US3683875A

US3683875A - Adjustable valve timing for no control

Info

Publication number: US3683875A
Application number: US47395A
Authority: US
Inventors: Alexander Chadwick
Original assignee: Chrysler Corp
Current assignee: Old Carco LLC
Priority date: 1970-06-18
Filing date: 1970-06-18
Publication date: 1972-08-15
Anticipated expiration: 1989-08-15

Abstract

A phase shift mechanism including a plate carrying a pair of oppositely disposed idler sprockets, the plate being pivotally mounted on the crankshaft of an internal combustion engine so that the idler sprockets engage the timing chain at opposite points of its internal periphery and may adjustably control the position of the chain relative to the camshaft and crankshaft by the pivotal movement of the plate on the crankshaft thus effecting phase shifting between the two shafts and changing valve timing relative to piston position.

Description

United States Patent Chadwick ADJUSTABLE VALVE TIMING FOR NO CONTROL Inventor: Alexander Chadwick, Farmington,

Mich.

Assignee: Chrysler Corporation,

Park, Mich.

Filed: June 18,1970 Appl. No.: 47,395

Highland US. Cl ..l23/90.l5, 74/395 Int. Cl .Q ..F0ll 1/34 Field of Search ..l23/90.15, 90.31; 74/395, 397,

References Cited UNITED STATES PATENTS I i 9/ 1 933 Hemmingsen ..123/90.15 X 2/1970 Finlay ..l23/90.l5 9/ 1926 Chisholm ..123/90. 15 X i 8/ 1931 Duncan l23/90.l5 X

151 3,683,875 451 Aug. 15, 1972 1,871,268 ,8/1932 Hildebrand. ..l23/90.l5X 2,279,413 4/1942 Read ..'......l23/90.l5 X 3,441,009 4/ 1969 Rafanelli 1'23/90. l 5

FORElGN PATENTS OR APPLICATIONS $49,175 11/1942 Great Britain ..l23/90 KL 760,499 12/1933 Primary Examiner-A1 Lawrence Smith Attorney-Talburtt and Baldwin [57] ABSTRACT A phase shift mechanism. including a plate carrying a ,pair ofoppositely disposed idler sprockets, the plate being pivotally mounted on the crankshaft of an internal combustion engine so that the idler sprockets engage the timing chain at opposite points of its internal periphery and may adjustably control the position of the chain relative to the camshaft and crankshaft by the pivotal movement of the plate on the crankshaft thus efiecting phase shifting between the two shafts and changing valve timing relative to piston position.

2 Claims, 3 Drawing Figures France ..123/9O KL United States Patent 11 3,683,875 Chadwick [451* Aug. 15, 1972 BACKGROUND This invention relates to a phase shift mechanism for changing the angular relationship between crankshaft and camshaft members while they are in motion. It has particular application to the control of emissions in-intemal combustion engines by effecting phase shifting between the crankshaft and camshaft and thus adjusting valve timing relative to piston position.

Workers in the art are already aware of the fact that the certain undesirable components present in engine exhaust can be decreased by providing certain timing modifications between the combustion chamber intake and exhaust valves.

Specifically, the object of the standard valve timing arrangement is to retain a minimum amount of exhaust in the combustion chamber. This is usually accomplished by arranging for the exhaust valves to close at just the moment the pistons reach the top of their stroke thereby allowing as much of the exhaust gases as possible to leave the combustion chambers of the engine.

If the valve timing is modified so as to close the exhaust valves early, that is before the pistons reach the top of their stroke, a certain amount of the exhaust gases are retained in the combustion chamber. The amount retained can be controlled by adjusting the time at which the exhaust valves are closed. I

When residual exhaust gases are retained by adjusting the valve timing, inter-mixing of the fuel mixture with the residuals occurs in the combustion chamberv during the subsequent steps of the combustion cycle. It has been demonstrated that such inter-mixing reduces the amount of carbon monoxide and unburned hydrocarbons in the exhaust. More importantly, it retards the formation of the oxides of nitrogen (N Since the amount of undesirable exhaust constituents produced vary with the speed of the engine, it is important that a valve timing arrangement for retaining residual exhaust gases be dynamic. That is, it should be capable of effecting adjustable variations in the valve timing while the engine is in operation and during different speeds.

Several adjustably variable valve timing arrangements have been suggested in the prior art to provide efficient engine operation at different speeds. However, none of these have been as readily incorporated into production engines as the arrangement disclosed herein.

SUMMARY OF THE INVENTION This invention has as its primary object the provision of a simplified mechanical arrangement for dynamically varying the rotational position between the camshaft and crankshaft in order to adjust valve timing. The purpose is to control the retention of residual exhaust gases in the combustion chambers of the engine and to thereby reduce the amount of certain constituents in the exhaust, particularly the amount of the nitrous oxides (N0 These and other objects are attained by providing a pair of idler sprockets on pivotally mounted support means which horizontally positions the sprockets between the crankshaft and camshaft whereby the valve operating times may be changed by the movement of the valve operating shaft or camshaft relative to the crankshaft when the support means is pivoted to move the sprockets relative to the chain. The support means comprises a plate pivoted from the crankshaft axis, the plate including a geared portion. A control gear, rotatably controlled bythe throttle for example, engages the geared portion of the support plate to control plate position. The mechanism is operable while the engine is running to provide dynamic phase variation.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an end view of an internal combustion engine including a phase control or phase shift mechanism by means of which the rotational relationship between the camshaft and crankshaft and thus justably controlling its position according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring specifically to FIGS. 1 and 2, an engine 10 is shown which includes a crankshaft 12 carrying a cranlmhaft gear 14 and a camshaft 16 carrying a camshaft gear 18. Gears 16 and l8are connected by timing chain 20 such that rotation of crankshaft 12 causes the simultaneous rotation of camshaft 16.

A phase shift mechanism generally indicated by numeral 22 is positioned

intermediate gears

14 and 16 at at least partially within the periphery of timing chain 20. The mechanism comprises support means such as plate 24 on which two oppositely disposed idler sprockets 26 and28 are carried in a position to engage chain 20 internally of its periphery as shown in FIG. 1. Plate 24 is pivotally disposed about the axis of crankshaft 12 by being mounted thereon.

Crankshaft gear 14 bears a fixed rotational relationship with crankshaft 12 on which it is fixedly mounted and thus its operation and position is directly related to piston position. Likewise, camshaft gear 16 bears a fixed rotational relationship with camshaft gear 18 on which it is fixedly mounted and thus its operation and position is directly related to valve position.

Usually, timing chain 20 provides a fixed rotational relationship between gears 14 and 18 and thus between

shafts

12 and 16 and ultimately between the piston and valve positions. However, in the engine shown in FIGS.

. 1 and 2 this is not the case. Pivo'tally mounted phase shift plate 24 provides a dynamic and adjustable or variable rotational relationship between crankshaft 12 and camshaft 16.

The rotational relationship or phase is determined by the pivotal position of plate 24 on. crankshaft 16. FIG. 1, by means of the solid lines, shows plate 24 in the operating position it would assume when the engine is operating at full load. As indicated by the horizontal position of the top of plate 24 and sprockets 26 and 28,

at full engine load crankshaft and

camshaft gears

14 and 16 are rotating in a given phase relationship whereby the valves and pistons (not shown) ofthe engine are operated in a predetermined sychronized relationship as is well established in the art.-

As the load decreases, plate 24 may be pivoted to a different position as shown in phantom. This change causes a positional change in the angular relationship between chain 20 and gears 14 and 18 due to the change in tension exerted by each of the sprockets 26 and 28 against chain 20. The decrease in distance between sprocket 28 and gear 14' and between sprocket 28 and gear 18 and the increase in distance between sprocket 26 and gears 14 and 18 result in re-adjustment of chain 20 and the rotation of gear 18 out of phase relative to gear 14.

The phase relationship between gears 14 and 18 is thereby shifted to one in which camshaft gear 18 lags behind crankshaft gear 14 slightly whereby the engine valves operate at a different time relative to the position of the pistons. Specifically, the lag causes the early closing of the exhaust valves and the retention of additional residual exhaust gas in the combustion chamber. Pivotal movement of plate 24 in the opposite direction will of course have the opposite effect.

The position of plate 24 is controlled by the arrangement shown in FIG. 3. Plate 24 is shaped to include a geared portion or ear 30. A rotatable control gear 32 engages portion 30 and may be rotated while the engine is running to adjust the position of plate 24 and thus vary the operating time of the valves.

Gear 32 may be controlled by the accelerator pedal position as indicated in FIG. 3'. However, it is possible to use other functions or schedules if desired such as, engine speed,.car speed, and the like.

The embodiments of the invention in which an exclusive property or right is claimed are defined as follows:

1. In an internal combustion engine, the combination with a camshaft, a crankshaft and a drive chain connecting the shafts, of a pair of idler sprockets for engaging the chain and a pivotally mounted support means carrying the idler sprockets and positioning them against the inside periphery of the chain at generally opposite points whereby the rotational relationship between the shafts may be varied by pivoting the support means and changing the relative tension exerted by the sprockets against the chain, the improvement wherein the support means comprises a single body pivotally mounted on the crankshaft and carrying both sprockets thereon, the support body including a geared portion, the combination further including a control gear for controlling the position of the support body, the control gear being rotatably carried by the engine to engage the geared portion on the support body whereby rotation of the control gear causes the support body to pivot on the crankshaft and change the position of idler sprockets.

2. The combination according to claim 1 wherein the control gear is operably connected to the engine accelerator.