GB2098005A

GB2098005A - A double-acting electromagnet device for controlling the movement of an injector valve of a fuel injector

Info

Publication number: GB2098005A
Application number: GB8212902A
Authority: GB
Original assignee: Sulzer AG; Gebrueder Sulzer AG
Current assignee: Sulzer AG
Priority date: 1981-05-05
Filing date: 1982-05-05
Publication date: 1982-11-10
Also published as: DE3118423C2; IT1195790B; JPS62351B2; GB2098005B; JPS57186055A; DK53582A; DE3118423A1; IT8220556A0

Abstract

A double-acting electromagnet device for controlling the movement of an injector valve of a fuel injector for a diesel engine, comprises an electromagnet body (1, 2) carrying an electrical winding arrangement (7), and an armature (8) movable relatively to the body (1, 2), the armature (8) being in the form of an obtuse-angled thin-walled hollow cone, the body having a respective conical surface adjacent each surface of the armature, and the winding arrangement (7) being disposed in at least two slots (3, 4, 3', 4') in each such conical surface concentrically about the axis (9) of the armature. <IMAGE>

Description

SPECIFICATION An electromagnet device for controlling the movement of an injector valve of a fuel injector The invention relates to a double-acting electromagnet device for controlling the movement of an injector valve of a fuel injector for a diesel engine, the electromagnet device having an electromagnet body a winding arrangement and an armature which is movable relative to the body.

Devices of this kind have been proposed with a substantially cylindrical armature surrounded by two electrically energized windings disposed consecutively in the direction of armature movement, the windings being received in a cylindrical casing which forms the magnet body and is made of a magnetic material. In such devices the cylindrical armature is a fairly massive member, since its cross-section is dimensioned in accordance with the total magnetic flux. Further disadvantages are that the magnetic flux path in the armature is relatively long and thus there is considerable leakage of flux near the air gaps.

It is the object of the invention to provide such an electromagnet device which has a reduced armature mass, a shorter magnetic flux path and a reduced leakage flux and is therefore of use for rapid movements.

Accordingly the present invention provides a double-acting electromagnetic device for controlling the movement of an injector valve of a fuel injector for a diesel engine, comprising an electromagnet body carrying an electrical winding arrangement, and an armature movable relatively to the body, the armature being in the form of an obtuse-angled thin-walled hollow cone, the body having a respective conical surface adjacent each surface of the armature, and the winding arrangement being disposed in at least two slots in each such conical surface concentrically about the axis of the armature.

The device has a rigid and very light armature, since the cross-section for the magnetic flux needs to be designed for only a small proportion of the total magnetic flux - i.e., for half the total flux in the case of two slots and for one-third of the total flux in the case of three slots. Leakage flux occurs only near the outermost and/or innermost slot.

The very short flux paths means that iron losses are minimal. The same armature mass is available for the windings associated with the two directions of movement. The device in accordance with the invention is therefore suitable for very rapid reciprocation, such as found in controlling the movement of injector valves of fuel injectors of diesel engines.

In order to promote a fuller understanding of the above and other aspects of the present invention, some embodiments will now be described, by way of example only with reference to the accompanying drawings in which: Figure 1 is a diagrammatic view of a fuel injector whose injector valve is controlled by an electromagnet device; Figure 2 is an axial section through an electromagnet device embodying the invention; Figure 3 is a simplified view of one of the two parts of the electromagnet body of Figure 2 seen from the armature side, but to a smaller scale than in Figure 2; and Figures 4 and 5 are views similar to Figure 3 of cores having different slot patterns.

In Figure 1 , there is shown a fuel injector 50 disposed in a cylinder head 51 (not shown in greater detail) of a diesel engine, which has in its body 52 a fuel supply duct 53 which extends to a chamber 54. Disposed in the body 52 is an injector valve 55 which co-operates at its lower end 49 which is in the form of a conical valve surface, with a seat surface in the valve body 52.

A central duct 48 extends from the chamber 54 below the injector valve end 49 in Figure 1 and merges at its bottom end into a number of orifices 47 which are distributed over the periphery'of the body 52, and through which, when the valve 55 is open, fuel is injected in finely divided form into a combustion chamber 46.

At its top end in Figure 1 the injector valve 55 has a piston 56 sliding in a cylinder 57. Connected to the cylinder is a hydraulic line 58, through which hydraulic medium is supplied from a source (not shown) to control actuation of the injector valve 55. A line 59 branches off line 58 and has a valve 60 controlled by means of an electromagnet device 61 whose construction is shown in greater detail in Figure 2. With the valve 60 in the position shown, the force applied to the piston 56 by the pressure medium supplied through the line 58 is such that the injector valve 55 remains closed.To inject fuel into the combustion chamber 46, the electromagnet device 61 is caused to disengage the valve 60 from its seat surface in line 59, so that the pressure produced by the hydraulic medium in the cylinder 57 decreases and the pressure of the fuel in the chamber or "gallery" 54 may force the injector valve 55 upwards, with the result that fuel is free to flow through the central duct 48 and the orifices 47.

Referring to Figure 2, the magnet device 61 has a body which is in two parts 1,2 which are substantially circular-shaped discs. The surface of the top part 1 which is the lower in Figure 2 is in the form of an obtuse-angled cone and is formed with two circular slots 3, 4 which are concentric with the cone axis 9-9. The slots 3,4 are open at the bottom, have an undercut cross-section and serve to receive parts of the electrical winding arrangement of the device.Similarly, that surface of the part 2 of the body, which is the upper in Figure 2 is in the form of a cone having a cone angle matching that of the part 1 of the body; and is formed with two concentric slots 3', 4' concentric with the cone axis 9-9. The slots 3', 4' are open at the top and have an undercut cross-section and serve to receive a second part of the electrical winding arrangement of the device.

The distance between the slots 3, 4 or 3', 4' and the cone axis 9-9 is such that the slots are distributed substantially uniformly over the air gap between the parallel cone surfaces of the two parts 1 and 2. As is apparent from Figure 3, the slots 3, 4 communicate with one another by way of two radial slots 5, 6 and there is a similar communication between the slots 3' and 4'.The winding arrangement 7, whose path is shown in chain lines in Figure 3, extend from the outside by way of the outer portion of the radial slot 5, then pass a number of times around the slot 4 over the entire periphery thereof, then go by way of the inner part of the slot 5 into the slot 3, which they also pass around a number of times over its entire periphery, whereafter the conductors issue from the body by way of the radial slotS. The arrows in Figure 3 indicate the direction of current flow.

An armature 8 in the form of a thin-walled obtuse-angled hollow cone is positioned in the space between the parts 1 and 2. The thickness of the armature 8 is preferably not more than one tenth of the outer diameter of the armature. The armature cone is formed with a number of apertures 10 through it whose axes extend parallel to the cone axis -- between the slots 3 and 4 and between the slots 3' and 4'. The axes of the apertures 10 are, therefore, disposed on circles. The diameter of the apertures 10 is at most 20% of the slot pitch or distance between the slot centre lines. Near the centre of the armature and near the outer edge of the armature the parts 1,2 each having a ring 12,13 and 12' 1 3' respectively.The rings are received in corresponding slots in the parts 1,2 and extend into the air gap therebetween to form an abutment which limits armature movement in respective directions. In the state illustrated, the armature abuts the two bottoms rings 1 2', 1 3' in the part 2, a gap s (Figure 2) of a few hundredths of a millimetre remaining between the underside of the armature and the upper surface of the part 2 to help prevent the armature from sticking. The armature is prevented from sticking in the upper position in a similar manner. The rings 12, 12', 1 3 and 13' are formed over their periphery with a number of apertures in the form of radial slots 14, 1 5 respectively which co-operate with the apertures 10 in ventilating armature movements.

Since the apertures 10 in the armature plate 8 are disposed centrally between two adjacent slots and are of relatively reduced diameter, disturbance of the magnetic flux is minimal, particularly since the flux is, in any case, insignificant at the centre position.

The body parts 1,2 are formed at the centre with bores 1 6, 1 6' respectively through which a rod 19 extends. The rod 1 9 is rigidly attached to the armature 8 by the armature being clamped between a thickened part 1 8 of the rod 1 9 and a coilar 1 7. A spring spider 20 is attached to the top end face of the part 18 and a spring spider 21 is attached to the bottom end of the rod 19 by means of nuts 23. Each spring spider has a number of radial arms. The outer ends of the arms of the top spider 20 bear on the upper surface of a cylindrical sleeve 22 enclosing the two body parts 1 and 2; and are retained between a cup spring 24 and a circlip 28.The outer ends of the bottom spider 21 bear on the lower surface of the sleeve 22, between an intermediate ring 25 retaining the body part 2 and a circlip 26 received in an annular groove in the sleeve 22. The spiders 20, 21 are made of a non-magnetic material such as non rusting steel or beryllium bronze. Their only function is to guide and centre the armature 8; the spring forces arising in this connection being negligible. The moving part of the valve 60 (Figure 1) is directly connected to the rod 19, but this feature is not shown in greater detail. A spacer ring 29 is positioned between the body parts 1 and 2. The ring 29 is located by way of its outer periphery in the sleeve 22 and determines the spacing between the rings 13 and 1 3' and between the body parts 1 and 2.

Figure 4 shows an alternative embodiment in which the slots, instead of being concentric, can extend in spirals in the body parts 1 and 2. The 'innermost ends of the two slots are interconnected by a radial slot 30. The manner in which the winding arrangement extends is indicated by a chain line and the arrows indicate the direction of current flow. This arrangement can be adapted so that there are more than three slots.

Figure 5 shows an arrangement in which there are three concentric slots in the body parts 1, 2.

The path of the windings differs from the path of Figure 3 and, as in the case of Figure 3, this is indicated by chain lines and the arrows indicate the direction of current flow. What is important for the path of the winding arrangement in all the enibodiments is that the current flow in adjacent slots is in opposite directions.

Claims

1. A double-acting electromagnet device for controlling the movement of an injector valve of a fuel injector for a diesel engine, comprising an electromagnet body carrying an electrical winding arrangement, and an armature movable relatively to the body, the armature being in the form of an obtuse-angled thin-walled hollow cone, the body having a respective conical surface adjacent each surface of the armature, and the winding arrangement being disposed in at least two slots in each such conical surface concentrically about the axis of the armature.

2. An electromagnet device as claimed in Claim 1 in which the body is divided into two parts adjacent the armature.

3. An electromagnet device as claimed in Claim 1 or 2, in which the conical surfaces of the body at least on the periphery of each such surface, have an abutment which projects from the conical surface and limits armature movement towards the surfaces.

4. An electromagnet device as claimed in Claim 3, in which such abutments are provided near the centre of the surfaces as well as at the periphery thereof.

5. An electromagnet device as claimed in Claim 3 or 4, in which each such abutment is formed with at least one aperture for the passage of air.

6. An electromagnet device as claimed in Claim 3, 4 or 5 in which the abutments are separate rings positioned in the body.

7. An electromagnet device as claimed in any one of Claims 1 to 6 in which the armature is formed with a number of apertures positioned between the slots in the body.

8. An electromagnet device as claimed in Claim 6 in which the diameter of the orifices in the cone is at most 20% of the body slot pitch.

9. An electromagnet as claimed in any one of Claims 2 to 8 in which the two body parts are secured in a cylindrical sleeve.

10. An electromagnet device as claimed in any one of Claims 1 to 9 in which the armature is attached to an axial rod which extends through the body and which has at each of its ends a respective spring spider having a number of radial arms, the spiders bearing by way of the outer ends of the arms on the body or a sleeve surrounding the body.

11. An electromagnet device as claimed in Claim 10 in which the spring spiders are made of a non-magnetic material.

12. An electromagnet device as claimed in any one of Claims 2 to 11 in which a spacer ring is disposed between the body parts to space them apart from one another.

13. An electromagnet device as claimed in any one of Claims 1 to 12, in which the ratio of armature wall thickness to the outer diameter of the armature is at most 0.1.

14. An electromagnet device substantially as herein described with reference to the accompanying drawings.