The present invention relates to electromechanical actuators; more particularly, to pressure control valves for application in gasoline internal combustion engines; and most particularly, to a pressure control valve for application in a fuel system of a gasoline direct injection engine.
Electromechanical actuators for applications in internal combustion engines are well known, and are typically used to control the flow and/or pressure of the supplied fluid through one or several fluid passages. In some cases it is desired that the control pressure or flow output is proportional to an input electrical signal to the coil of the electromagnet. In most specialized cases, the valve design must be customized to the needs of a specific application, for example, for very fast on and off pressure cycling requirements in fuel delivery and control systems, such as gasoline direct injection (GDI) engines. Another typical requirement for valve applications in GDI engines includes tight tolerances for the consistency in the pressure response times.
For example, a high-pressure single-piston pump driven via a pulley or directly from one of the engine shafts manages the GDI fuel rail pressure control. The pressure pulsations of such a pump are controlled entirely or partially by a normally open on/off control valve that creates pumping and spilling flow conditions. Such valve is typically synchronized to the camshaft that will trigger the valve according to the angle of the cam and the required flow or pressure delivery to the fuel rail assembly and injectors.
Different control valves exist in the art to achieve different kinds of performances. Material selected for the control valve has to be corrosion resistant to different blends of fuel and typically the design configuration makes such pump an expensive component that increases the overall system cost considerably.
Pressure control valves for high-pressure pumps that are able to deliver fuel from a fuel tank to a fuel rail assembly at a high-pressure must manage the occurring magnetic, mechanical, and hydraulic forces adequately to produce the desired pressure or flow output. Factors such as friction, hydraulic stiction, component misalignment, under-over damping, inertia, or mass must be minimized in order to reduce actuator performance variation and to enhance part reliability.
What is needed in the art is a pressure control valve that significantly simplifies the component design and reduces the amount of components used thereby reducing the complexity and cost of the assembly process.
It is a principal object of the present invention to provide a pressure control valve for controlling a high-pressure single-piston pump that has a low mass armature geometry and an integral seat with in line flow configuration for improved flow behavior and that is designed to reduce the pump packaging.
Briefly described, a pressure control valve for controlling a high-pressure single-piston or multiple-piston pump has the capability for controlling pressure or flow with a commanded input electrical voltage or current, while simplifying the component design and reducing the amount of components and, thus, the complexity of the assembly process. The pressure control valve in accordance with the invention may be used for, but is not limited to, applications in the automobile industry, for example, to manage the fuel rail pressure of a gasoline direct injection (GDI) internal combustion engine.
The pressure control valve in accordance with the invention includes a spring that biases the armature section to keep the valve normally open. The armature mechanical net load may be set in spring preload to prevent self-closure caused by reverse flow.
Utilization of a ball armature in accordance with the invention simplifies the valve design by reducing the number of components. The ball armature is self guided and, therefore, controls the occurring radial forces with tight clearances. The armature stroke may be determined by a retention cup positioned in line with the flow within the housing. Accordingly, a flow path that minimizes the force created by the back flow may be created making the design of the control valve robust for applications at different engine speeds. Consequently, the control valve in accordance with the present invention may have a fast response with low variation.
The magnetic ball armature is moved from an open position to a closed position by an electromagnetic field created with a solenoid. The coil of the solenoid is kept dry by positioning it outside of the valve body and by over molding the spool the coil is wound around with a plastic material. Using a dry coil design improves the body leakage performance and reduces hydrocarbon emissions typically carried by fuel vapors. Furthermore, the core of the solenoid is cooled by the flow of the fuel through the pressure control valve. Accordingly the pressure control valve in accordance with the invention has a self-cooling design.
Still further, the outlet port of the pressure control valve is designed to be received by the inlet port of a high-pressure single-piston pump, which may reduce the pump packaging and simplify the assembly process.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner.
Referring to
Fuel injectors 22 are adapted to receive fuel from fuel rail 18 and to deliver fuel directly into the combustion chamber of each cylinder (not shown). High-pressure pump 14 may be a single-piston reciprocating pump that has a piston (not shown) that draws fluid, in this case fuel, into a chamber when stroked in one direction and expels fluid from the chamber when stroked in the other direction. Thus, pump 14 delivers a single charge of fuel during each stroking cycle.
Fuel tank 12 stores the fuel required for operating the DIG engine. Low-pressure pump 28 delivers fuel with low pressure from tank 12 to high-pressure pump 14 via low-pressure line 32. High-pressure pump 14 delivers highly pressurized fuel to fuel rail 18 via high-pressure line 34. High-pressure fuel pump 14 is typically driven mechanically by the engine via a pulley or directly from one of the engine shafts.
Pressure control valve 20 is positioned between fuel pump 28 and high-pressure pump 14 and typically controls entirely or partially the pressure pulsations of high-pressure pump 14 and creates pumping and spilling flow conditions and, therefore, is operated as a fuel-metering device. Pressure control valve 20 controls flow and pressure of the fuel to fuel rail 18. Pressure control valve 20 is an on/off valve that is normally open allowing flow from fuel tank 12 to pump 14 and vice versa. Pressure control valve 20 may be controlled by an electric actuator, such as an electromagnet, and may continuously adjust the flow from low-pressure pump 28 to high-pressure pump 14. If pressure control valve 20 is operated in an open position, fuel flow from low-pressure pump 28 to high-pressure pump 14 or in inverse direction is enabled. If pressure control valve 20 is operated in a closed position, fuel flow from low-pressure pump 28 to high-pressure pump 14 is interrupted, high-pressure pump 14 pressurizes fuel previously suctioned in, and flow of the pressurized fuel to fuel rail 18 only is enabled. Pressure control valve 20 may enable pressurization of the fuel from about 4 to 6 bars at an outlet of low-pressure valve 28 to about 40 to 200 bars at an outlet of high-pressure pump 14.
Referring to
Inlet segment 52 has preferably a cylindrical shape and includes cylindrical center bore 64 that extends along axis 60. Cylindrical bore 64 includes a first section 641 positioned proximate to an upper end 521 and having a first diameter 642 and a second section 643 having a second diameter 644 that is larger than first diameter 642. Consequently, cylindrical bore 64 includes a shoulder 645 where first section 641 meets second section 643. Second section 643 receives and guides spring 48 and shoulder 645 is utilized to retain the position of spring 48 in an axial direction. At the outer circumference, inlet segment 52 may include connection features 646 that may enable preferably quick connection of inlet segment 52 to a low-pressure line of a fuel system, such as low-pressure line 32 of fuel system 10 shown in
Center segment 62 has preferably a cylindrical shape and includes a cylindrical center bore 68 that extends along axis 60. Bore 68 is designed to receive and retain inlet segment 52 and outlet segment 54. The size of bore 68 is adapted to the size of an outer circumference of inlet segment 52 and outlet segment 54 and to allow flow around ball 44. Retention cup 46 may be secured to the inner wall of center segment 62 that is formed by bore 68.
Outlet segment 56 has preferably a cylindrical shape and includes a cylindrical center bore 72 that extends along axis 60. An outer circumference of outlet segment 56 is preferably adapted to the size of an inlet port of a high-pressure pump, such as pump 14 shown in
Center bore 64 of inlet segment 52, center bore 68 of center segment 62, and center bore 72 of outlet segment 56 are in fluid communication and, thus, form a centered axial flow path 78 of valve 40 that extends from inlet port 54 to outlet port 58. Flow 74 is possible in both directions from inlet port 54 to outlet port 58 and from outlet port 58 to inlet port 54 when ball 44 is positioned in retention cup 46 and, thus, when valve 40 is open. Flow 74 is stopped when ball 44 is positioned in valve seat 66 and, thus, when valve 40 is closed. The flow direction is determined by the movement of a piston in a high-pressure pump, such as pump 14 in
Ball 44 is in a preferred embodiment movable by solenoid 50 from a first position in which ball 44 is positioned in retention cup 46 and a second position in which ball 44 is positioned in valve seat 66 and, therefore, from an open position to a closed position of valve 40. Spring 48 is preferably designed to normally maintain ball 44 positioned in retention cup 46 to keep valve 40 open even when the flow 74 from outlet port 58 to inlet port 46 occurs. Spring 48 maintains ball 44 in retention cup 46 and keeps valve 40 open until an electrical signal is sent. A current sent via an electrical connector 76 to solenoid 50 energizes valve 40 by creating a magnetic field that moves ball 44 from its position in retention cup 46 to valve seat 66, thereby blocking flow path 78 and stopping flow 74 towards inlet port 54 and, thus, closing valve 40. The force needed to move ball 44 into valve seat 66 may be lower compared to forces applied in prior art control pressure valves, since flow 74 towards inlet port 54 assists upward movement of ball 44 from retention cup 46 to valve seat 66. In a preferred embodiment, solenoid 50 is an electromagnet including a coil 82 wound around a spool 84. Spool 84 may be over molded with a plastic material 86 to protect coil 82 from the environment, for example, from corrosive fluids. By positioning solenoid 50 around the outer circumference of valve body 42, the core of solenoid 50 or coil 82 is cooled instantly by flow 74 passing through flow path 78.
Referring now to
While pressure control valve 40 has been described for application in a fuel system of a gasoline direct injection (GDI) engine other applications are possible.
While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the on not be limited to the described embodiments, but will have full scope defined language of the following claims.