Engine

Abstract

The present invention addresses the problem of disclosing a technique capable of firmly shielding heat of a maniverter having a catalyst case.　A maniverter 25 is constituted by a catalyst case 26, a joint 27, and an outlet pipe 28. A heat shield 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. This engine is provided with a cooling fan 58 that blows air toward an inlet side end part of the catalyst case 26, and an air guide port (front cutout) 44 is opened in an inlet side end plate 42a of the first main insulator 42. Cooling air is sent from the cooling fan 58 through the front cutout 44 into a space surrounded by insulators 42, 43, 63, 64, and can cool the catalyst case 26 and the outlet pipe 28. Since cooling is performed by the cooling fan 58, the maniverter 25 can be accurately cooled even in engines that cannot be expected to be cooled by wind while traveling, such as an engine disposed in a rear compartment of a vehicle body. It is also possible to keep the temperature without driving the cooling fan.

Description

engine

[0001] The present invention relates to an engine characterized by a heat insulating structure for exhaust system members, and is preferably applied to an automobile engine.

[0002] In engines such as gasoline engines, exhaust system components such as the exhaust manifold and catalyst case reach high temperatures, so the exhaust system components are surrounded by insulators to insulate them from heat.Alternatively, because catalysts for purifying exhaust gases require a certain degree of high temperature for activation, insulators are also used to function as heat-retaining materials.

[0003] As an example, Patent Document 1 discloses a vertical engine that is placed horizontally in the engine compartment at the front of a vehicle with rear exhaust, in which a group of components including a catalyst case (straight catalyst) connected to an exhaust manifold are surrounded by upper and lower insulators, and a running wind intake is opened in the upper insulator.

[0004] In this patent document, the insulator basically functions as a heat-retaining member to prevent the catalyst from dropping in temperature, and if the temperature of the catalyst case becomes higher than necessary while the vehicle is running, it takes in the running wind to cool the exhaust manifold and catalyst case. Furthermore, gaps are provided between adjacent insulators to allow the running wind to be discharged.

[0005] Japanese Patent Application Laid-Open No. 2017-165123

[0006] 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, but when the vehicle is stopped or traveling at a low speed, such as when driving slowly in a traffic jam, the wind cannot hit the exhaust manifold or catalyst case.

[0007] Therefore, if the vehicle is unable to take in wind while driving in a high-temperature environment such as summer, there is a concern that the interior enclosed by the insulator may become excessively hot, which could result in the insulator having an adverse effect.

[0008] 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 the vehicle as it is running, making it very difficult to control the temperature of the exhaust manifold and catalyst case using insulators.

[0009] The present invention aims to disclose a technique that improves this current situation.

[0010] The present invention is directed to an engine, which has the following basic configuration: "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 sends cooling air toward the exhaust system member; and a heat shield that surrounds the exhaust system member." In this basic configuration, "the cooling fan is positioned to send cooling air from a direction along the exhaust side of the engine body, while the heat shield device has a plurality of insulators that are positioned to sandwich at least a portion of the exhaust system member, and the space surrounded by the plurality of insulators has an air intake opening on the side of the cooling fan and an outlet opening on the opposite side of the cooling fan."

[0011] The present invention can be developed in various ways, and as an example, claim 2 adopts the following configuration: "The exhaust system member is a manifold-verter in which a joint or exhaust manifold fixed to the cylinder head, a catalyst case containing a catalyst, and an outlet pipe connected to the joint or exhaust manifold are integrated into one unit, and the heat shield device is composed of a plurality of main insulators that surround the joint or exhaust manifold and catalyst case of the manifold-verter, and a plurality of sub-insulators that surround 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."

[0012] The catalyst case is cylindrical and, in the case of a vertical engine, is often positioned with its axis extending almost vertically. On the other hand, in the case of an engine for a cab-over vehicle, where the cylinder bore axis is significantly inclined toward the horizontal, the catalyst case is often positioned in a nearly horizontal position with its axis extending in the direction of the crankshaft axis.

[0013] When the cooling fan blows cooling air, it is preferable to blow the cooling air evenly over the catalyst case, and therefore it is preferable to blow the cooling air in the axial direction of the catalyst case. That is, when the catalyst case is in a horizontal position, the cooling fan is preferably positioned so that the cooling air flows in the direction of the crankshaft, and when the catalyst case is in a substantially vertical position, the cooling fan is preferably positioned 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.

[0014] How the exhaust system members are surrounded by multiple insulators can be determined depending on the engine structure. It is possible to surround (sandwich) the exhaust system members between upper and lower insulators, or to surround the exhaust system members with insulators separated in a direction perpendicular to the exhaust side of the engine body. It is also possible to surround the exhaust system members with three or more insulators separated in the circumferential direction.

[0015] In the present invention, cooling air is sent to the exhaust system components by a cooling fan, so the exhaust system components can be cooled and thermal damage can be prevented even in situations where cooling from the wind while the vehicle is moving cannot be expected. That is, in the case of an automobile engine, the exhaust system components can be cooled even when the vehicle is stopped or moving slowly in a high-temperature environment, or even in situations where cooling from the wind while the vehicle is moving cannot be expected at all, thereby preventing thermal damage to the exhaust system components themselves and surrounding components such as harnesses. Therefore, this is suitable for engines arranged in a rear-exhaust position in the engine compartment or engines arranged in an engine compartment located in the rear of the vehicle body.

[0016] In addition, in the present invention, because cooling air is blown by a cooling fan, the cooling fan is not driven in low-temperature environments to keep the catalyst case warm and promote and maintain catalyst activation, and the cooling fan is driven when the temperature reaches a level where cooling air is required, thereby preventing excessive cooling 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 coolant temperature.

[0017] Furthermore, because the space enclosed by the insulator is open toward the cooling fan, cooling air can be efficiently drawn into the space enclosed by the insulator, cooling the exhaust system components evenly. This reduces the driving power of the cooling fan as much as possible, preventing a deterioration in fuel economy.

[0018] Although maniverters can have complex shapes, by configuring multiple heat shielding devices with main insulators and sub-insulators as in claim 2, heat can be accurately shielded (heat dissipated or retained) even if the maniverter has a complex shape. Furthermore, ventilation gaps are provided between adjacent sub-insulators and between the main insulator and sub-insulator, preventing heat buildup and ensuring accurate cooling. This also prevents noise caused by the edges of adjacent insulators colliding with each other due to vibration.

[0019] 1 is a view of the engine as seen from the crankshaft direction (as viewed from the right side of the vehicle body). 2 is a view of the engine as seen from the horizontal direction (as viewed from the rear of the vehicle body) perpendicular to the crankshaft direction. 3 (A) is a rear view of the maniverter, and 4 (B) is a view of (A) with an insulator added. 5 (A) is a view of the maniverter as viewed from the left side of the vehicle body, and 6 (B) is a view of (A) with an insulator added. 6 (A) is a perspective view of the maniverter with insulators as viewed from the right side of the vehicle body, and 7 (B) is a perspective view of the maniverter with insulators as viewed from the rear side of the vehicle body. 8 (A) is a side perspective view of the first main insulator, 9 (B) is a rear view of the first main insulator, 10 (C) is a CC view of (B), and 11 (D) is a rear perspective view of the second main insulator. 1A is a bottom perspective view of a second sub-insulator, FIG. 1B is a side view of the second sub-insulator, FIG. 1C is a right perspective view of a first sub-insulator, and FIG. 1D is a left side view of the first sub-insulator.

[0020] (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, motor, etc. are disposed in the front compartment 3. Therefore, the automobile to which this embodiment is applied is a hybrid vehicle.

[0021] As described above, the engine is disposed in the rear compartment 2, but as shown in Figure 1, the cylinder bore axis O1 is inclined at an angle of approximately 45° with respect to the vertical and horizontal. That is, the engine is mounted transversely with the crankshaft 4 elongated in the vehicle width direction, but is tilted backward with the crankshaft located on the front side of the vehicle body and the cylinder head located on the rear side. Therefore, the engine of this embodiment is a transversely mounted slant engine tilted toward the rear of the vehicle body.

[0022] In the following, the terms "front, rear" and "left, right" are used to specify directions, but these terms are based on the vehicle body (driver). In an engine, the direction of the crankshaft 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.

[0023] 1 and 2, the engine body comprises a cylinder block 5 in which cylinder bores (not shown) are 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 rearward, an auxiliary crankcase 8 that is triangular in side view is fixed to the underside of the cylinder block 5 as shown in FIG. 1, and an oil pan 9 is fixed to the underside of the auxiliary crankcase 8 as shown in FIG. 2.

[0024] In this embodiment, as partially shown in Figure 2, a chain cover 10 that covers the timing chain is fixed to the left end surfaces of the cylinder block 5 and cylinder head 6. On the other hand, the right end surface of the cylinder block 5 forms a transmission case mounting flange 11. In Figure 2, reference numeral 12 denotes an oil filler port, reference numeral 13 denotes an oil filter, reference numeral 14 denotes an ignition coil, and reference numeral 15 in Figures 1 and 2 denotes an EGR valve. In Figure 1, reference numeral 16 denotes a cooling water pipe. Note that one end of the crankshaft 4 is exposed outside (on the left side) of the chain cover 10 in Figure 2.

[0025] The engine is tilted backward, with the downward sloping surface serving as the exhaust side and the downward sloping surface serving as the intake side. A surge tank 17, which constitutes an intake-side member, is partially visible in Figure 1. Reference numeral 18 in Figures 1 and 2 denotes an air cleaner. The lower half of the air cleaner 18 forms a dirty chamber, with an intake duct 19 connected to its side, and the upper half forms a clean chamber, with an intake feed duct 20 connected to it. The intake feed duct 20 is connected to the surge tank 17 via a throttle valve (not shown).

[0026] At the engine factory, the engine is assembled with the cylinder bore axis O1 aligned vertically. However, at the automobile assembly factory, the engine is installed in an inclined position in the rear compartment 2 of the vehicle body. Therefore, at the engine factory, the engine must be lifted so that the cylinder bore axis O is aligned vertically. For this purpose, 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 position near the right end of the rear surface (exhaust side) 23 (see FIGS. 1 and 2(B)) of the cylinder head 6. Note that these hooks 21 and 22 are necessary at the engine factory and are removed after the engine is installed in the vehicle body.

[0027] (2) Structure of the manifold-verter As mentioned above, the exhaust side of the engine is inclined downward and rearward, and the manifold-verter 25, shown individually in Figures 3(A) and 4(A), is fixed to the exhaust side 23 of the cylinder head 6. The manifold-verter 25 has a cylindrical catalyst case 26 containing a catalyst, an elbow-shaped joint 27 integrally formed at the inlet end 26a of the catalyst case 26, and an L-shaped outlet pipe 28 integrally formed at the outlet end of the catalyst case 26.

[0028] 3A, the joint 27 is connected to the lower end of the inlet side end 26a of the catalyst case 26, and a flange 29 provided on the opening edge thereof is fixed with a group of stud bolts 30 and nuts 31 to a land portion 23a (see FIG. 4B) formed on the exhaust side surface 23 of the cylinder head 6. Therefore, the cylinder head 6 of this embodiment is of an internal manifold type with an exhaust gas collecting passage provided inside, and one exhaust outlet (not shown) opens in the land portion 23a.

[0029] 1 and 2, in the maniverter 25, the outlet pipe 28 is L-shaped and has a horizontal, lateral portion 28a welded to the catalyst case 26 and a downward portion 28b bent and formed at its rear end. A flange 32 for connecting an exhaust pipe (not shown) is fixed by welding to the lower end of the downward portion 28b. The starting end of an EGR pipe 33 is connected to the end of the downward portion 28b closer to the outlet. The terminal end of the EGR pipe 33 extends to the exhaust side surface 23 of the cylinder head 6, and as shown in FIG. 3B, a flange 34 fixed to the terminal end is fixed to the cylinder head 6 with a stud bolt 35 and a nut 36.

[0030] 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.

[0031] A front sensor mounting seat 37, on which an O2 sensor or A / F sensor is attached, protrudes 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 Figure 3(B), a front sensor plug 38 is connected to the front sensor mounting seat 37. 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.

[0032] (3) Main Insulator / Cooling Fan The catalyst case 26 and 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 roughly covers the upper half of the catalyst case 26, and has a half-split body as its main body, to which an inlet-side end plate 42a that covers the inlet-side end 26a of the catalyst case 26 is bent and formed integrally. A U-shaped front notch 44 is formed in the inlet-side end plate 42a to allow clearance for the front sensor mounting seat 37.

[0033] The second main insulator 43 has a main body that is a half-split body that surrounds the lower half of the catalyst case 26, and a shell-shaped extension 43a that surrounds the joint 27 from below and behind is integrally connected to this main body. Since the joint 27 is fixed to the cylinder head 6, it can only be surrounded from below and behind, but since the joint 27 extends diagonally downward from the inlet-side end 26a of the catalyst case 26, the extension 43a that covers the joint 27 is provided on the second main insulator 43.

[0034] When the joint 27 extends directly to the side from the inlet side end 26a of the catalyst case 26, the extension portion 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 side end 26a of the catalyst case 26, the extension portion 43a covering the joint 27 may be provided on the first main insulator 42.

[0035] 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 portions of the joint 27, and the rear surface of the middle left and right portions of the catalyst case 26, and the second main insulator 43 is fixed to these with bolts 45.

[0036] 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-shaped 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.

[0037] 7A to 7C, the first main insulator 42 has a boss-shaped fourth fixing portion 52 that bulges rearward at its lower end portion near the inlet-side end plate 42a, a boss-shaped fifth fixing portion 53 that bulges upward at the upper portion of the roughly left-right middle portion, and a visor-shaped sixth fixing portion 54 that bulges forward at its lower front end portion. As shown in FIG. 5A, the fourth fixing portion 52 is fixed with bolts (not shown) to a fourth bracket 55 that is fixed to the exhaust side surface 23 of the cylinder head 6.

[0038] The fifth fixing portion 53 is fixed to a fifth bracket 56 shown in Fig. 5 and a sixth bracket 57 shown in Fig. 3(A) by clamping them with bolts 59 (see Fig. 5). The fifth bracket 56 is fixed to the exhaust side surface 23 of the cylinder head 6 with bolts (not shown), and the sixth bracket 57 is fixed to the upper surface of the catalyst case 26 by welding, with nuts 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 with bolts 45.

[0039] 2, a cooling fan 58 is disposed on the left side of the manifold 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 manifold 25, and the cooling air flows into the front cutout 44 of the first main insulator 42 and into the space surrounded by the main insulators 42, 43. Therefore, in this embodiment, the front cutout 44 of the first main insulator 42 serves as the air guide port recited in the claims.

[0040] In Figure 2, the upper part of the cooling fan 58 partially overlaps with the lower part of the air cleaner 18, but since there is a high degree of freedom in the shape of the air cleaner 18, the lower surface may be recessed so as not to interfere with the cooling fan 58. Alternatively, the cooling fan 58 may 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.

[0041] 5A , a first ventilation gap 60 is formed between the rear left side of the first main insulator 42 and the rear side of the body of the second main insulator 43, communicating with the front notch 44 and reaching the third and sixth fixed portions 51, 54. An outlet 80 for releasing the outlet pipe 28 opens 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 ends of the third and sixth fixed portions 51, 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 this can be increased or decreased as necessary.

[0042] As shown in Figure 6 (also see Figure 4(B)), a third ventilation gap 62 communicating with the outlet 80 is provided between the front end edge of the first main insulator 42 and the front end 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 also be increased or decreased as necessary.

[0043] (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 horizontal portion and a downward portion following the outlet pipe 28.

[0044] As described above, the rear sensor mounting seat 39 protrudes from the horizontal portion 28a of the outlet pipe 28, and as shown in Figure 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.

[0045] As shown in FIG. 3(A), a rearward-facing seventh bracket 66 and a downward-facing eighth bracket 67 are formed integrally and continuously on the horizontal portion 28a of the outlet pipe 28, while a ninth bracket 68 protruding to the right (outside) and a tenth bracket 69 protruding to the left (inside) are formed on the downward portion 28b of the outlet pipe 28.

[0046] For example, as shown in Figure 5 (B), a rear-facing seventh fixing portion 70 is formed on the horizontal portion of the first sub-insulator 63, and this is fixed to the seventh bracket 66 with a bolt 71, and a right-facing eighth fixing portion 72 is formed on the downward portion of the first sub-insulator 63, and this is fixed to the ninth bracket 68 with a bolt 71.

[0047] 3(B), a downward-facing ninth fixing portion 73 is formed on the horizontally facing portion of the second sub-insulator 64, and this ninth fixing portion 73 is fixed to the eighth bracket 67 with a bolt 74, and a leftward-protruding tenth fixing portion 75 is formed on the downward-facing portion of the second sub-insulator 64, and this tenth fixing portion 75 is fixed to the tenth bracket 69 with a bolt 74. As shown in FIG. 3(B) (also see FIGS. 8(A) and 8(B)), a notch 76 is formed in the downward-facing portion of the second sub-insulator 64 to allow the EGR pipe 33 to escape.

[0048] As shown in Figure 6, an arc-shaped fourth ventilation gap 77 is formed between the second main insulator 43 and both sub-insulators 63, 64 at the outlet 80 of the main insulators 42, 43. Therefore, the fourth ventilation gap 77 communicates with 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 its narrowest point and approximately 20 mm at its widest point. The fourth ventilation gap 77 is closed at the upper end of the first sub-insulator 63, but it may also be formed in an annular shape.

[0049] As shown in Figure 3(B), 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 approximately 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 recited in the claims. The insulators 42, 43, 63, and 64 are sheet metal products made of metal plates such as stainless steel plates.

[0050] (5) Summary This embodiment has the above configuration, and 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 harnesses. Furthermore, 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, thereby cooling the catalyst case 26 and outlet pipe 28.

[0051] 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 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, which contributes to early activation and maintaining the catalyst in an active state. Furthermore, 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.

[0052] Because the maniverter 25 has a complex three-dimensional shape, 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.

[0053] In other words, by surrounding the large volume portion consisting of the catalyst case 26 and the joint 27 with a pair of main insulators 42, 43, the catalyst case 26 and the joint 27 can be securely covered while ensuring workability by pressing, and by covering them with the inner and outer L-shaped sub-insulators 63, 64 of the outlet pipe 28, heat insulation can be securely achieved while ensuring workability.

[0054] Furthermore, because the axes of the bolts 45, 59, 71, and 74 that secure the insulators 42, 42, 63, and 64 face rearward or toward open spaces in the vertical or horizontal directions, the bolts 45, 59, 71, and 74 can be easily rotated with a wrench. This allows for efficient engine assembly. Providing an extension 43a on the second main insulator 43 to cover the joint 27 is advantageous for simplifying 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.

[0055] When the front cutout 44 formed in the first main insulator 42 is used as an air guide port as in the embodiment, the cooling air can be guided evenly around the catalyst case 26, thereby uniformly cooling the catalyst case 26. Furthermore, part of the cooling air that hits the inlet side end 26a of the catalyst case 26 flows back downward toward the joint 27, thereby also cooling the joint 27. In addition to or instead of forming the front cutout 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.

[0056] When the front cutout 44 is used as an air intake port as in the embodiment, the first main insulator 42 can be attached and detached by moving it up and down, 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.

[0057] By providing the first ventilation gap 60 as in the embodiment, cooling air can also be introduced through the first ventilation gap 60, improving the efficiency of introducing cooling air. Furthermore, by providing the second ventilation gap 61 and the third ventilation gap 62, cooling air can be released in the radial direction, which is advantageous in preventing heat from building up around the joint 27 and the catalyst case 26. Furthermore, cooling air escapes through the fourth ventilation gap 77, effectively preventing heat from building up. Cooling air can also escape through the fifth ventilation gap 78, preventing heat from building up in the outlet pipe 28.

[0058] Although the preferred embodiment of the present invention has been described above, the present invention can be embodied in a variety of other ways. For example, the engine can be placed in a front compartment at the front of the vehicle. 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 a branch pipe.

[0059] The present invention can be embodied in an engine and is therefore industrially applicable.

[0060] REFERENCE SIGNS LIST 1 vehicle body 2 rear compartment 4 crankshaft 5 cylinder block 6 cylinder head 7 head cover 23 exhaust side 25 manifold 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 portion 44 front cutout (air inlet) 46, 47, 48, 55, 56, 57, 66, 67, 68, 69 bracket 49, 50, 51, 52, 53, 54, 70, 72, 73, 75 fixing portion 58 cooling fan 60, 61, 62, 77, 78 ventilation gap 63, 64 sub-insulator 80 Exit

Claims

1. An engine comprising: an exhaust system member having an upstream end fixed to the exhaust side of a cylinder head constituting an engine body and an exhaust pipe connected to its downstream end; a cooling fan which sends cooling air towards said exhaust system member; and a heat shield which surrounds said exhaust system member, wherein said cooling fan is arranged to send cooling air from a direction along the exhaust side of said engine body, while said heat shield comprises a plurality of insulators which are arranged to sandwich at least a portion of said exhaust system member, and wherein a space surrounded by said plurality of insulators has an air intake opening on the side of said cooling fan and an outlet opening on the opposite side to said cooling fan.

2. An engine as described in claim 1, wherein the exhaust system member is a manifold-verter in which a joint or exhaust manifold fixed to the cylinder head, a catalyst case containing a catalyst, and an outlet pipe connected thereto are integrated into one unit, and the heat shield device is composed of a plurality of main insulators surrounding the joint or exhaust manifold and catalyst case of the manifold-verter, and a plurality of sub-insulators surrounding the outlet pipe of the exhaust manifold, with ventilation gaps provided between adjacent sub-insulators and between the main insulators and the sub-insulators.

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