GB2314119A

GB2314119A - I.c. engine fuel injection valve with discharge channel in the valve element

Info

Publication number: GB2314119A
Application number: GB9701698A
Authority: GB
Inventors: Karl Hofmann; Johann Warga; Thomas Kuegler; Peter Kuegel; Gungor Yurtseven
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1996-06-13
Filing date: 1997-01-28
Publication date: 1997-12-17
Anticipated expiration: 2017-01-28
Also published as: CN1077222C; JPH1054328A; CN1171488A; GB2314119B; GB9701698D0

Abstract

The valve element 1 is axially displaceable in a bore 3 in the valve body 5 and has a cooling discharge channel 31 which communicates with the high-pressure channel 23 when the valve member 1 is lifted away from the seat 19. The discharge channel 31 comprises a blind bore 33 opening at the combustion chamber end of the valve member 1 and intersected at the other end by a transverse bore 35 which leads into a discharge chamber 39 formed between the valve member 1 and the wall of the bore 3. The discharge chamber 39 is connected to the relief chamber 17 except at the maximum opening position of the valve member 1 when a sealing surface 47 on the valve element 1 closes the connection to enable a delay in the opening stroke of the valve element. The construction of the discharge channel 31 with blind and transverse bores 33,35 permits easy manufacture of the valve element.

Description

Fuel inection valve for internal combustion engines Background art The invention proceeds from a fuel injection valve for internal combustion engines according to the preamble of claim 1. In such a fuel injection valve known from DE-OS 39 28 912, a valve element is guided in an axially displaceable manner in a pilot bore of a valve body, one end of which projects into the combustion chamber of the i.c. engine to be supplied. The valve element at its combustion chamber end has a valve sealing surface which cooperates with a valve seat formed at the combustion chamber end of the pilot bore. Lying adjacent to the valve seat surface in the direction remote from the combustion chamber is a fuel-carrying high-pressure channel in the valve body, which channel is partially formed by an annular gap between the valve element stem and the wall of the pilot bore. Adjoining the valve seat at the combustion chamber side is at least one injection opening, the fuel passage between high-pressure channel and injection opening being opened by the lifting of the valve element from the valve seat.

For cooling the valve element, there is additionally provided in the valve element a discharge channel, by which the highpressure channel is constantly connected to a relief chamber when the valve element is lifted off the valve seat and which is formed by a blind hole emanating from the combustion chamber end of the valve element and by a transverse bore which cuts said blind hole. The transverse bore opens into a discharge chamber, which is formed between the valve element and the wall of the pilot bore and is axially delimited by an intermediate disc of the injection valve applied against the valve body, a through-opening being provided in the intermediate disc in such a way that the discharge chamber is constantly connected to a relief chamber, which is formed by the spring chamber of the injection valve.

Said connection, which in the open position of the valve element constantly exists between the high-pressure channel and the relief chamber, does however have the drawback that during the actual injection process a relatively large quantity of fuel flows off through the discharge channel and is therefore not available for fuel injection, thereby impairing the efficiency of the system as a whole.

Furthermore, because of the undefined leakage quantity at the discharge channel, the fuel quantity to be injected may be metered only very imprecisely so that the known fuel injection valve does not meet the requirements of modern i.c. engines.

Advantages of the invention In contrast, the fuel injection valve according to the invention having the characterizing features of claim 1 has the advantage that the discharge channel provided in the valve element is closed when the valve element reaches its opening stroke position. Thus, in an advantageous manner it is possible to achieve a delay of the opening stroke movement of the valve element, said delay being necessary for good processing of the fuel in the combustion chamber, without substantially influencing the accuracy of the fuel injection quantity.

The construction of the discharge channel as a longitudinal and transverse bore, which opens at a ground portion of the valve element stem, moreover has the advantage that such a valve element is easy to manufacture.

Manufacture of the valve element may be effected by a creative forming technique, e.g. by means of powder metallurgy or the so-called metal injection method. An alternative possibility, however, is to introduce the longitudinal and transverse bores mechanically or by erosion into a tubular blank, optionally also having a pre-machined external geometry, and produce the ground portions by machining.

It is then possible in an advantageous manner for a defined discharge volume of the discharge chamber to be adjusted by means of the geometry and/or the dimensioning of the ground portions and the transverse bore, the part of the discharge chamber formed between the ground portions and the wall of the pilot formation then acting as a defined throttle cross section.

A further advantage is achieved by the provision, at the top end of the ground portions directed towards the intermediate disc, of a collar which projects into a cross-sectionally widened region of the pilot bore and by means of which the sealing contact surface between valve element and intermediate disc may be enlarged so that, given reliable sealing, the requirements regarding the tolerances of structural parts may be reduced, which in turn reduces the manufacturing outlay.

The ground surfaces, which preferably take the form of plane surfaces and form a part of the discharge chamber, may alternatively be formed by radial turned recesses on the valve element, which connect the outlet openings of the transverse bores to the upper part of the discharge chamber.

The fuel injection valve according to the invention in said case acts as an inwardly opening valve and may alternatively be designed as a so-called seat-hole nozzle, blind-hole nozzle or pintle-type nozzle, the longitudinal bore of the discharge channel in the form of a blind hole however being disposed in the valve element in such a way that, in the closed state of the fuel injection valve, it is closed off from the combustion chamber of the i.c. engine.

In order that a penetration of combustion gases into the discharge channel may be reliably prevented when the injection valve is closed, the blind hole may be closed at its bottom combustion chamber end. The connection to the high-pressure channel is then effected by means of at least one radial bore, which emanates from the blind hole and opens at the valve sealing surface of the valve element. The outlet opening of said radial bore is preferably disposed upstream of the injection opening, advantageously between the injection opening and a seat edge of the valve element. Said arrangement moreover has the advantage that, when used in an injection valve having two valve springs, the radial bore is throttled in the preliminary stroke region, with the result that initially a low discharge quantity (low pressure loss) flows off through the discharge channel, while in the second stroke phase up to reaching of the maximum stroke stop a large discharge quantity flows off so that the effect of a so-called 2-spring holder is intensified.

Further advantages and advantageous refinements of the subject matter of the invention are indicated in the description, the drawings and the claims.

Drawings Three embodiments of the fuel injection valve according to the invention for i.c. engines are illustrated in the drawings and described in detail below.

Of the drawings, Figure 1 shows a longitudinal section through a first embodiment of the fuel injection valve, Figure 2 two views of an enlarged detail in the region of the discharge chamber from Figure 1, Figure 3 a second embodiment in an identical manner to the representation of Figure 2, wherein a collar is additionally provided at the ground portions, and Figure 4 a third embodiment in a representation of the combustion chamber end of the fuel injection valve, wherein the blind hole of the discharge channel is closed and connected by a radial bore to the high-pressure channel.

Description of the embodiments In the first embodiment of the fuel injection valve according to the invention for i.c. engines which is shown in Figure 1, a piston-like valve element 1 is guided in an axially displaceable manner in a pilot bore 3 of a valve body 5. The cylindrical valve body 5 projects with its one end 7 into the combustion chamber (not shown in detail) of the i.c. engine to be supplied and is applied by its other end in the form of flat end face 9 against a first end face 13 of an intermediate disc 11 of the injection valve, of which disc the second end face 15 remote from the valve body 5 is adjoined by a spring chamber 17, which receives a restoring spring (not shown in detail) of the valve element 1, is connected by a return line (likewise not shown) permanently to a low-pressure fuel chamber and hence forms a relief chamber 17.

At its combustion chamber end, the valve element 1 has a valve sealing surface 18 which, in the embodiment, takes the form of a conical sealing surface and cooperates with a valve seat surface 19, which is provided at the combustion chamber end of the pilot bore 3 and takes the form of a hollow cone, the pilot bore 3 in the embodiment taking the form of a blind hole. Emanating from the valve seat surface 19 are two injection openings 21, which open into the combustion chamber of the i.c. engine to be supplied. Opening out at the end of the valve seat 19 remote from the injection opening 21 is a high-pressure channel 23 which, in the form of a bore emanating from the top end face 9 of the valve body 5, extends initially as far as into a pressure chamber formed by a widening of the diameter of the pilot bore 3 and continues from there through an annular gap between the stem of the valve element 1 and the wall of the pilot bore 3 up to the valve seat 19. Said high-pressure channel 23 is connected in a manner not shown in detail by means of an injection line to a high-pressure fuel pump, which supplies the fuel injection valve with highly pressurized fuel.

For a delayed opening stroke movement of the valve element 1, there is additionally provided in the valve element 1 a discharge channel 31 which, in the course of the opening stroke movement of the valve element 1, enables a connection between the high-pressure channel 23 and the relief chamber 17.

Said discharge channel 31, which is also shown to an enlarged scale in Figure 2, is formed by a blind hole 33, which emanates from the combustion chamber end of the valve element 1 projecting into the blind hole of the pilot bore 3 and in the embodiment extends axially, and a transverse bore 35 which cuts the blind hole 33 at the top end of the valve element 1.

In the region of the outlet openings of the transverse bore 35, the valve element 1 has on its lateral surface two, opposing, plane ground portions 37, between which and the wall of the pilot bore 3 a discharge chamber 39 is formed, the throughflow cross section of which forms an adjustable throttle cross section. The discharge chamber 39 extends in an axial direction relative to the valve element 1 from a step, which delimits the ground portions 37 in the direction of injection opening 21, up to the end face 13 of the intermediate disc 11, the diameter of the pilot bore 3 conically enlarging at its end directed towards the intermediate disc 13.

Relief of the discharge chamber 39 into the relief chamber 17 is effected via a throughflow cross section 45, which is formed between a through-bore 41 of the intermediate disc 11 and a reduced-diameter stem part 43 of the valve element 1 and which, when the valve element 1 is lifted fully off the valve seat 19, is closable in that an annular sealing surface 47 of the valve element 1 formed at the transition to the reduced diameter stem part 43 is applied against the end face 13 of the intermediate disc 11. For said purpose, the diameter of the through-bore 41 of the intermediate disc 11 is made smaller than the outside diameter of the sealing surface 47.

The second embodiment shown in Figure 3 differs from the first embodiment only in the valve element geometry in the region of the discharge chamber 39, for which reason the description is confined to said part of the injection valve.

The ground portions 37 in the second embodiment are delimited in the direction of the intermediate disc 11 by a collar 49, which projects into the cross-sectionally widened part of the pilot bore 3 and by means of which the radial extension of the sealing surface 47 on the valve element 1 is enlarged, thereby combining improved sealing with the possibility of a larger throughflow cross section 45 between discharge chamber 39 and relief chamber.

In the third embodiment, of which only the bottom, combustion chamber-side part 7 of the valve body 5 of the fuel injection valve is shown in Figure 4, the blind hole 33 of the discharge channel 31 in the valve element 1 is closed at its combustion chamber end by means of a plug 61, although other closure options are alternatively possible. The connection between the discharge channel 31 and the high-pressure channel 23 is effected here by a radial bores 63 [sic], which emanates from the blind hole 33 and opens into the valve sealing surface 18 of the valve element 1. The outlet opening 65 formed at the valve sealing surface 18 is disposed upstream of the injection opening 21 in the valve seat surface. The outlet opening is moreover disposed downstream below a seat edge 67 of the valve element 1, which seat edge delimits the conical valve sealing surface 18 at the end remote from the combustion chamber and is formed by a variation of the cone angle of the valve sealing surface 18.

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

In the closed state, the valve element 1 is held by the restoring spring with its valve sealing surface 18 applied against the valve seat 19 so that the injection openings 21 are closed off from the high-pressure channel 23.

At the start of the injection phase, fuel delivered by the high-pressure pump passes into the high-pressure channel 23 and in a known manner moves the valve element 1 counter to the action of the restoring spring off the valve seat 19 so that the highly pressurized fuel passes through the opened throughflow cross section between valve sealing surface 18 and valve seat 19 into the blind hole of the pilot bore 3 and through the injection openings 21 into the combustion chamber of the i.c. engine.

However, in the course of the opening stroke movement of the valve element 1 some of the fuel flows out of the blind hole of the pilot bore 3 through the discharge channel 31 in the valve element 1 into the discharge chamber 39 and then through the throughflow cross section 45 into the relief chamber 17, so that the opening stroke movement of the valve element 1 is delayed, which has an advantageous effect upon the processing of the fuel in the combustion chamber.

Upon attainment of the maximum opening stroke position of the valve element 1, the throughflow cross section 45 connecting the discharge chamber 39 to the relief chamber 17 is closed as a result of application of the sealing surface 47 of the valve element 1 against the intermediate disc 11, with the result that all of the delivered fuel quantity may then pass for injection into the combustion chamber.

Injection is terminated in a known manner by the pressure drop in the high-pressure channel 23, as a result of which the restoring spring moves the valve element 1 back into contact with the valve seat 19. In the course of the closing stroke movement of the valve element 1 some of the highly pressurized fuel flows off from the blind hole through the discharge channel 31, thereby increasing the speed of the closing stroke.

Claims

1. Fuel injection valve for internal combustion engines, having a valve element (1) which is guided in an axially displaceable manner in a pilot bore (3) of a valve body (5) and has at its combustion chamber end a valve sealing surface (18), which cooperates with a valve seat (19) formed at the combustion chamber end of the pilot bore (3) for control of the connection between a high-pressure channel (23) in the valve body (5) and at least one injection opening (21), and having a discharge channel (31) in the valve element (1), by means of which channel the high-pressure channel (23) is connectable to a relief chamber (17) when the valve element (1) is lifted off the valve seat (19) and which is formed by a blind hole (33) emanating from the combustion chamber end of the valve element (1) and by at least one transverse bore (35) which cuts the blind hole (33), the transverse bore (35) opening into a discharge chamber (39), which is formed between the valve element (1) and the wall of the pilot bore (3) and is connectable to the relief chamber (17), characterized in that the connection between discharge chamber (39) and relief chamber (17) is closed in the maximum opening stroke position of the valve element (1) by means of a sealing surface (47) provided on the valve element (1).

2. Fuel injection valve according to claim 1, characterized in that the sealing surface (47) on the valve element (1) takes the form of an annular end face which is formed at a cross-sectional reduction of the valve element (1), a reduced-diameter valve element part (43) projecting with clearance into a through-bore (41) of an intermediate disc (11), which is applied axially against the valve body (5) and of which the end face (13) directed towards the valve body (5) delimits the discharge chamber (39), a region of the end face (13) adjacent to the through-bore (41) forming a contact face for the sealing surface (47) of the valve element (1).

3. Fuel injection valve according to claim 2, characterized in that the intermediate disc (11) at its end face (15) remote from the valve body (5) lies adjacent to the relief chamber (17), preferably a spring chamber which receives a restoring spring of the valve element (1).

4. Fuel injection valve according to claim 1, characterized in that the discharge chamber (39) formed between the valve element stem and the wall of the pilot bore (3) is formed by at least one ground portion (37) of the valve element (1), which preferably takes the form of a plane surface and into which the transverse bore (35) opens.

5. Fuel injection valve according to claim 4, characterized in that two opposing ground portions (37) are provided on the valve element (1), into each of which an outlet opening of the transverse bore (35) designed as a through-bore opens.

6. Fuel injection valve according to claim 2, characterized in that the pilot bore (3) widens conically at its end lying adjacent to the intermediate disc (11).

7. Fuel injection valve according to claims 1 to 6, characterized in that the ground portion (37) delimiting the discharge chamber (39) is delimited at its end directed towards the intermediate disc (11) by a collar (49), of which the annular face directed towards the intermediate disc (11) forms the sealing surface (47) of the valve element (1).

8. Fuel injection valve according to claim 1, characterized in that the throughflow cross section of the discharge chamber (39) forms a defined throttle cross section.

9. Method of manufacturing a fuel injection valve according to claim 1, characterized in that the valve element (1) is manufactured using a creative forming technique, preferably the metal injection method.

10. Fuel injection valve according to claim 1, characterized in that the blind hole (33) is closed at its combustion chamber end and that at least one radial bore (63) emanates from the blind hole (33) and opens in the region of the valve sealing surface (18).

11. Fuel injection valve according to claim 10, characterized in that the outlet opening (65) of the radial bore (63) of the discharge channel (31) in the valve sealing surface (18) is disposed upstream of the injection opening (21) in the valve seat surface (19).

12. Fuel injection valve according to claim 11, characterized in that the outlet opening (65) of the radial bore (63) of the discharge channel (31) in the valve sealing surface (18) is disposed between the injection opening (21) of the valve seat surface (19) and a seat edge (67) of the valve element (1) delimiting the valve sealing surface (18) at the end remote from the combustion chamber.

13. Fuel injection valve according to claim 10, characterized in that the blind hole (33) is closed at its combustion chamber end by means of a plug (61).