A blow-by heater includes a tube member allowing a blow-by gas to flow through, and opening in a downstream side, and the tube member is formed such that a thickness of the downstream side decreases toward an opening end.

RELATED APPLICATIONS

The present application is National Phase of International Application No. PCT/JP2015/053776 filed Feb. 12, 2015, and claims priority from Japanese Application No. 2014-024699, filed Feb. 12, 2014, the disclosure of which is hereby incorporated by reference herein in its entirety.

FIELD OF TECHNOLOGY

The present invention relates to a blow-by heater heating a blow-by gas of an engine, and preventing moisture and the like contained in the blow-by gas from attaching to or freezing at an inner wall portion of a pipe line.

BACKGROUND ART

In order to avoid environmental pollution, the blow-by gas of the engine is circulated to a gas-intake route of the engine without ejecting the blow-by gas of the engine to the atmosphere. Then, in such a blow-by-gas-circulation pipe line, in order to prevent the moisture and the like contained in the blow-by gas from attaching to or freezing at the inner wall portion of the pipe line, conventionally, there is widely used a blow-by gas heater.

FIG. 6is a schematic perspective view showing a conventional blow-by gas heater (corresponding to FIG. 11 of Japanese Patent Application Publication No. 2012-215137), andFIG. 7is a schematic cross-sectional view showing an example wherein the blow-by gas heater inFIG. 6is provided in a blow-by-gas circulation passage (corresponding to FIG. 9 of the Japanese Patent Application Publication No. 2012-215137).

As shown inFIG. 6andFIG. 7, a metal pipe55which becomes a passage of the blow-by gas includes a smooth wall portion55dand a partially cylindrical wall portion55e(seeFIG. 6). Therefore, a cross-sectional opening shape of the metal pipe55has a partially circular shape. A tip of the smooth wall portion55dand a tip of the partially cylindrical wall portion55eform a common opening end face of the metal pipe55, and a whole tip of the smooth wall portion55dbecomes a last portion55cof an opening face of the metal pipe55, and a center portion of the tip of the partially cylindrical wall portion55ebecomes a forefront portion55bof the opening face of the metal pipe55(seeFIG. 6andFIG. 7). The smooth wall portion55dis disposed in such a way as to face a heating source56which is an electronic ceramic heater through a heating-source attachment pipe54. In the heating source56, electric power is supplied through a plug member57.

Also, the metal pipe55includes a throttle portion55fformed such that a cross-sectional opening area thereof becomes smaller toward a tip side.

As shown inFIG. 7, a protruding portion55aof the metal pipe55is disposed in such a way as to protrude to a gas-intake-passage axis-line side al more than to an inner wall face61din a connecting pipe61. Moisture or oil of the blow-by gas attached to the metal pipe55flows to a tip side thereof (downward) through the protruding portion55aso as to promote the moisture or oil of the blow-by gas to become a water droplet or an oil droplet.

SUMMARY OF THE INVENTION

When moisture or oil of a blow-by gas becomes a water droplet or an oil droplet, even in a case wherein the water droplet or the oil droplet freezes and the like thereafter, if an ice block thereof has a small volume, it is possible to suppress damages and the like of, for example, a turbo impeller. The smaller a size of the water droplet or the oil droplet is, the more significant an effect thereof becomes.

The present inventor has diligently considered a shape of an opening end of a blow-by gas heater, and found that the size of the water droplet or the oil droplet (a splash) can be significantly reduced compared to a structure described in Japanese Patent Application Publication No. 2012-215137.

The present invention is invented based on the aforementioned knowledge. An object of the present invention is to provide a blow-by gas heater which can significantly reduce the size of the water droplet or the oil droplet (the splash) of the moisture or oil and the like included in the blow-by gas.

The present invention is a blow-by heater comprising a tube member allowing a blow-by gas to flow through, and opening in a downstream side, and the tube member is formed such that a thickness of the downstream side decreases toward the opening end.

According to the present invention, a thickness of the tube member allowing the blow-by gas to flow through is formed so as to reduce the thickness toward the opening end, so that in an opening end face of the tube member, an area where the moisture or the oil can remain is small so as to reduce a remaining amount of the moisture or the oil in the opening end face. As a result, the size of the water droplet or the oil droplet scattered from the opening end face is significantly reduced. Thereby, even in a case wherein the scattered water droplet or oil droplet freezes and the like thereafter, the ice block thereof has a small volume so as to suppress the damages and the like of, for example, the turbo impeller.

Preferably, the tube member is formed such that a thickness of a whole circumferential edge of the downstream side decreases toward the opening end. In that case, the remaining amount of the moisture or the oil in a whole circumference of the opening end face is reduced, so that the size of the water droplet or the oil droplet scattered from the opening end face is significantly reduced in the whole circumference of the opening end face.

Generally, for example, the tube member is formed by a metal pipe including a portion (a throttle portion) wherein a cross-sectional area thereof decreases toward the downstream side. For example, such metal pipe can be formed by processing a metal plate formed by press punching into a tube shape.

Then, as a specific example wherein the thickness of the downstream side of the metal pipe which is the tube member decreases toward the opening end, for example, in an inner circumferential side in a vicinity of the opening end of the metal pipe, there is formed a slope face portion such that a thickness in the vicinity of the opening end decreases toward the opening end.

Even in that case, preferably, in a whole circumferential edge on the inner circumferential side in the vicinity of the opening end of the metal pipe, there is formed the slope face portion such that a thickness of a whole circumferential edge in the vicinity of the opening end decreases toward the opening end. In that case, the remaining amount of the moisture or the oil in the whole circumference of the opening end face is reduced, so that the size of the water droplet or the oil droplet scattered from the opening end face is significantly reduced in the whole circumference of the opening end face.

The slope face portion may include a cross-sectional linear surface portion, or a cross-sectional curved surface portion. In a case wherein the slope face portion includes the cross-sectional curved surface portion, it is preferable to continue smoothly (without forming a corner portion) from an inner circumferential face of the metal pipe. In that case, the moisture or the oil inside the metal pipe can be smoothly guided further toward the opening end from the inner circumferential face of the metal pipe. On the other hand, even in a case wherein the slope face portion includes the cross-sectional curved surface portion, in the opening end side, it is preferable to form the corner portion together with an outer circumferential face of the metal pipe. In that case, due to an action of a surface tension in the corner portion, splashing of the moisture or the oil in the corner portion is promoted (it is difficult to remain) so as to reduce the size of the water droplet or the oil droplet further significantly.

BEST MODES OF CARRYING OUT THE INVENTION

Hereinafter, with reference to the attached drawings, an embodiment of the present invention will be explained in detail.

FIG. 1is a schematic perspective view showing a blow-by gas heater of one embodiment of the present invention;FIG. 2is a schematic cross-sectional view of the blow-by gas heater inFIG. 1; andFIG. 3is a schematic cross-sectional view showing a shape of a vicinity of an opening end of a metal pipe of the blow-by gas heater inFIG. 1.

As shown inFIG. 1andFIG. 2, in a blow-by gas heater10of one embodiment of the present invention, a metal pipe5which becomes a passage of a blow-by gas includes a smooth wall portion5dand a curved wall portion5e(seeFIG. 1). A cross-sectional opening shape of the metal pipe5has an approximately half-moon shape. A whole tip of the smooth wall portion5d, and a tip of the curved wall portion5eform a common opening end face5aof the metal pipe5(seeFIG. 2). The smooth wall portion5dis disposed in such a way as to directly face a heating source6which is an electronic ceramic heater. In the heating source6, there is supplied electric power through a plug member7. Also, the metal pipe5includes a throttle portion5fformed such that a cross-sectional opening area thereof becomes smaller toward a tip side.

The opening end face5aof the metal pipe5is disposed in such a way as to protrude into a gas-intake passage pipe (not shown in the drawings).

Moisture or oil of the blow-by gas attached to the metal pipe5is guided up to the opening end face5aso as to become a water droplet or an oil droplet in the opening end face5a, and scatter into an air flow flowing inside the gas-intake passage pipe (not shown in the drawings).

In the present embodiment, a thickness of a downstream side of the metal pipe5is formed in such a way as to decrease toward the opening end face5a. Specifically, as shown inFIG. 3, in an inner circumferential side in a vicinity of the opening end face5aof the metal pipe5, there is formed a slope face portion5gsuch that a thickness in the vicinity of the opening end face5adecreases toward the opening end face5a. As shown inFIG. 3, in the present embodiment, the slope face portion5gincludes a cross-sectional linear surface portion.

According to the present embodiment as described above, a thickness of the metal pipe5allowing the blow-by gas to flow through is formed in such a way as to decrease toward the opening end face5a, so that in the opening end face5aof the metal pipe5, an area where the moisture or the oil can remain is small so as to reduce a remaining amount of the moisture or the oil in the opening end face5a. As a result, a size of the water droplet or the oil droplet scattered from the opening end face5ais significantly reduced. Thereby, even in a case wherein the scattered water droplet or oil droplet freezes and the like thereafter, an ice block thereof has a small volume so as to suppress damages and the like of, for example, a turbo impeller.

Incidentally, in the present embodiment, preferably, the slope face portion5gis formed in a whole circumferential edge on the inner circumferential side in the vicinity of the opening end face5aof the metal pipe5such that a thickness of a whole circumferential edge in the vicinity of the opening end face5adecreases toward the opening end face5a. In that case, the remaining amount of the moisture or the oil in a whole circumference of the opening end face5ais reduced, so that the size of the water droplet or oil droplet scattered from the opening end face5ais significantly reduced in the whole circumference of the opening end face5a.

Next,FIG. 4is a schematic cross-sectional view showing another example of the shape of the vicinity of the opening end of the metal pipe5. In an example shown inFIG. 4which is different from an example shown inFIG. 3, there are respectively formed the slope face portion5gand a slope face portion5hon both of the inner circumferential side and an outer circumferential side in the vicinity of the opening end face5aof the metal pipe5.

Even in such an example, in the opening end face5aof the metal pipe5, the area where the moisture or the oil can remain is small, and the remaining amount of the moisture or the oil in the opening end face5ais reduced, so that the size of the water droplet or oil droplet scattered from the opening end face5ais significantly reduced. Thereby, even in the case wherein the scattered water droplet or oil droplet freezes and the like thereafter, the ice block thereof has the small volume so as to suppress the damages and the like of, for example, the turbo impeller.

According to experiments by the present inventor, an excellent splashing can be obtained provided that an angle is set up to approximately 45 degrees with reference to the opening end face5aof the metal pipe5per an inclination angle of the slope face portion5gand the slope face portion5h.

Next,FIG. 5is a schematic cross-sectional view further showing another example of the shape of the vicinity of the opening end of the metal pipe5. In an example shown inFIG. 5which is different from the example shown inFIG. 3, the slope face portion5gincludes a cross-sectional curved surface portion. More specifically, in the example shown inFIG. 5, while the slope face portion5gcontinues smoothly (without forming a corner portion) from an inner circumferential face of the metal pipe5, the slope face portion5gforms a corner portion5ctogether with an outer circumferential face of the metal pipe5.

In such an example, the moisture or the oil inside the metal pipe5can be smoothly guided further from the inner circumferential face of the metal pipe5, and due to an action of a surface tension in the corner portion5c, splashing of the moisture or the oil in the corner portion5cis promoted (it is difficult to remain) so as to reduce the size of the water droplet or the oil droplet further significantly.

Incidentally, a tube member is not limited to the tube member formed by processing a metal plate formed by press punching into a tube shape, and may be a tube member made of metal molded by die casting, or made of resin having high thermal conductivity molded by injection molding.

EXPLANATION OF SYMBOLS