JP2016048066A - Electromagnetic fuel injection unit with hydraulic brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an electromagnetic fuel injection unit enabling an initial portion of an injection principle to be improved and concurrently showing an easy manufacturing and a high cost-effectiveness.SOLUTION: This invention relates to a fuel injection unit 1. The fuel injection unit 1 comprises an injection nozzle, an injection valve provided with a movable plunger 17, an electromagnetic actuator for moving the plunger 17 between a closing position and a releasing position of the injection valve and a hydraulic brake device 31 connected to a supply hole 30. There is provided a valve element 32 including a resilient blade 33 connected to a supply hole 30 of a movable armature 9 and partially fixed to the surface 34 of the movable armature 9 and there is provided a stopper element 36 connected to the resilient blade 33, arranged at a prescribed distance from the resilient blade 33 and arranged to cause a releasing motion of the resilient blade 33 itself to be stopped at a fixed and prescribed position.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an electromagnetic fuel injector.

  In general, an electromagnetic fuel injector (eg, of the type described in a patent document) has a fuel delivery function and is a cylindrical tubular body that terminates with an injection nozzle regulated by an injection valve controlled by an electromagnetic actuator (For example, refer to Patent Document 1). The injection valve is provided with a plunger, which is displaced by the action of the electromagnetic actuator itself between the closed position and the open position of the injection nozzle against the bias of a closing spring which tends to keep the plunger in the closed position. Be made. Electromagnetic actuators typically include a closing spring that pushes the plunger toward the closed position and an electromagnet that pushes the plunger toward the open position against the elastic force generated by the spring.

  The electromagnet includes a coil disposed outside at a fixed position around the tubular body, a movable armature that is rigidly connected to the plunger and is movably assembled inside the tubular body, and a ferromagnetic A stationary magnetic pole made of a material and disposed within the tubular body in the coil and adapted to magnetically attract the movable armature. The magnetic pole has a central through hole that functions to allow fuel to flow toward the injection nozzle. The closing spring is disposed inside the central hole and is compressed between the perforated catch body driven into the central hole and the movable armature, and the movable armature, and thus the plunger that is integral with the movable armature, is brought into the closing position of the injection nozzle. Push towards.

  Otto cycle (ie fireworks ignition engine) heat engine manufacturers increase fuel supply pressure (and can even exceed 60-70 Mpa) to mix combustion support (ie air drawn into the cylinder) and fuel To reduce the generation of black smoke (which represents poor combustion) and increase the dynamic performance of the electromagnetic injector (ie, increase the response speed of the electromagnetic injector to the command), thereby increasing the number of combustion injections. It is desired to be able to inject a small amount of fuel for the purpose of fractionation into separate injections (in this way, the production of pollutants during combustion can be reduced).

  When the injection valve is closed, the autoclave force derived from the hydraulic pressure presses the shutter and keeps the shutter in the closed position (obviously, the higher the fuel supply pressure, the higher the autoclave force). Thus, in order to allow the injection valve to open, the electromagnetic actuator must generate a force that overcomes the autoclave force added to the elastic force exerted by the closing spring on the plunger. However, the autoclave force suddenly disappears as soon as the injection valve opens, thus the injection valve opens very rapidly and vigorously with the very fast movement of the plunger. Such a fast and intense opening of the injection valve is very abrupt in the initial part of the injector injection law (ie the law that links the start-up time or control time to the amount of fuel injected) (called the ballistic zone). Determine the slope, which is often irregular.

  The fact that the initial part of the law of injection (i.e. the ballistic zone) has a very steep and often irregular (i.e. very low reproducibility) gradient is the fact that with such a very steep slope, the injection time That is, the proper control of fuel injection becomes very complex because a slight difference in control time determines a substantial difference in the amount of fuel injected.

  In order to obtain a more regular (ie more reproducible) operation of the fuel injector in the initial part of the injection law (ie the ballistic zone), the plunger is coupled to the moving armature of the electromagnet and the plunger is in the open position of the injection valve. Patent literature has proposed that a hydraulic brake device having a function of hydraulically dissipating kinetic energy in order to decelerate the opening stroke of the plunger when moved toward the front (for example, patent literature) 2). The hydraulic braking device includes a series of valve elements, each of which is coupled to a corresponding supply hole in the movable armature (through which fuel is flowing toward the injection nozzle) and the displacement direction of the plunger (ie, the plunger Have different permeabilities for the passage of fuel as a function of whether the injection valve is closed or open. Specifically, each valve element includes an elastic blade that is partially secured to the top surface of the movable armature and has a small size calibrated hole located in the supply hole.

  When the injection valve opens and the autoclave force suddenly disappears, the action of the braking device described above is that of the opening movement (i.e. upward movement) because it determines the hydraulic dissipation of the kinetic energy of the plunger. Decide on deceleration. Such a deceleration action, determined by the hydraulic braking device described above, is very beneficial because it prevents the injection valve from opening very rapidly and violently with the very fast upward movement of the plunger. In effect, the presence of the hydraulic braking device described above slows the opening of the injection valve, which improves the controllability of the fuel injection within the ballistic zone of the law of injection (i.e. accuracy and repeatability). Increase).

  However, the deceleration action of the hydraulic braking device described above is that the movement of the movable armature is such that the elastic blades forming the valve element are only depleted of oscillating movement after the initial part of the injection law (ie the ballistic zone) has been exhausted. It has been pointed out that due to the fact that it moves in, it may have irregular behavior within the initial part of the law of injection (ie the ballistic zone). In order to solve this problem, it has been proposed to stiffen the elastic foil of the valve element. However, such a solution can limit the vibration of the elastic foil of the valve element, but has the disadvantage of significantly reducing the opening speed of the elastic blade of the valve element, thus reducing the overall efficiency of the hydraulic braking device. Have.

European Patent Application No. 1619384 European Patent No. 141644844.4

  The object of the present invention is to produce an electromagnetic fuel injector which is free from the above-mentioned drawbacks, ie which makes it possible to improve the initial part of the law of injection (ie the ballistic zone) and at the same time is easy to manufacture and cost-effective .

  According to the invention, an electromagnetic fuel injector is manufactured as disclosed in the appended claims.

  The present invention will now be described with reference to the accompanying drawings illustrating non-limiting embodiments thereof.

1 is a longitudinal section of a fuel injector manufactured in accordance with the present invention. The injection valve of the injector in FIG. 1 is expanded and shown. FIG. 2 shows an enlarged part of the electromagnetic actuator of the injector in FIG. 1. FIG. 2 shows an enlarged part of a movable armature of the upper electromagnet of the electromagnetic actuator in FIG. 1. Fig. 5 shows a cross section of the injector of Fig. 1 in a hydraulic braking device coupled to the lower surface of the movable armature in Fig. 4; FIG. 6 is a plan view of corresponding elements forming the hydraulic braking device in FIG. 5. FIG. 6 is a plan view of corresponding elements forming the hydraulic braking device in FIG. 5. FIG. 6 is a plan view of corresponding elements forming the hydraulic braking device in FIG. 5. FIG. 6 is one of two enlarged views of the details of the hydraulic braking device in FIG. 5 during opening of the injection valve and closing of the injection valve, respectively. FIG. 6 is one of two enlarged views of the details of the hydraulic braking device in FIG. 5 during opening of the injection valve and closing of the injection valve, respectively.

  Reference numeral 1 in FIG. 1 represents a fuel injector as a whole, which has an essentially cylindrical symmetry about a longitudinal axis 2 and is a cylinder combustion chamber (not shown). 1) It is adapted to be controlled to inject fuel from the injection nozzle 3 which directly enters the inside. The injector 1 comprises a support 4 having a cylindrical tubular shape with a variable cross section along the longitudinal axis 2 and the entire length of the support 4 itself for supplying pressurized fuel towards the injection nozzle 3. And a supply channel 5 extending along the line.

  The support 4 houses an electromagnetic actuator 6 in its upper part and an injection valve 7 (shown in more detail in FIG. 2) in its lower part. In use, the injection valve 7 is activated by an electromagnetic actuator 6 to regulate the fuel flow rate through the injection nozzle 3, which is obtained at the injection valve 7 itself.

  As shown in FIG. 3, the electromagnetic actuator 6 includes a pair of twin electromagnets 8 (upper and lower, respectively) that are activated together to operate simultaneously. When energized, the electromagnet 8 pivots from the closed position to the open position of the injection valve 7 against the bias of a single common closing spring 10 that tends to keep the movable armature 9 in the closed position of the injection valve 7. 2 is adapted to displace the respective movable armatures 9 made of ferromagnetic material. Each electromagnet 8 is supplied with power by a control unit (not shown) and is stored outside in relation to the support 4 and the fuel is stored in the support 4 and the fuel flows toward the injection nozzle 3. And a movable armature 12 (or magnetic pole 12) having a central hole 13 for enabling. Common to a tubular cylindrical shape (which may be open along the busbar) and compressed against the movable armature 9 of the upper electromagnet 8 to allow fuel flow towards the injection nozzle 3 A catch body 14 (shown in FIG. 1) adapted to hold the spring 10 is driven into the central hole 13 of the movable armature 12 of the electromagnet 8.

  Each coil 11 is wound directly inside the annular cavity 15 which is obtained by material removal in the outer surface of the support 4. Each coil 11 is made of an enameled wire provided with a self-bonding paint, and has an axial dimension (that is, a dimension measured along the longitudinal axis 2) within a range that minimizes the dispersed magnetic flux. Have. In the coil 11, a protective body 16 is connected around the support 4, which has a tubular shape, ensures a suitable mechanical protection for the coil 11 and encloses the magnetic flux lines generated by the coil 11. And is used to increase the mechanical strength of the support 4 at structurally fragile points that are inevitably introduced by the presence of the cavities 15.

  The movable armature 9 is a part of the movable device, and the movable device further includes an upper portion integrally formed with each movable armature 9 and an injection nozzle in conjunction with a valve seat 18 (shown in FIG. 2) of the injection valve 7. A shutter or plunger 17 having a lower portion for adjusting the fuel flow rate through 3 in a known manner is included.

  In use, when the electromagnet 8 is de-energized, each movable armature 9 is not attracted by its magnetic armature 12 and the elastic force of the spring 10 pushes the movable armature 9 together with the plunger 17 downward. Under this situation, the injection valve 7 is closed. When the electromagnet 8 is excited, each movable armature 9 is magnetically attracted by the magnetic armature 12 against the elastic force of the spring 10, and the movable armature 9 moves upward together with the plunger 17 to move the injection valve 7. Decide on opening.

  In order to accurately determine the upward stroke of the plunger 17, the effective stroke of the movable armature 9 of the upper electromagnet 8 is shorter than the effective stroke of the movable armature 9 of the lower electromagnet 8. In this way, when the electromagnet 8 is excited, only the movable armature 9 of the upper electromagnet 8 always contacts and abuts the magnetic armature 12 regardless of the inevitable structural tolerances. In order to limit the effective stroke of the movable armature 9 of the upper electromagnet 8, either the lower surface of the armature 12 or the upper surface of the movable armature 9 is coated with a hard non-ferromagnetic metal material layer, preferably a chromium layer. . Thus, the thickness of the chrome layer determines the reduction of the effective stroke of the movable armature 9 of the upper electromagnet 8. A further function of the chromium layer is to increase the impact resistance of the zone and, among other things, avoid magnetic adhesion phenomena caused by direct contact between the ferromagnetic material of the movable armature 9 and the ferromagnetic material of the armature 12. There is. In other words, the chrome layer defines a gap that prevents the magnetic attraction caused by the remanence between the movable armature 9 and the armature 12 from reaching an excessively high value, i.e., exceeding the elastic force of the spring 10. doing.

  Furthermore, only the plunger 9 of the upper electromagnet 8 is subjected to precision machining to have a calibrated outer diameter substantially equal to the inner diameter of the supply channel 5 (apparently rounded down). In contrast, the movable armature 9 of the lower electromagnet 8 has an uncalibrated outer diameter that is always smaller than the inner diameter of the supply channel 5. In this way, only the movable armature 9 of the upper electromagnet 8 performs the upper guiding function of the plunger 17 in order to control the axial sliding of the plunger 17 along the longitudinal axis 2. Such a constructional selection makes it possible to reduce the manufacturing costs because only the movable armature 9 of the upper electromagnet 8 needs to be subjected to precise and thus costly machining operations.

  As shown in FIG. 2, the valve seat 18 is defined in a sealing element 19, which is monolithic and seals the bottom surface of the supply channel 5 of the support 4, and the injection nozzle 3. Intersect. In detail, the sealing element 19 includes a disc-shaped closure element 20 which seals the bottom surface of the supply channel 5 of the support 4 and the injection nozzle 3 intersects it. The guide element 21 rises from the capping element 20, which has a tubular shape, accommodates the plunger 17 therein, defines the lower guide of the plunger 17 itself, and from the inner diameter of the supply channel 5 of the support 4. Has a smaller outer diameter, thus defining an outer annular channel 22 through which pressurized fuel can flow.

  Four through feed holes 23 (only two of which are shown in FIG. 2) connected to the valve seat 18 to allow the flow of pressurized fuel towards the valve seat 18 itself are provided on the guide element 21. Provided in the lower part. The supply holes 23 may be offset in relation to the longitudinal axis 2 in order to cause a vortex in the corresponding fuel flow during use without converging towards the longitudinal axis 2 itself, or The holes 23 may converge towards the longitudinal axis 2. As shown in FIG. 4, the supply holes 23 are arranged in an inclined state with an angle of 80 ° (more generally 70 ° to 90 °) with the longitudinal axis 2. According to a different embodiment (not shown), the supply holes 23 form an angle of 90 ° with the longitudinal axis 2.

  Plunger 17 terminates in a substantially spherical shutter head 24 that is adapted to remain fluid tight with respect to valve seat 18. Alternatively, the shutter head 24 may have a substantially cylindrical shape and only the abutment zone may be spherical. In addition, the shutter head 24 remains slid on the inner surface of the guide element 21 and is guided in its movement along the longitudinal axis 2. The injection nozzle 3 is defined by a plurality of through injection holes 25 obtained starting from an injection chamber 26 arranged downstream of the valve seat 18.

  As shown in FIG. 3, each movable armature 9 has a cylindrical shape, one central through hole 27 adapted to receive a portion of the plunger 17, and a fuel flow toward the injection nozzle 3. With a plurality of peripheral through-feed holes 30 (only two of which are shown in FIG. 3) adapted to allow The plunger 17 is integrated with each movable armature 9 via an annular weld surrounding the central hole 29.

  As described above, the outer diameter of the movable armature 9 of the upper electromagnet 8 is substantially the same as the inner diameter of the corresponding portion of the supply channel 5 of the support 4. In this way, such a movable armature 9 can slide in relation to the support 4 along the longitudinal axis 2 but in a direction transverse to the longitudinal axis 2 in relation to the support 4. No exercise can be performed. Since the plunger 17 is rigidly connected to the movable armature 9 of the upper electromagnet 8, it is obvious that such a movable armature 9 also functions as an upper guide for the plunger 17. As a result, the plunger 17 is guided by the movable armature 9 of the upper electromagnet 8 on the upper surface side and by the guide element 21 on the lower surface side.

  When the hydraulic brake device 31 is connected to the upper surface of the upper movable armature 9 (that is, the movable armature 9 of the upper electromagnet 8), the plunger 17 moves from the open position to the closed position of the injection valve 7, and the plunger 17 is the injection valve. In both cases, the movement of the plunger 9 is braked (decelerated) both when moving from the closed position to the open position. When the plunger 17 moves from the open position of the injection valve 7 to the closed position, the hydraulic braking device 31 brakes (decelerates) the movement of the plunger 17 to limit the elastic repulsion of the plunger 17 with respect to the valve seat 18 (i.e., this). During the step, the hydraulic braking device 31 functions to prevent rebounding). When the plunger 17 moves from the closed position of the injection valve 7 to the opening, the hydraulic braking device 31 brakes (decelerates) the movement of the plunger 17 to limit the opening speed of the injection valve 7.

  The hydraulic braking device 31 includes a plurality of valve elements 32, each of which is coupled to a respective supply hole 30 of the upper movable armature 9, and the movement of the plunger 17 (ie the plunger 17 closes or opens the injection valve 7). Have different transmittances for the passage of fuel as a function. Specifically, each valve element 32 includes a resilient blade 33 that is partially secured to the lower surface 34 of the movable armature 9 only on one side of the respective supply hole 30 and aligned with the supply hole 30 itself. Small calibrated hole 35 size. Furthermore, each valve element 32 has a stopper element 36 which is rigid (ie has a substantially negligible elasticity) and is coupled to a corresponding elastic blade 33, Arranged at a given distance, the opening movement of the elastic blade 33 itself is stopped at a fixed predetermined position. In other words, each stopper element 36 limits (interrupts) the movement of the elastic blade 33 from the corresponding supply hole 30 (ie from the lower surface 34 of the movable armature 9) and establishes a maximum opening position of the elastic blade 33 itself. A stopper is formed.

  As a result, the stopper element 36 determines the maximum opening stroke of the elastic blade 33 of each valve element 32, thus determining the fuel passage cross section within each valve element 32.

  A spacer 37 is arranged between each elastic blade 33 and the corresponding stopper element 36, which spacer has a calibrated thickness and, in a sense, exists between the elastic blade 33 and the corresponding stopper element 36. Establish an axial distance (ie, a distance measured along the longitudinal axis 2).

  As shown in more detail in FIG. 6, an annular crown 38 is provided which is fixed to the lower surface 34 of the upper movable armature 9 by welding (preferably using laser spot welding) and supports the elastic blade 33 of the valve element 32. ing. Specifically, the elastic blades 33 extend inwardly from the annular crown 38 (i.e., toward the corresponding supply hole 30), and each elastic blade includes an annular shutter disposed in the respective supply hole 30. A thin shutter (i.e., having a length significantly greater than its width) that is adapted to connect the circular shutter to the annular crown 38 and to deform under fuel bias. In other words, for each elastic blade 33, the deformation that occurs under energization of the fuel during use is caused substantially by the elastic deformation of the corresponding stem (while the corresponding circular shutter has a smaller elastic deformation). ).

  As shown in FIG. 7, the spacer 37 is shaped as an annular crown that is superimposed on an annular crown 38 that supports the elastic blade 33 of the valve element 32.

  As shown in more detail in FIG. 8, the spacer 37 is fixed to the annular crown 38 that supports the elastic blade 33 of the valve element 32 with the spacer 37 interposed therebetween, and is projected from the annular crown 39 itself toward the inside. An annular crown 39 is provided for supporting the stopper element 36 protruding at the end.

  As shown in FIGS. 4 and 5, the annular crown 38 that supports the elastic blade 33 of the valve element 32, the annular crown 39 that supports the spacer 37 and the stopper element 36 are sandwiched with each other (ie, overlapped and packaged). Preferably joined by welding (usually using laser spot welding) to form a single body.

  According to the preferred embodiment shown in FIGS. 5 to 8, the annular crown 38 that supports the elastic blade 33 of the valve element 32, the spacer 37, and the annular crown 39 that supports the stopper element 36 are each fuel in the support 4. It has a pair of opposite centering recesses 40 that ensure proper positioning of the injector.

  The operation of the hydraulic braking device 31 will be described below with particular reference to FIGS.

  As shown in FIG. 9, the hydraulic braking device 31 decelerates the opening movement of the plunger 17, that is, the movement of the plunger 17 moving from the closing position to the opening position of the injection valve 7. In other words, when the plunger 17 moves from the closed position to the open position of the injection valve 7, the hydraulic braking device 31 determines the hydraulic dissipation of the kinetic energy that the plunger has (that is, the braking force derived from the hydraulic pressure acting on the plunger 17). Generate). Specifically, when the fuel flows downward, that is, toward the injection nozzle 3, the elastic blade 33 of each valve element 32 is deformed under the bias of the fuel and is detached from the lower surface 34 of the upper movable armature 9. And stays on the stopper element 36 (as shown in FIG. 9), creating a calibrated sized annular fuel passage gap, which locally creates a “bottleneck” for fuel flow and the hydraulic pressure Determine the onset of significant load loss (such hydraulic load loss dissipates some of the kinetic energy that the plunger 17 has and thus hydraulically decelerates the movement of the plunger 17 itself.

  When the injection valve 7 is closed, the autoclave force derived from the hydraulic pressure presses the shutter head 24 and keeps the shutter head 24 in the closed position. Therefore, in order to be able to open the injection valve 7, the electromagnetic actuator 6 needs to generate a force for overcoming the autoclave force added to the elastic force exerted by the closing spring 10 on the plunger 17. However, it is believed that the autoclave force suddenly disappears as soon as the injection valve 7 opens, and thus the injection valve 7 has a tendency to open very rapidly and vigorously with the very fast upward movement of the plunger 17. When the injection valve 7 is opened and the autoclave force suddenly disappears, the action of the hydraulic braking device 31 described above determines the hydraulic dissipation of part of the kinetic energy that the plunger 17 has, so that the plunger 17 Slows down the opening movement (ie upward movement). Such a deceleration action determined by the hydraulic braking device 31 is very beneficial as it prevents the injection valve 7 from opening very rapidly and violently with the very fast upward movement of the plunger 17. In essence, the presence of the hydraulic braking device 31 decelerates the opening of the injection valve 7 and thus in the ballistic zone of the injection law (ie the law that links the start-up time or control time with the amount of fuel injected). The benefits of increased fuel injection controllability (ie, improved accuracy and repeatability) are provided. In other words, the action of the hydraulic braking device 31 can stabilize the initial part of the injection law (that is, the trajectory zone).

  As shown in FIG. 10, the hydraulic braking device 31 decelerates the closing movement of the plunger 17, that is, the movement of the plunger 17 from the opening position to the closing position of the injection valve 7. In other words, when the plunger 17 moves from the open position of the injection valve 7 to the closed position, the hydraulic braking device 31 determines the hydraulic dissipation of the kinetic energy that the plunger 17 has (that is, derived from the hydraulic pressure acting on the plunger 17). Of braking force). Specifically, when the fuel flows upward, i.e., in the direction opposite to the injection nozzle 3, the elastic blade 33 of each valve element 32 is compressed under the bias of the fuel against the lower surface 34 of the upper movable armature 9. Leaving that calibrated hole 35 as the only opening for the fuel. The forced passage of fuel through each calibrated hole 35 locally causes a “bottleneck” to the fuel flow that determines the onset of significant loss of hydraulic load (such loss of hydraulic load is , Dissipating a part of the kinetic energy that the plunger 17 has, thus hydraulically decelerating the movement of the plunger 17 itself).

  Briefly, the same hydraulic braking device 31 is provided with the opening movement of the plunger 17, i.e. the movement of the plunger 17 from the closed position of the injection valve 7 to the open position, and the closing movement of the plunger, i.e. the plunger 17 is the injection valve 7. The movement from the open position to the closed position is decelerated. During the opening movement of the plunger 17, ie when the plunger 17 moves from the closed position to the open position of the injection valve 7, the elastic blade 33 of each valve element 32 leaves the lower surface 34 of the upper movable armature 9 and corresponds to the corresponding stopper element 36. Stay on (as shown in FIG. 9). Under this condition, the fuel passes through the annular gap defined by the lower surface 34 of the upper movable armature 9 on one side and on the opposite side by the elastic blade 33 of the corresponding valve element 32 to the injection nozzle 3. It flows toward. During the closing movement of the plunger 17, ie when the plunger 17 moves from the open position of the injection valve 7 to the closed position, the elastic blade 33 of each valve element 32 remains on the lower surface 34 of the upper movable armature. Under this condition, the fuel flows through the calibrated hole 35 of the elastic blade 33 of each valve element 32 in the opposite direction to the injection nozzle 3.

  In other words, the hydraulic braking device 31 is an asymmetric damping system of kinetic energy that the movable armature 9 of the upper electromagnet 8 has, and brakes the closing motion of the plunger 17 more than the opening motion of the plunger 17. In fact, this is because the passage area of the annular gap defined by the lower surface 34 of the upper movable armature 9 on one side and by the elastic blade 33 of each valve element 32 on the opposite side is greater than the passage area of the corresponding calibrated hole 35. Is also significantly larger.

  As described above, the hydraulic brake device 31 hydraulically transfers kinetic energy both when the plunger 17 moves toward the open position of the injection valve 7 and when the plunger 17 moves toward the closed position of the injection valve 7. To dissipate (i.e., generate a braking force) and decelerate the stroke of the plunger 17. Specifically, the hydraulic braking device 31 has an asymmetric behavior, and when the plunger 17 moves toward the closing position of the injection valve 7, the plunger 17 moves toward the opening position of the injection valve 7. A large amount of kinetic energy is hydraulically dissipated. That is, the hydraulic braking device 31 has an asymmetric behavior, and when the plunger 17 moves toward the closing position of the injection valve 7, compared to when the plunger 17 moves toward the opening position of the injection valve 7. A large braking force is generated hydraulically. According to one preferred (but not binding) embodiment, the hydraulic braking device 31 is such that when the plunger 17 moves towards the closed position of the injection valve 7, the plunger 17 moves towards the open position of the injection valve 7. In this case, kinetic energy of 1.25 to 5 times (preferably 1.25 to 2.5 times) the amount of kinetic energy dissipated hydraulically is hydraulically dissipated. That is, the hydraulic braking device 31 is hydraulically generated when the plunger 17 moves toward the closed position of the injection valve 7 and when the plunger 17 moves toward the open position of the injection valve 7. A braking force 1.5 to 10 times (preferably 1.5 to 5 times) the power is generated hydraulically.

  In the embodiment shown in the accompanying drawings, the same hydraulic braking device 31 has the function of decelerating the opening movement of the plunger 17, ie the movement of the plunger 17 from the closed position of the injection valve 7 to the open position, Both the closing movement, that is, the function of decelerating the movement of the plunger 17 from the opening position of the injection valve 7 to the closing position (the bounce prevention function) is provided. According to one different embodiment, not shown, implemented as described in EP 141644844.4, the hydraulic braking device 31 has an opening movement of the plunger 17, i.e. the plunger 17 is connected to the injection valve 7. It has only the function of decelerating the movement from the closed position to the open position, is arranged on the upper surface of the movable armature 9 of the upper electromagnet 8 (ie on the side opposite to the hydraulic braking device 31), and the closing movement of the plunger 17 In other words, a further hydraulic braking device having a function of decelerating the movement of the plunger 17 from the open position to the closed position of the injection valve 7 (a function of preventing rebound) is provided. In this embodiment, the mechanical inertia of the two brake devices of the hydraulic type is distinguished, thus allowing the hydraulic brake device 31 to intervene more quickly when operating during the opening movement of the plunger 17 and the plunger During the 17 closing movements (ie movements acting as bounce prevention), the other hydraulic brake is intervened more slowly.

  In the embodiment shown in the accompanying drawings, the plunger 9 of the upper electromagnet 8 is the only upper guide of the plunger 17 and supports the hydraulic braking device 31. The hydraulic braking device 31 is preferably coupled to the movable armature 9 of the upper electromagnet 8, which provides an excellent lateral hydraulic seal against the inner surface of the supply channel 5. This is because it is possible to obtain a more excellent operation of the hydraulic braking device 31 itself (that is, side leakage of fuel is reduced). According to one alternative embodiment (not shown) that is completely equivalent, the movable armature 9 of the lower electromagnet 8 forms the sole upper guide of the plunger 17, so that in this case the hydraulic braking device 31 is preferably lower It is considered that it is coupled to the movable armature 9 of the electromagnet 8. According to a further fully equivalent embodiment (not shown), both movable armatures 9 can form two upper guides of the plunger 17, so that in this case the hydraulic braking device 31 is connected to the plunger 9 of the lower electromagnet 8 or It seems that it can be indiscriminately coupled to any of the movable armatures 9 of the upper electromagnet 8.

  The plunger 17 has a cylindrical symmetric stem, to which a substantially spherical shutter head 24 is connected using annular welding. Similarly, the stem is connected to each movable armature 9 using an annular weld.

  The fuel injector 1 described above has many advantages.

  Firstly, the above-described fuel injector 1 has a linear and uniform (i.e. non-irregular) injection law (i.e. for short drive times (i.e. in the ballistic zone) and thus also for small amounts of injected fuel) , A law that links drive time to the amount of fuel injected). In this way, the above-described injector 1 can inject a small amount of fuel in an accurate and reproducible manner.

  Such a result is likewise due to the effect of the presence of the stopper element 36 that the opening movement of the elastic blade 33 of the hydraulic braking device 31 (ie the disengagement from the lower surface 34 of the upper movable armature 9) takes place virtually without vibration. That is also obtained by the fact that each elastic blade 33 leaves the lower surface 34 of the upper movable armature 9 and abuts the corresponding stopper element almost simultaneously without appreciable vibration. Since there is no vibration in the opening movement of the elastic blade 33 of the hydraulic braking device 31, the introduction of randomness in the dynamic behavior of the hydraulic braking device 31 is avoided, thus the dynamic performance of the hydraulic braking device 31. (And thus the dynamic behavior of the fuel injector 1) is much more stable, accurate and predictable and reproducible, and thus in a particularly short control time (ie within the ballistic zone) the linearity of the injection law Benefits of uniformity and uniformity.

  By varying the thickness of the spacer 37 (ie, replacing one spacer 37 with another spacer 37 of a different thickness), the stroke of the elastic blade 33 of the hydraulic braking device 31 is adjusted accurately, resulting in a plunger It is possible to adjust the strength of the braking action of the hydraulic braking device 31 during the 17 opening movement. Instead, by adjusting the diameter of the calibrated hole 35 of the elastic blade 33 of the hydraulic braking device 31, during the closing movement of the plunger 17 (bounce-back preventing function), the braking action of the hydraulic braking device 35 results. It is possible to adjust the strength.

  Similarly, the fuel injector 1 described above is hydraulic because the elastic blades 33 of the hydraulic braking device 31 are not substantially subjected to mechanical vibrations (i.e. vibration) due to the presence of the corresponding stopper elements 36. The fact that the brake system 31 is not very sensitive to fuel pressure oscillations is also very stable.

  Due to the presence of the stopper element 36 that blocks the vibration of the corresponding blade 33 of the hydraulic brake device 31, the elastic blade 33 is likewise very light (ie has a low mechanical inertia) and is therefore very much of the hydraulic brake device 31. It may allow rapid intervention.

  In the fuel injector 1 described above, the hydraulic braking device 31 functions by decelerating the movement of the plunger 17 both during the opening movement and during the closing movement, thereby removing the bounce of the plunger 17 during the opening movement ( That is, it is possible to perform the rebound from the impact of the upper movable armature 9 with respect to the corresponding magnetic armature 12 and the closing motion (that is, the rebound from the impact of the shutter head 24 to the valve seat 18). To do. Due to the complete absence of appreciable bounce of the plunger 17 during both the opening and closing movements, the uniformity of the law of injection (ie reproducibility) can be achieved with short control times (ie in the ballistic zone). ) But substantially improved. Furthermore, the noise produced by the fuel injector 1 described above during its operation is significantly reduced by the complete lack of appreciable rebound of the plunger 17 in the opening and closing movements.

  In addition to ensuring a very good controllability of the small-scale injection, the fuel injector 1 described above also has a collision force during the opening step (ie the impact of the upper movable armature 9 on the corresponding magnetic armature 12). ) And during the closing step (i.e., the impact force resulting from the impact of the shutter head 24 against the valve seat 18), the impact force of the plunger 17 can also be significantly reduced. By reducing the collision force of the plunger 17, it is possible to reduce mechanical wear and thus extend the useful life of the fuel injector 1 described above.

  When the injection valve 7 is open, fuel flows towards the injection nozzle 3 through the supply hole 30 of the upper movable armature 9 (ie the movable armature 9 of the upper electromagnet 8) and thus passes through the corresponding valve element 32; In this valve element, the elastic blade 33 detaches from the lower surface of the upper movable armature 9 and defines a corresponding annular gap through which the fuel must pass, above the stopper element 36 (as shown in FIG. 9). Stays on.

  As mentioned above, the passage of fuel in the open valve element 32 (i.e. the valve element in which the elastic blade 33 is detached from the lower surface 34 of the upper movable armature 9 and remains on the stopper element 36) The plunger 17 causes a hydraulic dissipation of a part of the kinetic energy that the plunger 17 has, and as a result, generates a braking force that actively decelerates the opening movement of the plunger itself.

  Further, the passage of fuel in the open valve element 32 (ie, the valve element with the elastic blade 33 leaving the lower surface 34 of the upper movable armature 9 and staying on the stopper element 36) It causes a small but non-negligible load loss at the front and back (ie, the fuel pressure above the upper movable armature 9 is higher than the fuel pressure below the upper movable armature 9). Such a pressure difference before and after the upper movable armature 9 (small but not negligible) acts on the entire surface of the upper movable armature 9 and pushes the upper movable armature 9 toward the injection nozzle 3. That is, an autoclave force derived from hydraulic pressure that pushes the plunger 17 toward the closing position of the injection valve 7 (having a strength equal to the pressure difference before and after the upper movable armature 9 multiplied by the area of the upper movable armature 9). . This autoclave force, derived from the hydraulic pressure that is present when the injection valve 7 is open and pushes the plunger 17, is added to the elastic force generated by the closing spring 10 and when the electromagnetic actuator 6 is switched off. 7 because it contributes to accelerating the closure of the valve 7 (ie, this hydraulically derived autoclave force substantially reduces the closing time of the injection valve 7 when the electromagnetic actuator 6 is switched off). Has an effect. This autoclave force derived from the hydraulic pressure present when the injection valve 7 is open allows the closing spring 10 to be made smaller (ie a closing spring 10 having a low elastic load can be used), as a result. The electromagnetic force generated by the electromagnetic actuator 6 can be reduced (i.e. using a smaller electromagnetic actuator 6, and thus a lighter, more economical and less mechanical or magnetic inertia electromagnetic actuator). it can).

  The autoclave force derived from the hydraulic pressure that is present when the injection valve 7 is open has a very low lateral clearance in relation to the support 4 (as described in more detail above) by the upper movable armature 9. It is also noteworthy that it is generated for the purpose of establishing a non-negligible pressure difference before and after the upper movable armature 9 itself.

  The fuel injector 1 described above is because the single component (hydraulic braking device 31) functions as a hydraulic braking device both during the opening movement of the plunger 17 and during the closing movement of the plunger 17. It is simple and cost effective to manufacture. In other words, in the injector 1 described above, the hydraulic braking device 31 performs a number of functions performed by two different and separate devices in a similar known fuel injector, and thus the overall cost effectiveness of the assembly. Benefits of simplicity and simplicity.

  In the injector 1 described above, the structure of the movable armature 9 is also simpler and more cost-effective than similar fuel injectors thanks to the special form of the hydraulic braking device 31. Deserves attention.

  Finally, the performance of the fuel injector 1 described above is very dynamic even when the fuel supply pressure is high (greater than 60-70 Mpa) (ie the injection valve 7 can be opened and closed very quickly). Such a result is substantially obtained by the fact that two twin electromagnets 8 of relatively small size are used and thus have low mechanical and magnetic inertia.

  The fuel injector 1 described above operates in accordance with an Otto cycle (ie with spark-controlled ignition of the mixture) or in accordance with a diesel cycle (ie with compression injection of the mixture). It is also worth noting that it may be used to inject any type of fuel.

Claims (16)

An injection nozzle (3);
An injection valve (7) provided with a movable plunger (17) for adjusting the flow rate of fuel through the injection nozzle (3);
At least one electromagnet comprising a coil (11), a stationary magnetic armature (12) and a movable armature (9) for the purpose of moving the plunger (17) between the closed and open positions of the injection valve (7). 8) an electromagnetic actuator (6) comprising at least a movable armature (9) mechanically connected to the plunger (17) and for passing fuel towards the injection nozzle (3) An electromagnetic actuator (6) having one supply through hole;
A hydraulic braking device (31) coupled to the supply hole (30) and having a function of hydraulically generating a braking force for decelerating the stroke of the plunger (17);
A closing spring (10) having a tendency to hold the plunger (17) in the closed position;
In a fuel injector (1) having a tubular shape, provided with a central channel (5) and comprising a support (4) containing a stationary magnetic armature (12) and a movable armature (9),
The stroke of the plunger (17) both in the case where the plunger (17) moves towards the open position of the injection valve (7) and in the case where the plunger (17) moves towards the closed position of the injection valve (7). A fuel injector (1), wherein a hydraulic braking device hydraulically generates a braking force for decelerating the engine.   The hydraulic braking device (3) has an asymmetric behavior, when the plunger (17) moves towards the closed position of the injection valve (7), the plunger (17) moves towards the open position of the injection valve (7). The injector (1) according to claim 1, wherein the braking force is hydraulically generated in comparison with the case of moving in a moving manner.   When the plunger (17) moves toward the closed position of the injection valve (7), 1 of the braking force generated hydraulically when the plunger (17) moves toward the open position of the injection valve (7). The injector (1) according to claim 2, wherein the hydraulic braking device (31) hydraulically generates 5 to 10 times the braking force.   When the plunger (17) moves toward the closed position of the injection valve (7), 1 of the braking force generated hydraulically when the plunger (17) moves toward the open position of the injection valve (7). The injector (1) according to claim 2, wherein the hydraulic braking device (31) hydraulically generates 5 to 5 times the braking force. The hydraulic braking device (31)
A valve element (32) comprising a resilient blade (33) coupled to the supply hole (30) of the movable armature (9) and partially fixed to the surface (34) of the movable armature (9);
It is coupled to the elastic blade (33) and is arranged at a given distance from the elastic blade (33) so as to stop the opening movement of the elastic blade (33) itself at a fixed predetermined position. The injector according to claim 1, comprising a stopper element (36).   The injector (1) according to claim 5, wherein the stopper element (36) has a higher stiffness than the elastic blade (33).   7. Stopper element (36) according to claim 5 or 6, wherein the stopper element (36) is a limit stopper that limits the movement of the elastic blade (33) leaving the supply hole (30) and establishes the maximum open position of the elastic blade (33). Injector (1).   A hydraulic braking device (31) is interposed between the elastic blade (33) and the stopper element (36) to establish an axial distance existing between the elastic blade (33) and the stopper element (36). The injector (1) according to claim 5, 6 or 7, comprising 37).   The injector (1) according to claim 8, wherein the spacer (37) has an annular shape.   The injector according to claim 9, wherein the spacer (37) has a calibrated thickness.   The hydraulic braking device (31) includes a first annular crown (38) that is fixed to the surface (34) of the movable armature (9) and supports the elastic blade (33) of the valve element (32). The injector (1) according to any one of claims 5 to 10, wherein:   The elastic blade (33) is adapted to be circularly arranged in the supply hole (30) and to connect the circular shutter to the first annular crown (38) and to elastically deform under the bias of the fuel. The injector (1) according to claim 11, comprising a stem.   The hydraulic braking device (31) comprises a second annular crown (39) supporting a stopper element (36), said stopper element projecting inwardly from the second annular crown (39). The injector (1) as described in any one of 5-12.   14. An injector according to any one of claims 5 to 13, wherein the elastic blade (33) of the valve element (32) has a calibrated through hole (35) arranged in the supply hole (30). (1).   The elastic blade (33) of the valve element (32) is partly fixed to the lower surface (34) of the movable armature (9) facing the injection nozzle (3). The injector (1) according to one paragraph.   Injector according to any one of the preceding claims, wherein the hydraulic braking device (31) exhibits asymmetric behavior with different permeabilities for the passage of fuel as a function of the direction of movement of the plunger (17). (1).

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