JP3570176B2

JP3570176B2 - Formed pulley

Info

Publication number: JP3570176B2
Application number: JP27606597A
Authority: JP
Inventors: 浩上田; 博介川本; 伸一田原; 友浩佐山
Original assignee: Shin Kobe Electric Machinery Co Ltd
Current assignee: Shin Kobe Electric Machinery Co Ltd
Priority date: 1997-10-08
Filing date: 1997-10-08
Publication date: 2004-09-29
Anticipated expiration: 2017-10-08
Also published as: JPH11108162A

Description

【０００１】
【発明の属する技術分野】
本発明は、動力伝達に用いるプーリに関するものであり、殊に、射出成形で成形されたプーリに関する。
【０００２】
【従来の技術】
プーリとプーリ取り付け周囲の装置との位置関係で、プーリのベルトを掛ける箇所を円筒にし、その内側を空洞にしたプーリが提案されている。このプーリは、回転軸に取り付けるボス部がベルトを掛ける円筒部と同心であり、かつ、ボス部が円筒部の外側に配置された構成となっている。円筒部の内側には別の部材が配置されるからである。
例えば、図４は、円筒部１の端を延長して椀形部２を形成し、椀形部２の頂部にボス部４を設けた歯付プーリの構成である。また、図５は、円筒部１の端を延長して円錐部３を形成し、円錐部３の頂部にボス部４を設けた歯付プーリの構成である。これらの構成のプーリは、円筒部１の径と椀形部２の基底部あるいは円錐部３の基底部の径とが同寸となっている。上記プーリはフェノール樹脂等の射出成形で成形され、樹脂の射出はボス部４に相当する位置から行なわれる。
【０００３】
ボス部４を円筒部１の外側に配置するために、ボス部４を支持する部材を椀形部２としたり円錐部３としているのは、次の理由による。すなわち、円錐部３を採用した構成は、円筒部１の端とボス部４を最短距離で連結するものであり、プーリ製作時の使用樹脂量を最小限にするためである。また、椀形部２を採用した構成は、前記円錐部３を採用した構成を基本に、極端な屈曲部をなくし、曲面構成としたものであり、円筒部１の円筒度を低下させないようにするためである。
【０００４】
【発明が解決しようとする課題】
しかし、上記成形プーリは、円筒部の円筒度が低い。円筒部横断面に現れる円の径が円筒高さ方向にわたって均一でなくバラツキがあるとき、ならびに、前記横断面に現れる円が真円でない箇所があるとき、円筒度が低いと言い、上記従来の成形プーリは、次の二原因により円筒度がよくない。
【０００５】
第一原因は、円筒部と円錐部あるいは椀形部との間の成形後残留応力の違いである。
すなわち、上記成形プーリは、ボス部に相当する位置から樹脂を成形金型に射出して成形される。射出された樹脂が成形金型に充填された時点での樹脂の応力は、樹脂流動の先端に相当する円筒部よりも、樹脂射出源に近いボス部周辺の方が大きい。従って、射出成形後の残留応力も円筒部よりもボス部周辺の方が大きくなっている。残留応力は、プーリを成形金型から取り出したときに樹脂が膨張して緩和されるが、残留応力のより大きいボス部周辺の膨張が大きくなる。ボス部周辺の径方向への膨張により、これに引きずられて円錐部あるいは椀形部の外径も拡大する。円錐部あるいは椀形部の外径の拡大に伴い、円筒部にも円筒径を拡大させる力が働くが、この力は、円錐部あるいは椀形部と結合している側（ボス側）で大きく、その反対側（反ボス側）では小さい。ボス側では円筒径の拡大が大きく、反ボス側では円筒径の拡大が小さいわけである。
この結果、円筒部は、ボス側と反ボス側とで外径に差を生じ、円筒度が低下する。
【０００６】
第二原因は、射出成形時の樹脂の追加充填が、放射状に均一に行なわれないことである。
すなわち、射出された樹脂が成形金型に充填された直後は、成形金型内の樹脂が圧縮された状態にある。このときに樹脂の射出圧力をなくすと、充填された樹脂が成形金型内から逆流する。これを防ぐために、成形金型ゲート部の樹脂が固化し逆流が起こらなくなるまでは、適当な大きさの射出圧力を掛け続ける必要がある。樹脂の射出充填直後は、射出圧力と成形金型内の樹脂が逆流しようとする圧力は均衡しているが、樹脂の固化収縮が始まると、成形金型内の樹脂が逆流しようとする圧力は低下し、射出圧力のほうが大きくなっていく。このように両圧力の均衡が破れると、樹脂の固化収縮に応じて成形金型内へ樹脂が追加充填される。
上記成形プーリの場合、樹脂はボス部周辺に追加充填されるが、樹脂の固化進行のバラツキによりボス部周辺には、樹脂の固化進行の早い部分と遅い部分ができるので、樹脂は放射状に均一に追加充填されず、固化の進んでいない部分に集中して充填される。その結果、成形時の残留応力は、ボス部周辺では不均一に分布することになり、プーリを成形金型から取り出したときに起こる残留応力緩和による径方向の膨張も、ボス部周辺では不均一になる。ボス部の膨張の影響を受ける円筒部の径拡大も不均一になり、円筒部横断面に現われる円が真円から遠ざかり、円筒度が低下する。
【０００７】
従来の成形プーリの場合、成形直後の上記二原因により、円筒部のボス側に集中して不均一な円筒径拡大ならびに真円度の低下が生じるため、円筒度が低下している。
本発明が対象とするのは、ベルトを掛ける円筒部と回転軸に取り付けるボス部で構成され、ボス部に相当する位置から樹脂を射出して成形されたプーリである。本発明が解決しようとする課題は、このような成形プーリにおいて、円筒部の円筒度を確保することである。
【０００８】
【課題を解決するための手段】
上記課題を解決するために、本発明に係る成形プーリは、ボス部が円筒部から突出した第二円筒部に配置される。第二円筒部は円筒部より小径であり、円筒部と第二円筒部の間に段差が付けられていることを特徴とする。
本発明に係る別の成形プーリは、ボス部が円筒部から突出した椀形部に配置される。椀形部の基底部は円筒部より小径であり、円筒部と椀形部の間に段差が付けられていることを特徴とする。
本発明に係るさらに別の成形プーリは、ボス部が円筒部から突出した空洞の円錐部に配置される。円錐部の基底部は円筒部より小径であり、円筒部と円錐部の間に段差が付けられていることを特徴とする。
【０００９】
上記のように、本発明に係る成形プーリは、円筒部と第二円筒部、椀形部あるいは円錐部との間に段差を付けている。従来の技術で説明したのと同様の理由で、第二円筒部、椀形部あるいは円錐部では不均一な径の拡大が起こる。しかし、前記段差を付けた部分は、径方向の面であり、第二円筒部、椀形部あるいは円錐部の径を拡大させようとする力に対しては、筒形状よりも強い反力を生む。その結果、段差を付けた部分の径方向の面では、全体が傘型に変形することはあっても、径拡大はほとんど発生せず、段差を付けた部分に続く円筒部では、ほとんど不均一な径拡大を起こさない。第二円筒部、椀形部あるいは円錐部の径を拡大させようとする力の影響が段差を付けた部分の径方向の面で止まるのである。このような作用で、ベルトを掛ける円筒部の円筒度を確保することができる。
【００１０】
【発明実施の形態】
図１、図２、図３、図４および図５は、射出成形により製作した歯付プーリを示している。図１、図２および図３に示したものが本発明の実施の形態の成形プーリであり、図４および図５に示したものが従来の成形プーリである。これらの成形プーリは、自動車エンジン吸排気バルブ駆動用のタイミングベルトプーリとして使用される。
上記成形プーリは、ガラス繊維入りフェノール樹脂の射出成形で製作したが、射出成形可能な樹脂材料であればすべて使用可能である。樹脂の射出は、ボス部に相当する位置から行なう。
【００１１】
実施例１
図１に示すように、ボス部４が円筒部１から突出した第二円筒部５に配置される。第二円筒部５は円筒部１より小径であり、円筒部１と第二円筒部５の間に段差が付けられている。段差が付いた部分は、径方向の面となっている。
円筒部１は、外径１２１ｍｍ、内径１０６ｍｍ、高さ３７ｍｍであり、外周部には歯付きベルトに噛み合う４８歯で構成された歯部が形成されている。第二円筒部５は、外径８３ｍｍ、内径６０ｍｍ、高さ２０ｍｍである。ボス部４は、第二円筒部５の端面に位置し、外径８３ｍｍ、肉厚１５ｍｍである。ボス部４には焼結金属製のブッシュが配置され、樹脂がブッシュを包み込んだ形となっている。
成形金型は、ボス部に相当する箇所がリングゲート部になっていて、この部分から樹脂を成形金型キャビティ内に射出する。射出した樹脂は、ボス部４、第二円筒部５、段差を付けた部分、円筒部１の順に、成形金型に充填される。その後、充填した樹脂の逆流を防止するために適当な大きさの射出圧力を掛け続け、リングゲート部の樹脂が充分固化するのを待つ。そして、射出圧力を落とす。その後、プーリ全体が充分固化するのを待って成形金型を開き、金型から取り出した成形プーリのゲート切断加工等を実施する。
【００１２】
実施例２
図２に示すように、ボス部４が円筒部１から突出した椀形部２に配置される。椀形部２の基底部は円筒部１より小径であり、円筒部１と椀形部２の間に段差が付けられている。段差が付いた部分は、径方向の面となっている。ボス部４は、椀形部２の頂部に位置する。各部の寸法、歯部の構成は、実施例１と同様であり、本実施例の場合、椀形部２の基底部の外径が８３ｍｍとなっており、これによって段差を付けた構成としている。成形法は、実施例１と同様である。
【００１３】
実施例３
図３に示すように、ボス部４が円筒部１から突出した円錐部３に配置される。円錐部３の基底部は円筒部１より小径であり、円筒部１と円錐部３の間に段差が付けられている。段差が付いた部分は、径方向の面となっている。ボス部４は、円錐部３の頂部に位置する。各部の寸法、歯部の構成は、実施例１と同様であり、本実施例の場合、円錐部３の基底部の外径が８３ｍｍとなっており、これによって段差を付けた構成としている。成形法は、実施例１と同様である。
【００１４】
従来例１
図４に示すように、ボス部４が円筒部１から突出した椀形部２に配置される。椀形部２の基底部の外径は円筒部１の外径と同寸法であり、椀形部２が円筒部１と直接結合した構成になっている。他の各部の寸法、歯部の構成は、実施例１と同様である。成形法も、実施例１と同様である。
【００１５】
従来例２
図５に示すように、ボス部４が円筒部１から突出した円錐部３に配置される。円錐部３の基底部の外径は円筒部１の外径と同寸法であり、円錐部３が円筒部１と直接結合した構成になっている。他の各部の寸法、歯部の構成は、実施例１と同様である。成形法も、実施例１と同様である。
【００１６】
上記実施例と従来例の成形プーリについて、円筒部１の円筒度を比較した結果を表１に示す。
円筒度の測定は、ＪＩＳＢ００２１「幾何公差の図示方法」記載の円筒度の定義に適合するように実施した。具体的には、三次元測定機を使用し、円筒部の中心軸から円筒部の１４４カ所の測定点までの距離を測定し、その最大値と最小値の差を円筒度とするものである。前記１４４カ所の測定点とは、円筒部外周４８歯の頂点毎に、円筒部のボス側の端と、反ボス側の端と、前記二点の中央の三点である。このように、成形プーリの１４４カ所にわたる測定値の最大値と最小値の差（円筒度）を求める作業を、５０個の成形プーリについて実施した。
表１に示した値は、５０個の成形プーリの円筒度の平均値、円筒度の標準偏差、５０個の成形プーリの円筒度の最大値と最小値である。
【００１７】
【表１】

【００１８】
また、図６と図７に、実施例と従来例の成形プーリについて、円筒部の横断面に現れる円の形状の代表例を示した。横断面は、円筒部のボス側の端と、反ボス側の端と、前記二点の中央の三ケ所である。図中の目盛の単位は「ｍｍ」である。
【００１９】
表１から、各実施例の成形プーリは円筒度が高い（円筒度の値が小さい）ことを理解できる。実施例の前記値は、従来例の１／２以下である。
また、図６と図７から明らかなように、各実施例の成形プーリは、円筒部のボス側の端と、反ボス側の端と、前記二点の中央の横断面に現れる三つの円がほぼ重なっている。これは、円筒部のボス側の端から反ボス側の端にわたって、外径が均一であることを示している。さらに、各実施例の成形プーリは、円筒部の横断面に現れる円がより真円に近いことも理解できる。
【００２０】
【発明の効果】
上述のように、本発明に係る成形プーリは、ベルトを掛ける円筒部とボス部を配置する第二円筒部や椀形部や円錐部の連結部に段差を付けたので、第二円筒部や椀形部や円錐部の変形の影響が及ぶ範囲を前記段差を付けた部分の径方向の面でくい止めることができ、円筒部の円筒度を良好に確保することができる。
【図面の簡単な説明】
【図１】本発明に係る成形プーリの実施の形態を示す斜視図である。
【図２】本発明に係る別の成形プーリの実施の形態を示す斜視図である。
【図３】本発明に係るさらに別の成形プーリの実施の形態を示す斜視図である。
【図４】従来の成形プーリの斜視図である。
【図５】従来の別の成形プーリの斜視図である。
【図６】実施例の成形プーリについて、円筒部の横断面に現れる円の形状の代表例を示した曲線図である。
【図７】従来例の成形プーリについて、円筒部の横断面に現れる円の形状の代表例を示した曲線図である。
【符号の説明】
１：円筒部
２：椀形部
３：円錐部
４：ボス部
５：第２円筒部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pulley used for power transmission, and more particularly, to a pulley formed by injection molding.
[0002]
[Prior art]
Due to the positional relationship between the pulley and the device around the pulley, there is proposed a pulley in which a portion where a belt of the pulley is hung is made cylindrical and the inside thereof is made hollow. This pulley has a configuration in which a boss attached to a rotating shaft is concentric with a cylindrical portion on which a belt is hung, and the boss is disposed outside the cylindrical portion. This is because another member is disposed inside the cylindrical portion.
For example, FIG. 4 shows a configuration of a toothed pulley in which a bowl-shaped portion 2 is formed by extending an end of a cylindrical portion 1 and a boss portion 4 is provided on a top of the bowl-shaped portion 2. FIG. 5 shows a configuration of a toothed pulley in which the end of the cylindrical portion 1 is extended to form a conical portion 3 and a boss portion 4 is provided at the top of the conical portion 3. In these pulleys, the diameter of the cylindrical portion 1 and the diameter of the base of the bowl-shaped portion 2 or the base of the conical portion 3 are the same. The pulley is formed by injection molding of phenol resin or the like, and the resin is injected from a position corresponding to the boss 4.
[0003]
The reason why the member supporting the boss portion 4 is the bowl-shaped portion 2 or the conical portion 3 in order to dispose the boss portion 4 outside the cylindrical portion 1 is as follows. That is, the configuration employing the conical portion 3 connects the end of the cylindrical portion 1 and the boss portion 4 at the shortest distance, and minimizes the amount of resin used when manufacturing the pulley. In addition, the configuration employing the bowl-shaped portion 2 is based on the configuration employing the conical portion 3 and eliminates an extremely bent portion and has a curved surface configuration, so that the cylindricity of the cylindrical portion 1 is not reduced. To do that.
[0004]
[Problems to be solved by the invention]
However, the forming pulley has a low cylindricity of the cylindrical portion. When the diameter of the circle appearing in the cross section of the cylindrical portion is not uniform over the height direction of the cylinder and there is variation, and when there is a place where the circle appearing in the cross section is not a perfect circle, it is said that the cylindricity is low. The formed pulley has poor cylindricity due to the following two reasons.
[0005]
The first cause is a difference in residual stress after molding between the cylindrical portion and the conical portion or the bowl-shaped portion.
That is, the molding pulley is molded by injecting a resin into a molding die from a position corresponding to the boss. The stress of the resin when the injected resin is filled in the molding die is larger around the boss near the resin injection source than at the cylindrical portion corresponding to the tip of the resin flow. Therefore, the residual stress after injection molding is larger around the boss portion than at the cylindrical portion. Residual stress is relaxed by expanding the resin when the pulley is removed from the molding die, but the expansion around the boss portion where the residual stress is larger increases. Due to the radial expansion around the boss, the outer diameter of the conical portion or the bowl-shaped portion is increased by being dragged by this. As the outer diameter of the conical portion or the bowl-shaped portion increases, a force to increase the cylindrical diameter also acts on the cylindrical portion, but this force is large on the side (boss side) connected to the conical portion or the bowl-shaped portion. , On the opposite side (anti-boss side). On the boss side, the expansion of the cylindrical diameter is large, and on the opposite boss side, the expansion of the cylindrical diameter is small.
As a result, the cylindrical portion has a difference in outer diameter between the boss side and the opposite boss side, and the cylindricity decreases.
[0006]
The second cause is that the additional filling of the resin during injection molding is not performed radially and uniformly.
That is, immediately after the injected resin is filled in the molding die, the resin in the molding die is in a compressed state. At this time, if the injection pressure of the resin is eliminated, the filled resin flows backward from the molding die. In order to prevent this, it is necessary to continue applying an injection pressure of an appropriate magnitude until the resin in the gate of the molding die solidifies and no backflow occurs. Immediately after injection filling of the resin, the injection pressure and the pressure at which the resin in the molding die flows backward are balanced, but when the solidification and contraction of the resin starts, the pressure at which the resin in the molding die flows backward is The injection pressure decreases and the injection pressure increases. When the balance between the two pressures is broken in this way, the resin is additionally filled into the molding die in accordance with the solidification shrinkage of the resin.
In the case of the above-mentioned forming pulley, the resin is additionally filled around the boss portion, but due to the variation in the solidification progress of the resin, a portion where the solidification progresses quickly and a portion where the resin solidification progresses are formed, so that the resin is radially uniform. Is not additionally charged, but is concentrated in the portion where solidification has not progressed. As a result, the residual stress during molding is unevenly distributed around the boss, and the radial expansion due to the relaxation of the residual stress that occurs when the pulley is removed from the molding die is also uneven around the boss. become. The diameter expansion of the cylindrical portion affected by the expansion of the boss also becomes non-uniform, the circle appearing in the cross section of the cylindrical portion moves away from the true circle, and the cylindricity decreases.
[0007]
In the case of the conventional forming pulley, the two causes immediately after the forming are concentrated on the boss side of the cylindrical portion, causing an uneven expansion of the cylindrical diameter and a decrease in the roundness, so that the cylindricity is reduced.
An object of the present invention is a pulley that includes a cylindrical portion on which a belt is hung and a boss portion attached to a rotating shaft, and is formed by injecting resin from a position corresponding to the boss portion. The problem to be solved by the present invention is to secure the cylindricity of the cylindrical portion in such a forming pulley.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the forming pulley according to the present invention is arranged in a second cylindrical portion whose boss protrudes from the cylindrical portion. The second cylindrical portion has a smaller diameter than the cylindrical portion, and a step is provided between the cylindrical portion and the second cylindrical portion.
In another forming pulley according to the present invention, the boss portion is disposed in a bowl-shaped portion protruding from the cylindrical portion. The base of the bowl is smaller in diameter than the cylinder, and a step is provided between the cylinder and the bowl.
Still another forming pulley according to the present invention is arranged in a conical portion of a cavity whose boss protrudes from a cylindrical portion. The base of the conical portion is smaller in diameter than the cylindrical portion, and a step is provided between the cylindrical portion and the conical portion.
[0009]
As described above, the forming pulley according to the present invention has a step between the cylindrical portion and the second cylindrical portion, the bowl-shaped portion, or the conical portion. For the same reason as described in the prior art, a non-uniform enlargement of the diameter occurs in the second cylindrical portion, the bowl-shaped portion or the conical portion. However, the stepped portion is a surface in the radial direction, and the second cylindrical portion, the bowl-shaped portion or the conical portion has a stronger reaction force than the cylindrical shape against a force for increasing the diameter of the conical portion. Spawn. As a result, on the radial surface of the stepped part, even though the whole may be deformed into an umbrella shape, the diameter expansion hardly occurs, and the cylindrical part following the stepped part is almost uneven. Does not cause large diameter expansion. The effect of the force for expanding the diameter of the second cylindrical portion, the bowl-shaped portion or the conical portion stops at the radial surface of the stepped portion. By such an operation, the cylindricity of the cylindrical portion on which the belt is hung can be ensured.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIGS. 1, 2, 3, 4 and 5 show a toothed pulley manufactured by injection molding. FIGS. 1, 2 and 3 show a forming pulley according to the embodiment of the present invention, and FIGS. 4 and 5 show a conventional forming pulley. These formed pulleys are used as timing belt pulleys for driving automobile engine intake and exhaust valves.
The molding pulley was manufactured by injection molding of a phenolic resin containing glass fiber, but any resin material that can be injection molded can be used. The resin is injected from a position corresponding to the boss.
[0011]
Example 1
As shown in FIG. 1, the boss portion 4 is disposed on a second cylindrical portion 5 protruding from the cylindrical portion 1. The second cylindrical portion 5 has a smaller diameter than the cylindrical portion 1, and a step is provided between the cylindrical portion 1 and the second cylindrical portion 5. The stepped portion is a radial surface.
The cylindrical portion 1 has an outer diameter of 121 mm, an inner diameter of 106 mm, and a height of 37 mm, and has an outer peripheral portion formed with a tooth portion including 48 teeth that mesh with the toothed belt. The second cylindrical portion 5 has an outer diameter of 83 mm, an inner diameter of 60 mm, and a height of 20 mm. The boss part 4 is located on the end face of the second cylindrical part 5 and has an outer diameter of 83 mm and a wall thickness of 15 mm. A bush made of a sintered metal is arranged on the boss portion 4, and has a shape in which the resin wraps the bush.
In the molding die, a portion corresponding to the boss portion is a ring gate portion, from which resin is injected into the molding die cavity. The injected resin is filled in a molding die in the order of the boss portion 4, the second cylindrical portion 5, the stepped portion, and the cylindrical portion 1. Thereafter, an injection pressure of an appropriate magnitude is continuously applied to prevent the backflow of the filled resin, and waits until the resin in the ring gate portion is sufficiently solidified. Then, the injection pressure is reduced. After that, the molding die is opened after the entire pulley is sufficiently solidified, and gate molding of the molding pulley taken out of the die is performed.
[0012]
Example 2
As shown in FIG. 2, the boss portion 4 is disposed on the bowl-shaped portion 2 protruding from the cylindrical portion 1. The base of the bowl 2 is smaller in diameter than the cylinder 1, and a step is provided between the cylinder 1 and the bowl 2. The stepped portion is a radial surface. The boss part 4 is located on the top of the bowl-shaped part 2. The dimensions of each part and the configuration of the teeth are the same as those in the first embodiment. In the present embodiment, the outer diameter of the base of the bowl-shaped part 2 is 83 mm, so that a step is provided. . The molding method is the same as in Example 1.
[0013]
Example 3
As shown in FIG. 3, the boss portion 4 is disposed on the conical portion 3 protruding from the cylindrical portion 1. The base of the conical portion 3 is smaller in diameter than the cylindrical portion 1, and a step is provided between the cylindrical portion 1 and the conical portion 3. The stepped portion is a radial surface. The boss part 4 is located at the top of the conical part 3. The dimensions of each part and the configuration of the teeth are the same as those in the first embodiment. In the present embodiment, the outer diameter of the base of the conical portion 3 is 83 mm, and thus a step is provided. The molding method is the same as in Example 1.
[0014]
Conventional example 1
As shown in FIG. 4, the boss portion 4 is disposed on the bowl-shaped portion 2 protruding from the cylindrical portion 1. The outer diameter of the base of the bowl 2 is the same as the outer diameter of the cylinder 1, and the bowl 2 is directly connected to the cylinder 1. The dimensions of the other parts and the configuration of the teeth are the same as in the first embodiment. The molding method is the same as that of the first embodiment.
[0015]
Conventional example 2
As shown in FIG. 5, the boss portion 4 is disposed on the conical portion 3 protruding from the cylindrical portion 1. The outer diameter of the base of the conical portion 3 is the same as the outer diameter of the cylindrical portion 1, and the conical portion 3 is directly connected to the cylindrical portion 1. The dimensions of the other parts and the configuration of the teeth are the same as in the first embodiment. The molding method is the same as that of the first embodiment.
[0016]
Table 1 shows the results of a comparison of the cylindricity of the cylindrical portion 1 between the formed pulleys of the above embodiment and the conventional example.
The measurement of the cylindricity was carried out so as to conform to the definition of the cylindricity described in JIS B 0021 “How to Show Geometric Tolerance”. Specifically, the distance from the central axis of the cylindrical portion to 144 measurement points of the cylindrical portion is measured using a coordinate measuring machine, and the difference between the maximum value and the minimum value is defined as the cylindricity. . The 144 measurement points are the boss-side end of the cylindrical portion, the opposite boss-side end, and the three central points of the two points for each vertex of the outer periphery of the cylindrical portion. In this manner, the operation of obtaining the difference (cylindricity) between the maximum value and the minimum value of the measured values of 144 forming pulleys was performed for 50 forming pulleys.
The values shown in Table 1 are the average value of the cylindricity of the 50 forming pulleys, the standard deviation of the cylindricity, and the maximum and minimum values of the cylindricity of the 50 forming pulleys.
[0017]
[Table 1]

[0018]
6 and 7 show typical examples of the shape of a circle appearing in the cross section of the cylindrical portion for the forming pulleys of the embodiment and the conventional example. The cross sections are the boss-side end of the cylindrical portion, the opposite boss-side end, and the center at the two points. The unit of the scale in the figure is “mm”.
[0019]
From Table 1, it can be understood that the forming pulleys of the respective examples have high cylindricity (the value of cylindricity is small). The value of the embodiment is 1/2 or less of the conventional example.
As is clear from FIGS. 6 and 7, the forming pulley of each embodiment has three ends of the cylindrical portion on the boss side, the end on the opposite boss side, and three circles appearing in the center cross section of the two points. Are almost overlapping. This indicates that the outer diameter is uniform from the boss-side end to the opposite boss-side end of the cylindrical portion. Further, in the forming pulleys of the respective embodiments, it can be understood that the circle appearing in the cross section of the cylindrical portion is closer to a perfect circle.
[0020]
【The invention's effect】
As described above, since the forming pulley according to the present invention has a step at the connecting portion between the cylindrical portion for hanging the belt and the second cylindrical portion or the bowl-shaped portion or the conical portion at which the boss portion is arranged, the second cylindrical portion or The range affected by the deformation of the bowl-shaped portion and the conical portion can be blocked by the radial surface of the stepped portion, and the cylindricity of the cylindrical portion can be sufficiently ensured.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an embodiment of a forming pulley according to the present invention.
FIG. 2 is a perspective view showing an embodiment of another forming pulley according to the present invention.
FIG. 3 is a perspective view showing another embodiment of a forming pulley according to the present invention.
FIG. 4 is a perspective view of a conventional forming pulley.
FIG. 5 is a perspective view of another conventional forming pulley.
FIG. 6 is a curve diagram showing a typical example of the shape of a circle appearing in a cross section of a cylindrical portion in the forming pulley of the embodiment.
FIG. 7 is a curve diagram showing a typical example of the shape of a circle appearing in a cross section of a cylindrical portion in a conventional forming pulley.
[Explanation of symbols]
1: cylindrical part 2: bowl-shaped part 3: conical part 4: boss part 5: second cylindrical part

Claims

A pulley formed by injecting a resin from a position corresponding to the boss portion, which is composed of a cylindrical portion for hanging a belt and a boss portion attached to the rotating shaft, the boss portion is arranged concentrically with the cylindrical portion and outside the cylindrical portion,
The boss is disposed on a second cylindrical portion protruding from the cylindrical portion,
A forming pulley wherein the second cylindrical portion has a smaller diameter than the cylindrical portion, and a step is provided between the cylindrical portion and the second cylindrical portion.

A pulley formed by injecting a resin from a position corresponding to the boss portion, which is composed of a cylindrical portion for hanging a belt and a boss portion attached to the rotating shaft, the boss portion is arranged concentrically with the cylindrical portion and outside the cylindrical portion,
The boss portion is disposed on a bowl-shaped portion protruding from the cylindrical portion,
A molded pulley in which a base of the bowl-shaped part has a smaller diameter than the cylindrical part, and a step is provided between the cylindrical part and the bowl-shaped part.

A pulley formed by injecting a resin from a position corresponding to the boss portion, which is composed of a cylindrical portion for hanging a belt and a boss portion attached to the rotating shaft, the boss portion is arranged concentrically with the cylindrical portion and outside the cylindrical portion,
The boss portion is disposed in a conical portion of a cavity protruding from the cylindrical portion,
A forming pulley in which a base of the conical portion is smaller in diameter than the cylindrical portion, and a step is provided between the cylindrical portion and the conical portion.