Abstract: Provided is a non-woven filtration material including a multilayer structure having a density gradient. The multilayer structure includes a coarse layer disposed at an upstream side of the non-woven filtration material and a dense layer disposed at a downstream side of the non-woven filtration material. The coarse layer and the dense layer are dry layers. The coarse layer contains 30% to 60% by weight of crimped conjugated fibers and contains 30% to 70% by weight of finer fibers. The crimped conjugated fibers have an average fiber diameter in a range from 15 ?m to 45 ?m. The finer fibers have an average fiber diameter that is in a range from 5 ?m to 20 ?m and smaller than the average fiber diameter of the conjugated fibers.

Abstract: Provided is a non-woven filtration material including a multilayer structure having a density gradient. The multilayer structure includes a coarse layer disposed at an upstream side of the non-woven filtration material and a dense layer disposed at a downstream side of the non-woven filtration material. The coarse layer and the dense layer are dry layers. The coarse layer contains 30% to 60% by weight of crimped conjugated fibers and contains 30% to 70% by weight of finer fibers. The crimped conjugated fibers have an average fiber diameter in a range from 15 ?m to 45 ?m. The finer fibers have an average fiber diameter that is in a range from 5 ?m to 20 ?m and smaller than the average fiber diameter of the conjugated fibers.

Abstract: A filter element comprises an oil-impregnated filtering member, and a transmission preventing layer formed on a downstream side of the filtering member, for restricting transmission of at least the carbon dusts from the oil-impregnated filtering member. The filtering member may be formed like a ridge-like-folded structure. The transmission preventing layer may be formed of a coating layer having a resistance against a viscous oil that is impregnated in the filtering member. This coating layer may be formed uniformly as a whole or the thickness or the content of the coating layer may be increased partially. A ventilation shutting-off member (filling layer) may be formed as the transmission preventing layer in the root portion areas of the ridge portions. The transmission preventing layer may comprise a resistant component that is insoluble in the oil that is impregnated in the filtering member.

Abstract: A filter element is made of a first filtering member, and a second filtering member that is arranged on a downstream side of the first filtering member and is impregnated with an oil. The first filtering member consists of a downstream wet layer that is impregnated with the oil, which is transferred by contact to the second filtering member, and an upstream dry layer that is not impregnated with the oil. A density of the first filtering member may be set smaller than that of the second filtering member.

Abstract: A filter element comprises an oil-impregnated filtering member, and a transmission preventing layer formed on a downstream side of the filtering member, for restricting transmission of at least the carbon dusts from the oil-impregnated filtering member. The filtering member may be formed like a ridge-like-folded structure. The transmission preventing layer may be formed of a coating layer having a resistance against a viscous oil that is impregnated in the filtering member. This coating layer may be formed uniformly as a whole or the thickness or the content of the coating layer may be increased partially. A ventilation shutting-off member (filling layer) may be formed as the transmission preventing layer in the root portion areas of the ridge portions. The transmission preventing layer may comprise a resistant component that is insoluble in the oil that is impregnated in the filtering member.

Abstract: A filter element is made of a first filtering member, and a second filtering member that is arranged on a downstream side of the first filtering member and is impregnated with an oil. The first filtering member consists of a downstream wet layer that is impregnated with the oil, which is transferred by contact to the second filtering member, and an upstream dry layer that is not impregnated with the oil. A density of the first filtering member may be set smaller than that of the second filtering member.