GB2303404A

GB2303404A - I.c. engine fuel-injection valve with spill channel

Info

Publication number: GB2303404A
Application number: GB9614070A
Authority: GB
Inventors: Gungor Yurtseven; Peter Kuegel; Thomas Kugler
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1995-07-21
Filing date: 1996-07-04
Publication date: 1997-02-19
Anticipated expiration: 2016-07-04
Also published as: GB9614070D0; GB2303404B; JPH0932694A; DE19623581A1; FR2736971A1

Description

Fuel-Iniection Valve for Internal Combustion Engines State of the Art The invention takes as its starting-point a fuel-injection valve for internal combustion engines of the class specified in Claim 1. With a fuel-injection valve of this type, known from DE-OS 39 28 912, a valve member is guided so as to be axially displaceable in a guide bore of a valve body, one end of said valve body projecting into the combustion chamber of the internal combustion engine to be supplied.

The valve member has at its end on the combustion-chamber side a valve-sealing face which interacts with a valve seat formed at the end of the guide bore on the combustionchamber side. A high-pressure channel in the valve body which conducts fuel borders the valve-seat face in the direction facing away from the combustion chamber, said high-pressure channel being partly formed by an annular gap between the shaft of the valve member and the wall of the guide bore. On the combustion-chamber side at least one injection aperture makes contact with the valve seat, the flow of fuel between high-pressure channel and injection aperture being opened in controlled manner by the valve member being lifted away from the valve seat.

With a view to cooling the valve member there is additionally provided within the valve member a spill channel, via which the high-pressure channel is constantly connected to a relief chamber when the valve member is lifted away from the valve seat and which is formed by a blind bore emanating from the end of the valve member on the combustion-chamber side and a transverse bore intersecting said blind bore. The transverse bore leads into a spill chamber formed between the valve member and the wall of the guide bore, said spill chamber being limited axially by an intermediate disk of the injection valve which is in contact with the valve body, a through aperture being provided in the intermediate disk in such a way that the spill chamber is constantly connected to a relief chamber formed by the spring chamber of the injection valve.

However, this constant connection between the high-pressure channel and the relief chamber in the open position of the valve member has the disadvantage that a relatively large amount of fuel flows away via the spill channel during the actual injection process and is consequently not available for fuel injection, thus impairing the effectiveness of the whole system. In addition, as a consequence of the undefined amount of leakage at the drainage channel the amount of fuel to be injected can only be dosed very imprecisely, so that the known fuel-injection valve does not satisfy the requirements of modern internal combustion engines.

Advantages of the Invention In contrast, the fuel-injection valve according to the invention having the characterising features of Claim 1 has the advantage that the spill channel provided in the valve member is sealed when the valve member reaches its openingstroke position. Consequently it is possible for a delay, necessary for good processing of the fuel in the combustion chamber, in the opening-stroke movement of the valve member to be achieved in advantageous manner without thereby significantly affecting the precision of the amount injected.

The design of the spill channel as longitudinal and transverse bores opening out on a polished face on the shaft of the valve member additionally has the advantage that a valve member of this type can be easily manufactured.

The valve member can be manufactured via a primary forming process - eg, by means of sintering technology or the socalled "metal-injection method". As an alternative, however, it is also possible for the longitudinal and transverse bores to be introduced into an unworked pipe, optionally also with preprocessed external geometry, by mechanical or erosive methods and for the polished faces to be produced by machining.

It is possible in advantageous manner for a defined spill volume at the spill chamber to be adjusted via the geometry or the design of the polished faces and of the transverse bore, whereby the part of the spill chamber that is formed between the polished faces and the wall of the guide bore then acts as a defined throttle cross-section.

A further advantage is achieved by the provision at the upper end of the polished faces facing the intermediate disk of a collar which projects into a region of the guide bore of enlarged cross-section and via which the sealing contact face between valve member and intermediate disk can be enlarged, so that with secure sealing the demands with regard to component tolerances can be reduced, again reducing the manufacturing effort. The polished faces which are preferably designed as plane faces and which constitute a part of the spill chamber may alternatively also be constituted by radial recesses on the valve member which connect the outlets of the transverse bores to the upper part of the spill chamber.

The fuel-injection valve according to the invention acts as a valve which opens inwardly and may alternatively be designed as a so-called seat-hole nozzle, a blind-hole nozzle or a pintle-type nozzle, whereby, however, the longitudinal bore of the spill channel which is designed as a blind bore is arranged within the valve member in such a way that in the closed state of the fuel-injection valve it is sealed in relation to the combustion chamber of the internal combustion engine.

Further advantages and advantageous configurations of the subject of the invention can be gathered from the description, the drawing and the claims.

Drawing Two examples of embodiments of the fuel-injection valve for internal combustion engines according to the invention are represented in the drawing and elucidated more fully in the following description.

Figure 1 shows a longitudinal section through a first example of an embodiment of the fuel-injection valve, Figure 2 shows, in two views, a detail from Figure 1 which is enlarged in the region of the spill chamber and Figure 3 shows a second embodiment example in a manner analogous to the representation of Figure 2 in which a collar is additionally provided on the polished faces.

Description of the Embodiment Examples In the first embodiment example of the fuel-injection valve for internal combustion engines according to the invention which is represented in Figure 1 a piston-shaped valve member 1 is guided so as to be axially displaceable in a guide bore 3 of a valve body 5. One end 7 of the cylindrical valve body 5 projects into the combustion chamber, which is not shown in any detail, of the internal combustion engine to be supplied, and the other end thereof, which is designed as a flat front face 9, is in contact with a first front face 13 of an intermediate disk 11 of the injection valve, the second front face 15 of which facing away from the valve body 5 is bordered by a spring chamber 17 accommodating a restoring spring, which is not shown in any detail, of the valve member 1, said spring chamber being constantly connected to a low-pressure fuel chamber via a return line, which is also not shown, and in this way constituting a relief chamber 17.

At its end on the combustion-chamber side the valve member 1 has a valve-sealing face 18 which in the embodiment example is designed as a conical sealing face and which interacts with a valve-seat face 19 provided at the end of the guide bore 3 on the combustion-chamber side, said valve-seat face taking the form of a hollow cone, with the guide bore 3 in the embodiment example taking the form of a blind bore.

From the valve-seat face 19 there branch off two injection apertures 21 which lead into the combustion chamber of the internal combustion engine to be supplied. At the end of the valve seat 19 facing away from the injection aperture 21 a high-pressure channel 23 opens out which extends in the form of a bore proceeding from the upper front face 9 of the valve body 5 firstly as far as a pressure chamber constituted by a region of the guide bore 3 of enlarged diameter and from there further leads through an annular gap between the shaft of the valve member 1 and the wall of the guide bore 3 as far as the valve seat 19. This highpressure channel 23 is connected, in a manner which is not shown in any detail, by means of an injection line to a high-pressure fuel pump which supplies the fuel-injection valve with fuel under high pressure.

For a delayed opening-stroke movement of the valve member 1 there is additionally provided in the valve member 1 a spill channel 31 which during the opening-stroke movement of the valve member 1 enables a connection between the highpressure channel 23 and the relief chamber 17.

This spill channel 31, which is also shown on an enlarged scale in Figure 2, is formed by a blind bore 33 which emanates from the end of the valve member 1 on the combustion-chamber side and projects into the blind hole of the guide bore 3 and which extends axially in the embodiment example and a transverse bore 25 which intersects said blind bore at the upper end of the valve member 1. In the region of the outlets of the transverse bore 35 the valve member 1 has on its circumferential surface two plane polished faces 37 located opposite one another, between which and the wall of the guide bore 3 a spill chamber 39 is formed, the flowthrough cross-section of which constitutes an adjustable throttle cross-section.The spill chamber 39 extends in the axial direction in relation to the valve member 1 from a shoulder bordering the polished faces 37 in the direction of the injection aperture 21 as far as the front face 13 of the intermediate disk 11, whereby the diameter of the guide bore 3 increases conically at its end facing the intermediate disk 11.

The spill chamber 39 is relieved via a flow-through crosssection 45 in the relief chamber 17 formed between a through bore 41 in the intermediate disk 11 and a shaft portion 43 of the valve member 1 which is diminished in diameter, whereby when the valve member 1 is completely lifted away from the valve seat 19 this flow-through cross-section 45 is capable of being sealed by an annular sealing face 47 of the valve member 1 which is formed at the transition to the shaft portion 43 which is diminished in diameter by contact with the front face 13 of the intermediate disk 11. To this end the diameter of the through bore 41 in the intermediate disk 11 is designed to be smaller than the outer diameter of the sealing face 47.

The second embodiment example represented in Figure 3 differs from the first embodiment example only by virtue of the valve member geometry in the region of the spill chamber 39, so that the description is restricted to this part of the injection valve.

The polished faces 37 in the second embodiment example are limited in the direction of the intermediate disk 11 by a collar 49 which projects into the part of the guide bore 3 that is enlarged in cross-section and by means of which the radial extent of the sealing face 47 on the valve member 1 is enlarged, so that with improved sealing a larger f low- through cross-section 45 is possible between spill chamber 39 and relief chamber.

The fuel-injection valve according to the invention operates in the following way.

In the closed state the valve member 1 is retained in contact with the valve seat 19 by means of the restoring spring with its valve-sealing face 18, so that the injection apertures 21 are sealed in relation to the high-pressure channel 23.

When the injection phase begins, fuel conveyed by the highpressure pump reaches the high-pressure channel 23 and displaces the valve member 1 from the valve seat 19 in known manner against the force of the restoring spring, so that the fuel under high pressure reaches the blind hole of the guide bore 3 via the flow-through cross-section between valve-sealing face 18 and valve seat 19 which is opened in controlled manner and reaches the combustion chamber of the internal combustion engine via the injection apertures 21.

In the process, however, a part of the fuel flows away during the opening-stroke movement of the valve member 1 out of the blind hole of the guide bore 3 via the spill channel 31 in the valve member 1 into the spill chamber 39 and further via the flow-through cross-section 45 into the relief chamber 17, so that the opening-stroke movement of the valve member 1 is delayed, which has an advantageous effect on the processing of the fuel in the combustion chamber.

When the maximal opening-stroke position of the valve member 1 is reached, the flow-through cross-section 45 connecting the spill chamber 39 to the relief chamber 17 by means of the contact of the sealing face 47 of the valve member 1 on the intermediate disk 11 is sealed, so that the entire quantity of fuel conveyed for injection now reaches the combustion chamber.

The injection is concluded in known manner by the fall in pressure in the high-pressure channel 23, as a consequence of which the restoring spring again displaces the valve member 1 into contact with the valve seat 19.

Claims

1. Fuel-injection valve for internal combustion engines, with a valve member (1) which is guided so as to be axially displaceable in a guide bore (3) of a valve body (5), said valve member having on its end on the combustion-chamber side a valve-sealing face (18) which interacts with a valve seat (19) formed at the end of the guide bore (3) on the combustion-chamber side for the purpose of controlling the connection between a high-pressure channel (23) in the valve body (5) and at least one injection aperture (21) and with a spill channel (31) on the valve member (1), via which the high-pressure channel (23) is capable of being connected to a relief chamber (17) when the valve member (1) is lifted away from the valve seat (19) and which is formed by a blind bore (33) emanating from the end of the valve member (1) on the combustion-chamber side and at least one transverse bore (35) intersecting the blind bore (33), whereby the transverse bore (35) leads into a spill chamber (39) which is formed between the valve member (1) and the wall of the guide bore (3) and is capable of being connected to the relief chamber (17), characterised in that the connection between spill chamber (39) and relief chamber (17) is sealed in the maximal opening-stroke position of the valve member (10) by a sealing face (47) provided on the valve member (1).

2. Fuel-injection valve according to Claim 1, characterised in that the sealing face (47) on the valve member (1) is designed as an annular front face which is formed on: a region of the valve member (1) of diminished cross-section, whereby a valve member part (43) of diminished diameter projects with clearance into a through bore (41) in an intermediate disk (11) in contact axially with the valve body (5), the front face (13) of said intermediate disk facing the valve body (5) limiting the spill chamber (39), whereby a region of the front face (13) adjacent to the through bore (41) forms a contact face for the sealing face (47) of the valve member (1).

3. Fuel-injection valve according to Claim 2, characterised in that the intermediate disk (11) on its front face (15) facing away from the valve body (5) borders the relief chamber (17), preferably a spring chamber accommodating a restoring spring of the valve member (1).

4. Fuel-injection valve according to Claim 1, characterised in that the spill chamber (39) formed between the shaft of the valve member and the wall of the guide bore (3) is formed by at least one polished face (37), preferably taking the form of a plane face, on the valve member (1), into which the transverse bore (35) leads.

5. Fuel-injection valve according to Claim 4, characterised in that two opposite polished faces (37) are provided on the valve member (1), into each of which there leads an outlet of the transverse bore (35) which is designed as a continuous bore.

6. Fuel-injection valve according to Claim 2, characterised in that the guide bore (3) widens conically at its end bordering the intermediate disk (11).

7. Fuel-injection valve according to Claims 1 to 6, characterised in that the polished face (37) limiting the spill chamber (39) is limited at its end facing the intermediate disk (11) by a collar (49), the annular face of which facing the intermediate disk (11) constitutes the sealing face (47) of the valve member (1).

8. Fuel-injection valve according to Claim 1, characterised in that the flow-through cross-section of the spill chamber (39) constitutes a defined throttle cross-section.

9. Process for the manufacture of a fuel-injection valve according to Claim 1, characterised in that the valve member (1) is manufactured by means of a primary forming process, preferably by the "metal-injection method".

10. A fuel-injection valve substantially as herein described with reference to Figures 1 and 2, or Figure 3 of the accompanying drawings.

11. A process for the manufacture of a fuel-injection valve substantially as herein described with reference to the accompanying drawings.