Internal-combustion engines – Poppet valve operating mechanism – Hydraulic system
Patent
1991-06-18
1992-10-13
Cross, E. Rollins
Internal-combustion engines
Poppet valve operating mechanism
Hydraulic system
123 9016, F01L 902, F01L 134
Patent
active
051541432
DESCRIPTION:
BRIEF SUMMARY
STATE OF TECHNOLOGY
The invention is based on an electrohydraulic valve control device for internal combustion engines. In a known valve control device of this type, each individually controllable engine valve is assigned a solenoid valve so that in a multi-cylinder engine, there must be a number of solenoid valves which corresponds to the number of cylinders. This not only drives the costs of the entire control equipment, but it also raises the equipment's susceptibility to faults. For example, individual electrical wiring must be present between each solenoid valve and the electronic control unit, and the individual outlets for this wiring and solenoid valves must have a correspondingly elaborate switching and programming facility within the electronic control unit.
In a non-controllable engine valve, the opening stroke curve of the valve corresponds to the curve of the path of the actuating cam. The opening time cross-section is arranged so that it satisfies the maximum requirements, namely the full load at maximum number of revolutions. In the case of lower speeds, the torque and the performance of the internal combustion engine can be improved, as is known, when the closing instant of the engine inlet valve is arranged to occur earlier. Due to the lower number of revolutions and the reduced load, the required opening time cross-section will naturally also be reduced. For the shortening of the opening time cross-section, the drain passage is opened during the opening control action of the engine valve, as is known, by the solenoid valve, which is problematic in that a high opening control pressure exists at this instant in the pressure chamber, by which pressure, the solenoid valve is also pressurized. In order to be able to overcome this pressure, the solenoid valve must have either a pilot control or a strong opening magnet, in which a pilot control is time intensive, whereas a strong magnet is weight, volume, and cost intensive.
ADVANTAGES OF THE INVENTION
The electrohydraulic valve control device has an advantage that the high pressure chamber is separated in a simple way from the solenoid valve by the shut-off valve for the period during which, in any case, no control is intended to take place. In the special operating range for low loads and rotational speeds in particular, the solenoid valve can therefore control to open, as long as the shut-off valve is closed, so that as soon as the shut-off valve opens, the hydraulic oil can flow to the oil vessel via the solenoid valve, without pressure, and without loading the control unit of the solenoid valve. As soon as the actuating cam has completed its lift, and the cam piston is thus changing over from pressure stroke to suction stroke, the pressure in the pressure chamber drops sufficiently for the shut-off valve to close automatically. Any cavities remaining in the pressure chamber are filled up with control oil which flows in via the feed channel.
Due to the function related conditions, the solenoid valve can fortunately remain open at all times under low speeds and loads--the time cross-section is determined only by the first section of the actuating cam path, namely for as long as the valve piston, indirectly driven via the pressure chamber, actuates the control channel to open and thus opens the shut-off valve, whereupon the pressure in the pressure chamber is reduced and the engine valve closed again. With intermediate rotational speeds, the solenoid valve can then cycle the solenoid valve in tune with requirements, and under high speeds and loads, the solenoid valve remains shut at all times.
Naturally, the control of the shut-off valve requires tuning between pressures and closing forces of pressure chamber and shut-off valve, with the pressure in the pressure chamber being governed by the closing force of the engine valve and hence by its opening force.
In accordance with an advantageous refinement of the invention, a non-return valve which opens in the direction of the solenoid valve is arranged in the drain passage, between the shut-o
REFERENCES:
patent: 4231543 (1980-11-01), Zurner et al.
patent: 4466390 (1984-08-01), Babitzka et al.
patent: 4671221 (1987-06-01), Geringer et al.
patent: 4674451 (1987-06-01), Rembold et al.
patent: 4696265 (1987-09-01), Nohira
patent: 4716863 (1988-01-01), Pruzan
patent: 4889084 (1989-12-01), Rembold
Cross E. Rollins
Greigg Edwin E.
Greigg Ronald E.
Lo Weilun
Robert & Bosch GmbH
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