US20090013967A1

US20090013967A1 - Spring-less valve train for internal combustion engine

Info

Publication number: US20090013967A1
Application number: US11/774,907
Authority: US
Inventors: George Louie
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-07-09
Filing date: 2007-07-09
Publication date: 2009-01-15
Also published as: WO2009035482A2; WO2009035482A3

Abstract

A rocker arm (210) for use in a reciprocating, internal combustion engine includes a tip (235) and a seat (240). The tip and seat are urged to move by cams (220, 225) on a shaft (230). As the shaft rotates, the cams alternately apply force to the tip and the seat, causing the rocker arm to rotate about a pivot shaft (215). A valve (100) and valve stem (110′) are attached to the rocker arm. The valve is urged to open and close by motion of the rocker arm. Thus the valve is opened and closed through the use of positive camming and reciprocating forces only. No conventional valve spring is required to close the valve. Thus valve floating at high engine speeds is prevented and engine performance is improved.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

My U.S. Pat. No. 7,228,829, granted 2007 Jun. 12, shows a valve timing adjustment system.

BACKGROUND

1. Field
The field is internal combustion engines and in particular valve trains therefor.
2. Prior Art
Internal combustion engines generally comprise an engine block with one or more cylinders. Each cylinder contains a reciprocating piston and at least two openings that are opened and closed by valves. An inlet valve admits a fuel-air mixture and an outlet valve permits exhaust gases to escape. Both valves are held normally closed by strong springs to prevent the unwanted escape of gases during the compression and power strokes of the engine. During operation of the engine, each valve is repeatedly pushed open at predetermined times and rates by lobes on a camshaft that cam, either directly or indirectly, the ends of the valve stems, in well-known fashion. In many cases, the camshaft lobes cam on one end of a rocker arm that pivots about a central axis; the other end of the rocker arm opens the valve. In either arrangement, the camshaft works against the force of the springs to open the valves periodically; the valves are closed by the springs when they are not cammed open.
FIG. 1 shows a side view of a prior-art valve 100 that seats within a cylinder 101 in an engine block 105. Valve 100 has a stem 110 that extends upward from block 105. The upper end of stem 110 is secured to a bushing 115 that holds a spring 120 in compression against the top of block 105, thereby holding valve 100 in a normally-closed (up) position as shown. A rocker arm 125 pivots on a shaft 130. A cam 135 having a lobe 140 rotates on a camshaft 145 that is connected to the crankshaft by a timing belt or chain (not shown) so that the camshaft rotates in synchronism with the engine's crankshaft (not shown). When lobe 140 rotates from the side position shown to an upward position (not shown) it pushes upward against the left side of rocker arm 125, causing arm 125 to rotate in a clockwise (CW) direction about shaft 130. Arm 125 pushes downward on valve stem 110, thereby opening valve 100, as indicated by dashed lines. When valve 100 is open gases can pass to or from cylinder 101 via an inlet or exhaust port 150. Each cylinder has a minimum of two such valves, an inlet and an outlet. The diameter of valve 100 is typically between 1.5 and 10 cm, depending upon the size of the engine. In an engine with a valve diameter of three cm, the travel of valve 100 between its open and closed conditions is about one cm.
Pushing the inlet and exhaust valves open against the opposing force of the springs uses energy that is derived from the combustion cycle of the engine. Friction at all points between the cam lobes and the valve stems contributes to wear and heating of the engine and adds strain to the engine's timing belt, motor oil, and starter. This energy is lost and not available at the engine's crankshaft. Also it creates additional heat in the engine. This results in a reduction in engine efficiency that is measurable in terms of shorter engine life and increased fuel consumption. In addition, when the engine is operated at very high speeds, the springs lack adequate force to close the valves before they are to be opened again. When this happens, the rocker arm separates from contact with the valve stem and the valves are said to float, i.e. remain open. In this condition, engine output and efficiency drop to nearly zero.

SUMMARY

In accordance with an aspect of one embodiment, an internal combustion engine uses no strong springs to hold the inlet and exhaust valves closed. Instead, the valves are opened and closed at predetermined times and rates by a camshaft that applies both opening and closing forces to the inlet and exhaust valve stems. Removing the requirement to compress the valve springs during engine operation results in improved engine efficiency that is realized in reduced fuel consumption, a lighter engine, lower engine wear, less heat, and improved engine performance. Since the valves are forced open and closed by the camshaft, floating of the valves at high speeds is prevented.

DRAWING FIGURES

FIG. 1 shows a prior-art valve system.

FIGS. 2 through 6 show aspects of a first embodiment.

FIG. 7 shows an alternative embodiment.

REFERENCE NUMERALS


100	Valve	101	Cylinder	105	Block
110	Stem	111	Shoulder	115	Bushing
120	Spring	125	Arm	130	Pivot
135	Cam	140	Lobe	145	Shaft
150	Port	200	Hole	205	Pin or rod
206	Spring	210	Arm	214	Fastener
215	Shaft	220	Cam	221	Lobe
225	Cam	226	Lobe	230	Shaft
235	Tip	240	Seat	500	Shaft
505	Shaft

FIRST EMBODIMENT

Description—FIGS. 2 through 4

FIG. 2 is a perspective view of a cam, rocker arm, and valve assembly. In one aspect of a first embodiment, a valve 100 seats in a cylinder 101 (FIGS. 3 through 6) of an internal combustion engine (not shown). A valve stem 110′ extends upward from valve 100. The diameter of the upper end of stem 110′ is reduced and passes through a hole 200 in a pin or rod 205 that is rotatably secured within a rocker arm 210. Stem 110′ has a shoulder 111 in where the diameter of the upper portion of stem 110′ decreases. This prevents the lower portion of stem 110′ from passing into hole 200. The upper end of stem 110′ extends above pin 205. The top of pin 205 and a fastener 214 hold a spring 206 in compression. Fastener 214 preferably is a bolt head that is secured to the top of stem 110′ but can also be a bushing, clevis, etc. Fastener 214 can be adjustable, as in the case of a screw or bolt that screws into the upper end of stem 110′, or non-adjustable as in the case of a clip. Thus valve 100 and its stem 110′ are springably held captive in pin 205. Spring 206 is pushed upwardly when rod 205 is moved upwardly by the rocker arm and in turn pushes fastener 214 and hence valve 100 upwardly to a closed position. Spring 206 also accommodates tolerance variations and holds valve 100 in a closed position as the engine wears or changes dimensions due to heating and cooling. Thus spring 206 and shoulder 111 form a pair of facing shoulders that are pushed up and down, respectively, by rod 205. The strength and compression of spring 206 is significantly less than that of spring 120 (FIG. 1). As such, the energy spent in further compressing spring 206 during operation of the engine is negligible.
Two cams 220 and 225 having lobes 221 and 226, respectively, extend radially from a camshaft 230 that turns in synchronism with the engine's crankshaft (not shown). Camshaft 230 is turned by a timing belt or chain (not shown) in conventional fashion. The shapes of cams 220 and 225 are complimentary, i.e., they work in concert to control the opening and closing of valve 100. Cam 220 varies in thickness from a low point to a long lobe 221 of uniform thickness. Cam 225 varies in thickness from a uniform low region to a relatively short lobe 226. In this example, cams 220 and 225 are shown in positions that cause valve 100 to be open. As lobe 226 of cam 225 forces seat 240 downward, cam 225 causes valve 100 to open and thus is an opening cam. When lobe 221 of cam 220 forces tip 235 to the left, in turn causing arm 210 to rotate CCW, cam 220 causes valve 100 to close and thus is a closing cam. Closing cam 220 has a relatively long lobe 221 that extends circumferentially approximately 180 degrees around cam 220, thereby holding valve 100 closed during the compression and combustion portions of the engine cycle. Opening cam 225 has a relatively short lobe 226 that extends circumferentially about 90 degrees around cam 225 resulting in a shorter open time for valve 100, suitable for the relatively shorter-duration intake and exhaust portions of the engine cycle. The difference in height between the low point and the high points of cams 220 and 225 is preferably about one cm, although other heights can be used. Other cam profiles are possible and provide for different opening and closing rates and travel of valve 100, as will be apparent to those skilled in the art.
Rocker arm 210 pivots about its central point on a shaft 215. Rocker arm 210 includes two cam follower surfaces: a tip 235 and a seat 240. Tip 235 is positioned to contact and follow cam 220. Seat 240 is positioned to contact and follow cam 225. All parts are made of steel, although other materials can be used. Tip 235, cams 220 and 225, and seat 240 are made of hardened steel.

Operation—FIGS. 3 and 4

FIGS. 3 through 6 show cross-sectional views of rocker arm 210 at various positions of cams 220 and 225, respectively. FIGS. 3 and 4 show the position of the various components at the instant when valve 100 is fully open. FIGS. 5 and 6 show the position of the components when valve 100 is fully closed. FIGS. 3 through 6 each show a valve in order to indicate operation of the valve assembly. However, only one valve is present for each pair of cams 220 and 225.
FIGS. 3 and 4 show the valve opened: lobe 221 (FIG. 3) of closing cam 220 is at its lowest point relative to shaft 230 and tip 235 of the rocker arm bears against the non-lobed portion of closing cam 220. At the same point in time, the highest point of lobe 226 (FIG. 4) cams seat 240, urging arm 210 to rotate CW about shaft 215 and forcing rod 205 to its lowest position, thereby moving shoulder 111 and hence valve 100 down to the valve's most open position.
FIGS. 5 and 6 show the valve closed: as shaft 230 rotates CW, lobe 221 of closing cam 220 rotates from its lowest point (FIG. 3) to its highest point (FIG. 5) where it cams tip 235 of arm 210, thereby causing arm 210 to rotate counter-clockwise (CCW) on shaft 215 and urging rod 205 in an upward direction, thereby forcing spring 206 and hence fastener 214 and valve 100 upwardly so that valve 100 seats in its closed position in block 105. At the same time, lobe 226 of cam 225 (FIG. 6) has rotated so that its lowest point relative to shaft 230 bears against seat 240, thereby permitting valve 100 to close.
Thus as shaft 230 turns CW, opening cam 225 and seat 240 urge rocker arm 210 to rotate CW about shaft 215, forcing valve 100 to open, and then closing cam 220 and tip 235 urge rocker arm to rotate CCW about shaft 215, forcing valve 100 to close, and so on. Thus the timing of the opening and closing of valve 100 is determined entirely by the shapes of closing and opening cams 220 and 225. The maximum height of closing cam 220 is chosen to cause arm 210 to rotate CCW sufficiently to compress spring 206 slightly, thereby assuring that valve 100 will fully close despite manufacturing tolerances and dimensional changes in the engine (not shown) as it heats and cools.
Closing cam 220 and tip 235 of rocker arm 210 ensure that valve 100 will fully close with each compression and combustion cycle of the engine. This prevents valve floating at high engine speeds.

FIRST ALTERNATIVE EMBODIMENT

Description and Operation FIG. 7

FIG. 7 shows one aspect of an alternative embodiment. Instead of being displaced side-by-side on rocker arm 210 (FIG. 2), tip 235 and seat 240 lie in the same vertical plane. Instead of rotating on a single camshaft 230 (FIG. 2), closing and opening cams 220 and 225 rotate on separate shafts 500 and 505, respectively. A timing belt or chain (not shown), well-known in the art, causes shafts 500 and 505 to rotate in synchronism with the engine's crankshaft (not shown).
As shaft 505 rotates, lobe 226 of opening cam 225 cams seat 240, forcing arm 210′ to rotate CW about shaft 215, thereby opening valve 100. As shaft 500 continues to rotate, lobe 221 of closing cam 220 cams tip 235 of arm 210′ to the left, causing arm 210′ to rotate CCW, thereby closing valve 100, and so on.
As in the previous embodiment, the present arrangement ensures that valve 100 is opened and closed at the proper times, without the use of the prior-art spring.

SUMMARY, RAMIFICATIONS, AND SCOPE

The embodiments shown of my improved valve driving arrangements for internal combustion engines result in an engine having improved performance, less internal wear, fewer parts, less heat, and lower cost. Without the large and forceful (stiff) prior-art valve springs, many components, such as the cylinder head, starter motor, rocker arm, and cam lobe can be made smaller and lighter. Those skilled in the art can shape the contours of the cam lobes for optimum performance of each engine.
While the above description contains many specificities, these should not be considered limiting but merely exemplary. Many variations and ramifications are possible. For example, instead of a finger on the rocker arm, a roller bearing can be used. Instead of a coil spring to compensate for dimensional changes, a leaf spring or Belleville spring washer can be used. Instead of the stem of the valve having a narrowed portion and extending through the rod, the stem can have a uniform diameter with two projecting spaced shoulders or collars that can be pushed up and down (either directly or via one or two springs similar to spring 206) by the rod. Also the rod can extend through a hole in the stem. While the description of the embodiments discusses one valve in one cylinder for ease and simplification of explanation, those skilled in the art will recognize that the embodiments will usually be used with and can readily be adapted to multiple-cylinder engines with multiple valves per cylinder.
While the present system employs elements which are well known to those skilled in the art of internal combustion engine design, it combines these elements in a novel way which produces one or more new results not heretofore discovered. Accordingly the scope of this invention should be determined, not by the embodiments illustrated, but by the appended claims and their legal equivalents.

Claims

1. An internal combustion engine having a rotatable camshaft, at least one cylinder having at least one valve coupled to said camshaft and arranged to open and close a port in said cylinder, an improvement comprising coupling means for coupling said valve to said camshaft such that rotation of said camshaft alternately (a) cams said valve to an open position that opens said port, and (b) cams said valve to an closed position that closes said port, whereby strong valve springs do not have to be compressed during engine operation, resulting in improved engine efficiency through reduced fuel consumption, a lighter engine, lower engine wear, less heat, and improved engine performance.

2. The internal combustion engine of claim 1 wherein said coupling means comprises at least one rocker arm that follows said camshaft and seesaws in response to rotation of said camshaft and thereby forces said valve between said open and closed positions in response to the seesaw movement of said rocker arm.

3. The internal combustion engine of claim 2 wherein said coupling means also comprises a rod that reciprocates with said seesaw movement of said rocker arm and couples said rocker arm to said valve, said valve having a stem that has a pair of facing shoulders that sandwich said rod, one of said rod and said stem having a hole therethrough, the other of said rod and said stem extending through said hole.

4. A rocker arm assembly for opening and closing a valve having a stem in a reciprocating, internal combustion engine, comprising:

a camshaft arranged to rotate with said engine and having first and second attached cams,

a rocker arm mounted on a pivot and having a pair of cam followers, namely a tip and a seat,

said tip of said rocker arm being arranged to follow said first cam, and said seat of said rocker arm being arranged to follow said second cam so that said rocker arm will rock back and forth in a seesaw movement when said engine runs,

a rod attached to said rocker arm and arranged to reciprocate in response to said seesaw movement of said rocker arm,

said stem of said valve being attached to said rod so that as said camshaft rotates, said second cam first urges said seat of said rocker arm and said rocker arm to move in a first direction, thereby causing said rod to open said valve, then said first cam urges said tip of said rocker arm and said rocker arm to move in the opposite direction, thereby closing said rod to close said valve

whereby strong valve springs do not have to be compressed during engine operation, resulting in improved engine efficiency through reduced fuel consumption, a lighter engine, lower engine wear, less heat, and improved engine performance.

5. The assembly of claim 4, further including a spring interposed between the end of said stem and said pin.

6. The assembly of claim 4, further including a fastener affixed to said stem for retaining said spring.

7. The assembly of claim 6 wherein said fastener is selected from the group consisting of adjustable and non-adjustable fasteners.

8. The assembly of claim 4 wherein said stem of said valve has a pair of facing shoulders that are moved in respectively opposite directions by said rod.

9. A rocker arm assembly for opening and closing a valve with a stem in a reciprocating, internal combustion engine, comprising:

a rocker arm mounted on a pivot and arranged to rock back and forth in a seesaw movement,

said rocker arm having a pair of cam followers, namely a tip and a seat,

a pin being attached to said rocker arm and arranged to reciprocate in response to said seesaw movement of said rocker arm,

said stem of said valve being attached to said pin,

said arm being arranged to rotate about said pivot,

said tip being arranged to follow a first cam,

said seat being arranged to follow a second cam,

said first cam being attached to a first camshaft,

said second cam being attached to a second camshaft, said first and said second camshafts being arranged to rotate synchronously with the crankshaft of said engine,

so that as said second camshaft rotates, said second cam urges said seat and said arm to move in a first direction, thereby opening said valve, and as said first camshaft rotates, said first cam urges said tip and said arm to move in the opposite direction, thereby rotating said arm in a second direction and closing said valve,

10. The assembly of claim 9, further including a spring interposed between the end of said stem and said pin.

11. The assembly of claim 9, further including a fastener affixed to said stem for retaining said spring.

12. The assembly of claim 11 wherein said fastener is selected from the group consisting of adjustable and non-adjustable fasteners.

13. The assembly of claim 9 wherein said stem of said valve has a pair of facing shoulders that are moved in respectively opposite directions by said rod.

14. A method for opening a valve in a reciprocating, internal combustion engine, comprising:

providing a valve with a stem, said valve being arranged to close a port in a cylinder when said valve is in a closed position and open said port when said valve is in a closed position,

providing a rocker arm having two cam followers, namely, a tip and a seat, said rocker arm mounted on a first shaft and being arranged to pivot on said first shaft,

providing a first cam having a first lobe and arranged to rotate in response to operation of said engine,

providing a second cam having a second lobe and arranged to rotate in response to operation of said engine,

said tip and said seat of said rocker arm being arranged to follow said first and second lobes of said first and second cams so that said rocker arm reciprocates in response to rotation of said engine,

providing a rod, said rod being attached to said stem of said valve and said rocker arm and arranged to cause said valve to open and close in response to reciprocation of said rocker arm,

so that when said tip is urged by said first cam, said valve is urged into a closed position, and when said seat is urged by said second cam, said valve is urged into an open position,

15. The method of claim 14, further including a spring interposed between an end of said stem and said pin.

16. The method of claim 14, further including a fastener affixed to said stem for retaining said spring.

17. The method of claim 16 wherein said fastener is selected from the group consisting of adjustable and non-adjustable fasteners.

18. The method of claim 14 wherein said stem of said valve has a pair of facing shoulders that are moved in respectively opposite directions by said rod.

19. The method of claim 14 wherein said first and second cams are mounted on a common camshaft.

20. The method of claim 14 wherein said first and second cams are mounted on first and second camshafts, respectively.

21. The method of claim 14 wherein said stem of said valve extends through a hole in said rod.

22. The method of claim 14 wherein one of said first and second lobes of said first and second cams is relatively long and the other of said lobes is relatively short.