JP3980239B2 - Resin gear and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a resin gear formed by casting a metal bush and a manufacturing method thereof. In particular, a resin in which a metal bush and a reinforcing fiber base disposed around the metal bush are accommodated in a molding die, and a liquid resin injected into the molding die is impregnated into the reinforcing fiber base to cast a metal bush. The present invention relates to a gear, that is, a resin gear by injection molding.
[0002]
[Prior art]
It is important to ensure the bond strength between the metal bush and the resin portion of the resin gear formed by casting the metal bush.
The resin gear is manufactured by the above-described injection molding by deforming the reinforcing fiber base with the pressure when the molding die is closed, so that a number of detents protruding radially from the outer surface of the metal bush are bitten into the reinforcing fiber base. In this state, the liquid resin is injected into the molding die. The reinforcing fiber base material is hardly deformed when the liquid resin is injected and cured, and the biting is hardly promoted. This is because the reinforcing fiber base material previously impregnated with the resin is heated and pressure-molded to form a metal. This is very different from the production of resin gears in which bushes are cast. That is, in the heat and pressure molding, since the reinforcing fiber base moves along with the flow of the resin and is filled around the rotation stopper, the resin portion including the reinforcing fiber base and the metal bush are securely bonded and the bond strength is large. Become. On the other hand, in the injection molding, the reinforcing fiber base material hardly moves due to the flow of the resin, and therefore the filling of the reinforcing fiber base material around the rotation stopper tends to be insufficient.
[0003]
In resin gears that require high strength, heat resistance, wear resistance, and dimensional stability (for example, for automobile parts), increasing the fiber length as a reinforcing fiber, adopting high-strength aramid fiber, etc. It is being considered. In addition, as for the form of the reinforcing fiber base, a knitted fabric, a woven fabric, a felt-like material in which fibers are connected by a needle punch, and the like have been studied. In the injection molding in such a case, the deformation of the reinforcing fiber base caused by the pressure for closing the molding die is reduced.
[0004]
[Problems to be solved by the invention]
In the resin gear by injection molding, if there is little deformation of the reinforcing fiber base caused by the pressure to close the molding die, filling of the reinforcing fiber base around the rotation stopper is insufficient, and this portion becomes resin-rich. The resin-rich portion with a small content of the reinforcing fiber base has a low mechanical strength, so that the bond strength between the metal bush and the resin portion may be lowered.
[0005]
In the present invention, a metal bush and a reinforcing fiber base disposed around the metal bush are accommodated in a molding die, and a liquid resin injected into the molding die is impregnated into the reinforcing fiber base to cast a metal bush. That is, it is intended for resin gears by injection molding. The problem to be solved by the present invention is to increase the bonding strength of the resin portion including the metal bush and the reinforcing fiber base by sufficiently filling the reinforcing fiber base around the rotation stop in the resin gear. It is.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the resin gear by injection molding according to the present invention is characterized in that a metal bush has the following configuration. That is,
The metal bush has a cylindrical outer peripheral surface, and a number of detents protrude radially from the metal bush outer circumferential surface, and the detents are arranged in a single line on the circumferential surface of only the central portion in the thickness direction of the metal bush. The thickness of the detent is thinner than the thickness of the metal bush. The concave surface formed between adjacent detents has a circular cross section in the direction of the metal bush. The detent is the thickness of the metal bush. Only in the direction, it is an undercut shape in which the thickness of the top portion is thick and the thickness of the base portion is thin .
[0007]
As described above, the filling of the reinforcing fiber base around the rotation stopper in the injection molding is performed by the deformation of the reinforcing fiber base due to the pressure when the molding die is closed. To the above concave arcuate cross-sectional shape, it enters as a reinforcing fiber substrate deformed slips. In addition to this, the detent is buried in the reinforcing fiber base by making the detent thickness thinner than the metal bush thickness. By these actions, the filling property of the reinforcing fiber base material around the rotation stopper becomes good, and it is difficult to form a resin-rich portion that does not include the reinforcing fiber base material around the rotation stopper. Since the resin-rich portion has a low mechanical strength, if a resin-rich portion is formed around the metal bush, the resin-rich portion is easily damaged, and damage starting from the resin-rich portion easily propagates toward the tooth portion of the resin gear. However, the resin gear according to the present invention is not easily damaged because the reinforcing fiber base is sufficiently filled around the metal bush, and as a result, the bond strength of the resin portion including the metal bush and the reinforcing fiber base is It will be big.
[0008]
The detent protruding radially on the outer peripheral surface of the metal bush has an undercut shape with a thick top and a thin base . Preferably, the undercut digging depth d is 30 to 85% of the detent height h.
[0009]
When the resin gear rotates, a force that causes the rotation stopper to shear the resin portion is generated, but since the area of the resin portion when viewed in cross section is increased by making the rotation stopper undercut, the shear force is received. Convenient as a side. Further, the thermal expansion coefficient of the resin portion is larger than that of the metal bush. Therefore, although the resin portion tends to be separated from the metal bush in the radial direction due to thermal expansion, the above-described undercut shape acts to prevent this movement.
In addition, when the undercut digging depth d exceeds 85% of the detent height h, the strength of the detent base becomes small, so it is preferable to keep it at about 85%.
[0010]
The resin gear by such injection molding is manufactured as follows.
The metal bush and the reinforcing fiber base disposed around the metal bush are accommodated in a molding die, and a liquid resin is injected into the molding die to impregnate the reinforcing fiber base and the metal bush is cast and molded. The metal bush has a cylindrical outer peripheral surface,
On its outer peripheral surface, a large number of detents are projected radially only in the thickness direction central portion , and the detents are arranged in a single line on the circumferential surface of only the central portion in the thickness direction of the metal bush,
Make the detent thickness thinner than the thickness of the metal bush,
The concave cross section (cross section in the metal bushing surface direction) formed between adjacent detents is an arc shape,
The rotation stopper is configured to have an undercut shape with a thick top portion and a thin base portion only in the thickness direction of the metal bush .
Then, by deforming the reinforcing fiber base with the pressure when the molding die is closed, the reinforcing fiber base is filled around the rotation stopper, and the rotation stopper is bitten into the reinforcing fiber base. In this state, a liquid resin is injected into the molding die and penetrated into the reinforcing fiber base.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, various forms can be adopted as the reinforcing fiber substrate. For example, as shown in FIG. 4, a reinforcing fiber substrate 2 is formed by winding up a cylindrical body 1 formed by weaving or knitting aramid fiber yarns in the axial direction and forming a ring shape. In addition, it is possible to employ a reinforcing fiber base or the like in which a felt-like material in which fibers are connected by a needle punch is wound in a cylindrical shape or a roll shape and compressed in a bellows shape in the axial direction. It is appropriate that the aramid fiber constituting the felt-like material has a fiber length of about 50 mm.
[0012]
The above reinforcing fiber base is disposed around the metal bush and accommodated in a molding die, and the reinforcing fiber base is impregnated with resin, and the metal bush is cast and formed. For example, as shown in FIG. 5, the reinforcing fiber base material 2 is overlapped in two stages in the molding die 21, a metal bush 11 is disposed at the center, and the molding die 21 is closed. The reinforcing fiber base 2 is compressed and deformed by the pressure at the time of closing the molding die so as to conform to the shape of the metal bush 11, the inside of the molding die is reduced in pressure, and a liquid resin (crosslinked polyaminoamide, epoxy resin, polyimide, etc.) Is injected to penetrate the reinforcing fiber base material and cured by heating.
Teeth are formed by cutting on the resin portion (outer periphery) including the reinforcing fiber base material to obtain a resin gear as shown in FIG. As shown in FIG. 2A, a large number of detents 12 project radially from the outer peripheral surface of the metal bush 11, and as shown in FIG. Is sufficiently filled, and the rotation stopper 12 and the resin portion including the reinforcing fiber base are integrated.
Aramid fibers, especially para-aramid fibers, are extremely strong. If the reinforcing fiber base is composed only of para-aramid fibers, the above-described machinability is lowered, so it is preferable to use meta-aramid fibers in combination. The cylindrical body 1 is formed by a blended yarn of both fibers, or a felt-like material is formed by using both fibers in combination. The combined use of both fibers is also advantageous for enhancing the reinforcing fiber base material filling ability around the rotation stopper.
[0013]
An important point in the present invention is the structure of the rotation stopper 12. Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, a large number of the rotation stoppers 12 project radially from the outer peripheral surface of the metal bush 11, and the number is 10 or more, preferably 15 or more. These are arranged on the outer peripheral surface of the metal bush 11 at an equal angle. In the case where several rotation stoppers are arranged, the force of one rotation stopper trying to shear the resin portion increases, and the resin portion is easily broken. By arranging a large number of detents at an equal angle, the force with which one detent attempts to shear the resin portion is reduced, and the shear force of each detent is uniform.
The concave surface 13 formed between the detents has a circular cross section in the metal bush surface direction . The radius R of the arc is suitably about 5 to 2 mm when the reinforcing fiber substrate is a combination of para-aramid fibers and meta-aramid fibers. When the thickness is about 1 mm, the filling property of the reinforcing fiber base material is lowered even in an arc shape.
The thickness of the rotation stopper 12 is suitably about 1/3 of the thickness of the metal bush 11. As shown in FIG. 1B, the rotation stopper 12 has an undercut shape with a thick top portion and a thin base portion . In particular, when the digging depth d of the undercut is 30 to 85% of the non-rotating height h, the bond strength between the metal bush and the resin portion can be further increased.
[0014]
【Example】
Example A cylindrical body 1 (weighing amount 130 g / m ² ) woven with a blended yarn of para-aramid fiber and meta-aramid fiber (mixed mass ratio 50/50, 20th) was prepared. Two reinforcing fiber bases 2 obtained by rolling up the cylindrical body 1 in the axial direction were used, and injection molding was performed by the method described with reference to FIG. 5 together with the metal bush 11. The resin impregnation into the reinforcing fiber base 2 was performed by injecting a crosslinked polyaminoamide into a molding die 21 in a reduced pressure state (1300 Pa).
Here, the metal (steel) bush 11 has a thickness of 9 mm, an outer diameter of 52 mm including the rotation stopper 12, and an outer diameter of 49 mm not including the rotation stopper 12. Twenty-four rotation stoppers 12 are arranged at intervals of 15 °. Its height h is 1.5 mm, and the top thickness is 3 mm. The concave surface 13 formed between the rotation stoppers has a radius R3 mm and a depth 1.3 mm. Accordingly, a step of 0.2 mm is formed between the deepest portion of the concave surface 13 and the outer peripheral surface not including the rotation stopper 12.
The resin part including the molded reinforcing fiber base had an outer diameter of 80 mm, and teeth were formed on the outer periphery by cutting (22 teeth).
A resin gear in which the above conditions are made constant and the undercut digging depth d described with reference to FIG. 1B is changed in the range of 0, 0.5, 0.75, 1, 1.25 mm. Prepared and evaluated the bond strength between the metal bush and the resin part. When the digging depth d is 0, it is not an undercut shape but the same thickness of 3 mm from the top to the base of the detent. When the undercut digging depth d is converted into a ratio to the rotation stop height h, they are 0, 33, 50, 67, and 83%, respectively.
The evaluation of the bond strength is to measure the breaking load at the interface between the metal bush and the resin portion by meshing each resin gear with a fixed steel gear and twisting the rotating shaft of the resin gear. The breaking load was the magnitude at which cracks occurred in the resin part at the joint between the two. Any cracks enter the teeth from the interface between the resin portion and the rotation stopper. The results are shown in FIG. From FIG. 3, it can be seen that when the undercut digging depth d is 30 to 85% of the detent height h, the bond strength becomes more remarkable.
[0015]
Conventional Example In the above embodiment, the concave surface 13 has a rectangular cross-sectional shape. The depth is 1.3 mm. The undercut digging depth d was set to 0.75 mm. FIG. 6 shows a plan view and an enlarged view of the main part of the metal bush.
The breaking load was measured in the same manner as in the example, and the results are shown in FIG.
[0016]
【The invention's effect】
As described above, the resin gear by injection molding according to the present invention can increase the bond strength between the metal bush and the resin portion by specifying the configuration of the rotation stop of the metal bush.
[Brief description of the drawings]
FIG. 1 is a plan view of a metal bush applied to a resin gear according to the present invention, an enlarged view of a main part (a), and a cross-sectional view (b) taken along line AA ′.
FIG. 2A is a plan view of a resin gear according to the present invention, and FIG. 2B is a cross-sectional view taken along line BB ′.
FIG. 3 is a curve diagram showing a breaking load at an interface between a resin bush and a metal bush of a resin gear.
FIG. 4 is an explanatory view showing an example of a reinforcing fiber base applied to the resin gear according to the present invention.
FIG. 5 is an explanatory view showing a state of molding a resin gear according to the present invention.
FIG. 6 is a plan view and an enlarged view of a main part of a metal bush applied to a conventional resin gear.
[Explanation of symbols]
1 is a cylindrical body 2 is a reinforcing fiber base material 11 is a metal bush 12 is a rotation stopper 13 is a concave surface 21 is a molding die

Claims (3)

In a resin gear in which a metal bush and a reinforcing fiber base disposed around the metal bush are accommodated in a molding die, a liquid resin injected into the molding die is impregnated into the reinforcing fiber base and the metal bush is cast and molded.
The metal bush has a cylindrical outer peripheral surface,
A number of detents protrude radially on the outer peripheral surface of the metal bush, and the detents are arranged on the peripheral surface of only the central portion in the thickness direction of the metal bush,
The detent thickness is thinner than the thickness of the metal bush,
The concave surface formed between adjacent detents has a circular cross section in the direction of the metal bush surface ,
The rotation stopper is an undercut shape having a thick top portion and a thin base portion only in the thickness direction of the metal bush . The depth d digging undercut, the resin gear according to claim 1, wherein 30 to 85% of the detent height h. Production of resin gears in which metal bushes and reinforcing fiber bases arranged around them are housed in molding dies, liquid resin is injected into the molding dies and impregnated into the reinforcing fiber bases, and metal bushes are cast and molded In
The metal bush has a cylindrical outer peripheral surface,
A number of detents are projected radially on the outer circumferential surface, and the detents are arranged on the circumferential surface of only the central portion in the thickness direction of the metal bush,
Make the detent thickness thinner than the thickness of the metal bush,
The concave cross section (cross section in the metal bushing surface direction) formed between adjacent detents is an arc shape,
Adopted a structure with an undercut shape for the rotation stopper only in the thickness direction of the metal bush, with a thick top and a thin base .
The reinforcing fiber base material is deformed by the pressure when the molding die is closed, so that the detent is bitten into the reinforcing fiber base material, and in this state, the liquid resin is injected into the molding die. A manufacturing method of resin gears.

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