It is well-known that efficiency of a spark-ignition engine suffers when torque demand is low. In engines provided with cylinder deactivation, efficiency at such low-torque operation conditions can be improved by deactivating some cylinders, which causes activated cylinders to operate at a higher torque operating condition than they would be otherwise if all the cylinders were activated. When cylinder deactivation mode is scheduled, the exhaust and intake valves are decoupled from the cam lobe motion by means of a switchable or deactivatable roller finger follower. The cam motion is absorbed as lost motion within the follower. Thus, the valves remain closed and their respective cylinders are inactive. Typically, a portion of the cylinders, often half, are equipped with deactivators, the packaging of which complicates the cylinder head layout because the deactivatable finger follower is bulkier. Such an engine is referred to as Variable Displacement Engine (VDE), Displacement on Demand, Cylinder Deactivation, Active Fuel Management, etc.
An illustration of a front end of an internal combustion engine 10 is shown in FIG. 1. Engine 10 has a block 12 to which an oil pan 14 is coupled. Engine 10 is a vee engine having two cylinder heads 16. A crankshaft (not shown) is coupled to a pulley 20. Camshafts (not shown) are coupled to pulleys 22. A belt 24 is driven by crankshaft pulley 20 to drive camshaft pulleys 22.
An underside of a cylinder head 30 is show in FIG. 2. The heads of two intake poppet valves 34 and the heads of two exhaust poppet valves 36 are contained within the upper portion of the combustion chamber 32. The combustion chamber is defined by the piston top (not shown), the cylinder wall (not shown), and the upper portion of the combustion chamber 32, called combustion chamber top herein. Orifice 38 is provided for a spark plug. A combustion chamber in a typical, internal-combustion engine is defined by a cylinder wall, a top of a piston that reciprocates within the cylinder wall, and a portion of a cylinder head that includes the intake and exhaust valves. Herein, the portion of the combustion chamber in the cylinder head is called a combustion chamber top.
A prior art cylinder head 50 having cylinder deactivation is shown in FIG. 3. Cylinder head 50 covers four cylinders with two intakes and two exhaust valves per cylinder, thus, 16 valves (not shown). A flange 52 is provided for a valve cover (not shown) to be affixed to the valve train side of cylinder head 50. In the embodiment shown in FIG. 3, valves associated with the outer cylinders are deactivatable and valves associated with the inner cylinders are fixed. Eight deactivatable roller finger followers 54, four exhausts on the left side of FIG. 3 and four intakes on the right side, have the ability to become lost motion devices based on hydraulic pressure provided to followers 54. Any other suitable mechanism or system to actuate may be substituted. Deactivatable followers 54 are wider than fixed roller finger follower 56 provided for the inside cylinders. Inner cylinders are provided with fixed roller finger followers 56: four for exhaust valves on the left hand side and four for intake valves on the right hand side. The deactivatable followers 54 complicate an already crowded cylinder head because they are wider than fixed followers 56. In addition to having four valves and the associated valvetrain hardware to actuate the valves, a spark plug and a direct injector, in some cases, must access the inside of the cylinder head.
The poppet valves are not visible in FIG. 3 due to the followers occluding the valve tip and valve springs occluding the valve stems. Numerals for only one each of sixteen valve springs 60 and sixteen retainers 62 are provided in FIG. 3 in the interest of clarity for other elements that will be discussed in more detail. FIG. 3 is a view of the valvetrain without at least the cam carrier, the camshafts, the cam towers, the cam caps, and the cam cover affixed. Head bolts 58 affix cylinder head 50 to the engine block (not shown in FIG. 3). Orifices 64 are provided for affixing the cam carrier (not shown in this view).
At the front of cylinder head 50 (bottom edge of FIG. 3) an exhaust camshaft pulley 42 and an intake camshaft pulley 44 are visible.
A cam carrier 180 is shown in FIG. 4. Cam carrier 180 has semicircular bearings 186 and 188. The left hand bearings support journals of an exhaust camshaft (not shown); the right hand bearings support journals of an intake camshaft (not shown). Orifices 164 and 165 provided through cam carrier 180 are used to secure cam caps (not shown) to secure the camshafts within bearings 186 and 188. Other orifices 167 are provided as bolt through holes to secure cam carrier 180 to the cylinder head.
In FIG. 5, cylinder head 50 is shown with cam carrier 80 installed via bolts 67. Cam carrier 80 has an outer wall 84 to provide structure for cam carrier 80. Bearings 88, that are essentially hemispherical, are provided to cradle camshafts (not shown). During operation, pressurized oil is provided to bearings 88 to lubricate the rotating camshaft (not shown) moving with respect to bearings 88. Bearings 88 of cam carrier 80 are mounted over head bolts 58 (shown in FIG. 3) with only a small portion of some of the head bolts visible beyond bearings 88. The width of bearings 88 are shown by dimension 90.
In FIG. 6, an exhaust camshaft 100 and an intake camshaft 102 are shown installed in cylinder head 50 with cam caps 104 and 108 capturing exhaust camshaft 100 and cam caps 106 and 109 capturing intake camshaft 102. Cam caps 104, 106, 108, and 109 are secured to the cylinder head via bolts 120 that extend through cam carrier 80 and into cylinder head 50. Bolts 120 assist in affixing cam carrier 80 to cylinder had 50. Cam caps 104, 106, 108, and 109 are secured on the inner side by bolts 122 that affix to cam carrier 80. Cam carrier is secured to cylinder head 50 via bolts 67. Intake and exhaust camshafts 102 and 100 are provided with lobes 112 and 110, respectively, that press on followers (not visible) to actuate intake and exhaust valves, respectively.
It would be desirable to obviate the cam carrier in such a cylinder head to simplify assembly, reduce weight, reduce cost, and reduce part count.