GB2285305A

GB2285305A - Pressure-compensated solenoid valve

Info

Publication number: GB2285305A
Application number: GB9424510A
Authority: GB
Inventors: Ulrich Augustin
Original assignee: Daimler Benz AG; Mercedes Benz AG
Current assignee: Daimler Benz AG
Priority date: 1993-12-16
Filing date: 1994-12-05
Publication date: 1995-07-05
Anticipated expiration: 2014-12-05
Also published as: GB2285305B; DE4342938C1; GB9424510D0

Description

1 Pressure-compensated solenoid valve 2285305 The invention relates to a

pressure-compensated solenoid valve for controlling the passage of a fluid through a connecting line between a high-pressure side connected to a fuel injection nozzle and a low- pressure side.

Solenoid valves of this kind are preferably intended for use in internal combustion engines with high engine speeds and with highly stressable high-pressure connections between fuel injection pumps and injection nozzles. Extremely rapid switching processes with a minimal application of energy can be carried out with these solenoid valves.

DE 37 32 553 Al discloses a solenoid valve of this kind in which a stepshaped control slide can be displaced in a step-shaped guide hole in a multi-component valve housing. The control slide is provided with an annular recess between the slide components which have diameters of different sizes, the enlarged slide component having a tapered axial boundary of the recess in order to form a sealing edge. Above the sealing edge, a high-pressure line opens radially into an annular space which is connected, only in the open position of the control slide, to a lowpressure line which opens radially into an annular recess. In addition, an actuation rod, to whose free ends a flat armature is attached, is screwed into the control slide which is of hollow design.

The present invention seeks to minimise the outlay in terms of production and costs for the solenoid valve referred to in the first paragraph with pressure compensation and to do this without adversely affecting a safe seat of the valve despite high pressures.

According to the present invention there is provided a pressurecompensated solenoid valve for controlling the passage of a fluid through a connecting line between a highpressure side connected to a fuel injection nozzle and a 2 low-pressure side, with a multi-component valve housing which has a line section of a high-pressure-side inflow line and has a step-shaped guide hole containing a step-shaped control slide having an armature displaceable as a valve closing element by an electromagnet counter to the force of a restoring spring, the control slide including a blind axial hole and a transverse hole in fluid connection therewith, two slide components of the slide having diameters of different sizes, and being guided in correspondingly matched stepped hole parts of the guide hole, wherein the end side of the larger slide component contains the axial hole and forms, together with a planar bearing face of a valve housing component which has a high pressure line section which interacts with the axial hole, and a high-pressure-side valve flat seat, and pressure shoulders, which are formed by junctions between the two slide components and stepped hole parts and bring about the pressure compensation, bound an annular space into which the transverse hole opens.

By means of the measures according to the invention it has been possible to reduce the constructional outlay on the solenoid valve, in particular by using extremely simple means for the pressure compensation which is made possible by the arrangement of a special annular space between the control slide and the guide hole in cooperation with the hole arrangement in the slide component and the highpressure-side line section. The flat seat ensures a reliable seal seat.

In one preferred embodiment, the solenoid valve comprises a 2-way flat seat valve and the larger slide component of the control slide bounds an annular relief space from which a low-pressure-side relief line leads away, which relief line is adapted to be connected, when the electromagnet is actuated, to the high-pressure-side line section which has a throttle and to a line which leads to the rear of the nozzle.

In another preferred embodiment, the solenoid valve 4 3 Fig. 2 comprises a 3-way flat seat valve and additionally has an enlarged armature-side slide component which, like the said larger slide component which faces the rear of the nozzle, is provided with an axial hole and a transverse hole in fluid communication therewith and which opens into a further annular space, and wherein the axial hole extends through the armature so as to be connectable to a relief channel. This embodiment has complete pressure compensation both in the closed position and in the open position.

Two embodiments of the invention are illustrated in the drawing and explained in greater detail below with reference to the said drawing, in which:

Fig. 1 shows the solenoid valve according to the invention as a 2-way flat seat valve and shows the solenoid valve as a 3- way flat seat valve.

A pressure-compensated solenoid valve 1, which is constructed according to Fig. 1 as a 2-way flat seat valve, is composed of a multi-component valve housing 2 with stepshaped guide hole 3 arranged therein, of a valve closing element 4 with step-shaped control slide 5 guided in the guide hole 3 and an electromagnet 6 with a flat armature 7 which is permanently connected to the narrow, elongate control slide 5.

The step-shaped guide hole 3 has stepped hole parts 3a, 3b which have diameters of different sizes and in which slide components Sa, 5b of the step-shaped control slide 5 are guided so as to be displaceable counter to the force of a restoring spring 8, the said slide components 5a and 5b being appropriately matched and thus also having diameters of different sizes. The junction between the two stepped hole parts 3a, 3b is f ormed by a pressure shoulder 3c and the junction between the two slide components Sa, 5b i s f ormed by a pressure shoulder 5c, both pressure shoulders 3c, Sc being at a distance from one another and thus bounding an annular space 9 in the axial direction.

The enlarged slide component 5b contains a blind 4 hole-like axial hole 10 from which a transverse hole 11 which opens into the annular space 9 branches.

The end side of the slide component 5b forms a highpressure-side valve flat seat 14 together with a planar bearing face 12 of the valve housing component 13 located below. In the central valve housing component 15 there is a recess 16 which forms with the valve housing component 13 a pressure relief space 17 from which a relief line 18 leads away laterally.

The axial hole 10 in the slide component 5b is arranged coaxially with respect to a high-pressure-side line section 19 which has a diameter of the same size and f rom which a line 20 which is connected to the rear of an injection nozzle (not illustrated) branches.

The line section 19 which has a throttle 21 upstream of the branch is connected to a high-pressure space (not illustrated in greater detail) of a fuel injection system which operates according to the common rail principle.

In order to ensure the pressure compensation on the control slide, the opening cross-section F1, located in the valve seat surf ace, of the line section 19 corresponds to the annular cross-section F2 formed by the pressure shoulder 5C.

The 2-way flat seat valve is shown in Fig. 1 in the closed position in which the control slide 5 is pressed on to its valve seat exclusively by the restoring spring 8. Small actuation f orces are suf f icient to open by means of the electromagnet 6.

In Fig. 2, a pressure-compensated solenoid valve 1 is constructed as a 3way flat seat valve which, in comparison with the embodiment according to Fig. 1, has a different line arrangement and an additional enlarged slide component 5d and an enlarged guide hole part 3d.

The line 20 runs parallel to the high-pressure side line section 19 which are both continuously connected to one another via a pressure space 22 when the electromagnet 6 is not activated. This pressure space 22 is connected via a connecting line 23 to a further pressure space 24 which contains the flat armature 7 which together with its protruding portion 25 and a planar bearing face 26 in the upper housing component 27, forms a valve flat seat 28.

The enlarged slide component 5d which adjoins the flat armature 7 has the same hole arrangement and the same annular space 9 as the enlarged slide component 5b located below. The axial hole 10' also penetrates the flat armature 7 and is directly connected to a relief channel 29.

In the illustrated position, the control slide 5 is pressed in a sealing fashion with its flat armature 7 on to its valve flat seat 28 by the restoring spring 8 provided in the pressure space 17 located below. Thus, the high-pressure side is disconnected from the low-pressure side.

When the electromagnet 6 is actuated, the control slide 5 lifts off from the valve flat seal 28 located above and closes the high-pressure-side line section 19 located opposite.

The connection to the rear of the nozzle is disconnected, the rear of the nozzle now being connected to the low-pressure-side relief channel 29 and causing the nozzle needle to open.

Thus, even in this solenoid valve the hydraulic forces which act on the control slide are completely pressure-compensated.

6

Claims

1. A pressure-compensated solenoid valve for controlling the passage of a fluid through a connecting line between a high-pressure side connected to a fuel injection nozzle and a low-pressure side, with a multi-component valve housing which has a line section of a high-pressure-side inflow line and has a step-shaped guide hole containing a step-shaped control slide having an armature displaceable as a valve closing element by an electromagnet counter to the force of a restoring spring, the control slide including a blind axial hole and a transverse hole in fluid connection therewith, two slide components of the slide having diameters of different sizes, and being guided in correspondingly matched stepped hole parts of the guide hole, wherein the end side of the larger slide component contains the axial hole and forms, together with a planar bearing face of a valve housing component which has a high pressure line section which interacts with the axial hole, and a high-pressure-side valve flat seat, and pressure shoulders, which are formed by junctions between the two slide components and stepped hole parts and bring about the pressure compensation, bound an annular space into which the transverse hole opens.

2. A solenoid valve according to Claim 1, wherein the solenoid valve comprises a 2-way flat seat valve and the larger slide component of the control slide bounds an annular relief space from which a low-pressureside relief line leads away, which relief line is adapted to be connected, when the electromagnet is actuated, to the highpressure-side line section which has a throttle and to a line which leads to the rear of the nozzle.

3. A solenoid valve according to Claim 1, wherein the solenoid valve comprising a 3-way flat seat valve and additionally has an enlarged armature-side slide component 7 which, like the said larger slide component which faces the rear of the nozzle, is provided with an axial hole and a transverse hole in fluid communication therewith and which opens into a further annular space, and wherein the axial hole extends through the armature so as to be connectable to a relief channel.

4. A solenoid valve according to Claim 3, wherein the said larger slide component bounds an annular high-pressure space from which a line adapted to be connected to the rear of the nozzle leads away, and a connecting line continuously connects the high-pressure space to an armature space containing the flat armature.

5. A solenoid valve according to any one of the preceding Claims 1, 3, and 4, in which the flat armature and an upper housing component which bounds the armature space together form the low-pressure-side valve flat seat.

6. A solenoid valve according to any one of the preceding claims, which is adapted to control a connecting line between a pump working space of a fuel injection pump and a low-pressure space.

7. A pressure-compensated solenoid valve substantially as described herein with reference to and as illustrated in the accompanying drawings.