Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
1999-07-30
2001-11-20
Paik, Sang (Department: 3742)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090150, C123S090170
Reexamination Certificate
active
06318315
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a valve operating system for an internal combustion engine, which uses a rollered cam follower including a pair of support walls which are integrally formed on a cam follower body and arranged in parallel to sandwich a roller therebetween, so that outer peripheries of opposite ends of a roller shaft having the roller rotatably carried thereon are supported in through-bores in the support walls, and particularly, to a valve operating system suitable for an internal combustion engine, which includes a plurality of rollered cam followers disposed adjacent one another and having rollers put into contact with a plurality of cams, respectively, at least a portion of the cam followers being operatively connected to an engine valve, so that the valve operating characteristic of the engine valve can be changed by the movement of a switching pin which is mounted to be slidingly movable astride adjacent cam followers, thereby enabling the connected and disconnected states of the cam followers to be switched over from one to another.
2. Description of the Related Art
The above-described rollered cam follower is designed so that the slidability and the followability with respect to a cam of the cam follower are enhanced by the roller placed in contact with the cam. Such rollered cam follower is conventionally widely used In valve operating systems for Internal combustion engines.
In the conventional rollered cam follower, there are known methods for fixing the roller shaft, for example, to strike and caulk the opposite end faces of the roller shaft with a caulking punch, as shown in Japanese Patent Application Laid-open No.5-321999, and to use a bolt-shaped roller shaft and tighten and fix the shaft end outside the support wall by a nut, as shown in Japanese Utility Model Application Laid-open No.57-98350.
However, when the roller shaft is fixed by caulking, there is a problem that equipment for caulking processing is specially required, resulting in an increase in cost.
When a hollow roller shaft is used, deformation or strain is liable to be produced in the roller shaft due to the caulking. Particularly, when the deformation or strain has been produced in an outer peripheral surface of the roller shaft, certain disadvantages are encountered, such that a roller-rolling face is not smooth and the roller cannot be rotated smoothly on the roller-rolling face. Particularly, when a switching pin capable of connecting the cam followers in order to change the valve operating modes has been slidably fitted In a hollow portion of the roller shaft, the slidability of the switching pin may be injured due to the deformation or strain of the inner peripheral surface of the roller shaft in some cases, whereby the changing of the valve operating modes cannot be performed properly.
On the other hand, when the roller shaft is fixed by the bolt and the nut, the following problem is encountered: The head of the bolt and the nut protrude from the outer surfaces of the support walls, and the width of the cam follower (the maximum dimension in a direction along the roller shaft) is increased more than required. To solve the above problem due to the bolt and the nut, it is conceived to fix the roller shaft in the through-bore in the support wall by use of a resilient fastener such as a circlip. In this case, however, it is desirable that the shape and the disposition of a groove for mounting of the fastener defined in the support wall is taken into a special consideration, so that problems in respect of the strength and the like may not arise despite the defining of the groove.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a valve operating system for an internal combustion engine, wherein the above problems associated with the conventional valve operating system can be solved.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a valve operating system for an internal combustion engine, comprising at least two rollered cam followers arranged adjacent each other and having rollers put in contact with a plurality of cams, at least one of the cam followers being operatively connected to an engine valve, so that the valve operating characteristic of the engine valve can be changed by moving a switching pin mounted in adjacent ones of the cam followers for sliding movement astride the adjacent cam followers, thereby enabling connected and disconnected states of the cam followers to be switched over from one to another, wherein each of the cam followers comprises a cam follower body having a pair of support walls integrally provided thereon and arranged in parallel to sandwich the roller therebetween, and a hollow roller shaft which is fitted and supported at outer peripheries of opposite ends thereof in through-bores in the support walls, the roller shaft having the roller rotatably carried at an intermediate portion thereof; and the system further includes a first groove defined in an inner peripheral surface of the through-bore in one of the support walls to extend in a circumferential direction of the through-bore, a second groove defined in an outer peripheral surface of the roller shaft at one end thereof corresponding to the first groove, and a C-shaped resilient fastener mounted in the first and second grooves and capable of engaging with inner surfaces of the grooves astride the grooves to limit an axial relative movement of the roller shaft and the support walls, the switching pin being slidably fitted to inner peripheral surfaces of the roller shafts of the adjacent cam followers.
With the above arrangement, the axial relative sliding movement of the roller shaft relative to the through-bores in the support walls in the roller shaft can be reliably inhibited by the C-shaped resilient fastener disposed between the fitted faces of one end of the roller shaft of the rollered cam follower and through bore in one of the support walls of the cam follower body (i.e., between the first and second grooves). Therefore, the roller shaft can be fixed in a slip-off preventing manner to the support wall without special use of a caulking equipment. Moreover, a protrusion for fixing the roller shaft is not present on the outer surface of the support wall and hence, the width of the cam follower can be decreased correspondingly. In addition, particularly, the roller shaft is hollow, and the switching pin for switching-over the connected and disconnected states of the adjacent cam followers is slidably fitted to the inner peripheral surface of the roller shaft. Therefore, the roller shaft can also be used as a portion of a cam follower connecting mechanism, leading to a correspondingly simplified structure. In fixing the roller shaft, there is not a possibility that any deformation or strain is produced in the roller shaft as when the roller shaft is fixed by caulking. Therefore, not only the outer peripheral surface (the roller rolling face) and the inner peripheral surface (the switching pin sliding face) of the roller shaft can be formed into smooth surfaces to the utmost. Therefore, the rotation of the roller on the outer peripheral surface of the roller shaft is smooth, but also the switching pin can be slid smoothly on the inner peripheral surface of the roller shaft, whereby the valve operating characteristic can be switched over precisely.
In addition to the above arrangement, if a closing wall is provided outside the other support wall in one cam follower to define a working oil chamber between the closing wall and the switching pin, the closing wall is positioned outside one of the pair of support walls of the cam follower, on which the resilient fastener is not present (i.e., the other wall). Therefore, even if the roller shaft is inserted into the support wall from the side opposite to the closing wall to keep out of the closing wall, the resilient fastener can be positioned on the side of insertion opening and hence, the
Harada Takeya
Kaburagi Akira
Kobayashi Toshiki
Armstrong Westerman Hattori McLeland & Naughton LLP
Dahbour Fadi H.
Honda Giken Kogyo Kabushiki Kaisha
Paik Sang
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