EP1047871B1 - Fuel injection system for internal combustion engines - Google Patents

Description

State of the art

The invention relates to a fuel injection system for Internal combustion engines according to the preamble of claim 1. A such is known from EP 0 778 413. There is one Valve piston opening from in a radial plane on the circumference of the Valve piston arranged control openings controlled. Furthermore are in this area - for example - EP 0 299 337 and DE 195 49 108.4 known.

In particular, the invention is based on a so-called common rail System (CR system). The peculiarity of such CR systems is that the amount of fuel required by a High pressure pump on a variable from each Operating state of the engine dependent pressure brought must become. The high-pressure pump is dependent on the engine speed driven what z. B. can be done by camshaft drive. The possible delivery rate of the high pressure pump is designed so that in an excess amount of fuel in each operating condition, i. H. more than the rail is required to build the desired pressure can.

It is known to use a rail fuel Pressure control valve to measure, which in the high pressure area behind the High pressure pump is arranged. Through this pressure control valve the high voltage fuel flow divided, once in Direction Rail, to increase / maintain pressure, and on the other hand in Towards the fuel tank. The latter partial stream is the overflow amount, which at the same time a corresponding loss of efficiency means.

At the current state of the art in CR systems fuel spanned by the pressure control valve deactivated. This leads to high fuel temperatures and poor efficiency. Furthermore, the strong leads Fuel temperature range in operation with pressure control valve, due to the temperature-dependent density to be scattered Injection quantities that are only partially above one Temperature compensation compensated using a temperature sensor can be.

Advantages of the invention:

By the from the characterizing part of claim 1 Removable solution according to the invention is for a generic CR system a fuel metering unit created that is capable of the high pressure pump of the CR system which in the respective operating state of the Internal combustion engine desired amount of fuel exactly to meter. By such an exact low-pressure side Measurement of the amount of fuel required for the high pressure pump are those incurred in the prior art and unnecessarily compressed amounts of overcurrent from the outset avoided. This leads to improved efficiency and thus fuel savings.

Further refinements and advantages of the invention can are taken from claims 2 to 16.

Drawings:

Fig. 1 eine Ausführungsform einer Kraftstoffzumeßeinheit, im vertikalen Längsschnitt,

Fig. 2 eine Variante eines Regelventils der Kraftstoffzumeßeinheit nach Fig. 1 mit drei Steueröffnungen (in Abwicklung über den Umfang dargestellt),

Fig. 3 die Einzelheit "A" aus Fig. 2, in Separatdarstellung,

Fig. 4 ein Diagramm, worin die Öffnungsfläche der Steueröffnung nach Fig. 3 über dem Magnethub aufgetragen ist,

Fig. 5 ein die Kennlinien des Elektromagneten und einer das Regelventil betätigenden Druckfeder enthaltendes Diagramm,

Fig. 6 eine gegenüber Fig. 1 etwas abgewandelte (und verkleinert dargestellte) Variante einer Kraftstoffzumeßeinheit, im vertikalen Längsschnitt,

Fig. 7 die Einzelheit "B" (Pfeil) aus Fig. 6, in gegenüber Fig. 6 vergrößerter Darstellung, und

Fig. 8 eine Abwandlung der Einzelheit "C" aus Fig. 7.

The invention is now illustrated by means of exemplary embodiments in the drawing, which are described in detail below. It shows:

1 shows an embodiment of a fuel metering unit, in vertical longitudinal section,

2 shows a variant of a control valve of the fuel metering unit according to FIG. 1 with three control openings (shown in processing over the circumference),

3 shows the detail "A" from FIG. 2, in a separate representation,

4 shows a diagram in which the opening area of the control opening according to FIG. 3 is plotted over the magnetic stroke,

5 is a diagram containing the characteristics of the electromagnet and a pressure spring actuating the control valve,

6 shows a variant of a fuel metering unit, somewhat modified (and shown in a reduced form) compared to FIG. 1, in a vertical longitudinal section,

Fig. 7 shows the detail "B" (arrow) of Fig. 6, in an enlarged view compared to Fig. 6, and

FIG. 8 shows a modification of the detail "C" from FIG. 7.

Description of the embodiments:

1 is based on a Electromagnet 10 with integrated control valve 11. In individual consists of the electromagnet 10 essentially a magnet coil 12, an armature 13 with armature bolts 14 and a magnetic pot 15 which holds the magnet coil 12 and the armature 13 partially encloses.

The entire assembly electromagnet 10 with integrated Control valve 11 is in a (not shown) High pressure fuel pump arranged. The magnetic pot 15 also serves as a sealing element magnetic yoke and as a fastening element (16) of the Electromagnet 10 in the high pressure pump.

The solenoid 12 is after it in the magnet housing 15th is completely overmolded. By the age of 17 overmolding is an optimal heat transfer from the coil 12 to the housing 15 guaranteed. one This can cause overheating in critical operating states be counteracted. The extrusion coating 17 also leads to a good vibration and shake resistance, which makes a Attachment of the fuel metering unit 10, 11 highly stressed areas, e.g. B. the high pressure fuel pump, in terms of vibrations, temperature and environmental pollution is made possible.

Furthermore, the coating 17 of the solenoid 12 in cooperation with two sealing points 18, 19 ensures that the contact points of the coil 12 to the Plug lugs (not shown) are "dry".

Magnet coil winding and contact points are thus in front Corrosive media attacks optimally protected.

To check that the encapsulation 17 the solenoid 12th completely encloses are on the circumference of the magnet housing 15th "Overflow holes" 20, 21 provided.

The control valve 11 has a valve housing 22, which in a flange-like widening 23 merges, which at the same time the front end of the electromagnet housing 15 forms. There is an axial bore 24 in the valve housing 22 formed coaxially to the armature bolt 14 of the electromagnet 10 is arranged. The axial bore 24 takes one displaceable sleeve-shaped valve piston 25, in whose interior 26 a compression spring 27 is arranged. The Compression spring 27 is supported on the front on a bottom 28 of the Valve piston 25 and on the back of one in the Axial bore 24 of the valve housing 22 located Spring plate 29 from. A paragraph 30 on the inner wall of the Valve piston 25 ensures that the compression spring 27 largely non-contact from the inner wall in the Valve piston 25 is. The valve piston head is on the outside 28 and thus the valve piston 25 with the front end of the anchor bolt 14 in plant.

An opening 31 connects the interior 26 of the Valve piston 25 with a (not shown) Pre-feed pump of the fuel injection system. By doing Valve housings 22 are also several radially directed Control openings arranged (see also Fig. 2 to 4), one of which can be seen in FIG. 1 and numbered 32 is. The control opening 32 stands with the low pressure area the (not shown) high pressure pump in hydraulic Operatively connected.

The flow principle can also be reversed. in this connection would then be the opening 31 with the low pressure area High pressure pump hydraulically connected while the Control opening 32 with the pressure side of the prefeed pump would be connected and thus the inflow into the metering unit would form.

The upper half of Fig. 1 - above the common Central axis 33 of valve bore 24, valve piston 25 and Anchor bolt 14 - shows the control valve 11 in Open position in which the control opening 32 through the Valve piston 25 is fully released. In the lower one Half of FIG. 1, however, is the control valve 11 in shown full closed position. Here the Magnetic force of the energized electromagnet 10 over the Anchor bolt 14 on the valve piston 25 and moves it against the resistance of the compression spring 27 in said Closed position of the control valve 11. Conversely, the Compression spring 27 the valve piston 25 in the open position (upper Half of Fig. 1) to move when energizing the Electromagnet 10 and thus its armature 13 and Anchor bolt 14 acting magnetic force is reduced accordingly becomes. In the open position of the control valve 10, the flows Control valve 11 at 31 fuel supplied by the Control opening 32 in the direction of the elements of the High pressure pump.

As already indicated above, in practice it has proven to be Proven to be useful, not just one, but several, on Circumference of the valve housing 22 distributed, radial Provide control openings. Fig. 2 shows a variant in of the three control openings - with 32, 34 and 35 designated, are provided. 3, result from the special design of the middle Control opening 32 two control areas of the control valve 11, on the one hand, an area 1 with a correspondingly smaller amount Fuel delivery and on the other an area 2 with in Dependence on the valve piston stroke (magnetic stroke) linearly strong increasing fuel delivery (see FIG. 4). Here is the Range 1 (low fuel delivery) to engine idling up to assigned to the lower partial load. Area 2 (strong increasing fuel delivery) corresponds to the medium partial load to full load of the internal combustion engine. Area 1 is characterized in that initially only the opening area of the slot-shaped part 36 of FIG Control opening 32, plotted over the stroke of the valve piston 25 (or the anchor bolt 14), a flat characteristic has. This is numbered 37 in FIG. 4. This is good controllability of the idle and the lower Partial load of the internal combustion engine possible. This is achieved due to the narrow, rounded design of the slot-shaped part 36 of the control opening 32. Manufactured this narrow slot 36 can be eroded, Punching or laser cutting.

Area 2 is characterized in that the opening area - in this case all three control openings 32, 34 and 35 involved (FIG. 2) - plotted over the stroke of the valve piston 25 or the anchor bolt 14 has a steep characteristic curve, cf. Curve sections 38, 39, 40 in Fig. 4. This ensures that a correspondingly large opening area is available after a defined stroke. A short overall length and a low energy expenditure of the electromagnet 10 are thus possible.
As an alternative to the variant shown in FIG. 2 with three circular control openings 32, 34, 35, large control opening areas can also be provided by a correspondingly wide slot or a control opening of correspondingly large diameter or also by several slots or bores with suitable geometries distributed around the circumference of the valve housing 22 (e.g. triangular shape).

The fuel meter in question is for various vehicle types (cars, commercial vehicles, special vehicles, Ships etc.), provided that they are with internal combustion engines operated, equally applicable. The required Adaptation can be done in a simple manner via the design the opening areas of the valve control openings (e.g. 32, 34, 35 in Fig. 2) accomplish.

As already mentioned and can be seen from FIG. 1, this is Control valve 11 in the housing 15, 33 of the electromagnet 10 integrated, and the complete fuel metering device 10, 11 is screwed directly into the high pressure pump. Thereby is an optimally small installation space and an inexpensive one Manufacturing guaranteed. The minimum that can be achieved Dead volume ensures exact metering of the required Fuel quantity and quick response times to changing Quantity requirement of the high pressure pump or the internal combustion engine.

From the preceding explanations it is already clear that exact for the valve of a fuel metering device Controllability is important. This requirement becomes present achieved by the measures specified below. First of all, it proves very useful for this Characteristic curve of the electromagnet 10 opposite to the characteristic curve to design the compression spring 27. Fig. 5 shows four parallel Magnetic characteristics 41 to 44 with different magnetic currents as a parameter. The spring characteristic (shown in dashed lines) is numbered 45. Control points result in each case the interfaces of the spring characteristic 45 with the Magnetic characteristics 41 to 44. This is achieved Characteristic curve assignment through a special magnetic core geometry as well as optimized material thicknesses on the magnet armature 13 and Magnet housing 15. A high spring stiffness (high c-value the compression spring 27) is advantageous. This will correspondingly steep transitions between the magnetic characteristic (41 or 42 or 43 or 44) and the spring characteristic 45 reached. This leads to stable control points.

An optimized interpretation of the electrical parameters (Inductance, wire thickness, number of turns of the solenoid 12) and the magnetic circuit allow flawless Function of the fuel metering unit even at minimum Battery voltages.

The control of the electromagnet 10 takes place pulse width modulated. An optimized control frequency gives movement ripple of the armature 13 and thus the Valve piston 25. These measures lead to reduced Friction hysteresis and good dynamics of the fuel metering unit.

Before putting the fuel metering unit 10, 11 into operation There is an adjustment of the control valve 11. This takes place by corresponding axial displacement of the spring plate 29 in the valve bore 24 and subsequent fixation thereof. In detail, the setting process is as follows performed. First, the electromagnet 10 with a defined current applied. Then the Insert spring plate 29 into valve bore 24 so far until it comes out of the control opening (e.g. 32, Fig. 1) defined volume flow results. In this position the Spring plate 29 fixed, e.g. B. by the spring plate 29 as Press-in part is formed or the valve housing 22 of is plastically deformed on the outside. It makes sense to do this Valve set point in the range of minimum fuel flow rates because this makes the tolerance sensitive Idle range is exactly realizable.

To optimize the magnetic force, the solenoid 12 is included a stage 46 has been designed. This allows the inner Space of the electromagnet 10 can be optimally used. The Working air gap of the electromagnet 10 was for reasons the magnetic force optimization placed in the middle of the coil 12. Due to the non-contact guidance of the compression spring 37 in Inside the valve piston 25, the spring and Magnetic hysteresis can be kept to a minimum, so that an exact fuel metering is guaranteed.

The entire control valve 11 and the electromagnet 10 are kraftstoffgeflutet. The control valve 11 is thus hydraulic balanced. Interferences do not affect the Metering out. The flooded electromagnet 10 acts as hydraulic cushion that both interference and counteracts fretting.

When the vehicle is coasting, it must be prevented that any leakage of the control valve 11 to the injections High pressure pump and thus to a pressure increase in the Guide the rail of the fuel injection system. The fuel metering unit 10, 11 must therefore be the one such zero delivery situation of the internal combustion engine meet the high demands made. The for this measures taken, which are so-called "Zero funding relief" acts from Fig. 6, 7 and 8 out. For reasons of clarity, there are the the embodiment of FIG. 1 structurally and functionally corresponding components with the same reference numerals as in Fig. 1 numbered.

If zero delivery is desired (electromagnet 10 energized) is a further radial bore via the valve piston 25 47 opened in the valve housing 22. This open position of the Valve piston 25 - caused by the anchor bolt 14 counter the resistance of the compression spring 27 - is in particular from Fig. 7 can be seen. In this valve piston position Control opening 32 via a recess 48 on the cylindrical The circumference of the valve piston 25 with the radial bore 47 hydraulically connected. At the same time, the hydraulic Connection of the control opening 32 to the pressure side of the Pre-feed pump (inlet 31 of control valve 11) interrupted. The radial bore 47 can - through a channel 49 - e.g. B. connected to the suction side of the pre-feed pump his. By the said, visible from Figs. 6 and 7 Position of the valve piston 25 thus results in a hydraulic connection between the control opening 32 and a channel 50 leading from there to the high pressure pump with the Suction side of the pre-feed pump. An (unwanted) Pressure build-up in front of the pump elements of the high pressure pump and a consequent (undesirable) fuel injection in the combustion chambers of those in overrun This advantageously avoids the internal combustion engine.

Alternatively or in addition to those from FIGS. 6 and 7 obvious and described above constructive features can also be achieved through zero funding the measures resulting from FIG. 8 are achieved. To For this purpose, the edge of the spring plate 29 on the valve side designed as an axial sealing seat 51, which with the End face 52 of the valve piston 25 on the spring plate side cooperates sealingly. The annular sealing seat 51 can z. B. as an elastomer flat sealing seat or as a steel cone seat be trained.

Claims (11)

1. Fuel injection system for internal combustion engines having a distributor pipe and a high-pressure pump which is driven as a function of the engine speed and has the purpose of generating the fuel pressure and fuel throughput rate which is required in the distributor pipe in the respective operating state of the internal combustion engine, and having a fuel metering unit which is embodied as an electromagnetically activated regulating valve and is arranged in the high-pressure pump, having an inlet (31) which is connected to the pressure side of a presupply pump, and an outlet (32, 34, 35) which is connected into the low-pressure region of the high-pressure pump, and having a valve piston (25) which is loaded (27) - into the open position - by a compression spring and which can be activated - into the closed position - counter to the force of the compression spring by an armature bolt (14) of the electromagnet (10), and having at least one, preferably a plurality of radial control openings (32, 34, 35) which are arranged in the wall of the valve housing (22) and are operatively connected to the low-pressure region of the high-pressure pump, characterized in that the control openings are shaped and/or arranged in such a way that at least two control regions are produced as a function of the stroke of the valve piston, the opening faces of the control openings having, plotted over the stroke of the valve piston, a flat characteristic curve (37) with a small angle of incline in a first control region (region 1), and a steep characteristic curve (38 or 39 or 40) with a large angle of incline in a second control region (region 2).
2. Fuel injection system according to Claim 1, characterized in that the regulating valve (11) adjoins the housing (15) of the electromagnet (10) axially and has a valve housing (22) on the end side of which an axial opening (31) which is operatively connected to the pressure side of the presupply pump is arranged.
3. Fuel injection system according to one of Claims 1 or 2, characterized in that, at the start of the stroke of the valve piston, a first control region (region 1) which is assigned to the idling mode and the lower partial load of the internal combustion engine, and, when the stroke of the valve piston continues, a second control region (region 2) - which corresponds to the partial load and the full load of the internal combustion engine - of the control openings (32, 34, 35) is provided.
4. Fuel injection system according to one or more of Claims 1 to 3, characterized in that the characteristic curve (41 to 44) of the electromagnet (10) is configured in the opposite direction to the characteristic curve (45) of the compression spring (27) which loads the valve piston (25).
5. Fuel injection system according to one of the preceding claims, characterized in that the electromagnet (10) can be actuated in a pulse-width-modulated fashion by a fuel-pressure sensor which is arranged in the distributor pipe (rail).
6. Fuel injection system according to one of the preceding claims, characterized in that the valve piston (25) is of sleeve-shaped design and holds in its interior space (26) the compression spring (27) which loads it into the open position, and in that the compression spring (27) is supported at the rear on a spring plate (29) which is arranged in the valve bore (24) of the valve housing (22).
7. Fuel injection system according to Claim 6, characterized in that the regulating valve (11) can be adjusted by means of corresponding axial displacement and subsequent fixing of the spring plate (29) in the valve bore (24).
8. Fuel injection system according to one of the preceding claims, characterized in that the entire fuel metering unit (10, 11) is integrated directly into the high-pressure pump, preferably screwed into it, and in that both the regulating valve (11) and the electromagnet (10) are flooded with fuel.
9. Fuel injection system according to Claim 8, characterized in that the coil (12) - inserted into a pot-shaped magnet housing (15) - of the electromagnet (10) is completely encapsulated with a plastic jacket (17).
10. Fuel injection system according to one of the preceding claims, characterized in that the valve piston (25) has a bore (48) at its cylindrical circumferential face and a radial bore (47) which is connected to the intake side of the presupply pump is arranged in the valve housing (22) in such a way that, in the closed position of the valve piston (25), the radial control openings (32) are hydraulically connected to the radial bore (47) and the valve housing (22) through the valve-piston bore (48).
11. Fuel injection system according to one of the preceding claims, characterized in that, on the edge of the spring plate (29) facing the valve piston (25), an axial sealing seat (51) is formed which, in the closed position of the valve piston (25), interacts in a sealing fashion with the edge (52) of said valve piston facing the spring plate (29).

Images