KR20210099585A - high pressure fuel pump - Google Patents

Abstract

A high-pressure fuel pump (10) for a fuel injection system of an internal combustion engine has a pump housing (12) having a driving-side cross-sectional area (44), a high-pressure outlet (24), and in the open state, a high-pressure fuel pump (10) for discharging fuel from the high-pressure outlet (24). and a pressure limiting valve (58). A pressure limiting valve 58 is arranged in a discharge flow path 52 in the pump housing 12 , which opens into a driving-side cross-sectional area 44 of the pump housing 12 .

Description

high pressure fuel pump

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

Such a high-pressure fuel pump is known from DE 10 2005 007 806 A1 and comprises a pump housing and a pressure limiting valve. It is received in a recess in the pump housing. A pressure limiting valve, in the open state, connects the high pressure outlet to the delivery chamber of the high pressure fuel pump. The pressure limiting valve opens when the pressure difference between the high pressure outlet and the delivery chamber of the high pressure fuel pump exceeds a limit value. Thus, the pressure limiting valve prevents the pressure in the high pressure outlet from becoming unacceptably high. Thus, the pressure-limiting valve has practically two functions: on the one hand the pressure release at the high-pressure outlet when the maximum permissible pressure is exceeded, and on the other hand the high-pressure outlet to the delivery chamber at a pressure lower than the maximum permissible pressure and this sealing of components connected to them (eg fuel rails).

The problem of the invention is solved by a high-pressure fuel pump having the features of claim 1 . Preferred developments of the invention are presented in the dependent claims.

The high-pressure fuel pump according to the invention is used to deliver fuel in a fuel injection system of an internal combustion engine. The fuel is in particular gasoline or diesel. The high-pressure fuel pump compresses the fuel to a high pressure and delivers it, for example, to a fuel rail to which an injection device is connected which injects the fuel directly into the corresponding combustion chamber of the internal combustion engine. The high pressure fuel pump contains a pressure limiting valve. The pressure limiting valve limits the pressure on or in the high pressure outlet of the high pressure fuel pump to a maximum allowable value. When the pressure there exceeds the opening pressure of the pressure limiting valve, the pressure limiting valve is opened, and fuel is discharged from the high pressure outlet.

The high-pressure fuel pump also includes a pump housing having a drive-side cross-sectional area. The use of the term “end region” does not imply that the pump housing must have a rotationally symmetrical shape. The entire pump housing nevertheless has a longitudinal axis extending parallel to the delivery piston. The drive-side cross-sectional area is the area of the end of the pump housing facing the drive device of the delivery piston. These drives generally include camshafts or eccentric shafts.

According to the invention, the pressure limiting valve is arranged in the discharge flow path in the pump housing which opens into the cross-sectional area of the drive side of the pump housing. In this way, wear-related pressure pulsations from the delivery chamber of the high-pressure fuel pump, as may occur when the discharge flow path is opened to the delivery chamber, are avoided. In addition, a dead volume in the delivery chamber of the high-pressure fuel pump is significantly reduced compared to the discharge passage opened to the delivery chamber of the high-pressure fuel pump, so that the delivery amount of the high-pressure fuel pump can be increased. The housing strength of the high-pressure fuel pump at a critical point may be increased by rearranging the pressure limiting valve in the pump housing of the high-pressure fuel pump. Overall, the efficiency of the high pressure fuel pump is increased and its reliability and service life are increased.

An improvement of the present invention includes a stepped delivery piston, the discharge passage opening to a stepped chamber in which steps of the delivery piston are disposed, the stepped chamber being formed in a driving-side cross-sectional area of the pump housing. The stepped chamber is normally sealed by a seal holder and a piston seal to the drive unit and the lubricant therein, and is connected via a flow path to the low pressure region of the high pressure fuel pump. The opening of the discharge flow path to the cascaded chamber creates a reliable relief option for the high-pressure outlet without the risk of fuel entering the drive unit and the lubricant therein when the pressure limiting valve is opened.

In a refinement of the invention, the pressure limiting valve is designed as a spring loaded check valve. These valves are inexpensive to manufacture and operate reliably. The size is also small.

In a refinement of the invention, the longitudinal axis of the pressure limiting valve is arranged parallel to the longitudinal axis of the delivery piston. This compares with the previous arrangement of the pressure-limiting valve (for example, an arrangement in which the pressure-limiting valve is arranged radially or tangentially to the longitudinal axis of the delivery piston and thus to the pump housing) the overall height of the high-pressure fuel pump can be reduced, so that the high-pressure fuel pump can be used in installation situations with narrow spaces.

In a refinement of the present invention, the pressure limiting valve is inserted into the discharge passage from the opening in the driving-side cross-sectional area. This greatly simplifies the assembly of the pressure-limiting valve, since, in general, the drive-side cross-sectional area can be accessed very easily.

In a refinement of the present invention, the pressure limiting valve is maintained in a press fit condition to the discharge passage. In this way, the pressure limiting valve can be installed and maintained easily and reliably.

In a development of the invention, the section of the pressure limiting valve, in particular the valve body, is formed by the section of the valve housing. For example, the valve body may be manufactured directly from the housing material or integrated directly into the housing. Thereby, the number of components to be manufactured and to be joined or pressed is reduced, thereby simplifying manufacturing.

In an improvement of the present invention, the high-pressure outlet is disposed on a side of the pump housing when viewed in the axial direction (ie, in the direction of the longitudinal axis) of the pump housing, and the outlet flow path extending from the delivery chamber to the high-pressure outlet is in the axial direction of the pump housing. It is arranged on the side of the section of the discharge flow path that opens to the high-pressure connection when viewed. This also allows the overall height of the high-pressure fuel pump to be reduced.

In a refinement of the present invention, the discharge flow path comprises at least two blind bores that are at least approximately orthogonal and intersecting, one of which extends substantially radially or tangentially of the pump housing from the high-pressure outlet, and the other has a driving-side cross-sectional area. from the substantially axial direction of the pump housing. Such a blind bore can be easily implemented so that the manufacturing cost of the high-pressure fuel pump can be kept low.

A possible embodiment of the invention is described below with reference to the drawings.

1 shows a partial cross-sectional view of a high-pressure fuel pump with a pressure limiting valve;
FIG. 2 shows a side perspective view of the high-pressure outlet of the high-pressure fuel pump of FIG. 1 ;
3 shows the components of the pressure limiting valve of FIG. 1 ;

In FIG. 1 , a high-pressure fuel pump for an internal combustion engine, which is not shown in detail, is generally denoted by reference numeral 10 . The high-pressure fuel pump 10 has a substantially cylindrical pump housing 12 in or on which the essential components of the high-pressure fuel pump 10 are arranged. The high pressure fuel pump 10 is reciprocated by an inlet/quantity control valve 14 and a drive shaft in which a first end region 16 protrudes into the delivery chamber 18 and a second end region 20 is not shown. and a delivery piston 22 capable of

On the side of the pump housing 12 there is a flat area defining a high pressure outlet 24 . The high pressure outlet 24 may be connected to the delivery chamber 18 via a discharge valve (not visible in FIG. 1 ) placed outside the cross section of FIG. 1 . A discharge connection 26 is attached to the high pressure outlet 24 . The exhaust connection 26 is fluidly connected to the high pressure region 28 , which may be, for example, a fuel rail to which a plurality of injectors are connected, which inject fuel directly into the corresponding combustion chamber of the internal combustion engine.

Although the pump housing 12 is not exactly rotationally symmetrical, it nevertheless has a longitudinal axis 30 . The top region 31 of the pump housing 12, as viewed in FIG. 1 , supports a hood-type housing cover 32 to which an inlet connection 34 is attached which connects to the low pressure region 36 . The low pressure region 36 may include, for example, an electric pre-delivery pump. Between the upper region 31 of the pump housing 12 and the housing cover 32, a fluid space (without reference numeral) in which the diaphragm pressure damper 38 is accommodated is formed.

The delivery piston 22 is designed as a stepped piston with an upper section with a larger diameter in FIG. 1 and a lower section with a smaller diameter in FIG. 1 . The step or shoulder between the two sections is indicated generally by reference numeral 40 in FIG. 1 . As can be seen in FIG. 1 , in the position shown in FIG. 1 of the delivery piston 22 , the step 40 is on the outside of the pump housing 12 , in particular of the pump housing 12 , on the lower driving side in FIG. 1 . Fitted in a so-called "stepped chamber" 42 formed between a cross-sectional area 44 and a seal holder 46 made as a sheet metal part, said seal holder 46 being a tubular fastening stub of the pump housing 12 ( 48) in a press fit condition to the driving side cross-sectional area 44 of the pump housing. The seal holder 46 supports a piston seal 50 sealing the stepped chamber 42 from a drive device, not shown, disposed below the second end region 20 of the delivery piston 22 .

The discharge flow path 52 is present in the pump housing 12 and is formed in the present case by, for example, two blind bores 54 , 56 orthogonal to and intersecting each other. A blind bore 54 extends from the high pressure outlet 24 in a substantially radial direction of the pump housing 12 , and the blind bore 56 extends substantially axially of the pump housing 12 from the drive-side cross-sectional area 44 . do. The axial blind bore 56 is designed as a stepped bore with a section with a larger diameter (not referenced) extending from the driving side cross-sectional area 44 . In this section, a pressure limiting valve 58 is arranged which opens towards the driving-side cross-sectional area 44 .

The pressure limiting valve 58 is designed as a spring loaded check valve. The valve comprises a valve element 60 designed as a valve ball (see FIG. 3 ), but other valve elements may also be used, for example conical valve elements. A valve spring 62 , designed in this case for example as a helical compression spring, supports the ball holder 64 at the top as viewed in FIG. 1 and at the left end as viewed in FIG. 3 and holds the valve element 60 into the valve body ( 66 , the valve body 66 is formed with a valve seat 68 which cooperates to seal with the valve element 60 during closing of the pressure limiting valve 58 . The end of the valve spring 62 facing away from the valve body 66 is supported on a sleeve 70 that, like the valve body 66 , is press-fitted into the blind bore 56 , ie held in a press fit there.

As can be seen in FIG. 1 , a longitudinal axis (not shown) of the pressure limiting valve 58 extends parallel to the longitudinal axis 30 of the pump housing 12 . Also, as can be seen in FIG. 1 , the components of the pressure limiting valve 58 are inserted from an opening on the driving side cross-sectional area 44 into the axial blind bore 56 of the discharge flow path 52 .

As shown in FIG. 2 , the outlet flow path 72 leading from the delivery chamber 18 to the high pressure outlet 24 through the above-described discharge valve is of the discharge flow path 52 when viewed in the axial direction of the pump housing 12 . , arranged on the side of the section that opens to the high-pressure outlet 24 , ie the radial blind bore 54 . The lateral offset is indicated by reference numeral 74 in FIG. 1 . The spoked end plate 76 of the outlet valve is also visible in FIG. 2 . Also, as can be seen in FIG. 2 , the outlet flow path 72 opens with a generally circular high pressure outlet 24 , centrally, laterally, and offset downwardly, while the radial blind bore 54 of the discharge flow path 52 . ) is open off center in FIG. 2 to the left and slightly above the center. In principle, other arrangements of the openings of the outlet flow path 72 and the discharge flow path 52 are possible.

During operation, fuel, for example gasoline or diesel, is drawn into the delivery chamber 18 through the inlet and quantity control valve 14 from the delivery piston 18 during the intake stroke. During the delivery stroke, the fuel in the delivery chamber 18 is compressed and discharged to the high pressure region 28 through the discharge valve and discharge connection 26 . The amount of fuel discharged during the delivery stroke is regulated by an electromagnetically actuated inlet and quantity control valve 14 .

If there is an unacceptable overpressure in the high pressure region 28 , the pressure limiting valve 58 is opened, as a result of which fuel can flow from the high pressure region 28 into the cascaded chamber 42 . The stepped chamber 42 is connected to a region located, for example, upstream of the delivery chamber 18 , via a flow path not shown here, which is connected to a low pressure region 36 .

10: high pressure fuel pump
12: pump housing
22: delivery piston
24: high pressure outlet
44: end region
58: pressure limiting valve

Claims (9)

A high-pressure fuel pump (10) for a fuel injection system of an internal combustion engine, the pump housing (12) having a driving-side cross-sectional area (44), a high-pressure outlet (24), and discharging fuel from the high-pressure outlet (24) in an open state In the high pressure fuel pump (10) comprising a pressure limiting valve (58),
The pressure limiting valve (58) is arranged in a discharge flow path (52) in the pump housing (12), wherein the flow path (52) opens into a driving side cross-sectional area (44) of the pump housing (12). a high-pressure fuel pump (10). The step chamber (42) according to claim 1, wherein the high-pressure fuel pump (10) comprises a stepped delivery piston (22), and the discharge flow path (52) is provided with a step (40) of the delivery piston (22). A high-pressure fuel pump (10), characterized in that the stepped chamber (42) is formed in a driving side cross-sectional area (44) of the pump housing (12). 3. High-pressure fuel pump (10) according to claim 1 or 2, characterized in that the pressure limiting valve (58) is designed as a spring loaded check valve. 4. High-pressure fuel pump according to any one of the preceding claims, characterized in that the longitudinal axis of the pressure limiting valve (58) is arranged parallel to the longitudinal axis (30) of the delivery piston (22) ( 10). The pressure limiting valve (58) or at least a part thereof is inserted into the discharge flow path (58) from an opening in the driving side cross-sectional area (44) according to any one of the preceding claims. high pressure fuel pump (10). 6. The high-pressure fuel pump (10) according to any one of the preceding claims, characterized in that the pressure limiting valve (58) or at least a part thereof is held press-fit to the discharge flow path (52). 7. The high-pressure fuel pump (10) according to any one of the preceding claims, characterized in that the section of the pressure limiting valve, in particular the valve body, is formed as a section of the valve housing. 8. The delivery chamber (18) according to any one of the preceding claims, wherein the high-pressure outlet (24) is arranged on a side of the pump housing (12) when viewed in the axial direction of the pump housing (12). An outlet flow path 72 extending from High-pressure fuel pump (10), characterized in that. 9. The pump housing according to claim 8, characterized in that the discharge passage (52) comprises two orthogonal and intersecting blind bores (52, 54), one of which is substantially radial or tangential to the pump housing from the high pressure outlet (24). direction, the other extending in the substantially axial direction of the pump housing (12) from the drive-side cross-sectional area (44).

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