Patent Application
20080135469
The invention relates to a device for filtering fuel, in particular diesel, for removing the particles and the water contained in the fuel.
Various devices of this type are known. US-2006/0006109 discloses a device comprising a housing containing:
The invention seeks to provide a device that is simple and robust, presenting improved quality when filtering particles and separating water, and without increasing price.
To do this, in accordance with the invention, the housing contains:
Thus, the first filter element performs coarse filtering, thereby defining a capacity filter element, while increasing the size of fine drops of water, while the second filter element performs fine filtering that is more effective against particles that have passed through the first filter element. The first filter element and the fabric have a combined effect of effectively separating the water from the fuel. The fuel passing through the second filter element contains very little water, so the particle filtering performed by the second element is improved. Furthermore, it enables filter materials to be used that are less good at withstanding water, but that are more effective in filtering particles.
In order to optimize the combined effects of the first filter element and the hydrophobic fabric, in accordance with the invention the first filter preferably presents surface energy lying in the range 40 millinewtons per meter (mN/m) to 60 mN/m, and the hydrophobic fabric presents surface energy lying in the range 20 mN/m to 30 mN/m.
Thus, the first filter avoids excessive accumulation of water droplets that would run the risk of closing certain pores of the filter, leading to head losses and flow disparities through the filter, thus generating a loss of efficiency. Furthermore, the first filter causes droplets of water group together in a manner that is adapted to the water barrier formed by the hydrophobic fabric.
According to another characteristic in accordance with the invention, the first filter element and the second filter element are preferably tubular, share a common axis, and are disposed one extending the other.
The ratio between the efficiency and the size of the filter is thus improved.
According to an additional characteristic in accordance with the invention, and preferably, the first filter element and the second filter element define internally an inside space in which a pump is disposed.
Thus, the pump can be integrated in the device without significantly increasing its size.
According to another additional characteristic in accordance with the invention, the pump is disposed downstream from the separation fabric in the fuel flow circuit.
Thus, the pump is less likely to reduce the efficiency with which water contained in the fuel is separated out.
According to another characteristic in accordance with the invention, and advantageously, the pump is disposed in a fuel-tight tubular sheath presenting a bottom, said sheath defining a container fed upstream from the pump in the fuel flow circuit by at least one feed orifice remote from the bottom, and the pump presenting an inlet and an outlet, said inlet being disposed between the feed orifice and the bottom of the sheath.
Thus, when the housing is open, in particular for the purpose of replacing the filters, there is a reduction in the risk of the pump no longer being lubricated or of the pump racing because it is sucking in air.
In accordance with the invention, the device also preferably presents the following characteristics:
The device is thus simpler to manufacture.
According to an additional characteristic in accordance with the invention, a secondary water separation fabric is disposed in said at least one feed orifice, and a bottom end plate secured to the bottom end of the first filter element includes a settling zone for collecting the water separated by the second fabric, and which is disposed between the first element and the secondary fabric in the fuel flow circuit.
This improves separation of water from the fuel.
According to another additional characteristic in accordance with the invention, the sheath is overmolded on the secondary water separation fabric.
According to another characteristic in accordance with the invention, the first filter element, the second filter element, and the separation fabric preferably define a removable one-piece filter unit.
This makes it easier to install and replace the first filter element, the second filter element, and the separation fabric.
According to an additional characteristic in accordance with the invention, and preferably, the filter unit having a plate separating the first filter element and the second filter element, said plate being provided with at least one lip facing towards the first filter element, and the pump is disposed between the first filter element and the second filter element in the fuel flow circuit.
Thus, when the plate and the sealing lip do not enable complete sealing to be achieved, leakage takes place from downstream to upstream in the fuel flow circuit. The quality of the filtering performed by the device is then not degraded.
According to another characteristic in accordance with the invention, the device further includes a valve having a closed position in which it prevents fuel from flowing through the outlet of the device, and an open position in which it allows fuel to flow through the outlet of the device, said valve being urged towards its closed position by pressure means and presenting a rod coming to bear against the filter assembly comprising the first filter element, the second filter element, and the separation fabric and serving to push the valve towards its open position.
Thus, in the absence of the filter, fuel cannot leave the device. Consequently, the risk of unfiltered fuel leaving the device is reduced.
According to an additional characteristic in accordance with the invention, and preferably, the filter assembly includes means for isolating the downstream end of the pump from the upstream end of the pump, such that in the absence of the filter assembly, the downstream end of the pump and the upstream end of the pump communicate with each other than through the pump.
This reduces the risk of excess pressure inside the device or of the pump becoming heated.
According to another characteristic in accordance with the invention, and preferably, the device further comprises a settling zone upstream from the first filter element in the fuel flow circuit for collecting the water separated from the fuel by the first filter element.
Larger droplets of water are thus separated from the fuel on entering the device.
Other characteristics and advantages of the present invention appear from the following detailed description given with reference to the accompanying drawings, in which:
The housing essentially comprises a cover 11, an upper body 3, a lower body 7, and a bottom 6 screwed onto the lower body 7. These four main elements of the housing are advantageously made of plastics material. The cover 11, the upper body 3, and the lower body 7 are preferably secured to one another by welding. This welding may be of the ultrasound, laser, hot-blade, or analogous type. Such methods serve to heat the plastics material so as to melt it locally at contacting surfaces between the pairs of parts to be assembled together. The parts to be assembled together are then pressed against one another so that the partially-molten plastics material of each part mixes with that of another part. When the plastics materials cool down, they bond together in definitive manner. The cover 11, the upper body 3, and the lower body 7 are thus bonded together in leaktight manner. In a variant, other means enabling these elements to be secured to one another in leaktight manner could alternatively be provided.
The bottom 6 is secured releasably on the body 7 by a screw thread, so as to come into abutment against an annular collar 33 projecting radially outwards from the lower body 7 to form an abutment for the bottom 6. An O-ring is provided to provide sealing between the bottom 6 and the lower body 7.
The filter unit 24 forms a one-piece structure shown more particularly in
The function of the first filter 4 is to retain the largest solid particles and to cause any water contained in the diesel that penetrates into the device 50 via the inlet 1 to coalesce. The first filter 4 advantageously presents straight pleating formed by a two-layer non-woven fabric. The first layer in the diesel flow direction (outer layer) is preferably a so-called “melt-blown” layer constituted by polyester fibers. It presents pores of a size such that about 50% of the flow of diesel passing through it passes through pores of a size smaller than 11 micrometers (μm), and about 50% of the flow of diesel passing through it passes through pores of a size greater than 11 μm. The second layer (inner layer) situated downstream from the first layer in the diesel flow direction is advantageously constituted by cellulose fibers impregnated with polymerized phenolic resin. It presents pores having a size such that 50% of the flow of diesel passing through it passes through pores of a size smaller than 9 μm and about 50% of the flow of diesel passing through it passes through pores of a size greater than 9 μm. Consequently, the mean size of the pores in the first layer is about 11 μm and that of the pores in the second layer is about 9 μm. There thus exists a porosity gradient that decreases going from upstream to downstream through the filter.
The surface tension (energy) of the first and second layers of the first filter 4 advantageously lies in the range 40 mN/m to 80 mN/m, preferably in the range 40 mN/m to 72 mN/m, and ideally in the range 40 mN/m to 60 mN/m. Since the surface tension of water is 72 mN/m, the first filter 4 is consequently preferably slightly hydrophobic.
The fabric-covered tube 5 comprises a perforated plastics tube 5″ carrying a fabric 5′. The fabric 5′ is advantageously made of polyester and preferably of polyester terephthalate (PET). The fabric 5′ advantageously constitutes a square-type mesh having openings (porosity) of about 25 μm to 27 μm. The fabric 5′ is preferably treated to be hydrophobic, having surface tension lying in the range 20 mN/m to 40 mN/m, and preferably in the range 20 mN/m to 30 mN/m. It is preferably overmolded onto the tube 5″ that constitutes a support therefor.
Preferably, the second filter 13 advantageously presents straight pleating constituted by a two-layer non-woven fabric. The (outer) first layer is advantageously a so-called “melt-blown” layer constituted by polyester fibers. The (inner) second layer is disposed downstream from the first layer relative to the diesel flow direction and is advantageously constituted by cellulose fibers impregnated with a polymerized phenolic resin. The mean size of the pores of the first layer is preferably 11 μm, and that of the pores of the second layer is preferably 5 μm, so that there exists a porosity gradient that decreases going from upstream to downstream through the filter. In a variant, the second filter 13 could be constituted, for example, by a single layer comprising cellulose fibers and glass fibers.
In
The diesel that has passed radially through the first filter 4, from the periphery towards the center, penetrates into a cavity 46 extending between the first filter 4 and the fabric-covered tube 5. Since droplets are enlarged in the first filter 4, most droplets are of a size that is too big to pass through the hydrophobic fabric 5′, so that the droplets move downwards under gravity along said fabric 5′ inside the cavity 46, so as to pass through an orifice 38 formed through the bottom end plate 18 and be collected in a settling zone 51 formed in the bottom 6, as represented diagrammatically by a dashed line 43 showing the main path of water droplets in
The diesel that has passed through the fabric 5′ penetrates into a cavity 47 extending between the fabric-covered tube 5 and the inlet 9a of a pump module 9. The upper body 3 includes a tubular sheath 8 extending along the longitudinal axis 60 and coaxial with the first filter 4, the second filter 13, and the fabric-covered tube 5. The sheath 8 presents a bottom 8a and defines an inside space 42. It presents inlet orifices 10 remote from the bottom 8a and situated above the inlet 9a of the pump module 9.
Diesel is delivered under pressure via the outlet 9b of the pump module 9 into a cavity 48 extending between the outlet 9b of the pump module 9 and the second filter 13. Diesel then passes through the second filter 13 radially from the periphery towards the center, after which it penetrates in a cavity 49. The second filter 13 retains the major fraction of the particles still remaining in the diesel present in the cavity 48. The diesel then leaves the device 50 via the outlet 16.
The bottom end plate 18 presents radial fingers 27 coming into abutment against a shoulder 28 of the lower body 7, in order to position the filter unit 24 in the housing.
In the embodiment shown in
The annular plate 19, and more precisely its top portion 19′ includes a first flexible lip 20a providing sealing between the plate 19 and the sheath 8, and a second flexible lip 20b providing sealing between the intermediate plate 19 and the upper body 3. More precisely, the lip 28a provides sealing between the cavity 49 and the cavity 47 towards which it faces, while the lip 20b provides sealing between the cavity 48 and the cavity 45 towards which it faces. Consequently, it should be observed that the lips 20a and 20b are flexed (oriented) in the upstream direction of the diesel flow circuit 29.
The top end plate 12 has a main portion extending perpendicularly to the longitudinal direction 60 and including a tubular portion 30 that is diesel-proof presenting an annular bead 22 or “pipe insert” that comes into contact with a tubular portion 54 of the upper body 3. The annular plates 18, 19, and 21 extend generally perpendicularly to the longitudinal direction 60 and are secured to the first filter 4 and to the second filter 13 by adhesive-bonding, welding, a hot-melt adhesive, or the like.
A tube 23 that is perforated to allow diesel to pass through extends coaxially with the second filter 13, axially between the top end plate 21 and the intermediate plate 19, and radially between the sheath 8 and the second filter 13. The perforated tube 23 is snap-fastened at its axial ends to the top end plate 21 and the intermediate plate 19. Similarly, the perforated tube 5″ is snap-fastened at its axial end to the intermediate plate 19 and the bottom end plate 18.
As shown in
As shown in
Close to the outlet 16, the device 50 further comprises a valve member 15 that is movable between an open position shown in
The gas that escapes through the space 52 between the portion 19′ and the portion 19″ of the intermediate plate 19 avoids bubbles of gas accumulating in the top portion of the first filter 4 in the cavity 45. In the absence of high pressure imposed by the pump unit 9, the gas finds it difficult to pass through the first filter 4. The accumulation of gas inside the top portion of the cavity 45, upstream from the first filter 4, reduces the surface area of the first filter 4 that is available for filtering diesel by a corresponding amount, thereby increasing the speed with which the fuel flows through the first filter 4 and the fabric 5′, and reducing the effectiveness of filtering and of water separation performed by the first filter and the hydrophobic fabric 5′. Once the gas has reached the cavity 47 it is exhausted under pressure by the pump 9 and forced to pass through the second filter 13 so as to be exhausted outside the device 50 via the outlet 16.
The device 50 shown in
In addition, a second fabric-covered tube 35 is placed at the inlets of the orifices 10 and a second settling zone 56 is provided in the bottom end plate 18 in order to recover droplets of water that have run down over the second fabric-covered tube 35 falling under gravity into the cavity 47. Advantageously, the fabric-covered tube 35 is constituted by a hydrophobic fabric overmolded on the plastics material of the sheath 8 and it is constituted by a hydrophobic fabric of material similar to that of the hydrophobic fabric 5′ but having pores that are smaller than those of the hydrophobic fabric 5′. The size of the pores in the hydrophobic fabric of the second fabric-covered tube 35 may lie in the range about 10 μm to about 20 μm, for example.
In certain applications, it is possible for the droplets of water to be larger, making it difficult for them to penetrate into the filter media of the first filter element 4, so that they accumulate upstream from the first filter element 4 inside the cavity 45. Consequently, the device 50 shown in
The device 50 shown in
In very cold weather, particles of paraffins (long molecular chains) form in the fuel and can temporarily clog the filter elements. Consequently, the filter of the invention may also be provided with means for heating the fuel upstream from the first filter element 4. By way of example, the heater means may be of the type comprising:
It should be observed that the valve 15 could optionally be mounted on a filter device other than a filter device of the invention, insofar as the filter device need merely be such that in the absence of the filter module 24, said valve is in the closed position, and when the filter module 24 is placed inside the filter device, the valve is opened.
| Number | Date | Country | Kind |
|---|---|---|---|
| 06 10841 | Dec 2006 | FR | national |
