JP7239289B2 - EGR device for internal combustion engine - Google Patents

Description

The present invention relates to an EGR device for recirculating part of exhaust gas to an intake system in an internal combustion engine.

In internal combustion engines for automobiles and the like, it is widely practiced to recirculate EGR gas, which is a part of the exhaust gas, into the intake system in order to improve fuel efficiency and exhaust gas purification. Finally, it flows through the intake port corresponding to each cylinder and enters the combustion chamber. Therefore, the EGR passage requires an EGR distribution passage for distributing the EGR gas to each intake port. It can be said that this EGR distribution passage is often formed in the intake manifold, as disclosed in Patent Document 1, for example.

JP 2018-71524 A

Since the intake manifold has a branch pipe corresponding to each cylinder, forming the EGR distribution passage in the intake manifold is rational, but some problems are conceivable. For example, since the intake manifold has a complicated shape, it can be said that it is often troublesome to design an EGR distribution passage in this.

In general, a pair of intake valves are arranged for each cylinder. Therefore, the intake port has one inlet and is divided into two branch ports in the middle, or two independent ports corresponding to one cylinder. Branch ports are formed, but if an EGR distribution passage is formed in the intake manifold, EGR gas cannot be supplied to a pair of branch ports individually, so there is a concern that EGR gas dispersion may be poor. be done.

In addition, EGR gas contains a small amount of solid components such as carbon, so in order to prevent contamination and deposits, it is preferable to mix it with the intake as close to the cylinder as possible. If it is formed in the manifold, the distance through which the EGR gas flows cannot be shortened, so there is a concern that solid components are likely to adhere to the inner surfaces of the intake manifold and the intake port.

Also, as a problem with the EGR passage, condensed water may accumulate after the operation is stopped, which may cause corrosion. There is also concern that water will easily accumulate.

In addition, most intake manifolds in recent years are made of synthetic resin, but since synthetic resin has a heat resistance of only about 150 ° C, EGR gas must be cooled by an EGR cooler, and it is said that it cannot handle high temperature EGR gas. There is also a problem.

Furthermore, the EGR distribution passage is formed by welding a cover member to the main body of the intake manifold. There was also anxiety about the face.

The present invention is made to improve such a situation.

The claimed invention is
"A cylinder head having an intake side wall and an exhaust side wall and opening upward, and a head cover fixed to the upper surface of the cylinder head, the head cover being a fixed intake side wall to the upper surface of the intake side wall in the cylinder head. having a side wall,
A plurality of EGR outlet passages communicating with each intake port formed in the cylinder head are opened on the upper surface of the intake side wall of the cylinder head,
EGR distribution passages for distributing EGR gas taken in from one inlet to each of the EGR outlet passages are formed in the thick portion of the intake side wall portion of the head cover in a state of being branched by a plurality of stages of branch portions. "
In the configuration
"In a portion of the intake side wall portion of the head cover, which is remote from the EGR distribution passage, an introduction passage having a lower end serving as the introduction port is formed so as to open downward,
The cylinder head is formed with an in-head EGR passage opening upward so as to communicate with the introduction port.
It has the characteristics of

The invention of claim 2 is, in claim 1,
"The EGR distribution passage is formed in a tournament shape branching from top to bottom ."
It is configured.

In the present invention, the EGR distribution passage is formed in the intake side wall of the head cover , but since the head cover has a simpler shape than the intake manifold, the EGR distribution passage can be formed using the peripheral wall of the head cover . Therefore, the structure is simple, and the design effort can be reduced.

Further, since the outlet passage communicating with the intake port is formed in the cylinder head, it is possible to easily form two outlet passages corresponding to a pair of branch ports corresponding to one cylinder. Therefore, it becomes possible to improve the dispersibility of the EGR gas. Further, when the intake port is branched in the middle, it is possible to form one outlet passage corresponding to each cylinder so that the outlet passage communicates with the portion of the intake port before branching. Therefore, flexibility in design is also excellent.

In addition, since the outlet passage is formed in the cylinder head, the EGR gas is supplied to the midway portion between the inlet and the outlet of the intake port. shorter than the case of forming in Therefore, the contamination of the intake passage and the formation of deposits can be prevented or significantly suppressed.

Furthermore, since the EGR distribution passage is located above the cylinder head and the EGR gas flows from top to bottom, it is easy to completely eliminate the areas where condensed water accumulates and eliminate the adverse effects of condensed water. .

Furthermore, aluminum head covers are often seen, but if applied to an aluminum (metal) head cover, it can handle high-temperature EGR gas, making it possible to eliminate the need for an EGR cooler. Therefore, the variation of applicable head covers can be expanded. Also, since the EGR distribution passage is built in the intake side wall of the head cover, even if an object hits the head cover during assembly of the internal combustion engine, the EGR distribution passage will not be damaged, which is advantageous in terms of strength.

Various forms can be adopted for the EGR distribution passage, but if a tournament shape is adopted as in claim 2, there is an advantage that the distribution to each intake port can be equalized.

As a method of introducing EGR gas from the exhaust system into the inlet of the head cover, it is possible to use an EGR pipe arranged outside the cylinder head and the head cover. The use of the inner EGR passage has the advantage of further promoting the compactness of the internal combustion engine, since the whole or most of the EGR passage can be formed in a state not exposed to the outside.

FIG. 4 is a plan view of a cylinder head according to an embodiment of an EGR distribution passage ; It is a side view of a cylinder head. It is a rear view of a cylinder head. FIG. 3 is a sectional view taken along line IV-IV of FIG. 2; (A) is a cross-sectional view taken along line VA-VA of FIG. 2, and (B) and (C) are views showing an embodiment of an EGR gas introducing portion . It is a vertical front view of 2nd Embodiment.

Next, embodiments of the present invention will be described based on the drawings. In the following description, terms such as front-rear and left-right are used to specify directions, but these directions follow the usage commonly used for internal combustion engines, with the crank axis direction being the front-rear direction, and the crank axis line and cylinder axis line. The orthogonal direction is defined as the left-right direction.

Further, with respect to the front-rear direction, the side on which the timing chain is arranged is the front, and the side on which the transmission is arranged is the rear. Just to make sure, the directions are clearly indicated in FIG.

(1).First Embodiment The internal combustion engine of this embodiment has three cylinders. Therefore, as shown in FIG. Lined up. The cylinder head 1 is of known form and is open upwards. For this reason, the cylinder head 1 has a peripheral wall consisting of a front wall 3 , a rear wall 4 , an intake side wall 5 and an exhaust side wall 6 .

In FIG. 1, reference numeral 7 denotes a bearing portion, reference numeral 8 denotes an intake valve insertion hole, and reference numeral 9 denotes an exhaust valve insertion hole. FIG. 3 shows a feed port 10 for sending cooling water to the radiator and a return port 11 for returning cooling water from the radiator.

As shown in FIG. 2, the intake side surface 1a of the cylinder head 1 is provided with three intake ports 12 corresponding to each cylinder. The intake port 12 has one collective portion 12a that opens outward and branches into two branch ports 12b in the middle. Therefore, a partition wall 13 appears that separates the two branch ports 12b.

As shown in FIGS. 2 and 3, a synthetic resin head cover 15 is superimposed on the upper surface of the cylinder head 1 . The head cover 15 is fixed to the cylinder head 1 by bolts 17 at an upper boss portion 16 protruding outward from its peripheral wall. The upper boss portion 16 is located outside the bearing portion 7 at the intake side wall 5 and the exhaust side wall 6 of the cylinder head 1 . For this reason, the cylinder head 1 also has a lower boss portion 18 projecting outward at the bearing portion 7 .

The head cover 15 has a tray-like shape that opens downward. Therefore, like the cylinder head 1, it has a peripheral wall. The side view of FIG. 2 and the rear view of FIG. 3 show the rear wall 19 and the intake side wall 22 of the peripheral walls.
As shown in FIG. 3, an EGR valve 20 is attached to a portion of the rear wall 19 of the head cover 15 near the intake side, and the end of an EGR pipe 21 is connected to its inlet. Therefore, the EGR gas introduction structure does not constitute a claim. The beginning of the EGR pipe 21 is connected to the exhaust system, while the outlet of the EGR valve 20 is connected to the EGR distribution passage 23 formed in the intake side wall portion 22 of the head cover 15 .

The EGR distribution passage 23 includes a horizontally long main passage 24, two front and rear first branch passages 25 branched from a downward portion 24a at the end of the main passage 24, and a downward portion at the tip of the first branch passage 25. The second branch passage 26 branches back and forth from 25a and extends in series, and the second branch passage 26 is formed with three downward portions 26a corresponding to the respective intake ports 12. , and downward portions 26a open to the upper surface of the intake side wall 5 of the cylinder head 1. As shown in FIG. Therefore, the EGR distribution passage 23 is formed in a tournament shape having a plurality of branches with different heights .

Furthermore, in the present embodiment, as shown in FIGS. 1 and 4, on the upper surface of the intake side wall 5 of the cylinder head 1, there are three pipes branched in the front-rear direction while communicating with the lower end of the downward portion of the second branch passage 26. A third branch passage 27 is formed, and front and rear ends of the third branch passage 27 are communicated with upper ends of outlet passages 27a extending vertically. The lower end of each outlet passage 27a communicates with the front and rear outer ends of the branch ports 12b of the intake port 12. As shown in FIG. The reason why the outlet passage 27a communicates with the front and rear outer ends of the branch port 12b is to avoid interference with the fuel injector.

In this embodiment, the main passage 24 forming the EGR distribution passage 23 is formed in the rear wall 19 and the intake side wall 22 of the head cover 15, and the first and second branch passages 25 and 26 are formed in the head cover 15. Although it is formed in the intake side wall portion 22, it is also possible to form the entire EGR distribution passage 23 only in the intake side wall portion 22. FIG.

Further, although the third branch passage 27 is formed in the cylinder head 1 in this embodiment, the third branch passage 27 may be formed in the intake side wall portion 22 of the head cover 15 . Further, the horizontal portion of the third branch passage 27 may be formed on the lower surface of the intake side wall portion 22 of the head cover 15 or may be formed on both the mating surfaces of the head cover 15 and the cylinder head 1 .

As a specific method of forming the EGR distribution passage 23 in the head cover 15, as shown in FIGS. While the back plate 29 is fixed to the recess 28 by vibration welding or the like, grooves forming the EGR distribution passage 23 are previously formed in the back plate 29 . That is, the EGR distribution passage 23 is formed by closing the groove with the main body of the head cover 15 .

Since the EGR distribution passage 23 also extends to the rear wall 19 of the head cover 15, the back plate 29 is substantially L-shaped in plan view. The groove forming the EGR distribution passage 23 can also be formed in the recess 28, but it is preferable to form it only in the back plate 29 from the standpoint of ease of demolding. A starting end 24 b of the main passage 24 is an inlet port described in the claims, which communicates with an outlet of the EGR valve 20 . Therefore, the starting end 24b of the main passage 24 opens rearward.

(2) Summary As can be understood from the above description, EGR gas is jetted out to the branch port 12b of each intake port 12 through the EGR distribution passage 23 formed in the head cover 15. As shown in FIG. Therefore, the distribution of EGR gas can be improved by eliminating the uneven flow of EGR gas through one of the branch ports 12b. There is also the advantage that the length of contact of the EGR gas with the intake passage can be made shorter than in the conventional art, thereby preventing or greatly suppressing the formation of deposits.

In addition, since the EGR distribution passage 23 is located above the cylinder head 1, there is no portion in the middle of the EGR distribution passage 23 where condensed water accumulates. Therefore, adverse effects of condensed water can also be prevented. If the horizontally long portion of the EGR distribution passage 23 is inclined so as to become lower from the upstream side to the downstream side, the condensed water can be removed more reliably.

As indicated by the dashed line in FIG. 4, if the partition wall 13 that separates the branch port 12b is positioned deeper than the outlet passages 27a, the outlet passages 27a may be arranged in the front and rear intermediate portions of the intake ports 12. As shown in FIG. In this case, since one outlet passage 27a is provided for each cylinder, the third branch passage 27 becomes unnecessary.

When the EGR valve 20 is attached to the head cover 15 as in the embodiment, most of the EGR device can be unitized with the head cover 15, thereby improving the ease of assembly of the internal combustion engine.

For the head cover 15, it is also possible to adopt an aluminum cast product or die cast product. In this case, since the heat resistance is excellent, the EGR gas can be taken in without passing through the EGR cooler. That is, since the EGR gas passes through the aluminum head cover 15 and the cylinder head 1 toward the intake port 12, even high-temperature EGR gas can be handled.

4, a cylinder block 30, a camshaft 31, an intake valve 32, and an intake valve spring 33 are shown.

(3). Reference Example and Other Embodiments Next, the modes shown in FIG. 5(B) and below will be described. In the mode shown in FIG. 5B, the EGR distribution passage 23 is formed in a form in which a plurality of branch passages 34 are branched from one main passage 24 toward the cylinder head 1 . The EGR distribution passage 23 is formed only in the intake side wall portion 22 of the head cover 15 .

In this aspect, as an embodiment of the EGR gas introduction structure, a left and right longitudinal first in-head EGR passage 36 opening to the exhaust side surface and a first in-head EGR passage 36 are provided at the rear portion of the intake side wall of the cylinder head 1 . A second in-head EGR passage 37 rising upward from the terminal end of the head cover 15 is formed, while a vertically elongated introduction passage 38 communicating with the second in-head EGR passage 37 is formed in the intake side wall portion 22 of the head cover 15 . ing. Therefore, the lower end of the introduction passage 38 serves as an introduction port. The introduction passage 38 and the main passage 24 communicate with each other via the EGR valve 20 . The EGR valve 20 is arranged with its axis extending vertically, and is partially exposed above the head cover 15 .

In this embodiment , the EGR distribution passage 23 has a simple form, so the main passage 24, each branch passage 34, and the introduction passage 38 can be formed by drilling. Therefore, it can be said that it is advantageous in terms of cost. The opening of the drilled hole for forming the main passage 24 may be closed with a plug 35 .

In this aspect , since the EGR passages 36 and 37 are also formed in the cylinder head 1, there is an advantage that the EGR device can be made more compact. As mentioned in the first embodiment, if the main passage 24 is inclined as indicated by the dashed line, it is possible to reliably prevent accumulation of condensed water.

The embodiment of FIG. 5(C) also has a vertically elongated introduction passage 38 communicating with the in-head EGR passage 37 . The EGR distribution passage is a reference example, and a branching buffer portion 24c having a large volume is formed at the end of the main passage 24, and branch passages 34 are branched from the branching buffer portion 24c toward the respective intake ports 12. there is In this reference example, the uniform distribution performance of EGR gas can be improved while simplifying the structure.

In the first embodiment, the back plate 29 for forming the EGR distribution passage 23 is fixed to the body portion of the head cover 15, but in the second embodiment shown in FIG. A recess 39 is formed in a portion higher than the EGR distribution passage 23, and the top plate 40 is fixed to the recess 39 by vibration welding or the like. . Forming the EGR distribution passage 23 only in the intake side wall portion 22 further simplifies the structure.

In the embodiment of FIG. 6, the branch passage 34 is shown branched from the main passage 24, but the portion of the branch passage 34 below the surface plate 40 may be formed by cutting with a drill. It is also possible to form by molding using a slide pin.

Although the embodiments of the present invention have been described above, the present invention can be embodied in various other ways. For example, the head cover 15 can employ a casting, and in this case, the EGR distribution passage can be formed by casting .

The present invention can be embodied in an EGR device for an internal combustion engine. Therefore, it can be used industrially.

REFERENCE SIGNS LIST 1 cylinder head 5 intake side wall of cylinder head 15 head cover 19 rear wall of head cover 22 intake side wall of head cover
23 EGR distribution passage 24 main passage 25 first branch passage 26 second branch passage 27 third branch passage 27a EGR outlet passage 36, 37 in-head EGR passage 38 introduction passage

Claims (2)

a cylinder head having an intake sidewall and an exhaust sidewall and opening upward; and a head cover fixed to an upper surface of the cylinder head, wherein the head cover includes an intake sidewall fixed to the upper surface of the intake sidewall in the cylinder head. has a part
A plurality of EGR outlet passages communicating with each intake port formed in the cylinder head are opened on the upper surface of the intake side wall of the cylinder head,
EGR distribution passages for distributing EGR gas taken in from one inlet to each of the EGR outlet passages are formed in the thick portion of the intake side wall portion of the head cover in a state of being branched by a plurality of stages of branch portions. An EGR device for an internal combustion engine,
An introduction passage having a lower end serving as the introduction port is formed in a portion away from the EGR distribution passage in the intake side wall portion of the head cover so as to open downward,
The cylinder head is formed with an in-head EGR passage opening upward so as to communicate with the introduction port.
An EGR device for an internal combustion engine. The EGR distribution passage is formed in a tournament shape branching from top to bottom,
An EGR device for an internal combustion engine according to claim 1.

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