Pressure pulsation damper with interated hot soak pressure control valve

Abstract: The integrated pressure pulsation damper and hot soak pressure valve lies normally open adjacent the fuel rail and damps fuel pressure pulsations during engine operation caused by opening and closing of the fuel injectors. When the engine is turned off, and a hot soak condition occurs, the valve automatically closes to retain a high fuel pressure in the fuel rail to facilitate hot restarts. Upon restarting the engine, the valve reverts to its normally open condition, serving as a pressure pulsation damper.

Description: TECHNICAL FIELD The present invention relates to a fuel system for supplying fuel at a regulated pressure to an automotive engine and particularly relates to an integrated pressure pulsation damper and hot soak pressure control valve for absorbing fuel pressure pulsations during normal engine operating conditions and closing the valve during a hot soak condition to enable quick engine restart. BACKGROUND Conventional non-return type fuel systems for automotive engines typically mount a fuel pressure regulator in the fuel tank. A pressure pulsation damping device is often located in the fuel line adjacent the fuel rail. A system of this type, however, can experience hot start and restart problems due to vapor lock. That is, when the engine is turned off and temperatures within the fuel rail are elevated, the fuel pressure in the fuel rail is checked by the regulator in the fuel tank. This pressure check is intended to be sufficiently high that fuel will not vaporize in the fuel rail and immediate hot restart of the engine is possible. However, if the pressure is not checked sufficiently high enough, restart or vapor lock problems occur. DISCLOSURE OF THE INVENTION US 5673670 discloses a fuel system and method as set forth in the precharacterising part of the independent claims having the aforementioned drawbacks. According to the invention there is provided a fuel system and method as set forth in the independent claims. A conventional fuel regulator is typically disposed within a fuel tank and provides fuel to a fuel rail at a regulated pressure. The fuel, however, is supplied through a normally open integrated pressure pulsation damper and hot soak pressure control valve. The control valve includes a diaphragm which is responsive to pressure pulsations in the fuel, e.g., as a result of the opening and closing of the fuel injectors in the fuel rail, to absorb or dampen the pressure pulses in the fuel system. The control valve serves no other purpose during normal operating conditions than as a pressure pulsation damper. However, when the engine is turned off and a hot soak condition occurs, the valve automatically closes to maintain a high pressure in the fuel rail. The fuel rail is therefore isolated from the balance of the fuel system to maintain the higher pressure and prevent fuel vaporization. That is, the control valve closes to check the pressure in the rail to a predetermined pressure higher than the normal operating pressure. Accordingly, when the engine is restarted, fuel under high pressure in liquid form is available in the fuel rail for delivery to the fuel injectors. Consequently, the present integrated control valve for pulsation damping and hot soak pressure control may replace existing pulsation dampers in most fuel systems, while avoiding recalibration of the engine or modifications to the conventional fuel pumps and pressure regulators. The system hereof, however, would result in quick hot start and restarts without vapor lock problems. In a preferred embodiment according to the present invention, there is provided a fuel system for an engine comprising a plurality of fuel injectors, a fuel rail for supplying fuel to said injectors, a fuel tank, a fuel pump for pumping fuel from the fuel tank to the fuel rail, a pressure regulator for supplying fuel at a regulated pressure to the fuel rail and a normally open integrated pressure pulsation damper and hot soak pressure control valve between the pressure regulator and the fuel rail, the valve having a spring-biased diaphragm operable to damp fuel pressure pulsations in the fuel system and to close the control valve in response to an increase in pressure in the fuel rail above the regulated pressure. In a further preferred embodiment according to the present invention, there is provided a method of operating a fuel system for an engine wherein the fuel system includes a fuel tank, a fuel rail in communication with a plurality of fuel injectors, a fuel pump and a pressure regulator, comprising the steps of pumping fuel from the fuel tank to the fuel rail, regulating the pressure of the fuel pumped to the fuel rail, providing an integrated pressure pulsation damper and hot soak pressure control valve between the pressure regulator and the fuel rail, damping fuel pressure pulsations in the fuel system using the integrated pressure pulsation damper and hot soak control valve and closing the control valve in response to an increase in pressure in the fuel rail. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a schematic illustration of a fuel system incorporating a pressure pulsation damper with integrated hot soak pressure relief control valve; and FIGURE 2 is a fragmentary enlarged cross-sectional view with parts in cross-section of a pressure pulsation damper with integrated hot soak pressure relief control valve disposed in the fuel system of Figure 1. BEST MODE FOR CARRYING OUT THE INVENTION Referring to Figure 1, there is illustrated a fuel system for an automotive engine, generally designated 10, and comprising a fuel tank 12 containing a fuel pump 14 and a pressure regulator 16 within the fuel tank for regulating the pressure of the fuel supplied from pump 14 through regulator 16 to a predetermined pressure for supply to the fuel rail 18. As illustrated, a plurality of fuel injectors 20 are in communication with the fuel rail. Consequently, fuel at a regulated pressure is supplied the fuel rail for flow into the engine by way of the injectors. An integrated pressure pulsation damper and hot soak pressure control valve, generally designated C.V., is provided in the fuel line 22 between the pressure regulator 16 and the fuel rail 18. In a preferred embodiment illustrated in Figure 2, the control valve comprises an upper, generally inverted cup-shaped housing section 24 having a fuel inlet 26 for connection to a fuel line 22 and a lower, generally cup-shaped housing 28 having a plurality of apertures 30 circumferentially spaced one from the other for supplying fuel from the inlet through the valve into the fuel rail 18. The upper and lower sections are joined one to the other with a diaphragm 32 disposed therebetween. The valve is mounted in a mounting cup 34 formed on the fuel rail 18. The diaphragm 32 has a central aperture 36 receiving a portion of a valve member 38. An annular part 39 lies on the opposite side of diaphragm 32 from a shoulder on valve member 38 wherein the diaphragm is clamped to the valve member 38. The valve member 38 includes a central opening 40. The lower cup-shaped section 28 fixedly mounts a valve abutment 41 having a post 42 projecting through the opening 40 of the valve member 38. Valve abutment 41 includes a passageway in communication with opening 40 and apertures 30 in housing 28. The valve member 38 includes a sleeve 44 which projects away from diaphragm 32 and surrounds a valve element 46, for example, a spherical ball valve. The valve element 46 is movable toward and away from a valve seat 48 formed on the valve member 38 about opening 40. The valve element 46 is biased toward a valve-closed position by a spring 50 having opposite ends bearing against the valve element 46 and the base of a housing 52. The housing 52 is fixed in the upper cup-shaped housing section 24 and includes a passageway 53 for fuel to flow within housing 52 and about valve element 46. In operation, the fuel is supplied to the control valve via inlet 26 under a regulated pressure. The fuel pressure on opposite sides of the diaphragm 32 maintains the diaphragm in a balanced position with member 38 normally spaced from abutment 41 with post 42 maintaining valve element 46 spaced from seat 48. Pressure pulsations are damped by movement of the diaphragm in response thereto with post 42 at all normal engine operating conditions maintaining element 46 off seat 48 and hence maintaining the valve in a normally open condition. Particularly, with lower than normal fuel pressure on the outlet side of diaphragm 32, diaphragm 32 moves member 38 toward the valve abutment 41. By displacing the valve member 38 toward abutment 41, post 42 displaces the valve element 46 further away from seat 48, causing the valve to open to a further extent. With higher than normal fuel pressure on the outlet side of the diaphragm 32, diaphragm 32 moves member 38 away from abutment 41, effectively reducing the valve opening between valve element 46 and the valve seat 48. The movement of the diaphragm 32 thus dampens pressure pulsations while maintaining the valve normally open under normal engine operating conditions. When the engine stops and a hot soak condition develops in the fuel rail, the higher developed pressure in the fuel rail causes the diaphragm 32 to be displaced away from the abutment 41, causing the valve seat 48 to engage the ball 46, closing the valve opening. Consequently, fuel at a higher pressure is maintained in the fuel rail when the control valve closes, enabling a hot start or restart. Upon a decrease in pressure in the fuel rail after starting, the diaphragm 32 is displaced toward the abutment 41 whereby the post 42 engages the ball valve 46 to open the valve whereby the integrated valve serves once again as a pulsation damper during normal engine operation.

Claims: A fuel system (10) for an engine comprising: a plurality of fuel injectors (20); a fuel rail (18) for supplying fuel to said injectors; a fuel tank (12); a fuel pump (14) for pumping fuel from the fuel tank (12) to the fuel rail (18); a pressure regulator (16) for supplying fuel at a regulated pressure to said fuel rail (18); and a normally open integrated pressure pulsation damper and hot soak pressure control valve (c.v.) between said pressure regulator (16) and said fuel rail (18), said valve having a spring-biased diaphragm (32) operable to damp fuel pressure pulsations in said fuel system (10) and to close said control valve (c.v.) in response to an increase in pressure in said fuel rail (18) above said regulated pressure characterised in that said control valve (c.v.) includes a diaphragm carrying a valve member having an opening (36), a valve element, a spring (50) for biasing said valve element (46) toward said valve member (48) to close said opening and a post (42) for engaging said valve element (46) to maintain said valve open during operation of the engine, enabling the valve element (46) to close the valve opening (36) in response to a pressure in the fuel rail (18) higher than the regulated pressure and movement of said diaphragm away from said post (42). A fuel system according to Claim 1 wherein said valve member includes a valve seat (48) surrounding said opening, a housing (24) for said spring enabling said spring (50) to bias said valve element (46) toward said seat (48), said diaphragm and said valve member carried thereby being movable away from said abutment member(41) in response to a pressure in said fuel rail (18) higher than the regulated pressure enabling said valve element (46) to engage said valve seat (48) closing said valve opening. A method of operating a fuel system (10) for an engine wherein the fuel system includes a fuel tank (12), a fuel rail (18) in communication with a plurality of fuel injectors (20), a fuel pump (14) and a pressure regulator (16), comprising the steps of: pumping fuel from said fuel tank (12) to said fuel rail (18); regulating the pressure of the fuel pumped to said fuel rail (18); providing an integrated pressure pulsation damper and hot soak pressure control valve (C.V.) between said pressure regulator (16) and said fuel rail (18); damping fuel pressure pulsations in said fuel system using said integrated pressure pulsation damper and hot soak control valve (C. V.); and closing said control valve in response to an increase in pressure in said fuel rail (18); maintaining said integrated pressure pulsation damper and hot soak control valve open during engine operation characterised in that said integrated pressure pulsation damper and hot soak control valve (C. V.) includes a diaphragm (32) dividing said valve into first and second chambers in respective communication with said fuel rail (18) and said fuel pump (14), and including the step of displacing a valve member carried by said diaphragm (32) toward said second chamber in response to an increase in pressure in said fuel rail in an engine-off condition to close said valve thereby isolating said chambers from one another.

Inventors: KILGORE JASON T, KILGORE, JASON T.
Applicants: SIEMENS VDO AUTOMOTIVE CORP, SIEMENS VDO AUTOMOTIVE CORPORATION
Application year: 2000
Main classification: F02M37
IPC codes: F02M37, F02M55, F02M69