Patent Application
20050058549
N/A
This invention relates to “on-demand” fuel pumps, and more particularly, to such a fuel pump which is capable of delivering fuel at different output pressure levels depending upon engine conditions.
In co-assigned U.S. Pat. No. 5,961,293, there is described an in-tank fuel pump assembly for use with an internal combustion engine. The pump assembly draws low pressure fuel from the fuel tank in which the assembly is installed and delivers fuel at a high pressure to an internal combustion engine. Fuel demand varies depending upon a variety of factors including whether the vehicle is accelerating, decelerating, or traveling at a constant speed, the altitude at which the vehicle is moving, air temperature, and whether the vehicle is traveling on a straight path, ascending or descending, or turning. Modern electronic engine control systems are responsive to inputs from various sensors to control operation of the fuel pump so the pump delivers only the amount of fuel required by the engine at any one time; more or less fuel being supplied as circumstances warrant. This is referred to as “on demand” fuel delivery.
Heretofore, the pressure at which the fuel pump delivered fuel to the engine has been a single pressure level value; e.g. 15 psi, 30 psi, etc. Now, however, it has been found to be desirable to vary both the pressure at which fuel is delivered to the engine, as well as the amount of fuel delivered. Current fuel pump assemblies cannot provide this capability, thereby limiting their performance capabilities and the efficiency of the fuel delivery system of which they are a part. Rather, to achieve a multiple pressure capability, multiple pressure regulators and/or multiple fuel flow regulators are required within the fuel system. These add both cost and complexity to the system.
In accordance with the present invention, an internal combustion engine has an associated controller which is responsive to inputs from various sensors to control operation of the engine. A fuel pump of the invention delivers fuel to the engine at a first and lower pressure (e.g., 300 kPa) and at a second and higher pressure (e.g., 800 kPa) upon a command from the controller. The actual pressure level settings can be any pressure levels within the span of control of a pressure sensor used in the fuel system. The fuel pump has a fuel inlet through which fuel is drawn into the pump and a motor driven pump assembly for delivering fuel to an outlet of the pump at a pressure higher than the pressure at the inlet. An outlet assembly of the pump includes a pressure sensor sensing the outlet pressure and a signal processor responsive to inputs from the controller to vary the outlet fuel pressure between the higher and lower levels depending upon the input from the controller. The desired outlet pressure is achieved by controlling the speed of the pump motor, sensing the output pressure, and comparing the desired pressure against the measured pressure.
The outlet pressure of the fuel pump can be controlled for more than two outlet pressure values by modifying an input signal from the controller to the processor.
Other objects and features will be in part apparent and in part pointed out hereinafter.
The objects of the invention are achieved as set forth in the illustrative embodiments shown in the drawings which form a part of the specification.
Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.
The following detailed description illustrates the invention by way of example and not by way of limitation. This description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention, including what I presently believe is the best mode of carrying out the invention. As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
Referring to
Heretofore, the fuel pressure at an outlet of pump 10 has been constant, regardless of the quantity fuel being delivered by the pump. However, in accordance with the present invention, fuel pump 10 is now capable of delivering fuel at at least two different outlet pressures in response to control inputs from controller 18.
In
Referring to
As shown in
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Cover 64 is of a molded plastic construction and the closed cap end portion 66 of the cover includes a nipple 68 for attachment of the fuel pump outlet to an inlet end of fuel line 16. A vertically extending fuel flow tube 69 is molded into the base plate of cap 42. Opening 60 in the base plate (see
Cap end portion 66 further has a molded electrical connector 70 for attaching power and control lines, including line 22, from electronic controller 18 to the fuel pump. Those skilled in the art will understand that the control line includes a plurality of separate electrical wires and that connector 70 is for a multiple pin connector designed to snap-fit onto connector 70 and not be readily dislodged. Next, the cap end portion of cover 64 has an opening 72 in which is seated a pressure sensing tube 74. The sensing tube is used when pressure is to be sensed externally of the fuel pump.
Mounted within the outlet assembly are a pressure sensor 76, a printed circuit board (PCB) 78 to which the pressure sensor is electrically connected, a signal processor 79, and a transistor 80 which is also electrically connected to the PCB. Signal processor 79 is incorporated on the printed circuit board and is responsive to inputs from controller 18 to control both the amount of fuel delivered by the fuel pump at a given time, and the pressure at which the fuel is delivered. Sensor 76 is responsive to the output pressure of the fuel system and converts a pressure signal into an electrical signal communicated to controller 18 over control line 20. Tube 74 provides a conduit for the pressure sensor; or, the pressure sensor is mounted in outlet tube 69 to sense the pressure.
Transistor 80 comprises a portion of the electrical circuitry controlling power to motor 38. The transistor, which is covered with a metallic heat sink material, is electrically connected to PCB 78. A rectangular slot 81 is formed in the upper face of the base plate and one end of transistor 80 is sized to be received in this slot. A unique feature of the fuel pump of the present invention is that the heat sink on transistor 80 is exposed to the fuel, via the slot. The slot is designed with a thin, controlled amount of “flash” that contacts the heat sink and prevents potting material, in its viscous state, from running through the slot until the material solidifies. When the pump is running, the contact between the heat sink and the fuel draws heat away from the transistor, keeping its operating temperature relatively cool.
In addition to the fuel flow tube 69, also molded into the base plate of cap 42 are a pair of hollow cylindrical supports 82, and a pedestal 84 which extends between the tubes 82. PCB 78 is disk shaped with a diameter slightly smaller than the inner diameter of cover 64. The disk has a central opening 86 and a corresponding opening 88 is formed in the top surface of pedestal 84. PCB 78 seats upon pedestal 84 and a screw 90 is insertable through opening 86 into opening 88 to mount the PCB in place. Although shown in the drawings as being mounted with a screw, it will be understood that the printed circuit board could be soldered directly to the brush fittings.
A pair of opposed openings 92 are also formed in PCB 78. Rubber grommets 94 which fit in these openings provide fluid seals. The grommets/seals each include a seat for one of the springs 58 and their associated brushes 56. The tubes 82 open into the wedge shaped openings 54 in base plate 42. During fabrication of the outlet assembly, the brushes, which are also wedge shaped in cross-section, are inserted through the tubes 82 and the openings 54 at the bottom of the tubes, so to be positioned with motor 38. The seals 94 prevent fluid pressure from penetrating from the spring/brush assembly to the printed circuit board.
Electrical terminals 96a-96c are electrically connected to the PCB and extend upwardly into electrical connector 70 to mate with the pins in the control line 22 connector which attaches to connector 70. The terminal pins provide an electrical interface between a power supply (not shown) and fuel pump 10. Two of the pins are for power and electrical ground. The third pin is used for a variety of functions. For example, it can be used to provide a signal to controller 18 to provide feedback to the controller about fuel pump 10 operation. In the present application of switching the fuel pump's outlet pressure between two or more pressure levels, the third pin is used to provide a signal path for an outside source, such as controller 18, a relay (not shown), or other electrical device (also not shown) which provides a control signal to the fuel pump. The control signal can be an analog signal such as a voltage signal or a current signal. In either instance, the amplitude of the voltage or current is used to command the fuel pump as to its output pressure level. The signal can also be a digital signal in which the presence of a signal (a digital “1”) signifies to the fuel pump that its outlet pressure should be one level; while the absence of a signal (a digital “0”) signifies to the fuel pump that its outlet pressure should a different level. The processor 79 incorporated on PCB 78 is programmed to differentiate between the respective analog or digital signals to cause changes in the operation of fuel pump 10, such as setting the outlet pressure of the pump. As discussed below, the present invention can also incorporate more than two set points for outlet fuel pressure.
Referring to
To control the outlet pressure from pump 10 between a low pressure 300 kPa, for example, and a high pressure 800 kPa, for example, the input to RPM module 104 is a digital signal. When the level of signal is low (a logic “0”), it signifies the pump is to provide a low pressure or LP output. When the level of the signal is high (a logic “1”), it signifies the pump is to provide a high pressure or HP output. The input to module 104 from pressure sensor 76 indicates whether or not the sensed pump output corresponds to the desired outlet pressure. A resulting output from module 104 is provided to a motor control (MTR CNTL) module 106 to produce the drive signal for the motor.
Those skilled in the art will understand that fuel pump 10 could provide fuel at more than two outlet pressures without departing from the scope of the invention. To achieve this, the signal supplied to module 104 from controller 18 could, for example, be a binary input signal. The value represented by the binary input would indicate which of a plurality of output pressure levels pump 10 is to pump fuel to engine 14. Or, the input signal from controller 18 could be an analog signal having a signal characteristic (amplitude or frequency, for example) which represents the desired output pressure level.
In view of the above, it will be seen that the several objects and advantages of the present invention have been achieved and other advantageous results have been obtained.
