I. Field of the Invention
The present invention relates to fuel pumps and, more particularly, to a high pressure fuel pump for use with a direct injection internal combustion engine.
II. Description of Related Art
Direct injection internal combustion engines are enjoying increased popularity, particularly in the automotive industry. In a direct injection internal combustion engine, the fuel is injected directly into the internal combustion chamber. Such direct injection engines enjoy increased engine efficiency, fuel economy, and reduced emissions.
Since the fuel is injected directly into the internal combustion chamber in a direct injection engine, the fuel supply to the fuel injectors must necessarily be provided at a high pressure. In order to accomplish this, a high pressure fuel pump provides high pressure fuel to fuel rails which are, in turn, fluidly connected to the fuel injectors for the engine.
With reference first to
Still referring to
In order to pump fuel from the pump chamber 24 out through the outlet port 26, a piston 34 has one end positioned within the pump chamber 24 and is reciprocally driven by the camshaft of the engine. Consequently, as the piston 34 moves into the pump chamber 24, the piston 34 pressurizes the fuel in the pump chamber 24 thus forcing the fuel out through the outlet port 26 and to the fuel rail assuming that the inlet port 32 is closed. Conversely, as the piston 34 moves outwardly from the pump chamber 24, the piston 34 inducts fuel through the inlet passage 30 and inlet port 32, assuming that it is open, and into the pump chamber 24.
A valve 36 is axially slidably mounted within the housing 22 and this valve 36 includes an enlarged diameter valve head 38 which overlies the inlet port 32 to the pump chamber 24. When the valve 36 is extended so that the valve head 38 is spaced apart from the port 32, the flow of fuel from the inlet passageway 30 and to the pump chamber 24 can occur through the inlet port 32. Conversely, with the valve head 38 abutting against the port 32, the valve head 38 closes the inlet port 32 so that fuel is pumped out through the outlet port 26 as the piston 34 moves into the pump chamber 24.
In order to control the movement of the valve 36 between its open and closed position, a spring 40 urges the valve 36 towards its closed position while a solenoid 42, when activated, holds the valve 36 in an open position. Consequently, upon deactivation of the solenoid 42, the spring 40 returns the valve to its closed position thus terminating fluid flow through the inlet port 32.
In operation, the movement of the piston 34 out from the pump chamber 24 creates a suction which moves the valve 36 to an open position. Once open, the actuation of the solenoid 42 maintains the valve 36 in its open position thus allowing fuel flow from the inlet passageway 30 into the pump chamber 24. As the piston 34 begins to move back into the pump chamber 24, deactivation of the solenoid 42 allows the spring 40 to return the valve 36 to its closed position so that the pressurized fuel in the pump chamber 24 flows out through the outlet port 26 as desired.
While the previously known fuel pumps for direct injection engines have proven adequate in supplying sufficient high pressure fuel to the fuel rails for the engine, the fuel pump creates an undesirable high level of noise for automotive uses. Most of this noise, furthermore, is attributable to contact or impact between the valve 36 and the pump housing 22 as the valve 36 reciprocates between its open and its closed position. This contact occurs not only between the valve head 38 and the valve seat 39 forming the inlet port 32, but also between an anchor 44 of the valve 36 and the pump housing.
The present invention provides a plurality of pump designs which overcome the above-mentioned disadvantages of the previously known pump designs.
The pump design of the present invention also includes a pump housing which defines a pump chamber as well as a piston reciprocally mounted to the housing and movable into and out from the pump chamber. The present design also includes a valve which is movably mounted in the housing and which establishes fluid communication between the inlet passageway and the pump chamber as well as blocks fluid flow from the fuel inlet passageway to the pump chamber in synchronism with movement of the piston 34.
In a first embodiment of the invention, an electrical control system is provided for controlling the actuation of the valve solenoid. This control circuit generates a pulse width modulated (PWM) signal to the solenoid. Unlike the previously known fuel pump designs, however, the control system varies the width of the pulses generated by the control system to decelerate the movement of the valve just prior to its contact with the housing. Consequently, by decelerating the valve prior to contact between the valve head and its valve seat, as well as contact between the valve anchor and the valve housing, pump noise is effectively reduced.
In a second embodiment of the invention, a chamber containing magneto-rheological fluid (MRF) is disposed around a portion of the valve while an MRF coil is disposed around the MRF chamber to control the activation of the fluid in the MRF chamber. In this embodiment of the invention, the MRF coil is activated just prior to contact between the valve and the pump housing to effectively decelerate the speed of movement of the valve just prior to impact between the valve and the pump housing. Such deceleration, as before, reduces the amount of noise caused by impact of the valve against the pump housing.
In one form, a solenoid is also contained within the housing and cooperates with the valve to hold the valve in an open position for a short period during the pump cycle. However, alternatively, the solenoid may be eliminated and the valve may be maintained open for that same period during the pump cycle by activation of the MRF coil. Such activation effectively operates to prevent movement of the valve and thus maintain it in an open position during that desired period of the pump cycle.
In a still further embodiment of the present invention, the valve head is slidably mounted within a valve chamber while an inlet passageway intersects that valve chamber at a predetermined location. As before, the valve is movable between an open and a closed position by operation of the spring and solenoid, but unlike the previously known fuel pumps, the valve head does not impact against the pump housing and thus does not create the noise of the previously known pumps. Instead, when in its open position, the valve head is retracted into the valve chamber by a distance sufficient to expose the fuel inlet passageway to the valve chamber thereby establishing fluid communication from the fuel source and to the pump chamber. Conversely, movement of the valve to its extended closed position causes the valve head to cover and fluidly seal against the walls of the valve cavity thus blocking communication between the inlet passageway and the pump chamber.
In a still further modification of the fuel pump of the present invention, the valve head is positioned within the valve chamber while the inlet fuel passageway intersects the valve chamber at a predetermined location. However, rather than reciprocally moving the valve within the valve chamber, the valve is instead rotatably driven by a motor so that the valve head rotates in the valve chamber.
In order to establish fluid communication between the fuel inlet passageway and the pump chamber, at least one, and preferably several circumferentially spaced and axially extending channels are formed on the outer periphery of the valve head. As each channel rotates into registration with the inlet fuel passageway, fluid communication is established between the inlet fuel passageway and the pump chamber through the valve head channel. However, since the valve head merely rotates within the valve chamber and does not impact against the pump housing, pump noise is effectively eliminated.
The present invention provides still further improvements to reduce pump noise. A still further noise reduction strategy is the provision of a turbulence surface along the outlet passage from the pump chamber. Such a turbulence surface effectively reduces pulsations caused throughout the fuel supply system and thus further reduces noise from that system.
In yet a further strategy, a diaphragm is positioned within the pump chamber. The diaphragm flexes in unison with the pressurization of the pump chamber by the piston and also reduces pulsations in the fuel system which otherwise would cause noise.
A better understanding of the present invention will be had upon reference to the following detailed description when read in conjunction with the accompanying drawing, wherein like reference characters refer to like parts throughout the several views, and in which:
With reference first to
The housing also includes a fuel inlet passageway 30 which fluidly communicates with the pump chamber 24 through the fluid port 32. A piston 34 is then reciprocally driven into the pump chamber 24 to pressurize the fuel in the pump chamber 24 and provide that pressurized fuel to the fuel rail and then, as the piston 34 moves out of the pump chamber 24, open the valve 36 and induct fuel from the inlet passageway 30, through the port 32, and into the pump chamber 24.
The elongated valve 36 is reciprocally movably mounted in the housing 22 and movable between an open position, illustrated in
In order to control the movement of the valve 36, a compression spring 40 is disposed around the valve 36 and urges the valve 36 towards its closed position. However, a solenoid 42, when activated, maintains the valve 36 in its open position (
Unlike the previously known fuel pumps, however, the fuel pump 20 of the present invention includes an electrical control circuit 50 which controls the voltage, and thus the current, to the solenoid 42. As best shown in
In particular, as shown in
Similarly, the electrical control circuit 50 may also be used to control the speed of impact of the valve anchor 44 against the pump housing 22. This also is achieved by varying the pulse width duration on the output 54 from the control circuit 50.
With reference now to
At step 186 it is determined whether or not the turn-off time, namely time 58, has been reached. If so, step 186 proceeds to step 188 and turns off the power to the solenoid. Otherwise, step 186 proceeds to step 190.
At step 190, the pulse width duty cycle is decreased in accordance with a schedule stored in memory 192. Step 190 then proceeds back to step 182 where the above process is reiteratively repeated until the turn-off time 58 has been reached.
With reference now to
Consequently, in operation, an MRF control circuit 74 generates a signal on its output 76 to control the magnitude of the magnetic field created by the MRF coil 72.
A flowchart illustrating the operation of the invention is shown in
At step 96, the circuit 74 determines the position of the valve 36 and then proceeds to step 98 and determines if the valve 36 is returning to a closed position. If not, step 98 branches back to step 96.
Otherwise, step 98 proceeds to step 100 where the MRF control circuit 74 energizes the MRF coil 72 to decelerate the valve 36 prior to its contact with the pump housing. Step 100 then proceeds back to step 92 where the above process is repeated.
An exemplary output from the MRF control circuit 74 is illustrated in
Consequently, by synchronizing the output from the MRF control circuit 74 with the desired movement of the valve 36, the MRF fluid in the MRF chamber 70 may be activated just prior to impact of the valve head 38 or valve anchor 44 with the pump housing 22 to decelerate the movement of the valve 36 and reduce the speed of the impact. In doing so, reduction of the impact speed simultaneously reduces the noise caused by that impact and thus reduces the noise from the pump 20.
With reference now to
With reference now to
However, at time t3 and thus prior to contact of the valve head 38 with its valve seat 39 on the pomp housing 22, the MRF coil is again activated with an increasing energy thus effectively increasing the viscosity of the MRF fluid and decelerating the movement of the valve 36 just prior to closure of the valve 36 at time t4 and thus just prior to the impact of the valve 36 against the housing 22.
With reference to
A portion of a fuel inlet passageway 116 intersects the valve chamber 114 at a predetermined location spaced from an end 118 of the valve chamber 114. The end 118 of the valve chamber, in turn, is open to the pump chamber 24.
With reference now to
As before, a compression spring 120 urges the valve 110 toward an open position while, when activated, the solenoid 122 maintains the valve in its closed position.
Unlike the previously known fuel pump designs for direct injection engines, the fuel pump design illustrated in
With reference now to
A part of an inlet fuel passageway 116 is also provided through the pump housing 22 so that the passageway 116 intersects the valve chamber 134 at a location spaced from the end 136 of the valve chamber 134. This end 136, furthermore, is open to the pump chamber 24.
In order to selectively fluidly connect the fuel inlet passageway 116 with the pump chamber 24 in synchronism with the reciprocation of the piston 34, at least one, and preferably several circumferentially spaced and axially extending channels 138 are formed along the outer periphery of the valve head 132. These channels 138 extend from the free end of the valve head 132 to at least the location of the inlet passageway 116. Consequently, upon rotation of the valve head 132, as each channel 138 registers with the inlet passageway 116, fluid communication is established between the inlet passageway 116 and the pump chamber 124. Conversely, the outer periphery of the valve head 132 sealingly engages the inner periphery of the valve chamber 134 thus preventing fluid flow from the inlet passageway 116 and to the pump chamber 24 when the channel 138 does not register with the inlet passageway 116.
Unlike the previously described embodiments of the invention, in this modification of the invention, the valve 130 is rotatably driven by a motor 140, such as a stepping motor or a DC controllable motor, such that rotation of the valve 130 is synchronized with the movement of the piston 34. However, the valve 130 is constrained against axial movement.
Since the valve 130 merely rotates within the pump housing 22, all impact of the valve with the pump housing 22 is eliminated along with noise created by such impact.
With reference now to
By increasing the laminar fuel flow through the outlet pipe 150, pressure pulsation throughout the remainder of the fuel system is reduced thus reducing noise created by such fuel pressure pulsation.
With reference now to
In operation, as the piston 34 compresses the fuel in the pump chamber 24 and forces that fuel out through the outlet 28, the diaphragm flexes from the position shown in
From the foregoing, it can be seen that the present invention provides a number of different strategies to reduce the noise from the fuel pump in a high pressure fuel pump of the type used for direct injection internal combustion engines. Having described our invention, however, many modifications thereto will become apparent to those skilled in the art to which it pertains without deviation from the spirit of the invention as defined by the scope of the appended claims.