AU2007304380A1 - Alternative fuel injector for dual fuel systems - Google Patents

Abstract

The present invention finds application in fuel systems for internal combustion engines using gaseous fuel and relates to an alternative fuel injector for dual fuel systems in which a coil bobbin (5) adapted to generate an electromagnetic field for actuating a movable member has a cavity (55) with a cylindrical extension (10a) of said movable member or shutter (10) directly fitted therein; a disk part (10b) of said movable menmber being adapted to abut either against the fuel hole (100) or against the bobbin (5) depending on whether the electromagnetic field is imparted or not. The disk part (10b) of said shutter (10) abuts against said bobbin (5) while leaving a gap with the support (15) of the bobbin (5) for preventing magnetic bonding.

Description

WO 2008/040581 PCT/EP2007/057764 TITLE: ALTERNATIVE FUEL INJECTOR FOR DUAL FUEL SYSTEMS DESCRIPTION The present invention relates to an alternative fuel injector for dual fuel systems, particularly for 5 use in the field of fuel systems of internal combustion engines using gaseous fuel. Use of the above injectors has been long known, for feeding fuel in the form or one or more adequately sprayed and properly oriented jets into the intake pipe 10 (in indirect injection gasoline engines) into the auxiliary chamber (in indirect injection diesel engines) or even directly into the combustion chamber. The injectors may be solenoid-operated, in which case they are under electronic control (electronically 15 controlled injectors), like in most mass-produced automotive gasoline engines or mechanical engines. A movable member, such as a shutter, allows high pressure fuel outflow. In electronically controlled injectors, an 20 electric current reaches a winding and, by generating a magnetic field, lifts an internal member which in turn moves the needle, thereby allowing fuel outflow. A problem arises in that, due to environment protection and cost saving issues, alternative gaseous 25 fuels, and particularly methane or LPG, are being increasingly used. Engines operating on these fuels are less pollutant than those that use traditional fuels, such as gasoline or diesel oil, and are usually sold at a 30 lower cost to promote use thereof. Many vehicle manufacturers sell gas-fuelled models, and engines of gasoline or diesel vehicles are being increasingly modified for additional gas WO 2008/040581 PCT/EP2007/057764 operation. For this purpose, certain shops are specialized in the installation of systems for gas-operation of vehicles. 5 These new-generation gas supply systems are usually composed of a tank for storage of the gaseous fuel, fuel check valves, a pipe that carries fuel from the tank to a pressure reducer, a pipe that carries the gas from the pressure reducer to a set of injectors 10 which are designed to dose the amount of gas to be supplied to the engine, and are controlled by a controller that is designed to control the whole system. Injectors have been heretofore the most 15 problematic part of the system. They are required to operate under very large temperature jumps, to last through millions of cycles, to be insensitive to oil, grease and other polluting agents in the gas, to withstand pressure jumps, to have 20 a fast opening and closing operation, not to change their response characteristics with time, to have a silent operation, etc. In prior art, one or more of these features is either already lacking in new injectors or is lost 25 during a certain operating time. Injector quality has been heretofore a serious problem in the art. A first apparent problem is noise: as fuel flow is opened, certain injectors emit a very high noise which, 30 in certain cases, can affect driving comfort. A second problem, that only arises after a certain operating time, is that they are sensitive to dirt, usually grease or oil, when these are present in the 2 WO 2008/040581 PCT/EP2007/057764 gas. Certain types of gases contain oil, grease or other impurities which infiltrate between the various components of the injectors and slow down or even stop 5 the motion of the movable member, i.e. the shutter, which causes opening and closing of the gas flow. This causes serious malfunctioning of the system, requiring technical service. Another problem is wear of internal components: 10 continuous "opening and closing" motion sometimes causes the shutter to wear out especially when the installation of the injector forces the shutter to have a horizontal and not downward motion, whereby the weight of the slipping shutter can cause abnormal wear, 15 and eventually affect its motion and sealing effect. Another frequent problem is degradation of the properties of the injector, with changing opening closing times and flow rates, this being usually caused by the changing size of the noise damping element, 20 which usually also sets the gap between the shutter and the stationary magnetic part. The size change has an effect on the flow rate, whereas the gap change usually causes an extension of the closing times of the injector. 25 Another problem, which usually occurs at low temperatures is that sometimes the injector is not able to open the fuel flow. In certain injectors the shutter has a barely sufficient force when all the operation parameters are 30 within certain limits, and a slight increase of the reducer pressure or a slight decrease of temperature can reduce the magnetic properties of the system, and increase the density of any grease present therein, to 3 WO 2008/040581 PCT/EP2007/057764 such an extent that the injectors can no longer operate. It shall be further noted that the solution of one of these problems increases another. 5 Therefore, the object of this invention is to provide an injector for dual fuel systems that has such a construction as to obviate all the above problems, by the provision of a multifunctional coil-, i.e. winding support bobbin, that has the additional function of a 10 directly driving the movable shutter of the injector. These objects and advantages are achieved by the alternative fuel injector for dual fuel systems of this invention, which is characterized by the annexed claims. 15 These and other features will be more apparent from the following description of a few embodiments, which are shown by way of example and without limitation in the accompanying drawings, in which: - Figure 1 is a view of a component, namely the 20 coil bobbin, of a fuel injector of this invention, - Figure 2 is a sectional view of a component as shown in Figure 1; - Figure 3 is a plan view of the component as shown in Figure 1; 25 - Figure 4 is a sectional view of an injector of this invention, - Figure 5 is a view of the injector shutter. Referring to Figures 1, 2 and 3, numeral 5 designates a coil bobbin of a fuel injector 1 of this 30 invention, which is shown in Figure 4 in sectional view. The bobbin 5 is essentially formed of a hollow cylindrical central body 50, with two outer flanges or 4 WO 2008/040581 PCT/EP2007/057764 edges 51 and 52 defining an annular space 70 in which an electric cable for generating the requested magnetic field is suitably wound. The above winding is designated in Figure 4 by 5 numeral 71. The bobbin 5 also has connectors 21 and 22 for the necessary electric contacts to be created therewith. A plurality of grooves 54 extend in rectilinear longitudinal directions over the skirt 53 of the 10 central cavity 55; such grooves 54, or slits, may also have a curvilinear extension. The coil bobbin 5 has a dual function: - creating a magnetic field, via the electric winding 71; 15 - guiding a movable member 10, i.e. the fuel shutter, which is directly fitted in the above mentioned central cavity 55. Thus, the bobbin 5 is substantially a multifunctional support. 20 The above mentioned slits 54 are formed for the purpose of avoiding pressure increase and decrease as the movable member 10 moves, particularly due to the presence of grease and oil, and allow ejection of dirt. Incidentally, it shall be reminded that the 25 problem of dirt in this injector 1 is negligible as these slits 54 on the bobbin 5 allow evacuation of dirt (in addition to relieving any positive or negative pressures that might build up without them). Referring to Figures 4 and 5, an injector 1 as 30 mentioned above is shown, which comprises a base revolving body 14 having a first support 15 fitted therein, for receiving at its center the bobbin 5 described above; said bobbin 5 being held in position 5 WO 2008/040581 PCT/EP2007/057764 by a second element 16, namely by the shank 16a thereof which is fitted in the central cavity 55 of the bobbin 5. This second element 16 closes on the first element 5 15 and both are clamped together by a cover 17 pressed or screwed thereon. All the elements 14, 15, 16, 17 and 5 (as well as the popped 10 as disclosed below) are interconnected with parallel and coincident axes of revolution Al. 10 The shutter 10 is interposed between the bobbin 5 and the base body 14, to open and close the body 100 of the latter and control fuel outflow, and is normally held in the flow stopping position by a suitable spring M, in the illustrated case a spring M that operates on 15 the shutter 10 and the support 16 in specially constructed recesses. More specifically, the shutter 10 is composed of two parts, a disk 10b and a cylindrical extension 10a extending therefrom, which is fitted, i.e. inserted in 20 the cavity 55 of the bobbin 5, the disk part 10b being adapted to alternately abut against the hole 100 or the bobbin 5, depending on the attractive action of the electromagnetic field. It will be appreciated that, when the shutter 10 25 opens the whole 100, by being attracted by the magnetic field of the bobbin 5, said shutter 10 does not close directly against the corresponding abutment surface of the element 15 but, due to a suitable abutment of the bobbin 5 (of such a length as to project out of the 30 surface of the support 15) a gap is created between the above parts to prevent any magnetic bonding. Thanks to the above solution, the injector 1 emits little noise, because the movable member, or shutter 6 WO 2008/040581 PCT/EP2007/057764 10, abuts against the bobbin 5 which is formed of non excessively rigid material and partly absorbs shocks thereby reducing noise. Two seals 31 and 32 are provided between the 5 bobbin 5 and its supports 15 and 16 to prevent any gas leakage. Finally, it should be noted that the bobbin 5 is formed of any non magnetic, self-lubricating material: this obviates or at least attenuates the problem of 10 wear of the movable parts; by this arrangement, the movable parts are exposed to much lower stresses caused by the contact with the self-lubricating material. Finally, it will be appreciated that the present injector 1 encounters no opening problem, even under 15 overpressure conditions, which means that the system has a very effective opening operation, because the magnetic assembly is easily oversized thanks to the dual cylinder-disk shape of the movable member 10, which ensures an effective operation of the 20 electromagnetic assembly, thereby providing a member that has a sufficiently light weight to allow displacement thereof while ensuring guidability within the cavity of the coil bobbin 5, as if it were a piston: this combines the advantages of the piston and 25 the disk when used as a movable member, and reduces the disadvantages of both. Finally, performances of this type of injector 1 are not markedly degraded with time, because it is little affected by dirt- and wear-related problems 30 (thanks to the provision of slits 54, the use of a movable member 10 of self-lubricating material and oversized driving forces). 7

Claims (8)

1. An alternative fuel injector for dual fuel systems, of the type comprising a coil bobbin (5) , which is composed of a hollow cylindrical central body 5 having an electric winding (71) externally wound thereon, which is designed to generate an electromagnetic field for actuating a fuel flow controlling shutter (10), said shutter being interposed between the bobbin (5) and the base body 14) of the 10 injector (1) to open and close a hole (100), characterized in that said shutter (10) has a cylindrical extension (10a) directly fitted, i.e. inserted, in the cavity (55) of the bobbin (5).

2. An injector as claimed in claim 1, 15 characterized in that said shutter (10) has a disk part (10b) which is adapted to abut either against the fuel hole (100) or against the bobbin (5) depending on whether the electromagnetic field is imparted or not.

3. An injector as claimed in claims 1 and 2, 20 characterized in that said cylindrical part (10a) extends from said disk part (10a).

4. An injector as claimed in claims 1 and 2, characterized in that the disk part (10b) of said shutter (10) abuts against said bobbin (5) while 25 leaving a gap with the support (15) of the bobbin (5) for preventing magnetic bonding.

5. An injector as claimed in claim 1, characterized in that said gap is designed to be as long as the cylindrical body (50) of the bobbin (5) 30 which, once the injector (1) is assembled, projects out of the surface of one of the supports (15) of the bobbin (5).

6. An injector as claimed in claim 1, 8 WO 2008/040581 PCT/EP2007/057764 characterized in that it has two seals (31, 32) between the bobbin (5) and its supports (15, 16) to prevent any gas leakage.

7. An injector as claimed in claim 1, 5 characterized in that the bobbin (5) is formed of any non magnetic, self-lubricating material.

8. An injector as claimed in claim 1, characterized in that said bobbin (5) is formed of a non excessively rigid material, to partly absorb the 10 shock caused by abutment of the disk part (10b), thereby reducing noise. 15 20 25 30 9