Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
1999-12-22
2001-02-13
Lo, Wellun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090390, C123S090420
Reexamination Certificate
active
06186102
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a valve operating system for an internal combustion engine wherein a support shaft supporting in a rotatable manner a roller which is in rolling contact with a valve operating cam is fitted in a fitting bore provided in a rocker arm, an engage groove which extends in a direction tangential to an imaginary circle about the axis of the aforementioned support shaft is provided on the outer surface of the aforementioned support shaft, and a pin engaging with the aforementioned engage groove is fixed in the aforementioned rocker arm.
2. Description of the Prior Art
In the art, such valve operating system is already known from Japanese Patent Application Laid-open No. 10-73009, etc.
In such valve operating system, the engagement of the pin, which is fixed in the rocker arm, with the engage groove on the support shaft prevents the support shaft from moving in its axial direction and rotating about its axis, and for the case above in the art the pin is press-fitted into a press-fit bore provided in the rocker arm so as to fix the pin in the rocker arm. However, in comparison with the support shaft which supports the roller in a rotatable manner, the pin has a smaller diameter and the press-fit bore also has a small diameter, and it is therefore difficult to enhance the precision of the internal diameter of the press-fit bore and the precision of the press-fit allowance of the pin. As a result, it is difficult to say that the operability of press-fitting a pin is excellent. Moreover, if the press-fit load against the pin is increased in order to effectively prevent it from falling out, a large load is applied to the rocker arm which is undesirable in terms of ensuring the rigidity of the rocker arm.
SUMMARY OF THE INVENTION
The present invention has been carried out in view of the abovementioned circumstances, and it is an objective of the present invention to provide a valve operating system for an internal combustion engine which can solve the above-mentioned problems caused by the press-fitting of a pin and can fix the pin in the rocker arm.
In order to achieve the above-mentioned objective, according to a first characteristic of the present invention, a valve operating system for an internal combustion engine is provided, the system comprising a support shaft for supporting in a rotatable manner a roller which is in rolling contact with a valve operating cam is fitted in a fitting bore provided in a rocker arm, an engage groove which extends in a direction tangential to an imaginary circle about the axis of the aforementioned support shaft is provided on an outer surface of the aforementioned support shaft and a pin which engages with the aforementioned engage groove is fixed in the aforementioned rocker arm, wherein an insertion bore which extends in a straight line and connects through to an inner surface of the aforementioned fitting bore at a position corresponding to the aforementioned engage groove of the support shaft is provided in the aforementioned rocker arm and the aforementioned pin inserted into the aforementioned insertion bore is engaged with the aforementioned rocker arm by crimping at least one end of the aforementioned pin with a flat punch so that it engages with the aforementioned rocker arm.
In accordance with the above-mentioned arrangement of the first characteristic, when the pin is fixed in the rocker arm, since at least one end of the pin is crimped, even if the pin having a small diameter is used, the fixing operation becomes easy in comparison with the case when a press fit type pin is used, and the pin can be effectively fixed in the rocker arm with improved operability. Moreover, since at least one end of the pin is crimped by a flat punch, by setting the diameter of the flat punch so that it is larger than the diameter of the pin, the pin can be crimped effectively even when the crimping position of the flat punch relative to the pin is slightly displaced and degradation of the rigidity of the crimped part due to displacement of the crimping position is not caused.
In addition to the above-mentioned first characteristic, according to a second characteristic of the present invention, a pair of recesses are provided on the aforementioned rocker arm, each of which is formed so as to have a diameter larger than the internal diameter of the aforementioned insertion bore, they are connected to the opposite ends of the aforementioned insertion bore, and open at an outer surface of the aforementioned rocker arm on opposite sides thereof to each other; one end of the aforementioned pin is crimped so as to engage with a step between one of the aforementioned two recesses and the insertion bore, another end of the pin is integrally formed with an engage flange which engages with a step between the other one of the aforementioned two recesses and the insertion bore, and at least a part of the aforementioned pin which engages with the aforementioned engage groove is formed to have a hardness higher than that of the opposite ends of the aforementioned pin.
In accordance with such second characteristic, when the pin is fixed in the rocker arm, since one end of the pin is crimped and engages with the step between one of the recesses and the insertion bore in a state in which the engage flange at the other end of the aforementioned pin is engaged with the step between the other recess and the insertion bore, the fixing operation is easy in comparison with the case in which both ends of the pin are crimped and the pin can be fixed effectively in the rocker arm with further improved operability. Furthermore, the crimped part at one end of the pin and the engage flange can be housed inside the two recesses and do not protrude from the outer surface of the rocker arm, the length of the insertion bore, that is to say, the length of the pin can be reduced by the portion corresponding to the recesses, the precision with which the support shaft is positioned by the pin can be improved while preventing as much as possible deformation of an intermediate part of the pin due to crimping, at the same time the inertial mass of the rocker arm can be reduced by the lightening of the whole rocker arm which is achieved, and high speed operation of the engine can advantageously be effected. Moreover, since the hardness of at least the part of the pin engaging with the engage groove is comparatively high, the support shaft can be positioned effectively while preventing abrasion and deformation of the pin as much as possible, and since the hardness of the two ends of the pin is comparatively low, the crimping operation becomes easy and the crimping precision is enhanced.
In addition to the above-mentioned first characteristic, according to a third characteristic of the present invention, a pair of recesses are formed so as to have a diameter larger than an internal diameter of the aforementioned insertion bore, and the recesses are connected to the opposite ends of the aforementioned insertion bore, and open at an outer surface of the aforementioned rocker arm on opposite sides thereof to each other, both ends of the pin which are inserted into the aforementioned insertion bore so as to engage with the aforementioned engage groove, and are respectively crimped by a flat punch so as to engage with the steps between the aforementioned two recesses and the insertion bore, and at least a part of the aforementioned pin which engages with the aforementioned engage groove is formed to have a hardness higher than that of the opposite ends of the aforementioned pin.
In accordance with such a third characteristic, when the pin is fixed in the rocker arm, since the opposite ends of the aforementioned pin are crimped even if the pin having a small diameter is used, the fixing operation becomes easy in comparison with the case when a press fit type pin is used, and the pin can be fixed effectively in the rocker arm with improved operability. Furthermore, since the opposite ends of the pin are crimped with the flat
Hayashi Kazuhiko
Kosuge Mamoru
Oomori Toshitsugu
Sato Toshiyuki
Arent Fox Kintner & Plotkin & Kahn, PLLC
Honda Giken Kogyo Kabushiki Kaisha
Lo Wellun
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