JP2016200185A - gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gear that can attain mechanical strength and rigidity and dimension stability required at a sleeve part, and abrasion resistance required at a tooth formation part, and in which the sleeve part and the tooth formation part are formed by the same resin.SOLUTION: A sleeve part and a tooth formation part are integrally molded by using raw material resin 26 obtained by mixing polyamide resin 39, filler 40 and carbodiimide 41, thereby to obtain a worm wheel. The worm wheel can attain mechanical strength and rigidity and dimension stability required at the sleeve part, and abrasion resistance required at the tooth formation part.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a resin gear.

For example, the electric power steering apparatus decelerates the rotation of the electric motor for assisting steering through a speed reducer and amplifies the output to transmit it to the steering mechanism. Thereby, torque assist is performed for the operation of the steering mechanism by the operation of the driver. The reduction gear normally includes a metal worm as a small gear meshing with each other and a resin worm wheel as a large gear.
For example, a worm wheel is formed by forming an annular resin member on the outer periphery of a metal core (sleeve) by injection molding (insert molding) or the like and then forming teeth on the outer periphery of the resin member by cutting or the like. Manufactured. The resin member is formed using a resin such as polyamide (PA6, PA66, PA46, etc.), polyphenylene sulfite (PPS), or the like.

For example, Patent Document 1 is prepared using a resin composition containing polyamide 66, a copper heat stabilizer, an aromatic polycarbodiimide, and an impact modifier made of EPDM rubber grafted with maleic anhydride. A gear for an electric power steering apparatus is disclosed.
The metal sleeve portion requires involute spline processing to prevent rotation of the tooth portion, and this is a factor in increasing the cost. In recent years, there has been a demand for weight reduction of automobile parts based on a demand for reducing environmental load, and a reduction gear of an electric power steering device is no exception. The sleeve portion of the worm wheel is made of metal, and the ratio to the total weight of the electric power steering device is high. Therefore, it is necessary to use a lighter material while maintaining the necessary mechanical strength and rigidity.

  On the other hand, in recent years, attempts have been made to reduce the weight by forming the sleeve portion with resin (see, for example, Patent Document 2). Here, a polyamide filled with glass fiber is used for the sleeve portion in order to impart mechanical strength, rigidity and dimensional stability. On the other hand, non-reinforced high molecular weight polyamide (not containing glass fiber) excellent in toughness is used for the tooth portion in order to impart wear resistance and creep resistance. A tooth portion is formed by inserting a resin sleeve portion into a mold of a molding machine and then injecting resin onto the outer periphery of the sleeve portion.

Special table 2009-536891 gazette US Patent Application Publication No. 2007/0087617

  The resin forming the sleeve part and the resin forming the tooth part have different linear expansion coefficients. Therefore, due to the difference in expansion / shrinkage ratio at high or low temperature, the product has poor impact resistance, heat shock cracking, etc. May occur. Further, the expansion may cause a gap between the sleeve portion and the tooth portion, which may shorten the durability life. Furthermore, since the sleeve portion and the tooth portion must be formed by separate injection molding processes, there is a problem that the manufacturing cost increases.

  As measures against these, it is conceivable that the tooth portion and the sleeve portion are integrally formed by using the same glass fiber reinforced resin as the sleeve portion for the tooth portion. However, in this case, wear of the tooth portion is increased, and as a result, it is expected that the durability life is reduced. This is because the glass fiber in the tooth part falls off due to contact sliding, acts like a hard abrasive, and wears and peels off the resin constituting the tooth part.

On the other hand, by increasing the molecular weight of the resin, it is possible to propose a technique for suppressing the abrasion and peeling of the resin due to the glass fiber, but there is a limit to increasing the molecular weight by polymerizing the monomer. Moreover, it is difficult to knead glass fibers with a resin having a high molecular weight in advance from the viewpoint of productivity.
Accordingly, an object of the present invention is to provide a resin having the same sleeve portion and tooth forming portion that can achieve both the mechanical strength / rigidity and dimensional stability required for the sleeve portion and the wear resistance required for the tooth forming portion. Is to provide a gear formed of.

The gear (20) of the present invention is a gear (20) including a sleeve portion (22) and a tooth forming portion (23), and the sleeve portion (22) and the tooth forming portion (23) are made of a polyamide resin ( 39), a raw material resin (26) obtained by kneading a filler (40) and a compound (41) having a carbodiimide bond (Claim 1).
According to this configuration, dehydration of the terminal carboxyl group (—COOH) and terminal amino group (—NH ₂ ) of the polyamide resin by the action of the compound having a carbodiimide bond during kneading and injection molding of the polyamide resin and the filler. The condensation reaction proceeds. As a result, the polymer chains of a plurality of polyamide resins previously formed by polymerization are linked together, and the molecular weight of the raw material resin is increased. Therefore, since abrasion and peeling of the resin due to the filler can be suppressed, the wear resistance required for the tooth forming portion can be achieved. Further, since the raw material resin contains a filler, it is possible to achieve mechanical strength / rigidity and dimensional stability required for the sleeve portion. Thereby, there are few concerns, such as a crack and a durable life short, cost can also be reduced, and also weight reduction can be achieved compared with the case where a metal sleeve part is used.

In the gear (20) of the present invention, the resin (26) constituting the sleeve portion (22) and the tooth forming portion (23) may further contain a lubricant (Claim 2).
Since the sliding effect between the molecules of the raw material resin can be obtained by the lubricant, the viscosity at the time of molding the gear can be reduced. Therefore, even if the molecular weight of the raw material resin is high, it can be molded at a relatively low temperature, so that thermal decomposition of the resin during molding can be suppressed. As a result, since molding can be performed while keeping the molecular weight of the raw material resin high, the mechanical strength and wear resistance of the raw material resin can be maintained well.

In the gear (20) of the present invention, the lubricant may be a metal soap (Claim 3).
In the gear (20) of the present invention, the resin (26) constituting the sleeve portion (22) and the tooth forming portion (23) is composed of 15% by mass to 50% by mass of glass fiber with respect to the total amount thereof. (40) (Claim 4).
By blending the glass fiber within this range, it is possible to secure sufficient mechanical strength and rigidity in the sleeve portion while suppressing the amount of glass fiber that is a factor causing wear of the tooth forming portion.

In the gear (20) of the present invention, the resin (26) constituting the sleeve portion (22) and the tooth forming portion (23) contains glass fibers having a diameter of 6 μm to 15 μm as the filler (40). (Claim 5).
By blending glass fibers having a diameter in this range, the contact area between the glass fibers and the polyamide resin can be made relatively large, so that the mechanical strength and rigidity of the sleeve portion can be improved satisfactorily. That is, since the mechanical strength of the sleeve portion can be ensured with a smaller amount of glass fiber, it is possible to suppress the amount of glass fiber that is a cause of wear of the tooth forming portion and improve the wear resistance of the tooth forming portion. it can. Further, the smaller the diameter of the glass fiber is, the lower the attack of the other party is. Therefore, the influence of abrasion and peeling of the resin is small, and in this respect also, the wear resistance of the tooth forming portion can be improved.

In the gear (20) of the present invention, the compound (41) having a carbodiimide bond of 0.5% by mass to 4% by mass may be blended with respect to the total amount of the raw material resin (26) (Claim 6). .
By blending a compound having a carbodiimide bond in this range, a raw material resin having a number average molecular weight Mn of 30,000 or more can be favorably obtained. On the other hand, since the compound having a carbodiimide bond is not excessive, increase in the resin pressure (viscosity) during kneading, heat generation, thermal decomposition of the polyamide resin and carbodiimide accompanying the heat generation, and decrease in adhesion strength with the resin due to filler degradation. Etc. can also be reduced.

FIG. 1 is a schematic view of an electric power steering apparatus incorporating a worm wheel according to an embodiment of the present invention. FIG. 2 is a schematic perspective view of the worm wheel. FIG. 3 is a flowchart for manufacturing the worm wheel. FIG. 4 is a diagram for explaining a process related to the preparation of the raw material resin. FIG. 5 is a diagram showing a reaction mechanism of dehydration condensation with carbodiimide. FIG. 6 is a diagram for explaining a process related to the preparation of the raw material resin. FIG. 7 is a graph showing the number average molecular weight Mn of Examples, Reference Examples, and commercially available products. FIG. 8 is a diagram showing the results of tensile strength tests of Examples and Reference Examples. FIG. 9 is a diagram showing the results of the friction and wear test of Examples and Reference Examples. FIG. 10 is a diagram showing the results of a frictional wear test of a commercial product.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic view of an electric power steering apparatus 1 incorporating an intermediate shaft 5 according to an embodiment of the present invention.
The electric power steering apparatus 1 includes a steering shaft 3 connected to a handle 2 so as to be integrally rotatable, an intermediate shaft 5 connected to the steering shaft 3 via a universal joint 4, and an intermediate shaft 5 via a universal joint 6. A rack bar 8 is provided as a steered shaft that extends in the left-right direction of the automobile, and includes a pinion shaft 7 that is connected and rack teeth 8 a that mesh with the pinion teeth 7 a of the pinion shaft 7.

The pinion shaft 7 and the rack bar 8 constitute a steering mechanism 9 composed of a rack and pinion mechanism.
The rack bar 8 is supported in a rack housing 10 fixed to the vehicle body so as to be linearly reciprocable via a plurality of bearings (not shown). Both end portions of the rack bar 8 protrude to both sides of the rack housing 10, and tie rods 11 are coupled to the respective end portions.

Each tie rod 11 is connected to a corresponding steering wheel 12 via a knuckle arm (not shown).
When the steering shaft 2 is rotated by operating the handle 2, the rotation is converted into a linear motion of the rack bar 8 along the left-right direction of the automobile by the pinion teeth 7a and the rack teeth 8a, and the steering wheel 12 is steered. Is achieved.

The steering shaft 3 is divided into an input shaft 3a connected to the handle 2 and an output shaft 3b connected to the pinion shaft 7, and both shafts 3a and 3b can be rotated relative to each other on the same axis via a torsion bar 13. Are connected to each other.
The torsion bar 13 is provided with a torque sensor 14 for detecting a steering torque from the amount of relative rotational displacement between both shafts 3a and 3b. The torque detection result of the torque sensor 14 is an ECU (Electric Control Unit: electronic control). Unit) 15.

The ECU 15 drives and controls the steering assist electric motor 17 via the drive circuit 16 based on a torque detection result, a vehicle speed detection result given from a vehicle speed sensor (not shown), and the like. Then, the output rotation of the electric motor 17 is decelerated via the speed reducer 18 and transmitted to the pinion shaft 7 and converted into a linear motion of the rack bar 8 to assist steering.
The speed reducer 18 is engaged with a worm shaft 19 (small gear) as an input shaft that is rotationally driven by the electric motor 17, meshed with the worm shaft 19, and coupled to the output shaft 3 b of the steering shaft 3 so as to be integrally rotatable. A worm wheel 20 (large gear) as an example of a gear is provided.

FIG. 2 is a schematic perspective view of the worm wheel 20.
The worm wheel 20 is formed in an annular shape having a through hole 21 at the center. The output shaft 3b (see FIG. 1) of the steering shaft 3 is inserted into the through hole 21.
The worm wheel 20 is formed of an integral resin molded product, and includes a sleeve portion 22 and a tooth forming portion 23 concentrically from the through hole 21. The sleeve portion 22 and the tooth forming portion 23 are formed as a continuous layer of resin. In this embodiment, the sleeve portion 22 is defined as an annular region, and the tooth forming portion 23 is defined as an annular region that is a peripheral region of the sleeve portion 22. A plurality of teeth 24 are carved on the outer periphery of the tooth forming portion 23 along the circumferential direction. Here, the configuration in which the two regions (in this embodiment, the sleeve portion 22 and the tooth forming portion 23) form a continuous layer means that there is no physical interface between the two regions. . For example, a boundary such as a crystal grain boundary of a material phase due to a difference in resin material may exist between the sleeve portion 22 and the tooth forming portion 23. On the other hand, the physical boundary surface may appear between the sleeve portion and the tooth forming portion when, for example, the tooth forming portion is separately injection-molded on the outer periphery of the metal or resin sleeve portion. In FIG. 2, an imaginary boundary 25 is shown between the sleeve portion 22 and the tooth forming portion 23 for the sake of clarity.

Next, a method for manufacturing the worm wheel 20 will be described.
FIG. 3 is a flowchart for manufacturing the worm wheel 20. FIG. 4 is a diagram for explaining steps related to the preparation of the raw material resin 26. FIG. 5 is a diagram showing a reaction mechanism of dehydration condensation by carbodiimide 41.
In order to manufacture the worm wheel 20, first, the raw material resin 26 constituting the worm wheel 20 is prepared (S1). For the preparation of the raw material resin 26, for example, a kneader 27 shown in FIG. 4 is used.

The kneader 27 mainly includes, for example, a main body 28, a tank 29, a cooling water tank 30, and a pelletizer 31.
The main body 28 includes a main feeder 32, a cylinder 33, a screw 34, and a nozzle 35, and a side feeder 36 is attached between the main feeder 32 and the nozzle 35 (on the downstream side of the main feeder 32). The main body 28 is not particularly limited, and for example, a known kneader such as a twin-screw (multi-screw) extruder or a single-screw extruder can be used.

A stirrer 37 is provided on the upstream side of the tank 29. The raw material mixed by the stirrer 37 is supplied to the main feeder 32 of the main body 28 via the tank 29 and the belt-type weight meter 38 on the downstream side.
In order to prepare the raw material resin 26, first, the polyamide resin 39 and an arbitrary additive are supplied to the cylinder 33 through the main feeder 32 as a common charging location. The polyamide resin 39 and the optional additive may be supplied by being put into the tank 29 alone, or may be supplied after being mixed (dry blended, master batch) by the stirrer 37.

  Examples of the polyamide resin 39 include aliphatic polyamides (PA6, PA66, PA12, PA612, PA610, PA11, etc.), aromatic polyamides (PA6T, PA9T, PPA), and the like. Of these, preferably, an aliphatic polyamide is used, and more preferably, polyamide 66 (PA66) is used. These may be used alone or in combination of two or more. The number average molecular weight Mn of the polyamide resin used may be, for example, 15,000 to 25,000. In addition to the polyamide resin 39, the base resin put into the main feeder 32 may contain, for example, a thermoplastic elastomer (acid-modified ethylene elastomer, EGMA, EPDM, polyamide elastomer, etc.). By blending a thermoplastic elastomer, impact resistance can be improved.

Moreover, 45 mass%-90 mass% may be sufficient as the mixture ratio of the polyamide resin 39 with respect to the total amount of the material used for preparation of the raw material resin 26, for example.
Moreover, as an arbitrary additive, Preferably, a lubrication agent is mix | blended. Since the sliding effect between the molecules of the raw material resin 26 can be obtained by the lubricant, the viscosity at the time of molding the worm wheel 20 can be reduced. Therefore, even if the molecular weight of the raw material resin 26 is high, it can be molded at a relatively low temperature, so that thermal decomposition of the resin during molding can be suppressed. As a result, since the molding can be performed while keeping the molecular weight of the raw material resin 26 high, the mechanical strength and the wear resistance of the raw material resin 26 can be favorably maintained.

  The lubricant is not particularly limited as long as it can reduce the viscosity of the raw material resin 26 when the worm wheel 20 is molded. For example, metal soaps such as stearic acid metal salts, hydrocarbons such as paraffin wax and synthetic polyethylene wax, fatty acids such as stearic acid, higher alcohols such as stearyl alcohol, aliphatics such as stearic acid amide and oleic acid amide Known lubricants such as amides, esters such as fatty acid esters of alcohol, silicone compounds, and the like can be used. Of these, a metal soap system is preferably used, and a metal stearate salt is more preferably used. The blending ratio in the case of blending the lubricant may be, for example, 0.01% by mass to 1% by mass with respect to the total amount of materials used for preparing the raw resin 26.

Then, the polyamide resin 39 supplied to the cylinder 33 and the additive added as necessary are kneaded by the rotation of the screw 34. The kneading conditions may be, for example, a temperature of the cylinder 33 of 275 ° C. to 325 ° C. and a rotational speed of the screw 34 of 100 rpm to 500 rpm.
Next, a filler 40 and a compound having a carbodiimide bond (hereinafter simply referred to as “carbodiimide”) 41 are simultaneously supplied to the cylinder 33 via a side feeder 36 as a common charging point.

  As the filler 40 to be used, for example, short fiber fillers such as glass fibers, carbon fibers, aramid fibers, and cellulose fibers, plate-like fillers such as glass flakes, or fine reinforcing such as carbon nanotubes and carbon nanofibers. 1 type or 2 types or more, such as a filler which can be used. Of these, short fiber fillers are preferably used, glass fibers are more preferably used, and flat glass fibers are particularly preferably used. By using a flat glass fiber, the surface roughness after tooth cutting of the tooth forming portion 23 can be reduced.

  When using glass fiber, it is preferable that the said glass fiber has a diameter of 6 micrometers-15 micrometers. By blending the glass fiber having a diameter in this range, the contact area between the glass fiber and the polyamide resin in the raw material resin 26 can be made relatively large. Therefore, when the worm wheel 20 is molded, the mechanical strength of the sleeve portion 22 is increased. And the rigidity can be improved satisfactorily. That is, since the mechanical strength and the like of the sleeve portion 22 can be ensured with a smaller amount of glass fiber, the amount of glass fiber that is a factor causing wear of the tooth forming portion 23 can be suppressed, and the wear resistance can be improved. Further, the smaller the diameter of the glass fiber is, the lower the attack of the other party is, so the influence of abrasion and peeling of the resin is small. Also in this respect, the wear resistance can be improved. Furthermore, if the glass fiber mating attack is reduced, the influence on the worm shaft 19 meshing with the worm wheel 20 can be reduced, so that the time for the hardening process (for example, heat treatment such as quenching) for the worm shaft 19 can be shortened. You can also.

  Moreover, the mixture ratio of the filler 40 (glass fiber) is 15 mass%-50 mass% with respect to the total amount of the material used for preparation of the raw material resin 26, for example, Preferably, it is 25 mass%-50 mass%, Also good. By blending the glass fiber in this range, it is possible to ensure sufficient mechanical strength for the sleeve portion 22 while suppressing the amount of glass fiber that is a factor causing wear of the tooth forming portion 23.

  The carbodiimide 41 to be used is not particularly limited as long as it is a compound having a carbodiimide group (—N═C═N—), and may be a monocarbodiimide having one carbodiimide group or a polycarbodiimide group having a plurality of carbodiimide groups. It may be a carbodiimide. In addition, all kinds of carbodiimides such as aliphatic carbodiimide, aromatic carbodiimide, modified carbodiimide, and the like can be used. Among these, Preferably, aliphatic carbodiimide is mentioned, As a specific commercial item, the Nisshinbo Chemical Co., Ltd. product (Carbodilite (trademark) "HMV-15CA") is mentioned, for example.

  Moreover, the mixing ratio of the carbodiimide 41 may be, for example, 0.5% by mass to 4% by mass with respect to the total amount of materials used for preparing the raw material resin 26. By blending the carbodiimide 41 in this range, the raw material resin 26 having a number average molecular weight Mn of 30,000 or more can be favorably obtained. On the other hand, since the carbodiimide 41 is not excessive, an increase in resin pressure (viscosity) during kneading, heat generation, thermal decomposition of the polyamide resin 39 and the carbodiimide 41 accompanying the heat generation, and decrease in adhesion strength with the resin due to focusing degradation of the filler 40. Etc. can also be reduced.

Further, when the carbodiimide 41 is a powder, the carbodiimide 41 may be supplied, for example, from the side feeder 36 alone or after being mixed with a polyamide resin (dry blending, master batch). .
Then, the filler 40 and the carbodiimide 41 are added to the kneaded material including the polyamide resin 39 being transferred through the cylinder 33 and the additive added as necessary, and further kneaded. The time from the supply of the carbodiimide 41 to the injection of the kneaded product from the nozzle 35 (kneading time of the carbodiimide 41) may be, for example, 1 second to 1 minute. Therefore, the distance from the nozzle 35 of the side feeder 36 may be set using the kneading time as a guide.

After the carbodiimide 41 is supplied, the kneaded product is injected from the nozzle 35 as a strand-shaped raw material resin 26, cooled and solidified in the cooling water tank 30, and then pelletized by the pelletizer 31. Through the above steps, raw material resin 26 made of polyamide resin 39 in which filler 40 is dispersed is obtained.
Regarding the manufacture of the worm wheel 20, the next step is the integral molding of the sleeve portion 22 and the tooth forming portion 23 (S2 in FIG. 3). In this process, a mold (not shown) is prepared, and the raw material resin 26 (pellet) obtained in the process of FIG. 4 is melted and injected into the mold. The mold may include a mold for forming a cylindrical structure in which a plurality of worm wheels 20 are connected in a cylindrical shape. Then, after cooling for a certain time to solidify the raw material resin 26, the integrally formed cylindrical structure of the worm wheel 20 is taken out from the mold. Then, the disk-shaped worm wheel 20 is cut out one by one from the cylindrical structure.

Finally, gear cutting (formation of teeth 24) of the tooth forming portion 23 of the worm wheel 20 is performed (S3), and the worm wheel 20 shown in FIG. 2 is obtained.
According to the above method, by supplying the carbodiimide 41 during the kneading of the polyamide resin 39 and the filler 40 (at the start of kneading of the polyamide resin 39 and the filler 40), the action of the carbodiimide 41 during kneading and injection molding. As shown in FIG. 5, the dehydration condensation reaction between the terminal carboxyl group (—COOH) and the terminal amino group (—NH ₂ ) of the polyamide resin 39 (polyamide 66 in FIG. 5) can proceed. Thereby, the polymer chains of a plurality of polyamide resins 39 formed in advance by polymerization can be connected in a chain, and the molecular weight of the resin can be increased. For example, the number average molecular weight Mn of the raw material resin 26 after the reaction can be increased to 30,000 or more.

And since the carbodiimide 41 is supplied in the middle of kneading | mixing, decomposition | disassembly of the polyamide resin 39 by dehydration condensation reaction becoming excessive can be suppressed. Therefore, the molecular weight of the polyamide resin 39 can be increased to a level that has not existed before.
Until the carbodiimide 41 is supplied, the polyamide resin 39 is not chain-reacted and does not have a high molecular weight (for example, about Mn = 20,000). In this state, the viscosity of the polyamide resin 39 is also relatively low. Therefore, the filler 40 can be well dispersed throughout the polyamide resin 39 by kneading the polyamide resin 39 and the filler 40.

  As a result, the mechanical strength / rigidity and dimensional stability required for the sleeve portion 22 can be ensured. In addition, since the resin has a number average molecular weight Mn of 30,000 or more and excellent resistance to crack growth, even if a crack is generated due to abrasion or peeling of the resin by the filler 40, the speed at which the crack progresses can be reduced. . As a result, since the amount of wear of the tooth forming part 23 can be reduced, the wear resistance required for the tooth forming part 23 can also be achieved. Thereby, there are few concerns, such as a crack and a durable life short, cost can also be reduced, and also weight reduction can be achieved compared with the case where a metal sleeve part is used.

  Moreover, since the increase in the change amount of the center distance of the worm wheel 20 can be suppressed, the generation of rattle noise due to the increase in the change amount can be prevented, and the durability life can be improved. In particular, with respect to the worm wheel 20, if the miniaturization is promoted in the future, the reduction ratio may be lowered more than ever and a large torque may be applied to the worm wheel 20. When the wear resistance is low with respect to such a large torque, the durability life of the worm wheel 20 is shortened. However, the worm wheel 20 capable of achieving excellent wear resistance as in this embodiment has a small size and high output. It can adapt well to the intended future use.

  When the polyamide resin 39, the filler 40 and the carbodiimide 41 are simultaneously supplied to the main body 28 to start kneading, or the polyamide resin 39 and the carbodiimide 41 are simultaneously charged from the main feeder 32 (first) of the kneader 27. As compared with the case of starting, the occurrence of torque over, heat generation, strand breakage, etc. of the main body 28 can be reduced. As a result, the worm wheel 20 can be produced stably.

As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form.
For example, the present invention can also be applied to various gears other than the worm wheel 20 described above.
Further, the main body 28 may include two side feeders 36 as shown in FIG. For example, the side feeder 36 may include a first side feeder 36a and a second side feeder 36b on the downstream side of the first side feeder 36a. In this case, the polyamide resin 39 may be supplied from the main feeder 32, the filler 40 may be supplied from the first side feeder 36a, and the carbodiimide 41 may be supplied from the second side feeder 36b.

Furthermore, the carbodiimide 41 may not be supplied from the side feeder 36, and may not be supplied during the kneading of the polyamide resin 39 and the filler 40. For example, it may be mixed with the polyamide resin 39 and supplied from the main feeder 32. Also by this, the effect of the present invention can be achieved.
In addition, various design changes can be made within the scope of matters described in the claims.

Next, although this invention is demonstrated based on an Example, a reference example, etc., this invention is not limited by the following Example.
<Example 1>
In the kneader 27 having the configuration shown in FIG. 4, 64.7% by mass of polyamide 66 (“1402S” number average molecular weight Mn = 23,000) manufactured by Asahi Kasei Chemicals Corporation, glass fiber (“ CS3PE-455S ") and 33.3% by mass of Nisshinbo Chemical Co., Ltd. and carbodiimide (Carbodilite (registered trademark)" HMV-15CA ") manufactured by Nisshinbo Chemical Co., Ltd. were kneaded at a ratio of 2% by mass to obtain a raw material resin. And the test sample was shape | molded using the raw material resin. Polyamide 66 was charged into the main feeder 32, and glass fiber and carbodiimide were charged into the side feeder 36.
<Reference Example 1>
A test sample was prepared under the same conditions as in Example 1 except that polyamide 66 having a number average molecular weight Mn = 27,000, glass fiber content of 15% by mass, and carbodiimide were not added. .
<Reference Example 2>
A test sample was prepared under the same conditions as in Example 1 except that carbodiimide was not added.
<Commercial item 1>
A test sample was molded using polyamide 66 (Leona (registered trademark) non-reinforced grade “1502S”) manufactured by Asahi Kasei Chemicals. Glass fibers and carbodiimide were not added.
<Commercially available product 2>
A test sample was molded using polyamide 66 (Zytel (registered trademark) “E51HSB NC010”) manufactured by DuPont. Glass fibers and carbodiimide were not added.
<Commercially available product 3>
A test sample was molded by adding 1% by mass of aromatic carbodiimide ("STABBACKZOL (registered trademark) P400") manufactured by Rhein Chemy Japan Co., Ltd. to the commercial product 1. Glass fiber was not added.
<Evaluation test>
(1) Number average molecular weight Mn
For the test samples except Reference Example 2, the number average molecular weight Mn was measured by GPC (gel permeation chromatography). The results are shown in FIG. From comparison between Example 1 and Reference Example 1 in FIG. 7, it was found that a number average molecular weight Mn of 30,000 or more can be achieved by kneading polyamide 66 and carbodiimide. Furthermore, from comparison between Example 1 and commercially available products 1 and 2, by introducing carbodiimide into the side feeder 36, the molecular weight is increased to a level that cannot be achieved with general commercially available products 1 and 2. I understood.
(2) Tensile strength For Example 1, Reference Example 1 and Reference Example 2, the tensile strength was measured according to JIS K 7161. The results are shown in FIG. From FIG. 8, it was found that even when carbodiimide was added (Example 1), excellent tensile strength (mechanical strength) equivalent to that when no carbodiimide was added (Reference Example 2) could be achieved.
(3) Friction and abrasion test For Example 1, Reference Examples 1 and 2, and commercially available products 1 and 3, a Suzuki friction and abrasion test was performed to measure the abrasion weight (g). The results are shown in FIG. 9 and FIG. The test conditions were as follows.

・ 4-point metal roller-sliding with resin ring ・ Grease lubrication ・ Test temperature: RT
-Intermittent contact by driving-stopping From FIG. 9, it was found that Example 1 having a high molecular weight with carbodiimide was superior in abrasion resistance as compared to Reference Examples 1 and 2 in which carbodiimide was not added.

  Further, FIG. 10 shows that even if carbodiimide is added to the non-reinforced high molecular weight grade polyamide 66, the effect of improving the wear resistance cannot be obtained. This is because almost no wear occurs under high surface pressure sliding under grease lubrication, creep deformation is the main component, and the effect of improving wear due to high molecular weight is not exhibited.

  DESCRIPTION OF SYMBOLS 20 ... Worm wheel, 22 ... Sleeve part, 23 ... Teeth formation part, 26 ... Raw material resin, 39 ... Polyamide resin, 40 ... Filler, 41 ... Carbodiimide

Claims (6)

A gear including a sleeve portion and a tooth forming portion,
The sleeve in which the sleeve portion and the tooth forming portion are integrally formed of a raw material resin obtained by kneading a compound having a polyamide resin, a filler, and a carbodiimide bond.   The gear according to claim 1, wherein the resin constituting the sleeve portion and the tooth forming portion further contains a lubricant.   The gear according to claim 2, wherein the lubricant is a metal soap.   The resin which comprises the said sleeve part and the said tooth | gear formation part contains the glass fiber of 15 mass%-50 mass% with respect to the total amount as said filler. Gear.   The gear as described in any one of Claims 1-4 in which the resin which comprises the said sleeve part and the said tooth | gear formation part contains the glass fiber which has a diameter of 6 micrometers-15 micrometers as the said filler.   The gear as described in any one of Claims 1-5 with which the compound which has a carbodiimide bond of 0.5 mass%-4 mass% with respect to the total amount of the said raw material resin is mix | blended.

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