WO2005070516A1

WO2005070516A1 - By pass filter and method of filtering

Info

Publication number: WO2005070516A1
Application number: PCT/IB2003/006133
Authority: WO
Inventors: Pierre Gerard Willem Nieuwland; Ron Borger
Original assignee: Ntz International Holding Bv
Priority date: 2003-12-23
Filing date: 2003-12-23
Publication date: 2005-08-04
Also published as: AU2003298461A1

Abstract

Micro-filter device (1) comprising a filter housing (2) and an essentially cylindrically shaped micro-filter element (3) having a central oil receiving chamber (6, 7, 8) for receiving oil filtered by the filter material (5), and a concentrically located oil chamber (17) present between a cylindrical part of the filter housing and the exterior wall of the filter element (3) for supplying oil to said filter element, the axial end faces of the filter element being closed by mutually non-attached closure elements (14). The closure elements (14) are formed by the respective axial end faces (14) of the housing and in that the central oil chamber (6, 7, 8) communicates with axially central oil entry and oil exit ports (9, 10) of the housing, while the concentrically located oil chamber (17) like-wise is provided with, at least communicates with eccentrically located oil entry and exit ports (12, 13) of the housing.

Description

BY PASS FILTER AND METHOD OF FILTERING The present invention relates to a filter device as defined in the preamble of claim 1. Such devices are generally known, e.g. from the PCT-patent publication WO- 0107142 in the name of Applicant, and from SAE paper 2001-01-0867 "Automatic transmission hydraulic system cleanliness - the effects of operating conditions, measurement techniques and high efficiency filters", which document is hereby regarded included. Such known filters may be used as a stand-alone means for filtering oil as operationally required by many mechanical devices such as transmissions and or engines. This type of filter than filters the oil at a pace that is lower than the pace of the oil stream that is fed, often pumped, through the mechanical device. Due to the high efficiency of micro-filters, all of the oil will be filtered to a very fine degree within a relatively short period from start of operation. It being a custom to filter all of the oil before it is fed to the mechanical device, the micro-filter is commonly used in addition to a conventional, in-line located filter which is based on a sieving principle and which filters to a relative to the micro-filter, rather coarse degree, thereby at a relatively low efficiency. Very often however, the additional use of the micro-filter is omitted because of at least initial costs associated with designing and implementing the so-called bypass route means within the mechanical device, costs of the by-pass filter device itself, and the space required for it. It is an object of the current invention to take away at least considerable part of the above-mentioned circumstances objecting the implementation of micro-filters in mechanical devices, in particular at automotive application. According to the invention, such goal is realised by applying a known filter device in accordance with the features of the characterising portion of claim 1. With such device, no other connection between supply and discharge line to and from the mechanical device to be applied with oil is to be made than a connection of the existing lines to the filter device according to the invention. The device itself is thereby produced relatively cheap by enclosing the filter element in a can-like housing. Further to this respect, the filter element is according to the invention sealed within the housing in a can-like manner, i.e. having the cylindrical portion and the axial end-faces mutually interconnected by flanging. In a favourable embodiment the housing is provided with a bulged out portion, so that oil may enter an oil chamber exterior to the filter element in axial direction. Advantages of the latter being that the entering oil does not impinge on the filter material directly, while moreover the oil may easily and quickly be spread along the circumference of the filter element. The latter is for the same reason secured centrally within the otherwise predominantly cylindrical housing by providing the latter with grooves for receiving protruding end parts of a central core of the filter element. The invention will now be elucidated further by way of example along a drawing. In the figure of this drawing identical structural features are correspondingly numbered by way of reference. The figure shows a filter device 1 comprising a filter housing 2 and a filter part or element 3. The filter element 3 is a so-called micro-filter, often used in by-pass configurations, and alternatively denoted in-depth filter so as to contrast with conventional filters based on a sieving principle and often using a pleated paper shape to enlarge sieving surface of it. High efficiency, cellulose fibre based micro filtration elements and its features are more extensively explained by the earlier mentioned SAE paper. Rather than conventional filters which in fact only rely on blocking particles through the provision of sufficiently small openings, and which therefore are surface based, cellulose fibre elements combine small openings with a feature of electrostatic forces within the material, binding particles while on their way through the filter material. For this reason micro filters rely on a relatively thick body of filtering material through which oil is to be passed, and within which the "filtering" effect takes place. At conventional filters on the other hand filtering takes place on the surface of the material, for which reason the latter is maximised by using folded paper or cardboard material. Consequently conventional filters have a relatively low resistance, allow a relative large flow and may in principle be cleaned by reversing a flow of medium through the filter. Micro filters may bind very small particles within its filtering body - are therefore here denoted in- body or in-depth filters, but have a relatively large flow resistance and are not reusable by inverting flow of medium. Micro filters therefore normally come in by pass configuration, whereas conventional filters are used full flow. The filter element 3 comprises a perforated central core 4 around which cellulose fibre filter material 5 is applied. The element 3 is essentially shaped cylindrical. The core 4 extends to a minor though substantial extend axially beyond the filter material 5, of which the axial end faces extend in a plane transverse to the longitudinal axis of the element 3. The central core 4 may be fitted with a venturi device 6, comprising a wall separating the interior chamber of the filter element 3 into a central part 8 and an eccentric part 7. The eccentric part 7 communicates with the central chamber part 8 via openings in said separating wall, located at or at least near a narrowest part of the chamber part 8. The latter chamber part 8 communicates with axially central ports forming inlet and outlet openings 9 and 10 respectively, here formed by pipe parts of the housing 2. In the current embodiment, the inlet 9 is preferably associated with a cooler device, while the outlet is associated with a gearbox or other type of transmission for supplying cooled hydraulic fluid. The housing 2 of the device closely follows the circumference of the filter element 3. At one location along the periphery of the housing, a bulged out portion 11 is provided, e.g. V-shaped as seen in cross section, preferably extending over the entire axial length of the housing 2. In the bulged out portion 11 there are, near the axial end faces of the device, provided further, axially eccentrically located ports, forming inlet and outlet openings 12 and 13 respectively. In operation, preferably the inlet 12 is provided near, i.e. at the axial side of the central outlet opening 10. In casu the eccentric inlet opening 12 receives hydraulic fluid from the transmission that is supplied via central outlet opening 10. The eccentric oil outlet opening 13 is associated to the earlier mentioned oil cooler device, like the transmission not depicted in the figure. The housing 2 is preferably shaped of sheet metal, however may alternatively also be composed of synthetic material. In the latter case a snap connection is used for closing the housing instead of a can-like flange connection. As depicted, preferably only one, e.g. largeriy axially centralised flange 18 is applied, rather than one a each axial end of the housing 2. At its axial end faces 14, the housing closely presses against the axial end faces of the filter material 5. Thereby it is shaped with axially concentric rings of projections 15 protruding into the filter material. In casu three rings of projections 15 are provided, each preferably essentially V-shaped as taken in cross section. In the close vicinity of each central port 9, 10, in an axially concentric ring, a relatively deeper groove 16 is provided, extending in the opposite direction of the protrusions 15, i.e. away from the filter material. The dimensions of groove 16, including diameter, width and depth are provided fit for receiving an end part of the central core 4. The depth of the groove 16, preferably is at least 100% of the length core part extending, i.e. protruding from the end face of the filter material 5. By the latter feature it is made sure that the end faces of material 5 will come into contact with the axial end faces 14 of the housing 2, while still a locating and centring means 16 is provided, promoting both a correct assembly of the filter device 1 and a proper functioning thereof, in that the filter element 3 will be located centred within the housing, thus receiving fluid in equally, at least unhampered from all directions along the circumference of the element 3. At its circumference some distance is maintained to the housing 2, creating a chamber 17 that communicates with the room 11 caused by the bulged out portion of the housing. The bulged out portion as taken in axial view preferably takes up less than 1/6'th of the projected circumference of the major part of the housing, however is at least sufficiently large to accommodate an appropriate entry and exit pipe matching the supplu and discharge lines in which the device is to be incorporated. By the end face 14 with the described features of the device 1 , at least virtually no oil can pass the filter element without being filtered. According to preference of the invention at least one of the axial end faces 14 of the housing 2 is connected to the main cylindrical part thereof by mutual flanging (dutch: "felsen"). In this manner, it is guaranteed that the filter is positioned in the housing, closely clamped between the axial end faces. The use of this can-like incorporation of a filter element, in accordance with an idea underlying the invention, the associated flexibility of the metal sheet material is relied on for coping with axial expansion of the filter material. Favourable use is thereby made of the room 17 external to the filter element 3, required for entry of oil all around the filter and the associated diametric protrusion of the housing wall 14 beyond the axial end faces of the filter material, allowing the material of the wall 14 to bend around the filter material to some extend. Any bulging out in axial direction of the end faces 14 is thereby functionally addressed by the presence of the protrusions 15, which force any oil passing by, through the filter material. The filter device 1 according to the invention sets forth a technically and economically favourable by pass filter device, in that no additional tubing is required for connecting a supply and a discharge line of hydraulic fluid for a transmission or comparable mechanic device requiring cooled fluid. Any presence of a venturi-device 6 may provide, or otherwise enhance any existing pressure difference between the hydraulic lines 9, 10 and 12, 13 to and from the mechanical device to be supplied with cooled hydraulic fluid. By the present device 1 a filtering action may take place in combination with such supply and discharge, the supply of cooled fluid thereby being mixed with part of the discharge stream 12, 13, filtered by the filter element 3. Since the filter element 3 is a micro-filter, requiring a relatively high pressure-difference for operation, it will only filter part of the discharge stream 12, 13, thereby ensuring that the main part of the oil stream exiting through outlet opening 10 is cooled. Favourably the present arrangement allows the warmest oil stream to pass through the filter, enhancing passing of oil through the filter, by the oil being relatively more fluid. The invention, apart from the following claims, also relates to the preceding description and all details and aspects in the drawing which are directly and unambiguously derivable there from, at least by a man skilled in the art.

Claims

1. Micro-filter device (1) comprising a filter housing (2) and an essentially cylindrically shaped micro-filter element (3) having a central oil receiving chamber (6, 7, 8) for receiving oil filtered by the filter material (5), and a concentrically located oil chamber (17) present between a cylindrical part of the filter housing (2) and the exterior wall of the filter element (3) for supplying oil to said filter element (3), the axial end faces of the filter element (3) being closed by mutually non-attached closure elements (14) preventing, at least hampering oil from passing the filter element (3) along an axial end face thereof, characterised in that the closure elements (14) are formed by the respective axial end faces (14) of the housing (2) and in that the central oil chamber (6, 7, 8) communicates with axially central oil entry and oil exit ports (9, 10) of the housing (2), while the concentrically located oil chamber (17) like-wise is provided with, at least communicates with eccentrically located oil entry and exit ports (12, 13) of the housing (2).

2. Filter according to claim 1, characterised in that the filter housing (2) is provided with a circumferentially bulged out portion, forming a chamber (11) for receiving and/or for discharging oil, respectively from and to said oil communication ports (12, 13), passing through the filter device (1).

3. Filter according to the preceding claim, characterised in that the bulged out portion extends over the entire axial length of the device (1), forming a channel between the axial ends (14) of the device (1), along the periphery of the filter element (3), oil the communication ports (12, 13) thereby preferably being directed axially.

4. Filter according to claim 1 , characterised in that the housing (2) is produced of one of sheet metal and synthetic material.

5. Filter according to any of the preceding claims, characterised in that at least one of the axial end faces (14) of the housing (2) is flanged to the main cylindrical part of the housing (2), preferably by a flange (18) located in a central part of the length of the cylindrical part of the housing (2).

6. Filter according to any of the preceding claims, characterised in that the axial end faces (14) of the housing (2) are provided with circumferentially present protrusions (15) for protruding into the material (5) of the axial end faces of the filter element (3), preferably three rings of protrusions (15) being applied.

7. Filter according to any of the preceding claims, characterised in that the axial end faces (14) of the housing (2) are in the vicinity of the central communication ports (9, 10) provided with an annular groove (16), protruding away from the location of the filter element (3), the protrusion preferably being larger than that of any anular protrusion for protruding into the material (5) of the element (3).

8. Filter according to the preceding claim, characterised in that the depth of the groove (16) is significantly greater than the length of a end portion of a tube-like core (4) of the element (3) protruding form the axial end faces of the filter element (3), preferably at least 100% of the length thereof.

9. Filter according to any of the preceding claims, characterised in that an inner chamber (6, 7, 8) of the filter element (3) is provided with a venturi device (6) separating the chamber into two parts (7, 8) by an at least mainly axially extending wall (6), provided with venturi openings known per se.

10. Method of filtering oil for a mechanical device to be applied with treated oil, e.g. treated by a cooling device, a filtering device and/or a pump device, in which the supply and discharge lines to and from said mechanical device connect to a filter device, in particular a filter device (1) according to any of the preceding claims, in which the supply line passes through a central core (6, 7, 8) of the filter device (1) and in which the discharge line passes to through an eccentric chamber (17) of the device (1), the supply and discharge line being capable to mutually exchange oil via a filtering element (3) separating said supply and discharge line within the housing (2) of the device.