Abstract: The width of at least one felt out of a plurality of felts (22 to 24) is formed of ceramic fibers superposed between two wire nets (26, 27) for a heater is made to be narrower than the width w of the wire nets for heater (26, 27), and the width of other felts (22, 24) is made to be the same as the width w of the wire nets (26, 27) for the heater. A superposed body (28) of the wire nets (26, 27) for a heater and the felts (22 to 24) is bent lengthwise to form a tube (21) having a petal shape in section, and a metal frame (31) is connected to both ends of the tube (21).

Abstract: In a diesel particulate filter unit 1 having a mat type filter member 15 which is laminated with inorganic fibers, a passing area altering means 30 is provided to alter the area of the exhaust gas G passing through the filter member 15 and the diesel particulate filter unit is so provided that a rise time of the trap efficiency can be shortened by speeding up it at the time of trap and after a high trap efficiency is obtained, PM trap can be continued with a high trap efficiency for a long time in preventing the filter from an increase of the pressurized damage.

Abstract: The width of at least one felt out of a plurality of felts (22 to 24) formed of ceramic fibers superposed between two wire nets (26, 27) for a heater is made to be narrower than the width w of said wire nets for heater (26, 27), and the width of other felts (22 to 24) is made to be the same as the width w of the wire nets (26, 27) for a heater. A superposed body (28) of the wire nets (26, 27) for a heater and the felts (22 to 24) is bended lengthwise to form a tube (21) having a petal shape in section, and a metal frame (31) is connected to both ends of the tube (21).

Abstract: The present invention provides a pre-combustion chamber-type engine, which optimizes the relation between the heat capacity of the pre-combustion chamber structure that forms the pre-combustion chamber and the displacement per cylinder and thereby improves the net average effective pressure and fuel efficiency. In this pre-combustion chamber-type engine, which has the pre-combustion chamber structure 15 installed in the cylinder head 3 so that it is surrounded by a heat insulating layer, the ratio of the heat capacity of the pre-combustion chamber structure to the displacement per cylinder is set to 0.35 cal/.degree.C..multidot.cm.sup.3 or less. Alternatively, the ratio of the heat capacity of the pre-combustion chamber structure to the inner surface area of the pre-combustion chamber is set to 0.55 cal/.degree.C..multidot.cm.sup.2 or lower.

Abstract: This heat insulating structure for swirl chambers enables the heat insulating capability of hot plugs, which form swirl chambers, to be improved by setting an area of contact surfaces of the hot plugs and walls surrounding the same to a proper level. A cylinder head is fixed on a cylinder block with a gasket interposed therebetween, and hot plugs constituting swirl chambers are provided in cavities in the cylinder head, whereby heat insulating air layers are formed between the hot plugs and the cavities. The hot plugs are formed out of a heat resisting ceramic material, and the sum of an area of contact portions of the outer surfaces of the hot plugs and the corresponding portions of the cavities and that of contact portions of the outer surfaces of the hot plugs and the corresponding portions of an upper surface of said cylinder block is set to not more than 1/5 of a total area of the outer surfaces of the hot plugs.