US 2003/0196628 A1 · VCT MECHANISM HAVING A LOCK PIN ADAPTED TO RELEASE AT A PRESSURE HIGHER THAN THE PRESSURE REQUIRED TO HOLD THE LOCK PIN IN THE RELEASED POSITION

Abstract

A variable camshaft timing phaser for an internal combustion engine that varies rotation phase including a housing, a rotor, a locking pin, and a piston. The locking pin is moveable in a first direction, which urges a tapered end of the locking pin to engage a tapered recess in the rotor, and a second direction, opposite the first direction, to disengage the rotor. The is driven by an engine output in synchronism with the engine revolutions, the rotor is connected to the camshaft and has a fluid passage connecting a source of engine oil to the tapered recess in the rotor. The piston is located within the fluid passage and has a piston surface contacting the locking pin. The piston has a cross-section that is less than the cross-section of the locking pin, and blocks the fluid passage when the locking pin is locked, moving to a position which allows fluid to pass by the piston in the recess and press on the locking pin, so that higher pressure is required to unlock the locking pin than to hold it in its unlocked position.

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Claims6

Dependent claims

A variable camshaft timing phaser for an internal combustion engine having at least one camshaft, comprising:

a housing having an outer circumference for accepting drive force;
a rotor for connection to a camshaft, coaxially located within the housing, capable of rotation to shift the relative angular position of the housing and rotor, having a tapered recess in an outer circumference and a fluid passage coupling the tapered recess to a source of engine fluid pressure;
a locking pin slideably located in a bore, comprising a body having a diameter adapted to a fluid-tight fit in the bore, and an inner end with a tapered portion adapted to fit in the tapered recess, the locking pin being moveable in the bore from a locked position in which the tapered end fits into the tapered recess, locking the relative angular position of the housing and the rotor, to an unlocked position in which the housing and the rotor are free to move;
a spring located in the bore opposite the inner end of the locking pin, urging the locking pin inward toward the locked position;
and
a piston located within the fluid passage with a fluid tight fit, the piston being movable from a first position inside the fluid passage and blocking fluid flow therein, to a second position at least partially in the tapered recess and allowing fluid to flow past the piston and into the tapered recess;
the piston being in the first position when the locking pin is in the locked position with the tapered end in the tapered recess, so that when the locking pin is in the locked position and fluid pressure is introduced into the fluid passage, the piston presses against the tapered end of the locking pin against the force of the spring, and when the pressure reaches a release level, the piston overcomes the force of the spring and moves the locking pin outwards toward the unlocked position, and when the piston reaches the second position fluid flows past the piston and applies pressure against the inner end of the locking pin, so that a holding level of pressure holds the locking pin in the unlocked position;
the piston having a cross-sectional area which is less than a cross-sectional area of the diameter of the body of the locking pin, so that the release level of pressure is greater than the holding level of pressure.

5 more elements

Dependencies are inferred from the claim text.

Description1,836 words

Summary923 words

#1. Field of the Invention

#The invention is related to a hydraulic control system for controlling the operation of a variable camshaft timing (VCT) system. More specifically, the present invention relates to a control system for vane-type or similar cam phasers utilizing oil pressure to vary the crankshaft-to-camshaft phasing.

#2. Description of Related Art

Brief description of the drawings1 figure

#FIG. 1 shows a front view of a VCT phaser incorporating the invention. FIG. 2a & 2b show engaged and disengaged positions of the present invention respectively, in a detail from within box 2 in FIG. 1.

Detailed description876 words

#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) are fluid chambers (6) and (7). 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 oil via passages (12) and (13) to chambers (6) and (7), respectively. Pressurized oil introduced by valve (4) into passages (12) will push vanes (5) counterclockwise relative to the housing (1), forcing oil out of chambers (6) into passages (13) and into valve (4). 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, a locking pin (10) slides in a bore (17) in the housing (1), and is pressed by a spring (21) into a recess (19) in the rotor (2) to lock the rotor (2) and housing (1) into a fixed rotational position. Vent (11) allows any oil which might leak past the piston (10) to be discharged. A bushing (16) may be provided in the bore, surrounding at least the inner end (20) of the locking pin, to provide a better seal.

#A fluid passage (15) feeds pressurized oil from the engine oil supply (not shown) into the recess (19). A ball-shaped or cylindrical piston (14) is located within the fluid passage (15) and contacts the inner tip (18) of locking pin (10). The piston (10) is sized so as to fit in and fully block passage (15) when the locking pin (10) is engaged, as shown in FIG. 2a.

Vct mechanism having a lock pin adapted to release at a pressure higher than the pressure required to hold the lock pin in the released position

Life of this patent

Vct mechanism having a lock pin adapted to release at a pressure higher than the pressure required to hold the lock pin in the released position

Life of this patent

Life of this patent

Abstract

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Claims6

Description1,836 words

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Classification8 codes

Life of this patent

Description1,836 words