JP2004360809A

JP2004360809A - Gear with torque limiter and power transmitting mechanism of electronic apparatus

Info

Publication number: JP2004360809A
Application number: JP2003160653A
Authority: JP
Inventors: Seiji Yotsuya; 清司四家; Masashi Suzuki; 昌司鈴木; Yasushi Shibuya; 康司渋谷
Original assignee: Alpine Electronics Inc
Current assignee: Alpine Electronics Inc
Priority date: 2003-06-05
Filing date: 2003-06-05
Publication date: 2004-12-24
Anticipated expiration: 2023-06-05
Also published as: JP4262527B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gear with a torque limiter capable of preventing the breakage of the gear, and reducing the uneven abrasion of steel balls. <P>SOLUTION: This gear 6 with the torque limiter is composed of a large gear 11 having four slots 10, four steel balls 12 movably mounted in each of the slots 10, first and second frictional plates 13, 14 holding the steel balls 12, a small gear 14 mounted coaxially with a central part of the large gear 11, a spindle 16 inserted into a central part of the small gear 15, a spring 17 for elastically energizing the small gear 15 in the axial direction of the spindle 16, and the like. Two of the slots 10 (first slot 10a) are formed in a state that their long axes are inclined by an angle +θ in the clockwise direction with respect to a straight line P which is radially extended from a center O of the large gear 11 toward each slot 10, and the remaining two slots 10 (second slot 10b) are formed in a state that their long axes are inclined by an angle -θ in the anticlockwise direction to the straight line P. The first and second slots 10a, 10b are alternately formed at equal intervals of 90 degrees in the rotating direction of the large gear 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、各種ローディング機構等に使用されるトルクリミッタ付きギアに係り、特に、モータの回転力を駆動源として可動体を動作させる電子機器の動力伝達機構に用いて好適なトルクリミッタ付きギアに関する。
【０００２】
【従来の技術】
近年、表示画面等を有する可動パネルをモータの回転力を駆動源として動作させることにより、この可動パネルを水平方向へスライド移動して筐体に出入動作させたり、筐体から引き出した可動パネルを回動して立ち上げ動作させるという車載用電子機器が普及している。
【０００３】
一般的にこの種の車載用電子機器においては、モータの回転力を可動パネルに伝達する動力伝達機構として、トルクリミッタ付きギアを含む複数の歯車によって構成された減速歯車列が使用されており、例えばモータの回転力を駆動源として可動パネルを回動させる場合は、減速歯車列の最初段の歯車をモータの回転軸に取り付けたウォームギアに噛合させると共に、減速歯車列の最終段の歯車を可動パネルあるいは可動パネルを支持するブラケットに取り付けた歯車に噛合させている。また、トルクリミッタ付きギアは、同軸上に連結された大径ギアおよび小径ギアと、これら両ギア間に介設されたフェルトと、一方のギアを他方のギアに軸線方向へ弾性付勢するコイルばねとによって構成されており、通常、両ギアはフェルトの摩擦力によって一体的に回転するが、動力伝達系に過度の負荷が生じた場合、両ギアはフェルトを介してスリップして過負荷を吸収するようになっている。
【０００４】
このように構成された動力伝達機構では、モータの回転力がウォームギアから減速歯車列を介して可動パネルに伝達されるため、水平状態にある可動パネルを立ち上げたり、その逆に起立状態にある可動パネルを水平状態に戻すことができる。また、この動力伝達系に過度の負荷が生じた場合、例えば回動中の可動パネルにユーザの手指が触れたり、ユーザが可動パネルの起立角度を無理に手動操作した場合、トルクリミッタ付きギアがスリップすることによって過負荷が吸収されるため、減速歯車列の破損が回避されるようになっている。
【０００５】
しかしながら、このようにフェルトを用いたトルクリミッタ付きギアは、フェルトが温度や湿度の影響を受けやすいため安定したトルクを発生することができず、しかも、せいぜい数百ｇｆ・ｃｍ程度の低トルクしか発生できないという難点がある。また、このように低トルクしか発生できないため、かかるフェルト式のトルクリミッタ付きギアを車載用電子機器の動力伝達機構に用いた場合、トルクリミッタ付きギアの配置可能な場所がモータ側から見て減速歯車列の最初段もしくはその近傍に限定されてしまい、設計上の自由度が小さいという問題もある。
【０００６】
一方、高トルクを発生させることができるトルクリミッタ付きギアとして、従来より、フェルトの代わりに複数の鋼球を用いたボールクラッチと呼ばれるものが知られている（例えば、特許文献１参照）。このトルクリミッタ付きギアは、一方のギアにその円周方向に所定間隔を存して複数の孔を形成し、これら孔内にそれぞれ鋼球を保持すると共に、これら鋼球を一対の摩擦板で弾性的に挟持するように構成されており、動力伝達系に過度の負荷が生じた場合、各鋼球が摩擦板に対してスリップすることによって過負荷が吸収されるようになっている。
【０００７】
【特許文献１】
特開平６−２２１３４３号公報（第３−４頁、図１，２）
【０００８】
【発明が解決しようとする課題】
前述したように、従来のボールクラッチ（トルクリミッタ付きギア）は高トルクを発生させることができるため、減速歯車列の中にボールクラッチを配置可能なレイアウト上の自由度を広げることができるが、スリップ動作を開始する時のトルク（鋼球の静摩擦係数）がスリップ動作を行っている時のトルク（鋼球の動摩擦係数）に対してかなり高くなるという特性を有している。このため、かかるボールクラッチを上述した車載用電子機器の動力伝達機構に使用した場合、可動パネルに過負荷が加えられて鋼球が摩擦板に対してスリップし始める時に、トルクが必要以上に高くなり過ぎてギアの破損を招来するという問題がある。このような理由から、スリップ動作時のトルクをある程度低く設定せざるを得ず、高トルク化という利点を十分に発揮することができなかった。
【０００９】
また、一般的にこの種の動力伝達機構においては、可動パネルが往路または復路の末端位置まで移動した後も、モータが僅かに回転し続けてボールクラッチをスリップ動作させるようになっているため、ギアの正転逆転時にボールクラッチがスリップ動作する頻度は高くなっているが、従来のボールクラッチはギアに形成した孔によって鋼球が位置規制されているため、ギアの正転時と逆転時に鋼球の同一個所が摩擦板とスリップしてしまい、鋼球が偏摩耗するという問題もあった。
【００１０】
本発明は、このような従来技術の実情に鑑みてなされたもので、その第１の目的は、ギアの破損を防止できると共に鋼球の偏摩耗を抑えることができるトルクリミッタ付きギアを提供することにあり、その第２の目的は、減速歯車列中に介在されるトルクリミッタ付きギアに安定した高トルクを発生させることができる電子機器の動力伝達機構を提供することにある。
【００１１】
【課題を解決するための手段】
本発明は、ギアに形成された複数の長孔内にそれぞれ鋼球を移動可能に配置すると共に、一部の長孔と残部の長孔をギアの回転方向に対して互いに逆向きに傾斜させることとする。このような長孔をギアに形成すると、ギアの一方向への回転中にスリップ動作が開始するとき、一部の鋼球が長孔の外周側へ移動すると共に、残部の鋼球が長孔の内周側へ移動し、その反対にギアの他方向への回転中にスリップ動作が開始するとき、一部の鋼球が長孔の内周側へ移動すると共に、残部の鋼球が長孔の外周側へ移動する。したがって、ギアの正転逆転時に各鋼球が回転方向に対して斜め内周と斜め外周に移動するため、スリップ動作時のトルクに対するスリップ開始時のトルクの差を小さくしてギアの破損を防止できると共に、鋼球の偏摩耗を抑えることができる。
【００１２】
【発明の実施の形態】
上述した第１の目的を達成するために、本発明のトルクリミッタ付きギアは、同軸的に配置された第１および第２のギアと、前記第１のギアに円周方向に所定間隔を存して形成された複数の長孔と、これら長孔内にその長手方向に沿って移動可能に配置された複数の鋼球と、これら鋼球に圧接され前記第２のギアと一体的に回転する摩擦体とを備え、前記複数の長孔のうち、一部の長孔が前記第１のギアの中心から該長孔を通る直線に対して一方向へ傾斜する第１の長孔であり、残部の長孔が前記第１のギアの中心から該長孔を通る直線に対して反対方向へ傾斜する第２の長孔であるように構成した。
【００１３】
このように構成されたトルクリミッタ付きギアでは、正逆いずれか一方向へ回転中に過負荷が発生したとき、一部の鋼球が第１の長孔の外周側へ移動すると共に、残部の鋼球が第２の長孔の内周側へ移動し、その反対に他方向へ回転中に過負荷が発生したとき、一部の鋼球が第１の長孔の内周側へ移動すると共に、残部の鋼球が第２の長孔の外周側へ移動するため、正転逆転時に各鋼球が回転方向に対して斜め内周と斜め外周に移動してスリップ動作し、その結果、スリップ動作時のトルクに対するスリップ開始時のトルクの差を小さくしてギアの破損を防止できると共に、鋼球の偏摩耗を抑えることができる。
【００１４】
上記の構成において、第１および第２の長孔の総個数は最小３個あれば良いが、これら第１および第２の長孔を第１のギアの円周方向に沿って交互にＮ個（Ｎは２以上の偶数）、すなわち４以上の偶数個形成した場合、第１および第２の長孔の直線に対する傾斜角の絶対値を略等しく設定すると共に、それぞれ第１のギアの中心から、第１の長孔の外周側端部に位置する鋼球の中心までの距離と第２の長孔の内周側端部に位置する鋼球の中心までの距離の和と、第１の長孔の内周側端部に位置する鋼球の中心までの距離と第２の長孔の外周側端部に位置する鋼球の中心までの距離の和とが略等しくなるように、第１および第２の長孔の位置と長軸寸法を設定することが好ましく、このようにすると正転逆転時に各鋼球を摩擦体に対してバランス良く移動させることができ、かつ、各鋼球を介して伝達されるトルクが正転時と逆転時とでほぼ一定となる。また、第１および第２の長孔の総個数を最小３個にした場合、第１のギアに１個の第１の長孔と２個の第２の長孔とを形成すると共に、これら第１および第２の長孔の長軸寸法と直線に対する傾斜角の絶対値との少なくとも一方を互いに異ならせることが好ましい。
【００１５】
また、上述した第２の目的を達成するために、本発明による電子機器の動力伝達機構は、上記の如く構成されたトルクリミッタ付きギアを用い、このトルクリミッタ付きギアを含む減速歯車列を介してモータの回転力を可動体に伝達するように構成した。
【００１６】
このように構成された動力伝達機構によれば、減速歯車列中に介在されるトルクリミッタ付きギアに安定した高トルクを発生させることができるため、減速歯車列の中にトルクリミッタ付きギアを配置可能なレイアウト上の自由度が広がり、しかも、このトルクリミッタ付きギアのスリップ動作時のトルクに対するスリップ開始時のトルクの差を小さくすることができるため、動力伝達系に過負荷が加えられた時のギアの破損を防止することができる。
【００１７】
【実施例】
実施例について図面を参照して説明すると、図１は本発明の実施例に係るトルクリミッタ付きギアの断面図、図２は該トルクリミッタ付きギアの分解斜視図、図３は該トルクリミッタ付きギアに備えられる第１のギアと鋼球の説明図、図４は本発明が適用される車載用可動モニタ装置の側面図、図５は該車載用可動モニタ装置に備えられる動力伝達機構の平面図である。
【００１８】
図４に示すように、車載用可動モニタ装置は箱形の筐体１を具備し、この筐体１は車内のインストルメントパネル等に設置されるようになっている。筐体１の内部にはスライド体２が収納されており、このスライド体２の先端にモニタ装置３が回動可能に連結されている。図示せぬが、モニタ装置３はＬＣＤ等の表示画面を有し、この表示画面にナビゲーションシステムやオーディオシステム等の各種情報が表示されるようになっている。スライド体２は筐体１内に配設された図示せぬモータによって前後進方向へスライド動作されるようになっており、このスライド体２が前進動作されて筐体１の前面から突出すると、それに伴ってモニタ装置３は水平姿勢を保った状態で筐体１の前面から引き出される。この引き出し状態において、モニタ装置３は後述する動力伝達機構によって回動動作され、図１の実線で示す水平状態から破線で示す起立状態への立ち上げ動作や、その逆に起立状態から水平状態への立ち下げ動作が行われる。
【００１９】
図５に示すように、前述した動力伝達機構は、スライド体２を動作する前記モータとは別のモータ４と、このモータ４の回転力を減速してモニタ装置３に伝達する減速歯車列５とで構成されており、この減速歯車列５の中にはトルクリミッタ付きギア６が介在されている。これらモータ４と減速歯車列５は図示せぬブラケットに取り付けられてユニット化されており、このブラケットはスライド体２に搭載されている。減速歯車列５はトルクリミッタ付きギア６を含む複数の歯車によって構成され、これら歯車は同軸配置された大径ギアと小径ギアをそれぞれ有し、最初段の歯車（符号５ａを付す）の大径ギアはモータ４の回転軸に取り付けられたウォームギア７に噛合している。以下、モータ４から見て上流側の歯車の小径ギアに下流側の歯車の大径ギアが順次噛合することにより、モータ４の回転力が減速歯車列５の各歯車で減速されるようになっており、トルクリミッタ付きギア６は減速歯車列５の最終段に配置されている。このトルクリミッタ付きギア６の具体的構成については後述するが、トルクリミッタ付きギア６の小径ギアに別の歯車８が噛合され、この歯車８はモニタ装置３に取り付けられた歯車９と噛合している。
【００２０】
なお、このようにモータ４の回転力を減速歯車列５で減速してモニタ装置３に伝達する動力伝達系においては、モニタ装置３に近くなるほどトルクは高くなるが、モータ４側に近い最初段の歯車５ａやその近傍の歯車はトルクが低い場所に配置されることになる。このような理由から本実施例では、減速歯車列５の最初段の歯車５ａを含む複数の歯車として、金属製ギアに比べて安価で軽量な合成樹脂製ギアを用いているが、必要に応じて減速歯車列５の全ての歯車を金属製ギアにしてもよい。
【００２１】
図１と図２に示すように、前述したトルクリミッタ付きギア６は、４つの長孔１０を有する入力側の大径ギア１１と、各長孔１０内に移動可能に配置された４個の鋼球１２と、各鋼球１２を挟持する第１および第２の摩擦板１３，１４と、大径ギア１１の中心部に同軸的に配置された出力側の小径ギア１５と、この小径ギア１５の中心部に挿通された支軸１６と、小径ギア１５を支軸１６の軸線方向へ弾性付勢するスプリング１７等によって構成されており、大径ギア１１と小径ギア１５ならびに第１および第２の摩擦板１３，１４は金属材料で形成されている。
【００２２】
大径ギア１１は外周面に歯部１１ａと中央部にガイド孔１１ｂを有し、図５に示すように、この歯部１１ａは上流側に位置する減速歯車列５の歯車（符号５ｂを付す）の小径ギアに噛合している。大径ギア１１にはガイド孔１１ｂを中心とする同一円上に４つの長孔１０が９０度の等間隔で形成されており、鋼球１２の直径は長孔１０の短軸方向の長さとほぼ等しく設定されている。これにより、各鋼球１２は対応する長孔１０の短軸方向に位置規制され、長孔１０の長軸方向に沿って移動可能となっている。
【００２３】
図３に示すように、４つの長孔１０の長軸方向の中心位置はガイド孔１１ｂを中心とする半径Ｒの同一円上にあり、大径ギア１１の中心Ｏから各長孔１０に向かって放射状に延びる直線をＰとすると、図示上下２つの長孔１０（以下これらを第１の長孔と称し、符号１０ａを付す）は、その長軸が直線Ｐに対して時計回り方向へ角度＋θだけ傾斜しており、残りの図示左右２つの長孔１０（以下これらを第２の長孔と称し、符号１０ｂを付す）は、その長軸が直線Ｐに対して半時計回り方向へ角度−θだけ傾斜している。すなわち、２つの第１の長孔１０ａと２つの第２の長孔１０ｂは平面的に見ると全て同一形状に形成されているが、大径ギア１１の回転方向について見ると、直線Ｐに対する第１の長孔１０ａの傾斜方向と第２の長孔１０ｂの傾斜方向は逆であり、それぞれの傾斜角（±θ）の絶対値は同じに設定されている。そして、４つの鋼球１２がこれら第１および第２の長孔１０ａ，１０ｂ内にそれぞれ長軸方向に沿って移動可能に配置されているため、大径ギア１１の中心Ｏから第１の長孔１０ａの外周側端部に位置する鋼球１２の中心までの距離Ｒ_１と第２の長孔１０ｂの内周側端部に位置する鋼球１２の中心までの距離Ｒ_２の和（２Ｒ_１＋２Ｒ_２）と、大径ギア１１の中心Ｏから第１の長孔１０ａの内周側端部に位置する鋼球１２の中心までの距離Ｒ_２と第２の長孔１０ｂの外周側端部に位置する鋼球１２の中心までの距離Ｒ_１の和（２Ｒ_１＋２Ｒ_２）とが略等しくなっている。
【００２４】
小径ギア１５は下部外周面に歯部１５ａを有し、図５に示すように、この歯部１５ａは下流側の歯車８に噛合している。小径ギア１５の上端中央部に円筒状のガイド筒１５ｂが突設されており、このガイド筒１５ｂは大径ギア１１のガイド孔１１ｂを挿通して上方へ突出している。ガイド筒１５ｂの下部周面には４つの係合突起１５ｃが形成されており、ガイド筒１５ｂの上端面には他の係合突起１５ｄが形成されている。第２の摩擦板１４には外周縁に４つの係合溝１４ａを有する係合孔１４ｂが形成されており、この係合孔１４ｂをガイド筒１５ｂに挿入して各係合溝１４ａを各係合突起１５ｃに係止することにより、第２の摩擦板１４は小径ギア１５と一体的に回転するようになっている。第１の摩擦板１３には係合孔１３ａが形成されており、この係合孔１３ａをガイド筒１５ｂの上端面の係合突起１５ｄに係止することにより、第１の摩擦板１３も小径ギア１５と一体的に回転するようになっている。
【００２５】
さらに、小径ギア１５の中央部には軸孔１５ｅとこの軸孔１５ｅに連通する中空部１５ｆが形成されており、支軸１６はこれら中空部１５ｆと軸孔１５ｅを挿通して小径ギア１５の上方へ突出している。この支軸１６の上端部には係止溝１６ａが形成されており、この係止溝１６ａにＥリングと称せられる止め金１８を係止することにより、第１の摩擦板１３は支軸１６からの脱落が防止されている。スプリング１７は中空部１５ｆの内部に配置されており、このスプリング１７の両端は中空部１５ｆの上面と支軸１６の下端に形成された鍔部１６ｂとにそれぞれ弾接している。これにより小径ギア１５が支軸１６の軸線方向へ付勢されるため、各鋼球１２は第１および第２の摩擦板１３，１４によって弾性的に挟持されることになる。
【００２６】
このように構成されたトルクリミッタ付きギア６では、大径ギア１１と各鋼球１２が小径ギア１５のガイド筒１５ｂを中心に一体的に回転すると共に、小径ギア１５と第１および第２の摩擦板１３，１４が支軸１６を中心に一体的に回転し、各鋼球１２と第１および第２の摩擦板１３，１４との間に摩擦力が発生するようになっている。したがって、モータ４の回転力によってモニタ装置３を回動させる場合は、入力側の大径ギア１１に連動して各鋼球１２が回転すると、各鋼球１２と第１および第２の摩擦板１３，１４間の摩擦力によって出力側の小径ギア１５もに回転し、大径ギア１１と小径ギア１５とはスリップすることなく一体的に回転する。一方、モニタ装置３に外部から過負荷が加えられた場合、例えば回動中のモニタ装置３にユーザの手指が触れたり、ユーザがモニタ装置３の起立角度を無理に手動操作した場合、入力側の大径ギア１１に連動して各鋼球１２は回転するが、出力側の小径ギア１５と第１および第２の摩擦板１３，１４は回転しないため、各鋼球１２が第１および第２の摩擦板１３，１４に対してスリップする。
【００２７】
ここで、モータ４の正転時に大径ギア１１が図３の時計回り方向（矢印Ａ）に回転し、モータ４の逆転時に大径ギア１１が図３の反時計回り方向（矢印Ｂ）に回転することとすると、大径ギア１１が矢印Ａ方向へ回転中に小径ギア１５からの出力側に過負荷が発生した場合、図示上下２つの鋼球１２が直線Ｐに対して傾斜する第１の長孔１０ａに沿ってその内周側へ破線で示すように移動し、図示左右２つの鋼球１２が同様に第２の長孔１０ｂの外周側へ破線で示すように移動する。このとき、鋼球１２が第１の長孔１０ａの外周側端部から内周側端部まで移動する移動量と、鋼球１２が第２の長孔１０ｂの内周側端部から外周側端部まで移動する移動量とはほぼ同じである。一方、大径ギア１１が矢印Ｂ方向へ回転中に小径ギア１５からの出力側に過負荷が発生した場合、図示上下２つの鋼球１２が第１の長孔１０ａの外周側へ実線で示すように移動し、図示左右２つの鋼球１２が第２の長孔１０ｂの内周側へ実線で示すように移動する。このときも、鋼球１２が第１の長孔１０ａの内周側端部から外周側端部まで移動する移動量と、鋼球１２が第２の長孔１０ｂの外周側端部から内周側端部まで移動する移動量とはほぼ同じである。
【００２８】
すなわち、トルクリミッタ付きギア６がスリップ動作するとき、各鋼球１２が第１および第２の長孔１０ａ，１０ｂの長軸方向に沿って斜め内周と斜め外周にほぼ同量ずつ移動した後、各鋼球１２が第１および第２の摩擦板１３，１４に対してスリップするため、第１および第２の長孔１０ａ，１０ｂの傾斜角によってスリップ開始時のトルクを低くすることができ、その結果、スリップ動作時のトルクに対するスリップ開始時のトルクの差を小さくし、大径ギア１１や小径ギア１５の破損を防止できると共に、各鋼球１２の偏摩耗を抑えることができる。なお、トルクリミッタ付きギア６のスリップ開始時のトルクは第１および第２の長孔１０ａ，１０ｂの傾斜角（±θ）によって変更可能であり、この傾斜角（±θ）の絶対値を大きくするのに伴ってスリップ開始時のトルクは低くなる。
【００２９】
また、前述したように、大径ギア１１の中心Ｏから第１の長孔１０ａの外周側端部に位置する鋼球１２の中心までの距離Ｒ_１と第２の長孔１０ｂの内周側端部に位置する鋼球１２の中心までの距離Ｒ_２の和（２Ｒ_１＋２Ｒ_２）と、大径ギア１１の中心Ｏから第１の長孔１０ａの内周側端部に位置する鋼球１２の中心までの距離Ｒ_２と第２の長孔１０ｂの外周側端部に位置する鋼球１２の中心までの距離Ｒ_１の和（２Ｒ_１＋２Ｒ_２）とが略等しくなるように、第１の長孔１０ａと第２の長孔１０ｂの位置および長軸寸法を設定したことにより、大径ギア１１の正転時と逆転時とで各鋼球１２から第１および第２の摩擦板１３，１４を介して小径ギア１５に伝達されるトルクはほぼ一定となり、モニタ装置３の立ち上げ動作と立ち下げ動作が安定して行える。
【００３０】
上記した実施例においては、筐体１から引き出されたモニタ装置３をモータ４を駆動源とする動力伝達機構で回動動作することにより、図１の実線で示す水平状態から破線で示す起立状態への立ち上げ動作や、その逆に起立状態からの立ち下げ動作が行われる。この場合、モータ４の回転力はウォームギア７から減速歯車列５の各歯車を経て最終段のトルクリミッタ付きギア６に伝達された後、歯車８，９を介してモニタ装置３に伝達されるため、モニタ装置３はモータ４を駆動源として電動動作される。ここで、トルクリミッタ付きギア６は各鋼球１２と金属製の第１および第２の摩擦板１３，１４との間で摩擦力を発生させるようになっているため、フェルト式のトルクリミッタ付きギアでは不可能であった高トルク、例えば数ｋｇｆ・ｃｍという高トルクを発生させることができるのみならず、温度や湿度の影響を受けにくい安定したトルクを発生させることができる。したがって、減速歯車列５の中でトルクが高い最終段にトルクリミッタ付きギア６を配置しても、モータ４の回転力によってモニタ装置３を確実に動作させることができ、トルクリミッタ付きギア６を配置可能なレイアウト上の自由度を広げることができる。
【００３１】
一方、このようなモニタ装置３を電動動作する動力伝達系に過度の負荷が生じた場合、例えば回動動作中のモニタ装置３にユーザの手指が触れたり、ユーザがモニタ装置３の起立角度を無理に手動操作した場合、前述したようにトルクリミッタ付きギア６の各鋼球１２と第１および第２の摩擦板１３，１４との間のスリップによって過負荷が吸収されるため、減速歯車列５の各歯車に大きな力は作用せず、これら歯車の破損を確実に回避することができる。
【００３２】
特に、本実施例においては、モニタ装置３の回動動作の途中でこのような過負荷が生じた場合に、モータ４を逆転させてモニタ装置３を回動動作前の状態（水平状態または起立状態）へ戻すように制御しており、かかるモータ４の逆転に伴ってトルクリミッタ付きギア６がスリップ動作する際に、各鋼球１２が第１および第２の長孔１０ａ，１０ｂ内を図３の破線位置から実線位置へと斜めに移動した後に、各鋼球１２が第１および第２の摩擦板１３，１４に対してスリップするため、スリップ動作時のトルクに対するスリップ開始時のトルクの差を小さくして大径ギア１１や小径ギア１５の破損を確実に防止することができる。
【００３３】
また、本実施例においては、モニタ装置３が立ち上げ方向と立ち下げ方向の末端位置まで移動した後も、モータ４が僅かに回転し続けてトルクリミッタ付きギア６をスリップ動作させるようになっているため、モニタ装置３が起立してトルクリミッタ付きギア６がスリップ動作を開始するときに、各鋼球１２が大径ギア１１の矢印Ａ方向の回転に伴って図３の破線位置から実線位置へと斜めに移動した後、各鋼球１２が第１および第２の摩擦板１３，１４に対してスリップし、その逆にモニタ装置３が水平に戻ってトルクリミッタ付きギア６がスリップ動作を開始するときも、各鋼球１２が大径ギア１１の矢印Ｂ方向の回転に伴って図３の実線位置から破線位置へと斜めに移動した後、各鋼球１２が第１および第２の摩擦板１３，１４に対してスリップする。このようにモニタ装置３の一連の回動動作中にトルクリミッタ付きギア６がスリップ動作する頻度は高くなっているが、かかるスリップ動作時に各鋼球１２が第１および第２の長孔１０ａ，１０ｂに沿って斜め内周と斜め外周に移動した後、各鋼球１２が第１および第２の摩擦板１３，１４に対してスリップするため、スリップ動作時のトルクに対するスリップ開始時のトルクの差を小さくすることができ、しかも、かかる大径ギア１１の正転逆転時に各鋼球１２の異なる部位が第１および第２の摩擦板１３，１４とスリップするため、各鋼球１２の偏摩耗を抑制することができる。
【００３４】
なお、上記実施例では、４個の鋼球１２を使用したトルクリミッタ付きギア６について説明したが、鋼球１２の数は４個に限定されず、鋼球１２の数が３以上の奇数個や６以上の偶数個であっても良い。
【００３５】
例えば６個の鋼球１２を使用する場合は、図６に示すように、大径ギア１１に３つの第１の長孔１０ａと３つの第２の長孔１０ｂとを６０度の等間隔で交互に形成し、これら第１および第２の長孔１０ａ，１０ｂ内にそれぞれ鋼球１２を移動可能に配置すれば良い。このように鋼球１２の数が６以上の偶数個である場合、大径ギア１１の同一円（半径Ｒ）上に第１の長孔１０ａと第２の長孔１０ｂとを交互に等間隔を保って形成すると共に、各第１の長孔１０ａの長軸を直線Ｐに対して時計回り方向へ角度＋θだけ傾斜させ、各第２の長孔１０ｂの長軸を直線Ｐに対して半時計回り方向へ角度−θだけ傾斜させれば、上記した鋼球１２が４個の場合と同様に、大径ギア１１の回転方向に拘わらずトルクリミッタ付きギア６のスリップ動作時に、各鋼球１２を第１および第２の長孔１０ａ，１０ｂの長軸方向に沿って斜め内周と斜め外周に移動せさた後、各鋼球１２を第１および第２の摩擦板１３，１４に対してスリップさせることができる。
【００３６】
また、３個の鋼球１２を使用する場合は、図７に示すように、大径ギア１１に１つの第１の長孔１０ａと２つの第２の長孔１０ｂを１２０度の等間隔で形成し、これら第１および第２の長孔１０ａ，１０ｂ内にそれぞれ鋼球１２を移動可能に配置すれば良い。ここで、第１および第２の長孔１０ａ，１０ｂの長軸方向の中心位置はガイド孔１１ｂを中心とする半径Ｒの同一円上にあるが、第１の長孔１０ａの長軸は直線Ｐに対して時計回り方向へ角度＋θだけ傾斜し、両第２の長孔１０ｂの長軸は直線Ｐに対して半時計回り方向へ角度−θだけ傾斜している。さらに、第１の長孔１０ａの長軸方向の長さに比べて第２の長孔１０ｂの長軸方向の長さは長さは短めに設定されており、大径ギア１１の中心Ｏから第１の長孔１０ａの外周側端部に位置する鋼球１２の中心までの距離Ｒ_１ａは第２の長孔１０ｂの内周側端部に位置する鋼球１２の中心までの距離Ｒ_１ｂよりも長く、大径ギア１１の中心Ｏから第１の長孔１０ａの内周側端部に位置する鋼球１２の中心までの距離Ｒ_２ａは第２の長孔１０ｂの内周側端部に位置する鋼球１２の中心までの距離Ｒ_２ｂよりも短くなっている。これらの距離Ｒ_１ａ，Ｒ_１ｂ，Ｒ_２ａ，Ｒ_２ｂは、大径ギア１１の正転時と逆転時とで、小径ギア１５に伝達されるトルクがほぼ一定となるような寸法に設定されている。
【００３７】
このように構成されたトルクリミッタ付きギア６において、大径ギア１１が図７の矢印Ａ方向へ回転中にスリップ動作した場合、図示上方の鋼球１２は第１の長孔１０ａの内周側へ破線で示すように大きく移動し、図示左右下方の２つの鋼球１２は第２の長孔１０ｂの外周側へ破線で示すように小さく移動する。一方、大径ギア１１が図７の矢印Ｂ方向へ回転した場合、図示上方の鋼球１２は第１の長孔１０ａの外周側へ実線で示すように大きく移動し、図示左右下方の２つの鋼球１２は第２の長孔１０ｂの内周側へ実線で示すように小さく移動する。すなわち、大径ギア１１の回転方向に拘わらずトルクリミッタ付きギア６のスリップ動作時に、各鋼球１２が長軸寸法を異にする第１および第２の長孔１０ａ，１０ｂの長軸方向に沿って斜め内周と斜め外周に移動した後、各鋼球１２が第１および第２の摩擦板１３，１４に対してスリップするため、第１および第２の長孔１０ａ，１０ｂの傾斜角によってスリップ開始時のトルクを低くすることができ、その結果、スリップ動作時のトルクに対するスリップ開始時のトルクの差を小さくし、大径ギア１１や小径ギア１５の破損を防止できると共に、各鋼球１２の偏摩耗を抑えることができる。しかも、かかるトルクリミッタ付きギア６のスリップ動作時に、数が少ない方の第１の長孔１０ａ内を移動する鋼球１２の移動量に対し、数が多い方の第２の長孔１０ｂ内を移動する鋼球１２の移動量を小さくしたので、大径ギア１１の正転逆転時に各鋼球１２を第１および第２の長孔１０ａ，１０ｂの長軸方向に沿って斜め内周と斜め外周にバランス良く移動させることができる。
【００３８】
なお、鋼球１２の数が３個を含む奇数個である場合、上記したように第１および第２の長孔１０ａ，１０ｂの長軸寸法を互いに異ならせることが好ましいが、その代わりに第１および第２の長孔１０ａ，１０ｂの傾斜角（±θ）の絶対値を互いに異ならせたり、第１および第２の長孔１０ａ，１０ｂの長軸寸法を互いに異ならせた上で両者の傾斜角（±θ）の絶対値を互いに異ならせても良い。例えば、第１の長孔１０ａの数を第２の長孔１０ｂよりも少なくした場合、数が少ない第１の長孔１０ａを所定方向へθ１だけ傾斜すると共に、数が多い第２の長孔１０ｂを反対方向へより小さい角度−θ２だけ傾斜すれば、大径ギア１１の正転逆転時に各鋼球１２を第１および第２の長孔１０ａ，１０ｂの長軸方向に沿って斜め内周と斜め外周にバランス良く移動させることができる。
【００３９】
また、上記実施例では、本発明によるトルクリミッタ付きギア６を車載用可動モニタ装置の動力伝達機構、すなわち可動体であるモニタ装置３の立ち上げと立ち下げを行う動力伝達機構に適用した場合について説明したが、前述したスライド体２を前後進方向へスライド動作する動力伝達機構や、車載用オーディオ装置の表示パネル（ノーズ）の駆動機構等、高トルクの駆動力が必要となる電子機器の動力伝達機構全般に適用可能である。
【００４０】
なお、上記実施例では、長孔１０ａ，１０ｂを大径ギア１１を貫通する貫通孔として形成しているが、有底の長孔として大径ギアの一側面に設けた摩擦板に鋼球１２を圧接させるようにしても良い。また、摩擦板を削除して小径ギアのフランジ面に鋼球１２を直接圧接させるようにすることもでき、この場合、小径ギアのフランジ面が摩擦板として機能する。
【００４１】
【発明の効果】
本発明は、以上説明したような形態で実施され、以下に記載されるような効果を奏する。
【００４２】
ギアに形成された複数の長孔内にそれぞれ鋼球を移動可能に配置すると共に、一部の長孔と残部の長孔をギアの回転方向に対して互いに逆向きに傾斜させたので、トルクリミッタ付きギアが正逆いずれか一方向へ回転中にスリップ動作するとき、一部の鋼球が第１の長孔の外周側へ移動すると共に、残部の鋼球が第２の長孔の内周側へ移動した後、各鋼球が摩擦体に対してスリップ動作し、その反対にトルクリミッタ付きギアが他方向へ回転中にスリップ動作するとき、一部の鋼球が第１の長孔の内周側へ移動すると共に、残部の鋼球が第２の長孔の外周側へ移動した後、各鋼球が摩擦体に対してスリップ動作する。このようにトルクリミッタ付きギアのスリップ動作時に、各鋼球が回転方向に対して斜め内周と斜め外周に移動した後にスリップ動作するため、スリップ動作時のトルクに対するスリップ開始時のトルクの差を小さくしてギアの破損を防止できると共に、鋼球の偏摩耗を抑えることができる。
【図面の簡単な説明】
【図１】本発明の実施例に係るトルクリミッタ付きギアの断面図である。
【図２】該トルクリミッタ付きギアの分解斜視図である。
【図３】該トルクリミッタ付きギアに備えられる第１のギアと鋼球の説明図である。
【図４】本発明が適用される車載用可動モニタ装置の側面図である。
【図５】該車載用可動モニタ装置に備えられる動力伝達機構の平面図である。
【図６】長孔の変形例を示す第１のギアの説明図である。
【図７】長孔の変形例を示す第１のギアの説明図である。
【符号の説明】
１筐体
２スライド体
３モニタ装置（可動体）
４モータ
５減速歯車列
６トルクリミッタ付きギア
１０長孔
１０ａ第１の長孔
１０ｂ第２の長孔
１１大径ギア（第１のギア）
１１ａ歯部
１１ｂガイド孔
１２鋼球
１３第１の摩擦板
１４第２の摩擦板
１５小径ギア（第２のギア）
１５ａ歯部
１５ｂガイド筒
１６支軸
１７スプリング
１８止め金[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a gear with a torque limiter used for various loading mechanisms and the like, and more particularly to a gear with a torque limiter suitable for use in a power transmission mechanism of an electronic device that operates a movable body by using a rotating force of a motor as a driving source. .
[0002]
[Prior art]
In recent years, by operating a movable panel having a display screen or the like using the rotational force of a motor as a drive source, the movable panel is slid horizontally to move in and out of the housing, or a movable panel pulled out of the housing is moved. 2. Description of the Related Art In-vehicle electronic devices that rotate and perform a start-up operation have become widespread.
[0003]
In general, in this kind of in-vehicle electronic device, a reduction gear train including a plurality of gears including a gear with a torque limiter is used as a power transmission mechanism for transmitting a rotational force of a motor to a movable panel, For example, when rotating the movable panel using the rotational force of the motor as a drive source, the first stage gear of the reduction gear train is engaged with the worm gear attached to the rotation shaft of the motor, and the last gear of the reduction gear train is movable. It engages with a gear attached to a panel or a bracket that supports a movable panel. The gear with a torque limiter includes a large-diameter gear and a small-diameter gear coaxially connected, a felt interposed between these gears, and a coil for elastically urging one gear to the other gear in the axial direction. Normally, both gears rotate integrally due to the frictional force of the felt.However, when an excessive load is applied to the power transmission system, the two gears slip through the felt to overload. It is designed to absorb.
[0004]
In the power transmission mechanism configured as described above, since the rotational force of the motor is transmitted from the worm gear to the movable panel via the reduction gear train, the movable panel in the horizontal state is started up, and conversely, the movable panel is in the upright state. The movable panel can be returned to a horizontal state. Further, when an excessive load occurs in the power transmission system, for example, when the user's finger touches the rotating movable panel, or when the user manually operates the rising angle of the movable panel, the gear with the torque limiter is Overload is absorbed by slipping, so that the reduction gear train is prevented from being damaged.
[0005]
However, a gear with a torque limiter using felt as described above cannot generate a stable torque because the felt is easily affected by temperature and humidity, and has a low torque of only several hundred gfcm at most. There is a disadvantage that it cannot occur. In addition, since only a low torque can be generated in this way, when such a felt-type gear with a torque limiter is used for a power transmission mechanism of an in-vehicle electronic device, a place where the gear with a torque limiter can be arranged is decelerated when viewed from the motor side. It is limited to the first stage of the gear train or its vicinity, and there is a problem that the degree of freedom in design is small.
[0006]
On the other hand, as a gear with a torque limiter capable of generating a high torque, a so-called ball clutch using a plurality of steel balls instead of felt is conventionally known (for example, see Patent Document 1). In this gear with a torque limiter, a plurality of holes are formed in one of the gears at predetermined intervals in a circumferential direction thereof, steel balls are held in these holes, and the steel balls are held by a pair of friction plates. The power transmission system is configured so as to be elastically sandwiched. When an excessive load occurs in the power transmission system, each steel ball slips against the friction plate to absorb the overload.
[0007]
[Patent Document 1]
JP-A-6-221343 (page 3-4, FIGS. 1 and 2)
[0008]
[Problems to be solved by the invention]
As described above, the conventional ball clutch (gear with torque limiter) can generate a high torque, so that the degree of freedom in layout in which the ball clutch can be arranged in the reduction gear train can be increased. The torque (coefficient of static friction of the steel ball) at the time of starting the slip operation is considerably higher than the torque (coefficient of dynamic friction of the steel ball) at the time of performing the slip operation. For this reason, when such a ball clutch is used for the power transmission mechanism of the above-mentioned in-vehicle electronic device, when an overload is applied to the movable panel and the steel ball starts slipping with respect to the friction plate, the torque becomes higher than necessary. There is a problem that the gear may be damaged due to too much. For these reasons, the torque during the slip operation has to be set to a certain low level, and the advantage of high torque cannot be sufficiently exhibited.
[0009]
In general, in this type of power transmission mechanism, even after the movable panel has moved to the end position of the outward or return path, the motor continues to rotate slightly to cause the ball clutch to perform a slip operation. The frequency of the ball clutch slipping during forward and reverse rotation of the gear is high, but the conventional ball clutch has a steel ball whose position is regulated by holes formed in the gear. There is also a problem that the same portion of the ball slips with the friction plate, causing uneven wear of the steel ball.
[0010]
The present invention has been made in view of such circumstances of the related art, and a first object of the present invention is to provide a gear with a torque limiter capable of preventing damage to the gear and suppressing uneven wear of a steel ball. A second object of the present invention is to provide a power transmission mechanism of an electronic device capable of generating a stable high torque in a gear with a torque limiter interposed in a reduction gear train.
[0011]
[Means for Solving the Problems]
The present invention arranges steel balls movably in a plurality of long holes formed in a gear, and inclines a part of the long holes and the remaining long holes in directions opposite to each other with respect to the rotation direction of the gear. It shall be. When such a long hole is formed in the gear, when the slip operation starts during rotation of the gear in one direction, some steel balls move to the outer peripheral side of the long hole, and the remaining steel balls move to the long hole. When the slip operation starts during rotation of the gear in the other direction, some steel balls move to the inner circumference of the long hole and the remaining steel balls move to the inner circumference of the long hole. Move to the outer periphery of the hole. Therefore, when the gear rotates forward and backward, each steel ball moves obliquely inward and outward with respect to the rotation direction, so that the difference between the torque at the time of slip operation and the torque at the start of slip is reduced to prevent gear damage. And uneven wear of the steel ball can be suppressed.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
In order to achieve the above-described first object, a gear with a torque limiter according to the present invention includes first and second gears coaxially arranged and a predetermined interval circumferentially between the first gear. A plurality of elongated holes formed therein, a plurality of steel balls movably disposed in the elongated holes along the longitudinal direction thereof, and pressed against the steel balls to rotate integrally with the second gear. A frictional body, wherein a part of the plurality of slots is a first slot inclined in one direction from a center of the first gear with respect to a straight line passing through the slot. The remaining slot is configured to be a second slot inclined from the center of the first gear in a direction opposite to a straight line passing through the slot.
[0013]
In the gear with the torque limiter configured as described above, when an overload occurs while rotating in one of the forward and reverse directions, some steel balls move to the outer peripheral side of the first long hole, and the remaining steel balls When the steel ball moves to the inner peripheral side of the second long hole, and conversely, when overload occurs while rotating in the other direction, some steel balls move to the inner peripheral side of the first long hole. At the same time, since the remaining steel balls move to the outer peripheral side of the second long hole, at the time of normal rotation and reverse rotation, each steel ball moves to the oblique inner circumference and the oblique outer circumference with respect to the rotation direction and performs a slip operation. The difference between the torque at the time of the slip operation and the torque at the start of the slip can be reduced to prevent the gear from being damaged, and the uneven wear of the steel ball can be suppressed.
[0014]
In the above configuration, the total number of the first and second long holes may be a minimum of three, but these first and second long holes are alternately N in number along the circumferential direction of the first gear. (Where N is an even number of 2 or more), that is, in the case of forming an even number of 4 or more, the absolute values of the inclination angles of the first and second long holes with respect to the straight line are set to be substantially equal, and each of them is set from the center of the first gear. The sum of the distance to the center of the steel ball located at the outer peripheral end of the first elongated hole and the distance to the center of the steel ball located at the inner peripheral end of the second elongated hole; The distance between the center of the steel ball located at the inner peripheral end of the elongated hole and the sum of the distance to the center of the steel ball located at the outer peripheral end of the second elongated hole is substantially equal. It is preferable to set the positions of the first and second long holes and the long axis dimension. In this case, each steel ball is balun to the friction body at the time of normal rotation and reverse rotation. Good can be moved, and becomes substantially constant at the time of reverse rotation torque transmitted through each steel ball at the time of normal rotation. When the total number of the first and second long holes is set to a minimum of three, one first long hole and two second long holes are formed in the first gear, and these are formed. It is preferable that at least one of the major axis dimension of the first and second long holes and the absolute value of the inclination angle with respect to the straight line be different from each other.
[0015]
Further, in order to achieve the second object described above, a power transmission mechanism of an electronic device according to the present invention uses a gear with a torque limiter configured as described above, via a reduction gear train including the gear with a torque limiter. Thus, the rotational force of the motor is transmitted to the movable body.
[0016]
According to the power transmission mechanism configured as described above, since a stable high torque can be generated in the gear with the torque limiter interposed in the reduction gear train, the gear with the torque limiter is arranged in the reduction gear train. The possible layout flexibility is expanded, and the difference between the torque at the time of slip operation and the torque at the time of slip operation of the gear with the torque limiter can be reduced, so that when the power transmission system is overloaded, Gear can be prevented from being damaged.
[0017]
【Example】
FIG. 1 is a sectional view of a gear with a torque limiter according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of the gear with a torque limiter, and FIG. 3 is a gear with the torque limiter. FIG. 4 is a side view of a vehicle-mounted movable monitor device to which the present invention is applied, and FIG. 5 is a plan view of a power transmission mechanism provided in the vehicle-mounted movable monitor device. It is.
[0018]
As shown in FIG. 4, the in-vehicle movable monitor device includes a box-shaped housing 1, which is installed on an instrument panel or the like in a vehicle. A slide body 2 is housed inside the housing 1, and a monitor device 3 is rotatably connected to an end of the slide body 2. Although not shown, the monitor device 3 has a display screen such as an LCD, and various information such as a navigation system and an audio system is displayed on the display screen. The slide body 2 is slid in the forward and backward directions by a motor (not shown) disposed in the housing 1. When the slide body 2 is moved forward and protrudes from the front surface of the housing 1, Accordingly, the monitor device 3 is pulled out from the front surface of the housing 1 while maintaining the horizontal posture. In this pulled-out state, the monitor device 3 is rotated by a power transmission mechanism to be described later, and starts up from a horizontal state shown by a solid line in FIG. 1 to an upright state shown by a broken line, and vice versa. Is performed.
[0019]
As shown in FIG. 5, the power transmission mechanism described above includes a motor 4 different from the motor that operates the slide body 2, and a reduction gear train 5 that reduces the rotational force of the motor 4 and transmits the rotational force to the monitor device 3. In this reduction gear train 5, a gear 6 with a torque limiter is interposed. The motor 4 and the reduction gear train 5 are mounted on a bracket (not shown) to form a unit, and the bracket is mounted on the slide body 2. The reduction gear train 5 is composed of a plurality of gears including a gear 6 with a torque limiter. These gears have a large-diameter gear and a small-diameter gear arranged coaxially, respectively, and have a large diameter of the first-stage gear (reference numeral 5a). The gear meshes with a worm gear 7 attached to the rotation shaft of the motor 4. Hereinafter, the rotational force of the motor 4 is reduced by each gear of the reduction gear train 5 by sequentially meshing the small-diameter gear of the upstream gear as viewed from the motor 4 with the large-diameter gear of the downstream gear. The gear 6 with the torque limiter is arranged at the last stage of the reduction gear train 5. Although a specific configuration of the gear 6 with the torque limiter will be described later, another gear 8 is meshed with a small diameter gear of the gear 6 with the torque limiter, and the gear 8 meshes with a gear 9 attached to the monitor device 3. I have.
[0020]
In this manner, in the power transmission system in which the rotational force of the motor 4 is reduced by the reduction gear train 5 and transmitted to the monitor device 3, the torque increases as the position approaches the monitor device 3; Gear 5a and gears in the vicinity of the gear 5a are arranged in a place where the torque is low. For this reason, in the present embodiment, as the plurality of gears including the first gear 5a of the reduction gear train 5, a synthetic resin gear which is cheaper and lighter than a metal gear is used. All the gears of the reduction gear train 5 may be metal gears.
[0021]
As shown in FIGS. 1 and 2, the gear 6 with the torque limiter described above includes a large-diameter gear 11 on the input side having four long holes 10 and four gears movably disposed in each long hole 10. A steel ball 12, first and second friction plates 13 and 14, which sandwich each steel ball 12, a small-diameter gear 15 on the output side coaxially arranged at the center of the large-diameter gear 11, and a small-diameter gear; 15, a support shaft 16 inserted through the center of the support shaft 15, a spring 17 for elastically biasing the small-diameter gear 15 in the axial direction of the support shaft 16, and the like. The second friction plates 13 and 14 are formed of a metal material.
[0022]
The large-diameter gear 11 has a tooth portion 11a on the outer peripheral surface and a guide hole 11b at the center, and as shown in FIG. 5, the tooth portion 11a is provided with a gear (reference numeral 5b) of the reduction gear train 5 located on the upstream side. ) Meshes with the small diameter gear. In the large-diameter gear 11, four long holes 10 are formed at equal intervals of 90 degrees on the same circle centered on the guide hole 11b, and the diameter of the steel ball 12 is equal to the length of the long hole 10 in the short axis direction. They are set almost equal. As a result, the position of each steel ball 12 is regulated in the short axis direction of the corresponding long hole 10, and the steel ball 12 is movable along the long axis direction of the long hole 10.
[0023]
As shown in FIG. 3, the center positions of the four long holes 10 in the long axis direction are on the same circle having a radius R centered on the guide hole 11 b, and are directed from the center O of the large-diameter gear 11 to each long hole 10. Assuming that a straight line extending radially is denoted by P, the upper and lower two elongated holes 10 in the figure (hereinafter referred to as a first elongated hole and denoted by reference numeral 10a) have their major axes angled clockwise with respect to the straight line P. + Θ, and the other two left and right long holes 10 (hereinafter, referred to as second long holes and denoted by reference numeral 10b) have their long axes angled counterclockwise with respect to the straight line P. It is inclined by -θ. That is, the two first long holes 10a and the two second long holes 10b are all formed in the same shape when viewed in plan, but when viewed in the rotation direction of the large-diameter gear 11, the second The inclination direction of the first long hole 10a and the inclination direction of the second long hole 10b are opposite, and the absolute values of the respective inclination angles (± θ) are set to be the same. Since the four steel balls 12 are arranged in these first and second long holes 10a and 10b so as to be movable along the long axis direction, the first steel ball 12 is moved from the center O of the large diameter gear 11 to the first long hole. Distance R to the center of steel ball 12 located at the outer peripheral end of hole 10a ₁ And the distance R to the center of the steel ball 12 located at the inner peripheral end of the second long hole 10b. ₂ Sum (2R ₁ + 2R ₂ ) And a distance R from the center O of the large-diameter gear 11 to the center of the steel ball 12 located at the inner peripheral end of the first elongated hole 10a. ₂ And the distance R to the center of the steel ball 12 located at the outer peripheral end of the second long hole 10b. ₁ Sum (2R ₁ + 2R ₂ ) Is approximately equal to
[0024]
The small-diameter gear 15 has a tooth portion 15a on a lower outer peripheral surface, and as shown in FIG. 5, the tooth portion 15a meshes with the gear 8 on the downstream side. A cylindrical guide tube 15b projects from the center of the upper end of the small-diameter gear 15, and this guide tube 15b protrudes upward through the guide hole 11b of the large-diameter gear 11. Four engagement projections 15c are formed on the lower peripheral surface of the guide cylinder 15b, and another engagement projection 15d is formed on the upper end surface of the guide cylinder 15b. An engagement hole 14b having four engagement grooves 14a is formed on the outer peripheral edge of the second friction plate 14, and the engagement holes 14b are inserted into the guide cylinder 15b so that the engagement grooves 14a are respectively engaged. The second friction plate 14 rotates integrally with the small-diameter gear 15 by being locked to the mating projection 15c. An engagement hole 13a is formed in the first friction plate 13, and by engaging the engagement hole 13a with an engagement projection 15d on the upper end surface of the guide cylinder 15b, the first friction plate 13 also has a small diameter. It rotates integrally with the gear 15.
[0025]
Further, a shaft hole 15e and a hollow portion 15f communicating with the shaft hole 15e are formed at the center of the small diameter gear 15, and the support shaft 16 is inserted through the hollow portion 15f and the shaft hole 15e to form the small diameter gear 15. It protrudes upward. An engagement groove 16a is formed at the upper end of the support shaft 16, and by locking a stopper 18 called an E-ring in the engagement groove 16a, the first friction plate 13 From falling off is prevented. The spring 17 is disposed inside the hollow portion 15f, and both ends of the spring 17 are in elastic contact with the upper surface of the hollow portion 15f and the flange 16b formed at the lower end of the support shaft 16, respectively. As a result, the small-diameter gear 15 is urged in the axial direction of the support shaft 16, so that each steel ball 12 is elastically held by the first and second friction plates 13 and 14.
[0026]
In the gear 6 with the torque limiter thus configured, the large-diameter gear 11 and the steel balls 12 rotate integrally around the guide cylinder 15b of the small-diameter gear 15, and the small-diameter gear 15 and the first and second gears. The friction plates 13 and 14 rotate integrally about the support shaft 16, and a friction force is generated between each steel ball 12 and the first and second friction plates 13 and 14. Therefore, when the monitor device 3 is rotated by the rotational force of the motor 4, when each steel ball 12 rotates in conjunction with the large-diameter gear 11 on the input side, each steel ball 12 and the first and second friction plates are rotated. The small-diameter gear 15 on the output side also rotates due to the frictional force between the gears 13 and 14, and the large-diameter gear 11 and the small-diameter gear 15 rotate integrally without slipping. On the other hand, when an overload is applied to the monitor device 3 from the outside, for example, when the user's finger touches the rotating monitor device 3 or when the user forcibly operates the standing angle of the monitor device 3, the input side Each steel ball 12 rotates in conjunction with the large-diameter gear 11, but the small-diameter gear 15 on the output side and the first and second friction plates 13 and 14 do not rotate. Slip with respect to the second friction plates 13 and 14.
[0027]
Here, the large-diameter gear 11 rotates clockwise (arrow A) in FIG. 3 when the motor 4 rotates forward, and the large-diameter gear 11 rotates counterclockwise (arrow B) in FIG. 3 when the motor 4 rotates reversely. If the large-diameter gear 11 rotates in the direction of arrow A and an overload occurs on the output side from the small-diameter gear 15, the upper and lower two steel balls 12 shown in FIG. Along the long hole 10a, as shown by the broken line, and the two steel balls 12 on the left and right similarly move as shown by the broken line toward the outer periphery of the second long hole 10b. At this time, the amount of movement of the steel ball 12 from the outer peripheral end to the inner peripheral end of the first elongated hole 10a and the amount of movement of the steel ball 12 from the inner peripheral end of the second elongated hole 10b to the outer peripheral side are determined. The amount of movement to the end is almost the same. On the other hand, when an overload occurs on the output side from the small-diameter gear 15 while the large-diameter gear 11 is rotating in the direction of the arrow B, the upper and lower two steel balls 12 are indicated by solid lines on the outer peripheral side of the first elongated hole 10a. , The two steel balls 12 on the left and right in the figure move toward the inner peripheral side of the second elongated hole 10b as shown by the solid line. Also at this time, the amount of movement of the steel ball 12 from the inner peripheral end to the outer peripheral end of the first elongated hole 10a and the amount of movement of the steel ball 12 from the outer peripheral end of the second elongated hole 10b to the inner periphery are determined. The amount of movement to the side end is almost the same.
[0028]
That is, when the gear 6 with the torque limiter performs the slip operation, after each steel ball 12 moves by approximately the same amount to the oblique inner circumference and the oblique outer circumference along the major axis direction of the first and second long holes 10a, 10b. Since the steel balls 12 slip with respect to the first and second friction plates 13 and 14, the torque at the start of slip can be reduced by the inclination angles of the first and second long holes 10a and 10b. As a result, the difference between the torque at the time of the slip operation and the torque at the time of the start of the slip operation can be reduced, the damage to the large-diameter gear 11 and the small-diameter gear 15 can be prevented, and the uneven wear of each steel ball 12 can be suppressed. The torque at the start of slipping of the gear 6 with the torque limiter can be changed by the inclination angle (± θ) of the first and second long holes 10a, 10b, and the absolute value of the inclination angle (± θ) is increased. As a result, the torque at the start of the slip decreases.
[0029]
Further, as described above, the distance R from the center O of the large-diameter gear 11 to the center of the steel ball 12 located at the outer peripheral end of the first long hole 10a. ₁ And the distance R to the center of the steel ball 12 located at the inner peripheral end of the second long hole 10b. ₂ Sum (2R ₁ + 2R ₂ ) And a distance R from the center O of the large-diameter gear 11 to the center of the steel ball 12 located at the inner peripheral end of the first elongated hole 10a. ₂ And the distance R to the center of the steel ball 12 located at the outer peripheral end of the second long hole 10b. ₁ Sum (2R ₁ + 2R ₂ ) Are set to be substantially equal to each other, the positions of the first long hole 10a and the second long hole 10b and the long axis dimension are set, so that each steel ball is used when the large-diameter gear 11 rotates forward and reverse. The torque transmitted from the motor 12 to the small-diameter gear 15 via the first and second friction plates 13 and 14 becomes substantially constant, so that the start-up operation and the start-down operation of the monitor device 3 can be performed stably.
[0030]
In the above-described embodiment, the monitor device 3 pulled out of the housing 1 is rotated by the power transmission mechanism using the motor 4 as a drive source, so that the horizontal state shown by the solid line in FIG. And a conversely, a falling operation from a standing state is performed. In this case, the rotational force of the motor 4 is transmitted from the worm gear 7 to the gear 6 with the torque limiter at the final stage via the respective gears of the reduction gear train 5, and then to the monitor device 3 via the gears 8 and 9. The monitor device 3 is electrically operated using the motor 4 as a drive source. Here, since the gear 6 with the torque limiter generates a frictional force between each of the steel balls 12 and the first and second friction plates 13 and 14 made of metal, a felt type torque limiter is provided. It is possible to generate not only a high torque that cannot be achieved with a gear, for example, a high torque of several kgf · cm, but also a stable torque that is hardly affected by temperature and humidity. Therefore, even if the gear 6 with the torque limiter is arranged at the final stage where the torque is high in the reduction gear train 5, the monitor device 3 can be reliably operated by the rotational force of the motor 4, and the gear 6 with the torque limiter can be used. The degree of freedom in layout that can be arranged can be expanded.
[0031]
On the other hand, when an excessive load occurs in the power transmission system that electrically operates the monitor device 3, for example, the user's finger touches the monitor device 3 that is rotating, or the user increases the standing angle of the monitor device 3. When the manual operation is forcibly performed, as described above, the overload is absorbed by the slip between each of the steel balls 12 of the gear 6 with the torque limiter and the first and second friction plates 13 and 14, so that the reduction gear train is used. No large force acts on each gear of No. 5, and damage to these gears can be reliably avoided.
[0032]
In particular, in the present embodiment, when such an overload occurs during the turning operation of the monitor device 3, the motor 4 is rotated in the reverse direction to bring the monitor device 3 into a state before the turning operation (horizontal state or standing up). When the gear 6 with the torque limiter slips with the reverse rotation of the motor 4, each steel ball 12 shows the inside of the first and second long holes 10 a and 10 b. Since the steel ball 12 slips with respect to the first and second friction plates 13 and 14 after moving obliquely from the position indicated by the dashed line to the position indicated by the solid line in FIG. By making the difference small, it is possible to reliably prevent the large-diameter gear 11 and the small-diameter gear 15 from being damaged.
[0033]
Further, in the present embodiment, even after the monitor device 3 has moved to the end positions in the rising direction and the falling direction, the motor 4 continues to rotate slightly to cause the gear 6 with the torque limiter to slip. Therefore, when the monitor device 3 stands up and the gear 6 with the torque limiter starts the slip operation, each steel ball 12 moves from the position indicated by the broken line to the position indicated by the solid line in FIG. After that, the steel balls 12 slip with respect to the first and second friction plates 13 and 14, and conversely, the monitor device 3 returns to a horizontal position and the gear 6 with the torque limiter performs a slip operation. When starting, the steel balls 12 move obliquely from the solid line position to the broken line position in FIG. 3 with the rotation of the large-diameter gear 11 in the direction of arrow B, and then the steel balls 12 move to the first and second positions. For friction plates 13 and 14 To slip. As described above, the frequency of the slip operation of the gear 6 with the torque limiter during the series of turning operations of the monitor device 3 is high. However, at the time of such a slip operation, each steel ball 12 causes the first and second long holes 10a, After moving to the oblique inner circumference and the oblique outer circumference along 10b, each steel ball 12 slips with respect to the first and second friction plates 13 and 14, so that the torque at the time of starting the slip with respect to the torque at the time of the slip operation. The difference can be reduced, and different portions of each steel ball 12 slip with the first and second friction plates 13 and 14 when the large-diameter gear 11 rotates in the normal direction and the reverse direction. Wear can be suppressed.
[0034]
Although the gear 6 with the torque limiter using the four steel balls 12 has been described in the above embodiment, the number of the steel balls 12 is not limited to four, and the number of the steel balls 12 is an odd number of three or more. Or even number of 6 or more.
[0035]
For example, when six steel balls 12 are used, as shown in FIG. 6, three first long holes 10a and three second long holes 10b are formed in the large-diameter gear 11 at equal intervals of 60 degrees. The steel balls 12 may be formed alternately and the steel balls 12 may be movably disposed in the first and second long holes 10a and 10b. When the number of the steel balls 12 is an even number equal to or greater than 6, the first long holes 10a and the second long holes 10b are alternately and equally spaced on the same circle (radius R) of the large-diameter gear 11. And the long axis of each first long hole 10a is inclined clockwise with respect to the straight line P by an angle + θ, and the long axis of each second long hole 10b is If the steel balls 12 are inclined in the clockwise direction by an angle -θ, the steel balls 12 can be slipped by the torque limiter-equipped gear 6 regardless of the rotation direction of the large-diameter gear 11, as in the case of four steel balls 12 described above. After moving the steel balls 12 to the oblique inner circumference and the oblique outer circumference along the long axis direction of the first and second long holes 10a, 10b, the steel balls 12 are transferred to the first and second friction plates 13, 14, respectively. You can slip it.
[0036]
When three steel balls 12 are used, one first long hole 10a and two second long holes 10b are formed in the large-diameter gear 11 at equal intervals of 120 degrees as shown in FIG. The steel ball 12 may be formed in each of the first and second long holes 10a and 10b so as to be movable. Here, the center positions of the first and second long holes 10a and 10b in the long axis direction are on the same circle having a radius R centered on the guide hole 11b, but the long axis of the first long hole 10a is a straight line. The second long holes 10b are tilted counterclockwise with respect to the line P by an angle -θ in the counterclockwise direction with respect to the straight line P. Further, the length of the second long hole 10b in the long axis direction is set to be shorter than the length of the first long hole 10a in the long axis direction. Distance R to the center of steel ball 12 located at the outer peripheral end of first long hole 10a _1a Is the distance R to the center of the steel ball 12 located at the inner peripheral end of the second long hole 10b. _1b A distance R from the center O of the large-diameter gear 11 to the center of the steel ball 12 located at the inner peripheral end of the first elongated hole 10a. _2a Is the distance R to the center of the steel ball 12 located at the inner peripheral end of the second long hole 10b. _2b Is shorter than These distances R _1a , R _1b , R _2a , R _2b Are set so that the torque transmitted to the small-diameter gear 15 is substantially constant when the large-diameter gear 11 rotates forward and when the large-diameter gear 11 rotates reversely.
[0037]
In the gear 6 with the torque limiter configured as described above, when the large-diameter gear 11 slips while rotating in the direction of arrow A in FIG. 7, the steel ball 12 in the upper part of the figure is on the inner circumferential side of the first elongated hole 10a. The steel ball 12 moves left and right as shown by the broken line, and the two steel balls 12 at the lower left and right in the figure move to the outer peripheral side of the second long hole 10b small as shown by the broken line. On the other hand, when the large-diameter gear 11 rotates in the direction of arrow B in FIG. 7, the steel ball 12 in the upper part of the figure moves largely to the outer peripheral side of the first long hole 10a as shown by the solid line, The steel ball 12 moves small to the inner peripheral side of the second elongated hole 10b as shown by a solid line. That is, regardless of the rotation direction of the large-diameter gear 11, when the gear 6 with the torque limiter slips, the first and second long holes 10a and 10b in which the steel balls 12 have different long-axis dimensions are formed in the long-axis direction. After moving along the oblique inner circumference and the oblique outer circumference along, the steel balls 12 slip with respect to the first and second friction plates 13 and 14, so that the inclination angles of the first and second long holes 10a and 10b. As a result, the torque at the start of the slip can be reduced, and as a result, the difference between the torque at the time of the slip operation and the torque at the time of the slip operation can be reduced. Uneven wear of the ball 12 can be suppressed. In addition, during the slip operation of the gear 6 with the torque limiter, the amount of movement of the steel ball 12 moving in the smaller number of the first long holes 10a corresponds to the amount of movement in the larger number of the second long holes 10b. Since the moving amount of the moving steel ball 12 is reduced, each steel ball 12 is inclined obliquely inward along the long axis direction of the first and second long holes 10a and 10b when the large-diameter gear 11 rotates forward and backward. It can be moved to the outer periphery in a well-balanced manner.
[0038]
In addition, when the number of the steel balls 12 is an odd number including three, it is preferable to make the major axis dimensions of the first and second long holes 10a and 10b different from each other as described above. The absolute values of the inclination angles (± θ) of the first and second long holes 10a and 10b may be different from each other, or the major axes of the first and second long holes 10a and 10b may be different from each other. The absolute values of the inclination angles (± θ) may be different from each other. For example, when the number of the first long holes 10a is smaller than that of the second long holes 10b, the first long holes 10a having a small number are inclined by θ1 in a predetermined direction, and the second long holes 10a having a large number are inclined. When the large-diameter gear 11 rotates forward and backward, the steel balls 12 are inclined obliquely along the major axis direction of the first and second long holes 10a and 10b by inclining the steel balls 10b in the opposite direction by a smaller angle -θ2. And can be moved to the outer periphery diagonally with good balance.
[0039]
Further, in the above embodiment, the case where the gear 6 with the torque limiter according to the present invention is applied to the power transmission mechanism of the in-vehicle movable monitor device, that is, the power transmission mechanism that starts and stops the monitor device 3 which is a movable body. As described above, a power transmission mechanism that slides the slide body 2 in the forward and backward directions, a drive mechanism of a display panel (nose) of an in-vehicle audio device, and a power source of an electronic device that requires a high torque driving force. Applicable to all transmission mechanisms.
[0040]
In the above embodiment, the long holes 10a and 10b are formed as through holes penetrating the large-diameter gear 11, but the steel balls 12 are formed on the friction plate provided on one side of the large-diameter gear as bottomed long holes. May be pressed against each other. Further, the steel plate 12 can be directly pressed against the flange surface of the small-diameter gear by removing the friction plate. In this case, the flange surface of the small-diameter gear functions as a friction plate.
[0041]
【The invention's effect】
The present invention is implemented in the form described above, and has the following effects.
[0042]
The steel balls are movably arranged in the plurality of long holes formed in the gear, and some of the long holes and the remaining long holes are inclined in opposite directions to the rotation direction of the gear. When the gear with limiter slips while rotating in one of the forward and reverse directions, some steel balls move to the outer peripheral side of the first long hole, and the remaining steel balls move inside the second long hole. After moving to the circumferential side, each steel ball slips with respect to the frictional body, and conversely, when the gear with the torque limiter slips while rotating in the other direction, some steel balls are in the first slot. After the remaining steel balls move to the outer peripheral side of the second elongated hole while moving to the inner peripheral side of each, the respective steel balls perform a slip operation with respect to the friction body. As described above, during the slip operation of the gear with the torque limiter, since each steel ball performs a slip operation after moving to the oblique inner circumference and the oblique outer circumference with respect to the rotation direction, the difference between the torque at the time of the slip operation and the torque at the start of the slip is calculated. It is possible to prevent the gear from being damaged by making it smaller, and to suppress the uneven wear of the steel ball.
[Brief description of the drawings]
FIG. 1 is a sectional view of a gear with a torque limiter according to an embodiment of the present invention.
FIG. 2 is an exploded perspective view of the gear with a torque limiter.
FIG. 3 is an explanatory view of a first gear and a steel ball provided in the gear with a torque limiter.
FIG. 4 is a side view of a vehicle-mounted movable monitor device to which the present invention is applied.
FIG. 5 is a plan view of a power transmission mechanism provided in the vehicle-mounted movable monitor device.
FIG. 6 is an explanatory diagram of a first gear showing a modified example of a long hole.
FIG. 7 is an explanatory diagram of a first gear showing a modified example of a long hole.
[Explanation of symbols]
1 housing
2 slide body
3 monitor device (movable body)
4 Motor
5 Reduction gear train
6 Gear with torque limiter
10 Slot
10a First slot
10b Second long hole
11 Large-diameter gear (first gear)
11a Tooth
11b Guide hole
12 Steel ball
13 First friction plate
14 Second friction plate
15 Small diameter gear (second gear)
15a Tooth
15b Guide tube
16 spindle
17 Spring
18 Clasp

Claims

First and second gears coaxially arranged, a plurality of long holes formed in the first gear at predetermined intervals in a circumferential direction, and a plurality of long holes formed in these long holes along the longitudinal direction. A plurality of steel balls movably arranged and a friction body pressed against the steel balls and integrally rotating with the second gear,
Among the plurality of slots, a part of the slots is a first slot inclined in one direction from a center of the first gear with respect to a straight line passing through the slot, and the remaining slots are the same. A gear with a torque limiter, wherein the gear is a second long hole inclined in a direction opposite to a straight line passing through the long hole from the center of the first gear.

2. The torque according to claim 1, wherein the first and second long holes are alternately formed N (N is an even number of 2 or more) along the circumferential direction of the first gear. Gear with limiter.

3. The outer peripheral surface of the first elongated hole according to claim 2, wherein the absolute values of the inclination angles of the first and second elongated holes with respect to the straight line are set substantially equal to each other, and from the center of the first gear. The sum of the distance to the center of the steel ball located at the side end and the distance to the center of the steel ball located at the inner peripheral end of the second elongated hole; The distance to the center of the steel ball located at the peripheral end and the sum of the distance to the center of the steel ball located at the outer peripheral end of the second elongated hole are substantially equal. A gear with a torque limiter, wherein the positions of the first and second long holes and the length of the long axis are set.

2. The first gear according to claim 1, wherein one first elongated hole and two second elongated holes are formed in the first gear, and major axes of the first and second elongated holes are formed. A gear with a torque limiter, wherein at least one of a dimension and an absolute value of an inclination angle with respect to the straight line are different from each other.

The gear with a torque limiter according to any one of claims 1 to 4, wherein the torque of the motor is transmitted to a movable body via a reduction gear train including the gear with a torque limiter. Power transmission mechanism for electronic equipment.