FR2878907A1 - FUEL PUMP CONTROLLED BY SOLENOID WITH REDUCED NOISE - Google Patents

Abstract

A high pressure fuel pump with reduced audible and hydraulic noise. The fuel pump incorporates a control program that uses an electronically controlled on / off type solenoid actuated valve (26) to control pump fuel delivery and / or fuel system rail pressure. The electrical impulse to switch on or off the solenoid is modified to slow down the force / time profile acting on the solenoid valve during the on / off transition.

Description

The present invention relates to a high pressure fuel pump of

  a type used with vehicle engines, particularly a demand-driven pump for supplying fuel to a common rail fuel injection system.

  Examples of such high pressure fuel pumps and associated fuel delivery systems are described in US Pat. No. 6,637,408, Common Rail Fuel System with High Pressure Accumulator; 6,494,182, Self-regulated direct fuel injection system; 6 694 950, Io Hybrid control method for fuel pump using intermittent recirculation at low and high engine speeds; and 6,422,203, variable efficiency pump for direct fuel injection, the disclosures of which are hereby incorporated by reference. At least a portion of the pumps disclosed in these patents utilize a solenoid controlled valve to selectively redirect the pumped fuel to a low pressure housing and thereby bypass the injectors.

  High speed on / off type solenoid operated valves are often used to control pump fuel delivery and / or fuel system boom pressure for common rail pumps and rotary type pumps. A common problem or common complaint associated with these pump types is the audible and hydraulic noise associated with the rapid flow of high pressure and / or impact between the solenoid and the valve. Hydraulic noise is caused by the rapid flow of high pressure into a low pressure. The audible noise is caused by this hydraulic noise as well as mechanical noise when the valve and / or solenoid armature suddenly hits its mechanical stop during opening and / or closing.

  According to the present invention, instead of a conventional instant on / off switching of the solenoid which causes rapid response of the armature and the control valve, the electrical pulse to energize (or de-energize) the solenoid is modified to slow down the force / time profile acting on the solenoid valve during the transition between walking and stopping or stopping and walking. This control program reduces hydraulic and mechanical noise by reducing the flow rate of the valve and / or the impact velocity. The other advantages are reduced cavitation and wear of the components. In addition, this control program can be transformed into a more conventional rectangular wave on / off type at higher operating speeds and cycles (when noise is a lesser problem) in order to meet fuel supply requirements if needed. .

  Fig. 1A-1D compares the rectangular wave control pulse of various embodiments of the present invention with a conventional positive-wave rectangular wave control pulse.

  Figure 2 is a schematic of a conventional ramp fuel system embodying an embodiment of the present invention.

  Figure 3 is a schematic diagram of a high pressure radial piston pump incorporating an embodiment of the present invention.

  Fig. 4 is a diagram showing the use of an active switching device which can recirculate the current selectively so as to slow down the rate of decay during solenoid discharge.

  A representation of the concept of the invention is shown in Figure 1A-1G. As shown in FIG. 1A, a conventional control pulse 10 is characterized by a positive rectangular wave having a rising or etching edge 11, a nominal pulse width 12, and a falling or trailing edge 13. In accordance with FIG. Embodiment of the present invention, Fig. 1B shows a Pulse Width Modulation (PWM) period or PWM boost 14 added at the end of each conventional rectangular wave control pulse 12 '. This performance would slow the release time of a solenoid actuated and electrically actuated normally open valve.

  The same operating principle applies to a solenoid operated valve, normally closed and electrically controlled. The PWM thrust 14 is triggered by the trailing edge 13 'of the normal control pulse 12', begins after a specified delay period 15, and continues for a specified number of pulses at a fixed frequency and duty cycle.

  Alternatively, a PWM boost 14 'may occur before the normal control pulse 12' as shown in FIG. 1C, or PWM pulses 14, 14 'can both precede and follow the normal control pulse 12' as shown in Figure ID.

  Alternative embodiments of the present invention include modulating the duty cycle, frequency, and pulse count during the release event.

  It should be understood that normally a nominal voltage pulse should be in a rectangular waveform, the associated current would increase and decrease with small non-instantaneous slopes, and the associated armature (motion) force of the solenoid valve would present the same way of modest rising and falling slopes. The present invention modifies the control electronic pulse with respect to the nominal, to "soften" the resulting force-time profile acting on the armature, for example by prolonging or increasing the upward or downward slope of the pulse of voltage or control current. The nominal control pulse is not necessarily a rectangular wave whatever the nominal form, the technique of the invention modifies it to soften the control force on the armature. For example, a nominal pulse may have a linear rise (not instantaneous), a constant peak amplitude, followed by a linear descent, the modified pulse being bell-shaped.

  Other methods of controlling the current decrease or current increase as shown in Figs. 1E-1G, which are covered by the present invention, include direct current control via linear voltage, control of a current chopper driver and decay rate control by selective current recirculation during discharge, such as using an active switching device.

  Although positive voltage control pulses are shown, the invention applies in the same way to the modification of negative voltages.

  Figures 2 and 3 show various embodiments of the present invention as incorporated into a common rail fuel supply system and a high pressure radial piston pump. FIG. 2 shows a fuel supply system having as basic components: an inlet reservoir feed pump (low pressure) 20, a fuel filter 21, and a high pressure pump 22, (shown in FIGS. dotted for clarity). The pump 22 maintains a high operating pressure in a common rail 23 which is in fluid connection with a plurality of fuel injector nozzles 24. Each fuel injector nozzle 24 is located to inject the fuel according to the ignition sequence controlled by the electronic control unit 25. The solenoid valve 26 which incorporates the control program of the present invention is located inside the high pressure pump 22. The valve control pulse generator 27 provides the control pulse for the solenoid valve 26. The ramp pressure is controlled by a ramp pressure sensor 28. Other features of this embodiment of a fuel supply system include an expansion valve 29, which is fluidly connected to a unidirectional check valve 30.

  As shown in FIG. 3, a fuel pump having at least one pumping plunger or piston 31 mounted to operate reciprocally in a respective pumping bore is associated with a pumping chamber whereby the fuel at a low pressure of 50.degree. The inlet is transmitted to the pumping bore during a plunger loading stroke within the bore and the supplied fuel is pressurized into the pumping chamber during a plunger discharge stroke within the bore. bore. In the embodiment shown in Fig. 3, a pressurized amount of fuel from a plurality of pumping chambers is discharged to a common discharge line 32 which is connected to the pump outlet for delivery to the ramp. external municipality 24.

  A flow control system is provided whereby while the fuel is pressurized in the pumping chamber or the discharge line, a solenoid actuated binary overflow valve 33 opens a flow path to divert a portion of the flow. pressurized fuel in the pumping chamber or in the discharge line 32, to a low pressure housing, such as the supply line 34 or the pump housing. As a result, the amount of pressurized fuel that is delivered to the outside of the pump (for example, enters the common rail) is less than the amount of fuel delivered to the bore or pumping bores during the race (s). loading. The valve then closes the flow path to restore the discharge to the common rail 24.

  The switching on and off of the overflow valve 33 is turned on by the valve control pulse generator 27 (shown in FIG. 2) according to the demand control programming as described in FIG. the aforementioned patents.

  The improvement in the embodiments shown in FIGS. 2 and 3 includes the electronic softening of the start and / or end of the energizing and / or de-energizing pulse and the resulting current to the solenoid, such as shown in Figures 1B to 1G.

  Thus, the discharge of a plurality of pumping chambers may be provided to a common discharge line which is fluidly connected to the common rail but has a bypass leg in which the control valve is present. In other contexts (not shown), spill-controlled dispenser type pumps may have a plurality of control valves that operate with a respective plurality of pump chambers that communicate with a respective plurality of injectors. Depending on the given configuration, it is possible for a control valve to control the output of each of the plurality of sequentially actuated pumping chambers. The pump plungers can operate reciprocally with a radially sequential outward pumping, whereby each bore has a respective separate pumping chamber (as in Figure 3) or in other types of pumps, the plungers pump radially. inwardly in a common volume from which the discharge path exits the pump to a discharge connection or the like.

  Fig. 4 shows an embodiment of a circuit that actively controls the recirculation current via an active switch 60 and a current or voltage sensor 62. Preferably, the switch 60 is a FET or other fast switching device. . A recirculating current control circuit provides the ability to enable or disable the soft flow mode. In addition, the control of the recirculation current also allows better management of the current decay and the impact on the armature. Finally, it is preferred that the fast switching / recirculation current cycle occur at least once per pulse change and preferably that the fast switching / recirculating cycle occur at least twice. Other current recirculation techniques also fall within the scope of the invention.

  These embodiments would also have similar noise control qualities.

Claims (1)

8 claims   A high pressure fuel pump, wherein a solenoid controlled valve (26) opens and closes a fuel flow path, characterized by a control pulse for energizing or de-energizing the solenoid which is modified to slow down the force / time profile acting on the valve.   A fuel pump according to claim 1, characterized by a control pulse having a nominal pulse width (12 ') and a pulse width modulation period (14, 14') at the rise (11, 11). ') and / or the descent (13, 13') of the nominal pulse.   A fuel pump according to claim 1, characterized by a control pulse which is essentially a rectangular wave of a predetermined magnitude with a series of pulse width modulations consisting of zero amplitude intervals and pulse intervals. pulses at said predetermined amplitude.   Fuel pump according to claim 1, characterized by a pulse width modulation period (14, 14 ') which is triggered by the falling edge of the control pulse (13') and / or the rising edge. (11, 11 '), begins after a predetermined delay period (15, 15'), and continues for a predetermined number of pulses at a certain frequency and duty cycle.   5. Fuel pump according to claim 1, characterized by a current decay rate (16) or a current rise rate (16 ') which is directly controlled (idle) by a linear voltage driver.   The fuel pump of claim 1, characterized by a current decay rate (16) or a current rise rate (16 ') which is controlled (idle) by a current chopper driver.   7. Fuel pump according to claim 1, characterized by a decay rate of the current (16) which is controlled (idle) by recirculation of the current.   8. Pump according to claim 7, characterized by a decay rate of the current (16) which is controlled (idle) by use of an active switching device.   9. Pump according to claim 7, characterized by a decay rate of the current (16) or increase of the current (16 ') which can be selectively switched to a rectangular wave pulse operating mode.   Pump according to claim 7, characterized by a control pulse having a nominal current pulse shape modified by recirculation of the current.   A fuel pump having at least one pumping plunger mounted for reciprocal operation in a respective pumping bore and defining with the bore a pumping chamber, the fuel at a low inlet pressure being supplied to the bore during a loading stroke of the plunger within the bore and the supplied fuel being pressurized into the pumping chamber during a discharge stroke of the plunger within the bore, such that a pressurized amount of fuel from the pump chamber is discharged to a discharge line, and having a flow control system with which, while the fuel is pressurized in the pump chamber or discharge line, a pressure relief valve solenoid-operated binary overflow (33) opens a flow path (32) for diverting a portion of the pressurized fuel to a low pressure housing (34), characterized in that e that the start and / or end of the energizing and / or de-energizing pulse to the solenoid is electrically smoothed.   The fuel pump according to claim 11, characterized by a power pulse having a nominal pulse width and an electronic softening achieved by a series of pulse width modulations at the rise and / or fall of the pulse. nominal.   A pump according to claim 7, characterized by a nominal pulse which is essentially a rectangular wave of a predetermined magnitude and an electronic softening which is a series of pulse width modulations consisting of zero amplitude intervals and pulse intervals at said predetermined amplitude.   Pump according to claim 7, characterized by a flow path which comprises a flow orifice in the wall of the bore at the pumping chamber and a flow line extending from the orifice. flow through the pump body and in fluid communication with said low pressure housing, and wherein the overflow valve is located in the flow line.   A fuel pump having at least one pumping diver mounted for reciprocal operation in a respective pumping bore and defining with the bore a pumping chamber whereby fuel at a low inlet pressure is transmitted to the chamber. during a loading stroke of the plunger within the bore and the supplied fuel is pressurized in the pumping chamber during a discharge stroke of the plunger within the bore, thereby discharging a pressurized amount of fuel from the pumping chamber through a discharge port to a discharge line, and a flow control system whereby during a discharge stroke a solenoid actuated binary overflow valve opens a flow path flow to deflect a portion of the pressurized fuel to a low pressure sump, so that the amount of pressurized fuel entering the liner e discharge is less than the amount of fuel supplied to the pumping chamber during the loading stroke, then closes the flow path before the start of the subsequent discharge stroke, characterized in that the start and / or end the power up and / or voltage pulse to the solenoid is electrically smoothed.