Four-Cycle Engine

This invention relates to a four-cycle engine and more particularly to an improved valve and combustion chamber arrangement for such an engine.

As is well known, the performance of a four-cycle engine may be improved through the use of multiple intake and/or exhaust valves. By using multiple valves, the valve area communicating with each chamber may be increased. The use of multiple valves permits an increased valve area without increasing the inertia of individual valve components as would be true if merely larger valves were employed. Hence, higher engine speeds may be attained through the use of multiple valves. In addition, the use of multiple valves permits a greater valve area in a given combustion chamber area. The use of multiple valves, however, does present some difficulties. As a number of valves in a given chamber is increased, it is necessary to place the valves so that they do not interfere with each other during their opening and closing movement. In addition, the use of a greater number of valves may complicate the actuating system for the valves.

It is, therefore, a principal object of this invention to provide an improved and simplified multiple valve arrangement for an internal combustion engine.

It is a further object of the invention to provide a multiple valve arrangement wherein more than one valve is operated by the same cam shaft.

It is desirable to provide a direct valve actuation wherein the cam lobes act directly on the valves to operate them. Such an arrangement reduces the complexity of the valve train and further permits higher speeds due to the lower inertia. However, where multiple valves are employed, and particularly if a greater number of valves than two for either the intake or exhaust are employed, it has been difficult if not impossible to provide such direct action on all valves.

It is, therefore, yet a further object of this invention to provide a combustion chamber for an engine that permits the use of multiple, directly actuated valves.

A first feature of this invention is adapted to be embodied in a valve train for an internal combustion engine that comprises a cam shaft and a plurality of valves operated by the cam shaft, at least two of which communicate with the same chamber of the engine. In accordance with this feature of the invention, the two valves reciprocate about respective axes that are not parallel to each other.

Another feature of the invention is also adapted to be embodied in a valve train for an internal combustion engine. In accordance with this feature of the invention, the valve train includes a cam shaft and at least three valves operated by the cam shaft and which communicate with the same chamber of the engine. In accordance with this feature of the invention, the three valves each reciprocate about a respective axis and the axis of one of the valves is not parallel to the axes of the remaining valves.

Yet another feature of this invention is adapted to be embodied in a combustion chamber for a reciprocating engine. In accordance with this feature of the invention, a cylinder head forms a closure for a cylinder bore and defines at least in part the engine combustion chamber. The cylinder head is configured with at least two valves of the same function that lie on one side of a plane containing the axis of the cylinder bore. At least three valves of a different function also lie within the combustion chamber. One of these three valves is positioned further from the plane than the other two valves and these three valves lie predominantly on the other side of the plan than the first two mentioned valves.

When the valves are described in the specification and claims thereof as being of "the same function," this is intended to refer to the valves as being either all intake valves or all exhaust valves. When the term "different function" is employed herein, it is intended to refer to exhaust valves if the "same function" valves are intake valves, or intake valves if the "same function" valves are exhaust valves.

Yet another feature of the invention is adapted to be embodied in a valve train for an internal combustion engine having a cam shaft and a plurality of valves operated by the same shaft. In accordance with this feature of the invention, the cam shaft is provided with a single lobe for operating plurality of valves. A single rocker arm is provided and is supported for pivotal movement with a follower portion adapted to be engaged by the cam lobe for pivoting the rocker arm. The rocker arm has individual finger portions adapted to cooperate with each of the valves for operating the valves upon pivotal movement of the rocker arm.

FIG. 1 is a cross-sectional view taken through a single cylinder of a multiple cylinder internal combustion engine employing this invention, and is taken generally along the line 1--1.

FIG. 2 is a cross-sectional view taken along the line 2--2 of FIG. 1, and also shows generally the combustion chamber configuration.

FIG. 3 is a partial cross-sectional view taken along the line 3--3 of FIG. 1.

FIG. 4 is a cross-sectional view taken generally along the line 4--4 of FIG. 2.

FIG. 5 is a cross-sectional view, in part similar to FIG. 1, and is taken generally along the line 5--5 of FIG. 6, showing another embodiment of the invention.

FIG. 6 is a cross-sectional view taken along the line 6--6 of FIG. 5.

FIG. 7 is a cross-sectional view taken along the line 7--7 of FIG. 6.

FIG. 8 is a cross-sectional view taken along the line 8--8 of FIG. 7.

FIG. 9 is a cross-sectional view, in part similar to FIGS. 4 and 7, and shows a still further embodiment of the invention.

FIG. 10 is a cross-sectional view taken along the line 10--10 of FIG. 9.

FIG. 11 is a partially schematic, perspective view showing the intake flow paths generated by the embodiments of FIGS. 1 through 4, 5 through 8, and 9 and 10.

In FIGS. 1 through 4 the reference numeral 11 indicates generally an in-line four-cycle internal combustion engine constructed in accordance with a first embodiment of the invention. Although all embodiments of the invention are described in conjunction with an engine of this cylinder number and configuration, it should be readily apparent that this invention is adapted to be employed with engine of other cylinder numbers and of other configurations. Since the invention is directed primarily toward the valve train and combustion chamber configuration, only this portion of the engine has been illustrated in detail, and for the same reason only the constructed associated with one of the cylinders in each embodiment will be described.

The engine includes a cylinder block 12 that is formed with cylinder bores 13. Pistons (not shown) are supported for reciprocation in the cylinder bores 13 and drive the crankshaft (which is also not shown) in a known manner. A cylinder head 14 is affixed to the cylinder block 12 in a known manner. The cylinder head 14 is formed with individual cavities 15 that cooperate with the cylinder bores 13 and respective pistons. At times the cavities 15 will be referred to as the combustion chamber.

The cylinder head 14 is formed with intake passages that communicate with each combustion chamber 15. The intake passages consist of pairs of first intake passages 16 that extend through an intake side of the cylinder head 14 and which terminate at respective intake ports. The passages 16 are configured as shown in FIG. 1. Between the intake passages 16, the cylinder head 14 is formed with a third intake passage 17 for each combustion chamber 15. The intake passage 17 also terminates at an intake port. As will be desribed, the intake port associated with the passage 17 is disposed between the ports formed by the passages 16 and is disposed outwardly of a plane 18 that contains the axis of the cylinder bore 13.

Intake valves 19 cooperate with valve seats formed in the intake ports associated with the intake passages 16 so as to control the flow of intake charge into the combustion chamber 15. An intake valve 21 cooperates with a valve seat formed at the intake port associated with the intake passage 17. The intake valves 19 reciprocate along respective parallel axes, indicated by the line 22 (FIG. 2). The intake valves 19 are supported for reciprocation along the axes 22 by valve guides 23 that are pressed into the cylinder head 14. The intake valve 22 for each cylinder 13 reciprocates along an axis 24 (FIG. 4) as defined by a valve guide 25 that is also pressed into the cylinder head 13. The axis 24 is not parallel to the axis 22 for a reason to be described.

The axes 22 and 24 all intersect the axis of rotation 0.sub.1 of an intake cam shaft, indicated generally by the reference numeral 26. The intake cam shaft 26 is supported for rotation in a cam tower 27 that is affixed to the cylinder head 14 in a known manner. Bearing caps 28 are affixed at spaced locations to the cam tower 27 and cooperate with the cam tower to journal the intake cam shaft 26. Because the intake valve axes 22 and 24 intersect the axis of rotation 0.sub.1 of the cam shaft 26, it is possible to directly operate each of the intake valves 19 and 21. The cam shaft 26 is provided with a first pair of lobes 29 that engage tappet followers 31 that are reciprocally supported in the valve tower 27 and which contact the stems of the intake valves 19 for their direct actuation. The cam shaft is also provided with a lobe 32 between the lobes which cooperates with a tappet follower 31 for directly actuating the intake valves 21.

Valve springs 33 encircle each of the intake valves 19 and 21 and act against keeper spring retainer assemblies 34 of urging the valves 19 and 21 to their closed positions.

The reciprocal axes 22 of the intake valves 19 lie at an angle .alpha..sub.3 to the plane 18 (FIG. 1). The axis 24 of the intake valves 21 lie at an angle .alpha..sub.1 to the plane 18. The angle .alpha..sub.1 is greater than the angle .alpha..sub.3. That is, the axes 22 of the intake valves 19 are at a lesser angle to the cylinder bore axis than is the axis 24 associated with the intake valve 21. As a result, the intake valve 21 is spaced radially outwardly from the plane 18 toward the periphal edge of the cylinder bore 13, as clearly shown in FIG. 2. This arrangement permits the three intake valves 19, 21 all to reciprocate between their open and closed positions without interference with each other, while at the same time maximizing intake valve area. Due to this different angle relative to the cam shaft rotational axis 0.sub.1, the cam lobe 32 is advanced relative to the cam lobes 29 so that all intake valves 19 and 21 will be operated simultaneously. Of course, if desired, a different valve timing might be employed. Since the axes 22 and 24 all intersect the cam shaft axis 0.sub.1, it is possible to operate more than two intake valves from the same cam shaft.

Exhaust passages 35 extend through the side of the cylinder head 14 opposite to the intake passages 16 and 17. There are a pair of exhaust passages 35 associated with each cylinder bore 13 in connection with this embodiment. The exhaust passages 35 terminate in exhaust ports and valve seats. Exhaust valves 36 cooperate with the valve seats and exhaust ports for controlling the communication of the combustion chamber 15 with exhaust passages 35. The exhaust valves 36 are supported for reciprocation about respective axes 37 by means of valve guides 38 that are pressed into the cylinder head 14. The exhaust valve axes 37 lie at angle .alpha..sub.2 to the plane 18. The angle .alpha..sub.2 is lss than the angle .alpha..sub.1 of the intake valves 21 but greater than the angle .alpha..sub.3 of the intake valves 19.

The exhaust valve axes 37 intersects the axis of rotation 0.sub.2 of an exhaust cam shaft 38. The exhaust cam shaft 38 is rotatably journaled in the cam tower 27 is journaled by the cam tower 27 and bearing caps 39 that are affixed in a known manner to the valve tower 27. Because the axes 37 intersects the exhaust cam axes 0.sub.2 it is possible to directly actuate the exhaust valves 36. For this purpose the exhaust cam shaft 38 is provided with lobes 41 that engage tappet followers 42 which, in turn, directly actuate the exhaust valves 36.

Valve springs 43 encircle the exhaust valves 36 and engage keeper spring retainer assemblies 44 for urging the exhaust valves 36 to their closed position.

As may be readily seen from FIG. 2, the centers of the exhaust valves 36 lie on a plane 45 that is offset from the plane 18 on the side opposite the intake valves 19 and 21.

A threaded spark plug opening 46 is formed in the cylinder head 14 on the plane 18 and at the center of the respective cylinder bore 13. A cam shaft cover 47 is affixed in any suitable manner to the cam tower 27 so as to enclose the cam shafts 26 and 38. The cover 47 is formed with openings 48 that are aligned with the spark plug openings 46 to permit insertion and removal of the spark plugs.

An engine constructed in accordance with a second embodiment of this invention is identified generaly by the reference numeral 61. The engine 61 has its intake and exhaust valves and intake and exhaust ports arranged as in the embodiment of FIGS. 1 through 4. Thus, these components have been identified by the same reference numeral and a detailed description of similar components will not be repeated. This embodiment differs from the embodiment of FIGS. 1 through 4 in that the intake and exhaust valves 19, 21 and 36 are not directly actuated by the cam shafts. Rather, the valves 19, 21 and 36 are operated by rocker followers, as will be described.

The axes of reciprocation 22 of the intake valves 19 are, as in the previously described embodiment, parallel to each other and lie at angle .alpha..sub.3 to the plane 18. The axis of reciprocation 24 of the intake valve 21 lies at angle .alpha..sub.1 to the plane 18, also as in the previously described embodiment. As in the previously described embodiment, the axes 22 and 24 all intersect along a line. However, in this embodiment the line of intersection is not coincident with the axis of rotation of the actuating cam shaft. Rather, in this embodiment the axes of reciprocation 22 and 24 intersect along a line 62 (FIG. 8) which generally lies along the center portion of the stems of the valves 19 and 21 when these valves are in their closed positions.

In this embodiment an intake cam shaft 63 is rotatably supported directly in the cylinder head 14 by means of bearings formed in the cylinder head 14 and bearing caps 64 that are affixed to the cylinder head 14. In accordance with this embodiment of the invention, the intake cam shaft 63 has only a single lobe 65 for operating all of the intake valves 19 and 21 associated with each cylinder bore 13. In this embodiment the axis of rotation of the cam shaft 63, which axis is identified by the line 66 (FIG. 8), is disposed outwardly from the plane 18 relative to the line 62 of intersection of the axes 22 and 24. A rocker arm assembly, identified generally by the reference numeral 67, is provided for each cylinder and is journaled in the cylinder head 14 on a respective rocker arm pivot 68. As may be readily seen from FIG. 8, the rocker arm 67 has a pair of outer finger portion 69 and a central finger portion 71. Adjusting screws and jam nuts 72 are associated with each of the finger portions 69 and 71 for coaction with the respective valve 19, 21 so as to transmit pivotal movement of the rocker arm assembly 67 into reciprocation of the respective intake valves. As is well known, the adjusting screw, jam nut assembly 72 permits adjustment of the clearance between the rocker arm 67 and the respective intake valve 19, 21.

The exhaust valves 36 are similarly operated by means of an exhaust cam shaft 73 that is journalled in the cylinder head 14 on its exhaust side by means of integral bearings and bearing caps 74. The exhaust cam 73 has individual lobes 75 that cooperate with bifurcated rocker arm assemblies, indicated generally by the reference numeral 76, which are supported on rocker arm pivots 77. Adjusting screws and jam nuts 78 transmit the pivotal movement of the rocker arms 76 into reciprocation and exhaust valves 36.

A cam cover 79 is affixed to the cylinder head 14 to enclose the valve actuating mechanism. The cam cover 79 is formed with spark plug access openings 81 to permit insertion and removal of spark plugs from the cylinder head spark plug openings 46.

The reference numeral 101 illustrates an internal combustion engine having a valve train constructed in accordance with a still further embodiment of the invention. As with the embodiments of FIGS. 1 through 4 and FIGS. 1 through 8, the orientation of the valves and main components are the same and for that reason these components have been identified by the same reference numerals and detailed description of them will not be repeated. Like the embodiment of FIGS. 5 through 8, the intake valves and exhaust valves of the embodiment are operated through rocker arm assemblies rather than directly as in the embodiment of Figures 1 through 4. Thus, the axes of reciprocation of the intake valves all intersect the line 62 which lies generally along the center of the stems of the intake valves. Unlike the embodiment of FIGS. 5 through 8, however, this embodiment employs an individual rocker arm for operating each valve. Therefore, only this portion of the construction will be described in detail and reference may be had to the description of the remaining embodiment for components which are not described in this embodiment, and for that reason have been identified by the same reference numerals.

In this embodiment an intake cam shaft 102 is journaled directly by the cylinder head 14 and by bearing caps 64 that are affixed to the cylinder head 14. The intake cam shaft 102 rotates about the axis 66. In this embodiment the intake cam shaft 102 is provided with individual lobes comprising a pair of lobes 103 and an intermediate lobe 104. The lobes 103 coacts with the intake valves 19 whereas the lobe 104 cooperates with the intake valve 21.

A rocker arm 105 is provided for each intake valve 19, 21 and is supported for pivotal movement by means of a respective pivot assembly 106 carried in the cylinder head 14. Each pivot assembly 106 may constitute either a mechanically adjustable assembly of a known type or an automatic, hydraulically operated tappet assembly of any known type; thus, lash adjustment is afforded by the individual pivots 106.

The exhaust valves which are not shown in this embodiment are operated by individual rocker arm assemblies which are the same as those employed in connection with the intake valves 19, 21. For that reason, this portion of the assembly has not been illustrated, nor is description believed to be necessary.

It should be readily apparent that the described configuration permits valve area and, hence, breathing of the engine to be maximized without resulting in interference between the valves. Furthermore, by providing the offsetting of one valve relative to other valves of the same function, while maintaining intersection of their reciprocal axes at the appropriate location, it is possible to actuate all of the valves of the same function from a single cam shaft.

In addition to affording a larger valve area and reduced inertia, the described valve placement also promotes more uniform charging of the cylinder and better scavenging of it. FIG. 11 is a schematic view that shows generally the flow pattern of the intake charge which would be typical of each of the described embodiments. As seen in this figure, the intake charge flowing through the intake passages 16 past the intake valves 19 generally follows the pattern of the lines S.sub.1 and S.sub.2. The flow through the intake passage 17 past the intake valves 21 follow the path indicated by the arrow S.sub.3. Because of the lesser inclination of the intake valves 19 to the center plane 18, the charge flowing through the intake passages 16 will impinge on the opposing portion of the cylinder wall 13 and be directed generally toward the center of the wall. The charge from the intake passage 17 will not impinge upon the cylinder wall as soon and, hence, this charge will be directed more toward the center of the cylinder bore 13. As the piston C moves upwardly, the flow from the intake passages 16, as indicated by the arrows S.sub.1 and S.sub.2 will impinge on the head of the piston and be redirected to flow in a generally circumferential direction to improve charge distribution within the combustion chamber 15.

In the illustrated embodiments there are three intake valves and only two exhaust valves. It is believed to be readily apparent to those skilled in the art that an arrangement may be employed with the exhaust valves similar to that employed with the intake valves so that three exhaust valves may also be utilized. Furthermore, more than three valves of each function may also be used in conjunction with the engine. Various other changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.