Internal-combustion engines – Charge forming device – Fuel flow regulation between the pump and the charge-forming...
Reexamination Certificate
1999-10-06
2001-12-04
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel flow regulation between the pump and the charge-forming...
C123S447000, C417S499000
Reexamination Certificate
active
06325051
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. HEI 10-300124 filed on Oct. 21, 1998 including the specification, drawings and abstract, is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a return-less type high-pressure fuel supplying apparatus and method for an internal combustion engine that has a high-pressure pump for supplying high-pressure fuel to the internal combustion engine but does not have a return passage for returning surplus fuel from the high-pressure pump to a fuel tank.
2. Description of Related Art
In a fuel supplying apparatus applied to a generally termed in-cylinder fuel injection type internal combustion engine in which fuel is directly injected into the cylinders of the internal combustion engine, fuel is first pumped from a fuel tank into a fuel gallery via a feed pump, and then introduced into a pressurizing chamber of a high-pressure pump during descent of a plunger of the high-pressure pump. Fuel introduced into the pressurizing chamber is pressurized by the plunger to a pressure that is suitable for in-cylinder injection. Fuel pressurized in this manner then is supplied to a delivery pipe to which fuel injection valves are connected.
In this type of fuel supplying apparatus, after a certain amount of fuel is supplied to the high-pressure pump, a surplus amount thereof, which does not need to be pumped toward the engine, is normally returned to the fuel tank through a return passage. In a typical construction, however, the high-pressure pump is disposed near the internal combustion engine, so that fuel introduced into the high-pressure pump is likely to undergo a temperature increase due to heat from the engine. Therefore, when surplus fuel returns to the fuel tank through the return passage, the fuel temperature in the fuel tank rises, so that the amount of fuel vapor occurring in the fuel tank increases.
As a countermeasure, a return-less type high-pressure fuel supplying apparatus has been proposed (for example, in Japanese Laid-Open Patent Application No. HEI 9-25860) in which the need for a return passage is eliminated by controlling the amount of fuel pumped from the feed pump into the high-pressure pump to a minimum amount that is actually needed. Therefore, this return-less apparatus prevents an undesired event in which heated fuel returns to the fuel tank. Hence, the apparatus is able to prevent or curb fuel temperature increases in the fuel tank and reduce the occurrence of fuel vapor in the fuel tank.
However, since fuel circulation between the high-pressure pump and the fuel tank is eliminated, the return-less type fuel supplying apparatus tends to have relatively high fuel temperatures in the fuel gallery and in the pressurizing chamber. Therefore, if the engine is stopped immediately after the engine temperature has increased due to, for example, a high-load operation or the like, heat from the engine may increase the fuel temperature in the fuel gallery or in the pressurizing chamber approximately to the boiling point of the fuel, so that a portion of the fuel may vaporize and add fuel vapor.
Furthermore, if the engine is restarted at an increased fuel temperature, there is a further increased likelihood of a phenomenon (cavitation) in which when fuel is moved from the fuel gallery into the pressurizing chamber by reciprocations of the plunger, the fuel pressure temporarily drops so that vapor occurs.
The produced vapor is continually moved back and forth between the fuel gallery and the pressurizing chamber by reciprocations of the plunger. If fuel pressurization is performed in the pressurizing chamber when a large amount of vapor has moved into the chamber, the plunger merely compresses fuel vapor, and it becomes difficult for the plunger to sufficiently pressurize liquid fuel. In this manner, the conventional return-less type high-pressure fuel supplying apparatus may fail to secure a predetermined fuel injection pressure when the engine temperature is high. Therefore, the conventional return-less apparatus may cause deterioration of the restarting performance, resulting in, for example, a prolonged time required for a start, occurrence of an engine stall immediately following a start, or the like.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a high-pressure fuel supplying apparatus and method for an internal combustion engine that secures good restarting performance when the engine temperature is high.
In accordance with one aspect of the invention, a high-pressure fuel supplying apparatus for an internal combustion engine includes a high-pressure pump having a fuel gallery and a pressurizing chamber. The high-pressure pump introduces fuel from the fuel gallery into the pressurizing chamber, pressurizes fuel to a high pressure in the pressurizing chamber, and supplies pressurized fuel to an in-cylinder fuel injection valve. The high-pressure fuel supplying apparatus further has a feed pump that pumps fuel from a fuel tank to the fuel gallery. A vapor discharging passage is provided for discharging vapor from the fuel gallery. The vapor discharging passage is located above or at substantially the same vertical level as an upper end of the fuel gallery in a vertical direction.
In this high-pressure fuel supplying apparatus, vapor dwelling in the fuel gallery is discharged into the vapor discharging passage. Therefore, the apparatus curbs the fuel pressure reduction that is caused by vapor moving from the fuel gallery into the pressurizing chamber during fuel pressurization.
In the above-described high-pressure fuel supplying apparatus, the vapor discharging passage may be connected to an upper end portion of the fuel gallery. This construction further ensures discharge of vapor.
Furthermore, the vapor discharging passage may also be formed by a low-pressure fuel passage that introduces fuel pumped from the feed pump into the fuel gallery. This construction makes it possible to form a vapor discharge space by utilizing an existing or conventional construction or structure, such as a low-pressure fuel passage or the like.
The vapor discharging passage may also be formed by a passage that connects the fuel gallery to an auxiliary fuel injection valve that injects fuel into an intake passage of the internal combustion engine. This construction makes it possible to form a vapor discharge space by utilizing an existing construction or structure of an internal combustion engine that has an auxiliary fuel injection valve.
The high-pressure fuel supplying apparatus may further include a controller that determines whether fuel vaporization has occurred in the fuel gallery, and when it has been determined that fuel vaporization has occurred, opens the auxiliary fuel injection valve so as to discharge vapor from the vapor discharging passage into the intake passage. Since vapor in the vapor discharge passage is discharged into the intake passage, this construction substantially prevents vapor from returning from the vapor discharge passage to the fuel gallery. The controller may determine that fuel vaporization has occurred when the engine is being started. The controller may also determine that fuel vaporization has occurred when the engine is being started, provided a temperature of the engine is higher than a predetermined temperature.
In the high-pressure fuel supplying apparatus, the vapor discharging passage may include a reservoir that is formed by expanding a portion of the vapor discharging passage vertically upward. In this construction, vapor discharged from the fuel gallery into the vapor discharging passage resides in an upper portion of the reservoir. Therefore, this construction substantially prevents fuel that has been discharged from the fuel gallery into the vapor discharging passage from flowing back into the fuel gallery.
Furthermore, in the high-pressure fuel supplying apparatus, the high-pressure pump may be connected to and driven by a camshaft of the interna
Ohmi Masanobu
Oomori Yuzuru
Miller Carl S.
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
LandOfFree
High-pressure fuel supplying apparatus and method for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High-pressure fuel supplying apparatus and method for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High-pressure fuel supplying apparatus and method for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2560158