JPH10156903A - Resin product molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding method for a resin product wherein generation of void, crack, weld, etc., are prevented. SOLUTION: A resin product molding method comprises a mold arranging process for arranging a mold 1 having a cavity space 1e of piston-like shape, an injecting process for injecting a melt resin 5 into the cavity space 1e, and a pressing process for pressing the resin in the cavity space 1e before the resin injected into the cavity space 1e solidifies so as to move the resin to a predetermined part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a resin product, and more particularly, to a method for molding a synthetic resin piston used for a master cylinder used for a brake device or a clutch device of a vehicle.

[0002]

2. Description of the Related Art A conventional method for molding a resin product comprises a mold disposing step for disposing a molding die having a space having the shape of a resin product, and an injection step for injecting a molten resin into the space. A product made of a synthetic resin material is molded by filling a molten resin into a molding die.

In general, when a resin product is molded with a resin (molded with a thermoplastic resin), molten resin is injected in the axial direction of the resin product so that the resin is uniformly filled in a mold. Improving roundness and dimensional accuracy is performed. Further, the strength of the resin is improved by mixing glass fibers.

[0004]

However, in the above-described method for molding a resin product, if the resin product to be molded has a thick portion, voids and cracks may occur.

An object of the present invention is to provide a method for molding a resin product that suppresses the occurrence of voids, cracks, welds, and the like.

[0006]

In order to solve the above technical problems, a mold disposing step for disposing a mold having a space having a shape of a resin product, and an injection step for injecting a molten resin into the space are provided. By pressing the resin in the space before the resin injected into the space is solidified,
And a pressing step of moving the resin to a predetermined portion.

Preferably, the resin product is a piston, and the piston has a flange portion substantially equal to a diameter of a cylinder hole of a cylinder body into which the piston is slidably inserted. It is preferable that the resin part is formed in the vicinity of a part where the resin forms the flange part in the molding die.

Preferably, the cylinder body is a cylinder body of a master cylinder for a vehicle, and the piston has two flange portions at a front side and a rear side.

According to the method for molding a resin product of claim 1,
By disposing a mold and injecting the molten resin into the mold, the mold is filled with the molten resin. In the flow of the resin in the molding die, there is no situation in which the resins are separated and the separated resins are merged.

Further, before the molten resin in the mold is solidified, the resin in the pressed part is moved in a predetermined direction by pressing the resin in the mold. It is presumed that the step of pressing the resin allows the molten resin to spread to a portion having a low resin density in the molding die, and it is considered that the molten resin can be more uniformly filled.

Further, it is presumed that the effect of randomly dispersing the orientation of the molten resin can be obtained by pressing the molten resin.

According to the method for molding a resin product of claim 2,
In addition to the effect of the first aspect, in the molding die, the vicinity of the portion where the resin is molding the flange portion is pressed, and particularly when the piston is molded, the resin is molding the flange portion. It is presumed that the effect of randomly dispersing the orientation of the resin in the vicinity of the portion can be obtained.

[0013] According to the method for molding a resin product of claim 3,
In addition to the effect of the second aspect, in the molding die, the vicinity of the portion where the resin is molding the front and rear flange portions is pressed. It is presumed that the effect of randomly dispersing the orientation of the resin in the vicinity of the portion where the flange is formed can be obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be specifically described below.

FIG. 1 is a sectional view of a resin molding die 1 for molding a synthetic resin piston according to the present embodiment, and FIG. 2 is a sectional view of a synthetic resin piston 4 molded by the resin molding die 1 of FIG. It is. As shown in FIGS. 1 and 2, the resin molding die 1 for molding the synthetic resin piston 4 includes a fixed die 1a, a movable die 1b, an upper slide 1c, and a lower slide 1d.

The molding die 1 is provided with a cavity 1e having the shape of the synthetic resin piston 4 therein.
In FIG. 5A, an injection hole 1f is provided on an extension of the axis of the cavity space 1e.

On the outer periphery of the upper slide 1c and the lower slide 1d, there are provided a first pressing device 2 and a second pressing device 3 for pressing the resin in the molding die 1 to form through holes 4g and 4f of the piston 4. ing. The first and second pressing devices 2, 3 have hydraulic cylinders 2a, 3a and processing pins 2b, 3b. The processing pins 2b, 3b are located near portions 1f, 1g for forming the flanges 4b, 4d, and are slidably disposed in holes formed in the upper slide 1c and the lower slide 1d. In the initial state shown in FIG. 1, only the tip portions of the processing pins 2b and 3b protrude into the cavity space 1e.

When the hydraulic fluid is supplied to the hydraulic cylinders 2a, 3a, the working pins 2b, 3b
a and slides in the holes of the slides 1c and 1d, and is moved toward the inside of the cavity space 1e.

The slides 1c and 1d are processed pins 2b and 3
b has contact portions 1ca and 1da that contact the processing pins 2b and 3b by moving in the cavity space 1e. The contact portions 1ca and 1da are slidably disposed with respect to the slides 1c and 1d.
For example, it is urged toward the cavity space 1e by a hydraulic member, a spring, or the like.

FIG. 3 is a view showing a state in which the molten resin is injected into the resin molding die 1. FIG. 4 is a diagram showing a state in which the pressing devices 2, 3 are operated after the molten resin is injected into the resin molding die 1. FIG. 5 is a view showing a state in which the resin is solidified in the resin mold 1. Based on FIGS. 1 to 5,
A method for forming the synthetic resin piston 2 will be described.

First, as shown in FIG. 1, a resin molding die 1 is arranged.

Next, as shown in FIG. 3, the molten synthetic resin 5 (aromatic nylon mixed with glass fiber) is injected from the resin injection hole 1f. The injected molten resin 5 has a front part 4a of the piston 4 (in FIG. 2),
In order to form the front flange 4b, the main body 4c, the rear flange 4d, and the rear 4e, the fluid flows from the right side to the left side in FIG. 3 in the axial direction of the cavity space 1e.

When the molten resin 5 is injected into the cavity space 1e, the contact portion 1ca is pressed upward in FIG. 3 and the contact portion 1da is pressed downward in FIG. . However, since the contact portions 1ca and 1da are urged by the urging member toward the cavity space 1e with the pressing force of the molten resin 5 or more, the contact portions 1ca and 1da are moved upward by the molten resin 5 in FIG. And will not be moved down.

Next, as shown in FIG. 4, when the molten resin 5 is filled into the cavity 1e of the resin molding die 1 by about 90%, the hydraulic fluid is supplied to the cylinders 2a, 3a of the pressing devices 2, 3. The processing pins 2b, 3b are
It is moved forward toward the cavity space 1e so that the axis of b is perpendicular to the axis of the cavity space 1e.

When the processing pin 2b is moved, the processing pin 2
b is a front end portion of which the molten resin 5 presses a portion near the rear side of the portion 5a forming the front flange portion 4b to form a hole 4b.
It moves forward in FIG. 4 while forming f. The processing pin 2b moves forward and the processing pin 2b and the upper slide 1c
When the contact portion 1ca abuts, the working pin 2b advances while pushing the contact portion 1ca upward in FIG. 4 against the urging force of the urging member. Therefore, the processing pin 2b penetrates the cavity space 1e in the radial direction of the cavity space 1e. When the processing pin 2b passes through the cavity space 1e, a hole 4g, which is a through hole, is formed.

Similarly, when the processing pin 3b is moved, the processing pin 3b presses a portion near the front side of the portion 5b where the molten resin 5 forms the rear flange portion 4d at the tip portion, thereby opening the hole 4g. It moves forward in FIG. 4 while forming. When the working pin 3b moves forward and comes into contact with the contact portion 1da of the lower slide 1d, the working pin 3b pushes the contact portion 1da downward in FIG. 4 against the urging force of the urging member. Advance. Therefore, the processing pin 3b penetrates the cavity space 1e in the radial direction of the cavity space 1e. When the processing pin 3b passes through the cavity space 1e, a hole 4g, which is a through hole, is formed.

The molten resin 5 is still injected from the injection hole 1f into the molding die 1 during the movement of the working pins 2b, 3b, so that the molten resin 5 in the shaft portion of the cavity space 1e in the molding die 1. It is considered that the density is higher than the density of the molten resin 5 on the cavity surface side. However, by pressing the molten resin by advancing the processing pins 2b and 3b, the resin in the pressed portion and in the vicinity thereof is diffused and moved, and the molten resin is melted into a portion having a low resin density with the movement of the resin. It is assumed that the resin can be spread. Therefore, it seems that the molten resin 5 can be more uniformly filled.

Further, it is presumed that the effect of randomly dispersing the orientation of the glass fibers in the molten resin in particular is obtained by moving the processing pins 2b and 3b to press the molten resin.

The molten resin 5 continues to be injected from the injection hole 1f, and the resin mold 1 is eventually filled with 100% of the molten resin 5.

As shown in FIG. 5, after the molten resin is cooled and solidified, the hydraulic fluid in the hydraulic cylinder 2a is discharged from the cylinder 2a.
Then, the processing pin 2b is retracted downward in FIG. 5 and returned to the initial position. Similarly, the hydraulic cylinder 3a
The working fluid inside the cylinder 3a is discharged to the outside of the cylinder 3a,
Retreats upward in FIG. 5 and returns to the initial position.

Therefore, after the resin is solidified, the piston 4 made of a synthetic resin material having through holes 4f and 4g is formed in the molding die 1. Molded piston 4
In FIG. 5, the movable mold 1b is moved leftward in FIG. 5, the upper slide 1c is moved upward in FIG. 5, and the lower slide 1d is moved in FIG.
It is moved down and down to be taken out of the mold 1.

As shown in FIG. 2, the molded piston 4
Includes a front portion 4a of the length L ₁ portion, and the front side flange portion 4b of the length L ₂ portions, and an intermediate portion 4c is thick portion of the length L ₃ portion, the length L ₄ portion of the rear side and the flange portion 4d, composed of a rear portion 4e of the length L ₅ parts. The diameter of the front flange portion 4b and the rear flange portion 4d is substantially equal to the diameter of a cylinder hole 11a described later, and the intermediate portion 4c is substantially equal to the diameter of the front flange portion 4a and the rear flange portion 4d at both ends thereof. It has a tapered shape whose diameter is gradually reduced from both ends toward the center thereof. In the vicinity of the rear side of the front side flange portion 4b, a small hole 4g which extends in the radial direction of the synthetic resin piston 4 (vertical direction in FIG. 2) and penetrates through the axis of the synthetic resin piston 4 is formed. Near the front of the portion 4d, a small hole 4 penetrating through the axis of the synthetic resin piston 4 in the radial direction of the synthetic resin piston 4
g is molded.

Further, a hole 4h is provided in the front portion 4a, and a communication hole 4i for communicating the hole 4h with the through hole 4f.
Is formed.

Next, an embodiment in which the synthetic resin piston 4 is used for a tandem master cylinder 10 for a vehicle brake will be described with reference to FIG. 6, the cylinder body 11 has a cylinder hole 11a, and the left end in FIG. 6 is closed and the right end is open. Cylinder body 11
A pair of left and right reservoir coupling portions 12 and 13 connected to an oil reservoir (not shown) are formed on the outer periphery of the cylinder body 11.
Supply ports 14a, 14b, and 14c are formed to communicate the cylinders 2 and 13 with the inside of the cylinder body 11.

A metal piston 15 is inserted into the opening of the cylinder hole 11a, and a synthetic resin piston 4 is inserted in the center thereof so as to be able to reciprocate. In the cylinder hole 11a,
A second pressure chamber 17 is defined by the pistons 4 and 15, and a first pressure chamber 16 is defined by the synthetic resin piston 4 and the bottom surface of the cylinder hole 11a. Further, in order to keep the first and second pressure chambers 16 and 17 in a liquid-tight manner, cup materials 18, 19, 20, and 21 as sealing materials are provided.
a, and supported by the rear flange portion 4d, fitted to the front portion 4a and the rear portion 4e of the synthetic resin piston 4, and the cup members 20, 21 are fitted to the metal piston 15.

The first brake supply chamber 22 is formed between the cylinder hole 11a and the front flange portion 4b and the rear flange portion 4d of the synthetic resin piston 4, that is, the outer peripheral surface of the intermediate portion 4c. The second brake fluid supply chamber 23 is defined by the cylinder hole 11 a and the outer peripheral surface of the metal piston 15.

A retainer 24 is provided at the bottom of the cylinder hole 11a.
A spring 25 is interposed between the retainer 24 and the retainer fitted to the front portion 4a of the synthetic resin piston 4, and constantly biases the synthetic resin piston 4 rightward in FIG. doing. A spring 26 is interposed between the retainer fitted to the rear part 4e of the synthetic resin piston 4 and the metal piston 15, and constantly biases the metal piston 15 rightward in FIG. An inlet valve 27 is provided between the retainer 24 and the synthetic resin piston 4. The inlet valve 27 is slidably disposed on the retainer 24, and the valve portion 27a of the inlet valve 27 is
It is inserted into a hole 4h formed in the front part 4a of the synthetic resin piston 4.

When a pressing force is applied to the metal piston 15 in the state of FIG. 6 (non-operating state), the metal piston 15 is moved leftward in FIG. Cup material 20 attached to 15
Shuts off the supply port 14b and the pressure of the brake fluid in the second pressure chamber 17 is increased. When the synthetic resin piston 4 is moved to the left in FIG. 6 by the pressure increase of the brake fluid in the second pressure chamber 17, the valve portion 27a of the inlet valve 27 shuts off the communication hole 4i of the synthetic resin piston 4 and The pressure of the brake fluid in one pressure chamber 16 is increased. Both pressure chambers 16, 1
The brake fluid is pressure-fed to the wheel brakes via the outlet port 28 by the pressure increase of the brake fluid of the seventh step.

When the pressing force on the metal piston 15 is released, the pistons 4 and 15 are returned to the right in FIG. 6 by the urging forces of the springs 25 and 26. That is, with the return movement of the pistons 4 and 15, the valve portion 27a opens the communication hole 4i to allow the first pressure chamber 16 to communicate with the first brake fluid supply chamber 22, and the cup material 20 becomes the supply port 1
By opening 4b, the second pressure chamber 17 is communicated with the second brake fluid supply chamber 23, and the brake fluid pressure is reduced.

As described above, according to the method of molding the synthetic resin piston 4 of the present embodiment, the resin in the molding die 1 is moved by the pressing devices 2 and 3, and the molten resin is moved to a portion having a low resin density. By spreading, the molten resin 5 can be more uniformly filled. Furthermore, when a piston having a flange portion substantially equal to the diameter of a cylinder hole is molded by a conventional method of molding a synthetic resin piston, the resin and glass fiber flow because the direction in which the injected resin flows is the axial direction of the cavity space. It will cool and harden alongside the axial direction. Generally, when the resin cools and hardens, it shrinks in the direction perpendicular to the direction of the flow of the resin. When the resin shrinks in the above, there is a possibility that the piston rattles in the cylinder hole, which may hinder smooth sliding of the piston. However, according to the molding method in the present embodiment,
When the synthetic resin piston 4 is formed, the front flange 4
a, since the orientation of the resin can be dispersed in the vicinity of the molded portions 1g and 1f of the rear side flange portion 4d, when the resin cools and hardens, both the flange portions 4b and dimensional accuracy are particularly required. 4d and its vicinity are suppressed from shrinking in the radial direction of the piston 4 and the shrinkage of the piston 4 in the axial direction is also suppressed, so that dimensional accuracy can be ensured. In addition, the generation of voids and cracks can be suppressed.

Further, by forming the small holes 4f and 4g, the intermediate portion 4c, which is a thick portion, and thus the flange portion 4b,
The thickness around 4d can be reduced, and the occurrence of voids, cracks, and the like is also suppressed.

Further, since there is no situation in which the molten resin is separated in the cavity space 1e and the separated molten resins are merged, there is no possibility that welding occurs.

Therefore, it is possible to provide a method of molding the synthetic resin piston 4 which suppresses the generation of voids, cracks, welds, and the like.

In the present embodiment, the resin mold 1
Are a fixed mold 1a, a movable mold 1b, and an upper slide 1c.
And the lower slide 1d, but it is needless to say that the present invention is not limited to this configuration.

In this embodiment, the pressing devices 2 and 3 are composed of the hydraulic cylinders 2a and 3a and the working pins 2b and 3b.
However, it goes without saying that the present invention is not particularly limited to this configuration. Therefore, the holes 4f and 4g are not formed only by the rod-shaped processing pins 2a and 3a, but may be any as long as they can press and move the molten resin 5.

Further, in this embodiment, the synthetic resin piston 4 is formed as a resin product, but it is needless to say that the present invention is not particularly limited to this.

In this embodiment, the synthetic resin piston 4 for the master cylinder is formed, but it is needless to say that the present invention is not particularly limited to this.

In this embodiment, the front part 4a
And a synthetic resin piston 4 composed of a front flange portion 4b, an intermediate portion 4c which is a thick portion, a rear flange portion 4d, and a rear portion 4e, but is not particularly limited to this shape. Needless to say, there is nothing.

In the present embodiment, the molten resin 5
When the mold is filled 90% in the mold 1, the pressing devices 2, 3
Although the working pins 2b and 3b are moved forward, it goes without saying that the present invention is not particularly limited to this configuration. That is, it is only necessary that the resin can be moved to a predetermined portion by moving the processing pins 2 and 3 forward and pressing the resin in the mold 1.

In this embodiment, the holes 4g, 4g
fg is a through hole, but is not particularly limited to this shape.

In this embodiment, the piston 4
Is formed from a mixture of an aromatic nylon and a glass resin, but it goes without saying that the present invention is not particularly limited to this configuration.

Although the present invention has been described based on the above embodiment, the present invention is not limited to the above embodiment, but includes various embodiments according to the principle of the present invention.

[0053]

As described above, according to the first aspect of the present invention, the resin is moved to the predetermined portion by the pressing step, so that the molten resin can be more uniformly filled in the molding die.

Furthermore, since the orientation of the resin can be dispersed at and around the pressed portion during molding of the resin product, shrinkage of the resin is suppressed when the resin cools and hardens, and dimensional accuracy is ensured. Is possible. In addition, generation of voids, cracks, and the like can be suppressed.

Further, by forming a hole in the thick part of the resin product, it is possible to make the thick part thinner, and it is possible to further suppress the occurrence of voids and cracks.

Further, the molten resin diverges in the space,
Since the situation where the separated molten resins join does not occur, there is no possibility that welding occurs.

Accordingly, it is possible to provide a method for molding a resin product that suppresses the occurrence of voids, cracks, welds, and the like.

According to the invention of claim 2, in addition to the effect of the invention of claim 1, it is possible to provide an optimal molding method for molding a resin piston.

During the molding of the piston, the orientation of the resin can be randomized in the vicinity of the part to be pressed, and thus the part for forming the flange part. The resin shrinkage in the vicinity of the portion where the resin is molded is suppressed, and dimensional accuracy can be ensured, and voids, cracks, and the like can be suppressed.

Further, since the piston provided with a hole in the vicinity of the flange is formed, it is possible to make the piston thinner by providing the hole.
It is also possible to suppress the occurrence of cracks and the like.

Accordingly, it is possible to provide a piston which secures the dimensional accuracy by preventing the resin from shrinking at and around the flange portion where the dimensional accuracy is particularly required, and further, prevents the occurrence of voids and cracks. I have.

According to the invention of claim 3, in addition to the effect of the invention of claim 2, it is possible to provide a molding method for molding an optimum piston for the master cylinder.

During molding of the piston, the orientation of the resin can be dispersed around the portion to be pressed, and thus the portion where the front and rear flanges are formed. As a result, the contraction of the resin piston near the part where the front and rear flanges are formed is suppressed,
It is possible to reduce the dimensional accuracy and further suppress the occurrence of voids, cracks, and the like.

Further, since the piston having the holes formed near the front and rear flange portions is formed, it is possible to make the piston thinner by providing the holes, and it is possible to further reduce the voids and cracks. It is also possible to suppress the occurrence of.

Therefore, the dimensional accuracy is ensured by preventing the resin from shrinking at the flange portion and the vicinity thereof where dimensional accuracy is particularly required, and further, it is used for a vehicle master cylinder which prevents the occurrence of voids and cracks. It is possible to provide a synthetic resin piston that can be used.

[Brief description of the drawings]

FIG. 1 is a sectional view of a molding die 1 according to an embodiment.

FIG. 2 is a cross-sectional view of a piston 4 formed by the forming die 1 of FIG.

FIG. 3 is a view showing a state in which a molten resin 5 has been injected into the mold of FIG. 1;

FIG. 4 is a view showing a state in which the processing pins 2b and 3b of FIG. 3 are moved forward.

FIG. 5 is a view showing a state in which the molten resin of the mold 1 of FIG. 4 has solidified.

FIG. 6 is a sectional view of a vehicle brake master cylinder 10 employing the synthetic resin piston 4 of FIG. 2;

[Explanation of symbols]

Reference Signs List 1 Mold 1e Cavity space 4 Piston 4b Front flange 4d Rear flange 4f, 4g Hole 5 Molten resin 5a, 5b Flange molded part 11 Cylinder body 11a Cylinder hole

Claims (3)

[Claims] A mold disposing step for disposing a mold having a space having a shape of a resin product; an injection step for injecting a molten resin into the space; and a step before the resin injected into the space is solidified. Pressing the resin in the space to move the resin to a predetermined portion. 2. The resin product is a piston, and the piston has a flange portion substantially equal to a diameter of a cylinder hole of a cylinder body into which the piston is slidably inserted, and the resin is pressed. The method according to claim 1, wherein the portion is in the vicinity of a portion of the molding die where the resin forms the flange portion. 3. The method for molding a resin product according to claim 2, wherein the cylinder body is a cylinder body of a vehicle master cylinder, and the piston has the flange portions at two positions, a front side and a rear side.