GB2078344A - Pressure-controller for injection systems of controlled ignition internal combustion engines - Google Patents

Abstract

A valve closure member 7 for a pressure controller of the fuel spill valve type as in GB 2,013,838 A has a part-spherical portion 72 to allow relative rotation between the member 7 and a support member (8, Figure 1, not shown), a plane sealing surface 73 and a cylindrical part 74 to support a biasing spring. A blind bore 76 is disposed coaxially within the member 7 and a cylindrical tailpiece 70 is provided on the opposite face. The arrangement allows the closure member to be produced from low stock and to allow the valve to be assembled easily. <IMAGE>

Description

SPECIFICATION Pressure controller for injection systems of controlled ignition internal combustion engines The invention relates to fuel pressure controllers, more particularly a controller having the operative elements forming the subject of Italian patent application No. 3325-A/78 filed on 7 February 1978.

The function of a pressure controller for injection systems is to control the positive pressure at which fuel is supplied to the injectors by referring such pressure continuously to a predetermined value in order to ensure that the proportions of the fuel-air mixture remain correct in all engine operating conditions.

As a rule, pressure controllers take the form of an arrangement of various mechanical parts which sub-divide into two unequal parts a flow of fuel from a feed pump. One part of the flow is made available to the injectors, which use the amount necessary for engine operating conditions, and the remainder returns to the vehicle fuel pump.

The operative feature of the controller disclosed in the Italian Patent Application is the use of a hemispherical valve lid whose centre is contained in the plane surface which bounds the lid and which controls the orifice of the tank return line; the valve lid is biassed by resilient means into engagement with the walls of a recess in a support rigidly secured to the diaphragm so that movements of the valve lid plane are equal to the movements of the support.

This pressure controller comprises original and technically viable features; unfortunately, it presents constructional and assembly difficulties for long-run production.

It is the object of this invention to solve these problems by means of a valve lid which operates similarly to the valve lid disclosed by the aforesaid Italian patent application but is free from the constructional and assembly problems making long-run production difficult.

According to the present invention there is provided a pressure controller for injection systems of controlled ignition internal combustion engines, the controller comprising: a casing; a diaphragm disposed therein to sub-divide the interior thereof into a first chamber and a second chamber; a first duct connected to the casing as a means of communication between the first chamber and the intake manifold; second ducts connected to the casing and serving to connect the second chamber to a fuel pump and to the injectors; and a fourth duct connected to the casing and having the return nozzle, which latter extends into the second chamber to provide communication therebetween and the fuel tank and has a plan seat acted on by means adapted to shut off and control the amount of fuel returned to the tank, such means comprising a valve lid bounded by a generally spherical part and by a plan surface, the valve lid having a defined axis of symmetry and the latter means also being formed with a recess in a support rigidly secured to the diaphragm, the valve being free to rotate in the recess to maintain its plane part near the plane seat of the nozzle, characterised in that the valve lid is formed with a blind bore extending towards its interior from the plane surface and has a cylindrical tail piece extending outwardly from the part opposite the plane surface, the axes of symmetry of the aperture and tailpiece coinciding with one another and with the axis of symmetry of the valve lid, resilient means being provided to urge the spherical part of the valve lid into engagement with the recess walls, the plane surface being bounded by a plane diameter of the spherical surface or by a plane surface parallel to the diametric plane and offset slightly towards the cylindrical tailpiece.

The invention will be described by way of example and with reference to the drawings wherein: Figure 1 shows a controller in accordance with the invention partly sectioned in a plane containing the axis of symmetry of the system, and Figure 2 is a view, also in partial section, of the valve lid forming part of the controller shown in Figure 1.

The controller shown in Figure 1 comprises a metal casing 1 divided internally by a diaphragm 2 into two non-communicating chambers 3, 4. Chamber 3 is also bounded by a cover 30 and chamber 4 is also bounded by a cover 40. Edges 31,41 of the covers 3, 4 respectively support the diaphragm 2 and are clamped by means of a ring 9 whose parts 90,92 engage with trunco-conical parts 32, 45 respectively of the edges 31,41 respectively. Chamber 3 is connected to an intake manifold (not shown) by way of a first duct (not shown) received in spigot 10; consequently, the reference pressure of the intake manifold is operative in chamber 3.Chamber 4 is connected to the fuel supply pump by means of a second duct (not shown) disposed in spigot 11, to the injectors of the injection system by means of a third duct (not shown) received in spigot 12, and to the vehicle fuel tank by means of a fourt duct (not shown) received in spigot 5. If convenient, the spigots 11, 12 can be combined to form a single spigot or connection 11.

Spigot 5 has a part 50 which is engaged in a continuous aperture 44 in the bottom of cover 40.

Above and coaxial of aperture 44 there is a polygonal cross-section recess 46 which receives the hexagonal head of spigot 5 and prevents accidental rotation thereof. By way of a trunco-conical surface 43 aperture 44 communicates with recess 46; the same has a trunco-conical surface 52 which forms part of spigots. This connection provides satisfactory sealing tightness of the fuel in relation to the outside of chamber 4, the sealing being boosted by the clamping provided by a nut disposed in the screw-threaded part 53 of spigot 5.

Spigot 5 is also formed with a cylindrical recess 54 in which body 6 of a sealing and control seat is a force fit. The main parts of body 6 are a plane sealing seat 61 and a plane surface 62 bounded by a circular sling-like periphery. The body 6, supported by spigot 5, forms an exit orifice which extends into the interior of the second chamber 4. The plane seat 61 is controlled by the plane surface of a valve lid 7: a spring 63 is disposed between surface 62 and a similar surface 73 of lid 7. Spring 63 retains the spherical part of valve lid 7 in engagement with a conical surface 81 of a recess 80 in a support member rigidly secured to diaphragm 2 by means of a disc 20.Bearing thereon is the bottom end of a control spring 21 whose other end is borne by a spring-adjusting plate 22; the same is formed with a central aperture 23 receiving a conical tip 14 of a hexagonal-head dished screw introduced into a screwthreaded aperture 32 extending through a projection 33 above cover 30.

Screw 13 is preloaded to an extent defined by spring 21. At the top the screwthreaded aperture widens to become the cylindrical recess 34 containing an expansion plug 15 serving to prevent unauthorised tampering with the screw 13.

Figure 2 shows more particularly the valve lid 7 disposed in the recess 80 of Figure 1. Lid 7 comprises: a part-spherical portion 72 which engages with the trunco-conical part 81 of recess 80 so as to form a ball joint; a plane surface 75 which is in sealing-tight engagement with the plane surface 61 defining the outflow cross-section for excess fuel; a plane surface 73 in the form of a circular peripheral ring on which the top end of spring 63 bears; a cylindrical surface 74 which interconnects the surfaces 73 and 75 and on which a number of turns of the spring 63 engage in a phase preceding assembly of the complete regulator; a blind aperture 76 extending substantially perpendicularly to the plane surface 75; and a cylindrical tailpiece 70 which extends upwards from the plane surface 71 and which is disposed in that part of the element 7 which is opposite the surface 75.

Lid 7 has an axis of symmetry A-A coinciding with the axes of symmetry of aperture 76 and tailpiece 70.

Centre C of the part-spherical part 72 is contained in plane 75 or in a plane offset downwardly from and parallel to plane 75.

Even though the following is not of direct importance for the present invention, a brief description will now be given of how a pressure controller operates, in order to show the importance of disposing the rotational centre Cofthevalve lid 7 in the plane 75.

With the engine running, the difference between, on the one hand, the pressure in the injector fuel supply line connected to control chamber 4 by way of spigot 12 and, on the other hand, the pressure in the inlet manifold where the injectors are disposed is required to remain constant in all engine operating conditions. Accordingly, the controller varies the outflow cross-section bounded by surface 75 and by the seat 61 of nozzle 6. In orderto maintain this pressure difference constant, in response to a hypothetical increase in manifold pressure the surface 75 moves towards nozzle 61 because of the thrust caused by the increased pressure acting on diaphragm 2 by way of its surface associated with chamber 3 in which, as previously stated, the pressure is the manifold pressure.The resulting reduction in the tank return flow cross-section increases the pressure in chamber 4 by an amount substantially identical to the pressure in chamber 3, so that the difference between the injector supply line pressure and the intake manifold pressure remains constant. Conversely, by the surface 75 moving away from the nozzle 61 the controller adapts the injector supply line pressure to a hypothetical reduction in manifold pressure.

In relation to the disclosure in Italian patent application 3325-N78, the system just described is easier to carry into effect, as will be seen hereinafter, and also boosts the self-stabilising features of the lid 7,, since it now becomes possible to shift further below the sealing plane embodied by the surface 75 the centre of application of the resultant of the lid closure forces and to shift higher in relation to the plane 75 the resultant of the opening forces applied by the spring 63 to the ring-like periphery of the lid 7.

The invention overcomes special productions and assembly problems.

The lid 7 can be produced on automatic machine tools from appropriate cylindrical rod stock.

Lid 7 can be produced in a variety of ways and two of them will be mentioned to show the simplicity of the invention.

The first method is to use a shaping tool on an automatic lathe. The tool has the shape of the figure generated by the element 7 (excluding the aperture 76) when the rod or bar stock rotates round the axis of revolution A-A. The aperture 76 is produced by drilling.

The second method is to use a programmed lathe which proceeds by crossed feeds to fully define the lid 7.

Four a better understanding of the function of the tailpiece 70 which defines the axis of symmetry of the lid 7, regard should be had to the need for ensuring that the surface 75 is very smooth, otherwise the contrioller will not operate properly. To ensure this high level of smootheness the surface 75 must be lapped after the definition of the lid 7. This operation can be carried out on as many elements as can be received by a single device. The same comprises a metal plate formed with a number of apertures each adapted to receive a tailpiece 70 and maintain its axis of symmetry perpendicular to the plane of the plate consequently, the plane surface 75 is parallel to the surface of the plate and faces outwards whereas the surface 75 is in engagement with the surface of the plate.When the lids 7 have been fitted to the plate and the tailpieces 70 have been engaged in the respective apertures, a lapping tool treats all the surfaces 75 which are in a clearly defined and strictly located plane.

Using the valve lid shape shown in Figure 2 makes it possible for the controller 1 to be assembled by automatic machines, since the presence of the aperture 76 enables the lid 7 to be supported during - one phase of the assembly by an appropriate automatic machine faicility. The same maintains the lid 7 coaxial of the cover 40, thus making it possibie' to ensure immediately that the cover 40 is coaxial of the support element 8 whose truncoconical recess 81 is borne by the spherical surface 72 of the lid 7.

The diaphragm 2 is therefore correctly located relatively to edge 41 of cover 40. The subsequent steps of assembling and adjusting the spring 21 and assembling and clamping the cover 30 by means of the ring 9 can be carried out immediately and are very simple.

The foregoing description relates to just one of the possible embodiments of the invention, the construction of which can be varied without departure from its essential features. The shapes, dimensions and materials used do not limit the scope of this invention.

Claims (6)

1. A pressure controller for injection systems of controlled ignition internal combustion engines, the controller comprising: a casing; a diaphragm disposed therein to sub-divide the interior thereof into a first chamber and a second chamber; a first duct connected to the casing as a means of communication between the first chamber and the intake manifold; second ducts connected to the casing and serving to connect the second chamber to a fuel pump and to the injectors; and a fourth duct connected to the casing and having the return nozzle, which latter extends into the second chamber to provide communication therebetween and the fuel tank and has a plane seat acted on by means adapted to shut off and control the amount of fuel returned to the tank, such means comprising a valve lid bounded by a generally spherical part and by a plane surface, the valve lid having a defined axis of symmetry and the latter means also being formed with a recess in a support ridigly secured to the diaphragm, the valve being free to rotate in the recess to maintain its plane part near the plane seat of the nozzle, characterised in that the valve lid is formed with a blind bore extending towards its interior from the plane surface and has a cylindrical tail piece extending outwardly from the part opposite the plane surface, the axes of symmetry of the aperture and tail piece coinciding with one another and with the axis of symmetry of the valve lid, resilient means being provided to urge the spherical part of the valve lid into engagement with the recess walls, the plane surface being bounded by a plane diameter of the spherical surface or by a plane surface parallel to the diametric plane and offset slightly towards the cylindrical tailpiece.

2. A pressure controller according to claim 1 characterised in that the valve lid has a cylindrical part and a plane surface with a circular ring-like periphery, the cylindrical part being adapted to carry a number of turns of a spring whose top end bears on the latter surface, the same being the base of the cylindrical part and co-operating with the plane sealing surface to control the amount of fuel returning to the tank.

3. A pressure controller according to Claims 1 and 2, characterised in that the surface (73) on which the spring (63) bears is the bottom boundary of the part-spherical member (72), is disposed parallel to the diametric plane and is offset towards the tailpiece from the surface containing the centre of the spherical surface.

4. A pressure controller according to Claims 1,2 and 3, characterised in that the spring biassing the valve lid into engagement with the walls bears at its bottom end on a plane surface which has a circular periphery and which forms part of the body of the return nozzle.

5. A pressure controller according to Claim 1, characterised in that the valve lid has a second plane surface which extends parallel to the plane sealing and control surface and from which the cylindrical tail piece extends.

6. A pressure controller substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.