US3066659A - Exhaust valve lifter for internal combustion engines - Google Patents

Description

Dec. 4, 1962 R. J. COLTON 3,066,659

EXHAUST VALVE LIFTER FOR INTERNAL COMBUSTION ENGINES Filed May 2, 1961 United States Patent Office 3,%h,h59 l atented Dec. 4, 11962 3,066,659 EXHAUST VALVE LE TER INTERNAL QQMEUS'HQN Ehlfilldllfi Roland .l. Colton, 41 Vista Way, llort Washington, NY. Filed May 2, 196 Ser. No. ?,265 6 Qiairns. (fill. l23--9tl) My invention relates to internal combustion engines, and more particularly to poppet type exhaust valves.

The objective of my invention is to provide an improved means for obtaining higher average valve lift of the poppet type exhaust valve.

Heretofore a high average valve lift has been obtained through the utilization of so-called racing cams wherein contours of the leading flank of the cam lobe is dangerously near the angle of repose in relation to the cam follower which condition imposes an extra dynamic load on the cam-shaft as well as increasing the friction load of the cam follower.

As a means of achieving the objective, my invention embodies structure and elements compelling a function wherein a sprin element is flexed, stressed or compressed by action of the leading flank of the cam lobe which action accumulates usable potential energy within the said spring element prior to the time at which it is desirable to lift the exhaust valve from its valve seat, after which time release of the said potential energy of the said spring element assists the cam in opening the exhaust valve at high velocity, while the closing action of the said exhaust valve is in accordance with the accepted conventional closing action for poppet type exhaust valves.

Persons versed in the arts to which my invention pertains will be enabled to make and use this device by refer ence to the specification and drawings in which FIG. 1 shows a fragmental cross section of some elements of an internal combustion engine in operation with conventional poppet type exhaust valve in the closed position, unconventional rocker arm, conventional type push rod and guided cam follower being moved by a cam lobe at the instant the said exhaust valve is about to be lifted from its valve seat. The guide of the cam follower is omitted in the drawings.

FIG. 2 shows a part of an exhaust valve stem of a conventional poppet type exhaust valve which valve is in the closed position, part of a conventional type of valve closing spring, unconventional type of cam follower and a cam in the act of moving to lift the said exhaust valve away from its seat. All relative conditions are identical with FIG. 1.

Referring to FIG. 1, a. cam is shown at l, firmly affixed to a cam-shaft at 2 with the said cam-shaft rotating in a counterclockwise direction while the leading flank of the cam lobe is lifting the cam follower element 28 due to pressure at the current point of contact indicated at 33, While a conventional pushrod is shown at 21.

A rocker arm is indicated at 22 which arm is pivotally retained on a fixed rocker arm shaft indicated at 23 which shaft is supported on the pedestal 31 which in turn is secured to the cylinder head 27 by the cap screw indicated at 32.

A leaf spring indicated at 3 is firmly affixed at one of its ends to the rocker arm 22. by any well known means such as the rivet indicated at 2 While the opposite end of the said spring is capable of limited arcuate movement due to spring flexion with positive stops provided to limit the flexion of the spring element 3 to an amount which is less than the distance between the broken lines shown at 6 and 7. The natural shape of this spring 3 is approximately straight before attachment to the rocker 22.

The limitation of spring fiexion may be provided by any Well known means such as the means shown, wherein the spring 3 makes contact with the end of the rocker arm as at 1% which shows the limit to which the said spring 3 may be forcibly bent, while the lines 4- and 5 indicate the amount of spring flexion in the opposite direction wherein the said spring tends to approach a straight form when opposed by a spring force of less magnitude. Obviously the hook which is shown as a continuation of the spring 3 does not change its shape as the flexing of the spring 3 occurs between the said hook and the opposite end of the said spring 3 with the said hook providing a simplified positive stop for the said spring.

A section of a cylinder head is shown at 27 with an exhaust gas conduit shown at 26 while a poppet type exhaust valve is shown in the closed position and it is assumed that combustion is in progress Within a cylinder located below the face of the said poppet type exhaust valve indicated at 25, while the exhaust valve stem is shown at 9 and extending to make contact with the spring 3 at 8.

A valve closing spring is shown in section at in while interposed between the outer surface of the cylinder head at 30 and a conventional valve spring retainer element attached to the valve stem 9 and indicated at 29.

The numeral 23 indicates a position above the surface 3%) where a rebound spring may terminate. This spring is not shown and the description gains further clarification in later paragraphs of this specification.

In FIG. 2 as well as in FIG. 1, all elements performing the same function have identical numerals.

Referring to FIG. 2, it is assumed that the valve stem Q and the spring it) are identical with those shown in FIG. 1.

In FIG. 2, the cam follower is a guided cylinder 11, housing a slideable plunger 12 which plunger is capable of axial movement equal to the distance between the surfaces indicated at 4 and 5 which is slightly less than the distance between the broken lines 6 and 7, with 4 and 19 being positive stops for the plunger 12.

Within the cylinder 11 is a helical cylindrical compression spring under stress of compression and shown at 3 while interposed between an annular shoulder on the plunger 12 and the head of the guided cylinder 11 while the said spring is compressed to a predetermined point which is reached when the slideable plunger 32 makes contact with the cylinder head of the said guided cylinder as shown at lif This contact renders the cam follower incapable of further resilience.

To retain the plunger 12 within the cylinder 11, an annular retainer ring is shown at 13 which ring is firmly afiixed within the cylinder 11 by any Well known means, such as the use of holes drilled radially with matching pins, one of which pins is shown at M, while a small cylinder is shown at 17 which is slideable upon the plunger 12. The elements 15 and 16 are solid discs of the desired thickness and placed Within the cylinder 17 to provide adjustment means for the desired overall length between the point indicated at 8 and the point indicated at 19, while the surface indicated at 4 is the surface of the element shown at 18 which may be a hardened wearing element, a spacer, or both, or this element may be omitted while the annular retainer ring 13 is made to extend to the line 4.

The essence of my invention resides in the comparative strength or rigidity of the springs shown at 3 and it) and the use I have made of the ability of pneumatic pressure to hold a poppet valve closed under the conditions described and shown pictorially herein, while the general embodiment in combination with the engine, comprises a cam, a resilient cam follower or resilient cam follower linkage, a poppet type exhaust valve, 2-. poppet valve closing spring wherein the said cam follower resila scess 3 ience will not yield to the said valve closing spring when the said valve closing spring is unassisted by an auxiliary force.

The said auxiliary force in my invention is pneumatic force within the engine cylinder during combustion, which pneumatic force cooperates with the said valve closing: spring.

The behavior of the valve lifter will be readily understood by referring to FIG. 1, where the cam follower has. been raised to a distance equal to the distance between. the lines 6 and '7 which through action of the push rod 21 rocks the rocker arm 22 while the spring 3, being unable to unseat the poppet valve under the conditions shown here, is pressed in contact with the rocker arm at 19 which action flexes the said spring 3 to an amount equal to thedistance between the lines 4 and 5.

At this time the poppet valve is being held on its seat as shown by the valve closing spring it} assisted by the pneumatic pressure created by combustion within the cylinder, which pressure acts against the face of the poppet valve shown at 25, while no resiliency remains in the cam follower linkage due to the positive stop of the spring 3 at 19, when further movement of the cam causes a positive transmission of motive power from the said cam to the said poppet valve While overcoming all resistance, thus unseating the poppet valve through various linkageelements, releasing the products of combustion and cansing a rapid decrease in the pneumatic force tending to hold. the said poppet valve near the poppet valve seat at which time the spring 3 quickly overcomes the force of the: spring 10 plus residual pneumatic force while flexing to a position wherein the lines 4 and 5 are together while the said spring 3 is restrained from further flexion to- Wards a straightened position by the stop limit previously described.

During the above described action of the straightening movement of the spring 3, the lift, velocity and acceleration of the poppet type exhaust valve will not correspond with the contours of the leading cam flank but will each have a higher value without regard as to whether the cam.

follower arrives at the dwell position before the flexion of the spring 3 is completed.

With the variations in valve sizes and engine speed, obviously a condition may arise where the excessively high valve velocity during the exhaust valve opening action would interfere with the closing action due to the overtravel of the valve due to inertial force. This would necessitate the use of a rebound spring which would be of the helical cylindrical type and surrounding the poppet type exhaust valve stem while small enough to be within the confines of the valve closing spring. This is further clarified by referring to the position indicated at 23 in FIG. 1 at which point the said rebound spring would extend from the surface indicated at 3% to the position indicated at 28 while the valve retainer would bounce only at high speeds during overtravel of the valve While at low speed the spring retainer would not make contact with the said rebound spring.

The term bounce is used to describe sudden reversal of the whole cam follower linkage as well as the poppet valve and valve closing spring after the cam follower is out of contact with the cam.

While FIG. 2 slightly resembles a hydraulic valve lifter, valve action compelled is identical with the valve action compelled by the structure shown in PEG. 1, but would be hampered by excessive lubricating oil within the cylinder 11. Therefore it is desirable that vent holes be provided for oil entrance and oil drainage. In lieu of a flat spring as in PEG. 1, the helical spring 3 in FIG. 2 performs the same function as the spring 3 in FIG. 1.

Without departure from my invention, this exhaust valve lifter may cooperate with a poppet valve which is spaced concentric with an exhaust conduit as well as with an inlet conduit of an internal combustion engine of the four stroke cycle type, or any type of valve lash adiuster may be included in the cam follower linkage elements.

This device is not to be confused with a valve lash adjuster wherein all elements of the cam follower train maintain their relative linear positions and overall length during the valve opening action, whereas the structure of my device compels an action wherein the length of the cam follower elements is decreased prior to the valve opening action, after which these elements are lengthened during the said valve opening action when accumulated spring power is released in order to cooperate with the cam in accelerating the exhaust valve.

Having described my invention, I claim:

1. in an internal combustion engine having a cylinder, an exhaust poppet valve adapted to move inwardly, a valve stem projecting from said cylinder, a valve closing spring on said stem, a rotatable cam, a push rod operable by said cam, means connected to said push rod for contacting the free end of said valve stem, the improvement which comprises an auxiliary spring interposed between said push rod and said stem, the pressure of the exhaust gas acting against the face of said exhaust valve during the period when the auxiliary spring is compressed, the potential energy stored in said auxiliary spring, when said cam has raised said push rod to a point short of opening said valve, being greater than that of said valve closing spring, the relative spring rates being such that the auxiliary spring will yield when opposed by the combined forces of the exhaust gas pressure and the valve closing spring but will not yield when opposed by the force of the valve closing spring alone, said valve closing spring adapted to hold said valve closed, means for providing a firm connection from said cam to said valve stem when said auxiliary spring is compressed, said valve closing spring releasing said valve when the apex of said cam raises said push rod, whereby the release of said potential energy causes said auxiliary spring to open said valve.

2. An internal combustion engine according to claim 1 characterized in that a pivoted rocker arm is contacted at one end by said push rod and the other end terminates in proximity to said valve stem, the lower face of said rocket arm being convex, said auxiliary spring being on said lower face and anchored at one end thereon.

3. An internal combustion engine according to claim 2 characterized in that said auxiliary spring is substantially flat when not in tension.

4. An internal combustion engine according to claim 2 characterized in that the other end of said auxiliary spring is bent on itself to loosely embrace the adjacent end of said rocker arm.

5. An internal combsution engine according to claim 2 characterized in that free end of said auxiliary spring is interposed between the end of said valve stem and the end of said rocker arm to provide a valve tappet.

6. An internal combustion engine according to claim 2 characterized in that said aumliary spring is a leaf spring.

References fi ted in the file of this patent UNITED STATES PATENTS 1,866,293 Chandler luly 5, 1932 1,928,678 Sjolander Oct. 3, 1933 2,109,8l5 Best Mar. 1, 1938 FOREIGN PATENTS 2,381 Great Britain Ian. 31, 1903

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