EP2409015B1 - High pressure pump - Google Patents

Description

The present invention relates to a high pressure pump for a fuel injection system of an internal combustion engine, in particular for a common rail injection system, according to the preamble of claim 1.

State of the art

In the prior art as example as EP 1911964 A1 For example, high-pressure pumps are known for common-rail systems in which a drive shaft is mounted via pressure-supplied plain bearings, which ensure optimum lubrication and cooling. In addition, valves arranged in a hydraulic circuit in series with the bearings may be disposed downstream of the bearings to inhibit the bearing flow rates at startup.

For example, it is off DE 10 2006 048 356 A1 a high-pressure fuel pump for an internal combustion engine, in which the bearings of the drive shaft are forcibly traversed by fuel and thereby the mechanical and thermal capacity of the bearing and thus the entire high-pressure fuel pump is significantly increased. For storage of the drive shaft while a first and a second sliding bearing are provided. Thus, the pressure build-up within the high-pressure fuel pump and the high-pressure accumulator of the common rail system is accelerated, downstream of and in series with the first bearing, a first check valve is arranged. Accordingly, a second check valve is arranged downstream and in series with the second bearing. However, the opening pressure of the check valves is chosen so that they are closed when starting the internal combustion engine and open only when the internal combustion engine is running.

The opening pressure, which have the non-return valves used in the prior art, is in a range which is greater than 1.0 bar. This opening pressure is so high that the check valves open only after the suction valves of the high-pressure fuel pump, so that z. B. in the start case no leakage through the bearing occurs, which is disadvantageous for this.

Also, the pressure on the downstream side of the bearings in front of the valves increases. If a shaft seal is positioned there, the load can rise to impermissible values. For this reason, usually no valve can be provided on such bearings.

A disadvantage of the known configurations also that in cases with poor fuel supply, when a mass balance violation occurs, the high-pressure accumulator is still supplied with fuel, while the valves close to the camps already. The lubrication and cooling of the bearings is no longer ensured in this case.

Therefore, it is necessary to provide a high-pressure fuel pump which can be used in a fuel injection system, in particular in a common rail system, in which the mass balance situation is improved, in particular at the start of the internal combustion engine without having the disadvantages mentioned above.

Disclosure of the invention Advantages of the invention

According to the invention, a high-pressure pump is provided for a fuel injection system of an internal combustion engine, in particular for a common rail injection system, which has one of at least one arranged in a bearing return bearing bearing drive shaft, wherein downstream of the at least one bearing at least one valve is arranged, which is an opening pressure which is in a range of 0.1 bar to 0.8 bar. With the high-pressure pump according to the invention, which has the at least one valve with a low opening pressure, the mass balance situation becomes particularly at start-up the internal combustion engine improved. The valve reduces the leakage through the at least one bearing in the starting of the internal combustion engine and thus improves the starting power (the required speed or the time to start). The valve with a low opening pressure, which is below or equal to 0.8 bar, opens early enough so that the permissible pressure on the commonly existing shaft seal is not exceeded, which in turn does not unduly shorten the service life.

In addition, the valve does not close even if there is a violation of the low-pressure quantity balance, so that a bearing flow is ensured in all operating cases. Therefore, the high pressure pump as a whole becomes more robust both in terms of functionality and durability.

The opening pressure of the valve in an opening pressure range of less than or equal to 0.8 bar and greater than or equal to 0.1 bar has the advantage that on the one hand - as already mentioned above - at low speeds and in particular at the operating point of the engine start to a significant reduction of Leakages leads, but on the other hand ensures a minimum leakage at the start. Even with massive violation of the low pressure quantity balance in the low pressure circuit of the fuel injection system, a minimum leakage for the at least one bearing is therefore ensured.

Preferably, the at least one valve is a check valve, in particular a ball check valve.

According to a preferred embodiment, the fuel can flow through at least one bearing.

According to yet a preferred embodiment, the at least one bearing is a plain bearing. Therefore, when flowing through the bearing with fuel forms a hydrostatic lubricating wedge, which improves the load capacity of the bearing.

Preferably, in the high pressure pump according to another embodiment, a first bearing and a second bearing for supporting the drive shaft are provided.

According to yet another preferred embodiment, a first valve is provided in the bearing return downstream of the first bearing and a second valve is provided in the bearing return downstream of the second bearing.

According to a further preferred embodiment, the first valve is arranged in series with the first bearing and the second valve in series with the second bearing.

Depending on the bearing point, a valve, in particular a ball check valve, individually or after merging of individual or all bearing returns for these can be positioned together. The further fuel supply of the bearing returns is irrelevant.

Preferably, the respective bearing return of the first bearing and the second bearing opens into a common bearing return, wherein a common valve is provided in the common bearing return.

Preferably, the drive shaft is a camshaft or an eccentric shaft, which is arranged in an interior of a pump housing.

It is also preferred if the bearing return and the interior of the pump housing are hydraulically connected.

The configuration according to the invention can be used particularly advantageously in all fuel injection systems which have a mechanical feed pump in the pump inlet, the use being particularly advantageous in cases where there are no further consumers in the fuel return (eg tank jet pumps, temperature circuits, etc.) is, because then the maximum potential, d. H. the highest opening pressure in the opening pressure range of 0.1 to 0.8 bar according to the invention can be utilized.

Brief description of the drawings

Fig. 1

ein Blockschaltbild eines Kraftstoffeinspritzsystems mit einer Hochdruckpumpe gemäß dem Stand der Technik;

Fig. 2

ein Blockschaltbild eines Abschnitts des Kraftstoffeinspritzsystems mit einer Hochdruckpumpe gemäß einer Ausführungsform; und

Fig. 3

ein Blockschaltbild eines Abschnitts des Kraftstoffeinspritzsystems mit einer Hochdruckpumpe gemäß einer weiteren Ausführungsform.

Hereinafter, embodiments of the invention will be described in more detail with reference to the accompanying drawings. It shows:

Fig. 1

a block diagram of a fuel injection system with a high-pressure pump according to the prior art;

Fig. 2

a block diagram of a portion of the fuel injection system with a high pressure pump according to an embodiment; and

Fig. 3

a block diagram of a portion of the fuel injection system with a high pressure pump according to another embodiment.

Embodiments of the invention

In Fig. 1 a block diagram of a common rail fuel injection system 1 is shown with a high pressure pump 2, which consists essentially of a tank 3, a feed pump 4 with an element for flow limitation 5, a filter 6, a rail 7 and a pressure relief valve 8 and pressure control valve. The injectors, which are connected to the rail 7, are in Fig. 1 not shown.

The element for limiting the flow rate 5 is designed as a throttle, which is arranged directly at the entrance of the prefeed pump 4. The throttle causes the total compressed in the high-pressure pump 2 amount of fuel is limited. Furthermore, the pressure resulting in an inner space 9 of the high-pressure pump 2 is limited in accordance with a characteristic curve of a pressure regulating valve 10. The pressure relief valve 8 opens into a return line 11, in which the leakage quantities of the injectors, not shown, are discharged. The return line 11 opens into the tank 3 and drives there possibly a jet pump (not shown).

In the interior of the high-pressure pump 2, the temperature sensor T can also be arranged. The high-pressure pump 2 is hydraulically connected to the tank 3 via a fuel inlet 12, the filter 6 and the prefeed pump 4. The fuel inlet 12 connects a delivery side of the prefeed pump 4 with the interior 9 of the pump housing, so that the entire flow of the prefeed pump 4 passes into the interior 9.

The prefeed pump 4 is designed as a gear pump. Between the prefeed pump 4 is a gap between the rotating components and the pump housing, causing leakage losses, which in FIG. 1 is represented by the symbol of a throttle (see reference numeral 29). The leaked through the gap leakage amount is discharged through a leakage line 30. The leakage line 30 opens in front of a first valve 27 in the line (without reference numeral), which supplies the flowing through a first bearing 23 amount of fuel via the first valve 27 of the return line 11.

A fuel return 13 provides a hydraulic connection between the interior 9 of the pump housing on the one hand and a metering unit 14 and the return line 11 on the other. Between the fuel return line 13 and the return line 11, the pressure regulating valve 10 is arranged.

The metering unit 14 serves to control the amount of fuel sucked by pump elements 15 of the high-pressure pump and thus also the delivery rate thereof. For this purpose, the suction sides of the pump elements 15 are hydraulically connected via a distribution line to the output of the metering unit 14.

The pump elements 15 consist essentially of suction valves 16, high pressure side check valves 17 and a piston 18 which oscillates in a cylinder bore (not shown). The pistons 18 of the pump elements 15 are driven via roller tappet 19 by cams 20 of a drive shaft 21. The pump elements 15 convey fuel under high pressure via a high-pressure line 22 into the rail 7.

The cams 20 are part of the drive shaft 21 which is rotatably mounted on both sides of the cams 20 in a first bearing 23 and in a second bearing 24 (each shown as a throttle in the figure) in a pump housing (not shown). The drive shaft 21 is arranged in the interior 9 of the pump housing.

Furthermore, the pressure regulating valve 10 is downstream of the interior 9 of the high-pressure pump 2 arranged. The pressure regulating valve 10 comprises a leakage line 25 in which optionally a throttle 26 may be provided. As a result of the arrangement of the pressure regulating valve 10 downstream of the interior 9, almost the same pressure prevails in the interior 9 as on the pressure side of the prefeed pump 4.

The increased internal pressure in the interior 9 of the pump housing leads inter alia to the fact that, depending on the pressure prevailing in the interior 9, the viscosity of the fuel and the flow resistance of the first bearing 23 and a second bearing 24 of the drive shaft 21, a defined amount of fuel through the bearings 23 and 24 is pressed. This leads to a significant increase in the load capacity of both the first bearing 23 and the second bearing 24th

Since the first bearing 23 and the second bearing 24 are formed as sliding bearings, formed by the forced flow through the bearings 23 and 24 in the bearings 23 and / or 24, a hydrostatic lubricating wedge. As a result, the load capacity of the first bearing 23 and the second bearing 24 increases considerably and at the same time the heat dissipation from the first bearing 23 and the second bearing 24 is improved.

Thus, the pressure build-up within the high-pressure fuel pump 2 and in the rail 7 is accelerated, downstream of and in series with the first bearing 23, a first valve 27 is arranged, which is formed as a check valve. Accordingly, downstream of and in series with the second bearing 24, a second valve 28 is arranged, which is also designed as a check valve. The first valve 27 and the second valve 28 open into the return line 11. The opening pressure of the valves 27 and 28 according to the prior art is more than 1 bar and is chosen so that they are closed when starting the engine and only open when the internal combustion engine is running.

FIG. 2 shows a block diagram of a portion of the fuel injection system, which substantially like the fuel injection system 1 of FIG. 1 is constructed with a high-pressure pump 2 according to one embodiment. A drive shaft accommodated in the interior 9 and not shown in detail is supported on both sides of the interior 9 by a first bearing 23 and a second bearing 24. The first bearing 23 and the second bearing 24 are formed as sliding bearings and are each arranged in a bearing return 31 and 31 '. Downstream of the first bearing 23 and in series with it, a first valve 27 is arranged, which is designed as a check valve or as a ball check valve. Downstream of the second bearing 24 and in series with it, a second valve 28 is arranged, which is likewise designed as a check valve or as a ball check valve. The effect and operation is essentially the same as that already associated with the first and second valves 27, 28 of FIG FIG. 1 has been described, but with the difference that the first valve 27 and / or the second valve 28 according to the embodiment have an opening pressure which is less than or equal to 0.8 bar and greater than or equal to 0.1 bar. Therefore, in contrast to the first and second valves 27, 28 of FIG. 1, the first valve 27 and / or the second valve 28 are open when the internal combustion engine is started.

FIG. 3 shows a further block diagram of a portion of the fuel injection system with a high pressure pump 2 according to another embodiment. Unlike the in FIG. 2 shown embodiment, only a common valve 32, which is designed as a check valve or as a ball check valve is provided. The common valve 32 is arranged in a common bearing return 31 "into which the bearing returns 31, 31 'open, and the common valve 32 in this embodiment also has an opening pressure which is less than or equal to 0.8 bar and greater than or equal to zero , 1 bar, so that the common valve 32 is open at the start of the internal combustion engine.

Overall, the configuration according to the invention provides a high-pressure pump 2 which is improved in terms of its functionality and more robust in terms of its durability.

Claims (10)

1. High-pressure pump (2) for a fuel injection system (1) of an internal combustion engine, in particular for a common rail injection system, which high-pressure pump (2) has a drive shaft (21) which is mounted by at least one bearing (23, 24) which is arranged in a bearing return (31, 31', 31"), at least one valve (27, 28, 32) being arranged downstream of the at least one bearing (23, 24), characterized in that the at least one valve (27, 28, 32) has an opening pressure which lies in a range from 0.1 bar to 0.8 bar.
2. High-pressure pump (2) according to Claim 1, characterized in that the at least one valve (27, 28, 32) is a check valve, in particular a ball check valve.
3. High-pressure pump (2) according to Claim 1 or 2, characterized in that the at least one bearing (23, 24) is a plain bearing.
4. High-pressure pump (2) according to one or more of Claims 1 to 3, characterized in that fuel can flow through the at least one bearing (23, 24).
5. High-pressure pump (2) according to one or more of Claims 1 to 4, characterized in that a first bearing (23) and a second bearing (24) are provided for mounting the drive shaft (21).
6. High-pressure pump (2) according to Claim 5, characterized in that a first valve (27) is provided in the bearing return (31) downstream of the first bearing (23) and a second valve (28) is provided in the bearing return (31') downstream of the second bearing (24).
7. High-pressure pump (2) according to Claim 6, characterized in that the first valve (27) is arranged in series with the first bearing (23) and the second valve (28) is arranged in series with the second bearing (24).
8. High-pressure pump (2) according to Claim 5, characterized in that the respective bearing return (31, 31') of the first bearing (23) and of the second bearing (24) open into a common bearing return (31"), a common valve (32) being provided in the common bearing return.
9. High-pressure pump (2) according to one of Claims 1 to 8, characterized in that the drive shaft (21) is a camshaft which is arranged in an interior space (9) of a pump housing.
10. High-pressure pump (2) according to Claim 9, characterized in that the bearing return (31, 31', 31") and the interior space (9) of the pump housing are connected hydraulically.

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