EP1073839A1

EP1073839A1 - Fuel injection valve

Info

Publication number: EP1073839A1
Application number: EP99966897A
Authority: EP
Inventors: Patrick Mattes
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1999-02-20
Filing date: 1999-12-30
Publication date: 2001-02-07
Also published as: DE19907348A1; KR20010042833A; WO2000049288A1; JP2002537517A; US6371441B1

Abstract

The invention aims to improve the means of control of a fuel injection valve, comprising a valve member (1) which controls the opening and closing of a fuel outlet (4), actuation elements to adjust the valve member (1), in addition to compensation elements to subject the valve member (1) to compensation forces that oppose the opening stroke of the valve member (1). The compensation elements have a piston (10) that can be adjusted in its corresponding cylinder (11). The piston (10) delimits a hydraulic chamber (12) in the cylinder (11) that is subjected to a reference pressure and is supported in its initial position on a stop (18) that is fixed in relation to the cylinder (11). The piston can be driven away from its initial position against the stop (18) by the valve member (1) using force transmission means. To this end, the force transmission means are embodied as spring elements (15, 16) that are tensioned by the valve member (1) at the opening stroke of said member (1).

Description

Fuel injector

State of the art

The invention is based on a fuel injection valve with the features of the preamble of claim 1.

Such a fuel injection valve is from DE

(Official file number: 197 27 896.5, filing date July 1, 1997) and contains a bidirectionally adjustable valve member with which a fuel outlet opening for opening and closing can be controlled. Actuating means are provided with which the valve member for opening and closing the fuel outlet opening is adjustable. These actuating means here comprise an electrically actuable control valve and a relief pressure chamber which communicates with a closing pressure chamber on the one hand via a connection which can be controlled by the control valve for opening and closing and on the other hand with a relatively unpressurized fuel tank. The closing pressure chamber is delimited on one side by a closing pressure surface formed on the valve member and communicates via a throttle with a high-pressure fuel source, the pressure in the closing pressure chamber on the closing pressure surface generating a closing force acting on the valve member. When the control valve is closed, the pressure in the closing pressure chamber generates a closing force that is sufficiently large to hold the valve member in its closed position. When the control valve is opened, it comes in Closing pressure chamber to a pressure drop because more fuel in the

Relief pressure chamber can flow out, as flows through the throttle into the closing pressure chamber. This has the consequence that the closing force generated by the pressure in the closing pressure chamber is reduced to such an extent that opening forces acting on the valve member predominate and the valve member carries out an opening stroke.

When the valve member is in its closed position, a sealing zone of the valve member interacts with a valve seat such that a surface section of the valve member in the sealing zone or downstream of the sealing zone is decoupled from the high pressure prevailing upstream of the sealing zone. As soon as an opening stroke of the valve member lifts the sealing zone from the valve seat, high pressure can also build up downstream of the sealing zone, since less fuel can flow through the fuel outlet opening than through the now opened connection to the high-pressure fuel source. The result of this is that, during the opening stroke of the valve member, the high pressure is also applied to the aforementioned surface section downstream of the sealing zone and introduces an additional opening force into the valve member. In order to reduce the influence of these dynamic additional opening forces on the adjustment movement of the valve member and thus on the control behavior of the fuel injection valve, the known fuel injection valve has compensating means with which the valve member can be acted upon with compensating forces which counteract an opening stroke of the valve member. In the known fuel injection valve, these compensating means have a piston which is adjustably mounted in an associated cylinder. On the one hand, the piston limits one in the cylinder with a reference pressure, in particular the pressure of the

High pressure fuel source, pressurized hydraulic Room. On the other hand, in an initial position, the piston is supported on a stop which is stationary relative to the cylinder and can be driven from its initial position by the valve member via force transmission means, wherein it moves away from the stop. In the known fuel injection valve, the force transmission means are formed by an additional hydraulic space which is delimited on the one hand by the piston and on the other hand by a compensating pressure surface formed on the valve member. With an opening stroke of the valve member, a pressure can therefore build up in this additional hydraulic space of the power transmission means, which quickly increases to a maximum value, but then remains constant, since the position of the piston can change from this maximum pressure value, so that the volume in the additional hydraulic Space remains constant. This results in a stabilizing compensating force on the valve member, which makes the opening process of the fuel injector member more uniform and improves the controllability of the fuel injector. The mode of operation of these compensating means, in particular when the valve member closes, depends on the leakage occurring and the rigidity of the hydraulic medium used for power transmission, in particular fuel, which can have a particularly strong effect at high injection pressures.

Advantages of the invention

In the fuel injection valve according to the invention, the compensating forces, in particular their dependence on the opening stroke of the valve member, can be predetermined more precisely, since the elasticities or the stiffness of the springs used can be specified with high precision. In addition, an increased for the closing process of the valve member Functional reliability can be guaranteed, since spring means work independently of leaks.

Further important features and advantages of the fuel injection valve according to the invention result from the subclaims, from the drawings and from the associated description of the figures with reference to the drawings.

drawings

Exemplary embodiments of the fuel injection valve according to the invention are shown in the drawings and are explained in more detail below. Each shows schematically

Fig. 1 shows a longitudinal section through an area containing a compensating means

Fuel injection valve according to the invention according to a first embodiment,

FIG. 2 shows a diagram which shows a relationship between the needle stroke and the balancing force that can be achieved in the embodiment according to FIG. 1, FIG.

3 shows a longitudinal section as in FIG. 1, but of a second embodiment of the fuel injection valve according to the invention,

4 shows a longitudinal section as in FIG. 1, but of a third embodiment of the fuel injection valve according to the invention,

Fig. 5 is a diagram as in Fig. 2, which can be achieved with the embodiments of Figs. 3 and 4 Shows the relationship between the needle stroke and the balancing force,

Fig. 6 shows a longitudinal section as in Fig. 1, but a fourth embodiment of the

Fuel injection valve according to the invention, and

FIG. 7 shows a diagram as in FIG. 2, but of the relationship between the needle stroke and that which can be achieved with the embodiment according to FIG. 6

Balancing force.

Description of the embodiments

1, a needle-like valve member 1 is mounted and guided in the interior of a fuel injection valve for performing bidirectional adjustment movements or stroke adjustments. The valve member 1 has a sealing zone 2 which interacts with a valve seat 3. With the

Valve element 1, fuel outlet openings 4, which open into a combustion chamber of an internal combustion engine, in particular a diesel engine, can be controlled for opening and closing. Sealing zone 2 and valve seat 3 open or close a connection between a sack space 5 arranged downstream of the sealing zone 2 and containing the fuel outlet openings 4 and a pressure space 7 arranged upstream of the sealing zone 2 via an annular space 6. This pressure space 7 communicates via a high-pressure line 8 with a high-pressure fuel source 9.

When the valve member 1 is in its closed position, the bag space 5 is depressurized, so that there is a low pressure downstream of the sealing zone 2, while the high fuel pressure is present upstream of the sealing zone 2. As soon as the valve member 1 does not perform an opening stroke Actuating means shown is controlled and thus the pressure chamber 7 communicates with the bag space 5, is also downstream of the sealing zone 2 essentially

High fuel pressure, so that there forms an additional opening force acting on the valve member 1. In order to compensate as much as possible for this additional opening force, compensating means are provided with which the valve member 1 can be acted upon with compensating forces which counteract these additional opening forces.

The compensating means mentioned here have a piston 10 which is adjustably mounted in a cylinder 11. The piston 10 and the cylinder 11 are penetrated concentrically by the valve member 1 or arranged coaxially therewith, the piston 10 being designed as an annular piston. The piston 10 delimits a hydraulic compensation pressure chamber 12 in the cylinder 11, which is connected to the high-pressure fuel source 9 via a corresponding high-pressure line 13, so that the high-pressure fuel forms the reference pressure prevailing in the chamber 12. In particular, the connection of the hydraulic space 12 to the high-pressure fuel source 9 is not throttled. The pressure chamber 7 and the chamber 12 can preferably communicate directly with one another via the high-pressure lines 8 and 13.

Coaxially to the valve member 1, spring means, namely a first helical compression spring 15 and a second helical compression spring 16, are arranged axially between the piston 10 and an annular shoulder 14 formed on the valve member 1, which are supported on the one hand on the piston 10 and on the other hand on the annular shoulder 14. An annular support element 17 is arranged axially between the springs 15 and 16, the first spring 15 being supported on the one hand on the ring shoulder 14 and on the other hand on the support element 17 and the second spring 16 on the one hand on the piston 10 and on the other hand on the support element 17. The compensating force applied to the piston 10 by the pressure in the compensating pressure chamber 12 is transmitted to the support element 17 via the second spring 16. The axial adjustability of the support element 17 coaxially along the valve member 1 is limited by a stop 18 which is stationary with respect to the cylinder 11, so that the second spring 16 is biased by the pressure prevailing in the compensation pressure chamber 12.

2, the stroke of the valve member 1 is plotted in the X direction and the compensating force exerted on the valve member 1 as a function of the stroke is plotted in the Y direction. In the embodiment according to FIG. 1, at the beginning of the opening stroke of the valve member 1, only the spring force of the first spring 15, which increases linearly with the valve stroke X, acts as a compensating force Y. This area is identified by I in FIG. 2. As soon as the first spring 15 is pretensioned to the pretensioning force of the second spring 16 (II), the support element 17 lifts off the stop 18 and - since the pretensioning of the second spring 16 with the pressure in

Compensation pressure chamber 12 correlated - the piston 10 is moved into the compensation pressure chamber 12. Since the fuel can escape from the compensation pressure chamber 12 via the high pressure line 13, the pressure remains in the compensation pressure chamber 12 and thus the resulting one

Restoring force of the first spring 15 and the second spring 16 constant, so that the compensating force remains essentially constant in a stroke range marked III in FIG. 2.

In a variant, the annular piston 10, the support element 17 and the second spring 16 arranged between them can be replaced by a sleeve-like piston which is supported directly on the stop 18. Likewise, in a further variant, the support element 17 and the second spring 16 could be omitted, the first spring 15 then being directly on Piston 10 supports and for the piston 10 a directly cooperating with this, shown in Fig. 1 with broken lines stop 19 is provided.

In a further variant of that shown in FIG. 1

Embodiment is provided in addition to the stop 18 on which the support element 17 is supported, the stop 19 on which the piston 10 is supported. The distance between the stops 18 and 19 is coordinated with the second spring 16 so that in the closed position of the

Valve member 1 in the second spring 16 forms a biasing force which is less than the force applied to the piston 10 by the pressure in the compensating pressure chamber 12. In such an embodiment, the result is that shown in broken lines in FIG. 2

Context. In a first stroke range IV, only the restoring force of the first spring 15 acts as a compensating force. At V, the restoring force of the first spring 15 reaches the biasing force of the second spring 16, so that in a second stroke range VI both springs 15, 16 contribute to the compensating force. In VII the resulting total restoring force of the springs 15 and 16 reaches the force applied to the piston 10 in the pressure chamber 12, so that in a third stroke area VIII the compensating force remains essentially constant due to the adjustability of the piston 10.

3, the spring means with which the compensating forces are transmitted to the valve member 1 are formed from a first helical compression spring 20, which is supported on the one hand on the piston 10 and on the other hand on the ring shoulder 14, and a second spring 21, which is on the one hand on Ring shoulder 14 and on the other hand is supported on a stationary abutment 22 with respect to the cylinder 11. A stop 23 is assigned to the side of the piston 10 facing away from the compensation pressure chamber 12, against which the piston 10 passes the pressure prevailing in the compensation pressure chamber 12 is biased.

The embodiment shown in FIG. 3 gives the relationship shown in FIG. 5 between the

Opening stroke X of the valve member 1 and the compensating force Y. In a first stroke range I, both springs 20 and 21 are tensioned by the opening stroke of the valve member 1 without the piston 10 moving. At II, the restoring force of the first spring 20 reaches the pressure in

Equalization pressure chamber 12 force applied to the piston 10. In the subsequent stroke range III, further tensioning of the first spring 20 is prevented by the adjustment movement of the piston 10, while the second spring 21 can be pre-tensioned even more. In the second stroke range III, there is a different proportionality between the opening stroke X and the compensating force Y.

According to a variant, according to FIG. 4, an annular collar 24 is formed on the valve member 1, to which a stop 25, which is stationary with respect to the cylinder 11, is assigned, on which the annular collar 24 comes to rest when the valve member 1 is in its closed position. As in the embodiment according to FIG. 3, the piston 10 is biased against the stop 23 by the pressure in the compensating pressure chamber 12. A first spring 26 is supported on the one hand on the piston 10 and on the other hand on the ring collar 24 and a second spring 27 is supported on the one hand on the ring shoulder 14 and on the other hand on the stop 25 on a side facing away from the ring collar 24. 4, the same relationship between the opening stroke X of the valve member 1 and the compensation force Y can be achieved, as is already shown for the embodiments according to FIG. 3 in FIG. 5. In the first stroke range I, both springs 26 and 27 are tensioned. At II, the biasing force of the first spring 26 reaches Force with which the piston 10 is biased against the stop 23 by the pressure in the compensating pressure chamber 12, and in the second stroke range III, only the second spring 27 is increasingly tensioned, while the first spring 26, due to the adjustability of the piston 10, maintains a constant pretensioning force having.

6, in another embodiment, a first helical compression spring 28 is arranged axially between the piston 10 and the ring shoulder 14 coaxially with the valve member 1. This first spring 28 is dimensioned in such a way that, when the valve member 1 is in its closed position and the piston 10 abuts the stop 23, it has a clearance ΔX, so that the first spring 28 extends with an opening stroke X up to the value ΔX cannot support the piston 10 and the ring shoulder 14 at the same time.

A second spring 29 is arranged coaxially to the first spring 28 or coaxially to the valve member 1 and is supported on the one hand on the ring shoulder 14 and on the other hand on the abutment 22, which is formed here at the stop 23.

The embodiment shown in FIG. 6 gives the relationship shown in FIG. 7 between the opening stroke X of the valve member 1 and the compensating force Y. In a first stroke range I, only the second spring 29 is tensioned due to the clearance ΔX. At II, the opening stroke reaches the value of the free movement ΔX, so that the second spring 29 and the first spring 28 are also tensioned in a second stroke region III adjoining them. at

IV, the pretensioning force of the first spring 28 reaches the force with which the piston 10 is prestressed against the stop 23 by the pressure in the compensating pressure chamber 12, so that in a subsequent third stroke range

V only the preload of the second spring 29 increases, while the bias of the first spring 28 remains essentially constant due to the displacement of the piston 10.

Claims

Expectations

1. Fuel injection valve with the following features:

A: the fuel injection valve contains a bidirectionally adjustable valve member (1) with which a fuel outlet opening (4) for opening and closing can be controlled, B: the fuel injection valve has actuating means with which the valve member (1) for opening and closing the fuel outlet opening (4) is adjustable,

C: the fuel injection valve has compensating means with which the valve member (1) can be acted upon with compensating forces (Y) which counteract an opening stroke of the valve member (1), D: the compensating means have a piston (10) which is in an associated cylinder (11) is adjustable, E: the piston (10) delimits on the one hand in the cylinder (11) a hydraulic space (12) to which a reference pressure is applied,

F: the piston (10) on the other hand is in one

Starting position supported on a stop (18, -19, -23) which is stationary relative to the cylinder (11), G: the piston (10) is through the valve member (1) via force transmission means (15, 16; 20, 21; 26, 27 ; 28, 29) its starting position can be driven to move away from the stop (18, -19, -23), characterized by the following feature: H: the force transmission means are spring means (15, 16; 20, 21; 26, 27; 28, 29), which during the opening stroke ( X) des

Valve member (1) are tensioned by the valve member (1).

2. Fuel injection valve according to claim 1, characterized in that the piston is designed as the valve member (1) coaxially enclosing annular piston (10).

3. Fuel injection valve according to claim 1 or 2, characterized in that the spring means have a first spring element (15) and a second spring element (16) and that the piston (10) is supported with a support element (17) on the stop (18), wherein the first spring element (15) is supported on the valve member (1) and on the support element (17) and the second spring element (16) is supported on the piston (10) and on the support element (17).

4. Fuel injection valve according to claim 1 or 2, characterized in that the spring means a first spring element

(20; 26), which is supported on the piston (10) and on the valve member (1), and that a second spring element (21 j.27) is provided, which is on the valve member (1) and on one of the cylinders ( 11) supports a fixed stop element (22; 25).

5. Fuel injection valve according to claim 4, characterized in that the spring elements (20, 21) are arranged coaxially to one another and coaxially to the valve member (1) on the valve member (1).

6. Fuel injection valve according to claim 4, characterized in that the spring elements (26,27) axially are arranged one behind the other and coaxially to the valve member (1) on the valve member (1).

7. Fuel injection valve according to one of claims 1 to 6, characterized in that the first spring element (28) has a clearance ΔX, such that the first spring element (28) in a, in a closed position of the valve member (1) beginning first stroke range ( I) transmits no forces between the piston (10) and the valve member (1) and is only used in a second stroke range (III) adjoining the first stroke range (I) for power transmission between the piston (10) and the valve member (1).

8. Fuel injection valve according to one of claims 1 to 7, characterized in that the spring elements

(15, 16; 20,21; 26, 27 / 28,29) are arranged coaxially to the valve member (1).

9. Fuel injection valve according to one of / claims 3 to 8, characterized in that the support element (17) as the

Valve member (1) coaxial ring element is formed.