Patent Application
20070240659
The present invention relates to a cylinder deactivation system for an internal combustion engine.
Variable displacement internal combustion engines provide improved fuel economy and torque on demand by operating on the principle of cylinder deactivation. During operating conditions that require high output torque, every cylinder of a variable displacement internal combustion engine is supplied with fuel and air. Alternately, during operating conditions at low speed, low load, and/or other inefficient conditions for a fully displaced internal combustion engine, cylinders may be deactivated to improve the fuel economy of a vehicle equipped with the variable displacement internal combustion engine. For example, in the operation of a vehicle equipped with an eight cylinder variable displacement internal combustion engine, fuel economy will be improved if only four cylinders of the internal combustion engine are operated during relatively low torque operating conditions by reducing throttling losses. Throttling losses, also known as pumping losses, are the extra work that an internal combustion engine must perform to pump air from the relatively low pressure of an intake manifold, across intake and exhaust valves, and out to the atmosphere. The deactivated cylinders will disallow airflow across their respective intake and exhaust valves, thereby reducing pumping losses by forcing the internal combustion engine to operate at a higher intake manifold pressure. Since the deactivated cylinders do not allow air to flow, additional losses are avoided by operating the deactivated cylinders as “air springs” due to the compression and decompression of the air within each deactivated cylinder.
It is known in the art of engine cylinder deactivation to provide switchable hydraulic lash adjusters operable to either actuate the valves of a deactivatable cylinder or to maintain the valves in a closed position through lost motion features of the hydraulic lash adjusters. Similar mechanisms may be provided within a hydraulic valve lifter, which includes a hydraulic lash adjusting mechanism and so may be referred to broadly as a hydraulic lash adjuster.
Hydraulic lash adjusters are supplied with pressurized oil through a lash adjuster gallery or lifter oil passage to annular feed grooves, which provide oil pressure to take up the lash in the valve train between the valve tip and its associated rocker arm or other-actuator. Hydraulic lash adjusters and hydraulic valve lifters that are configured to effect cylinder deactivation typically have an additional port for a locking pin, which connects through feed passages with a valved oil pressure supply. A solenoid-actuated hydraulic control valve may be used to selectively communicate oil pressure from a main source of pressurized oil to the locking pin for cylinder deactivation. Alternately, the solenoid-actuated hydraulic control valve operates to exhaust oil pressure from the locking pin and feed passage. Traditionally, one solenoid-actuated hydraulic control valve is provided for each cylinder that is to be deactivated. Such a system is described in commonly assigned U.S. Pat. No. 6,584,951, entitled “Individual Hydraulic Circuit Modules for Engine With Hydraulically-Controlled Cylinder Deactivation”, which is hereby incorporated by reference in its entirety.
Accordingly, an internal combustion engine is provided with a cylinder block defining a plurality of cylinders at least half of which are selectively deactivatable by a plurality of switching hydraulic lifters. A source of pressurized oil is also provided. At least one solenoid-actuated hydraulic control valve, such as an on/off type valve, operates to selectively communicate pressurized oil from the source of pressurized oil to actuate the plurality of switching hydraulic lifters thereby deactivating the at least half of the plurality of cylinders. The number of the at least one solenoid-actuated hydraulic control valves is fewer than the number of the at least half of the plurality of cylinders that are selectively deactivatable.
The source of pressurized oil may be a main passage defined within the cylinder block. A pump may be provided to draw oil from a reservoir and provide pressurized oil to the main passage. At least one rotatable camshaft may be provided, wherein the at least one rotatable camshaft engages the plurality of switchable hydraulic lifters to effect reciprocal movement thereof.
Additionally, an oil manifold assembly may be removably mounted with respect to the internal combustion engine. The oil manifold assembly defines at least one feed passage and a control passage operable to receive pressurized oil from the main source of pressurized oil. Each of the at least one solenoid-actuated hydraulic control valve may be mounted with respect to the oil manifold assembly and selectively communicate pressurized oil from the control passage to a respective one of the at least one feed passage. The at least one feed passage operates to selectively communicate pressurized oil to the plurality of switching hydraulic lifters.
The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.
Referring to the drawings wherein like reference numbers correspond to similar components, there is shown in
The valves 28 and 30 are actuated by valve actuation mechanisms including a camshaft 32 rotatably driven by the crankshaft 18. The camshaft 32 engages valve lifters including, both hydraulic lifters, such as 34 and so called switching hydraulic lifters, such as 36. The hydraulic lifters 34 are reciprocally movable respectively within bores, such as 35, while the switching hydraulic lifters 36 are reciprocally movable respectively within bores, such as 37. The lifters 34 and 36 engage push rods 38, which connect with rocker arms 40 to actuate the valves 28 and 30 against the bias force of valve springs 42.
The engine 10 includes a lubrication and cylinder deactivation control circuit 44, which includes an oil pump 46 that is driven by the crankshaft 18. The oil pump 46 is a positive displacement-type pump that draws oil 47 from a reservoir or oil pan 48 mounted below the crankcase portion 20 of the cylinder block 12. The oil pump 46 supplies pressurized oil to a main passage 50, defined by the cylinder block 12, which operates as a source of pressurized oil.
The engine 10 also includes an oil manifold assembly 52 removably mounted thereto and defining a control passage 54 that receives pressurized oil from the main passage 50. The oil manifold assembly 52 includes solenoid-actuated hydraulic control valves 56 and 56′ (shown in
Referring now to
The operation of the engine 10 can best be understood with reference to
Additionally, the main passage 50 supplies pressurized oil to the control passage 54 within the oil manifold assembly 52. The pressurized oil from within the control passage 54 is selectively communicated to the feed passages 58 and 58′ by a respective one of the solenoid-actuated hydraulic control valves 56 and 56′. The pressurized oil, when present within the feed passages 58 and 58′, is communicated via the plurality of passages 60 to a respective one of the bores 37. When full displacement, i.e. all cylinders 14 and 14′ producing power, is desired, the solenoid-actuated hydraulic control valves 56 and 56′ exhaust or de-pressurize the respective feed passages 58 and 58′ and the plurality of passages 60. With the plurality of passages 60 de-pressurized, the switching hydraulic lifters 36 remain locked in the operating position. When deactivation of the cylinders 14 and 14′ associated with the switching hydraulic lifters 36 is desired, the ECU 61 commands the solenoid-actuated hydraulic control valves 56 and 56′ to open thereby pressurizing the feed passages 58 and 58′, respectively, and hence the plurality of passages 60. The pressurized oil unlatches locking pins disposed within the switching hydraulic lifters 36, which allow the lifter bodies to telescope around their lash adjusters and thus disable operation of the valves 28 and 30 in mechanical communication with the switching lifters 36.
By deactivating half of the eight cylinders 14 and 14′ of the engine 10 during low torque demand modes of engine operation, the operating efficiency of the engine 10 may be improved. Additionally, it is preferred that every other cylinder 14 and 14′ within the firing sequence of the engine 10 be deactivated such that engine balance is maintained.
With reference to
By employing such a strategy, the fuel and air charge can be introduced into the selectively deactivatable cylinder 14 or 14′, which is then combusted. Since the exhaust valves 30 are deactivated, the products of combustion will remain within the deactivated cylinder 14 or 14′ until reactivated. This strategy is preferable since the products of combustion exiting the deactivated cylinder 14 or 14′, upon reactivation, will contain very little oxygen. Therefore, the need for complex control algorithms within the ECU 61 to momentarily deactivate oxygen sensors, not shown, within the vehicle exhaust system in order to maintain proper fuel injection control is obviated.
The engine 10 can, by manifolding the solenoid-actuated hydraulic control valves 56 and 56′ with the bores 37, deactivate the four selectively deactivatable cylinders using only two solenoid-actuated hydraulic control valves 56 and 56′. By reducing the number of solenoid control valves required to effect cylinder deactivation, the cost and complexity of the engine 10 may be reduced while maintaining proper control of the cylinder deactivation functionality.
While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.
