JP3573365B2 - Method and apparatus for controlling pressure pin in pressure casting machine - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a control method and a control device for a pressure pin used to locally press a molten metal filled in a mold in a pressure casting machine such as a die casting machine.
[0002]
[Prior art]
In general, in pressure casting, when the molten metal is cooled and solidified after being filled in a cavity in a mold, shrinkage in volume tends to cause shrinkage in the structure of the cast product. Further, since the molten metal is injected into the cavity at a high speed, air is entrained in the molten metal, and a cavity is formed inside the casting. In order to eliminate such defects as shrinkage and voids, shrinkage cavities are prevented by pressing a pressing pin into the molten metal immediately before the molten metal in the cavity is solidified and locally applying pressure. ing.
[0003]
When performing the local pressing method using the pressing pin, it is important to appropriately determine the appropriate pressing force according to the casting conditions and the timing of pressing. Known techniques related to the control of this type of pressure pin are disclosed, for example, in Japanese Patent Publication No. 59-156560, Japanese Patent Application Laid-Open No. 58-9758, and Japanese Patent Application Laid-Open No. 4-118167.
[0004]
In the pressure pin control disclosed in Japanese Patent Publication No. 59-156560, the pressure timing of the pressure pin is controlled to be constant using a timer. According to Japanese Patent Application Laid-Open No. 58-9758, the mold temperature is controlled. This is detected by a sensor, and the operation of the pressure pin is controlled based on the detected temperature. In Japanese Patent Application Laid-Open No. HEI 4-118167, the stroke of the pressure pin is detected, and the timing at which the pressure pin is advanced into the cavity is controlled so that the detected value becomes a predetermined stroke. There has been proposed a method of controlling a pressure pin which presses a molten metal below.
[0005]
[Problems to be solved by the invention]
However, in the technique disclosed in Japanese Patent Publication No. 59-156560, the mold temperature at the start of casting differs from the solidification temperature at the time of stable mold. The quality sometimes fluctuated. According to the technique disclosed in Japanese Patent Application Laid-Open No. 58-9758, there is a problem that it is difficult to control the operation of the pressing pin unless the relationship between the mold temperature or the molten metal temperature and the timing of the pressing timing is clear. As for the temperature, it was difficult to make the relationship between the molten metal temperature and the injection pressure constant.
[0006]
Further, the pressure pin control method disclosed in Japanese Patent Application Laid-Open No. 4-118167 has an advantage that the position of the pressure pin can be directly measured. However, a sensor is attached to each mold and the optimal stroke of the pressure pin is set in advance. It is necessary to set for each pressure pin according to the mold and casting conditions. When the stroke of the pressure pin is set incorrectly, there is a problem that the pressure pin is controlled with the set value.
[0007]
In addition, if a plurality of pressure pins are provided in one mold, and the strokes of the cylinders that drive the pressure pins are different from each other, a sensor must be installed for each of them, and the optimal pressure pin stroke must be adjusted. No. Such setting of the stroke of the pressure pin is slightly different for each pressure pin and for each casting condition, and requires complicated labor.
Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to improve the quality of a casting by automatically controlling the stroke of a pressure pin so as to be optimal for preventing shrinkage cavities. It is an object of the present invention to provide a pressure pin control method and a control device therefor that contribute to the above.
[0008]
[Means for Solving the Problems]
To achieve the above object, the present invention provides a method for controlling a pressure pin in a pressure casting machine that locally pressurizes a molten metal filled in a cavity of a mold with at least one pressure pin. , The pressure pin cylinder driving the pressure pin with no loadfullThe stroke S is measured and the pressure pinfullFrom the stroke S,Predetermined equivalent to the remaining stroke amount for applying pressure at the position before the full stroke and determined regardless of the diameter of the pressure pin or the size of the mold(S-α) in which the minute amount α is reduced is set as the stroke of the pressure pin, and after a predetermined waiting time has elapsed since the filling of the melt into the cavity is started, the pressure pin is advanced, The actual stroke Sf of the pin was measured, and the stroke detection value Sf of the pressure pin was compared with the set stroke (S-α). As a result of the comparison, Sf was not equal to (S-α). Sometimes during the next casting cycleKeIn order to make the stroke detection value Sf close to the set stroke (S-α), the pressure and flow rate of the pressure oil supplied to the pressure pin cylinder and the waiting time from the completion of the filling of the molten metal to the time when the pressure pin is advanced. It is characterized in that at least one parameter is corrected.
[0009]
Further, the present invention is a pressure pin control device in a pressure casting machine for locally pressing a molten metal filled in a cavity of a mold with a pressure pin immediately before solidification, wherein the stroke of the pressure pin is Stroke detecting means for detecting the pressure, the pressure of the fluid supplied to the pressure pin cylinder driving the pressure pin, the pressure pin hydraulic control circuit for controlling the flow rate,From the full stroke S of the pressure pin detected in the no-load state of the pressure pin cylinder, it corresponds to the remaining stroke for applying pressure at a position short of the full stroke, and is related to the diameter of the pressure pin and the size of the mold. Predetermined(S-α) with the minute amount α reduced is set as the stroke of the pressure pin,In the casting cycleThe stroke detection value Sf of the pressure pin is compared with a set stroke (S-α). If the result of the comparison is that Sf = (S-α), the stroke in the next casting cycle is not determined. In order to make the detection value Sf close to the set stroke (S-α), at least one of the pressure and flow rate of the pressure oil supplied to the pressure pin cylinder and the waiting time from the completion of filling of the molten metal to the advancement of the pressure pin is described. Stroke correction means for correcting the parameters of the pressure pin and the pressure pin based on the correction result by the stroke correction meansHydraulic controlA control unit for controlling a circuit is provided.
[0010]
In the pressure pin control device, the stroke detection means can use an absolute type or an incremental type displacement sensor, and also a flow counter for detecting a flow rate of the pressure oil supplied to the pressure pin cylinder. And means for converting the flow rate detected by the flow rate counter into the stroke amount of the pressure pin.
[0011]
In addition, the present inventionThen, the pressure pin hydraulic control circuitA pressure adjusting unit that adjusts the pressure of the hydraulic oil from the hydraulic supply source, a pressure compensating unit that compensates for the pressure of the hydraulic oil that has been pressure-adjusted by the pressure adjusting unit, and a hydraulic oil that has been adjusted by the pressure compensating unit A flow rate adjusting unit for adjusting the flow rate of the hydraulic fluid, a directional switching valve for switching the direction of the hydraulic oil whose flow rate has been adjusted by the flow rate adjusting unit, and a hydraulic cylinder connected to the directional switching valve for performing a reciprocating operation of a pressurizing pin. When, Can be configured.
[0012]
The stroke detecting means includes a flow counter that counts a flow rate of the hydraulic oil that has passed through the direction switching valve in a predetermined unit. And the flow rate measured by the flow counter can be configured to indirectly measure the position of the pressure pin from the correspondence data between the flow rate and the position of the pressure pin stored in advance.
[0013]
Further, it is preferable that the pressure pin hydraulic pressure control circuit be provided independently of the core cylinder hydraulic circuit of the pressure casting machine.
[0014]
[Action]
First, before filling the cavity with the molten metal, the stroke S of the pressure pin is measured in a no-load state, and the predetermined minute amount α at the near position is slightly reduced from the measured stroke S of the pressure pin (S− α) is set as the optimal stroke of the pressure pin in the casting cycle.
When the cavity is filled with the molten metal and a predetermined time has elapsed, the pressure pin moves forward and its actual stroke Sf is measured.
The stroke value Sf of the pressure pin is compared with the value of the set stroke S-α, and the pressure oil supplied to the pressure pin cylinder is adjusted so that the stroke of the pressure pin becomes the set stroke (S-α). The pressure, flow rate, or the value of the parameter that determines the actual stroke of the pressure pin, such as the wait time from the completion of filling of the molten metal to the advancement of the pressure pin, is corrected, and from the next casting cycle, the corrected value is corrected. The pressurizing pin hydraulic pressure control circuit operates based on the parameters, and the stroke of the pressurizing pin is controlled to a fixed set value.
[0015]
Further, in the present invention, a pressure pin pressed immediately before solidification is used to reduce or eliminate a casting cavity by pressing a squeeze pin with a hydraulic cylinder immediately before solidification on a casting during pressure casting using a mold. The stroke amount is measured indirectly from the flow rate measured by a flow counter or the like and the correspondence between the position of the pressurizing pin and the flow rate obtained in advance, and compared with the appropriate stroke of the pressurizing pin. Stroke is in proper rangeToThe operation of the pressure pin is controlled so as not to come off.
[0016]
【Example】
Hereinafter, an embodiment of a method and a device for controlling a pressure pin according to the present invention will be described with reference to the accompanying drawings.
[0017]
FIG. 1 is a block diagram showing a configuration of an apparatus for implementing a method of controlling a pressure pin. Reference numeral 10 indicates a pressure pin. The pressure pin 10 is connected to a piston rod 11 of a pressure pin cylinder 12, and when driven, its tip projects through a mold 14 into the cavity 13. As shown in FIG. 2, the mold 14 includes a fixed mold 16 attached to a fixed board of a die casting machine and a movable mold 17 installed on a movable board. The molten metal 18 is formed by an injection sleeve (not shown). It is filled under pressure.
[0018]
The hydraulic source 2 that supplies pressure oil to the pressure pin cylinder 12 includes a tank 3, a filter 4, a hydraulic pump 5, and a pump motor 6. The hydraulic pressure source 2 is designed to be shared with a hydraulic circuit for a core cylinder (not shown) of a die casting machine.
[0019]
The pressure oil is introduced from the hydraulic pressure source 2 to the pressurizing pin cylinder 12 via the electromagnetic directional control valve 22. In its neutral position, the electromagnetic directional control valve 22Pump 5The port P is connected to the cylinder chamber 12a on the head side of the pressurizing pin cylinder 12, and the port 23 is connected to the cylinder chamber 12a on the end side of the pressurizing pin cylinder 12. The port 24 communicating with the tank port T is connected to communicate with the tank port T. The solenoids 22a and 22b are connected to a control panel 26 of the die casting machine, and are configured so that the electromagnetic direction control valve 22 is switched through the control panel 26 in conjunction with the operation of a release agent spray (not shown) of the die casting machine. I have.
[0020]
The pressure pin cylinder control circuit 28 for controlling the pressure and flow rate of the pressure oil supplied to the pressure pin cylinder 12 includes an accumulator 30, a pressure compensating valve 31, a proportional electromagnetic relief valve 32, a proportional electromagnetic directional flow control valve 33, a check valve. 34.
[0021]
The pressure compensating valve 31 is connected downstream of the accumulator 30, and is introduced into the proportional electromagnetic directional flow control valve 33 in accordance with the fluctuation of the load pressure and the fluctuation of the pressure controlled by the proportional electromagnetic relief valve 32. This is for keeping the pressure of the pressure oil constant. The flow rate of the hydraulic oil actually supplied to the pressurizing pin cylinder 12 through the proportional electromagnetic direction flow control valve 33 is controlled by adjusting the opening of the proportional electromagnetic direction flow control valve 33. When the solenoid 33a is energized, the proportional electromagnetic directional flow control valve 33 is configured such that an inlet-side conduit and an outlet-side conduit communicate with each other and incorporates a microprocessor described later. The opening amount is controlled by the control unit 40 via the amplifier 35 in accordance with the degree of excitation of the solenoid 33a.
[0022]
On the other hand, the proportional electromagnetic relief valve 32 has a solenoid 32a that is excited according to a set pressure via an amplifier 36, and a pressure setting signal output is given from the control unit 40 to the amplifier 36, and the maximum pressure of the hydraulic circuit is Is configured to be set.
[0023]
Next, the control unit 40 includes a central processing unit 41 equipped with a microprocessor, a main storage device 42 having a ROM in which a program is stored and a RAM capable of reading and writing data as needed, an input device 43 and an output device 44. And The central processing unit 41 receives, via the input device 43, a stroke detector 45 for detecting a stroke amount of the pressure pin cylinder 12, a control panel 26 of the die casting machine, and necessary setting data required for controlling the pressure pin. Is connected to a keyboard 46 for inputting a.
[0024]
In this embodiment, the stroke detector 45 is an absolute displacement detector, and uses a differential transformer. In the absolute type stroke detector 45, the output value in a certain stroke is always constant because the origin position is determined by the sensor itself. The stroke detector 45 can be housed and provided in the pressure pin cylinder 12.
[0025]
That is, as shown in FIG. 6, the coil portion 82 is fixed to the cylinder head 80 of the pressure pin cylinder 12, and a sleeve-shaped core 81 is built in the piston 83 so as to cover the coil portion 82. When the piston 83 moves, the built-in sleeve core 81 moves together, so that the positional relationship between the coil portion 82 and the sleeve core 81 is shifted, and a voltage corresponding to the position of the piston 83 is output. Since the piston 83 and the pressure pin 10 are integrally connected, the stroke of the pressure pin 10 can be detected by detecting the position of the piston 83.
[0026]
By using the pressure pin cylinder 12 incorporating the absolute type stroke detector 45 in this manner, the space dedicated to the stroke detection sensor 45 can be reduced, and the restriction due to the pressure pin unit in the mold is minimized. can do. The stroke detector 45 is not limited to the absolute type, but may be an incremental type.
[0027]
The control unit 40 receives a spray operation signal when the casting cycle is started and the spraying device for the release agent is operated, and when the filling of the molten metal into the cavity of the mold 14 is completed, the filling is completed. A signal is input. A known technique of detecting a change in the pressing force of an injection plunger (not shown) or a decrease in injection speed and outputting a filling completion signal is applied to the detection of the completion of filling of the molten metal.
[0028]
On the other hand, a CRT 47 is connected to the output device 44 as a display device, and setting data necessary for controlling the pressure pins 12 can be input from a keyboard 46 in accordance with an instruction displayed on the screen of the CRT 47. Various data indicating the progress of the casting cycle are displayed. The control unit 40 is connected to the amplifier 35 of the flow control valve 34 and the amplifier 36 of the proportional electromagnetic relief valve 33 via signal lines 50 and 51.
[0029]
Next, a method of controlling the pressure pin will be described below with reference to the flowchart of FIG.
First, various data, that is, a constant α, a pressure P, a flow rate Q, a waiting time T1, and a pressing time T2 are input from the keyboard 46 (step S1). These are data input as parameters for determining the optimal stroke of the pressure pin 10.
The constant α is a minute constant determined in advance for each pressure pin according to the casting conditions. Here, the value of the predetermined minute amount α is a value corresponding to the remaining stroke amount for pressing at a position one step before the full stroke, regardless of the diameter of the pressing pin 10 or the size of the mold. Determined, usually in the range of 2-3 mm. In the present invention, the nest generation is performed by controlling the movement of the pressure pin 10 so that the actual stroke detection amount Sf approaches or matches the set value (S-α), where S is the no-load stroke. Suppress.
[0030]
In FIG. 2, assuming that the entire stroke when the pressing pin 10 advances to the most advanced end in a no-load state is S, the central processing unit 41 calculates the stroke amount of S-α as an optimal stroke, The pressure P, P is compared with the stroke Sf, which is the measured value of the stroke actually advanced, and based on the comparison result, the stroke detection amount Sf of the pressure pin 10 approaches the set value (S-α). The parameters such as the flow rate Q and the waiting time T1 are corrected.
[0031]
The pressure P is the operating pressure of the pressure oil supplied to the pressurizing pin cylinder 12 and particularly affects the cracking of the product, and is set by the proportional electromagnetic relief valve 32. The flow rate Q has a great effect on the reduction or elimination of the porosity located at a position farther than the position pressed by the pressure pin. This flow rate Q is a flow rate of the pressure oil per unit time supplied to the pressurizing pin cylinder 12, measured by the flow counter 25, and set by adjusting the opening of the proportional electromagnetic direction flow control valve 33. ing. The waiting time T1 is a time for pressing the pressure pin 10 immediately before solidification, and affects the density of the entire casting. This represents a waiting time from the time when the filling of the molten metal into the cavity 13 is completed to the time when the pressing pin 10 actually starts moving forward. The pressing time T2 represents the time from when the forward movement of the pressure pin 10 starts to the time when the pressure pin 10 stops moving forward any more and the position at that time is actually measured. These α, the waiting time T1, and the pressing time T2 are:Appropriate value based on data obtained from past experience depending on casting conditionsThe waiting time T1 and the pressing time T2, which are set in advance, are measured by timer means (not shown) built in the control unit 40.
[0032]
Next, the mold 14 is opened at the start of the casting cycle, and a release agent is sprayed on the cavity molding surface by a release agent spray (not shown). Pressurized oil is supplied to the pressure pin cylinder 12 at the same time as the application of the release agent. Further, since the operation signal of the release agent spray is output from the control panel 26 of the die casting machine to the control unit 40 (step S2), the central processing unit 41 taking this signal reciprocates a full stroke with no load. The full forward stroke S of the pressure pin 10 is detected via a stroke detector 45. The central processing unit 41 calculates the total stroke S of the pressure pin cylinder 12 based on the output signal of the stroke detector 44, and stores the resulting data in the storage device 42 (step S3).
[0033]
The filling of the molten metal into the cavity 13 of the mold 14 starts, and a filling completion signal notifying the completion of filling is given from the die casting machine control panel 26 to the control device 40 (step S4). When a timer (not shown) is activated from the completion of the filling of the molten metal and the first waiting time T1 elapses (step S5), the solenoid 22a of the electromagnetic direction control valve 22 is energized, and the pressure oil is released from the pressure pin cylinder 12 Is supplied to the cylinder chamber 12a on the head side.
[0034]
As a result, the pressurizing pin 10 starts moving forward to locally pressurize the molten metal just before solidification, and pressurization of the molten metal in the cavity 13 is started. At the same time, the measurement of the stroke of the pressure pin 10 is started, and the timer for measuring the second waiting time T1 is activated (step S6). When the time T2 of the pressing pin 10 elapses (step S7), the stroke Sf at which the pressing pin 10 has actually advanced is detected at this time via the stroke detector 45, and the measured value is stored in the storage device 42. (Step S8).
[0035]
The detection stroke Sf of the pressure pin 10 obtained in this way is compared with the set stroke (S-α). In this comparison, in consideration of the allowable error β, it is actually determined whether or not the stroke Sf is within the range of the set stroke (S−α) ± β (step S9). Processing is executed. The relative relationship between the detection stroke Sf, the set stroke (S-α), and the allowable error β is as shown in FIG.
[0036]
Step S10 is a process when Sf <(S-α) -β, that is, when the pressing of the pressure pin 10 is insufficient. In this case, since the pressure pin 10 does not reach the value (S-α) −β obtained by subtracting the allowable error from the stroke (S−α) set as the optimum value from the casting conditions, the stroke is increased. Need to be done. Therefore, in order to bring the stroke of the pressure pin cylinder 10 closer to the initial set value (S-α) in the next casting cycle, the pressure pin 10 starts to advance from the hydraulic oil pressure P, the flow rate Q, or the end of the molten metal filling. At least one of the parameters in the time period T1 is corrected by adding or subtracting a fixed minute amount, and these parameters are reset in order to perform the next cycle with this correction value.
[0037]
In this case, as for the pressure P and the flow rate Q, as the values are increased, the pressing force of the pressure pin 10 is increased, and the forward speed is also increased. Therefore, ΔP and ΔQ are added to increase the stroke. Conversely, for the standby time T1 from the start of filling to the start of operation of the pressure pin cylinder 12, the correction amount ΔT is used in order to increase the stroke of the pressure pin 10.ButThe data is subtracted, and T1-ΔT data is stored in the storage device 42 as the set time of the timer. In this case, when a parameter that is not corrected, for example, ΔQ and ΔT1, are added, ΔP is set to a value of 0. Note that the values of the correction amounts ΔT1, ΔP, and ΔQ are empirically determined according to casting conditions as appropriate.
Thus, for example, when the pressure P is corrected to P + ΔP, in the next casting cycle, a pressure setting signal corresponding to the correction value is output to the amplifier 36 via the output device 44, and the output of this amplifier is The set pressure of the proportional electromagnetic relief valve 33 is set to P + ΔP. Similarly, when the flow rate Q is corrected to Q + ΔQ, an opening setting signal is output to the amplifier 35, and the proportional electromagnetic direction flow control valve 33 is controlled to an opening proportional to the output of the amplifier 35.
[0038]
On the other hand, step S11 is a process when Sf> (S−α) + β, that is, when the pressure pin 10 is excessively pressed. In this case, since the tip position of the pressure pin 10 actually advances too far beyond the set stroke (S-α), it is necessary to reduce the stroke in the next and subsequent casting cycles. Therefore, as opposed to step S10, for the hydraulic oil pressure P and the flow rate Q of the pressurizing pin cylinder 12, the correction amounts ΔP and ΔQ are subtracted, and for the standby time T until the pressurizing pin 10 cylinder is operated, ΔT Only add.
[0039]
In step S9, (S−α) −β ≦ Sf ≦ (S−α) + β
Is satisfied, there is no need to perform the correction process, and therefore, without performing the correction, the process in the current cycle ends, and the process waits for the start of the next cycle.
[0040]
As described above, the stroke of the pressure pin is corrected toward the optimum value by learning as the casting cycle is repeated, so that the occurrence of nests is effectively prevented and the quality of the cast product is improved. Can be done.
[0041]
In the embodiment described above, control of a single pressure pin 10 has been described. However, the present invention is not limited to this, and may be applied to a die casting machine having a plurality of pressure pins 10. Can be. That is, the pressurizing pin cylinder 12 is connected to the hydraulic pressure source 20 via the direction control valve 23 for each pressurizing pin, and the hydraulic pipes 54 and 55 are branched off for each pressurizing pin on the downstream side of the accumulator 30, respectively. By providing a control circuit equivalent to the pressure pin cylinder control circuit 28, a plurality of pressure pins can be handled.
Even in the case of such a plurality of pressure pins, the stroke after completion of filling the molten metal is detected for each pressure pin, and the stroke detection value Sf and the set stroke (S-α) are determined according to the processing of the above-described flowchart. Based on the comparison result, the pressure P and the flow rate Q of the pressurized oil supplied to the pressurizing pin cylinder 12, the waiting time T1 from the completion of filling the molten metal to the operation of the pressurizing pin, or a combination of these parameters By making the correction, the set stroke can be automatically adjusted without having to adjust the stroke for each individual pressure pin.
[0042]
Next, another embodiment of the present invention will be described with reference to FIG.
[0043]
In the hydraulic circuit diagram of FIG. 5, the hydraulic supply source 60 is shared with the hydraulic circuit of the core cylinder of the die casting machine, as in the first embodiment. The hydraulic source 60 includes a hydraulic pump 62 driven by a pump motor 61. The oil sucked from the tank 65 through the filter 63 is supplied to a pressurizing pin cylinder 67 which is pressurized by the hydraulic pump 62 and drives the pressurizing pin 10 via the electromagnetic directional control valve 66 at the 4-port, 3-position. You.
[0044]
In this embodiment, when the solenoid 66a is energized and the electromagnetic direction control valve 66 is switched so that the port P and the port A communicate with each other, the pressure oil is supplied via the pilot check valve 68 to the cylinder on the end side of the pressure pin cylinder 67. The pressure pin 10 is supplied to the chamber 67a and advances. When the solenoid 66b is excited and the port P communicates with the port B, the pressure pin 10 returns. Since the pilot check valve 68 guides the pressure oil returning from the cylinder chamber 67b on the head side of the pressure pin cylinder 67 to the pilot pressure, it is opened when the load on the pressure pin 10 is too large, Is discharged to the tank side.
[0045]
Such an electromagnetic directional control valve 66 is used for initial adjustment and for pressurizing the pressurizing pin 10 with no load in order to measure the entire stroke S in the same manner as in the first embodiment described above. It is mainly used for controlling the flow direction of the hydraulic oil of the pin cylinder 67. When the molten metal immediately before solidification is locally pressurized by the pressurizing pin 10, a pressurizing pin hydraulic circuit 70 provided exclusively for local pressurization is provided. Thereby, the pressure and the flow rate of the pressure oil supplied to the pressure pin 10 are controlled.
[0046]
The pressurizing pin hydraulic circuit 70 includes an accumulator 71 for accumulating pressure oil supplied from a hydraulic pump 62, a pressure reducing valve 72, a pressure compensating valve 73, a proportional electromagnetic directional flow control valve 74, a proportional electromagnetic relief valve 75, and a relief valve. 76 and the like.
[0047]
Pressure oil is supplied to the accumulator 71 from the hydraulic pump 62 through a filter 77, and the pressure oil pressurized to a predetermined pressure by the accumulator 71 is adjusted to a predetermined pressure at the outlet side by a pressure reducing valve 72. Fluctuations in the pressure of the hydraulic oil due to the operation of the pressure pin 10 are compensated by the proportional electromagnetic relief valve 73. The proportional electromagnetic directional flow control valve 74 switches the direction of the hydraulic oil, adjusts the flow rate, opens when the solenoid is excited, and supplies pressure oil to the cylinder chamber 67a on the end side of the pressurizing pin cylinder 67. Supply.
[0048]
The setting pressure of the hydraulic oil supplied to the pressurizing pin cylinder 67 is set and adjusted by the proportional electromagnetic relief valve 75, and the flow rate of the hydraulic oil is set and adjusted by the proportional electromagnetic directional flow control valve 74. This embodiment is the same as the embodiment, but does not show details of the control device in FIG.
[0049]
The relief valve 76 is a valve that opens when discharging the pressure oil stored in the accumulator 71 to the tank side. The pressure oil is reduced in pressure through the orifice 79 and is led out to the tank side.
[0050]
In this embodiment, a flow counter 78 for counting the flow rate of the pressure oil supplied to the pressurizing pin cylinder 67 in a predetermined unit is provided between the pressurizing pin cylinder 67 and the electromagnetic direction control valve 66. Since the stroke of the pressure pin 10 is proportional to the flow rate of the pressure oil, the position of the pressure pin 10 is indirectly measured using this relationship. In FIG. 5, reference numeral 85 denotes a relief valve for setting the upper limit of the discharge pressure of the hydraulic pump 62.
[0051]
A procedure for operating the pressure pin 10 in the configuration of the above embodiment will be described.
First, when the molten metal is put into the injection sleeve and injected, the molten metal is filled in the cavity. At that time, since the pressure of the injection cylinder rises, this is detected and sent to the control device 40. The control device 40 controls the proportional electromagnetic directional flow control valve 74, the proportional electromagnetic relief valve based on the waiting time T1, the pressing time T2, the flow rate Q, and the pressure P set according to the measured stroke of the pressure pin 10. 75 is controlled. By controlling the flow rate Q and the pressure P independently or individually, it is possible to control the start timing, the operation time, and the stroke (position) of the pressure pin 10.
[0052]
As the control of the pressure pin 10, for example, the same control as in the first embodiment is performed. That is, when the plunger chip steps on the high-speed injection limit switch, the solenoid of the proportional electromagnetic directional flow control valve 74 is excited after the waiting time T1 when the pressure set by the pressure compensating valve 73 and the pressure reducing valve 72 is reached. At this time, the flow rate Q supplied to the pressure pin cylinder 67 is finely controlled, and the casting is squeezed with respect to the pressure pin 10. Since the count value of the flow counter at this time is proportional to the stroke of the pressure pin 10, data on the correspondence between the count value and the stroke is stored in advance, and the arithmetic unit of the control device refers to this data. Thus, the stroke value of the pressure pin 10 pushed immediately before coagulation can be indirectly measured.
[0053]
The measured stroke value is compared with the appropriate value of the stroke of the pressure pin 10. When the pressure pin 10 stops at an appropriate position, the pressure pin 10 is held in the pressurized state for a time T2. Then, the proportional electromagnetic directional flow control valve 74 is de-energized, and the pressure pin 10 retreats and waits until the start of injection in the next casting cycle.
[0054]
On the other hand, when the stroke of the pressure pin 10 deviates from the appropriate value, the same correction processing as in the first embodiment is executed. That is, when the stroke of the pressure pin 10 is shorter than the appropriate value, the flow rate Q is increased, the pressure P is increased, and the time T1 is shortened in proportion to the stroke. When the stroke of the squeeze pin 10 is longer than the appropriate value, the flow rate Q is reduced, the pressure P is reduced, and the waiting time T1 is increased.
[0055]
Thus, the flow rate Q, the pressure P, and the waiting time T1 are corrected, and the stroke of the pressure pin 10 is corrected by learning toward the optimum value after the next casting cycle, as in the case of the first embodiment. It is.
[0056]
【The invention's effect】
As is apparent from the above description, according to the present invention,From the full stroke S of the pressing pin, a predetermined minute amount α corresponding to the remaining stroke amount for pressing at a position before the full stroke and determined regardless of the diameter of the pressing pin or the size of the mold is subtracted (S −α) is set as the stroke of the pressure pin,By comparing the pressure detection value with the stroke detection value of the pressure pin, and correcting the parameters that determine the stroke of the pressure pin, such as the pressure and flow rate of the hydraulic oil of the pressure pin, according to the result of this comparison,OptimalStrokeFor each moldLearning as you go through the casting cycle without the need to pre-set,Within an appropriate range before full strokestrokeButSince the pressure is controlled, the pressure of the molten metal can be effectively pressurized by the pressure pin, so that the occurrence of shrinkage cavities can be prevented and the quality of the cast product can be improved.
In addition, by applying the present invention to a mold having a plurality of pressure pin cylinders, it is possible to automatically control the stroke to an optimum stroke without having to set a stroke for each pressure pin. Is played.
[0057]
In addition, by measuring the stroke of the pressure pin using a flow meter in addition to a displacement sensor, the operation of the pressure pin is controlled, and the hydraulic cylinder is used for the casting during the pressure casting using the mold. The pressure pin can be properly pressed immediately before solidification to reduce or eliminate the cavities.
[0058]
Further, by independently controlling the hydraulic circuit for operating the pressure pin, the pressure pin can be operated with high precision without receiving a pressure fluctuation on the casting machine side.
[Brief description of the drawings]
FIG. 1 is a configuration explanatory diagram showing a configuration of an embodiment of a pressure pin control device according to the present invention.
FIG. 2 is a sectional view showing a pressing pin and a mold.
FIG. 3 is a flowchart showing processing contents of pressure pin control.
FIG. 4 is a diagram for explaining a setting stroke and an allowable range of a pressure pin.
FIG. 5 is a hydraulic circuit diagram showing a main part of a pressure pin control device according to another embodiment.
FIG. 6 is a sectional view showing a configuration of a displacement sensor used as a stroke detector.
[Explanation of symbols]
10 Pressure pin
12 Pressure pin cylinder
13 cavities
20 Hydraulic power source circuit
22 Electromagnetic directional control valve
26 Control panel
28 Pressure pin cylinder control circuit
30 Accumulator
31 Pressure compensating valve ratio
32 proportional solenoid relief valve
33 proportional electromagnetic directional flow control valve
35 amplifier
36 amplifier
40 control unit
60 Hydraulic power source
62 Hydraulic pump
66 solenoid directional control valve
67 Pressure pin cylinder
68 Pilot check valve
70 Pressure pin hydraulic circuit
71 Accumulator
72 Pressure reducing valve
73 Pressure compensating valve
74 proportional electromagnetic directional flow control valve
75 proportional solenoid relief valve

Claims (6)

A method for controlling a pressure pin in a pressure casting machine for locally pressing a molten metal filled in a cavity of a mold with at least one pressure pin,
The full stroke S of the pressure pin cylinder for driving the pressure pin without load is measured,
From the full stroke S of the pressure pin, a predetermined minute amount α corresponding to the remaining stroke amount for pressing at a position just before the full stroke and determined regardless of the diameter of the pressure pin or the size of the mold is reduced (S −α) is set as the stroke of the pressure pin,
After a predetermined waiting time has elapsed since the filling of the molten metal in the cavity was started, the pressure pin was advanced,
The actual stroke Sf of the pressure pin is measured, and the stroke detection value Sf of the pressure pin is compared with a set stroke (S-α). As a result of the comparison, Sf = (S-α) If not, in order to make the stroke detection value Sf in the next casting cycle close to the set stroke (S-α), the pressure and flow rate of the pressure oil supplied to the pressure pin cylinder and the pressure pin A method for controlling a pressure pin in a pressure casting machine, wherein at least one parameter of a waiting time until the steel is advanced is corrected. A pressure pin control device in a pressure casting machine that locally pressurizes a molten metal filled in a mold cavity with a pressure pin immediately before solidification,
Stroke detection means for detecting the stroke amount of the pressure pin;
A pressure pin hydraulic control circuit for controlling the pressure and flow rate of the fluid supplied to the pressure pin cylinder that drives the pressure pin;
From the full stroke S of the pressure pin detected in the no-load state of the pressure pin cylinder, it corresponds to the remaining stroke for applying pressure at a position short of the full stroke, and is related to the diameter of the pressure pin and the size of the mold. (S−α) obtained by subtracting the predetermined minute amount α that is no longer determined is set as the stroke of the pressure pin, and the value of the stroke detection value Sf of the pressure pin and the set stroke (S−α) in the casting cycle is calculated. If Sf is not equal to (S-α) as a result of the comparison, in order to bring the stroke detection value Sf in the next casting cycle closer to the set stroke (S-α), the pressure pin cylinder is moved to the pressure pin cylinder. Stroke correction means for correcting at least one parameter among the pressure of the pressure oil to be supplied, the flow rate, and the waiting time from when the filling of the molten metal is completed to when the pressure pin is advanced;
A control device for a pressure pin in a pressure casting machine, comprising: a control unit that controls the pressure pin hydraulic pressure control circuit based on a correction result by the stroke correction means. The stroke detecting means includes a flow counter for detecting a flow rate of the pressure oil supplied to the pressurizing pin cylinder, and means for converting a flow rate detected by the flow counter into a stroke amount of the pressurizing pin. The control device for a pressure pin in the pressure casting machine according to claim 2. The pressure pin hydraulic control circuit
A pressure adjusting unit that adjusts the pressure of the pressure oil from the hydraulic pressure source,
A pressure compensator that compensates for the pressure of the hydraulic oil that has been pressure-adjusted by the pressure adjuster;
A flow rate adjustment unit that adjusts the flow rate of the hydraulic oil pressure-adjusted by the pressure compensation unit, and a direction switching valve that switches the direction of the hydraulic oil flow rate that is adjusted by the flow rate adjustment unit,
A hydraulic cylinder connected to the direction switching valve and performing a reciprocating operation of a pressure pin;
The control device for a pressure pin in a pressure casting machine according to claim 2, comprising: The stroke detecting means includes a flow counter that counts a flow rate of the hydraulic oil that has passed through the direction switching valve in a predetermined unit. connected to the flow rate measured by the flow counter according to claim 2, characterized in that to indirectly measure the position of the pressure pin from the mapping data of the position of the previously stored flow rate and the pressure pin Control device of pressure pin in pressure casting machine. The control of the pressure pin in the pressure casting machine according to claim 2 or 4, wherein the pressure pin hydraulic pressure control circuit is provided independently of a core cylinder hydraulic circuit of the pressure casting machine. apparatus.

Images