US2307926A - Camshaft for internal combustion engines - Google Patents

Description

INVENTORS Jan. 12, 1943. J. E. GRIFFITH ETAL 2,307,926

CAM SHAFT FOR INTERNAL CQMBUSTION ENGINES Filed June 15, 1940 2 Sheets-Sheet 1 Jqnrcs Gim- Jan. 12, 1943.

J. E. GRIFFITH ETAL CAM SHAFT FOR INTERNAL COMBUSTION ENGINES 2 Shets-Sheet 2 Filed June 15, 1940 INVENTORS. JAMES E. GRIFFITH BY fawqe% 1m;

Patented Jan. 12, 1943 CAMSHAFT FOR INTERNAL COMBUSTION ENG NES

James E. Grifiith and Edward Ronald Burke,

Denver, (3010.; said Burke assignor to said Grif- Application June 15, 1940, Serial No. 340,708

8 Claims.

This invention relates to a cam shaft construction for internal combustion engines. The intent and desire of all cam shaft designers is to obtain the fastest opening and closing movement of the valves that it is possible to attain. Naturally, a valve port is only functioning at full efliciency when fully open, and the sooner it can attain,

and the longer it can retain, this fully open position, the greater the effective efficiency.

Up to the present, the only method of attaining quicker opening and closing has been to shorten the length of and increase the angle of the cam so as to attain the full movement with a minimum degree of rotation of the cam shaft. There is a practical limit to the steepness of the cam surfaces, however, which can not be exceeded. The speed of action increases as the cam faces approach a radial position but th difficulty of operation also increases as the radial position is approached until at full radial angle the cam becomes inoperative.

The principal object of this invention is to provide means which will allow the cam profile to be brought more closely to a radial angle without imparting strain or stress on the valve tappets or the cam shaft and its operating mechanism so that the valves will be fully opened and closed with a minimum degree of rotation of the cam shaft.

Another object of the invention is to combine a longitudinal movement of the cam shaft with its rotative movement so that the total of the two movements will be employed in the valve lifting operation. This allows the rotative movement to be decreased so as to obtain full opening in fewer degrees of rotation thus decreasing the time element and increasing the efficiency of the engine.

Other objects and advantages reside in the detail construction of the invention, which is designed for simplicity, economy, and efficiency. These will become more apparent from the following description.

In the following detailed description of the invention reference is had to the accompanying drawings which form a part hereof. Like numerals refer to like parts in all views of the drawings and throughout the description.

In the drawings- Fig. l is a side view of a typical automotive engine, partially broken away to illustrate the position of the invention therein.

Fig. 2 is an enlarged, detail, fragmentary, longitudinal section through a portion of the length of the cam shaft of the engine of Fig. 1.

Figs. 3 and 4 are detail face and side views, respectively, of one of the shaft cams.

Fig. 5 is a fragmentary side elevation of the cam shaft at one limit of its longitudinal movement.

Fig. 6 is a similar view of a portion of the cam shaft at th opposite limit of its longitudinal movement.

Fig. 7 is a cross section through the cam shaft drive gear, taken on the line 'l1, Fig. 5.

Fig. 8 is a detail view illustrating the type of valve tappet preferred for use with this invention.

Various related parts of a standard internal combustion engine are indicated by numeral as follows: engine block l0, valve tappet plate ll, tappets I2, valves l3, cam shaft bearing bosses I4, cam shaft bearing bushings l5, and cam shaft drive chain I6.

In applying this invention to the engine a cam shaft l1, having a combined reciprocating and rotating movement is employed. The cam shaft is preferably, but not necessarily hollow, as illustrated, to provide a passage for lubricating oil. The cam shaft carries a series of cams [8, either formed integrally with or secured thereon. As is usual, the cams are spaced along the cam shaft corresponding to the spacing of the valve tappets 12 in the engine.

The cams are of unusual design adjacent one face, hereinafter known as the high side, the cams resemble the usual cams except for the fact they are much steeper than it would be possible for the usual cam to be. Adjacent the other face, hereinafter called the low side, the cams are cylindrical. The surface inclines from the low side to the apex of the high side from all directions.

The cam shaft is supported by cylindrical journals I9 at its extremities and at spaced points throughout its length. The journals are arranged so that they may both reciprocate and rotate in the bearing bushings I5. I The reciprocation is accomplished by means of a cylindrical cam 20 having an indented cam track 2|. The cam 20 is keyed onto the extremity of the cam shaft I! so that it must reciprocate therewith.

A cam sleeve plate 22 is secured to the face of the engine block I0 and provided'with a cam follower sleeve 23 which surrounds the cam 20. The cam sleeve supports a pair of radially extending roller shafts 24 on each of which a tapered cam follower roller 25 is mounted. These rollers ride in the cam track 2| to reciprocate the cam shaft back and. forth simultaneously with its rotation.

A cam shaft drive gear, or an annular chain sprocket 26, delivers the rotative power to the cam shaft. The annular sprocket is slidably mounted on a drive drum 2'! through the medium of splines 28 formed on the drum. The drum 2! is clamped against the cam by means of a headed shaft screw 29 which is threaded into the extremity of the cam shaft ll.

The screw, the drum, and the cam 20 are locked together against differential rotation by means of a set screw 30 which is threaded through the first two members and into the latter. The drum 2'! is formed with an annular series of openings 3| through any of which the screw 30 may be passed. This allows a timing adjustment to be made of the cam shaft ll.

During rotation, the sprocket 2B is held from sidewise reciprocation by means of the action of the sprocket chain It. An additional guide member 32 may be provided to hold the sprocket from reciprocation. The drum is free to reciprocate within the sprocket without moving the latter.

Since in this invention the cams move against the valve tappets in all directions, it is necessary that the latter have a rounded contact surface. This has been accomplished by securing steel contact balls 33 on the lower extremity of the valve tappets 12. These balls are constantly held against the cams by means of the Valve springs as is usual in internal combustion engines.

Lubricating oil is conducted to the cam shaft bearings through an oil pressure line 34 feeding through the first bearing box M. This oil flows into a peripheral oil groove 35 in the journal thence through an oil hole 36 to the hollow interior of the cam shaft. From thence it flows outwardly through oil holes 31 into oiling grooves 38 in each of the shaft journals.

The cam track 2| is contoured so as to give two complete forward and back reciprocations to the cam shaft on each revolution thereof. The longitudinal inclines on the cams are so arranged that they will be faced in alternate directions, that is, the incline on each alternate cam on the cam shaft will face toward one extremity of the shaft while the incline on the intermediate cams will face toward the other extremity of the shaft.

The cam track is so positioned relative to the cams that as the high point on each cam approaches its tappet, the shaft will be moved to cause the high side of that cam to be pulled toward the tappet simultaneously as the cam rotates toward that tappet. This causes the tappet balls 33 to travel to the high point of the cam on a spiral path and results in lengthening the path from the low to the high point for any given number of degrees of rotation. Thus, the lateral incline of the cams can be increased until it is so steep that it would not be practical for operation with the usual revolving cam shaft. However, by combining a longitudinal movement with the revolving movement, the length of the inclined path is increased and the steepness thereof is decreased to a point where practical operation is possible, yet the time element or degree of rotation is not changed. This enables the valves to be opened and closed in a much shorter time interval than would be practically possible with a simple rotating shaft.

By facing the cams in alternate directions, one set of valve tappets climbs its cams as the shaft moves in one direction and another set climbs its cams as the shaft moves in the other direction.

A typical path of travel between the cam and its cam tappet is indicated in broken line at A.

While the invention has been described and illustrated as applied to a four-cylinder, fourcycle engine, it is to be understood that the invention is not limited to this particular type of engine but will be found valuable wherever poppet or tappet types of valves are used, and whereever it is desired to obtain complete opening and closing of the valves in a minimum degree of rotation of the cam shaft.

While a specific form of the improvement has been described and illustrated herein, it is desired to be understood that the same may be varied, within the scope of the appended claims, without departing from the spirit of the invention.

Having thus described the invention, what is claimed and desired secured by Letters Patent is:

1. In an internal combustion engine having tappet valves, a cam member for lifting said valves from their seats, means for rotating said cam member, and means for simultaneously reciprocating said cam member through a complete cycle during every revolution thereof, said reciprocation and rotation constituting necessary components of movement for the operation of said tappet valves.

2. In an internal combustion engine having a plurality of valve tappets arranged in alignment along a valve cam shaft; means for rotating said shaft; and means for reciprocating said shaft forward and back longitudinally at every revolution thereof, said reciprocation and rotation constituting necessary components of movement for the operation of said valve tappets,

3. In an internal combustion engine having a plurality of valve tappets arranged in alignment along a valve cam shaft; means for rotating said shaft; means for reciprocating simultaneously said shaft longitudinally through a complete cycle during every revolution thereof; and cams on said shaft beneath said valve tappets, the surface of said cams being inclined axially from one face thereof to a high point adjacent the other face thereof, said reciprocation and rotation constituting necessary components of movement for the operation of said valve tappets.

4. In an internal combustion engine having a plurality of valve tappets arranged in alignment along a valve cam shaft; means for rotating said shaft; means for imparting a complete axial reciprocation to said shaft during each complete revolution thereof; and cams on said shaft beneath said tappets, each of said cams comprising a cylindrical element having a high point adjacent one face thereof, the peripheral surface of said element inclining from said high point on" cumferentially in both directions and axially toward the other face thereof, said reciprocation and rotation constituting necessary components of movement for the operation of said valve tappets.

5. In an internal combustion engine having a plurality of valve tappets arranged in alignment along a valve cam shaft; means for rotating said shaft; cams on said shaft beneath said tappets, each of said cams comprising a cylindrical element having a high point adjacent one face thereof, the peripheral surface of said element inclining from said high point circumferentially in both directions and axially toward the other face thereof; and means for imparting a complete forward and back axial reciprocation to said shaft at each complete revolution thereof, so that the line of rotation contact between a tappet and its cam will describe a spiral, helical path, said reciprocation and rotation constituting necessary components of movement for the operation of said valve tappets.

6. A valve cam shaft construction for internal combustion engines of the type having an aligned series of valve tappets comprising: a plurality of bearings in alignment with said series of tappets; cam shaft journals formed on said cam shaft and positioned to slidably and rotatably ride in said bearings; and means for simultaneously rotating and reciprocating said shaft through a complete, similar cycle during each revolution thereof, said reciprocation and rotation constituting necessary components of movement for the operation of said valve tappets.

7. A valve cam shaft construction for internal combustion engines of the type having an aligned series of valve tappets comprising: a plurality of bearings in alignment with said series of tappets; cam shaft journals formed on said cam shaft and positioned to slidably and rotatably ride in said bearings; a cylindrical cam affixed to said shaft and provided in its cylindrical surface with a cam track; and fixed cam followers extending into said track so as to impart similar, repeating endwise movements to said shaft at each revolution thereof.

8. A valve cam shaft construction for internal combustion engines of the type having an aligned series of valve tappets comprising: a plurality of hearings in alignment with said series of tappets; cam shaft journals formed on said cam shaft and positioned to slidably and

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