WO2008125377A1

WO2008125377A1 - Fuel injector

Info

Publication number: WO2008125377A1
Application number: PCT/EP2008/052109
Authority: WO
Inventors: Juergen Frasch
Original assignee: Robert Bosch Gmbh
Priority date: 2007-04-11
Filing date: 2008-02-21
Publication date: 2008-10-23
Also published as: DE102007017126A1

Abstract

The invention relates to a fuel injector (22) with a nozzle body (50) for accommodating an injection valve element (34) which is actuated by the relief of pressure from or the exertion of pressure on a control space (36). The control space (36) is filled with fuel via an inlet (58, 62). Pressure on the control space (36) is relieved by means of a centrally disposed discharge throttle (60) which can be closed off by means of an end surface (72) of the injection valve element (34).

Description

description

title

FUEL INJECTOR

State of the art

In injection systems used today for supplying fuel to internal combustion engines, for example, high-pressure accumulator injection systems (common rail) are used. From a fuel tank fuel is conveyed by means of a pump in a generally tubular-shaped high-pressure storage body. The high-pressure accumulator body (common rail) is acted upon by a high-pressure delivery unit, which maintains a system pressure level within the high-pressure accumulator body. Corresponding to the number of fuel injectors to be supplied, the high-pressure accumulator body comprises connection points to which high-pressure lines to the individual fuel injectors are connected. In today used fuel injectors two solenoid valves and a pressure booster are used. The pressure booster is controlled by one of the solenoid valves, which is designed as a 3/2-way valve, while a 2/2 valve is used to control the usually needle-shaped injection valve.

The previously used control of the usually needle-shaped injection valve member has during injection a leakage amount due to the AblaufVZulauf- throttle combination and the used 2/2-way valve.

Disclosure of the invention

Advantages of the invention

The present invention has for its object to reduce the leakage amount at the fuel injector and to improve the hydraulic efficiency of the fuel injector.

According to the invention, a fuel injector is proposed, in which a needle-shaped injection valve member actuating the control chamber via an outlet throttle and a Inlet throttle controls. If the 2/2-way valve used at the fuel injector is opened, the pressure inside the control chamber controlling the injection valve member drops, as a result of which the needle-shaped injection valve member opens. This moves against an above-arranged plate, which is also referred to as throttle plate and which represents the stroke stop of the needle-shaped injection valve member.

In contrast to fuel injector constructions used today, in which the outlet throttle, via which the control chamber pressure is relieved, is arranged eccentrically and a leakage flow occurs during the injection, the fuel injector proposed according to the invention, the pressure relief flow restrictor is arranged centrally in the control chamber of the injection valve member. It is thereby achieved that the needle-shaped injection valve member closes the flow restrictor arranged in the throttle plate representing the stroke stop and thus substantially reduces the amount of leakage which flows through the outlet throttle. The closing of the needle-shaped injection valve member is not affected by this measure. If the 2/2-way valve replaced by a 3/2-way valve, so occurs during the control of preferably needle-shaped injection valve member no leakage amount, since the high-pressure inlet for the control chamber of the preferably needle-shaped injection valve member is closed. Of the hitherto required chokes, i. The inlet throttle and the outlet throttle can account for a throttle, since a single throttle can simultaneously implement drain and inlet throttle function. As a result, the production costs of a flow-through throttle can be saved. The used 3/2-way valve can be designed in various design variants. Thus, a flat seat / slide seat construction of the 3/2-way valve is possible as well as a flat seat / conical seat construction or a conical seat construction. The controlled from the control chamber amount is passed by means of a bore in the throttle plate in a space between the nozzle retaining nut, throttle plate or the injection valve member. About trained in a nozzle retaining nut bores, for example, the diverted fuel quantity can leave the injector body of the fuel injector.

Brief description of the drawings:

With reference to the drawing, the invention will be described below in more detail.

It shows:

FIG. 1 shows the essential components of a high-pressure accumulator injection system; FIG. 2 shows a section through an embodiment variant of the fuel injector proposed according to the invention with a centrally arranged outlet throttle,

FIG. 3 is a sectional view of the fuel injector proposed according to the invention with a centrally arranged outlet throttle and a reduction on the steering chamber side,

FIG. 4 shows a further embodiment variant of the fuel injector proposed according to the invention with a 3/2 valve arranged in the injector,

Figure 5 shows the hydraulic circuit diagram of the embodiment of the fuel injector shown in Figure 4 and

Figure 6 shows a variant of the fuel injector shown in Figure 4 with a 3/2 valve with flat and conical seat.

embodiments

The illustration according to FIG. 1 shows the components of a high-pressure accumulator injection system in a schematic representation.

A high-pressure accumulator injection system 10 (common rail) comprises a fuel tank 12 and a high-pressure delivery unit 14. The high-pressure demand unit 14 conveys fuel from the fuel tank 12 into an essentially tubular storage body 16 (common rail). Corresponding to the number of fuel cylinders to be supplied to an internal combustion engine, 16 ports 18 are provided on the circumference of the essentially tubular storage body. At each of the terminals 18, a high pressure line 20 is connected, which leads to each one to be supplied with fuel fuel injector 22. The fuel injector 22 on the one hand comprises an injector body 24 which, for example, comprises a pressure booster 28 and an injection valve member 34, which is generally needle-shaped. For controlling the pressure booster 28 accommodated in the injector body 24 of the fuel injector 22, a 3/2 solenoid valve 26 is provided. From the pressure booster 28 controlled control amount passes into a low-pressure side return 32, via which the taxed amount controlled the fuel tank 12 is supplied again.

In addition, the fuel injector 22 shown schematically in Figure 1 comprises a 2/2-solenoid valve 30. About this, the pressure relief and the pressurization of a valve provided in the injector 24 control chamber 36 is controlled. About the pressure To suppress or depressurize the control chamber 36, the hub-shaped injection valve member 34 is impressed with a vertical lifting movement, in which this opening at the combustion chamber end of the fuel injector 22 opens or closes. When pressure relief of the control chamber 36 passes from this taxed control amount in the low-pressure side return 32 and the fuel tank 12 of the high-pressure injection system 10 is supplied. The injection valve member 34 includes a return spring 38 and at the combustion chamber end at least one injection port 40, via which fuel is injected into the combustion chamber, not shown in Figure 1 of the internal combustion engine.

For completeness, it should be mentioned that the pressure booster 28 comprises a pressure booster piston 44. The vertical lifting movement of the pressure booster 28 takes place via the pressure relief of a differential pressure chamber 42. The control quantity diverted from the differential pressure chamber 42 is conducted via the 3/2 solenoid valve 26 into the low-pressure side return 32. When pressure relief of the differential pressure chamber 42 of the pressure booster piston 44 enters a compression chamber. The compression chamber of the pressure booster 28 is hydraulically connected via a high-pressure line to the control chamber 36 and a further high-pressure chamber on the needle-shaped injection valve member 34. By applying a pressure booster 28, the stored in the tubular memory body 16 under system pressure, stored fuel volume can be compressed again in terms of pressure, so that in the combustion chamber end of the fuel injector 22 in comparison to the pressure prevailing in the storage body 16 system pressure level again increased pressure level for the respective injection process is available.

FIG. 2 shows a section through an embodiment variant of the fuel injector proposed according to the invention.

The sectional illustration according to FIG. 2 can be taken away from the fact that the fuel injector 22 has a nozzle body 50 which is clamped on the fuel injector via an indicated nozzle clamping nut 56. In addition, the nozzle retaining nut 56 also encloses an injector body 52.

A throttle plate 54 is located between the injector body 52 and the upper annular surface of the nozzle body 50. In the first embodiment of the fuel injector 22 proposed according to the invention, the throttle plate 54 has an inlet throttle 58 arranged eccentrically with respect to an injector main shaft 74. Via the inlet throttle 58, the control chamber 36 of the fuel injector 22 is either under Sys- temdruck standing fuel acted upon or fuel, whose pressure is raised by a not shown in the embodiment in Figure 2 pressure booster above the system pressure level. An inlet 62 pressurizes the inlet throttle 58 either with the fuel under system pressure or with fuel whose pressure level has been increased in a pressure booster. At the same time, via a feed formed in the throttle plate 54 under system pressure or in a pressure booster, fuel compressed via system pressure level flows into a high-pressure space 64 bounded by the wall of the nozzle body 50.

In the first embodiment variant shown in FIG. 2, a centric outlet throttle 60 is located coaxially with the injector main axis 74 in the throttle plate 54. The central outlet throttle 60 extends through the throttle plate 54 from its first end face 76, which assigns an outlet space 98 and a second end face 78, which limits the high-pressure chamber 64 and the control chamber 36. The control chamber 36 is limited by a control chamber sleeve 70, which in turn is acted upon by a spring 38. The spring 38, which acts on the lower annular surface of the control chamber sleeve 70, is supported on a collar 68 formed on the lateral surface of the preferably needle-shaped injection valve member 34. The high-pressure chamber 64 opens into an annular gap 66, which extends below the collar 68 in the nozzle body 50 and flows to the combustion-chamber-side end of the fuel injector 22 via the fuel either under system pressure or fuel flows to the combustion chamber end of the fuel injector 22, the pressure of which by means of a Pressure booster 28 - as shown schematically in Figure 1 - is brought from the system pressure to a further increased pressure level.

As can be seen from the first variant of the solution proposed according to the invention shown in FIG. 2, the needle-shaped injection valve member 34 has an end face 72 at its ends facing away from the injection openings 40, which is preferably crowned. About the crowned design of the end face 72 of the injection valve member 34 is achieved that at druckentlastetem control chamber 36, this end face 72 closes the centrally disposed in the throttle plate 54 outlet throttle 60 as possible, so that the leakage, ie the short circuit between the inlet throttle 78 and the central outlet throttle 60th can be minimized as possible. The smaller the control quantity flowing out via the centric outlet throttle 60, which is closed by the spherical end face 72 in the solution proposed by the invention, the greater the hydraulic efficiency of the fuel injector 22 proposed according to the invention Outflow throttle 60, which is formed in the throttle plate 54 opens into a drain chamber 98, from which in turn a return 32 extends to the low pressure side of the high-pressure injection system 10. The erf vorgeschlagenndungsgemäß proposed solution according to the embodiment, which is shown in Figure 2, is particularly suitable for fuel injectors 22, which are controlled by means of a schematically indicated in Figure 1 2/2-solenoid valve 30. In this embodiment of the proposed invention Krafstoffϊnjektors 10, the throttle plate 54, which is located between the injector 52 and the nozzle body 50, the upper stop of the preferably needle-shaped injection valve member 34. The occurring in known from the prior art constructions disadvantage, an off-center Arrangement of the outlet throttle and a leakage current associated therewith during the injection is avoided according to the invention proposed fuel injector 22 according to the first, shown in Figure 2 embodiment variant in that the outlet throttle 60 is arranged centrally in the throttle plate 54. The spherically formed end face 72 of the preferably needle-shaped injection valve member 34 "closes" - taking into account the hydraulic forces during the ballistic operating phase of the injection valve member - the central outlet throttle 60 and thus reduces the leakage amount occurring, ie the short circuit between the inlet throttle 58 and the The hydraulic efficiency of the fuel injector 22 proposed according to the invention, according to the first embodiment of the proposed invention, is markedly increased, whereas the closing of the preferably needle-shaped injection valve member 34 is not influenced by this measure.

The illustration according to FIG. 3 shows a further illustration of the first embodiment variant of the fuel injector proposed according to the invention, as shown in FIG.

FIG. 3 essentially corresponds to the representation according to FIG. 2, with the difference that in this embodiment the outlet throttle 60 comprises a reduction facing the control chamber. By lowering the outlet throttle 60, the closing behavior and the mechanical wear can be favorably influenced.

The illustration according to Figure 4 is shown in a further embodiment of erfϊndungsgemäß proposed fuel injector.

In the embodiment according to FIG. 4, the fuel injector 22 is actuated by means of a 3/2-way magnetic valve 80. In contrast to the first embodiment variant of the fuel injector 22 proposed in accordance with the invention, in the throttle plate 54 there is a centric outlet throttle 60, which can be used simultaneously as an inlet throttle. This means that in the embodiment of Figure 4 formed in the throttle plate 54 concentric outlet throttle 60 is flowed through in both flow directions with respect to the control chamber 36. The illustration according to FIG. 4 shows that in the injector body 52 there is an inlet 62 from a high pressure source (not shown in FIG. 4). Via the inlet 62 and a corresponding opening in the throttle plate 54, either fuel under system pressure or fuel compressed by a pressure intensifier flows at a pressure level above the system pressure level to the high-pressure space 64 defined by the nozzle body 50. From the high pressure chamber 64 of the fuel flows through the annular gap 66 below the collar 68 at the combustion chamber end of the fuel injector 22 formed, but not shown in Figure 4 injection ports.

From the illustrated in Figure 4 further embodiment of the present invention proposed fuel injector 22 shows that in the injector body 52, a solenoid valve 80 - indicated by a magnetic coil - is arranged. By means of the solenoid valve 80, which acts as a 3/2-way valve, a valve element 84 is driven. On the valve element 84, a flat seat 82 is formed on the one hand above the first end face 76 of the throttle plate 54, and a first control edge 86 and a second control edge 88 within a slide region 90. The low pressure side return 32 is via the first control edge 86 and the second control edge 88 connected to the central outlet throttle 60 and the inlet 62 separated from the drain chamber 98. In this case, the centrally arranged outlet throttle 60 is relieved in the low-pressure side return 32, whereby the pressure level in the control chamber 36 decreases. Otherwise, by means of the valve acting as a 3/2-way solenoid valve, the return flow 32 is closed by the flat seat 82 formed on the valve element 84 and the first control edge 86 and the second control edge 88 release the inlet 62 so that fuel flows through the latter and the drainage space 98 via the flowed through in the opposite direction centric outlet throttle 60 flows into the control chamber 36 and consequently enters this in a pressure build-up.

By this solution, the production of a second throttle in the throttle plate 54 can be bypassed.

4, the central outlet throttle 60 lies coaxially with the injector main axis 74. Also in the further embodiment variant shown in FIG. 4, the end face of the throttle plate 54 facing the second end face 78 is located. surface 72 of the preferably needle-shaped injection valve member 34 executed spherical. As a result, in the ballistic operating phase of the preferably needle-shaped injection valve member 34, an almost complete closing of the concentrically formed outlet throttle 60 opening into the second end face 78 of the throttle plate 54 results. In the embodiment variant shown in FIG. 4, compare in particular the corresponding hydraulic shown in FIG Circuit diagram, occurs during the activation of the preferably needle-shaped injection valve member 34 no longer leakage, since the high-pressure inlet 62 is closed by the control edges 86, 88 of the valve element 84, acting as a 3/2-solenoid valve. Moreover, in the embodiment according to the illustration in FIG. 4, only one throttle point, namely the centrally arranged outlet throttle 60, is to be embodied in the throttle plate 54. This takes over both the inlet and the drain function at the same time. With this further embodiment of the solution proposed according to the invention, as shown in FIG. 4, it is possible to avoid an expensive throttling point produced on flow, which otherwise would have to be formed in the throttle plate 54. 4 shows that the valve element 84 of the 3/2-way valve function representing solenoid valve 80 has a flat seat 82 and a slider portion 90 includes, in which the first control edge 86 and the second control edge 88 respectively cooperating with control edges in the injector 52, lie. Instead of the embodiment variant of flat seat 82 with slide area 90 shown in FIG. 4, a flat seat / conical seat construction or a conical seat / conical seat construction can also be selected. The rejected fuel quantity is conducted by means of a bore in the throttle plate 54 into a space between the inside of the nozzle retaining nut 76 and the injector body 52 or throttle plate 54 and nozzle body 50. The diverted fuel is transported away via these cavities from the fuel jet to the low-pressure side.

The illustration according to FIG. 4, which reproduces a further embodiment of the concept on which the invention is based, shows that, according to this embodiment, only modifications of the throttle plate 54 and of the injector body 52 are compared with the first embodiment of the inventively proposed FIG Solution are required.

The second embodiment of the invention on which the invention is based, as shown in FIG. 4, shows that in this embodiment too, the high-pressure chamber 64 which is bounded by the nozzle body 50 is delimited by the second end face 78 of the throttle plate 54. This contains in the embodiment shown in Figure 4 only one throttle point, namely the centrally disposed outlet throttle 60, but according to this embodiment in both flow directions, ie in the discharge direction and load direction - in relation to the control chamber 36 - flows through. The control chamber 36 in turn is limited by the control chamber sleeve 70. The control chamber sleeve 70 is acted upon by the spring 38, which is supported on the collar 68 of the lateral surface of the preferably needle-shaped injection valve member 64. The nozzle body 50, the throttle plate 54 and the injector body 52 are clamped sealingly against each other via the nozzle retaining nut 56 and form a screw connection of the fuel injector 22.

The illustration in accordance with FIG. 5 can be seen schematically in the hydraulic circuit diagram of the fuel injector in the embodiment shown in FIG.

From the illustration according to FIG. 5, it can be seen that the high-pressure feed line 20 is connected to the 3/2-way valve 92 and, on the one hand, can be connected to the central flow restrictor 60, which can flow in both flow directions and is formed in the throttle plate 54. In this case, the control chamber 36, via which the injection valve member 34 is actuated, pressurized and consequently the injection valve 34 is brought into its closed position.

On the other hand, when the solenoid valve 80 is energized to actuate the 3/2-way valve 92, it is also possible to disconnect the high-pressure line 20 from the control chamber 36. In this case, the control chamber 36 is connected in the second switching position of the 3/2-way valve 92, through the flow in the relief direction centric outlet throttle 60 with the low-pressure side return 32. In the illustration according to FIG. 5, the spring, which acts on the injection valve member 34, is indicated only schematically. If the magnet 80 is de-energized, the spring 38 presses the 3/2-way valve 92 in a flat seat.

5 discloses that in order to prevent leakage through the 3/2 valve 92, the inlet for the filling of the control chamber 36 for actuating the preferably needle-shaped injection valve member 34 (see FIG occurring leakage is zero.

The illustration according to FIG. 6 shows an embodiment of the further embodiment of the fuel injector proposed in accordance with the invention shown in FIG.

The illustration according to FIG. 6 shows that the solenoid valve 80 actuates the valve element 84. The valve element 84 is omitted instead of the slide region 90 with the first control edge 86 and the second control edge 88 as shown in Figure 4 of the slide area 90. In place of the slide area 90, a conical seat identified by reference number 94 has entered. The conical seat 94 on the valve element 84 the solenoid valve 80 cooperates with a seat 96 formed on the injector body 52 of the fuel injector 22. The seat 96 is located on the boundary wall of the drain chamber 98, below which - but not shown in Figure 6 - the first end face 76 of the throttle plate 54 is located. In the injector body 52 as shown in FIG. 4, the inlet 62 runs, via which either fuel under system pressure flows from the storage body 16 or in a pressure booster further via system pressure level compressed fuel to the 3/2-way valve 92. Analogous to the embodiment of the fuel injector 22 shown in FIG. 4, the valve element 84 comprises the flat seat 82, which cooperates with the return flow 32 formed in the throttle plate 54 as shown in FIG. In the drain chamber 98 shown in Figure 6, not shown in Figure 6, but Figure 4 removable flows through in both flow directions centric outlet throttle 60. Below the flat seat 82 is the return 32 from the return direction 100 from the control chamber 36 on the in Relief direction flowed through the central outlet throttle 60 appropriate control amount flows into the low pressure region of the fuel injector 22. The embodiment of the injector body 52 shown in FIG. 6 can easily be replaced by the embodiment of the injector body 52 shown in FIG.

Claims

claims

1. fuel injector (22) with a nozzle body (50) for receiving an injection valve member (34) which is actuated by a pressure relief or pressurization of a control chamber (36) which is filled via an inlet (62) with fuel, characterized in that the control chamber (36) is associated with a centrally arranged outlet throttle (60) which can be closed via an end face (72) of the injection valve member (34).

2. Fuel injector (22) according to claim 1, characterized in that the outlet throttle (60) assigning end face (72) of the injection valve member (34) is rounded spherical.

3. fuel injector (22) according to claim 1, characterized in that the outlet throttle (60) extends coaxially to the injector main axis (74).

4. fuel injector (22) according to claim 1, characterized in that the outlet throttle (60) in a throttle plate (54) is formed, the first end face (76) assigns a drain chamber (98) and the second end face (78) the control chamber ( 36).

5. fuel injector (22) according to claim 1, characterized in that in the throttle plate (54) has a low-pressure side return (32), which opens at the the drain chamber (98) facing first end face (76).

6. Fuel injector (22) according to claim 4, characterized in that the valve element (84) has a flat seat (82) via which the low-pressure side return (32) on the first end face (76) of the throttle plate (54) to open or closed close is.

7. Fuel injector (22) according to claim 4, characterized in that in the injector body (52) a 3/2-way valve (92) is received, via which a high-pressure side inlet (60, 62) from the low-pressure side return (32 ) is separable.

8. fuel injector (22) according to claim 7, characterized in that the valve element (84) of the 3/2-way valve (92) has a slide region (90) having a first control edge (86) and a second control edge (88) and a conical seat (82) or a conical seat (94) and a flat seat (82).

9. Kraftstoffϊnjektor (22) according to claim 7 or 8, characterized in that at the closed low-pressure side return (32) of the control chamber (36) via the high-pressure side inlet (62), the open conical seat (94) or the open slide valve area (90) and the discharge space (98) via the centrally arranged outlet throttle (60) is filled.

10. Fuel injector (22) according to one or more of the preceding claims, characterized in that in the throttle plate (54) a central Ablaufdros- (60) is formed, via which the control chamber (36) both in the drain chamber (98) and the low-pressure side return (32) can be filled with pressure relief and also with the low-pressure-side return (32) and opened 3/2 way valve (92) can be filled via the inlet (62).