JP2017082591A - Blow-by gas recirculation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent water due to moisture contained in external air from freezing in a blow-by gas passage.SOLUTION: A blow-by gas recirculation device comprises: a passage forming member 23 which is arranged outside of an engine body and forms a passage where blow-by gas is distributed therein; a heat insulation cover 30 which covers the passage forming member; and a water-resistant film 71 which forms outer surface sections 37, 38 39 of the heat insulation cover and coats surface sections of the heat insulation cover except a lower surface section 42 thereof.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a blowby gas recirculation device, and more particularly to a blowby gas recirculation device suitable for a vehicle internal combustion engine.

  In a vehicle internal combustion engine, a blow-by gas recirculation device (PCV (Positive Crankcase Ventilation) system) is known in which blow-by gas leaked into a crankcase from a gap between a cylinder and a piston is recirculated to an intake system and burned. In this blow-by gas recirculation device, the engine body and the intake system components are connected to each other by piping or the like outside the engine body, and the blow-by gas is circulated through a blow-by gas passage inside the piping or the like.

JP 2014-185540 A

  In places such as cold districts where the outside air temperature is low, there is a problem that water contained in the blow-by gas is solidified or frozen in an internal passage such as a pipe exposed to the outside air, and the passage is blocked. For this reason, measures are taken to cover piping and the like with a heat insulating cover, to keep the inside of the passage warm, and to prevent moisture freezing in the passage.

  However, the heat insulating cover is exposed to moisture (rain water or the like) contained in the outside air (running wind or the like). When the moisture in the outside air adheres to the heat insulating cover and penetrates into the heat insulating cover, the water freezes in the heat insulating cover when the outside air temperature becomes the freezing point or lower, thereby cooling the piping and the like. Due to this, there is a possibility that moisture in a passage such as a pipe freezes.

  Accordingly, the present invention has been made in view of such circumstances, and an object thereof is to provide a blow-by gas recirculation device that can suppress moisture freezing in the blow-by gas passage due to moisture contained in the outside air.

According to one aspect of the invention,
A passage defining member disposed outside the engine body and defining a passage through which blow-by gas flows;
A heat insulating cover covering the passage defining member;
A water-resistant film that is an outer surface portion of the heat insulating cover and is coated on a portion excluding a lower surface portion of the heat insulating cover;
A blow-by gas recirculation device is provided.

Preferably, the engine body includes a head cover,
The passage defining member includes a cover upper pipe disposed on the head cover,
The heat insulating cover includes a pipe cover that covers the pipe on the cover.

Preferably, the passage defining member includes an extraction member that is disposed on the head cover and extracts blow-by gas from the head cover.
The pipe cover also covers the take-out member together with the pipe on the cover.

Preferably, the engine body includes a crankcase,
The passage defining member includes an oil separator that is installed on a side portion of the crankcase and separates oil from blow-by gas,
The heat insulating cover includes a separator cover that covers the oil separator.

Preferably, the oil separator includes a separator main body, a separator cap detachably attached to the separator main body, and a protruding tube protruding from the separator main body.
The separator cover is divided into a main body covering portion that covers the separator main body, a cap covering portion that covers the separator cap, and a tube covering portion that covers the protruding pipe.

  ADVANTAGE OF THE INVENTION According to this invention, the outstanding effect that the water | moisture content freezing in the blowby gas channel | path resulting from the water | moisture content contained in external air can be suppressed is exhibited.

It is a schematic perspective view which shows the internal combustion engine from which the heat insulation cover was removed. It is a schematic perspective view which shows the internal combustion engine with which the heat insulation cover was attached. It is a schematic perspective view which shows the attachment state of a separator cover. It is a left view which shows the attachment state of a separator cover. It is a top view of a pipe cover. It is VI-VI sectional drawing of FIG. It is a schematic perspective view which shows the main body coating | coated part of a separator cover. It is VIII-VIII sectional drawing of FIG. It is a schematic perspective view which shows the cap coating | coated part of a separator cover. It is XX sectional drawing of FIG. It is a schematic perspective view which shows the pipe | tube coating | coated part of a separator cover. It is a XII arrow directional view of FIG.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows an internal combustion engine according to an embodiment of the present invention, and particularly shows a state when a heat insulating cover is removed. The internal combustion engine (engine) 1 is a multi-cylinder compression ignition internal combustion engine for a vehicle, that is, a diesel engine. The illustrated example shows an in-line 6-cylinder engine. However, the engine type, application, cylinder arrangement type, number of cylinders, etc. are arbitrary. For convenience, the front, rear, left, right, up and down directions of the engine 1 are defined as shown. In this embodiment, these directions coincide with the directions of the vehicle. However, each direction in the figure does not necessarily coincide with each direction of the vehicle.

  The engine 1 includes an engine body 2. The engine body 2 includes a cylinder block 3, a crankcase 4 integrally formed at the lower part of the cylinder block 3, a ladder frame 5 attached to the lower part of the crankcase 4, and an oil pan attached to the lower part of the ladder frame 5. 6, a cylinder head 7 attached to the upper part of the cylinder block 3, and a head cover 8 attached to the upper part of the cylinder head 7. Each part of the engine body 2 is a structural part. Note that the cylinder head 7 and the head cover 8 are shown by being transmitted through phantom lines. In the engine body 2, movable parts such as a piston, a crankshaft, and a valve (not shown) are provided.

  The engine 1 also includes an intake pipe 9. The intake pipe 9 is connected to the cylinder head 7 via a compressor and an intake manifold of a turbocharger (not shown). The intake air into the intake pipe 9 is indicated by a white arrow in the figure. The engine 1 also includes exhaust system parts (not shown), but description thereof is omitted here.

  The engine 1 also includes a blow-by gas recirculation device A for circulating the blow-by gas in the crankcase 4 to the intake system. Hereinafter, this blow-by gas recirculation apparatus A will be described.

  The blow-by gas recirculation device A is generally configured to return the blow-by gas in the crankcase 4 to the intake pipe 9 through a passage defining member outside the engine body 2. Accordingly, the blow-by gas recirculation device A includes a passage defining member that is disposed outside the engine body 2 and defines a passage through which the blow-by gas flows.

  Specifically, the blow-by gas recirculation device A connects an oil separator 11 that is installed on a side portion (left side surface portion) of the crankcase 4 and is supplied with blow-by gas in the crankcase 4, and the oil separator 11 and the intake pipe 9. And a feed pipe 12 for sending blow-by gas after the oil is separated by the oil separator 11 to the intake pipe 9. The blow-by gas recirculation apparatus A connects the take-out member 13 that is arranged on the head cover 8 and takes out the blow-by gas from the head cover 8, the take-out member 13 and the oil separator 11, and sends the blow-by gas from the take-out member 13 to the oil separator 11. And a transfer pipe 14. The flow direction of blow-by gas is indicated by black arrows in the figure.

  The oil separator 11 is for separating oil contained therein from blow-by gas supplied from the crankcase 4. The oil separator 11 includes a cylindrical separator body 15, a separator cap 16 detachably attached to the top of the separator body 15, and two projecting pipes 17 and 18 projecting from the separator body 15.

  The separator body 15 introduces blow-by gas in the crankcase 4 through an introduction pipe (not shown). An oil separation chamber is formed inside the separator body 15, and oil is separated from blow-by gas in the oil separation chamber. The separated oil is returned to the ladder frame 5 through the oil return pipe 19. A filter is provided on the downstream side of the oil separation chamber, and the blow-by gas separated from the oil is filtered by passing through the filter. The filtered blow-by gas is sent to the delivery pipe 12 connected thereto through the first projecting pipe, that is, the delivery projecting pipe 17.

  The separator cap 16 is fixed by being coaxially screwed into the top opening of the separator body 15. The filter can be replaced by removing the separator cap 16.

  The delivery projecting tube 17 projects from the left side surface portion of the separator body 15 toward the left side, and is then bent obliquely upward. The upstream end portion 12A of the delivery pipe 12 is fitted and connected to the upward tip portion from the outside. The second projecting tube, ie, the projecting projecting tube 18 is arranged in parallel obliquely below and behind the delivery projecting tube 17 and, like the projecting projecting tube 17, projects from the left side surface portion of the separator body 15 toward the left side. Then, it is bent obliquely upward. The downstream end portion 14B of the transfer pipe 14 is fitted and connected to the upward leading end portion from the outside.

  A bracket 20 is attached to the separator body 15 with bolts or the like in advance, and the oil separator 11 is fixed to the side surface of the crankcase 4 by attaching the bracket 20 to the side surface of the crankcase 4 with bolts or the like.

  The delivery pipe 12 generally extends upward from the upstream end portion 12A as it goes from the upstream side to the downstream side, and is then bent at a substantially right angle toward the head cover 8 side (right side), and then bent into a crank shape. It extends along the longitudinal direction (front-rear direction) above, is bent to the right side and the lower side, and is finally connected to the connection portion 9A of the intake pipe 9 at the downstream end portion 12B. Accordingly, the delivery pipe 12 includes a rising portion 21 extending upward from the upstream end portion 12A, a first extending portion 22 extending in the left-right direction from the downstream end portion of the rising portion 21 toward the head cover 8 side, and a first extending portion. The crank part 24 formed in the downstream end part of 22 and the 2nd extension part 23 extended in the front-back direction toward the front from the downstream end part of the crank part 24 are provided. In particular, the second extending portion 23 is disposed on the head cover 8 and corresponds to the cover upper pipe of the present invention.

  The delivery pipe 12 is formed of a resin hose having higher heat insulation than a metal pipe. For this reason, it is advantageous to insulate the pipe passage from the outside air and suppress moisture freezing in the passage. The delivery pipe 12 may be a single unit structure or may be a structure divided and connected in the longitudinal direction.

  The transfer pipe 14 has an upstream end portion 14 </ b> A connected to the take-out member 13 and a downstream end portion 14 </ b> B connected to the transfer projecting pipe 18. In general, the transfer pipe 14 extends in the left direction from the upstream side toward the downstream side, and then is bent downward, is lowered, and is finally connected to the transfer projecting pipe 18. Similarly to the delivery pipe 12, the transfer pipe 14 is formed of a resin hose having high heat insulation.

  The above-described passage defining member refers to all members that are disposed outside the engine body 2 and that define a passage through which blow-by gas flows. The passage here includes a chamber or a chamber in which blow-by gas is stored. Accordingly, the passage defining member of this embodiment includes the oil separator 11, the delivery pipe 12, the takeout member 13 and the transfer pipe 14.

  In the present embodiment, the delivery pipe 12 and the oil separator 11 are covered with a heat insulating cover to prevent moisture freezing inside them.

  FIG. 2 shows the engine 1 with a heat insulating cover attached. As illustrated, the heat insulating cover includes a pipe cover 30 that covers the second extending portion 23 of the delivery pipe 12 and a separator cover 50 that covers the oil separator 11. The separator cover 50 in the attached state is shown enlarged in FIGS.

  As shown in detail in FIGS. 5 and 6, the pipe cover 30 extends in the longitudinal direction (front-rear direction) of the second extension portion 23 so as to cover substantially the entire second extension portion 23 of the delivery pipe 12 from above. It has an extended shape and has a substantially inverted U-shaped cross-sectional shape. The pipe cover 30 extends rearward and covers the takeout member 13 together with the second extending portion 23. After the pipe cover 30 is placed on the second extending portion 23 and the take-out member 13 from above, the head cover 8 is formed by a plurality of (three) brackets 31, 32, 33 having a cantilevered U shape or a U shape. It is fixed so as to be pressed against the upper surface of the plate. The brackets 31, 32 and 33 are fixed to the upper surface of the head cover 8 by bolts 35 after being fitted into a bracket groove 34 provided in the pipe cover 30 from above. A pipe groove 36 for receiving the second extension 23 is formed inside the pipe cover 30.

  The pipe cover 30 is integrally formed of a foamed resin material having high heat insulating properties, is formed to be relatively thick, and has flexibility. In this embodiment, polyurethane foam is used as the foamed resin material, but this can be changed as appropriate.

  The delivery pipe 12 and the transfer pipe 14 are detachably fixed to the engine body 2 with clips or the like at appropriate places.

  As shown in FIGS. 2 to 4, the separator cover 50 includes a main body covering portion 51 that covers the separator main body 15, a cap covering portion 52 that covers the separator cap 16, and a tube covering portion 53 that covers the protruding tubes 17 and 18. It is divided and configured. As can be seen from FIG. 1, the oil separator 11 has a relatively complicated outer shape. Thus, by making the separator cover 50 into a divided structure, it is possible to cover the complicated outer shape of the oil separator 11 without any problem and to improve the heat insulating property with respect to the oil separator 11. Similarly to the pipe cover 30, the separator cover 50, or the main body covering portion 51, the cap covering portion 52, and the tube covering portion 53, which are constituent parts thereof, are integrally formed of a foamed resin material having high heat insulating properties (polyurethane foam in this embodiment). It is relatively thick and has flexibility.

  As shown in detail in FIGS. 7 and 8, the main body covering portion 51 is formed in a substantially cubic shape as a whole, and includes a fitting recess 54 for fitting the separator main body 15, and the protruding tubes 17 and 18. An elongated hole portion 55 to be passed, a slit portion 56 that is pushed and spread when the main body covering portion 51 is put on the separator body 15 from the left side, and allows the projecting tubes 17 and 18 to pass temporarily; And a hole 57 through which the oil return pipe 19 is inserted.

  As shown in detail in FIGS. 9 and 10, the cap covering portion 52 is formed in a substantially cylindrical shape whose upper end is closed as a whole, and a fitting recess 58 for fitting the separator cap 16, and a bracket And a cut-out portion 59 for avoiding interference with 20.

  As shown in detail in FIGS. 11 and 12, the tube covering portion 53 includes a main body portion 53A, a first fitting recess 60 formed in the main body portion 53A and into which the delivery projecting pipe 17 is fitted, and the main body portion 53A. A second fitting recess 61 that is fitted with the projecting pipe 18 for transfer, and a shielding wall portion 62 that is attached to the main body portion 53A and shields rainwater and the like coming from the front of the vehicle and riding on the traveling wind. Have The first fitting recess 60 and the second fitting recess 61 are formed so as to receive portions from the upstream end portion to the bent portion of the delivery projecting tube 17 and the transfer projecting tube 18, respectively. The shielding wall portion 62 is attached to the front surface portion of the main body portion 53A and protrudes downward from the main body portion 53A like a hanging wall. The shielding wall portion 62 can prevent rainwater and the like from entering the inside of the main body covering portion 51 located below the main body portion 53A as much as possible (see FIG. 4). In the present embodiment, the shielding wall 62 is formed separately from the main body 53A, and is adhered to the main body 53A with an adhesive or the like. However, the shielding wall 62 may be formed integrally with the main body 53A.

  Regarding the method of attaching the separator cover 50, first, the main body covering portion 51 is attached over the separator main body 15, and then the cap covering portion 52 is attached over the separator cap 16. Thereafter, the tube covering portion 53 is attached over the protruding tubes 17 and 18. Finally, the entire body covering portion 51, cap covering portion 52, and tube covering portion 53 are bound together with the oil separator 11 by a plurality of binding bands (not shown). Thereby, the separator cover 50 is detachably fixed to the oil separator 11.

  By the way, the heat insulation cover (the pipe cover 30 and the separator cover 50) of this embodiment is made of a material that has high heat insulation properties, such as a foamed resin material, but at the same time can penetrate water. The heat insulating cover is exposed to moisture (rain water, etc.) contained in the outside air (running wind, etc.) in addition to the outside air. When the moisture in the outside air adheres to the heat insulating cover and penetrates into the heat insulating cover, the water freezes in the heat insulating cover when the outside air temperature becomes the freezing point or lower, and the passage defining member (second extending portion 23 and oil) The separator 11) is cooled. As a result, the moisture contained in the blow-by gas may freeze in the blow-by gas passage of the passage defining member.

  For example, if water vapor contained in the outside air itself or rainwater that arrives on the wind during running of the vehicle penetrates into the heat insulation cover, the moisture that penetrates when the outside temperature falls below the freezing point is insulated. Freezing in the cover, which may directly contact the passage defining member and significantly cool the passage defining member. Then, the passage in the passage defining member is also below the freezing point, and as a result, the water in the passage is frozen, and there is a risk that the passage will be blocked.

  Therefore, in this embodiment, a water-resistant film that covers the outer surface portion of the heat insulating cover is provided. Thereby, the penetration | invasion of the water | moisture content in the heat insulation cover can be suppressed, and the water freezing in the blowby gas channel | path resulting from the water | moisture content contained in external air can be suppressed effectively.

  The water-resistant film is made of a thin and flexible resin film that does not penetrate water. Although it consists of a polyurethane film in this embodiment, the material can be changed suitably. The film can be attached to the outer surface portion of the heat insulating cover by an adhesive layer previously formed on the back surface or by an adhesive that is separately applied. Since the film is flexible, it can follow the complicated outer surface shape of the heat insulating cover. You may install by forming a film with a heat-shrinkable film and heat-shrinking a film.

  Here, the film is covered on the outer surface portion of the heat insulating cover exposed to the outside, and is not covered on the inner surface portion of the heat insulating cover not exposed to the outside. Moisture in the outside air mainly adheres to the outer surface of the heat insulating cover exposed to the outside and penetrates from there, so if you coat the outer surface of the heat insulating cover with a film, the film covers the inner surface of the heat insulating cover. This is because the desired purpose can be achieved without this.

  Here, the outer surface portion of the heat insulating cover refers to a surface portion of the heat insulating cover exposed to the outside or a surface portion visible from the outside in the heat insulating cover in the attached state. The surface portion that does not belong to the outer surface portion is the inner surface portion. The inner surface portion refers to a surface portion of the heat insulating cover that is not exposed to the outside or a surface portion that is not visible from the outside in the heat insulating cover in an attached state. Typically, the inner surface portion is a surface portion facing or contacting the passage defining member covered by the heat insulating cover.

  Further, the film is not coated on the lower surface portion of the heat insulating cover. A lower surface part is a surface which is located in the lower end part of a heat insulation cover, and faces a perpendicular direction downward. Therefore, in the heat insulating cover, even if the portion belongs to the outer surface portion, the portion belonging to the lower surface portion is not covered with the film. In short, the water-resistant film of the present embodiment is coated on the outer surface portion of the heat insulating cover and excluding the lower surface portion of the heat insulating cover. More specifically, the water-resistant film of this embodiment is covered over the entire part.

  The reason why the film is not coated on the lower surface portion of the heat insulating cover is to secure a separation or evaporation route of moisture that has penetrated into the heat insulating cover. In other words, if the entire outer surface of the heat insulating cover is covered with a film, if moisture penetrates into the heat insulating cover, the water cannot be easily removed (that is, drying of the heat insulating cover is delayed), and freezing in the cover is caused. It will be difficult to resolve it early. In addition, the moisture in the outside air often falls on the heat insulating cover from above, flows down along the heat insulating cover, and drops from the lower end of the heat insulating cover in many cases. For this reason, when a film non-installation part is provided in the outer surface part other than the lower surface part of the heat insulating cover, moisture in the outside air permeates into the heat insulating cover from the part, which is not preferable. On the other hand, even if a film is not installed on the lower surface of the heat insulating cover, moisture in the outside air immediately drops and detaches at this height position, so there is no particular problem. Therefore, based on the above consideration, in this embodiment, it was decided not to provide a film in the lower surface part of a heat insulation cover. As a result, even if moisture penetrates into the heat insulating cover, it can be removed quickly, and moisture freezing in the blow-by gas passage can be more effectively suppressed. In addition, since the installation area of a film is also reduced, it is advantageous in terms of production and cost.

  Hereinafter, the suitable installation example of a water-resistant film is demonstrated. 5 and 6 show examples of the film 71 installed on the pipe cover 30. FIG. In FIG. 5, the installation site | part (covering site | part) of the film 71 is represented by the dot area | region. In FIG. 6, for convenience, the film 71 is shown slightly spaced from the outer surface portion of the pipe cover 30, but in actuality, the film 71 is coated in close contact with the outer surface portion of the pipe cover 30. 2 to 4, the installation site of the film 71 on the pipe cover 30 is represented by a dot area.

  As can be seen from these drawings, the film 71 is covered on the upper surface portion 37, the left side surface portion 38, the right side surface portion 39, the front surface portion 40 and the rear surface portion 41 of the pipe cover 30, but is covered on the lower surface portion 42. Absent. Further, the film 71 is not covered with the inner surface portion of the pipe cover 30, specifically, the surface portion of the pipe groove 36.

  By providing such a film 71, the moisture in the outside air that tends to adhere to the pipe cover 30 can be blocked by the film 71, and the penetration of moisture in the outside air into the heat insulating cover, and hence the freezing in the cover, can be suppressed or prevented. Can do. And the freezing of the water | moisture content in the blowby gas channel | path resulting from this can be suppressed effectively.

  Further, since the film 71 is not provided on the lower surface portion 42, even if moisture penetrates into the pipe cover 30, it can be removed and dried quickly, and freezing in the cover and thus freezing in the blow-by gas passage can be performed. Can be more effectively suppressed.

  7 and 8 show examples of the film 72 placed on the main body covering portion 51 of the separator cover 50. FIG. Similarly to the above, the installation site of the film 72 is represented by a dot area in FIG. 7, and details are shown in FIG. In FIG. 8, the film 72 shows only the cross section. 2 to 4, the installation site of the film 72 on the main body covering portion 51 is represented by a dot area.

  Also for the main body covering portion 51, the film 72 is covered on the outer surface portion of the main body covering portion 51 and is not covered on the inner surface portion. Specifically, the film 72 is not covered with the inner surface portion 63 and the bottom surface portion 64 of the fitting recess 54 and the inner surface portion of the hole portion 57. The film 72 is not covered with the lower surface portion 65 of the main body covering portion 51. The effect of this installation example is the same as that of the installation example to the pipe cover 30 mentioned above.

  FIG. 9 and FIG. 10 show an installation example of the film 73 on the cap covering portion 52 of the separator cover 50. Similarly to the above, the installation site of the film 73 is represented by a dot area in FIG. 9, and details are shown in FIG. In FIG. 10, the film 73 shows only its cross section. 2 to 4, the installation site of the film 73 on the cap covering portion 52 is represented by a dot area.

  Also for the cap covering portion 52, the film 73 is covered on the outer surface portion of the cap covering portion 52 and is not covered on the inner surface portion. Specifically, the film 73 is not covered with the inner surface portion of the fitting recess 58. The film 73 is not covered with the lower surface portion 66 of the cap covering portion 52. The effect of this installation example is the same as that of the installation example to the pipe cover 30 described above.

  FIGS. 11 and 12 show an installation example of the film 74 on the tube covering portion 53 of the separator cover 50. Similarly to the above, the installation site of the film 74 is represented by a dot area in FIG. 11, and details are shown in FIG. In FIG. 12, the film 74 shows only its cross section. 2 to 4, the installation site of the film 74 on the tube covering portion 53 is represented by a dot area.

  Also for the tube covering portion 53, the film 74 is covered on the outer surface portion of the tube covering portion 53 and is not covered on the inner surface portion. Specifically, the film 74 is not covered with the inner surface portions of the first fitting recess 60 and the second fitting recess 61. The film 74 is not covered with the lower surface portion 67 of the tube covering portion 53. The effect of this installation example is the same as that of the installation example to the pipe cover 30 described above.

  As mentioned above, although embodiment of this invention was described in detail, other embodiment is possible for this invention. For example, the separator cover 50 may be a single structure instead of a divided structure. At least one of the other part of the delivery pipe 12 and the transfer pipe 14 may be covered with a heat insulating cover coated with a water resistant film.

  The embodiment of the present invention is not limited to the above-described embodiment, and includes all modifications, applications, and equivalents included in the concept of the present invention defined by the claims. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention.

A Blow-by gas recirculation device 2 Engine body 4 Crankcase 8 Head cover 11 Oil separator 12 Delivery pipe 13 Extraction member 15 Separator body 16 Separator caps 17 and 18 Projection pipe 23 Second extending part 30 Pipe cover 37 Upper surface part 38 Left side part 39 Right side Surface 40 Front surface 41 Rear surface 42, 65, 66, 67 Lower surface 50 Separator cover 51 Main body cover 52 Cap cover 53 Tube cover 71, 72, 73, 74 Film

Claims (5)

A passage defining member disposed outside the engine body and defining a passage through which blow-by gas flows;
A heat insulating cover covering the passage defining member;
A water-resistant film that is an outer surface portion of the heat insulating cover and is coated on a portion excluding a lower surface portion of the heat insulating cover;
A blow-by gas recirculation device comprising: The engine body includes a head cover,
The passage defining member includes a cover upper pipe disposed on the head cover,
The blow-by gas circulation device according to claim 1, wherein the heat insulating cover includes a pipe cover that covers the pipe on the cover. The passage defining member includes an extraction member that is disposed on the head cover and extracts blow-by gas from the head cover.
The blow-by gas recirculation device according to claim 2, wherein the pipe cover covers the take-out member together with the pipe on the cover. The engine body includes a crankcase,
The passage defining member includes an oil separator that is installed on a side portion of the crankcase and separates oil from blow-by gas,
The blow-by gas circulation device according to any one of claims 1 to 3, wherein the heat insulating cover includes a separator cover that covers the oil separator. The oil separator includes a separator body, a separator cap detachably attached to the separator body, and a protruding tube protruding from the separator body,
The separator cover is configured by being divided from a main body covering portion that covers the separator main body, a cap covering portion that covers the separator cap, and a tube covering portion that covers the protruding pipe. The blowby gas recirculation device described.

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