JPH06248911A - Valve system cam shaft provided with decompression device for engine - Google Patents

Abstract

PURPOSE:To obviate the need for corrective operation of a crank shaft, and cope with a high load applied to a gear part of a cam gear part by forming a shaft part, cam parts, and the cam gear part of a valve-cam shaft body by one piece synthetic resin, and forming a recessed part on the end face on the opposite side from the cam parts of the cam gear part to accomodate a centrifugal weight and a decomp. spring. CONSTITUTION:A valve-cam shaft body 23 is made of one piece synthetic resin, and is formed integrally by a shaft part 1, cam parts 2, 25, and a cam gear part 3. A circular ring-shaped recessed part 6 is formed on the end face 5 on the opposite side from the camm parts opposite the end face 4 on the cam parts side out of both the end faces 4, 5 of the cam gear part 3 in order to accomodate a decomp. centrifugal weight 8 pivoted to a pivoting shaft 7 so that it can freely oscillate, and a decomp. spring 11 provided between an oscillating end part 9 and a spring locking part 10. Thus, interference of a crank shaft with a counterweight is prevented to obviate the need for corrective operation of the crank shaft. Further, since the width of the gear part 19 of the cam gear part 3 can be kept wide, the cam gear part can be used for an engine, in which a high load is applied to the gear part 19.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】本発明は、エンジンのデコンプ装
置付き動弁カム軸に関し、詳しくは合成樹脂一体型の動
弁カム軸本体にデコンプ装置を組み込んだものに関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine valve camshaft with a decompression device, and more particularly to a synthetic resin integrated valve camshaft body incorporating a decompression device.

【０００２】[0002]

【従来技術】エンジンの動弁カム軸の従来技術として図
４に示すものがある。この従来技術１は、いわゆる合成
樹脂一体型の動弁カム軸であり、合成樹脂で軸部１０１
とカム部１０２・１２５とカムギヤ部１０３とを一体に
形成してある。一方、デコンプ装置付き動弁カム軸の従
来技術として図５に示すものがある。この従来技術２
は、カムギヤ部１０３の両端面１０４・１０５のうち、
カム部側端面１０４に凹設部１０６を形成し、この凹設
部１０６に、枢軸１０７で揺動自在に枢支したデコンプ
用の遠心錘１０８と、この遠心錘１０８の揺動端部１０
９とバネ係止部１１０との間に架設したデコンプバネ１
１１とを収容してある。2. Description of the Related Art As a conventional valve camshaft for an engine, there is one shown in FIG. This prior art 1 is a so-called synthetic resin integrated valve camshaft, which is made of synthetic resin to form a shaft portion 101.
The cam portions 102 and 125 and the cam gear portion 103 are integrally formed. On the other hand, there is a conventional valve camshaft with a decompression device shown in FIG. This prior art 2
Of the both end surfaces 104 and 105 of the cam gear 103,
A concave portion 106 is formed on the cam portion side end surface 104, and a decompression centrifugal weight 108 pivotally supported by a pivot shaft 107 in the concave portion 106 and a swing end portion 10 of the centrifugal weight 108.
9 and the decompression spring 1 installed between the spring locking portion 110
11 and 11 are accommodated.

【０００３】この図５に示すデコンプ装置付き動弁カム
軸の動弁カム軸本体１２３は、カム部１０２・１２５を
一体形成した金属製の軸部１０１と、金属製のカムギヤ
部１０３とを、別々に形成し、軸部１０１にカムギヤ部
１０３を嵌着固定したものである。The valve camshaft main body 123 of the valve camshaft with decompression device shown in FIG. 5 includes a metal shaft portion 101 integrally formed with cam portions 102 and 125 and a metal cam gear portion 103. The cam gear portion 103 is formed separately, and the cam gear portion 103 is fitted and fixed to the shaft portion 101.

【０００４】[0004]

【発明が解決しようとする課題】本発明者は、本発明に
先立ち、図４に示す従来技術１の合成樹脂一体型の動弁
カム軸のカムギヤ部１０３に、図５に示す従来技術２と
同様にして、デコンプ装置を組み込むことを考えた。す
なわち、図４に示すカムギヤ部１０３のカム部側端面１
０４に図５に示す凹設部１０６を設け、ここに遠心錘１
０８とデコンプバネ１１１を収容することを考えた。し
かし、図４に示す合成樹脂一体型の動弁カム軸の場合、
成型の都合上、カム部側端面１０４に凹設部１０６を形
成することができない。Prior to the present invention, the inventor of the present invention has shown that the cam gear portion 103 of the valve housing cam shaft of the synthetic resin integrated type of the prior art 1 shown in FIG. In the same way, we considered incorporating a decompression device. That is, the cam portion side end surface 1 of the cam gear portion 103 shown in FIG.
04 is provided with a recessed portion 106 shown in FIG.
It was considered to accommodate 08 and the decompression spring 111. However, in the case of the synthetic resin integrated valve camshaft shown in FIG.
For convenience of molding, the recessed portion 106 cannot be formed on the cam portion side end surface 104.

【０００５】すなわち、図４に示す合成樹脂一体型の動
弁カム軸を成型する場合には、カムギヤ部１０３のカム
部側端面１０４とその横側の軸部１０１及びカム部１０
２・１２５を成型するためのカム部側形成型１５０、カ
ム部側端面１０４とは反対側の反カム部側端面１０５と
その横側の軸部１０１を成型するための反カム部側形成
型１５１、カムギヤ部１０３の歯部１１９を形成するた
めの歯部形成型１５２を用いる。そして、反カム部側形
成型１５１と歯部形成型１５２とは、矢印１５３・１５
４のように、軸部１０１と平行な向きに型抜きを行うこ
とができるが、カム部側形成型１５０は、軸部１０１の
周側面からカム部１０２・１２５が膨出している関係
上、軸部１０１と平行な向きに型抜きを行うことができ
ない。このため、カム部側形成型１５０は、二つ割り型
にして、この各割り型１５５・１５５を矢印１５６・１
５７のように、軸部１０１の径方向に型抜きする必要が
ある。このため、カムギヤ部１０３のカム部側端面１０
４には、図５のような軸部１０１と平行な向きに窪んだ
凹設部１０６を形成することはできない。That is, in the case of molding the synthetic resin integrated valve camshaft shown in FIG. 4, the cam portion side end surface 104 of the cam gear portion 103 and the shaft portion 101 and the cam portion 10 on the side thereof.
Cam part side forming mold 150 for molding 2.125, anti-cam part side forming face for molding the cam part side end face 105 opposite to the cam part side end face 104 and the shaft part 101 on the side thereof. 151, a tooth portion forming mold 152 for forming the tooth portion 119 of the cam gear portion 103 is used. The non-cam portion side forming die 151 and the tooth portion forming die 152 are indicated by arrows 153, 15
4, it is possible to perform die cutting in a direction parallel to the shaft portion 101, but the cam portion side forming die 150 has the cam portions 102 and 125 bulging from the peripheral side surface of the shaft portion 101. Die cutting cannot be performed in a direction parallel to the shaft portion 101. For this reason, the cam portion side forming die 150 is divided into two halves, and the respective halves 155, 155 are indicated by arrows 156, 1.
Like 57, it is necessary to perform die cutting in the radial direction of the shaft portion 101. Therefore, the end portion 10 of the cam gear portion 103 on the cam portion side is formed.
4, it is not possible to form a recessed portion 106 that is recessed in a direction parallel to the shaft portion 101 as shown in FIG.

【０００６】そこで、まず、図６（Ａ）に示すように、
先行試作例１として、図４の合成樹脂一体型の動弁カム
軸のカムギヤ部１０３のカム部側端面１０４に、遠心錘
１０８とデコンプバネを取り付けたものを試作した。し
かし、このようにすると、遠心錘１０８とデコンプバネ
がカム部側端面１０４から横に大きく張り出すため、こ
れらがクランク軸１２０のカウンタウェイト１２１の側
面と干渉する場合がある。このため、カウンタウェイト
１２１の側面に除肉部１５８を形成する必要があるとと
もに、この除肉によるクランク軸１２０のバランスの崩
れを修正するため、更に、クランクピン１２２側の肉も
削る必要がある等、クランク軸１２０の修正作業が必要
となり、エンジンの製造工程が繁雑になることがわかっ
た。Therefore, first, as shown in FIG.
As a first prototype, a prototype in which a centrifugal weight 108 and a decompression spring were attached to the cam portion side end surface 104 of the cam gear portion 103 of the valve housing cam shaft of the synthetic resin integrated type shown in FIG. However, in this case, the centrifugal weight 108 and the decompression spring largely project laterally from the cam portion side end surface 104, so that they may interfere with the side surface of the counterweight 121 of the crankshaft 120. For this reason, it is necessary to form the thickness-reduced portion 158 on the side surface of the counterweight 121, and to correct the imbalance of the crankshaft 120 due to this thickness-reduction, it is also necessary to scrape the thickness of the crankpin 122 side. As a result, it has been found that the work of correcting the crankshaft 120 is required and the manufacturing process of the engine becomes complicated.

【０００７】次に、図６（Ｂ）に示すように、先行試作
例２として、カムギヤ部１０３の厚さを一律に薄くする
ことにより、遠心錘１０８とデコンプバネがカウンタウ
ェイト１２１の側面と干渉しないものを試作した。この
ようにすると、クランク軸１２０の修正作業は不要にな
るものの、カムギヤ部１０３の歯部１１９は、その幅が
短くなる分だけ強度が低下する。このため、このような
ものは、歯部１１９に高負荷がかかる仕様のエンジンに
は使用できないことがわかった。Next, as shown in FIG. 6 (B), as a second prototype, the cam gear portion 103 is uniformly thinned so that the centrifugal weight 108 and the decompression spring do not interfere with the side surface of the counterweight 121. I made a prototype. In this way, although the work of correcting the crankshaft 120 is unnecessary, the strength of the tooth portion 119 of the cam gear portion 103 is reduced as the width thereof is shortened. Therefore, it has been found that such a product cannot be used in an engine of a specification in which a heavy load is applied to the tooth portion 119.

【０００８】本発明の課題は、樹脂一体型の動弁カム軸
本体にデコンプ装置を組み込むに当たり、遠心錘やデコ
ンプバネがカムギヤ部のカム部側端面から横側に張り出
すのを防止でき、また、カムギヤ部の歯部の強度を高く
維持できるものを提供することにある。An object of the present invention is to prevent the centrifugal weight and the decompression spring from protruding laterally from the cam portion side end surface of the cam gear portion when the decompression device is incorporated into the resin-integrated valve camshaft body. An object of the present invention is to provide a cam gear that can maintain high strength of the teeth.

【０００９】[0009]

【課題を解決するための手段】[Means for Solving the Problems]

（第１発明）第１発明は、図１に例示するように、合成
樹脂で軸部１とカム部２・２５とカムギヤ部３とを一体
に形成したものを動弁カム軸本体２３とした。(First Invention) As shown in FIG. 1, the first invention is a valve camshaft body 23 in which the shaft portion 1, the cam portions 2 and 25, and the cam gear portion 3 are integrally formed of synthetic resin. .

【００１０】そして、カムギヤ部３の両端面４・５のう
ち、カム部側端面４とは反対側の反カム部側端面５に、
軸部１と平行な向きに窪ませた凹設部６を形成し、この
凹設部６に、枢軸７で揺動自在に枢支したデコンプ用の
遠心錘８と、この遠心錘８の揺動端部９とバネ係止部１
０との間に架設したデコンプバネ１１とを収容した、こ
とを特徴とする。Of the both end surfaces 4 and 5 of the cam gear portion 3, the end surface 5 on the side opposite to the cam portion side end surface 4 is
A concave portion 6 is formed which is recessed in a direction parallel to the shaft portion 1. A decompression centrifugal weight 8 pivotally supported by a pivot shaft 7 in the concave portion 6 and a swing of the centrifugal weight 8 are provided. Moving end 9 and spring locking portion 1
It accommodates the decompression spring 11 which is installed between 0 and 0.

【００１１】（第２発明）第２発明は、図２（Ａ）・
（Ｄ）に例示するように、第１発明のエンジンのデコン
プ装置付き動弁カム軸において、バネ係止部１０を、凹
設部内底面１２から軸部１と平行な向きに***させた突
起１３と、この突起１３に挿通した頭付きピン１４とで
構成し、突起先端面に段差を設け、この突起先端面の段
上がり部１５で頭付きピン１４の頭部１６を受け止める
ことにより、突起先端面の段下がり部１７と頭付きピン
１４の頭部１６との間にバネ端部係合隙間１８を設けた
ことを特徴とする。(Second Invention) The second invention is shown in FIG.
As illustrated in (D), in the valve camshaft with decompression device for the engine of the first aspect of the invention, the spring locking portion 10 is a protrusion 13 that is raised from the inner bottom surface 12 of the recessed portion in a direction parallel to the shaft portion 1. And a headed pin 14 inserted through the protrusion 13, a step is provided on the tip end surface of the protrusion, and the stepped portion 15 of the tip end surface of the protrusion receives the head 16 of the headed pin 14 to obtain the tip end of the protrusion. A spring end engaging gap 18 is provided between the step-down portion 17 of the surface and the head 16 of the headed pin 14.

【００１２】[0012]

【発明の作用及び効果】[Operation and effect of the invention]

（第１発明） 図１に例示するように、遠心錘８とデコンプバネ１１
とを、カムギヤ部３の反カム部側端面５に形成した凹設
部６に収容するため、これらがカム部側端面４から横に
張り出す余地がない。このため、図３に例示するよう
に、これらがクランク軸２０のカウンタウェイト２１の
側面と干渉する余地がなく、カウンタウェイト２１の側
面の除肉等、クランク軸２０の修正作業が不要となり、
エンジンの製造工程を煩雑化することがない。(First Invention) As illustrated in FIG. 1, a centrifugal weight 8 and a decompression spring 11 are provided.
Since and are accommodated in the recessed portion 6 formed in the end surface 5 of the cam gear portion 3 on the side opposite to the cam portion, there is no room for them to laterally project from the end surface 4 on the side of the cam portion. Therefore, as illustrated in FIG. 3, there is no room for these to interfere with the side surface of the counterweight 21 of the crankshaft 20, and the correction work of the crankshaft 20 such as the removal of the side surface of the counterweight 21 becomes unnecessary,
It does not complicate the engine manufacturing process.

【００１３】図１に例示するように、遠心錘８とデコ
ンプバネ１１とを、カムギヤ部３の反カム部側端面５に
形成した凹設部６に収容するため、カムギヤ部３の歯部
１９の幅を広いまま維持でき、その強度を高く維持でき
る。このため、歯部１９に高負荷がかかる仕様のエンジ
ンにも使用できる。As illustrated in FIG. 1, since the centrifugal weight 8 and the decompression spring 11 are housed in the recessed portion 6 formed in the end surface 5 of the cam gear portion 3 opposite to the cam portion 3, the tooth portion 19 of the cam gear portion 3 is accommodated. The width can be kept wide and its strength can be kept high. Therefore, it can be used for an engine of a specification in which a heavy load is applied to the tooth portion 19.

【００１４】図１に例示するように、凹設部６を、反
カム部側端面５に軸部１と平行な向きに窪ませて形成す
るので、軸部１と平行な向きに行う反カム部側形成型１
５１（図４参照）の型抜き作業に支障を及ぼすことな
く、凹設部６を容易に形成できる。As shown in FIG. 1, since the recessed portion 6 is formed in the end surface 5 on the side opposite the cam portion in a direction parallel to the shaft portion 1, it is formed in the direction opposite to the shaft portion 1. Part-side forming mold 1
The recessed portion 6 can be easily formed without hindering the die cutting work of 51 (see FIG. 4).

【００１５】（第２発明）第２発明は、第１発明の作用
効果〜に加え、次の作用効果をも奏する。 図２に例示するように、バネ係止部１０の一部を構成
する突起１３を、凹設部内底面１２から軸部１と平行な
向きに***させるので、軸部１と平行な向きに行う反カ
ム部側形成型１５１（図４参照）の型抜き作業に支障を
及ぼすことなく、突起１３を容易に形成できる。(Second Invention) In addition to the effects and advantages of the first invention, the second invention also exhibits the following effects. As illustrated in FIG. 2, since the protrusion 13 forming a part of the spring locking portion 10 is raised from the inner bottom surface 12 of the recessed portion in a direction parallel to the shaft portion 1, it is performed in a direction parallel to the shaft portion 1. The protrusion 13 can be easily formed without affecting the die-cutting work of the anti-cam portion side forming die 151 (see FIG. 4).

【００１６】[0016]

【実施例】本発明の実施例を図面に基づいて説明する。
図１は本発明の実施例に係るエンジンのデコンプ装置付
き動弁カム軸を説明する図で、図１（Ａ）は縦断側面
図、図１（Ｂ）は図１（Ａ）のＢ方向矢視図である。図
２は図１の動弁カム軸本体のカムギヤ部を説明する図
で、図２（Ａ）はバネ係止部の斜視図、図２（Ｂ）は図
１（Ａ）のII方向矢視図、図２（Ｃ）は図２（Ｂ）のＣ
−Ｃ線断面図、図２（Ｄ）は図２（Ｂ）のＤ−Ｄ線断面
拡大図である。図３は図１のデコンプ装置付き動弁カム
軸を組み込んだエンジンの横断平面図である。Embodiments of the present invention will be described with reference to the drawings.
1A and 1B are views for explaining a valve operating camshaft with a decompression device for an engine according to an embodiment of the present invention. FIG. 1A is a vertical side view, and FIG. 1B is a direction B arrow in FIG. 1A. It is a perspective view. 2A and 2B are views for explaining the cam gear portion of the valve operating camshaft main body of FIG. 1, FIG. 2A is a perspective view of the spring locking portion, and FIG. 2B is a view in the direction II of FIG. 1A. Fig. 2 (C) is C of Fig. 2 (B)
2C is a cross-sectional view taken along line C, and FIG. 2D is an enlarged view taken along line DD of FIG. FIG. 3 is a cross-sectional plan view of an engine incorporating the valve operating cam shaft with the decompression device of FIG.

【００１７】図３に示すエンジンは、強制空冷式で縦型
単気筒の頭上弁ガソリンエンジンで、クランクケース３
０の上側（紙面手前側）にシリンダ（図外）とシリンダ
ヘッド（図外）とを順に設け、クランクケース３０の前
側に冷却ファン（図外）を取り付けてある。また、冷却
ファンの前側には、手動のリコイルスタータ（図外）を
取り付けてある。クランクケース３０内には、クランク
軸２０と動弁カム軸本体２３とを平行に架設し、クラン
ク軸２０のクランクギヤ２４と動弁カム軸本体２３のカ
ムギヤ部３とを噛み合わせ、クランク軸２０から動弁カ
ム軸本体２３を回転連動するようにしてある。図１
（Ａ）に示すように、動弁カム軸本体２３の排気弁用カ
ム部２と吸気弁用カム部２５には、その上側に排気弁用
タペット３１と吸気弁用タペット３２とを載置し、各カ
ム部２・２５による各タペット３１・３２の押し上げに
より、吸排気弁（図外）を開弁するようにしてある。The engine shown in FIG. 3 is a forced air-cooled, vertical single-cylinder overhead valve gasoline engine.
A cylinder (not shown) and a cylinder head (not shown) are sequentially provided on the upper side of 0 (front side of the drawing), and a cooling fan (not shown) is attached to the front side of the crankcase 30. A manual recoil starter (not shown) is attached to the front side of the cooling fan. In the crankcase 30, the crankshaft 20 and the valve camshaft main body 23 are installed in parallel with each other, and the crank gear 24 of the crankshaft 20 and the cam gear portion 3 of the valve camshaft main body 23 are meshed with each other. Therefore, the valve operating cam shaft main body 23 is rotationally interlocked. Figure 1
As shown in (A), an exhaust valve tappet 31 and an intake valve tappet 32 are mounted on the exhaust valve cam portion 2 and the intake valve cam portion 25 of the valve camshaft main body 23 on the upper side thereof. The intake / exhaust valve (not shown) is opened by pushing up the tappets 31/32 by the cam portions 2/25.

【００１８】動弁カム軸本体２３の構成は次の通りであ
る。図１（Ａ）に示すように、動弁カム軸本体２３は合
成樹脂一体型のもので、フェノール樹脂で軸部１とカム
部２・２５とカムギヤ部３とを一体に形成してある。こ
の動弁カム軸本体２３は、軸部１の左側から右側に、カ
ムギヤ部３、排気弁用カム部２、吸気弁用カム部２５を
順に配置してある。The structure of the valve operating camshaft body 23 is as follows. As shown in FIG. 1A, the valve operating cam shaft main body 23 is of a synthetic resin integrated type, and the shaft portion 1, the cam portions 2 and 25, and the cam gear portion 3 are integrally formed of phenol resin. In the valve operating cam shaft body 23, a cam gear portion 3, an exhaust valve cam portion 2, and an intake valve cam portion 25 are sequentially arranged from the left side to the right side of the shaft portion 1.

【００１９】この動弁カム軸本体２３には、デコンプ装
置を次のようにして組み込んである。すなわち、図１
（Ａ）に示すように、カムギヤ部３の両端面４・５のう
ち、カム部側端面４とは反対側の反カム部側端面５に、
軸部１と平行な向きに窪ませた円環状の凹設部６を形成
し、図１（Ｂ）に示すように、この凹設部６に、枢軸７
で揺動自在に枢支したデコンプ用の遠心錘８と、この遠
心錘８の揺動端部９とバネ係止部１０との間に架設した
デコンプバネ１１とを収容し、デコンプバネ１１の張力
３３で遠心錘８を向心方向に付勢してある。尚、遠心錘
８はＣ字形に形成してある。A decompression device is incorporated in the valve camshaft body 23 as follows. That is, FIG.
As shown in (A), of the opposite end surfaces 4 and 5 of the cam gear portion 3, on the end surface 5 opposite to the end portion 4 on the side opposite to the cam portion,
An annular recessed portion 6 is formed which is recessed in a direction parallel to the shaft portion 1. As shown in FIG.
The decompression centrifugal weight 8 pivotally supported by the decompression spring 8 and the decompression spring 11 installed between the rocking end 9 of the centrifugal weight 8 and the spring locking portion 10 are accommodated, and the tension 33 of the decompression spring 11 is accommodated. The centrifugal weight 8 is biased in the centripetal direction. The centrifugal weight 8 is formed in a C shape.

【００２０】遠心錘８に遠心力が発生していない場合、
或いは、遠心錘８に発生する遠心力が小さい場合には、
遠心錘８は、図１（Ｂ）に実線で示すように、デコンプ
バネ１１の張力３３により、円環状の凹設部６の小径内
周面３５に接当したデコンプ姿勢３６を維持する。ま
た、遠心錘８に大きな遠心力が発生した場合には、遠心
錘８はデコンプバネ１１の張力３３に抗して揺動し、図
１（Ｂ）に鎖線で示すように、円環状の凹設部６の大径
内周面３７に接当したデコンプ解除姿勢３８を維持す
る。遠心錘８の揺動端部９の内側には、デコンプ面３９
とデコンプ解除面４０とを形成してある。When no centrifugal force is generated in the centrifugal weight 8,
Alternatively, when the centrifugal force generated in the centrifugal weight 8 is small,
As shown by the solid line in FIG. 1B, the centrifugal weight 8 maintains the decompression posture 36 in contact with the small diameter inner peripheral surface 35 of the annular recessed portion 6 by the tension 33 of the decompression spring 11. Further, when a large centrifugal force is generated in the centrifugal weight 8, the centrifugal weight 8 swings against the tension 33 of the decompression spring 11, and as shown by the chain line in FIG. The decompression releasing posture 38 in contact with the large-diameter inner peripheral surface 37 of the portion 6 is maintained. Inside the swinging end 9 of the centrifugal weight 8, the decompression surface 39
And a decompression releasing surface 40 are formed.

【００２１】図１（Ａ）に示すように、軸部１には凹設
部６から排気弁用カム２付近にかけて斜め向きのデコン
プピン挿通孔４１をあけ、ここにデコンプピン４２を摺
動自在に挿通してある。デコンプピン４２の基端部４３
付近には抜け止めリング４４を外嵌固定し、デコンプピ
ン４２がその先端部４５方向に抜けるのを防止するとと
もに、デコンプピン４２の重心４６が軸部１の軸線４７
よりも基端部４３側に偏るようにしてある。動弁カム軸
本体２３の回転中は、デコンプピン４２はその重心４６
の偏りのため、遠心力によって基端部４３方向に抜けよ
うとする。As shown in FIG. 1 (A), a decompression pin insertion hole 41 is formed obliquely in the shaft portion 1 from the recessed portion 6 to the vicinity of the exhaust valve cam 2, and a decompression pin 42 is slidably inserted therein. I am doing it. Base end portion 43 of decompression pin 42
A retaining ring 44 is externally fitted and fixed in the vicinity to prevent the decompression pin 42 from coming off in the direction of the tip portion 45 thereof, and the center of gravity 46 of the decompression pin 42 is set to the axis line 47 of the shaft portion 1.
It is biased toward the base end portion 43 side. During rotation of the valve operating cam shaft body 23, the decompression pin 42 moves toward its center of gravity 46.
Due to the unevenness, the centrifugal force tends to come out toward the proximal end portion 43.

【００２２】そして、図１（Ｂ）に示すように、遠心錘
８がデコンプ姿勢３６にある場合には、デコンプピン４
２の基端部４３が遠心錘８のデコンプ面３９に接当し、
デコンプピン４２の基端部４３方向への移動が阻止さ
れ、図１（Ａ）に示すように、デコンプピン４２の先端
部４５がその側近のカム面４８よりも所定寸法４９だけ
飛び出すようにしてある。この側近のカム面４８は、ピ
ストンヘッド（図外）が圧縮工程の上死点手前側に来た
時に、排気弁用タペット３１と接当する部分である。ま
た、図１（Ｂ）に示すように、遠心錘８がデコンプ解除
姿勢３８にある場合には、デコンプピン４２の基端部４
３が遠心錘８のデコンプ解除面４０に接当するまで、デ
コンプピン４２がその基端部４３方向に大きく移動する
ため、図１（Ａ）に示すデコンプピン４２の先端部４５
の飛び出しがなくなる。As shown in FIG. 1 (B), when the centrifugal weight 8 is in the decompression posture 36, the decompression pin 4
The base end portion 43 of the second contacting the decompression surface 39 of the centrifugal weight 8,
The decompression pin 42 is prevented from moving in the direction of the base end portion 43, and as shown in FIG. 1A, the tip end portion 45 of the decompression pin 42 protrudes from the cam surface 48 near the side thereof by a predetermined dimension 49. The cam surface 48 near this side is a portion that comes into contact with the exhaust valve tappet 31 when the piston head (not shown) comes to the front dead center side of the compression process. Further, as shown in FIG. 1B, when the centrifugal weight 8 is in the decompression releasing posture 38, the base end portion 4 of the decompression pin 42.
Since the decompression pin 42 moves largely toward the base end portion 43 until the decompression release surface 40 of the centrifugal weight 8 comes into contact with the centrifugal weight 8, the tip end portion 45 of the decompression pin 42 shown in FIG.
There is no popping out.

【００２３】このデコンプ装置の作動は次の通りであ
る。すなわち、エンジン始動のために、リコイルスター
タによりクランク軸２０（図３参照）を回転させると、
動弁カム軸本体２３が回転連動され、デコンプ装置も一
体に回転を始める。この回転初期は、未だ回転数が低い
ため、遠心錘８に発生する遠心力は小さく、図１（Ｂ）
に示すように、遠心錘８はデコンプバネ１１の張力３３
によりデコンプ姿勢３６を維持する。この場合、図１
（Ａ）に示すように、デコンプピン４２の先端部４５が
その側近のカム面４８よりも所定寸法４９だけ飛び出し
た状態に維持されるので、ピストンヘッドが圧縮工程の
上死点手前側に来た時に、このデコンプピン４２の先端
部４５により排気弁用タペット３１が押し上げられる。
このため、排気弁が開弁され、燃焼室からの圧力の抜け
により、ピストンヘッドが圧縮上死点を容易に乗り越
え、エンジン始動操作を小さな力で行うことができる。The operation of this decompression device is as follows. That is, when the crankshaft 20 (see FIG. 3) is rotated by the recoil starter to start the engine,
The valve operating cam shaft body 23 is interlocked with the rotation, and the decompression device also starts to rotate integrally. At the initial stage of this rotation, since the rotation speed is still low, the centrifugal force generated in the centrifugal weight 8 is small, and the centrifugal force shown in FIG.
As shown in FIG.
Thus, the decompression posture 36 is maintained. In this case,
As shown in (A), since the tip end portion 45 of the decompression pin 42 is maintained in a state of protruding by a predetermined dimension 49 from the cam surface 48 near its side, the piston head comes to the front dead center side of the compression process. At this time, the exhaust valve tappet 31 is pushed up by the tip portion 45 of the decompression pin 42.
For this reason, the exhaust valve is opened, and the pressure release from the combustion chamber allows the piston head to easily overcome the compression top dead center, and the engine starting operation can be performed with a small force.

【００２４】また、この始動操作によって、クランク軸
２０（図３参照）の回転速度が上昇し、動弁カム軸本体
２３の回転速度が所定の回転速度にまで上昇すると、遠
心錘８に発生する遠心力が強まり、図１（Ｂ）に示すよ
うに、遠心錘８が揺動して、デコンプ解除姿勢３８に切
り替わる。この場合、図１（Ａ）に示すデコンプピン４
２の先端部４５の飛び出しがなくなるため、排気弁の開
弁作動が正常に行われ、エンジンが始動する。Further, by this starting operation, the rotation speed of the crankshaft 20 (see FIG. 3) is increased, and when the rotation speed of the valve operating camshaft main body 23 is increased to a predetermined rotation speed, the centrifugal weight 8 is generated. The centrifugal force is increased, and the centrifugal weight 8 swings to switch to the decompression releasing posture 38 as shown in FIG. 1 (B). In this case, the decompression pin 4 shown in FIG.
Since the tip portion 45 of No. 2 does not jump out, the exhaust valve is normally opened and the engine is started.

【００２５】このデコンプ装置のバネ係止部１０の構成
は次の通りである。すなわち、図２（Ａ）・（Ｄ）に示
すように、バネ係止部１０を、凹設部内底面１２から軸
部１と平行な向きに***させた突起１３と、この突起１
３に挿通した頭付きピン１４とで構成してある。突起先
端面には段差を設け、この突起先端面の段上がり部１５
で頭付きピン１４の頭部１６を受け止め、突起先端面の
段下がり部１７と頭付きピン１４の頭部１６との間にバ
ネ端部係合隙間１８を設け、ここにデコンプバネ１１の
端部５０を係止してある。このため、この端部５０のず
れ動きが防止される。また、図２（Ｄ）に示すように、
頭付きピン１４のピン部はカムギヤ部３に貫通させ、そ
の先端部にカシメ部５７を形成して抜け止めしてある。The structure of the spring locking portion 10 of this decompression device is as follows. That is, as shown in FIGS. 2 (A) and 2 (D), a protrusion 13 in which the spring engaging portion 10 is raised from the inner bottom surface 12 of the recessed portion in a direction parallel to the shaft portion 1, and the protrusion 1
3 and a headed pin 14 which is inserted through 3. A step is provided on the tip end surface of the protrusion, and the stepped portion 15 of the tip end surface of the protrusion is
The head 16 of the headed pin 14 is received by, and a spring end engaging gap 18 is provided between the step-down portion 17 of the tip end surface of the protrusion and the head 16 of the headed pin 14, and the end of the decompression spring 11 is provided there. 50 is locked. Therefore, the displacement of the end portion 50 is prevented. In addition, as shown in FIG.
The pin portion of the headed pin 14 is passed through the cam gear portion 3, and a caulking portion 57 is formed at the tip end thereof to prevent the pin from coming off.

【００２６】また、このデコンプ装置の遠心錘８の枢支
部の構成は次の通りである。すなわち、図２（Ｃ）に示
すように、枢軸７には頭付きで段付きのものを用い、枢
軸７の小径部５１をカムギヤ部３に貫通させ、その先端
部にカシメ部５３を形成して抜け止めしてある。そし
て、枢軸７の大径部５２に遠心錘８の基端部を外嵌状に
枢支してある。このカシメ部５３は、カムギヤ部３に埋
設した座金５４に着座させてある。The structure of the pivot portion of the centrifugal weight 8 of this decompression device is as follows. That is, as shown in FIG. 2 (C), the pivot 7 having a head and a step is used, and the small diameter portion 51 of the pivot 7 is passed through the cam gear portion 3 and a caulking portion 53 is formed at the tip thereof. To prevent it from slipping out. Then, the base end portion of the centrifugal weight 8 is pivotally supported by the large diameter portion 52 of the pivot shaft 7 in an externally fitted shape. The crimp portion 53 is seated on a washer 54 embedded in the cam gear portion 3.

【００２７】また、図２（Ｂ）に示すように、カムギヤ
部３のカム部側端面４には、頭付きピン１４のカシメ部
５７の着座部分及びその周辺から歯部１９にわたり、ま
た、枢軸７のカシメ部５３の着座部分である座金５４及
びその周辺から歯部１９にわたり、それぞれ段落ち面５
５・５６を形成し、図２（Ｃ）・（Ｄ）に示すように、
各カシメ部５３・５７がカム部側端面４から横に飛び出
さないようにしてある。また、この段落ち面５５・５６
は、図４（Ａ）に示す割り型１５５・１５５の型抜きが
支障なく行えるように、この型抜き方向１５６・１５７
に沿う形状にしてある。Further, as shown in FIG. 2 (B), the end surface 4 of the cam gear portion 3 on the cam portion side extends from the seated portion of the caulking portion 57 of the headed pin 14 and its periphery to the tooth portion 19, and also to the pivot shaft. 7, the washer 54, which is the seating portion of the caulking portion 53, and the periphery thereof to the tooth portion 19, respectively
5 ・ 56 are formed, and as shown in FIG. 2 (C) ・ (D),
The caulking portions 53 and 57 are prevented from protruding laterally from the cam portion side end surface 4. Also, this step drop surface 55/56
In order that the split dies 155 and 155 shown in FIG.
It is shaped according to.

【００２８】また、図２（Ｂ）に示すように、この段落
ち面５５・５６は、カムギヤ部３の歯部１９のうち、排
気弁開弁時にクランクギヤ２４とかみ合う部分５８を避
けて形成し、この部分５８の歯幅が薄くなるのを避けて
いる。排気弁開弁時には、排気弁（図外）の開弁に抗す
る弁バネ（図外）のバネ力や燃焼室（図外）内の膨張圧
力が、排気弁、プッシュロッド（図外）、排気弁用タペ
ット３１、排気弁用カム部２、軸部１等を順に介してカ
ムギヤ部３に回転反力として伝達され、この部分５８の
負担が大きくなるからである。尚、図２（Ｂ）中の矢印
６０はクランクギヤ２４の回転方向、矢印６１はカムギ
ヤ部３の回転方向を示す。As shown in FIG. 2B, the step-down surfaces 55 and 56 are formed so as to avoid the portion 58 of the tooth portion 19 of the cam gear portion 3 that meshes with the crank gear 24 when the exhaust valve is opened. However, the tooth width of this portion 58 is prevented from becoming thin. When the exhaust valve is opened, the spring force of the valve spring (not shown) against the opening of the exhaust valve (not shown) and the expansion pressure in the combustion chamber (not shown) may affect the exhaust valve, push rod (not shown), This is because a rotational reaction force is transmitted to the cam gear portion 3 through the exhaust valve tappet 31, the exhaust valve cam portion 2, the shaft portion 1 and the like in this order, and the load on this portion 58 increases. 2B, the arrow 60 indicates the rotation direction of the crank gear 24, and the arrow 61 indicates the rotation direction of the cam gear portion 3.

【００２９】この動弁カム軸本体２３は、図４に示す従
来技術１のものと同様、カム部側形成型１５０、反カム
部側形成型１５１、歯部形成型１５２を用いて、樹脂成
型する。型内にはデコンプピン挿通孔４１を形成するた
めのピン中子（図外）を入れておき、樹脂成型後、この
ピン中子を抜き取ると、デコンプピン挿通孔４１が形成
される。デコンプピン挿通孔４１は、凹設部６と排気弁
用カム部２付近にわたって斜めに形成されるため、ピン
中子の抜き取りは、その両端いずれ方向にも行える。This valve camshaft main body 23 is molded by resin using a cam portion side forming die 150, an anti-cam portion side forming die 151, and a tooth portion forming die 152, as in the prior art 1 shown in FIG. To do. A demold pin insertion hole 41 is formed by inserting a pin core (not shown) for forming the decompression pin insertion hole 41 into the mold and removing the pin core after resin molding. Since the decompression pin insertion hole 41 is formed obliquely in the vicinity of the recessed portion 6 and the exhaust valve cam portion 2, the pin core can be removed in either direction.

【００３０】本発明の実施例の内容は以上の通りである
が、本発明は上記実施例に限定されるものではない。例
えば、上記実施例では、始動補助装置として手動式のリ
コイルスタータを用いたが、これに代えて、スターティ
ングモータを用いるものであってもよい。また、デコン
プ装置は他の構造のものであってもよい。The contents of the embodiment of the present invention are as described above, but the present invention is not limited to the above embodiment. For example, in the above embodiment, a manual recoil starter was used as the starting assist device, but a starting motor may be used instead of this. Further, the decompression device may have another structure.

【図面の簡単な説明】[Brief description of drawings]

【図１】本発明の実施例に係るエンジンのデコンプ装置
付き動弁カム軸を説明する図で、図１（Ａ）は縦断側面
図、図１（Ｂ）は図１（Ａ）のＢ方向矢視図である。FIG. 1 is a diagram illustrating a valve operating camshaft with a decompression device for an engine according to an embodiment of the present invention, FIG. 1 (A) is a vertical side view, and FIG. 1 (B) is a B direction in FIG. 1 (A). FIG.

【図２】図１の動弁カム軸本体のカムギヤ部を説明する
図で、図２（Ａ）はバネ係止部の斜視図、図２（Ｂ）は
図１（Ａ）のII方向矢視図、図２（Ｃ）は図２（Ｂ）の
Ｃ−Ｃ線断面図、図２（Ｄ）は図２（Ｂ）のＤ−Ｄ線断
面拡大図である。2A and 2B are views for explaining a cam gear portion of the valve operating camshaft main body of FIG. 1, FIG. 2A is a perspective view of a spring locking portion, and FIG. 2B is a II direction arrow of FIG. 1A. 2C is a sectional view taken along the line CC of FIG. 2B, and FIG. 2D is an enlarged view taken along the line DD of FIG. 2B.

【図３】図１のデコンプ装置付き動弁カム軸を組み込ん
だエンジンの横断平面図である。3 is a cross-sectional plan view of an engine incorporating the valve operating camshaft with the decompression device of FIG. 1. FIG.

【図４】従来技術１に係る動弁カム軸を説明する図で、
図４（Ａ）は縦断側面図、図４（Ｂ）は図４（Ａ）のＢ
方向矢視図である。FIG. 4 is a diagram illustrating a valve operating cam shaft according to prior art 1,
FIG. 4A is a vertical side view, and FIG. 4B is B of FIG. 4A.
FIG.

【図５】従来技術２に係るデコンプ装置付き動弁カム軸
を説明する図で、図５（Ａ）は縦断側面図、図５（Ｂ）
は図５（Ａ）のＢ−Ｂ線断面図である。5A and 5B are views for explaining a valve operating camshaft with a decompression device according to prior art 2, FIG. 5A being a vertical side view and FIG. 5B.
FIG. 6 is a sectional view taken along line BB of FIG.

【図６】先行試作例の説明図で、図６（Ａ）は先行試作
例１の平面図、図６（Ｂ）は先行試作例２の平面図であ
る。6A and 6B are explanatory views of a preceding trial manufacture example, FIG. 6A is a plan view of the preceding trial manufacture example 1, and FIG. 6B is a plan view of the preceding trial manufacture example 2.

【符号の説明】[Explanation of symbols]

１…軸部、２…（排気弁用）カム部、３…カムギヤ部、
４…カム部側端面、５…反カム部側端面、６…凹設部、
７…枢軸、８…遠心錘、９…８の揺動端部、１０…バネ
係止部、１１…デコンプバネ、１２…凹設部内底面、１
３…突起、１４…頭付きピン、１５…段上がり部、１６
…段下がり部、１８…バネ端部係合隙間、２３…動弁カ
ム軸本体、２５…（吸気弁用）カム部。1 ... Shaft part, 2 ... (for exhaust valve) cam part, 3 ... Cam gear part,
4 ... Cam portion side end surface, 5 ... Non-cam portion side end surface, 6 ... Recessed portion,
Reference numeral 7 ... Axis, 8 ... Centrifugal weight, 9 ... Swing end portion of 8, 10 ... Spring locking portion, 11 ... Decompression spring, 12 ... Inner bottom surface of recessed portion, 1
3 ... Protrusion, 14 ... Headed pin, 15 ... Ascended part, 16
... step-down part, 18 ... spring end engaging gap, 23 ... valve camshaft main body, 25 ... (for intake valve) cam part.

Claims (2)

【特許請求の範囲】[Claims] 【請求項１】 合成樹脂で軸部(１)とカム部(２)・(２
５)とカムギヤ部(３)とを一体に形成したものを動弁カ
ム軸本体(２３)とし、 カムギヤ部(３)の両端面(４)・(５)のうち、カム部側端
面(４)とは反対側の反カム部側端面(５)に、軸部(１)と
平行な向きに窪ませた凹設部(６)を形成し、この凹設部
(６)に、枢軸(７)で揺動自在に枢支したデコンプ用の遠
心錘(８)と、この遠心錘(８)の揺動端部(９)とバネ係止
部(１０)との間に架設したデコンプバネ(１１)とを収容
した、ことを特徴とするエンジンのデコンプ装置付き動
弁カム軸。1. A shaft (1) and a cam (2). (2) made of synthetic resin.
5) and the cam gear portion (3) are integrally formed as a valve camshaft main body (23). Among the both end surfaces (4) and (5) of the cam gear portion (3), the cam portion side end surface (4) ) Is formed on the end surface (5) on the side opposite to the cam portion, which is recessed in a direction parallel to the shaft portion (1).
In (6), a centrifugal weight (8) for decompression pivotally supported by a pivot (7), a swing end (9) of this centrifugal weight (8), and a spring locking portion (10). A valve camshaft with a decompression device for an engine, which accommodates a decompression spring (11) installed between the two. 【請求項２】 請求項１に記載したエンジンのデコンプ
装置付き動弁カム軸において、バネ係止部(１０)を、凹
設部内底面(１２)から軸部(１)と平行な向きに***させ
た突起(１３)と、この突起(１３)に挿通した頭付きピン
(１４)とで構成し、突起先端面に段差を設け、この突起
先端面の段上がり部(１５)で頭付きピン(１４)の頭部
(１６)を受け止めることにより、突起先端面の段下がり
部(１７)と頭付きピン(１４)の頭部(１６)との間にバネ
端部係合隙間(１８)を設けた、ことを特徴とするエンジ
ンのデコンプ装置付き動弁カム軸。2. The engine valve camshaft with decompression device according to claim 1, wherein the spring locking portion (10) is raised from the inner bottom surface (12) of the recessed portion in a direction parallel to the shaft portion (1). The protrusion (13) and the pin with a head inserted through this protrusion (13)
(14) and a step is provided on the tip end surface of the protrusion, and the stepped portion (15) on the tip end surface of the protrusion causes the head of the headed pin (14)
By receiving (16), a spring end engaging gap (18) is provided between the step-down portion (17) of the tip end surface of the protrusion and the head portion (16) of the headed pin (14). Characteristic engine camshaft with decompression device.