JPH0220807B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION This invention relates to an exhaust manifold in a multi-cylinder internal combustion engine.

BACKGROUND ART Conventionally, for example, an exhaust manifold in a six-cylinder internal combustion engine was formed at each mounting flange 11 formed on a cylinder head 1 and at each branch 3 of an exhaust manifold 2, as shown in FIG. The exhaust manifold mounting flanges 12 are brought into close contact with each other through the gaskets 4, and the nuts 8 screwed onto the stud bolts 5 planted in the cylinder head 1 through the flat washers 6 and spring washers 7 are tightened to attach the cylinder head 1. installed on. Further, bolt holes 9 for inserting the stud bolts 5 are formed in the exhaust manifold mounting flanges 12, respectively, and the inner diameter of the bolt holes 9 is the same as that of the two adjacent central ones as shown in FIG. mounting flange 12,
Only one of the inner diameters of the stud bolts 12 is formed to have approximately the same diameter as the outer diameter of the stud bolt 5 for positioning when installing the exhaust manifold 2, but the other inner diameters are approximately the same as the outer diameter of the stud bolt 5.
As shown in the figure, the stud bolt 5 is formed to have a relatively large diameter with constant gaps S ₃ and S ₄ on both sides.
The gaps S ₃ and S ₄ are provided to absorb the deformation and movement of the mounting flanges 12 caused by thermal expansion and contraction of the exhaust manifold 2 as the engine starts and stops. Therefore, this gap S ₃ ,
If _S4 is too large, the amount of movement of the mounting flange 12 will also increase and the sealing width of the gasket 7 will decrease due to misalignment with the mounting flange 11 of the cylinder head 1, so it is generally kept within 1 to 6 mm. (For example, see Japanese Patent Application Laid-Open No. 181916/1983).

Problems to be Solved by the Invention Incidentally, by repeating the heat cycle as described above, the exhaust manifold 2 increases the amount of thermal contraction that occurs when the operation is stopped. As shown in Fig. 4, it is not so large near the 3rd and 4th cylinder positions 23 and 24 near the center of the engine, but the 2nd and 5th cylinder positions 22 and 24 are not so large.
It gradually increases from around 25 to around the first and sixth cylinder positions 21 and 26. That is, the branches 3, 3 and the mounting flanges 12, 12 on the front and rear ends of the engine are the largest.

However, in the conventional exhaust manifold 2, as shown in FIG.
Since the gaps S ₃ and S ₄ of the bolt holes 9 and the stud bolts 5 are all the same size except for these points, the gaps S ₃ and S ₄ can be calculated by the amount of movement of the exhaust manifold mounting flange 12. For example, the second and fifth cylinder positions 22,
25, the bolt holes 9, 9 on the 1st and 6th cylinder positions 21, 26 side will hit the stud bolts 5, 5 during the contraction process, and this stud Since excessive shear stress is applied only to the bolts 5, 5, there is a risk that the exhaust manifold 2 and the stud bolts 5 may break or break, or that the cylinder head 1 near the stud bolts 5, 5 may be cracked.

In addition, in the exhaust manifold 2 heated to a high temperature by exhaust gas, the gathering portion 2a expands due to thermal expansion, but the expansion of the mounting flanges 12 is restricted by the stud bolts 5 and nuts 8, so as shown in FIG. Excessive stress is also generated at the indicated point A (root of branch 3). As shown in Fig. 8, this stress exceeds the limit of the material durability σ ₁ of the exhaust manifold 2, and when the exhaust manifold 2 is cooled down to room temperature, it remains as a permanent strain, so over time. A
There is a problem in that the exhaust manifold 2 becomes brittle and can be damaged. The amount of heat shrinkage at the base of this branch 3 is also the same as that of the first
The sixth cylinder positions 21 and 26 are the largest. Other conventional examples include forming a recess around the opening of the exhaust port of the cylinder head, such as the technology described in Japanese Utility Model Application Publication No. 57-164209 and Japanese Utility Model Publication No. 57-50492. Although some attempts have been made to absorb thermal deformation of the exhaust manifold by forming relief recesses on one or both of the contact surfaces between the cylinder head and the exhaust manifold, simply forming each recess does not prevent the inner surface of the recess from forming. Since it is difficult to set the set width of the gap between the mounting flange outer surface and the mounting bolt outer surface with high accuracy, it cannot be an effective means for solving the above-mentioned problems.

Means for Solving the Problems The present invention has been devised in view of the above-mentioned problems, and in particular, the inner diameter of the positioning bolt hole of the exhaust manifold mounting flange located approximately in the center of the engine can be adjusted for positioning. The outer diameter of the bolt is set to be approximately the same as the outer diameter of the bolt, and the gap for absorbing thermal deformation formed between the inner surface of the bolt hole other than the positioning bolt hole and the outer surface of the mounting bolt is set from the center side of the engine to the front and back. It is characterized by being formed gradually larger toward the end.

According to the present invention, the set width of the gap between the bolt hole and the mounting bolt is set according to the amount of thermal deformation of each cylinder with reference to the center positioning bolt hole and the mounting bolt that do not have the gap. Since the settings can be made with high precision, the inner surfaces of the bolt holes of the mounting flanges, which have different amounts of thermal deformation movement for each cylinder position, can be brought into contact with the mounting bolts substantially simultaneously and uniformly. This prevents unbalanced loads from being applied to specific mounting bolts, thereby reliably preventing breakage of the mounting bolts and damage to the cylinder head and exhaust manifold.

Embodiments Hereinafter, embodiments of the exhaust manifold for a multi-cylinder internal combustion engine according to the present invention will be described in detail with reference to the drawings.

The exhaust manifold of this embodiment is applied to a six-cylinder internal combustion engine, similar to the one shown in FIGS. 3 and 4, and this exhaust manifold 2
consists of six branches 3 integrally formed on the gathering part 2a and a cylinder head mounting flange 12 formed at each end of each branch 3; An exhaust manifold mounting flange 11 corresponding to the mounting flange 12 is provided, and both flanges 11,
12... through the stud bolt 5 through the gasket 4
Tighten the nut 8 screwed onto the exhaust manifold 2.
is attached to the cylinder head 1.

As shown in FIG. 5, positioning stud bolts 5, 5 are embedded in the mounting flange 11 of the cylinder head 1 located on the engine center side, while the exhaust manifold mounting bolts 5, 5 are used for mounting the exhaust manifold 2. Bolt holes 9 for inserting stud bolts 5 are formed in the flange 12, respectively. The inner diameters of these bolt holes 9 are set to be approximately the same as the outer diameters of the positioning stud bolt holes 5, 5 only at the center two through which the positioning stud bolt holes 5, 5 are inserted. The inner diameters of the other bolt holes 9 are set larger than the outer diameters of the stud bolts 5. That is, if explained based on FIG. 1 showing the exhaust manifold mounting flange 12 located in the first cylinder of the engine, the bolt holes 9, 9
A first gap S1 that absorbs the thermal deformation and shrinkage movement of the mounting flange 12 and a second gap S2 that absorbs the expansion movement of the mounting flange 12 are formed between the inner surfaces 9a, 9a of the stud bolts ₅ , and the outer surfaces 5a, 5a of the stud bolts 5, _5, respectively. It is formed. This first
The gap S ₁ is gradually increased from the center side of the engine where the amount of contraction movement is relatively small to the front and rear end sides where the amount of contraction movement is large. Specifically, as shown by the shaded area on the thick solid line in FIG. 7, the third and fourth cylinder positions 23,
24 mounting flanges 12, 12 positioning bolt holes 9, 9 and positioning stud bolts 5,
The first gap S ₁ (hatched area) other than the gap S 5 is set to a value smaller than the simple proportional value X point, and the second and fifth gaps
The first gap S ₁ at cylinder positions 22 and 25 is also a simple proportional value Y
It is set to a value smaller than the point. Further, at the first and sixth cylinder positions 21 and 26 on the front and rear sides of the engine, a value larger than the simple proportional value Z point is set.

Therefore, according to the above configuration, the set width of the first gap S ₁ is determined by thermal deformation at both ends of the positioning bolt holes 9, 9 and the positioning stud bolts 5, 5 with the vicinity of the center of the engine as a reference. It can be set gradually larger and with higher precision depending on the amount. Therefore, even if the heat shrinkage of the mounting flange 12 increases due to repeated engine stops, the inner surface of each bolt hole 9 of each mounting flange 12 is simultaneously and simultaneously against the outer surface of the stud bolt 5. Contact with uniform pressure. As a result, the loads applied to the stud bolts 5 and the mounting flanges 12 are distributed over the whole, and it is possible to prevent excessive loads from being applied to specific stud bolts 5 and mounting flanges 12. As a result, breakage and damage to the stud bolt 5 and the mounting flange 12 can be reliably prevented.

Moreover, cylinder head 1 of exhaust manifold 2
Since the mounting position can be performed at approximately the center of the engine, compared to the case where positioning is performed at either the front or rear end of the engine, for example, the exhaust gas can be removed from the fixed positioning bolt holes 9, 9. The length to the second end of the manifold is half the length. Therefore, it is possible to reduce the absolute value of the maximum amount of thermal deformation of the exhaust manifold 2 to half,
Coupled with the highly accurately set width of the gap _S1 , concentrated shear stress on the stud bolts 5 and the like can be sufficiently prevented.

In addition, in this embodiment, the first gap on the front and rear ends of the engine
Although the value of S ₁ is set larger than the simple proportional value,
This is to prevent the mounting flanges 12 at the front and rear ends of the engine from coming into contact with the stud bolts 5 earlier than at the center, which may occur due to manufacturing variations or the like. Furthermore, even if the first gap _S1 is set to be larger than the simple proportional value, it is of course within a range that does not interfere with the sealing performance of the gasket.

Furthermore, although the above embodiment has mainly been described with reference to the first gap _S1 , if the second gap _S2 on the extension side is also constructed in the same manner as above, it will prevent the branch root part (A part) of the exhaust manifold from thermal expansion. Since the amount of shrinkage strain is reduced, damage to the exhaust manifold can be reliably prevented.

FIG. 2 shows a second embodiment of the present invention, in which the shape of the bolt holes 9 including the first and second gaps S ₁ and S ₂ is formed into a perfect circle, Forming a perfect circle makes processing work extremely easy.

Although the above embodiment is applied to a 6-cylinder engine, it is also possible to apply it to other multi-cylinder engines such as 4-cylinder or 8-cylinder engines, depending on the implementation.

Effects of the Invention As is clear from the above explanation, the exhaust manifold for a multi-cylinder internal combustion engine according to the present invention has, among other things:
The gap for absorbing thermal deformation can be set gradually larger and with higher accuracy toward the front and rear ends with reference to the approximately center position of the engine where the positioning bolt holes and positioning mounting bolts are provided. Alternatively, during movement in the expansion direction, the inner surface of each bolt hole can be brought into contact with each stud bolt substantially simultaneously and uniformly. As a result, the loads applied to the stud bolts and the exhaust manifold mounting flange are distributed over the entire body, and damage to the stud bolts and the exhaust manifold is reliably prevented. Furthermore, uniform contact between the stud bolt and the bolt hole provides sufficient contact with the gasket, thereby improving sealing performance.

In addition, since the exhaust manifold can be positioned approximately at the center of the engine, the maximum amount of thermal deformation of the exhaust manifold can be reduced compared to, for example, positioning at either the front or rear end of the engine. The absolute value can be suppressed to half, and in combination with the highly precisely set width of the gap, uneven loads on mounting bolts and the like can be further prevented.

[Brief explanation of drawings]

FIG. 1 shows the first exhaust manifold according to the present invention.
A rear view of the cylinder side exhaust manifold mounting flange seen in the cross-sectional direction along the line in Figure 4, Figure 2 is a rear view showing different examples of the same mounting flange, and Figure 3 is an exploded view of the cylinder head and exhaust manifold. FIG. 4 is a plan view showing the exhaust manifold of the first embodiment of the present invention, FIG. 5 is a rear view showing the exhaust manifold mounting flange seen from the - line cross-sectional direction in FIG. 4, and FIG. is a rear view showing the conventional mounting flange on the first cylinder side, Fig. 7 is a characteristic diagram showing the amount of thermal contraction of the exhaust manifold, and Fig. 8 shows the relationship between stress and strain when the exhaust manifold thermally contracts. FIG. 9 is a characteristic diagram showing the relationship between the number of cooling and heating cycles of the exhaust manifold and the amount of thermal contraction of the branch. 2... Exhaust manifold, 5... Stud bolt (mounting bolt), 5a... External surface, 9... Bolt hole,
9a...Inner surface, 12...Exhaust manifold mounting flange, 21...1st cylinder position, 22...2nd cylinder position, 23...3rd cylinder position, 24...4th cylinder position, 25...3rd cylinder position 5th cylinder position, 26...6th cylinder position, _S1 , _S3 ...contraction side gap, _S2 , _S4 ...extension side gap.

Claims (1)

[Claims] 1. In an exhaust manifold in which a plurality of exhaust manifold mounting flanges provided in the longitudinal direction of the engine are attached to the cylinder head using mounting bolts, the positioning bolt hole of the exhaust manifold mounting flange located approximately in the center of the engine is The inner diameter is set to be approximately the same as the outer diameter of the mounting bolt for positioning, and a gap for absorbing thermal deformation is formed between the inner surface of the bolt hole other than the positioning bolt hole and the outer surface of the mounting bolt. An exhaust manifold for a multi-cylinder internal combustion engine, characterized in that the exhaust manifold is gradually enlarged from the center side of the engine to the front and rear ends.