WO2002090766A1

WO2002090766A1 - Accumulator injection system (common rail) for internal combustion engines

Info

Publication number: WO2002090766A1
Application number: PCT/DE2002/001680
Authority: WO
Inventors: Peter Schubert
Original assignee: Robert Bosch Gmbh
Priority date: 2001-05-08
Filing date: 2002-05-08
Publication date: 2002-11-14
Also published as: DE10122242A1

Abstract

The invention relates to an accumulator injection system (Common Rail) for internal combustion engines, comprising a quantity-regulated high pressure pump (CP3), such that the rail pressure produced by the high pressure pump can be regulated by variable opening and closing of the suction line of the high pressure pump. Said injection system comprises a fuel pressure accumulator (rail) (10) which is fed by the high pressure pump, by which means a number of injectors corresponding to the number of cylinders of the internal combustion engine are supplied with fuel as consumers. The invention is characterised in that a valve (12) comprising a valve body (21) which can be actuated in the opening position by means of the rail pressure (PRail) against the resistance of a valve spring, a valve seat (20) and an liquid outlet (28) which is embodied in the form of a throttle, is connected to the fuel accumulator (10) - in the form of an additional consumer for controlling the volume flow in such a way that the throttle (28) can only be passed through when the valve (12) is open.

Description

Accumulator injection system (common rail) for internal combustion engines

State of the art

The invention relates to an accumulator injection system according to the preamble of patent claim 1.

Accumulator injection systems for internal combustion engines are known. In this regard, the German publication "Diesel accumulator injection system common rail, technical information Bosch No. 1987722054; KH / VDT-0997-DE" is called.

A distinction is made between common rail systems, in which a high-pressure pressure control valve is used to lower the system pressure, and common rail systems with volume-controlled high-pressure pump (so-called CP 3 systems), in which pressure reduction in the fuel pressure accumulator (rail) only possible via injection, control quantity and leakage. The present invention specifically relates to such a CP3 system.

In such CP3 systems, the pressure control takes place in detail by variably opening and closing the suction line of the high pressure pump (CP3 high pressure pump). At low engine speeds and low engine load, only a very small fraction of the possible delivery capacity of the high-pressure pump is required to build up the required pressure in the Raii. However, since the high-pressure pump is essentially designed for higher delivery quantities, such as are required at partial or full load of the internal combustion engine and at correspondingly high engine speeds, the equal delivery of the high-pressure pump, which is nevertheless required even at low load and low engine speeds, has proven itself in these special operating conditions as unsatisfactory, ie the individual elements of the pump are unable to produce a uniform flow. Furthermore, the ripples on the pressure signal are relatively high because the pump elements only deliver at a short angle and injections take place in the delivery gaps.

The object of the present invention is to ensure, by means of less complex measures, that even in operating states which require only low delivery rates of the high-pressure pump, the necessary constant delivery of the high-pressure pump is guaranteed.

Advantages of the invention

According to the invention, the object is achieved in an injection system of the type described at the outset by the characterizing features of patent claim 1.

Through the valve according to the invention or the additional leakage caused thereby in the special operating points of the internal combustion engine in question, the set goal of better uniform delivery of the high-pressure pump can be achieved without great technical effort, namely that the additional leakage provides the necessary volume flow. The valve according to the invention is thus to a certain extent a constant leakage valve.

In addition, the valve according to the invention also contributes to an improvement in the pressure control, since it helps to prevent the pressure control circuit from swinging up. Another special feature of the invention is the generation of an additional volume flow, which is coupled to a control in the valve. The pilot control can be designed so that the leakage is covered by injectors and valve.

Advantageous refinements and developments of the basic idea of the invention can be found in patent claims 2-11.

drawing

An exemplary embodiment, which is described in detail below, serves to illustrate and explain the invention in greater detail. In detail shows:

Fig. 1 - in vertical longitudinal section and in a greatly enlarged

Representation - an embodiment of a constant leakage valve, and

Fig. 2 - in a diagram - the course of the rail pressure (PRail) plotted against the rail throughput (Q).

Description of the embodiment

In FIG. 1, 10 designates a (only partially shown) pressure accumulator (rail) with an interior 11 serving to receive fuel. The pressure accumulator 10 is known in a known and therefore not shown manner by a high-pressure pump (so-called. CP3) supplied with fuel. The pressure accumulator 10 in turn feeds injectors (not shown), the number of which depends on the number of cylinders of the internal combustion engine in question. The high-pressure fuel reaches the combustion chambers of the assigned cylinders of the internal combustion engine through the injectors. In addition to the injectors mentioned, a total of 12 valve is connected to the pressure accumulator 10 - as a further consumer, so to speak. The valve 12 has an essentially cylindrical valve housing 13 with two end surfaces 14 and 15 and an essentially cylindrical interior (valve chamber) 16. A peg-shaped extension 17 is formed on the end surface 14 of the valve housing 13, which has an external thread 18 and one to the valve chamber 16 has coaxial valve inlet 19 which opens into it. The valve housing 13 and thus the valve 12 as a whole is fastened to the pressure accumulator 10 by means of the extension 17 which is screwed into a corresponding internal thread of the pressure accumulator 10. The valve inlet 19 creates a hydraulic connection between the interior 11 of the pressure accumulator 10 and the valve chamber 16.

At the transition of the valve inlet 19 in the valve chamber 16, a conical valve seat 20 is formed which interacts with a spherical valve body 21. The valve body 21 is acted upon by a compression spring 22 in the closing direction of the valve 12 indicated by an arrow 23. Contrary to the closing force of the compression spring 22, and thus in the opening direction 24 of the valve 12, acts on the valve body 21 via the valve inlet 19 of the rail pressure prevailing in the interior 11 of the pressure accumulator 10, which therefore strives to make the valve 12 visible in FIG. 1 To open position.

On the back, the compression spring 22 is supported on a screw element 25 which is screwed into a threaded bore 26 of the valve housing 13. The screw element 25 here forms part of a bottom surface of the valve chamber 16, numbered 27. The screw element 25 functions as a pressure adjusting device for the valve 12, since - depending on how far the screw element 25 is screwed into the threaded bore 26 - an adjustment of the Preload of the compression spring 22 can effect. Overall, valve body 21, valve seat 20 and preload of the compression spring 22 should be designed and matched to one another such that the valve 12 only above a specified minimum rail pressure P _m j _n (see also FIG. 2 ) opens in the interior 11 of the pressure accumulator 10. Another peculiarity is that the valve outlet (when valve 12 is open) is a throttle, designated overall by 28, which is incorporated into the valve housing 13 as a radial bore with a variable diameter. The actual throttle cross-section here is a central section, numbered 29, with a minimal cross-section of the throttle 28.

As can be seen in particular from FIG. 2, the valve arrangement described in FIG. 1 described above works in detail as follows. In the valve 12, the built-in compression spring 22 regulates the pressure to a minimum pressure P j _n , which can be, for example, 150 bar. When the valve 12 opens at this pressure, the amount of fuel flowing into the valve chamber 16 can initially be completely discharged from the throttle 28, so that the pressure PRail * ^m system practically up to a volume flow value Qj (depending on the cross section of the throttle bore section 29) cannot increase (see Fig. 2). If the volume flow (Q) delivered by the high-pressure pump continues to increase, there is a continuous pressure increase in the system, due to the fact that it is no longer possible, desirably and very specifically, for the throttle cross-section 29 to completely discharge this increased fuel flow. The low volume flow derived by the throttle 28 thus represents a (additional) leakage in relation to the volume flow delivered by the high pressure pump.

As far as the different cross-sections of the throttle 28 are concerned, they have a different function in detail: the two sections - with 30, 31 numbered - of larger cross-section have the task of regulating the pressure in the throughput range a (throughput O - Q- |), during the Section 29 with the narrow cross section serves to limit the maximum flow rate. In the control range a of the valve 12, the increasing leakage of the injectors (not shown) is compensated for by the wear over the service life, because the compression spring 22 reduces the flow cross section via the valve body 21, and thus the pressure (P _m j _n ) is kept constant again can.

Claims

claims

1.Storage injection system (common rail) for internal combustion engines, with a quantity-controlled high-pressure pump (so-called CP3), such that the rail pressure (PRail) generated by the high-pressure pump can be regulated by variable opening and closing of the intake line of the high-pressure pump, and with one from the high-pressure pump fed fuel pressure accumulator (so-called. Rail) (10), through which a number of injectors corresponding to the number of cylinders of the internal combustion engine are supplied with fuel as a consumer, characterized in that to the fuel pressure accumulator (10) - as an additional consumer for Volume flow limitation - a valve (12) is connected to a valve body (21) which can be actuated by the rail pressure (PRail) against the resistance of a valve spring (22) in the open position, a valve seat (20) and a liquid drain (28) designed as a throttle, such that flow through the throttle (28) only when the valve (12) is open.

2. Accumulator injection system according to claim 1, characterized in that the valve body (21), valve seat (20) and pretension of the valve spring (22) are matched to one another in such a way that the valve (12) only opens above a specified minimum pressure (Pmin).

3. Accumulator injection system according to claim 1 or 2, characterized in that the valve body (21), valve seat (20), preload of the valve spring (22) and throttle cross-section (29, 30, 31) are matched to one another so that the pressure (PRail) ⁱⁿ Fuel pressure accumulator (10) can only rise from a specified minimum volume flow (Qj) to above the specified minimum pressure (Pmin) (Fig. 2).

4. Accumulator injection system according to claim 1, 2 or 3, characterized in that the valve (12) has a substantially cylindrical valve chamber (16) in which a valve body (21) acted on the front by the rail pressure and on the back by a compression spring (valve spring 22). "floating" is arranged to move back and forth.

5. Accumulator injection system according to one or more of the preceding claims, characterized in that the valve body (21) is a ball and the compression spring (valve spring 22) acting on it rearwards on a bottom surface (27) of the valve housing (13) opposite the valve inlet (19) ) or a component (25) at least partially forming the floor surface (27).

6. Accumulator injection system according to claim 4 or 5, characterized in that in the valve housing (13), in the region of the bottom surface (27) of the same, an adjusting screw (25) is screwed, on which the pressure spring (valve spring) acting on the valve body (21) 22) is supported in such a way that the pretension of the compression spring (valve spring 22) and thus the minimum pressure (min) _' can be adjusted or adjusted.

7. Accumulator injection system according to one or more of the preceding claims, 20 characterized in that the liquid outlet (28) designed as a throttle radially penetrates the valve housing (13).

8. The storage injection system according to claim 7, characterized in that the radial liquid outlet (28) starts from the front region of the valve chamber (16), adjacent to a front end face of the valve chamber (16) forming the valve seat (20).

9. The storage injection system according to one or more of the preceding claims, characterized in that the throttle (28) has a constriction (29) which is located between two coaxial liquid drain holes (30, 31). is arranged, one (30) of the valve chamber (16) and the other (31) of the outer circumferential surface of the valve housing (13).

10. Accumulator injection system according to one or more of the preceding claims, characterized in that on the substantially cylindrical valve housing (13), on its end (14) facing the fuel pressure accumulator (10), a diameter tapered to the valve housing (13) concentric thread extension (17) - forming a shoulder - and that the valve (12) by means of the thread extension (17) is screwed into a corresponding threaded bore of the fuel pressure accumulator (10).

11. Accumulator injection system according to claim 10, characterized in that in the interior (19) of the threaded extension (17) the liquid inlet (19) to the valve (12) and - at the transition into the valve chamber (16) - a conical with the valve body (21 ) cooperating valve seat (20) is formed.