GB2576559A

GB2576559A - Solenoid activated fuel injector with flux washer

Info

Publication number: GB2576559A
Application number: GB1813806.5A
Authority: GB
Inventors: Kolkman Manfred
Original assignee: Delphi Automotive Systems Luxembourg SA
Current assignee: BorgWarner Luxembourg Automotive Systems SA
Priority date: 2018-08-24
Filing date: 2018-08-24
Publication date: 2020-02-26
Also published as: GB201813806D0

Abstract

A solenoid actuated fuel injector (1, figure 1) including a solenoid actuator (4). The injector includes an injector body 3 adapted to contain a pole piece 9 and armature of the solenoid actuator. A pintle 2 is fixedly attached to an armature, the distal portion of which includes a valve needle. Also included is a solenoid housing sleeve 11, generally surrounding the injector body at the location of the actuator, which comprises a circumferential recess and ledge or shoulder 24 containing a bobbin or coil arrangement, characterised by a flux washer element located within said recess at its distal end. The solenoid housing sleeve may include a narrowed portion at its distal end so as to form the shoulder portion, and where said washer element is located on the internal surface of the shoulder portion. The washer element may be located between the bobbin and the internal surface of the shoulder portion. The flux washer element is preferably located within the recess at its distal end, below the bobbin/coil. The washer element may be formed as a circumferential disc and / or of steel.

Description

SOLENOID ACTIVATED FUEL INJECTOR WITH FLUX WASHER

TECHNICAL FIELD

This relates to fuel injectors which have solenoid actuated valves and has particular application to injectors for direct injection of fuel in combustion engines.

BACKGROUND OF THE INVENTION

Known injectors such as direct injectors typically include a solenoid controlled actuator adapted to generate the required force to open the injector against a closing spring, fuel pressure and combustion chamber pressure. The movement of a solenoid armature acts against a pintle (attached to a valve needle) which move the valve needle away from a seat to dispense fuel. Typically the pintle is urged in a closed position by spring means.

For gasoline applications, there is a trend to use higher fuel pressure in order to improve combustion efficiency. This implies the need for a stronger actuator, which can be realized via geometrical and/or material changes. This may be achieved by , e.g. maximizing the area size at the axial interface between armature and pole-piece, within the given packaging restrictions; alternatively maximizing the magnetic flux at this interface, via minimizing flux leakage, magnetic gaps or other flux restrictions.

However a problem with this is that the fuel injector needs to be re-dimensioned larger which has a number of disadvantages. It is an object of the invention to overcome these.

SUMMARY OF THE INVENTION

In one aspect is provided a solenoid actuated fuel injector including an solenoid actuator, said injector including an injector body adapted to contain a pole piece and armature of the solenoid actuator, said pintle being fixedly attached to an armature, the distal portion of pintle including a valve needle, said needle adapted to move to and from a valve seat depending on actuation of said solenoid, and including a solenoid housing sleeve, generally surrounding the injector body at the location of the actuator, said sleeve member including a circumferential recess containing a bobbin/coil arrangement, characterised in including a flux washer element located within said recess at its distal end.

Said solenoid housing sleeve may include a narrowed portion at its distal end so as to form a shoulder portion, and where said washer element is located on the internal surface of said shoulder portion

The washer element may be located between the distal end of the bobbin and the internal surface of the shoulder portion.

Said flux washer element may be located within said recess at its distal end, below the bobbin/coil.

Said washer element may be formed as a circumferential disc

Said washer element may be made of steel.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now described by way of example with reference to the accompanying drawings in which:

- Figure la shows a direct injection injector with solenoid actuator;.

- Figure lb shows a more detailed view of the actuator section of figure la;

- Figure 1c shows the same figure of figure 1 with flux lines and shows a concentration of flux lines in the solenoid housing;

- Figure 2 shows the magnetic material properties of the solenoid housing;

- Figure 3 shows the a schematic view of inside the solenoid housing

- Figure 4 shows one example of the invention;

Figure 5 shows a schematic exploded isometric view of certain components of one example

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A direct injection injector 1 with solenoid actuator is are shown in figure la. This shows the injector body 3, pintle (needle) 2,, and solenoid actuator arrangement

4. The pintle/needle is urged in a downward direction by spring means 5 such that the needle tip 6 is urged in a closed position against the valve seat 7. Actuation of the solenoid actuator moves an armature 8 (which is fixedly connected with the pintle) to an upwards position to move the needle tip upwards away from the seat to open the valve and dispense fuel. Typically the fuel injector housing body includes a cylindrically shaped recess to accommodate the armature. At the bottom of the recess is provided a bore for the pintle.

Figure lb shows a more detailed view of the actuator section 4 in figures la in more detail. The figure shows the injector body 3 with shunt, pole-piece 9, un upper (flux) washer 10, solenoid housing 11, the (non-magnetic coil), 12 the (non-magnetic) bobbin 13, armature (non-magnetic) 8, stop ring 14 and the pintle 2. Other reference numerals are as in figure la.

Figure 1c shows the same figure with flux lines and shows a concentration of flux lines in the solenoid housing. A steady state magnetic simulation was performed using a 2D-model of the injector in opened condition. The results of magnetic field strength for a current of 4A and 110 coil turns showed a high magnetic field strength is visible in the neck area of the solenoid housing, with local values of more than 60000A/m. Thus in the region of the neck area of solenoid housing, pointed to by arrow A in the figure, the inventors have identified the occurrence of magnetic saturation and realized the component (fuel injector can be improved) according got embodiments of the invention as described herein after.

The magnetic material properties of the solenoid housing as shown in figure 2, which shows flux density against field strength for the housing 16 and also for air and shows that the material is magnetically saturated when the field strength has reached 60000A/m. From then onwards, the slope of the flux density is only equal to the one for air.

Figure 3 shows the a schematic view of inside the solenoid housing 11 and in particular surface area sizes in the solenoid housing. Reference numeral shows the surface area 18 in the neck of the housing is reduced to 57% of the original size area 19. The solenoid housing is manufactured from sheet metal using a deep drawing process. Although such a process requires high tooling investment, it has the advantage of being able to manufacture low-cost parts in case of high-volume production. Drawback of deep drawing is the gradual decrease in wall thickness and the limitation in geometrical shape. This is clearly shown in figure 3. The surface is strongly reduced in the neck area, which generates a bottleneck for the magnetic flux.

In aspect of the invention is provide means to remove this flux restriction. The flux restriction at the neck area of the solenoid housing is removed via the addition of a (thin-walled flux) washer element 20 . This as shown in figure 4, which is the same view and has the same components with similar reference numerals as figure lb but with addition of a washer element 20. As can be seen the distal end of the solenoid housing (sleeve portion) which contains the bobbin/coil has reduced diameter so as to form a neck portion 22 and a shoulder portion 23. The internal surface of the shoulder portion thus forms a circumferential ledge 24 on which is located the washer 20. There may be no neck portion just a shoulder portion.

Figure 5 shows a schematic exploded isometric view of certain components of one example and shows the solenoid housing (or solenoid body) 11, (lower_ flux washer element 20, upper flux washer 10 and bobbin assembly 40 (consisting of the bobbin, terminals and magnet wire (coil).

The flux washer 20 may be a low-cost product, manufactured by stamping from sheet metal and is located inside the housing and is therefore not subjected to environmental corrosion. It can therefore be made from a lower grade stainless steel (12-13% Cr instead of 18% Cr) which generally has better magnetic properties and will be cheaper.

A solenoid assembly having the flux washer can be assembled on to the injector from the top-side until seated on the shoulder 24 of the injector body. This eliminates Injector-to-injector performance deviation that is linked to variation in the axial position to the solenoid assembly.

The solenoid assembly according to the invention can be applied for any solenoid fuel injector: inwardly opening as well as outwardly opening injectors.

The invention provides elimination of flux restriction resulting from solenoid housing geometry, which will result in more magnetic flux and thus more force. It can be applied and maintained to the use of existing, low-cost solenoid housing. There is minor/no impact on existing solenoid over-moulding tooling.

Claims

1. A solenoid actuated fuel injector including an solenoid actuator, said injector including an injector body adapted to contain a pole piece and armature of the solenoid actuator, said pintle being fixedly attached to an armature, the distal portion of pintle including a valve needle, said needle adapted to move to and from a valve seat depending on actuation of said solenoid, and including a solenoid housing sleeve, generally surrounding the injector body at the location of the actuator, said sleeve member including a circumferential recess containing a bobbin/coil arrangement, characterised in including a flux washer element located within said recess at its distal end.

2. An injector as claimed in claim 1 where said solenoid housing sleeve includes a narrowed portion at its distal end so as to form a shoulder portion, and where said washer element is located on the internal surface of said shoulder portion

3. An injector as claimed in claims 1 or 2 where the washer element is located between the distal end of the bobbin and the internal surface of the shoulder portion.

4. An injector as claimed in claims 1 to 3 where said flux washer element located within said recess at its distal end, below the bobbin/coil.

5. An injector as claimed in claims 1 to 4 wherein said washer element is formed as a circumferential disc

6. An injector as claimed in claims 1 to 5 where said washer element is made of steel.