Patent Application
20200018197
This application relates to cylinder deactivation of a multi-cylinder diesel engine and provides methods and systems for managing cylinder pressure and lubrication system.
Cylinder deactivation (CDA) differs from cylinder cut-out. Cylinder cut-out cuts off fuel to a cylinder, but continues to cycle the cylinder valves and piston. Cylinder cut-out is an inefficient energy drain.
Cylinder deactivation stops valve motion and fuel injection for a cylinder. The piston continues to cycle. A quantity of fluid is trapped in the cylinder, but is prone to leaking out. The leaking can cause a negative pressure. The negative pressure can draw excess lubricants into the cylinder and result in contamination.
The systems and methods disclosed herein overcome the above disadvantages and improves the art by way of strategies to recharge a cylinder and manage a negative pressure condition developed in a selected cylinder of a multiple-cylinder engine operating in cylinder deactivation (CDA) mode. The strategy comprises of both cylinder pressure management and the lubrication system management.
A method of managing the cylinder pressure of an engine in CDA mode can comprise of intermittently selecting opening of deactivated intake valves or exhaust valves on the selected cylinder and allow fuel from the respective intake or exhaust manifold. The method can further comprise of managing the selective opening to be a low lift late intake valve, or to be on a pre-programmed timing strategy, or be coordinated to follow the respective cycling of a cylinder's piston positions. The method to manage cylinder pressure can also comprise switching between any of 4-stroke mode, 6-strokemode, 8-stroke mode or 2-stroke mode of combustion.
A method of managing an internal lubrication system can comprise of adjusting the metering of oil through a piston ring pack of the selected cylinder to operate in CDA mode. The method can further comprise reducing the lubricating oil pressure to a second ring or the oil ring of the piston pack, addition of a second oil pump and adjusting the pump speeds, adjusting pressure regulators connected to the pistons of the set of reciprocating cylinders, or reducing the amount of lubricating oil sprayed at the selected cylinder.
A method of managing an internal lubrication system to reduce lubricant “leak down” in operating a multiple-cylinder engine in CDA mode can comprise of selectively adjusting pressure of an oil feed entering the deactivated cylinders. This can further comprise of addition of oil pumps, pressure regulators, and bypass systems to selectively adjust the oil feed to the selected deactivated cylinders while maintaining pressure of the oil feed to at least one of the firing cylinders.
A multiple-cylinder diesel engine system comprises a multiple cylinder diesel engine comprising a respective intake valve and a respective exhaust valve for each of the multiple cylinders. A valve control system is connected to selectively deactivate a respective intake valve and a respective exhaust valve for a selected cylinder of the multiple cylinder diesel engine. A fuel injection control system is connected to selectively deactivate fuel injection to the selected cylinder while increasing fuel to firing cylinders. The multiple cylinder diesel engine enters a cylinder deactivation mode whereby the valve control system deactivates the respective intake valve and the respective exhaust valve and the fuel injection control system deactivates the fuel injection to the cylinder while continuing to fire other cylinders of the multiple cylinder diesel engine. The valve control system selectively opens the deactivated intake valve, or the deactivated exhaust valve to relieve a negative pressure condition in the deactivated cylinder.
Additional objects and advantages will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the disclosure. The objects and advantages will also be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the claimed invention.
Reference will now be made in detail to the examples which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Directional references such as “left” and “right” are for ease of reference to the figures. Phrases such as “upstream” and “downstream” are used to assist with directionality of flow from a fluid input point to a fluid output point. Fluids in this disclosure can comprise a variety of compositions, including fresh or ambient air, exhaust gas, other combustion gasses, vaporized fuel, among others. Lubrication fluids, such as oil or synthetic lubricant are combustible, per se, but are to be considered part of a separate fluid circuit from the combustion circuit outside of incidental cross-contamination. This disclosure primarily focusses on diesel engine operation, but tenets of the disclosure can be applied to other fueled engines and engine systems, including those fueled by biofuels and other petroleum products such as gasoline, and including hybrid-electric vehicles. Heavy-duty, light-duty, and medium-duty vehicles can benefit from the techniques disclosed herein. Hybrid vehicles and vehicles such as buses that have start/stop/load duty cycles can also benefit from the disclosure.
Turning to
Fuel is injected to individual cylinders via a fuel injection controller 300. The fuel injection controller 300 can adjust the amount and timing of fuel injected in to each cylinder and can shut off and resume fuel injection to each cylinder. The fuel injection for each cylinder 1-6 can be the same or unique for each cylinder 106, such that one cylinder can have more fuel than another, and one cylinder can have no fuel injection, while others have fuel.
A user input sensor 900 can be linked to the engine system 10 to sense user inputs such as braking, acceleration, start-up mode selection, shut-down mode selection, auxiliary device activation, among others. The user selections can impact the load requirements for the engine system 10, and the power settings for the cylinders 1-6 can be adjusted in response to the user selections. The valve control by VVA controller 200 and fuel injection from fuel injection controller 300 can be tailored based on the user selections sensed by user input sensor 900.
A variable valve actuator (VVA) controller 200 couples to the cylinders 1-6 to actuate intake valves 130 and exhaust valves 150. The VVA controller 200 can change the actuation of the intake valves 130 and exhaust valves 150 so as to open or close the valves normally, early, or late, or combinations thereof, or cease operation of the valves. Early Intake Valve Opening (EIVO), Early Intake Valve Closing (EIVC), Late Intake Valve Opening (LIVO), Late Intake Valve Closing (LIVC), Early Exhaust Valve Opening (EEVO), Early Exhaust Valve Closing (EEVC), Late Exhaust Valve Opening (LEVO), Late Exhaust Valve Closing (LEVC), a combination of EEVC and LIVO or Negative Valve Overlap (NVO) can be implemented by the VVA controller 200. Compression release breaking (CRB) can also be implemented by VVA controller 200. VVA controller 200 can cooperate with valve actuators 185, such as one or more of a hydraulic system, electric latch system, or electric solenoid system to control the intake and exhaust valves 130, 150.
The valve actuators 185 for each cylinder 1-6 can be the same for all cylinders 106, thus enabling each valve of each cylinder to switch between, for example, combustion mode, deactivated mode, or compression release braking (CRB) mode. Or, the valve actuators 185 can differ between the intake valves 130 and the exhaust valves 150, so that certain functionality is only enabled on one or the other of those valves, such as LIVO on intake valves and CRB on exhaust valves. Or, commensurate with below discussions, the functionality can be distributed so that some valves can switch between combustion mode and deactivated mode, while others can switch between, for example combustion mode and CRB mode. And, when more than one intake valve or more than one exhaust valve are used per cylinder 106, the valve actuators 185 can be the same or different for each of those valves.
For example, as shown in
In order for a diesel engine to operate, all of its components must perform their functions at very precise intervals in relation to the motion of the piston. To accomplish this, the engine 100 can be cam or camless, or a hybrid “cam-camless VVA.” So, the intake and exhaust valves 130, 150 can either couple to a cam system for actuation, as the camshafts 181, 182 example of
Turning to
In
Other mechanisms can achieve the valve lift profiles drawn in
Camshafts 181, 182 can be coupled to be driven by the engine's crankshaft 101 and transfer energy between the two via a torque transfer mechanism 115, which can comprise series of gear sets, belts, or other transfer mechanisms (
While
A diesel engine works by compressing intake fluid in a cylinder 1-6 using a piston 160. Fuel is injected via fuel injector 310. The high heat and compression ignites the fuel, and combustion forces the piston from top dead center (TDC) shown in
In 4-stroke combustion mode, the piston 160 moves from TDC to BDC to fill the cylinder with intake fluid (stroke 1). The start of the cycle is shown in
Turning to
Exhaust gases leave cylinders through exhaust ports 155 in engine block 102. Exhaust ports 155 communicate with an exhaust manifold 105. An exhaust manifold sensor 175 can monitor the pressure, flow rate, oxygen content, nitrous or nitric oxide (NOx) content, sulphur content, other pollution content or other qualities of the exhaust gas.
A controllable valve 516 can be included to direct timing and quantity of fluid to the turbine 510 and catalyst 800 or to an optional EGR cooler 455 and EGR circuit that returns exhaust gases to the intake manifold 103 for exhaust gas recirculation (EGR).
Exhaust gas is filtered in an aftertreatment system comprising catalyst 800. At least one exhaust sensor 807 is placed in the aftertreatment system to measure exhaust conditions such as tailpipe emissions, NOx content, exhaust temperature, flow rate, etc. The exhaust sensor 807 can comprise more than one type of sensor, such as chemical, thermal, optical, resistive, velocity, pressure, etc. A sensor linked with the turbocharger 501 can also be included to detect turbine and compressor activity.
Exhaust can exit the system after being filtered by the at least one catalyst 800. Or, exhaust can be redirected to the intake manifold 103. An optional EGR cooler 455 is included. An EGR controller 400 actuates an EGR valve 410 to selectively control the amount of EGR supplied to the intake manifold 103. The exhaust recirculated to the intake manifold 103 impacts the air fuel ration (AFR) in the cylinder. Exhaust dilutes the oxygen content in the intake manifold 103. Unburned fuel from an aftertreatment fuel doser, or unburned fuel remaining after combustion increases the fuel amount in the AFR. Soot and other particulates and pollution gases also reduce the air portion of the air fuel ratio. While fresh air brought in through the intake system 700 can raise the AFR, EGR can lower AFR, and fuel injection to the cylinders can lower the AFR further. Thus, the EGR controller 400, fuel injection controller 300 and intake assist controller 600 can tailor the air fuel ratio to the engine operating conditions by respectively operating EGR valve 410, fuel injector 310, and intake assist device 610. So, adjusting the air fuel ratio to a firing cylinder can comprise one of boosting fresh air from intake system 700 to the at least one firing cylinder by controlling an intake air assist device 601, such as a supercharger, or decreasing air fuel ratio to a firing cylinder by boosting with exhaust gas recirculation to the firing cylinder. A charge air cooler 650 can also optionally be included to regulate intake flow temperature.
An engine, as discussed in
A computer control network is outlined in
Memory device 1401 is a tangible readable memory structure, such as RAM, EPROM, mass storage device, removable media drive, DRAM, hard disk drive, etc. Signals per se are excluded. The algorithms necessary for carrying out the methods disclosed herein are stored in the memory device 1401 for execution by the processor 1403. When variable valve control is implemented, the VVA control 1412 is transferred from the memory device 1401 to the processor for execution, and the computer control system functions as a VVA controller. Likewise, the computer control system 1400 implements stored algorithms for EGR control 1414 to implement an EGR controller 400; implements stored algorithms for intake assist device control 1416 to implement intake assist controller 600; and implements stored algorithms for fuel injection control 1413 to implement fuel injection controller 300. When implementing stored algorithms for VVA control 1412, various intake valve controller and exhaust valve controller strategies are possible relating to valve timing and valve lift strategies, as detailed elsewhere in this application, and these strategies can be implemented by VVA controller 200. The processor can combine outputs from the various controllers, for example, the processor can comprise additional functionality to process outputs from VGT controller 500 and intake assist controller 600 to determine a command for valve 516. A controller area network (CAN) can be connected to appropriate actuation mechanisms to implement the commands of the processor 1403 and various controllers.
While the computer control system 1400 is illustrated as a centralized component with a single processor, the computer control system 1400 can be distributed to have multiple processors, or allocation programming to compartmentalize the processor 1403. Or, a distributed computer network can place a computer structure near one or more of the controlled structures. The distributed computer network can communicate with a centralized computer control system or can network between distributed computer structures. For example, a computer structure can be near the EGR valve 410 for EGR controller 400, another computer structure can be near the intake and exhaust valves for variable valve actuator 200, yet another computer controller can be placed for fuel injection controller 300, and yet another computer controller can be implemented for intake assist controller 600. Subroutines can be stored at the distributed computer structures, with centralized or core processing conducted at computer control system 1400.
It is possible for the stored processor-executable control algorithms to be called up from the memory device 1401 in to the processor 1403 for execution when, for example, a start-up or shut-down operation mode is selected, as by a user pressing a button, turning a key, engaging a manual brake, etc. Or, user input calls up an acceleration algorithm or a deceleration algorithm from the memory device 1401 for execution by the processor 1403 by increasing or decreasing pressure on an accelerator pedal or a brake pedal. User input can be used alone or in combination with sensed operating conditions to implement the strategies outlined herein.
For a multiple-cylinder engine in a cylinder deactivation (CDA) mode, the selected cylinders have both intake valves 130 and exhaust valves 150 closed, but the piston 160 reaches top dead center and bottom dead center as usual, because the piston is not deactivated from the crankshaft 101. The piston recuperates most of the energy spent rising to top dead center (compressing the fluid in the closed cylinder) when that fluid expands and the piston cycles to bottom dead center. However, fluid losses occur, and eventually a negative pressure (or vacuum) develops in the cylinder. As the piston continues to cycle, the deactivated cylinder develops such vacuum, which then can contaminate the engine by drawing oil from the internal engine lubrication system into the cylinder. This loss of oil into the cylinder disrupts the engine's lubrication system as well as creates engine pollution. Therefore, cylinder pressure management strategies to recharge deactivated cylinders are needed to bias the oil back to the oil pan and prevent engine contamination.
A method and pressure management strategy for a deactivated cylinder can comprise of recharging the deactivated cylinder with fluid from either the intake manifold 103, exhaust manifold 105, or fuel injectors 310. For this, the variable valve actuator (VVA) controller 200 can couple to the respective deactivated cylinders to intermittently actuate the intake valves 130 to open and then close. Depending on the engine operation, pressure in the intake and exhaust manifolds 103, 105, vibration, and exhaust temperature of the engine, the VVA controller 200 can couple instead to exhaust valves 150 to open and then close. It is also possible to intermittently selectively open both the intake valves 130 and exhaust valves 150.
In another aspect of recharging a deactivated cylinder, in addition to selectively opening the deactivated intake or exhaust valves, a selected volume of fuel can be added by actuating the deactivated fuel injector 310. The additional fluid can compensate for the loss of fluid and leading to the negative pressure condition in a deactivated cylinder.
In another aspect of recharging a cylinder to combat a negative pressure condition in a selected cylinder, the 4-stroke operation technique can be switched between a 4-stroke combustion technique to art-recognized 6-stroke or a 8-stroke combustion techniques which include additional aspects of compression and injection after the intake valve has closed and prior to the exhaust valve opening. Furthermore, the typical 4-stroke engine can be also switched to art-recognized 2-stroke operation.
In one aspect of the pressure management strategy, either intake valves 130 or exhaust valves 150 can be pulsed periodically to open, such as every piston cycle (T0 to T1 in the case of a 4-stroke example), to allow higher pressure fluid to enter the cylinder from respective intake manifold or exhaust manifold 103, 105. The valve opening can be timed to take advantage of a boosting of the pressure in the intake manifold 103 or a back-pressure in the exhaust manifold 105. So, the valve opening strategy can be linked to the operation of valves 410 or 516, or action by compressor 512 or intake air assist device 601, or inaction of turbine 510. Or, the intermittent period could be a pre-determined timing strategy. Selection of a timing set point can be part of the engine computer system, for example, valve opening could be done at 20 to 30 second intervals, or after a predetermined number of piston reciprocations. Other ranges of time for selecting a timing set point can be a time around 5 minutes of deactivation or around 20 minutes of deactivation. The timing set point depends in large part on the rate at which oil builds up in the cylinder to an unacceptable contamination level. Reducing oil pressure to the oil feed can extend the timing set point, because there is less oil pressure and less sprayed oil to bias back towards the oil pan.
Comparison of
In one aspect of the pressure management strategy, the VVA controller 200 actuator can couple with the intake valves 130 to open valves in a low-lift, late intake (LIVO) modified mode. Similarly, the VVA controller 200 actuator can couple with the exhaust valves 150 to open exhaust valves in LEVO mode.
Or, if the engine is a cam system, the cam can be modified to include a minor blip in the design. Then the intake valve can couple to this cam system for actuation of the intake valve such that the valve is opened slightly.
Another method of pressure management in the deactivated cylinder can comprise of opening the intake valve as a piston of the set of reciprocating pistons approaches or reaches the bottom dead center of the cylinder. At this point, the cylinder is fully expanded and beneficial to maintain the cylinder pressure. This action can keep the pressure in the cylinder at or above the crank-case pressure. This can be seen in
Turning to
Another method of pressure management can include a boost device to add pressure to the intake manifold of the diesel engine.
Another method of pressure management in the deactivated cylinder can comprise of the VVA controller 200 valve actuators 185 being coupled with control logic comprising of maintaining a pressure in the cylinder that expels more oil than leaks down, or maintaining a pressure above a certain vacuum point, or maintaining a positive pressure in the cylinder, or biasing the travel of the oil towards the oil pan as discussed elsewhere.
The use of the disclosed strategies can vary based on the power demands of the engine.
A multiple-cylinder engine entering the CDA mode is beneficial because it prevents fluid-flow through the cylinder, prevents the cylinder from robbing resources allocated to the other active cylinders, and prevents energy drain to activate the valves.
A multiple-cylinder engine can have support systems comprising, engine cooling, engine lubrication, fuel system, air intake systems, exhaust system, etc. The internal engine lubrication system provides a flow of lubricants (or oil) to all metal-to-metal moving parts of an engine and create a thin film between them. Without the oil film, the heat generated due to the friction between the metal-to-metal contacts could melt the engine parts or otherwise destroy the operability of the engine. Once between the moving parts, the oil serves to lubricate the surfaces. When part of a circuit, the oil can cool the surfaces by absorbing the friction-generated heat.
Turning to
A diesel engine operating in the normal mode ordinarily maintains a positive pressure from entering fluid and from the expansion and compression of the fluids. This positive pressure pushes the oil out of the cylinder, keeping the oil in its desired position. However, in the CDA mode, by selectively deactivating the intake and exhaust valves and fuel, the only fluid inside the cylinder is trapped fluid in the deactivated cylinder. Over time, the cycling piston, that is still connected to the moving crankshaft, inside the deactivated cylinder causes the trapped fluid to leak out creating a negative pressure condition. Thus, oil from various valves and lubrication areas around the deactivated cylinder can be vacuumed into the cylinder, or oil on the piston “leaks down” in the cylinder, which robs from the engine lubrication system and ends up causing engine contamination. One of the strategies to reduce the oil entering the deactivated cylinder is to adjust the oil flow of the internal lubrication system into the oil galleries 1575. This can be achieved by reducing the pump speed of the lubricating oil pump 1501 when cylinder deactivation mode is entered. Or, the pressure setting of the pressure regulator 1520 can be adjusted to restrict the oil pressure to the deactivated cylinder. If all cylinders 1-4 or 1-6 are configured to switch between firing mode and deactivation mode, then the oil galleries to these cylinders can be shared, and the pressure settings can be shared as in
A method to reduce oil feed entering the deactivated cylinder can comprise of deactivating the pressure of the oil feed towards a plurality of oil galleries towards the CDA cylinders while maintaining the pressure of the oil feed to the firing cylinders. This can be accomplished by individual control of the pressure regulators 1521 as in
Another method to reduce oil entering the deactivated cylinder can comprise of a lubrication system wherein the oil flow into selected deactivated cylinders is curtailed by opening a series of bypass lines 1577 with one-way valves 1578 back to oil feed lines or the oil galleries 1575, 1576.
Reducing oil in the deactivated cylinders is possible without destroying the engine because CDA changes the need for lubrication. During CDA mode, the engine forces are lower for the deactivated cylinders. There are less friction losses, so there is less need for oil. Repeated compression strokes on the trapped gasses can increase heat, but the heat can be lower than that experienced during combustion. Because of this, it is possible to separate cooling and lubrication circuits and strategies. For example, it is possible to reduce the amount of lubricant sprayed in the cylinder to cool it, and it is possible to deactivate oil to the valve altogether. Using a controllable valve, such as a three way valve, such as a spool valve, for pressure regulator 1521 permits tailoring what portions of the oil supply lubricate the valves and what portions lubricate the cylinder walls, cylinder liner or sleeve 162.
Turning to
The piston 160 in
In CDA mode, as the deactivated cylinder approaches negative pressure conditions, the cylinder can be over-lubricated by the sprayer. This can cool the cylinder too much, waste oil, or contaminate the charge with oil unnecessarily. In addition, the CDA mode can create a vacuum condition that pulls the lubrication oil past the oil control ring 1720. This can unnecessarily coat the top ring 1711 and second ring 1712 and further contaminate the cylinder when the vacuumed oil is pulled in to the cylinder. The vacuum condition can also pull the oil off the valves and into the cylinder causing the oil “leak down” situation. This can result in engine contamination. To reduce such engine contamination, the cylinder can be recharged with positive pressure and effectively push the oil back towards the oil ring 1720. The oil ring can then continue to maintain a thin lubrication film between moving parts while preventing excess oil leakage.
A method to manage over-lubrication of the cylinder can include adjustments of the oil ring. The oil ring can be modified to curtail metering of oil through the piston rings because the building negative pressure in CDA mode. Also, the over-lubrication can be combatted by recharging the cylinder.
A method to adjust metering of oil in a deactivated cylinder is possible by opening either of the intake valve or exhaust valve on the respective cylinder to restore the positive pressure. It is also possible to operate a boost device, such as compressor 512 or intake air assist device 601, to increase positive pressure in the intake manifold 103 and then selectively open an intake valve 130 to allow fluid into the deactivated cylinder. The additional fluid can supply positive pressure in the subsequent compression stroke to bias the oil back into the oil pan instead of into the cylinder and effectively reverse the “leak down” condition. Also, a back pressure in the exhaust manifold 105 can permit the use of exhaust valve 150 opening to recharge the deactivated cylinder.
A method to adjust metering of oil in a deactivated cylinder is also possible by opening one of the intake valve while the respective piston of the set of reciprocating pistons is either near or reaches the bottom dead center of the cylinder in CDA mode.
Other implementations will be apparent to those skilled in the art from consideration of the specification and practice of the examples disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope of the invention being indicated by the following claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2017/014184 | 1/19/2017 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62280379 | Jan 2016 | US |
