JP2005186104A - Die casting machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extend the service life of an injection cylinder by suppressing the damage due to wearing at an outlet side oil chamber side fitted to the outer periphery of a piston to the utmost in the injection cylinder in which a speed control is performed by an inlet side throttle valve. <P>SOLUTION: The die casting machine has a hydraulic cylinder for driving a plunger rod for injecting/filling molten metal into a die and performs the speed control of the hydraulic cylinder by the inlet side throttle valve. In the die casting machine, a gap in radius direction between the inner peripheral surface of the cylinder and the outer peripheral surface of the piston in the hydraulic cylinder is set within the range of 0.030-0.006 mm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a cold chamber type die casting machine having a hydraulic cylinder (hereinafter referred to as an injection cylinder) that drives a plunger rod for injecting and filling molten metal into a mold. The present invention relates to a technique suitable for application to a die casting machine driven forward at high speed.

  In a cold chamber type die casting machine that requires a very high injection speed (for example, 8 m / second or more), in order to feed high-pressure oil into the injection cylinder at a stroke, a gas compression force of 1 is used. In many cases, the pressure oil is increased by an accumulator for each shot, and the high-pressure pressure oil stored in the accumulator is sent to the injection cylinder at the time of injection.

  By the way, as a method for controlling the injection speed of the injection cylinder, as shown in FIG. 4A, a flow control valve (throttle valve) on the oil inflow side (in side) to the injection cylinder 51 when the piston 52 is advanced. ) 54, and the speed control referred to as in-throttle, in which speed control is not performed on the oil outflow side (out side) from the injection cylinder 51 when the piston 52 is advanced, and FIG. As shown in FIG. 3, speed control is not performed on the in-side to the injection cylinder 51 when the piston 52 is advanced, and speed control is performed on the out-side from the injection cylinder 51 when the piston 52 is advanced. There is speed control called out-throttle. In FIG. 4, 53 is a piston rod integral with the piston 52, and although not shown, a plunger rod (injection sleeve into which a molten metal is poured every shot through a coupling, not shown). The rear end of the plunger rod that moves back and forth inside is connected.

  The latter out-throttle is in a state where an excessive pressure is applied to the in-side of the injection cylinder 51 during injection (in other words, the brake is applied from the out-side), and the out-side is adjusted to the set speed. Since the speed is adjusted by the strength of the brake, there may be cases where the required output does not follow even if only the speed is met.

  On the other hand, since the former in-throttle controls the speed on the in-side of the injection cylinder 51, the set speed can be transmitted to the molten metal without any resistance while maintaining the output corresponding to the speed.

  By the way, the speed control by the in-throttle has the above-mentioned advantages, but the wear ring on the out side oil chamber side attached to the outer periphery of the piston 52 is damaged, and the durability performance of the injection cylinder 51 is remarkably deteriorated. It turned out to be. This is because in the speed control by the in-throttle, when the plunger rod connected to the piston rod 53 collides with the biscuit portion (the disc-shaped metal material portion remaining on the distal end surface side of the plunger rod) at the end of the injection stroke, Although the piston 52 and the piston rod 53 are rapidly stopped, the oil further flows out due to the inertia of the oil on the out side of the injection cylinder 51. Therefore, a negative pressure is generated in the out side oil chamber of the injection cylinder 51, As a result, a cavitation phenomenon is likely to occur, and it is assumed that the wear ring on the out side oil chamber side attached to the outer periphery of the piston 52 is damaged by the cavitation.

  FIG. 5 shows the results of measuring the pressure (hydraulic pressure) on the in-side and out-side of the injection cylinder when the in-throttle control injection cylinder is driven at an injection speed of 8.4 m / sec. FIG. 5A shows the in-side pressure, and FIG. 5B shows the out-side pressure. Here, the pressure detector used to measure the oil pressure does not give a measured value on the negative side (negative pressure side), and it is not certain how much negative pressure is generated, but the piston is moving forward. After the sudden stop, it was confirmed that negative pressure was generated on the out side. Even when the in-throttle control injection cylinder was driven at an injection speed of 5.5 m / sec, 3.4 m / sec, it was confirmed that negative pressure was generated on the out side. It was confirmed that the pressure period was shortened. Therefore, it is inferred that a larger negative pressure is generated as the injection speed is higher. As a result, it is assumed that cavitation is more likely to occur as the injection speed is higher. This coincides with the result of actual operation that the wear ring on the out-side oil chamber side attached to the outer periphery of the garment is damaged early.

  The present invention has been made in view of the above points, and an object of the present invention is to damage the wear ring on the out side oil chamber side mounted on the outer periphery of the piston in the injection cylinder that performs speed control by the in-throttle. Therefore, it is intended to extend the durable life of the injection cylinder.

  In order to achieve the above object, the present invention provides a hydraulic cylinder in a die casting machine having a hydraulic cylinder for driving a plunger rod for injecting and filling a molten metal into a mold and performing speed control of the hydraulic cylinder by in-throttle. The radial clearance between the cylinder inner peripheral surface and the piston outer peripheral surface is set in a range of 0.030 to 0.006 mm.

In the present invention, the radius gap between the cylinder inner peripheral surface and the piston outer peripheral surface of the hydraulic cylinder is in the range of 0.030 to 0.006 mm, which is a value smaller by one order than the manufacturer's recommended value for the piston wear ring. According to experiments, when the radius gap is set to the manufacturer's recommended value, for example, after about 470,000 shots under the injection speed condition of 5.5 m / sec, the outer periphery of the piston is Whereas the wear ring on the out-side oil chamber side was cracked, the radial clearance according to the present invention showed that the piston of the piston could not be used even after 2 million shots had elapsed under an injection speed condition of 8.0 m / sec. No damage was seen in the wear ring on the outer oil chamber side attached to the outer periphery. Although confirmation after the shot exceeding 2 million shots has not been taken due to time restrictions, no abnormality is seen in the wear ring even after 2 million shots have passed, so durability exceeding 5 million shots It can be expected that performance will be obtained.
The reason why the above results are obtained is that the bubbles (cavitation bubbles) separated from the oil by cavitation collapse or vibrate at a high speed due to a sudden change in oil pressure, and the impact pressure generated thereby propagates. It is assumed that the impact pressure transmitted to the out-side oil chamber side wear ring attached to the outer periphery of the piston is greatly relieved because the radius gap is very small.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of an injection cylinder used in a die casting machine according to an embodiment of the present invention (hereinafter referred to as the present embodiment).

  In FIG. 1, 1 is an injection cylinder (hydraulic cylinder for injection), 2 is a cylinder, 3 is a piston that reciprocates in the cylinder 2, 4 is a piston rod fixed integrally to the piston 3, 5 is an oil chamber A, 6 is an oil distribution port of the oil chamber A5, 7 is an oil chamber B, and 8 is an oil distribution port of the oil chamber B7.

  In the configuration shown in FIG. 1, the piston rod 4 has a plunger rod (a plunger rod that moves forward and backward in the injection sleeve into which the molten metal is poured every shot) via a coupling (not shown) at the tip of the piston rod 4. The ends are connected, and the plunger rod (not shown) moves forward by the advancement of the piston 3 and the piston rod 4 (movement in the leftward direction in FIG. 1), and the molten metal is injected and filled into the mold. It has come to be.

  The injection cylinder 1 shown in FIG. 1 is omitted from illustration, but injection and filling are performed by the same speed control by the in-throttle as described with reference to FIG. Yes. That is, speed control is performed by the flow control valve (throttle valve) on the oil inflow side (in side) to the injection cylinder 1 when the piston 3 is advanced, and the oil outflow side from the injection cylinder 1 when the piston 3 is advanced. On the (outside) side, injection / filling is performed by speed control by in-throttle without speed control. Further, although not shown, during injection / filling, high-pressure pressure oil stored in the accumulator is stored in the oil chamber A5 through the oil circulation port 6 by using the compressive force of the gas. As a result, an injection speed of 8.0 m / second or more can be obtained.

  FIG. 2 is an enlarged view of a main part showing the relationship between the piston 3 and the cylinder 2 of the present embodiment. Here, the illustration of the piston rod 4 screwed and fixed to the piston 3 is omitted.

  In FIG. 2, reference numeral 11 denotes two annular wear ring mounting grooves formed on the outer periphery of the piston 3, and 12 denotes a seal ring mounting formed on the outer periphery of the piston 3 and positioned between the two wear ring mounting grooves 11. It is a groove. A wear ring (slide ring) 13 for ensuring good sliding characteristics of the piston 3 is mounted in the wear ring mounting groove 11, and oil is sealed in the seal ring mounting groove 12 to form an oil chamber A5. A seal ring 14 for shutting off the oil chamber B7 is mounted, and the seal ring 14 is constituted by two rings 14a and 14b.

  In FIG. 2, D is the inner diameter (inner diameter) of the cylinder 2, d is the outer diameter (outer diameter) of the piston 3, and S is the radial gap between the inner peripheral surface of the cylinder 2 and the outer peripheral surface of the piston 3. In the present invention, the radial gap S is set in the range of 0.030 to 0.006 mm, and the value of the radial gap S in the range of 0.030 to 0.006 mm The value is one order of magnitude smaller than the manufacturer's recommended value for wear rings (value listed in the catalog).

  FIG. 3 is a table showing a comparison of the radial gap S according to the present invention and the radial gap S according to the manufacturer's recommended value when the outer diameter d of the piston 3 is 90, 110, and 120 mm. As shown in FIG. 3, the radial gap S according to the present invention is significantly smaller than the manufacturer's recommended value. As described as the experimental result on the right side of FIG. 3, 2 million shots (injection speed 8.0 m / No more damage was seen on the wear ring 13 on the oil chamber B7 side even after exceeding (second). On the other hand, when the radius clearance S according to the manufacturer's recommended value was adopted, cracks occurred in the wear ring 13 on the oil chamber B7 side before and after 500,000 shots (injection speed 5.5 m / sec). Although the confirmation after the shot exceeding 2 million times has not been confirmed due to time restrictions, the radial gap S of the present invention has an abnormality in the wear ring 13 on the oil chamber B7 side even after 2 million shots have passed. Therefore, it can be expected that durability performance exceeding 5 million shots can be obtained.

  The reason why the above results are obtained is that the above-mentioned radial gap S through which the impact pressure due to cavitation propagates is very small, so that the impact pressure transmitted to the wear ring 13 on the oil chamber B7 side mounted on the outer periphery of the piston 3 However, it is presumed that this is because it is greatly eased.

  Although the present invention has been described above with reference to the illustrated embodiment, a known labyrinth seal is formed by forming a labyrinth groove on the outer peripheral surface of the piston 3 closer to the oil chamber B7 side than the wear ring 13 on the oil chamber B7 side. It is considered that the impact pressure caused by cavitation can be further reduced by attaching the

It is sectional drawing of the injection cylinder used with the die-casting machine which concerns on one Embodiment of this invention. It is a principal part enlarged view in the injection cylinder used with the die-casting machine which concerns on one Embodiment of this invention. It is a table | surface figure which shows the radial clearance by this invention, and the radial clearance by a manufacturer recommendation value, and shows with an experimental result. It is explanatory drawing of the speed control by an in aperture, and the speed control by an out aperture. It is a measurement figure of the pressure change of the in side at the time of speed control by an in throttling.

Explanation of symbols

1 Injection cylinder (hydraulic cylinder for injection)
2 Cylinder 3 Piston 4 Piston rod 5 Oil chamber A
6 Oil distribution port 7 Oil chamber B
8 Oil distribution port 11 Wear ring mounting groove 12 Seal ring mounting groove 13 Wear ring 14 Seal ring D Cylinder inner diameter d Piston outer diameter S Radial gap between the inner peripheral surface of the cylinder and the outer peripheral surface of the piston

Claims (4)

There is a hydraulic cylinder that drives a plunger rod for injecting and filling molten metal into the mold. When the piston of the hydraulic cylinder is advanced, speed control is performed on the oil inflow side to the hydraulic cylinder, and the piston is advanced. In the die casting machine that does not perform speed control on the oil outflow side from the hydraulic cylinder in
A die casting machine, wherein a radial gap between a cylinder inner peripheral surface and a piston outer peripheral surface of the hydraulic cylinder is set in a range of 0.030 to 0.006 mm. In the die casting machine according to claim 1,
A seal ring mounting groove and a wear ring mounting groove located on both outer sides of the seal ring mounting groove are formed on the outer periphery of the piston, and a seal ring is mounted on the seal ring mounting groove, and the wear ring mounting groove Is a die-casting machine that features a wear ring. In the die-casting machine according to claim 1 or 2,
A die casting machine, wherein a labyrinth seal is provided between the cylinder inner peripheral surface and the piston outer peripheral surface. In the die-casting machine according to claim 1, 2 or 3,
A die casting machine, wherein the maximum forward speed of the piston is 8 m / sec or more.

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