Poiseuille law. The injection pressure of the molten metal is a condition that directly affects the supply state of the molten metal to the mold. Therefore, an appropriate molten metal supply state can be realized by controlling the injection pressure of the molten metal. That is, it is possible to avoid problems that the injection pressure is too high and the molten metal spouts from the mating surfaces of the molds, or the injection pressure is too low and the hot water is insufficient and the product becomes defective.

  According to the present invention, a high-quality cast product can be manufactured by a stable casting process.

  As shown in FIG. 1, the die casting apparatus according to the embodiment of the present invention includes a sleeve 12, an injection plunger 14, an injection cylinder 16, a rod 18, a hydraulic pressure adjustment unit 20, a control unit 22, and a storage unit 24. . A die 10 is attached to the die casting apparatus to perform casting.

  As shown in the cross-sectional view of FIG. 2, the mold 10 includes a plurality of constituent members 10a and 10b. The component members 10a and 10b are brought into contact with each other face to face by a mold clamping device (not shown). A cavity 10c is formed at the boundary surface between the constituent members 10a and 10b. The cavity 10c is shaped along the outer shape of the cast product to be formed. The component member 10b is provided with a through hole communicating with the cavity 10c, and a sleeve 12 serving as a metal melt supply path is connected to the through hole. That is, the sleeve 12 is attached in the vicinity of the supply port when the molten metal is supplied to the cavity 10c. Further, an overflow portion 10d is provided at the end of the cavity 10c farthest from the molten metal supply port to receive and buffer the overflow of the molten metal when the molten metal is overfilled.

  An injection plunger 14 is slidably fitted to the sleeve 12. The injection plunger 14 is connected by an injection cylinder 16 and a rod 18. The injection cylinder 16 is connected to the hydraulic pressure adjustment unit 20. The injection cylinder 16 is provided with a hydraulic pressure sensor (not shown). The hydraulic pressure adjusting unit 20 is configured to receive a hydraulic pressure control signal from the control unit 22 and supply pressurized oil to the injection cylinder 16 with a hydraulic pressure corresponding to the hydraulic pressure control signal based on a measured value of the hydraulic pressure by the hydraulic pressure sensor. ing.

  A predetermined amount of molten metal is supplied to the sleeve 12 in accordance with control from the control unit 22. The injection cylinder 16 causes the injection plunger 16 to move back and forth in the sleeve 12 via the rod 18 by the hydraulic pressure of the pressurized oil supplied from the hydraulic pressure adjusting unit 20, and fills the cavity 10c with the molten metal supplied to the sleeve 12. .

  In the present embodiment, temperature sensors 30 and 32 are provided on the mold 10 and the sleeve 12, respectively. The temperature sensor 30 is disposed near the inner surface of the extreme end, for example, the overflow portion 10d. The temperature sensor 32 is disposed in the vicinity of the inner surface of the joint between the mold 10 and the sleeve 12. The temperature sensors 30 and 32 are electrical signals for the temperature (overflow temperature Ta) near the extreme end of the mold 10 (overflow section 10d) and the temperature near the molten metal supply section of the mold 10 (sleeve 12) (sleeve temperature Tb). And output to the control unit 22. Since the sleeve 12 is positioned in the vicinity of the molten metal supply portion to the mold 10, it can be said that the sleeve temperature Tb directly indicates the temperature of the molten metal immediately after being supplied to the mold 10. In general, the overflow part 10d is provided at the end most distant from the molten metal supply part, so the overflow temperature Ta is cooled through the cavity of the mold and reaches the end of the mold 10. It can be said that the temperature of the molten metal is directly indicated.

  The control unit 22 is a microcomputer. The control unit 22 is connected to the storage unit 24 so that information can be transmitted. The storage unit 24 stores and holds a control program executed by the control unit 22 and data necessary for the control. The control unit 22 appropriately reads out and uses the control program or control data.

  The control of the die casting apparatus by the control unit 22 is executed along the flowchart of FIG. The control unit 22 stores and holds a preprogrammed control program in the storage unit 24 and executes control of the die casting apparatus by executing the control program. The control unit 22 receives signals from the temperature sensors 30 and 32 and controls conditions for die casting using the mold 10 according to at least one of the overflow temperature Ta and the sleeve temperature Tb. Examples of the die casting conditions include a molten metal injection pressure, a molten metal injection speed, and a temperature of the mold 10. When the viscosity of the molten metal is low and the molten metal may be ejected, the injection pressure of the molten metal is reduced. On the other hand, when the viscosity of the molten metal is high and the hot water is likely to be insufficient, the injection pressure of the molten metal is increased. Moreover, when the viscosity of a molten metal is low and there exists a possibility that a molten metal may eject, the injection speed of a molten metal is reduced. On the other hand, when the viscosity of the molten metal is high and the hot water is likely to be insufficient, the injection speed of the molten metal is increased. Moreover, when the viscosity of a molten metal is low and there exists a possibility that a molten metal may eject, the metal mold | die 10 is cooled and the viscosity of a molten metal is made high. On the other hand, when the viscosity of the molten metal is high and the hot water is likely to be insufficient, the mold 10 is heated to lower the viscosity of the molten metal.

  In the present embodiment, a case where the hydraulic pressure of the pressurized oil supplied from the hydraulic pressure adjustment unit 20 is adjusted will be described as an example. The injection pressure of the molten metal is easier to control than other die casting conditions, and is excellent as a control target in that the supply state of the molten metal to the mold 10 can be directly controlled. Hereinafter, a control method is demonstrated along a flowchart.

  In step S10, a hot water supply instruction signal is output from control unit 22 to a hot water supply apparatus (not shown). The hot water supply device receives a hot water supply instruction signal and supplies a predetermined amount of molten metal into the sleeve 12.

  In step S <b> 12, the control unit 22 reads the sleeve temperature Tb using the temperature sensor 32 provided in the sleeve 12. In the present embodiment, by disposing the temperature sensor 32 in the vicinity of the inner surface of the sleeve 12, the sleeve temperature Tb can be made substantially equal to the temperature of the molten metal supplied to the sleeve 12.

  In step S14, the overflow temperature when the molten metal is filled in the cavity 10c is estimated based on the measured sleeve temperature Tb. Hereinafter, the estimated overflow temperature is expressed as an estimated overflow temperature Tc. The estimated overflow temperature Tc is substantially proportional to the sleeve temperature Tb, and can be expressed as Tc = cTb using the temperature correlation coefficient c. The temperature correlation coefficient c is determined by the material of the molten metal, the shape of the mold, the position of the mold, and the like. The temperature correlation coefficient c is preferably corrected as appropriate during a continuous casting process.

  In step S16, the optimum injection pressure P is determined based on the estimated overflow temperature Tc. The optimum injection pressure P can be determined based on Hagen-Poiseuille's law. Hagen-Poiseuille's law is expressed by equation (1). Here, μ is the viscosity of the molten metal, and a is a coefficient specific to the mold 10.

(Equation 1)
P = μ × a (1)

  As shown in FIG. 4, the viscosity μ of the molten metal can be determined as a function of the temperature of the molten metal for each material of the molten metal. The viscosity μ of the molten metal tends to increase as the temperature of the general molten metal decreases. It is preferable to measure in advance the relationship between the viscosity μ and the temperature for the molten metal to be used, and store and hold it in the storage unit 24 as a correlation table or approximate function of the viscosity μ and temperature.

  Based on the estimated overflow temperature Tc, the control unit 22 obtains the melt viscosity μ using the correlation table or the correlation function held in the storage unit 24. At this time, it is preferable to determine the viscosity μ of the molten metal using the estimated overflow temperature Tc that is an estimated value of the temperature of the overflow part 10d that is considered to be most difficult to fill when the cavity 10c is filled with the molten metal. As a result, the optimum injection pressure P can be appropriately determined so that the molten metal reaches the overflow portion 10d generally located at the end of the cavity 10c without excess or deficiency.

  The coefficient a is the limit coefficient a1 at which the molten metal just spouts when the molten metal having a predetermined viscosity is supplied to the mold to be used at a predetermined pressure. It is defined as a = (a1 + a2) / 2 based on the limit coefficient a2 that occurs. The coefficient a1 and the coefficient a2 are parameters specific to the material and structure of the mold, and are measured in advance for the mold used for die casting and stored in the control unit 22.

  The control unit 22 determines the optimum injection pressure P based on the formula (1) based on the viscosity μ of the molten metal and the coefficient a, and outputs a hydraulic pressure control signal for instructing the optimum injection pressure P to the hydraulic pressure adjustment unit 20.

  In step S18, the molten metal is filled into the cavity 10c with the optimum injection pressure P. The hydraulic pressure adjusting unit 20 receives a hydraulic pressure control signal from the control unit 22 and supplies pressurized oil to the injection cylinder 16 at the optimum injection pressure P. As a result, the molten metal supplied into the sleeve 12 is filled into the cavity 10 c of the mold 10. It is preferable that the temperature correlation coefficient c in the initial state is set high so that the molten metal reaches at least the overflow portion 10d when casting is started.

  In step S20, the control unit 22 reads the overflow temperature Ta of the overflow unit 10d using the temperature sensor 30. In the present embodiment, by disposing the temperature sensor 30 in the vicinity of the inner surface of the overflow part 10d, the overflow temperature Ta can be made substantially equal to the temperature of the molten metal supplied to the overflow part 10d.

  In step S22, the casting is removed from the mold 10. For example, the controller 22 lowers the clamping pressure of the mold clamping device after a predetermined time has elapsed after the melt is filled in the cavity 10c, and separates the constituent members 10a and 10b. As a result, the casting can be removed from the mold 10.

  In step S24, the estimated overflow temperature Tc and the overflow temperature Ta are compared, and it is determined whether or not to correct the temperature correlation coefficient c according to the comparison result. The controller 22 determines whether or not the absolute value of the difference between the estimated overflow temperature Tc estimated in step S14 and the overflow temperature Ta measured in step S20 is within a predetermined threshold. If the absolute value of the difference between the two temperatures is within the predetermined threshold, the process proceeds to step S28, and if not, the process proceeds to step S26.

  In step S26, the temperature correlation coefficient c is corrected. For example, it is preferable that a quotient obtained by dividing the overflow temperature Ta measured in step S20 by the sleeve temperature Tb measured in step S12 is a new temperature correlation coefficient c. However, the present invention is not limited to this, and it is also preferable to perform processing such as correcting the temperature correlation coefficient c by appropriately weighting according to the magnitude of the difference between the estimated overflow temperature Tc and the overflow temperature Ta. It is.

  In step S28, it is determined whether or not to end the casting process. When continuing the casting process, the process returns to step S10.

  As described above, the die casting is appropriately performed by measuring the sleeve temperature Tb, estimating the estimated overflow temperature Tc based on the sleeve temperature Tb and the temperature correlation coefficient c, and changing the die casting conditions based on the estimated overflow temperature Tc. be able to. In particular, by calculating the optimum injection pressure P and injecting the molten metal at the optimum injection pressure P, the molten metal can be supplied to the mold in an appropriate state. Further, by actually measuring the overflow temperature Ta and reviewing the temperature correlation coefficient c based on the overflow temperature Ta, the die casting conditions can be optimized each time the casting process is repeated. In this way, it is possible to suppress the occurrence of defective products due to the injection of the molten metal from the mating surfaces of the molds accompanying the change in the viscosity of the molten metal and the lack of hot water.

It is a figure which shows the structure of the die-casting apparatus in embodiment of this invention. It is a figure which shows the structural example of the metal mold | die used with the die-casting apparatus in embodiment of this invention. It is a figure which shows the flowchart of the control method of the die-casting apparatus in embodiment of this invention. It is a figure which shows the correlation of the viscosity (mu) of a molten metal, and the temperature of a molten metal.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Mold, 10a, 10b Constituent member, 10c Cavity, 10d Overflow part, 12 Sleeve, 14 Injection plunger, 16 Injection cylinder, 18 Rod, 20 Hydraulic adjustment part, 22 Control part, 24 Storage part, 30, 32 Temperature sensor.

Claims (9)

An injection cylinder for injecting molten metal into the mold cavity;
A die casting apparatus comprising: a control unit that controls conditions when performing die casting using a mold;
A sleeve serving as a supply path for supplying molten metal to the mold cavity;
And a temperature sensor disposed on the sleeve. An injection cylinder for injecting molten metal into the mold cavity;
A die casting apparatus comprising: a control unit that controls conditions when performing die casting using a mold;
The control unit obtains a first temperature when the molten metal is supplied to the vicinity of the supply unit from a first temperature sensor disposed in the vicinity of the supply unit of the molten metal to the cavity of the mold, and the first temperature sensor An estimated value of the temperature at the extreme end of the mold is estimated based on the temperature of 1, and a condition for performing the die casting is controlled based on the estimated value. The die casting apparatus according to claim 2,
Further, the control unit obtains a second temperature when the molten metal is filled into the cavity of the mold from a second temperature sensor disposed in the vicinity of the endmost part, and the estimated value is obtained from the first value. A die-casting apparatus, wherein the correction is performed based on the temperature of 2. The die casting apparatus according to claim 2 or 3,
The injection cylinder can control the injection pressure of the molten metal when injecting the molten metal into the mold cavity,
The said control part controls the injection pressure of the said injection cylinder based on the said estimated value, The die-cast apparatus characterized by the above-mentioned. The die casting apparatus according to claim 4, wherein
The control unit estimates the viscosity μ of the molten metal based on the estimated value, calculates the optimum injection pressure P as the optimum injection pressure P = viscosity μ × coefficient a, and sets the injection pressure of the injection cylinder as the optimum injection pressure P. The die-casting device characterized by performing. An injection cylinder for injecting molten metal into the mold cavity;
A control unit for controlling conditions when performing die casting using a mold, and a method for controlling a die casting apparatus comprising:
Measuring the temperature in the vicinity of the molten metal supply part to the mold cavity as a first temperature;
Estimating an estimated value of the temperature of the endmost part of the mold based on the first temperature,
A method for controlling a die casting apparatus, wherein conditions for performing the die casting are controlled based on the estimated value. In the control method of the die-casting device according to claim 6,
Measuring the temperature near the end as the second temperature when the mold cavity is filled with molten metal;
Correcting the estimated value based on the second temperature;
A control method for a die casting apparatus, comprising: In the control method of the die-casting device according to claim 6 or 7,
A control method for a die casting apparatus, wherein an injection pressure of the injection cylinder is controlled based on the estimated value. In the control method of the die-casting device according to claim 8,
Estimating the viscosity μ of the molten metal based on the estimated value;
Calculating the optimum injection pressure P as the optimum injection pressure P = viscosity μ × coefficient a,
A control method for a die casting apparatus, wherein an injection pressure of the injection cylinder is controlled as an optimum injection pressure P.

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