JPH08300430A - Molding of brake piston made of resin - Google Patents

Abstract

PURPOSE: To obtain a resin brake piston of high quality while keeping good injection molding productivity by closing a mold in such a state that a movable core retreats from a predetermined position by a definite distance to inject and charge a resin into a cavity and subsequently advancing the movable core to the predetermined position. CONSTITUTION: A mold is closed in such a state that a movable core 15 retreats from a predetermined position by a definite distance to inject and charge a resin into a cavity. Subsequently, a gate seal pin 14 is allowed to advance to seal a gate and the movable core 15 is advanced to the predetermined position for constituting the final molded product shape of a brake piston. Next, the mold is opened and the movable core 15 is allowed to retreat and the product is taken out by an ejection pin. Herein, by allowing the piston of a hydraulic cylinder to advance and retreat, the movable core 15 is allowed to advance and retreat in arbitrary timing through the ejection plates 9, 10 for the hydraulic cylinder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of injection compression molding a resin brake piston.

[0002]

2. Description of the Related Art Conventionally, resin brake pistons are generally molded by compression molding or injection molding.
When compression molding is used, strength and other practical problems can be obtained, but it takes time to mold because it requires a long curing time, and unmanned because it requires preheating and insertion of the tablet. There is a drawback that the production cost becomes high, such as difficult to remove.

On the other hand, although injection molding is a molding method with good productivity, it has the following quality problems. That is, when the center direct gate method is used, residual strain occurs near the gate, or a semi-cured material is mixed,
There was a drawback that the performance as a brake piston could not be fully satisfied, such as cracking in the durability evaluation. Further, when the side gate method is used, there is a drawback in that the weld is generated on the side opposite to the gate, so that the strength is reduced.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made as a result of various studies in order to solve the problem that it is difficult to achieve both production cost and quality in the conventional resin brake piston molding method. The purpose is to provide a resin-made brake piston which is excellent in quality while maintaining good productivity in injection molding.

[0005]

According to the present invention, there is provided a method of molding a resin brake piston, wherein a movable core is retracted by a certain distance from a predetermined position for forming the shape of the final molded product of the brake piston. Close the mold,
The present invention relates to an injection compression molding method for a resin brake piston, which comprises injecting a resin into a cavity and then moving the movable core forward to the predetermined position.

In the mold used in the present invention, resin is injected and filled in a state in which the movable side core is retracted to make the cavity space larger than the shape of the molded product, and then the movable side core is advanced to finalize the brake piston. It has a structure to form the shape of a molded product.

An example of the mold used in the present invention is shown in FIGS. 1 to 3 along with the operation process. In these drawings, (1) is a fixed-side mounting plate, (2) is a fixed-side template, (3) is a movable-side template, (4) is a protruding plate 1 (top),
(5) is the protruding plate 1 (bottom), (6) is the protruding plate 2
(Upper), (7) is the protruding plate 2 (lower), (8) is the movable side mounting plate, (9) is the protruding plate for the hydraulic cylinder (upper),
(10) is a protruding plate (lower) for the hydraulic cylinder, (11)
Is a mounting plate for a hydraulic cylinder, (12) is a fixed cavity, (13) is a movable cavity, (14) is a gate seal pin, (15) is a movable core, (16) is a hydraulic cylinder, and (17) is The protruding plate connecting rod (18) represents a return pin.

FIG. 1 shows a state in which the movable core (15) is retracted from a predetermined position by a certain distance, the mold is closed, and resin is injected and filled into the cavity. FIG. 2 shows a state in which the movable core (15) is advanced to a predetermined position for forming the final molded product shape of the brake piston after the gate seal pin (14) is advanced to perform gate sealing. FIG. 3 shows a state in which the mold is opened, the movable core (15) is retracted, and then the product is taken out by the protruding pin.

In the ordinary injection molding (side gate), since the movable core (15) is in the advanced position when the resin is injected and filled, the movable core (15) impedes the flow of the resin and the side opposite the gate. Weld occurs at. on the other hand,
In the method of the present invention in which the movable side core (15) is advanced after injection-filling with resin, there is nothing that hinders the flow of the resin, so that no weld is generated on the side opposite to the gate, and the molding obtained by compression molding The same strength as the product can be obtained.

In the present invention, the timing at which the movable core (15) is advanced is any timing until the mold is opened after the resin is injected and filled in the cavity and within the range in which the fluidity of the resin does not decrease. However, in reality, it is not necessary to wait for the advance of the movable core to be completely filled with the resin as long as the obtained molded product is within the range where no weld occurs. After the curing of the resin progresses and the fluidity decreases, the movable core (15) cannot advance to a predetermined position.

Further, it is preferable that the movable core (15) is moved forward after the resin is injected into the cavity and the gate seal pin (14) is moved forward to perform gate sealing. In this method, the backflow of the resin from the gate due to the advance of the movable core (15) can be prevented, so that the packing density is improved and a molded product of higher quality can be obtained.

[0012]

The mechanism for advancing / retracting the movable core (15) and operating the gate seal pin (14) according to the present invention will be described below.

As shown in FIG. 1, the movable core (15) is connected to the projecting plates (9, 10) for the hydraulic cylinder. The piston of the hydraulic cylinder (16) is also connected to the hydraulic cylinder protruding plate (9, 10) from the side opposite to the movable core (15). In addition to standard timing (that is, after mold opening, during mold opening / closing, after mold closing and before injection) operation of this hydraulic cylinder, the electric circuit settings are changed so that it can be performed at any time from injection start to mold opening. ing. Based on the above configuration, the hydraulic cylinder (1
By moving the piston of 6) forward and backward, the movable core (1) is moved through the protrusion plate (9, 10) for the hydraulic cylinder.
This is to allow the forward / backward movement of 5) to be performed at any timing.

The gate seal pin (14) is connected to the projecting plate connecting rod (17) through the projecting plate 2 (6, 7), and is arbitrarily set from the injection start to the mold opening depending on the setting of the molding machine. The gate can be cut at the timing.

[0015]

The resin brake piston molding method of the present invention can completely prevent the decrease in strength due to welding, which is a problem in injection molding, without impairing the productivity of injection molding. It is extremely useful as a molding method for resin-made brake pistons in terms of both quality and cost.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a resin brake piston injection compression molding die of the present invention, in which the die is closed with a movable core retracted from a predetermined position by a certain distance, and resin is injected into a cavity. The filled state is shown.

FIG. 2 shows a state in which, after the gate seal pin is advanced to perform gate sealing, the movable core is advanced to a predetermined position for forming the final molded product shape of the brake piston.

FIG. 3 shows a state in which the mold is opened, the movable core is retracted, and then the product is taken out by a protruding pin.

[Explanation of symbols]

 1 Fixed Side Mounting Plate 2 Fixed Side Mold Plate 3 Movable Side Mold Plate 4 Projection Plate 1 (Upper) 5 Projection Plate 1 (Lower) 6 Projection Plate 2 (Upper) 7 Projection Plate 2 (Lower) 8 Movable Side Installation Plate 9 Hydraulic Pressure Cylinder protruding plate (upper) 10 Hydraulic cylinder protruding plate (lower) 11 Hydraulic cylinder mounting plate 12 Fixed side cavity 13 Movable side cavity 14 Gate seal pin 15 Movable side core 16 Hydraulic cylinder 17 Protruding plate connecting rod 18 Return pin

Claims (3)

[Claims] 1. A method of molding a resin brake piston, wherein the mold is closed with a movable core forming a recess of the piston retracted by a predetermined distance from a predetermined position for forming the shape of the final molded product of the brake piston. The injection compression molding method for a resin brake piston, comprising: injecting and filling a resin into a cavity, and then advancing the movable side core to the predetermined position. 2. The molding method according to claim 1, wherein the resin is injected and filled into the cavity, and the gate seal pin is advanced to advance the gate seal before the movable side core is advanced. 3. The molding method according to claim 1, wherein the movable core is moved forward and backward at an arbitrary timing from injection start to mold opening.