EP2013469A1 - High pressure fuel pump - Google Patents

Abstract

A high pressure fuel pump (16) encompasses at least one conveyor space (32) and one high pressure discharge unit (26). In addition, a pressure limiting valve (42) with a valve that is actuated by the pressure difference (56) is provided that can open from the high pressure discharge unit (26) to the conveyor space (32). From the point of view of the valve seating (54) of the pressure limiting valve (42),it is recommended that a choke arrangement (64) is provided at its high pressure side, whose free cross section (F<SUB>D1</SUB>)is at most approximately equal to a desired maximum opening cross section of the pressure limiting valve (42).

Description

description

Title: High-pressure fuel pump

State of the art

The invention relates to a high-pressure fuel pump according to the preamble of claim 1.

A high pressure fuel pump of the type mentioned is known from DE 10 2004 013 307 Al. In this single-cylinder piston pump, the delivery chamber can be connected to a high-pressure outlet via a spring-loaded outlet valve. Fluidically parallel to the outlet valve, a pressure limiting valve is provided which has a spring-loaded valve ball as the valve element. The pressure relief valve opens to the pumping chamber and connects in the open state, the high-pressure outlet with the pumping chamber. A pressure relief valve arranged in this way has the advantage that it protects the high-pressure region against impermissibly high pressures, but at the same time does not worsen the degree of delivery of the high-pressure fuel pump, since the pressure relief valve only opens when there is a significantly lower pressure in the delivery chamber than in the high-pressure outlet.

Disclosure of the invention

Technical task

Object of the present invention is to provide a high pressure fuel pump of the type mentioned, which works very reliable.

Technical solution

This object is achieved by a high-pressure fuel pump with the features of claim 1. Advantageous developments of the invention are specified in subclaims. Furthermore, for the invention essential features in the following description and the - 7 -

Drawing. The features may also be essential for the invention in completely different combinations, without any explicit reference to this.

Advantageous effects

According to the invention, it has been recognized that when opening the pressure limiting valve, there is the danger that the valve element lifts off from the valve seat so far by dynamic pressure surges that it is forced out of the valve seat and jammed between valve seat body and spring plate. Thus, the pressure relief valve could not close, with the result that pumping would no longer be possible. All this is prevented by the measure according to the invention: By means of the throttle device, the maximum flow rate flowing through the pressure limiting valve is limited so that the valve element of the pressure limiting valve can not exceed a maximum opening stroke. The throttling device thus acts as a kind of hydraulic stroke limitation.

This is achieved by the special vote of the free cross section of the throttle device with the desired maximum Öffhungsquerschnitt the pressure relief valve, which corresponds to a stroke of the valve member, in which it is still ensured that the valve element can not jam. In most cases, this maximum Öffhungsquerschnitt should be an annular surface. The measure according to the invention prevents the valve element from being pushed out of the valve seat area at maximum flow through the pressure limiting valve, and it is ensured that the valve element easily returns to the valve seat when the pressure limiting valve closes. The throttle device also reduces the dynamic behavior of the pressure relief valve, which also has a positive effect on the wear. Pressure peaks are only attenuated transferred to the valve element.

If the throttle device comprises a high pressure side arranged from the pressure relief valve and separated from the pressure relief valve part with a flow restrictor, the previously used pressure relief valves can remain unchanged. This lowers the manufacturing costs.

In the same direction aims that development in which the separate part is held in a press fit in a transfer port of a pump housing.

The separate part may be cup-shaped with a bottom portion, wherein the Flow restrictor is formed by at least one Öfϊhung in the bottom portion. Such a part can be inexpensively manufactured as Blechform- and stamped part.

In the case of a throttle device arranged on the high-pressure side from the pressure-limiting valve, it is advantageous if its free cross-sectional area amounts to at least approximately 0.6 to 1.1 times the cross-sectional area of a valve seat of the pressure-limiting valve.

Alternatively or in addition to a separate from the pressure relief valve flow restrictor, the throttle device may also include a flow restrictor, which is arranged in a valve seat body of the pressure relief valve near or immediately adjacent to the valve seat and from this high pressure side. This eliminates the handling of a separate part, which simplifies the assembly of the erfmdungsgemäßen fuel high-pressure pump.

In this case, the flow restrictor can be easily formed by a constriction in an inflow channel in the valve seat body.

In such a throttle device, the free cross-sectional area of the flow restrictor should be at least approximately 0.5 times to 0.75 times the cross-sectional area of the valve seat of the pressure relief valve. With such a design, a good function of the pressure relief valve is ensured with good security against jamming of the valve element.

As a valve element of the pressure relief valve is a spring-loaded ball in question, which can be loosely installed, which is very cost. The valve seat for such a ball is advantageously conical with a cone angle approximately between 30 ° and 50 °. The smaller the angle, the better the seal in the closed state of the pressure relief valve.

It is also proposed that a free cross-sectional area of an inflow channel immediately upstream (ie high pressure side) from the valve seat (the term upstream is here based on the flow direction of the pressure relief valve) at least approximately 0.8 times to 0.95 times the cross-sectional area of the valve seat of the pressure relief valve. Such a narrow valve seat is advantageous in order to ensure good Schmutzunempfmdlichkeit the pressure relief valve can. Furthermore, the seat can be embossed particularly well during operation by such a narrow valve seat. A particularly advantageous embodiment of the high-pressure fuel pump according to the invention provides that a valve seat body of the pressure relief valve comprises a securing section extending in the opening direction of the valve element for the valve element, which is designed as a substantially annular collar. By this securing portion, the valve element is secured in the open, so lifted from the valve seat state in the lateral direction, so that it is impossible even when dynamic pressure surges and large opening stroke that the valve element between valve seat body and a valve element acting on the valve spring is jammed. Ultimately, the reliability of the fuel high-pressure pump is improved by this measure according to the invention, since it prevents the pressure relief valve jammed in the open state and thereby a high-pressure construction of the high-pressure fuel pump is impossible. The securing section ultimately ensures that the valve element finds its way back safely to the valve seat even with a large stroke.

A development for this purpose provides that the securing portion is formed on a valve seat portion of the pressure relief valve in the vicinity of the valve seat. This reduces the number of parts to be handled during assembly, which simplifies assembly. In addition, the manufacturing costs for the securing portion are reduced, since the valve seat portion of the pressure relief valve must be processed anyway.

It is particularly advantageous if at least one flow channel, in particular a flow pocket, is formed on the radially inner side of the securing section, preferably at least one flow channel which extends essentially over the length of the securing section. Such a flow channel introduced, for example, through a recess allows it to open

Pressure relief valve a low-resistance flow between the valve element and the inside of the securing portion, while at the same time closely guiding the valve member by the securing portion. Through the flow channel, the fluid can easily flow past between the inside of the securing portion and the open valve element and a possibly this holding valve element holder.

In the same direction, that embodiment of the fuel high-pressure pump according to the invention, in which the securing portion has at least one preferably substantially extending over its length slot. Such a slot is particularly inexpensive to produce. It is also proposed that the radial inner side of the securing section comprises a conical surface that widens in the direction of opening of the pressure limiting valve. Thus, with free pressure relief valve that clearance is created, which allows a low-resistance flow of the fluid between securing portion on the one hand and valve element and valve element holder on the other. In this case, the cone angle of the conical surface at least approximately correspond to the cone angle of the valve seat, which allows a relatively simple production. The cone angle of the conical surface can also be greater than the cone angle of the valve seat, which leads to a comparatively large clearance between the radial inner side of the securing section on the one hand and the valve element or valve element holder on the other hand even with a small opening stroke of the valve element.

It is furthermore particularly advantageous if the valve seat body has a shoulder adjacent to the valve seat and extending at least approximately radially, from which the radial inner side of the securing section extends in the opening direction of the pressure limiting valve. This measure can be used both in connection with the above-mentioned flow pockets or flow slots and the above-mentioned conical surface. The heel closing flow forces are avoided on the valve element in its open state.

The pressure limiting valve may comprise a piston-like valve element holder, which acts on the valve element in the closing direction and immersed in both the closed and open pressure relief valve in the securing portion. As a result, a particularly secure guidance of the valve element is ensured.

Brief description of the drawings

Hereinafter, particularly preferred embodiments of the present invention will be explained in more detail with reference to the accompanying drawings. In the drawing show:

Figure 1 is a schematic representation of a fuel system with a high-pressure fuel pump;

FIG. 2 shows a partial section through the high-pressure fuel pump of FIG. 1 with a first embodiment of a pressure-limiting valve and a throttle device; Figure 3 is an enlarged detail view of a portion of the high-pressure fuel pump of Figure 2;

Figure 4 is a detail IV of Figure 3;

Figure 5 is a view similar to Figure 3 of a second embodiment;

Figure 6 is a view similar to Figure 5 with the pressure relief valve open;

Figure 7 is a view similar to Figure 5 of a third embodiment;

Figure 8 is a section along the line VIII-VIII of Figure 7;

Figure 9 is a view similar to Figure 7 of a fourth embodiment;

Figure 10 is a section along the line X-X of Figure 9;

Figure 11 is a view similar to Figure 7 of a fifth embodiment;

Figure 12 is a view similar to Figure 7 of a sixth embodiment; and

Figure 13 is a view similar to Figure 7 of a seventh embodiment.

Embodiments of the invention

In FIG. 1, a fuel system as a whole bears the reference numeral 10. The fuel system 10 shown only in simplified form in FIG. 1 comprises a fuel tank 12, from which a feed pump 13 conveys the fuel into a low-pressure fuel line 14. This leads to a high-pressure fuel pump 16, which further compresses the fuel and delivers it to a fuel rail 18, in which the fuel is stored under high pressure and which is also referred to as "rail". To the rail 18 a plurality of injectors 20 are connected, which inject the fuel directly into them associated combustion chambers (not shown) of an internal combustion engine to which the fuel system 10 belongs. As can be seen from FIG. 2, the high-pressure fuel pump 16 has a housing 22 with a low-pressure inlet 24 and a high-pressure outlet 26. From the low-pressure inlet 24, an inlet channel 28 leads to an inlet valve 30 (not visible in FIG. 2) and on to a delivery chamber 32, which is bounded by a pump piston 34. An outlet passage 36 leads to the high-pressure outlet 26 via an outlet valve 38. The inlet valve 30 is integrated into a quantity control valve 40, by means of which the delivery space 32 can be forcibly connected to the region of the inlet passage 28 located upstream of the inlet valve 30. In this way, during a delivery stroke, fuel can be conveyed back to the low-pressure inlet 24 and the delivery rate of the high-pressure fuel pump 16 can be adjusted.

Fluidically parallel to the outlet valve 38, a pressure limiting valve 42 is arranged. This is shown in greater detail in FIG. 3: It comprises a valve seat body 44 which is arranged in an overflow channel 46 leading from the high pressure outlet 26 to the delivery chamber 32 with a fastening region 48 in a press fit. Toward the delivery chamber 32, the outer diameter of the valve seat body 44 tapers toward a valve seat region 50. The outer contour of the valve seat body 44 in this area can also be referred to as bottle neck. This prevents that this valve seat portion 50 is deformed during the pressing of the valve seat body 44 in the overflow 46.

The valve seat body 44 is penetrated by an inflow channel 52 in the longitudinal direction, which is designed as a stepped bore, the inner diameter in the valve seat portion 50 is smaller than in the mounting portion 48. At the right in Figures 3 and 4 end of the inflow 52, the actual valve seat 54 for a Valve ball trained valve element 56 incorporated. The valve seat 54 is conical with a cone angle in the present case of approximately 30 °. The half cone angle is indicated in Figure 4 by an arrow with the reference numeral 58. In principle, the cone angle should be approximately between 30 ° and 50 °, with a small cone angle having advantages with respect to the seal. The point of contact of the valve element 56 with the valve seat 54 is linear with a diameter di. The diameter d _{2 of} the inflow channel 52 is smaller than the diameter di. In this way, a free cross-sectional area Fd ₂ of the valve seat 54 from the high pressure port 26 and thus high pressure side arranged inflow 52 immediately adjacent to the valve element 56 at least about 0.8 times to 0.95 times as large as the cross-sectional area F. _d i, which is defined by the valve seat diameter di on the valve seat 54. The valve element 56 is urged towards the valve seat 54 by a valve element holder 60, which in turn engages a valve spring 62. An immersion depth of the valve element 56 in the inflow channel 52 of the valve seat body 54 is designated T in FIG.

From the pressure relief valve 42 and its valve seat 54 as seen from the high pressure port 26, as on the high pressure side of the pressure relief valve 42, a throttle device 64 is held in the overflow 46 in a press fit. This throttle device 64 is formed in the embodiment shown in Figures 2 to 4 as separate from the pressure relief valve 42 and cup-shaped part 65 which has a bottom portion 66 and an approximately rectangular and peripheral wall portion 68 to this. The part 65 may be made, for example, as sheet metal and stamped part. In the bottom portion 66 there is an opening 70 which has a diameter Di and forms a flow restrictor. In the present embodiment, the free cross-sectional area F _D i on the basis of the diameter Dl of the flow restrictor 70 is 0.6 times the cross-sectional area F _d i on the basis of the diameter di of the valve seat 54 of the pressure relief valve 42. However, values between the 0.6 times to 1.1 times.

The high-pressure fuel pump 16 operates as follows: During a suction stroke of the pump piston 34 opens the inlet valve 30 and fuel flows from the low-pressure fuel line 14 in the delivery chamber 32. In a subsequent delivery stroke of trapped in the delivery chamber 32 fuel is compressed until finally the exhaust valve 38th opens and the fuel is pressed under high pressure in the rail 18. If there is too high a pressure in the rail 18 and thus also in the area of the high-pressure outlet 26, the valve element 56 lifts off from the valve seat 54 and against the force of the valve spring 62 due to the then prevailing pressure difference during a suction stroke of the pump piston 34. In this way, fuel can flow out of the rail 18 or the high-pressure outlet 26 via the overflow channel 46 and the pressure-limiting valve 42 into the delivery chamber 32. As a result, the rail 18 and the high-pressure outlet 26 is relieved.

An alternative embodiment is shown in Figures 5 and 6. Here and in subsequent embodiments, it applies that such elements and regions which have equivalent functions to previously described elements and regions bear the same reference numerals and are not explained again in detail. In the embodiment of a fuel high pressure pump 16 shown in Figures 5 and 6, the throttle device 64 is not formed as a separate part, but integrated into the valve seat body 44 of the pressure relief valve 42, namely the high pressure side and very close or even immediately adjacent to the valve seat 54 in shape a constriction 70. Their free cross-sectional area F _D i, based on their diameter Di, in the present case is about 0.5 times the cross-sectional area Fdi of the valve seat 54 of the pressure limiting valve 42, based on the diameter di.

In both embodiments according to Figures 2 to 4 or 5 and 6, the free cross section of the flow restrictor 70 is designed so that it is at an open pressure relief valve 42, ie when the valve member 56 is lifted from the valve seat 54 (see Figure 6), at most approximately the then adjusting annular opening cross-section F _R corresponds, which is formed by the gap 72 between the valve element 56 and the valve seat 54. In this way it is ensured that the thus adjusting stroke H of the valve member 56 is smaller than the immersion depth T, thereby preventing that the valve element 56 between the valve seat body 44 and the valve member holder 60 can jam.

FIG. 7 shows a portion of yet another alternative embodiment of a high-pressure fuel pump 16. This corresponds to the embodiment shown in FIGS. 5 and 6 with regard to the design of the flow restrictor 70. In addition, however, an annular collar 76 extending in the opening direction (arrow 74) of the valve element 56, that is to say in the axial direction of the pressure limiting valve 42, which forms a securing section for the valve element 56, is integrally formed on the valve seat body 44 of the pressure limiting valve 42. The collar 76 has a radial outer side 78, with which it bears against the inside of the overflow channel 46. A radial inner side 80 of the collar 76 leads from a radially extending shoulder 82 to the projecting end of the collar 76. The shoulder 82 extends in the radial direction approximately from the valve seat 54, thus adjacent thereto.

The valve element holder 60 is piston-like in the embodiment shown in FIG. 7, with an annular collar 84 arranged approximately in its axial center, against which the valve spring 62 is supported. A pin-like portion 86 of the valve element holder 60 extends from the annular collar 84, starting from the valve spring 62 limited annular space (without reference numeral), similar to the embodiments shown in Figures 3 and 5 and 6 in. A lying in the vicinity of the annular collar 84 region 88 of the peg-like portion 86 has an outer diameter that is only slightly smaller than the inner diameter of the valve spring 62. In this way, the valve element holder 60 is held tilt-proof on the valve spring 62.

On the opposite side of the annular collar 84 extends from this a holding portion 90 to the valve member 56. In the embodiment shown in Figure 7, the holding portion 90 has a cylindrical outer contour with constant over its length diameter. A blind hole (without reference numeral) serves for the radial retention of the valve element 56 on the valve element holder 60. The outer diameter of the holding section 90 is selected so that the holding section 90 in the closed position of the pressure limiting valve 42 shown in FIG. 7 still faces the radial inner side 80 of the collar 76 has a small distance. In this way it is ensured that the holding portion 90 does not abut the collar 76 before the valve element 56 fully abuts the valve seat 54.

However, the length of the collar 76 and the holding portion 90 are coordinated so that the holding portion 90 of the valve element holder 60 immersed in both the closed and open pressure relief valve 42 in the limited of the radial inner surface 80 interior of the collar 76. Also in this way is ensured by the collar 76 that even with dynamic pressure surges and thereby caused large opening strokes of the valve element 56 this out of the limited space by the collar 76 and instead can reliably find back when closing the pressure relief valve 42 into the valve seat 54 ,

In order then, when the valve element 56 has lifted from the valve seat 54, to ensure a possible unimpeded outflow of the fluid to the pumping chamber 32, are distributed over the circumferential extent of the collar 76 away three flow pockets 92 on the radial inside 80 of the

Collar 76 is formed. These extend from the shoulder 82 over the entire length of the collar 76 away to its abragendem end and have a circular-segment-shaped edge contour. This can be seen in particular from FIG.

An alternative embodiment shown in Figures 9 and 10 differs from that of Figures 7 and 8 in that instead of the flow pockets in the collar / securing portion 76 of its entire thickness penetrating slots 94 are introduced, which are also from the shoulder 82 over the entire length of the collar 76 extend to its abragendem end. A further variant is shown in FIG. 11: In this case, the radial inner side 80 of the collar 76 is designed as a conical surface widening in the direction of opening 74 of the pressure-limiting valve 42. The holding portion 90 of the valve element holder 60 is similarly conical, but with a smaller cone angle than the radial inner side 80 of the collar 76. Upon an opening movement of the valve element 56 and the valve element holder 60 in the opening direction 74 results in an increasing distance between these elements on the one hand and radial inside 80 of the collar 76 on the other hand, through which the fluid can flow to the pumping chamber 32 out. The cone angle can have approximately the same cone angle as the valve seat 54 (compare in particular FIG. 4), or a larger cone angle than the valve seat 54.

In the embodiment shown in FIG. 11, the valve seat 54 transitions directly into the radial inner side 80. In the embodiment shown in FIG. 12, on the other hand, a shoulder 82, which extends in the radial direction, initially adjoins the valve seat 54, and only then does the conical surface of the radial inside 80 of the collar 76 come off. Here too, the shoulder 82 prevents or at least reduces a force acting on the valve element 56 in the closing direction when the valve element 56 is open.

A further variant of FIG. 12 is shown in FIG. 13, in which the cone angle of the conical surface forming the radial inner side 80 of the collar 76 is comparatively steep and the holding portion 90 is cylindrical with a constant diameter. This variant has the advantage that the

Abströmverhalten with open pressure relief valve 42 from the opening stroke of the valve element 56 is largely independent.

Claims

claims 1. High-pressure fuel pump (16), with at least one delivery chamber (32), a high-pressure outlet (26) and a pressure relief valve (42) with a pressure difference-operated valve element (56), which from the high-pressure outlet (26) to the delivery chamber (32) open can, characterized in that from a valve seat (54) of the pressure relief valve (42) seen on its high pressure side, a throttle device (64) is arranged, the free one Cross-section (F _D i; F _D2 ) is at most approximately equal to a desired maximum opening cross-section (F _R ) of the pressure relief valve (42). 2. High-pressure fuel pump (16) according to claim 1, characterized in that the throttle device (64) from the pressure relief valve (42) seen from the high pressure side and the pressure relief valve (42) separate part (65) with a flow restrictor (70). 3. High-pressure fuel pump (16) according to claim 2, characterized in that the separate part (65) is held in an interference fit in an overflow channel (46) of a pump housing (22). 4. high-pressure fuel pump (16) according to any one of claims 2 or 3, characterized in that the separate part (65) pot-shaped with a bottom portion (66) and the flow restrictor through at least one opening (70) in the bottom portion (66) is. 5. high-pressure fuel pump (16) according to one of claims 2 to 4, characterized in that the throttle device (64) by the flow restrictor (70) is formed, the free cross-sectional area (F _D i) at least approximately the 0.6- times to 1.1 times the cross-sectional area (F _d i) of a valve seat (54) of the pressure relief valve (42). 6. high-pressure fuel pump (16) according to any one of the preceding claims, characterized in that the throttle device (64) comprises a flow restrictor (70) in a valve seat body (44) of the pressure limiting valve (42) near or immediately adjacent to the valve seat (54 ) and seen from this high pressure side is arranged. 7. High-pressure fuel pump (16) according to claim 6, characterized in that the Flow restrictor is formed by a constriction (70) in an inflow channel (52) in the valve seat body (44). 8. High-pressure fuel pump (16) according to any one of claims 5 or 6, characterized in that the throttle device (64) by the flow restrictor (70) is formed, the free cross-sectional area (F _D2 ) at least approximately 0.5 times to 0.75 times the cross-sectional area (F _d i) of the valve seat (54) of the pressure relief valve (42). A high pressure fuel pump (16) according to any one of the preceding claims, characterized in that the valve element of the pressure relief valve (42) comprises a spring loaded ball (56) and the valve seat (54) is conical with a cone angle (58) approximately between 30 ° and 50 °. 10. High-pressure fuel pump (16) according to any one of the preceding claims, characterized in that a free Querschnittsfiäche (F &) of the inflow channel (52) immediately upstream of the valve seat (54) at least about 0.8 times to 0.95 times the cross-sectional area (F _d i) of the valve seat (54) of the pressure-limiting valve (42). 11. High-pressure fuel pump (16) according to one of the preceding claims, characterized in that a valve seat body (44) of the pressure limiting valve (42) extending in the opening direction (74) of the valve element (56) securing portion (76) for the valve element (56 ) formed as a substantially annular collar (76). 12. High-pressure fuel pump (16) according to claim 11, characterized in that the securing portion (76) to a valve seat portion (50) of the pressure limiting valve (42) in the vicinity of the valve seat (54) is integrally formed. 13. High-pressure fuel pump (16) according to any one of claims 11 to 12, characterized in that on the radial inner side (80) of the securing portion (76) at least one preferably substantially over the length of the securing portion (76) extending flow channel, in particular a flow pocket (92) is formed. 14. High-pressure fuel pump (16) according to any one of claims 11 to 13, marked thereby, that the securing portion (76) has at least one preferably substantially over its length extending slot (94). 15. High-pressure fuel pump (16) according to any one of claims 11 to 14, characterized in that the radial inner side (80) of the securing portion (76) in the opening direction (74) of the pressure relief valve (42) widening conical surface. 16. High-pressure fuel pump (16) according to claim 15, characterized in that the cone angle of the conical surface (80) at least approximately corresponds to the cone angle of the valve seat (54). 17. High-pressure fuel pump (16) according to claim 15, characterized in that the cone angle of the conical surface (80) is greater than the cone angle of the valve seat (54). 18. High-pressure fuel pump (16) according to one of claims 11 to 17, characterized in that the valve seat body (44) has a valve seat (54) adjacent and at least approximately radially extending shoulder (82) from which in Opening direction (74) of the pressure relief valve (42) extends the radial inner side (80) of the securing portion (76). 19. High-pressure fuel pump (16) according to any one of claims 11 to 16, characterized in that the pressure limiting valve (42) comprises a piston-like valve element holder (60) which acts on the valve element (56) in the closing direction and both in the closed and in the open Pressure relief valve (42) immersed in the limited by the securing portion (76) interior.