JP4352667B2 - Electric power steering device - Google Patents

Description

【００３０】
・エステル系化合物Ｉ：モンタン酸エステル部分けん化ワックス（ＢＡＳＦジャパン（株）製「Ｌｕｗａｘ ＯＰ」）
・エステル系化合物II：ペンタエリスリトールテトラオレエート（ヘンケル白水（株）製「ＥＭＥＲＹ２８９８」）
・エステル系化合物III：ジ−２−エチルヘキシルセバケート（大八化学工業（株）製ＤＯＳ）
・エステル系化合物IV：ソルビタンモノオレエート（花王（株）製「レオドールＳＰ−０１０」）
・酸化防止剤：４，４´−ジオクチルジフェニルアミン（精工化学（株）製「ノンフレックスＯＤ−ＲＨ」）
・防錆剤：中性カルシウムスルホネート（（株）松村石油研究所製「モレスコアンバーＳＣ４５Ｎ（鉱油含有量５４％）」）
【００３１】
〔ウォームホイール試験体の作製〕
クロスローレット加工を施し、脱脂した外径４５ｍｍ、幅１３ｍｍのＳ４５Ｃ製の芯管を、スプルー及びディスクゲートを装着した金型に配置し、ガラス繊維を３０重量％含有するポリアミド６６（宇部興産（株）製「ＵＢＥナイロン２０２０ＧＵ６」、銅系添加剤含有）を射出成形して外径６０ｍｍ、幅１３ｍｍのウォームホイールブランク材とし、次いで樹脂部の外周を切削加工してギア歯を形成して図３に示すウォームホイール試験体を作製した。
【００３２】
〔耐久性の評価〕
作製したウォームホイール試験体を実際の電動パワーステアリング装置の減速ギアに組み込み、更に上記で調製した試験グリースをウォームホイールのギア歯表面及びウォームのギア歯表面に満遍なく塗布し、雰囲気温度８０℃に維持して操舵を行い、１万回毎にギア歯の摩耗量を測定した。試験前に比べて摩耗量が４０μｍ以下を合格とした。結果を表２に示す。
【００３３】
【表２】

【００３４】
表２に示すように、エステル系化合物を含有しない比較例１の試験グリースでは、２万回操舵で摩耗量が４０μｍを超えており、耐久性が十分ではない。これに対し、エステル系化合物を含有する実施例１〜４の試験グリースでは、１０万回操舵後も摩耗量４０μｍ以下であり、耐久性の向上に効果があることがわかる。
【００３５】
【発明の効果】
以上説明したように、本発明によれば、鉱油、ポリα−オレフィン油、アルキルポリフェニルエーテルから選ばれる少なくとも１種を基油とし、これに増ちょう剤及びエステル系化合物を配合したグリースを用いることにより、ウォームホイールのポリアミド樹脂製のギア歯へのグリースの濡れ性が高まり、歯車間の潤滑性が向上して、より耐久性に優れる電動パワーステアリング装置を提供できる。
【図面の簡単な説明】
【図１】パワーステアリング装置の一例を示す一部断面構成図である。
【図２】図１のＡＡ断面図であり、電動モータと減速ギアとの連結部周辺を示す概略構成図である。
【図３】減速ギアの一例（円筒ウォームギア）を示す斜視図である。
【図４】減速ギアの他の例（平歯車）を示す斜視図である。
【図５】減速ギアの更に他の例（はすば歯車）を示す斜視図である。
【図６】減速ギアの更に他の例（かさ歯車）を示す斜視図である。
【図７】減速ギアの更に他の例（ハイボイドギア）を示す斜視図である。
【符号の説明】
１ 芯管
３ 樹脂部
４ スプルー
５ ディスクゲート
８ 接着層
１０ ギア歯
１１ ウォームホイール
１２ ウォーム
２０ 減速ギア
５０ ステリングコラム
７０ ステアリングシャフト
８０ トーションバー
９０ 軸受
９１ 軸受
１００ 電動モータ
１１０ 転がり軸受
１２０ ハウジング
１３０ ダンパー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering device that transmits an auxiliary output from an electric motor to a steering mechanism of a vehicle via a reduction gear mechanism, and in particular, the outer periphery of a metal cored bar is made of a resin composition and has gear teeth on the outer peripheral surface. The present invention relates to an electric power steering apparatus including a driven gear integrally formed with a formed resin portion and grease-lubricated.
[0002]
[Prior art]
In an electric power steering apparatus incorporated in an automobile, an electric motor having a relatively high rotation and low torque is used. Therefore, a speed reduction mechanism is incorporated between the electric motor and the steering shaft. As a speed reduction mechanism, a reduction gear for an electric power steering apparatus including a worm 12 and a worm wheel 11 meshing with the worm 12 as shown in FIG. 20 (hereinafter also simply referred to as “reduction gear”) is generally used. Here, the worm 12 is connected to the rotating shaft of the electric motor 100 shown in FIG. 2 and corresponds to a drive gear, while the worm wheel 11 corresponds to a driven gear.
[0003]
In such a reduction gear 20, when both the worm wheel 11 and the worm 12 are made of metal, there is a problem that unpleasant sounds such as rattling noises and vibration sounds are generated when the steering wheel is operated. Therefore, the worm wheel 11 is obtained by integrating the resin portion 3 made of resin and having the gear teeth 10 formed on the outer peripheral surface thereof on the outer periphery of the metal core tube 1 by using an adhesive 8 or the like. Uses noise countermeasures.
[0004]
For example, as described in Japanese Patent Publication No. 6-60674, the resin portion 3 is made of a base resin such as polyamide 6, polyamide 66, polyacetal, polyether ether ketone (PEEK), polyphenylene sulfide (PPS), or the like. In addition to materials blended with reinforcing materials such as glass fibers and carbon fibers, MC (monomer cast) nylon, polyamide 6, polyamide 66, etc. that do not contain reinforcing materials are used. Among these, in consideration of dimensional stability and cost, MC nylon not containing a reinforcing material, polyamide 6, glass 66 containing polyamide, polyamide 46, and the like are mainly used.
[0005]
Further, as shown in FIG. 2, the worm 12 of the reduction gear 20 is supported by a rolling bearing 110 such as a pair of ball bearings and connected to the electric motor 100, and between the pair of rolling bearings 110 of the housing 120. The space is usually filled with grease for lubrication between the gear teeth of the worm 12 and the worm wheel 11. Furthermore, preload is applied to the rolling bearing 110, and when a minute kickback input is input from the tire side, the worm 12 is moved in the axial direction to prevent the electric motor 100 from rotating, and only the kickback is applied to the handle side. In order to convey the above information, it is also known that a rubber damper 130 is attached to the worm side of the rolling bearing 110 as shown in the figure. As the rubber used, ethylene acrylic rubber having a small compression set is used. Acrylic rubber represented by is generally used.
[0006]
[Problems to be solved by the invention]
The above grease is generally based on mineral oil or poly α-olefin oil. However, although mineral oil and poly α-olefin oil have good wettability to metal, they have poor wettability to highly polar polyamide resin. Therefore, the gear teeth of the metal worm 12 and the worm wheel 11 The state of lubrication with the gear teeth 10 formed on the resin part 3 is not always sufficient.
[0007]
As a result, in the electric power steering apparatus, temporary oil shortage occurs during a long-term operation, and the wear of the gear teeth 10 of the worm wheel 11 gradually progresses so that the worm 12 and the worm wheel 11 are engaged. The backlash (backlash) at the part increases. As a result, the smooth operation of the worm 12 is hindered, and the steering feeling may be deteriorated or abnormal noise (gap sound) may be generated. Furthermore, the gear teeth 10 of the worm wheel 11 may be deformed or damaged in some cases, and the entire device may not function.
[0008]
The present invention has been made in view of such a situation, and an object of the present invention is to provide an electric power steering device having excellent durability and high reliability by using grease having improved wettability to polyamide resin. And
[0009]
[Means for Solving the Problems]
Another object of the present invention is to provide an electric power steering apparatus for transmitting auxiliary output from an electric motor to a vehicle steering mechanism via a reduction gear mechanism according to the present invention, wherein the driven gear of the reduction gear mechanism is a metal core tube. A resin portion comprising a resin composition containing a polyamide resin as a resin component, and a resin portion having gear teeth formed on the outer peripheral surface, and at least between the driven gear and the drive gear, mineral oil, Ester compound selected from partial α-olefins and alkylpolyphenyl ethers, base oils, urea compounds as thickeners, esters having a hydroxyl group in the molecular structure and partially saponified esters with fatty acids This is achieved by an electric power steering device characterized by interposing a grease containing
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail.
[0011]
In the present invention, the configuration of the electric power steering apparatus itself is not limited, and for example, the electric power steering apparatus shown in FIG. 1 can be exemplified. In the illustrated electric power steering apparatus, on the output shaft 60 side of the steering column 50, a gear box configured by housing the reduction gear 20 as shown in FIGS. Yes.
[0012]
Further, the steering column 50 is hollow, the steering shaft 70 is inserted, and is rotatably supported by rolling bearings 90 and 91 housed in the housing 120. The steering shaft 70 is a hollow shaft and accommodates a torsion bar 80. A worm wheel 11 is provided on the outer peripheral surface of the steering shaft 70, and a worm 12 is engaged with the worm wheel 11. Further, as shown in FIG. 2, an electric motor 100 is connected to the reduction gear 20 including the worm wheel 11 and the worm 12.
[0013]
As shown in FIG. 3, the reduction gear 20 is formed of a polyamide resin composition on the outer periphery of a metal core tube 1, and a worm wheel 11 in which a resin portion 3 having gear teeth 10 formed on the outer peripheral end surface thereof is integrated. And a metal worm 12. In the worm wheel 11, the metal core tube 1 and the resin portion 3 may be bonded together with an adhesive 8. As the adhesive 8, for example, a silane coupling agent, a titanate coupling agent, or a triazine thiol compound is used. be able to.
[0014]
As the polyamide resin forming the resin portion 3, from the viewpoint of water absorption and fatigue resistance, polyamide 6, polyamide 66, polyamide 46, polyamide 610, polyamide 612, polyamide 12, polyamide 11, polyamide MXD6, polyamide 6I6T, modified polyamide Although 6T, etc. preferably, among others polyamide 6, polyamide 66, polyamide 46 is not preferable excellent fatigue resistance.
[0015]
These polyamide resins are resins alone shows a certain level of durability, it favors to abrasion of the metal of the worm 12 is a mating member of the worm wheel 11, to function well as a reduction gear. However, since the gear teeth 10 may be damaged or worn when used under more severe use conditions, it is preferable to add a reinforcing material in order to further improve the reliability.
[0016]
As the reinforcing material, glass fiber, carbon fiber, potassium titanate whisker, aluminum borate whisker or the like is preferable, and a surface treated with a silane coupling agent is more preferable in consideration of adhesiveness with the polyamide resin mentioned above. . Moreover, these reinforcing materials can be used in combination of multiple types. Considering the impact strength, it is preferable to mix a fibrous material such as glass fiber or carbon fiber, and considering the damage of the worm 12, it is preferable to combine the whisker-like material with the fibrous material. The mixing ratio in the case of using the mixture varies depending on the types of the fibrous material and the whisker-like material, and is appropriately selected in consideration of impact strength, damage to the worm 12, and the like. These reinforcing materials are preferably blended in a proportion of 5 to 40% by weight, particularly 10 to 30% by weight. When the blending amount of the reinforcing material is less than 5% by weight, the mechanical strength is hardly improved, which is not preferable. When the blending amount of the reinforcing material exceeds 40% by weight, the worm 12 is likely to be damaged, wear of the worm 12 is promoted, and durability as a reduction gear may be insufficient.
[0017]
Furthermore, in order to prevent deterioration due to heat at the time of molding and use, an iodide-based heat stabilizer and an amine-based antioxidant may be added to the polyamide resin composition alone or in combination. Good.
[0018]
In the electric power steering apparatus schematically configured as described above, the space between the pair of rolling bearings 110 of the housing 120 is further lubricated between the gear teeth of the worm 12 and the worm wheel 11 as in the prior art. Grease is filled (see FIG. 2). In the present invention, as the grease, a base oil containing at least one selected from mineral oil, poly α-olefin oil, and alkyl polyphenyl ether, and a thickener and an ester compound are blended is used.
[0019]
Mineral oil, poly α-olefin oil, and alkyl polyphenyl ether are not limited, and those conventionally used as base oils for grease can be used. Moreover, you may mix these as needed. In addition, 40-220 mm < ² > / s (40 degreeC) is suitable for the kinematic viscosity of a base oil.
[0020]
The thickener, port structures similar to polyamide, using urea compound because of excellent adhesion to the polyamide resin is a resin portion 3 of the c Omuhoiru 11. Further, the blending amount of the thickener is not limited as long as the grease can be formed with the base oil, but 10 to 20% by weight of the total amount of the grease is appropriate.
[0021]
Ester compounds, Ri component der blended in order to improve the wettability of the grease of the polyamide resin, strong interaction to the amide bond of the polyamide resin, the molecular structure because it is particularly useful for improving wettability esters having a hydroxyl group in, Ru using partially saponified esters of fatty acids. The partially saponified esters of fatty acids, mention may be made of montanic acid ester partially saponified wax scan the like.
[0022]
Examples of the ester having a hydroxyl group in the molecular structure include stearic acid monoglyceride, oleic acid monoglyceride, behenic acid monoglyceride, sorbitan monolaurate, sorbitan monostearate , partial ester of fatty acid and polyhydric alcohol such as sorbitan monooleate. , it can be mentioned hydroxy fatty acid esters such as hydroxycarboxylic stearic acid triglyceride.
[0024]
Further, the above ester compounds are blended individually or in combination so as to be 1 to 20% by weight, preferably 2 to 10% by weight, based on the total amount of grease. If the blending amount is less than 1% by weight, the effect of improving wettability cannot be obtained sufficiently. On the other hand, even if it exceeds 20% by weight, no further improvement in wettability can be expected. Furthermore, in the electric power steering apparatus provided with the rubber damper 130 as shown in FIG. 2, the rubber tends to swell. It is also assumed that other parts will be adversely affected.
[0025]
The grease is configured as described above, but other additives may be added as long as the wettability improving effect by the ester compound is not adversely affected. For example, an amine-based or phenol-based antioxidant, a rust-preventing agent such as calcium sulfonate, or an extreme pressure additive such as molybdenum dithiocarbamate can be added.
[0026]
In the electric power steering apparatus of the present invention, as the reduction gear 20, in addition to the worm wheel 11 and the worm 12, the spur gear shown in FIG. 4, the helical gear shown in FIG. 5, and the bevel gear shown in FIG. The hypoid gear shown in FIG. 7 or the like is possible. In either case, the worm wheel 11 is made of a polyamide resin composition on the outer periphery of the metal core tube 1 and the resin portion 3 having the gear teeth 10 formed on the outer peripheral surface thereof. , And the like, using an adhesive 8 or the like.
[0027]
【Example】
Examples The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited thereby.
[0028]
(Examples 1-4, Comparative Example 1)
[Preparation of test grease]
An ester compound shown in Table 1 in a base grease in which a poly α-olefin oil having a kinematic viscosity at 100 ° C. of 8 mm ² / s is used as a base oil and a diurea compound as a thickener is mixed at a ratio of 13% by weight. Antioxidants and rust inhibitors were added to prepare test greases. Each test grease has a consistency of NLGI No. 2 was prepared.
[0029]
[Table 1]

[0030]
-Ester compound I: Montanic acid ester part saponified wax ("Luwax OP" manufactured by BASF Japan Ltd.)
Ester compound II: pentaerythritol tetraoleate (“EMERY2898” manufactured by Henkel Hakusui Co., Ltd.)
Ester compound III: di-2-ethylhexyl sebacate (DOS, manufactured by Daihachi Chemical Industry Co., Ltd.)
Ester compound IV: sorbitan monooleate (“Reodol SP-010” manufactured by Kao Corporation)
Antioxidant: 4,4′-dioctyldiphenylamine (“Nonflex OD-RH” manufactured by Seiko Chemical Co., Ltd.)
Antirust agent: Neutral calcium sulfonate (“Morresco Amber SC45N (mineral oil content 54%)” manufactured by Matsumura Oil Research Co., Ltd.)
[0031]
[Preparation of worm wheel specimen]
A cross-knurled and degreased S45C core tube with an outer diameter of 45 mm and a width of 13 mm is placed in a mold equipped with a sprue and a disk gate, and polyamide 66 containing 30% by weight of glass fiber (Ube Industries, Ltd.) 3) “UBE nylon 2020GU6” (containing copper additive) is injection molded into a worm wheel blank with an outer diameter of 60 mm and a width of 13 mm, and then the outer periphery of the resin part is cut to form gear teeth. A worm wheel specimen as shown in FIG.
[0032]
[Evaluation of durability]
The manufactured worm wheel specimen is incorporated into the reduction gear of the actual electric power steering device, and the test grease prepared above is applied evenly to the gear tooth surface of the worm wheel and the gear tooth surface of the worm, and the ambient temperature is maintained at 80 ° C. Steering was performed, and the amount of gear tooth wear was measured every 10,000 times. The amount of wear was 40 μm or less compared to before the test. The results are shown in Table 2.
[0033]
[Table 2]

[0034]
As shown in Table 2, in the test grease of Comparative Example 1 that does not contain an ester compound, the wear amount exceeds 40 μm after 20,000 steering operations, and the durability is not sufficient. On the other hand, in the test greases of Examples 1 to 4 containing an ester compound, the wear amount is 40 μm or less even after 100,000 times of steering, and it can be seen that the durability is effective.
[0035]
【The invention's effect】
As described above, according to the present invention, a grease in which at least one selected from mineral oil, poly α-olefin oil, and alkyl polyphenyl ether is used as a base oil, and a thickener and an ester compound are blended therein is used. As a result, the wettability of the grease to the gear teeth made of polyamide resin of the worm wheel is increased, the lubricity between the gears is improved, and an electric power steering device with higher durability can be provided.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional configuration diagram showing an example of a power steering device.
FIG. 2 is a cross-sectional view taken along the line AA in FIG.
FIG. 3 is a perspective view showing an example of a reduction gear (cylindrical worm gear).
FIG. 4 is a perspective view showing another example (spur gear) of a reduction gear.
FIG. 5 is a perspective view showing still another example (helical gear) of the reduction gear.
FIG. 6 is a perspective view showing still another example (bevel gear) of a reduction gear.
FIG. 7 is a perspective view showing still another example (high void gear) of the reduction gear.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Core pipe 3 Resin part 4 Sprue 5 Disc gate 8 Adhesive layer 10 Gear tooth 11 Worm wheel 12 Worm 20 Reduction gear 50 Steering column 70 Steering shaft 80 Torsion bar 90 Bearing 91 Bearing 100 Electric motor 110 Rolling bearing 120 Housing 130 Damper

Claims (6)

An electric power steering device that transmits auxiliary output by an electric motor to a steering mechanism of a vehicle via a reduction gear mechanism,
The driven gear of the reduction gear mechanism is integrally provided with a resin portion made of a polyamide resin composition and having gear teeth formed on the outer peripheral surface thereof on the outer periphery of the metal core tube, and
At least one selected from mineral oil, poly α-olefin oil, and alkyl polyphenyl ether is used as a base oil between at least the driven gear and the drive gear, a urea compound is used as a thickener , and a hydroxyl group is included in the molecular structure. An electric power steering apparatus characterized by interposing a grease containing an ester compound selected from partially saponified esters with esters and fatty acids . 2. The electric power steering apparatus according to claim 1 , wherein the ester compound is sorbitan monooleate . Ester compound, electric power steering apparatus according to claim 1 Symbol mounting characterized in that it is a montanic acid ester partially saponified waxes. The electric power steering apparatus according to any one of claims 1 to 3, wherein the driven gear and the driving gear are a cylindrical worm gear, a helical gear, a spur gear, a bevel gear, or a hypoid gear .   5. The electric power steering apparatus according to claim 1, wherein the amount of the ester compound is 1 to 20% by weight of the total amount of grease. 6. The electric power steering apparatus according to claim 1, wherein the base oil has a kinematic viscosity of 40 to 220 mm ² / s (40 ° C.).

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