JPH0440049B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a filter material, and particularly to a filter material suitable for oil filters, air filters, etc. of internal combustion engines. [Technical Background of the Invention] The requirements for a filtration material used in automobile oil filters and air filters include having filtration performance that effectively removes particulates such as dust present in the fluid to be filtered; Moreover, it is especially important to continue to maintain good filtration performance over a long period of time. From this point of view, various filtration media have been proposed in the past, but conventional filtration media are not necessarily fully satisfactory in terms of simultaneously improving filtration performance and prolonging the service life. It's not a thing. For example, filter media in which a density gradient is created in the pressure direction of the filter paper by combining filter papers with different fiber densities are known (for example,
Publication No. 40778). These density gradient type filter media are formed so that the flow of the fluid to be filtered changes from coarse to dense in the direction from the upstream side to the downstream side, so the low density layer traps large particles and the high density layer Although it is excellent in that it can achieve a good sieving effect and improve life to some extent by trapping fine particles in the layer, it has the following drawbacks. (b) In conventional density gradient type filter media, the flow velocity when passing through the filter media is high, and dust is difficult to adhere (capture) due to mere contact, and the dust is firmly captured so that it penetrates into the deep layer. (So-called deep filtration), there is a problem that the filter material is easily clogged and the pressure loss increases considerably. (b) In conventional filter media, the porosity of the surface of the filter media on the upstream side of the fluid to be filtered is large, so dust is easily incorporated into the surface layer of the filter media, resulting in the formation of a dust cake layer on the surface layer of the filter media. The drawback is that it is difficult. Therefore, a filtration function (that is, a primal filter function) by the cake layer cannot be expected, and there are major limitations in achieving a long life. [Summary of the Invention] The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a filter material that is excellent in both filtration performance and long life. In order to achieve the above object, the filter material of the present invention has a density gradient in the thickness direction, and has a high density on the upstream side of the flow of the fluid to be filtered and a low density on the downstream side of the flow of the fluid to be filtered. On the high-density side surface of the filtration medium, the ends of the constituent fibers of the filtration medium are raised to protrude from the surface, and are sufficient to prevent sagging due to the weight of the dust cake layer when it is formed. It is characterized by being provided with a raised layer made of raised fibers having strength. [Specific Description of the Invention] The present invention will be described in more detail below with reference to the drawings. FIG. 1 is a conceptual diagram showing a cross section of the filter medium of the present invention. First, as shown in FIG. 1, in the filter material of the present invention, the diameter of the pores 2 formed in the base material 1 is from the upstream side with respect to the flow of the fluid to be filtered (in the direction of the arrow in the figure). It gradually becomes larger towards the downstream side. For example, when the filter medium is made of a fibrous material such as filter paper, the layer on the upstream side of the fluid to be filtered has a high fiber density, and the layer on the downstream side has a low fiber density. . In this case, the fiber density of the dense layer varies depending on the type of fluid to be filtered, but in the case of automobile oil filters, it is preferably in the range of 0.18 to 0.25 g/ ^cm3 , and the density of the coarse layer is 0.10 g/cm3. A range of 0.15 g/cm ³ is preferred. In this way, by configuring the inlet side of the fluid to be filtered to be dense and the outlet side to be coarse, relatively large particles are prevented from being taken into the filter medium, and conversely, a dust cake layer is formed on the surface of the filter medium. It has a great effect on promoting the formation of Furthermore, since the flow rate when passing through the filter medium tends to gradually slow down, relatively large dust particles that have passed through the dense layer tend to adhere to the inside of the filter medium. This has the effect that the flow resistance due to such dust adhesion does not increase significantly. Therefore, by reducing clogging inside the filter medium and utilizing the filtration action (primal filter function) by the cake layer formed on the surface, it is possible to improve filtration performance and life. Formation of such a cake layer is further promoted by providing the nap 3 on the upstream side of the fluid flow. That is, as shown in FIG. 1, the dust is captured like a rime by the raised layer composed of the raised naps 3, and a dust cake layer 4 is easily formed on the raised layer, resulting in good cake layer filtration. Demonstrated.
Further, since a certain space is formed between the cake layer 4 and the base material 1, the flow resistance can be kept low (that is, the pressure loss can be kept low). Furthermore, since the nap 3 is formed on the dense layer side of the base material 1, it has sufficient strength to prevent the nap from flattening when a cake layer is formed, which is also advantageous in this respect. It is. In addition, the above-mentioned raised layer is
Usually, the ends of the fibers constituting the filter medium may be configured to protrude from the surface of the filter medium in a fluffy state. The nap from the surface is sufficient to easily collect coarse dust particles and form a dust cake layer, and the density of the nap does not necessarily have to be as dense as that of a lawn. For example, when the size of the dust is 5 to 70 μm, it is sufficient that the size of the fiber protrusion is 80 to 300 μm. Next, a method for manufacturing the filter medium of the present invention will be explained. As constituent materials for the filter medium of the present invention, conventionally used natural fibers, synthetic fibers, and mixtures thereof can be used. Moreover, a binder made of phenolic resin or the like and other additives can also be used as necessary. Methods of creating a density gradient in the thickness direction of the filter media include a method of sequentially combining filter media with different densities and integrating them, or a method of supplying papermaking raw material slurry with different properties and fiber distribution in stages during the papermaking process. For example, a method of making paper using In addition, as a method for raising the surface of the filter material, for example, by supplying a flow of papermaking raw material slurry to one side of a papermaking net and at the same time suctioning it from the other side of the papermaking net, the longitudinal direction of the fibers is perpendicular to the papermaking surface. A raised layer can be effectively formed by orienting the material in the same direction. When the filter material of the present invention is used in an air filter or an oil filter for an internal combustion engine, it is preferable to form the filter material into a cylindrical shape with a chrysanthemum-like cross section in order to expand the filtration area, and furthermore, the end portion is provided with a disc-shaped metal plate. The filter structure is made by joining the two or by integrally molding or gluing a resin plate. [Examples] Manufacturing Example 1 An example of manufacturing a filter medium with a basis weight of 145 g/m ² and a paper thickness of 0.8 mm using a paper machine will be shown. A papermaking slurry having the following composition was prepared, and its concentration was controlled to 0.07% using a concentration controller. Linter...50% by weight Wood pulp...30-40% by weight Chemical fiber (4-8d, fiber length 6mm)
...10 to 20% by weight The above slurry was supplied to a papermaking net (70 mesh plain weave wire) via a pump while stirring with a multilayer impeller (slurry flow rate was 66 m/min). At the same time as the slurry was being supplied, suction was drawn from four suction boxes provided on the opposite side of the screen. The suction pressure is 13in Hg and 10in Hg from the upstream side of the slurry, respectively.
Hg, 5in Hg and 11in Hg. Next, the surface layer of the wet sheet on the papermaking wire was compressed with a roll and further dried in a drier to obtain a filter material. The obtained filter medium had a density gradient in the thickness direction, and a raised layer in which fibers were raised in a warp shape was formed on the surface of the filter medium on the high-density layer side. The pore diameter on the high-density layer side was 30 to 40 μm, the pore diameter on the low-density layer side was 70 to 100 μm, and the height of the raised fiber protrusion was 80 to 300 μm. Figure 2 shows
It is a micrograph of the cross section of the filter material thus obtained. Test Example 1 Using the filter material obtained in Production Example 1 above, JIS
- The filtration performance test described in D1611 was conducted.
The effective filtration area of the filter material at this time is ^1000cm2 ,
The test flow rate was 10/min, and the oil temperature was 80°C. After 55 hours had passed from the start of the test, a dust cake layer with a thickness of about 0.3 to 1 mm was formed on the surface of the filter medium (upstream side). Compared to conventional filters, the rate of increase in pressure loss is also lower, and the lifespan has been improved by approximately 180%. Figure 3 shows the above filter material A and the conventional filter material B.
(The filter material described in Japanese Patent Publication No. 54-40778) is a graph showing the test results when the above-mentioned filtration performance test was conducted. In this fluff, the solid line represents the change in incremental pressure drop and the dotted line represents the filtration efficiency. Third
As is clear from the figure, the filter medium of the present invention can gradually increase the pressure loss due to dust capture in the fluid to be filtered without any change in filtration efficiency, and therefore the filter medium can have a long lifespan. can be further improved. Production Example 2 Two types of filter media were produced using a paper machine (rotoformer). The compositions of these two types of papermaking slurries are as follows. Linter: 50% by weight Wood pulp: 15% by weight Other natural fibers: 10% by weight Chemical fibers: 25% by weight A filtration material having a density gradient in the thickness direction) and a filtration material according to an example of the present invention (a filtration material having a density gradient in the thickness direction and a raised layer) were manufactured. In both cases, 70-mesh plain weave wire was used as the paper-making net.

【table】

[Table] Test Example 2 A filtration performance test was conducted according to JIS-D1611 using the filter media according to the above examples and comparative examples.
The test conditions are as follows. Form of filter media Outer diameter: 74cm Height: 57cm Folding width: 20cm Filtration area 1000cm ² Test oil SAE〓30 motor oil (manufactured by Idemitsu Oil Co., Ltd.) Test oil temperature 80±3℃ Test flow rate 10 liters/min Dust SOFT C -2A (JIS-D1611 standard product) Dust input amount 0.6 g/hour Tank oil amount 5000 cm ³ The results of the above filtration performance test were as follows.

〔Effect of the invention〕

The filter medium of the present invention has a density gradient in the thickness direction, and has a high density on the upstream side of the fluid to be filtered and a low density on the downstream side, and a raised layer is formed on the surface of the filter medium on the high density side. Therefore, a dust cake layer is easily formed on the surface of the filter medium, and the primal filter effect of this cake layer can improve filtration performance and life at the same time. Also,
Relatively large particles in the fluid can be effectively captured on the surface of the filter medium and prevented from being taken into the inside of the filter medium, so clogging can be suppressed to a lower level than in conventional filter media.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of a cross section of a filter medium according to the present invention, FIG. 2 is a micrograph showing the shape of fibers in a cross section of a filter medium according to an embodiment of the present invention, and FIG.
It is a graph which shows the comparative test result of the filtration performance about the conventional filter medium and the filter medium of this invention. 1... Base material, 2... Pores, 3... Raised, 4...
Dust cake layer.

Claims (1)

[Claims] 1 In a filter medium having a density gradient in the thickness direction, the upstream side of the flow of the fluid to be filtered has a high density and the downstream side has a low density, and the constituent fibers of the filter medium are on the surface of the high density side of the filter medium. It is characterized by having a raised layer formed by having the ends thereof protruding from the surface and having sufficient strength to prevent the dust cake layer formed thereon from sagging due to the weight of the raised layer. and filter media.