Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Patent
1995-05-12
1998-01-06
Lo, Weilun
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
123 9031, F01L 1300, F01L 3100
Patent
active
057043167
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a valve drive system for opening and closing an intake valve or an exhaust valve of an internal combustion engine, and more particularly, to a valve drive system having therein a mechanism for varying a valve timing.
BACKGROUND ART
Valve drive systems having a variable valve timing mechanism therein are disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication Nos. 59-54713 and 59-110816. These conventional systems comprise a cam rotatably mounted on a camshaft; and a connecting device for connecting the camshaft and the cam and adjusting a rotational phase of the cam with respect to the camshaft. This connecting device includes a pressure chamber for hydraulically connecting the camshaft and the cam, and a hydraulic circuit for adjusting a hydraulic pressure in the pressure chamber in accordance with the operation state of an internal combustion engine, and the rotational phase of the cam with respect to the camshaft is adjusted by means of the pressure in the pressure chamber.
In the case of the connecting device described above, accurate control of the rotational phase of the cam with respect to the camshaft, that is, valve timing, entails fine control of the pressure in the pressure chamber by means of a solenoid-controlled valve in the hydraulic circuit. Moreover, the hydraulic circuit requires use of a hydraulic pump, as a hydraulic pressure source, for generating a high hydraulic pressure, and oil leakage from the hydraulic circuit must be prevented securely. Consequently, components of the connecting device require high-accuracy machining, and the number of components of the connecting device increases.
The object of the present invention is to provide a valve drive system of a simple construction, capable of varying a timing for opening or closing a valve without requiring an electronic control, and improving the output of an internal combustion engine throughout an operational region of the internal combustion engine.
SUMMARY OF THE INVENTION
The above object is achieved by a valve drive system of the present invention. The valve drive system of the present invention comprises, a first rotating member adapted to be rotated in association with a crankshaft of an internal combustion engine, a second rotating member rotatably provided with respect to the first rotating member, a cam provided for the second rotating member and adapted to cooperate with one valve of intake and exhaust valves, and connecting means for connecting the first rotating member and the second rotating member to allow the first and second rotating members to relatively rotate each other. This connecting means has a transmission function to transmit the rotatory force of the first rotating member to the second rotating member, thereby causing the cam to rotate together with the second rotating member. The connecting means also has a variable function to restrict an increase of the rotating speed of the second rotating member based on the restoring force of a valve spring of the valve in accordance with the operation state of the internal combustion engine, in a process of reducing the cam lift as the cam rotates, and settle the time of termination of the cam lift with respect to the rotational phase of the crankshaft.
According to the valve drive system, as described above, the speed of rotation of the second rotating member relative to the first rotating member is increased by means of the valve spring in the process of reducing the cam lift. However, this increase of the speed of rotation is restricted by the variable function of the connecting means depending on the operation state of the internal combustion engine, whereby the time of termination of the cam lift, that is, valve closing timing, is controlled.
The transmission and variable functions of the connecting means can be effectuated by means of a fluid coupling which connects the first and second rotating members.
If the second rotating member has a hollow shape, the relative rotation of the first and second
REFERENCES:
patent: 5105679 (1992-04-01), Voigt
patent: 5168772 (1992-12-01), Adamis et al.
patent: 5219313 (1993-06-01), Danieli
patent: 5239885 (1993-08-01), Voigt
patent: 5333579 (1994-08-01), Hara et al.
patent: 5417186 (1995-05-01), Elrod et al.
Fujimoto Akihiro
Higashi Hirofumi
Isomoto Jun
Miyamura Noriyuki
Murata Shinichi
Lo Weilun
Mitsubishi Jidosha Kogyo Kabushiki Kaisha
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