US2761436A - Yielding spacer - Google Patents

Description

D. H. PIERCE YIELDING SPACER Sept. 4, 1956 Filed Dec. 6, 1952 INVENTOR. fl /v/fl fl. Hmcs H/s Arra/e/vfr United States Patent "ice YELDING SPACER Daniel H. Pierce, Birmingham, lvich.

Application December 6, 1952, Serial No. 324,458 6 Ciaims. (Cl. 123-90.

This invention relates to a valve train mechanism particularly adapted for the intake and exhaust valves of an internal combustion engine.

In the early design of automobile engines a low speed valve timing and sufficient valve clearance were provided which resulted in even and steady engine running at very low speeds, say around 200 P. M. Present day automobile engines have a much higher speed timing and a compromise valve clearance to give quiet valve operation. The present valve lifting cams are designed with large quieting contours at the opening and closing points so that with the valve clearance set for quiet operation, say ten thousandths of an inch instead of fifteen thousandths, the overlapping of valve vents and the duration of valve openings are increased. As a result the idle operation becomes erratic and unstable. To avoid stalling the idle speed must be increased to four hundred or five hundred R. P. M.

When self-adjusting tappets are used in engines designed for solid tappets and cams with large quieting contours, a valve clearance unit must be included in the valve lifting train to obtain a satisfactory idle and to avoid valve burning and cam and tappet face wear. This is particularly true in service installations where it is desired to adapt self-adjusting tappets to engines having large quieting contours and built for solid tappets or screw adjustable tappets.

It is therefor an object of the present invention to provide a preloaded, resilient valve clearance unit in the valve lifting train, either in the valve stem, push rod, or the valve tappet, which is desirable when self-adjusting tappets are used in engines designed for solid tappets to provide proper valve timing.

Another object of the invention is to preload the clearance unit to a predetermined force which is greater than the force exerted by the self-adjusting tappet, and to limit the action of the clearance unit after a compression force has been reached which is less than the valve spring force when the valve is closed; that is, the preloaded resilient means permits relative movement of the valve and cam only between forces which are above the self-adjusting force and below the valve spring force when the valve is closed.

A further object of the invention is to incorporatethe preloaded resilient means within a valve tappet of the selfadjusting type, hereinafter more fully described.

Other objects and advantages of the invention will more fully appear from the following description taken in connection with the accompanying drawings in which:

Fig. l is a cross sectional view of a valve operating mechanism embodying my improved clearance unit between a valve or push rod and the cam shaft of an internal combustion engine, parts being broken away in section and parts in elevation;

Fig. 2 is a fragmentary view of a valve stem or push rod showing a modified form of the invention; and

Fig; 3 is a sectional view taken on line 33 of Fig. 1, showing a bottom view of the spider spring.

Patented Sept. 4, 1956 Referring to the drawings, I have illustrated the invention as applied to a self-adjusting tappet of an internal combustion engine. The cylinder block 10 of the engine is provided with the usual combustion port 12 having a valve seat 14 engageable with the usual poppet valve 16. The valve stem 18 is slidably mounted in the block 10 and is urged to valve closing position by the valve spring 20, surrounding the valve stem 18 and bearing between the block 10 and a washer 22 held on the stem 18 by a key 24.

A tappet member 26, embodying my improved construction is slidably mounted in the cylinder block 10, below and in axial alignment with the valve stem 18. The valve 16 and tappet 26 are periodically lifted by a cam 28 on a cam shaft 30.

in the operation of the valve mechanism, the parts are elongated by heat and the valve body 16 moves away from the valve seat 14, consequently not properly seating, unless suflicient clearance is provided between the bottom of the valve stem 18 and the top of the valve tappet 26. Sufficient clearance to eliminate over expansion by heating results in noisy operation of the parts and wear, reducing the overall length of the parts which causes noise as well as inefiicient operation.

There have been provided self-adjusting tappets which compensate for the valve stem longation caused by heat, and shortening caused by wear. These devices have been satisfactory when used in connection with engines having the valve train lifting mechanism designed for use with the self-adjusting tappets, that is, where the cam shafts have been designed with short quieting contours. However, some difiiculty has been experienced in adapting the self-adjusting tappets, where no clearance is maintained, to cams designed for high speed timing and valve clearances to give quiet valve operation, and particularly so with cams having large quieting contours at the opening and closing points.

The terms, self-adjusting tappets, will be clearly understood by reference to my United States patents, 2,570,853 and 2,570,854, issued October 9, 1951, wherein a yielding spacer is disclosed for use in the valve train of an internal combustion engine to compensate for the variations in length of the valve stem caused by temperature changes and wear.

In the above identified patents there is disclosed a pair of intercommunicating chambers, each of variable capacity, having a means for permitting restricted how of material from one chamber to the other. The material in the chambersis described as a mass of soft, solid but flowable, viscous material which is freely flowable under pressure, and when controlled by suitable valving, the tappet is highly resistant to sudden shock. In operation the overall length of the tappet is varied to compensate for the elongation or contraction of the valve lifting mechanism and provides for no clearance at a1 times. It has been found that in engines having large quieting contours, it is desirable to have some freedom of relative movement between the valve stem and the tappet, in the valve lifting mechanism; such movement being present only between the compensating pressure of the selfadjusting mechanism and the pressure of the valve seating spring.

The tappet 26 is formed as a cylinder having a tubular side wall 32 and a closed bottom portion 34, the. latter adapted to seat on the cam 28. An upper plunger 36 is slidably mounted in the open end of the tubular portion 32. The plunger 36 carries a tappet valve stem 38. The inner end of the tappet valve stem 38 is provided with a tappet valve head 42. A lower plunger 44 is slidably mounted on the tappet valve stem 38 and is arranged between the tappetvalve head 42 and the upper plunger 36. A- shoulder 46 is provided on the tappet valve stem 38 and a pressure deformable flange 48 is provided on the lower plunger 44 cooperating with the shoulder 46 to provide a stop for limiting the sliding movement of the lower plunger 44 on the tappet valve stem 38 toward the tappet valve head 42. A compression spring 50 is arranged between the upper and lower plungers 36 and 44. A lock ring 52 is provided in the inner wall of the tubular side wall 32 for limiting the outer movement of the upper plunger 36. A sealing ring 54, of flexible material such as rubber, is carried in a groove 58 in the wall of the plunger 36 for sealing engagement with the inner periphery of the tubular side wall 32, at its outer open end.

The lower plunger 44 forms a chamber with the tubular side wall 32 and its closed end 34. This chamber is divided into an upper chamber A and a lower chamber B by the tappet valve head 42.

A predetermined quantity of flowable material is placed in the chambers A and B at the opposite sides of the tappet valve head 42. As one example of the flowable material which may be successfully used, reference is again made to my patents, above referred to, wherein I have disclosed the use of a silicone polymer compound which has a high cold flow characteristic.

The tappet valve head 42 has an outer diameter less than the diameter of the inner periphery of the cylinder 32 so that the material may flow around the valve head 42 from chamber A to chamber B, or vice versa. To increase the flow of material from chamber A to chamber B, I have provided a choke ring 60 co-operating with the valve head 42. The valve head 42 has its inner face provided with a tapered seat 62 for contact with a correspondingly tapered face 64 on the choke ring 60. A compression spring in the form of spider spring 65 is received on the end of the valve stem 38 and exerts a force less than the spring 50 for urging the tapered face 64 of the choke ring 63 normally into contact with the tapered seat 62 of the valve head 42.

The outer diameter of the choke ring 60 is greater than the outer diameter of the valve head 42 but is less than the diameter of the inner wall of the cylinder 32 so that there may be a flow of the material around the outside of the choke ring 60 but less than the flow of material around the valve head 42 when the choke ring surface 64 is moved away from the valve head seat 62. Thus the material may flow from the chamber A to chamber B in greater volume than in flowing from chamber B to chamber A.

When the parts are assembled, the flowable material is placed in the chambers A and B on opposite sides of the tappet valve head 42. The lower plunger 44, with flanged ring 4-3 in place, is then slid in the cylinder with the upper plunger 36. A sealing ring 56 is provided between the lower plunger 44 and the flowable material to prevent leak around the valve stem 38 and the side wall of the cylinder 32. If desired, the flowable material may be placed in the chamber B, then the assembly of stem 38, choke ring 69, valve head 42, lower plunger, spring 65, spring 50 and upper plunger 36, are placed into the flowable material. Pressure on the valve stem 38 will cause the assembled choke ring 60, valve head 42, and spring 65 to sink into the flowable material, so that the latter is on opposite sides of the valve head 42 and the parts are immersed in the material.

This assembly is done in a vacuum so that all air is removed from the chambers A and B and the flowable material.

The spring 50, after the tappet parts are assembled into a self-contained unit, urges the upper plunger 36 outwardly into engagement with the locking ring 52 and the lower plunger 44 into pressure engagement with the flowable material in chambers A and B.

When the tappet assembly is in operating position between the valve stem 18 and the cam 28, the upper phmger 36 is moved inwardly of the tappet cylinder 32 by the pressure of the spring 26. The load force of the spring on the plunger 36 is less than the load of the spring 26 on the valve stem 18 so that the plunger 36 is moved inwardly of the tappet cylinder, thereby adjusting the overall dimension of the tappet to a distance corresponding to the distance between the lower end of the valve stem 18 and the outer surface of the cam 28.

The inward movement of the plunger 36 causes inward movement of the tappet valve head 42. The outer diameter of the valve head 42 is less than the inner diameter of the chamber A and B. As the valve head 42 is moved inwardly, the flowable material in chamber B is moved through the passage between the outside diameter of the choke ring and the cylinder 32 into the chamber A.

Sudden shock or a blow on the material, as caused by lifting the valve 16, will be transmitted through the material without appreciable flow, but there will be a slight extrusion of the material through the space between the cylinder wall 32 and the outer periphery of the choke ring 60, transferring the material from chamber B to chamber A.

Assuming that the valve train linkage is in no clearance position, the amount of material extruded from chamber B to chamber A, during the valve lifting period, is exceedingly small and is immediately transferred back to chamber B during the closed position of the valve 16 due to the pressure of the spring urging the plunger 44 inwardly and the valve head 42 outwardly. The compensating action causes relative axial movement of the cylinder 32 and the upper plunger 36, increasing or decreasing the overall length of the tappet assembly.

If there is clearance between the end of the valve stem 18 and the valve tappet 26, the spring 50 will urge the plunger 36 and valve head 42 axially of the cylinder 32 and force the material in chamber A around the valve head 42 and choke ring 66 into chamber B, thereby raising the plunger 36 to contact the end of the valve stem 18, and compensate for the clearance. Continued outward movement of the plunger 36 is resisted by the pressure of the spring 26 which is greater than the pressure of the spring 56. The material may flow from the chamber A to the chamber B in greater volume than in flowing from chamber B to chamber A. The plunger 36 is moved outwardly of the cylinder 32 more rapidly than it is moved inwardly of the cylinder.

The self-adjusting tappet structure above described forms the subject matter of my co-pending application, Serial No. 271,897, filed February 16, 1952, and has been herein described in detail to present a clear understanding of one of many forms of a self-adjusting tappet which may be used in connection with the improved structure forming the present invention.

In order to provide limited freedom of movement between the valve stem and the self-adjusting tappet, I have provided a socket 66 which slidingly fits in a bore 68 in the upper plunger 36. The socket 66 receives the ball end 70 of the valve stem 18 and is provided with an outwardly extending flange 72 over the outer end face of the plunger 36. The flange 72 is spaced from the outer end face of the plunger 36. A resilient means is provided between the adjacent faces of the flange 72 and the plunger 36 which may be a coil compression spring or a dished spring steel washer, herein shown as a pair of dished spring steel washers 74. These springs are assembled on the outer periphery of the socket 66 and held in pressure engagement with the under surface of the flange 72 by a ring 78 in the outer periphery of the socket 66. The springs are preloaded during assembly to approximately fifty pounds and are flexed to a flat, inactive and solid position at approximately sixty pounds during a relative movement of the plunger 36 and the socket 66 of approximately fifteen thousandths of an inch. The preloaded clearance spring is not active on the valve train; that is, the fifty pound force, above referred to, is not exerting any force on the valve train throughout the valve cycle when used with self-adjusting tappets. It is to be understood that the limit pressures may be varied to suit conditions of the selfadjusting tappet mechanism, and the relative movement may be varied in accordance with the cam quieting contour.

The valve clearance springs '74 should function to provide a valve clearance of from ten thousandths to twenty thousandths of an inch, as required by the particular engine when originally equipped with manually adjustable or solid tappets. The preloading of the springs 74 is important when used in conjunction with a self-adjusting tappet so that the tappet, during its elongation period, will not destroy the predetermined clearance; that is, the preloading pressure of the springs '74 must be greater than the pressure of the spring 50. The load pressure of the spring 74, before the solid position, must be less than the load pressure of the valve spring 20 so that the springs 74 function to provide the predetermined clearance only when the valve 16 is closed. The function of the clearance springs is to provide a special clearance in the valve train which the self-adjusting tappet has no control over.

In Fig. 1, I have illustrated the clearance unit embodied in the self-adjusting tappet, the two forming a unitary structure which may be used to replace the tappets in engines provided with the usual solid tappets without altering the original valve timing, valve clearance, or quieting contours. If desired the clearance unit may be embodied in the valve stem, rocker arm or pushrod. In Fig. 2, I have illustrated the clearance unit as embodied in the end of the valve stem. A sleeve 80 is slid over the end of the valve stem 18, the latter being provided with a reduced end portion 82 forming a shoulder 84. The sleeve 80 has a closed end portion 86, the outer surface of which is curved for reception in the concave surface in the end of the tappet. A coil spring 88 is compressed between the shoulder 84 and a lower ring 90, the latter being held in place on the end of the valve stem 155 by a ring 92. A shoulder 94 is formed at the lower end of the inner periphery of the sleeve 80 for engagement with the ring 90. In the normal position of the parts, a predetermined clearance is provided between the end of the valve stem 18' and the closed end of the sleeve 80 when the shoulder 94 engages the ring 90. The spring 83 is preloaded so that the clearance is not reduced by the elongation forces of the self-adjusting tappet. If desired, a dished spring steel Washer or disc may be inserted between the lower end of the valve stem 18' and the closed end of the sleeve 80, as a substitute for the spring 38 and ring 90.

When the parts are assembled in an engine, an adjustment is made in the valve train such that the valve is riding, that is, not fully closed while the tappet is riding the base circle of the cam. The preloaded clearance unit 74 is compressed solid by the valve spring 20, for example, by a force of 85 pounds. This force also acts on the self-adjusting tappet so that it is shortened by the flow of the material from chamber B to chamber A. When the valve 16 seats, the valve spring pressure on the tappet and cam shaft is zero, but the clearance unit 74, having a pressure force greater than the pressure force of the tappet spring 50, shortens the self-adjusting tappet by the expansion of the clearance unit to the predetermined clearance, for example, .015. When the clearance unit reaches its reloaded pressure there is no force exerted on the tappet valve 42 and the valve train has no clearance without pressure forces on the seated valve head 16 or the cam 28 at its base circle.

Starting the ope-rating cycle at the valve closed position, as shown in Fig. l, with the clearance unit 74 elongated and the self adjusting tappet taking up any clearance betweenthe cam 28: and the bottom of the: valve stem 18, the cam 28 first raises the: self-adjusting tappet 26, compressing the: clearance unit 74 to. a. solid state. Further rotation of the cam starts lifting of the valve 16. against the pressure of the valve spring 20. When. the valve closes, the clearance unit expands before the tappet elongates. Some clearance is left and this is taken up. by the selfadjusting tappet while in contact with the base circle of the cam.

At high speeds when the valve train inertia force exceeds the valve spring restraining force, the tappet face may leave contact with the cam and tappet, pumping up or elongation takes place. Before elongation occurs the valve clearance unit expands and nullifies the tappet'elomgation. After the train returns to the cam, the clearance unit is compressed solid and the tappet subsequently shortens to its working length.

In some engines for example, a solid tappet is given an exhaust valve clearance of say .010 in order to provide a hot or operating clearance of .004. In other engines there may be an exhaust valve clearance, cold, of .035 in order to obtain a safe working clearance of .010 when hot. With self-adjusting tappets the clearance under all conditions is very small (.001 to .003) depending uponthe leak down of the tappet. When the clearance unit is used in combination with a self-adjusting tappet, thevalve clearance can be predetermined under all conditions as desired, such as .002, .005, or .020. Thus the correct valve timing can be obtained on a solid tappet engine when equipped with self-adjusting tappets. By varying the movement of the clearance unit, various compromises between correct valve timing and valve noise may be obtained.

While I have herein illustrated and described a specific embodiment of the invention, it will be understood that various changes including the size, shape, degree of pressure forces, and arrangement of parts may be made which fall within the spirit of my invention and it is my intention to include within the scope of the appended, claims such reasonable changes.

I claim:

1. In a valve tappet for use in an internal combustion engine, the combination of a body having a bore therein. which is closed at one end and opened at its opposite end, a valve within said bore having oppositely disposed side walls and having a diameter less than the diameter of the bore to permit a restricted fiow of viscous material between said valve and the wall of the bore, a movable end wall sealing the open end of the bore, resilient means urging said end wall inwardly, a valve rod connected to said valve and extending through said movable end wall, a choke ring co-operating with said valve on the side of said valve adjacent the closed end of the bore, said choke ring having an outer diameter greater than the diameter of said valve and only slightly less than the diameter of the bore, resilient means carried by said rod below said choke ring for urging said choke ring into sealing relation with said valve, and a mass of flowable viscous material in the bore on opposite sides of the valve.

2. An automatic regulator comprising, a housing having a closed end and an open end with a cylindrical wall therebetween, a lower plunger member slidable on said wall for confining fluid in the closed end of the housing, a thrust load transmitting valve member between said lower plunger and the closed end of said housing having a stem slidable through said lower plunger, an upper plunger on said valve stem slidable on said wall and having a recess in the outer face thereof, a socket member extending into said recess having an outturned flange and overlying the outer face of said upper plunger, a pair of oppositely disposed dished spring washers surrounding said socket and bottomed on said flange and on said outer face of the plunger, a lock ring secured around the socket in spaced relation from said flange and engaging the adjacent washers to preload the washers, a spring between said plungers urging the lower plunger against a body of fluid in the bottom'of said housing and urging the upper plunger against the washers with a force less than the preload on the washers created by the lock ring, a choke ring in cooperation with said valve member immersed in the body of fluid beneath the lower plunger adapted to receive fluid between said valve and said choke ring and between said housing wall and said choke ring, and a spring on said valve member urging said choke ring adjacent said valve to prevent flow of fluid therebetween, said spring on the valve member moving therewith through the body of the fiuid but being deflected to permit separation of the choke ring and valve member for accommodating rapid flow of fluid therebetween when thrust load on the valve is released suificiently to accommodate expansion of the dished washers to their preloaded conditions and expansion of the spring between the plungers to move the upper plunger and valve toward the open end of the housing.

3. An automatic clearance regulator comprsing, a housing having a closed end and an open end with a cylindrical wall therebetween, a lower plunger member slidable on said wall for confining fluid in the closed end of the housing, a thrust load transmitting valve member between said lower plunger and the closed end of said housing and having a stem slidable through said lower plunger, an upper plunger on said valve stem and on said wall spaced from said lower plunger, a shoulder on said valvelstem, means on said lower plunger cooperating with said shoulder for limiting axial movement of said lower plunger toward the closed end of said housing, a compression spring between said upper plunger and said lower plunger, a choke ring cooperating with said valve member adapted to receive fluid between said valve and said choke ring and between said housing wall and said choke ring, and a spring carried by said valve member urging said choke ring into sealing engagement with said valve to prevent a flow of fluid therebetween, said last named spring having a force less than the force of said spring between said plungers.

4. A clearance regulator which comprises, a housing having a closed end and an open end, a choke ring freely slidable in the body accommodating flow of fluid therearound and therethrough, a valve member slidable in said housing and coacting with said choke ring to control flow therethrough, a spring carried by said valve member urging said choke ring toward the valve to seat the choke ring on the valve, a plunger slidable in said housing and on said valve member for confining fluid in the closed end of the housing, and a spring bottomed on the plunger and acting on the valve to move the valve toward the open end of the housing and away from the choke ring, said spring carried by the valve being deflectable to accommodate separation of the choke ring and valve.

5. A clearance regulator comprising, a housing, a plunger slidably mounted in said housing and having a recess in the outer face thereof, a push rod receiving socket member extending into said recess, a spring Washer assembly surrounding said socket member, means on said socket member pre-loading said assembly, said assembly being bottomed respectively on said plunger and on said socket member for transmitting thrust therebetween, and a spring in said body acting on said plunger to increase the operating length of the regulator, said spring washer assembly resiliently carrying said socket member providing a predetermined clearance in the regulater.

6. A self-adjusting hydraulic tappet which comprises a housing having an open end and a closed end, a valve seat in said housing, a thrust transmitting valve coacting with said seat, a spring biasing said valve toward said open end of the housing and away from said seat, and a pre-loaded clearance regulating spring bottomed on and movable with said valve to maintain its pre-load in all positions of the valve.

References Cited in the file of this patent UNITED STATES PATENTS Re. 21,931 Voorhies et al. Oct. 21, 1941 1,445,118 Ware Feb. 13, 1923 1,623,043 Brown 1. Apr. 5, 1927 2,066,976 Holmes Jan. 5, 1937 2,119,096 Buckley May 31, 1938 2,250,752 Dayton July 29, 1941 2,468,332 Johnson Apr. 26, 1949

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