JPS607879Y2 - die casting machine injection equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a die casting machine injection device, and more particularly to a die casting injection device that prevents generation of large peak injection pressure during injection.

A conventional die-casting machine is provided with an injection device for supplying a large amount of molten metal into its cavity.

This injection device consists of an injection sleeve connected to a runner opened in a mold, a plunger tip slidably mounted inside the sleeve, a piston rod connected to the plunger tip, and an injection cylinder inside the injection sleeve. It consists of an injection piston that gives reciprocating motion to a piston rod housed in the piston rod.

The injection device supplies molten metal by driving the injection piston by supplying hydraulic pressure to the injection cylinder, and presses the molten metal previously injected into the injection sleeve into the cavity via a plunger tip connected to the piston rod. It is done by doing.

However, in the conventional die casting machine injection device mentioned above,
Due to the influence of hydraulic oil flowing into the injection cylinder at high speed and the inertia of parts that move during injection, such as the piston rod,
When the molten metal is filled, a very high peak pressure is generated in the cavity, resulting in an abnormally high pressure. Sometimes, the peak pressure exceeds the clamping force of the mold, causing the mold to open and causing flash. There is a problem with hot water blowing out, which adversely affects the quality of the cast product.

That is, as shown in Fig. 1, the injection speed change of the moving member such as the plunger tip of the injection device is shown as diagram A, and the movement suddenly stops from the final speed (point a) after moving forward at high speed. As shown in diagram B, the injection pressure changes due to the movement of the molten metal, and as shown in diagram B, the peak pressure (b
point) occurs.

Further, the molten metal is supplied into the cavity by the injection pressure, and the pressure inside the cavity changes as shown in diagram C, and a peak pressure (point C) occurs as the injection pressure peaks.

The above-mentioned problem occurs when the peak pressure within the cavity becomes abnormally high.

This phenomenon has hindered the development of high-speed injection molding methods because the higher the final injection speed (point a), the higher the peak pressure (point C).

On the other hand, as shown in Fig. 2, the high-speed filling time is kept constant to prevent peak pressure in the cavity, and the high-speed advance speed is changed stepwise (d1e in the figure) to reduce the final speed. has been proposed, but although this method reduces the occurrence of casting burrs, the rapid change in speed causes rapid changes in the flow state of the metal in the cavity, leading to problems such as the formation of cavities and poor hot water circulation. There are problems and drawbacks that result in deterioration of product quality.

This invention focuses on the above-mentioned conventional problems, and achieves high-quality molding by preventing the occurrence of cast burrs and the blowing of hot water from the mold dividing surface, without causing problems such as poor hot water circulation due to sudden changes in leakage flow. An object of the present invention is to provide a die casting machine injection device that can cast products.

In order to achieve the above object, the die casting machine injection device according to the present invention includes a tension spring whose end is supported by a fixed side such as an injection cylinder and a movable member such as a piston rod. Applying a tensile force to the moving member in
The final injection speed in the press-fitting process is gradually reduced by the spring action.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a die casting machine injection device according to the present invention will be described in detail below with reference to the drawings.

FIG. 3 shows a sectional view of the injection device according to this embodiment.

As shown in this figure, the injection device includes an injection sleeve 1
0, and a plunger tip 12 is slidably inserted into this injection sleeve 10.

The injection sleeve 10 is connected to a runner that communicates with a mold cavity (not shown), and allows the molten metal to be injected into the sleeve 10 to be press-fitted into the cavity by movement of the plunger tip 12.

Further, a piston rod 14 is integrally connected to the plunger tip 12, and this piston rod 14 is coupled to an injection piston 18 housed in an injection cylinder 16.

Hydraulic oil from a hydraulic supply source can flow into the injection cylinder 16 on both sides of the injection piston 18, and the injection piston 18 can reciprocate within the cylinder 16 depending on the direction in which the hydraulic oil flows.

Therefore, the plunger tip 12 is driven by the reciprocating motion of the piston 1B, and slides on the sleeve 10.

In such an injection device, a tension spring 20 is wound around the piston rod 14 and attached thereto.

One end of this tension spring 20 is a fixed end supported by the injection cylinder 16, and the other end is a movable end supported by a support 22 attached to the outer peripheral surface of the piston rod 14.

When the plunger tip 12 is press-fitted, the tension spring 20 generates a biasing force on the piston rod 14 in a direction opposite to the press-fitting direction, so that the injection speed of the plunger tip 12 can be gradually reduced by the tensile force.

The spring constant of this tension spring 20 is determined by the following formula.

F<Fi<'r...
...(1) Pmax = F1-F
””(2)K≧(Pmax−Po)/(H
p - Ho) ... (31 Here, F is the force necessary to make a good product when no spring is used, and is a value determined by the product's wall thickness, projected area, etc.
T is the maximum mold clamping force of the die casting machine used,
F□ is the set injection force when using a spring, and is arbitrarily determined within the range of equation (1).

In addition, Hp is the extended length of the tension spring 20 at the most advanced position of the injection stroke, and Ho is the length of the tension spring 20 at the most advanced position of the injection stroke.
This is the length when installed.

Pmax indicates the maximum load when the tension spring 20 is extended at the injection advance limit, and Po indicates the load when the tension spring 20 is attached.

In the injection device configured in this manner, the tension spring 20 acts to gradually reduce the injection speed when molten metal is press-in, and after reaching the maximum forward speed, as shown in the injection speed diagram in FIG. The speed will decrease smoothly.

Therefore, the peak pressure (point C in FIG. 1) that would otherwise be generated due to the inertia of the moving member of the injection device or the action of the hydraulic oil is prevented from occurring.

As a result, no pressure that exceeds the mold clamping force is generated in the cavity, so it is possible to obtain a product with stable quality without casting burrs or hot water blowing out.

Moreover, it becomes possible to obtain a good molded product without particularly increasing the filling time.

In the above embodiment, the case where the end of the tension spring 20 is supported by the injection cylinder 16 and the piston rod 14 has been explained, but the invention is not limited to this. Just install it.

As explained above, according to the die casting machine injection device according to the present invention, it is possible to gradually reduce the injection speed, thereby preventing cast burrs and hot water from blowing out without causing poor hot water circulation. However, it has the excellent effect of making it possible to cast high-quality molded products.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing changes in injection speed, injection pressure, and cavity pressure with respect to injection time, FIG. 2 is a diagram showing changes in conventional injection speed, and FIG. 3 is a cross-sectional view of the injection device according to this embodiment. , FIG. 4 is a diagram of changes in injection speed of the same apparatus. 10... Injection sleeve, 12... Plunger tip, 14... Piston rod, 16
...Injection cylinder, 18...Injection piston, 20...Tension spring.

Claims (1)

[Scope of utility model registration request] In an injection device that presses molten metal into a cavity of a die-casting machine, a tension spring is installed, one end of which is supported by a fixed side such as an injection cylinder, and the other end of which is supported by a moving member such as a piston rod. A die casting machine injection device characterized in that the injection speed of a moving member is gradually reduced by applying a tensile force to the moving member.