Abstract
A method and apparatus for controlling a solenoid actuated inlet valve to a pump chamber of a piston pump. A control circuit energizes the solenoid to open the inlet valve in synchronism with the reciprocation of the piston and thereafter de-energize the solenoid to initiate closure of the inlet valve. The inlet valve is decelerated following de-energization of the solenoid thus effectively reducing engine noise attributable to the inlet valve.
Claims
1. A method for controlling an inlet valve actuated by a solenoid, the method comprising: providing a pump having a pump chamber, a piston reciprocally mounted in the pump chamber, the inlet valve fluidly connected to the pump chamber, energizing the solenoid to open the inlet valve in synchronism with reciprocation of the piston, thereafter de-energizing the solenoid to initiate closure of the inlet valve in synchronism with the reciprocation of the piston, and decelerating the closure of the inlet valve following de-energization of the solenoid by: connecting a resistor-capacitor network across energization terminals of the solenoid, wherein the resistor-capacitor network includes a variable resistor, and varying a value of the variable resistor as a function of a fuel pressure after an outlet of the pump and a speed of the piston of the pump.
2. An apparatus for controlling an inlet valve actuated by a solenoid, the apparatus comprising: a pump having a pump chamber having an inlet, said inlet valve being fluidly connected to said pump chamber, a piston reciprocally mounted in the pump chamber, a controller configured to: energize the solenoid to open the inlet valve in synchronism with the reciprocation of the piston, de-energize the solenoid to initiate closure of the inlet valve in synchronism with the reciprocation of the piston, and generate output signals which decelerate the closure of the valve following de-energization of the solenoid, wherein: the controller comprises a resistor-capacitor network electrically connected across energization terminals of the solenoid, the resistor-capacitor network includes a variable resistor, and the controller is configured to vary a value of the variable resistor as a function of a fuel pressure at an outlet of the pump and a speed of the piston of the pump.
Description
BRIEF DESCRIPTION OF THE DRAWING
(1) A better understanding 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:
(2) FIG. 1 is a diagrammatic view illustrating a prior art fuel pump system for an automotive internal combustion engine;
(3) FIG. 2 is a timing chart illustrating the operation of the fuel delivery system;
(4) FIG. 3 is a view illustrating a first embodiment of a fuel system for an automotive internal combustion engine;
(5) FIG. 4 is a timing chart illustrating the fuel system timing for the fuel system of FIG. 3;
(6) FIG. 5 is a view similar to FIG. 3, but illustrating a modification thereof;
(7) FIG. 6 is a flowchart illustrating the operation of the fuel system of FIG. 5;
(8) FIG. 7 is a diagrammatic view of a fuel system illustrating yet a further embodiment;
(9) FIG. 8 is a diagrammatic schematic view of a portion of the fuel system of FIG. 7;
(10) FIG. 9 is a timing diagram of the fuel system of FIG. 7;
(11) FIG. 10 is a diagrammatic schematic view illustrating a modification of FIG. 8;
(12) FIG. 11 is a schematic view illustrating the variable receiver;
(13) FIG. 12 is a graph illustrating the duty ratio versus rise time; and
(14) FIG. 13 is a flowchart illustrating the operation of the FIG. 10 embodiment.
DETAILED DESCRIPTION OF PREFERRED
Embodiments of the Present Invention
(15) With reference first to FIG. 3, an exemplary fuel pumping system 100 is illustrated. Like the previously described systems, the fuel system 100 includes a fuel pump 101, a fuel tank 102 which is fluidly connected through a port 105 and a fuel inlet valve 104 to a pump chamber 106. A piston 108 is reciprocally driven in the pump chamber by a rotating cam 110 which rotates in synchronism with the engine crankshaft or output shaft (not shown).
(16) An electronic control circuit 112, which preferably includes a programmed processor, is electrically connected via a solenoid connector 152 to the input terminals 114 of a solenoid 116 that is mechanically connected to the inlet valve 104. Upon energization of the solenoid 116, the solenoid moves the valve to its open position. Conversely, upon de-energization of the solenoid 116, a spring 118 returns the valve 104 to its closed position. In addition, a one way outlet valve 120 fluidly connects the pump chamber 106 to a fuel rail 122 of an automotive internal combustion engine.
(17) During the operation of the fuel system 100, the cam 110 is rotatably driven by the engine which, in turn, reciprocally drives the piston 108 in the pump chamber 106. During the downstroke of the piston 108 and with the valve 104 in an open position, the piston 108 inducts fuel through the valve port 105 and into the pump chamber 106. Conversely, upon closure of the valve 104 and during the upstroke of the piston 108, the piston 108 pumps fuel through the outlet valve 120 and to the fuel rail 122.
(18) With reference now to FIGS. 4a-4e, timing graphs are illustrated of the fuel pumping system. Specifically, graph 130 in FIG. 4a represents the movement of the piston 108 between top dead center position and bottom dead center position of the plunger. The position of the plunger as represented by graph 4a is substantially identical to that shown in graph 40 in FIG. 2.
(19) In FIG. 4b, graph 132 represents the voltage applied by the control circuit 112 to the solenoid 116. The energization of the valve occurs at time t.sub.1 at which time voltage is applied to the solenoid 116 and the initiation of the valve opening begins. At time t.sub.2, the solenoid 116 is de-energized by removing the voltage from the solenoid 116. However, unlike the previously described fuel systems, following the de-energization of the solenoid 116 at time t.sub.2 and during the closure of the valve 104, the electronic control circuit 112 generates a back pulse 134. This back pulse 134 effectively decelerates the closure of the valve 104. Consequently, as shown by graph 136 in FIG. 4c, the deceleration of the valve closure caused by the back pulse 134 causes the pump inlet valve displacement to taper more slowly to a closed position as shown by portion 138 in FIG. 4c. This deceleration not only reduces the shock imparted by the valve 142 as it contacts its housing, but also reduces the mechanical noise caused by the impact of the valve 104 against its housing.
(20) The pump chamber pressure graph 140 shown in FIG. 4d demonstrates the net effect of the deceleration of the inlet valve closure immediately following time t.sub.2. More specifically, although the pump chamber pressure does incur a pressure shock at time 142 followed by a pressure peak at time 144, the magnitude between the low pump pressure at time 142 and the pump pressure at time 144 is much less than the pressure swing between times 56 and 58 as shown in FIG. 2 without the back pulse 134. Furthermore, the overall effect on the graph 146 of the rail pressure in FIG. 4E is negligible, if any, as compared to graph 66 in FIG. 2. This demonstrates that there is no degradation in the overall performance of the pump.
(21) Consequently, it can be seen that, by providing the back pulse 134 to decelerate the valve during closure, a substantial reduction in engine noise is achieved without any degradation of fuel pump performance.
(22) With reference now to FIG. 5, a modification is shown for a fuel system 100. The fuel system 100 illustrated in FIG. 5 is similar to the fuel system illustrated in FIG. 3 and like reference numerals will refer to like parts in both FIG. 3 and FIG. 5. Therefore, the overall description of the fuel system 100 in FIG. 3 shall apply equally to FIG. 5 and will not be repeated.
(23) FIG. 5 differs, however, from FIG. 3 in that a pressure shock sensor 150 is mechanically attached to the pump system in any conventional fashion. For example, the pressure shock sensor may be mounted to the solenoid 116, valve housing 105, or even the pump chamber 106 to detect the pressure shock caused by the fuel system. The pressure shock sensor 150 generates an output signal representative of the pressure shock and this signal is electrically connected through a solenoid connector 152 back to the control circuit 112. In FIG. 5, the output signal of the pressure shock is transferred from the shock sensor 150 to the ECU 112 via independent signal line 153. For this purpose, the connector 152 may have 3 leads, 2 for solenoids 116 and one for shock signal from the shock sensor 150. But these 3 lines may be aggregated to 1 or 2 lines.
(24) The use of the pressure shock sensor 150 enables the control circuit 112 for the solenoid 116 to more accurately calculate not only the time of initiation of the back pulse 134, i.e. the delay of the initiation of the back pulse 134 following the de-energization of the solenoid at time t.sub.2 (FIG. 4) but also the duration of the back pulse for maximum engine efficiency and greatest noise reduction. The calculation of the initiation and width of the back pulse 134 will vary as a function of the magnitude of the shock signal from the shock sensor 150 and also the fuel pressure at the outlet for the fuel pump system 100.
(25) With reference now to FIG. 6, a flowchart is shown which illustrates the operation of the pressure shock sensor. This flowchart will be executed typically by a microprocessor contained in the control circuit 112. The program first starts at step 154 which then proceeds to step 156.
(26) At step 156, the control circuit 112, typically the Engine Control Unit (ECU) for the engine, reads not only the signal from the shock sensor 150 but also from a separate fuel pressure sensor 158 (FIG. 5). Once these values are obtained, the program proceeds to step 160.
(27) At step 160, the program calculates the shock intensity and shock timing from the first maximum peak value of the shock signal after the pulse width modulation used to energize the solenoid 116 is turned off. Typically, a lookup table is used at step 160 to simplify the necessary calculations. Step 160 then proceeds to step 162.
(28) At step 162, the pulse width of the back pulse 134 is determined from the gradient change of the fuel pressure as determined from the fuel pressure sensor 155. Step 162 then proceeds to step 164 where the end timing of the back pulse is determined in accordance with the following formula:
(29)
Step 164 then proceeds to step 166. At step 166, the program determines the delay of the back pulse, i.e. the delay following the de-energization of the solenoid coil, in order to minimize shock intensity. Again, a lookup table may be used to simplify any desired calculations. Step 166 then proceeds to step 168 where the program is terminated.
(30) With reference now to FIG. 7, a still further embodiment is shown. FIG. 7 is similar to previously described FIG. 3 and like reference characters in FIG. 7 refer to like parts in FIG. 3. Therefore, the description of FIG. 3 is incorporated by reference and will not be repeated.
(31) Unlike the previously described embodiments, the embodiment shown in FIG. 7 does not utilize a back pulse to decelerate the closure of the valve 104. Instead, a passive rise time controller 170 is connected across the solenoid terminals 114 to decelerate the closure of the valve 104 and thus diminish the valve noise caused by the fuel pump. In FIG. 7, rise time control signal is transferred from the ECU 112 to the passive rise time controller 170 via independent signal line 173. For this purpose, the connector 152 may have 3 leads, 2 for the solenoid 116 and one for rise time control signal from the ECU 112. But these 3 lines may be aggregated to 1 or 2 lines.
(32) One exemplary raise time controller is illustrated in FIG. 8 as including a resistor 172 and capacitor 174 which are connected in series with each other across the solenoid terminals 114. With the RC series components connected across the solenoid terminals 114, upon energization of the solenoid, the voltage increases exponentially up to the voltage of the power source, PWM voltage power 179, at a rate dependent upon the values of both the capacitor 174 and the resistor 172.
(33) With reference now to FIGS. 9A-9E, a timing chart for the overall fuel system of FIG. 7 is shown. Specifically, graph 180 in FIG. 9A represents the position of the plunger position which corresponds identically to the plunger position graph 4 in FIG. E and 40 in FIG. 2.
(34) Graph 182 in FIG. 9B represents the voltage across the voltage terminals and in which, as before, the solenoid coil is de-energized at time T1. However, as shown at portion 184 of graph 182, upon de-energization of the solenoid coil, the voltage across the solenoid coil terminals 114 will decrease slowly or exponentially as shown at 184. This exponential decrease of the solenoid voltage is caused by the discharge of the capacitor 174 and serves to effectively decelerate the closure of the valve 104 in the desired fashion.
(35) Additionally, because the capacitor 174 initially charges once the control circuit 114 energizes the solenoid coil, the rise time at t.sub.1 following the energization of the solenoid occurs exponentially as shown at 186. The gradated increase of the voltage output to the solenoid following its energization at time t.sub.1 also reduces the pump noise.
(36) Graph 190 in FIG. 9C illustrates the position of the intake valve 104 with its more gradual rise and fall at times t.sub.1 and t.sub.2 respectively. This, in turn, provides for a pump pressure output graph 192 in FIG. 9D in which the magnitude between the pressure shocks at low pressure at time 194 and high pressure at time 196 is much less than without the RC network 170. The inlet valve displacement graph 190 at 50 exhibits a more gradual rise as shown at 191 in FIG. 9C.
(37) With reference now to FIG. 10, a still further modification is shown which is essentially identical to the system shown in FIG. 7, except that the RC network 170 is replaced by an RC network 200 having a variable resistor 202 and a fixed capacitor 204. As before, the RC network 200 is electrically connected in between the terminals 114 for the solenoid coil 116.
(38) With reference now to FIG. 11, one way of implementing the variable resistance 202 is illustrated in which two resistors 206 and 208 are connected in parallel in each other and in series with the capacitor 204. However, one resistor 206 is connected in series with a switch 210, such as a field effect transistor (FET). The input to the switch 210 may be controlled in any suitable fashion, such as by pulse width modulation (PWM), and effectively varies the resistance of the overall variable resistor 202 depending on the duty cycle.
(39) The effect of the pulse width modulation of the switch 210 is illustrated in FIG. 12. For example, assuming a pulse width modulation having a zero duty cycle, the resistor 206 is effectively removed from the variable resistor 202 so that the rise time in seconds is equal to 2.197 R.sub.208 C. Conversely, as shown by graph 220 of the rise time as a function of duty cycle of the switch 210, at a 100% duty cycle, the resistor 206 is effectively connected in series with the resistor 208. As such, the overall resistance for the variable resistor 202 is equal to 2.197 R.sub.206 R.sub.208/(R.sub.206+R.sub.208) C. Consequently, since the rise time of the RC circuit 200 may be varied by varying the duty cycle or pulse width modulation of the switch 210, the rise time of the voltage applied to the solenoid as well as the decay time of the voltage present in the solenoid at de-energization can be controlled for minimum engine noise.
(40) With reference now to FIG. 13, a flowchart is there illustrated which is executed by the control circuit or ECU to determine the desired duty cycle for the switch 210. The routine starts at step 222 which then proceeds to step 224.
(41) At step 224, the control circuit 112 obtains the value of both the engine RPM (rotation per minute) as well as the fuel pressure from the fuel pressure sensor 155. Step 224 then proceeds to step 226.
(42) At step 226, the control circuit 112 calculates the duty cycle to minimize the engine noise as a function of both the engine RPM and the fuel pressure. Step 226, which may use a lookup table, is then used to control the pulse width modulation of the switch 210 to thus vary the rise time and decay time for the voltage on the solenoid terminals 114.
(43) From the foregoing, it can be seen that the present invention provides a simple and yet effective mechanism to decelerate the closure of a fuel pump inlet valve in order to minimize fuel pump noise without degradation of fuel pump performance. 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.
