CN109715933B

CN109715933B - Relief valve for use in a fuel injection system, high-pressure pump and fuel injection system

Info

Publication number: CN109715933B
Application number: CN201780056819.1A
Authority: CN
Inventors: H·艾泽勒; M·法特达乔
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2016-09-16
Filing date: 2017-09-12
Publication date: 2021-06-01
Anticipated expiration: 2037-09-12
Also published as: CN109715933A; WO2018050609A1; DE102017212003A1; KR20190047049A

Abstract

The invention relates to a relief valve, a high-pressure pump and a fuel injection system having a high-pressure pump (5) for generating an injection pressure, the pump inlet pressure of which can be set by means of a relief valve (8) having a piston unit (13) which is arranged so as to be longitudinally displaceable in a valve housing (10) provided with an inlet connection (11) and a return connection (12) and which interacts as a valve element with the return connection (12) and which is acted on at the rear by at least one valve spring (14) which is arranged in a spring chamber (15) of the valve housing (10) and is used for generating a switching pressure, wherein the spring chamber (15) is connected to a device for removing fuel penetrating there in order to generate gas bubbles in the spring chamber (15).

Description

Relief valve for use in a fuel injection system, high-pressure pump and fuel injection system

Technical Field

The invention relates to a spill valve, in particular for use in a fuel injection system, and to a high-pressure pump, in particular for generating a fuel injection pressure, and to a fuel injection system, wherein the spill valve of the fuel injection system has a piston unit which is arranged so as to be movable in a valve housing provided with an inlet connection and a return connection in the direction of a force acting against at least one valve spring.

Background

DE 102009027146 a1 discloses a high-pressure fuel pump having a low-pressure region on the suction side, in which a relief valve is arranged, which has a valve housing, which is fixed in the pump housing and has an inlet and one or more outlets, a piston unit as a valve element, and a valve spring. The valve element, which is arranged in the valve housing, is displaceable in an axial direction parallel to the longitudinal axis of the excess flow valve and is held in an initial position, in which the valve is closed, by an associated valve spring. If the fuel flows on the end side onto the spring-return valve element, the latter is displaced accordingly until the lateral outlet cross section is released by the continued axial displacement. The spring rate of the valve spring and the piston surface of the overflow valve determine the pump inlet pressure generated by the overflow valve.

In such relief valves of the prior art, fuel may undesirably enter the rearward spring chamber due to leakage in the dynamic seal between the valve element and the valve housing. The spring chamber filled with fuel makes the springing up of the valve element difficult and in extreme cases locks the valve element. In order to empty the spring chamber, attempts have been made to connect the spring chamber to the return via an orifice. It has been shown, however, that the throttle quantity flowing out of it can flow back again into the spring chamber in the opposite direction.

Disclosure of Invention

The object of the present invention is therefore to provide a fuel injection system of the generic type with a relief valve which reliably ensures the valve spring springing.

This object is achieved in accordance with the invention by means of a spill valve, a high-pressure pump and a fuel injection system. The preferred embodiment of the invention provides an advantageous development of the overflow valve.

The present invention comprises the following technical teaching: the spring chamber of the overflow valve is connected to a device for removing fuel penetrating there, in order to generate and retain air bubbles in the spring chamber.

In other words, the relief valve is supplemented by technical means which ensure that the fuel which has penetrated into the spring chamber as a result of the leakage of the dynamic seal is reliably drained away. This can be achieved, for example, by pumping away or sucking away the invading fuel. Thereby, an improved damping of vibrations is achieved by the formation of air bubbles in the spring chamber. The response of the spring-piston system is improved by the gas bubbles in the spring chamber and the system can accommodate a greater stroke, which leads to improved damping. The control parameters of the check valve can thus be better controlled and the pulsations of the hydraulic system for charging the high-pressure pump are counteracted. With reduced pulsations, fewer cavitation is also generated in the pump input circuit.

According to a first preferred embodiment, the means for removing fuel penetrating into the spring chamber is a non-return valve which is connected on the inlet side to the spring chamber in order to drain fuel in the throughflow direction towards the return line. In the opposite locking direction, the fuel displaced by the pumping action is prevented from flowing back into the spring chamber. In this way, the desired gas bubbles can be formed or obtained in the spring chamber by vaporizing the fuel which has penetrated into it and is removed again.

In a first variant of purging the spring chamber of fuel by means of a check valve, it is proposed that the check valve be arranged in or on the piston unit. The fuel discharged from the spring chamber flows in the direction of the return connection via the through-opening of the piston unit. This variant has the advantage that the fuel to be drained off can be supplied to the return connection of the overflow valve on a short path.

According to a second variant, it is proposed that the non-return valve be integrated in the housing plug or in the valve housing on the bottom side, i.e. on the immovable part of the overflow valve. The fuel removed from the spring chamber is again supplied to the return line. The advantage of this variant is that the additional mass associated with the integration of the non-return valve does not affect the dynamics of the overflow valve. This creates a precondition for the following situations: a particularly light piston unit is used and a valve spring with a lower spring rate can be employed. The lower the spring rate of the return spring, the better the pulsation of the hydraulic circuit can be counteracted. Therefore, in fuel injection systems according to the type, return springs with a spring rate of only 3N/mm to 4N/mm are possible.

It is also proposed that the non-return valve itself forms a housing plug on the bottom side of the valve housing. By this functional integration, no separate components are required. Alternatively, it is also conceivable to use a prefabricated non-return valve in the base bore of a conventional housing plug, in which a preferably transversely extending drainage channel must additionally be introduced.

According to a further measure which improves the invention, it is proposed that the piston unit be of pot-shaped design, wherein the inner chamber of the pot-shaped piston unit can be used for guiding the valve spring. Such a pot piston is particularly lightweight due to the construction, so that a valve spring with a low spring rate can be used. It is additionally conceivable for the piston unit to be made of a light metal material, preferably aluminum. The sliding coating, for example an anodized surface, at least on the circumferential surface, increases the wear resistance and serves as a sealing partner for the inner surface of the valve housing, minimizing friction forces.

According to a further measure which improves the invention, it is proposed that the piston unit has a radially outer circumferential leakage collection groove. The axial extent of the leakage collection groove on the outside of the piston unit and the positioning of the leakage collection groove relative to the valve housing-side return connection are thereby matched to the amount of piston leakage to be removed in such a way that the connection of the leakage collection groove to the return connection is preferably ensured in any piston position.

According to a further preferred embodiment of the invention, it is provided that the device for removing fuel penetrating into the spring chamber is realized as a venturi nozzle. The venturi nozzle preferably draws off fuel which has intruded into the spring chamber via a transverse bore at the narrow end of the nozzle body. The venturi nozzle is driven by the fuel flowing through the pump inlet pressure circuit. Thereby, an active suction of the spring chamber is achieved. The venturi nozzle simultaneously acts as a bypass cooling throttle device, whereby a pressure regulation can be achieved in the pump inlet pressure circuit. The separate cooling volume flow thus produced promotes the robustness of the system.

It is conceivable to integrate a venturi nozzle into the housing plug of the valve housing, which however imposes restrictions in terms of possible suction power, which are determined by the installation space. It is therefore preferably provided that the venturi nozzle is integrated into a venturi housing of the housing plug, which extends cylindrically coaxially along the spring chamber and can be embodied integrally with the housing plug or coupled thereto. Thus, the spring chamber is used as an installation space for arranging the venturi nozzle. In order to compensate for component tolerances, the venturi housing is coupled at the end close to the center to the housing plug via a hinge, preferably a ball hinge. Thereby, the perpendicularity deviation can be compensated. With this configuration, the coaxiality deviation can be compensated for in the following manner: the venturi housing is guided at the end remote from the center at the piston unit via a sliding sleeve which rests against the piston unit with a radial clearance for the venturi housing ensured. The end of the venturi housing remote from the center thus protrudes from the valve housing and can be attached together to the inlet connection for operating the venturi nozzle. The opposite end of the venturi housing forms the discharge of the venturi nozzle, which is coupled to the return connection via a channel in the housing plug.

Drawings

Further measures to improve the invention are set forth in more detail below together with the description of embodiments of the invention with reference to the attached drawings. The figures show:

figure 1 is a schematic connection diagram of a fuel injection system with a high-pressure pump,

fig. 2 is a schematic longitudinal section of a relief valve according to a first embodiment, with a non-return valve integrated in the piston unit,

fig. 3 is a schematic longitudinal section of a relief valve according to a first embodiment, with a non-return valve integrated in the housing plug,

fig. 4 is a detail view of a relief valve of the type according to fig. 3, with a non-return valve integrated in the housing plug,

fig. 5 is a detail view of a relief valve of the type according to fig. 3, having a check valve as a housing plug,

FIG. 6 is a partial longitudinal section of the overflow valve in the region of a piston unit comprising a leakage collection groove and

fig. 7 is a schematic longitudinal section of a second embodiment of a relief valve with an integrated venturi nozzle.

Detailed Description

The fuel injection system according to fig. 1 delivers fuel from a fuel tank 2 via a filter 1 by means of a fuel delivery pump 3 via a fuel line 4 to a high-pressure pump 5, which is designed here as a radial piston pump.

The fuel injection system furthermore comprises a metering unit 6 and a high-pressure accumulator 7, which is also referred to as a rail, which is in turn connected to injection valves, not shown in detail here, which inject fuel into the combustion chambers of the internal combustion engine.

The metering unit 6 serves to variably adjust the fuel supply from the fuel delivery pump 3 to the high-pressure pump 5 as required. In the feed line from the fuel delivery pump 3 to the metering unit 6, there is arranged an overflow valve 8 for the controlled draining of fuel excessively delivered by the fuel delivery pump 3, which cannot reach the high-pressure pump 5 with the metering unit 6 completely or partially closed, and which is returned via a return line 9 into the fuel tank 2. The fuel delivery pump 3, the metering unit 6 and the overflow valve 8 are assigned to the low-pressure circuit of the fuel injection system. Instead, the high-pressure pump 5 and the high-pressure accumulator 7 are assigned to the high-pressure circuit.

The overflow valve 8 comprises a valve housing 10 provided with an inlet connection 11 and a return connection 12, in which a longitudinally displaceably arranged piston unit 13 is accommodated, which interacts as a valve element with the return connection 12. The piston unit 13 is acted upon from the rear by a valve spring 14, which is arranged in a spring chamber 15 of the valve housing 10 and serves to generate the switching pressure.

The overflow valve 8' of the first embodiment, which is shown in detail in fig. 2, is composed of a piston unit 13, which is arranged in a valve housing 10 and in which a non-return valve 16a is inserted, which is connected on the inlet side to a spring chamber 15 and discharges fuel from the spring chamber 15 in the throughflow direction to a return connection 12, which is connected to a return line, which is not shown in detail here. Here, the fuel reaches the return connection 12 from the check valve 16a via the through hole 17 of the piston unit 13. The valve spring 14, which is arranged in the spring chamber 15, is supported on the one hand coaxially on the piston unit 13 and on the other hand on a housing plug 18, which belongs to the valve housing 10 and which is pressed into the valve housing 10 on the bottom side.

According to the variant shown in fig. 3, the non-return valve 16b is arranged in the bottom housing plug 18 and not at the piston unit 13. The fuel which is discharged from the spring chamber 15 via the non-return valve 16b reaches the return line 9 via a bypass line which is not shown in detail here.

In the variant of the housing plug 18 shown in fig. 4, which is embodied with a check valve 16c, this check valve is integrated in the pot-shaped housing plug 18 and consists of a check valve housing 19, a closure body 20 and a valve spring 21 acting on the closure body. The fuel is discharged in the direction of the return line 9 via a transverse bore 22 arranged in the check valve housing 19.

In the variant according to fig. 5, the non-return valve 16d itself forms the housing plug 18. The base bore in the housing plug 18 simultaneously serves as a check valve housing and is closed by a threaded sleeve 23 which forms the inlet to the check valve 16 d. This valve mechanism, which is known per se, is also arranged in a usual manner in said base bore of the non-return valve 16 d.

According to fig. 6, the piston unit 13' is pot-shaped. The inner chamber 24 of the pot-shaped piston unit 13' serves for guiding the valve spring 14. On the lightweight pot-shaped piston unit 13', a circumferential leakage collection groove 25 is formed radially on the outside. In this embodiment, the piston unit 13' is composed of aluminum and is anodized at least on the circumferential surface side in order to minimize sliding friction with respect to the valve housing 10 and reduce wear associated therewith. The piston unit 13' is here suitably used in combination with a non-return valve integrated on the housing side.

The embodiment according to fig. 7 is characterized in that a venturi nozzle 26 is integrated in the overflow valve 8' ″. The venturi nozzle 26 actively removes fuel that has intruded into the spring chamber 15. For this purpose, a continuous fuel volume flow flows from the inlet opening 11 in the direction of the return line 9 through the venturi nozzle 26 and in this case generates a pressure drop in the region of the narrow region 28 according to the bernoulli principle, so that a suction effect occurs in the transverse bore 27 branching off from this. A transverse bore 27 is attached to the spring chamber 15 of the overflow valve 8' ″ in order to evacuate fuel, so that a correspondingly continuous evacuation of the spring chamber 15 is achieved.

The venturi nozzle 26 is integrated in a venturi housing 29 extending along and coaxially with the spring chamber 15. The venturi housing 29 is fixed relative to the valve housing 10 by the housing plug 18. The housing plug 18 is pressed into the spring chamber 15 on the bottom side. In order to compensate for component position deviations in terms of coaxiality and perpendicularity, which occur as a function of manufacturing tolerances during the axial movement of the piston unit 13 relative to the valve housing 10, special measures are taken here. The perpendicularity deviation with respect to the longitudinal axis of the venturi housing 29 is compensated for by the hinge 30 between the approximately central end of the venturi housing 29 and the housing plug 18. The end of the venturi housing 29 near the center is the end facing the housing plug 18 and sealing against it. Instead, the coaxiality deviation is compensated for by the end of the venturi housing 29 remote from the center, opposite to the end near the center. The sliding sleeve 31 provided for this purpose is provided with a narrow guide along the circumferential surface of the venturi housing 29 and has a radial degree of freedom on the inner end face of the bowl-shaped piston element 13. This radial degree of freedom can be achieved by a large-scale clearance fit with respect to the venturi housing 29 passing through the piston element 13. The valve spring 14, which is arranged in the spring chamber 15 around the venturi housing 29 and acts in the axial direction, is supported at the end remote from the center on a sliding sleeve 31, as a result of which an axial sealing force is generated in the contact region between the sliding sleeve 31 and the piston element 13 when the valve spring 14 is compressed, so that a seal is generated which prevents fuel from penetrating from the inlet opening 11 into the spring chamber 15 even in the presence of a radial degree of freedom.

The fuel driving the venturi nozzle 26 therefore flows from the inlet connection 11 via the narrow region 28 of the venturi nozzle 26 and via the hinge 30 into the housing plug 18 and from the channel guide introduced therein via the return connection 12 in the valve housing 10 to the return line 9 of the fuel supply circuit.

In the context of the relief valve function, the piston unit 13, which is arranged so as to be displaceable in the direction of the force against the valve spring 14, interacts as a valve element with a return connection 12', which is also connected to the return line 9, as a function of the pressure exerted by the fuel via the inlet connection 11.

The invention is not limited to the preferred embodiments described above. Rather, variations of these embodiments are also contemplated which are encompassed by the scope of the following preferred embodiments. The metering unit 6 and the overflow valve 8 can therefore also be implemented as part of a high-pressure pump. For example, it is also possible to integrate the non-return valve directly into the valve housing 10 or to arrange the venturi nozzle 26 of the last exemplary embodiment close to the bottom transversely through the valve housing 10, if the piston stroke is not influenced thereby. It is likewise conceivable for the venturi nozzle 26 of the last exemplary embodiment to also be pressed firmly into the housing plug 18, if the manufacturing tolerances that can be achieved are small. Furthermore, the venturi housing 29 can also be clipped into a corresponding recess of the housing plug 18 for simplified installation. Likewise, the sliding sleeve 31 can also be clamped into the associated piston unit 13 in order to simplify the installation.

Claims

1. A relief valve (8) comprising a piston unit (13) which is arranged in a valve housing (10) provided with an inlet connection (11) and a return connection (12) in a longitudinally displaceable manner and which interacts as a valve element with the return connection (12) and which is acted upon on the rear side by at least one valve spring (14) which is arranged in a spring chamber (15) of the valve housing (10) and is used to generate a switching pressure, wherein the spring chamber (15) is connected to a device for removing fuel penetrating into the spring chamber in order to generate gas bubbles in the spring chamber (15), wherein the device for removing fuel penetrating into the spring chamber (15) comprises a venturi nozzle (26) which is driven by fuel flowing through the pump inlet pressure circuit, wherein, a transverse bore (27) at a narrow portion (28) of the venturi nozzle (26) is in connection with the spring chamber (15) in order to remove fuel intruding therein by suction, characterized in that the venturi nozzle (26) is integrated in a venturi housing (29) of the piston unit (13) which extends coaxially along the spring chamber (15).

2. The excess flow valve (8) of claim 1 wherein the venturi housing (29) is coupled at an end near the center to a housing plug (18) via a hinge (30) and thereby attached to the return fitting (12).

3. The excess flow valve (8) according to claim 1, characterized in that the venturi housing (29) is guided at the end remote from the center via a sliding sleeve (31) which bears against the piston unit (13) with a guaranteed radial clearance for the venturi housing (29), wherein the input connection (11) is attached on the end remote from the center of the venturi housing (29) for operating the venturi nozzle (26).

4. Overflow valve (8) according to claim 1, characterized in that the piston unit (13) has a radially outwardly surrounding leakage collection groove (25) establishing a connection with the return connection (12).

5. Relief valve (8) according to claim 1, characterized in that the piston unit (13) is made of a light metal material which is provided with a sliding coating at least on the circumferential surface side.

6. The excess flow valve (8) according to one of claims 1 to 5, characterized in that the excess flow valve (8) is intended for use in a fuel injection system.

7. High-pressure pump (5) in the pump input cycle of which a spill valve (8) according to one of the preceding claims is arranged.

8. The high-pressure pump (5) as claimed in claim 7, characterized in that the high-pressure pump (5) is used for generating injection pressure in a fuel injection system.

9. Fuel injection system for a motor vehicle, having a spill valve (8) according to one of claims 1 to 6.