WO2008017544A1

WO2008017544A1 - Fuel injection system with a pressure oscillation damper

Info

Publication number: WO2008017544A1
Application number: PCT/EP2007/056814
Authority: WO
Inventors: Le-Thanh-Son Tran
Original assignee: Robert Bosch Gmbh
Priority date: 2006-08-09
Filing date: 2007-07-05
Publication date: 2008-02-14
Also published as: DE102006037179A1

Abstract

The invention relates to a fuel injection system (1), comprising a high-pressure source (2) for feeding the highly pressurized fuel to at least one fuel injector (3), wherein the fuel injector (3) is fluidically connected by means of a fuel pressure line (4) to the high-pressure source (2), and at least one pressure oscillation damper (5) is arranged in the fuel pressure line (4), wherein the pressure oscillation damper (5) has a tubular line section (6) for conducting the fuel, in which line section (6) is provided at least one radial throttle bore (7) for discharging fuel into a pressure damping space (8). A fuel injection system (1) with a pressure oscillation damper (5) is therefore created which has a low level of flow resistance and permits sufficient damping of pressure waves and line oscillations which occur within the fuel injection system (1).

Description

Fuel injection system with a pressure vibration damper

The present invention relates to a fuel injection system with a pressure vibration damper according to the closer defined in the preamble of claim 1. Art.

Such a fuel injection system includes a high pressure source for delivering the high pressure fuel to at least one fuel injector, the high pressure source communicating with at least one fuel injector via a fuel pressure line and the pressure dampening damper disposed within the fuel pressure line.

State of the art

Such a fuel injection system is known from DE 10 2004 016 508 Al. Herein, a high-pressure pump is provided, which with a plurality of

Fuel injectors is connected via a fuel pressure line. The fuel injectors are each connected to the fuel pressure line, wherein in the immediate vicinity of each injector, a pressure vibration damper is arranged in the form of a throttle. This has a flow resistance which is greater in the return direction of the high-pressure pump than in the flow direction to the respective Einspritzöffhung, wherein in the fuel pressure line at least a second throttle is provided as a pressure vibration damper. This arrangement of a pressure vibration damper, which is based on the principle of the throttle with a narrowed flow cross-section, has the disadvantage that there is a high flow resistance and thereby high pressure losses and

System line losses are caused. Other possible pressure oscillation dampers exist in so-called resonators or membrane drums, which, however, do not offer any possibility of converting the pressure energy into another type of energy, for example heat energy. The pressure energy is stored only for a short time and fed back into the system with a time delay. The published patent application DE 10 2004 007 342 A1 discloses a fuel injector which comprises in integrated form a pressure vibration damper. This is designed as a blind hole-like damping channel and filled with an elastic material. The damping channel is fluidly connected to the fuel pressure line with a throttle in

Connection. However, due to the limited installation space within the holding body of the fuel injector, the pressure damping space available for damping is severely limited. Each individual injection process of the fuel injector triggers a line vibration or pressure waves in the system of the fuel pressure line, which can affect downstream injections in terms of their quantities in a systematic manner. Although with the elastic material in the damping channel an improvement of the pressure damping capacity is achieved, a satisfactory damping or elimination of emerging line vibrations or pressure waves can not be achieved due to the limited volume. Furthermore, the rigid arrangement of the damping channel within the fuel injector does not allow optimization of the arrangement of the pressure swing damper within the system of fuel pressure lines.

It is therefore the object of the present invention to provide a fuel injection system with a pressure swing damper which is a drag resistance arm and which permits sufficient damping of occurring pressure waves and line vibrations within the fuel injection system.

This object is achieved on the basis of a fuel injection system with a pressure vibration damper according to the preamble of claim 1 in conjunction with its characterizing features. Advantageous developments of the invention are specified in the dependent claims.

The invention includes the technical teaching that the pressure vibration damper has a tubular conduit section for passage of the fuel, in which at least one radial throttle bore for discharging fuel is provided in a pressure damping chamber. The advantage of the embodiment of the pressure vibration damper according to the invention lies ostensibly in an unimpeded flow of the fuel through the pressure vibration damper, without pressure losses and system line losses being caused. The proposed Pressure vibration damper is not based on the principle of flow restriction, which causes a high flow resistance and does not unnecessarily throttle the fuel allocation from the high pressure source to the fuel injectors. The flow cross-section of the tubular line section may, for example, have the same or at least a similar flow cross-section as the

Fuel pressure line itself. Thus, the fuel in the direction of the fuel injectors unhindered flow through the pressure vibration damper. In a closing operation of a fuel injector and a pressure peak caused thereby reaches the line section, wherein the pressure peak value is reduced by a passage of the fuel through the throttle bores in the damping chamber. As a result of the discharge of the fuel into the damping chamber, the pressure in the damping chamber is increased at short notice, whereby the radially applied throttle bores within the line cross-section constitute a flow resistance, and the pressure energy is converted into heat energy. The result is a smoothing of the vibration behavior of the pressure within the fuel pressure line, wherein no short-term storage of the pressure energy takes place, which would be fed back into the system with a time delay.

A further advantageous embodiment of the invention provides that the pressure vibration damper further comprises a housing which inside the

Damping room forms. Due to the design of the pressure vibration damper in a housing, this is carried out separately and can be arranged arbitrarily within the fuel injection system. The pressure vibration damper thus forms a structurally independent unit, wherein the dimensions of the pressure vibration damper are limited to the dimensions of the housing substantially. In this case, the line section extends through the housing, and the pressure damping chamber surrounds the line section. In this case, the housing, the line section and the damping chamber is formed radially symmetrically about a common axis of symmetry around, wherein the arrangement of housing, damping chamber and line section can also be eccentric, and thus not radially symmetrical. This can also be a damping chamber are formed, which is present on only one side of the line section. Overall, therefore, the pressure vibration damper forms a cylindrical shape, so that it can be integrated within the fuel pressure line in the form of a coupling piece or the like. A further advantageous embodiment of the invention provides that the pressure damping chamber in the direction of the axis of symmetry is pressure-tightly sealed at least at one end side by means of a connecting piece. Preferably, both on the input side, ie on the side of the fuel supply line and at the

Output side, i. be provided on the side of the derivative of the fuel from the line section a connector. There is also the possibility, depending on the constructional embodiment, of integrally constructing at least one connecting piece with the housing, so that the pressure damping space is introduced as a bore in the direction of the symmetry axis from the opposite side into the housing with a single separate connecting piece. Between the connection piece and the housing, a seal may be provided, which is introduced as a ring seal within a sealing seat in the housing. The orifices within the conduit section may be equally spaced along the length of the conduit section, either in a radial position or at various radial positions and in various longitudinal sections, which bores may be cylinder bores or bores extending over their length, i. the wall thickness of the line section have a variable cross-section.

According to a further advantageous embodiment of the invention, the line section 1-10, preferably 3-7 and more preferably 4 radial throttle bores. The conduit section extends through the entire length of the housing through this, whereas the pressure damping chamber can be formed only over a portion of the housing length. Thus, a part of the results

Line section, which passes through the housing without being surrounded by the pressure damping chamber. The number of throttle bores relates to the section of the line section which is surrounded by a pressure damping chamber. The throttle bores may be circumferentially formed on the conduit section in various radial directions, or located in a plane opposite the conduit section.

According to a further advantageous embodiment of the invention, the throttle bores have a diameter of 0, 1 mm to 1 mm, preferably from 0.2 mm to 0.5 mm and particularly preferably of 0.3 mm. There is also the possibility that the throttle bores within a line section have different diameters. It should be noted at this point that a bore generally describes a passage or opening without being limited to production by means of a drill. The holes can be introduced, for example, in the erosion process, in the stamping process or in the laser cutting process in the tubular line section.

According to a further advantageous embodiment of the fuel injection system, this may comprise a high pressure accumulator, which is arranged between the high pressure source and the at least one Kraftstoffϊnjektor. Such a

High-pressure accumulator is also referred to as a common rail, which comprises a volume within which the fuel is stored with the appropriate high pressure. By branching the fuel flows in each case to a Kraftstoffϊnjektor, so that the fuel injectors are fed in total by the high-pressure accumulator. To maintain the high pressure within the high-pressure accumulator this is with the

High-pressure source connected, which may include a high-pressure pump. The delivery strokes of a high-pressure pump create pressure surges that travel through the high-pressure lines and reflect on the rail system and on the pump itself. This creates pressure oscillations in the pump rail lines, which lead to increased pump element pressure. Therefore, it is provided according to the invention that the pressure vibration damper is arranged between the high-pressure source and the high-pressure accumulator. Thus, it is possible to connect the pressure vibration damper to the high pressure pump itself, whereby the pressure pulsations are smoothed by the high pressure source. The pressure oscillations are strongly damped, whereby the flow resistance between the pump and the

Rail is not increased, so that the pump element pressure is clearly reducible.

According to a further advantageous embodiment of the invention, the pressure vibration damper between the high-pressure accumulator and the Kraftstoffϊnjektor is arranged. This can be arranged in each of the fuel pressure lines, which runs between the high-pressure accumulator and the respective Kraftstoffϊnjektor, so that the fuel first flows through the pressure vibration damper before it reaches the Kraftstoffϊnjektor. Furthermore, it can be provided that both a pressure vibration damper between the high-pressure source and the high-pressure accumulator is arranged and at the same time in a respective fuel pressure line to the fuel injectors further pressure dampers are used.

The pressure swing damper may be disposed within the fuel injection system as a separate component within the fuel pressure line, with the possibility also that the pressure swing damper be mechanically connected to the fuel injector, i. For example, is screwed, or is used depending on the place of use mechanically with the high pressure source or on the input side or on the respective output side of the common rail.

Further, measures improving the invention will be described in more detail below together with the description of preferred embodiments of the invention with reference to figures.

embodiments

It shows:

Figure 1 is a schematic representation of a pressure vibration damper according to the present invention;

Figure 2 is a cross-sectional view of a possible embodiment of the pressure swing damper;

Figure 3 is a schematic representation of a fuel injection system with a

Pressure vibration damper, which is arranged between the high-pressure source and a high-pressure accumulator; and

Figure 4 is a schematic representation of another embodiment of a fuel injection system in which between the high-pressure accumulator and the fuel injectors each a pressure vibration damper is disposed within the fuel pressure line.

The pressure vibration damper 5 shown in Figure 1 is used within a - not shown here - fuel pressure line. The fuel pressure line will both Fluidly connected on the left side and the right side with a line section 6, so that the fuel flows through the line section 6. The line section 6 is arranged concentrically about an axis of symmetry 10, wherein a cylindrical damping chamber 8 extends around the line section 6 likewise concentric to the symmetry axis 10. The damping chamber 8 is formed by a housing 9, which is radially symmetrical and also concentric with the axis of symmetry 10. Thus, the pressure vibration damper 5 forms a cylindrical member, which is either disposed within the fuel pressure line or by means of a both right-hand fitting 11 and a left-side fitting 11 'mechanically with another

Component within the fuel injection system such as a high pressure source, a high-pressure accumulator or a fuel injector can be connected. The connecting pieces 11 and 11 'are likewise formed concentrically around the axis of symmetry 10 and can constitute a connection between the line section 6 and the housing 9. Furthermore, the connecting pieces 11 and 11 'seal the

Pressure damping chamber 8 in the direction of the symmetry axis 10 from.

The line section 6 has a plurality of radially outwardly extending throttle bores 7. The extension direction of the throttle bores 7 is formed perpendicular to the symmetry axis 10, wherein the throttle bores 7, the inner region of the

Line section 6 connect to the region of the pressure damping chamber 8. Thus, the throttle bores 7 represent fluid channels through which the fuel can pass from the inside of the line section 6 into the damping chamber 8. If a pressure peak, i. a pressure peak within the conduit section 6, the fuel can pass through the throttle bores 7 into the damping chamber 8. The

Throttle holes 7 include a small diameter of, for example, 0.3 mm, so that when passing the fuel through the throttle bores 7, a damping effect is achieved.

FIG. 2 shows a cross-sectional view of a technical embodiment of the invention

Pressure Vibration Damper 5. According to this embodiment, the line section 6 extends concentrically around the symmetry axis 10 through the housing 9. The damping chamber 8 is formed concentrically only around a partial length of the housing 9 to the line section 6. The line section 6 comprises eight throttle bores 7, which on the free length of the line section 6 in the Damping chamber 8 open. The line section 6 is added to the left side in a connection piece 11 '. Further, the line section 6 passes through the housing 9 on a portion within which the pressure damping chamber 8 is not yet formed. On the right side of the pressure damping chamber 8 is limited by a sealing element 13, in which the connecting piece 11 'opposite end of the

Line section 6 is added.

The sealing element 13 is clamped to the right-side connecting piece 11, which is screwed endwise by means of a thread within the housing 9. The connector 11 in turn has an external thread to the

Pressure swing damper 5 either fluidly connect to the fuel pressure line, or mechanically connect to at least one further component within the fuel injection system. The pressure vibration damper 5 may be made of a steel material with respect to the components of the housing 9, the connector 11 and 11 'and the line section 6, whereas the

Sealing element 13 may be formed, for example, a non-ferrous metal. Thus, fluid pressures in the fuel of one Kbar or even more than two Kbar can be passed through the pressure vibration damper.

The volume of the pressure damping chamber 8 can according to the embodiment in

2 with 4 cm ³ are given, wherein the free length of the line section 6 within the housing 9 comprises about 30 mm. Due to the length of the housing 9 of the pressure damping chamber 8 can be increased through a widening of the bore in the direction of the connecting piece 11 ', so that with a free length of the line section 6 within the casing 9 of for example 60 mm, a volume of the pressure damping chamber 8 of 8 cm ³ is feasible.

FIG. 3 shows a fuel injection system 1 according to an embodiment of the invention. The fuel injection system 1 comprises a high pressure source 2, which via a fuel pressure line 4 with a high pressure accumulator 12 in

Is connected. The high-pressure accumulator 12 is generally referred to as a common rail, from which the fuel injectors 3 are brought into communication via the respective fuel pressure lines 4. Thus, the fuel is provided by the high-pressure source 2 with a corresponding pressure to the high pressure accumulator 12, so that the fuel injectors 3 at a respective Open period of the fuel injectors (3) supply the fuel. For damping of pressure pulsations, which are caused by the high pressure source 2, a pressure vibration damper 5 is arranged in the fuel pressure line 4 between the high pressure source 2 and the high pressure accumulator 12. In delivery strokes of a high-pressure pump, pressure surges that migrate through the high-pressure lines and reflect at the high-pressure accumulator 12 and again at the high-pressure source 2 respectively. This results in pressure oscillations within the fuel pressure line 4 between the high pressure source 2 and the high pressure accumulator 12, which lead to increased pump element pressure. The pressure vibration damper 5 causes a damping of these pressure oscillations.

It is also possible to introduce the pressure vibration damper 5 in front of the high pressure source 2 within the low pressure circuit system.

Figure 4 shows a schematic representation of another embodiment of the present invention, which in turn shows a fuel injection system 1 with a high pressure source 2, a high-pressure accumulator 12 and a total of four fuel injectors 3. The pressure vibration damper 5 are arranged in the respective fuel pressure line 4 between the high-pressure accumulator 12 and the fuel injectors 3. Pressure oscillations caused by the periodic

Opening operations and closing operations of the fuel injectors 3 caused can be attenuated within the fuel pressure line 4 between the fuel injectors 3 and the high-pressure accumulator 12. It should also be noted that 12 may be provided between the fuel injectors and the high-pressure accumulator 12 each pressure vibration damper, wherein also within a single system, a further pressure vibration damper 5 can be introduced within the fuel pressure line 4 between the high pressure source 2 and the high pressure accumulator 12.

The invention is not limited in its execution to the above

Embodiments. Rather, a number of variants is conceivable, which makes use of the illustrated solution even with fundamentally different types of use. For example, it is also possible to introduce the pressure vibration damper 5 in front of the high-pressure source 2 within the low-pressure circuit system or even within the return lines of the fuel injectors.

Claims

claims

A fuel injection system (1) comprising a high pressure source (2) for delivering the high pressure fuel to at least one fuel injector (3), the fuel injector (3) via a fuel pressure line

(4) is in fluid communication with the high-pressure source (2), and at least one pressure vibration damper (5) in the fuel pressure line (4) is arranged, characterized in that the pressure vibration damper (5) has a tubular conduit portion (6) for passage of the fuel in which at least one radial throttle bore (7) for discharging fuel into one

Pressure damping chamber (8) is provided.

2. Fuel injection system (1) according to claim 1, characterized in that the pressure vibration damper (5) further comprises a housing (9) which on the inside forms the pressure damping chamber (8).

3. Fuel injection system (1) according to claim 1 or 2, characterized in that the line section (6) through the housing (9) extends therethrough, and the pressure damping chamber (8) surrounds the line section (6).

4. Fuel injection system (1) according to any one of the preceding claims, characterized in that the housing (9), the line section (6) and the pressure damping chamber (8) extend radially symmetrically about an axis of symmetry (10).

5. Fuel injection system (1) according to any one of the preceding claims, characterized in that the pressure damping chamber (8) in the direction of the axis of symmetry (10) at least at one end side by means of a connecting piece (11, 11 ') is pressure-tight manner.

6. Fuel injection system (1) according to any one of the preceding claims, characterized in that the line section (6) 1 to 10, preferably 3 to 7 and more preferably 4 radial throttle bores (7).

7. Fuel injection system (1) according to any one of the preceding claims, characterized in that the throttle bores (7) have a diameter of 0.1mm to lmm, preferably from 0.2mm to 0.5mm and more preferably from 0.3mm.

8. Fuel injection system (1) according to one of the preceding claims, characterized in that the pressure damping chamber (8) has a volume of 2cm ³ to 10cm ³ , preferably from 3cm ³ to 8cm ³ and more preferably from 4cm ³ .

9. Fuel injection system (1) according to any one of the preceding claims, characterized in that the fuel injection system (1) comprises a high pressure accumulator (12) which is arranged between the high pressure source (2) and the least one Kraftstoffϊnjektor (3).

10. Fuel injection system (1) according to claim 8, characterized in that the pressure vibration damper (5) between the high pressure source (2) and the high-pressure accumulator (12) is arranged.

11. Fuel injection system (1) according to claim 8, characterized in that the pressure vibration damper (5) between the high-pressure accumulator (12) and a respective fuel injector (3) is arranged.

12. Fuel injection system (1) according to one of the preceding claims, characterized in that the pressure vibration damper (5) mechanically with the

Fuel injector (3) is connectable.