JPS6088847A - Cylinder head structure - Google Patents

Abstract

PURPOSE:To constitute a simple exhaust passage, in a cylinder head, having a heat-insulating structure, by press-fitting a port liner formed of a thin metal pipe made of stainless steel onto the outer surface of a ceramic coating layer formed on the inner surface of the exhaust passage. CONSTITUTION:An exhaust passage 13 having a passage area slightly larger than a specified size, is integrally incorporated with a cylinder 21 by casting. Further, on the inner peripheral surface of the exhaust passage 13 is coated a ceramic material such as, for example, partially stable zirconia having a thermal expansion coefficient substantially equal to the material of the cylinder head 31 so that a coating layer 14 is formed. Further, a port liner 15 made of stainless steel or the like is press-fitted on the inner peripheral surface of the cating layer 14.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of a cylinder head in an adiabatic engine using ceramic materials.

Although ceramics have excellent heat resistance, they are expensive and difficult to use as casting parts such as castings, and although they have problems such as cracking after long-term use, they can be cured if appropriate measures are taken. The heat insulation effect can be effectively exhibited. However, even if the combustion chamber has an insulated structure, the temperature of the exhaust gas drops rapidly in the exhaust passage after blowdown, so an insulated structure is required for the exhaust passage leading to the turbocharger etc. that utilizes the thermal energy of the exhaust gas. It is said that

Various proposals have been made to install a port liner in the cylinder head to prevent the temperature of the exhaust gas from decreasing in the exhaust passage, but most of them use metal pipes such as stainless steel to form a double-weight boat liner. This is cast into the cylinder head. Furthermore, instead of using a metal tube, a method has been proposed in which a port liner is formed in advance from ceramics and the port liner is cast into the cylinder head.

However, such a port liner not only takes time and effort to position with respect to the mold, but also the former one may deform or locally melt the cylinder head casting liner. However, there are some difficult problems such as cracking.

SUMMARY OF THE INVENTION An object of the present invention is to provide a cylinder head structure with a heat-insulated exhaust passage that is simple in construction and easy to manufacture.

For this reason, the configuration of the present invention is such that a ceramic coating layer is provided on the inner surface of the exhaust passage of the cylinder head, and a boat liner made of a thin metal tube such as stainless steel is crimped onto the outer surface of the ceramic coating layer.

To explain the present invention based on an embodiment, as shown in FIG.
0 is provided, and a cylinder liner 2 made of ceramics is fitted and supported in the cylindrical portion. Then, the cylinder head 21 is coupled to the upper end surface of the cylinder block 26 via a gasket 25 with a tightening bolt. An air chamber 22.33 is provided in the upper half of the cylinder head 21 made of metal such as aluminum, and a cylindrical portion 39 is provided in the lower half, and a gasket 8 is attached to the upper end wall of the cylinder head 21.
A headliner 4 made of ceramic is fitted and supported on the peripheral wall through a pair of upper and lower rings 23, respectively.

The cylindrical portion of the headliner 4 and the cylindrical portion of the cylinder liner 2 form a continuous inner circumferential surface, into which the piston 38 is slidably fitted. This piston 38 is made of a metal such as aluminum, and a crown 31 with a combustion chamber made of ceramics is attached to the upper end of a main body 37 that supports a piston pin 29, and a bolt 27 is attached so as to form an air M6.
and are connected by a nut 28. In this way, a combustion chamber 40 is formed that is surrounded by the cylinder liner 2, headliner 4, and piston crown 31, each made of ceramics. In the upper half of the combustion chamber 40, which is exposed to the highest temperature, air 1ii17 is provided between the headliner 4 and the cylindrical portion 39 of the cylinder head 21.

An exhaust port 41 is formed in the headliner 4 . The exhaust valve 3 for opening and closing the exhaust port 41 is also molded from ceramics, and the stem 3 traverses the exhaust passage 13 and is slidably supported by a guide tube 36 made of ceramics. The guide tube 36 is fitted and supported by a reinforcing metal sleeve 35, and this metal sleeve 35 is supported by the cylinder head 21.

Although not shown, the intake boat and the intake valve are similarly configured.

In the present invention, an exhaust passage 13 having a passage area slightly larger than a specified size is integrally formed with *i in a cylinder head 21 made of aluminum or cast iron, and the cylinder head 2 The coating layer 14 is formed by coating a ceramic such as partially stabilized zirconia whose coefficient of thermal expansion is almost the same as that of the material;
Furthermore, a port liner 15 made of a thin metal tube such as stainless steel is crimped onto this inner peripheral surface.

The port liner 15 is a thin metal tube with an inner diameter smaller than that of the exhaust passage 13, which is curved approximately along the shape of the exhaust passage 13, and is inserted into the exhaust passage 13, with plugs 17 at both ends, as shown in FIG. .18 is combined and the liquid injection pipe 1 provided in the stopper 18.
Pressure liquid is forced into the port liner 15 from 8a to expand the port liner 15 and press it against the coating layer 14.

The shape of the exhaust passage 13 is generally curved in an arc, but its cross-sectional shape changes slightly, so there is little risk of misalignment just by pressing the port liner 5 against the coating [14]. However, there is an annular groove 13 in the middle of the exhaust passage 13.
If the annular groove 13a is formed in advance and the protrusion 15a deformed by hydraulic pressure is engaged with the boat liner 5,
Misalignment between the exhaust passage 13 of the cylinder head 21\ and the boat liner 5 can be completely prevented. Then, when the hydraulic pressure inside the port liner 5 is released, the outer diameter of the port liner 5 becomes slightly smaller due to springback, and a thin air layer is formed between the port liner 5 and the coating layer 14.

Finally, attach the end of the port 1-liner 5 to the cylinder head 2.
The starting end 1511 is cut along the wall surface of the cylinder head 21 or bent along the wall surface of the exhaust passage 1 of the cylinder head 21.
3 and is press-fitted into the exhaust port 41 of the headliner 4, thereby sealing between the cylinder head 21 and the end wall 4a of the headliner 4.

In the case of a diesel engine, the combustion gas rises to about 1200°C at about 3/4 load. However, since the crown 31 of the piston 38 surrounding the combustion chamber 40, the cylinder liner 2, the intake and exhaust valves 3, and the headliner 4 are each made of partially stable zirconia or silicon nitride, they can sufficiently withstand the temperature of the combustion gas. By providing an air layer 6 between the crown 31 and the main body 37 of the piston 38 and an air layer 7 between the headliner 4 and the cylinder head 21, heat transfer is suppressed and heat dissipation to the outside is prevented. can do.

Note that for the cylinder block 26, the piston 38
Since the crown 1 is fitted inside the helad liner 4 during most of the combustion stroke, no air layer is provided.

When the exhaust valve 3 opens after the combustion stroke ends, the combustion gas of the combustion exhaust 40 is guided from the exhaust boat 41 to the exhaust passage 13. In the present invention, an air layer is formed between the boat liner 15 and the coating layer 14 due to springback when the boat liner 15 makes a correct answer, so that heat transfer from the port liner 15 to the coating layer 14 is suppressed.
Partially stable zirconia, which makes up the coating layer 14, has a coefficient of thermal expansion almost equal to that of cast iron, so it is stable against thermal deformation.Furthermore, it has a relatively low thermal conductivity among ceramics, so it does not transfer heat to the cylinder head 21. Dissipation can be kept to a minimum. Such a heat insulating structure of the exhaust passage 13 allows the exhaust gas from the combustion chamber 40 to be sent in a high temperature state to a heat recovery device such as a turbocharger.

As described above, the present invention provides the exhaust passage 13 of the cylinder head.
A ceramic coating layer 14 is bonded to the outside of the ceramic coating layer 14, and a boat liner 15 made of stainless steel or the like is bonded to the outside of the coating. A port liner 15 made of a thin metal tube such as stainless steel that is curved along the same direction is inserted into the exhaust passage 13, and both ends are opened and pressurized liquid is forced into the inside of the exhaust passage 13 to insert the port liner 15 into the exhaust passage 13. Since it is pressure-bonded to the coating layer 14, it is easy to manufacture and a product with stable quality can be obtained.

By interposing the ceramic coating layer 14 and the air layer between the boat liner 15 made of stainless steel and the cylinder head 21 made of aluminum, the heat dissipated from the exhaust passage 13 to the cylinder head 21 is minimized. Since the exhaust gas can be supplied in a high temperature state to a heat recovery device such as an exhaust turbo supercharger, it is possible to increase the output of the engine and improve the thermal efficiency.

[Brief explanation of drawings]

FIG. 1 is a front sectional view of an engine equipped with a cylinder head according to the present invention, and FIG. 2 is a front sectional view illustrating the manufacturing process of the cylinder head. 2 Nijilina liner 3: Exhaust valve 4: Herad liner
13: Exhaust passage 13a: Annular groove 14: Coating layer 15: Boat liner 15a: Projection 21 Niji cylinder head 26: Cylinder block 31: Crown
38: Piston 40: Combustion chamber Patent applicant: Isuri Motors Co., Ltd. Patent attorney Toshio Yamamoku

Claims (1)

[Scope of Claims] (1) An adiabatic engine characterized in that a ceramic coating layer is provided on the inward side of the exhaust passage of a cylinder head, and a boat liner made of a thin metal tube such as stainless steel is crimped onto the outer surface of the ceramic coating layer. The structure of the cylinder head in <2) An annular groove is provided on the inner circumferential surface of the exhaust passage, and a protrusion that engages with the annular groove is formed on the outer circumferential surface of the boat liner. Structure of the cylinder head described in box (1).