Patent Application
20210131394
The present disclosure relates to fuel injection systems for motor vehicles, and more particularly, to a dual injection system including multiple port injection assemblies and direct injection assemblies including a fuel pump and a follower mechanism that mitigates pump losses and increases the life cycle of the pump.
Automotive manufacturers are continuously developing fuel injection systems for increasing fuel flexibility, improving engine performance, and reducing engine-out emissions. Examples of fuel injection include port injection (PI) and direct injection (DI).
PI systems can include fuel injectors for injecting fuel into the intake manifold, such that the air fuel mixture is drawn into the engine cylinder when the intake valve opens. Because the fuel absorbs heat when it is transitions from liquid to gas, the fuel cools down the intake air before it reaches the combustion chamber. The decrease in temperature of the intake air increases its density and allows more fuel to added so as to increase the power of the engine. Because the injectors are disposed upstream of the intake ports away from the valves and spark plugs, there is ample time for the fuel to fully vaporize before it reaches the engine cylinder.
DI systems can include fuel injectors for injecting fuel directly into the engine cylinder instead of injecting fuel into the intake manifold upstream of the engine cylinder. As compared to PI systems, DI systems improve combustion efficiency, increase fuel economy, and reduce emissions. However, small particles of oil and dirt can blow back from the crankcase ventilation system and deposit onto the walls of the intake port and the back of the valve. Carbon can adhere to the valve because fuel does not spray down the back of the valves as it does in a PI system. The buildup can become significant enough that carbon deposits can break off and damage the catalytic converter or cause ignition problems. DI systems may also experience low-speed pre-ignition (LSPI), which is an abnormal combustion event caused by higher cylinder pressures common in turbocharged DI engines running in low-speed, high-torque conditions.
Dual injection systems can include both PI fuel injectors for delivering fuel to associated intake ports at a first pressure and DI fuel injectors driven by a camshaft for delivering fuel at a second pressure higher than the first pressure. When the dual injection system uses only the PI fuel injectors to deliver fuel to the engine, the camshaft continues to drive the DI fuel injectors, which are moved to a full bypass mode to recirculate fuel without delivering any to the engine. This continued operation of the DI injectors can reduce the life cycle of the DI fuel injectors, cause pump losses, and reduce the fuel economy of the vehicle.
Thus, while DI fuel system arrangement of motor vehicles achieve their intended purpose, there is a need for a new and improved DI fuel system arrangement that addresses these issues.
According to several aspects of the present disclosure, a direct injection assembly is provided for use with a camshaft to pressurize a volume of fuel for an internal combustion engine of a motor vehicle. The assembly includes a follower mechanism having an input piston operably engaged with the camshaft and moving between first and second input positions along a first follower axis, in response to the camshaft rotating about a camshaft axis. The follower mechanism further includes an output piston movable between first and second output positions along a second follower axis. The follower mechanism further includes a coupler mechanism movable between a deactivated state and an activated state where the coupler mechanism holds the input piston and the output piston in fixed positions relative to one another while moving along a corresponding one of the first and second follower axes for transmitting, using the coupler mechanism, a force from the input piston to the output piston. The assembly further includes a pump having a plunger engaged with the output piston of the follower mechanism and movable from a first plunger position to a second plunger position where the plunger pressurizes the volume of fuel, in response to the plunger receiving the force from the output piston of the follower mechanism.
In one aspect, the input and output pistons move along a respective one of the first and second follower axes, in response to the coupler mechanism being disposed in the activated state while the camshaft is rotating about the camshaft axis.
In another aspect, the input piston moves along the first follower axis and the output piston remains in a fixed position along the second follower axis, in response to the coupler mechanism being disposed in the deactivated state and the camshaft rotating about the camshaft axis.
In another aspect, the coupler mechanism is a hydraulic lost motion device including a body defining a hydraulic chamber with the input and output pistons disposed at least partially within the hydraulic chamber. The follower mechanism further includes a working fluid disposed within the hydraulic chamber. In addition, the follower mechanism also includes a variable-bleed valve in fluid communication with the hydraulic chamber and an outlet channel, wherein the variable-bleed valve is configured to selectively vary a bleed rate between the hydraulic chamber and the outlet channel. The variable-bleed valve and the input and output pistons are in fluid communication with the working fluid in the hydraulic chamber, such that displacement of the input piston into the hydraulic chamber causes a proportional displacement of the output piston, and the proportional displacement of the output piston is dependent on the bleed rate.
In another aspect, the follower mechanism further includes a roller follower configured to follow motion of the camshaft, with the input piston being spring-biased to follow motion of the roller follower. The follower mechanism further includes a finger carrying the roller follower, wherein the finger pivots about a first end and further includes a second end configured to transfer motion of the finger to the input piston. The roller follower is disposed between the first end and the second end, such that the motion of the cam is proportionally transferred to the input piston.
In another aspect, the assembly further includes a lash adjuster pivotably attached to the first end of the finger.
In another aspect, the lash adjuster is a mechanical lash adjuster.
According to several aspects of the present disclosure, a dual fuel injection system is provided for use with a camshaft to pressurize a volume of fuel for an internal combustion engine of a motor vehicle. The system includes a camshaft for rotating about a camshaft axis, a port injection assembly for delivering a first volume of fuel to a first pressure, and a direct injection assembly for delivering a second volume of fuel to a second pressure that is above the first pressure. The direct injection system includes a follower mechanism. The follower mechanism includes an input piston operably engaged with the camshaft and moving between first and second input positions along a first follower axis, in response to the camshaft rotating about a camshaft axis. The follower mechanism includes an output piston movable between first and second output positions along a second follower axis. The follower mechanism includes a coupler mechanism movable between a deactivated state and an activated state where the coupler mechanism holds the input piston and the output piston in fixed positions relative to one another while moving along a corresponding one of the first and second follower axes for transmitting, using the coupler mechanism, a force from the input piston to the output piston. The direct injection assembly further includes a pump having a plunger engaged with the output piston of the follower mechanism and movable from a first plunger position to a second plunger position where the plunger pressurizes the volume of fuel, in response to the plunger receiving the force from the output piston of the follower mechanism. The system further includes a controller coupled to the direct injection assembly and configured to move the coupler mechanism to the activated state where the direct injection assembly pressurizes the second volume of fuel to the second pressure, and the controller is further coupled to the port injection assembly and configured to actuate the port injection assembly to pressurize the first volume of fuel to the first pressure.
In one aspect, the input and output pistons move along a respective one of the first and second follower axes, in response to the coupler mechanism being disposed in the activated state while the camshaft is rotating about the camshaft axis.
In another aspect, the input piston moves along the first follower axis and the output piston remains in a fixed position along the second follower axis, in response to the coupler mechanism being disposed in the deactivated state and the camshaft rotating about the camshaft axis.
In another aspect, the coupler mechanism is a hydraulic lost motion device including a body defining a hydraulic chamber with the input and output pistons disposed at least partially within the hydraulic chamber. The follower mechanism further includes a working fluid disposed within the hydraulic chamber. In addition, the follower mechanism also includes a variable-bleed valve in fluid communication with the hydraulic chamber and an outlet channel, wherein the variable-bleed valve is configured to selectively vary a bleed rate between the hydraulic chamber and the outlet channel. The variable-bleed valve and the input and output pistons are in fluid communication with the working fluid in the hydraulic chamber, such that displacement of the input piston into the hydraulic chamber causes a proportional displacement of the output piston, and the proportional displacement of the output piston is dependent on the bleed rate.
In another aspect, the follower mechanism further includes a roller follower configured to follow motion of the camshaft. The follower mechanism further includes a finger carrying the roller follower, wherein the finger pivots about a first end and further includes a second end configured to transfer motion of the finger to the input piston. The follower mechanism further includes a spring for biasing the input piston against the second end of the finger to follow motion of the roller follower. The roller follower is disposed between the first end and the second end, such that the motion of the cam is proportionally transferred to the input piston.
In another aspect, the assembly further includes a lash adjuster pivotably attached to the first end of the finger.
In another aspect, the lash adjuster is a mechanical lash adjuster.
According to several aspects of the present disclosure, a method for operating a direct injection assembly, with the direct injection assembly including a camshaft, a pump, a controller, and a follower mechanism having input and output pistons and a coupler mechanism. The method includes rotating the camshaft about a camshaft axis. The input piston of the follower mechanism moves between the first and second input positions along a first follower axis, in response to the camshaft rotating about a camshaft axis. The coupler mechanism moves between deactivated and activated states. The coupler mechanism holds the input piston and the output piston in fixed positions relative to one another, in response to the coupler mechanism being disposed in the activated state. The coupler mechanism transmits a force from the input piston to the output piston, in response to the input and output pistons being held in fixed positions relative to one another. The output piston moves between first and second output positions along a second follower axis, in response to the coupler mechanism being disposed in the activated state while the camshaft is rotating about the camshaft axis. A plunger of the pump moves from a first plunger position to a second plunger position where the plunger pressurizes a first volume of fuel, in response to the output piston moving from the first output position to the second output position.
In one aspect, the method further includes disposing the output piston in one fixed position along the second follower axis, in response to the coupler mechanism being disposed in the deactivated position while the camshaft is rotating about the camshaft axis.
In another aspect, the method further includes defining, within a body, a hydraulic chamber with the input and output pistons disposed at least partially within the hydraulic chamber. A working fluid is disposed within the working fluid, and a variable-bleed valve is used to fluidly communicate the hydraulic chamber and an outlet channel with one another. The variable-bleed valve selectively varies a bleed rate between the hydraulic chamber and the outlet channel. The method further includes displacing the input piston of the follower mechanism and displacing the output piston of the follower mechanism in proportion to displacement of the input piston and the bleed rate.
In another aspect, the method further includes a roller follower following the motion of the camshaft such that the input piston follows the motion of the roller follower.
In another aspect, the method further includes a finger carrying the roller follower; and a first end of the finger transferring the motion of the finger to the input piston.
In another aspect, the method further includes the roller follower proportionally transfers the motion of the camshaft to the input piston.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
Referring to
Referring to
Each direct injection assembly 28 includes a follower mechanism 36 having an input piston 38 operably engaged with the actuator 30. Continuing with the previous example, the actuator 30 is the camshaft 16, and the input piston 38 is operably engaged with the camshaft 16. The input piston 38 is movable between a first input position (
The direct injection assembly 28 further includes a pump 48 having a plunger 50 configured to engage the output piston 42 of the follower mechanism 36. The plunger 50 is movable from a first plunger position (
Referring back to
Referring to
More specifically, in this example, the follower mechanism 136 further includes a roller follower 170 engaging the cam lobe 134 and configured to receive a linear force, in response to the camshaft 116 rotating about the camshaft axis 132. The roller follower 170 maintains contact with camshaft 116 without relative motion between the contact surfaces to avoid the associated sliding friction losses.
The follower mechanism 136 further includes a finger 172 rotatably carrying the roller follower 170. The finger 172 includes first and second ends 174, 176 with a center portion 178 therebetween. The finger 172 is disposed at the center portion 178 between the first and second ends 174, 176 such that the motion of the camshaft 116 is proportionally transferred to the input piston 138. The finger 172 pivots about the first end 174, which in this example takes the form of a hemi-spherical socket 180. The second end 176 of the finger 172 is configured to transfer motion of the finger 172 to the input piston 138. The second end 176 has a defined radius of curvature and contacts the tip of the input piston 138. As the camshaft 116 rotates, the input piston 138 is driven in a reciprocating linear motion by the finger 172 against a spring 182, which maintains contact between the input piston 138 and second end 176 of the finger 172. With each rotation of the camshaft 116, the roller follower 170 moves from riding on the base circle portion (
The follower mechanism 136 further includes a lash adjuster 184 pivotably attached to the hemi-spherical socket 180 of the finger 172. In this example, the lash adjuster 184 is a mechanical lash adjuster, with lash compensation for closing any gaps in fixed cam-follower-to-pump connections. These gaps are designed expansion joints and are normally closed by thermal expansion as the engine heats up. Without some form of lash compensation, there may be gaps between the moving elements of the direct injection assembly, especially while the engine is cold, which may result in increased noise or wear. Furthermore, wear of components of the assembly may cause gaps over time. A hydraulic lash adjuster is a mechanism which closes gaps during both cold and hot operating conditions by using pressurized fluid to move the lash compensator into contact with the follower element, regardless of engine and fuel injection system temperature. The mechanical lash adjuster 184 is a support element that provides mechanical lash compensation. An initial adjustment, usually at the time of assembly of the direct injection assembly 128, is made to contact the mechanical lash adjuster 184 to the first end 174 of the finger 172.
As shown in
While the first and second follower axes 140, 144 are spaced apart from one another, it is contemplated that the first and second follower axes 140, 144 may be collinear such that the input piston and the plunger may be movable along a common axis. In addition, it is contemplated that the first and second follower axes may be angularly spaced from one another such that the plunger is movable along the second follower axis that is angularly spaced from the first follower axis of the input piston. Those having ordinary skill in the art will recognize that the tip geometry of the input piston 138 may be comparable to the tip of a plunger used in conventional engines not having a hydraulic linkage.
Displacement by input piston 138 results in hydraulic pressure generation in the chamber 162. If the chamber 162 is otherwise closed—such that the volume of fluid 164 within the chamber 162 remains essentially constant without substantial leakage—and the working fluid 164 is substantially incompressible, the output piston 142 will be displaced by an equal volume. If the input and output pistons 138, 142 have substantially equal diameter (a hydraulic diameter ratio of 1:1), the axial displacement of the input piston 138 results in a substantially equal axial displacement of the output piston 142, thereby displacing the plunger 150 by the same distance.
A checked supply line 194 connects the chamber 162 to a hydraulic pressure source, such as the oil pump (not shown), and permits flow into the hydraulic linkage 158 when the pressure inside the hydraulic linkage 158 falls below the supply pressure. A check valve 196 located on the supply line 194 prevents backflow towards the pressure source when the pressure inside of hydraulic linkage 158 is above the supply pressure.
The variable-bleed valve includes a variable-bleed orifice 198 configured to selectively vary the bleed rate of fluid 164 from the chamber 162. In this example, the variable-bleed orifice 198 includes a flow control valve 200 configured to selectively vary the size of a drain port 202 in fluid communication with the chamber 162. The variable-bleed orifice 198 connects the fluid 164 to a drain 202, which may connect to an oil sump (not shown) or a pressure accumulator (not shown). The flow control valve 200 is shown for exemplary purposes only. Those having ordinary skill in the art will recognize numerous types of valves, or combinations of valves, that may be used within variable-bleed orifice 198 to selectively control the bleed rate of fluid 164 from chamber 162. Furthermore, it is contemplated that neither the variable-bleed orifice 198 nor the drain 202 have to be located in the either the block 192. The variable-bleed orifice 198 need only be in fluid communication with chamber 162 and the drain 202. Furthermore, the drain 202 may feed the pressurized fluid 164 escaping chamber 162 into an accumulator which supplies downstream components with pressurized fluid instead of re-pressurizing fluid for those components directly with a pump. Furthermore, the accumulator could also return the bled volume of fluid 164 back to the hydraulic chamber 162 during the base-circle event (during which the chamber 162 is re-pressurized).
The proportion of the displaced volume of working fluid 164 converted into motion of the output piston 142 is dependent on the bleed rate through the variable-bleed orifice 198 to the drain port. The principle of volume continuity requires that the sum of the bled volume and the volume swept by the output piston 142 equals the volume displaced by the input piston 138—neglecting any leakage and fluid compressibility effects.
Referring to
Referring to
In other embodiments, the linear displacement of the input and output pistons 138, 142 may not be exactly equal even where the variable-bleed orifice 198 has completely closed the drain port 202 for the zero lost-motion condition. Leakage of fluid 164 from the chamber 162 will reduce the displaced volume transferred to outlet piston 142, and compression of the (non-ideal) fluid 164 may also reduce the displacement of outlet piston 142. Furthermore, it is contemplated that, even in a perfectly sealed chamber 162 filled with an incompressible fluid Y, displacement of the output piston 142 is dependent upon the hydraulic diameter ratio of the input and output pistons 138, 142. Matching linear displacement of the plunger 150 (through the output piston 142) to the axial displacement of input piston 138 (through linear displacement by the camshaft 116), dictates a 1:1 ratio of hydraulic diameters.
Where the input and output pistons 138, 142 are not equal in diameter, the linear displacement ratio is inversely related to the hydraulic diameter ratio. The linear displacement ratio of the input piston 138 over the output piston 142 is equal to the ratio of the area of output piston 142 over the area of input piston 138 (if there is no lost motion). For example, where the hydraulic diameter ratio (input:output diameter) is 2:1, the output piston 142 will have four times the linear displacement of the input piston 138 (the input:output linear displacement ratio will be 1:4). A configuration having a smaller output piston 142 allows a relatively smaller camshaft 116, because displacement of the input piston 138 is multiplied through the hydraulic linkage 158 to result in larger displacement of the plunger 150.
Referring now to
At step 304, the input piston 138 of the follower mechanism 136 moves between the first and second input positions along the first follower axis 40, in response to the camshaft 116 rotating about a camshaft axis 132. In this example, the cam lobe 134 transmits a linear force to the roller follower 170, such that the roller follower 170 follows the motion of the camshaft 116, and the input piston 138 follows the oscillatory motion of the roller follower. More specifically, the finger 172 carries the roller follower 170, and the finger 172 pivots about its first end 174 with the second end 176 transmitting the linear force to the input piston 138, in response to the roller follower 170 receiving the linear force from the cam lobe 134. The roller follower 170 proportionally transfers the motion of the camshaft 116 to the input piston 138, in response to for example the location of the roller follower on the finger 172 between the first and second ends of the finger 172. In other examples, the cam lobe can transmit the linear force directly to the finger. In still other examples, the cam lobe can transmit he linear force directly to the input piston.
At step 306, the controller 152 determines the volume of fuel to be pressurized by the direct injection assembly 128. In one example, the controller 152 can determine that the direct injection assembly 128 will deliver none of the fuel to be delivered to the engine. As but one non-limiting example, the controller can determine that the direct injection assembly 128 will deliver none of the fuel to the engine and the port injection assembly 120 will deliver all the fuel to the engine, in response to the controller 152 determining that the engine speed is below a predetermined speed threshold and the engine torque is below a predetermined torque threshold. However, it is contemplated that the controller can determine that the direct injection assembly 128 will deliver any volume of fuel to the engine in response to other vehicle condition.
At step 308, the controller 152 determines whether it will actuate the coupler mechanism 146 to move between deactivated and activated states, in response to the controller determining the volume of fuel to be pressurized by the direct injection assembly 128. If the controller 152 determines that that it will actuate the coupler mechanism 146 to move to the deactivated state, the method proceeds to step 310. If the controller 152 determines that that it will actuate the coupler mechanism 146 to move to the activated state, the method proceeds to step 312.
At step 310, the output piston 142 remains disposed in one fixed position along the second follower axis 144, in response to the coupler mechanism 146 being disposed in the deactivated position while the camshaft 116 is rotating about the camshaft axis 132. Continuing with the previous example, the controller 152 actuates the coupler mechanism 146 to move to the deactivated state in response to the controller determining that the direct injection assembly will deliver none of the fuel to the engine. Because the output piston remains in one fixed position, the friction losses can be mitigated, and the associated fuel economy of the vehicle can be improved.
At step 312, the controller actuates the coupler mechanism to move to the activated state in response to the controller determining that the direct injection assembly will deliver at least a portion of the fuel to the engine. The coupler mechanism 146 holds the input piston 138 and the output piston 142 in fixed positions relative to one another, in response to the controller actuating the coupler mechanism 146 to be disposed in the activated state. The coupler mechanism 146 transmits a force from the input piston 138 to the output piston 142, in response to the input and output pistons 138, 142 being held in fixed positions relative to one another.
In this example, the coupling mechanism 146 is the hydraulic lost motion device 156, which includes the hydraulic linkage 158 having the variable-bleed valve 166 fluidly communicating with the hydraulic chamber 162 and the outlet channel 166. The variable-bleed valve 166 selectively varies the bleed rate between the hydraulic chamber 162 and the outlet channel 166, such that the bleed rate inversely corresponds with the volume of fuel to be pressurized and delivered by the direct injection assembly. The body 160 defines the hydraulic chamber 162 containing the working fluid, and the input and output pistons 138, 142 are disposed at least partially within the hydraulic chamber 162.
At step 314, the output piston 142 moves between first and second output positions along the second follower axis 144, in response to the coupler mechanism 146 being disposed in the activated state while the camshaft 116 is rotating about the camshaft axis 132. Continuing with the previous example, the output piston 142 of the follower mechanism 136 is displaced in direct proportion to displacement of the input piston 138 and inversely proportion to the bleed rate.
At step 316, the plunger 150 of the pump 148 moves from the first plunger position to the second plunger position where the plunger 150 pressurizes the first volume of fuel, in response to the output piston 142 moving from the first output position to the second output position.
The description of the present disclosure is merely exemplary in nature and variations that do not depart from the general sense of the present disclosure are intended to be within the scope of the present disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure.
