EP1537324A1

EP1537324A1 - Device for ventilation of a supply unit

Info

Publication number: EP1537324A1
Application number: EP03708025A
Authority: EP
Inventors: Armin Merz; Walter Fuchs; Andreas Dutt
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2002-08-29
Filing date: 2003-02-13
Publication date: 2005-06-08
Anticipated expiration: 2023-02-13
Also published as: US20050031472A1; JP4309841B2; WO2004022967A1; ATE435971T1; CN1553992A; DE10239777A1; CN100436807C; DE50311688D1; EP1537324B1; US7029248B2; JP2005537426A

Abstract

A pump unit for the metered delivery of fuel to internal combustion engines. The pump unit comprises a housing which comprises a longitudinal bore. Located in the longitudinal bore is an overflow valve, via which fuel flows back through a channel into a fuel tank. The passage can be opened or closed by a spring-loaded closing element. Fastened to the valve shaft of the overflow valve is a ring fitting. In the longitudinal bore of the housing there is an additional thread section, via which air flows out through vent gaps into a cavity of the ring fitting.

Description

Device for venting a conveyor unit

Technical field

In the case of delivery units, such as, for example, fuel distributor injection pumps in fuel injection systems in motor vehicles, the delivery unit must be vented safely. A distributor injection pump is vented, for example, when it is started up. In addition, when the fuel tank is empty, air can also be drawn into the ner splitter injection pump, the escape of which from the delivery spaces of the distributor injection pump must be ensured, since otherwise no fuel can flow in.

State of the art

From DE-OS 25 22 374 a fuel injection pump is known, in the pump pistons of which recesses are embedded as cross-sections on the outer surface. These extend from the outlet openings of the relief duct to the side of the pump work space. The recesses can have a right-angled contour, which have a width that differs from one another in the circumferential direction of the pump piston and can also differ in their axial extent, ie their length. With such an arrangement, a kinking cross-sectional profile is to be achieved in the course of the opening stroke of the pump piston. Thereby, after the initially throttled relief via one of the connection openings, the relief cross section is to be enlarged by the addition of the second connection opening. In the connection cross-sections proposed here, the throttling effect which occurs at different speeds of the fuel injection pump is particularly emphasized. These control cross sections are provided in particular for the adjustment of the fuel injection quantity as a function of the speed. One of the cross-sections is designed in the manner of a throttle slot. In the case of self-igniting internal combustion engines, there is a requirement in the low-load range, in particular when idling, that the fuel is introduced into the combustion chamber in an exactly time-controlled manner but with an extended injection duration. With this approach, this can be particularly true in the idle range noticeable "nailing" of the derating machine can be prevented. The prolonged injection period ensures that the amount of fuel introduced during the ignition delay does not become too large and so too much fuel is not suddenly burned, which would lead to a steep pressure increase which promotes nailing.

DE 36 44 150 AI has the object of a fuel injection pump for internal combustion engines. This comprises a pump cylinder, which is designed on the one hand to move back and forth and at the same time rotates and serves as a distributor of pumped fuel to several injection pistons supplying injection points. The pump piston delimits a pump work space in the pump cylinder. The fuel injection quantity conveyed by the pump piston is varied in that the opening of an outlet opening on the circumference of the pump piston of a relief channel arranged in the pump piston and leading from the pump working chamber to a relief chamber is varied by means of an annular slide which is axially displaceable on the pump piston by a fuel injection quantity regulator within the relief chamber. This has a control edge and at least two connection cross-sections which differ from one another in shape and which lie in the connection between the outlet opening and the connection to the relief chamber made by the control edge on the ring slide in the course of the pump piston delivery stroke. One of the connection cross-sections has a reduced cross-section which acts as a throttle and which, in the course of the pump piston delivery stroke, comes into contact with the relief chamber first and before another, non-throttling connection cross-section which is larger in the cross-section.

EP 0 323 984 AI relates to a fuel injection system for internal combustion engines. This comprises a high-pressure pump delivering a certain amount of fuel per per-cycle from a pump work space with a first control valve arranged in a first relief channel and controlling a first return amount, in particular determining the start and end of delivery of the fuel injection. Furthermore, a control throttle with a constant cross-section and an electrically controlled second control valve lying in series are provided, which is arranged in a second relief channel for a second return flow quantity. An electronic control unit processes: parameters of the internal combustion engine and the injection pump into variables that influence the injection. In the second relief duct for quantity measurement ^, a differential caliper is provided which has a member which is flexible against a restoring force and which is acted upon on the one hand by the pressure on the pump work space side upstream of the control throttle against the restoring force and on the other hand by the relief side pressure downstream of the control throttle. Its deflection is recorded as a characteristic value of the differential pressure meter by means of a displacement sensor. In the electronic control unit, in addition to the characteristic values of the differential pressure meter and the second control valve, the amount of fuel flowing off via the second relief channel is determined as a control value and the control time of the first control valve is changed in accordance with this control value.

Presentation of the invention

With the solution proposed according to the invention, an additional bypass hole in the overflow valve on a distributor injection pump - to name one example - can be saved. This additional bypass hole on overflow valves represents an additional step in the large-scale production of overflow valves, which on the one hand requires the workpiece to be re-clamped in the processing machine concerned and on the other hand has a considerable influence on the accuracy of the calibration of the overflow valve. With the solution proposed according to the invention, the bypass bore previously formed in the overflow valve can advantageously be integrated into the longitudinal bore of the pump housing in a technically particularly simple manner by introducing an additionally deepened thread cutout during circular milling of the thread into the housing. This thread exclusion is produced in one operation with the internal thread in the longitudinal bore into which the overflow valve is introduced, the tool descending a helical path during the machining process.

The thread exclusion is preferably introduced into the longitudinal bore of the housing in such a way that it is spaced a distance, i.e. an eccentricity, based on the outer flank of the overflow valve. The eccentrically formed thread exclusion creates a cascade-shaped gap between the internal and external threads. This gap forms a defined throttle point

Due to the thread cut made in one process in the internal thread of the longitudinal bore of the pump housing, which is preferably carried out by milling in one operation, the escape of sucked-in air from the fresh room of a delivery unit, such as a distributor injection pump, is ensured. The escape of fuel through the gap between the internal and external threads is negligible, since the air has a significantly lower viscosity than fuel and is therefore easier to escape through the gap between the internal and external threads than fuel. An annular nozzle is assigned to the overflow valve, which is introduced into the longitudinal bore of the pump housing of a distributor injection pump, for example, and has a cavity. The cavity of the ring connector is connected to the longitudinal bore of the overflow valve via a transverse bore on the valve stem. The ring connector can be sealed on the valve flange of the overflow valve using two sealing washers, on the one hand in the head region of the overflow valve and on the other hand opposite a flat surface of the pump housing. Advantageously, the outside diameter of the valve stem on the overflow valve and the inside diameter of the two sealing disks are matched to one another in such a way that ventilation gaps are set, via which escape of air from the interior of the delivery unit is ensured.

In addition to use on fuel delivery units, for example on distributor injection pumps, the solution proposed according to the invention can also be used for delivery units of hydraulic oil, for example in power steering systems. The solution proposed according to the invention can generally be used with low-pressure inlet and outlet lines which are fastened with ring sockets and ensure a bypass throttle function.

drawing

The invention is explained in more detail below with reference to a drawing.

It shows:

FIG. 1 shows the longitudinal section through an overflow valve integrated in the housing of a distributor injection pump,

FIG. 1.1 the relative position between the internal thread of the longitudinal bore and the additional thread cutout and

2 shows the top view of the housing inner contour without screwed-in overflow valve according to FIG. 1. design variants

FIG. 1 shows the longitudinal section through an overflow valve integrated in the housing of a distributor injection pump.

The housing of a fluid-conveying pump, such as a fuel, for example a distributor injection pump in direct-injection and air-compressing internal combustion engines, is designated by reference number 1 and delimits an interior space 2 of the pump. The interior 2 of the delivery unit is connected via a first bore 3 to an overflow valve 7 received in a longitudinal bore 4. The overflow valve 7 can be screwed into an internal thread section corresponding to this in the longitudinal bore 4 via a threaded section 5 designed as an external thread. The threaded connection shown in FIG. 1 ensures a connection which withstands even higher pressures between the overflow valve 7 and the housing 1, for example a distributor injection pump for internal combustion engines.

In the upper area of the housing 1, enclosing the longitudinal bore 4 in the housing 1 in a ring, a flat surface 6 can be formed, in which a ring 15 made of a soft metal material, taking over the function of a first sealing washer, can be inserted. The first sealing disk 15 obtained in this way is inserted according to the embodiment variant in FIG. 1 between an annular connector 15 surrounding the valve stem 14 of the overflow valve 7 and the flat surface 6 of the housing 1 of the delivery unit for sealing. The first sealing washer 15, made of a soft-metallic material, is opposite a second sealing washer 17, which can also be made of a soft-metallic material, underneath a head region 13 of the overflow valve 7. To ensure a sealing system and to apply the necessary pretensioning force, the second sealing disk 17 rests on a flat surface 18 on the head region 13 of the overflow valve 7 and is analogous to the first sealing disk 15, which is accommodated on the flat surface 6 of the housing 1, with an outside of the Ring connector 19 in connection.

By screwing the overflow valve 7 into the internal thread closure 5 of the longitudinal bore 4, the pretensioning force required for sealing is applied and the ring connector 19 is attached to the outside of the valve stem 14 of the overflow valve 7.

The overflow valve 7 itself comprises a through hole 8 which is connected to the first hole 3 of the housing 1 of the delivery unit. The Durchgangssbohπmg 8 can be closed or released according to the pressure prevailing inside the housing 2 by means of a spherical closing element 9. For this purpose, the spherically configured closing element 9 is acted upon by a spiral spring 11, which in turn is supported on an abutment 12 in the head region 13 of the overflow valve 7. In the embodiment variant of the solution according to the invention in FIG. 1, the abutment 12 is designed as a ball shrunk in the head region 13 of the overflow valve 7. In addition to the shrinking of a spherical abutment 12, an abutment of the spring acting on the spherical closing body 9 can also be applied by an abutment screwed into the head region 13 of the overflow valve 7.

The spherical closing element 9 closes a valve seat 10 which is formed in the through bore 8 below a transverse bore 20 penetrating the wall of the valve stem 14 of the overflow valve 7. Depending on the pressure level prevailing in the interior of the pump 2, the closing body 9 is raised when the pressure in the through bore 8 reaches a certain pressure limit, counter to the spring action of the spring 11, so that fuel from the interior of the pump 2 via the cross bore 20 of the overflow valve 7 into one flow out with the reference numeral 23 of the annular connector 19 and from there flow back into the fuel tank, not shown here, of a motor vehicle.

By a distance 22, i.e. an eccentricity, shifted to the center line of the through bore 8, a thread exclusion 24 is formed in the internal thread section 5 of the longitudinal bore 4 of the housing 1. Since the additional thread cutout 24 penetrates the threads of the first threaded section formed in the longitudinal bore 4 and thus forms an air passage channel to the outside of the valve stem 14 of the overflow valve 7, the center of the additional thread cutout 24 is about the mentioned eccentricity 22 to the center line of the through bore 8 in moved inside the valve stem 14 of the overflow valve 7. The thread cut-out 24 is advantageously produced in one work step with the production of the internal thread section 5 in the longitudinal bore 4 of the housing 1 of the conveying unit. Circular milling can be regarded as the preferred manufacturing method, in which the additional thread cutout 24 in the threads of the first thread portion 5 of the longitudinal bore 4 in the housing 1 is produced simultaneously with the first internal thread portion 5 of the longitudinal bore 4.

The sealing disks 15 and 1.7, which have already been described, are arranged on both sides of the annular connector 19 surrounding the outer circumference of the valve stem 14 of the overflow valve 7. The Inner diameter 16 of the first sealing disk 15 is selected such that air can flow via the bore 3 along the channel formed between the internal thread section 5 of the longitudinal bore 4 and the additional thread cutout 24 on the outside of the valve stem 14 of the overflow valve 7 in the direction of the first sealing disk. Between the inner diameter 16 of the first sealing disk 15 and the outer diameter of the valve stem 14, a first ventilation gap 26 is formed, through which air can escape from the pump interior 2. An escape of fuel is not possible because of the narrow dimensioning of the ventilation gap 26; in addition, the leakage of fuel is prevented by the closing element 9 placed in its seat 10 by means of the spring element 11. The escape of air from the pump interior 2 of the delivery unit 1 also takes place at a substantially lower pressure level, compared to the excess pressure level at which the closing element 9 exits its seat 10 at the top of the through bore 8 against the action of the spring element 11.

In addition to the venting gap 26, which is formed between the circumference of the valve stem 14 of the overflow valve 7 and the inner diameter 16 of the first sealing disk 15, there is a further venting gap 27 between the inside diameter of the annular connector 19 and the outside diameter of the valve stem 14 of the overflow valve 7. Via this air gap , which is sealed to the outside due to the pretension of the first sealing disk 15 and the second sealing disk 17, the air escaping from the interior 2 of the delivery unit 1 flows into the cavity 23 of the annular connector 19 and from there, for example, into a tank ventilation or directly into the fuel reservoir of a motor vehicle back.

FIG. 1.1 shows in a schematic manner the configuration and the position of the first threaded section and the additional threaded cutout in relation to one another in the longitudinal bore 4.

It can be seen from the illustration in FIG. 1.1 that a first internal thread 5 has been slit into the longitudinal bore 4 in the housing 1 of the delivery unit. In its threads, an additional thread exclusion 24 is milled in one step on the way of circular milling, which in turn passes through the threads of the first internal thread section 5 within the longitudinal bore 4, so that, seen in the axial direction, a channel is formed along the longitudinal bore 4, through which a channel is formed Air inside the pump chamber 2 of the delivery unit 1 can flow out. Since the diameter of the additional thread cutout 24 is smaller than the diameter of the first thread section 5 in the longitudinal bore 4 of the housing 1 of the conveying unit, the additional thread exclusion 24 is about an eccentricity 22 with respect to the center of the first thread section. Cut 5 postponed. In terms of manufacturing technology, the additional thread cutout 24 can therefore be produced together with the production of the first thread section 5 - which is formed with a larger thread diameter. Calibration of bypass openings to be formed in an overflow valve 7, as was necessary in previous overflow valves, can now be omitted by means of the solution proposed according to the invention, since the bypass opening can be integrated directly into the longitudinal bore 4 of the housing 1 of a delivery unit.

FIG. 2 shows the top view of the threaded bore in the housing 2.

FIG. 2 shows that the overflow valve 7 can be screwed into a longitudinal bore 4 of the housing 1 with its first threaded section 5. The threaded section 5 - formed as an external thread in the lower region of the valve stem 14 of the overflow valve 7 - engages with the corresponding threaded portion 5 of the longitudinal bore 4 in the housing 1, the additional threaded cutout 24 between the external thread of the valve stem 14 and the An internally threaded section 5 of the longitudinal bore 4 forms a channel which escapes from air, but which is let in through the first sealing washer 15 and sealed to the outside in the flat surface 6 of the housing 1. This allows air to flow out of the interior through the ventilation gaps 26 and 27 shown in FIG. 1 into the interior 23 of the annular connector 19 surrounding the valve stem 14 and from there into the motor vehicle tank or tank ventilation.

The eccentricity 22, by which the additional thread exclusion 24 is offset with respect to the center of the internal thread 5 of the longitudinal bore 4, is also identified in FIG. 2 by reference number 22. The eccentricity 22 results from the formation of the additional thread cutout 24 in a smaller thread diameter compared to the diameter of the internal thread 5 in the longitudinal bore 4 of the housing 1, for example a distributor injection pump for air-compressing internal combustion engines. In addition to the use for venting ner splitter injection pumps, which can occur, for example, when a tank of a motor vehicle is completely empty and when the distributor injection pump 1 is started up for the first time, the venting option of a pump interior proposed according to the invention can also be used in hydraulic fluid pumps in motor vehicles, for example in the context of power steering. The solution proposed according to the invention for venting a pump interior can be used in fuel delivery units both for diesel fuel and for gasoline. With the venting option proposed according to the invention of a pump housing interior 2 of a delivery unit, the incorporation of a venting channel functioning as a bypass into the longitudinal bore 4 of the housing 1 can be implemented by using the manufacturing method of circular milling. As a result, the formation of an additional bypass bore in the overflow valve 7, which is screwed into the longitudinal bore 4 on the housing 1, can be avoided. As a result, the number of rejects in the setting of the overflow valves 7 installed in each case on the conveying units can be reduced, since the influence of the bypass hole is now eliminated and this additional processing step in the production of overflow valves 7 in large-scale production can now be dispensed with. The bypass bore is advantageously formed in an additional thread cutout 24 that can be produced in one work step in the internal thread section 5 of a longitudinal bore 4 on the housing 1 of the conveyor unit in question.

LIST OF REFERENCE NUMBERS

Housing pump interior first bore Longitudinal bore first thread section (internal / external thread) flat surface overflow valve Bore overflow valve spherical body ball seat spring element abutment spring element head area overflow valve valve stem first sealing washer inner diameter first washer second sealing washer inner diameter second washer ring spigot cross hole spigot diameter ring spigot eccentricity hollow space ring spigot additional thread excl

Claims

claims

1. Delivery unit for metering fuel for internal combustion engines with a housing (1) which encloses an interior (2) and comprises a longitudinal bore (4) in which an overflow valve (7) is received, through which fuel is passed through a through bore (8) flows back into a fuel reservoir, the through hole (8) being closable or releasable by a spring-loaded closing element (9) and an annular connector (19) being received on the circumference of the overflow valve (7), characterized in that in the longitudinal bore (4) Housing (1), an additional thread cutout (24) is formed, through which air can escape through ventilation gaps (26, 27) into a cavity (23) of the ring connector (19).

2. Conveying unit according to claim 1, characterized in that the additional thread cutout (24) in a first internal thread section (5) for receiving the

Overflow valve (7) of the longitudinal bore (4) is formed.

3. Conveying unit according to claim 2, characterized in that the center of the additional thread exclusion means (24) is arranged in the longitudinal bore (4) at a distance (22) with respect to the center of the first internally threaded section (5).

4. Conveyor unit according to claim 2, characterized in that the additional thread cutout (24) in the first internal thread section (5) is made by circular milling or in an additional operation.

5. Delivery unit according to claim 1, characterized in that between the circumferential surface of a valve stem (14) of the overflow valve (7) and sealing washers (15, 17) on the valve stem (14) ventilation gaps (26, 27) are formed, via which Air flowing out of the interior (2) of the delivery unit flows out into the ring connector (19) via the additional thread cutout (24) of the longitudinal bore (4).

6. Conveyor unit according to claim 5, characterized in that the ventilation gaps (26, 27) by the respective inner diameter (16, 18) of the first sealing disc (15) and the second sealing disc (17) are defined.

7. Delivery unit according to claim 5, characterized in that the first sealing disc (15) in a to the longitudinal bore (4) in the housing (1) adjacent plane surface (6) is embedded.

8. Conveying unit according to claim 5, characterized in that the second sealing disc (17) abuts an annular flat surface (25) in the head region (13) of the overflow valve (7).

9. Conveyor unit according to claim 1, characterized in that the overflow valve (7) has a through bore (8) and with the cavity (23) of the annular connector (19) in connection transverse bore (20), the through bore (8) through a spring-loaded closing element (9) is closed and opens depending on the pressure in the interior space (2) of the housing (1).

10. Conveyor unit according to claim 9, characterized in that the abutment (12) of the closing element (9) acting spring (11) as in the head region (13) of the overflow valve (7) is pressed or shrunk ball.