JP2025093046A - engine - Google Patents

Abstract

To provide technique capable of surely heat-insulating a manifold converter equipped with a catalyst case.SOLUTION: A manifold converter 25 is constituted by a catalyst case 26, a joint 27, and an outlet pipe 28. A heat insulating device is constituted by upper and lower main insulators 42, 43 covering the catalyst case 26 and the joint 27, and inner and outer sub insulators 63, 64 covering the outlet pipe 28. An engine includes a cooling fan which blows air toward an inlet side end of the catalyst case 26, and an air introduction port (front cutout) 44 is opened to an inlet side end plate 42a of the first main insulator 42. Cooling air is sent to a space surrounded by the insulators 42, 43, 63, 64 from the cooling fan via the front cutout 44, and the catalyst case 26 and the outlet pipe 28 can be cooled. Cooling is performed by the cooling fan, and therefore, the manifold converter 25 can be accurately cooled even in the engine arranged in a rear compartment of a vehicle body where cooling by travel wind cannot be expected.SELECTED DRAWING: Figure 3

Description

The present invention relates to an engine characterized by a heat-shielding structure for exhaust system components, and is particularly suited to automobile engines.

In engines such as gasoline engines, exhaust system components such as the exhaust manifold and catalyst case become very hot, so the exhaust system components are surrounded by insulators to insulate them from heat. Alternatively, because catalysts for purifying exhaust gas require a certain degree of high temperature to become active, insulators are also used to function as heat retaining materials.

As an example, Patent Document 1 discloses that a vertical engine is placed horizontally in the engine compartment at the front of the vehicle with rear exhaust, and that a group of components including a catalyst case (straight catalyst) connected to the exhaust manifold are surrounded by upper and lower insulators, with a running wind intake opening opened in the upper insulator.

In this patent document, the insulator basically functions as a heat-retaining material that prevents the temperature of the catalyst from dropping, and if the temperature of the catalyst case becomes higher than necessary while the vehicle is moving, it takes in the wind from the vehicle and cools the exhaust manifold and catalyst case. Furthermore, there is a gap between adjacent insulators to allow the wind to escape.

JP 2017-165123 A

The engine in Patent Document 1 is mounted horizontally in an engine room (engine compartment) located at the front of the vehicle body with rear exhaust, and when the vehicle is traveling at a certain speed, it is possible for some of the wind that flows around to the rear of the engine and out under the floor to enter the wind intake provided in the insulator. However, when the vehicle is stopped or traveling slowly, such as when driving slowly in a traffic jam, the wind cannot hit the exhaust manifold or catalyst case.

Therefore, if the vehicle cannot take in airflow while driving in a hot environment such as summer, there is concern that the interior enclosed by the insulator will overheat. In other words, there is concern that the insulator may end up having the opposite effect.

It is also possible to place the engine in an engine room at the rear of the vehicle, but in this case, it is not possible to take in the wind from driving into the engine room, making it very difficult to control the temperature of the exhaust manifold and catalyst case using insulators.

The present invention aims to disclose technology that improves this current situation.

The present invention is directed to an engine, the engine comprising:
"The engine is equipped with an exhaust system member having an upstream end fixed to the exhaust side of a cylinder head constituting the engine body and an exhaust pipe connected to its downstream end, a cooling fan that blows cooling air toward the exhaust system member, and a heat shield that surrounds the exhaust system member."
This is the basic configuration. In this basic configuration,
"The cooling fan is arranged to blow cooling air from a direction along the exhaust side of the engine body,
The heat shield device includes a plurality of insulators arranged to sandwich at least a portion of the exhaust system member, and the space surrounded by the plurality of insulators has an air inlet opening on the side of the cooling fan and an outlet opening on the side opposite the cooling fan.
The structure is as follows.

The present invention can be developed in various ways. For example, in claim 2,
"The exhaust system member is a manifold in which a joint or an exhaust manifold fixed to the cylinder head, a catalyst case containing a catalyst, and an outlet pipe connected to the catalyst case are integrated into a single unit,
The heat shield device is composed of a plurality of main insulators surrounding the joints of the manifold or the exhaust manifold and the catalyst case, and a plurality of sub-insulators surrounding the outlet pipe of the exhaust manifold, and ventilation gaps are provided between adjacent sub-insulators and between the main insulators and the sub-insulators.
The following configuration is adopted.

Now, the catalyst case has a cylindrical shape, and in the case of a vertical engine, it is often arranged with its axis extending almost vertically. On the other hand, in the case of engines for cab-over type automobiles, where the cylinder bore axis is largely slanted toward the horizontal side, the catalyst case is often arranged in a roughly horizontal position with its axis extending in the direction of the crankshaft.

When blowing cooling air with a cooling fan, it is preferable to blow the cooling air evenly onto the catalyst case, and therefore it is preferable to blow the cooling air in the axial direction of the catalyst case. In other words, when the catalyst case is in a horizontal position, it is preferable to position the cooling fan so that the cooling air flows in the direction of the crank axis, and when the catalyst case is in a roughly vertical position, it is preferable to position the cooling fan so that the cooling air flows from top to bottom. When the catalyst case is inclined relative to the vertical line and the horizontal, the cooling fan should also be positioned in an inclined position.

How the exhaust system components are surrounded by multiple insulators can be determined according to the engine structure. It is possible to surround (sandwich) the exhaust system components with upper and lower insulators, or to surround the exhaust system components with insulators separated in a direction perpendicular to the exhaust side of the engine body. It is also possible to surround the exhaust system components with three or more insulators separated in the circumferential direction.

In the present invention, the cooling air for the exhaust system members is sent by a cooling fan, so that the exhaust system members can be cooled and thermal damage can be prevented even in a state where cooling from the wind while driving cannot be expected. That is, in the case of an automobile engine, the exhaust system members can be cooled even when the vehicle is stopped or driving slowly in a high-temperature environment, or even in a state where cooling from the wind while driving cannot be expected in the first place, and thermal damage to the exhaust system members themselves and to surrounding members such as harnesses can be prevented. Therefore, this is suitable for engines that are placed in the engine room in a rear exhaust position or engines that are placed in an engine room provided at the rear of the vehicle body.

In addition, in the present invention, cooling air is blown by a cooling fan, so in low-temperature environments, the cooling fan is not driven to keep the catalyst case warm and promote and maintain catalyst activation, and when the temperature environment reaches a level where cooling air is required, the cooling fan is driven. In this way, the cooling fan is driven only when necessary to prevent overcooling of exhaust system components. Furthermore, when cooling is required, it is possible to cool the exhaust system components just enough by, for example, changing the amount of air blown in stages or continuously in proportion to the cooling water temperature.

And because the space surrounded by the insulator is open toward the cooling fan, cooling air can be efficiently drawn into the space surrounded by the insulator, cooling the exhaust system components evenly. This makes it possible to suppress the driving power of the cooling fan as much as possible and prevent a deterioration in fuel efficiency.

Maniverters can have complex shapes, but as in claim 2, by configuring multiple heat shielding devices with main insulators and sub-insulators, heat can be accurately shielded (heat dissipation or heat retention) even if the maniverter has a complex shape. Furthermore, since there are ventilation gaps between adjacent sub-insulators and between the main insulator and sub-insulator, heat is prevented from building up and cooling can be performed accurately. It is also possible to prevent the edges of adjacent insulators from colliding with each other due to vibration, which would cause noise.

FIG. 2 is a view of the engine as viewed from the crankshaft direction (as viewed from the right side of the vehicle body). FIG. 2 is a view of the engine as viewed from a horizontal direction (as viewed from the rear of the vehicle body) perpendicular to the crank axis. (A) is a rear view of the manifold, and (B) is a view of (A) with an insulator added. 1A is a view of the manifold as seen from the left side of the vehicle body, and FIG. 1B is a view of A with an insulator added. 1A is a perspective view of a maniverter with insulators as viewed from the right side of the vehicle body, and FIG. 1B is a perspective view of the maniverter with insulators as viewed from the rear side of the vehicle body. 2 is a perspective view of a portion of a manifold with insulators as viewed from the front side of the vehicle body. FIG. 1A is a side perspective view of the first main insulator, FIG. 1B is a rear view of the first main insulator, FIG. 1C is a CC view of FIG. 1B, and FIG. 1D is a rear perspective view of the second main insulator. 1A is a bottom perspective view of the second sub-insulator, FIG. 1B is a side view of the second sub-insulator, FIG. 1C is a right side perspective view of the first sub-insulator, and FIG. FIG. 2 is a diagram showing a state in which the engine is mounted on a vehicle body.

(1) Arrangement and Basic Structure Next, an embodiment of the present invention will be described with reference to the drawings. This embodiment is applied to a three-cylinder engine for an automobile. As shown in FIG. 9, the engine is disposed in a rear compartment (rear engine room) 2 provided at the rear of a vehicle body 1. A front compartment 3 is formed at the front of the vehicle body 1, and a battery, a motor, and the like are disposed in the front compartment 3. Therefore, the automobile to which this embodiment is applied is a hybrid vehicle.

As described above, the engine is disposed in the rear compartment 2, but as shown in FIG. 1, the cylinder bore axis O1 is inclined at an angle of approximately 45° with respect to the vertical and horizontal. In other words, the engine is mounted horizontally with the crankshaft 4 elongated in the vehicle width direction, but tilted backward with the crankshaft positioned on the front side of the vehicle body and the cylinder head positioned on the rear side. Therefore, the engine of this embodiment is a horizontally mounted slant engine tilted toward the rear of the vehicle body.

In the following, the terms front, rear, left and right are used to specify directions, but these terms are based on the vehicle body (driver). In an engine, the direction of the crank axis is often defined as the front-rear direction, but the front-rear direction used in this embodiment differs from this general definition. The up-down direction is the vertical direction. Directions are clearly indicated in the drawings as appropriate.

The basic structure of the engine is the same as that of a conventional engine, and as shown in Figures 1 and 2, the engine body comprises a cylinder block 5 in which a cylinder bore (not shown) is formed, a cylinder head 6 fixed to the top surface of the cylinder block 5, and a head cover 7 fixed to the top surface of the cylinder head 6. Because the cylinder bore axis O1 is tilted significantly backward, as shown in Figure 1, an auxiliary crankcase 8 that is triangular in side view is fixed to the underside of the cylinder block 5, and as shown in Figure 2, an oil pan 9 is fixed to the underside of the auxiliary crankcase 8.

In this embodiment, a chain cover 10 that covers the timing chain is fixed to the left end faces of the cylinder block 5 and cylinder head 6, a portion of which is shown in FIG. 2. On the other hand, the right end face of the cylinder block 5 is a transmission case mounting flange 11. In FIG. 2, reference numeral 12 denotes an oil inlet, reference numeral 13 denotes an oil filter, reference numeral 14 denotes an ignition coil, and reference numeral 15 in FIGS. 1 and 2 denotes an EGR valve. In FIG. 1, reference numeral 16 denotes a cooling water pipe. Note that one end of the crankshaft 4 is exposed on the outside (left side) of the chain cover 10 in FIG. 2.

The engine is tilted backwards, with the downward inclined surface serving as the exhaust side and the downward inclined surface serving as the intake side. In FIG. 1, the surge tank 17 constituting the intake side member is partially visible. In FIGS. 1 and 2, the reference numeral 18 denotes an air cleaner. The lower half of the air cleaner 18 is a dirty chamber to which an intake duct 19 is connected on its side, and the upper half is a clean chamber to which an intake feed duct 20 is connected. The intake feed duct 20 is connected to the surge tank 17 via a throttle valve (not shown).

At the engine factory, the engine is assembled with the cylinder bore axis O1 vertical. At the automobile assembly factory, the engine is installed in an inclined position in the rear compartment 2 of the vehicle body, so it is necessary to lift the engine at the engine factory with the cylinder bore axis O vertical. For this reason, a first hook indicated by reference numeral 21 in Figs. 1 and 2 and a second hook 22 indicated by a dashed line in Fig. 1 are used. The first hook 21 is fixed to the left end of the cylinder head 6, and the second hook 22 is fixed to a portion near the right end of the rear surface (exhaust side surface) 23 (see Figs. 1 and 2 (B)) of the cylinder head 6. These hooks 21 and 22 are necessary at the engine factory and are removed after the engine is installed in the vehicle body.

(2) Structure of the maniverter As mentioned above, the exhaust side of the engine is inclined downward and rearward, and the maniverter 25, shown alone in Figures 3(A) and 4(A), is fixed to the exhaust side 23 of the cylinder head 6. The maniverter 25 has a cylindrical catalyst case 26 containing a catalyst, an elbow-shaped joint 27 provided integrally with the inlet end 26a of the catalyst case 26, and an L-shaped outlet pipe 28 provided integrally with the outlet end of the catalyst case 26.

As shown in FIG. 3A, the joint 27 is connected to the lower end of the inlet end 26a of the catalyst case 26, and a flange 29 provided on the opening edge is fixed to a land portion 23a (see FIG. 4B) formed on the exhaust side surface 23 of the cylinder head 6 with a group of stud bolts 30 and nuts 31. Therefore, the cylinder head 6 of this embodiment is an internal manifold type with an exhaust gas collection passage provided inside, and one exhaust outlet (not shown) opens into the land portion 23a.

As shown in Figures 1 and 2, in the maniverter 25, the outlet pipe 28 is L-shaped with a horizontal lateral portion 28a welded to the catalyst case 26 and a downward portion 28b bent and formed at its rear end, and a flange 32 that connects to an exhaust pipe (not shown) is fixed by welding to the lower end of the downward portion 28b. The start end of an EGR pipe 33 is connected to the end of the downward portion 28b closer to the outlet. The end of the EGR pipe 33 extends to the exhaust side surface 23 of the cylinder head 6, and as shown in Figure 3(B), a flange 34 fixed to the end is fixed to the cylinder head 6 with a stud bolt 35 and a nut 36.

In addition, an internal EGR passage that communicates with the EGR pipe 33 is formed in the cylinder head 6, and the EGR gas sent to the internal EGR passage is sent to the intake passage (e.g., surge tank 17) via the EGR valve 15 described above.

A front sensor mounting seat 37 for mounting an O2 sensor or A/F sensor is protruding from the inlet end 26a of the catalyst case 26. The front sensor mounting seat 37 is located slightly above the inlet end 26a, and as shown in FIG. 3B, a front sensor plug 38 is connected to it. On the other hand, a rear sensor mounting seat 39 for measuring exhaust gas temperature is provided on the horizontal portion 28a of the outlet pipe 28, and a rear sensor plug 40 equipped with a temperature sensor is connected to the rear sensor mounting seat 39.

(3) Main insulator/cooling fan The catalyst case 26 and the joint 27 of the maniverter 25 are surrounded from above and below by a first main insulator 42 and a second main insulator 43, as shown in Figures 3(B) and 5, for example. The first main insulator 42 covers roughly the upper half of the catalyst case 26, and has a half-split trunk portion as its main body, to which an inlet-side end plate 42a that covers the inlet-side end portion 26a of the catalyst case 26 is integrally bent and formed. A U-shaped front cutout 44 is formed in the inlet-side end plate 42a to allow the front sensor mounting seat 37 to escape.

The second main insulator 43 has a half-split body that surrounds the lower half of the catalyst case 26 as its main body, and a shell-shaped extension 43a that surrounds the joint 27 from below and behind is connected to this main body. The joint 27 can only be surrounded from below and behind because it is fixed to the cylinder head 6, but because the joint 27 extends diagonally downward from the inlet end 26a of the catalyst case 26, the extension 43a that covers the joint 27 is provided on the second main insulator 43.

When the joint 27 extends directly to the side from the inlet end 26a of the catalyst case 26, the extension 43a covering the joint 27 may be formed on both the first main insulator 42 and the second main insulator 43, and when the joint 27 extends diagonally upward from the inlet end 26a of the catalyst case 26, the extension 43a covering the joint 27 may be provided on the first main insulator 42.

The second main insulator 43 is fixed to the catalyst case 26 and the joint 27 at three positions on the left and right with bolts 45. That is, first to third brackets 46, 47, 48 are provided on the upper right end of the joint 27, the rear surface of the middle left and right parts of the joint 27, and the rear surface of the middle left and right parts of the catalyst case 26, and are fixed to these with bolts 45.

As shown in FIG. 7(D), the second main insulator 43 is formed with a tongue-shaped first fixing portion 49 corresponding to the first bracket 46, a square protruding second fixing portion 50 corresponding to the second bracket 47, and a horizontally elongated protruding third fixing portion 51 corresponding to the third bracket 48. Nuts are fixed to the brackets 46, 47, and 48. The third bracket 48 is gate-shaped in side view, and two bolts 45 are screwed into it.

On the other hand, as shown in Figures 7(A) to (C), the first main insulator 42 has a boss-shaped fourth fixing portion 52 that bulges backward at the lower end close to the inlet end plate 42a, a boss-shaped fifth fixing portion 53 that bulges upward at the upper part of the roughly left-right middle part, and a visor-shaped sixth fixing portion 54 that bulges at the lower end of the front part. As shown in Figure 5(A), the fourth fixing portion 52 is fixed with a bolt (not shown) to a fourth bracket 55 that is fixed to the exhaust side surface 23 of the cylinder head 6.

The fifth fixing portion 53 is fixed between the fifth bracket 56 shown in FIG. 5 and the sixth bracket 57 shown in FIG. 3(A) by a bolt 59 (see FIG. 5). The fifth bracket 56 is fixed to the exhaust side 23 of the cylinder head 6 by a bolt (not shown), and the sixth bracket 57 is fixed by welding to the upper surface of the catalyst case 26, with a nut fixed to its inner surface. The sixth fixing portion 54 of the first main insulator 42 overlaps the third bracket 48 provided on the catalyst case 26 from behind, and the third fixing portion 51 of the second main insulator 43 overlaps this sixth fixing portion 54, and the sixth fixing portion 54 and the third fixing portion 51 are fastened together to the third bracket 48 by the bolt 45.

As shown by the dashed line in FIG. 2, a cooling fan 58 is disposed to the left of the maniverter 25, generally concentric with the axis of the catalyst case 26. The cooling fan 58 is disposed so that the center 58a of the cooling air faces the front sensor mounting seat 37 of the maniverter 25, and the cooling air flows into the front notch 44 of the first main insulator 42 and into the space surrounded by the main insulators 42, 43. Therefore, in this embodiment, the front notch 44 of the first main insulator 42 serves as the air guide port described in the claims.

In FIG. 2, the upper part of the cooling fan 58 and the lower part of the air cleaner 18 partially overlap, but since there is a high degree of freedom in the shape of the air cleaner 18, the underside can be recessed so as not to interfere with the cooling fan 58. Alternatively, the cooling fan 58 can be lowered below the air cleaner 18 and tilted so that the cooling air is directed toward the front cutout 44. The cooling fan 58 is preferably an electric type with an inverter, but it can also be driven by the crankshaft 4. In this case, it is preferable to provide a clutch to connect and disconnect power.

As shown in FIG. 5(A), a first ventilation gap 60 is formed between the rear left side of the first main insulator 42 and the rear side of the main body of the second main insulator 43, communicating with the front notch 44 and reaching the third and sixth fixed parts 51 and 54. In addition, an outlet 80 for releasing the outlet pipe 28 is opened between the right end of the first main insulator 42 and the right side of the second main insulator 43, and a second ventilation gap 61 is formed between the rear right end of the first main insulator 42 and the rear right side of the second main insulator 43, starting from the end of the third and sixth fixed parts 51 and 54 and communicating with the outlet 80. The groove width between the first ventilation gap 60 and the second ventilation gap 61 is set to about 4 mm, but can be increased or decreased as necessary.

As shown in FIG. 6 (also see FIG. 4(B)), a third ventilation gap 62 communicating with the outlet 80 is provided between the front edge of the first main insulator 42 and the front edge of the second main insulator 43. The groove width of the third ventilation gap 62 is set to about 10 mm, but this dimension can be increased or decreased as necessary.

(4) Sub-insulator The outlet pipe 28 constituting the maniverter 25 is surrounded by a first sub-insulator 63 arranged on the outer corner side and a second sub-insulator 64 arranged on the inner corner side as shown in Figures 2 to 6. Therefore, for example, as shown in Figure 8, the first sub-insulator 63 and the second sub-insulator 64 are also formed in an L shape having a lateral portion and a downward portion following the outlet pipe 28.

As mentioned above, the rear sensor mounting seat 39 protrudes from the horizontal portion 28a of the outlet pipe 28, and as shown in FIG. 8(C), the horizontal portion of the first sub-insulator 63 has an escape hole 65 that opens upward to avoid interference with the rear sensor mounting seat 39.

As shown in FIG. 3(A), the horizontal portion 28a of the outlet pipe 28 is formed with a rearward facing seventh bracket 66 and a downward facing eighth bracket 67 that are integrally connected, while the downward portion 28b of the outlet pipe 28 is formed with a ninth bracket 68 that protrudes to the right (outside) and a tenth bracket 69 that protrudes to the left (inside).

For example, as shown in FIG. 5B, a seventh fixing portion 70 facing backward is formed on the sideways portion of the first sub-insulator 63, which is fixed to the seventh bracket 66 by a bolt 71, and an eighth fixing portion 72 facing right is formed on the downward portion of the first sub-insulator 63, which is fixed to the ninth bracket 68 by a bolt 71.

As shown in FIG. 3(B), the lateral portion of the second sub-insulator 64 is formed with a downwardly facing ninth fixing portion 73, which is fixed to the eighth bracket 67 with a bolt 74, and the downward portion of the second sub-insulator 64 is formed with a tenth fixing portion 75 that protrudes to the left, which is fixed to the tenth bracket 69 with a bolt 74. As shown in FIG. 3(B) (also see FIGS. 8(A) and (B)), the downward portion of the second sub-insulator 64 is formed with a notch 76 to allow the EGR pipe 33 to escape.

As shown in FIG. 6, at the outlet 80 of the main insulators 42, 43, an arc-shaped fourth ventilation gap 77 is provided between the second main insulator 43 and both sub-insulators 63, 64. Therefore, the fourth ventilation gap 77 is connected to the third ventilation gap 62. The groove width of the fourth ventilation gap 77 increases from front to rear, and is approximately 10 mm at the narrowest point and approximately 20 mm at the widest point. The fourth ventilation gap 77 is closed at the upper end of the first sub-insulator 63, but it can also be formed in a ring shape.

As shown in FIG. 3B, an L-shaped fifth ventilation gap 78 is provided between the rear edge of the first sub-insulator 63 and the rear edge of the second sub-insulator 64. The groove width of the fifth ventilation gap 78 is set to about 10 mm, but the dimensions can be changed as appropriate. In this embodiment, the fourth ventilation gap 77 and the fifth ventilation gap 78 correspond to the ventilation gaps described in the claims. The insulators 42, 43, 63, and 64 are sheet metal products made of metal plates such as stainless steel plates.

(5) Summary With the above-described configuration of this embodiment, the maniverter 25 is entirely surrounded by a heat shielding device consisting of four insulators 42, 43, 63, and 64, which prevents heat damage to surrounding components such as the harness. In addition, when the cooling fan 58 is driven, cooling air enters the space surrounded by the insulators 42, 42, 63, and 64 from the front cutout 44, which allows the catalyst case 26 and the outlet pipe 28 to be cooled.

Therefore, when the temperature of the space surrounded by the insulators 42, 43, 63, and 64 rises above a predetermined level, the catalyst case 26 and the outlet pipe 28 can be thoroughly cooled by driving the cooling fan 58. On the other hand, when operating in a low-temperature environment, the cooling fan 58 is not driven to keep the catalyst case 26 warm, contributing to early activation of the catalyst and maintaining its active state. In addition, since the engine is located in the rear compartment 2, cooling by the wind from traveling cannot be expected, but in this embodiment, cooling air is sent from the cooling fan 58, so the maniverter 25 can be adequately cooled even with an engine located in the rear compartment 2.

The maniverter 25 has a complex three-dimensional shape, so it needs to be surrounded by multiple insulators to provide adequate heat insulation. However, as in the embodiment, by covering the portion consisting of the catalyst case 26 and the joint 27 with a pair of upper and lower main insulators 42, 43, and covering the outlet pipe 28 with inner and outer sub-insulators 63, 64, the entire unit can be securely covered with as few insulators 42, 42, 63, 64 as possible.

In other words, the large volume portion consisting of the catalyst case 26 and the joint 27 is surrounded by a pair of main insulators 42, 43, which allows the catalyst case 26 and the joint 27 to be securely covered while ensuring workability by pressing, while covering the outlet pipe 28 with the inner and outer sub-insulators 63, 64 formed in an L-shape provides secure heat insulation while ensuring workability.

In addition, the axis of the bolts 45, 59, 71, 74 that secure the insulators 42, 42, 63, 64 faces the rear or the open space in the vertical or horizontal directions, so that the bolts 45, 59, 71, 74 can be easily rotated with a wrench. This allows efficient engine assembly. Providing an extension 43a on the second main insulator 43 to cover the joint 27 is preferable because it simplifies the structure. Furthermore, when the first fixing portion 49 of the extension 43a is fixed to the first bracket 46 provided on the joint 27, the extension 43a that protrudes from the main body of the second main insulator 43 can be firmly fixed.

As in the embodiment, when the front notch 44 formed in the first main insulator 42 is used as an air guide port, the cooling air can be evenly guided around the catalyst case 26, thereby cooling the catalyst case 26 evenly. In addition, a portion of the cooling air that hits the inlet end 26a of the catalyst case 26 flows back downward toward the joint 27, so that the joint 27 can also be cooled. In addition to or instead of forming the front notch 44 as an air guide port in the first main insulator 42, it is also possible to open an air guide port in the extension portion 43a of the second main insulator 43.

When the front cutout 44 is used as an air guide port as in the embodiment, the first main insulator 42 can be attached and detached by moving it in the vertical direction, so that the first main insulator 42 can be easily attached and detached even with the front sensor plug 38 attached. Fastening the first main insulator 42 and the second main insulator 43 together to the third bracket 48 as in the embodiment is preferable because it simplifies the structure.

When the first ventilation gap 60 is provided as in the embodiment, cooling air can also be introduced through the first ventilation gap 60, improving the introduction of cooling air. Furthermore, when the second ventilation gap 61 and the third ventilation gap 62 are provided, the cooling air can be released in the radial direction, which is preferable for preventing heat from building up around the joint 27 and the catalyst case 26. Furthermore, the cooling air escapes through the fourth ventilation gap 77, effectively preventing heat from building up. The cooling air can also be released through the fifth ventilation gap 78, preventing heat from building up in the outlet pipe 28.

Although the embodiment of the present invention has been described above, the present invention can be embodied in various other ways. For example, the engine can be placed in a front compartment located at the front of the vehicle body. If the catalyst case extends downward, the cooling fan can be positioned so that the cooling air flows from top to bottom. A sub-insulator is not necessarily required. The present invention can also be applied to a manifold equipped with an exhaust manifold with branch pipes.

The present invention can be embodied in an engine, and therefore has industrial applicability.

REFERENCE SIGNS LIST 1 vehicle body 2 rear compartment 4 crankshaft 5 cylinder block 6 cylinder head 7 head cover 23 exhaust side 25 maniverter 26 catalyst case 27 joint 28 outlet pipe 37 front sensor mounting seat 38 front sensor plug 39 rear sensor mounting seat 40 rear sensor plug 42 first main insulator 42a inlet side end plate 43 second main insulator 43a extension 44 front cutout (air guide port)
46, 47, 48, 55, 56, 57, 66, 67, 68, 69 Bracket 49, 50, 51, 52, 53, 54, 70, 72, 73, 75 Fixing part 58 Cooling fan 60, 61, 62, 77, 78 Ventilation gap 63, 64 Sub-insulator 80 Outlet

Claims (2)

The engine includes an exhaust system member having an upstream end fixed to an exhaust side surface of a cylinder head constituting an engine body and an exhaust pipe connected to a downstream end thereof, a cooling fan that blows cooling air toward the exhaust system member, and a heat insulating device that surrounds the exhaust system member,
The cooling fan is disposed so as to blow cooling air from a direction along the exhaust side of the engine body,
The heat shield device includes a plurality of insulators arranged to sandwich at least a portion of the exhaust system member, and a space surrounded by the plurality of insulators has an air guide opening on the side of the cooling fan and an outlet opening on the side opposite to the cooling fan.
engine. the exhaust system member is a manifold in which a joint or an exhaust manifold fixed to the cylinder head, a catalyst case containing a catalyst, and an outlet pipe connected to the catalyst case are integrated into a single unit;
The heat shield device is composed of a plurality of main insulators surrounding a joint of the manifold or an exhaust manifold and a catalyst case, and a plurality of sub-insulators surrounding an outlet pipe of the exhaust manifold, and ventilation gaps are provided between adjacent sub-insulators and between the main insulators and the sub-insulators.
An engine as claimed in claim 1.

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