WO2009146974A1

WO2009146974A1 - Fuel injector with perforated seat nozzle

Info

Publication number: WO2009146974A1
Application number: PCT/EP2009/054730
Authority: WO
Inventors: Wilhelm Christ; Thomas Pauer; Werner Teschner
Original assignee: Robert Bosch Gmbh
Priority date: 2008-06-02
Filing date: 2009-04-21
Publication date: 2009-12-10
Also published as: EP2286080A1; DE102008002146A1

Abstract

The invention relates to a fuel injector (110) for injecting fuel into a combustion chamber of an internal combustion engine. The fuel injector (110) has at least one injection valve member (120), which is mounted in an axially movable manner in a valve body (114), for opening up and closing off at least one injection opening (124). The valve body (114) has at least one valve seat surface (122) at an end facing toward the combustion chamber. The injection opening (124) is provided in the valve seat surface (122). The injection valve member (120) has at least one valve sealing surface (126, 128, 130). The valve sealing surface (126, 128, 130) closes off the injection opening (124) in a closed state of the fuel injector (110). The fuel injector (110) also has at least one control valve (112) for hydraulically activating the injection valve member (120). The control valve (112) is designed such that, in a closed state of the control valve (112), substantially no axial hydraulic force acts on the control valve (112).

Description

May 23, 2008

description

title

Fuel injector with seat hole nozzle

State of the art

The invention is based on known fuel injectors for supplying combustion chambers of self-igniting internal combustion engines with fuel. For this purpose, both stroke-controlled and pressure-controlled injection systems can be used. In addition to pump-nozzle units, pump-line-nozzle units, fuel injection systems are also used as fuel injection systems. Storage injection systems (common rail systems) advantageously make it possible to adapt the injection pressure to the load and speed of the internal combustion engine. In accumulator injection systems, a fuel injector is generally pressurized with pressurized fuel from a high pressure accumulator (common rail). The fuel injector has an actuator, by means of which the injection process is controlled. The present invention particularly relates to common rail systems, but in principle also an application to other types of fuel injectors is possible.

Fuel injectors generally have a valve body in which an injection valve member is mounted axially displaceable. For metering the fuel, in particular diesel fuel, one or more injection openings are provided at the lower, the combustion chamber facing the end of the valve body, which are closed or opened by the injection valve member, that are separated from the fuel supply or connected thereto.

The design of the injection process, in particular the release or the closing of Einspritzöffhungen, for the combustion process is of crucial importance. Here, a distinction is made between so-called blind-hole nozzles and seat-hole nozzles. In blind-hole nozzles remains after injection in a so-called blind hole below the injection valve member, a small amount of fuel. The at least one injection valve opening usually branches off in the region of this blind hole. Such blind hole nozzles, as described for example in DE 196 34 933 Al in various Although embodiments are described, while having the advantage of increased long-term stability and good controllability, but sometimes lead to an increased emissions problem. So remains in the blind hole after injection usually a small remainder of fuel, so that the blind hole has a high Schadvolumen. If this fuel evaporates, the hydrocarbon emission generally increases.

In the case of seat-hole nozzles, which are often referred to as "valve covered orifices", the injection opening is closed by the valve sealing surface of the injection valve member in a closed state of the fuel injector and are covered so that evaporation of fuel can be avoided.

However, it has been shown that seat hole nozzles lead to strong pressure fluctuations in the injection system even at absolutely constant injection pressure. For example, cavitations frequently occur in the region of the needle seat and in a residual volume below the injection valve member, which cavities can lead to rapidly changing, greatly varying inlet conditions for the flow through the injection openings and thus to different injection jet properties. In addition, fluctuations in the position of the injection valve member are noticeable in asymmetric flows in these injection valve types, which also leads to a non-uniform injection jet pattern.

This comparatively poor stability of the injection process in conventional seat-hole nozzles has, despite the reduced pollutant emission behavior, led to this nozzle design being more or less completely displaced from the market and largely replaced by blind-hole applications. However, the hydrocarbon emission problem of such blind-hole nozzles is still of considerable importance, in particular for newer emission limit values.

Disclosure of the invention

The invention is based on the recognition that the properties of fuel injectors with seat hole nozzles can be significantly improved if the actuator control of the fuel injectors is made uniform. In particular, pressure fluctuations, such as the pressure fluctuations caused by the described cavitations, can lead to a feedback to the actuator, which in turn can adversely affect the injection process. To effectively avoid the effects described, therefore, an actuator must be used, which acts on the injection valve member such that it quickly releases the openable cross-section and thus a fast-switching valve provides. By such a fast-switching valve, the use of a seat hole nozzle is possible, and it can be the emission advantages of such seat hole nozzles realize at the same time high stability of the injection process.

A basic idea of the present invention is therefore that the fast-opening properties which are required for seat-hole nozzles can be realized, in particular, by means of force-balanced or pressure-balanced actuators.

Accordingly, a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine is proposed which has at least one injection valve member axially displaceably mounted in a valve body for releasing and closing at least one injection opening. Preferably, as described above, this fuel injector may be a fuel injector for a storage injection system.

According to the invention, the fuel injector is designed according to the seat hole nozzle principle. For this purpose, the valve body has at least one valve seat surface, in particular at least one conical valve seat surface, at an end facing the combustion chamber. As an alternative or in addition to conical valve seat surfaces, however, other configurations of valve seat surfaces may also be provided, for example stepped valve seat surfaces or the like. The term tapering refers to a surface with an angle different from 0 ° to the injector axis, in particular an angle between 0 ° and 90 °, for example between 10 ° and 80 °. The at least one injection opening is wholly or partly provided in this conical valve seat surface. The injection valve member in turn has at least one valve sealing surface, in particular at least one conical valve sealing surface, which closes the injection opening in a closed state of the fuel injector. Again, however, other configurations of valve sealing surfaces may in turn be provided instead of or in addition to conical valve sealing surfaces.

In other words, should the at least one valve sealing surface in the closed state of the fuel injector rest on the valve seat surface, wherein the at least one injection port is directly in contact with the valve sealing surface and thus is closed by the latter. For example, the at least one valve sealing surface and the at least one valve seat surface may at least partially have the same cone angle in the region of the at least one injection opening, so that the valve sealing surface rests flush on the valve seat surface in the region of the injection opening. In this way, as described above, even in the closed state of the fuel injector no evaporation of Hydrocarbons from an optionally present below the injection valve member space or a bore occur.

To realize the above-described idea of a fast opening, a control valve is furthermore provided, which is designed to be force-balanced and / or pressure-balanced. This control valve is used for hydraulic actuation of the injection valve member. This control can be done for example via one or more control chambers, for example by means of the control valve by opening the control valve causes a pressure relief of the control chamber and thus a stroke of the injection valve member can be effected.

The control valve is designed according to the invention force or pressure balanced. Accordingly, the control valve is arranged such that substantially no net axial hydraulic force acts on the control valve in a closed state of the control valve. In particular, it should not be possible to exert an axial force in the closed state of the control valve on the control valve or an actuator of the control valve in a hydraulic fluid, for example fuel, which is present between the control valve and the injection valve member.

Such force or pressure balanced control valves are described for example in DE 10 2006 021 736 Al. Reference may be made in full to the embodiments described in the following. The finding of the invention is based on the fact that such pressure-balanced control valves can be used in particular for solving the control problem described above in seat hole nozzles.

The injection valve member may have one, two or more (eg, conical) valve sealing surfaces. At least one of these valve sealing surfaces is intended to find a correspondence in the at least one (for example conical) valve seat surface, so that, as described above, the at least one injection opening is closed in the closed state of the fuel injector. If at least two conical valve seat surfaces are provided, then it is particularly preferred if these two conical valve sealing surfaces have different cone angles. In this regard, reference may be made, for example, to the embodiments constructed according to the VCO principle of DE 196 34 933 A1. At least one step and / or at least one groove can be provided between the at least two valve sealing surfaces.

The at least one control valve may in particular comprise at least one actuator. It is particularly preferred if the control valve has at least one solenoid valve. This solenoid valve may in turn have at least one armature, on which a sealing surface may be formed. This sealing surface should be adjustable to close the control valve in a valve seat. The anchor in turn should be movable between an upper and a lower stroke stop. Preferably, the armature without armature guide is designed.

In order to achieve the above-described pressure balance or force balance, the control valve, in particular the solenoid valve, preferably be designed such that this in the closed state of the control valve no hydraulic surface perpendicular to the axial direction, ie the direction of the longitudinal extent of the fuel injector or the injection valve member , having. Slight bevelled edges can be neglected, provided that they are small compared to, for example, a spring force of a spring element provided in the actuator, for example a helical valve spring.

For example, in the above-described solenoid valve with the at least one anchor, a bore may be provided in the armature. This bore, which can be configured for example as a central, concentric bore relative to the axis of the fuel injector, can serve to receive a push rod. This push rod, which is preferably not connected to the armature, but which is preferably mounted slidably in the armature, or the bore, can serve to absorb axial pressure forces. For this purpose, for example, the push rod may be fixedly mounted at its upper end and at a lower end of a control chamber or a hole to assign a control chamber with an end face. This push rod thus serves by means of, for example, said end face for receiving axial pressure forces, whereas the armature and thus the solenoid valve are not acted upon by hydraulic forces, provided that the solenoid valve is in its closed state.

The anchor can, as proposed in DE 10 2006 021 736 Al, further comprise at least one resilient guide lip. This resilient guide lip can rest for example on the lower stroke stop on a support surface, so that the armature is aligned. The guide lip and the sealing surface on the armature and the bearing surface and the valve seat of the control valve can be ground in particular at the same height, which considerably simplifies the manufacturing process of the solenoid valve.

It is particularly preferred if the diameter of the push rod is at least approximately equal to an inner diameter of the valve seat. In other words, the push rod be mounted sealingly in the bore in the anchor, so that between the push rod and the armature escape of pressure is prevented.

As described above, a distinction is made linguistically between a closed and an open state of the fuel injector and a closed and open state of the control valve. The closed state of the fuel injector is defined such that in this closed state, the at least one Einspritzöffhung is closed by the injection valve member, whereas in an open state of the fuel injector, the Einspritzöffhung is released. The closed state of the control valve, however, corresponds to a state in which the control valve is pressed into the valve seat, so that the armature is located in the lower stroke stop. In the open state of the control valve, however, the armature is in the upper stroke stop, so that, for example, a control chamber can be pressure relieved.

In this case, the erfmdungsgemäße fuel injector can be driven in principle inverse or non-inverse, with the non-inverse control is preferred due to the simple control. With this non-inverse control, when the magnet is energized, the at least one injection opening is released and fuel is injected into the combustion chamber of the internal combustion engine. By energizing the magnet, however, the armature is lifted from the valve seat, so that a pressure relief can take place, and the injection process is triggered.

The proposed fuel injector in one or more of the embodiments described above thus has the advantage over conventional fuel injectors of reduced pollutant emission while maintaining high stability and reliability. In addition, the fuel injector is comparatively easy to manufacture and differs in the manufacturing cost is not or only slightly different from conventional, corresponding to the prior art Rraftstoffϊnjektoren.

Brief description of the drawings

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

Show it:

Figure 1 is a fragmentary sectional view of a control valve of a fuel injector according to the invention; and Figure 2 is a fragmentary sectional view of one end of an injection valve member of the inventive fuel injector.

In FIGS. 1 and 2, various regions of a fuel injector 110 according to the invention are shown by way of example. 1 shows a detail of the fuel injector, in which a control valve 112 is shown as an example, whereas FIG. 2 shows a section of a nozzle region of the fuel injector 110. In the following, reference is made to both figures, but this does not preclude a different embodiment of the exemplary embodiments. For example, the control valve 112 according to FIG. 1 can be combined with other types of nozzle areas, and the configuration of the nozzle area according to FIG. 2 with other types of control valves 112 according to the invention.

The fuel injector 110 has a valve body 114, which may have a modular design, for example. The valve body 114 has an injector axis 116. In the valve body 114, a needle chamber 118 is arranged, which extends parallel to the injector axis 116. In this needle chamber, an injection valve member 120 is received and movably mounted parallel to the injector axis 116. For example, the injection valve member 120 may be guided at one or more locations within the needle chamber 118. The valve body 114 has a conical valve seat surface 122 in the end region of the needle chamber 118 at its lower region, which is assigned to the combustion chamber when used in an internal combustion engine. In the region of this valve seat surface 122, at least one injection opening 124 is provided, wherein usually a plurality of such injection openings 124 are present.

The injection valve member 120 has a conical valve sealing surface 126 at its lower end. 2, which may correspond to one or more of the exemplary embodiments listed in DE 196 34 933 A1, is divided into two parts and has a first valve sealing surface 128 and a second valve sealing surface 130. In this case, the first valve sealing surface 128, which is arranged below the second valve sealing surface 130, is adapted from its cone angle to the cone angle of the valve seat surface 122. The second valve sealing surface 130, however, has a smaller cone angle. Between the two valve sealing surfaces 128, 130, a step 132 is arranged with a groove 134. In this way, an annular space 136 is formed in the region of the groove 134. The arrangement shown has the advantage that it has a particular low wear. If the injection valve member 120 is pressed into the valve seat surface 122 in a closing direction 138 of the fuel injector, the first valve sealing surface 128 contacts the wall of the valve body 114 in the region of the injection opening 124 and closes the injection opening 124. The state shown in FIG on the other hand, when the injection valve member 120 is moved against the closing direction 138, the valve sealing surface 126 lifts from the valve seat surface 122, and fuel from the needle chamber 118 can flow to the injection port 124 and be injected from there into the combustion chamber. Usually, the injection valve member 120 is acted upon by a nozzle spring, not shown in the figures, with a spring force in the closing direction 138. Via a hydraulic surface, which is also not shown, this spring force counteracts a hydraulic force through the fuel, wherein the spring force usually exceeds the hydraulic force.

For controlling the fuel injector, the injection valve member 120 has at its upper end a control piston 140 and / or is connected to such a control piston 140. Also, this control piston 140 is mounted in the axial direction movable in the needle chamber 118 and / or in a separate control piston chamber. The movement of the control piston 140 takes place in the embodiment shown in Figure 1, which corresponds for example to an embodiment of DE 10 2006 021 736 Al, hydraulically. For this purpose, the control piston 140 opens with its side facing away from the injection valve member 120 in a control chamber 142. Via an inlet throttle 144, the control chamber 142 is connected to a fuel inlet 146. As a result, fuel under system pressure can flow into the control chamber 142. About an outlet throttle 148 of the control chamber 142 is relieved. For this purpose, the outlet throttle 148 is hydraulically connected to a return, not shown in Figure 1. In order to fill the control chamber 142 with fuel under system pressure, the outlet throttle 148 can be closed by means of the control valve 112. In the embodiment shown in Figure 1, the control valve 112 comprises a solenoid valve 150. In principle, however, other types of actuators can be used, for example piezo actuators, which can be operated according to the invention pressure-balanced.

For closing the outlet throttle 148 with the aid of the solenoid valve 150, a sealing surface 152, which is formed on an armature 154 of the solenoid valve 150, is placed in a valve seat 156 in the case of the solenoid valve 150 designed according to the invention. In the illustrated embodiment, the sealing surface 152 and the valve seat 156 form a flat seat. However, it is also conceivable any further, known in the art valve seat, in which no axial forces acting on the closing element. FIG. 1 shows a closed state of the control valve 112, in which the inlet throttle 144 is hydraulically separated from the return flow by the control valve 112 by means of the control valve 112. In order to receive the pressure force acting in the axial direction in the case of such a closed magnetic valve 150, a bore 158 is formed in the armature 154. In this bore 158, a push rod 160 is added. So that no axial pressure forces act on the armature 154 when the solenoid valve 150 is closed, the diameter of the bore 158 is substantially equal to the inner diameter of the sealing surface 152. Another object of the push rod 160 is to seal the bore 158 against leakage currents. For this reason, preferably the push rod 160 and the bore 158 are made in a tight guide play.

To move the armature 154 at the lower stroke stop, i. when the sealing surface 152 is in the valve seat 156 to align, an elastic guide lip 162 is disposed on the armature 154. The upper stroke stop of the armature 154 is formed by an annular surface 164 which is designed as a lower end face of a stroke stop sleeve 166. In the embodiment shown in Figure 1, a bore 168 is formed in the Hubanschlagshülse 166, in which a spring element 170 is received. The spring element 170 is preferably a helical spring designed as a compression spring, which is supported on one side by the armature 154 and on the other side by a disk 172. The disk 172 is placed against an end face 174 of the bore 168. By means of the axial extent of the disk 172, the spring force with which the spring element 170 acts on the armature 154 can be adjusted.

Furthermore, the solenoid valve 150 includes a magnet 176 received in a magnetic core 178. The voltage supply of the magnet 176 via pins 180th

In order to facilitate a flat support of the sealing surface 152 on the armature 154 on the valve seat 156, the valve seat 156 and a support surface 182, on which the elastic guide lip 162 rests when the armature 154 is located at the lower stroke stop, are ground to a height. Likewise, the support of the elastic guide lip 162, which rests on the support surface 182, and the sealing surface 152 are ground on the armature 154 to a height. The stroke of the armature 154 is limited by the Hubanschlaghülse 166. To adjust the stroke, the armature 154 and the magnetic core 178 are enclosed by a sleeve 184, by the axial extent of the stroke is determined. To adjust the stroke, the stroke stop sleeve 166 with an end face 186 on the sleeve 184 is located for this purpose.

The inlet throttle 144, the outlet throttle 148 and the valve seat 156 and the bearing surface 182 are formed on a valve piece 188, which is part of the valve body 114 and which is accommodated in an injector 190. Also, the injector 190 is the part of the valve body 114. The attachment of the valve member 188 in the injector housing 190 by means of a valve clamping screw 192. To guide the pins 180 through the Hubanschlaghülse 166, a bore 194 is formed in this for each pin 180. For sealing and centering the pins 180 in the bore 194, the pins 180 are each enclosed by a lower disk 196, an upper disk 198 and a sealing ring 200 located therebetween. The attachment of the Hubanschlagshülse 166 on the injector 190 takes place in the embodiment shown here by means of a clamping nut 202nd

For the implementation of the injection process can be made to DE 10 2006 021 736 Al extensively. Thus, in the case of the noninverted fuel injector 110 shown in FIG. 1, the magnet 176 of the solenoid valve 150 is energized to start the injection process, so that the armature 154 is lifted off its valve seat 156. As a result, the control chamber 142 is pressure-relieved via the outlet throttle 148, as a result of which the control piston 140 and the injection valve member 120, driven by the hydraulic force of the fuel, can move upwards. Thereby, the injection valve member 120 is lifted at its lower end with its valve sealing surface 126 from the valve seat surface 122, and the injection ports 124 are released. In order to end the injection process again, the energization of the solenoid valve 150 is interrupted so that the spring element 170 presses the armature 154 back into the valve seat 156. The control chamber 142 is refilled with fuel via the inlet throttle 144 so that the control piston 140 and the injection valve member 120 move downwards again, whereby the injection openings 124 are again fired via the valve sealing surface 126.

It should be noted that, as described also DE 10 2006 021 736 Al, instead of the non-inverse embodiment shown in Figure 1, a control valve 112 may be provided with an inverse drive, so with a control in which, for example, when energized Magnet 176, the at least one injection port 120 is closed.

The particular advantage of the arrangement of the control valve 112 shown in Figure 1 is that the control valve 112 in the closed state, as shown in Figure 1, is pressure balanced. In this case, no axial hydraulic forces act on the control valve 112 or the armature 154 of the control valve 112. As a result of the fact that the sealing surface 152 is formed on the armature 154, an additional closing element for closing the outlet throttle 148 can be dispensed with. As a result, the mass of the moving components can be minimized, and it can be shorter switching times realize. However, these shorter switching times are for the inventive design of the Kxaftstoffϊnjektors 110 with a Seat hole nozzle of essential importance, since in this way the openable cross-section can be released very quickly and, for example, the described cavitation effects can be avoided. In this way, a low-emission fuel injector 110 can be realized by the embodiment according to the invention, which maintains the advantages of seat hole nozzles, but largely avoids their disadvantages and shows a reproducible and fast injection behavior.

Claims

claims

A fuel injector (110) for injecting fuel into a combustion chamber of an internal combustion engine, said fuel injector (110) having at least one injection valve member (120) axially slidably mounted in a valve body (114) for releasing and closing at least one injection port (124) the valve body (114) has at least one valve seat surface (122), in particular at least one conical valve seat surface (122), wherein the injection opening (124) is provided in the valve seat surface (122), the injection valve member ( 120) has at least one valve sealing surface (126, 128, 130), the valve sealing surface (126, 128, 130) closing the injection opening (124) in a closed state of the fuel injector (110), the fuel injector (110) further comprising at least one control valve (112) for hydraulically driving the injection valve member (120), wherein d the control valve (112) is configured such that substantially no axial hydraulic force acts on the control valve (112) in a closed state of the control valve (112).

2. Fuel injector (110) according to the preceding claim, wherein the injection valve member (120) has at least two valve sealing surfaces (128, 130), in particular two conical see valve sealing surfaces (128, 130).

3. fuel injector (110) according to the preceding claim, wherein at least two valve sealing surfaces (128, 130) are provided with different cone angle.

4. Fuel injector (110) according to one of the two preceding claims, wherein between at least two valve sealing surfaces (128, 130) at least one step (132) and / or at least one groove (134) is provided.

5. Fuel injector (110) according to any one of the preceding claims, wherein the control valve (112) has at least one solenoid valve (150).

6. Fuel injector (110) according to the preceding claim, wherein the solenoid valve (150) has at least one armature (154), wherein on the armature (154) a sealing surface (152) is formed, which for closing the control valve (112) in a Valve seat (156) is adjustable, wherein the armature (154) between an upper and a lower stroke stop is movable, wherein the armature (154) is preferably guided without armature guide, wherein in a bore (158) in the armature (154) a push rod ( 160) is received for receiving axial compressive forces.

7. fuel injector (110) according to the preceding claim, wherein on the armature (154) at least one resilient guide lip (162) is formed, which rests on the lower stroke stop on a support surface (182), so that the armature (154) aligned becomes.

8. Fuel injector (110) according to the preceding claim, wherein the guide lip (162) and the sealing surface (152) on the armature (154) and the bearing surface (182) and the valve seat (156) of the control valve (112) ground to the same height are.

9. fuel injector (110) according to one of the three preceding claims wherein a diameter of the push rod (160) is at least approximately equal to an inner diameter of the valve seat (156).

10. Fuel injector (110) according to one of the preceding claims, wherein the fuel injector (110) is designed as a non-inversely controlled fuel injector (110).