FR2779774A1 - Diesel fuel injector performance enhancing device - Google Patents

Abstract

The device comprises a stop for an intermediate needle (21), coupled to the main injector spring (22), limiting the opening of the injector (2). A detection accumulator (25) is supplied by the high pressure duct (13), through a valve (27). A control valve (26), biased into its rest position by a spring (28) is operated by the pressure in the accumulator and controls the injector. A control piston (29) carries the injector needle (6) and opens the connection to the discharge orifice (30).

Description

The present invention relates to an injection optimization device

  of fuel for depollution, which can be integrated into the injector holders of diesel engines fitted with pulsed-flow injection pumps. 10 Traditional injection devices, consisting of a simple return of the injector needle by one or several springs, present more and more difficulties to answer the evolution of the specifications of development of Diesel engines. This constraining effect15 is mainly linked to environmental and economic fields such as pollutant emissions (nitrogen oxides, carbon monoxide, hydrocarbons, particles, etc.), the noise emitted by the engine or consumption in fuel.20 The operation of traditional injection systems is essentially conditioned by the adjustment of: * The force of the injector calibration spring, which must be sufficient for the pressure waves in the high pressure pipe circulating after injection will not cause uncontrolled reopening of the injector and the pressure of the high pressure line does not decrease below the pressure of the gases in the combustion chamber during the closing path of the needle d 'injector. * The speed of the discharge of the high-pressure pipeline regulated by the characteristics of the pipeline (internal diameter, length) as well as the non-return or discharge valves of the injection pump. The main drawbacks of traditional injection systems are as follows: * The start of injection occurs when the pressure in the high pressure line becomes sufficient to cause the opening of the injector, the start of injection is often abrupt . This effect is even more serious if the force of the calibration spring

injector is important.

  * The closure of the injector needle can only be carried out if the pressure in the high pressure line is sufficiently low, it follows that the fuel introduced at the end of the injection period is not introduced into good conditions. The most classic solution for obtaining correct operation of injection systems

  Traditional methods consist in choosing the force of the injector calibration spring sufficient to stabilize the injection system and to be satisfied with the poor performance of the end of injection.

  The need to optimize combustion systems adapted to both pollution control, noise reduction and engine efficiency requires a special effort on the injection process. It can be characterized by: * An introduction of fuel at low flow rate at the start of the injection process in order to avoid excessive accumulation of fuel in the

  combustion during the time required for self

  ignition of this fuel. The expected result is mainly the reduction of combustion noise and vibration stresses on engine components. * Increasing fuel pressure and flow as combustion continues in the combustion chamber. The expected result is mainly the good adaptation to the energy need associated with the work provided to the piston

of the engine at the start of expansion.

  a The clearest possible closure at the end of injection to prevent a significant amount of fuel from being introduced late under poor conditions compared to the need for rapid mixing with the air, increasingly rare, contained in the combustion chamber. The expected result is mainly the reduction of soot emissions and greater flexibility on the compromise to be established between fuel consumption and emissions

  pollutants, including nitrogen oxides.

  A known alternative partially provides the solution. In fact, the injector holders equipped with a double injector needle stop, with two needle return springs, allow: * To cause a step of opening the injector, at the start of the injection, during which the flow

injected will be strangled.

  * At the end of injection, close the injector slightly earlier than the device with a single spring under the effect of the combined forces of the two springs. This limits the amount of poorly sprayed fuel to the

  end of injection, but this effect remains very limited.

  The practical arrangements adopted, leading to the device according to the invention, are chosen to: * Allow the injector to open for low levels of injection pressure, possibly modulated by

  depending on the load requested from the motor.

  * Keep the injector ajar for a moment to strictly limit the fuel flow at the start of

the injection phase.

  * Dampen the opening of the injector in order to best limit the growth of the fuel flow in the

following the injection.

  * Close the injector before the injection is done

at too low pressures.

  * Keep the injector closed for the entire period during which the injection system is still under high pressure. * Complete the discharge, so that the additional fuel compressed but not introduced into the combustion chamber can be evacuated and the pressure

  in the pipeline returns to the resting situation.

  * Organize the discharge of the injection system over a long period in order to limit the noise emitted by the injection equipment and to calm the

pressure oscillations.

  Observing that during the part of the injection period for which the injection pump pushes the fuel, the pressure in the injection system is, to within a few tens of bars, always increasing, the choice of basic principle of the device is to use the detection of the start of the pressure drop

  in the high pressure line at the entrance of the carrier

  injector to trigger closure of the injector.

  This is obtained by exploiting the energy still stored in the injection system, more particularly in the high pressure pipeline, to push the needle

injector.

  The combination of staggered opening by the effect of a double injector needle opening stop and early closing by the push of a control piston, as in injection devices o30 the injector is controlled by a solenoid valve, but controlled here by a differential hydraulic valve is the basis of the device according to the invention. This combination responds particularly well to the requirements for controlling the injector for depolluted diesel engines. 35 The voluntary closure of the end of injection means that the excess fuel still present in the high-pressure line must be discharged. To introduce the same amount of fuel into the engine as with a traditional injection system, the quantity delivered by the injection pump is therefore slightly greater, but this excess allows the injection device to be controlled. The device according to the invention makes it possible to improve the performance of the injection system in order to effectively satisfy the increasingly severe requirements,

set out above.

  It includes, for this purpose: * an intermediate needle stop, associated with a main injector spring, limiting the opening of the injector as long as the injector supply pressure remains moderate in order to limit the flow instantaneous fuel, * a volume used as a detection accumulator in communication with the high pressure pipe internal to the injector holder by a valve flap which allows the maximum pressure to be memorized during the injection period, * a control valve, returned to the closed position by a spring and actuated by the pressure of the fuel present in the accumulator, which, when the pressure drop of the high pressure line begins, controls the closing of the injector by applying the pressure of the high pressure line on * a control piston acting on the injector needle, preferably by the needle plunger on which the calibration spring of said injector rests, * and a discharge orifice, the passage cross section of which is significantly smaller than that of the assembly of the injector holes, opened by the control valve simultaneously with the action of closing the injector

  in order to release the pressure in the pipes.

  Another characteristic consists in the fact that the diameter of the control piston is greater than or equal to that of the guide of the injector needle so that the thrust on the piston, added to the force of the calibration spring can guarantee that the The injector remains closed while pressure is applied to the control piston. Another characteristic consists in the fact that the control valve, of diameter greater than that of the control piston, is installed like a cap and guided by this piston. The volume between the bottom of the control valve and the control piston, which we will call braking volume, has two functions: It allows braking of the opening of the injector and is used to hold the valve in the open position for the time required to discharge the injection system by limiting the relative speed of movement of the control valve relative to the control piston. Another advantageous characteristic consists in the fact that two orifices made in the bottom of the control valve perform the braking functions of the opening of the injector and hydraulic balancing of said control valve. One of the orifices, called braking, puts the braking volume into communication with the discharge orifice, while the other orifice, called of balancing, puts the braking volume into communication with a volume of thrust, of annular shape, used to apply hydraulic thrust to the valve assembly

  control and control piston. The hydraulic balancing thus ensured prevents the pressure in the braking volume preventing the control valve from intervening during the opening path of the injector.

  Another feature is that a valve supply port can be installed

  between the high pressure pipe and the valve supply volume35, upstream of the valve flap, in order to moderate the closing speed of the injector.

  Another characteristic consists in the fact that the control piston can be provided with a hole which makes it possible to release, at the end of discharge, the pressure which prevails in the volume containing the calibration spring and the main injector spring. Which pressure is induced by the leakage of the injector needle and control piston guides. This hole is closed by the needle plunger when it is in contact with the control piston, in particular during the injection period,

  then discharge of the high pressure pipes.

  A final feature consists in the fact that a return pressure adjustment valve, individual or common to several injectors, can be installed on the return circuit in order to adjust the opening pressure of the injector (s) as well as the pressure in the high pressure lines at the start of injection. Furthermore, it will be noted that the routing of the fuel to the injector is not hampered by the

  components of the device according to the invention.

  It will also be noted that the practice of a controlled discharge at the level of the injector holder makes it possible to dispense with the discharge valve of the injection pump. The injection pump valve is then a very simple non-return valve. This seriously simplifies the

  specification of the injection pump.

  Each of the engine injector holders will receive the same device, only the pressure adjustment valve

  return could be common to several injector holders, or even unique for the engine.

  The invention will in any case be better understood at

  using the following description, with reference to the drawing

  appended diagram representing, by way of examples, embodiments of the traditional devices and of the device optimizing the fuel injection: * FIG. 1 is a schematic diagram, seen in section, of an injector holder of the system traditional injection. * Figure 2 is a block diagram, seen in section, of a double injection system injector holder

  needle stopper and double spring.

  * Figure 3 shows an overall diagram of a

  traditional injection system illustrated in Figure 1.

  * Figure 4 shows an overall diagram of an injection system with double needle stopper and double

spring illustrated in Figure 2.

  * Figure 5 shows an overall diagram of an injection system equipped with one of the variants of the

device according to the invention.

  * Figure 6 shows an example of integration into an injector holder, seen in section, of one of the variants of the

  device according to the invention described in FIG. 5.

  * Figure 7 represents a partial diagram, in section,

  of the zone including the valve and the control piston.

  * Figure 8 represents a partial diagram, in section,

  of a control valve variant.

  * Figure 9 represents a diagram of operation of a traditional injection device according to the

diagrams of Figures 1 and 3.

  * Figure 10 shows an operating diagram of an injection device with double needle stopper and double spring according to the diagrams

Figures 2 and 4.

  * Figure 11 shows an operating diagram of an injection device equipped with one of the variants of the device according to the invention described

  in the diagrams in Figures 5 to 8.

  * Figure 12 groups together the operating diagrams presented in the diagrams of Figures 9 to 11, relating to the various injection devices

  shown in the diagrams of Figures 1 to 8.

  In general, with reference to these figures, we consider a pulsed-flow injection assembly comprising * an injector holder assembly 1 which receives * an injector proper 2, supplied by * an injection pump assembly 3, connected by

  * a high pressure pipe 4.

  The injector 2 comprises: * an injector body 5, in which is housed and guided in translation * an injector needle 6, which cooperates with * a needle seat 7, to control the supply * of a or more injector holes 8 supplying * one or more fuel jets 9 propagating

  in the combustion chamber, not shown.

  In order to limit the path of the injector needle 6: * a needle stopper 10 is inserted between the

injector holder 1 and injector 2.

  The injector holder 1 is made up of: * an injector holder body 11, possibly with * an injector holder cover 12, and contains * an internal high pressure channel 13, * a calibration spring 14 which acts on th a needle plunger 15, in permanent support on the injector needle 6 and * a low pressure return 16, which drains the leaks

guides.

  The injection pump assembly 3, supplied by a low pressure supply circuit 17, comprises * one or more elements of the injection pump 18 proper, at pulsed flow rate, * a non-return valve 19 and * an injection pump relief valve 20,

  optional, per pump element.

  The injector holders fitted with a double injector needle stop additionally comprise: * An intermediate needle stop 21, erasable and contiguous to the needle stop 10. This intermediate needle stop 21 intervenes for a

  fraction of the path of the injector needle 6.

  * A main injector spring 22 which, housed in the injector holder 1, applies a significant force to the

intermediate stop 21.

  The device according to the invention comprises additional elements, housed in the injector holder 1:

  * A valve supply port 23, optional.

  * A valve supply volume 24.

* A detection accumulator 25.

  * A control valve assembly 26, fitted * with a valve flap 27 and recalled by

* a valve spring 28.

  * A control piston 29, pressing on the injector needle plunger 15 and separated from the valve

  control 26 by the valve spring 28.

  * A discharge port 30, placed in the injector holder cover 12 and connected to the low return circuit

pressure 16.

  The control valve assembly 26, illustrated in FIGS. 6 to 8 is, for example, composed of: * a valve body 31, guided on the control piston 29, receives the valve valve 27 and * a valve bottom 32 who, at rest, is in contact

  with the injector holder cover 12.

  The valve bottom 32, here in the form of a disc, performs various functions such as: * A thrust valve 33 connects, when the control valve 26 opens, the detection accumulator 25 to * a thrust volume 34, located between the valve bottom

  32 and the injector holder cover 12.

  * A discharge valve 35 connects, when the control valve 26 opens, the thrust volume 34 to

the discharge port 30.

  * An opening braking orifice 36 connects * the braking volume 37, located between the valve bottom 32 and the control piston 29, to the orifice of

discharge 30.

  * A hydraulic balancing orifice 38 connects the

  braking volume 37 to thrust volume 34.

  The stabilization pressure, between two injections, of the injection system as well as the opening pressure

  of the injector can be modulated by: * A return pressure adjustment valve 39.

  The choice of the diameters of the dummy, push 33 and discharge 35 valves, in comparison with the diameter of the guide of the control valve 26 on the control piston 29, makes it possible to control the pressure drop in the high pressure channel 13 for which the device causes the injector to close 2.20 The curves shown in the operating diagrams of the different configurations of the injection devices (figure 9 to 12) represent: * The internal delivery pressure 40 of the pump

injection 18.

  * The pressure 41 in the high pressure pipe 4,

at the inlet of the injector holder 1.

  * The pressure 42 in the detection accumulator 25.

  * The pressure 43 in the thrust volume 34.

  * The pressure 44 in the braking volume 37,

  applied to the control piston 29.

  * The fuel flow 45 actually injected.

  * The displacement 46 of the injector needle 6.

  * The displacement 47 of the control piston 29.

  * The displacement 48 of the control valve 26.

  * The movement 49 of the lip of the valve flap 27.

  The curves shown in these operating diagrams are noted:

  * "a" for the traditional injection system.

  * "b" for the double stop injection system.

  e "c" for the injection system according to the invention. The abscissa of these diagrams, representing time, is, for the part represented, limited to only a fraction of the period of a complete cycle. The opening time of the injector does not represent, in these

  examples, that 4 to 4.5% of this same period.

  The operation of a traditional type injection device, used as a reference, illustrated by the diagrams in Figures 1 and 3 and the diagram in Figure 9, can be described as follows: * At rest the injector is closed by the spring effect

taring 14.

  * At the start of the discharge, when the injection pump 18 supplies flow to the high-pressure line 4 through the non-return valve 19, the pressure increases until the injector is opened by

  push on the injector needle 6.

  * The injection continues, the fuel jets 9 advancing in the combustion chamber. Pressure continues to increase in the high pressure line

4.

  * At the end of the discharge, when the injection pump 18 no longer supplies flow to the high pressure pipe 4, the latter discharges through the injector 2 to the combustion chamber and to the pump discharge valve d injection 20 to the

  low pressure supply circuit 17.

  * The pressure in the high pressure pipe 4 decreases to a low level which is no longer sufficient to keep the injector needle 6 raised. The thrust of the injector calibration spring 14 closes the injector 2 while the pressure in the high pressure pipe 4 is very low. Fuel jets 9

are interrupted.

  * The end of the discharge of the high pressure line 4 through the injection pump discharge valve 20 brings the injection system back to its

  rest position, ready for a new injection.

  The operation of a traditional type injection device, equipped with a double needle stop, illustrated by the diagrams in FIGS. 2 and 4 and the diagram 10 in FIG. 10, can be described as follows: * At rest the injector is closed by spring effect

taring 14.

  * At the start of delivery, when the injection pump 18 supplies flow to the high-pressure line 4 through the non-return valve 19, the pressure increases until the injector opens by

  push on the injector needle 6.

  * The path of the injector needle 6 is interrupted by the contact of the intermediate stop 21, which has the effect of limiting the instantaneous flow of

  fuel introduced into the combustion chamber.

  * When the pressure acting on the injector needle 6 is sufficient to push both the calibration spring 14 and the main injector spring 22, the injector needle 6 continues its opening path, possibly up to 'at the stop

needle 10.

  * The injection continues, the fuel jets 9 advancing in the combustion chamber. The pressure continues to increase in the high pressure line 4. * At the end of delivery, when the injection pump 18 no longer supplies flow to the high pressure line 4, the latter discharges through the injector 2 to the combustion chamber and the injection pump discharge valve 20 to the

  low pressure supply circuit 17.

  * The pressure in the high pressure pipe 4 decreases to a low level which is no longer sufficient to keep the injector needle 6 raised. The thrust of the injector calibration spring 14, combined with that of the main injector spring 22, closes the injector 2 while the pressure in the high pressure line 4 is relatively low. The jets of

fuel 9 are interrupted.

  * If the pressure during closing is too great, the injector calibration spring 14 may not be enough to keep the injector needle 6 in contact with the needle seat 7. Reopenings

  parts of injector 2 may occur.

  * The end of the discharge of the high pressure line 4 through the injection pump discharge valve 20 brings the injection system back to its

  rest position, ready for a new injection.

  The operation of the device according to the invention, illustrated by the diagrams in FIGS. 5 to 8 and the diagram in FIG. 11, can be described as follows: * At rest the injector is closed by the effect of the calibration spring 14. The valve of control 26 is closed under the effect of the valve spring 28. The assembly is therefore

  closed as for a traditional injection system.

  * At the start of the discharge, when the injection pump 18 supplies flow to the high-pressure line 4 through the non-return valve 19, the pressure increases until the injector is opened by

  push on the injector needle 6.

  * The path of the injector needle 6 is interrupted by the contact of the intermediate stop 21, which has the effect of limiting the instantaneous flow of

  fuel introduced into the combustion chamber.

  * When the pressure acting on the injector needle 6 is sufficient to push both the calibration spring 14 and the main injector spring 22, the injector needle 6 continues its opening path. * The opening of the injector, from the intermediate needle stop 21 to possibly the needle stop 10, braked by the discharge orifice 30 and the braking orifice 36, is progressive. This has the effect of limiting the flow rate at the start of injection and increasing the pressure in the upper pipe.

pressure 4.

  * During the opening path of the injector, the pressure generated in the braking volume 37 is transmitted by the hydraulic balancing orifice 38 to the thrust volume 34. This has the effect of avoiding blockage of the valve 26 during the journey

opening of the injector.

  * The injection continues, the fuel jets 9 advancing in the combustion chamber. The pressure continues to increase in the high pressure line 4. The very small flow rate passing through the valve flap 27 supplies the detection accumulator 25 without penalizing the injection. The pressure in this accumulator 25 increases with that of the pipeline

high pressure 4.

  * At the end of the delivery, when the injection pump 18 no longer supplies flow to the high-pressure pipe 4, the latter begins to partially discharge through the injector 2 to the

combustion chamber.

  * The pressure in the high pressure pipe 4 decreasing, this no longer suffices to maintain the control valve 26 which, pushed by the pressure in the detection accumulator 25, opens. The pressure of the detection accumulator 25 is transmitted by the thrust valve 33 (functionality of the control valve 26) to the thrust volume 34. The movement of the control valve 26 compresses the braking volume 37 which pushes the control piston

29.

  * The pressure from the high-pressure pipe 4, is conveyed by the valve flap 27 to the detection accumulator 25, the thrust volume 34 and the volume

braking 37.

  * The opening of the relief valve 35 (functionality of the control valve 26), simultaneous with that of the push valve 33, ensures communication towards the discharge port 30. The greater permeability of the push valve 33, compared to the relief valve 35, guarantees the good

  applying pressure to thrust volume 34.

  * The effect of the hydraulic thrust on the control piston 29, combined with that of the injector calibration spring 14 and the main injector spring 22, closes the injector 2 while the pressure has only slightly decreased in the high pressure pipeline 4. The jets

  of fuel 9 are clearly interrupted.

  * During the end of the discharge of the high-pressure pipe 4 through the discharge orifice 30, the flows passing through the hydraulic balancing and braking orifices 36 ensure that the pressure in the braking volume 37 remains slightly lower to that of the thrust volume 34, which

  slows down the closing of the control valve 26.

  * The thrust on the control piston 29 is maintained throughout the discharge of the high pressure pipe 4 and the injector 2 cannot in any case

reopen uncontrollably.

  * When the pressure in the high pressure pipe 4 is very close to that of the low pressure return circuit 16, the control valve 26 returns to close the communications. The device, returned to its rest position, is ready for a

new injection.

  * The end of discharge pressure can optionally be controlled by a return pressure adjustment valve 39, preferably single, placed on the

common return of injectors.

  In this device, the injection pump discharge valve 20 is unnecessary and the injection pump 3 will not be equipped with it. Simple check valves 19 are sufficient, which greatly simplifies the specification

of the injection pump 3.

  The device according to the invention allows: * The clear closure of the injection by forced closing of the injector. This is the main function

of the device.

  * A particularly moderate start of injection

  the effect of reduced injector opening pressure.

  This is achievable by a lower injector setting than that of traditional injectors, since the closing pressure of the injector does not depend

no opening pressure.

  * The possible adjustment, depending on the engine operating conditions, of the injector opening pressure by the effect of the valve for adjusting the

return pressure 39.

  * Control of the flow rate at the start of injection, in a first step by the effect of the intermediate needle stop 21 and the main injector spring 22, then by the effect of the braking orifice 36 and of

the discharge port 30.

  The device according to the invention is particularly intended to supplement and improve the devices

  of diesel engines using pulsed injection pumps35.

Claims (4)

  1- Device making it possible to improve the fuel injection for diesel engines with low emission of pollutants equipped with pulsed flow injection pumps, 5 characterized in that it comprises: - An intermediate needle stop (21) , coupled to a main injector spring (22), used to limit the opening of the injector (2) as long as its supply pressure remains moderate, 10 - A volume used as detection accumulator (25), supplied from the high pressure channel (13) of the injector holder (1) by a valve flap (27), - A control valve (26) which, brought back to its rest position by a valve spring (28) and actuated by the pressure of the detection accumulator (25) as soon as the pressure of the high pressure channel (13) decreases, controls the closing of the injector (2) by applying the pressure of the fuel contained in the high pressure lines ( 4 and 13) on - A control piston (29), which pushes the inject needle eur (6), and at the same time opens the communication with - A discharge port (30) which ensures the discharge of excess fuel in the high pipes pressure (4 and 13).   2- Device according to claim 1, characterized in that the diameter of the control piston (29) is   greater than or equal to that of the guide of the injector needle (6). 30 A device according to one of claims 1 or 2, characterized in that the control valve (26),   diameter greater than that of the control piston (29), is installed as a cap and guided on said control piston (29) and is separated from the latter by a braking volume (37) limiting their relative speed of movement.   4- Device according to claim 3, characterized in that the bottom (32) of the control valve (26) has two orifices, braking (36) and hydraulic balancing (38), used to modulate the movements of the 5 control piston (29) and of the control valve (26). The brake port (36) connects the brake volume (37) to the discharge port (30). The hydraulic balancing orifice (38) connects the braking volume (37) to a thrust volume (34), located on either side of the bottom (32) of the control valve (26) in order to neutralize the thrust of the braking volume (37) on the   control valve (26). 5- Device according to one of claims 1 to 4, characterized in that a valve supply orifice   (23) is interposed between the high pressure channel (13) and   the volume which feeds the valve flap (27).   6- Device according to one of claims 1 to 5, characterized in that the control piston (29) is pierced   a hole which allows the pressure to be discharged into the volume containing the calibration spring (14) and the main injector spring (22). This hole is closed when the   control piston (29) is in contact with the needle plunger (15). 7- Device according to one of claims 1 to 6,   characterized in that a return pressure adjustment valve (39), individual or common to several   injectors, is installed on the return circuit (16) in order to adjust the opening pressure of the injector (s) (2).