JPS6050217A - Exhaust manifold for engine - Google Patents

Abstract

PURPOSE:To keep off a large shrinkable deformation as preventing any crack from occurring, by installing such a stopper as checking the shrinkage deformation in making contact with each other when a distance between branch parts is shrunk and deformed more than the specified value, in position between each of these branches of an exhaust manifold. CONSTITUTION:An exhaust manifold 2 is provided with a branch part 8 to be connected to each of exhaust ports 4 and 5, a branch part 9 to be connected to each of exhaust ports 6 and 7, and a collector part 10 where both branch parts 8 and 9 gather. From each of partial positions 8a and 9a nearby a cylinder head 1 of both branch parts 8 and 9, each of projection parts 14 and 15, which extend in almost parallel with the side wall of a cylinder head as a stopper and being opposed with each other via a clearance 16, is formed whereby shrinkage deformation is controlled to be within a smaller range than a residual elastic deformation value owing to the stopper.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust manifold that collects exhaust gas from each cylinder of an engine and guides it to an exhaust pipe.

(Prior art) When the engine is operating, the exhaust manifold attached to the cylinder head becomes significantly hotter than the cylinder head, which is cooled by cooling water, etc., and the exhaust manifold, which is restrained by the cylinder head, is subject to large thermal stress. This generates thermal deformation, and a portion of the stress is accumulated in the exhaust manifold as residual compressive stress. For this reason, there are problems in that it is difficult to remove the exhaust manifold from the cylinder head during maintenance or the like, and once removed, the exhaust manifold shrinks and deforms and cannot be reattached. Therefore, conventionally, for example,
As disclosed in Japanese Patent No. 142214, measures have been taken to prevent thermal deformation by providing reinforcing ribs between the branches of the exhaust manifold. However, due to the difference in thermal expansion with the cylinder head, especially the reinforcing ribs expand and contract freely with respect to the parts that are fixed to the cylinder head.
It has become clear that the problem is that cracks occur due to the exhaust gas leakage caused by exhaust gas leakage.

(Object of the Invention) An object of the present invention is to prevent cracks from occurring due to stress concentration in an exhaust manifold attached to an engine body, and to prevent thermal deformation, particularly large shrinkage deformation thereof.

In order to achieve this objective, the present inventors conducted repeated research and obtained the following findings. In other words, from engine start to engine stop, the aluminum cylinder head (thermal expansion coefficient 2)
3.9X 10-'m/deg, ) and a steel exhaust manifold (coefficient of thermal expansion i1.oxi.

``''m/deg, ), as shown in Figure 1, the temperature of the cooled cylinder head remains at most 120°C, whereas the temperature of the exhaust manifold exceeds 500°C. . Quantitatively examining the thermal deformation at this time, we found that when the exhaust manifold is connected and fixed to the cylinder head, the deformation of the exhaust manifold is restricted by the cylinder head, as shown by the dashed line in Figure 2. The deformation of the cylinder head follows the deformation of the cylinder head, but if the exhaust manifold is allowed to follow the temperature course shown in FIG. 1 while the exhaust manifold is not connected and fixed, the deformation will be as shown by the dotted line in FIG. 2. Therefore, there is a difference Δ in the amount of deformation of the exhaust manifold between the free state and the restrained state. For this difference, the coefficient of thermal expansion of the cylinder head made by A fl (23,9X 10-'+n/
Even though the thermal expansion coefficient (1i, ox 10-6 m/deg,) of the cast iron exhaust manifold is smaller than the thermal expansion coefficient (1i, ox 10-6 m/deg,), it becomes extremely large because the temperature differs by more than four times as described above. On the other hand, the exhaust manifold that is connected and fixed has the above difference of 66% due to the excessive thermal stress that occurs in the high temperature range.
Therefore, when the temperature drops to room temperature when installed in the cylinder head, the plastic deformation remains as internal stress that causes elastic deformation. This is the knowledge that when removed, the internal stress causes a negative deformation of l in the elastic deformation plane, that is, contraction deformation.

(Structure of the Invention) The present invention was devised based on the knowledge described in "#)71! The basic feature is that a stopper is provided between each branch part into which exhaust gas is introduced, which contacts each other to prevent contraction and deformation when the distance between the branch parts shrinks and deforms by a predetermined amount or more. The shrinkage deformation is suppressed by the stopper to a range smaller than the remaining elastic deformation amount Δl.

(Effects of the Invention) Therefore, when the exhaust manifold is removed from the engine body, the exhaust manifold does not contract or deform to a large extent due to the stopper, and it is not difficult to reinstall it. In addition, the structure of the stopper is not one in which each branch part is connected integrally, but a gap is provided mainly so that they come into contact with each other during contraction and deformation when removed.
There is no stress acting on the connection base between the stopper and the branch portion at room temperature, and stress at high temperature is either zero or negligibly small, and the occurrence of cracks can be prevented.

(Example) The present invention will be specifically explained by referring to an example shown in the accompanying drawings.

4- As shown in Figures 3 and 4, 1 is an aluminum cylinder head (hereinafter simply referred to as cylinder head) that forms the engine body together with the cylinder block, and 2 is a cylinder head that is connected and fixed to the engine body 1. This is a cast iron exhaust manifold.

The cylinder head 1 has a stat pole for attaching the exhaust manifold 2) 3,3. ... is screwed into a predetermined bell position in advance. Cylinder head 1 is a 4-cylinder engine, with 4 exhaust bows) 4. ,S.

6.7.

The exhaust manifold 2 includes a branch portion 8 that introduces exhaust gas discharged from an exhaust port 4.5, and an exhaust port 6.5.
a branch part 9 that introduces exhaust gas discharged from 7;
A gathering section 10 where the branch sections 8 and 9 are assembled is provided. A collar-shaped attachment part 11 is formed at the end of the gathering part 10, and a bolt is attached to an exhaust pipe 13 having an attachment part 12 of the same shape.
Connected by nuts.

From a portion 8a of the branch portion 8 close to the cylinder head 1, a solid protrusion extends substantially parallel to the side wall of the cylinder head 1 toward the other branch portion 9 as a stopper]4
Another protrusion 15 linearly aligned with the protrusion 14 is integrally formed in a portion 9a of the branch portion 9 near the cylinder head 1, and the end surface 14a of the protrusion 14 and the protrusion The end face 15a of 15 faces each other with a gap 16 interposed therebetween.

The distance Δeo of the gap 16 is selected in advance to a predetermined value when manufacturing the exhaust manifold 2 as a component. That is,
The length that cylinder head 1 extends due to thermal expansion during engine operation is subtracted from the length that exhaust manifold 2 would theoretically expand due to thermal expansion under the same conditions in its natural state and not fixed to cylinder head 1. The value is chosen to be sufficiently lower than the value (at 8.〈ΔC).

A collar-shaped exhaust port attachment portion 17.18 is formed on the engine side of each of the branch portions 8 and 9, and the above-mentioned stud bolt 3 is attached to the exhaust port attachment portion 17.18 in advance.
Through holes 19, 19... and through holes 20.
20... are formed. In addition, through hole 1.9.20
The diameter of is usually slightly larger than the diameter of stud bolt 3!
#, to be done. The exhaust boat mounting portions 17.18 fit the through holes 19.2+1 into the stud bolts 3 through gaskets 21.22, respectively, and the nuts 2 through the washers.
By tightening 3, it is fixed to the cylinder rad 1.

When the exhaust manifold 2 is removed and the engine is operated, the cylinder head 1 is cooled by circulating cooling water and reaches a temperature of about 120°C. On the other hand, the exhaust manifold 2 has an exhaust bow) 4. The temperature reaches 5()0°C or higher due to the high temperature control gas derived from S, 6.7.

The exhaust manifold 2 fixed to the cylinder head 1 is
It deforms following the expansion of the cylinder head 1. At this time, the protrusions 14 and 15 also expand in a vertical direction V and increase their length, but since they are a certain distance from the main body of the exhaust manifold 2, the main body does not become hot, and the branch part Since 8 and 9 are deformed away from each other, their elongation is canceled out, and the gap 16 does not become so narrow. If the W11 separation ΔCo of the gap 16 is selected to a preferable value, even if the exhaust manifold 2 reaches its maximum temperature, the protrusion 14
．． 15 can also be made so that they do not come into contact with each other. However, even if the end surfaces 14a and 15a of the protrusions 14 and 15 come into contact with each other at high temperatures, the elongation force of the protrusions 14 and 15 acting on the connection bases to the branch parts 8 and 9 will not be the same as in the case of conventional reinforcing ribs. Since it is not applied continuously from the initial stage of expansion, the shear stress is so small that it can be ignored.

This advantage is due to the gap 16 being formed in advance.

When the engine operation is stopped, the cylinder head 1 and exhaust manifold 2 are cooled and their temperature gradually decreases. As the temperature decreases, the exhaust manifold 2 contracts together with the rad 1 into the cylinder.

Even when the temperature reaches room temperature, stress corresponding to the plastic deformation at high temperature remains in the exhaust manifold 2 as elastic stress. Both branch parts 8, 9 try to contract and deform further than the cylinder head 1 which has returned to its original state, and the branch parts 8, 9
It acts to shorten the distance between. As a result, the distance of the gap 16 is the initial distance - 8 = distance Δ. The distance is slightly smaller than Δ. It becomes ゛. However, since the exhaust manifold 2 is fixed to the cylinder head 1, it will not contract or deform any further.
At normal temperatures, the gap 16 causes the protrusion 14.15 to exert no stress on the mounting base of the exhaust manifold 2.

If the exhaust manifold 2 were to be removed from the cylinder head 1 in this state, both branch portions 8 and 9 would tend to narrow due to the remaining elastic stress. However, the end surfaces 14a and ISa of the protrusions 14 and 1s abut against each other, preventing the shrinkage deformation of ΔL'l; Projection 14.
15 together act as a stopper. Therefore, when reattaching the exhaust manifold 2 to the cylinder rad 1, no jig or the like is required, and the attachment can be easily done manually without much difficulty. Furthermore, it is possible that no stress acts on the attachment bases of the branch parts 8 and 9 to the cylinder head 1 at room temperature, and that shear stress may only temporarily act on them only at high temperatures. No fatigue phenomenon occurs and no cracks occur.

In addition, in the above embodiment, the end surface 14, a of the protrusion 14.15
, 15. The gap 16 formed by a is a predetermined interval (Δf
, ). However, if you look at it differently here, especially at eight. It is not necessary to set the interval to , but it may be set to a larger interval. In this case, when removing the exhaust manifold 2 from the shilling head 1, it is easy to shrink and deform the exhaust manifold 2 by inserting a rigid spacer, such as a steel plate, with a thickness commensurate with the distance of the gap 1G currently existing. There is no difficulty in reattaching the cylinder head 1 to the cylinder head 1. Of course, the spacer must be removed after installation.

In the above embodiment, a four-cylinder engine was used as an example, but in general, an engine with two or more cylinders can be used.
In this example, the branch portion covers two exhaust ports, but the present invention is similarly applicable to an exhaust manifold having a branch portion for each exhaust port. In this case, a plurality of pairs of protrusions (14, 15) are formed.

[Brief explanation of the drawing]

FIG. 1 and FIG. 4S2 are graphs for explaining the knowledge forming the background of the present invention, and FIGS. 3 and 4 are a plan view and a side view, respectively, of an exhaust manifold showing an embodiment of the present invention. 1... Schilling head as the main body of Ennon, 2...
・Exhaust manifold, 4+ 5+ 61 7... Exhaust port, 8, 9... Branch part, 13... Exhaust pipe,
14゜15... Protrusion as a stopper, 16...
A gap at a predetermined distance. Patent applicant: Toyo Kogyo Co., Ltd. Agent: Patent attorney: 2 people 12-

Claims (1)

[Claims] (1) Each branch part is connected and fixed to the engine body and introduces exhaust gas discharged from a plurality of cylinders, and the collecting part is connected and fixed to the exhaust pipe and collects the above branch parts and leads exhaust gas to the exhaust pipe. An engine exhaust manifold comprising: an engine exhaust manifold comprising a stopper that abuts against each other to prevent contraction and deformation when the distance between the branch parts shrinks and deforms by a predetermined amount or more. exhaust manifold.