GB2298897A

GB2298897A - I.c.engine fuel injector

Info

Publication number: GB2298897A
Application number: GB9604404A
Authority: GB
Inventors: Erguen Filiz; Friedrich Boecking
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1995-03-17
Filing date: 1996-03-01
Publication date: 1996-09-18
Anticipated expiration: 2016-03-01
Also published as: JPH08261113A; GB2298897B; GB9604404D0; DE29504608U1

Abstract

The valve member 1 is guided at spaced regions 21, 23 of the valve body 5 receiving the guide portion 17 of the valve member. The recess 25 spacing the regions 21, 23 may have a curved wall (27, Fig. 2) and may be located in the guide portion 17 (Fig. 3).

Description

Fuel-iniection valve for internal-combustion engines Prior art The invention proceeds from a fuel-injection valve for internal-combustion engines according to the pre-characterizing clause of Patent Claim 1. In fuelinjection valves of this type, a piston-shaped valve member is guided in a bore of a valve body, that end of the valve member located on the combustion-space side having a valve sealing face, by means of which it cooperates with a valve seat at that end of the bore in the valve body located on the combustion-space side. Downstream of this valve seat is at least one injection port which commences from the bore in the valve body and which opens into the combustion space of the internal-combustion engine to be supplied.The opening stroke movement of the valve member takes place counter to a return force, usually a valve spring, by means of a high injection pressure applied to the valve member in the opening direction. At the same time, to transmit the force of this opening pressure to the valve member, the valve member has a pressure shoulder which is formed by an annular step and which projects into a pressure space formed by a cross-sectional widening of the bore. At the same time, the valve member is sealingly guided, with its part of enlarged cross-section facing away from the combustion space, in a part of the bore in the valve body which forms a guide portion.The valve-member part of reduced cross-section projects into a part of the bore facing the combustion space, and there remains there, between the wall of the bore and the valve member, an annular gap which, commencing from the pressure space, leads as far as the valve seat and via which the fuel to be injected arrives at the injection ports.

At the same time, fuel-injection valves of this type have the disadvantage that the relatively slender and long valve member is guided only in the region of the guide portion of the bore in the valve body, the axial length of the guide portion usually being very small in relation to the length of the throughflow region. Thus, this small guide length of the valve member causes the valve member to pivot out at its free end, thereby impairing both the quality of a sealing valve closure and the durability of the injection valve.In this case, this effect is further reinforced, particularly at high injection pressures and with high clamping forces on the valve body, in that an upsetting of the valve body occurs, and as a result of this the bore guiding the valve member is deformed convexly inwards so that the valve member is then actually guided only in a small central region of the guide portion, thereby additionally increasing the risk that the valve member will pivot out about this one guide face.

EP 0 429 212 Al has already disclosed a fuelinjection valve, in which a second guide face of the valve member is provided in order to avoid the disadvantages described above. This second guide is formed by a sliding sleeve which is additionally attached onto the valve-member shank of smaller diameter and which is to guide the relatively long valve member once again, at its free end located on the combustion-space side, in the bore of the valve body, in order thereby to prevent the valve member from pivoting out. In this case, however, this known solution of so-called lower double valve-member guidance has the disadvantage that, on the one hand, it increases the outlay in terms of the manufacture of the fuel-injection valve and, moreover, the conditions of flow between the pressure space and the injection ports are influenced adversely.

Advantages of the invention In contrast to this, the advantage of the fuelinjection valve according to the invention for internal combustion engines, having the characterizing features of Patent Claim 1, is that the quality of guidance of the valve member in the bore of the valve body can be considerably improved even without additional lower needle guidance. This is achieved in an advantageous way by the provision of two guide faces which are independent of one another and are located in that guide portion of the bore guiding the valve member or on the valve-member shank guided therein and which are separated from one another by a recess or a cross-sectional enlargement of the bore or an annular groove on the valve-member shank.In this way, even in the event of a possible upsetting deformation of the valve member, the valve member is guided reliably on two bearing faces, so that a deflecting movement of the valve member about a pivot axis is not possible. In this case, the recess between the guide faces can be formed in a constructively simple way by means of an outwardly curved bore shape in the region of the guide portion of the bore or by means of an annular groove. At the same time, the axial extent of the recess is greater than that of the guide faces, in order, even in the event of a deformation of the bore, to guarantee reliably that the valve member will bear on the two guide faces, and these guide faces separated from one another can be arranged on the bore or on the valve-member shank guided therein.

Improved valve-member guidance of this type can be employed both on inwardly opening fuel-injection valves (for example, seat-hole and blind-hole nozzles) and on outwardly opening fuel-injection valves.

Further advantages and advantageous embodiments of the subject of the invention can be taken from the description, the drawing and the patent claims.

Drawing Three exemplary embodiments of the fuel-injection valve according to the invention for internal-combustion engines are represented in the drawing and are explained in more detail below.

Figure 1 shows a first exemplary embodiment in a longitudinal section through that part of the injection valve essential to the invention, in which the recess between the guide faces of the bore receiving the valve member is designed as an annular groove, Figure 2 a second exemplary embodiment similar to the representation of Figure 1, in which the recess is formed by an outwardly curved bore shape, and Figure 3 a third exemplary embodiment with two guide faces on the valve member which are separated from one another by an annular groove.

Description of the exemplary embodiments In the fuel-injection valve for internalcombustion engines, which is represented in Figure 1 only in its region essential to the invention, a piston-shaped valve member 1 is guided axially displaceably in a bore 3 of a valve body 5. The valve member 1 is made conical at its lower end located on the combustion-space side, the cone surface forming a conical valve sealing face 7 which cooperates with a conical valve seat 9 limiting the bore 3 on the combustion-space side. At the same time, in the exemplary embodiment described, this valve seat 9 is followed downstream by two injection ports 11 which open into the combustion space of the internal-combustion engine to be supplied.Furthermore, the valve member 1 has a pressure shoulder 13 which is formed by a reduction in diameter of the valve member 1 and points in the direction of the sealing face 7 and which projects into a cross-sectional widening of the bore 3 in the valve body 5, the said cross-sectional widening forming a pressure space 15. This pressure space 15, into which opens a pressure conduit (not shown) of the high-pressure feed pump, divides the bore 3 into a guide portion 17, facing away from the combustion space and axially guiding the valve member 1, and a throughflow portion 19 which surrounds the part of smaller cross-section of the valve member 1 and which opens onto the valve seat 9, at the same time forming an annular gap between the shank of the valve member 1 and the wall of the bore 3.

For better axial guidance of the valve member 1 in the bore 3, the guide portion 17 is subdivided into two guide faces which are independent of one another and of which a first lower guide face 21 is adjacent to the pressure space 15 and a second upper guide face 23 is arranged near that end of the valve body 5 facing away from the combustion space. At the same time, the guide faces 21, 23, which are offset axially relative to one another and on which the valve member 1 bears slide displaceably with its part of larger cross-section, are separated from one another by a recess in the wall of the bore 3 in the region of the guide portion 17, the said recess being designed as an annular groove 25 in the first exemplary embodiment. In this case, the axial length of the annular groove 25 is preferably larger than the length of the guide faces 21, 23.

The second exemplary embodiment represented in Figure 2 differs from the first exemplary embodiment represented in Figure 1 only in the design of the guide portion 17 of the bore 3 in the valve body 5. In this case, the guide portion 17 in Figure 2 is designed as an outwardly curved bore 27, of which the largest crosssection arranged approximately in the axial centre of the guide portion 17 forms the recess between the guide faces 21, 23 which, at the same time, are designed in such a way that the valve member 1 bears slide-displaceably on them.

In the third exemplary embodiment represented in Figure 3, the guide portion 17 of the bore 3 is made continuous. The guide faces separated from one another are, in this case, arranged on that part of the valvemember shank projecting into the bore 3 in the region 17, an annular groove 33 provided on the valve member 1 separating an upper guide face 29 from a lower guide face 31.

The fuel-injection valve according to the invention works as follows. In the closed position, the valve member 1 is held with its valve sealing face 7 in bearing contact on the valve seat 9 by a valve spring (not shown) counter to the residual pressure prevailing in the pressure space 15 and applied to the valve member 1 in the opening direction via the pressure shoulder 13.

The opening stroke movement takes place by loading the pressure space 15 with high pressure, and the pressure force then applied to the pressure shoulder 13 of the valve member 1 in the opening direction exceeds the spring force and thus lifts off the valve member 1 from the valve seat 9, so that the high-pressure fuel is injected out of the pressure space 15 via the throughflow portion 19 and the opened injection ports 11 into the combustion space of the internal-combustion engine to be supplied.

At the same time, the design according to the invention of that guide portion 17 of the bore 3 axially guiding the valve member 1 or of the valve-member part guided therein guarantees, even in the case of high axial forces on the valve body 5 and the possible upsetting deformation of the latter, that the valve member 1 always bears on two guide faces 21, 23 or 29, 31 which are offset axially relative to one another, so that the free end of the valve member 1 can be reliably prevented from pivoting out about a pivot axis.

By means of the fuel-injection valve according to the invention, therefore, it is possible in a constructively simple way, even in the case of high pressure forces and clamping forces on the valve body, to prevent the valve member from pivoting out, without the use of additional lower valve-member guidance, and thus to enhance the quality of guidance of the valve member.

Claims

Patent Claims

1. Fuel-injection valve for internal-combustion engines, with a piston-shaped valve member (1) which is axially displaceable in a bore (3) of a valve body (5) and of which the end located on the combustion-space side has a valve sealing face (7) which, for the opening and closing of at least one injection port (11) commencing from the bore (3), cooperates with a valve seat (9) provided at that end of the bore (3) located on the combustion-space side, and with a pressure shoulder (13) which is located on the valve member (1) which points in the direction of the sealing face (7) and which projects into a cross-sectional widening of the bore (3) in the valve body (5), the said cross-sectional widening forming a pressure space (15) and dividing the bore (3) into a guide portion (17), facing away from the combustion space and guiding the valve member (1), and a throughflow portion (19) which faces the combustion space and surrounds the part of smaller cross-section of the valve member (1) and which opens onto the valve seat (9), at the same time forming an annular gap between the valve member (1) and the wall of the bore (3), characterized in that that guide portion (17) of the bore (3) in the valve body (5) axially guiding the valve member (1) or that part of the valve member (1) projecting therein has two axially offset guide faces (21, 23; 29, 31) which are separated from one another and on which the valve member (1) is guided slide-displaceably in the bore (3).

2. Fuel-injection valve according to Claim 2, characterized in that the two guide faces (21, 23) of the bore (3) are separated from one another by a recess located in the bore (3) in the region of the guide portion (17), the said recess widening the bore cross-section.

3. Fuel-injection valve according to Claim 2, characterized in that the recess located in the bore (3) and separating the guide faces (21, 23) from one another is formed by an annular groove (25).

4. Fuel-injection valve according to Claim 3, characterized in that the axial extent of the annular groove (25) is greater than the axial extent of the guide faces (21, 23).

5. Fuel-injection valve according to Claim 2, characterized in that the recess located in the bore (3) and separating the guide faces (21, 23) from one another is formed by an outwardly curved bore shape (27), the largest cross-section of which is located approximately in the middle region of the guide portion (17).

6. Fuel-injection valve according to Claim 1, characterized in that the valve seat (9) on the valve body (5) and the valve sealing face (7) cooperating therewith and located on the valve member (1) are made conical.

7. Fuel-injection valve according to Claim 1, characterized in that two guide faces (29, 31), which are separated from one another by an annular groove (33), are provided on the valve member (1) in the region of the guide portion (17) of the bore (3).

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