WO2013110514A1

WO2013110514A1 - High-pressure fuel pump for an injection system

Info

Publication number: WO2013110514A1
Application number: PCT/EP2013/050534
Authority: WO
Inventors: Friedrich Boecking; Andreas Dutt
Original assignee: Robert Bosch Gmbh
Priority date: 2012-01-23
Filing date: 2013-01-14
Publication date: 2013-08-01
Also published as: DE102012200894A1; EP2807365A1

Abstract

The invention relates to a high-pressure fuel pump for an injection system, in particular a common rail injection system in an internal combustion engine, comprising a pump housing (1) in which a camshaft (3) and at least one pump piston that cooperates with the camshaft (3) are arranged in a fuel-filled engine compartment (2) which is connected to a low pressure system of the injection system via an overflow valve (4) that has a spring-loaded control piston (11) and is inserted in a cavity (7) of the pump housing (1). According to the invention, the high-pressure fuel pump comprising an overflow valve (4) is to be optimized in terms of the components to keep costs low. In order to do so, an insert (8) which accommodates at least the control piston (11) is inserted in the cavity (7), and at least one duct for delivering fuel is formed between the insert (8) and the cavity (7).

Description

Description Title:

High-pressure fuel pump of an injection system

The present invention relates to a high-pressure fuel pump of an injection system, in particular for a common-rail injection system of an internal combustion engine, with a pump housing, in which in a fuel-filled engine room a

Drive shaft is arranged through which at least one pump piston is at least indirectly driven in a lifting movement, and wherein the engine room via a spring-loaded control piston exhibiting overflow valve, which is inserted into a recess of the pump housing, is connected to a low pressure system of the injection system.

State of the art

Such a high-pressure fuel pump is known from DE 10 2009 027 1 6 6 A1. This high-pressure fuel pump has a suction-side low-pressure region, in which an overflow valve is arranged, which has a housing secured in a pump housing with an inlet, an outlet, a valve body and a valve spring. The device is characterized in that the

Valve housing of the spill valve is pressed or caulked in the pump housing.

The invention is based on the object, a high-pressure fuel pump

to provide that is cost optimized component.

This object is achieved in that in the recess at least one of the control piston receiving insert is inserted and wherein at least one channel for guiding fuel is formed between the insert and the recess. The Overflow valve does not have its own, in contrast to the prior art

Valve housing, but the components of the spill valve are inserted directly into the recess, further forming the recess or the insert in their cooperating areas a channel for guiding fuel. As a result, this requires no separate channel, for example, be incorporated into the pump housing. In this respect, the insert according to the invention also differs from a known valve housing, which may have any channels in the interior, but not in cooperation with the pump housing on the outer circumference of the valve housing.

In a further development of the invention, the channel is formed by an outer recess in the insert. In this case, a plurality of outer recesses may be arranged distributed on the circumference of the insert. This channel or this outer recess establishes the flow guidance of the fuel to the overflow valve and / or from the overflow valve to other components of the high-pressure fuel pump.

In Weiterillilldung of the invention, the outer recess extends axially along the cylindrical insert and is in turn formed in a further embodiment as a semi-circular groove. Such an outer recess can be easily incorporated or cast in the insert and therefore does not cause any significant manufacturing costs.

In a further development of the invention, the channel or the outer recess is an overflow channel for fuel diverted from the overflow valve. This diverted fuel is continued along the channel and into one of the

Recess inserted return connection piece introduced. As a result, a very compact overflow valve is realized, whereby the integration of the

Overflow channels in the insert and the corresponding arrangement of an inlet channel to the spill valve at geodetically high point of the pump housing, a gain in vent height can be achieved. In a further embodiment of the invention, the channel is a compensation channel which connects the spring chamber with the low-pressure system of the high-pressure fuel pump. This embodiment also integrates functions into the overflow valve without additional components and production outlay. In this case, the compensation channel and the

Overflow, which are both parts of the channel to be produced in a manufacturing process.

In a further development of the invention, the material of the control piston has an at least similar, preferably the same, thermal expansion coefficient as the material of the insert. This design ensures that at

different operating temperatures a smooth movement of the

Control piston is ensured without the risk of jamming in the insert.

In a further development of the invention, a return connection piece is inserted into the recess. This return connection piece is for example pressed into the recess and holds the components of the overflow valve in the recess, without the need for a separate component must be used.

In a further embodiment of the invention, the control piston has a spring recess for substantially receiving the control piston spring. This embodiment allows a space-saving accommodation of the control piston spring and thus a compact construction of the overflow valve.

In a further development of the invention, a pressure-holding valve is provided which in a

Low pressure line is used. This pressure-holding valve adjusts a pressure increase in the spring chamber for damping the movements of the control piston.

Further advantageous embodiments of the invention are described in the drawings, are described in more detail in the embodiments illustrated in the figures of the invention

Brief description of the drawings Show it:

Figure 1 is a sectional view of a first variant of a in a

Recess of a pump housing built-in overflow valve;

Figure 2 is a sectional view of a second variant of a in a

Recess of a pump housing built-in overflow valve,

Figure 3 is a sectional view of a third variant of a in a

Recess of a pump housing built-in overflow valve and

FIG. 3 is a sectional view of a fourth variant of a in a

Recess of a pump housing built-in overflow valve.

Embodiments of the invention

Figure 1 shows a sectional view through a fragmentary shown

Pump housing 1 a high-pressure fuel pump. The fuel high-pressure pump promotes fuel supplied from a low-pressure system, in particular

Diesel fuel, in a high-pressure accumulator, from which the fuel from

Fuel injectors for injection into combustion chambers of an internal combustion engine is removed. The internal combustion engine is preferably a self-igniting internal combustion engine.

The high-pressure fuel pump has the pump housing 1, in which a

Engine room 2 is formed. The engine compartment 2 is the fuel from the fuel low pressure system, or arranged in this one

Low pressure fuel pump supplied. In the pump housing 1, a drive shaft 3 is mounted, which projects into the engine room 2 and the at least one

Pump piston at least indirectly in a lifting movement drives. By the Pump piston is conveyed into a pump working chamber introduced fuel into the high-pressure accumulator. The drive shaft 3 may be a camshaft or eccentric shaft. Between the drive shaft 3 and the pump piston, a roller tappet may be arranged with a on a cam or eccentric

Drive shaft 3 running role. The introduced into the pump working space fuel is metered by a metering unit, which is also installed in the pump housing 1 and connected to the engine room 2. Parallel to the

Metering unit, a spill valve is installed in the pump housing 1, being discharged from the spill valve unnecessary fuel into the low pressure system. It should be noted that in the engine room 2, for example, a constant amount of fuel is introduced and the metering unit initiates different amounts of fuel in the pump working space depending on operating conditions of the internal combustion engine.

The camshaft 3 is fuel lubricated and has a housing bearing 5 and opposite flange bearing. The housing bearing 5 is with a

Fuel storage channel 6 connected in a suitable manner with the

Fuel low pressure system is interconnected.

In the pump housing 1, a recess 7 is incorporated, in which an insert 8 is inserted. The insert 8 has an inner recess 9, which in the lower area a control spring chamber 10, lying above the guide for a control piston 11 and lying above a valve chamber 12 forms. In the control spring chamber 10 is a

Control piston spring 13 is inserted, which is supported on a bottom wall of the insert 8 and an annular shoulder of the control piston 11. Opposite to the

Control piston spring 13 is in the insert 8 a stroke stop 1 ^, for example, used in an inner ring groove. The stroke stop \ forms the upper attachment for the

Control piston 11. The insert 8 is pressed into the recess 7 and / or held by a likewise pressed into the recess 7 return connection pipe 15 in the recess 7. The valve chamber 12 is connected to an inlet channel 1 6, which opens into the engine compartment 2 of the high-pressure fuel pump. Through the inlet channel 16 fuel is introduced into the valve chamber 12. In accordance with the fuel pressure, the spool 11 is moved downwardly against the force of the spool spring 13 and connects the spool space 12 via one or more control ports 17 in the spool 8 to a channel for guiding fuel. This channel for guiding fuel is formed as an overflow 18 formed outer recess in the insert 8. The outer recess or the overflow channel is semicircular and extends at least from the control channel 17 via the upper end of the insert 8 into the region of the return connection piece 15 to from there via a

Inlet bore 19 to get into the interior of the return connection piece 15. From the partially illustrated sectional view A-A it can be seen that two or more overflow channels 18 are incorporated into the insert 8 enclosing a control channel 17.

The control piston 11 has a bore recess 20, which is connected via an optionally existing throttle 21 with the control spring chamber 10. Through this flow connection, a small amount of fuel flows continuously from the valve chamber 12 into the control spring chamber 10 and from there via a compensation channel 22 into the overflow channel 18. The compensation channel 22 is likewise formed as an outer recess in the insert 8 and preferably arranged in extension from the overflow channel 18 , The compensation channel 22 ensures regardless of the

Presence of a throttle 21, that the control spring chamber 10 with the

Low pressure system is connected and there can not build up an undesirably high pressure. In the compensation channel 22 or a connection bore to the

Control spring chamber can be installed a damping throttle, which dampens the movements of the control piston 11.

Due to the illustrated construction and installation of the overflow in the

Pump housing 1 is the illustrated with the arrow 23 profit of vent height in the engine room 2 with respect to a conventionally constructed spill valve reached. Incidentally, the insert 8 is aligned with the inlet channel 16 and is inserted sealingly in the recess 7.

The embodiment according to Figure 2 differs from the

Embodiment according to Figure 1 substantially by a different arrangement of

Components of the overflow valve. The insert 8 is inserted into the recess 7 with the insertion of an O-ring 2h and held by the return connection piece 15 in the recess. The inlet channel 1 6 opens in this embodiment in a bottom wall 25 of the recess 7 and is connected directly to the valve chamber 12 in the insert 8. In the insert 8, the control piston 11 is inserted and its

Movement possibility in the direction of the bottom wall 25 bounded by the stroke stop \ h. In the region of the valve chamber 12 at least two control channels 17 are embedded in the insert 8, the valve chamber 12 with overflow 18 on

Connect outer circumference of the insert 8. The overflow channels 18 are connected via a transverse bore 26 at the upper end of the insert 8 with the return connection piece 1.

In the control piston 11, a spring recess 27 is inserted for substantially receiving the control piston spring 13, wherein the control piston spring 13 at a

Plant body 29 opposite to the spring recess 27 abuts. In the

Control piston 11 is incorporated a throttle 21, flows through which a constant amount of fuel from the valve chamber 12 into the spring recess 27 and further through an arranged in the plant body outlet throttle 28 in the low pressure system. The embodiment according to FIG. 2 differs from the embodiment according to FIG. 3 in that here no throttle 21 is inserted into the control piston 11 and the outlet throttle 28 is optionally present in this embodiment (an embodiment without outlet throttle is shown). Above the transverse bore 26, a pressure-maintaining valve 30 is integrated in the overflow valve h, which consists of a spring plate 31 and a closure body 32. For example, the opening pressure of

Pressure relief valve 30 0, 2 bar and the maximum flow 150 l / h at 0.3 bar. Of the pressure-holding valve 30 is in the transfer channels 18 and in particular in the Spring recess 27 and the control spring chamber 10 set a pressure increase, which among other things lead to a damping of the movements of the control piston 11.

The embodiment of Figure shows a simplified construction of a spill valve. In the recess 7, an insert 8 is used, wherein the valve chamber 12 is connected via an inlet channel 16 with the engine room 2. In the insert 8, the control piston 11 is inserted, which in turn has a spring recess 27 for substantially receiving the control piston spring 13. Furthermore, at least one control channel 17 is inserted into the insert 8, which in turn with the

Overflow 18 cooperates on the outer circumference of the insert 8. Of the

Overflow channel 18 is hardly used in this embodiment, however, since directly adjacent to the control channel 17, a discharge line 33 is inserted into the pump housing 1, in which the return connection port 15 is inserted. The adjustment of the control piston 11 is limited in this embodiment by a stroke stop \, while a holding part 3 defines the components of the overflow in the recess 7.

Claims

High-pressure fuel pump of an injection system, in particular for a common-rail injection system of an internal combustion engine, with a

Pump housing (1), in which in a fuel-filled engine room (2) a drive shaft (3) is arranged, is driven by the at least one pump piston at least indirectly in a lifting movement, and wherein the engine compartment (2) via a spring-loaded control piston (11) having overflow valve (16), which in a recess (7) of the

Pump housing (1) is used, is connected to a low-pressure system of the injection system,

characterized in that in the recess (7) at least one of the control piston (11) receiving insert (8) is inserted, and that between the insert (8) and the recess (7) is formed at least one channel for guiding fuel.

High-pressure fuel pump according to claim 1,

characterized in that the channel is formed by an outer recess in the insert (8).

High-pressure fuel pump according to claim 2,

characterized in that the outer recess extends axially of the cylindrical insert (7).

High-pressure fuel pump according to claim 2 or 3,

characterized in that the outer recess is semicircular.

5. high-pressure fuel pump according to one of claims 2 to,

characterized in that the outer recess is an overflow channel (18).

6. High-pressure fuel pump according to one of claims 2 to 5,

characterized in that the outer recess is a compensation channel (22).

7. High-pressure fuel pump according to one of the preceding claims,

characterized in that the material of the control piston (11) has the same thermal expansion coefficient as the material of the insert (8).

8. High-pressure fuel pump according to one of the preceding claims,

characterized in that in the recess (7) a

Return connection piece (15) is inserted.

9. High-pressure fuel pump according to one of the preceding claims,

characterized in that the control piston (11) has a spring recess (27) for substantially receiving the control piston spring (13).

10. High-pressure fuel pump according to one of the preceding claims,

characterized in that a pressure holding valve (30) is provided, which is inserted into the insert (8).