JP7734124B2 - engine - Google Patents

Description

The present invention relates to an engine, and more specifically to an engine in which the heat shield cover has high heat insulation properties and does not require the removal of stud bolts from the exhaust outlet flange when attaching or detaching the heat shield cover to the exhaust manifold.

2. Description of the Related Art Conventionally, there is an engine equipped with an exhaust manifold and a heat insulating cover that covers the exhaust manifold (see, for example, Patent Document 1).
In this engine, the portion of the exhaust manifold between the exhaust outlet flange and the head flange, which is sandwiched between the cylinder head, is exposed above the heat insulating cover.

JP 2013-199880 A (see FIG. 1)

<Problem> The heat-shielding cover has poor heat-shielding properties.
In the engine of Patent Document 1, the portion of the exhaust manifold between the head flanges is exposed above the heat shield cover, so the heat shield cover has poor heat insulation properties.

<<Prototype engine prior to the present invention>>
In order to solve the above problems, the inventor of the present invention produced a prototype engine shown in FIGS. 14 to 17 prior to the present invention.
In this prototype engine, the heat shield cover (4) is provided with upper and lower heat shield plates (4a) and (4b) and an anti-head side heat shield plate (4c) that cover the exhaust manifold (3) from the top, bottom, and anti-head side, and the anti-head side has an anti-head side cover opening (4d) that exposes the end face (3ba) of the exhaust outlet flange (3b) on the anti-head side, and a stud bolt (3c) protrudes from the end face (3ba) of the exhaust outlet flange (3b) on the anti-head side.

The portion of the exhaust manifold (3) sandwiched between the exhaust outlet flange (3b) and the cylinder head (2) is called the head flange portion (3d), and this portion (3d) is covered from above by the flat portion (4ag) of the upper heat shield plate (4a).

In this prototype engine, the portion 3d between the head flanges of the exhaust manifold 3 is not exposed upward, and the heat insulating cover 4 has a high heat insulating property.
13(A) to 13(F) are explanatory diagrams of the heat insulating cover 4 used in the prototype engine.

<<New Problems with the Prototype>> When attaching or detaching the heat insulating cover (4) to the exhaust manifold (3), it is necessary to remove the stud bolts (3c) from the exhaust outlet flange (3b).
In this prototype engine, as shown in Figure 12(A), if the upper and lower heat shields 4a, 4b are moved closer to the head flange portion 3d in order to prevent the portion 3d from being exposed through the anti-head side cover opening 4d, a new problem will arise.
That is, as shown in Figures 12(A) to (D), when the heat shield cover (4) is detached from the exhaust manifold (3) to the anti-head side, or when the heat shield cover (4) is attached to the exhaust manifold (3) from the anti-head side, if the flat portion (4ag) of the upper heat shield plate (4a) is tilted downward toward the anti-head side and the heat shield cover (4) is slid sideways along this tilt, as shown in Figures 12(B) to (D), the lower heat shield plate (4b) does not interfere with the exhaust outlet flange (3b), but the flat portion (4ag) of the upper heat shield plate (4a) will interfere with the tip portion (3ca) of the stud bolt (3c).
Therefore, when attaching or detaching the heat insulating cover (4) to or from the exhaust manifold (3), it is necessary to remove the stud bolts (3c) from the exhaust outlet flange (3b).
12(E) to 12(H) are side views of FIGS. 12(A) to 12(D) viewed from the side opposite the head.

The objective of the present invention is to provide an engine in which the heat shield cover has high heat insulation properties and in which there is no need to remove the stud bolts from the exhaust flange when attaching or detaching the heat shield cover to the exhaust manifold.

The main features of the present invention are as follows.
As shown in Figures 3 and 4, the portion of the exhaust manifold 3 that is sandwiched between the exhaust outlet flange 3b and the cylinder head 2 is defined as a head-flange portion 3d, and as shown in Figures 3 to 5, the upper heat shield plate 4a has an upper protrusion 4aa formed by protruding a portion of the upper heat shield plate 4a upward above the head-flange portion 3d.
As shown in Figures 1(A) to 1(D), when the heat shield cover (4) is detached from the exhaust manifold (3) toward the opposite head side, or when the heat shield cover (4) is attached to the exhaust manifold (3) from the opposite head side, as shown in Figures 1(B) to 1(D), the upper end wall (4ad) of the upper raised portion (4aa) is tilted downward toward the opposite head side, and the heat shield cover (4) is slid laterally along the direction of this tilt, so that the tip portion (3ca) of the stud bolt (3c) passes through the internal space (4ae) of the upper raised portion (4aa), as shown in Figures 1(C) and 1(D).

The present invention has the following advantages.
Effect 1: The heat-shielding cover (4) has high heat-shielding properties.
As shown in Figures 4 and 5, in this engine, the portion 3d between the head flanges of the exhaust manifold 3 is not exposed above the upper heat shield plate 4a due to the upper raised portion 4aa, and the heat shield cover 4 has high heat insulation properties.

<Effect 2> When attaching or detaching the heat insulating cover (4) to or from the exhaust manifold (3), it is not necessary to remove the stud bolts (3c) from the exhaust outlet flange (3b).
As shown in Figure 1(A), in this engine, even if the upper and lower heat shield plates 4a, 4b are brought close to the portion between the head flanges 3d in order to prevent the portion between the head flanges 3d from being exposed from the anti-head side cover opening 4d, when attaching or detaching the heat shield cover 4 to the exhaust manifold 3 as shown in Figures 1(A) to 1(D), the tip portions 3ca of the stud bolts 3c pass through the internal space 4ae of the upper raised portion 4aa as shown in Figures 1(C) and 1(D), so there is no need to remove the stud bolts 3c from the exhaust outlet flange 3b.

Effect 3: The heat-shielding cover (4) has high rigidity.
As illustrated in Figures 3 to 5, in this engine, the upper raised portion (4aa), which is a part of the upper heat shield plate (4a) raised upward in a embossed shape, also functions as a reinforcing rib for the upper heat shield plate (4a), making the heat shield cover (4) less susceptible to thermal deformation.

1(D) is a front view of the heat shield cover just before the removal is completed or the installation has begun. FIG. 1(E) to (H) are side views of FIGS. 1(A) to 1(D) as viewed from the opposite head side. In all of the drawings, the sheet metal heat shield cover (4) is made transparent except for its outline so that the relationship between the internal space (4ae) of the upper protrusion (4aa) and the tip (3ca) of the stud bolt (3c) can be seen. 2(A) is an explanatory diagram of a heat-shielding cover used in an engine according to an embodiment of the present invention; FIG. 2(A) is a side view seen from the opposite head side; FIG. 2(B) is a view taken in the direction of the arrow B in FIG. 2(A); FIG. 2(C) is a view taken in the direction of the arrow C in FIG. 2(A); FIG. 2(D) is a view taken in the direction of the arrow D in FIG. 2(A); FIG. 2(E) is a view taken in the direction of the arrow E in FIG. 2(A); and FIG. 2(F) is a view taken in the direction of the arrow F in FIG. 2(D). 1 is a perspective view of an engine according to an embodiment of the present invention, viewed diagonally downward from the front side opposite the head, and is an exploded view with a heat insulating cover detached from an exhaust manifold. In the perspective view of the engine shown in FIG. 3 with the heat insulating cover attached to the exhaust manifold, the heat insulating cover made of sheet metal is transparent except for the outline. 4, in which the sheet metal heat shield is left opaque. 1 is a perspective view of an engine according to an embodiment of the present invention, viewed obliquely upward from the front side opposite the head side. FIG. FIG. 1 is a plan view of an engine according to an embodiment of the present invention. FIG. 8 is a side view of the exhaust side of the engine of FIG. 7. FIG. 8 is a front view of the engine of FIG. 7. FIG. 8 is a side view of the intake side of the engine of FIG. 7. FIG. 8 is a rear view of the engine of FIG. 7.

12(A) to 12(H) are side views of FIGS. 12(A) to 12(D) seen from the opposite head side of FIGS. 12(A) to 12(D). In all of the drawings, the sheet metal heat shield cover (4) is transparent except for the outline so that the relationship between the flat portion (4ag) of the upper heat shield plate (4a) and the tip portion (3ca) of the stud bolt (3c) can be seen. 13(A) is an explanatory diagram of a heat-shielding cover used in a prototype engine prior to the present invention, in which FIG. 13(A) is a side view from the opposite head side, FIG. 13(B) is a view taken in the direction of arrow B in FIG. 13(A), FIG. 13(C) is a view taken in the direction of arrow C in FIG. 13(A), FIG. 13(D) is a view taken in the direction of arrow D in FIG. 13(A), FIG. 13(E) is a view taken in the direction of arrow E in FIG. 13(A), and FIG. 13(F) is a view taken in the direction of arrow F in FIG. 13(D). FIG. 1 is a perspective view of a prototype engine prior to the present invention, viewed diagonally downward from the front side opposite the head, and is an exploded view with a heat insulating cover detached from the exhaust manifold. In the perspective view of the engine shown in Figure 14 with the heat insulating cover attached to the exhaust manifold, the heat insulating cover made of sheet metal is transparent except for the outline. 15 is a perspective view of the engine, with the sheet metal heat shield remaining opaque. FIG. 1 is a perspective view of a prototype engine prior to the present invention, viewed obliquely upward from the front side opposite the head side.

Figures 1 to 11 are diagrams illustrating an engine according to an embodiment of the present invention. In this embodiment, a vertical, water-cooled, in-line, multi-cylinder, four-cycle, spark-ignition engine is described.

This engine is a dual-fuel engine, and as shown in Figure 5, it includes a cylinder block 9, a cylinder head 2 attached to the top of the cylinder block 9, a cylinder head cover 17 attached to the top of the cylinder head 2, a gear case 18 attached to the front of the cylinder block 9, and an oil pan 19 attached to the bottom of the cylinder block 9. The cylinder block 9 includes an upper half cylinder section 9b and a lower half crankcase 9a. The crankcase 9a houses the crankshaft 1.
The engine includes an intake system, a fuel supply system, an ignition system, an engine cooling system, and an exhaust system.

The intake system is configured as follows.
As shown in Figures 3 to 11, the direction in which the crankshaft 1 is installed is the front-to-rear direction, one side of the front-to-rear direction is the front, the other side is the rear, and the width direction of the engine perpendicular to the front-to-rear direction is the lateral direction.
As shown in Figures 7 and 10, the intake system includes an intake manifold (20) arranged on one side (right side) of the cylinder head (2) and an electronic throttle (21) attached to the front of the intake manifold (20), and the throttle opening of the electronic throttle (21) is controlled by an electronic control device (22) shown in Figure 10.
The electronic control unit 22 is an engine ECU 22a. EUC is an abbreviation for electronic control unit.
As shown in Figure 10, the intake manifold (20) has a rectangular parallelepiped intake collector (20a) that is long in the front-to-rear direction, and four intake branch pipes (20b) that branch off from the intake collector (20a), and an electronic throttle (21) is attached to the front of the intake collector (20a).
Although not shown, an intake valve that opens and closes the valve opening of the intake port in the cylinder head 2 is driven to open and close by a cam on a valve camshaft.

The fuel supply device is configured as follows.
As shown in Figures 7 and 10, the fuel supply device includes a gas mixer (24) mounted in front of the electronic throttle (21), and as shown in Figures 9 and 11, a delivery pipe (25) installed in the front-to-rear direction on the intake side has a plurality of fuel injectors (26) attached in a branched manner at predetermined intervals in the front-to-rear direction to the delivery pipe (25). By switching the operation, it is possible to select between supplying gas fuel to the gas mixer (24) and supplying liquid fuel to the delivery pipe (25).
The gas fuel supplied to the gas mixer (24) is mixed with air to form an air-fuel mixture, which is then supplied to each cylinder from the intake manifold (20). The liquid fuel supplied to the delivery pipe (25) is supplied to each cylinder from the fuel injector (26) via the intake port of each cylinder, where it forms an air-fuel mixture within each cylinder.
The fuel gas may be LNG (liquefied natural gas), LPG (liquefied petroleum gas), or the like.
The liquid fuel may be gasoline or the like.

The ignition device is configured as follows.
As shown in Figures 7 and 11, the ignition device has a plurality of coil-on plugs (27) corresponding to each cylinder, and the air-fuel mixture in each cylinder is ignited by a spark generated by the coil-on plugs (27).
The amount of gas fuel supplied to the gas mixer (24), the timing of fuel injection from the fuel injector (26), the amount of fuel injection, and the ignition timing of the coil-on plug (27) are controlled by the engine ECU (22a) according to the engine rotation speed and engine load.
The injection timing from the fuel injector (26) and the ignition timing of the coil-on plug (27) are set based on the crank angle.
The engine rotation speed and crank angle are calculated by the engine ECU 22a based on the detection of the rotation state of the crankshaft 1 by the rotation detection sensor 10 shown in FIG.
The rotation detection sensor (10) comprises a sensor body (10a) inserted into the gear case (18) and a connector (10b) connected to the sensor body (10a), and a cable (8) extending from the connector (10b) is electrically connected to the engine ECU (22a).

The engine cooling system is configured as follows.
As shown in Figures 7 and 8, the engine cooling system has an engine cooling fan (7) located at the front of the engine, and the engine cooling fan (7) passes cooling air backward through a radiator (not shown) located in front of the engine, dissipating heat from the engine cooling air passing through the radiator and air-cooling the engine by using the cooling air that has passed through the radiator.
The engine cooling fan (7) is driven by the crank pulley (1a) through a fan belt (12).
The fan belt (12) is tensioned by a generator that also serves as a belt tensioner (13).

The exhaust system is configured as follows:
As shown in Figures 7, 8 and 11, the exhaust system includes an exhaust manifold (3) arranged on the other lateral side (left side) of the cylinder head (2), opposite to the intake manifold (20) on one lateral side, and a heat insulating cover (4) that covers the exhaust manifold (3).
As shown in Figures 3 to 6, the side of the exhaust manifold 3 that faces outward from the exhaust side wall 2a of the cylinder head 2 in the lateral direction is defined as the anti-head side, and the exhaust manifold 3 includes an exhaust collector portion 3a and an exhaust outlet flange 3b provided on the anti-head side of the exhaust collector portion 3a.

As shown in Figures 3 to 6, the heat shield cover (4) includes upper and lower heat shield plates (4a) and (4b) and a counter-head side heat shield plate (4c) that cover the exhaust manifold (3) from the upper, lower, and counter-head side, and the counter-head side heat shield plate (4c) is provided with a counter-head side cover opening (4d) that exposes the end face (3ba) of the exhaust outlet flange (3b) on the counter-head side.
As shown in FIGS. 4 to 6, a stud bolt 3c protrudes from an end face 3ba of the exhaust outlet flange 3b toward the opposite side of the head.

As shown in Figures 3 and 4, the portion of the exhaust manifold (3) sandwiched between the exhaust outlet flange (3b) and the cylinder head (2) is the inter-head flange portion (3d), and as shown in Figures 3 to 5, the upper heat shield plate (4a) has an upper raised portion (4aa) above the inter-head flange portion (3d), where a portion of the upper heat shield plate (4a) is raised upward in a embossed manner.

As shown in Figures 1(A) to 1(D), when the heat shield cover (4) is removed from the exhaust manifold (3) toward the anti-head side, or when the heat shield cover (4) is attached to the exhaust manifold (3) from the anti-head side, as shown in Figures 1(B) to 1(D), the upper end wall (4ad) of the upper raised portion (4aa) is tilted downward toward the anti-head side, and the heat shield cover (4) is slid laterally along this tilt, so that the tip portion (3ca) of the stud bolt (3c) passes through the internal space (4ae) of the upper raised portion (4aa), as shown in Figures 1(C) and 1(D).

As shown in Figures 4 and 5, in this engine, the portion (3d) between the head flanges of the exhaust manifold (3) is not exposed above the upper heat shield plate (4a) due to the upper raised portion (4aa), and the heat shield cover (4) has high heat insulation properties.

As shown in Figure 1(A), in this engine, even if the upper and lower heat shields (4a) and (4b) are brought close to the head flange section (3d) to prevent the section (3d) from being exposed through the anti-head cover opening (4d), when attaching or detaching the heat shield cover (4) to the exhaust manifold (3) as shown in Figures 1(A) to 1(D), the tip (3ca) of the stud bolt (3c) passes through the internal space (4ae) of the upper raised portion (4aa), as shown in Figures 1(C) and 1(D), so there is no need to remove the stud bolt (3c) from the exhaust outlet flange (3b).

As shown in Figures 3 to 5, in this engine, the upper raised portion (4aa), which is a protruding portion of the upper heat shield plate (4a) that also functions as a reinforcing rib for the upper heat shield plate (4a), makes the heat shield cover (4) less susceptible to thermal deformation.

The procedure for removing the heat insulating cover (4) from the exhaust manifold (3) is as follows.
To remove the heat shield cover 4 shown in FIG. 1(A) from the exhaust manifold 3, the upper end wall 4ad of the horizontally oriented upper raised portion 4aa is tilted downward toward the opposite side of the head as shown in FIG. 1(B), and the heat shield cover 4 is slid laterally toward the opposite side of the head along the slope of the upper end wall 4ad of the upper raised portion 4aa as shown in FIG. 1(C) so that the tip portions 3ca of the stud bolts 3c pass through the internal spaces 4ae of the upper raised portion 4aa. Once the tip portions 3ca of the stud bolts 3c have passed through the internal spaces 4ae of the upper raised portion 4aa as shown in FIG. 1(D), the heat shield cover 4 is removed from the exhaust manifold 3 toward the opposite side of the head.

The procedure for attaching the heat insulating cover (4) to the exhaust manifold (3) is as follows.
To attach the heat shield cover 4 to the exhaust manifold 3, as shown in FIG. 1(D), the heat shield cover 4 is brought close to the exhaust manifold 3 from the side opposite the head, with the upper end wall 4ad of the upper protrusion 4aa tilted downward toward the side opposite the head. Then, the tip end 3ca of the stud bolt 3c is inserted from the head side into the internal space 4ae of the upper protrusion 4aa. Then, as shown in FIG. 1(C), the heat shield cover 4 is attached to the exhaust manifold 3 along the direction of the tilt of the upper end wall 4ad of the upper protrusion 4aa. By sliding the heat shield cover 4 laterally toward the head, the tip 3ca of the stud bolt 3c passes through the internal space 4ae of the upper raised portion 4aa, and as shown in Figure 1(B), once the tip 3ca of the stud bolt 3c has passed through the internal space 4ae of the upper raised portion 4aa, the upper end wall 4ad of the inclined upper raised portion 4aa is brought into a horizontal position as shown in Figure 1(A), and the heat shield cover 4 is attached to the exhaust manifold 3.

As shown in FIG. 1(E), when viewed from the side opposite the head, the end face (3ba) of the exhaust outlet flange (3b) is formed in a rectangular shape with both upper and lower edges (3bb) and (3bc) horizontal, and stud bolts (3c) protrude from each of the four corners of the end face (3ba).
As shown in Figure 2(D) , the upper raised portion (4aa) is formed in a horizontally elongated rectangular shape when viewed from above, and as shown in Figures 1(C)(D)(G)(H) , when the heat shield cover (4) is attached to or detached from the exhaust manifold (3), the tip portions (3ca) of a pair of front and rear stud bolts (3c) protruding from a pair of front and rear upper corner portions (3bc) protruding from the upper corners of the end face (3ba) of the exhaust outlet flange (3b) are configured to pass through the internal space (4ae) of the upper raised portion (4aa).

As shown in Figure 1(E), in this engine, when viewed from the side opposite the head, the end face (3ba) of the exhaust outlet flange (3b) is square, and stud bolts (3c) protrude from each of the four corners of the end face (3ba). Therefore, when connecting a vertical or horizontal exhaust outlet passage (not shown) to the exhaust outlet flange (3b), the stud bolts (3c) are not hidden behind the exhaust outlet passage piping when viewed from the side opposite the head, making it easy to attach the exhaust outlet passage to the exhaust outlet flange (3b).

Furthermore, as shown in Figure 1(E), in this engine, the end face (3ba) of the exhaust outlet flange (3b) is rectangular, which allows for a shorter vertical height compared to when it were circular. This in turn allows for a shorter height of the cover opening (4d) on the opposite side of the head, and therefore a shorter separation distance between the upper and lower heat shields (4a) and (4b). Furthermore, the horizontal upper and lower edges (3bb) and (3bc) are less likely to interfere with the upper end wall (4ad) of the upper protrusion (4aa) or the lower heat shield (4) when the heat shield cover (4) is attached or detached from the exhaust manifold (3), allowing for a more compact heat shield cover (4).

As shown in Figures 1(E)(H) and 2(A)(D)-(F), the upper heat shield (4a) has an upper additional raised portion (4af) formed by raising a portion of the upper heat shield (4a) upward in a embossed shape behind the upper raised portion (4aa), and the upper additional raised portion (4af) is formed in a horizontally elongated rectangular shape when viewed from above. The upper additional raised portion (4af) may also be located in front of the upper raised portion (4aa).

As shown in Figures 1(E)(H) and 2(A)(D)-(F), in this engine, the upper additional raised portion (4af), which is a raised portion of the upper heat shield plate (4a) in an upward projection-like shape, functions as a reinforcing rib for the upper heat shield plate (4a), giving the heat shield cover (4) high rigidity and making it less susceptible to thermal deformation.

As shown in FIG. 2(D), the front-to-rear width of the upper additional protrusion (4af) is formed to be shorter than the front-to-rear width of the upper protrusion (4aa).
In this engine, the upper additional raised portion (4af) functions as a reinforcing rib, so the heat insulating cover (4) has high rigidity and is less likely to be deformed by heat.

As shown in Figures 3 to 5, the upper heat shield plate (4a) has an upper raised portion (4aa) and an additional upper raised portion (4af) as well as a flat portion (4ag), and the heat shield cover (4) is fixed to the exhaust manifold (3) with fasteners (5) that press the additional upper raised portion (4af) and the flat portion (4ag) from above.

As shown in Figures 3 to 5, in this engine, the flat portion (4ag) of the upper heat shield (4a), which is resistant to deformation due to pressure from above, and the upper additional raised portion (4af), which has a short front-to-rear width, absorb pressure from above on the fastener (5), making it difficult for the fastener (5) to loosen.

As shown in Figure 3, the exhaust manifold (3) has multiple exhaust branch pipes (3e) lined up in the front-to-rear direction that guide exhaust from multiple cylinders. The portion of the exhaust collector section (3a) adjacent to the anti-head side of each exhaust branch pipe (3e) is designated as the anti-head side collector section (3ab). As shown in Figures 3 to 5, each fastener (5) is fixed to each exhaust branch pipe (3e) or the anti-head side collector section (3ab).

As shown in Figure 3, in this engine, the heat shield cover (4) is pressed by each fastener (5) at equal distances in the front-to-rear direction according to the arrangement of each exhaust branch pipe (3e) or anti-head collector portion (3ab). This results in an equal distribution of pressure on the heat shield cover (4) from each fastener (5), thereby suppressing distortion of the heat shield cover (4) due to the pressing force of the fasteners (5).

As shown in Figures 2(A) to 2(C), 2(E), 2(F), and 6, the lower heat shield (4b) has a lower raised portion (4ba) formed by raising a portion of the lower heat shield (4b) downward in a embossed shape, and the lower raised portion (4ba) is formed in a horizontally elongated rectangular shape when viewed from below.

As shown in Figures 2(A)-(C), (E), (F) and Figure 6, in this engine, the lower raised portion (4ba), which is a protruding portion of the lower heat shield plate (4b) that functions as a reinforcing rib for the lower heat shield plate (4b), increases the rigidity of the heat shield cover (4) and makes it less susceptible to thermal deformation.

As shown in Figures 1(A)(D) and 2(A)(B)(D) to (F), the upper protrusion (4aa) has standing walls (4ab) that surround its internal space (4ae) from the front, rear, and opposite-head sides, and a head-side opening (4ac) that opens the internal space (4ae) toward the cylinder head (2).
In this engine, heat within the internal space 4ae of the upper protrusion 4aa escapes to the cylinder head 2 side through the head-side opening 4ac, so that the upper protrusion 4aa is less likely to be thermally deformed.

As shown in Figures 3 to 5, this engine is a four-cylinder engine, and the portion between the head flanges (3d) includes a part of the exhaust collector portion (3a), a part of each exhaust branch pipe (3e) for the first and second cylinders, and the space between each exhaust branch pipe (3e) for the first and second cylinders.
The portion between the head flanges (3d) may be located between the exhaust branch pipes (3e) of the second and third cylinders, or between the exhaust branch pipes (3e) of the second and third cylinders.
In this engine, the first cylinder is the front and the fourth cylinder is the rear.

As shown in Figures 1(A) and 2(A) and (B), the upper opening edge (4da) of the cover opening (4d) on the opposite side to the head is positioned at the same height as the flat portion (4ag) of the upper heat shield (4a), and the lower opening edge (4db) of the cover opening (4d) on the opposite side to the head is positioned at the same height as the flat portion (4bb) of the lower heat shield (4b).

As shown in Figure 1(E), when viewed from the opposite head side, the exhaust outlet flange (3b) is formed in a rectangular shape that is slightly longer in the front-to-rear direction, with its upper edge (3bb) at the same height as the upper end of the exhaust collector portion (3a), and its lower edge (3bc) positioned at a height lower than the flat portion (4bb) of the lower heat shield plate (4b).
Of the four corners of the end face (3ba) of the exhaust outlet flange (3b), a pair of upper front and rear semicircular arc-shaped upper protrusions are provided on the upper side, and a pair of lower front and rear semicircular arc-shaped lower protrusions are provided on the lower side, and stud bolts (3c) are threadedly fitted into threaded holes provided in these upper and lower protrusions.

As shown in FIGS. 7 and 8, the heat insulating cover 4 includes front and rear heat insulating plates 4e, 4f that cover the exhaust manifold 3 from the front and rear sides.
As shown in Figure 7, the front heat shield (4e) is formed in an inclined shape that moves away from the cylinder head (2) toward the opposite side of the head as it approaches the rear, and the engine cooling air that passes between the belt tensioner (13) and the cylinder head (2) is guided by the inclination of the front heat shield (4e) to an exhaust outlet passage (not shown) connected to the exhaust outlet flange (3b).
As shown in Figure 7, the rear heat shield plate (4f) is formed in an inclined shape that approaches the cylinder head (2) as it approaches the rear, and a rear opening (4fa) is opened at the very rear, and heat inside the heat shield cover (4) is released rearward from the rear opening (4fa).

As shown in FIG. 9, the engine cooling fan (7) is an axial flow type and can be arranged in two different positions: upper position or lower position.
In the case of an upper positioning, the crankshaft sensor (10) is positioned so that a portion of the connector (10b) overlaps with the projection area of the engine cooling fan (7) located inside the upper fan rotation trajectory (7a) when viewed from the front.
In the case of the lower positioning, the crankshaft sensor (10) is positioned so that the exposed portion of the sensor body (10a) and the entire connector (10b) overlap with the projection area of the engine cooling fan (7) located inside the lower fan rotation trajectory (7b) when viewed from the front.
In this engine, the crankshaft sensor (10) is cooled by the engine cooling air flowing backward, and overheating of the crankshaft sensor (10) due to heat generated by the engine is suppressed, resulting in high accuracy in detecting the rotation state of the crankshaft (1).

As shown in Figure 9, when viewed from the front side of the engine, the cable 8 led out from the connector 10b is introduced into the head exhaust side gap 2b between the belt tensioner 13 of the fan belt 12 of the engine cooling fan 7 and the exhaust side wall 2a of the cylinder head 2, and from this head exhaust side gap 2b, it passes through the front side of the heat insulating cover 4 shown in Figure 8 and the upper side of the engine shown in Figure 7 and is led out to the intake side of the engine.
In this engine, the cable (8) does not come into contact with the heat shield cover (4) or the exhaust guide pipe (not shown) connected to the exhaust outlet flange (3b) of the exhaust manifold (3), and the cable (8) is less likely to be damaged by heat.

(1)...Crankshaft, (2)...Cylinder head, (3)...Exhaust manifold, (3a)...Exhaust collector section, (3ab)...Collector section on the opposite side of the head, (3b)...Exhaust outlet flange, (3ba)...End face, (3bb)...Upper edge, (3bc)...Lower edge, (3c)...Stud bolt, (3ca)...Tip, (3d)...Section between head flanges, (3e)...Exhaust branch Pipe, (4)...heat shield cover, (4a)...upper heat shield plate, (4aa)...upper raised portion, (4ab)...standing wall, (4ac)...head side opening, (4ad)...upper end wall, (4ae)...internal space, (4af)...upper additional raised portion, (4b)...lower heat shield plate, (4ba)...lower raised portion, (4c)...opposite head side heat shield plate, (4d)...opposite head side cover opening, (5)...fastener.

Claims (8)

The crankshaft (1) is installed in a longitudinal direction, and the width direction of the engine, which is perpendicular to the longitudinal direction, is the horizontal direction. The engine is provided with an exhaust manifold (3) arranged on one side of the cylinder head (2) in the horizontal direction, and a heat insulating cover (4) that covers the exhaust manifold (3).
The exhaust manifold (3) includes an exhaust collector portion (3a) and an exhaust outlet flange (3b) provided on the opposite side of the exhaust collector portion (3a), with the side facing outward from the exhaust side wall (2a) of the cylinder head (2) being the opposite side of the head in the lateral direction.
The heat shield cover (4) includes upper and lower heat shield plates (4a) and (4b) and a counter-head-side heat shield plate (4c) that cover the upper, lower, and counter-head-side sides of the exhaust manifold (3). The counter-head-side heat shield plate (4c) is provided with a counter-head-side cover opening (4d) that exposes the end face (3ba) of the exhaust outlet flange (3b) to the counter-head side. A stud bolt (3c) protrudes from the end face (3ba) of the exhaust outlet flange (3b) to the counter-head side.
The portion of the exhaust manifold (3) sandwiched between the exhaust outlet flange (3b) and the cylinder head (2) is defined as a head flange portion (3d), and the upper heat shield plate (4a) is provided with an upper raised portion (4aa) formed by raising a part of the upper heat shield plate (4a) upward in a embossed shape above the head flange portion (3d).
This engine is characterized in that, when the heat shield cover (4) is detached from the exhaust manifold (3) toward the opposite head side, or when the heat shield cover (4) is attached to the exhaust manifold (3) from the opposite head side, the upper end wall (4ad) of the upper raised portion (4aa) is tilted downward toward the opposite head side, and the heat shield cover (4) is slid laterally along the direction of this tilt, so that the tip portion (3ca) of the stud bolt (3c) passes through the internal space (4ae) of the upper raised portion (4aa). 2. The engine according to claim 1,
When viewed from the opposite side of the head, the end face (3ba) of the exhaust outlet flange (3b) is formed in a rectangular shape with both upper and lower edges (3bb) and (3bc) horizontal, and stud bolts (3c) protrude from each of the four corners of the end face (3ba).
When viewed from above, the upper raised portion (4aa) is formed in a horizontally elongated rectangular shape, and is configured so that, when the heat shield cover (4) is attached to or detached from the exhaust manifold (3), the tip portions (3ca) of a pair of front and rear stud bolts (3c) protruding from the upper corners of the end face (3ba) of the exhaust outlet flange (3b) pass through an internal space (4ae) of the upper raised portion (4aa). 3. The engine according to claim 2,
The engine is characterized in that the upper heat shield (4a) is provided with an upper additional raised portion (4af) on the rear or front side of the upper raised portion (4aa) by raising a part of the upper heat shield (4a) upward in a embossed shape, and the upper additional raised portion (4af) is formed in a horizontally elongated rectangular shape when viewed from above. 4. The engine according to claim 3,
An engine characterized in that the front-to-rear width of the upper additional protrusion (4af) is formed shorter than the front-to-rear width of the upper protrusion (4aa). 5. The engine according to claim 4,
The engine is characterized in that the upper heat shield plate (4a) has an upper raised portion (4aa) and an upper additional raised portion (4af) as well as a flat portion (4ag), and the heat shield cover (4) is fixed to the exhaust manifold (3) with fasteners (5) that press the upper additional raised portion (4af) and the flat portion (4ag) from above. 6. The engine according to claim 5,
The engine is characterized in that the exhaust manifold (3) is provided with a plurality of exhaust branch pipes (3e) arranged in a longitudinal direction for guiding exhaust gas from a plurality of cylinders, and the portions of the exhaust collector section (3a) adjacent to the opposite side of the head of each exhaust branch pipe (3e) are defined as opposite-head-side collector sections (3ab), and each fastener (5) is fixed to either each exhaust branch pipe (3e) or the opposite-head-side collector section (3ab) of each exhaust branch pipe (3e). In the engine according to any one of claims 1 to 6,
The engine is characterized in that the lower heat shield (4b) has a lower raised portion (4ba) formed by raising a part of the lower heat shield (4b) downward in a embossed shape, and the lower raised portion (4ba) is formed in a horizontally elongated rectangular shape when viewed from below. In the engine according to any one of claims 1 to 6,
The upper raised portion (4aa) is provided with a standing wall (4ab) that surrounds the internal space (4ae) from the front, rear, and opposite head sides, and a head-side opening (4ac) that opens the internal space (4ae) to the cylinder head (2).