Patent Application
20070272192
The invention relates to a device for filtering lubricating oil in the course of a mechanical valve train of an internal combustion engine according to the preamble of claim 1.
All working components involved in the operation of internal combustion engines, especially in motor vehicles, are subject to generally increasing demands with regard to reliability and durability. One existing problem area is the lubricating oil supply, especially the supply of dirt-particle-free oil to the valve train. These contaminating particles may get into the oil circuit for a variety of reasons, for example as metal particles from the final machining of internal combustion engine components, as abrasion particles resulting from routine operation or through use of the internal combustion engine in a dirt-laden environment.
A device disclosed by US 2002/0108894 A1 for filtering lubricating oil in the course of a mechanical valve train of an internal combustion engine, with at least one force-transmitting and oil-lubricated component operative between gas exchange valves and their periodic drive, has a filter element assigned to a component in the form of a valve tappet.
This known filter element is a mechanical separator, which takes the form of an approximately canister-shaped component with an enclosed, impermeable surface. The proposed separation is intended to take place on or in the valve tappet in a total of three stages. The first two separators take the form of gaps of defined width, at which coarse particles are to be separated out. Fine particles, which overcome the first two barriers are intended to be diverted in a specific direction with the oil flow by means of the separator inserted into the oil reservoir. For this purpose the oil flow fed to the oil reservoir is conducted along a gap formed between the separator and the oil reservoir wall away from the non-return valve and towards the ball socket facing a push rod.
In operation these finer particles will then be led off via a bore in the ball socket and via the push rod, so that they cannot clog the non-return valve or lead to seizing of the entire tappet in the further oil discharge.
The filtering in this known device is therefore achieved by purposely diverting the oil flow. The use of mesh-like filters is termed unsuitable.
A disadvantage with this known device is that the volume of the oil reservoir is severely limited by the comparatively voluminous design of the separator. The separator can ultimately not directly prevent fine particles getting in, but can only attempt to direct the oil flow. Given an inclined or horizontal installation position, reliable functioning is no longer feasible.
The object of the invention is to specify a device for filtering lubricating oil, which very largely prevents fine particles getting into components in the course of a valve train of an internal combustion engine, especially in inclined installation positions.
The stated object is achieved by a device for filtering lubricating oil in the course of a mechanical valve train of an internal combustion engine, especially for motor vehicles, having at least one force-transmitting and oil-lubricated component operative between gas exchange valves and their periodic drive, the device comprising a filter element assigned to the component, the surface of the filter element being of oil-permeable design.
This design construction has the advantage that a targeted filtering of the contamination matched to the prevailing operating conditions can take place, in that the filter element allows the oil to pass through whilst retaining the particles. In contrast to the known state of the art, a filtering in the strict sense actually takes place, rather than just a deliberate directing of the oil flow. As a result the efficiency of the filtering is advantageously assured irrespective of the installation position.
The dependent claims describe preferred developments or further developments of the invention.
In an advantageous development, for example, it can be provided that the filter element takes the form of a strainer provided with a mesh fabric. This has the advantage that the maximum admissible passage for a form of contamination can be adjusted for the prevailing operating application through the choice of mesh width. Furthermore, mesh fabrics are commercially available in standard form.
Instead of the mesh fabric, it is also possible to use filter elements, the surface of which is provided with pores. Filters of widely varying types can therefore be used, such as fan filters or spiral filters, for example.
At least two filter elements can advantageously be arranged in series one behind the other in the oil flow direction, a combination of mesh fabric and porous filters being possible. The connection in series is capable of leading to an improved separation, especially of elongate particles, without significantly increasing the flow resistance.
In another further development of the invention, the component in the course of the valve train takes the form of a tubular push rod, the filter element being inserted into the tube. The existing overall space inside the oil-conducting push rod is in this case advantageously used for filtration, providing a filter area of comparatively large dimensions.
In a further development, the filter element, in the area of a tube end of the push rod, may have a diameter that permits a tightly sealing fit to the tube. If the flow of oil is admitted via this tube end, the entire volume of oil has to flow through the filter element. In addition, the tightly sealing fit may take the form of a press fit, thereby giving the filter element a hold consistent with accelerations in operation.
In this development, in the longitudinal direction of the push rod the filter element may advantageously and preferably have a smaller area adjoining the tightly sealing fit. This roof-shaped design of the filter element has the advantage that the entire oil volumetric flow must always flow through the filter element. Making the longitudinal extent of the filter element substantially equal to the internal length of the push rod provides a maximum surface for filtration.
According to another advantageous variant, the component in the course of the valve train takes the form of a valve tappet with integral valve clearance compensation having, in the oil flow direction: an oil admission, an oil reservoir, a high-pressure chamber and a non-return valve acting between the oil reservoir and the high-pressure chamber, the filter element being arranged inside the oil reservoir.
This has the advantage that contaminations which penetrate as far as the valve clearance compensation element cannot pass to the non-return valve. The further passage of particles into the high-pressure chamber, which via the leakage oil gap might lead to seizing and hence total failure of the component, is therefore prevented.
It may be preferable here, in the case of a two-part piston which is displaceably supported in the valve tappet and in which the oil reservoir is formed, and with a piston upper part associated with a gas exchange valve and a piston lower part carrying the non-return valve, for the oil admission to be assigned to the piston upper part.
This design has the advantage that, on the one hand, an initial filtering can take place in the push rod acting on the compensation piston and delivering the oil, and a further filtration occurs via the filter element inserted either into the piston upper part or the piston lower part.
If, in another installation situation, the oil is admitted laterally into the valve tappet, with a piston displaceably supported in the valve tappet and in which the oil reservoir is formed, the piston being of two-part design with a piston upper part associated with a gas exchange valve and a piston lower part carrying the non-return valve, the filter element is then preferably arranged in the piston lower part. This has the advantage that, after entering, the entire oil admission flow has to flow through the filter element via the lateral opening.
In a preferred development of the invention, the filter element is provided with a mesh fabric, this being of roof-shaped design and inserted in a holding element, which with an outer surface is wedged into the component.
This has the advantage that, in contrast to the known state of the art, a clear separation of functions and a separation of functional components is achieved with regard to filtration and the wedging arrangement. The outer surface of the holding element may be optimized for insertion into the respective component (push rod, valve tappet or other oil-carrying components of the valve train), whilst the mesh fabric is designed exclusively for optimum filtration.
The invention may be used to advantage in all oil-carrying components arranged in the course of the valve train, such as valve tappets, push rods, rocker arms or valve levers and/or their axes and in oil lines in the cylinder head or cylinder block.
The invention is described in more detail below on the basis of some embodiments and with reference to the drawings attached, in which:
A valve train (known in the art and therefore not shown in more detail) of an internal combustion engine used in a motor vehicle has, among other things, a push rod 4 in the form of a tube 2, which with one of its end areas 6 or 8 and via a spherical element 10 engages in a corresponding socket 12 of a valve tappet 14.
At its lower end (not shown) the valve tappet 14, only partially represented in
A filter element 16 provided with an oil-permeable surface is inserted into the tube 2. This filter element is of roof-shaped design such that in one end area 6 it has a diameter allowing a tight sealing fit, whilst in the further course of the longitudinal extent of the push rod 2 it has a smaller area.
Along the end area 6 the filter element 16 carries a fitting section 18 for a stable, stress-resistant fixing, which is pressed into the tube 2 by means of a press fit, forming an oil-tight seal.
The valve tappet 14 according to
In a piston upper part 26 the socket 12 is formed with an oil admission bore 28, which allows the lubricating oil to flow into an oil reservoir 30.
At the outlet flow end an adjoining piston lower part 32 carries a non-return valve 34, which controls a connecting duct 36 in a high-pressure chamber 38.
Arranged inside the oil reservoir 30 is a further filter element 16, which is only represented schematically in
Since the oil admission is assigned to the piston upper part 26, the entire oil volumetric flow must first flow via the oil admission bore 28 through a mesh fabric 42 of the filter element 16, thereby preventing a possible contamination of the valve tappet (
Should the oil in a laterally fed valve tappet be admitted through a skirt 44 of the compensation piston 24, the filter element is alternatively inserted into the piston lower part 32, as is represented schematically in
According to
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2004 033 500.1 | Jul 2004 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP05/06384 | 6/15/2005 | WO | 1/9/2007 |
