JPH02182365A - Pressurized casting method - Google Patents

Abstract

PURPOSE:To effectively prevent shrinkage hole and to surely execute cutting of a gate by executing pressurizing to molten metal with a pressurizing plunger while lowering action pressure to an injection plunger for filling up the molten metal into a die. CONSTITUTION:The molten metal 37 in an injection sleeve 39 is filled up into cavity 38 with ascending action of a plunger tip 36a of the injection plunger 36. Successively, the pressurizing plunger 40 fitted to a cylinder piston 32 of a pressurizing cylinder 31 projects in the cavity 38 to execute feeder head action and the gate cutting after solidifying the molten steel, is executed. In this pressurized casting method, while lowering the action pressure to the injection cylinder 19 by controlling a pressure control valve 17 with an injection pressure controller 16, a solenoid 23a in a direction changing-over valve 23 is excited, and by projecting the pressurizing plunger 40 fitted to the cylinder piston 32 of the pressurizing cylinder 31 into the cavity 38, the feeder head action corresponding to shrinkage size accompanied with cooling of the molten metal 37 is executed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a casting method for molding a molded product by injecting molten metal into a cavity of a die of a die-casting machine, and particularly,
This invention relates to a pressure casting method in which the process of pressurizing the molten metal in the mold in the latter half of the injection process is improved and computer-controlled.

[Prior Art] FIGS. 2 and 3 are longitudinal sectional views showing the main parts of a tie casting machine for forming disc wheels, and FIG. 2(a)
- (e) are diagrams showing the molding process, and Figure 2 (f) is the second
As shown in FIG. 3, which is an enlarged view of part A in FIG. 3(d) and FIG. The lower mold 35 and the four horizontally movable cores 34 are aligned and clamped from above and below in the figure by a mold clamping mechanism (not shown), and the injection sleeve 39 is inserted into the cavity 38 formed thereby. The molten metal 37 of
Filling is performed by the lifting action of the injection plunger 36 and the plunger tip 36a that operates integrally with the injection plunger 36 by the action of an injection cylinder (not shown).

FIG. 2(a) shows an injection sleeve 39 containing molten metal 37.
FIG. 2(b) shows a state in which the injection sleeve 39 and the cavity 38 are brought into contact with the lower die 35 and the runners of the cavity 38 are connected, and FIG. For example, as shown in Japanese Unexamined Patent Application Publication No. 63-40659, the rising speed of the injection plunger 36 is reduced and the molten metal 37 is kept quiet without scattering. cavity 38
Normally, this timing is determined by detecting the position of the injection plunger 36 with a limit switch (not shown), and at the same time a cooling timer is started. FIG. 2(C) shows a state in which the cavity 38 has been filled with the molten metal 37, and the molten metal obtained by detecting that the working pressure of an injection cylinder (not shown) has exceeded a predetermined pressure value. After a predetermined time (pressurization time lag) has elapsed from the time of completion of filling of 37, the direction switching valve 2 shown in FIG.
By energizing the solenoid 23a of No. 3, the pressurizing plunger 4o attached to the cylinder piston 32 of the pressurizing cylinder 31 is made to protrude into the cavity 38 as shown in FIG. The molten metal 37 inside is pressurized to perform a feeder action commensurate with the shrinkage allowance (solidification shrinkage) accompanying cooling of the molten metal 37. In FIG. 3, 5 is a pump, 4 is a motor for driving the pump 5, and 7 is a tank, which constitutes a pressure source for driving the pressurizing cylinder 31. As shown in FIGS. 2(d) and 2(f), in the final stage of pressurization, the pressurizing plunger 40 is inserted into the cavity 3.
8 to the position of the gate portion 38a (gate seal position M). That is, a thin molten metal solidified material 41 is formed by lowering the pressure plunger 40, which has a diameter slightly smaller than the gate part 38a and has a narrow gap d between it and the inner peripheral surface of the gate part 38a, to the gate sealing position. Then, when the cooling timer described above completes timing, the clamping by the mold clamping mechanism and the pressurization by the injection plunger 36 are released, and as shown in FIG. 2(e),
A mold opening operation is performed between the upper mold 33 and the core 34 and the lower mold 35 so that the biscuit 43 can be easily cut from the thin part 41 formed between the molded product 42 and the biscuit 43.

[Problems to be Solved by the Present Invention] At this time, the operation of the pressurizing plunger 40 is, for example, as previously proposed in Japanese Patent Application No. 63-244552 by the present applicant. The best method is to control the history of the protrusion stroke amount into the cavity 38 so that it follows a predetermined target trajectory over time. This is because the amount of heat from the molten metal 37 causes the pressure plunger 4 to
0. Although the upper die 33 undergoes dimensional changes, the condition is not uniform due to differences in the coefficient of thermal expansion and cooling conditions of the two, so simply controlling the operating pressure of the pressurizing plunger 40, that is, the feeder force, will not reduce the frictional resistance. This is because the stroke of the pressurizing plunger 40 is not uniform due to external factors such as changes in the molten metal and insertion of molten metal, and the above-mentioned feeder action is not stable.

When controlling the protrusion stroke amount of the pressure plunger 40 to follow a predetermined target trajectory, first, the pressure plunger 40 is adjusted based on the time t from the start of operation of the pressure plunger 40 (1=0). 40 into the cavity 38 is predetermined in the model unit 9 as a target trajectory, the movement stroke amount s with this target trajectory.
t and 1 Cylinder piston 32 detected by position detector 3
, that is, the actual movement stroke of the pressurizing plunger 40!
The deviation amount e (e=st-stb) from 1stb is determined by the deviation detection section 10, and upon receiving this deviation amount e, the gain setting section 8 processes it appropriately, and outputs a predetermined output signal V corresponding to the deviation amount e to the driver 12. Output.

The driver 12 outputs an output signal p according to the magnitude of the output signal V from the gain setting section 8 to adjust the pressure regulating valve 6 and control the pressure P of the pressure source.

In addition, model part 9. The deviation detection section 10 and the gain setting section 8 constitute a feedback controller 11.

In this way, by changing the working pressure that drives the pressurizing plunger 40 according to the deviation amount e between the target locus st and the actual moving stroke amount sob of the pressurizing plunger 40, the moving stroke of the pressurizing plunger 40 with respect to time can be changed. By configuring the control so that the amount follows the target trajectory, it is possible to eliminate the factors of unstable operation such as fluctuations in the sliding resistance of the pressurizing plunger 40 mentioned above.

In this technical background, it was possible to simultaneously lower the pressurizing plunger 40 to the gate sealing position shown in FIGS. 2(d) and (f) in the final stage of pressurizing. ) Due to the structure of the mold, the movement stroke of the pressurizing plunger 40 until reaching the gate sealing position is long, and the volume of the molten metal 37 removed by the pressurizing plunger 40 until reaching the gate sealing position is insufficient for cooling the molten metal 37. 2) As the molding process continues, the temperature of the mold becomes stable and the injection plunger 36 cools the molten metal 37. At the filling stage, when the molten metal 37 becomes sufficiently easy to flow into the cavity 38 and the filling force from the injection plunger 36 acts effectively and the filling density increases relatively, the pressurizing cylinder 31 outputs its maximum output. However, the pressurizing plunger 40 may not reach the gate sealing position. Particularly, in the gate sealing stage, the biscuit part 43 (molten metal 37 of the injection sleeve 3
9) has already solidified, so the working pressure from the pressurizing plunger 40 does not act on the injection plunger 36 as pressure propagation. 36 will not be pushed back.

If the pressurizing plunger 40 does not finally reach the gate sealing position, the cross-sectional area of the solidified molten metal in the gate portion 38a becomes equal to the gate area, and therefore becomes extremely large compared to the normal state. Therefore, in the gate cutting operation shown in FIG. 2(e), the force required for cutting is very large.As shown in FIG. The cutting force is large because the mold is opened by opening the mold with a
The force pulling the disc wheel downward in the state shown in the figure was nothing short of great, which caused distortion in the disc wheel and resulted in a defective product.

[Means for Solving the Problems] In the present invention, in order to solve such problems,
When filling the mold with molten metal by the action of an injection device having a plunger and pressurizing the molten metal in the mold by the action of a pressurizing device having a pressurizing plunger, the pressure applied to the injection plunger is released. However, the molten metal was pressurized using a pressure plunger.

[Function] By pressurizing the molten metal with the pressurizing plunger while releasing the acting pressure on the injection plunger, the pressurizing plunger 40 can finally reach the gate sealing position reliably,
A thin solidified molten metal is formed and penetrated. As a result, the molded product and biscuit portion are easily cut from the formed thin wall portion by a mold opening operation.

[Example] This will be explained with reference to FIG. Note that elements having the same functions as those explained in FIG. 2.3 above are given the same numbers, and detailed explanations are omitted here.

Model part 9. The signal V processed and outputted through the deviation detection section 10 and the gain setting section 8 is outputted to the driver 12. The pressure reduction command unit 14 is programmed, for example, as shown in FIG.
A time tl at which a movement stroke st is received and which is set in advance.

Alternatively, the pressure reduction command da is applied to the injection pressure controller 16 at the time when the movement stroke st1 or more is reached.

The injection pressure controller 16 adjusts the pressure control valve 17 to
By controlling the pressure generated by the pressure source 18, that is, the working pressure of the injection cylinder 19, the filling pressure into the cavity 38 by the injection plunger 36 of melt/1!37 is controlled. In addition, model part 9. Deviation detection section lO, gain setting section 8
The mold opening command device 14 constitutes a feedback controller 15.

Now, as in FIG. 2.3, the upper mold 33. which can be opened and closed in the vertical direction. The lower mold 35 and the four horizontally movable cores 34 are aligned and clamped from above and below in the figure by a mold clamping mechanism (not shown), and the injection sleeve 39 is inserted into the cavity 38 formed thereby. The piston 20 of the injection cylinder 19 raises the injection plunger 36 and the plunger tip 36a that operates integrally with the injection plunger 36 to fill the cavity 38 with the molten metal 37. state).

After a predetermined time (pressurization time lag) has elapsed since the completion of filling the molten metal 37, the solenoid 23a of the direction switching valve 23 is energized to move the pressurization plunger 40 attached to the cylinder piston 32 of the pressurization cylinder 31 into the cavity. 38, the molten metal 37 in the cavity 38 is pressurized, and a riser action corresponding to the shrinkage allowance (solidification yield 1 il) accompanying cooling of the molten metal 37 is performed. Pressure plunger 40
The operation of the feed bar 2 is controlled by the feed bar controller 15 as described above.
The configuration is such that follow-up control is performed with respect to the target trajectory st. That is, the operation of the pressurizing plunger 40 is performed by predetermining the movement stroke amount of the pressurizing plunger 40 into the mold cavity 38 as a target trajectory st, and following this target trajectory i.
! By changing the working pressure that drives the pressurizing plunger 40 according to the deviation amount between the moving stroke amount of the pressurizing plunger 40 set as JsL and the actual moving stroke amount,
The moving stroke amount of the pressurizing plunger 40 is controlled in a follow-up manner. At this time, the feedback controller 15 outputs the time E or the movement stroke st from the model section 9 to the pressure reduction command unit 14, and the fourth
As shown in the figure, the preset time t1. or
It is determined whether the movement stroke st1 or more has been reached. Incidentally, as shown in the model section 9, the time t+ or the moving stroke stl mainly applies to the area r1 that provides the feeder effect and the gate that mainly causes the pressurizing plunger 40 to reach the gate seal position stg. r which is the cutting area
A boundary point with 2 is set.

If the determination condition by the pressure reduction command device 14 is satisfied, a pressure reduction command dC is outputted to the injection pressure controller 16. In response to the pressure reduction command dc, the injection pressure controller 16 gradually reduces the filling pressure pm of the molten metal 37 into the cavity 38 by the injection plunger 36, as shown in the time-pressure P diagram in FIG.

The pressure control valve 17 is controlled so that the tc waiting time drops to zero. Here, the tc waiting time is determined by taking into consideration the time required for the pressurizing plunger 40 to finally reach the gate sealing position, but usually it takes a relatively long time, several seconds or more, to reduce the filling force by the injection plunger 36. do. Therefore, in the final stage of pressurization, when the pressurizing plunger 40 moves to the gate sealing position, the filling force by the injection plunger 36 is simultaneously reduced, making it easier to operate.
It becomes possible to reliably reach the gate seal position without being affected by the problems l) and 2) described above. Moreover, it does not impair the boiling water effect,
It is also possible to effectively provide a feeder against solidification shrinkage caused by cooling of the molten metal 37.

[Effects of the Invention] In the present invention, as described above, not only is it possible to effectively prevent so-called cavities that tend to occur during solidification and shrinkage of molten metal, but also it is possible to achieve reliable gate cutting. This eliminates the possibility of causing severe distortion, and improves both the molding yield rate and the yield rate.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of a device for implementing the method of the present invention, and FIGS. 2(a) to (e) show the operating sequence in an example of a conventional device similar to the present invention. FIG. 2(f) is a partially enlarged view of FIG. 2(d), and FIG. 3 is a block diagram showing an example of the conventional device as shown in FIGS. 2(a) to (e). FIG. 4 is a flow diagram showing a part of the control state in the present invention, and FIG. 5 is a time pressure diagram showing the control state in the present invention. 3...Position detector, 6...Pressure regulating valve,
8...Gain setting section, 9...Model section. lO... deviation detection section, 12... driver,
14...Decompression command device. 15...Feedback controller. 16... Injection pressure controller, 17... Pressure control valve, 19... Injection cylinder, 31... Pressure cylinder, 34... Core, 36... Injection plunger, 38... Cavity , 40...pressure plunger. 33...upper mold, 35...lower mold. 37... Molten metal, 39... Injection sleeve,

Claims (1)

[Claims] In a pressure casting method in which a mold is filled with molten metal by the action of an injection device having an injection plunger, and the molten metal in the mold is pressurized by the action of a pressure device having a pressure plunger, the pressure applied to the injection plunger is A pressure casting method characterized in that the molten metal is pressurized by a pressure plunger while the molten metal is being drawn out.