JP4697887B2 - A pair of plastic helical gears - Google Patents

Description

  The present invention relates to a pair of resin blind gears constituting a part of a gear train for power transmission.

Conventionally, a part of a gear train for power transmission has been used with a pair of meshing splint gears in order to reduce operating noise and suppress vibration during power transmission (see Patent Document 1). ).
JP 2005-69458 A

  However, since a pair of meshing tooth-gear gears that are meshed with each other, a stress larger than the tooth root stress of the teeth excluding the vicinity of the top portion acts on the root portion of the top portion located in the center of the entire tooth width direction of the chevron shaped teeth. The lifetime is first reached due to the stress difference. Therefore, from the engineer in charge of mechanism design, the technology that can reduce the tooth root stress value of the top located in the center of the entire tooth width direction of the resin-made helical gear, and can increase the strength of the tooth of the plastic-made blind gear The offer of was desired.

  Therefore, an object of the present invention is to effectively increase the strength of the teeth of a resin-made spur gear and to prolong the life of a pair of resin-made spur gears that mesh with each other.

  According to the first aspect of the present invention, there is provided one resin-made helical gear having a plurality of angle-shaped teeth obtained by bonding helical gears having opposite torsion at the center in the tooth width direction, and this one resin-made helical gear. The present invention relates to a pair of resin-made spur gears comprising the other resin-made spur gear having a large number of teeth meshing with the teeth. In the present invention, the teeth of the one resin-made spur gear are formed so that at least the pressure angle near the center in the tooth width direction is larger than the pressure angle other than near the center in the tooth width direction. Further, the teeth of the other resin blind gear are formed to have the same pressure angle change as the teeth of the one resin blind gear.

  A second aspect of the present invention is the pair of resin blind gears according to the first aspect of the present invention, and has the following characteristics. That is, the pressure angle in the vicinity of the tooth width direction center of the tooth of the one resin-made spur gear gradually decreases from the tooth width direction center toward the end in the tooth width direction. Further, the pressure angle of the one resin-made helical gear other than the vicinity of the center of the tooth width direction of the tooth continuously changes with the change of the pressure angle near the center of the tooth width direction.

  A third aspect of the present invention is the pair of resin blind gears according to the first aspect of the present invention, and has the following characteristics. In other words, the tooth of the one resin-made spur gear has a constant pressure angle near the center in the tooth width direction, and a pressure angle other than near the center in the tooth width direction is away from the vicinity in the center in the tooth width direction. Therefore, it gradually decreases.

  According to a fourth aspect of the present invention, the pair of resin blind gears according to the first aspect of the present invention has the following characteristics. That is, the teeth of the one resin-made spur gear have a constant pressure angle near the center in the tooth width direction, and pressure angles other than the vicinity in the center in the tooth width direction are pressure angles near the center in the tooth width direction. Smaller and constant.

  According to the present invention, it is possible to efficiently increase the strength of the teeth of a pair of meshed helical gears at least in the vicinity of the center of the entire tooth width at which stress concentration is likely to occur. As a result, the present invention can prolong the life of a pair of resin-made helical gears.

  Hereinafter, the best embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a pair of intermeshing gears 1 made of resin. A pair of resin spur gears 1 shown in FIG. 1 is injection-molded using the same resin material (polyacetal (POM), polyamide, polycarbonate, ABS resin, etc.), and has a small diameter and the number of teeth. First helical gear (one resin-made helical gear) 2 and a second helical gear (the other plastic-made helical gear) 3 having a larger diameter and a larger number of teeth than the first helical gear 2. It consists of and. The teeth 4 and 5 of the first helical gear 2 and the second helical gear 3 have a chevron shape in which helical gears whose teeth twist directions are opposite to each other (the planar shape in FIG. 2 is substantially V-shaped). Shape). The pair of resin-made spur gears 1 is configured such that the number of teeth of the first spur gear 2 is Z1, and the number of teeth of the second spur gear 3 is Z2. For example, the speed reduction ratio when power is transmitted to the gear 3 is Z2 / Z1, and the speed increase ratio is Z1 / Z2.

  In the first helical gear 2 shown in FIG. 1, a shaft hole 7 is formed at the center of the web 6, and a plurality of teeth 4 are formed on the outer peripheral side of the web 6. Then, as shown in FIG. 2, the teeth 4 of the first spur gear 2 are in the vicinity of the center of the total tooth width (center in the tooth width direction) Wc (for example, if the total tooth width is W, L = W In the range of the larger dimension of / 5 or 1 mm), the pressure angle gradually increases toward the center Wc of the entire tooth width. Here, the pressure angle of the tooth 4 in the vicinity of the center of the tooth width direction (a predetermined range in the tooth width direction centering on the center of the tooth width direction) L is gradually increased toward the center of the tooth width direction, The reason for increasing the tooth thickness on the tooth base side is that in the case of a resin-made helical gear having a tooth twist angle of 15 °, the tooth root stress at the center of the tooth width direction is the tooth root other than the center of the tooth width direction. Focusing on the fact that the tooth root in the vicinity of the center in the tooth width direction is reinforced by focusing on the fact that it is about 20% larger than the stress, the strength of the whole tooth can be increased efficiently, and the reduction in the engagement rate must be suppressed as much as possible. Is taken into account. The dimension L in the vicinity of the center in the tooth width direction is set to W / 5 (L = W / 5) because the range of about W / 5 is reinforced in order to reduce the tooth root stress in the center in the tooth width direction by about 20%. This is considered to be sufficient if it is considered as a range to be applied, and if it is determined that a change in pressure angle in the range of 1/5 of the total tooth width W will not cause a large change in the meshing rate. . Further, the central width L in the tooth width direction, which is the range in which the pressure angle changes, is set to the larger one of W / 5 and 1 mm. When W / 5 is smaller than 1 mm, the tooth profile shape is formed with high accuracy. This is in consideration of the point that it becomes difficult to do so. In other words, the center vicinity L in the tooth width direction is W / 5 when W / 5> 1 mm, and 1 mm when W / 5 <1 mm.

  As shown in FIG. 2 (c), the first helical gear 2 formed in this way is near the center Wc of the total tooth width of the tooth 4 and is closer to the center Wc of the total tooth width. The tooth thickness dimension is increased, and the strength in the vicinity of the top 8 of the tooth 4 where stress concentration is likely to occur can be efficiently increased.

  Here, as shown in FIG. 4, when the pressure angle of the teeth 4 other than the vicinity of the center in the tooth width direction is 14.5 °, when the pressure angle at the center in the tooth width direction is 20.8 °, the tooth strength is 20 % (The root stress can be reduced by 20%). FIG. 4 shows that the pressure angle needs to be increased by 1.04 ° to increase the strength of the tooth 4 by 1%. That is, the straight line T1 shown in FIG. 4 shows a relationship of α = 14.5 ° + 1.04β, where α is the pressure angle and β is the strength increase rate.

  The first blind gear 2 as described above is used as, for example, a pinion gear fixed to the output shaft of the motor, and constitutes a part of the speed reducer or is used as a driven side gear. Part of it.

  A second helical gear 3 shown in FIG. 1 includes a boss part 11 having a shaft hole 10 formed in the center part, and a center part in the width direction (the center in the direction along the axis CL2) on the outer peripheral side of the boss part 11. Part) and a cylindrical rim 13 formed on the outer periphery of the web 12, and a first helical gear 2 on the outer peripheral side of the rim 13. A plurality of teeth 5 meshing with the teeth 4 are formed.

  As shown in FIG. 3, the teeth 5 of the second spur gear 3 are formed to have the same shape as the teeth 4 of the first spur gear 2 in the vicinity of the center Wc of the entire tooth width. Yes. That is, the teeth 5 of the second helical gear 3 are within the same tooth width direction range (near the center L in the tooth width direction) as the teeth 4 of the first helical gear 2. The pressure angle change is the same as the pressure angle change. Further, the teeth 5 of the second blind gear 3 have a pressure angle at the meshing position with the teeth 4 of the first blind gear 2 equal to the pressure angle of the teeth 4 of the first blind gear 2. Is formed.

  The second helical gear 3 formed in this manner can efficiently increase the strength in the vicinity of the top 14 of the tooth 5 where stress concentration is likely to occur, similarly to the first helical gear 2. The root stress in the center in the tooth width direction can be reduced.

  The second helical gear 3 having such a shape is used as a pair with the first helical gear 2 and constitutes a part of the speed reducer or the speed increasing device.

  As described above, according to the present embodiment, the strength of the teeth 4 of the first helical gear 2 can be increased, and the strength of the teeth 5 of the second helical gear 3 can also be increased. The lifetime as a pair of resin-made blind gears 1 can be extended.

(Modification)
The present invention is not limited to the above embodiment, and as shown in FIG. 5, the pressure angle of the tooth width direction center vicinity L of the teeth 4, 5 is the other part (the part other than the tooth width direction center vicinity L). As long as the pressure angle of the teeth 4 and 5 is changed, various methods are conceivable. For example, as shown in the pattern A of FIG. 5, the tooth width direction center vicinity L of the teeth 4 and 5 is set to a constant pressure angle, and the pressure angle of the portion other than the tooth width direction center vicinity of the teeth 4 and 5 is set to the tooth width direction center. You may make it reduce gradually as it goes to the tooth width direction edge part from the vicinity L. FIG. Further, as shown in the B pattern of FIG. 5, the pressure angle may be gradually decreased from the tooth width direction center (Wc) of the teeth 4, 5 toward both ends in the width direction. Further, as in the pattern C in FIG. 5, the portions other than the vicinity of the center of the teeth width direction of the teeth 4 and 5 are set as a constant reference pressure angle, and only the vicinity L of the teeth in the center of the tooth width direction is larger and constant than the reference pressure angle. You may comprise so that it may become the pressure angle of. In FIG. 5, a and b are one end in the tooth width direction and the other end in the tooth width direction of the teeth 4 or 5, or one end of the teeth 4 and 5 in the tooth width direction and the vicinity L in the tooth width direction. It is good also as the arbitrary locations between the arbitrary location between and the other end of the tooth width direction, and the tooth width direction vicinity L.

It is a figure which shows a pair of resin-made bevel gears which concern on embodiment of this invention. It is a figure which shows a 1st spur gear among a pair of resin spur gears concerning embodiment of this invention. Among these, (a) is a partial plan view schematically showing the first spur gear, (b) is a cross-sectional view taken along line AA of (a), and (c) is (a). It is the figure seen from the B direction. It is a figure which shows a 2nd spur gear among a pair of resin spur gears concerning embodiment of this invention. Among these, (a) is a partial plan view schematically showing the second spur gear, (b) is a cross-sectional view taken along line CC of (a), and (c) is (a). It is the figure seen from D direction. It is a figure which shows the relationship between the pressure angle of a tooth width direction center, and intensity | strength improvement rate target value. It is a figure which shows the modification of the resin-made bevel gears which concern on embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Pair of resin blind gears, 2 ... 1st helical gear (one plastic helical gear), 3 ... 2nd helical gear (other plastic helical gear), 4, 5 ...... Tooth, L ... Near the center of tooth width direction, Wc ... Center of all tooth widths (center of tooth width direction)

Claims (4)

One resin-made spur gear having a number of chevron-shaped teeth such that helical gears with opposite torsion are bonded together in the center in the width direction of the tooth, and a number of gears that mesh with the teeth of this one resin-made spur gear In a pair of resin-made spur gears comprising the other resin-made spur gears having teeth,
The teeth of the one resin spur gear are formed such that at least the pressure angle near the center in the tooth width direction is larger than the pressure angle other than near the center in the tooth width direction,
The teeth of the other resin-made spur gear are formed to have the same pressure angle change as the teeth of the one-made resin-made spur gear,
A pair of resin-made helical gears. The pressure angle in the vicinity of the tooth width direction center of the tooth of the one of the resin blind gears gradually decreases from the tooth width direction center toward the tooth width direction end side,
The pressure angle other than the vicinity of the center of the tooth width direction of the tooth of the one resin-made spur gear is configured to change continuously with the change of the pressure angle near the center of the tooth width direction.
The pair of resin blind gears according to claim 1. The teeth of the one of the resin blind gears have a constant pressure angle in the vicinity of the center in the tooth width direction, and the pressure angles other than the vicinity in the center of the tooth width direction gradually decrease as the distance from the center in the tooth width direction increases. Is supposed to
The pair of resin blind gears according to claim 1. The teeth of the one resin spur gear have a constant pressure angle near the center in the tooth width direction, and a pressure angle other than near the center in the tooth width direction is larger than a pressure angle near the center in the tooth width direction. Small and constant,
The pair of resin blind gears according to claim 1.

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