GB2226455A - Electromagnetic actuator - Google Patents

Abstract

The electromagnetic actuator for a fuel control valve in an internal combustion engine comprises a core member 28 which extends through the opposite walls 12, 13 of an open ended housing. The open end of the housing is closed by a cover 16 and surrounding the core member within the housing is a winding 29. Seals are provided between the core member and the wall of the housing and pole pieces 27 are connected to the opposite ends of the core member exterior of the housing. When the winding is de-energised, fuel pressure in a passage 18 lifts ball valve 23 as well as a cap 22 and armature 25 to supply fuel to a passage 20. The housing isolates winding 29 from the fuel. <IMAGE>

Description

ELECTROMAGNETIC ACTUATOR This invention relates to an electromagnetic actuator more particularly but not exclusively, to an actuator for a control valve forming part of the fuel system of an internal combustion engine, the actuator comprising a core member, a pair of pole pieces connected to the opposite ends of the core member respectively and an output member which is movable towards the pole pieces when the solenoid is energised.

The output member may form the valve member of a control valve or at least be connected thereto so that the winding may be surrounded by fuel. It is known to protect the winding from the fuel by encapsulation in a resin but this is not always satisfactory since the encapsulation must be carefully carried out to avoid air pockets and also to avoid deposition of the resin on the working surface such as the pole faces of the core member.

The object of the present invention is to provide an actuator of the kind specified in a simple and convenient form.

According to the invention an electromagnetic actuator comprises a hollow open ended housing, said core member extending through a pair of opposite side walls of the housing, seal means for providing a liquid seal between the walls of the housing and the core member, said pole pieces being secured to the opposite end portions of the core member and extending around the housing, said winding being mounted about the core member and within the housing and a cover for the open end of the housing.

According to a further feature of the invention the housing defines a recess the walls of which guide the movement of the output member.

An example of an electromagnetic actuator in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a sectional side elevation of the actuator shown secured to a body of a fuel pumping apparatus, the actuator serving to control the operation of a fluid control valve, Figure 2 is plan view of the actuator seen in Figure 1 with the cover removed, Figure 3 is a perspective view of part of the actuator seen in Figures 1 and 2, and Figure 4 is a perspective view showing the disposition of the magnetic parts of the actuator.

Referring to the drawings the actuator comprises a hollow open ended housing 10 at the open end of which there is formed an outwardly directed flange 11. The housing is formed from plastics and defines a pair of opposite side walls 12, 13. The side walls have thickened portions 14 extending towards the flange 11 and formed in the thicker portions are a pair of openings 15 respectively. A cover 16 is provided for the open end of the housing and this is retained relative to the housing by means of screws (not shown) which extend through apertures in the flange into engagement with walls 16A, the walls being integrally formed with the body 17 of a pumping apparatus.

Within the apparatus is a fuel supply passage 18 in which in use is contained fuel under pressure and the passage 18 leads into a recess 19 from which extends a further passage 20. Secured in the end of the passage 18 and located within the recess, is a valve mounting 21 about which is slidable a top hat section member 22 which is apertured near its closed end, and engages a ball valve member 23 which can be urged into contact with a seating defined by the mounting 21. When urged into contact with the seating the flow of fuel from the passage 18 to the passage 20 is prevented.

The housing 10 defines a recess 24 the walls of which serve to guide a generally rectangular plate like armature 25 and as will be seen in Figure 3, one pair of side walls of the recess are cut away to form slots 26 in which are laid the end portions respectively of a pair of strip like pole pieces 27 of generally "L" shape. The end portions of the pole pieces extend partly across the recess 24 and beneath the armature 25. They terminate short of the member 22 which can be engaged by the armature.

At their opposite ends the pole pieces are secured to the ends respectively of a core member 28. The core member extends through the openings 15 and whilst it is possible to secure the pole pieces to the core member after the latter has been inserted through the openings, it is preferred to construct the core member in two parts one of which has a spigot which locates in a complementary recess in the other part. In this way the pole pieces can be more securely fastened to the ends of the core member.

The two parts of the core member are each provided wth a groove in which is located a seal ring which co-operates with the wall of the respective opening to establish a fuel tight seal.

Surrounding the core member 28 is a winding 29 which is wound about a former. The connections to the winding pass through an opening in the cover 16 and the winding is located in the housing by the core member.

Although the screws which secure the flange 11 to the walls 16A will tend to locate the housing 10 within the walls 16A more accurate location is achieved by forming slots 30 in the opposite walls the surfaces of the slots being engaged by the pole pieces 27.

In operation, with fuel under pressure in the passage 18, energisation of the winding will cause the pole pieces to assume opposite magnetic polarity and the armature will be urged downwardly to urge the ball valve member 23 into contact with the seating. When the solenoid is de-energised the fuel pressure will lift the ball valve member from the seating to allow fuel flow through the passage 20. Fuel will in the use of the pumping apparatus, accumulate in the spaces about the housing 10 but by virtue of the housing the winding 29 will be isolated from the fuel. Leakage of fuel along the joint between the flange 11 and the walls 16A is prevented by a seal member 31 which is disposed in a groove in the walls 16A, the apertures for the retaining screws being located outside the groove.

The top hat section member 22 is preferably formed from non-magnetic material so as not to provide a shunt for the magnetic flux and to avoid so far as possible, the retention of any particles of magnetic material in the vicinity of the valve member and the seating.

Claims (4)

1. An electromagnetic actuator more particularly but not exclusively an actuator for a control valve forming part of the fuel system of an internal combustion engine, and comprising a core member, a pair of pole pieces connected to the opposite ends of the core member respectively and an output member which is movable towards the pole pieces when a solenoid is energised, a hollow open ended housing, the core member extending through a pair of opposite end walls of the housing, seal means for providing a liquid seal between said end walls and the core member, said pole pieces being secured to the opposite end portions of the core member and extending around the housing, said winding being mounted about the core member and being located within the housing and a cover for the open end of the housing.

2. An actuator according to Claim 1 in which the housing defines a recess the walls of which guide the movement of the output member.

3. An actuator according to Claim 1 in which the core member is divided intermediate its ends to facilitate its assembly within the housing.

4. An electromagnetic actuator for a control valve comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.