GB2107781A

GB2107781A - Fuel injection nozzle with valve element damping

Info

Publication number: GB2107781A
Application number: GB08227244A
Authority: GB
Inventors: Paul Fussner; Karl Hofmann; Iwan Komaroff; Odon Kopse; Kurt Seifert; Dietrich Trachte; Wilhelm Vogel; Hans-Jorg Vogtmann
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1981-09-24
Filing date: 1982-09-23
Publication date: 1983-05-05
Also published as: GB2107781B; JPS5865967A; DE3137972A1

Abstract

Outwardly opening valve 14 is provided with damping device 50 Fig. 2 which is only effective during the opening stroke of valve 14. Just prior to the opening of fuel pressure operated valve 14 annular element 50 is in the position shown in Fig. 2 which defines throttling gap S with wall 24 of the injector body. On the valve return stroke element 50 moves to abut spring collar 46 thus opening circumferential ports 52 to allow relatively unrestricted fuel flow therethrough and undamped return of valve 14. <IMAGE>

Description

SPECIFICATION Improvements in or relating to fuel injection nozzles for internal combustion engines The present invention reiates to fuel injection nozzles for internal combustion engines.

One form of fuel injection nozzle has a nozzle body in which a valve seat is formed and in which a valve needle is displaceably mounted; the valve needle is subjected to the force of a closing spring and, in the opposite direction thereto, to fuel pressure and moves in the direction of flow of the fuel during an opening stroke (A-nozzle). The fuel injection nozzle also has a damping device having a throttle plate which reciprocates with the valve needle and which is coupled to the valve needle in a positive manner during the opening stroke and, together with a wall secured relative to the housing, defines a throttle gap which leads from a first chamber connected to a fuel supply line into a second chamber accommodating the closing spring.In one such fuel injection nozzle (German Patent Specification No. 1,048,085) a helical spring presses the throttle plate against an annular shoulder of an annular body connected to the valve needle. In this construction, an additional part, that is to say, the helical spring, is required which takes up a considerable amount of installation space, thus correspondingly increasingly the overall length of the injection nozzle. Furthermore, in the known arrangement, the fuel to be injected flows through the second chamber accommodating the closing spring, the throttle plate also performing the function of the closure member of a valve which opens a larger flow-through cross section in addition to the throttling gap when the fuel pressure upstream of the throttling gap has reached a predetermined value.The additional flow-through cross section is formed between the interior wall of the throttle plate and a second annular body which is also mounted on the valve needle and supports the closure spring. Although this second flow-through cross-section accelerates the return stroke of the valve needle upon a drop in the fuel pressure, the actual purpose of the throttle plate resides in forcing oscillatory opening of the valve and an intermittent injection characteristic.

According to the present invention a fuel injection nozzle for internal combustion engines comprises a nozzle body in which a valve seat is formed, a valve needle displaceably mounted in the nozzle body and subjected to the force of a closing spring and, in the opposite direction thereto, to fuel pressure and which moves in the direction of flow of the fuel during stroke (Anozzle), and a damping device having a throttle plate which reciprocates with the valve needle and which is coupled to the valve needle in a positive manner during the opening stroke and, together with a wall secured relative to the housing, defines a throttle gap which leads from a first chamber connected to a fuel supply line into a second chamber accommodating the closed spring, and a part which is moved with the valve needle is provided with openings or passages which interconnect the first and second chambers and whose total aperture cross section is larger than the cross section of the throttle gap and which under the influence of fuel pressure difference between the first and second chambers are closed during the opening stroke of the valve needle and are opened during the closing stroke of the valve needle.

A fuel injection nozzle embodying the present invention can have the advantage that an additional spring for displacement of the throttle plate is not required, and consequently that the injection nozzle can be of shorter construction.

Preferably the part which is moved with the valve needle is the throttle plate.

A particularly simple construction is provided when the throttle plate is in the form of an annular plate located with axial play in an annular groove between parts which reciprocate together with the valve needle and have an external diameter smaller than that of the throttle plate, and the inner edge of the throttle plate incorporates at least one cut-away portion or a port which, during the opening stroke of the valve nsedle, is covered by one of the parts which define the annular groove. In this construction, the closing and the opening of an additional larger aperture cross section are effected solely by the position of the throttle plate in the annular groove the position of the throttle plate in turn being dependent upon the pressure difference between the first and second chambers interconnected by way of the throttle gap.In this construction moreover, the damping action can be mitigated during the course of the opening stroke, or can be eliminated at the end of the opening stroke, when the wall secured to the housing, and which surrounds the throttle plate, is provided with an undercut which increases the size of the throttle gap.

A wear-resistant construction can be provided when the throttle plate is provided with at least one port which is controlled by a resilient valve plate which rests on that side of the throttle plate which faces said second chamber. In this construction the throttle plate can be rigidly connected to the valve needle or can be at least untiltably guided over a sufficiently iarge support surface. The valve plate requires no appreciable additional installation space, so that this construction is also shorter than the known injection nozzles of the form described above.

Preferably the throttle plate abuts against an annular shoulder of the valve needle, and the closing spring acts upon the throttle plate by way of a support member which is guided on the valve needle and which holds the valve plate in abutment against the throttle plate and centres the valve plate relative thereto.

In many cases it is desirable to make the damping action independent of the quantity of fuel which has flowed through and vice versa.

Preferably therefore a fuel passage leading to the valve seat of the nozzle body by-passes the second chamber accommodating the closing spring. It can be advantageous to use a closing spring having a non-linear or kinked characteristic and to dispose a throttle, controlled by the stroke of the valve needle, upstream or downstream of the passage through the valve.

The invention will be further described by way of example with reference to the accompanying drawings, in which: Figure 1 is a section through an injection nozzle in accordance with a first embodiment of the present invention; Figure 2 is a detail section to a larger scale showing parts of the injection nozzle of Figure 1 during the opening stroke of the valve needle; Figure 3 shows the parts of Figure 2 during the closing stroke of the valve needle; Figure 4 is a plan view of the throttle plate of the injection nozzle of Figures 1 to 3; and Figure 5 is a section through an injection nozzle in accordance with a second embodiment of the invention.

Referring first to Figures 1 to 4 of the drawings, an injection nozzle has a nozzle body 10 in which a valve seat 12 is formed and in which a valve needle 14 is displaceably guided in a guide bore.

The front end of the valve needle has a sealing cone 1 6 cooperating with the valve seat 1 2 and, at a distance therefrom, an annular-groove-like recess 1 8 which is located in the region of the point at which a fuel passage 20, passing obliquely through the nozzle body 10, enters the guide bore for the valve needle 14. A screwthreaded part 22 clamps the nozzle body 10 to a nozzle holder 24 provided with a fuel passage 26 which leads from a connection piece 28 into a chamber 30 of the nozzle holder 24.The chamber 30 is connected by way of a throttle gap (further described hereinafter) to a coaxial chamber 31 whose end is closed by the nozzle body 10 and which communicates by way of the fuel passage 20 in the nozzle holder 10 with the annular chamber between the recess 18, the valve needle 14 and the guide bore of the latter in the nozzle body 10.

The chamber 31 accommodates a closing spring 32 which abuts against a shoulder 34 of the nozzle body 10 and which acts upon a head 38 of the valve needle 14 in the closing direction by way of parts which will be further described hereinafter. A sleeve 42 is movably guided on the valve needle 14 and has a flanged rim 40 which abuts against a stop disc 38 (Figure 2) mounted below the head 36. The closing spring 32 abuts directly against a spring washer 46 which abuts against a spacer ring 44 which is slipped onto the sleeve 42. The closing spring 32 holds the parts 42, 44, 46 in permanent abutment against one another. An annular groove 48 is formed between the parts 42, 44, 46 and its width B is determined by the length of the spacer ring 44.

A throttle plate 50 is fitted in the annular groove 48 and its external diameter is smaller than the diameter of the chambers 30 and 31 by an amount equal to twice the width of a throttle gap S. The two chambers 30 and 31 are interconnected by way of a throttle gap S. The internal diameter d (Figure 4) of the throttle plate 50 is somewhat greater than the external diameter of the spacer ring 44, and the inner edge of the throttle plate incorporates four cut-away portions 52 which are uniformly distributed around the circumference and between which are located four original edge regions 54. The depth T of the cut-away portion 52 is chosen such that the cut-away portions 52 are fully covered by the flange 40 when the throttle plate 50 is in abutment against the flange 40 and in any position within the range of movement determined by the radial play between adjacent parts.

The spring washer 46 has a stepped edge 56 which extends approximately around a central pitch circle and at which the annular groove 48 is radially outwardly wider by the amount of the height of the step. The chamber 31 is provided with an undercut 58 in the region of the stroke of the throttle plate 50, whereby the throttle gap S becomes wider during the course of the opening stroke of the valve needle 1 4.

The parts assume the relative positions illustrated in Figures 1 and 2 when the valve 12, 1 6 is closed. When the parts are in these positions, the throttle gap S is at its minimum value. As is shown in Figure 2, the throttle plate 50 is subjected to the pressure difference between the chambers 30 and 31 during the opening stroke of the valve needle 14 and abuts against the flange 40 of the sleeve 42, so that fuel flowing to the valve 12, 16 has to pass through the throttle gap S, and the opening stroke is thereby damped in a desired manner.The width of the throttle gap S increases in the region of the undercut 58, and, as a result of this, the damping of the opening movement and the throttling of the throughput of fuel decreases until the fuel can finally flow from the chamber 30 into the chamber 31 at the end of the opening stroke without any appreciable obstruction, and thence to the injection orifice.

During the closing stroke of the valve needle 14, the throttle plate 50, under the influence of the reversal of the pressure difference between the chambers 30 and 31, assumes the position illustrated in Figure 3 in which the throttle plate 50 abuts against the spring washer 46. The stepped edge 56 on the spring washer 46 thereby ensures that an annular gap 60 of sufficient size is retained between the throttle plate 50 and the spring washer 46, so that, up to the end of the closing stroke, the fuel can flow in a largely unobstructed manner from the chamber 30 which decreases in size into the chamber 31 which increases in size.

The injection nozzle of Figure 5 has a nozzle body 62 in which a valve seat 64 is formed and in which a valve needle 66 is displaceably guided.

The front end oF the valve needle 66 has a sealing cone 68 which cooperates with the valve seat 64 and to which a slightly conical portion 70 and a spray-forming portion 72 are contiguous. The other end of the sealing cone 68 merges into an annular groove 74 in the nozzle needle 66. A cylindrical bore portion 76 contiguous to the valve seat 64 is formed in the nozzle body 62 and, together with the portion 70 of the valve needle 66, defines a stroke-dependent controlled throttle gap downstream of the valve seat 64. A longitudinal bore 80 opens into a transverse bore 78 provided in the valve needle 66 in the region of the annular groove 74, and extends through the valve needle 66 up to the top end face 82 thereof.

The nozzle body 62 is clamped to a nozzle holder 86 by means of a screw-threaded part 84.

The nozzle holder 86 is provided with a fuel passage 88 which leads from a connection piece 90 into a chamber 92. The chamber 92 is formed between the conically recessed end face of the nozzle holder 86, the cylindrical wall of the nozzle body 62 and a damping piston 94 which is slipped onto the valve needle 66 and which abuts against an annular shoulder on the valve needle 66 by way of a spring ring 96. The periphery of the damping piston 94 is of conical configuration, and the damping piston is dimensioned such that its larger diameter annular edge together with the adjacent wall of the nozzle body 62 defines a throttling gap 98.The throttling gap 98 connects the chamber 92 to a second chamber 100 which is located in the nozzle body 62 and which accommodates a closing spring 162 which comprises a plurality of cup springs and which has a non-linear spring characteristic.

The closing spring 102 is supported on the nozzle body 62 and acts upon the damping piston 94 by way of a spring abutment plate 104. The spring abutment plate 104 has a hub 106 which projects beyond the spring abutment plate at both sides thereof and which is displaceably mounted on the valve needle 66 and thrusts against the damping piston 94. A valve plate 108 made from steel is centred and mounted without axial play on that portion of the hub 1 06 which is directed towards the damping piston 94, the valve plate 108 being provided with a plurality of resilient tongues 110 which are punched free from the plate. The tongues 110 are uniformly distributed around the periphery of the valve plate 108 and each tongue has an associated bore 112 in the damping piston 94.The total aperture cross section of the bores 112 is a multiple of the cross section of the throttle gap 98.

The parts assume the relative positions shown in Figure 5 when the valve is closed. When the valve is opened, the fuel to be injected by-passes the throttle gap 98 and flows to the injection orifice by way of the longitudinal bore 80, the transverse bore 78 and the annular groove 74 in the valve needle 66, the fuel being subjected to a further throttling action by the portion 70 of the valve needle 66 during a first partial stroke of the latter. The closing spring 102 is dimensioned and constructed such that the spring force increases abruptly at the end of this first partial stroke.

In this embodiment, the opening stroke of the valve needle 66 is damped independently of the quantity of fuel flowing to the injection orifice. The fuel is displaced from the chamber 100 into the chamber 92 by way of the throttle gap 98 during the opening stroke, and the resilient tongues 110 are pressed firmly against the damping piston 98 and close the bores 112 in a sealed manner. At the commencement of the closing stroke of the valve needle 66, the tongues 110 are lifted in a resilient manner from the damping piston 94 by the reversal of the pressure difference between the chambers 92 and 100 which then occurs. A larger cross section for the fuel to be displaced from the chamber 92 is thereby opened by way of the bores 112, so that the return stroke of the valve needle 66 takes place in a largely unthrottled manner.

Claims

1. A fuel injection nozzle for internal combustion engines, comprising a nozzle body in which a valve seat is formed, a valve needle displaceabiy mounted in the nozzle body and subjected to the force of a closing spring and, in the opposite direction thereto, to fuel pressure and which moves in the direction of flow of the fuel during an opening stroke (A-nozzle), and a damping device having a throttle plate which reciprocates with the valve needle and which is coupled to the valve needle in a positive manner during the opening stroke, and, together with a wall secured relative to the housing, defines a throttle gap which leads from a first chamber connected to a fuel supply line into a second chamber accommodating the closing spring, in which leads from a first chamber connected to a fuel supply line into a second chamber accommodating the closing spring, in which a part which is moved with the valve needle is provided with openings or passages which interconnect the first and second chambers and whose total aperture cross section is larger than the cross section of the throttle gap and which under the influence of fuel pressure difference between the first and second chambers are closed during the opening stroke of the valve needle and are opened during the closing stroke of the valve needle.

2. An injection nozzle as claimed in claim 1, in which said part which is moved with the valve needle in said throttle plate.

3. An injection nozzle as claimed in claim 1 or 2, in which the throttle plate is in the form of an annular plate located with axial play in an annular groove between parts which reciprocate together with the valve needle and have an external diameter smaller than that of the throttle plate, and the inner edge of the throttle plate incorporates at least one cut-away portion or a port which, during the opening stroke of the valve needle, is covered by one of the parts which define the annular groove.

4. An injection nozzle as claimed in claim 3, in which the throttle plate and/or that one of the parts defining the annular groove which is at the closing spring side of the annular groove has a continuous stepped edge which is located in the region of said at least one cut-away portion or port of the throttle plate and which increase the axial width of the annular groove radially outwardly.

5. An injection nozzle as claimed in claim 3 or 4, in which the annular throttle plate is provided with four cut-away portions uniformly distributed around its internal circumference.

6. An injection nozzle as claimed in claim 3, 4 or 5, in which said wall secured relative to the housing, and which surrounds the throttle plate is provided with an undercut which increases the size of the throttle gap.

7. An injection nozzle as claimed in claim 1 or 2, in which the throttle plate is provided with at least one port which is controlled by a resilient valve plate which rests on that side of the throttle plate which faces said second chamber.

8. An injection nozzle as claimed in claim 7, in which the throttle plate abuts against an annular shoulder of the valve needle and the closing spring acts upon the throttle plate by way of a support member which is guided on the valve needle and which holds the valve plate in abutment against the throttle plate and centres the valve plate relative thereto.

9. An injection nozzle as claimed in any preceding claim, in which a fuel passage leading to the valve seat of the nozzle body by-passes the second chamber accommodating the closing spring.

10. An injection nozzle as claimed in claim 9, in which the fuel passage by-passing the second chamber leads through a longitudinal bore which is disposed in the valve needle and which opens by way of a transverse bore into an annular groove incorporated in the valve needle upstream of the valve seat surface.

11. A fuel injection nozzle for internal combustion engines, constructed and arranged and adapted to operate substantially as hereinbefore particularly described with reference to and as illustrated in Figures 1 to 4 or Figure 5 of the accompanying drawings.