Air venting mechanism for variable camshaft timing devices

#1. Field of the Invention

#The invention pertains to the field of Variable Camshaft Timing (VCT). More particularly, the invention pertains to air venting mechanism for variable camshaft timing devices.

#2. Description of Related Art

#FIG. 1 shows a schematic of a phaser of the present invention.

#FIG. 2a shows a first aspect of the present invention.

#FIG. 2b shows a second aspect of the present invention.

#Referring to FIG. 1, a vane-type VCT phaser comprises a housing (1), the outside of which has sprocket teeth (8) which mesh with and are driven by timing chain (9). Inside the housing (1), a cavity including fluid chambers (6) and (7) is defined. Coaxially within the housing (1), free to rotate relative to the housing, is a rotor (2) with vanes (5) which fit between the chambers (6) and (7), and a central control valve (4) which routes pressurized fluid via passages (12) and (13) to chambers (6) and (7), respectively. Pressurized fluid introduced by valve (4) into passages (12) will push vanes (5) counterclockwise relative to the housing (1), forcing fluid out of chambers (6) into passages (13) and into valve (4). A fluid passage (15) supplies fluid such as engine oil and suitably pressurizes a lock pin (10) slidably fitted within a casing (17). It will be recognized by one skilled in the art that this description is common to vane phasers in general, and the specific arrangement of vanes, chambers, passages and valves shown in FIG. 1 may be varied within the teachings of the invention. For example, the number of vanes and their location can be changed, some phasers have only a single vane, others as many as a dozen, and the vanes might be located on the housing and reciprocate within chambers on the rotor. The housing might be driven by a chain or belt or gears, and the sprocket teeth might be gear teeth or a toothed pulley for a belt.

#Referring to FIG. 1 and the detail of FIG. 2a, in the phaser of the invention, lock pin (10) slides along the walls of casing (17) which may be a bore in the housing (1), and is engaged by a spring (21) for allowing an inner end (20) of pin (10) to fit into a recess (19) formed in the rotor (2) to lock the rotor (2) and housing (1) into a fixed rotational position. Vent (11) allows any fluid which might leak past passage (15) before recess (19) is closed by an inner end (20) of lock pin (10) to be discharged.

#The fluid passage (15) feeds pressurized fluid from the engine oil supply (not shown) into the recess (19). The dimensions of relevant parts such as passage (15) and lock pin (10) are chosen such that at engine start-up, the piston cannot push the lock pin (10) back against the force of the spring (21) until the supply oil pressure has risen to a level which is sufficient that fluid in passages (12) or (13) can fully fill chambers (6) and (7) and purge any air which might have been introduced due to leakage while the engine was shut down. In order to facilitate an improved means of purging the air inside the chambers (6) and (7), a vent passage (18) is provided which interposed between one of the chambers (6) and (7), and lock pin mechanism that has a suitable air outlet. For example, chamber (7) is connected via vent passage (18) to the lock pin mechanism as shown in FIG. 2a, wherein vent (11) serves the dual purpose of both purging the air inside the chamber (7) and allowing any fluid which might leak past passage (15) to be discharged. In this case, lock pin (10) may have structure similar to a spool valve in that at a first position, air within chamber (7) is purged. Whereas, on the other hand, when the lock pin (10) is at a second position as shown in FIG. 2b, vent passage (18) is structurally stopped from acting as a conduit for communicating between one chamber and the lock pin mechanism. The stoppage can be achieved in various ways. Depending on the shape of the lock pin, a flange can be formed around the same if the pin is of annular shape. If the lock pin body has an elongated polygonal shape, any element extending from the lock pin body that is sufficient to block vent passage (18) thereby stopping fluid communication function of the same is contemplated by the present invention. The flange or the element is denoted by numeral (23).