US2279413A - Internal combustion engine - Google Patents

Description

A ril 14, 1942. a. READ INTERNAL COMBUSTION ENGINE Filed Feb. 23', 1959 s Sheets-Sheet 1 AM 14, 1942. B. READ 2,219,413

INTERNAL COMBUSTION ENGINE Filed Feb. 23, 1939 5 Sheets-Sheet 2 [N VEN TOR A TTORNE Y5.

April 14, 1942 D INTERNAL COMBUSTION ENGINE Filed Feb. 23, 1939 5 Sheets-Sheet 3 INVENTOR Feai ORNE Y5.

April 14, 1942. B. READ 2,279,413

INTERNAL COMBUSTION ENGINE Filed Feb. 23, 1939 5 Sheets-Sheet 4 11v VENTOR B /faur BY A TTORNE Ys'.

April 14, 1942. E 2,279,413

INTERNAL COMBUSTION ENGINE Filed Feb. 25, 1939 5 Sheets-Sheet 5 ENTOR. 1842 00 7' AITO RJVEYS Patented Apr. 14, 1942 INTERNAL COMBUSTION ENGINE Ball'om- Read, Detroit, Mich.

Application February 23, 1939, Serial No. 257,779 In Great Britain February 24, 1938 Claims.

This invention relates to internal combustion engines and particularly such engines as operate upon the four stroke principle, the principal object being the provision of an engine of the type described of improved construction capable of operating in an improved and more economical manner.

Objects of the invention include the provision of a four cycle internal combustion engine having intake and exhaust valves and a pair of cam shafts for operating the same, together with means for varying the angular relationship of the cam shafts relative to the crankshaft of the engine; the provision of an improved construction for varying the angularity of the cam shaft in an engine of the type described; the provision of means in an engine of the type described for automatically varying the angular adjustment of the cam shaft in response to predetermined conditions of operation of the engine; the provision of an adjusting mechanism of the type described including pairs of intermediate driving gears for the cam shafts and means for simultaneously moving such pairs of intermediate gears about the axes of the driving and driven shafts, respectively, to alter the angular relationship of both cam shafts relative to the crankshaft or other driving shaft of the engine; the provision of an adjusting mechanism of the type described employing a chain as a driving medium between the cam shafts and the driving shaft together with bodily shiftable chain wheels or sprockets interposed between the driving shaft and each of the cam shafts and between the two cam shafts, re-

-spectively, together with means for simultaneously shifting the positions of the chain or sprocket wheels; and to provide an adjusting mechanism of the type described including automatically actuated hydraulic means the effects of which are controlled by the speed of rotation of the engine.

Other objects of the invention include means for effecting a satisfactory scavenging of the engine cylinders of a carburetor fed engine and particularly in an engine where the inlet valves and the exhaust valves therefor are controlled by separate cam shafts; the provision of an internal combustion engine having a pair of independent existing types and particularly the unsatisfactory performance of such engines in the lower speed ranges due to the falling off of the velocity cam shafts each of which controls one inlet and I of the combustible mixture particularly where large carburetors and mixture passages are employed; the provision of a construction as above described in which scavenging air is introduced into the cylinders of the engine and separate throttle means are provided for controlling the flow of scavenging air and the combustible mixture to the cylinders; and the provision of means automatically operable during operation of the engine for varying the proportional amounts of scavenging air and combustible mixture fed to the cylinders of the engine in accordance with certain operating conditions in the engine.

The above being among the objects of the present invention the same consists in certain novel features of construction and combinations of parts to be hereinafter described with reference to the accompanying drawings, and then claimed, having the above and other objects in view.

In the accompanying drawings which illustrate suitable embodiments of the present invention and in which like numerals refer to like parts throughout the several different views,

Fig. 1 isa partially broken, partially sectioned front elevational view of the front end of an internal combustion engine embodying one form of timing gear constructed in accordance with the invention;

Fig. 2 is a sectional view thereof taken mainly on the line 2-2 of Fig. 1;

Fig. 3 is a fragmentary plan view of the engine shown in the preceding figures showing the valves for one cylinder thereof;

Fig. 4 is a view similar to Fig. 1 but illustrating an alternative form of cam shaft drive;

Fig. 5 is a fragmentary transverse sectional elevational view of a known form of cylinder head which may be used in carrying out one feature of the invention;

Fig. 6 is a fragmentary sectional elevational view of a modified arrangement of the construction shown in Fig. 4 whereby the angular relationship of the two cam shafts relatively to the crankshaft can be adjusted automatically by bydraulic means;

Fig. 7 is a fragmentary, partially broken, par- I tially sectioned view taken on the line 11 of Fig. 6;

Fig. 8 is a more or less diagrammatic, partially broken, partially sectioned end elevational view of a cylinder head, incorporating a pair of inlet valves, respectively, operable from the two adjustable cam shafts, arrang according to the invention, the view also owing a throttle valve,

ing an alternative arrangement according to the invention, in which throttle valves controlling the air passage and the mixture passage are interconnected, the former also being associated with means by which the angular relationship between the cam shafts and the crankshaft can be adjusted.

Fig. 10 is a more or less diagrammatic partially broken, partially sectioned and elevation of an engine combining the features brought out individually in Figs. 4 and 9.

This invention relates to internal combustion engines, particularly to such as operate on the four stroke cycle, of the kind having two cam shafts the angular relationship of both of which can be adjusted relatively to the crankshaft, the

valve mechanism being such that by this angular adiustment, the overall inlet and/or exhaust period of each cycle can be increased or reduced.

Thus each cam shaft may control one inlet and one exhaust valve per cylinder, or instead of their being two inlet and exhaust valves per cylinder, there may be but a single inlet and a single exhaust valve, each of these being connected with the two cam shafts in such a manner that the overall inlet and exhaust period of each cycle can be increased or reduced. The

presentinvention provides improved means for adjusting such cam shafts and particularly to such means as will be automatically operated in response to predetermined conditions of operation of the engine.

According to one feature of the invention, each cam shaft is driven through a pair of intermediate gears, both intermediate gear pairs being simultaneously movable about the axes of the driving and driven shafts, respectively, to alter the angular relationship of both cam shafts relatively to the crankshaft. Obviously, the driving shaft may be the crankshaft or some other shaft driven therefrom, and the driven shafts may be the cam shafts or other shafts from which the cam shafts are driven.

According to another feature of the invention, both cam shafts are driven by means of an endless chain embracing a driving chain wheel and two driven chain wheels, in combination with intermediate chain wheels disposed in such manner that two of them can be positively moved, while the third is automatically moved by a spring maintaining substantially constant tension in the chain, to alter the angular relationship of both cam shafts relatively to the crankshaft. The invention further includes an engine, of the kind specified, of which the angular relationship of the two cam shafts relatively to the crankshaft can be adjusted automatically by hydraulic means, dependently upon the engine speed.

The invention further embraces the combination with a carburetor fed internal combustion engine, of which each cam shaft controls one inlet and one exhaust valve per cylinder, of means for supplying air only to the inlet valve of a cylinder which opens first when the cam shafts have been angularly adJusted, with the object of scavenging a cylinder by air during the overlap period between the exhaust and inlet periods. It is well known that conventional types of carburetor fed internal combustion engines. designed to give a high volumetric efliciency at high speeds, must be equipped with relatively large carburetors if full advantage is to be taken of their capabilities. Such carburetors, however, do not generally give very satisfactory'performances in the lower speed ranges, due to the compiazatively low velocity of the air flowing through in. Accordingto a further feature of the invention, the first opening inlet valve of a cylinder is supplied with air only through a throttle valve, the carburetted mixture to the other inlet valve being supplied through another throttle valve (or valves). By closing the air throttle valve to a greater extent thanthe other at low engine speeds, the velocity of the air flow through the carburetor can be increased. The throttle valves maybe linked together or'otherwise interconnected so that the air throttle valve will automatically throttle to a greater extent than the mixture throttle valve, as the latter is progressively closed from the wide open position.

The differential throttle action above mentioned may be automatically controlled in response to the adjustment of the'angular relationship between the cam shafts and the crankshaft, as by means of the oil pressure of the engine. Thus, the adjusting means of the cam shafts, automatically'controlled responsively to the engine speed, may be arranged to act on the first-mentioned throttle valve.

It should be understood that the principles of the cam shaft drives shown in the drawings may be used for the adjustment of cam shafts mounted in any position on an engine. For example, it is common; practice to mount two cam shafts on the cylinder head of an overhead valve engine, and operate two or four valves by direct action. In cases of this kind, a single -chain embracing both cam shaft chain wheel and a sprocket on the crankshaft may be impracticable; and it may be necessary to mount the driving wheel for the cam shafts on a layshaft substantially above the crankshaft center, and to drive the layshaft from the'crankshaft by an auxiliary chain or other suitable means. Such auxiliary chain can also be conveniently used for driving accessories. For similar reasons, it may be desirable to add auxiliary gears to the train shown in Fig. 1. However, where possible it will usually be desirable to mount the driving gear or wheel for the cam shafts on the engine crankshaft and it is shown in this position in the drawings by way of illustration. It is also obvious that a variety of means for changing the position of the shiftable gears or chain wheels may be employed, those shown in the drawings being illustrated only in the broader sense.

, Referringnow to the drawings and particularly to the construction shown in Figs. 1 to 3, II and I 2 are cam shafts driven at half the speed of the crankshaft II by gears ll, l5, Ii

I1, l8, l9 and 20.. The cam shafts. II and I2 at the proper center tance by the links 26, and the gears l8 an by the links 21 and 8 which maybe operated by one of several methods to be later described.

When the centers of the gears i8 and I8 are moved to positions I and I8 (orto some intermediate positions) by movements of the links 21, 28 to the positions 21 28 the cam shafts II and I2 are respectively advanced and retarded with relation to the crankshaft l3. Obviously the angular adjustment of each cam shaft may be made equal or otherwise, dependent upon the geometry and proportionsof the gear train.

Each cylinder of the engine is provided with four conventional valves 38, 3|, 82 and 33 (as shown by Fig. 3) actuated, respectively, by the rockers 34, 35, 36 and 31 from the cam shafts II and I2 through the medium of push rods 38 and tappets 39. The valves 38, 3|, 32 and 33 include two intake valves and two exhaust valves and in the broader aspects of the invention these may be arranged as desired. In other words both exhaust valves may be located on one side of the engine and both intake valves on the other, or one inlet valve and one exhaust valve may be located on each side, but in any case each cam shaft must operate one exhaust valve and one inlet valve. As a matter of illustration it is assumed that and 3| are exhaust valves, and 32 and 33 are inlet valves and the rocker arms are arranged accordingly. When the gears l5 and iii are in the slow speed position shown, the exhaust cams 40 and 4| are preferably set to operate the exhaust valves 30 and 3| in unison. When, however, the gears l5 and I8 are moved respectively anti-clockwise and clockwise with reference to the crankshaft axis, the exhaust cam 48 on the cam shaft ll opens the valve 30 earlier, and the exhaust cam 4| on the cam shaft i2 closes the valve 3| later, thus increasing the total opening period of the two valves by an amount equal to the total angular adjustment of the cam shafts II and I2 with respect to crankshaft l3.

In a similar manner, the inlet cams 42 and 43 on the cam shafts II and I2, respectively, may be set to operate the valves 32 and 33 in unison at slow speeds, and to open the valve 32 earlier and to close the valve 33 later as their respective cam shafts are advanced and retarded.

It will be understood that in the broader aspects of the present invention any suitable means may be provided for operating the links 21, 28 and, therefore, controlling the rotational positions of the cam shafts II and i2 with respect to the crankshaft i3. One such means is illustrated in Fig. 1 including a cylinder 63, suitably mounted on the engine frame, fitted with a piston or plunger 64 pivoted to a connecting rod 65 which in turn is connected to the upper and inner ends of the links 21 and 28. The closed end of the cylinder 63 is connected to a source of oil under pressure, which is responsive to the engine speed, through an orifice 66. At low engine speeds when the oil is warmed up (when the oil pressure is low,) the piston 64 is held at the top of its stroke by a suitable spring 61. As the engine speed increases the rising oil pressure forces the piston outwardly of or downwardly in the cylinder 63 against the action of the spring 51, thus causing shifting of the links 21 and 28 whereby as previously described, one cam shaft will be. advanced and the other retarded.

II by the links 23. The. movement of the ge r l6 and I8 is controlled.

. and 58.

In Figs. land 10 the crankshaft 44 drives the cam shafts 46 and 48 in the same direction and at one-half crankshaft speed through the medium of a chain 41 and chain wheels 48, 48 and 56. Idler chain wheels 5|, 52 and 53 are provided for the purpose of cam shaft adjustment, and to maintain correct tension in the chain. Assuming that the cam shafts 45 and 46 are in. optimum relationship to the crankshaft 44 for slow speed performance, it is obvious that a movement of the center of the chain wheel 5| to a new position il will advance the cam shaft 45 and retard the cam shaft 46.

In order to support the chain wheel 52 and 53 for their required movement, they are mounted between the free. ends of pairs of links 54 the opposite ends of which are pivotally secured to the engine frame as indicated. In the construction illustrated in Fig. 4 a piston 63', piston or plunger 64', piston rod 65, and spring 61' corresponding to the similarly numbered parts shown in Fig. l are employed but in this case the rod 65 is fixed with respect to the piston 64 and extends downwardly therefrom where its lower end is guided in a bearing member 18 fixed with respect to the engine frame at such point. Intermediate its length the rod 65' is provided with a fixed bracket 13 upon whichlthe chain wheel 5| is rotatably mounted. A cross-bar 68 is also mounted upon the bracket 65 by means of a pin 1| located midway between the ends thereof. One end of the cross-bar 68 is connected by means of a link 12 with the journal for the chain wheel 53 supported between the free ends of the corresponding pair of links 54. The opposite end of the cross-bar 68' is connected to the journal for the chain wheel 52, carried between the free ends of the corresponding pair of links 54,

by means of a coil spring 55.

In compression ignition and other engines in which the fuel is injected after the valves have closed, a duplication of inlet valves would be of no advantage so far as scavenging is concerned. For engines of this type, and in cases where the complication of multiple valves is not warranted, a method whereby the opening and closing points of an individual valve may be controlled by means of two cam shafts is shown by Fig. 5. Thus, both the cam shafts (of Fig. l or of Fig. 4) may be provided with an inlet and exhaust cam for each cylinder, together with tappets and push rods and 6| for operating the rockers 51 One of the two similar valves is shown at 56, and each is provided with a rocker lever 59, which is preferably universally mounted on a hemispherical bearing 62, capable of sliding across the end of the valve stem, to accommodate the small lateral motion of the lever 58 which follows the movement of the end of the rocker 51. When the cam shafts have been advanced and retarded respectively from the slow speed position, the two cams which operate the valv 56 are out of phase. The rocker 51, for instance, will, therefore, depress the end of the lever 59 in contact with it, thus opening the valve 56 approximately one-half the amount, since the other rocker 58 forms a fulcrum for the lever 59. When the other rocker 58 depresses the end of the lever, both the rockers 51 and 58 cooperate in opening the valve 56. At the end of the opening period, the rocker 51 will come to rest first, and the closing point will be controlled by the rocker 58.

In carrying out the invention use may be made of a standard pressure lubrication system having the relief valve located in the pump itself. Such a relief valve is usually of the ball variety, but if it is of the plunger type coacting with a progressively opening orifice the pressure will be found to be nearly proportionalto the speed after the oil has attained a fairly uniform temperature. The orifices 66 and 68' should preferably be quite small in order to prevent the adjustment from being carried out too actively when the oil is cold. On the other hand, if the relief valve is placed where shown in Fig. 6, the orifice 56'', corresponding to the orifices 86 and 86' previously described, should be at least as large as the effective opening of said relief valve. The representation in Fig. 6 is substantially the same in general as that in Fig. 4 and consequently like parts are indicated by the same numerals except that such numerals bear a double prime mark.

It is, of course, not necessary, in accordance with the invention, that the angular adjustment of the cam shafts should vary exactly proportionally with the engine. speed throughout the whole range. In some cases it may be desirable that the ratio of the angular adjustment to the increase in speed should bedifierent at slow and high speeds. It may even be desirable to make arrangements for the cam shaft adjustment to be reduced when the oil is cold.

Figs. 6 and 7 actually show a pressure-relief valve, of the progressively opening type, incorporated in the cylinder 63", such relief valve including a pointed ended plunger 80 pressed in the closing direction by means of a spring 8| held in position by an adjustment nut 82,

In addition, a thermostatically controlled ar rangement is introduced for taking care of the varying viscosity of the oil, as the hole 66" cannot in these conditions be a small one. This is shown in Fig. 7 and includes a slidable valve member 83 controlled by a bi-metallic strip 84 shown in full lines in the position it occupies when the engine and oil are cold. In these conditions an opening 85 in the valve member is aligned with similar small openings 86 in the head of the cylinder 63". As the oil reaches its normal running temperature the bi-metallic strip flexes (to the position shown by chain lines), and drawing with it the valve member progressively closes its passage.

If desired the spring 61 opposing the movement of the plunger 64" may be of the type having coils of a variable pitch in order to vary the timing characteristics.

Obviously other hydraulic means, the pressure of which varies with the engine speed, may be used instead of that specifically illustrated, and the thermostatic arrangement may be disposed elsewhere in the system. It will also be evident that the arrangement illustrated may be applied to the construction of Figs. 1 to 3, or to other types of engine to which the invention relates.

In Fig. 8, 88 and 89 represent the axes of the two cam shafts which can be angularly adjusted relatively to the crankshaft (not shown), as by the means shown in previous views. 90 and 9| are the two inlet valves for one cylinder of the engine, an inlet passage 92 for the former having a throttle valve 93 in it by means of which air' alone can be supplied, whilst 94 is a throttle valve in the passage 95 by which carburetted mixture, from the carburetor 96, is conveyed to the inlet valve 9 I.

In the particular arrangement shown. which is by way of example only, one arm of a bellcrank lever I1 is linked at I. to an arm I! fixed with respect to the mixture throttle valve 24, whilst the other arm is linked at II! to an arm IIII fixed with respect to the air throttle valve 03. The full lines in the drawing show the position of the parts when the mixture throttle valve I4 is closed and the chain lines the posi-- tion occupied thereby when the mixture throttle valve is fully open. The angular setting is such, it will be observed, that the air throttle valve 83 opens at a slower rate than the mixture throttle valve 9| during the initial opening of the latter, owing to the substantial alignment of the link II and arm 8! when the mixture throttle valve is closed.

Thus when the. engine is idling, all the air for the engine passes through the carburetor. But at high engine speeds, when the cam shafts have been adjusted such that there will be an overlap between the air inlet valve and the exhaust valve, or that which opens last, the combustion space of the cylinder will be scavenged with air without there being any loss of combustible mixture.

In the construction of Figs. 9 and 10, the latter of which combines the constructions of Figs. 4 and 9 but in which the push rods and tappets are indicated by the same numerals as are .employed in Fig. 2, and the cylinder valves by the same numerals as employed in Fig. 8, and which constructions are also given by way of example, there is indicated at 63' an hydraulic cylinder, corresponding to the cylinder 63' shown in Fig. 4, by which the angular adjustment of the cam shafts relatively to the crankshaft can be automatically effected responsively to the engine speed as in the first described constructions. IIII represents an arm, with an arcuate slot in it, which is pivotally mounted at its lower end. Its upper end is linked at I to a bellcrank lever II2 linked at II3 to an arm I fixed with respect to the mixture throttle valve 5. Disposed in the arcuate slot is a pin H6 which is linked at I" to a lever II8 connected to the cross-bar 68 operable by the piston of the hydraulic cylinder 63'. The pin H6 is also linked at Illa to a bellcrank lever II! which is in turn linked at I20 to an arm I2I fast on the air throttle valve I22. It will be understood that the valves I22 and H5 and their corresponding passages I23 and I24, correspond to the valves 93 and 94, respectively, and passages 92 and 95, respectively, in Fig. 8.

Figs. 9 and 10 show in full lines the position of the parts when both throttle valves are closed and the cam shafts are adjusted for the idling speed of the engine. Opening the mixture throttle valve I I5, while the engine is still idling, allows the arm IIII to swing idly about its pivotal mounting, as indicated by the chain lines, without the air throttle valve I22 being moved. Consequently, at this time all the air for the engine is being taken through the carburetor. Conversely, if the mixture throttle valve be fully closed, adjustment of the cross-bar 68 dependently upon the speed of the engine will serve for moving the pin IIB idly along the arcuate slot in the arm IIII, as indicated by the chain lines.

. But if the cam shafts have been adjusted to any By means of the invention, it is possible at low engine speeds for the pure air to the one inlet valve of each cylinder to be throttled to a greater extent than the carburetted air, thus to increase the velocity of the air flow through the carburetor, and the arrangement may be such that, when the engine is running idle, all the air supply passes through the carburetor. As the engine speed increases the air throttle valve may be arranged to open progressively in relation to the mixture throttle valve so that at any desired speed between maximum and minimum both throttle valves will be open to the same degree.

Formal changes may be made in the specific embodiments of the invention described without departing from the spirit or substance of the broad invention, the scope of which is commensu rate with the appended claims.

What I claim is: Y

1. In combination with an internal combustion engine having a cylinder provided with two inlet valves and two exhaust valves, a crankshaft, a pair of cam shafts, an operative connection between one of each of said pairs of valves with each of said cam shafts for operating said valves, one of said cam shafts being arranged to open and close the cooperating inlet valve in advance of the opening and closing of the remaining inlet valve by the remaining cam shaft during operation of said engine, means forming a driving connection between said cam shafts and said crankshaft for driving said cam shafts in timed relation with said crankshaft, shiftable elements associated with said driving connection operable to vary said timed relation whereby to enable the overall inlet and' exhaust periods of each cycle of operation of said engine to be varied, means for shifting said shiftable elements during operation of said engine in response to variations of speed of said engine, a throttle valve associated with each of said inlet valves for controlling the feed of fluid thereto, means for feeding air only to the first mentioned inlet valves, means for feeding a carburetted mixture to said remaining inlet valve, and means interconnecting said throttle valves so constructed and arranged as to cause said throttle valve controlling the flow of air to one of said inlet valves to close in advance to closing of the throttle valve controlling the flow of carburetted mixture to the other of said inlet valves during closing movements of both of said throttle valves.

2. The combination called for in claim 1 together with means operatively interconnecting said shifting means and said throttle valve for inter-related movements.

3. The combination called for in claim 1 in which said drive forming means comprises a sprocket wheel secured to each of said cam shafts and to said crankshaft, and a chain drivingly engaging all of said sprocket wheels, and said shiftable elements comprise a bodily shiftable sprocket wheel engaging said chain between each of the first mentioned sprocket wheels.

4. The combination called for in claim 1 in which said drive forming means comprises a sprocket wheel secured to each of said cam shafts and to said crankshaft, and a chain drivingly engaging all of said sprocket wheels, said shiftable elements comprise a bodily shiftable sprocket wheel engaging said chain between each of the first mentioned sprocket wheels, and said means for shifting said shiftable elements comprises a piston operatively interconnected with all of said bodily shiftable sprocket wheels, spring means constantly urging said piston in one direction, and means subjecting the opposite face of the piston to the pressure of the engine lubricating system.

5. The combination called for in claim 1 in which said drive forming means comprises a sprocket wheel secured to each of said cam shafts and to said crankshaft and a chain drivingly engaging all of said sprocket wheels, and said shiftable elements comprise a sprocket wheel engaging said chain between each of the first mentioned sprocket wheels, one of the last mentioned sprocket wheels being mounted for rectilinear movement and the remaining of the last mentioned sprocket wheels being mounted for bodily swingable movement, said one of said last mentioned sprocket wheels being positively connected to one of said remaining of said last mentioned sprocket wheels for movement simultaneously therewith and being connected to the other of said remaining of said last mentioned sprocket wheels by yieldable means.

BALFOUR READ.

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