JPH068265Y2 - Exhaust manifold structure - Google Patents

Description

The present invention relates to an exhaust manifold structure, and more particularly to an exhaust manifold structure formed to have heat insulation.

[Prior Art] Generally, in the case of an internal combustion engine equipped with a turbocharger, the turbine of the turbocharger is capable of suppressing the heat loss of the exhaust gas discharged from the internal combustion engine to generate high-temperature exhaust gas with large energy. It is preferable to supply it.

Therefore, various proposals have been made to make the exhaust manifold, which guides the exhaust gas to the downstream side (turbine side), a heat insulating structure. Among them, a structure is known in which a heat insulating material is attached to the inner surface of the main body of the exhaust manifold to insulate the heat (Actual No. 57-47710).
Issue).

As shown in FIG. 4, in this proposal, a heat insulating material e made of a ceramic material is shared in an exhaust pipe a made of cast iron that defines an exhaust passage, leaving both ends d of an exhaust inlet b and an outlet c thereof. It is characterized by being provided by casting.

The exhaust gas inlet b is formed as an end portion of an inflow pipe f that is juxtaposed in the longitudinal direction of the exhaust pipe a, and is connected to each exhaust port of a cylinder head (not shown) to exhaust the exhaust gas a. It is designed to guide you inside. Exhaust outlet c is inlet b
The exhaust gas is discharged to the downstream side at one location on the opposite side to the approximate center in the longitudinal direction. And insulation e
Is configured to guide the exhaust gas from the upstream side to the downstream side along the circumferential direction and the longitudinal direction of the exhaust pipe a, that is, substantially forming an exhaust passage.

Therefore, when the high-temperature exhaust gas enters the exhaust pipe a from the inflow pipe f insulated from the inflow port b, it is changed in the longitudinal direction to the flow direction and is collected at the outlet c to reduce the heat loss to the downstream side. Will be discharged. Further, since both ends d are cast with cast iron, the strength for connection is not impaired.

[Problems to be solved by the invention] By the way, the co-cast heat insulating material (ceramic material) e having the above-mentioned structure withstands exhaust gas temperatures of up to 850 ° C for a long time and has a large heat insulating property (thermal conductivity). Is required to be small). Further, since it also partitions the exhaust passage, it is also necessary that the thermal deformation during casting is small (the linear expansion coefficient is small).

Therefore, as shown in FIG. 5, the heat insulating material e in the section formed by bending, which is the connecting portion between the exhaust pipe a and the inflow pipe f.
Means that an inward force as shown by an arrow A in the figure is applied due to a difference in thermal expansion, that is, cast iron having a larger thermal expansion amount. This force may cause cracks in the heat insulating material e, reduce the heat insulating property, and lead to damage.

Further, as shown in FIG. 6, at the exhaust inlet / outlet positions b and c, when the ceramic material is co-cast and the exhaust pipe a is cast, the cast iron solidifies and shrinks, as shown by arrow B in the figure. The force on the heat insulating material e acts from the outside in the circumferential direction. For this reason, a stress difference is generated at the bent portions of the heat insulating material e extending to the entrances and exits b and c, and the stresses from the entrances and exits b and c side where this force does not work, which also causes cracks and the like.

In view of the above circumstances, the present invention was devised to realize an exhaust pipe co-cast with a heat insulating material and provide an exhaust manifold structure having heat insulating properties.

[Means for Solving the Problems] The present invention forms an exhaust pipe partitioning an exhaust passage with cast iron and an inflow pipe arranged in parallel along the longitudinal direction of the exhaust pipe,
The exhaust pipe and the inflow pipe are made of straight-cylindrical ceramics along the circumferential and longitudinal directions on the inner wall of a straight section excluding the connecting portions where these are connected to each other and the portions defined by the curves. The member is embedded by co-casting.

[Operation] The inflow pipe guides the exhaust gas into the exhaust pipe and discharges the exhaust gas to the downstream side of the exhaust passage.

The heat insulating member in the form of a straight cylinder cuts off heat of exhaust gas and reduces heat loss without being affected by a difference in thermal expansion amount between the exhaust pipe and the inflow pipe, contraction during casting, and the like.

[Embodiment] An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of an exhaust manifold structure according to the present invention. The exhaust manifold 1 is formed of cast iron as in the conventional case, and an exhaust pipe 3 that defines an exhaust passage 2 is formed. And an inflow pipe 4 arranged in parallel in the exhaust pipe 3 along the longitudinal direction thereof. The heat insulating member 5, which is a feature of the present invention, is provided on the inner peripheral wall 7 of the straight section 6 of the exhaust pipe 3 and the inflow pipe 4.

The exhaust passage 2 is appropriately bent so as to smoothly guide the exhaust gas from the internal combustion engine (not shown) to the downstream side 8 of the exhaust gas, and from the exhaust inlet 9 which is the inflow end of the inflow pipe 4 to the opposite side. The exhaust outlet 10 is located at. In particular, in this embodiment, the inflow pipe 4 has its root portion 11 bent and attached at the connecting portion 12 toward the discharge port 10, that is, toward the center, and is attached at both ends in the longitudinal direction of the exhaust pipe 3. In 13,
It is bent at about 90 ° and extends to the cylinder head side 14.

For this reason, the straight section 6 includes the attachment portion 15 of the inflow pipe 4 to the cylinder head and each connecting portion of the exhaust pipe 3 to the exhaust pipe 4.
Limited to 16 parts sandwiched between 12.

As shown in FIG. 2, the heat insulating member 5 is made of ceramics having high heat resistance and low heat conduction in the shape of a right cylinder, and its inner diameter 17 is the same as that of the passage 2. That is, when it is buried in the straight section 6, the section 6
Other than the exhaust pipe 3 and the inflow pipe 4 communicate with the inner peripheral wall 7, and along the circumferential direction and the longitudinal direction thereof, the passage 2 for the exhaust gas is substantially formed.
Are to be partitioned.

The inlet 9 of the inflow pipe 4 attached to the cylinder head
Although the side end and the outlet 10 side end supporting the downstream exhaust pipe (supercharger turbine) are linear, they are formed of cast iron in the same manner as in the conventional case in order to maintain the member strength. .

Next, the operation of this embodiment will be described.

The inflow pipe 4 guides the exhaust gas of the internal combustion engine to the passage 2 in the exhaust pipe 3. The exhaust pipe 3 collects the exhaust gas that has passed through the respective inflow pipes 4, and discharges it to the downstream side 8 via the outlet 10. Inflow pipe 4
The heat insulating member 5 buried in the inner peripheral wall 7 of the straight section 6 of the exhaust pipe 3 other than the connecting portion 12 blocks the transfer of exhaust heat to the outside in the radial direction, and reduces the heat loss.

As described above, since the heat insulating member 5 is embedded only in the straight section 6, the heat insulating effect is inferior to that of the case where it is provided on the entire inner peripheral wall 7, but the heat insulating member 5 which has been an obstacle to practical use is damaged. Can be avoided. That is, the difference in the amount of thermal expansion that occurs does not cause harmful bending stress to the heat insulating member 5 in the straight section 6, and only the movement of the heat insulating member 5 in the longitudinal direction corresponding to the difference in the amount of deformation occurs.

Further, as shown in FIG. 3, solidification shrinkage of cast iron during casting results in a uniform load on the outer peripheral surface 18, as indicated by arrow C in the figure, because the heat insulating member 5 has a cylindrical shape. A compressive stress mainly occurs along the circumference to resist this load,
It will prevent damage.

In addition to the circular cross-sectional shape of the heat insulating member, as shown in FIG. 3, the heat insulating member has an elliptical shape within a range that does not receive an extreme unbalanced load, that is, in consideration of the strength of the heat insulating member. I don't mind. The ceramic material is aluminum titanate (Al ₂ TiO ₂₎ which has low heat conduction, high heat resistance and low thermal expansion.
₅ ) or equivalent.

Further, in order to manufacture the exhaust manifold of the present invention, a preformed heat insulating member may be used as a core and cast. In this case, since the shape of the heat insulating member is a straight cylinder, it can be molded relatively easily.

[Effects of the Invention] In short, according to the present invention, the bending stress due to the difference in solidification shrinkage of cast iron during casting and the difference in thermal expansion during operation does not occur in the heat insulating member, and there is no possibility of damage. Shows excellent effects.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of an exhaust manifold structure according to the present invention, FIG. 2 is a partially enlarged schematic view showing a main part thereof, and FIG. 3 is a III-III line in FIG. A sectional view, FIG. 4 is a partially cutaway side view showing a conventional exhaust manifold, FIG. 5 is an enlarged view of an essential part thereof, and FIG. 6 is a sectional view taken along line VI-VI in FIG. In the figure, 2 is an exhaust passage, 3 is an exhaust pipe, 4 is an inflow pipe, 5 is a heat insulating member, 6 is a straight section, and 12 is a connecting portion.

Claims (1)

[Scope of utility model registration request] 1. A connection in which an exhaust pipe for partitioning an exhaust passage and an inflow pipe arranged in parallel along a longitudinal direction of the exhaust pipe are molded by cast iron, and the exhaust pipe and the inflow pipe are connected to each other. Exhaust, characterized in that a heat insulating member made of straight cylindrical ceramics is embedded by co-casting along the circumferential direction and the longitudinal direction of the inner peripheral wall of the straight section excluding the section and the section defined by the curved line. Manifold structure.