JP2526927Y2 - Gear device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear device mainly used for an engine, and more particularly to a gear device comprising a metal gear and a resin gear.

[0002]

2. Description of the Related Art In recent years, reduction of gear noise in an engine,
From the viewpoint of cost reduction and weight reduction, gear resin is widely used. Such a resin gear is generally manufactured by integral molding of a thermoplastic resin such as a nylon resin.

[0003] The above-mentioned resin gear has a tooth flank shape in which one tooth surface is viewed along a tooth width direction, and is enlarged in a tooth thickness direction.
As shown in (1), due to shrinkage sink after molding, the central portion 21a of the tooth tends to be slightly dented with respect to the ideal tooth trace 21d, and the portion 21b near the tooth end tends to be slightly expanded in a convex shape. Further, burrs 21c due to molding pressure are likely to be generated along the tooth edges of the gear 21 in the mold matching portion.

Therefore, in order to reduce the influence of protrusions and burrs near the tooth ends of the resin gear 21, the tooth width of the metal gear 31 is made larger than that of the resin gear 21 as shown in FIG. If the width is reduced, the contact pressure increases due to a smaller engagement width, and the tooth surface of the resin gear 21 wears stepwise as shown in FIG. 5 (b), and the stepped wear portion 22 gradually advances. , There is a problem in durability. Therefore, when the resin gear is combined with the metal gear, conventionally, the tooth width of the metal gear 31 is made slightly wider than that of the resin gear 21 as shown in FIG.

[0005] As another prior art, Japanese Patent Publication No.
There is one described in JP-A-9-41056.

[0006]

However, when a gear device is constructed by combining a resin gear with a metal gear having a slightly wider tooth width (FIG. 4), there are the following inconveniences.

1) When the backlash with the metal gear is set to an appropriate value at the center of the tooth width of the resin gear, the backlash becomes zero or less (minus) at the tooth end due to the projections and burrs due to sink marks. In particular, a whistling sound is generated at the beginning of driving.

2) If the backlash is set to an appropriate value at the tooth end in order to avoid the occurrence of the pickling noise in the above 1), the burrs are removed after the sliding operation, and the backlash increases. A sound is generated.

3) When finishing such as buffing is performed to remove burrs of the resin gear after molding, the number of processing steps is increased and the cost is increased.

4) Depending on the molding conditions and post-processing conditions of the resin gear, the unevenness of the protrusion of the tooth end and the height of the burr due to sink are large, so that the meshing with the metal gear is unstable.

The present invention has been made in view of the above points, and avoids poor meshing caused by protrusions of tooth ends and burrs due to sinks without impairing the durability of a resin gear. It is an object of the present invention to provide a gear device that realizes stable meshing with the gear.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, a gear device according to the present invention includes: a) a metal gear and a resin gear which mesh with each other at substantially the same tooth width at a root portion. A gear device, wherein b) at least one end of the metal gear in the face width direction extends from the tooth tip to the vicinity of the root of the tooth.
Chamfered so as to be inclined with respect to the tooth length direction over the entire surface , c) Near the root of the chamfered portion of the metal gear,
Mutually pass inside the end of the tooth tip of the resin gear
Is engaged .

[0013]

According to the gear device of the present invention having the above-described configuration, the tooth end of the metal gear has a tooth height extending over the entire end surface of the tooth.
Beveled to the vicinity of the root of the gear, so that the meshing of the metal gear with the tooth end of the metal gear with the resin gear is difficult to be affected by the convex part of the tooth end of the resin gear and the burr. , Thereby reducing backlash variations.

As compared with the case where the tooth width of the metal gear is narrower than that of the resin gear (see FIG. 5 (a)), FIG.
Since the meshing width of the shaded portion (b) increases, the surface pressure acting on the resin gear can be reduced, and the durability is improved.

[0015] Further, the resin gears tend to escape because the tooth thickness at the tooth tip side becomes thinner as compared with the involute tooth profile due to shrinkage shrinkage after molding, so that the surface pressure at the tooth root side tends to increase. teeth but in this invention the tooth end portion of the metal gear
Since the is inclined with respect to the chamfered tooth depth direction over the entire end face, as shown in FIG. 2 (c), but engagement of the resin gear in the tooth end portion, displaced from point A to point B As a result, the ideal engagement along the involute tooth profile is approached, and the increase in the surface pressure on the root side of the resin gear is alleviated.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a gear device according to the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing a part of a gear device according to the present embodiment.
Is formed by two gears 2.3 in which a metal gear 3 made of a helical gear meshes with a resin gear 2 made of a helical gear integrally formed of a thermoplastic resin such as nylon 66 resin. It is configured. Each of the gears 2 and 3 is not a helical gear, but may be, for example, a spur gear.

As shown in FIG. 2 (a), the metal gear 3 has a tooth width approximately equal to that of the resin gear 2 at the root portion (to be precise,
The metal gear 3 is slightly wider), both ends 3a of the teeth 3a
Is chamfered at an inclination angle of about 45 ° with respect to the tooth tip circle diameter 3 s. Reference numeral 4 in FIG. 2A denotes a flange of a rotating shaft driven by the resin gear 2, and a rim portion 2b of the resin gear 2 is sandwiched between the flange and the reinforcing member 4b, and integrally joined by a stopper 4a. ing.

The gears 2 and 3 are mutually connected so that the chamfered line (near the root of the tooth) of the tooth end 3a of the metal gear 3 passes slightly inward from the end of the tooth tip of the resin gear 2. They are combined with each other. That is, the tooth end portion (chamfered portion) 3a of the metal gear 3 is meshed with the convex portion of the tooth end of the resin gear 2 and a portion which is not easily affected by burrs. And both gears 2
・ Set the backlash to an appropriate value near the tooth end of 3
There Ru.

FIG. 2 (b) shows one end of the meshing portion of the two gears 2, 3 and FIG. 2 (c) shows the resin gear 2 shown in FIG. 2 (b).
Gear 3 in the XX line section and the YY line section
Represents an engaged state. As shown in FIG. 2C, the meshing with the metal gear 3 progresses relatively from the point A to the point B of the resin gear 2, so that the meshing state of the involute teeth is close to each other. Therefore, an increase in surface pressure on the root side of the resin gear 2 is reduced, and smooth and stable meshing with the metal gear 3 is obtained.

Although the above embodiment does not specifically show where the gear device 1 is used, for example, a metal gear 3 is used for a crankshaft gear of an engine, and a camshaft gear meshed with the crankshaft gear is used for the camshaft gear. A resin gear 2 is used. Although not particularly limited, usually, the metal gear 3 is used for the driving gear, and the resin gear 2 is used for the driven gear. Also, the resin gear 2
Are often used in engines such as balance shaft gears and governor gears.

In the above embodiment, the metal gear 3
Although the case where both ends of the tooth are chamfered has been shown, the effect is slightly reduced, but chamfering one end of the tooth is also effective.

When chamfering the end of the metal gear 3, it is necessary to chamfer from the tooth tip to the vicinity of the tooth root.
The angle of the chamfer is appropriately set according to the occurrence of sink marks, burrs, and the like at the tooth ends of the resin gear 2.

Further, a gear device in which a plurality of resin gears 2 are simultaneously meshed with a metal gear 3 can be provided.

[0025]

[Effect of the invention] As is clear from the above explanation,
The gear device of the present invention has the following effects.

(1) Poor meshing caused by protrusions and burrs at the tooth end due to shrinkage sink after molding of the resin gear is avoided, and smooth and stable meshing with the metal gear is achieved.

(2) Since it is only necessary to perform simple processing such as chamfering the end of the metal gear, the manufacturing cost is low, economical and economical as compared with the case where the finish such as deburring is performed on the resin gear. is there.

(3) Since the reduction in the mesh width with the resin gear due to the chamfering of the end of the metal gear is small, the durability is hardly affected.

[Brief description of the drawings]

FIG. 1 is a partially omitted perspective view showing an embodiment of a gear device according to the present invention.

2 (a) is a cross-sectional view showing an enlarged part of the gear device of FIG. 1, and FIG. 2 (b) is an enlarged view of one end of a meshing portion of the two gears of FIG. FIG. 2C is a sectional view, and FIG.
The enlarging process of the meshing state of the metal gear in the XX line cross section and the YY line cross section of the resin gear of FIG.
FIG. 3 is a view as viewed in the direction of the arrow Z in FIG.

FIG. 3 is a plan view showing a tooth ridge shape when one tooth surface of a resin gear is viewed along a tooth width direction, which is enlarged about 100 times in a tooth thickness direction with respect to the tooth width direction.

FIG. 4 is an enlarged sectional view showing a meshing portion between a metal gear and a resin gear whose tooth width is slightly widened.

FIG. 5 (a) is an enlarged sectional view showing a meshing portion of a metal gear and a resin gear with a reduced tooth width;
FIG. 3B is a sectional view showing a stepped wear portion generated on the tooth surface of the resin gear and an enlarged portion thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gear apparatus 2 Resin gear 3 Metal gear 3a Tooth end part (chamfer part)

Claims (1)

(57) [Scope of request for utility model registration] 1. A gear device comprising a metal gear and a resin gear meshing with each other at substantially the same tooth width at a root portion, wherein at least one end of the metal gear in the tooth width direction is formed. ,
Tooth length from the tip of the tooth to the vicinity of the root of the tooth
The metal gear is chamfered so as to be inclined with respect to the direction.
Mesh with each other so that it passes inside the tip of the tip of the fat gear
Gearing is characterized in that is.