Heat insulating structure for internal combustion engine

A heat insulating structure of an internal combustion engine (engine 1) includes a cylinder-head-side heat insulating cover (30) and a cylinder-block-side heat insulating cover (40). Each of the first side walls (32) of the cylinder-head-side heat insulating cover (30) is disposed outwardly of, and is spaced apart from, a corresponding one of the second side walls (43) of the cylinder-block-side heat insulating cover (40) in the width direction of the vehicle. The lower edge of each of the first side walls (32) is positioned below the upper edge of the corresponding one of the second side walls (43) to overlap with the corresponding one of the second side walls (43) when viewed from the side of the vehicle.

TECHNICAL FIELD

The present disclosure relates to a heat insulating structure of an internal combustion engine, in particular, a heat insulating structure of an internal combustion engine which is housed in an engine compartment provided in the front of a vehicle, and closed/opened by a bonnet, and which includes a cylinder block and a cylinder head coupled to the top of the cylinder block.

BACKGROUND ART

Conventionally, heat insulating structures for heat insulating an internal combustion engine including a cylinder block and a cylinder head coupled to the top of the cylinder block are known in the art. Patent Document 1 discloses a heat insulating structure of an internal combustion engine configured as an engine encapsulation structure including an engine compartment encapsulation member surrounding the upper portion of a power train configured as an assembly of an engine (internal combustion engine) and a transmission in an engine compartment, and an underbody encapsulation member surrounding the lower portion of the power train. The engine compartment encapsulation member and the underbody encapsulation member are provided such that the engine compartment encapsulation member and the underbody encapsulation member are vertically assembled together in a space between the power train and a vehicle body to surround the power train, and that air, for cooling the power train, flowing from an inlet of a front surface in the state where the engine compartment encapsulation member and the underbody encapsulation member are vertically assembled together is discharged from an outlet of a rear surface where the underbody encapsulation member is opened.

CITATION LIST

Patent Document

SUMMARY OF THE INVENTION

Technical Problem

In the heat insulating structure of the internal combustion engine as disclosed in Patent Document 1, the engine compartment encapsulation member and the underbody encapsulation member can heat insulate the internal combustion engine and the transmission. On top of that, allowing headwind from the front inlet to be introduced in each encapsulation member can substantially prevent an excessive increase in the temperature of the entire internal combustion engine.

However, respective components constituting the internal combustion engine have different types of demands for heat insulation. For example, a cylinder head including low-heat-resistant components such as a fuel injection system is required to have high cooling performance in addition to heat insulating performance. In contrast, a cylinder block having cylinders is required to keep the temperature of the cylinders, and thus, the heat insulating performance has priority over the cooling performance.

That is to say, although the heat insulating structure of the internal combustion engine disclosed in Patent Document 1 can heat-insulate the internal combustion engine and the transmission and also can cool the internal combustion engine, it is difficult, for example, to cool the cylinder head while heat-insulating the cylinder block.

The present disclosure is conceived in view of the above problems, and intends to provide a technique capable of cooling a portion of an internal combustion engine while heat-insulating the entire internal combustion engine.

Solution to the Problem

The present disclosure is directed to a heat insulating structure of an internal combustion engine which is housed in an engine compartment provided in a front of a vehicle, and closed/opened by a bonnet, and which includes a cylinder block and a cylinder head coupled to the top of the cylinder block. The heat insulating structure includes: a cylinder-head-side heat insulating cover having a top wall facing, and spaced apart from, a head top surface of the cylinder head, and covering a whole of the head top surface, first side walls extending in a longitudinal direction of the vehicle, each facing, and spaced apart from, a corresponding one of both side surfaces of the cylinder head in a width direction of the vehicle and a corresponding one of upper portions of both side surfaces of the cylinder block in the width direction of the vehicle, and each covering the corresponding one of the both side surfaces of the cylinder head in the width direction of the vehicle and the corresponding one of the upper portions of the both side surfaces of the cylinder block in the width direction of the vehicle, and releasing portions formed at respective both edges of the cylinder-head-side heat insulating cover in a longitudinal direction of the vehicle; and a cylinder-block-side heat insulating cover having a front wall covering a front surface of the cylinder block closer to a front of the vehicle, a rear wall covering a rear surface of the cylinder block closer to a rear of the vehicle, and second side walls each covering a corresponding one of the both side surfaces of the cylinder block in the width direction of the vehicle. Each of the first side walls is disposed outwardly of, and is spaced apart from, a corresponding one of the second side walls in the width direction of the vehicle, and a lower edge of each of the first side walls is positioned below an upper edge of the corresponding one of the second side walls to overlap with the corresponding one of the second side walls when viewed from a side of the vehicle.

According to this configuration, the cylinder-head-side and cylinder-block-side heat insulating covers are provided. The cylinder-head-side heat insulating cover covers the whole of the head top surface of the cylinder head, both side surfaces of the cylinder head in the width direction of the vehicle, and upper portions of both side surfaces of the cylinder block in the width direction of the vehicle. The cylinder-block-side heat insulating cover covers the front and rear surfaces of the cylinder block closer to the front and rear of the vehicle, and both side surfaces of the cylinder block in the width direction of the vehicle. Furthermore, the lower portion of the first side wall of the cylinder-head-side heat insulating cover overlaps with the upper portion of the corresponding second side wall of the cylinder-block-side heat insulating cover when viewed from the side of the vehicle. Therefore, the interior of the cylinder-head-side and cylinder-block-side heat insulating covers can be sufficiently heat-insulated. This allows for heat-insulating the entire internal combustion engine, compared with a case where there is no cylinder-head-side and cylinder-block-side heat insulating covers.

Heat of the cylinder head2and the cylinder block3dissipates due to heat transmission and radiation to air after the internal combustion engine is stopped. The air, around the cylinder head and the cylinder block, that has been heated because of heat transmission from the cylinder head and the cylinder block moves upward and stays in the cylinder-head-side heat insulating cover. Allowing the lower edge of the first side wall of the cylinder-head-side heat insulating cover to be positioned below the upper edge of the second side wall can increase the volume of the air housed inside the cylinder-head-side heat insulating cover. Therefore, the cylinder head can be covered with a large amount of air that has been heated, thereby making it possible to efficiently heat-insulate the cylinder head. Furthermore, the lower portion of the first side wall and the upper portion of the second side wall overlap with each other when viewed from the side of the vehicle. The coinciding portion can double shield radiation from the cylinder block, and thus, the cylinder block can also be efficiently heat-insulated.

The cylinder-head-side heat insulating cover is provided with the releasing portions at both edges of the cylinder-head-side heat insulating cover in the longitudinal direction of the vehicle. Thus, the headwind during running of the vehicle can flow from the front releasing portion of the cylinder-head-side closer to the front of the vehicle into the cylinder-head-side heat insulating cover, and passes along the rear releasing portion of the cylinder-head-side heat insulating cover closer to the rear of the vehicle to be able to pass through the cylinder-head-side heat insulating cover. When the headwind during running of the vehicle passes through the cylinder-head-side heat insulating cover, the headwind passes through the space between the top wall and the top surface of the cylinder head, the space between each of the first side walls and the corresponding one of the side surfaces of the cylinder head in the width direction of the vehicle, and the space between each of the first side walls and the corresponding one of the side surfaces of the cylinder block in the width direction of the vehicle. The front surface of the cylinder block closer to the front of the vehicle is covered with the front wall of the cylinder-block-side heat insulating cover. Thus, no headwind blows against the front surface of the cylinder block closer to the front of the vehicle. Also, each of the first side walls is disposed outwardly of, and spaced apart from, the corresponding one of the second side walls in the width direction of the vehicle. Thus, the space between the second side wall and the corresponding side surface of the cylinder block in the width direction of the vehicle is narrower than the space between the first side wall and the corresponding side surface of the cylinder block in the width direction of the vehicle. Therefore, the headwind hardly enters the space between the second side wall and the corresponding side surface of the cylinder block in the width direction of the vehicle. Thus, the cylinder block is less likely to be cooled by the headwind than the cylinder head. As a result, the cylinder block can be kept warm while the cylinder head can be actively cooled.

Accordingly, it becomes possible to cool a portion of the internal combustion engine while heat-insulating the entire internal combustion engine.

In one embodiment of the heat insulating structure of the internal combustion engine, in the cylinder-block-side heat insulating cover, the front wall is in contact with the front surface of the cylinder block closer to the front of the vehicle, the rear wall is in contact with the rear surface of the cylinder block closer to the rear of the vehicle, and each of the second walls is in contact with the corresponding one of the both side surfaces of the cylinder block in the width direction of the vehicle.

That is to say, with the front wall in contact with the front surface of the cylinder block closer to the front of the vehicle, the rear wall in contact with the rear surface of the cylinder block closer to the rear of the vehicle, and each of the second walls in contact with the corresponding one of the both side surfaces of the cylinder block in the width direction of the vehicle, no headwind during running of the vehicle blows against the portions of the cylinder block in contact with the top wall, the rear wall, and the second side walls. Thus, the portions of the cylinder block in contact with the top wall, the rear wall, and the second side walls are not cooled by the headwind. As a result, the cylinder-block-side heat insulating cover can more effectively heat-insulate the cylinder block.

In the heat insulating structure of the internal combustion engine, it is preferable that an exhaust emission control device be disposed behind the internal combustion engine in the longitudinal direction of the vehicle, and below an edge of the top wall closer to the rear of the vehicle, a space between the cylinder-head-side heat insulating cover and the internal combustion engine form a flow channel in which headwind during running of the vehicle flows from the releasing portion closer to the front of the vehicle, and is discharged from the releasing portion closer to the rear of the vehicle, and a portion of the top wall closer to the rear of the vehicle be curved obliquely downward such that the headwind that has flowed in the flow passage flows toward the exhaust emission control device.

For example, under high speed driving conditions, since high temperature exhaust gas is likely to flow in the exhaust emission control device, the temperature of the exhaust emission control device is likely to rise. Under such conditions, if the temperature of the exhaust emission control device exceeds the upper limit of the activation temperature of the catalyst in the exhaust emission control device, the exhaust gas purification performance of the catalyst is deteriorated.

In order to prevent deterioration of the exhaust gas purification performance of the exhaust emission control device due to such high temperature exhaust gas, a method of cooling the exhaust emission control device may be applicable, the method including mixing unburned fuel into exhaust gas, vaporizing the unburned fuel with heat of the exhaust emission control device, and cooling the direct catalyst using the heat of vaporization. However, according to this method, fuel consumption increases by such the amount of such unburned fuel to be mixed into the exhaust gas.

A portion of the top wall closer to the rear of the vehicle is obliquely curved downwardly such that the headwind that has flowed in the flow passage formed in the space between the cylinder-head-side heat insulating cover and the internal combustion engine flows toward the exhaust emission control device. This configuration allows the headwind that has flowed in the flow passage to blow against the exhaust emission control device. As a result, the headwind can cool the exhaust emission control device. Thus, cooling the unburned fuel as described above is not needed or, even if such cooling of the unburned fuel is performed, the amount of the unburned fuel to be mixed can be reduced. As a result, deterioration of the exhaust purification performance of the exhaust emission control device can be prevented. On top of that, an increase in the fuel consumption due to cooling of the exhaust emission control device can be prevented, too.

In the heat insulating structure of the internal combustion engine in which the flow passage is formed in the space between the cylinder-head-side heat insulating cover and the internal combustion engine, it is preferable that a grille shutter be disposed in a front part of the vehicle at a position closer to the front of the vehicle than an edge of the cylinder-head-side heat insulating cover closer to the front of the vehicle, and control a flow rate of the headwind to be introduced into the flow passage in the space between the cylinder-head-side heat insulating cover and the internal combustion engine.

That is to say, if the temperature of the cylinder head has to be raised, it is not preferable to allow the headwind during running of the vehicle to flow into the flow passage. After the rise of the temperature of the cylinder head, it is preferable to actively introduce the headwind in the flow passage such that the temperature of the cylinder head rises excessively. Providing the grille shutter at the position closer to the front of the vehicle than the edge of the cylinder-head-side heat insulating cover closer to the front of the vehicle allows for adjusting the introducing amount of the headwind into the flow passage according to the requirement for cooling the cylinder head. As a result, the appropriate temperature of the cylinder head can be kept.

In the heat insulating structure of the internal combustion engine, it is preferable that the cylinder-head-side heat insulating cover be vertically divided into an upper cylinder-head-side heat insulating cover and a lower cylinder-head-side heat insulating cover, the upper cylinder-head-side heat insulating cover being detachable from the lower cylinder-head-side heat insulating cover, the upper cylinder-head-side heat insulating cover include the top wall and upper portions of the first side walls, the lower cylinder-head-side heat insulating cover include lower portions of the first side walls, and the lower cylinder-head-side heat insulating cover of the upper and lower cylinder-head-side heat insulating covers overlap with an upper portion of the cylinder-block-side heat insulating cover when viewed from the side of the vehicle.

According to this configuration, the cylinder-head-side heat insulating cover is vertically divided into the upper cylinder-head-side heat insulating cover and the lower cylinder-head-side heat insulating cover, the upper cylinder-head-side heat insulating cover being detachable from the lower cylinder-head-side heat insulating cover. Thus, when the upper cylinder-head-side heat insulating cover is detached, the internal combustion engine becomes visible from above. If the upper and lower cylinder-head-side heat insulating covers are integrally formed together, it is necessary to detach the entire cylinder-head-side heat insulating cover from the vehicle body. On the other hand, if the upper cylinder-head-side heat insulating cover is configured to be detachable from the lower cylinder-head-side heat insulating cover, the upper cylinder-head-side heat insulating cover may be detached from the lower cylinder-head-side heat insulating cover. As a result, the cover can be easily detached during the maintenance of the internal combustion engine.

In the heat insulating structure of the internal combustion engine, it is preferable that a coinciding portion of the first side wall of the cylinder-head-side heat insulating cover and the second side wall of the cylinder-block-side heat insulating cover have a vertical length set to 40 mm or more.

That is to say, if the vertical length of the coinciding portion of the first side wall of the cylinder-head-side heat insulating cover and the second side wall of the cylinder-block-side heat insulating cover is too short, the cylinder-head-side heat insulating cover might not sufficiently heat-insulate the cylinder head. Setting the vertical length of the coinciding portion to 40 mm or more allows the cylinder-head-side heat insulating cover to sufficiently heat-insulate the cylinder head.

Advantages of the Invention

In view of the foregoing description, according to the heat insulating structure of the internal combustion engine in the present disclosure, each of the first side walls is disposed outwardly of, and spaced apart from, the corresponding one of the second side walls in the width direction of the vehicle, and the lower edge of each of the first side walls is positioned below the upper edge of the corresponding one of the second side walls to overlap with the corresponding one of the second side walls when viewed from the side of the vehicle. Thus, the cylinder head can be kept warm and cooled appropriately, whereas the cylinder block has improved heat insulating performance. As a result, it becomes possible to cool a portion of an internal combustion engine while heat-insulating the entire internal combustion engine.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present disclosure will now be described in detail with reference to the drawings.

FIG. 1is a cross-sectional view of a multi-cylinder engine (hereinafter referred to as “engine1”) that is an internal combustion engine having a heat insulating structure according to the embodiment. This engine1is horizontally disposed in an engine compartment in the front of the vehicle such that the cylinder bank direction coincides with the vehicle width direction (the lateral direction inFIG. 1). That is to say, the engine1is a transverse engine. The engine1is arranged such that its upper portion is slanted toward the rear of the vehicle.

The engine1is comprised of a cylinder head2, a cylinder block3, and an oil pan4which are arranged vertically in this order and coupled together. In the following description, a side adjacent to the cylinder head2will be referred to as an “upper side,” and a side adjacent to the oil pan4will be referred to as a “lower side.”

In the upper portion of the cylinder block3, four cylinders5are arranged in a single row to form a cylinder bank. In the lower portion of the cylinder block3, a crankcase7in which a crankshaft6is disposed is provided.

A piston8is inserted into each of the cylinders5to be slidable in the inner periphery of the respective cylinder5. The piston8is coupled to the crankshaft6through a connecting rod9. A combustion chamber10is provided in each cylinder5(only one is illustrated inFIG. 1), i.e., is defined by a top surface of the piston8, the inner wall surface of the cylinder5, and the bottom surface of the cylinder head2.

The cylinder head2is provided with, for each cylinder5, an intake port (not illustrated) for introducing fresh air into the combustion chamber10, and an exhaust port (not illustrated) for discharging exhaust gas from the combustion chamber10. The cylinder head2is also provided with an inlet (not illustrated) and an outlet (not illustrated) for allowing the intake and exhaust ports to communicate with the combustion chamber10. The cylinder head2is further provided with an intake valve (not illustrated) and an exhaust valve (not illustrated) which are configured to open/close the inlet and the outlet, and is further provided with a valve opening/closing mechanism (not illustrated) for opening/closing the intake and exhaust valves.

The cylinder head2is further provided with a fuel injection valve11and an ignition plug12for each cylinder5(only one valve and one plug are illustrated inFIG. 1). The fuel injection valve11injects fuel into the combustion chamber10, and the ignition plug12ignites the fuel injected into the combustion chamber10by the fuel injection valve11.

A head cover2ais attached to the top of the cylinder head2.

The oil pan4stores oil which is supplied to, e.g., a bearing metal (not illustrated) of the crankshaft6and a valve opening/closing mechanism, particularly a hydraulic valve opening/closing mechanism. Although not illustrated, an oil pump is disposed in the lower portion of the cylinder block3to supply oil to each component of the engine1.

A transmission20is coupled to one side of the engine1in the cylinder bank direction (on the left of the vehicle (on the right ofFIG. 1) in this embodiment). The engine1and the transmission20constitute a power plant. The transmission20is an automatic transmission, and has a transmission mechanism such as a torque converter (not illustrated) in a transmission case. The transmission20is horizontally disposed in which input and output shafts, which are not illustrated, extend in the vehicle width direction. The input shaft is coupled to the crankshaft6of the engine1, and the output shaft is coupled to a differential gear23(seeFIG. 2) disposed in a portion of the transmission20closer to the rear of the vehicle. Although not illustrated, right and left front-wheel-drive shafts respectively coupled to right and left front wheels extend from the differential gear23toward both sides in the vehicle width direction.

As illustrated inFIG. 2, an intake manifold13is provided to a portion of the engine1closer to the front of the vehicle to introduce intake air into each cylinder5of the engine1. This intake manifold13has four intake air branch pipes associated with respective four cylinders5of the engine1. The intake air branch pipes are curved from a surge tank extending in the cylinder bank direction (the vehicle width direction) toward an end of the intake port away from the combustion chamber10. The intake air branch pipes associated with the respective cylinders5are connected to openings of the intake ports of the cylinders5open to side surfaces of the engine1closer to the front of the vehicle to communicate with the respective cylinders5.

As illustrated inFIG. 2, an exhaust manifold is provided, covered with a heat insulator16, to a portion of the engine1closer to the rear of the vehicle to exhaust gas from each cylinder5of the engine1. The exhaust manifold has four exhaust gas branch pipes associated with the four cylinders5of the engine1, though the four exhaust gas branch pipes cannot be viewed inFIG. 2since they are covered with the heat insulator16. The four exhaust gas branch pipes converge into one concentrate pipe in a downstream side of a flow of exhaust air. The concentrate pipe is connected to a direct catalyst17functioning as an exhaust emission control device for purifying exhaust gas (seeFIG. 7). The exhaust air branch pipes associated with the respective cylinders5are connected to openings of the exhaust ports of the cylinders5away from the combustion chamber10, the openings being open to side surfaces of the engine1closer to the rear of the vehicle, to communicate with the respective cylinders5. An upper portion of the heat insulator16is provided with a plurality of openings19for introducing headwind during running of the vehicle into the heat insulator16.

The engine1is covered with a heat insulating cover30adjacent to the cylinder head (hereinafter referred to as a “cylinder-head-side heat insulating cover”), and a heat insulating cover40adjacent to the cylinder block (hereinafter referred to as a “cylinder-block-side heat insulating cover”). Here, with reference toFIGS. 1-5, the configurations of the respective heat insulating covers30and40will be described.

The cylinder-head-side heat insulating cover30is a heat insulating cover covering an entire top surface the cylinder head2, the whole of both side surfaces of the cylinder head2in the vehicle width direction, and the upper portions of both side surfaces of the cylinder block3in the vehicle width direction. The cylinder-block-side heat insulating cover40is a heat insulating cover covering the entire cylinder block3. Each of the cylinder-head-side heat insulating cover30and cylinder-block-side heat insulating cover40is comprised of a fiber material, such as glass wool, having heat insulating and sound absorbing properties. This allows the cylinder-head-side heat insulating cover30and the cylinder-block-side heat insulating cover40not only to heat-insulate the engine1, but also to substantially prevent engine sound leakage to the outside of the vehicle.

The cylinder-head-side heat insulating cover30includes a top wall31and first side walls32, as illustrated inFIG. 1. The top wall31covers the entire top surface of the cylinder head2. The first side walls32cover side surfaces of the cylinder head2in the vehicle width direction, and upper portions of both side surfaces of the cylinder block3in the vehicle width direction.

The top wall31faces, and is spaced apart from, the top surface of the cylinder head2(i.e., the head top surface of the head cover2a). Each of the first side walls32faces, and is spaced apart from, a corresponding one of the side surfaces of the cylinder head2in the vehicle width direction, and faces, and is spaced apart from, a corresponding one of the side surfaces of the cylinder block3in the vehicle width direction.

Each of the first side walls32is vertically divided into an upper side wall32aand a lower side wall32b. The upper side wall32acovers an upper portion of the corresponding side surface of the cylinder head2in the vehicle width direction. The lower side wall32bcovers the lower portion of the corresponding side surface of the cylinder head2in the vehicle width direction, and the upper portion of the corresponding side surface of the cylinder block3in the vehicle width direction.

In other words, each of the first side walls32is vertically divided into the upper and lower portions. Thus, the cylinder-head-side heat insulating cover30is vertically divided into an upper cylinder-head-side heat insulating cover33and a lower cylinder-head-side heat insulating cover34. The upper cylinder-head-side heat insulating cover33includes the top wall31and the upper side wall32awhich is the upper portion of the first side wall32, and which is integrally formed with the top wall31. The lower cylinder-head-side heat insulating cover34includes the lower side wall32bthat is the lower portion of the first side wall32.

Both edges of the cylinder-head-side heat insulating cover30in the longitudinal direction of the vehicle are provided with a releasing portion39(seeFIGS. 5 and 7) where no wall is formed.

The top wall31of the upper cylinder-head-side heat insulating cover33, as illustrated inFIG. 2, covers the entire top surfaces of the cylinder head2and the intake manifold13. The length of the top wall31in the vehicle width direction is extended or reduced in conformity with the shape of the components connected to the cylinder head2.

Specifically, the portion of the top wall31closer to the front of the vehicle is provided with a radiator shroud60fixed to a front side frame (not illustrated). The top wall31extends from the position of the radiator shroud60toward the rear of the vehicle with a predetermined length in the vehicle width direction, and extends toward the outside in the vehicle width direction so as to avoid the right side surface of the cylinder head2(in the vehicle width direction) and the surge tank. The top wall31further extends to the end of the cylinder head2closer to the rear of the vehicle with the extended length in the vehicle width direction, and both sides of the top wall31in the vehicle width direction is reduced inwardly in the vehicle width direction to reach a position near a dash panel61located in a portion of the upper cylinder-head-side heat insulating cover33closer to the rear of the vehicle. Also, as illustrated inFIG. 2, cutouts31bare formed at positions close to both ends, in the vehicle width direction, of the top wall31on the edge closer to the rear of the vehicle. The cutouts31bare cut upward to allow a hinge mechanism36, which will be described later, to open/close the upper cylinder-head-side heat insulating cover33.

The top wall31, as illustrated inFIGS. 3 and 4, extends obliquely upwardly from the location of the radiator shroud60toward the rear of the vehicle when viewed from the side of the vehicle. The top wall31is then curved obliquely downward from a position corresponding to an end of the exhaust manifold on the upstream side of the flow of exhaust air (a connection portion between the exhaust manifold and the exhaust port) in the longitudinal direction of the vehicle, and reaches a position near the dash panel61. The curved shape of the top wall31closer to the rear of the vehicle is appropriately adjusted such that headwind, during running of the vehicle, introduced from the opening39a(seeFIG. 5) in the front of the vehicle into the cylinder-head-side heat insulating cover30flows toward the direct catalyst17(seeFIG. 7) connected to an end of the exhaust manifold on the downstream side of the flow of exhaust air.

Further, as illustrated inFIGS. 3 and 4, the edge of the top wall31closer to the front of the vehicle protrudes toward the front of the vehicle beyond the edge of the upper side wall32acloser to the front of the vehicle. This protrusion (hereinafter referred to as “protrusion31a”) is mounted on the front support35.

As illustrated inFIG. 1, the upper side wall32aof the upper cylinder-head-side heat insulating cover33has the upper edge integrally formed with both edges of the top wall31in the vehicle width direction. The upper side wall32ais therefore integrally formed with the top wall31, and extends substantially perpendicularly downwardly from the portion integrally formed with the top wall31.

Also, as illustrated inFIG. 4, the upper side wall32aon the left in the vehicle width direction has a downwardly open cutout at a portion corresponding to the surge tank. This cutout and a cutout formed in the lower side wall32bform a through-hole30a. This through-hole30ais provided to allow, e.g., an intake pipe to extend to the outside of the cylinder-head-side heat insulating cover30. Although not illustrated, the through-hole30ais sealed after the extension of, e.g., the intake pipe by a cushioning material, such as urethane, having a heat insulating property.

The upper cylinder-head-side heat insulating cover33is supported by vehicle body members near the front and rear of the vehicle, as illustrated inFIGS. 2-4. How the vehicle body members support the upper cylinder-head-side heat insulating cover33will specifically be described.

As illustrated inFIG. 2, the top surface of the radiator shroud60is provided with the front support35supporting the portion of the upper cylinder-head-side heat insulating cover33closer to the front of the vehicle. The front support35is fixed to the radiator shroud60. As described above, the radiator shroud60is fixed to the front side frames constituting the vehicle body members. Thus, the front support35is supported by the vehicle body members through the radiator shroud60. As illustrated inFIGS. 3 and 4, a step35ais formed in a portion of the front support35closer to the rear of the vehicle. The above-described protrusion31aof the top wall31is mounted on the step35a. This allows the front support35to support the portion of the upper cylinder-head-side heat insulating cover33closer to the front of the vehicle. The top surface of the front support35is tilted upward toward the rear side of the vehicle so as to be continuous with the shape of the top surface of the top wall31with the protrusion31amounted on the step35a.

As illustrated inFIGS. 3 and 4, a space62is formed between the radiator shroud60and the edge of the upper side wall32a, closer to the front of the vehicle, of the upper cylinder-head-side heat insulating cover33with the protrusion31amounted on the step35aof the front support35. This space62is a space for avoiding contact between the edge of the upper side wall32acloser to the front of the vehicle (in particular, the lower edge of the upper side wall32acloser to the front of the vehicle) and the radiator shroud60when the upper cylinder-head-side heat insulating cover33is rotated upward by a hinge mechanism36, which will be described later.

The portion of the upper cylinder-head-side heat insulating cover33closer to the rear of the vehicle is provided with hinge mechanisms36functioning as a rear support supporting the portion of the upper cylinder-head-side heat insulating cover33closer to the rear of the vehicle. As illustrated inFIG. 2, the hinge mechanisms36are provided at both sides of the portion of the upper cylinder-head-side heat insulating cover33closer to the rear of the vehicle in the vehicle width direction. Each of the hinge mechanisms36, as illustrated inFIGS. 3 and 4, is comprised of a bracket36aand a pin36b. The bracket36ais fixed to the dash panel61that is one vehicle body member. The pin36bis attached to the bracket36a. Specifically, a portion of each bracket36acloser to the rear of the vehicle is fixed to the dash panel61with, e.g., a bolt, and extends toward the front of the vehicle from the fixed portion in the longitudinal direction of the vehicle. The pin36bis attached to a portion of the bracket36acloser to the front of the vehicle so as to protrude outwardly of the bracket36ain the vehicle width direction. The portion of the pin36bprotruding outwardly in the vehicle width direction is inserted through the edge of the upper side wall32a, closer to the rear of the vehicle, of the upper cylinder-head-side heat insulating cover33. This allows the upper cylinder-head-side heat insulating cover33to be rotated vertically with the pin36bas a fulcrum. With the pin36binserted through the edge of the upper side wall32acloser to the rear of the vehicle, the portion of the upper cylinder-head-side heat insulating cover33closer to the rear of the vehicle is supported on the dash panel61, that is the vehicle body member, by the hinge mechanism36. That is to say, the hinge mechanism36rotatably supports the cylinder-head-side heat insulating cover30, specifically, the upper cylinder-head-side heat insulating cover33.

The cylinder-head-side heat insulating cover30is vertically divided into the upper cylinder-head-side heat insulating cover33and the lower cylinder-head-side heat insulating cover34, and the upper cylinder-head-side heat insulating cover33is vertically rotatably supported by the hinge mechanisms36. This allows the upper cylinder-head-side heat insulating cover33to rotate, with the pin36aof the hinge mechanism36as a fulcrum, between a close position of the cylinder-head-side heat insulating cover30where the engine1is covered, and shielded, from above, and an open position where the engine1is visible from above.

As illustrated inFIG. 5, when the upper cylinder-head-side heat insulating cover33is rotated upward with the pin36aas a fulcrum, the upper cylinder-head-side heat insulating cover33is positioned at the open position where the engine1is visible from above. In contrast, when the upper cylinder-head-side heat insulating cover33is rotated downward from the open position, the upper cylinder-head-side heat insulating cover33is positioned at the close position where the engine1is covered, and shielded, from above, as indicated by the imaginary line inFIG. 5.

As illustrated inFIG. 1, each lower cylinder-head-side heat insulating cover34is disposed outwardly of the upper cylinder-head-side heat insulating cover33in the vehicle width direction. The upper edge of the lower cylinder-head-side heat insulating cover34, i.e., the upper edge of the lower side wall32bis provided with a rubber member37extending across the entire upper edge in the longitudinal direction of the vehicle. The upper cylinder-head-side heat insulating cover33(strictly speaking, the upper side wall32aof the upper cylinder-head-side heat insulating cover33) is configured, when being at the close position, to abut on the rubber member37in the lower cylinder-head-side heat insulating cover34(i.e., the lower side wall32b) from the side of the vehicle. As a result, no gap is formed between the lower edge of the upper cylinder-head-side heat insulating cover33and the upper edge of the lower cylinder-head-side heat insulating cover34, more specifically, between the upper side wall32aand the lower side wall32bacross the longitudinal direction of the vehicle. This prevents deterioration of heat insulating performance of the cylinder-head-side heat insulating cover30due to dividing the cylinder-head-side heat insulating cover30into the upper cylinder-head-side heat insulating cover33and the lower cylinder-head-side heat insulating cover34.

The length of the lower cylinder-head-side heat insulating cover34in the longitudinal direction of the vehicle is shorter than that of the upper side wall32ain the longitudinal direction of the vehicle, as illustrated inFIGS. 3 and 4. Specifically, the edge of the lower cylinder-head-side heat insulating cover34closer to the front of the vehicle is positioned at substantially the same position as the edge of the upper side wall32acloser to the front of the vehicle. The edge of the lower cylinder-head-side heat insulating cover34closer to the rear of the vehicle is closer to the front of the vehicle than the edge of the upper side wall32acloser to the rear of the vehicle in the longitudinal direction of the vehicle. As a result, there is a space behind the edge of the lower cylinder-head-side heat insulating cover34closer to the rear of the vehicle, i.e., below the portion of the upper cylinder-head-side heat insulating cover33closer to the rear of the vehicle, specifically, below the portion of the upper cylinder-head-side heat insulating cover33where the hinge mechanism36is attached. As a result, when the upper cylinder-head-side heat insulating cover33is rotated between the closed position and the open position by the hinge mechanism36, such a space is used to allow the upper cylinder-head-side heat insulating cover33near the hinge mechanism36to be rotated.

On the other hand, the vertical length of the lower cylinder-head-side heat insulating cover34is long enough to sufficiently heat-insulate the cylinder head2. Specifically, the lower edge of the lower side wall32bthat is the lower cylinder-head-side heat insulating cover34is positioned below an upper edge of a corresponding one of the second side walls43. Thus, a predetermined length or more of the lower side wall32bwhen viewed from the side of the vehicle overlaps with the corresponding second side wall43.

That is to say, heat of the cylinder head2and the cylinder block3dissipates due to heat transmission and radiation to air after the engine1is stopped. The air, around the cylinder head2and the cylinder block3, that has been heated because of heat transmission from the cylinder head2and the cylinder block3moves upward and stays in the cylinder-head-side heat insulating cover30. Allowing the lower edge of the first side wall32of the cylinder-head-side heat insulating cover30(strictly speaking, the lower side wall32bof the lower cylinder-head-side heat insulating cover34) to be positioned below the upper edge of the second side wall43can increase the volume of the air housed inside the cylinder-head-side heat insulating cover30. Therefore, the cylinder head2can be covered with a large amount of air that has been heated, thereby making it possible to efficiently heat-insulate the cylinder head2. Further, the first side wall32(strictly speaking, the lower side wall32b) and the second side wall43overlap with each other when viewed from the side of the vehicle. The coinciding portion can double shield radiation from the cylinder block3, and thus, the heat of the cylinder block3can also be efficiently insulated.

The vertical length of the lower cylinder-head-side heat insulating cover34will now be described, specifically, with reference toFIG. 6.

FIG. 6is a graph showing a calculation result of a relationship between the vertical length of the first side wall32(i.e., the total of the vertical length of the upper side wall32aand the vertical length of the lower side wall32b) and the heat insulating state of the cylinder head2. This relationship is calculated through a simulation. InFIG. 6, the abscissa represents the vertical length of the first side wall32, whereas the ordinate represents the temperature of the cylinder head2after a lapse of one hour from the stop of the engine1that had been driven for raising the temperature of the cylinder head2(hereinafter referred to as a “temperature after one hour”).

In this simulation, the calculation is performed using a model in which the first side wall32is not divided into the upper side wall32aand the lower side wall32b, and in which the upper side wall32aand the lower side wall32bare integrally formed with each other. In this embodiment, when the upper cylinder-head-side heat insulating cover33is at the closed position, the upper cylinder-head-side heat insulating cover33abuts on the rubber member37provided in the lower heat insulating cover34to form no gap between the upper side wall32aand the lower side wall32b, such that the upper side wall32aand the lower side wall32bare almost integrally formed with each other. The configuration of the above model is equivalent in heat insulating performance to that of this embodiment. InFIG. 6, the interval between the top wall31and the top surface of the cylinder head2is assumed to be 100 mm, and the vertical length of the cylinder head2is assumed to be 180 mm. That is to say, in this simulation, when the vertical length of the first side wall32is 100 mm, the height position of the lower edge of the first side wall32is the same as that of the top surface of the cylinder head2. When the vertical length of the first side wall32is 280 mm, the height position of the lower edge of the first side wall32is the same as that of the bottom surface of the cylinder head2. Also, in this simulation, the temperature of the cylinder head2is calculated when one hour has passed after the stop of the engine1that had been driven for raising the temperature to 90° C. The temperature of outdoor air is assumed to be 25° C.

With reference toFIG. 6, when the vertical length of the first side wall32is 100 mm, i.e., when the height position of the top surface of the cylinder head2is the same as that of the lower edge of the first side wall32, and the side surface of the cylinder head2in the vehicle width direction is not covered with the first side wall32, the temperature after one hour decreases to 71° C. If the vertical length of the lower side wall32is increased from this length, the temperature after one hour rises with the increase in the vertical length of the first side wall32. When the vertical length of the first side wall32is about 280 mm, i.e., when the height position of the bottom surface of the cylinder head2is the same as that of the lower edge of the first side wall32, the temperature after one hour reaches 83° C. That is to say, even when the height position of the bottom surface of the cylinder head2is the same as that of the lower edge of the first side wall32, the temperature after one hour drops by about 10° C. In a situation where the vertical length of the lower side wall32is further increased to allow the lower portion of the first side wall32to overlap with the side surface of the cylinder block3in the vehicle width direction, if the vertical length of the first side wall32is about 320 mm, the temperature after one hour reaches 85° C. If the vertical length of the first side wall32is further increased from this length, the temperature after one hour rises slightly.

That is to say, according to this simulation, in order to keep the temperature after one hour of the cylinder head2at 85° C. or more, the vertical length of the first side wall32has to be long enough to allow the lower edge of the first side wall32to overlap with the side surface of the cylinder block3in the vehicle width direction. Specifically, suppose that calculate the coinciding portion of the first side wall32and the side surface of the cylinder block3in the vehicle width direction such that the temperature after one hour is 85° C. or more. When the one hour after temperature is 85° C. or more, the vertical length of the first side wall32is 320 mm. Thus, the coinciding portion is 40 mm which is a result of subtracting, from this vertical length, the interval between the top wall31and the top surface of the cylinder head2(100 mm), and the vertical length of the cylinder head2(180 mm). In other words, in order that the temperature after one hour is 85° C. or more, the coinciding portion of the first side wall32and the side surface of the cylinder block3in the vehicle width direction should have a length of 40 mm or more. In this embodiment, the vertical length of the lower side wall32b, i.e., the vertical length of the lower cylinder-head-side heat insulating cover34is determined such that the coinciding portion of the lower cylinder-head-side heat insulating cover34with the side surface of the cylinder block3in the vehicle width direction, more specifically, the second side wall43of the cylinder-block-side heat insulating cover40covering the cylinder block3, when viewed from the side of the vehicle has a length of about 40 mm or more.

The lower cylinder-head-side heat insulating cover34on the right in the vehicle width direction is fixed to a door frame (not illustrated), whereas the lower cylinder-head-side heat insulating cover34on the left in the vehicle width direction is fixed to a bracket (not illustrated) of a battery.

The cylinder-block-side heat insulating cover40includes, as illustrated inFIG. 3, a front wall41, a rear wall42, the second side walls43, and a bottom44. The front wall41covers a surface of the cylinder block3closer to the front of the vehicle. The rear wall42covers a surface of the cylinder block3closer to the rear of the vehicle. The second side walls43cover both sides of the cylinder block3in the vehicle width direction. The bottom44substantially covers the whole of the oil pan4.

The elements41-44of the cylinder-block-side heat insulating cover40are disposed inward of the cylinder-head-side heat insulating cover30in the vehicle width direction. Specifically, the elements41-44are disposed so as to be in contact with the surfaces of the cylinder block3and the oil pan4. More specifically, as illustrated inFIG. 3, the elements41-44are in contact with the surfaces of the cylinder block3and the oil pan4while avoiding contact with auxiliary machines, such as a water pump (not illustrated), an alternator (not illustrated), an air compressor (not illustrated), and a timing chain sprocket18, provided to the cylinder block3, and a connection between the transmission20and the engine1, as illustrated inFIG. 1.

The front wall41, the rear wall42, and the second side walls43of the cylinder-block-side heat insulating cover40extend toward upper edges of the respective side surfaces of the cylinder block3so as to cover the respective side surfaces. This allows, as illustrated inFIG. 3, the lower portion of the first side wall32of the cylinder-head-side heat insulating cover30, specifically, the lower portion of the lower cylinder-head-side heat insulating cover34to overlap vertically with the upper portion of the second side wall43of the cylinder-block-side heat insulating cover40when viewed from the side of the vehicle.

Although not illustrated, the cylinder-block-side heat insulating cover40is bolted to brackets provided to the side surfaces of the cylinder block3and the oil pan4to be attached to the cylinder block3and the oil pan4.

In this embodiment, as illustrated inFIG. 4, the transmission20is also covered with a cover for heat-insulating the transmission20(hereinafter referred to as a “transmission heat insulating cover50”).

Similarly to the cylinder-block-side heat insulating cover40, the transmission heat insulating cover50is disposed in contact with the entire surface of the transmission20so as to avoid contact with, e.g., auxiliary machines connected to the transmission20.

The transmission heat insulating cover50is attached to the transmission20with, e.g., a bolt, as illustrated inFIG. 4.

In this way, the transmission20is covered with the transmission heat insulating cover50to heat-insulate the transmission20. This reduces the viscosity of lubricating oil supplied to, e.g., a torque converter of the transmission20. This makes it possible to supply a necessary amount of lubricating oil for lubricating, e.g., the torque converter even if the drive force of the oil pump disposed in the transmission20, driven by the engine1, and supplying, e.g., the torque converter with lubricating oil is decreased. As a result, the engine output for generating the drive force of the oil pump can be reduced to improve fuel economy. If the transmission20is a manual transmission, it is necessary to cool the manual transmission itself with headwind entering the vehicle during running of the vehicle, and thus, it is preferable not to provide the transmission heat insulating cover50.

Next, with reference toFIG. 7, a grille shutter70for adjusting the amount of the headwind entering the cylinder-head-side heat insulating cover30during running of the vehicle will be described. InFIG. 7, regarding the cylinder head2and the cylinder block3, only its outline is illustrated, and illustration of its inner configuration will be omitted.

As illustrated inFIG. 7, the grille shutter70is disposed before the edge of the cylinder-head-side heat insulating cover30closer to the front of the vehicle in the longitudinal direction of the vehicle, specifically, before the radiator shroud60in the longitudinal direction of the vehicle. The grille shutter70includes a plurality of vertically rotatable fins71(five fins inFIG. 7) disposed in the vertical direction, and rotation of the fins71adjusts the open degree of the grille shutter70. Specifically, the grille shutter70is configured such that the degree of opening of the grille shutter70is minimum in a situation where the orientation of the fins71are perpendicular to the running direction of the vehicle, whereas the degree of opening of the grille shutter70is maximum in a situation where the fins71are rotated (rotated counterclockwise inFIG. 7) to allow the orientation of the fins71to be parallel to the running direction of the vehicle. The amount of headwind entering the cylinder-head-side heat insulating cover30during running of the vehicle is set to be increased with the increase in the open degree of the grille shutter70.

The rotation angle of each fin71(i.e., the open degree of the grille shutter70) is configured to be changed by a control signal from a control unit which is not illustrated. The control unit, if there is a requirement for cooling the engine1, in particular, for cooling the cylinder head2, adjusts the amount of headwind entering the cylinder-head-side heat insulating cover30during running of the vehicle by adjusting the angle of each fin71in accordance with the requirement. Specifically, the control unit detects the temperature of engine cooling water (hereinafter referred to as an “engine water temperature”) based on a signal from a water temperature sensor (not illustrated) inserted into a water jacket (not illustrated) of the cylinder head2, and estimates the temperature of exhaust gas based on an engine torque or an introduction amount of fresh air. The control unit houses, in advance, a map for determining the rotation angle of each fin71based on the detected engine water temperature and the estimated exhaust gas temperature. The control unit determines the rotation angle of each fin71based on the map. As a result, the appropriate amount of headwind enters the vehicle during running of the vehicle in accordance with the requirement for cooling the cylinder head2. The control unit may be configured to estimate the temperature of the cylinder head2based on the detected engine water temperature and the estimated exhaust gas temperature to determine the rotation angle of each fin71based on the thus estimated temperature.

Keeping the temperature of the engine1by the cylinder-head-side and cylinder-block-side heat insulating covers30and40enables quick warming of the engine1in a situation where the engine1is restarted after temporary stop of the engine1or a situation where the engine1is started from its cold state. In particular, in this embodiment, when viewed from the side of the vehicle, the vertical length of the first side wall32(strictly speaking, the lower side wall32b) is long such that the lower portion of the first side wall32overlaps with the side surface of the cylinder block3in the vehicle width direction, i.e., the upper portion of the second side wall43. Thus, sufficient heat insulation effect can be obtained. In this way, if the engine1can be warmed quickly, it is possible to reduce the exhaust gas amount at the start of the engine1.

Here, under high speed driving conditions, heat is confined in the cylinder-head-side and cylinder-block-side heat insulating covers30and40, resulting in excessively high temperature of the cylinder head2. A fuel injection valve11and an ignition plug2provided to the cylinder head2have relatively low heat resistance. Therefore, it is necessary to cool the cylinder head2not to cause malfunction of these components. It is not preferable that the cylinder block3be cooled as much as the cylinder head2in order to keep appropriate temperature of the inner cylinder.

In this embodiment, the cylinder-head-side heat insulating cover30is disposed apart from the top surface of the cylinder head2and both side surfaces of the cylinder block3in the vehicle width direction. Thus, headwind entering the front of the vehicle during running of the vehicle through the grille shutter70is introduced from the releasing portion39a(seeFIG. 5) of the cylinder-head-side heat insulating cover30in the front of the vehicle into a space between the cylinder-head-side heat insulating cover30and the engine1(the cylinder head2and the cylinder block3), and flows through a space between the cylinder-head-side heat insulating cover30and the cylinder head2and the cylinder block3to cool the cylinder head2. In other words, the space between the cylinder-head-side heat insulating cover30and the engine1constitutes a flow channel through which the headwind flows.

The cylinder-block-side heat insulating cover40is provided to the cylinder block3so as to be in contact with surfaces of the cylinder block3, namely, the surface closer to the front of the vehicle, the surface closer to the rear of the vehicle, and both side surfaces in the vehicle width direction. Thus, the headwind during running of the vehicle is not brought into direct contact with the cylinder block3, and the cylinder block3is not cooled by the headwind. That is to say, the cylinder block3can be kept warm while the cylinder block2can be actively cooled.

Furthermore, in this embodiment, the grille shutter70can adjust the amount of the headwind, during running of the vehicle, flowing into the flow passage in the space between the cylinder-head-side heat insulating cover30and the engine1(the cylinder head2and the cylinder block3). Thus, it is possible to restrict the amount of the headwind during running of the vehicle in order not to introduce, into the flow passage, an unnecessarily large amount of the headwind for cooling the cylinder head2.

Therefore, according to the embodiment, the cylinder block2that is a part of the engine1can be actively cooled while the entire engine1can be kept warm.

In this embodiment, the portion of the top wall31closer to the rear of the vehicle is obliquely curved downwardly such that the headwind, during running of the vehicle, that has been introduced into the flow passage in the space between the cylinder-head-side heat insulating cover30and the engine1(the cylinder head2and the cylinder block3) flows toward the exhaust manifold and the direct catalyst17. This can prevent deterioration of exhaust gas purification performance of the direct catalyst17at the time of exhausting high temperature exhaust gas under high speed driving conditions. On top of that, this can avoids deterioration of fuel consumption due to cooling the direct catalyst17.

That is to say, under high speed driving conditions, since high temperature exhaust gas is likely to flow in the direct catalyst17, the temperature of the direct catalyst17is likely to rise. The exhaust gas purification performance of the direct catalyst17is improved by raising the temperature of a catalyst in the direct catalyst17and activating the catalyst. However, if the temperature of the catalyst in the direct catalyst17exceeds the upper limit of the activation temperature, the exhaust gas purification performance of the catalyst is deteriorated.

In order to substantially prevent deterioration of the exhaust gas purification performance of the direct catalyst17(strictly speaking, the catalyst in the direct catalyst17), a method of cooling the direct catalyst17may be applicable, the method including mixing unburned fuel into exhaust gas, vaporizing the unburned fuel with heat of the direct catalyst17(strictly speaking, the catalyst in the direct catalyst17), and cooling the direct catalyst17using the heat of vaporization. However, according to this method, fuel consumption increases by the amount of such unburned fuel to be mixed into the exhaust gas.

In this embodiment, the portion of the top wall31closer to the rear of the vehicle is obliquely curved downwardly such that the headwind during running of the vehicle flows toward the exhaust manifold and the direct catalyst17. Accordingly, as indicated by the open arrows shown inFIG. 7, the headwind during running of the vehicle is introduced from the releasing portion39a(seeFIG. 5) of the cylinder-head-side heat insulating cover30closer to the front of the vehicle into the cylinder-head-side heat insulating cover30, and then, flows through the space between the cylinder head2and the cylinder-head-side heat insulating cover30toward the rear of the vehicle. The orientation of the headwind is changed in the curved portion of the top wall31closer to the rear of the vehicle such that the headwind flows toward the exhaust manifold and the direct catalyst17. Then, the headwind is exhausted from a releasing portion39bof the cylinder-head-side heat insulating cover30closer to the rear of the vehicle so as to flow toward the exhaust manifold and the direct catalyst17. As described above, the top surface of a heat insulator16covering the exhaust manifold and the direct catalyst17is provided with a plurality of openings19(seeFIG. 2) for allowing the headwind during running of the vehicle to flow in the heat insulator16. Thus, the headwind that has flowed from the opening19into the heat insulator16can cool the direct catalyst17. This can substantially prevent not only the deterioration of the exhaust gas purification performance of the direct catalyst17but also an increase in the fuel consumption due to cooling of the direct catalyst17.

Furthermore, in this embodiment, the upper cylinder-head-side heat insulating cover33of the cylinder-head-side heat insulating cover30is provided with the hinge mechanisms36capable of opening/closing the upper cylinder-head-side heat insulating cover33. Thus, for example, oil in the engine1can be exchanged with the upper cylinder-head-side heat insulating cover33rotated to the open position. This can simplify the maintenance of the engine1even if the cylinder head2is covered with the cylinder-head-side heat insulating cover30from above.

FIG. 8illustrates a variation of the embodiment. Specifically, in the above embodiment, the upper side wall32aof the upper cylinder-head-side heat insulating cover33is provided with the hinge mechanisms36to open/close the entire upper cylinder-head-side heat insulating cover33. Alternatively, as illustrated inFIG. 8, instead of providing the upper side wall32awith the hinge mechanism36, the substantially entire top wall31may be cut to form a lid38, and the lid38may be provided with hinge mechanisms136. In such a configuration, the hinge mechanism136rotates the lid38upward to open the lid38, thereby making it possible to view the engine1from above. Such a configuration can also simplify the maintenance of the engine1even if the cylinder head2is covered with the cylinder-head-side heat insulating cover30from above.

Also, in the above embodiment, a space is needed for avoiding contact between the edge of the upper side wall32acloser to the front of the vehicle does and the radiator shroud60when the upper cylinder-head-side heat insulating cover33is rotated by the hinge mechanism36. In this variation, the lid38does not abut on the radiator shroud60, and thus, such a space is not needed, which is an advantage of the variation.

In this variation, as long as the lid38can be opened/closed, the hinge mechanism136may be provided to, e.g., an edge of the lid38in the vehicle width direction or an edge of the lid38closer to the front of the vehicle. A bonnet80is provided above the cylinder-head-side heat insulating cover30. In order to increase the rotation range of the lid38, as illustrated inFIG. 8, it is preferable to provide the hinge mechanism136to the edge of the lid38closer to the rear of the vehicle.

The present disclosure is not limited to this embodiment. Any change can be made within the scope of the claims as appropriate.

For example, in the above embodiment, the cylinder-head-side heat insulating cover30is divided into the upper and lower cylinder-head-side heat insulating covers33and34. However, this is merely an example of the present disclosure. The upper and lower cylinder-head-side heat insulating covers33and34may be integrally formed with each other.

In the above embodiment, the second side walls43of the cylinder-block-side heat insulating cover40are in contact with the both side surfaces of the cylinder block3in the vehicle width direction. However, this is merely an example of the present disclosure. As long as the second side walls43are disposed inward of the first side walls32in the vehicle width direction, an interval may be formed between each of the second side walls43and the corresponding one of the both side surfaces of the cylinder block3in the vehicle width direction. The interval between each of the second side walls43and the corresponding one of the side surfaces of the cylinder block3in the vehicle width direction is narrower than an interval between each of the first side walls32and the corresponding one of the both side surfaces of the cylinder head2in the vehicle width direction, and an interval between the each of the first side walls32and the corresponding one of the both side surfaces of the cylinder block3in the vehicle width direction.

Furthermore, in the above embodiment, the cylinder-head-side heat insulating cover30(strictly speaking, the upper cylinder-head-side heat insulating cover33) is provided with the hinge mechanism36(136). Alternatively, the hinge mechanism36(136) does not have to be provided. In this case, during the maintenance of the engine1, the entire cylinder-head-side heat insulating cover30has to be detached from the vehicle body, or the upper cylinder-head-side heat insulating cover33has to be detached from the lower cylinder-head-side heat insulating cover34, or the lid38has to be detached from the top wall31.

The above embodiment is directed to the transverse engine. However, this is merely an example of the present disclosure. The heat insulating structure according to the embodiment may be applied to a vertical engine in which the cylinder bank direction coincides with the longitudinal direction of the vehicle, and a V-engine in which cylinders are arranged to form a V-shape.

The foregoing embodiment is a merely preferred example in nature, and the scope of the present disclosure should not be interpreted in a limited manner. The scope of the present disclosure is defined by the appended claims, and all variations and modifications belonging to a range equivalent to the range of the claims are within the scope of the present disclosure.

INDUSTRIAL APPLICABILITY

The present disclosure is useful as a heat insulating structure of an internal combustion engine which is housed in an engine compartment provided in the front of a vehicle, and closed/opened by a bonnet, and which includes a cylinder block and a cylinder head coupled to the top of the cylinder block.

DESCRIPTION OF REFERENCE CHARACTERS