Internal-combustion engines – Engine speed regulator – Responsive to deceleration mode
Reexamination Certificate
1999-12-16
2001-03-27
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Engine speed regulator
Responsive to deceleration mode
Reexamination Certificate
active
06205975
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to engine compression release brakes, and more particularly, to a method and apparatus of controlling the actuation of a compression brake.
BACKGROUND ART
Engine retarding devices of the compression release type may utilized in work machines such as on-highway trucks and the like. A compression release brake assembly utilizes compression within the truck's engine to assist the truck's main braking system in order to slow the truck. In effect, such compression release brake assemblies convert the truck's internal combustion engine into an air compressor in order to develop retarding horsepower which is utilized to assist in slowing the truck.
Compression release brake assemblies which have previously been designed typically include a fluid system having a master cylinder having a piston which is actuated by a cam lobe or push rod associated with an exhaust valve, intake valve, or fuel injector corresponding to a first engine cylinder. Actuation of the piston associated with the master cylinder controls actuation of a piston associated with a slave cylinder which selectively opens and closes the exhaust vale of a second, different engine cylinder near the end of the compression stroke thereby causing the mechanical work performed during the compression stroke to be dissipated and hence not “recovered” during the subsequent power stroke.
In one embodiment of a hydraulically actuated compression brake, controlling the pressure of the hydraulic fluid may be useful in achieving the desired timing of the opening of the exhaust valve, with the desired force. As the cylinder pressure varies within a cylinder, the desired force for opening the exhaust valve also varies. Excessive exhaust actuation speed, which may be caused by excessive actuating fluid pressure, may cause a reduction in the service life of the exhaust valve. For example, if the actuating fluid pressure is too high, the lift of the exhaust valve may potentially overshoot and interfere with the piston, thereby potentially damaging the piston or valve. In addition, the faster the exhaust valve closes, which may be influenced by fluid pressure, the greater the velocity at which the exhaust valve seats. If the exhaust valve closes too rapidly, damage to the exhaust valve and/or the associated valve seat may occur. An inadequate actuating fluid pressure may result in the exhaust valve not being opened.
The present invention is directed to overcoming one or more of the problems identified above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention, a method of controlling an actuation of a compression brake associated with a combustion engine is disclosed. The engine has a fluid circuit for delivering a fluid to the compression brake. The engine also includes a cylinder having an associated exhaust valve. The method includes the steps of determining a desired timing of an actuation of the brake, determining an air pressure of the engine, and determining a desired fluid pressure in response to said timing and said air pressure.
In another aspect of the present invention, an apparatus adapted to control an actuation of a compression brake associated with a combustion engine is disclosed. The engine includes a fluid circuit for delivering a fluid to the compression brake, the fluid enabling the control of the compression brake. The engine includes a cylinder having an associated exhaust valve. The apparatus includes a speed sensor adapted to sense an engine characteristic indicative of an engine speed and responsively generate a speed signal, an air pressure sensor adapted to sense a characteristic indicative of an engine air pressure and responsively generate an air pressure signal, and a controller adapted to receive the speed signal and the air pressure signal, establish a desired timing of an actuation of said brake, determine an air pressure of said engine in response to said air pressure signal, and determine a desired fluid pressure in response the air pressure.
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Funke Steven J.
Leman Scott A.
Mickiewicz Matthew G.
Ruedin Joshua C.
Caterpillar Inc.
Dolinar Andrew M.
McPherson III W. Bryan
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