JP2004218712A - Resin gear suitable for transmitting power - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin gear suitable for transmitting power having durability such as excellent resistance to fatigue of polyamide resin, having excellent dimensional stability by suppressing dimensional change due to absorption of water, and having high reliability. <P>SOLUTION: In this gear, a resin part 43 is provided around a metallic hub 42 and is constituted by resin component containing polyamide resin as base resin. Water absorption treatment is applied so that water absorption rate becomes 2 to 5 weight % for resin weight. A bonding layer of silane coupling agent having any of epoxy group and amino group is provided at a terminal on one side between the metallic hub and the resin part of the gear to suppress dimensional change due to water absorption. Non-reinforced polyamide 46 resin which is difficult for use because of dimensional change due to water absorption and has the most excellent resistance to fatigue can also be used. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a resin gear suitable for power transmission, and more particularly to a gear used for a gear reduction mechanism or the like constituting a power assist unit of an electric power steering device.
[0002]
[Prior art]
In an electric power steering apparatus for a vehicle, since a relatively high-speed and low-torque electric motor is used, a gear reduction mechanism is incorporated between the electric motor and the steering shaft. As a gear reduction mechanism, a gear reduction mechanism using spur gears or other gears is also known, but a known worm composed of a worm and a worm wheel is used because a large reduction ratio can be obtained in one set. It is common to use a gear reduction mechanism.
[0003]
Such a worm gear reduction mechanism (hereinafter simply referred to as a reduction gear) includes a worm which is a drive gear connected to a rotating shaft of an electric motor, and a worm wheel which meshes with the worm.
[0004]
In such a reduction gear, if both the worm and the worm wheel are made of metal, there is an inconvenience that unpleasant noise such as rattling noise and vibration sound is generated at the time of operating the steering wheel. When made of metal, a blank disk made of a synthetic resin material is integrally formed on the outer periphery of a metal hub, that is, a metal core, as a worm wheel, and cutting and other means are performed on the circumference of the blank disk. The use of a worm wheel having synthetic resin teeth in which resin teeth are integrally formed with the teeth formed by using a worm wheel suppresses generation of unpleasant noise such as rattling noise and vibration noise.
[0005]
As a material of the resin tooth portion, a fiber reinforcing material such as glass fiber or carbon fiber is mixed with a base resin such as polyamide 6, polyamide 66, polyacetal, polyetheretherketone (PEEK), or polyphenylene sulfide (PPS). In addition to the above-mentioned materials, MC (monomer cast) nylon, polyamide 6, polyamide 66 and the like which do not contain a reinforcing material are also used.
[0006]
In consideration of dimensional stability and cost, MC nylon not containing a fiber reinforcing material is used, and polyamide 6, polyamide 66, polyamide 46, or the like containing glass fiber is used as the fiber reinforcing material (for example, Patent Document 1).
[0007]
[Patent Document 1]
Japanese Patent Publication No. 6-60674
[Problems to be solved by the invention]
However, although the polyamide resin, which is a synthetic resin material constituting the resin portion integrally formed on the outer peripheral portion of the core metal, has excellent fatigue resistance, it has high water absorption, absorbs moisture, and has a worm wheel gear. The tooth portion of the worm may expand, and the gap existing between the worm and the worm wheel in the early stage of manufacture may be lost, or the worm may be further expanded to compress the worm.
[0009]
When the worm wheel expands in this manner, the frictional resistance between the worm and the worm wheel increases and the steering operation becomes heavy, and the gear portion wears or breaks due to the compression of the gear portion and the increase in the frictional resistance. There is a disadvantage that the power steering device does not function.
[0010]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem. The resin portion made of a polyamide resin is subjected to a water-absorbing treatment in advance to suppress a dimensional change due to further water absorption, and the gear portion is worn or damaged. An object of the present invention is to provide a gear of an electric power steering device having high reliability which is not likely to be caused.
[0011]
[Means for Solving the Problems]
The present invention solves the above problems, and the invention of claim 1 is a resin gear suitable for power transmission, wherein the resin gear is made of a resin composition containing a water-absorbed polyamide resin as a base resin. A resin gear suitable for power transmission, characterized in that the resin part is formed integrally with the outer periphery of a metal hub, and the resin part is a gear in which meshing teeth are formed.
[0012]
The water-absorbed polyamide resin is water-absorbed so that the water absorption is 2 to 5% by weight based on the weight of the resin.
[0013]
Further, an adhesive layer made of a silane coupling agent having either an epoxy group or an amino group at one end may be provided between the metal hub and the resin portion.
[0014]
Further, the gear may be a worm wheel, a helical gear, a spur gear, a bevel gear, or a hypoid gear.
[0015]
The polyamide resin may be at least one polyamide resin selected from polyamide 6, polyamide 66, and polyamide 46.
[0016]
Further, the gear can be configured by press-fitting the resin portion alone into the metal hub after water absorption treatment. At this time, it is preferable to press-fit the resin portion which has been subjected to the water absorption treatment alone into a metal hub having an adhesive layer made of a silane coupling agent formed on the joining surface.
[0017]
However, when an adhesive layer made of a silane coupling agent is formed, a rust-proof treatment may be applied to the metal hub, and a water-absorbing treatment may be performed after press-fitting the resin portion.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0019]
FIG. 1 is a front view illustrating an example of a configuration of an electric power steering device 10 in which a resin gear suitable for power transmission according to the present invention is applied to a reduction mechanism, and is a column-type electric power steering device. In FIG. 1, reference numeral 11 denotes a steering wheel shaft, 12 denotes a steering wheel shaft housing, 13 denotes an electric motor, and 20 denotes a rack and pinion type motion conversion mechanism.
[0020]
Although not shown in FIG. 1, the steering shaft 11 includes an upper steering wheel shaft 11a and a lower steering wheel shaft 11b. The steering wheel shaft 11 is supported inside a steering wheel shaft housing 12 so as to be rotatable around an axis. The steering shaft housing 12 is fixed to a predetermined position in the vehicle interior such that a lower portion thereof is inclined forward. A steering wheel (not shown) is fixed to the upper end of the upper steering shaft 11a.
[0021]
Further, the upper steering wheel shaft 11a and the lower steering wheel shaft 11b are connected by a not-shown torsion bar, and the steering torque transmitted from the steering wheel to the lower steering wheel shaft 11b via the upper steering wheel shaft 11a is detected by the torsion bar. The output of the electric motor 13 is controlled based on the detected steering torque.
[0022]
The rack and pinion type motion conversion mechanism 20 is disposed substantially horizontally in the engine room at the front of the vehicle with the longitudinal direction being the left-right direction of the vehicle, and the rack shaft 21 is movable in the axial direction. It comprises a pinion shaft 22 including a pinion having a tooth portion that is supported obliquely with respect to the tooth portion of the rack shaft 21, and a cylindrical rack shaft case 23 that supports the rack shaft 21 and the pinion shaft 22. You.
[0023]
The pinion shaft 22 and the lower part of the lower steering wheel shaft 11b are connected by two universal joints 25 and 26. A worm gear reduction mechanism 30 described later is arranged in an intermediate portion of the lower steering wheel shaft 11b, and is configured so that a steering assist force is supplied from the electric motor 13 to the lower steering wheel shaft 11b.
[0024]
FIG. 2 is a partial cross-sectional view showing the configuration of the worm gear reduction mechanism 30 of the electric power steering device 10 described above. Reference numeral 31 denotes a worm wheel, 32 denotes a worm that meshes with the worm wheel 31, and 33 denotes a gear case. The worm 32 has worm shafts 32a and 32b integrally formed at both ends thereof. The worm shafts 32a and 32b are rotatably supported by ball bearings 34a and 34b mounted on the gear case 33, respectively. The worm shaft 32b is splined or serrated to the drive shaft 13a of the electric motor 13.
[0025]
The hub of the worm wheel 31, that is, the core metal 42 is connected to the lower steering wheel shaft 11 b, and the rotation of the electric motor 13 is transmitted to the lower steering wheel shaft 11 b via the worm 32 and the worm wheel 31.
[0026]
FIG. 3 is a perspective view showing the configuration of the worm wheel 31 of the worm gear reduction mechanism 30 according to the embodiment of the present invention. A cylindrical resin portion 43 integrally formed of synthetic resin is provided on the processed surface, and gear teeth 44 are formed on the outer peripheral surface of the resin portion 43. On the other hand, the worm 32 is made of metal like the conventional worm.
[0027]
The resin portion 43 of the worm wheel 31 is preferably made of polyamide 6, polyamide 66, or polyamide 46 having excellent fatigue resistance as a base resin. In addition, these base resins are modified with other polyamide resins or acid anhydrides that improve the wettability to a grease base oil composed of a low-polar base oil generally used between a worm and a worm wheel. Or a rubbery substance such as ethylene propylene non-conjugated diene rubber (EPDM) for improving impact resistance.
[0028]
These base resins alone exhibit a certain level of durability even when used alone, work favorably against abrasion of the metal worm 32 which is a mating material of the worm wheel 31, and sufficiently function as a reduction gear. However, if the gear teeth 44 are used under more severe use conditions, the gear teeth 44 are expected to be worn or broken. Therefore, it is preferable to add a reinforcing material to enhance reliability.
[0029]
As the reinforcing material, glass fiber (GF), carbon fiber, potassium titanate whisker, aluminum borate whisker and the like are preferable, and those which have been surface-treated with a silane coupling agent in consideration of the adhesiveness with the polyamide resin described above are further used. preferable. In addition, these reinforcing materials can be used in combination of a plurality of types.
[0030]
In consideration of impact strength, it is preferable to mix a fibrous material such as glass fiber or carbon fiber, and further, in consideration of damage to the worm 32, it is preferable to mix a whisker-like material with the fibrous material. The mixing ratio in the case of mixing and using differs depending on the types of the fibrous material and the whisker-like material, and is appropriately selected in consideration of impact strength and damage to the worm 32.
[0031]
It is preferable that these reinforcing materials have a compounding ratio of 5 to 40% by weight, particularly 10 to 30% by weight of the whole resin. If the compounding ratio of the reinforcing material is less than 5% by weight, the mechanical strength is not improved, which is not preferable. On the other hand, if the compounding ratio of the reinforcing material exceeds 40% by weight, the worm 32 is likely to be damaged, and abrasion of the worm 32 is promoted, and durability as a reduction gear may be insufficient, which is not preferable.
[0032]
Furthermore, in order to prevent deterioration due to heat during molding and use, it is preferable to add an iodide-based heat stabilizer and an amine-based antioxidant to the base resin alone or in combination.
[0033]
The resin portion 43 of the worm wheel 31 is controlled to have a water content of 2 to 5% by weight with respect to the weight of almost only the resin component excluding the reinforcing material (100% by weight). ing.
[0034]
FIG. 4 shows the equilibrium water content (saturated water content) of unreinforced polyamide 6 (PA6), polyamide 66 (PA66), and polyamide 46 (PA46) when left in an environment at 23 ° C. and a relative humidity of 60% and 80%. FIG.
[0035]
As shown in FIG. 4, the equilibrium water content tends to increase as the relative humidity increases. Further, the equilibrium water content of the polyamide is related to the ratio of amide bonds in the molecular structure, and the order of amide bonds is large (PA46>PA6> PA66).
[0036]
Accordingly, the dimensional change accompanying this also corresponds to this order, and since the polyamide 46 is the largest, it is preferable to increase the water content by the water absorption treatment to 3 to 5% by weight.
[0037]
If the water content by the water absorption process is less than 2% by weight, the change in water absorption dimensions during actual use of the electric power steering device cannot be sufficiently offset, and it is difficult to suppress the problem due to swelling. On the other hand, when the water content by water absorption exceeds 5% by weight, the effect of suppressing dimensional change due to swelling is expected to be high, but when exposed to high temperatures during actual use, water is conversely released. It is also conceivable that the size may be reduced and the transmission efficiency may be reduced.
[0038]
As the water absorption treatment, a resin part molded separately (preferably having a tooth shape on the outer diameter part with a cutting allowance) or an insert molded resin part integrated with a metal core as a core is subjected to water or high humidity. In a constant temperature and humidity chamber (for example, a temperature of 80 ° C. and a relative humidity of 90%).
[0039]
In the case where the water absorption treatment is performed on the resin portion 43 and the water absorption treatment is performed integrally with the metal core 42, in order to prevent the generation of rust, grease is applied to the exposed surface of the metal core 42 and a masking agent that can be removed. , And rust-proof plating on the surface of the cored bar 42. It is more preferable that the application of grease and the application of a removable masking agent be performed to a point where the water enters the resin portion 43 from the seam while preventing moisture from entering between the cored bar 42 and the resin portion 43.
[0040]
In addition, if the water absorption treatment is performed integrally with the cored bar 42, a small gap is generated between the metal part and the resin part in addition to the rust, but this gap has a bad influence on the durability of the gear teeth 44 of the resin part 43. Therefore, it is preferable that the water absorption process be performed only on the resin portion 43 alone.
[0041]
After the resin portion 43 that has been subjected to the water absorption treatment alone is press-fitted into the cored bar 42 (press-fitted while the resin portion 43 is expanded by heating in a thermostatic bath), the gear teeth 44 of the resin portion 43 are cut.
[0042]
Before press-fitting the resin portion 43 into the metal core 42, a silane coupling agent is applied to the metal core 42, and after the press-fitting, high-frequency heating is performed, so that a gap between the outer peripheral portion of the metal core 42 and the inner peripheral portion of the resin portion 43. When the adhesive layer is formed on the substrate, the dimensional change due to further water absorption can be suppressed, which is more effective. When high-frequency heating is performed, only the inner peripheral portion (interface) of the resin portion 43 adjacent to the outer peripheral portion of the cored bar 42 is melted, and the residual stress generated by press-fitting can be removed.
[0043]
When an adhesive layer made of a silane coupling agent is formed on the outer periphery of the metal hub, that is, the core bar 42, the core bar 42 is subjected to a rust-proof treatment (for example, chrome plating), and then the silane coupling agent adhesive layer is formed. May be formed, and a water absorption process may be performed after the resin portion 43 is press-fitted therein.
[0044]
At the time of high frequency heating, if the temperature of the cored bar 42 is heated to 200 ° C. to 450 ° C., the adhesive strength becomes strong. The heating atmosphere may be the air, but it is preferable to perform the heating in an atmosphere of an inert gas such as an argon gas because oxidation deterioration of the resin or the like can be suppressed.
[0045]
The silane coupling agent has, at one end of its chemical structure, an alkoxy group that is a hydrolyzable group.The alkoxy group is hydrolyzed and changes to a hydroxyl group, and this hydroxyl group undergoes dehydration condensation with a hydroxyl group on the metal surface. This causes a covalent bond with a high bonding force to be formed with the metal. The other end has an organic functional group, and this organic functional group bonds to an amide bond in the molecular structure of the polyamide resin. And the core metal 42 and the resin part 43 are firmly connected by these connections.
[0046]
In addition, as an organic functional group, an amino group and an epoxy group are preferable, and as such a silane coupling agent having an organic functional group, γ-glycidoxypropyltrimethoxysilane, β (3,4-epoxy Cyclohexyl) ethyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltriethoxysilane, γ-ureidopropyltriethoxysilane, and the like. In particular, those having an epoxy group as an organic functional group have high reactivity with an amide bond, and are more preferable.
[0047]
In order to more firmly bond the adhesive layer to the outer peripheral portion of the cored bar 42, it is preferable to increase the number of surface hydroxyl groups on the outer peripheral surface of the cored bar 42. It is suitable.
[0048]
In addition, in order to improve the adhesion between the metal core 42 and the resin part 43 and to prevent the boundary between the metal core 42 from slipping out, including the increase in the adhesive force, the outer peripheral surface of the metal core 42 is Shot blasting or knurling may be performed, and knurling is particularly preferable. The depth of the knurled V-shaped groove is suitably 0.2 to 0.8 mm, particularly 0.3 to 0.7 mm.
[0049]
As described above, the worm wheel of the cylindrical worm gear has been described as an embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made. For example, the spur gear shown in FIG. 6, the helical gear shown in FIG. 7, the bevel gear shown in FIG. 8, the hypoid gear shown in FIG.
[0050]
Next, evaluation results of dimensional stability and durability of a plurality of examples and a plurality of comparative examples of the worm wheel will be described.
[0051]
(Example 1)
Core metal: steel steel (material symbol: S45C) with a knurled groove depth of 0.5 mm and an outer diameter of 65 mm and a width of 16 mm. After the degreasing treatment, it is immersed in a 10% by weight methanol solution of γ-glycidoxypropylmethoxysilane (“A-187” manufactured by Nippon Unicar Co., Ltd.), which is a silane coupling agent having an epoxy group, for the purpose of forming an adhesive layer. Then, it dried in air | atmosphere and formed the film of the silane coupling agent.
[0052]
Resin part: Polyamide 66 (containing 30% by weight of GF, UBE nylon 2020GU6 manufactured by Ube Industries, Ltd., containing Cu-based additive) as resin used. It has a helical shape with a cutting margin left in the outer diameter part, and a resin part having dimensions of 64 mm in inner diameter, 83 mm in outer diameter, and 15.5 mm in width is separately manufactured by injection molding, and is manufactured at a temperature of 80 ° C. The sample was placed in a thermo-hygrostat at a humidity of 90% and subjected to water absorption treatment (water absorption: 1.54% by weight based on the total weight, 2.2% by weight based on the resin weight).
[0053]
High-frequency fusion: The resin part subjected to the water absorption treatment was heated at a temperature of 140 ° C. for 20 minutes to expand the resin part and then press-fit the core part. Thereafter, high-frequency heating was performed in an argon gas until the core metal temperature rose to 350 ° C., and the resin portion was fused (adhered) to the core metal, and was rapidly cooled by being put in water. Thereafter, the resin portion was cut with teeth, and finally finished into a worm wheel. The water content of the resin portion after the final processing was slightly reduced by heating, and was 2.0% by weight based on the resin weight.
[0054]
(Example 2)
It was almost the same as Example 1, except that the resin used was changed to the following.
[0055]
Resin used: Polyamide 6 (containing 30% by weight of GF, UBE nylon 1015GU6 manufactured by Ube Industries, Ltd., containing Cu-based additive). High frequency welding is also performed. The water content of the resin part after the final processing is 2.5% by weight based on the resin weight.
[0056]
(Example 3)
It was almost the same as Example 1, except that the resin used was changed to the following.
[0057]
Resin used: Polyamide 46 (unreinforced, DSM JSR Engineering Plastics Co., Ltd. Stanyl TW341, containing heat stabilizer). High-frequency fusion was performed in the same manner. The water content of the resin part after the final processing was 4.5% by weight based on the resin weight.
[0058]
(Example 4)
Approximately the same as Example 1 (the same resin and water content are used). The difference is that no silane coupling agent was applied. Implements high-frequency heating to remove residual stress due to press fitting.
[0059]
(Example 5)
Approximately the same as Example 3 (the same resin and water content are used). The difference is that no silane coupling agent was applied. Implements high-frequency heating to remove residual stress due to press fitting.
[0060]
(Comparative Example 1)
The same core metal as in Example 1 was used, and the resin part was insert-molded with an injection molding machine using the core metal as a core. Resin used: Same as in Example 1. Moisture content of resin part after final processing: 0.2% by weight based on resin weight (left in air).
[0061]
(Comparative Example 2)
The same core metal as in Example 1 was used, and the resin part was insert-molded with an injection molding machine using the core metal as a core. Resin used: Same as in Example 2. Moisture content of resin part after final processing: 0.2% by weight based on resin weight (left in air).
[0062]
(Comparative Example 3)
The same core metal as in Example 1 was used, and the resin part was insert-molded with an injection molding machine using the core metal as a core. Resin used: Same as in Example 3. Moisture content of resin part after final processing: 0.3% by weight based on resin weight (left in air).
[0063]
(Comparative Example 4)
It is almost the same as Example 1, and the water absorption treatment and the high frequency fusion were also performed in the same manner. The water content of the resin part after the final processing was 1.0% by weight based on the resin weight.
[0064]
(Comparative Example 5)
It is almost the same as Example 3, and the water absorption treatment and the high frequency fusion were also performed in the same manner. The water content of the resin part after the final processing was 1.0% by weight based on the resin weight.
[0065]
(Comparative Example 6)
It is almost the same as Example 3, and the water absorption treatment and the high frequency fusion were also performed in the same manner. The water content of the resin portion after the final processing was 7.0% by weight based on the resin weight.
[0066]
FIG. 5 is a diagram for explaining the evaluation results of the dimensional stability and the durability of the above-described Examples 1 to 4 and Comparative Examples 1 to 6.
[0067]
First, regarding the dimensional stability, the above Examples 1 to 4 and Comparative Examples 1 to 6 were left under the following environmental conditions A and B, and the change in the outer diameter of the gear after 70 hours and 300 hours passed. The amount was measured. Under any of the conditions, a change amount of 40 μm or less was indicated as “O” as a pass, and a change amount exceeding 40 μm was indicated as “X” as a reject.
[0068]
Condition A: temperature 60 ° C., relative humidity 90%
Condition B: temperature 80 ° C., relative humidity 90%
Regarding durability, the above Examples 1 to 4 and Comparative Examples 1 to 6 were incorporated into an actual electric power steering apparatus, and the steering operation was repeated under the following environmental conditions C, D, E, and F to endurance. Was determined. Under any of the conditions, a gear that could withstand 100,000 steering operations was displayed as “O” as a pass, and a gear that could not withstand 100,000 steering operations was displayed as “X” as a reject, Gears that could withstand 100,000 steering operations but reduced efficiency by 10% or more were indicated as “Δ” as efficiency reduction.
[0069]
Condition C: temperature 30 ° C., relative humidity 50%
Condition D: temperature 50 ° C., relative humidity 90%
Condition E: temperature 80 ° C., relative humidity 50%
Condition F: temperature 80 ° C., relative humidity 90%
As shown in FIG. 5, Examples 1 to 3 in which an adhesive layer was provided between the outer peripheral portion of the cored bar 42 and the inner peripheral portion of the resin portion 43 and the water content was adjusted were the most excellent in dimensional stability. It was also found that it was excellent in durability under severe environment of high temperature and high humidity.
[0070]
In Examples 4 and 5 in which only moisture adjustment was performed, the dimensional stability was slightly inferior, and in a high-humidity environment, the higher the temperature was, the larger the change in the dimensions was, and the lower the durability was. In Comparative Example 6 in which the water content exceeds 5%, the dimensional change due to water absorption is offset and there is no problem. However, when used at high temperature and low humidity, the water content decreases, and the efficiency decreases due to dimensional shrinkage. I understood.
[0071]
In the embodiment described above, an example is described in which the resin gear suitable for power transmission of the present invention is applied to the speed reduction mechanism of the electric power steering device. However, the gear according to the present invention is only the speed reduction mechanism of the electric power steering device. However, it goes without saying that the present invention can be applied to gear mechanisms in general regardless of the application.
[0072]
【The invention's effect】
As described above, the present invention relates to a resin gear suitable for power transmission, wherein the resin portion of the gear is made of a resin composition containing a polyamide resin as a base resin, and the water absorption is 2 to 5 with respect to the weight of the resin. % By weight so that the polyamide resin maintains excellent durability such as fatigue resistance, suppresses dimensional changes due to water absorption, and has high dimensional stability and high reliability. A resin gear suitable for transmission can be provided.
[0073]
Further, by providing an adhesive layer made of a silane coupling agent having either an epoxy group or an amino group at one end between the metal hub and the resin portion of the gear, dimensional change due to further water absorption is suppressed. be able to. This makes it difficult to use due to dimensional changes due to water absorption, and also allows the use of non-reinforced polyamide 46 resin, which is the most excellent in fatigue resistance. Is played.
[Brief description of the drawings]
FIG. 1 is a front view illustrating an example of a configuration of an electric power steering device suitable for carrying out the present invention.
FIG. 2 is a partial sectional view showing a configuration of a worm gear reduction mechanism of the electric power steering device shown in FIG.
FIG. 3 is a perspective view showing a configuration of a worm wheel of the worm gear reduction mechanism.
FIG. 4 shows the equilibrium water content (saturated water content) of unreinforced polyamide 6 (PA6), polyamide 66 (PA66), and polyamide 46 (PA46) when left in an environment of 23 ° C. and a relative humidity of 60% and 80%. FIG.
FIG. 5 is a diagram illustrating evaluation results of dimensional stability and durability of Examples 1 to 4 and Comparative Examples 1 to 6.
FIG. 6 is a view showing the appearance of a spur gear as an example of a gear to which the present invention can be applied.
FIG. 7 is a view showing the appearance of a helical gear as an example of a gear to which the present invention can be applied.
FIG. 8 is a view showing the appearance of a bevel gear as an example of a gear to which the present invention can be applied.
FIG. 9 is a diagram showing the appearance of a hypoid gear as an example of a gear to which the present invention can be applied.
[Explanation of symbols]
Reference Signs List 10 electric power steering device 11 steering wheel shaft 11a upper steering wheel shaft 11b lower steering wheel shaft 12 steering wheel shaft housing 13 electric motor 13a drive shaft 20 rack-pinion type motion conversion mechanism 21 rack shaft 22 pinion shaft 23 rack shaft cases 25, 26 universal joint 30 Worm gear reduction mechanism 31 Worm wheel 32 Worm 32a, 32b Worm shaft 33 Gear case 34a, 34b Ball bearing 42 Hub (core metal)
43 resin part 44 gear teeth

Claims (7)

A resin gear suitable for power transmission,
The resin gear is a gear in which a resin portion made of a resin composition having a polyamide resin subjected to water absorption treatment as a base resin is integrally formed on an outer periphery of a metal hub, and teeth for meshing are formed on the resin portion. A resin gear suitable for power transmission characterized by the following. The resin gear suitable for power transmission according to claim 1, wherein the water-absorbed polyamide resin is water-absorbed so that the water absorption is 2 to 5% by weight based on the weight of the resin. The power transmission according to claim 1, wherein an adhesive layer made of a silane coupling agent having either an epoxy group or an amino group at one end is provided between the metal hub and the resin portion. Resin gears. The resin gear according to claim 1, wherein the gear is a worm wheel, a helical gear, a spur gear, a bevel gear, or a hypoid gear. The resin gear suitable for power transmission according to claim 1, wherein the gear is configured by subjecting the resin portion to water absorption treatment alone and then press-fitting the resin portion into the metal hub. 2. The gear according to claim 1, wherein the gear portion is configured by press-fitting the resin portion that has been independently subjected to water absorption treatment into the metal hub having an adhesive layer made of a silane coupling agent formed on a joint surface. 3. Resin gear suitable for power transmission. The resin gear according to claim 1 or 2, wherein the polyamide resin is at least one polyamide resin selected from polyamide 6, polyamide 66, and polyamide 46.

Images