US2827887A - Hydraulic valve lifter - Google Patents

Description

1.. J. VAN SLOOTEN HYDRAULIC VALVE LIFTER March 25, 1958 Filed May 14, 1956 INVENTOR. 01121; v! [fan 5100;? MC? ATTORNE K United rates HYDRAULIC VALVE LIFTER Louis J. Van Slooten, Holland, Mich., assignor to General Motors Corporation, Detroit, Mich a corporation of Delaware Application May 14,1956, Serial No. 584,561

4 Claims. (Cl. 12390) its upper end by a piston or plunger telescopically slidable and supported therein on a column of oil or other incompressible fluid confined in the bottom of the cylinder. The cylinder is slidably supported in the engine frame for longitudinally reciprocable movement in following one of the lobes on the cam shaft, the piston moving therewith under the action of the oil column and effecting through suitable linkage a corresponding movement of the engine valve which is biased to closed position by a relatively stiff spring. The piston is provided with a passage extending longitudinally therethrough which is closable by a check valve sensitive to pressure within the chamber below the piston but which opens upon removal of that pressure to permit a flow of oil into the chamber from a reservoir above the piston, thereby tending to keep the pressure chamber filled at all times. A light spring is provided to bias the piston upwardly in the cylinder end thereby expanding the adjuster to take up the valve lash during the interval between lifting strokes when the engine valve is unstressed. Such lash adjusters when used in internal combustion engine valve trains which include valves normally urged closed by relatively stifI' valve springs are subject to what is known as valve lifter pump-up, particularly during so-called valve spring surge.

Valve spring surge is a term used to describe high frequency less-than-normal oscillatory movements of the valve springs which occur at certain engine speeds usually spaced by definite increments in an engine-speed scale.

One of the results of valve spring surge is to increase the amount of lash in the valve train. To compensate for this increase in lash the lash adjuster pumps-up, i. e., the spring of the adjuster further separates the cylinder and piston to increase the column of oil acting therebetween. If, for example, the engine speed is passing through a valve spring surge range to perhaps a higher speed range where there will be no valve spring surge and the lash adjusters are pumped-up to compensate for the increased lash caused by the surge the valves will no longer seat, resulting in severe losses of engine power as well as other extremely undesirable conditions such as valve burning, etc.

It is therefore an object of this invention to delay pump-up of such lash adjusters during valve spring surge so that the ranges of engine speeds at which valve spring surge" occurs may be passed through without lash adjuster pump-up occurring under such conditions.

It is a further object of this invention to provide means for delaying lash adjuster pump-up so that it occurs at atent Patented Mar. as, was

higher engine speeds than would otherwise be the case without such means.

For a clearer understanding of the invention and the objects thereof, the invention will now be described in detail with reference to the accompanying drawing, in which:

' Figure l is a transverse sectional view through a porion of an internal combustion engine Whose valve-operating train includes a hydraulic valve lifter incorporating the novel means for delaying pump-up of the lash adjuster in accordance with the invention; and,

Figure 2 is an enlarged fragmentary view of the engine and the hydraulic valve lifter of Figure 1 showing the parts in greater detail.

Referring now to the drawing, in Figure 1 the engine is illustrated as having a cylinder block and crankcase 1 in which a power piston 2 operates in a cylinder 3. The numeral 4 designates the engine cylinder head in which is reciprocably mounted a poppet valve 5 biased to its closed position by a returnspring 6 and movable in the opening direction bya cylinder head mounted valve rocker 7 in response to upward movement of a push rod 8 operatively connecting the push rod to an engine-driven cam 9 through a hydraulic lash adjuster or valve lifter 10.

The valve lifter 10, as best seen in Figure 2 comprises a pair of telescopically slidable cup-shaped members 11 and 12. The outer member 12 has its bottom end resting on the operating surface of the cam 9 and forms a cylinder in which the inner member 11 constitutes a piston or plunger. Within the cylinder 12 below the plunger 11 is an oil cushion chamber 13 in which a body of incompressible fluid is contained. In the particular arrangement illustrated this fluid is oil which is supplied from the engine-lubricating system by an oil gallery 14 in the block communicating with the bore 15 in which the cylinder is slidably reciprocable. The oil delivered by the gallery 14 to the bore 15 passes through the side Walls of the plunger and cylinder via the cylinder external groove 16 and cylinder and plunger ports Hand 18, respectively, into the reservoir 19 formed by the hollow interior of the Plunger 11. This supply of oil to the reservoir is for the purpose of replenishing that which is regularly lost from the chamber 13 during operation by leakage between the plunger and cylinder side walls with each lift stroke of the cam 9 in opening the engine valve 5. A passage 21 extending through the bottom of the cup-shaped plunger serves to connect the reservoir 19 and the cushioning chamber 13 for this purpose. To insure against backflow through passage 21 during the lift stroke there is provided a check valve in the form of a ball 22 which is retained in proximity to the lower port of passage 21 by a small retaining cup 20. A plunger spring 23 is also placed in the chamber 13 to effect re-lengthening of the lifter 10 through successive lift strokes of the cam 9 and further serves to maintain the ball check valve cup 20 in place against the bottom of piston or plunger 11. During each interval between lift strokes the engine valve 5 is closed and the plunger spring 23 acts against plunger 11 to take up clearance or lash between it and the engine valve, while causing the lifter cylinder to remain in contact with the operating surface of the cam. In so doing, and immediately upon closure of the engine valve 5, the lifter cylinder moves downward toward the cam axis relative to the lifter plunger 11 and effects an enlargement of the oil cushion chamber 13, producing a consequent drop in pressure therein and unseating of the check valve 22.

With the structure so far described if the engine speed should be such that the valve spring 6 is surging, valve 5 will tend not to seat thereby increasing the lash in the valve train between the cam 9 and the rocker 7 engaging the stern of valve 5. As a result of this increase in lash the spring 23 will act against the plunger '11 to take up of the valve train as to maintainth'e valve off its seat throughout entire engine cycles. This, of course, results in a severe loss of power which may even prevent further acceleration of the engine. If the speed range at which the valve spring surge occurs should also happen to be the range in which, say, a shift in an automatic transmission is normally made, such sur e and pump-tip may prevent the shift from taki'nglpla'ce due to the loss of power and inability of the engine to further accelerate. To alleviate this Condition and prevent its occurrence, the present invention has been proposed which upon reference to Figure .2 primarily comprises in s'e'ftiii'g resilient means (in this instance in the form of a helical'coil spring 24) between the cylinder and the piston which yieldingly opposes the action of spring 23 tending to cause pumpup. The usual hydraulic lifter normally includes a plug 25 closing the upper end of the piston 11 and a retaining ring 26" which holds the plug and the piston in the cyiim,

der 12 and more or less maintains the valve lifter assembly intact. Spring 24, then, as shown by Figure 2, is positioned so as to abut 'the retaining ring 26 at its upperend and the upper side of the plug 25 at its lower end which in turn rests against the upper end of the piston 11. The characteristic of the spring 24 is such that it yieldingly opposes the action of spring 23, i. e'., spring 23' is somewhat stiffer than spring 24.

The efiect of. spring 24', then, is to ofie'r increasing re sistance to the action of spring 23 as valve lifter pum up begins to take place. By proper selection of the characteristic'of spring 24 pump-up can be retarded or delayed so as to allow the engine to pass through the ranges of engine speed at which valve spring fsurgefoc' curs before valve lifter pump-up takes place. The springs 23 and 24 preload each other to some extent in their initial state. When valve spring surge'occurs in the valve train it causes the lower spring and thelifter to expand upward to take up the clearance in the valve train caused by valve spring surge. Due to the lower spring expanding it begins to lose its initial load while the upper spring is being compressed and its load is increased. Be-

cause of these opposing spring forces the lifter assembly] will react slower in taking up valve train clearance when valve spring surge occurs. Due to the slower reaction asaaesv continue to seat at proper intervals in the engine cycle throughout the speed range of the engine resulting in better engine performance.

I claim:

1. A hydraulic valve lifter having a cylinder with a slidably fitted piston defining an oil cushion chamber and an oil reservoir therein below and above the piston respectively, said piston having .a passage for flow of oil from said reservoir to said chamber, a check valve adapted to prevent reverse flow through said passage;

resilient means acting between said piston and cylinder'to urge its movement within the cylinder in the directionto enlarge said chamber, and resilient means acting between said piston and cylinder opposing said movement.

2. In a hydraulic lash adjuster having two telescopioally associated members in thrust-transmitting relation with a body of fluid therebetween and a check valve controlling a passage in one of said members communicating with said body, resilient means acting between said members urging movement of said members to increase the space therebetween wherein said body is located and further resilient means acting between said members ieldi'ngiy opposing such movement. I

3 A hydraulic tappet comprisinga cylinder having one end closed and the other open, a piston in the cylinder defining an on cushion chamber and an oil reservoir therein below and above the piston respectively, a first spring act-ing' between said piston and cylinder normally urging the piston out of the cylinder, said piston having a passage connecting the chamber and reservoir on opposite sides of the piston, a non-return valve permitting flow into the chamber beneath the piston, and a second spring acting between said piston and cylinder tending to ur e the pistoninto the cylinder, said first spring effecting a greater initial biasing on said, piston than said second spring.

4. In a valve train including a valve and spring therefor, a hydraulic valve lifter having'means tending to re taid pump-up of said lifter during surge of said valve spring comprising a cylinder having one end closed and the other open, a piston in the cylinder defining an oil cushion chamber and an oil reservoir therein below and above the piston respectively, a first spring in said chamher acting between said piston and cylinder normally urging the piston out of the cylinder, said pistonhaving a passage connecting the chamber and reservoir on opposite sides of the piston, a non-return valve preventing flow into the chamber beneath the'piston, retaining means in the open end of the -cylinder-above the piston preventing its removal from the cylinder, and a second spring between thepiston and the retaining means yielding'ly opposing the action of said first spring.

References Cited in the file of this patent UNITED STATES PATENTS 2,595,583 Johnson May 6, 1952 2,746,437 .Vaii Slooten May 22, 1956 2,761,433 Kilgoie Sept. 4, 1956

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