WO2013110513A1

WO2013110513A1 - High-pressure fuel pump for an injection system

Info

Publication number: WO2013110513A1
Application number: PCT/EP2013/050533
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: DE102012200909A1

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 (9). The high-pressure fuel pump of the invention is to be optimized in terms of the components to keep costs low. In order to do so, the control piston (9) is inserted without a housing into a cavity (7) in the pump housing (1), and a supply duct (8) that is connected to the engine compartment (2) as well as a control duct (12) that is connected to the low pressure system extend into said cavity (7) in the area of a valve chamber (26).

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 compartment, 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 is connected via a spring-loaded control piston exhibiting overflow valve with a low pressure system of the injection system.

State of the art

Such a high-pressure fuel pump is known from DE 10 2009 027 146 A1. This high-pressure fuel pump has a suction side

Low-pressure region in which an overflow valve is arranged, which has a fixed housing in a pump housing valve housing having an inlet, an outlet, a valve body and a valve spring. In this case, the device is characterized by the fact that the valve body of the

Overflow valve in the pump housing is pressed or caulked.

The invention has for its object to provide a high-pressure fuel pump, which is cost optimized component. Disclosure of the invention

Advantages of the invention

This object is achieved in that the control piston is houseless inserted into a recess in the pump housing, and that in the Recess in the region of a valve chamber open an inlet connected to the engine room inlet channel and connected to the low-pressure system control channel. By this configuration or the direct insertion of the components of the overflow valve, for example the control piston in a recess in the pump housing is a separate

Saved valve housing for the overflow valve. The recess, which is drilled, for example, in the pump housing into it, must be made only in the field of leadership of the control piston with a precision that is sufficient for the reliable management of the control piston, for example, with a game of 10 to 30 μηι.

It is also conceivable to design the recess as a stepped recess which, in the region of the guide of the control piston, has a smaller diameter compared with the remaining region of the recess, which diameter is processed correspondingly precisely. Overall, the inventive design, namely in particular to use the control piston without housing in the recess in the pump housing, a cost-effective component optimization of the overflow, in which the valve housing at a low

Extra effort in the processing by the control piston and the other components of the spill valve receiving recess in the

Pump housing is replaced.

In a further development of the invention, the material of the control piston at least approximately the same thermal expansion coefficient as the material of the pump housing. This embodiment ensures that jamming of the control piston in the recess during heating or cooling of the components is excluded. For example, the pump housing and the control piston can be made of aluminum. In a further embodiment of the invention, a contact body for the control piston spring is inserted into the recess. This system body may be formed, for example, as a ball, wherein the ball is pressed into the recess. In this case, the contact body is pressed so far into the recess for biasing the control piston spring until a desired opening pressure is set. In a further development of the invention is in the recess

Return connection piece used, the return connection piece forms a spring system for the control piston spring. This embodiment forms a further simplification, in which the separate contact body for the

Tax piston spring is saved.

In a further embodiment of the invention, a control piston spring receiving a control spring chamber via a compensation channel with the

Low pressure system connected. This embodiment ensures that during operation of the high-pressure fuel pump or the overflow valve of the control spring chamber is pressure-balanced to the low pressure system. This ensures that the control characteristic of the overflow valve is the same in all operating conditions. In this case, in addition to the compensation channel a damping throttle can be used.

In a further development of the invention, a control spring chamber accommodating a control piston spring is connected to the intake passage communicating with the valve chamber via a throttling channel embedded in the control piston. In this case, the control spring chamber is then connected via an equalization channel optionally with inserted damper throttle to the low pressure system. In this case, the throughput through the throttle channel is still lower than the throughput through the compensation channel optionally with the inclusion of the damper throttle. This embodiment ensures that, on the one hand, reliable venting of the system takes place, and, on the other hand, a minimum amount of fuel, for example for cooling purposes, flows through the overflow valve.

In a further development of the invention, the control piston has a spring recess for largely receiving the control spring. This embodiment contributes to a space-saving design of the overflow valve.

In a further development of the invention, a pressure-holding valve is provided, which is inserted into the recess, preferably directly adjacent to the

Receiving body for the control piston spring. With the pressure-holding valve, a pressure increase in the spring chamber is set, this pressure increase causes a damping of the movement of the control piston. In a further embodiment of the invention, the recess

Guide sections for guiding the control piston. In turn, in another embodiment, in the region between adjacent guide sections, an at least one subsection of the control channel is formed

Flow recess arranged. On the one hand, this embodiment represents a reliable guide for the control piston, with the control piston and the pump housing in turn having an at least very similar coefficient of thermal expansion in this embodiment. Using the area between the guide sections as a control channel offers the advantage of a space-saving design, which is also easy to implement in terms of manufacturing technology. Advantageously, three guide portions are distributed over the circumference of the recess, while the intermediate flow recesses can be milled, for example, as grooves in the pump housing. The opening cross-sectional area of the overflow valve, which in a

Adjusting pressurization can be set by the groove depth and the axial position of the grooves to each other targeted.

Further advantageous embodiments of the invention are the

Drawing description can be seen in the embodiments illustrated in the figures of the invention are described in more detail.

Brief description of the drawings

Show it:

FIG. 1 shows a sectional representation of a first exemplary embodiment of the overflow valve according to the invention,

Figure 2 is a sectional view of a second embodiment of the

Invention,

FIG. 3 shows a sectional illustration of a third exemplary embodiment of the invention

Overflow valve and FIG. 4 shows a section AA according to FIG. 3.

DETAILED DESCRIPTION FIG. 1 shows a section of a section in a sectional view

Pump housing 1 of a high-pressure fuel pump. The

High-pressure fuel pump is designed for a common rail injection system of an internal combustion engine, wherein the high-pressure fuel pump is supplied from a low-pressure fuel system and is introduced into an engine compartment 2 of the high-pressure fuel pump. From the engine room 2 the

High-pressure fuel pump is the introduced fuel via a

Inserting metering unit introduced into a pump working space in which the introduced fuel from a pump piston moved at least indirectly by a drive shaft 3 in a lifting movement conveys the fuel introduced into the pump working chamber into a high-pressure accumulator. The drive shaft 3 may be formed as a camshaft or eccentric shaft. Between the drive shaft 3 and the pump piston, a roller tappet may be provided with a roller running on a cam of the drive shaft. From the

High-pressure accumulator stored there fuel is needed and controlled by fuel injectors for injection into the combustion chambers of the engine.

Since the metering unit to introduce the in the pump workspace

Controls fuel as needed, is a spill valve 4 at the

High-pressure fuel pump installed, with the example, at constant

Quantity promotion by the low pressure system the excess fuel is diverted back to the low pressure system or the fuel tank.

The overflow valve 4 is integrated in the pump housing 1 in the region above a housing bearing 5 of the camshaft 3. The housing bearing 5 of

Camshaft 3 is fuel lubricated and connected to a fuel storage channel 6, through which the lubricating the housing bearing 5 fuel is discharged into the low pressure system. In the pump housing 1 is a recess 7 for receiving the

Components of the overflow valve 4 inserted, for example, drilled into it. In the recess 7, an inlet channel 8 opens, which connects the recess 7 with the engine room 2. The inlet channel 8 can as a combination of a casting recess and a bore in

Extension of the recess 7 may be formed. In the recess, a control piston 9 is used, for example, with a game of 10 to 30 μηι, which is pressed by a arranged in a control spring chamber 13 control piston spring 10 against the bottom of the recess. The control piston spring 10 is held by a contact body 1 1, which is formed in this embodiment as a ball, and is pressed into the recess 7. The extent of the depth of the injection of the ball determines the opening pressure of the control piston 9. In addition to the inlet channel 8 opens into the cylinder wall of the recess 7, a control channel 12 which is merged with the fuel storage channel 6. The control channel 12 is designed as a bore which is incorporated from the engine room 2 into the pump housing 1.

With increasing fuel pressure in the engine compartment 2, the control piston 9 is moved by the fuel in the direction of the spring chamber 13 and connects the resulting by the adjustment of the control piston 9 valve chamber above the inlet channel 8 with this and the control channel 12 so that fuel is diverted into the control channel 12 becomes. In the area above the junction of the control channel 12 and the fuel storage channel 6, a return connection piece 15 is inserted into a corresponding bore recess 14, for example, pressed. At the return connection 15 is

For example, a hose connected, which is connected to the fuel tank.

The control piston 9, which like the pump housing 1 is preferably made

Aluminum is made, has a Steuerkolbenausnehmung 16 which is connected via a throttle channel 17 with the control spring chamber 13. Furthermore, the control spring chamber 13 is connected via a compensation channel 18 with the control channel 12. Through the throttle passage 17 continuously flows a small amount of fuel from the inlet channel 8 in the control spring chamber 13 and further into the low pressure system. In contrast to the embodiment of Figure 1 is in the

Embodiment according to Figure 2 of the fuel storage channel 6 than in the

Control spring chamber 13 opening inclined bore formed. Furthermore, the control channel is in the form of two superimposed control bores 19a, 19b, which open into the fuel storage channel 6. Finally, the return connection piece 15 is used in this embodiment directly into the recess 7 and replaced as a spring system, the plant body for

Control piston spring 10. By the superimposed and different diameter having control bores 19a, 19b, the hydraulic

Flow through the spill valve 4 are formed via the pressure.

The embodiment of Figure 3 differs from the

Embodiments of Figures 1 and 2 essentially in that the recess 7 arranged three distributed on the circumference of the cylinder

Guide portions 20 (Figure 4) for guiding the control piston 9 has. Between the guide portions 20 Strömungsausnehmungen are incorporated in the form of grooves 21 in the pump housing 1. The

Opening cross-sectional area of this overflow valve 4 and the valve chamber 26 in the grooves 21 is determined by the depth of the grooves 21 and their axial position. The grooves 21 in this embodiment form the control channel 12. The control piston 9 has in this embodiment, a spring recess 22 for substantially receiving the control piston spring 10. The control piston spring 9 is held by the hollow contact body 11, which is discharged through the contact body 11 of the diverted fuel - as shown by the flow arrows -. Subsequent to the contact body 1 1, a pressure-maintaining valve 23 is inserted into the recess 7, which adjusts an excess pressure for damping the movements of the control piston 9, in particular in the spring recess 22. For example, the opening pressure of the pressure holding valve 23 is 0.2 bar and the maximum flow

150 l / h. The pressure-holding valve 23 has a closing body 25 held on a spring plate 24, which cooperates with the contact body 11 and dominates the passage bore through it. After that

Pressure retention valve 23, the return connection piece 15 is inserted into the recess 7, which forms the system for the spring plate 24 and the contact body 1 1.

Claims

claims

1. 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, through which at least one

Pump piston is at least indirectly driven in a lifting movement and wherein the engine room (2) via a spring-loaded control piston (9) exhibiting overflow valve (4) with a

Low-pressure system of the injection system is connected,

characterized in that the control piston (9) without a housing in a recess (7) in the pump housing (1) is inserted, and in that in the recess (7) in the region of a valve chamber (26) connected to the engine room (2) inlet channel ( 8) and a connected to the low-pressure system control channel (12) open.

2. High-pressure fuel pump according to claim 1,

characterized in that the material of the control piston (9) at least approximately the same thermal expansion coefficient as the material of the pump housing (1).

3. high-pressure fuel pump according to claim 1 or 2,

characterized in that in the recess (7) a

Plant body (11) for the control piston spring (10) is inserted.

4. high-pressure fuel pump according to claim 1 or 2,

characterized in that in the recess (7) a

Return connection piece (15) is inserted, and that the

Return connection piece (15) a spring system for the

Control piston spring (10) forms. High-pressure fuel pump according to one of the preceding claims, characterized in that a control piston spring (10) receiving the control spring chamber (13) via a compensation channel (18) is connected to the low-pressure system.

High-pressure fuel pump according to one of the preceding claims, characterized in that a control piston spring (10) receiving the control spring chamber (13) via a in the control piston (9) embedded throttle channel (17) with the valve chamber (26) in connection inlet channel (8) connected is.

High-pressure fuel pump according to one of the preceding claims, characterized in that the control piston (9) a

Spring recess (22) for largely receiving the

Control piston spring (10).

High-pressure fuel pump according to one of the preceding claims, characterized in that a pressure-retaining valve (23) is provided which is inserted into the recess (7).

High-pressure fuel pump according to one of the preceding claims, characterized in that the recess (7)

Having guide portions (20) for guiding the control piston (9).

High-pressure fuel pump according to claim (9),

characterized in that in the region between adjacent Führungsabschitten (20) is at least a portion of the control channel (12) forming flow recess is arranged.