JP2011508853A - Fuel injector - Google Patents

Abstract

The invention relates to a fuel injector, comprising an injector nozzle arrangement for injecting fuel into an internal combustion engine, a control piston moving back and forth inside a piston working space for the actuation of a closing element of an injector nozzle arrangement, a seat-controlled servo-valve arrangement which permits the connection of the piston working space of the control piston, said piston working space communicating with a high-pressure fuel source via an intake throttle, to a relatively pressure-less discharge space in such a way that the control piston, which is biased upon pressure application by the high-pressure fuel source in the direction of the end position associated with the closed position of the closing element of the injector nozzle arrangement, makes a stroke motion which moves the closing element to the open position thereof, wherein the servo-valve arrangement, which is located in an injector body, comprises a valve seat body and a sleeve-like closing body that can be shifted to the open position thereof by an electromagnet against a closing force, said closing body cooperating with an annular seat at the valve seat body and being slideably movable on an axial projection located at the valve seat body centrally with respect to the annular seat.

Description

  The present invention relates to a fuel injector, an injector nozzle device for injecting fuel into an internal combustion engine, a control piston that operates a closing element of the injector nozzle device and that can move in a piston working chamber, and a seat. A servo valve device to be controlled, the servo valve device being able to connect the piston working chamber of the control piston, which communicates with the fuel high pressure source via the inflow restrictor, to a substantially non-pressure outflow chamber. The control piston, which is loaded toward the end position corresponding to the closed position of the closing element of the injector nozzle device when pressure is applied by the fuel high pressure source, carries out a stroke leading the closing element to its open position. The servo valve device arranged in the injector body is connected to the valve seat and the actuator or electromagnet. A sleeve-shaped closure that can be moved to an open position against chain forces, the closure cooperating with a ring-shaped seat in the valve seat and against the ring-shaped seat And is slidably guided along an axial extension disposed concentrically on the valve seat, the axial extension being different from the inner cross-section of the sleeve-shaped closure. A valve chamber, which is provided with a transverse section and is formed in an axial extension inside the closure and in communication with the piston working chamber of the control piston in the open position of the sleeve-like closure, It relates to the type connected to the outflow chamber.

  Today's automobiles usually have a fuel injection type internal combustion engine. In an internal combustion engine, in particular, a direct-injection diesel engine, a fuel injector provided with an injector nozzle device is assigned or correspondingly disposed in each cylinder or combustion chamber of the internal combustion engine in order to inject fuel into each combustion chamber. Such a fuel injector has one control piston, which can be moved in a piston working chamber, for operating the closing element of the injector nozzle device, and a servo valve device whose seat is controlled. The servo valve device can connect the piston working chamber of the control piston, which communicates with the high-pressure fuel source via the inflow restrictor, to the almost non-pressure outflow chamber. A control piston loaded towards the end position corresponding to the closing position of the closing element of the device is adapted to carry out a stroke leading towards the opening position towards the opening position, the injector body Servo valve device placed inside the sleeve and a sleeve that can move to the open position against the closing force by an electromagnet And an axial extension disposed on the valve seat concentrically with the ring seat in the valve seat. A valve chamber which is slidably guided along the sleeve and is formed in an axial extension inside the closure body in the open position of the sleeve-shaped closure body and communicates with the piston working chamber of the control piston Is connected to the outflow chamber under pressure relief.

  Such a fuel injector is described, for example, in EP1612403A1. In this known fuel injector, the axial extension arranged on the valve seat body is axial and penetrates the entire inner chamber of the sleeve-shaped closure body of the servo valve device. A stopper for restricting the axial stroke of the sleeve-shaped closing body is arranged at a portion extending from the end of the closing body away from the valve seat. In the vicinity of the valve seat, a ring groove-shaped recess is formed in the axial extension, and as a result, a valve chamber formed in a corresponding ring shape is provided inside the valve closing body. The valve chamber is in communication with the piston working chamber of the control piston through a hole arranged in the valve seat body and provided with an outflow restrictor as soon as the sleeve-shaped closure is lifted from its seat in the valve seat body, and the sleeve Connected to the outflow chamber located outside the shaped closure.

  Seal the ring gap between the inner periphery of the sleeve-shaped closure and the outer periphery of the axial extension on the side of the ring-shaped valve chamber away from the valve seat inside the sleeve-shaped closure This is done by a high pressure resistant seal member.

  This known fuel injector has a troublesome or costly structure for the manufacturer. In the inside of the sleeve-shaped closure of the servo valve device, an axial blind hole is provided in the axial extension to connect the piston working chamber of the control piston and the valve chamber so that the liquid flows. The blind hole is penetrated by a radial hole with a plurality of openings leading to the valve chamber in the region of the narrow portion of the ring groove shape forming the valve chamber of the axial extension. Depending on the cycle of the opening and closing stroke of the servo valve device, these holes are loaded by extremely large pressure pulsations, so that the material forming the valve seat and the axial extension has the stability of known fuel injectors. High demands must be made to guarantee.

  According to an undisclosed patent application (R.316364, R.314516), a valve chamber formed in a sleeve-shaped closure is located in the closure at the end of the closure opposite the valve seat. It is closed by a guide rod that enters in the form of a plunger, which is pressed against the bottom surface of the injector body by the pressure in the valve chamber, and thus is pushed to a position perpendicular to the bottom surface, thereby closing the closure body accordingly. Orient. The closing body cooperates with a flat seat parallel to the bottom surface, and this flat seat surrounds the opening in the valve seat body connecting the piston working chamber with the valve chamber in a ring shape that leads to the valve chamber. It is out. Such an injector has the advantage of having a very high pressure load resistance. However, the longitudinal axis of the closure may shift somewhat laterally due to the fact that the guide rod has a corresponding mobility. As a result, the closure must cooperate with the correspondingly offset ring area of the seat in a sealing action. This makes the closing characteristic of the servo valve device critical. This is basically true even when the valve seat according to the patent application has a spherically-shaped surface.

  Therefore, an object of the present invention is to provide a fuel injector that has a structure that is relatively insensitive to pressure pulsation, can be easily manufactured, and the servo valve device has good closing characteristics. It is.

  In order to solve this problem, according to the present invention, in a fuel injector of the type described at the beginning, a valve as described in the characterizing portion of claim 1, i.e., a valve chamber or an inner chamber of a sleeve-shaped closing body. The end of the seat opposite to the axial extension is closed by a plunger rod that is axially entering the sleeve-shaped closure, the side of the plunger rod opposite the axial extension Is supported at the bottom of the injector body in the axial direction, and the valve chamber communicates with the piston working chamber via a passage extending axially through the axial extension and provided with a throttle. I was like that.

  The present invention is based on the general idea that a member separate from the valve seat is provided in order to close the end of the sleeve-shaped closure of the servo valve device opposite to the valve seat. Yes. This simplifies the construction and manufacture of the valve seat body and avoids the need to place an area sensitive to strong alternating loads in the axial extension of the valve seat body.

  Further, according to the present invention, since the closing body is guided on the valve seat side, the ring area on the valve seat side on which the closing body cooperates with a sealing action has a fixed position that cannot change in principle. Have. In the present invention, a guide on the valve seat side of the closing body and a member separate from the valve seat, which serves to seal the end of the closing body opposite to the valve seat, are provided. This makes it possible to achieve a high stability of the injector against pressure pulsations and a very good closing characteristic of the servo valve device of the injector. At the same time, since the passage connecting the valve chamber and the piston working chamber is formed as an axial passage in the axial extension portion, simple manufacturability is guaranteed.

  In an advantageous configuration of the invention, the end of the plunger rod opposite to the valve seat body is supported in surface contact with the bottom by a disc-shaped base member arranged immovably on the plunger rod. In this case, further, the base member is arranged with radial play at the bottom, and the sleeve-shaped closure body is guided at least restricted in the axial extension of the valve seat body in a swingable manner. Is advantageous. During operation of the fuel injector, the base member of the plunger rod is pressed against the bottom of the injector body by the hydraulic pressure in the valve chamber inside the sleeve-shaped closure of the servo valve device. The plunger rod thereby occupies a position perpendicular to the bottom and guides the sleeve-shaped closure in a direction perpendicular to the bottom. The centering of the closure body relative to the seat in the valve seat body is undertaken in this configuration by the axial extension of the valve seat body. That is, as a result, an arrangement form having a self-adjustment capability is obtained.

  In an alternative configuration, the end of the plunger rod opposite to the valve seat is supported on the bottom of the injector body in a radially movable and swingable manner, and the sleeve-shaped closure is Along the axial extension of the valve seat body, it is guided so as to be able to move in a non-oscillating manner. In this configuration, the exact stroke direction of the sleeve-shaped closure and the radial orientation of the sleeve-shaped closure are determined by the valve seat or the guide element arranged on the valve seat, and the plunger rod Mainly takes on the problem of wear at the end of the sleeve-shaped closure opposite the valve seat.

  The ring gap between the inner periphery of the sleeve-shaped closure and the outer periphery of the plunger rod is a general-purpose seal member inserted into a ring groove in the outer periphery of the plunger rod, such as a high-pressure resistant seal member. Can be sealed. This is true for all embodiments of the invention. Alternatively, however, it is also advantageous to form the ring gap as a throttle gap which has a sealing action against high pressures, i.e. in this case the radial dimension of the ring gap is correspondingly small and the axial dimension is corresponding. Even in the operation stage where the maximum pressure in the valve chamber is generated inside the sleeve-shaped closing body, very little leakage flow is generated. With this configuration, the sleeve-shaped closure body is hydraulically supported by the plunger rod during operation of the fuel injector, and as a result, direct contact between the inner periphery of the closure body and the outer periphery of the plunger rod is achieved. The advantage is that it can be avoided. Furthermore, assembly is simplified by eliminating a separate sealing element.

  An advantageous embodiment of the invention will now be described with reference to the drawings.

  In addition, the present invention is not limited to the illustrated and described embodiments, and the individual features illustrated and described can be arbitrarily combined.

It is a longitudinal cross-sectional view which shows 1st Embodiment of a fuel injector. It is a longitudinal cross-sectional view which shows another embodiment of a fuel injector.

  The fuel injector shown in FIG. 1 in a longitudinal section including an axis has an injector body 1 with a stepped axial hole 2. 1, the valve seat body 3 is supported in the axial direction by a collar 3 'formed integrally with the valve seat body 3. In order to fix the valve seat 3 in the axial hole 2, a male threaded ring 4 works, this male threaded ring 4 is screwed into the female thread section of the axial hole 2 and is adjusted by screwing. Are fastened to the opposite end faces of the collar 3 '. The high-pressure region 2 'is separated from the outflow region or low-pressure region 2' 'in the axial hole 2 by the valve seat body 3 or its collar 3', and the high-pressure region 2 'is separated by a conduit not shown. Always in communication with a high pressure source for fuel, the outflow region or low pressure region 2 '' is connected to a substantially non-pressure fuel reservoir via a return line (not shown).

  A blind hole serving as a piston working chamber 5 for the control piston 6 is arranged at the lower end of the valve seat body 3.

  The control piston 6 is coupled to a nozzle needle or other closing element of an injector nozzle device (not shown) of the fuel injector. In the illustrated lower end position of the control piston 6, the injector nozzle device is closed. When the control piston 6 is moved upward as seen in FIG. 1, the injector nozzle device is opened, so that fuel is injected into the combustion chamber to which the internal combustion engine belongs or is correspondingly arranged.

  The piston working chamber 5 communicates with the high pressure region 2 ′ of the axial hole 2 through an inflow restrictor 7 formed as a radial hole of the valve seat body 3. The piston working chamber 5 communicates with the valve chamber 10 via an axial hole 2 which is arranged in the valve seat body 3 and is provided with an outflow throttle and is coaxial with the piston working chamber 5. The valve chamber 10 is disposed inside the sleeve-shaped closing body 12 of the servo valve device 13 in front of the end surface of the axial extension 11 disposed in the valve seat body 3 when viewed in the axial direction. At the end of the sleeve-shaped closure 12 opposite to the valve seat body 3, it is closed by a plunger rod 14 entering the sleeve-shaped closure 12. In the valve chamber 10, against the hydraulic pressure generated in some cases, the plunger rod 14 uses a disk-shaped base member 15 that is immovably disposed at the upper end portion as viewed in FIG. Is supported in a large area. The base member 15 serves as a receiver for a closing spring 17 formed as a compression coil spring, which forms a sleeve-shaped closing body 12 as a valve seat body 3 at its lower end as viewed in FIG. And pressed against a conical valve seat 18 coaxial with the axis of the axial extension 11. Against the closing force of the closing spring 17, the sleeve-shaped closure 12 can be lifted from the closed position shown in FIG. 1 by means of a ring-shaped electromagnet 19, which electromagnet 19 is 12 cooperates with a radial mover web 20 arranged in a star shape. In the open position of the closing body 12 of the servo valve device 13, the valve chamber 10 communicates with the outflow region or the low pressure region 2 ″ of the axial hole 2. At this time, a connection with almost no squeezing action is produced between the valve chamber 10 and the low pressure region 2 ″ of the axial hole 2. This is because the cross-section of the axial extension 11 of the valve seat body 3 is substantially star-shaped, the axial extension 11 being an axial web arranged in a star shape, and a sleeve-shaped closure. This is because it is slidably in contact with the 12 inner peripheral surfaces. In the circumferential direction, a large free space remains between the axial webs, through which the valve chamber 10 can be connected to the axial hole 2 when the closure 12 is lifted from the valve seat 18. Communicated with the low pressure region 2 ″.

  Instead of the axial extension 11 with an axial web arranged in a star shape, axial extensions formed in the form of triangles, squares or polygons may be provided.

  The edge that is radially connected to the axial hole of the closure 12 on the end face side is formed as a conical hole, the opening angle of which is larger than the conical angle of the conical valve seat 18. . This ensures, on the one hand, a ring-like line contact between the closing body 12 and the valve seat 18 when the closing body 12 occupies the closed position. On the other hand, when the closing body 12 occupies the open position, a ring-shaped open gap in which the axial cross section increases radially outward is obtained.

The fuel injector shown in FIG. 1 operates as described below:
When the closed body 12 of the servo valve device 13 occupies the closed position shown in the drawing, the high pressure region 2 'of the axial hole 2 communicating with the high fuel pressure source is provided in the piston working chamber 5 of the control piston 6. There is pressure at. By supplying power to the electromagnetic coil 19 ′ of the electromagnet 19, the electromagnet 19 is activated, and as a result, the mover web 20 that magnetically cooperates with the electromagnet 19 is pulled up, and the closing body 12 resists the force of the closing spring 17. Then, it is lifted from the closed position shown in FIG. As a result, the piston working chamber 5 of the control piston 6 is connected via the valve chamber 10 to the outflow region or the low pressure region 2 ″ of the axial hole 2 which is connected to a substantially non-pressure fuel tank. The pressure in the chamber 5 drops correspondingly, in which case the time lapse of the pressure drop is substantially due to the dimensions of the inlet throttle 7 and the dimensions of the outlet throttle 9 which has a throttle resistance smaller than the throttle resistance of the inlet throttle 7. Predetermined. Based on the pressure drop, the control piston 6 is lifted by hydraulic pressure, which is coupled to the control piston 6 and is against the normally needle-shaped closing element of the injector nozzle device (not shown), Acts in the opening direction. At the same time, the high-pressure region 2 ′ of the axial hole is connected to the fuel chamber to which the internal combustion engine belongs or correspondingly arranged via the now open injector nozzle device, and fuel is injected into this fuel chamber. .

  During the stroke movement of the closing body 12, a conical valve seat 18 is provided by the axial extension 11 or an axial web of the axial extension 11 slidably contacting the inner peripheral surface of the closing body 12. Are centered and held in the radial direction. In this case, the plunger rod 14 occupies a correspondingly centered position, ie occupies a coaxial position with respect to the axial extension 11. This is because the disk-shaped base member 15 is arranged with sufficient radial play inside the ring-shaped electromagnet 19 and makes contact with the bottom 16 perpendicular to the axis of the axial extension 11 in plane. Because. In order to keep the unfavorable forcing acting on the closure body 12 as small as possible, in an advantageous embodiment, the closure body 12 is pivotally guided in the axial extension 11, so that the closure body 12. The direction of the stroke is determined solely by the plunger rod 14, which is oriented perpendicular to the bottom 16 using a base member 15 that is in surface contact with the bottom 16. It is supposed to be retained.

  The first point in which the embodiment shown in FIG. 2 differs from the embodiment shown in FIG. 1 is that the plunger rod 14 is swingably supported on the bottom 16 of the injector body 1. The supported end of the plunger rod 14 is arranged inside the ring disc 21 with a certain amount of radial play, or the ring disc 21 has a certain amount of radial play inside the ring-shaped electromagnet 19. Is arranged so that the support point of the plunger rod 14 at the bottom 16 can be shifted radially relative to the rod axis. Further, the closing body 12 shown in FIG. 2 is guided so as to be slidable in the axial direction along the axial extension 11 of the valve seat body 3 so as not to swing, that is, with respect to the axis of the valve seat body 3. The position of the closing body 12 in the radial direction and the stroke direction of the closing body 12 are determined solely by the axial extension 11, so that the axial extension 11 has a sufficient axial length and is Full overlap with the closure 12 in the direction. The position of the plunger rod 14 and the orientation of the plunger rod 14 in the axial direction are then defined by the closure 12 and correspondingly indirectly by the axial extension 11. Further, in the embodiment of FIG. 2, a ring disc-shaped flat or smooth valve seat 18 is provided on which the closing body 12 rests or contacts in a circular line contact in the closed position. To do. For this purpose, the end face of the closing body 12 facing the valve seat 18 is lightly conical, so that the transition between the end face on the valve seat side of the closing body 12 and the axial hole of the closing body 12 is achieved. The part is formed with an acute ring edge that cooperates with the valve seat 18.

  Since the mode of operation of the embodiment of FIG. 2 corresponds to the mode of operation of the embodiment of FIG. 1, repeated description is omitted.

  In both the embodiment of FIG. 1 and the embodiment of FIG. 2, the ring gap between the outer peripheral portion of the plunger rod 14 and the inner peripheral portion of the closing body 12 is sealed with high pressure resistance by a seal ring. This seal ring can be arranged in the circumferential groove of the plunger rod 14 in the form of a piston ring similar to the seal ring 22 of the control piston 6.

  Instead of the above arrangement, another advantageous embodiment of the invention is such that, in the event of a large hydraulic pressure difference between the axial ends of the ring gap, in practice very little leakage flow can occur. It is also possible to form the ring gap as a high-pressure sealable throttle gap. This can be ensured by an extremely narrow radial gap dimension and a sufficiently large axial overlap between the closure 12 and the plunger rod 14. Special advantages of such a configuration include the following. That is, with this configuration, during the stroke movement of the closing body 12 relative to the plunger rod 14, no mechanical contact or friction occurs between the plunger rod 14 and the closing body 12, and the closing body 12 14 will be supported hydrodynamically through the liquid layer.

  In some cases, the control piston 6 may be arranged in the axial hole of the valve seat body 3 forming the piston working chamber 5 with a high-pressure sealed throttle gap.

  Such a throttling gap provides another advantage of eliminating a seal ring that must be carefully handled during assembly.

  Unlike the embodiment shown in FIG. 2, the end of the plunger rod 14 supported by the bottom 16 may be formed as a mushroom-shaped head, omitting the ring disc 21, and this mushroom-shaped head. Is supported by the bottom 16 on its spherical side and forms a spring receiving surface for the closing spring 17 on the opposite side of the bottom 16. The diameter of the mushroom head in this case advantageously still leaves some radial play inside the ring-shaped electromagnet 19 to direct the plunger rod 14 without forcing, ie the plunger rod 14 It is possible to occupy a coaxial position with respect to the closing body 12 without forcing.

Claims (8)

A fuel injector,
An injector nozzle device for injecting fuel into the internal combustion engine;
A control piston (6) operable in a piston working chamber (5) for operating a closing element of the injector nozzle device;
A servo valve device (13) for controlling the seat, the servo valve device (13) having a piston working chamber of a control piston communicating with a fuel high pressure source via an inflow throttle (7), A control piston (6) which can be connected to a substantially pressureless outlet chamber (2 ″) and is loaded towards the end position corresponding to the closing position of the closing element of the injector nozzle device when pressure is applied by the high-pressure fuel source. ) To carry out the process of leading the closing element to its open position,
A servo-valve device (13) disposed in the injector body (1) can be moved to an open position against a closing force (17) by a valve seat (3) and an actuator or an electromagnet (19). And the closure (12) cooperates with the ring-shaped seat (18) in the valve seat (3) and is against the ring-shaped seat (18). Are slidably guided along an axial extension (11) arranged concentrically on the valve seat (3), the axial extension (11) being sleeve-shaped closure (12 ) With a non-circular cross-section different from the inner cross-section of the sleeve) and formed in the axial extension (11) inside the closure (12) in the open position of the sleeve-like closure (12) Valve chamber in communication with the piston working chamber (5) of the control piston (6) 10), in what format are connected to the outflow chamber (2 '') in discharge pressure,
The end of the inner chamber of the valve chamber (10) or the sleeve-shaped closure (12) opposite to the axial extension (11) of the valve seat (3) is the sleeve-shaped closure in the axial direction. (12) Closed by a plunger rod (14) entering the inside, the end of the plunger rod (14) opposite to the axial extension (11) is located on the injector body (1). Is supported axially on the bottom (16),
The valve chamber (10) communicates with the piston working chamber (5) via a passage (8) that passes through the axial extension (11) in the axial direction and is provided with a throttle (9). A fuel injector characterized by   The end of the plunger rod (14) opposite the valve seat (3) faces the bottom (16) by means of a disc-shaped base member (15) which is immovably arranged on the plunger rod (14). The fuel injector according to claim 1, wherein the fuel injector is supported in contact.   3. The fuel injector according to claim 1, wherein the base member (15) or the plunger rod (14) is arranged with radial play on the bottom (16).   4. The fuel injector according to claim 1, wherein the sleeve-shaped closure body (12) is pivotally guided in the axial extension (11).   The plunger rod (14) is supported at the bottom (16) in a radially movable and swingable manner at the end opposite to the valve seat (3). The fuel injector according to item.   The fuel injector according to claim 5, wherein the end of the plunger rod (14) supported by the bottom (16) is formed with a spherical end face.   7. The fuel injector according to claim 1, wherein the sleeve-shaped closure is guided in a non-swingable manner along the axial extension. 11.   The ring gap between the inner circumference of the sleeve-shaped closure (12) and the outer circumference of the plunger rod (14) is formed as a throttle gap which has a sealing action against high pressure. The fuel injector according to any one of the above.

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