Engine

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

Technical Field

[0001] The invention of the present application relates to an engine having a heat insulation structure for exhaust system members, and preferably targets an automotive engine.

Background Art

[0002] In an engine such as a gasoline engine, exhaust system members such as an exhaust manifold and a catalyst case become hot, so the exhaust system members are surrounded by an insulator for heat insulation. Alternatively, since a catalyst for purifying exhaust gas requires a certain degree of high temperature for activation, the insulator is also made to function as a heat retaining member.

[0003] As an example, Patent Document 1 discloses a vertical engine disposed in a front engine room of an automobile in a horizontal rear exhaust posture, in which a group of members in which a catalyst case (direct catalyst) is connected to an exhaust manifold is surrounded by upper and lower insulators, and an air intake opening for running wind is opened in the upper insulator.

[0004] In this Patent Document 1, the insulator basically functions as a heat retaining member for preventing a decrease in the temperature of the catalyst. When the temperature of the catalyst case becomes higher than necessary due to the running of the automobile, the running wind is taken in to cool the exhaust manifold and the catalyst case. And a gap for discharging the running wind is provided between adjacent insulators.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The engine in Patent Document 1 is arranged horizontally in the engine room (engine compartment) provided at the front part of the vehicle body with a rear exhaust posture. When the vehicle is running at a certain speed, it can be said that a part of the running wind that wraps around the rear of the engine and passes under the floor enters the running wind intake provided in the insulator. However, when the vehicle is stopped or running at a low speed such as in a crawl during traffic congestion, the running wind cannot be applied to the exhaust manifold or the catalyst case.

[0007] Therefore, when the running wind cannot be taken in during driving in a high-temperature environment such as in summer, there is a concern that the interior surrounded by the insulator will overheat. That is, there is a concern that the insulator will have a reverse effect.

[0008] Also, it is possible to provide an engine room at the rear part of the vehicle body and arrange the engine here. However, in this case, since the running wind cannot be taken into the engine room, it becomes very difficult to control the temperature of the exhaust manifold and the catalyst case by the insulator.

[0009] The present invention aims to disclose a technology that improves such a current situation.

Means for Solving the Problems

[0010] The present invention is directed to an engine, and this engine "comprises an exhaust system member whose upstream end is fixed to the exhaust side surface of the cylinder head constituting the engine body and whose downstream end is connected to an exhaust pipe, a cooling fan that sends cooling air toward the exhaust system member, and a heat insulation device that surrounds the exhaust system member." has the following basic configuration. In this basic configuration, "the cooling fan is arranged to send cooling air from a direction along the exhaust side surface of the engine body, while The heat insulation device includes a plurality of insulators arranged so as to sandwich at least a part of the exhaust system member, and an air guide opening is formed on the side of the cooling fan in the space surrounded by the plurality of insulators, and an outlet is formed on the side opposite to the cooling fan. It has such a configuration.

[0011] The invention of the present application can be developed in various ways. As an example, in claim 2, The exhaust system member is a manifold in which a joint fixed to the cylinder head or an exhaust manifold, a catalyst case containing a catalyst, and an outlet pipe connected thereto are integrally unitized, The heat insulation device is composed of a plurality of main insulators surrounding the joint or exhaust manifold of the 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 insulator and the sub-insulator. It adopts such a configuration.

[0012] Now, the catalyst case has a cylindrical shape, and in the case of a vertical engine, it is often arranged with its axis in a substantially vertical and long posture. On the other hand, in the case where the cylinder bore axis is largely slanted to the horizontal side like the engine of a cab-over type automobile, the catalyst case is often arranged in a substantially horizontal posture that is long in the crankshaft axis direction.

[0013] When sending cooling air with the cooling fan, it is preferable to evenly apply the cooling air to the catalyst case. Therefore, it is preferable to send the cooling air in the axial direction of the catalyst case. That is, when the catalyst case is in a horizontal posture, it is preferable to arrange the cooling fan so that the cooling air flows in the crankshaft axis direction, and when the catalyst case is in a substantially vertical posture, it is preferable to arrange the cooling fan so that the cooling air flows from top to bottom. When the catalyst case is inclined with respect to the vertical line and the horizontal, the cooling fan may also be arranged in an inclined posture.

[0014] How to surround the exhaust system member with a plurality of insulators may be set according to the structure of the engine. It is possible to surround (clamp) the exhaust system member with upper and lower insulators, or it is also possible to surround the exhaust system member with insulators separated in a direction orthogonal to the exhaust side surface of the engine body. It is also possible to surround the exhaust system member with three or more insulators separated in the circumferential direction.

Advantages of the Invention

[0015] In the present invention, since the cooling air for the exhaust system member is sent by the cooling fan, the exhaust system member can be cooled to prevent the occurrence of heat damage even in a state where cooling by the running wind cannot be expected. That is, in the case of an automotive engine, the exhaust system member can be cooled even in a state of being stopped in a high-temperature environment, a slow-driving state, or a state where cooling by the running wind cannot be expected in the first place, so as to prevent heat damage from occurring to the exhaust system member itself or to peripheral members such as harnesses. Therefore, it is suitable for an engine arranged in a rear-exhaust posture in the engine room or an engine arranged in an engine room provided at the rear part of the vehicle body.

[0016] Also, in the present invention, since the cooling air is sent by the cooling fan, in a low-temperature environment, the catalyst case is kept warm without driving the cooling fan to promote and maintain the activation of the catalyst, and when the temperature environment requires cooling air, the cooling fan is driven. In this way, the cooling fan can be driven only when necessary to prevent overcooling of the exhaust system member. Furthermore, in a state where cooling is required, for example, by changing the air volume stepwise or steplessly in proportion to the cooling water temperature, it is also possible to cool the exhaust system member without excess or deficiency.

[0017] And since the space surrounded by the insulator is open toward the cooling fan, the cooling air can be efficiently taken into the space surrounded by the insulator to uniformly cool the exhaust system member. Therefore, the driving power of the cooling fan can be suppressed as much as possible to prevent deterioration of fuel consumption.

[0018] The manifold may have a complex shape. However, as described in claim 2, when the plurality of heat insulation devices are composed of a main insulator and a sub-insulator, even if the manifold has a complex shape, it can accurately insulate heat (radiate heat or keep warm). And since there are ventilation gaps between adjacent sub-insulators or between the main insulator and the sub-insulator, it can prevent heat accumulation and accurately cool. Also, it can prevent the edges of adjacent insulators from colliding due to vibration and generating noise.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0020] (1). Arrangement Mode and Basic Structure Next, embodiments 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 the vehicle body 1. Note that a front compartment 3 is formed at the front of the vehicle body 1, and, for example, a battery, a 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. However, as shown in FIG. 1, the cylinder bore axis O1 is inclined at an angle of approximately 45° with respect to the vertical line and the horizontal. That is, the engine is horizontally mounted with the crankshaft 4 in a posture that is long in the vehicle width direction, but is 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 the embodiment is a horizontally mounted slant engine that has fallen to the rear side of the vehicle body.

[0022] Hereinafter, the terms "front and rear" and "left and right" will be used to specify directions, but these terms "front and rear" and "left and right" are based on the vehicle body (driver). In an engine, the crankshaft axis direction is often defined as the front-rear direction, but the front-rear direction used in this embodiment is different from this general definition. The up-down direction is the vertical line direction. The directions are clearly indicated in the drawings as appropriate.

[0023] The basic structure of the engine is the same as the conventional one. As shown in FIGS. 1 and 2, as the engine body, it includes 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. Since the cylinder bore axis O1 is largely tilted backward, as shown in FIG. 1, an auxiliary crankcase 8 having a triangular shape in side view is fixed to the lower surface of the cylinder block 5, and as shown in FIG. 2, an oil pan 9 is fixed to the lower surface of the auxiliary crankcase 8.

[0024] In this embodiment, although partially shown in FIG. 2, a chain cover 10 covering the timing chain is fixed to the left end surfaces of the cylinder block 5 and the cylinder head 6. On the other hand, the right end face portion of the cylinder block 5 forms a transmission case mounting flange 11. In FIG. 2, reference numeral 12 indicates an oil inlet, reference numeral 13 indicates an oil filter, reference numeral 14 indicates an ignition coil, and reference numeral 15 shown in FIGS. 1 and 2 is an EGR valve. In FIG. 1, reference numeral 16 indicates a cooling water pipe. In FIG. 2, one end portion of the crankshaft 4 is exposed outside (left side) of the chain cover 10.

[0025] The engine is slanted in a rearward-tipped posture, with the downward inclined surface as the exhaust side surface and the downward inclined surface as the intake side surface. In FIG. 1, a surge tank 17 constituting the intake side member partially appears. In FIGS. 1 and 2, reference numeral 18 indicates an air cleaner. The air cleaner 18 has a dirty chamber in the lower half and an intake suction duct 19 is connected to the side surface thereof, and a clean chamber in the upper half and an intake feed duct 20 is connected thereto. The intake feed duct 20 is connected to the surge tank 17 via a throttle valve (not shown).

[0026] The engine is assembled in the engine factory with the cylinder bore axis O1 vertical. In the automobile assembly factory, since it is installed in the rear compartment 2 of the vehicle body in an inclined posture, it is necessary to lift the engine in a posture with the cylinder bore axis O vertical in the engine factory. For this reason, the first hook indicated by reference numeral 21 in FIGS. 1 and 2 and the second hook 22 indicated by the dashed-dotted 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 surface) 23 of the cylinder head 6 (see FIGS. 1 and 2(B)). These hooks 21 and 22 are necessary in the engine factory and are removed after the engine is mounted on the vehicle body.

[0027] (2). Structure of the Manifolder As described above, the exhaust side surface of the engine is inclined downward to the rear. However, a manifolder 25 shown alone in FIGS. 3(A) and 4(A) is fixed to the exhaust side surface 23 of the cylinder head 6. The manifolder 25 has a cylindrical catalyst case 26 containing a catalyst, an elbow-shaped joint 27 integrally provided at the inlet side end 26a of the catalyst case 26, and an L-shaped outlet pipe 28 integrally provided at the outlet side end of the catalyst case 26.

[0028] As shown in FIG. 3(A), 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 at the opening edge thereof is fixed to a land portion 23a (see FIG. 4(B)) formed on the exhaust side surface 23 of the cylinder head 6 by a group of stud bolts 30 and nuts 31. Therefore, the cylinder head 6 of the present embodiment is of an internal manifold type in which an exhaust gas collecting passage is provided inside, and one exhaust outlet (not shown) opens in the land portion 23a.

[0029] As shown in FIGS. 1 and 2, in the manifold 25, the outlet pipe 28 is in an L-shaped form having a horizontal lateral portion 28a welded to the catalyst case 26 and a downward portion 28b bent at its rear end. At the lower end of the downward portion 28b, a flange 32 for connecting an exhaust pipe (not shown) is fixed by welding. Further, at the end of the downward portion 28b near the outlet, the starting end of the EGR pipe 33 is connected. 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. 3(B), the flange 34 fixed to the terminal end is fixed to the cylinder head 6 by stud bolts 35 and nuts 36.

[0030] Note that an internal EGR passage communicating 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 (for example, the surge tank 17) via the above-described EGR valve 15.

[0031] At the inlet side end portion 26a of the catalyst case 26, a front sensor mounting seat 37 for mounting an O2 sensor or an A / F sensor projects. The front sensor mounting seat 37 is disposed slightly above the inlet side end portion 26a, and as shown in FIG. 3(B), a front sensor plug 38 is connected thereto. On the other hand, in the lateral portion 28a of the outlet pipe 28, a rear sensor mounting seat 39 for measuring the exhaust gas temperature is provided, and a rear sensor plug 40 provided with a temperature sensor is connected to the rear sensor mounting seat 39.

[0032] (3). Main insulator · Cooling fan The catalyst case 26 and the joint 27 in the manifold 25 are surrounded from above and below by a first main insulator 42 and a second main insulator 43, for example, as shown in FIG. 3(B) and FIG. 5. The first main insulator 42 generally covers the upper half of the catalyst case 26, and with a semi-cylindrical body as the main body, an inlet side end plate 42a covering the inlet side end portion 26a of the catalyst case 26 is integrally bent and formed thereon. A U-shaped front notch 44 for passing the front sensor mounting seat 37 is formed in the inlet side end plate 42a.

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

[0034] When the joint 27 extends horizontally from the inlet-side end portion 26a of the catalyst case 26, the extension portion 43a that covers the joint 27 may be formed on both the first main insulator 42 and the second main insulator 43. When the joint 27 extends obliquely upward from the inlet-side end portion 26a of the catalyst case 26, the extension portion 43a that covers 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 with bolts 45 at three positions on the left and right. That is, first to third brackets 46, 47, and 48 are provided on the upper right end of the joint 27, the rear surfaces of the left and right middle portions of the joint 27, and the rear surfaces of the left and right middle portions of the catalyst case 26, and are fixed to these with bolts 45.

[0036] Therefore, as clearly 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 ridge-shaped second fixing portion 50 corresponding to the second bracket 47, and a horizontally long ridge-shaped 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 U-shaped in side view, and two bolts 45 are screwed into it.

[0037] On the other hand, as shown in FIGS. 7(A) to 7(C), the first main insulator 42 has a boss-shaped fourth fixing portion 52 bulging rearward at the lower end portion close to the entrance-side end plate 42a, a boss-shaped fifth fixing portion 53 bulging upward at approximately the upper portion of the left-right middle portion, and a eaves-shaped sixth fixing portion 54 bulging at the lower end portion of the front portion. As shown in FIG. 5(A), the fourth fixing portion 52 is fixed to a fourth bracket 55 fixed to the exhaust side surface 23 of the cylinder head 6 with a bolt (not shown).

[0038] The fifth fixing portion 53 is clamped and fixed between a fifth bracket 56 shown in FIG. 5 and a sixth bracket 57 shown in FIG. 3(A) with a bolt 59 (see FIG. 5). The fifth bracket 56 is fixed to the exhaust side surface 23 of the cylinder head 6 with a bolt (not shown), and the sixth bracket 57 is fixed to the upper surface of the catalyst case 26 by welding, and a nut is fixed to the inner surface thereof. The sixth fixing portion 54 of the first main insulator 42 overlaps the third bracket 48 provided on the catalyst case 26 from the rear, and the third fixing portion 51 of the second main insulator 43 overlaps the sixth fixing portion 54, and the sixth fixing portion 54 and the third fixing portion 51 are jointly tightened to the third bracket 48 with a bolt 45.

[0039] As shown by the dashed-dotted line in FIG. 2, a cooling fan 58 is disposed generally concentric with the axis of the catalyst case 26 on the left side of the manifold 25. The cooling fan 58 is disposed such 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 notch 44 of the first main insulator 42 and into the space surrounded by the main insulators 42 and 43. Therefore, in the present embodiment, the front notch 44 of the first main insulator 42 serves as the air guide port described in the claims.

[0040] In Fig. 2, the upper part of the cooling fan 58 and the lower part of the air cleaner 18 partially overlap. However, since the shape of the air cleaner 18 has a high degree of freedom, 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 arranged to flow toward the front notch 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 for interrupting the power.

[0041] As shown in Fig. 5(A), a first ventilation gap 60 that communicates with the front notch 44 and reaches the third and sixth fixing portions 51 and 54 is formed between the left rear side portion of the rear side of the first main insulator 42 and the rear side of the main body of the second main insulator 43. Also, an outlet 80 for passing 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. However, a second ventilation gap 61 that starts from the ends of the third and sixth fixing portions 51 and 54 and communicates with the outlet 80 is formed between the right rear end of the rear side of the first main insulator 42 and the right rear side of the rear side of the second main insulator 43. The groove widths of the first ventilation gap 60 and the second ventilation gap 61 are set to about 4 mm, but can be increased or decreased as necessary.

[0042] As shown in Fig. 6 (also refer to Fig. 4(B)), a third ventilation gap 62 that communicates with the outlet 80 is formed 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 also be increased or decreased as necessary.

[0043] (4). Sub-insulator The outlet pipe 28 that constitutes the manifold 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 Figs. 2 to 6. Therefore, for example, as shown in Fig. 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 lateral portion 28a of the outlet pipe 28. However, as shown in FIG. 8(C), an escape hole 65 for avoiding interference with the rear sensor mounting seat 39 is opened upward in the lateral portion of the first sub-insulator 63.

[0045] As shown in FIG. 3(A), a rearward seventh bracket 66 and a downward eighth bracket 67 are integrally and continuously formed on the lateral portion 28a of the outlet pipe 28. On the other hand, on the downward portion 28b of the outlet pipe 28, a ninth bracket 68 protruding rightward (outward) and a tenth bracket 69 protruding leftward (inward) are formed.

[0046] For example, as clearly shown in FIG. 5(B), a rearward seventh fixing portion 70 is formed on the lateral portion of the first sub-insulator 63, and this is fixed to the seventh bracket 66 with a bolt 71. A rightward 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] Also, for example, as clearly shown in FIG. 3(B), a downward ninth fixing portion 73 is formed on the lateral portion of the second sub-insulator 64, and this ninth fixing portion 73 is fixed to the eighth bracket 67 with a bolt 74. A tenth fixing portion 75 protruding leftward is formed on the downward 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) (see also FIGS. 8(A) and 8(B)), a notch 76 is formed in the downward portion of the second sub-insulator 64 to allow the EGR pipe 33 to pass through.

[0048] As shown in FIG. 6, at the exit 80 of the main insulators 42 and 43, an arcuate fourth ventilation gap 77 is formed between the second main insulator 43 and the two sub-insulators 63 and 64. Therefore, the fourth ventilation gap 77 communicates with the third ventilation gap 62. The fourth ventilation gap 77 has a groove width that widens from front to back, with a groove width of about 10 mm at the narrow part and about 20 mm at the wide part. 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.

[0049] As shown in FIG. 3(B), an L-shaped fifth ventilation gap 78 is formed 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 processed products made of a metal plate such as a stainless steel plate.

[0050] (5). Summary This embodiment has the above configuration. Since the entire manifold 25 is surrounded by a heat insulation device composed of four insulators 42, 43, 63, and 64, peripheral members such as harnesses can be prevented from being damaged by heat. Also, when the cooling fan 58 is driven, cooling air enters the space surrounded by the insulators 42, 42, 63, and 64 from the front notch 44, so the catalyst case 26 and the outlet pipe 28 can be cooled.

[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 the outlet pipe 28 can be firmly cooled by driving the cooling fan 58. On the other hand, in operation under a low-temperature environment, the cooling fan 58 can be not driven to keep the catalyst case 26 warm, contributing to the early activation and maintenance of the active state of the catalyst. Further, since the engine is disposed in the rear compartment 2, cooling by the running wind cannot be expected. However, in the embodiment, since the cooling air is sent from the cooling fan 58, even an engine disposed in the rear compartment 2 can accurately cool the manifold 25.

[0052] Since the manifold 25 has a complex three-dimensional shape, it is necessary to surround it with a plurality of insulators in order to firmly insulate it. However, as in the embodiment, if the portion composed of the catalyst case 26 and the joint 27 is covered with the pair of upper and lower main insulators 42 and 43, and the outlet pipe 28 is covered with the inner and outer sub-insulators 63 and 64, the entire unit can be firmly covered with the minimum number of insulators 42, 42, 63, and 64.

[0053] That is, the large-volume portion composed of the catalyst case 26 and the joint 27 can be firmly covered by surrounding it with the pair of main insulators 42 and 43 while ensuring workability in pressing, while the inner and outer sub-insulators 63 and 64 formed in an L shape of the outlet pipe 28 can firmly insulate while ensuring workability.

[0054] Further, since the axial centers of the bolts 45, 59, 71, and 74 for fixing the insulators 42, 42, 63, and 64 face the open space in the rear, vertical, or horizontal direction, the rotation operation of each bolt 45, 59, 71, and 74 by a wrench can be easily performed. Therefore, the engine can be assembled efficiently. It is preferable to provide an extension portion 43a on the second main insulator 43 to cover the joint 27, which can simplify the structure. Further, when the first fixing portion 49 of the extension portion 43a is fixed to the first bracket 46 provided on the joint 27, the extension portion 43a protruding from the main body portion of the second main insulator 43 can be firmly fixed.

[0055] As in the embodiment, when the front notch 44 formed in the first main insulator 42 is used as the air inlet, the cooling air can be evenly guided around the catalyst case 26, and the catalyst case 26 can be evenly cooled. Further, since a part of the cooling air hitting the inlet-side end portion 26a of the catalyst case 26 flows backward toward the joint 27 downward, the joint 27 can also be cooled. In addition to or instead of forming the front notch 44 as the air inlet in the first main insulator 42, it is also possible to open an air inlet in the extending portion 43a of the second main insulator 43.

[0056] When the front notch 44 is adopted as the air inlet as in the embodiment, since the first main insulator 42 can be moved vertically for attachment and detachment, the first main insulator 42 can be easily attached and detached even with the front sensor plug 38 attached. When the first main insulator 42 and the second main insulator 43 are clamped together with the third bracket 48 as in the embodiment, the structure can be simplified, which is preferable.

[0057] When the first ventilation gap 60 is provided as in the embodiment, the cooling air can also be introduced from the first ventilation gap 60, so that the introducibility of the cooling air can be improved. Further, when the second ventilation gap 61 and the third ventilation gap 62 are provided, the cooling air can be released in the radial direction, so that it is possible to prevent heat from accumulating around the joint 27 and around the catalyst case 26, which is preferable. Further, since the cooling air escapes from the fourth ventilation gap 77, the accumulation of heat can be accurately prevented. The cooling air can also be released from the fifth ventilation gap 78 to prevent the accumulation of heat at the outlet pipe 28.

[0058] The embodiments of the present invention have been described above, but the present invention can be embodied in various other ways. For example, the engine can also be arranged in a front compartment provided at the front part of the vehicle body. When the catalyst case extends downward, the cooling fan may be arranged so that the cooling air flows from top to bottom. The sub-insulator is not necessarily required. Further, the present invention can also be applied to a manifold provided with an exhaust manifold with branch pipes.

Industrial Applicability

[0059] The invention of the present application can be embodied in an engine. Therefore, it can be industrially used.

Explanation of Signs

[0060] 1 Vehicle body 2 Rear compartment 4 Crankshaft 5 Cylinder block 6 Cylinder head 7 Head cover 23 Exhaust side 25 Manifolder 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 part 44 Front notch (air inlet) 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

1. An exhaust system member having an upstream end fixed to the exhaust side surface of a cylinder head constituting an engine body and an exhaust pipe connected to a downstream end, a cooling fan for sending cooling air toward the exhaust system member, and a heat insulation device surrounding the exhaust system member. The cooling fan is arranged to send cooling air from a direction along the exhaust side surface of the engine body. The heat insulation device includes a plurality of insulators arranged to sandwich at least a part of the exhaust system member. A 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 to the cooling fan. An engine.

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 thereto are integrally unitized. The heat insulation device is composed of a plurality of main insulators surrounding the joint or the exhaust manifold and the catalyst case of the manifold, and a plurality of sub-insulators surrounding the outlet pipe of the exhaust manifold. Ventilation gaps are provided between adjacent sub-insulators and between the main insulators and the sub-insulators. The engine according to Claim 1.

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