Internal-combustion engines – Poppet valve operating mechanism – Lubrication
Reexamination Certificate
1999-08-31
2001-07-10
Leung, Philip H. (Department: 3742)
Internal-combustion engines
Poppet valve operating mechanism
Lubrication
C123S1950HC, C123S19800E
Reexamination Certificate
active
06257188
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a structure for mounting a cylinder head cover of an overhead valve-type internal combustion engine having a valve mechanism in a cylinder head.
2. Description of the Related Art
As internal combustion engines in which a cylinder head cover is mounted on a cylinder head by using bolts and coil springs, those which are disclosed in Japanese Utility Model Unexamined Publication Nos. 101449/1981 and 162395/1983 are known.
In the internal combustion engine disclosed in Japanese Utility Model Unexamined Publication No. 101449/1981, each bolt is split into a bolt head and an externally threaded portion, upper and lower end portions of the coil spring are integrally coupled to a lower end of the bolt head and an upper end of the externally threaded portion, a collar portion is formed on an upper end of a rubber boot capable of fitting over an outer periphery of the coil spring, and the rubber boot is fitted and inserted in a through hole formed in a flange portion of the cylinder head cover. The externally threaded portion, the coil spring, and the bolt head are consecutively fitted and inserted in the rubber boot, and after a tip of the externally threaded portion is made to abut against an internally threaded portion in the cylinder head, the bolt head is rotated so as to screw the externally threaded portion into the internally threaded portion, thereby mounting the cylinder head cover onto the cylinder head.
In this device, since the torque applied to the bolt head is transmitted to the externally threaded portion by means of the coil spring, unless the torsional rigidity of the coil spring is very high, the externally threaded portion cannot be securely threadedly engaged in the internally threaded portion and is liable to come off. If the torsional rigidity of the coil spring is increased to overcome this problem, the compressive rigidity of the coil spring also becomes high correspondingly, so that there is a drawback in that the effect of resiliently mounting the head cover declines appreciably.
Meanwhile, with the internal combustion engine disclosed in Japanese Utility Model Unexamined Publication No. 162395/1983, internally threaded portions are formed in a rocker shaft holder for pivotally supporting a rocker arm, coil springs are loosely fitted over external threads which penetrate the cylinder head cover from above to below, and the external threads are threadedly secured in the internally threaded portions, wherein the peripheral edge portion of the cylinder head cover is pressed against the cylinder head through packing by means of the spring forces of the coil springs.
With the with the internal combustion engine disclosed in Japanese Utility Model Unexamined Publication No. 162395/1983, top portions of the external threads substantially project upward from the top surface of cylinder head cover, and the overall height of the internal combustion engine becomes high, so that it is difficult to make the internal combustion engine compact.
In addition, if the amount of projection of the external threads from the cylinder head cover is made small, the rigidity of the coil springs becomes high, and the force with which the cylinder head cover is pressed changes substantially with respect to the change in the amount of screwing in of the external threads, making it difficult to obtain an appropriate pressing force.
SUMMARY OF THE INVENTION
The invention of this application relates to an improvement of the structure for mounting a cylinder head cover of an internal combustion engine which overcomes the above-described drawbacks. According to a first aspect of the invention, there is provided a structure for mounting a cylinder head cover of an internal combustion engine in which an outer peripheral edge of a cylinder head cover abuts against a cylinder head, and the cylinder head cover is mounted on the cylinder head, including: a connecting member passed through a recessed portion which is formed in a central portion of the cylinder head cover as viewed in a widthwise direction perpendicular to a crankshaft, the connecting member having one end fixed to the cylinder head and the other end provided with a spring receiving portion, and a coil spring arranged around the connecting member, the coil spring being clamped in a compressed state between a bottom surface of the recessed portion of the cylinder head cover and the spring receiving portion. The coil spring, the connecting member, and the spring receiving portion are accommodated within the recessed portion of the cylinder head cover.
Since the present invention is arranged as described above, the connecting member does not project upward from the recessed portion of the cylinder head cover, and the coil spring and the spring receiving portion are accommodated within the recessed portion of the cylinder head cover, thereby making it possible to attain a compact internal combustion engine.
In addition, since the length and the winding diameter of the coil spring can be made large in correspondence with the depth and area of the recessed portion of the cylinder head cover, it is possible to use a coil spring having a large amount of deformation and a small spring constant. Hence, the cylinder head cover can be mounted on the cylinder head with a pressing force of a such a magnitude that allows the cylinder head cover to be pressed against the cylinder head appropriately. In addition, its pressing force can be finely adjusted.
Further, according to a second aspect of the invention, there is provided a structure for mounting a cylinder head cover of an internal combustion engine in which an outer peripheral edge of a cylinder head cover abuts against a cylinder head, and the cylinder head cover is mounted on the cylinder head, including: a connecting member passed through a recessed portion which is formed in an upper portion of the cylinder head cover, the connecting member having one end fixed to the cylinder head and the other end provided with an upper spring receiving portion; and a coil spring arranged around the connecting member, the coil spring being clamped in a compressed state between the upper spring receiving portion and a lower spring receiving portion provided in a bottom surface-side of the recessed portion of the cylinder head cover and by means of an annular elastic member. The lower spring receiving portion is accommodated within the recessed portion of the cylinder head cover.
With the above structure, the projecting length of the connecting member projecting from the upward portion of the cylinder head cover can be formed as short as possible, thereby making it possible to attain a compact internal combustion engine.
Further, according to a third aspect of the invention, there is provided a structure for mounting a cylinder head cover of an internal combustion engine in which an outer peripheral edge of a cylinder head cover abuts against a cylinder head, and the cylinder head cover is mounted on the cylinder head, including: a connecting member passed through a recessed portion which is formed in an upper portion of the cylinder head cover, the connecting member having one end fixed to the cylinder head and the other end provided with a spring receiving portion; and a coil spring arranged around said connecting member, the coil spring being clamped in a compressed state between a bottom surface of said recessed portion of the cylinder head cover and the spring receiving portion. The connecting member is secured to the cylinder head between an intake camshaft and an exhaust camshaft, which are provided within the cylinder head cover.
In a conventional case that the connecting member such as a bolt is mounted on a camshaft holder or the like, located above the cam shaft, it is difficult to secure the length of a fastening portion of the bolt, whereby there is a fear that the retaining force of the coil spring is decreased. In addition, when the length of the fastening portion is increased, the size of the internal co
Fujii Noriaki
Yoshiura Kouta
Armstrong Westerman Hattori McLeland & Naughton LLP
Dahbour Fadi H.
Honda Giken Kogyo Kabushiki Kaisha
Leung Philip H.
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