JP2017531765A - Fuel injector - Google Patents

Abstract

The present invention is a fuel injector comprising a needle (72), a two-way solenoid valve (24) in which the pressure rises in the control chamber when the solenoid valve (24) is in the open position, and a solenoid valve (24 And a means (26, 114) for reducing dynamic leakage that prevents fuel from flowing directly from the supply channel (146) to the return circuit (148) when in the open position.

Description

  The present invention relates to a fuel injector with means for reducing dynamic leakage.

  Conventionally, a fuel injector includes a needle whose opening and closing is controlled based on a pressure difference between a control chamber and an injection nozzle. Within the control chamber, the pressure depends on the position of a two-way solenoid control valve or all-or-nothing valve that switches between an open position and a closed position. When the solenoid valve is in the closed position, high pressure fuel can enter the control chamber, push the needle toward the closed position, and when the solenoid valve changes to the open position, the fuel previously trapped in the control chamber Can exit through the exhaust channel and reduce the pressure in the control chamber. During this time when the solenoid valve is open, the high pressure fuel continues to flow into the control chamber, but it only passes through the control chamber because it flows directly through the exhaust channel. Although this dynamic leakage can be controlled in an injector having a three-way solenoid valve as described in Patent Document 1, it is known that in an injector having a two-way valve, this dynamic flow continues to cause a loss of energy. It has been.

European Patent Application No. 2711537

  It is an object of the present invention to have a body in which a needle moves between an open position and a closed position under the influence of fuel pressure in a control chamber, into which a high pressure supply channel enters and from there a two-way The problem is at least partially solved by providing a fuel injector that includes a chamber in which an exhaust channel controlled by a solenoid valve leads to a low pressure return circuit.

  When the solenoid valve is in the closed position, the pressure in the control chamber increases, pushes the needle toward the closed position, and when the solenoid valve is in the open position, fuel is released from the control chamber where the pressure decreases, The needle can move to the open position.

  The injector further includes means for reducing dynamic leakage that prevents fuel from flowing directly from the supply channel to the return circuit when the solenoid valve is in the open position. The means for reducing dynamic leakage is a moving member that moves between an open position and a closed position under the influence of a fuel pressure difference between the control chamber and a second control chamber in fluid communication with the exhaust channel. including.

  More particularly, the moving member is a cylindrical piston arranged to slide within a bore in the injector body, and the supply channel opens into the bore. The piston moves to the open position when the solenoid valve is in the closed position so that high pressure fuel can enter the control chamber, and the solenoid valve is in the open position to prevent high pressure fuel from entering the control chamber. Move to the closed position at some point.

  More specifically, the bore is coaxial with the bore in which the needle moves.

  In one embodiment, the piston comprises a large diameter base on which a smaller diameter cylindrical body rests. The lower surface of the base faces the needle, and the joint surface between the base and the body forms a sealing surface that works with a seat provided in the injector body. When the piston is in the closed position, the sealing surface and seat are in a leak-proof contact state that prevents high pressure fuel from entering the control chamber, and when the piston is in the open position, the sealing surface and seat are both high pressure fuel. Move away to be able to pass between.

  In this embodiment, the piston also comprises a channel that opens and provides permanent fluid communication between the control chamber and the second control chamber. The channel may be an axial channel. In addition, the open channel may include a restriction in cross section that causes a pressure drop so that the pressure in the control chamber is higher than the pressure in the second control chamber.

  Further, the piston is gauged (standardized) extending radially between the outer cylindrical surface of the cylindrical body and the open channel so as to establish fluid communication between the high pressure supply and the second control chamber. ) Channels.

  In another embodiment, the piston is a single cylindrical body that extends axially between a lower surface facing the needle (the lower surface forms the top surface of the control chamber) and an upper surface opposite the lower surface. The upper surface is in contact with the cross section of the injector body when the piston is moved to the closed position. In addition, a spring is provided in the control chamber, and a shoulder integral with the needle and a lower surface of the piston so that the needle is always pressed toward its closed position and the piston toward its closed position. Compressed between.

  More specifically, the piston is provided with a first channel extending from the outer wall of the piston to the upper surface and a second channel extending between the lower surface and the upper surface, and the piston has a first supply channel. So that it is in permanent fluid communication with the other channel.

  The first channel may comprise an annular groove provided in the outer wall of the piston, the first channel extends from the groove and opens at the upper surface of the piston, and the supply channel is defined by the annular groove. Open into the space.

  The piston also includes a ridge on its upper surface that forms a leak-proof barrier when the piston is in the closed position, the barrier being in leak-tight contact with the cross-section of the injector body, the first channel and the second channel And the second control chamber is disposed between the lateral surface of the injector body and the upper surface of the piston, and the second channel is open to the upper surface of the piston on either side of the barrier. And the space defined by the edge of the barrier where the drain line opens.

  More specifically, the barrier is a closed circular lip, with the first channel opening into the central portion and the second channel opening outward.

  In an alternative to the other embodiment described above, the injector has a closing force directed towards the tip of the needle, i.e. the pressure of the fuel injected when the needle is in the open position is the fuel inlet pressure into the injector. A device is provided that allows a force to act on the needle that is greater than the opening force directed toward the head of the needle to be equal.

  The device comprises a piston whose cross section is larger than the cross section of the needle so that pressurized fuel flowing into the second control chamber applies an increased force to the piston.

  In certain embodiments, the piston is dimensioned to contact the needle head as soon as the piston begins to move toward the open position. The increased force applied by the high pressure fuel in the second control chamber is then fully applied to the needle so that the needle receives a closing force that is greater than the opening force exerted by the fuel on the needle tip. Communicated.

  An embodiment of the present invention will be described with reference to the following drawings.

It is an axial sectional view of an injector provided with means for reducing dynamic leakage according to the present invention. It is an enlarged detail drawing of the axial cross section of the area | region of an injector provided with the said means comprised according to 1st Embodiment. Fig. 3 is a more detailed view of the means similar to Fig. 2; FIG. 4 is a detailed view from above of the means of FIGS. 2 and 3. 5 is a perspective view of a moving piston of the means of FIGS. It is an axial sectional view of the piston of FIG. FIG. 6 is an axial cross-sectional view of an alternative to the first embodiment of FIGS. It is an enlarged detail drawing in the axial cross section of the area | region of the injector provided with the said means comprised according to 2nd Embodiment. FIG. 9 is a more detailed view similar to FIG. 8. FIG. 10 is a perspective view of the moving piston of the means of FIGS. 8 and 9. Figure 6 is a rough graph of the operation of a means for reducing dynamic leakage, irrespective of the embodiment.

  FIG. 1 is an axial cross-sectional view of a fuel injector 10 extending along a longitudinal axis A1 from an injector head 12 depicted at the top of the figure to an injection nozzle 14 depicted at the bottom of the figure.

  Any orientation in FIG. 1 is also used for clarity of explanation, and terms such as “up, down, up or down” can be used without limiting the description or scope of the invention.

  The injector 10 includes a head 12 with a high pressure inlet opening 16 and a low pressure outlet opening 18 that is only partially recognizable. The injector head 12 is integral with the body of the actuating means 20, which is itself fixed by the injector nut 22 to the control valve 24, the upper guide 26 and the body 28 of the injection nozzle 14.

  Overall, the body of the actuating member 20 has a rotating cylindrical shape centered on the longitudinal axis A <b> 1 and extends from the head 12 to the lower surface 30. In its outer cylindrical surface in the vicinity of the lower surface 30, it further comprises a male thread designed to engage in a matching manner with the female thread 34 of the injector nut 22 and is parallel to the longitudinal axis A1. Comprises an inner cylindrical bore 36 extending along a second axis A2 slightly offset therefrom. The bore 36 opens onto the lower surface 30 and the coil 38 of the electromagnet 40 (whose bottom surface is flush with the lower surface 30 of the actuating body 20) is disposed within the bore 36. Electrical connection means 42 such as a wire exits the coil 38 in the direction of the injector head 12. These means 42 extend in a specific line to a connector 44 with terminals, so that the coil 38 can be connected to an external control unit (not shown). The coil 38 itself is provided with a central bore 46 in which a valve spring 48 is arranged.

  The control valve 24 is a rotating cylinder centered about a longitudinal axis A1 extending between the upper surface 52 and the lower surface 54, and includes an axial bore that includes two coaxial sections along the second axis A2. The first section having a valve body 50 having an opening 56 and opening on the upper surface 52 is a large diameter shallow counterbore forming a low pressure chamber 58, and the second section extends from the center of the bottom 60 to the lower surface 54. The hydraulic distribution turbo-a 62 is formed. Several channel openings open laterally into the distributor but are blocked along the axis A2. A set of channels and pipelines provided in the injector 10 will be described below.

  In addition, the injector shown in FIG. 1 and upon which this description is based is only one non-limiting example, and there are many alternative configurations and mentions that are omitted. Such alternatives are not excluded from the scope defined by the claims. For example, it has been described that the longitudinal axis A1 and the second axis A2 are separate and parallel. This offset between the axes introduced in the patent EP 1693563 has many advantages, but is not essential, there is an injector with the two axes merged and it can benefit without any problems from the teachings of the present invention.

  The control valve 24 further includes an armature rod assembly 64 that includes a magnetic armature 66 and a valve rod 68 arranged to move within the axial bore 54. The armature 66 has a generally shaped thick disk disposed within the low pressure chamber 58, and the valve rod 68 is a cylindrical shaft containing sections of different diameters, one end of which is the center of the armature 66. Is inserted and caulked. When mounted in this manner, the valve rod 68 extends perpendicular to the armature 66 and slides into the distribution turbo-a 62. The valve rod 68 slides directly in the distribution turbo-a 62 or, alternatively, as shown in FIG. 2, in a cylindrical plug 70 with at least one radial hole drilled radially, the plug 70 being distributed. It is firmly inserted into the turbo-a 62.

  As shown, coil 38, its central bore 46, valve spring 48, valve body axial bore 56, magnetic armature 66 and valve rod 68 are coaxial and extend along a second axis A2. The valve spring 48 compressed between the bottom of the coil's central bore 46 and the valve rod 68 whose head appears in the center of the armature 66 always positions the armature rod assembly 64 away from the coil 38, the valve's open position. The valve is pressed toward a position called a closed position PFV of the valve opposite to a position near the coil called POV.

  With respect to the injection nozzle 14, it comprises a nozzle body 28, an upper guide 26, a needle 72 and a needle spring 74. In the example described, the nozzle body 28 and the upper guide 26 are two separate parts. In an alternative not shown, there are injectors in which the nozzle body includes an upper guide, which can also benefit from the present invention.

  The nozzle body 28 includes a spindle-shaped cylindrical wall 76 that extends from the upper surface 78 along the longitudinal axis A1 in a first larger diameter section 80 and a second smaller diameter section 82 that approaches the point at its lower end. Have The outer surfaces of the two sections 80, 82 are joined to each other by a transverse disk-shaped surface 84 on which the injector nut 22 rests.

  Similar to the outer surface, the wall 76 is a continuous interior space 86 that is divided into a large cylindrical chamber 88 disposed within the first section 80 and a small diameter chamber 90 disposed within the second section 82. Is defined.

  A large diameter cylindrical chamber 88 opens over a lower surface 78 that forms a high counterbore 92 designed to receive and position the upper guide 26.

  The small diameter chamber 90 defines a lower slide guide 94 in a portion of its transverse cylindrical wall, and the end of the small diameter chamber 90 penetrates the nozzle body wall 76, similar to the second section 82. The nozzle body is closed so as to be within a reentrant cone forming a sheet 96 of the nozzle body surrounded by the plurality of injection holes 98.

  In the described non-limiting example, the upper guide 26 is a separate part of a rotating cylinder that extends from the transverse upper surface 100 along the longitudinal axis A1 and into the smaller diameter lower cylinder 104 and the larger diameter upper cylinder 102. The two cylinders 102, 104 meet at the shoulder surface 106. The upper guide 26 further includes an open axial bore 108 that extends through the two cylinders 102, 104, a bore 108 that defines an upper slide guide 110 in its upper portion disposed within the small diameter cylinder 104, and a large diameter cylinder. The control chamber 112 in the upper part arranged in 102 includes a control chamber 112 in which a moving piston 114 described later is arranged.

  The moving piston 114, shown in greater detail in FIGS. 4, 5 and 6, extends axially between the upper surface 116 and the lower surface 118, and the upper surface 116 rises slightly above the upper surface 116. A concave upper housing 120 is provided at the center of the boss so that the boss surrounds the opening of the upper housing 120 and forms a peripheral circular lip 122. In the center of its lower surface 116, the piston 114 also includes a lower concave housing 124.

  Upper housing 120 and lower housing 124 are functional centering holes for certain forms of machining. In alternatives not shown corresponding to different embodiments, these housings may not be provided.

  Piston 114 is also on its lateral cylindrical surface a first channel 128 connecting the annular groove 126 and the inner surface of the upper housing 120 and the groove 126, the opening of the first channel 128 being within the lip 122. And a second channel 130 connecting the upper surface 116 with the inner surface of the lower housing 124, the upper opening comprising a second channel 130 existing outside the lip 122. .

  Needle 72, so called to those skilled in the art in view of its general shape, is an elongated cylindrical arm that extends from needle head 132 to a conical tip 134 that defines a seat for needle 136. As can be seen in particular in FIGS. 2 and 3, the needle head 132 includes a small cylindrical protrusion 138 connected to the body of the needle by a bearing shoulder 140, the needle body being the upper needle guide 142 in this portion of the head. On the opposite side of the head 116 near the tip 134, the needle 72 has an enlarged portion that forms a lower needle guide 144.

  As shown, the nozzle body 28 receives the large diameter cylindrical portion 102 of the upper guide 26 within its upper counterbore 92 and the small diameter portion 104 extends into the large diameter chamber 88 of the nozzle body 28. The upper guide shoulder surface 106 rests against the bottom of the upper counterbore 92 and the upper guide 26 is held radially in place by the inner edge of the counterbore 92.

  By arranging the upper guide 26 in this way, the upper slide guide 110 and the lower slide guide 92 are coaxial along the longitudinal axis A1 and receive the needle 72 for matching, and the upper needle guide 142 is Slide in the upper slide guide 110 and the lower guide 144 slides in the lower slide guide 92 of the nozzle body. Above the needle head 116, the needle spring 74 is compressed in the control chamber 112 between the bearing shoulder 104 integral with the needle 72 and the lower surface 118 of the moving piston 114.

  Upper surface 100 of the upper guide is held in leak-proof surface contact with the lower surface of valve body 54, and upper surface 52 of the valve body is itself in contact with the lower surface 30 of the actuating body. This integral leak-proof stack is possible via the injector nut 22, but this nut, which is screwed around the second small diameter portion 82 of the nozzle body 28, abuts the disk-shaped surface 84 of the nozzle body, which When screwed into the body of the opening member 20 using the matching screws 32 and 34 described above, it extends in the axial direction along the longitudinal axis A1 so as to surround the upper guide 26 and the control valve 24. The surface seal is partly due to the specular quality condition of the contacting surface and partly the nut 22 which creates strong compression between the bottom of the body of the actuating member, the valve body, the upper guide and the nozzle body. Guaranteed by a sufficiently large tightening torque.

  With respect to the injector 10, the valve spring 48 is pressed against it, but the armature rod assembly 64 has a closed position PFV of the valve, i.e. a lower position where the armature rod assembly 64 is away from the coil 38, and an open position POV of the valve, i. It has already been described that the armature rod assembly 64 can move axially along the second axis A2 between the upper position close to the coil 38. Similarly, the needle spring 74 presses it, but the needle 72 is in leak-tight contact with the nozzle body seat 96 so as to prevent fuel injection axially along the longitudinal axis A1. The needle closed position PFA, also commonly referred to as the bottom position, and the needle open position POA, ie, the upper position where the needle seat 136 is separated from the seat 96 of the nozzle body to allow fuel to pass and be injected. Can be moved between. Similarly, the moving piston 114, which also presses the needle spring 74, is positioned axially along the longitudinal axis A1 in the piston open position POP, ie, the lower position where the peripheral lip 122 is separated from the lower surface 54 of the valve body. The piston closed position PFP, that is, the peripheral lip 122 can move between the lower surface 54 of the valve body and the upper position in a leak-proof contact state.

  Injector 10 further comprises channels and conduits that include matching sections between the injector elements, which channels and conduits form a high pressure circuit 146 and a low pressure return circuit 148 through which fuel circulates during use. .

  The high-pressure circuit 146 includes a first main line 150 extending in the body of the actuating member 20 between the inlet opening 16 and the lower surface 30 of the body of the actuating means. Is extended by a second conduit 152 that passes through the large diameter cylindrical portion 102 of the upper guide, followed by a third conduit 154 that passes through the large diameter cylindrical portion 102 of the upper guide. It opens onto the shoulder surface 106 of the upper guide between the inner side of the body wall 76 and into the large diameter channel 88 of the nozzle body 28. The high pressure circuit 146 continues in the internal space 86 of the nozzle body to the injection hole 98. A high pressure circuit 146 is further provided in the upper guide 26 and connects the shoulder surface 106 with the interior of the axial bore 108 where it opens into the annular space defined by the annular groove 126 of the piston 114. A path 156 is further provided.

  Thus, the high pressure fuel that flows in through the inlet opening 16 and circulates in the high pressure circuit 114 reaches the space of the annular groove 126 and then flows through the first channel 128 of the piston 114 and passes through the upper concave housing. It is understood that 120 is satisfied.

  When the piston is in the open position POP, the high pressure fuel can follow the path indicated by arrow F1 in FIG. From the upper housing 120, it passes between the lip 122 and the lower surface 54 of the valve body above the lip 122 and then flows in the second channel 130 of the piston to fill the control chamber 112.

  Conversely, when the piston is in the closed position PFP, high pressure fuel exits the first channel 128 and is no longer in leak-tight contact with the lower surface 54 of the valve body because the upper concave housing 120 is filled. It cannot pass through the lip 122.

  With respect to the low pressure return circuit 148, this includes a drain line 158 provided in the valve body and depicted translucently in FIGS. This drain line 158 then extends from the lower surface 54 of the valve body, which opens outside the lip 122 of the piston 114 and onto the outer portion of the axial bore 108 of the upper guide, and the bore of the hydraulic distributor Extends in 62 until it opens. This space between the lip 122 of the piston 114 and the lower surface 54 of the valve body (the space into which the discharge line 158 opens) forms a second control chamber. As shown, the drain line is provided in a first short section 162 that opens below the valve body 50 and is connected vertically to a second longer section 164 that extends linearly to the bore 62. . For feasibility reasons, the second section 164 opens onto the lower surface 54 of the valve body, but this end is blocked during assembly by the upper guide upper surface 100.

  The return circuit 148 extends within the bore 62 of the hydraulic distributor, i.e., through the hole in the plug 70, and then rises toward the low pressure chamber 58 of the circuit 148 through a main return line 166 (not shown). This extends parallel to the main high pressure line 150 from the lower surface 30 to the outlet opening 18 in the body of the actuating member 20.

  The return circuit 148 further comprises a valve leak recovery line, which is also shown translucent in FIG. 2 and extends from the bottom of the axial bore 56 to the side cylindrical wall of the valve body 50. The recovery line opens into the annular space between the side wall and the injector nut 22 so as to reach the low pressure chamber 58 and the main return line 166 again.

  When the piston 114 is in the closed position PFP or in the upper position where the lip 122 is in leaktight contact with the lower surface 54 of the valve body, the fuel placed in the control chamber 112 passes through the channel 130 of the second piston. And then flow through a return circuit 148 that continuously passes through the two sections 162, 164 of the discharge line.

  Hereinafter, general functions of the injector 10 and various operations of the movable parts will be described.

  Initially, no current is supplied to the coil 38, which does not generate a magnetic field and therefore does not attract the magnetic armature 66. The valve spring 48 pushes the armature rod assembly 64 into the closed position PFV, in which the valve rod 68 interrupts the hydraulic communication between the axial bore 56 and the low pressure chamber 58 so that fuel enters the return circuit 148. Prevent recombination. As high pressure fuel enters the injector continuously, if there is no discharge, pressure increases in the two sections 162, 164 of the valve body discharge line, especially above the piston 114 in the second control chamber 160. Thus, the moving piston 114 is pushed down to the open position POP and, as described above, high pressure fuel can flow into the control chamber 112, where the pressure increases, causing the needle 72 to move down to the closed position PFA. Push it. The pressure is then equilibrated on either side of the piston 114. Needle 72 moves in relation to the pressure differential between the needle head and tip. Therefore, in order to move the needle 72 downward when the pressure in the control chamber 112 increases, the injector 10 needs to include a device that reduces the pressure toward the tip. One skilled in the art will appreciate an injector where the high pressure circuit includes a gauged opening disposed between the inlet to the control chamber and the injection hole. Such a function can also be implemented using a collar known as a boost flange in English or NMC (needle motion control) that is integral with the needle and allows only a small passage for high pressure fuel flow. This passage produces the desired pressure drop on the tip side.

  Thereafter, power is supplied to the coil 38, which subsequently generates a magnetic field that attracts the armature 66, which raises the coil 38 despite being pressed by the valve spring 48, causing it to open valve position. Approach to POV. The fuel previously confined in the discharge lines 62 and 164 can be discharged toward the low pressure chamber 58 and the main return line 16. This rapid discharge creates a negative pressure in the second control chamber 160 and a negative pressure that pulls the piston upward, the moving piston 114 then moves to the closed position PFP, and the lip 122 moves against the lower surface 54 of the valve body. A leak-proof contact state is established. As explained above, high pressure fuel can no longer flow out of the upper piston housing 120 and fuel trapped in the control chamber 112 flows out through the second channel 130 and passes around the lip 122. , And can then rejoin the discharge lines 162, 164 and subsequently to the return circuit.

  FIG. 11 is a two-dimensional graph roughly showing a graph of pressure change in the control chamber 112 as a function of time. The table on the graph shows the positions taken by the armature rod assembly 64, the moving piston 114 and the needle 72.

  Point P1, which is the intersection of the graph with the vertical axis and the pressure axis, represents the moment when power begins to be applied to the coil 38, and the armature rod assembly 64 subsequently moves to the open position POV, while the pressure in the control chamber 112 Is still high and the needle 72 is in the closed position PFV. From point P1, the piston assumes the closed position PFP, and the pressure in the control chamber 112 decreases until the time when the needle returns to the open position POA.

  The subsequent point P2 shows the moment when the power supply to the coil 38 is turned off and the armature rod assembly 64 is immediately pushed back to the closed position PFV by the valve spring 48 while the pressure in the control chamber 112 is still low. The needle 72 is in the open position POA. Immediately after point P2, the piston assumes the open position POP and the pressure in the control chamber 112 increases again to the point where the needle again falls to the closed position PFA.

  The cycle begins again and subsequent points P3 and P4 are similar to points P1 and P2, respectively.

  An alternative example of the first embodiment will be described with reference to FIG. In this alternative, the piston 114 has an outer diameter that is significantly larger than the diameter of the needle 72. As shown, the lower housing 124 of the lower surface 118 of the piston can be expanded to a counterbore of sufficient size to accept the needle head 132 and spring. Such a configuration of the piston 114 clearly requires that the upper end emerging from the axial bore of the upper guide 108 should itself be enlarged to accept a new larger piston. The advantages of this alternative embodiment will be clear from the description of its operation. When the needle 72 is in the open position POA, the upper position, the coil 38 is not powered, the valve is closed again (PFV), and the pressure is again in the second control chamber directly above the upper surface 116 of the piston. It begins to rise within 160. Since this surface has a larger surface area, the force generated by the pressure on the piston 114, the force proportional to the surface area to which the pressure is applied, is greater than the force of the first embodiment, and the piston 114 is As soon as it begins to move down to the open position POP, this ensures that the needle 72 moves down more quickly towards the closed position PFA.

  Furthermore, with the new configuration of the lower housing 124 receiving the needle head and spring in mind, as soon as the piston 114 begins to move downward, it comes into mechanical contact with the needle head, followed by the upper surface of the piston. The dimensions can be easily selected so that the axial force acting on 116 is completely transmitted to the needle 72.

  Alternatively, the axial force may be transmitted by hydraulic pressure acting on the needle head without contact. Here, high pressure acts on the needle 72 to generate an axial closing force on the head directed toward the tip and an axial opening force on the weaker tip directed toward the head. Let These antagonistic forces are not balanced. This is because the surface area of the needle exposed to high pressure is not equal and the upper surface of the piston is larger. Therefore, it is possible to consider an injector 10 that does not include a device that artificially reduces the pressure on the tip side, such as the gauged opening or collar described above. In fact, rather than reducing the pressure and the corresponding force at the tip of the needle (this is equivalent to a loss of energy), a larger piston will increase the force on the needle head without loss of energy. Obviously, the pressure of the fuel injected through the injection hole 98 is the pressure at which the fuel flows into the injector 10 without intentional pressure loss.

  With respect to the second embodiment, mainly referring to the differences from the first embodiment described above, the reference numerals and numbers already used are maintained as much as possible, and referring to FIGS. 8, 9 and 10 The present invention will be described.

  These differences are structural differences concentrated on the upper guide 26 and the moving piston 114, and the general function of the injector 10 configured according to the second embodiment is the same as that in the first embodiment already described. .

  The main difference is in the shape of the axial bore 108 of the upper guide and the shape of the moving piston 114. Bore 108 is configured with an upper section 170 that acts only as a slide guide for piston 114, which is higher than the lower section forming upper slide guide 110 in which needle head 132 is disposed. Also has a small diameter. The two sections 170, 110 are joined by a disk-shaped linking surface 172, which may be slightly tapered as shown.

  The moving piston 114 includes a cylindrical body 174 arranged to slide within the upper section 170 of the axial bore 108, a lower collar 176 positioned within the control chamber 112, a collar 176 and a piston body 174. And a connecting shoulder 178 therebetween. The piston further comprises an axial opening 180, which in the illustrated alternative comprises a cross-sectional restriction 182. Further, according to the illustrated alternative, the piston 114 includes a small gauged channel 184 that extends radially and leads to the outer surface of the piston 114 at an axial opening 180. This gauged channel 184 establishes a permanent hydraulic link between the high pressure inlet and the axial orifice 180.

  When the piston 114 is in position within the upper guide 26, the fourth high pressure line 156 opens into the axial bore 108 just above the collar 176. Similar to the previous description, the moving piston 114 has an upper or closed position where the piston shoulder 178 is in leak-proof contact with the disk-shaped surface 172 of the bore and a lower position where the shoulder 178 and the disk-shaped surface 172 are spaced apart from each other. It can move to and from the open position POP.

  From the drawing, when the piston 114 is in the closed position PFP, the fuel placed in the control chamber 112 exits it through the axial opening 180, followed by two sections 162, of the exhaust line. It will be understood that it flows continuously through 164 and through all through return circuit 148 as previously described. Furthermore, when the piston is in the closed position PFP, a small amount of high pressure fuel can circulate through the gauged channel 184 between the inlet and the top surface of the piston. When the valve 24 is closed (PFV), this allows to accelerate the filling of the second control chamber 160 and the pressure rise therein, which pushes the piston back towards the open position POP. Make it possible.

  If the piston 114 does not have a gauged channel 184, when the valve is closed (PFV), the second control chamber 160 is only filled with fuel that passes between the piston 114 and the upper section 170 of the bore 108. Can be done. This filling takes a relatively long time, and the configuration of gauged channel 184 would be preferred without excluding this solution.

  When the piston is in the open position POP, high pressure fuel flows into the control chamber 112, follows the path of arrow F2, passes between the shoulder 178 and the disk-shaped surface 172, pressurizes the chamber 112 and closes the needle 72. It will also be obvious to push back to position PFA.

DESCRIPTION OF SYMBOLS 10 Fuel injector 12 Injector head 14 Injection nozzle 16 High pressure inlet 18 Low pressure outlet 20 Actuating member body 22 Injector nut 24 Control valve 26 Upper guide 28 Nozzle body 30 Lower surface of actuating member body 32 Male screw of actuating member body 34 Female screw of injector nut 36 Bore of Actuating Body 38 Coil 40 Electromagnet 42 Electrical Connection Means 44 Connector 46 Coil Center Bore 48 Valve Spring 50 Valve Body 52 Valve Body Upper Surface 54 Valve Body Lower Surface 56 Axial Bore in Valve Body 58 Low Pressure Chamber 60 Low Pressure Bottom of chamber 62 Bore of hydraulic distributor 64 Armature rod assembly 66 Magnetic armature 68 Valve rod 70 Plug 72 Injector Needle 74 Needle spring 76 Nozzle body wall 78 Nozzle body top surface 80 First large diameter section 82 Second small diameter section 84 Transverse disk-shaped surface of nozzle body 86 Internal space in nozzle body 88 Large chamber 90 Small diameter chamber 92 Upper side Counter bore 94 Lower slide guide 96 Nozzle body seat 98 Injection hole 100 Upper guide upper surface 102 Upper guide large diameter cylindrical portion 104 Upper guide small diameter cylindrical portion 106 Upper guide shoulder surface 108 Upper guide axial bore 110 Upper slide Guide 112 Control chamber 114 Moving piston 116 Upper surface of piston 118 Lower surface of piston 120 Upper housing 122 Peripheral lip 124 Lower housing 126 Annular groove 128 First channel 1 0 second channel 132 needle head 134 needle tip 136 needle seat 138 small cylindrical ridge 140 support shoulder 142 upper needle guide 144 lower needle guide 146 high pressure circuit 148 low pressure return circuit 150 first main high pressure line 152 valve body Second HP line through 154 Third HP line through upper guide 156 Fourth HP line 158 Drain line 160 Second control chamber 162 First short section of discharge line 164 Drain line Second section 166 Main return conduit 170 Upper section of upper guide axial bore 172 Disc shaped connection surface of upper guide axial bore 174 Cylindrical body of piston 176 Lower collar of piston 178 Shoulder of piston 1 80 Axial opening of piston 182 Restriction of section 184 Radial channel A1 Longitudinal axis A2 Second axis PFV Valve closed position POV Valve open position PFA Needle closed position POA Needle open position PFP Piston closed position POP Piston piston Open position

Claims (15)

A fuel injector (10),
A body in which a needle (72) moves between an open position (POA) and a closed position (PFA) under the influence of fuel pressure in the control chamber (112);
When the high pressure supply channel (146, 156, 130) is opened in the chamber (122) and the solenoid valve is in the closed position (PFV) in the direction of the low pressure return circuit (148). When the pressure in the control chamber (112) increases to push the needle (72) toward the closed position (PFA) and when the solenoid valve is in the open position (POV) Controlled by a two-way solenoid valve (24) to allow the needle (72) to move to the open position (POA) as it is evacuated from the control chamber (112) and the pressure therein drops. And a chamber (122) from which a discharge channel (158, 162, 164) is provided. ,
The injector (10) further prevents fuel from flowing directly from the supply channel (146) to the return circuit (148) when the solenoid valve (24) is in the open position (POV). Means (26, 114) for reducing dynamic leakage, said means (26, 114) for reducing dynamic leakage being in fluid communication with said control chamber (112) and said exhaust channel (148) A moving member (114) that moves between an open position (POP) and a closed position (PFP) under the influence of a fuel pressure difference in the second control chamber (160) in a state;
The moving member (114) is a cylindrical piston with an annular groove (126) on its side cylindrical surface, the cylindrical piston being arranged to slide within the bore (108) of the injector body; The supply channel (148, 156) opens into the annular space defined by the annular groove (126) in the bore (108), and the piston (114) allows high pressure fuel to flow into the control chamber (112). The solenoid valve (24) moves to the open position (POP) when the solenoid valve (24) is in the closed position (PFV) and prevents high pressure fuel from flowing into the control chamber (112). When the solenoid valve (24) is in the open position (POV), the fuel moves to the closed position (PFP). Injector (10).   The injector (10) of claim 1, wherein the bore (108) is coaxial (A1) with the bore (110) in which the needle (72) slides.   The piston (114) includes a large-diameter base on which a cylindrical body having a smaller diameter is placed, and a lower surface (118) of the base is disposed to face the needle, and the base and the body The joint surface between the injector body and the sealing body so that when the piston is in the closed position (PFP), the sealing surface and the seat are in a leak-proof contact state that prevents high pressure fuel from flowing into the control chamber. Injector (10) according to claim 1 or 2, wherein the sealing surface acting with the provided sheet is formed.   The injector (1) according to claim 3, wherein the piston (114) further comprises an open channel (180) that causes the control chamber (112) and the second control chamber (160) to be in fluid communication at all times. 10).   The open channel (180) comprises a restriction in cross section that causes a pressure drop so that the pressure in the control chamber (112) is higher than the pressure in the second control chamber (160). 4. The injector (10) according to 4.   The piston (114) is located between the outer cylindrical surface of the cylindrical body and the open channel (180) so as to establish hydraulic communication between the high pressure supply and the second control chamber (160). An injector (10) according to claim 4 or 5, comprising a gauged channel extending radially in the direction.   The piston (114) has a lower surface (118) that faces the needle (72) and forms a top surface of the control chamber (112), and an upper surface (116) that faces the lower surface (118). ) With a single cylindrical body extending in the axial direction (A1), the upper surface (116) being transverse to the injector body when the piston (114) is moved to the closed position (PFP). The injector (10) according to claim 2, wherein the injector (10) is in contact with the surface (54).   Arranged in the control chamber (112) and constantly pressing the needle (72) towards its closed position (PFA) and the piston (114) towards its closed position (PFP). The injector (10) of claim 7, further comprising a spring (74) compressed between a shoulder (140) integral with the needle (72) and the lower surface (118) of the piston (114).   The piston (114) extends between a first channel (128) extending from an outer wall of the piston (114) to the upper surface (116), and between the lower surface (118) and the upper surface (116). A second channel (130), wherein the piston (114) has a bore so that the supply channel (148, 156) is in permanent fluid communication with the first channel (128). 9. The injector (10) according to claim 8, which is disposed within.   The first channel (128) includes an annular groove (126) provided in an outer wall of the piston (114), the first channel (128) extending from the groove (126) and the piston. The injector (10) according to claim 9, wherein said injector (10) opens on said upper surface (116) and said supply channel (148, 156) opens into a space defined by said annular groove (126).   The piston (114) further comprises a ridge on its upper surface (116) that forms a leakage barrier (122) when the piston (114) is in the closed position (PFP), the barrier (122) The cross section (54) of the injector body is in leaktight contact with the first channel (128) and the second channel (138) on either side of the barrier (122). The second control chamber (160) is between the cross section (54) of the injector body and the upper surface (116) of the piston (14). And is defined by the side of the barrier (122) where the second channel (130) and the drain line (158) are open. It is a space, the injector according to claim 9 or claim 10 (10).   12. The barrier (122) is a closed circular lip, the first channel (128) opens into a central portion and the second channel (130) opens into an outer portion. The injector (10) described in 1.   When the needle is in the open position (POA), it is directed towards the needle head (132) so that the pressure of the injected fuel is equal to the fuel inlet pressure in the injector (10). 13. A device according to any one of claims 7 to 12, comprising a device capable of generating a force on the needle (72) directed towards the tip (134) of the needle that is greater than an opening force. The injector (10) described in 1.   The device has a transverse cross section of the needle (72) such that pressurized fuel flowing into the second control chamber (160) applies an increased force to the piston (114). 14. Injector (10) according to claim 13, comprising a larger piston (114).   The piston (114) is less than the opening force applied by the fuel to the tip (134) of the needle (72) when the piston (114) begins to move toward the open position (POP). The increased force applied by the high pressure fuel in the second control chamber (160) to receive a large closing force causes mechanical contact between the piston (114) and the needle (72). The injector (10) according to claim 14, wherein the injector (10) is dimensioned to be completely transmitted to the needle (72) by or by a hydraulic pressure acting on the needle (72).

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