JP5458587B2 - Resin gear - Google Patents

Description

  The present invention relates to a resin gear whose entire tooth portion is made of resin.

  Resin gears are used as counterpart gears that mesh with metal gears in order to suppress the generation of noise when teeth mesh, and require high strength and dimensional stability.

For example, aramid fibers are extremely high in strength. Aramid fiber reinforced resin gears filled with aramid fibers in a matrix resin, or aramid fiber substrates reinforced with an aramid fiber substrate that contains aramid fibers as the main component. Resin gears are attracting attention.
However, aramid fibers are easy to absorb moisture, and their saturated moisture absorption exceeds 1% by mass. Therefore, the aramid fiber reinforced or aramid fiber base reinforced resin gear easily absorbs moisture. The fiber reinforced resin gear causes a dimensional change due to swelling due to moisture absorption.

It is considered that the above problem can be solved by improving the adhesion between the aramid fiber and the matrix resin, and as a means for improving the adhesion, for example, a technique described in Patent Document 1 has been proposed. In this technique, the surface of an aramid fiber is coated with a polyamide having a phenolic hydroxyl group, and a polyamide layer is formed on the surface of the aramid fiber.
However, even with the technique described in Patent Document 1, it has been insufficient to reduce the hygroscopicity of the resin gear.

Japanese Patent Laid-Open No. 09-124801

  As described above, a resin gear whose entire tooth portion is made of resin undergoes a dimensional change due to swelling due to moisture absorption, and the tooth profile changes. As a result, there is a problem that an abnormality occurs at the time of meshing such that the rotation speed of the gear varies or the gear does not rotate smoothly. Further, there is a problem that the amount of backlash is reduced and abnormal noise is generated when meshing.

  The problem to be solved by the present invention is to provide a resin gear that does not cause abnormalities or abnormal noises when meshed even when the resin gear undergoes dimensional changes due to swelling due to moisture absorption.

  As a result of intensive studies on the dimensional change due to moisture absorption of the resin gear, the present inventors have found that the tooth shape part has a particularly large tooth tip portion, and have reached the present invention.

That is, the resin gear according to the present invention is a resin gear in which the entire tooth portion is made of a resin containing aramid fibers, and the tooth surface of the tooth tip portion is positioned inside the tooth surface of the reference tooth profile shape. It is a thing.
Then, the tooth tip portion is defined as a portion corresponding to 20 to 50% of the total tooth height from the tooth tip, and in the tooth tip portion, the tooth tip is a reference corresponding to a distance corresponding to 0.2 to 1.2% of the total tooth height. It is located inside the tooth-shaped tooth tip (Claim 1 ).

  In the present invention, the reference tooth profile shape refers to a shape in which the gear tooth profile along the involute curve is viewed from the plane in which the rotation axis of the gear stands vertically. Further, the tooth surface refers to a surface where the teeth mesh with each other.

  Since the conventional resin gear is formed in a reference tooth profile shape, the tooth profile shape of the tooth tip portion changes particularly greatly due to moisture absorption. As a result, there are problems that the rotation speed of the gears varies, the gears do not rotate smoothly, an abnormality occurs at the time of meshing, the backlash amount is reduced, and an abnormal noise is generated at the time of meshing. .

  In the resin gear according to the present invention, the tooth surface of the tooth tip portion is positioned on the inner side of the tooth surface of the reference tooth profile shape. Can be suppressed to a small extent. For this reason, there is no fear that abnormalities or abnormal noises occur during the engagement.

Then, the tooth tip portion is defined as a portion corresponding to 20 to 50% of the total tooth height from the tooth tip, and in the tooth tip portion, the tooth tip is a reference corresponding to a distance corresponding to 0.2 to 1.2% of the total tooth height. Ru is located inside the tooth tip of the tooth profile. Within this range, there is no concern that the gears will rattle or the rattling noise will increase even in the initial state (before moisture absorption).

It is an enlarged view of the tooth part for demonstrating the tooth profile shape of the resin gear concerning embodiment of this invention.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an enlarged view of a tooth portion of a resin gear according to an embodiment of the present invention. In the resin gear according to the present invention, the entire tooth portion 1 is made of a resin containing an aramid fiber . Then, the tooth surface of the tooth tip portion 3 is formed so as to be positioned inside the tooth surface of the reference tooth profile shape 5. Further, the tooth tip portion 3 is a portion corresponding to 20 to 50% of the total tooth height 4 from the tooth tip 2, and the tooth tip 2 is a reference by a distance corresponding to 0.2 to 1.2% of the total tooth height. It is located inside the tooth tip of the tooth profile shape 5.

The resin gear according to the present invention includes a resin gear having a tooth profile formed by molding, a resin gear having a tooth profile formed by hobbing, a resin gear having a tooth profile formed by a shaving finish after hobbing.
In particular, when a tooth profile is formed by a shaving finish after hobbing, the tooth profile accuracy is improved and the tooth surface roughness is reduced, so that vibration and noise during meshing are reduced, which is preferable.

Reference example 1
The following were prepared as a liquid resin (thermosetting resin). 2,2 ′-(1,3-phenylene) bis-2-oxazoline (component (A)) and 4,4′-diaminodiphenylmethane (component (B)) in a molar ratio of 2/1 (mass ratio 69/31) It is heated and mixed and dissolved at a mixing ratio to obtain a liquid. To this, n-octyl bromide is blended as a curing accelerator. The compounding quantity of a hardening accelerator is 1 mass part with respect to 100 mass parts of total amounts of (A) and (B) component.

In this example , the following were prepared as the reinforcing fiber base. However, it is not limited to this.
A circular knitted cylindrical body is formed by circularly knitting a mixed yarn of meta-type aramid fiber and para-type aramid fiber. The circular knitted tubular body is turned upside down and wound up in the axial direction to obtain a ring-shaped reinforcing fiber substrate having an outer diameter of 77 mm, an inner diameter of 50 mm, and a thickness of 10 mm.

  Two ring-shaped reinforcing fiber bases stacked one above the other and a metal bush as an insert at the center thereof are accommodated in a 200 ° C. molding die. The molding die opens and closes in the thickness direction of the ring-shaped reinforcing fiber base material, and the ring-shaped reinforcing fiber spreads in the surface direction by compressing the ring-shaped reinforcing fiber base material by closing the molding die. The substrate is pressed around the metal bush to conform to its shape. Then, the inside of the molding die is brought into a reduced pressure state. Next, the liquid resin is injected into a closed mold, and the liquid resin that has permeated the ring-shaped reinforcing fiber base is heated and cured to form an aramid fiber base reinforced resin molded body using a metal bush as an insert. To do.

The aramid fiber base reinforced resin molded body was cut into the dimensions shown in Table 1 to obtain a resin gear. The tooth tip portion was formed so as to be positioned inside the tooth surface of the reference tooth profile shape. The tooth tip portion at this time is a portion corresponding to 18% of the total tooth height from the tooth tip (hereinafter referred to as (a)), and in the tooth tip portion, the tooth tip corresponds to 0.3% of the total tooth height. The distance was set to the inside (hereinafter referred to as (b)) from the tooth tip of the reference tooth profile shape.
The cutting process described above was a hobbing process followed by a shaving finish.

Examples 1 to 4, Reference Examples 2 to 4
In Reference Example 1, resin gears were obtained in the same manner as Reference Example 1 except that (a) and (b) were as shown in Table 2 for each example.

Conventional Example 1
In Reference Example 1, a resin gear was obtained in the same manner as in Reference Example 1 except that the tooth tip portion had a reference tooth profile shape.

Table 2 shows the results of measuring the pressure angle error change amount and the 1-pitch meshing error of both tooth surfaces using the resin gears produced in the above examples, reference examples, and conventional examples. The measuring method is as follows.
Pressure angle error variation: The pressure angle error of the resin gear before and after the treatment was measured to determine the pressure angle error variation. In addition, a process condition is 60 degreeC-200 hours in the engine oil containing 10 mass% of water. The pressure angle error was measured according to the former JIS-B-1752 (spur gear and helical gear measuring method).
1 pitch meshing error of both tooth surfaces: Measured according to old JIS-B-1752 (spur gear and helical gear measuring method).

As shown in Table 2, the resin gear according to the present invention has a small change in pressure angle error because the tooth surface of the tooth tip portion is positioned on the inner side of the tooth surface of the reference tooth profile, and the tooth profile due to moisture absorption. Even when the shape changes, the swelling change from the reference tooth profile shape can be kept small (contrast of Examples 1 to 4, Reference Examples 1 to 4 and Conventional Example 1). For this reason, there is no fear of meshing abnormalities such as fluctuations in the rotation speed of the gears or the gears not rotating smoothly, or abnormal noise due to a decrease in the amount of backlash.

Then, the tooth tip portion is defined as a portion corresponding to 20 to 50% of the total tooth height from the tooth tip, and in the tooth tip portion, the tooth tip is a reference corresponding to a distance corresponding to 0.2 to 1.2% of the total tooth height. By being positioned inside the tooth tip of the tooth profile shape, the pressure angle error change amount can be further reduced, and the change in swelling can be further suppressed from the reference tooth profile shape (Examples 1 to 4 and Reference Examples 1 to 4). Contrast). In Reference Examples 3 and 4 , the tooth face 1 pitch meshing error becomes large, and in the initial state (before moisture absorption), the gear rotation rattles or generates rattling noise within the practically unused range. It may become bigger.

1 is a tooth part 2 is a tooth tip 3 is a tooth tip part 4 is a total tooth height 5 is a reference tooth profile shape

Claims (1)

The entire tooth portion is a resin gear made of resin containing aramid fiber ,
The tooth surface of the tooth tip part is located inside the tooth surface of the reference tooth profile ,
The tooth tip portion is a portion corresponding to 20 to 50% of the total tooth height from the tooth tip,
In the tooth tip portion, the tooth tip is positioned inside the tooth tip of the reference tooth profile shape by a distance corresponding to 0.2 to 1.2% of the total tooth height .

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