JP2005098369A - Resin-made herringbone gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To transmit power by both of a first gear part and a second gear part even if a difference in level is caused in a butt surface of the first gear part and the second gear part due to shifting of the butt parts of a first metal mold for forming the first gear part extending from the central part in the direction of face width to one end side in the direction of face width in the resin-made herringbone gear and a second first metal mold for forming the second gear part extending from the central part in the direction of face width to the other end side in the direction of face width in the resin-made herringbone gear. <P>SOLUTION: An angled top 4 of the central part 3 in the direction of face width positioned in the butt part of the first metal mold and the second metal mold is cut out in the direction of decreasing the tooth thickness from the tooth crest to the vicinity of the bottom land to form a meshing flank part 13. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a resin blind gear formed by injection molding.

  Conventionally, plastic helical gears have a smooth meshing even at high speeds and can transmit quiet power, and the load is easily distributed along the tooth traces, enabling high load power transmission. Therefore, it has been widely used in power transmission mechanisms such as automobile parts, precision machines, various electronic devices as well as office machines such as copiers, printers, and facsimile machines.

  However, since the helical gear made of resin has twisted teeth, it has a drawback that an axial thrust load proportional to the torque is generated. In order to eliminate the drawbacks of such helical gears made of resin, the thrust load generated during power transmission must be received by the thrust bearing. However, there are restrictions on space and the structure of the power transmission mechanism. Due to restrictions, thrust bearings may not be arranged.

  Therefore, a technology has been developed to form resin-made helical gears by injection molding that is quiet and capable of high-speed, high-load power transmission as well as resin helical gears, but does not generate thrust load during power transmission. (See Patent Document 1).

  As shown in FIG. 16, the resin blind gear 30 of Patent Document 1 includes a first mold 33 that molds a portion (first gear portion 32) on one end side in the tooth width direction from the tooth width direction center portion 31. The second mold 35 that molds the portion (second gear portion 34) on the other end side in the tooth width direction from the tooth width direction central portion 31 is abutted against the cavity 36 of the first mold 33 and the second mold 33. After the molten resin is injected into the cavity 36 and the resin in the cavity 36 is cooled and solidified, the first mold 33 and the second mold 35 are separated, and the cavities of the first mold 33 and the second mold 35 are separated. By taking out the hardened resin from the inside 36, a large amount can be molded in a short time.

JP 10-315344 A (see FIGS. 3 and 4)

  However, the two divided molds (the first mold 33 and the second mold 35) are brought into contact with each other in this manner, and the molten resin is injected into the cavities 36 of both the molds 33 and 35 to form a resin slab. When the gear 1 is molded, if even a slight deviation occurs in the abutting surfaces 37 of the molds 33 and 35, as shown in FIG. 5, the first gear portion of the injection-molded resin blind gear 30 is shown in FIG. There is also a problem that a deviation occurs on the abutting surface 37 of the second gear portion 34 and the second gear portion 34, and a step 17 is produced between the top 4 of the chevron tooth 38 and its back surface 16. When the step 17 occurs at the top 4 and the back surface 16 of the chevron tooth 38, power is transmitted only by the half tooth portion (the first gear portion 32 or the second gear portion 34) in the tooth width direction. As a result, a thrust similar to that of a helical gear is generated.

  In such a case, as shown in FIG. 17, by forming a slit 40 along the abutting surface 37 of the first gear portion 32 and the second gear portion 34, the teeth of the mating resin spur gear 30 to be engaged with each other. It is conceivable to prevent the occurrence of defects such as a meshing failure caused by interference with the step 4 of the top portion 4 or the back surface 16 of this, but this does not only complicate the mold structure but also the bending strength of the teeth. This causes a new problem of reducing the effective tooth width.

  Therefore, the present invention has developed a resin splint gear that can effectively prevent incomplete meshing without impairing the strength of the teeth even when the butt surfaces of the two divided dies are misaligned.

  According to the first aspect of the present invention, the first metal has a shape in which helical gears having opposite torsion are bonded together, and forms a first gear portion on one end side in the tooth width direction from the top of the chevron in the center portion in the tooth width direction. A mold and a second mold that forms a second gear portion on the other end side in the tooth width direction from the top of the chevron at the center in the tooth width direction are abutted, and resin is contained in the cavities of the first mold and the second mold. The present invention relates to a resin-made splint gear that is integrally molded. And this resin-made helical gear has a tooth thickness from the tooth tip surface to the vicinity of the tooth bottom surface at the top of the chevron in the center in the tooth width direction located at the butt portion of the first die and the second die. It is characterized by notching in the decreasing direction and forming a meshing escape portion.

  Further, the invention of claim 2 has a shape in which helical gears having opposite torsion are bonded together, and forms a first gear portion on one end side in the tooth width direction from the top of the chevron in the center portion in the tooth width direction. 1 mold and a second mold forming the second gear part on the other end side in the tooth width direction from the top of the chevron at the central part in the tooth width direction are brought into contact with each other, and the inside of the cavity of the first mold and the second mold The present invention relates to a resin splint gear that is integrally molded by injecting resin. And this resin-made spur gear is provided on the back surface of the top of the chevron at the center in the tooth width direction located at the butt portion of the first mold and the second mold, from the tooth tip surface to the vicinity of the tooth bottom surface. Further, the present invention is characterized in that a meshing escape portion that is recessed so as not to come into contact with the tooth surfaces of the meshing gear is formed.

  In the resin spur gear of the present invention, a deviation occurs in the abutting surfaces of the two divided molds (first mold and second mold), and a deviation occurs in the abutting surfaces of the first gear portion and the second gear portion. Even if it occurs, since the meshing relief portion is formed on the top of the tooth chevron or the back surface thereof, there is no interference with the step on the top or back surface of the chevron mating gear (resin blind gear). The first gear portion and the second gear portion of the mating gear with which the gear portion and the second gear portion mesh with each other can be contacted to transmit power without generating a thrust load.

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

  FIG. 1 shows a resin-made helical gear 1 according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of an injection mold 2 used for forming the resin blind gear 1.

  As shown in FIG. 1, the resin-made helical gear 1 of the present embodiment has a shape in which two helical gears having opposite torsional directions are bonded together. A first gear portion 5 on one end side in the tooth width direction from the top portion 4 of the chevron, and a second gear portion 6 on the other end side in the tooth width direction from the top portion 4 of the chevron in the center portion 3 in the tooth width direction (see FIG. 4). It is made up of. In FIG. 1 and FIG. 4, the first gear portion 5 of the resin-made helical gear 1 has a shape in which the teeth 7 are left-down from the top 4. In FIG. 1 and FIG. 4, the second gear portion 6 of the resin-made helical gear 1 has a shape in which the teeth 7 are right-down from the top 4. The teeth 7a of the first gear portion 5 and the teeth 7b of the second gear portion 6 are integrated to form a chevron-shaped (substantially inverted V-shaped) tooth 7.

  As shown in FIG. 2, such a resin splint gear 1 is formed by abutting a first mold 8 that forms the first gear portion 5 and a second mold 10 that forms the second gear portion 6. In this state, a molten resin (for example, a molten resin such as polyacetal, polyamide, polyphenylene sulfide, polybutylene terephthalate) is injected from the gate 12 into the cavity 11 formed in the first mold 8 and the second mold 10. It is a molded gear. Then, as shown in FIG. 3, after at least one of the first mold 8 and the second mold 10 for injection molding is separated from the other (in this embodiment, the second mold 10 is replaced with the first mold). After being separated from the mold 8), the resin-made spur gear 1 cooled and solidified in the cavity 11 of the first mold 8 and the second mold 10 is released.

  FIG. 4 schematically shows an enlarged plan view of the teeth 7 of the resin-made helical gear 1 injection-molded as described above. As shown in FIG. 4, the resin-made helical gear 1 of the present embodiment has a chevron-shaped top portion 4 extending from the tooth tip surface to the vicinity of the tooth bottom surface (a position where the distance from the tooth bottom surface is smaller than the crest dimension). A meshing escape portion 13 is formed by cutting out so as to reduce the tooth thickness. The meshing escape portion 13 is formed by transferring the shape in the cavity 11 of the first mold 8 and the second mold 10 during the above-described injection molding, and the meshing relief portion 13 is connected to the first mold 8. It is located on the butting portion 14 side of the second mold 10 (see FIG. 2).

  As described above, when the butt portion 14 of the first mold 8 and the second mold 10 is misaligned when the resin-made helical gear 1 is injection-molded, as shown in FIG. The abutting surface 15 of the second gear portion 6 is also displaced (L2), and a step 17 is formed between the top 4 of the chevron and its back surface. In such a case, if the meshing escape portion 13 is not formed as shown in FIG. 4, the pair of resin-made helical gears 1 (1a, 1b) are meshed as shown in FIG. 7, the first gear portion 5 and the second gear portion 6 are meshed with the teeth 7 of the mating gear (resin blind gear 1) meshed with only one of the first gear portion 5 and the second gear portion 6. Power is transmitted only in half of the direction. As a result, even the resin helical gear 1 generates a thrust similar to that of the helical gear. 7A illustrates a mode in which power is transmitted only by the second gear portion 6 of the teeth 7, and FIG. 7B shows only the first gear portion 5 of the teeth 7. The mode which transmits motive power with is illustrated.

  However, as shown in FIG. 4, the resin-made helical gear 1 of the present embodiment has a meshing escape portion 13 formed at the top 4 of the chevron teeth 7. The first gear portions 5, 5 and the second gear portions 6, 6 of the pair of resin-made splint gears 1 are engaged with each other without the meshing escape portion 13 interfering with the step 17 on the back surface 16 side of the gear teeth 7. It is possible to contact and transmit power in the entire region in the tooth width direction.

  Here, FIGS. 8A to 8C show a state in which the first gear portion 5 of the resin-made spur gear 1 on the upper side in the drawing is shifted to the upper side in the drawing with respect to the second gear portion 6. FIG. (D)-(f) has shown the state which the 2nd gear part 6 shifted | deviated to the upper side rather than the 1st gear part 5 of the resin-made splint gear 1 of the upper side in the figure. 8 (a) and 8 (d) show a state in which the first gear portion 5 and the second gear portion 6 of the resin-made spur gear 1 on the lower side in the figure do not shift. 8 (b) and 8 (e), the first gear portion 5 and the second gear portion of the resin-made blind gear 1 on the lower side in the drawing are the same as those of the resin-made blind gear 1 on the upper side in the drawing. The state which shifted | deviated is shown. 8 (c) and 8 (f), the first gear portion 5 and the second gear portion 6 of the resin-made blind gear 1 on the lower side in the drawing are the same as those of the resin-made blind gear 1 on the upper side in the drawing. The state which shifted | deviated to the direction opposite to the shift | offset | difference of the 1st gear part 5 and the 2nd gear part 6 is shown. As shown in FIGS. 8 (a) to 8 (f), since the meshing escape portion 13 is formed at the abutting portion of the first gear portion 5 and the second gear portion 6, the first gear portion 5 and the second gear portion 5. Even if the abutting surfaces of the gear portion 6 are misaligned, the first gear portions 5 and 5 and the second gear portions 6 and 6 of the pair of intermeshing gears 1 are engaged with each other.

  Note that the amount of deviation between the butted portions 14 of the first mold 8 and the second mold 10 is measured for each injection molding machine to be used, or predicted by a simulation experiment or the like. Then, the notch amount L1 of the meshing escape portion 13 is determined so as to have a dimension that is equal to or larger than the actual measurement value or the predicted value.

  According to the resin-made helical gear 1 of the present embodiment having such a configuration, even when the abutting surface 15 between the first gear portion 5 and the second gear portion 6 is misaligned, the abutting surface 15 is misaligned. It can be absorbed by the meshing escape portion 13 and power can be transmitted almost in the entire width direction of the chevron teeth 7 so that power transmission can be performed quietly and with high load and high rotation.

  In addition, according to the resin-made helical gear 1 of the present embodiment, it is possible to transmit power almost in the entire width direction of the chevron teeth 7, so that a thrust load like a helical gear is generated. There is no need to receive a thrust load with a thrust bearing. As a result, according to the present embodiment, it is possible to arrange a pair of resin splint gears in a narrow space as much as thrust bearings are not required, and to reduce the weight and cost. it can.

  FIG. 9 is an enlarged plan view of the teeth 7 of the resin helical gear 1 according to the first embodiment, corresponding to FIG. 4. In other words, the teeth 7 of the resin-made helical gear 1 of the present embodiment are views showing a mode in which the back surface 16 side of the top portion 4 is recessed in a substantially arc shape to form a meshing relief portion 18.

  The meshing relief portion 18 is formed by denting the tooth surface on the back surface 16 side of the top portion 4 from the tooth tip surface to the vicinity of the tooth bottom surface along the central portion 3 in the tooth width direction. 8 and the shape in the cavity 11 of the second mold 10 are transferred (see FIG. 2). As shown in FIG. 10, the indentation L3 and the width W of the meshing escape portion 18 are the same as those of the first gear portion 5 and the second gear due to the amount of displacement between the butted portions 14 of the first mold 8 and the second mold 10. The shift (step 17) of the butting surface 15 of the gear portion 6 can be absorbed, and the first gear portions 5 and 5 and the second gear portions 6 and 6 of a pair of meshed splint gears 1 and 1 that are meshed with each other rotate. The dimensions that can be transmitted are determined.

  Here, in FIGS. 10 (a) to 10 (f), the displacement of the first gear portion 5 and the second gear portion 6 corresponds to FIGS. 8 (a) to 8 (f).

  This example having such a configuration can also obtain the same effects as those of the above-described embodiment.

  The meshing escape portions 13 and 18 are not limited to the shapes of the above-described embodiments and examples, and even if the butted portions 14 of the first mold 8 and the second mold 10 are misaligned, a pair of meshing relief portions 13 and 18 are engaged. As long as the first gear portions 5 and 5 and the second gear portions 6 and 6 of the resin splint gears 1 and 1 are in contact with each other so as to transmit power, for example, as shown in FIG. In this manner, the vicinity of the top 4 of each of the first gear portion 5 and the second gear portion 6 can be cut out into a substantially arc shape to form the meshing relief portion 20.

  Here, as specific means for making the vicinity of the top of the first gear portion 5 or the second gear portion 6 into an arc shape, for example, the following can be cited.

  a. The tooth profile is designed so that the portion is crowned (in this case, even if the crowning is attached only to one end on the top 4 side of the first gear portion 5 or the second gear portion 6, It may be attached to both ends).

  b. A tooth profile shape in which the portion is thicker than other portions is adopted, and sink marks at the time of molding the resin in the portion are used.

  Further, as shown in FIG. 12, the back surface 16 side of the top portion 4 is recessed in a rectangular shape from the tooth tip surface to the vicinity of the tooth bottom surface along the tooth width direction center portion 3 to form a meshing escape portion 21 or an arc shape. Alternatively, it may be recessed into a shape other than a rectangular recess to form a meshing relief portion.

  Further, when the resin-made spur gear 1 is shaped as shown in FIG. 13, the web 23 is designed to be relatively thick, and the resin-made spur gear 1 is formed at the center of the tooth width direction of the teeth 7. The sink marks 24 may be intentionally generated, and the sink marks 24 may be engaged with each other to serve as escape portions.

  Further, as shown in FIG. 14, substantially triangular meshing escape portions 22, 22 are formed on the back surface 16 of the first gear portion 5 and the second gear portion 6 equally on the left and right sides, and a step is formed by these meshing relief portions 22, 22. By absorbing 17, the first gear portions 5, 5 and the second gear portions 6, 6 may be meshed together to transmit power (see FIG. 15). Here, the dimensions L4, L5, and W1 of the meshing escape portion 22 are determined so as to absorb the shift amount (step size) of the step 17.

  Further, the teeth 7 may be formed with meshing relief portions 13 and 20 and meshing relief portions 18, 21 and 22 on both the top 4 side and the back surface 16 side.

  The resin splint gear 1 of the present invention needs to perform high-speed rotation and high-load power transmission quietly, and also needs to be reduced in weight and product price, etc. Widely used in power transmission mechanisms such as image forming apparatuses, automobile parts, precision machines, and electronic devices.

It is a front view of resin-made helical gears according to an embodiment of the present invention. It is sectional drawing which shows schematic structure of the metal mold | die for injection molding. It is sectional drawing which shows the state at the time of mold release of the metal mold | die for injection molding. It is a top view which expands and shows the tooth | gear of the resin-made bevel gear which concerns on this Embodiment. It is a figure which shows the shift | offset | difference state of the 1st gear part and 2nd gear part of resin-made helical gears, FIG.5 (a) is a figure which shows a 1st aspect, FIG.5 (b) is a 2nd aspect. FIG. It is a figure which shows the use condition of the resin-made bevel gears of this Embodiment. It is a figure which shows the malfunction generation | occurrence | production situation at the time of meshing of the conventional resin-made splint gears, FIG.7 (a) is a figure which shows the 1st aspect, FIG.7 (b) is a figure which shows the 2nd aspect. is there. It is a meshing state diagram of the teeth of the resin-made helical gear according to the present embodiment. It is a top view of the tooth | gear of the resin made helical gear which concerns on Example 1 of this invention. It is a meshing state diagram of the teeth of the resin-made helical gear according to the first embodiment of the present invention. It is a top view of the tooth | gear which shows the 1st aspect of the other Example of this invention. It is a top view of the tooth | gear which shows the 2nd aspect of the other Example of this invention. It is a front view which shows the upper half of the resin-made helical gear which shows the 3rd aspect of the other Example of this invention in cross section. It is a top view of the tooth | gear which shows the 4th aspect of the other Example of this invention. It is a figure which shows the meshing state of the tooth which concerns on the 4th aspect of the other Example of this invention. It is sectional drawing of the injection-molding die which forms the resin-made helical gears in the 1st prior art example. It is a top view which shows the meshing state of the resin bevel gears concerning a 2nd prior art example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Plastic blind gear, 3 ... Central part of tooth width direction, 4 ... Top part, 5 ... 1st gear part, 6 ... 2nd gear part, 8 ... 1st metal mold | die, 10 ... Second mold, 11 ... cavity, 13, 18, 20, 21, 22 ... meshing relief part, 14 ... butting part

Claims (2)

It is shaped like a helical gear with opposite torsion,
A first mold that forms a first gear portion on one end side in the tooth width direction from the top of the chevron in the center portion in the tooth width direction, and a second gear portion on the other end side in the tooth width direction from the top portion of the chevron in the center portion in the tooth width direction. In a resin blind gear formed by abutment with a second mold that forms a shape and injecting resin into the cavities of the first mold and the second mold,
The top of the chevron at the central portion in the tooth width direction located at the butt portion of the first die and the second die is cut out in the direction in which the tooth thickness decreases from the tooth tip surface to the vicinity of the tooth bottom surface, and the meshing escape portion A plastic spear gear characterized by forming It is shaped like a helical gear with opposite torsion,
A first mold that forms a first gear portion on one end side in the tooth width direction from the top of the chevron in the center portion in the tooth width direction, and a second gear portion on the other end side in the tooth width direction from the top portion of the chevron in the center portion in the tooth width direction. In a resin blind gear formed by abutment with a second mold that forms a shape and injecting resin into the cavities of the first mold and the second mold,
The back surface of the top of the chevron at the central portion in the tooth width direction located at the butt portion of the first die and the second die contacts the top of the chevron of the mating gear from the tooth tip surface to the vicinity of the tooth bottom surface. A resin-made spur gear characterized in that a meshing relief portion that is recessed so as not to be formed is formed.

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