DE102008057089A1 - Pump unit for a high-pressure pump - Google Patents

Abstract

The invention relates to a pump unit (10) for a high-pressure pump for producing high-pressure fuel for a fuel injection system of an internal combustion engine, comprising: a cylinder housing (11) with a cylinder chamber (13) in which a pump piston (12) is mounted so as to be axially movable, at least one suction valve (17) via which the cylinder chamber (13) fuel is supplied from a low pressure region, and at least one pressure valve (22) via which the compressed fuel from the cylinder chamber (13) is discharged into a high-pressure region. According to the invention, for an improved connection of at least one of the valves (17, 22) the relevant valve (17, 22) is formed largely integrated with the cylinder housing (11), including at least one valve body (18, 24) of the suction valve (17) and / or the pressure valve (24) in the cylinder housing (11) of the pump unit (10) is mounted.

Description

The The present invention relates to a pump unit for a High pressure pump for a fuel injection system Internal combustion engine, such as for an internal combustion engine a motor vehicle.

A high-pressure pump in question may include one or more such pump units and in particular for fuel supply in a high-pressure accumulator injection system, such as B. in a common rail injection system for diesel fuels, provided for the internal combustion engine of a motor vehicle be.

A Such a high pressure pump delivers the fuel from a Low pressure range in a high-pressure accumulator (often referred to as "rail"). There, the fuel is constantly at high pressure for injection ready in the respective engine cylinder. In a preferred use Such a high-pressure pump supplies these on the output side Pressure of more than 1000 bar, preferably more than 1500 bar and in particular up to over 2000 bar.

Such high-pressure pumps are known in many designs. For example only, the publications WO 2004/027263 A1 and DE 198 14 506 A1 called. The high-pressure pumps described herein comprise a plurality of pump units ("pump cylinders") which comprise at least one pump piston axially movably mounted in a cylinder space. Each cylinder or cylinder chamber is associated with a low-pressure side suction valve and a high-pressure side pressure valve.

adversely in the known high-pressure pumps for high-pressure fuel production is a relatively expensive attachment of the suction valve and the pressure valve on the cylinder housing or the respective Pump units.

So For example, the sealing contact surfaces On the one hand have a high quality and may on the other hand not damaged during assembly become. Even with the utmost care is the sealing at the contact surfaces is a weak point, which possibly also only after a longer operating time makes the high pressure pump noticeable.

It An object of the invention is a pump unit of the aforementioned To provide a type, which improved connection of the suction valve and / or the pressure valve.

These Task is solved by a pump unit with the features of claim 1. Preferred and advantageous developments are the subject the dependent claims.

• – ein Zylindergehäuse mit einem Zylinderraum, in dem ein Pumpenkolben axialbeweglich gelagert ist,
• – wenigstens ein Saugventil, über das dem Zylinderraum Kraftstoff aus einem Niederdruckbereich zugeführt wird, und
• – wenigstens ein Druckventil, über das der komprimierte Kraftstoff aus dem Zylinderraum in einen Hochdruckbereich abgeleitet wird,

wobei erfindungsgemäß vorgesehen ist, dass das Saugventil und/oder das Druckventil weitgehend integriert mit dem bzw. im Zylindergehäuse ausgebildet ist, wozu wenigstens ein Ventilkörper des Saugventils und/oder des Druckventils im bzw. am Zylindergehäuse der Pumpeneinheit gelagert ist.According to the invention, a pump unit for a high-pressure pump is proposed, for producing high-pressure fuel for a fuel injection system of an internal combustion engine, the pump unit comprising:

• A cylinder housing with a cylinder space in which a pump piston is mounted axially movable,
• - At least one suction valve, via which the cylinder chamber fuel is supplied from a low pressure region, and
• At least one pressure valve via which the compressed fuel is discharged from the cylinder space into a high-pressure region,

wherein the invention provides that the suction valve and / or the pressure valve is formed largely integrated with the or in the cylinder housing, for which purpose at least one valve body of the suction valve and / or the pressure valve is mounted in or on the cylinder housing of the pump unit.

The using the pump unit according to the invention trained high-pressure pump can in particular for high-pressure fuel production in a common-rail injection system (eg for diesel fuel) serve.

According to the invention provided that at least the suction valve or at least the pressure valve largely integrated with the cylinder housing of the pump unit is trained. By this is meant that one or more essential functional parts of these valves or valve units directly are arranged in or on the cylinder housing and preferred are integrally formed with the cylinder housing. In this Senses can be provided in particular that at least one functional part one of the valves through a portion of the cylinder housing even realized.

One such essential functional part is for example a storage area for a valve body of these valves.

According to the invention therefore specifically proposed, at least one valve body the suction valve or the pressure valve in the cylinder housing to store the pump unit, d. H. to arrange or move attach, causing the valve in question no longer as before must be provided as a separate unit or unit.

This eliminates the effort previously had to be operated with respect to the sealing and / or attachment of the suction valve and / or the pressure valve. In addition, separate Be fastening components that were previously required, eg. B. connecting parts such as screws and the like.

One Another advantage of the solution according to the invention is a more compact and, above all, more robust design of the High pressure pump in the whole. Furthermore, there is also a cost savings.

According to one preferred development is provided that the valve body the suction valve and / or the pressure valve against a in or on Cylinder housing seals sealing surface formed. Also the sealing surface is an essential functional part of this Valves, so this is a consistent and special advantageous development is. The sealing surface can thereby formed directly on or in the cylinder housing be, or as a separate component, for example, as a seat ring formed and be arranged directly on or in the cylinder housing.

According to one preferred development is provided that the sealing surface of the suction valve is arranged on the front side of the cylinder space. The cylinder space is of a lateral surface and of a Limited front, wherein the front side of the cylinder chamber in axial Direction of movement of the pump piston limited.

According to one preferred development is provided that the suction valve as Poppet valve or seat valve is formed and its valve actuation moving valve body by means of a valve stem immediately or indirectly stored and / or guided in Zy cylinder housing is. An indirect storage, for example, by means of a Sliding bush, in particular a sliding sleeve, done. It is preferably provided that a linear axis of movement of the valve body of the suction valve to the linear axis of movement of the pump piston in parallel is or coincides with this.

According to one preferred development is provided that the pressure valve on Is arranged at the end or at the flow end of a high-pressure channel, which goes from the cylinder space and in a direction across and preferably orthogonal to the axis of movement of the pump piston the cylinder housing extends.

According to one preferred development is provided that the high-pressure channel essentially a straight longitudinal extent and preferably one having circular cross-sectional area. This cross-sectional area corresponds to the flow cross-section in the high-pressure channel. Preferably, this cross-sectional area is smaller, in particular significantly smaller than the piston area of the pump piston trained (eg less than 60%, in particular less than 30% the piston surface). The high-pressure channel can, for example be formed in the form of a straight bore extending through the Cylinder housing extends to the cylinder chamber. The volume of the high-pressure channel preferably carries less than 50% to the dead volume of the pump unit.

According to one preferred development is provided that the high-pressure channel near the front side or the end face of the cylinder chamber from this. It is preferably provided that in the jacket wall of the cylinder chamber, the inlet opening to the high pressure passage very close, preferably as close as technically possible to the end face of the cylinder space is arranged, or reaches to this.

According to one preferred training is provided that the length or the longitudinal extent of the high-pressure channel from the cylinder space to the pressure valve less than three times the pump piston diameter is preferably less than twice the pump piston diameter and in particular less than the pump piston diameter. This results in a high pressure side advantageously short flow path for the fuel. The length of the high-pressure channel, for example, as the axial length of the lateral surface of the cylinder chamber to the sealing surface be dimensioned the valve body. Especially if about it In addition, the cross-sectional area of z. B. cylindrically shaped High-pressure channel smaller than the pump piston surface (or Cross-sectional area of the cylinder space) is provided so results in a further advantageous low dead volume, what follows will be explained in more detail.

According to one preferred development is provided that the pressure valve a includes spring-loaded valve body and the linear axis of motion this valve body to the longitudinal direction the high-pressure channel is parallel or coincides with this. In particular, in the case of a substantially straight high-pressure channel Optimal flow conditions are obtained in an advantageous manner for the high-pressure fuel, over there the flow path no significant deflection of the flow direction takes place, especially not at the pressure valve.

According to one preferred development is a (favorable) ratio From Pumpenkolbenhubvolumen to dead volume vorgese hen, which is larger Is 1, preferably greater than 2, and in particular is greater than 3.

The Pump piston stroke volume corresponds to the displacement of the pump piston, while this is from bottom to top Dead center (or vice versa) moves.

The Dead volume is that in the cylinder space and in adjacent flow areas up to the valves (ie eg in the high-pressure channel) remaining volumes, when the pump piston is at its upper, d. H. the front of the cylinder chamber reached dead center reached.

Of the In this dead volume fuel is indeed through the Pump piston compressed, but not via the pressure valve promoted or derived, resulting in losses in the Efficiency of the high pressure pump brings with it.

According to one preferred development is provided that the pressure valve as Inserted part formed and in the cylinder housing of is inserted externally (eg in a lateral recess of the cylinder housing).

According to one preferred development is provided that the insert part in a stepped bore is inserted in the cylinder housing, this stepped bore preferably from outside to inside a threaded portion and a fitting portion and in particular the bore axis with the longitudinal axis of the high pressure passage coincides. As a result of a common axis can the stepped bore and the high-pressure channel also made simplified become.

According to one preferred development is provided that the pressure valve of a screwed into the cylinder housing spigot in is held in its position, or arrested in this position or is attached.

According to one preferred development is provided that by means of a flow channel in the nozzle via this a high-pressure flow connection to produce a high-pressure accumulator of the fuel injection system is. Such a high-pressure accumulator is in particular the rail of a common-rail injection system. Preferably, the nozzle is with one end in the stepped bore screwed into the cylinder housing. In a further education has the neck at its two ends in each case a threaded portion for mechanical fastening (on the one hand in the cylinder housing and on the other hand at a high-pressure discharge area).

According to one Particularly preferred development is provided that at least that part of the cylinder housing formed integrally is, which the cylinder space and the intake of the suction valve and / or of the pressure valve. Preferably, the entire cylinder housing formed in one piece.

at a preferred embodiment of a high-pressure pump is provided that these at least two pump units of the above explained type, each in a cylinder recess of a (one or more parts) high-pressure pump housing are incorporated and for example by means of a likewise in this Housing arranged rotatably mounted drive shaft (z. B. camshaft) are operated. The pump units can here in a common radial plane (with respect to the Drive shaft), or arranged in different such radial planes be.

The Invention will be described below with reference to an embodiment further described with reference to the accompanying drawings. They show:

1 a pump unit according to an embodiment of the invention in a perspective view; and

2 a section through the pump unit of 1 ,

1 shows a total with 10 designated pump unit ("pump cylinder") for use (installation) in a high-pressure pump. Such a high-pressure pump, for example, for fuel supply in a high-pressure accumulator injection system, such. B. in a common rail injection system for diesel fuels, may be provided.

The high-pressure pump in question can be a single pump unit 10 or a plurality of such pump units 10 include (eg, two or three pump units disposed in a common radial plane of a multi-cylinder radial piston pump).

The pump unit 10 includes a housing 11 in which a pump piston 12 in a cylinder room 13 is mounted axially movable, as described below in connection with the 2 explained in more detail. The pump piston 12 is operated in pump mode via a plunger located on the pump piston foot (in one piece or separately) 14 driven, in turn, for example, by means of a (not shown) "Exzentertriebs" can be driven.

For such an eccentric drive quite different constructive variants come into consideration, for example, a crank mechanism, in which an eccentric portion of a rotationally driven pump drive shaft is pivotally connected to one end of a connecting rod, the other end is pivotally connected to the Pumpenkolbenfuß. Another variant provides that a cam ring encompassing the eccentric section drives the pump piston foot counter to a resetting spring preload in the radial direction. Also, a Rol be provided lenstösseltrieb, in which a rotatably mounted in the region of the Pumpenkolbenfußes plunger roller on the eccentric portion ("cam") of the drive shaft unrolls.

The illustrated pump piston 12 can z. B. be actuated by a (not shown) camshaft from which one or more cams (eccentric) the Pumpenkolbenfuß or plunger 14 in pumping direction (in 2 upward), with the return of the pump piston 12 by a (not shown) on the plunger 14 acting return spring can be accomplished.

Furthermore, the pump unit comprises 10 a neck 26 , on the output side, a high pressure-resistant flow connection to a high-pressure accumulator can be produced. The supply of the pump unit 10 with fuel from a low pressure range (eg 1-2 bar) or by a backing pump is not shown.

2 shows an axial section through the pump unit 10 of the 1 , In the cylinder housing 11 is a cylinder room 13 formed in which the pump piston 12 can move axially, ie, as shown from top to bottom and vice versa, wherein the pump piston 12 this alternately reaches a top dead center and bottom dead center. In the illustration shown is the pump piston 12 at bottom dead center. The pump piston 12 is with the pestle 14 formed or provided, in turn, in a hollow cylindrical guide area 15 of the cylinder housing 11 is added in a sliding manner.

The cylinder space 13 is via a suction valve 17 filled with fuel while the pump piston 12 is in the suction stroke, ie moves down as shown.

The suction valve 17 is located at the front of the cylinder chamber 13 , The suction valve 17 is designed as a poppet valve or seat valve and includes an axially movable valve body 18 acting as a plunger with a valve stem 19 and a valve disc arranged thereon 20 is trained.

The valve stem 19 of the suction valve 17 is directly in the cylinder housing 11 stored, including the cylinder housing 11 has a corresponding bore whose lateral surface the bearing surface for the valve stem 19 formed. The bore or its lateral surface can be prepared accordingly, and in particular has a suitable surface roughness. Alternatively and / or additionally, it is also possible between the valve stem 19 and the bore in the cylinder housing 11 a bearing bush, in particular a sliding bush to use.

The valve plate 20 of the valve body 18 seals against a directly in the cylinder housing 11 trained sealing surface. This sealing surface can, as well as the location surface for the valve stem 19 , be prepared, and has z. B. a suitable, ie in particular low roughness. Furthermore, this sealing surface can be hardened separately to reduce their susceptibility to wear. Alternatively, the sealing surface may for example also be formed as an annular separate insert part, which in the cylinder housing 11 angeord net is. The return of the valve body 18 towards the end of the suction stroke of the pump piston 12 done by a valve spring 20 ,

In the prior art, a suction valve is designed as a separate unit. Due to the here shown and described integrated design of the suction valve 17 However, expensive sealing measures and fastening measures for the suction valve are no longer necessary. In addition, the overall result is a compact and robust construction of the pump unit 10 ,

The pump unit 10 further includes a pressure valve 22 , which is designed as an insert. Alternatively, the pressure valve 22 also in a comparable way to the suction valve 17 be formed, as explained above. Also, only the pressure valve can 22 in a similar way to the suction valve explained above 17 be educated. About the pressure valve 22 the fuel is at high pressure (eg more than 2000 bar) from the cylinder chamber 13 discharged or diverted while the pump piston 22 is in the working stroke, that is moved as shown from bottom to top.

The pressure valve 22 is located at the flow end of a high-pressure channel 23 in the illustrated embodiment orthogonal straight line from the cylinder space 13 going on. The high pressure channel 23 has a relatively small longitudinal extent in its axial direction, whereby the distance between the jacket wall of the cylinder space 13 and the pressure valve 22 is meant. This results in favorable flow conditions for the fuel under high pressure.

Furthermore, this results in a small dead volume, which in the high-pressure channel 23 remains, although the pump piston 12 has already reached its top dead center. This allows the efficiency of the pump unit 10 or the high-pressure pump can be significantly improved. The dead volume can, moreover, also the remaining volume in the cylinder chamber 13 be attributed when the pump piston 12 located at top dead center.

The high pressure channel 23 goes in close proximity to the front of the cylinder chamber 13 or in the immediate vicinity of the suction valve 17 laterally from the Lateral surface of the cylinder space 13 from. This may well be the case that the valve disc 20 of the valve body 18 during the opening movement of the suction valve 17 the inlet opening to the high-pressure channel 23 at least partially overrun or covered.

The pressure valve 22 opens automatically when the pressure in the cylinder chamber 13 due to the lifting movement of the pump piston 13 exceeds a defined pressure level. In the example shown, the pressure valve comprises 22 a movable valve body 24 that has a valve spring 25 is biased and can open the valve by its movement against the spring force. The valve body 24 is arranged such that in the high-pressure channel 23 and in the pressure valve 22 can form almost optimal flow conditions for the fuel under high pressure. This is achieved in particular by deflections in the flow path being largely avoided. This also makes the efficiency of the pump unit 10 or the high pressure pump equipped with it significantly improved.

The pressure valve 22 is as a unit in a lateral recess of the cylinder housing 11 used. For this purpose, the cylinder housing 11 a stepped bore, which from outside to inside a threaded portion and a fitting portion summarizes, wherein the pressure valve 22 is positioned in the fitting section of this bore. The bore axis of the stepped bore coincides with the longitudinal axis of the high pressure passage 23 together.

In the threaded portion of the stepped bore is a nozzle or high-pressure nozzle 26 screwed. The stub 26 locks and holds the pressure valve 22 in its position. Likewise, one is in the neck 26 trained flow channel 27 a high-pressure flow connection to a high-pressure accumulator, not shown, (rail) produced or produced. For this purpose, the nozzle 26 also at his from the cylinder housing 11 remote axial end on a threaded portion which is screwed into a corresponding port of the high-pressure accumulator or a leading there line connection.

10

pump unit

11

cylinder housing

12

pump pistons

13

cylinder space

14

tappet

15

guide region

17

suction

18

valve body

19

valve stem

20

valve disc

21

valve spring

22

pressure valve

23

High pressure passage

24

valve body

25

valve spring

26

Support

27

flow channel

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• WO 2004/027263 A1 [0004]
• - DE 19814506 A1 [0004]

Claims (15)

Pump unit ( 10 ) for a high-pressure pump for fuel high-pressure generation for a fuel injection system of an internal combustion engine, in particular for a common rail injection system, comprising: - a cylinder housing ( 11 ) with a cylinder space ( 13 ), in which a pump piston ( 12 ) is mounted axially movable, - at least one suction valve ( 17 ), via which the cylinder space ( 13 ) Fuel is supplied from a low-pressure region, and - at least one pressure valve ( 22 ), via which the compressed fuel from the cylinder space ( 13 ) is derived in a high-pressure region, characterized in that the suction valve ( 17 ) and / or the pressure valve ( 22 ) largely integrated with the cylinder housing ( 11 ), for which purpose at least one valve body ( 18 . 24 ) of the suction valve ( 17 ) and / or the pressure valve ( 22 ) in the cylinder housing ( 11 ) of the pump unit ( 10 ) is stored. Pump unit ( 10 ) according to claim 1, characterized in that the valve body ( 18 . 24 ) of the suction valve ( 17 ) and / or the pressure valve ( 22 ) against a in the cylinder housing ( 11 ) sealing surface formed seals. Pump unit ( 10 ) according to claim 2, characterized in that the sealing surface of the suction valve ( 17 ) on the front side of the cylinder space ( 13 ) is arranged. Pump unit ( 10 ) according to claim 1, 2 or 3, characterized in that the suction valve ( 17 ) is designed as a poppet valve and the valve body ( 18 ) by means of a valve stem ( 19 ) directly or indirectly in the cylinder housing ( 11 ) is stored and / or guided. Pump unit ( 10 ) according to one of the preceding claims, characterized in that the pressure valve ( 17 ) at the end of a high pressure channel ( 23 ) is arranged, which from the cylinder space ( 13 ) and in a direction transversely and preferably orthogonal to the axis of movement of the pump piston ( 12 ) through the cylinder housing ( 11 ). Pump unit ( 10 ) according to claim 5, characterized in that the high-pressure channel ( 23 ) has substantially a straight longitudinal extent and preferably a circular cross-sectional area. Pump unit ( 10 ) according to claim 5 or 6, characterized in that the high-pressure channel ( 23 ) near the front side of the cylinder space ( 13 ) depart from this. Pump unit ( 10 ) according to one of claims 5 to 7, characterized in that the length of the high-pressure channel ( 23 ) from the cylinder space ( 13 ) to the pressure valve ( 22 ) is less than three times the pump piston diameter, preferably less than twice the pump piston diameter and in particular less than the pump piston diameter. Pump unit ( 10 ) according to one of claims 5 to 8, characterized in that the pressure valve ( 22 ) a spring-loaded valve body ( 24 ) and the linear axis of movement of this valve body ( 24 ) to the longitudinal direction of the high-pressure channel ( 23 ) is parallel or coincides with this. Pump unit ( 10 ) according to one of claims 5 to 9, characterized by a ratio of Pumpenkolbenhubvolumen to dead volume, which is greater than 1, preferably greater than 2 and in particular greater than 3. Pump unit ( 10 ) according to one of the preceding claims, characterized in that the pressure valve ( 22 ) formed as an insert and in the cylinder housing ( 11 ) is inserted from the outside. Pump unit ( 10 ) according to claim 11, characterized in that the insert part in a stepped bore in the cylinder housing ( 11 ), wherein this stepped bore preferably comprises a threaded portion and a fitting portion from the outside in and in particular the bore axis with the longitudinal extension axis of the high-pressure channel ( 23 ) coincides. Pump unit ( 10 ) according to claim 11 or 12, characterized in that the pressure valve ( 22 ) from one into the cylinder housing ( 11 ) screwed neck ( 26 ) is held in position. Pump unit ( 10 ) according to claim 13, characterized in that by means of a flow channel ( 27 ) in the neck ( 26 ) via this a high pressure flow connection to a high-pressure accumulator of the fuel injection system can be produced. High-pressure pump, comprising at least one pump unit ( 10 ) according to any one of the preceding claims.