JP7614047B2 - engine - Google Patents

Description

This invention relates to an engine in which a catalyst case or turbocharger is directly attached to the exhaust side of the cylinder head via a gasket.

Gasoline engines use catalysts as a means of purifying exhaust gas, but because catalysts have the characteristic of not being fully activated until they are heated to a certain degree, there is a problem in that their exhaust gas purification ability remains low for a certain amount of time after a cold start.

Now, the catalyst is heated by the heat of the exhaust gas, but in order to heat the catalyst quickly, it is necessary to effectively utilize the heat of the exhaust gas. However, unless special measures are taken, a significant proportion of the heat of the exhaust gas will be dissipated to the outside from the exhaust pipe such as the exhaust manifold before the exhaust gas discharged from the cylinder head reaches the catalyst, and the heat of the exhaust gas cannot be effectively used to heat the catalyst. Therefore, it has been proposed to increase the efficiency of using the heat of the exhaust gas and to heat the catalyst quickly by configuring the exhaust manifold with a double structure and suppressing heat dissipation from the exhaust manifold (for example, Patent Document 1).

On the other hand, when fixing the exhaust manifold to the cylinder head, a gasket is placed between the flange of the exhaust manifold and the exhaust side of the cylinder head to ensure a seal. Patent Document 2 discloses a technology in which a gasket made of a thin metal plate is formed with a cylindrical flow control means that protrudes slightly toward the inside of the exhaust manifold, allowing the exhaust gas to be smoothly guided into the exhaust manifold without generating vortexes.

JP 2015-113741 A JP 2001-235033 A

Conventional double-structure exhaust manifolds, such as those described in Patent Document 1, have a number of branch pipes equal to the number of cylinders, which are joined together into one and connected to a catalyst case (or turbocharger). This can suppress heat dissipation from the exhaust gas compared to a single-layer exhaust manifold, but because the internal surface area (heat dissipation surface area) of the exhaust manifold is very large, even if heat dissipation can be suppressed, the efficiency of using the heat from the exhaust gas is originally low. Therefore, it is questionable whether the catalyst can be quickly activated after a cold start.

In addition, conventional double-structure exhaust manifolds such as those in Patent Document 1 are problematic in that not only are their structures complex, resulting in significant increases in cost, but also in the weight of the exhaust manifold, which is a negative factor in fuel economy. Furthermore, in conventional structures, the inner tube and outer cylinder are joined together, so thermal strain is unavoidable, especially in the thin inner tube. As a result, it is necessary to use a heat-resistant stainless steel plate with high thermal fatigue strength for the inner tube, which increases costs.

On the other hand, Patent Document 2 uses a gasket to smooth the flow of exhaust gas, and is noteworthy for making effective use of the gasket. However, since it only controls the flow of exhaust gas as it flows from the cylinder head into the exhaust manifold, it does not have the function of suppressing heat dissipation, and therefore the effect of early activation of the catalyst after a cold start cannot be expected.

The present invention was made to improve this current situation.

The present invention is directed to a multi-cylinder engine, which comprises:
"A cylinder head with an exhaust outlet opening on the exhaust side,
a catalyst case or a turbocharger fixed to the exhaust side surface of the cylinder head via a gasket,
The catalyst case and turbocharger have an exhaust gas inlet tube section bent like an elbow so as to redirect the exhaust gas discharged sideways from the exhaust outlet downward, a flange plate is provided at the beginning of the exhaust gas inlet tube section, and the gasket made of a thin metal plate is sandwiched between the flange plate and the exhaust side surface of the cylinder head.
This is the basic structure.

The invention of claim 1 is as follows:
"An inner guide that enters the inside of the exhaust gas introduction tube and changes the direction of the exhaust gas downward is formed integrally with the gasket with a heat insulating space between the inner guide and the exhaust gas introduction tube."
It has the following characteristics:

The inner guide is formed integrally with the gasket by sheet metal processing, but it can also be formed by simple bending alone, and combining bending and stretching is preferable because it increases the protruding dimension of the inner guide. Therefore, it is preferable to use a highly ductile, heat-resistant, corrosion-resistant metal plate as the material for the gasket.

The invention of claim 2 has the same basic configuration as claim 1,
"A collecting passage is formed inside the cylinder head to direct exhaust gas discharged from a plurality of cylinders toward one of the exhaust outlets,
The gasket is composed of a plurality of overlapping thin metal plates, and inner guides, each of which is trough-shaped and tubular as a whole, are integrally formed with the plurality of thin metal plates so as to enter the inside of the exhaust gas inlet portion with a gap between them,
At least a portion of the inner guide is formed with a bent portion that redirects exhaust gas downward.
It has the following characteristics:

The present invention can be developed in various ways. For example, in claim 3, in claim 2,
"The plurality of inner guides are separated into an upper inner guide and a lower inner guide, and the curved portion is formed in the upper inner guide."
The structure is as follows.

As a preferred embodiment of claim 3, claim 4 states:
"The upper inner guide and the lower inner guide are fitted together vertically with their side edges not touching each other."
The structure is as follows.

In this case, the upper and lower inner guides fit together in three ways: a first way in which the side edge of the upper inner guide fits inside the lower inner guide; a second way in which the side edge of the lower inner guide fits inside the upper inner guide; and a third way in which the side edges of the upper and lower inner guides fit together while being shifted in the cylinder row direction. In the first way, the upper inner guide is narrower than the lower inner guide, in the second way, the lower inner guide is narrower than the upper inner guide, and in the third way, the upper and lower inner guides are about the same width.

In the present invention, exhaust gas flows from one exhaust outlet into the inside of the catalyst case or the inside of the turbocharger (scroll chamber or wastegate passage) through the exhaust gas inlet tube, but because the exhaust gas inlet tube is elbow-shaped and short, the heat dissipation area of the exhaust gas is significantly smaller than that of an external collection type exhaust manifold such as that in Patent Document 1. Therefore, whether a catalyst case or a turbocharger is provided, the efficiency of exhaust gas heat utilization is significantly higher than that of an external collection type such as that in Patent Document 1.

In the present invention, the exhaust gas is guided into the inside of the catalyst case or the inside of the turbocharger using an inner guide formed in the gasket, and because there is an insulating gap between the inner guide and the exhaust gas inlet tube, the rate at which the heat of the exhaust gas is dissipated to the outside through the exhaust gas inlet tube can be greatly reduced. Moreover, because the inner guide is formed integrally with the gasket, the structure is simple, and compared to conventional double pipes, costs can be significantly reduced, and fuel efficiency can be improved by reducing weight.

In other words, this invention effectively utilizes the direct mounting method, which can shorten the length of the exhaust gas inlet tube, and guides the flow of exhaust gas with an inner guide attached to the gasket, thereby achieving early activation of the catalyst after cold start and ensuring the supercharging performance of the turbocharger with a simple structure.

One of the features of the present invention is that the inner guide is separate from the exhaust gas inlet tube and can expand and contract freely. Therefore, no thermal strain occurs in the inner guide, making it highly reliable and durable, and it can be applied to conventional gaskets, ensuring cost reduction effects.

Now, conventional double-pipe exhaust manifolds have an inner pipe covered by an outer pipe, so when manufacturing them, the outer pipe must be made into multiple parts and then welded together, which doubles the manufacturing effort and makes them less versatile as they cannot be applied to cast products.

In contrast, in the present invention, the inner guide simply enters the exhaust gas inlet tube, so it can be used without any problems even when the exhaust gas inlet tube is formed by casting. Therefore, it can also be used for turbocharger housings, which are often made by casting, making it highly versatile.

Gaskets may have a single layer structure made of inorganic material, but are often made up of multiple thin metal plates (usually stainless steel plates). In this case, a bead is formed on each thin metal plate, and the bead is crushed and deformed when the flange is tightened to ensure sealing.

Conventionally, when constructing a gasket from a thin metal plate, the portion corresponding to the exhaust outlet was punched out and discarded, but in the present invention, the portion that was conventionally punched out and discarded is processed so that it faces the inside of the exhaust gas introduction tube, forming it into an inner guide. In this case, forming the inner guide into a trough shape as in the invention of claim 2 makes sheet metal processing easier and improves the exhaust gas guide function by increasing the protruding length.

Forming a trough-shaped inner guide on multiple thin metal plates means dividing the cylinder into two or three pieces, but by dividing the inner guide into an upper inner guide and a lower inner guide and forming a bent section in the upper inner guide as in claim 3, the exhaust gas that has traveled straight from the exhaust outlet can be smoothly redirected downward by the upper inner guide, which has the advantage of preventing or significantly suppressing the exhaust gas that has traveled straight from the exhaust outlet from leaking out and hitting the inner surface of the exhaust gas inlet tube, improving the exhaust gas guiding function.

Now, with the internal collection method, where an exhaust collection passage is provided inside the cylinder head, the exhaust outlet has a long (oval) shape along the cylinder row. If the inner guides were separated in the direction of the cylinder row, there is a risk that exhaust gas would leak upwards through the gap between one inner guide and the other, resulting in high heat dissipation. To prevent this, measures must be taken, such as welding the inner guides together to make them one unit.

In this regard, if the inner guide is separated into upper and lower parts as in claim 3, even if there is a gap between the upper and lower inner guides, the exhaust gas can be accurately guided by the upper inner guide. Therefore, claim 3 enjoys the advantage of forming the inner guides individually on each thin metal plate, and can effectively utilize the heat of the exhaust gas while simplifying the structure. Since the upper and lower inner guides are separate from each other and can expand and contract freely, as mentioned above, no problems arise due to thermal strain (the upper inner guide receives a large amount of heat and therefore has a larger thermal expansion than the lower inner guide, but since the upper and lower inner guides are separate and both can expand freely, there is no thermal strain due to differences in expansion).

In particular, as in claim 4, when the upper and lower inner guides are fitted together with some play without abutting each other, this is particularly preferable because it ensures the free expansion and contraction of the upper and lower inner guides while preventing exhaust gas leakage. In addition, because the upper and lower inner guides are independent and do not abut each other, even if the upper and lower inner guides vibrate due to the flow of exhaust gas, there is no noise generation or loss of strength.

Now, because the exhaust gas inlet tube is elbow-shaped, the exhaust gas discharged from the exhaust pipe travels straight sideways before changing direction to face downwards. However, because the exhaust gas is under positive pressure, some of the exhaust gas tends to be pushed downwards while traveling straight sideways. In this case, if the lower inner guide penetrates inside the upper inner guide, there is a concern that the exhaust gas may easily leak out to the outside of the lower inner guide.

In contrast, as in the first aspect of claim 4, when the side edge of the upper inner guide is inserted into the inside of the lower inner guide, the exhaust gas pushed downward is received by the lower inner guide and directed toward the curved portion of the exhaust gas introduction tube, which is advantageous in that it prevents or significantly suppresses the exhaust gas from escaping from the side edge of the inner guide and heading toward the inner surface of the exhaust gas introduction tube.

FIG. 2 is a side view of the engine according to the embodiment, seen from a direction perpendicular to the exhaust side. FIG. 2 is a vertical sectional front view taken along line II-II of FIG. 1 . FIG. 3 is a cross-sectional view taken along line III-III of FIG. 2 . 1A and 1B are side views of a gasket.

Next, an embodiment of the present invention will be described with reference to the drawings. In the following, the terms front-rear and left-right are used to specify directions, but these directions conform to common engine nomenclature, with the crank axis direction being the front-rear direction, and the direction perpendicular to the crank axis and the cylinder bore axis being the left-right direction. When referring to front and rear, the side where the timing chain is located is referred to as the front, and the side where the transmission is located is referred to as the rear. To be clear, the directions are clearly shown in Figures 1 to 3. The up-down direction is approximately vertical.

(1) Overview of the engine The basic structure of the engine is the same as that of a conventional engine, and includes a cylinder block 1 that constitutes the engine body and a cylinder head 2 fixed to its upper surface. Although not shown, a gasket is interposed between the cylinder head 2 and the cylinder block 1.

As shown in FIG. 3, the engine of this embodiment is a three-cylinder engine having three cylinder bores 3, and the cylinder head 2 is formed with a plug hole 4 concentric with the cylinder bores 3, a pair of exhaust ports 5, an exhaust collection passage 6 that connects the group of exhaust ports 5, and one exhaust outlet 8 that opens into the exhaust side surface 7. Note that the reference numeral 9 in FIG. 3 and FIG. 2 denotes a water jacket.

The exhaust outlet 8 is located in the front-rear center of the exhaust collection passage 6, and a land portion 7a where the exhaust outlet 8 opens is formed on the exhaust side surface 7 of the cylinder head 2. An elbow-shaped exhaust gas introduction tube portion 11 formed integrally with the catalyst case 10 is fixed to the land portion 7a with a stud bolt 13 and a nut 14 via a flange plate 12. The flange plate 12 is welded to the exhaust gas introduction tube portion 11.

As shown in FIG. 1, the exhaust outlet 8 is oval-shaped and long in the front-rear direction, and the land portion 7a has a doughnut-shaped portion that surrounds the exhaust outlet 8 and four peninsula-shaped portions that protrude diagonally from this, with stud bolts 13 fixed to the tip of each peninsula-shaped portion. Therefore, the flange plate 12 of the catalyst case 10 has the same shape as the land portion 7a, and the flange plate 12 is fixed to the land portion 7a with nuts 14.

The catalyst case 10 is made of a metal plate such as a stainless steel plate, and has a straight section 16 in which the catalyst 15 is built in, and an upper cone section 17 that is tapered upward and is integrally formed at the upper end of the straight section 16, with the exhaust gas introduction tube section 11 being integrally formed with the upper cone section 17. The exhaust gas introduction tube section 11 can also be called an elbow-shaped joint section. The engine is slanted so that the exhaust side 7 is slightly tilted forward with respect to the vertical line. Reference numeral 18 in FIG. 2 denotes an air-fuel ratio sensor (A/F sensor).

(2) Gasket A gasket 19 is interposed between the flange plate 12 of the catalyst case 10 and the land portion 7a of the cylinder head 2. The gasket 19 is composed of two thin metal plates, a first thin metal plate 20 overlapping the flange plate 12 and a second thin metal plate 21 overlapping the land portion 7a, and although not shown, both plates have bulging beads surrounding the exhaust outlet 8, and the beads are crushed flat to maintain sealing performance.

The first thin metal plate 20 and the second thin metal plate 21 are formed by sheet metal processing with inner guides 22, 23 that fit inside the exhaust gas introduction tube 11. The first inner guide (upper inner guide) 22 formed on the first thin metal plate 20 is gutter-shaped and opens downward, while the second inner guide (lower inner guide) 23 formed on the second thin metal plate 21 is gutter-shaped and opens upward, and the two form a roughly cylindrical shape. A small insulating space 24 is provided between the outer surfaces of the inner guides 22, 23 and the inner surface of the exhaust gas introduction tube 11.

The exhaust gas introduction tube 11 has an elbow shape that guides the exhaust gas downward, and has an inner bent portion 11a and an outer bent portion 11b. The first inner guide 22 has a bent portion 22a that follows the outer bent portion 11b, and the second inner guide 23 has a bent portion 23a that follows the inner bent portion 11a. The bent portion 22a of the first inner guide 22 guides the exhaust gas downward.

As shown in Figures 3 and 4, the front-rear width W1 of the first inner guide 22 is slightly smaller than the front-rear width W2 of the second inner guide 23. Therefore, in plan and side views, the front and rear side edges 23b of the second inner guide 23 extend outward from the front and rear side edges 22b of the first inner guide 22.

In Figures 2 and 4(A), the front and rear side edges 22b of the first inner guide 22 are slightly higher than the front and rear side edges 23b of the second inner guide 23, but in Figure 4(B), the front and rear side edges 22b, 23b of both inner guides 22, 23 fit together with a small gap between them. In either case, the two inner guides 22, 23 are independent and do not come into contact with each other, so there is no distortion due to thermal expansion or noise due to vibration. The embodiment in Figure 4(B) can further improve the exhaust gas leakage function.

As shown in Figures 2 and 4, the tip 22c of the first inner guide 22 is slightly lower than the vertical center 25 of the exhaust outlet 8. The inner guides 22 and 23 are pressed to protrude into the inside of the exhaust gas introduction tube 11 without removing the portion corresponding to the exhaust outlet 8, so that the area of the inner guides in their raw state is approximately the same as the area of the exhaust outlet 8.

If the portion corresponding to the exhaust outlet 8 were simply bent, the protruding dimension of the first inner guide 22 would be the same as the vertical width of the exhaust outlet 8. However, in this embodiment, by using highly ductile stainless steel plates such as SUS310 for both thin metal plates 20, 21, the inner guides 22, 23 are formed by bending while stretching, and this ensures a large protruding dimension for the first inner guide 22 so that its tip is positioned below the center of the exhaust outlet 8 while aligning it with the inner surface of the exhaust gas introduction tube portion 11.

As can be seen from the drawing, the exhaust gas ejected sideways (left-right direction) from the exhaust outlet 8 is guided by the upper and lower inner guides 22, 23, changes direction downward, and is ejected into the inside of the catalyst case 10. In this case, since the exhaust gas ejects from the exhaust gas casing in a straight line, if the first inner guide 23 did not exist, the exhaust gas would collide with the outer bent portion 11b of the exhaust gas inlet tube portion 11 and change direction, increasing the amount of heat released from the exhaust gas inlet tube portion 11 and reducing the amount of heat received by the catalyst 15.

However, in this embodiment, the heat insulating space 24 is provided between the inner guides 22, 23 and the exhaust gas introduction tube 11, and the exhaust gas is guided downward by the first inner guide 22, so that the amount of exhaust gas that comes into contact with the exhaust gas introduction tube 11 is small. This significantly reduces the amount of heat dissipated through the exhaust gas introduction tube 11, and increases the amount of heat received by the catalyst 15. This promotes early heating of the catalyst 15 even during a cold start.

The thin metal plates 20, 21 are thin due to the nature of the beads being crushed and deformed, so the amount of heat absorbed by the inner guides 22, 23 is small, and the amount of heat dissipated through the thin metal plates 20, 21 is also small. In this respect, too, the efficiency of heat utilization can be improved when using the heat of the exhaust gas to raise the temperature of the catalyst 15.

In addition, because the inner guides 22, 23 are separated from each other and each has a free end that allows for free thermal expansion, no thermal distortion occurs in the inner guides 22, 23, ensuring high durability. Furthermore, the inner guides 22, 23 are trough-shaped and have a stable shape, so they do not deform or vibrate due to exhaust gas pressure. Because the gasket 19 is effectively used to change the direction of the exhaust gas, costs can be significantly reduced compared to conventional double pipes.

Although the embodiment of the present invention has been described above, the present invention can be embodied in various other ways. For example, although the embodiment is applied to a catalyst case, it can also be applied to an exhaust turbocharger. In this case, the high temperature exhaust gas can be sent to the scroll chamber, improving the supercharging efficiency. It is also possible to form a second inner guide on the first thin metal plate, and form a first inner guide on the second thin metal plate.

When the gasket is made of three thin metal plates, each thin metal plate can have a trough-shaped inner guide split into three, or the inner guide can be made of only two thin metal plates. The same applies when there are four or more plates. When the first inner guide is narrower than the second inner guide as in the embodiment, it is also possible to abut the side edge of the first inner guide against the inside surface of the second inner guide. In this case, each inner guide is free to expand and contract, so no thermal strain occurs (if the first inner guide is elastically abutted against the second inner guide and kept in a state where they do not separate, noise caused by vibration can be prevented).

For example, in the case of a six-cylinder engine, one exhaust outlet is provided for every three cylinders, and a catalyst case or turbocharger is connected to each of the exhaust outlets, and the present invention can be applied to such types of engines. The invention of claim 1 can also be applied to single-cylinder engines.

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

REFERENCE SIGNS LIST 1 Cylinder block 2 Cylinder head 6 Exhaust collecting passage 7 Exhaust side surface 7a Land portion 8 Exhaust outlet 10 Catalyst case 11 Exhaust gas inlet tube portion 11b Outer bent portion 12 Flange plate 15 Catalyst 19 Gasket 20 First thin metal plate 21 Second thin metal plate 22 First inner guide (upper inner guide)
22a: Bent portion that changes the direction of exhaust gas downwards 23: Second inner guide (lower inner guide)
23a Bending portion 24 Heat insulating space

Claims (4)

A cylinder head having an exhaust outlet opening on an exhaust side;
a catalyst case or a turbocharger fixed to the exhaust side surface of the cylinder head via a gasket,
The catalyst case and the turbocharger have an exhaust gas inlet tube section bent in an elbow shape so as to redirect exhaust gas discharged sideways from the exhaust outlet downward, a flange plate is provided at the beginning of the exhaust gas inlet tube section, and the gasket made of a thin metal plate is sandwiched between the flange plate and the exhaust side surface of the cylinder head.
The engine has the following configuration:
An inner guide that enters the inside of the exhaust gas introduction tube portion and changes the direction of the exhaust gas downward is integrally formed with the gasket with a heat insulating space between the inner guide and the exhaust gas introduction tube portion.
engine. A cylinder head having an exhaust outlet opening on an exhaust side;
a catalyst case or a turbocharger fixed to the exhaust side surface of the cylinder head via a gasket,
The catalyst case and the turbocharger have an exhaust gas inlet tube section bent in an elbow shape so as to redirect exhaust gas discharged sideways from the exhaust outlet downward, a flange plate is provided at the beginning of the exhaust gas inlet tube section, and the gasket made of a thin metal plate is sandwiched between the flange plate and the exhaust side surface of the cylinder head.
The engine has the following configuration:
A collecting passage is formed inside the cylinder head to direct exhaust gas discharged from a plurality of cylinders toward one of the exhaust outlets,
The gasket is composed of a plurality of overlapping thin metal plates, and inner guides, each of which is trough-shaped and tubular as a whole, are integrally formed with the plurality of thin metal plates so as to enter the inside of the exhaust gas inlet portion with a gap between them,
At least a part of the inner guide is formed with a bent portion that changes the direction of exhaust gas downward.
engine. The plurality of inner guides are separated into an upper inner guide and a lower inner guide, and the curved portion is formed in the upper inner guide.
An engine as claimed in claim 2. The upper inner guide and the lower inner guide are fitted vertically together with their side edges not in contact with each other.
An engine as claimed in claim 3.

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