JPH08284744A - Piston and its manufacture - Google Patents

Abstract

PURPOSE: To control a knocking phenomenon for making a high compression ratio possible by preparing a short cylindrical annular heat conducting ring made of copper plate, and making its upper end approach the high temperature zone of a piston and its lower end approach the piston back having low temperature to insert-cast the heat conducting ring in aluminium alloy for manufacturing the piston. CONSTITUTION: In a reentrant type piston made of aluminium alloy, a part shown by a slanting line is formed of copper ring-shaped high heat conduction rate material, and moreover surface treatment such as oxidation inhibitation or the like is given to this part. In this case, a high heat conduction material part 3 is made to approach a cavity opening throttle end part 2 expected to be the highest temperature, and heat is quickly moved for controlling the temperature of the high temperature part. For the effective execution of this action, in the structure of a copper core, the upper end of the copper core heat conduction ring is made to approach the cavity opening part, and the lower end is extended to the low temperature zone 4 of the piston back to compose a heat conduction ring. In addition, a plurality of holes 6 is window- shapedly provided on a ring wall 5 as a means for reinforcing the joint between the aluminium alloy part and the heat conduction ring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston cooling technique for an internal combustion engine and its manufacturing technique.

[0002]

2. Description of the Related Art A piston of an internal combustion engine is a movable part that directly receives high temperature and pressure because it forms a part of a combustion chamber. It is known that the durability and reliability are greatly affected.

Therefore, the piston is made of an alloy mainly composed of aluminum, which is lightweight and has good heat conductivity. For the combustion chamber, cooling means is used to inject cooling oil to the back surface of the piston to maintain an allowable temperature. Has been.

Further, the shape of the piston differs depending on each combustion method. Particularly, in recent years, in order to improve the thermal efficiency and reduce the exhaust pollution, it is required to increase the engine output by high supercharging and increase the linburn combustion and high compression ratio. Therefore, the heat load on the piston becomes more severe, and countermeasures against it become a problem.

In this regard, the prior art has dealt with the method of providing a cooling oil flow path in the piston crown (cooling channel), but this method still provides sufficient high temperature in the vicinity of the opening (lip) of the reentrant cavity. The current situation is that the squish lip type combustion chamber engine, which cannot be controlled and is advantageous for combustion, is not put into practical use.

[0006]

If it is possible to further lower the piston temperature, the ring position can be brought closer to the top surface of the head, so that the air utilization rate is improved, which is advantageous in terms of output and fuel consumption. Improving durability may also be realized.

Therefore, it can be said that the piston temperature control and control technology should be developed with the highest priority in order to improve engine performance and reduce exhaust gas pollution.

[0008]

As a means for controlling the piston temperature, the present invention has a copper core structure in which the circumference of the piston combustion chamber is annularly surrounded by copper or a copper alloy having high thermal conductivity,
This copper-based part with high thermal conductivity is exposed directly in the combustion chamber,
The piston structure is cast in order to protect it with an aluminum alloy piston material so as to prevent oxidation.

That is, a piston material surrounds a copper material having a high heat conductivity in an annular shape as a heat transfer material, and one end thereof is cast in the vicinity of a combustion chamber portion having a high heat load to cast heat of a high temperature portion of the copper portion. It is a piston temperature control technology characterized by rapidly moving heat to a low temperature part and dissipating it to a low temperature region by utilizing high thermal conductivity and mass of a heat conductor.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. In the cross-sectional view of the reentrant piston shown in Fig. 2, the shaded area is made of copper annular high thermal conductivity material, and this area is subjected to surface treatment such as oxidation prevention to enable production in normal casting atmosphere. I am trying.

In the piston structure having such a configuration, the high thermal conductive material portion (3) is brought close to the cavity opening throttle end portion (2) where the temperature is the highest, and the heat is rapidly moved so that the temperature of the high temperature portion is increased. Can be suppressed.

In a copper core structure such as B as means for effectively performing this action, the upper end of the copper core heat conduction ring is brought close to the cavity opening, and the lower end communicates with the low temperature region (4) on the rear surface of the piston. The heat conducting ring has a structure in which the heat in the high temperature region can be quickly transferred to the low temperature region and a plurality of holes are formed in the ring wall (5) as a means for strengthening the joint with the aluminum alloy part. It is opened as a window (6). Further, the partial mass of the heat conducting ring is set to be larger in the low temperature part than in the high temperature part to promote heat transfer due to the heat difference.

Further, if the heat of the ring portion (7) is also constituted as A, the temperature of the ring peripheral region is suppressed by the heat transfer action similar to the above, so that the ring is placed at a position higher than the conventional top ring position. Even if it is provided, the cooling action of the ring groove prevents thermal deterioration of the tissue due to a decrease in temperature in the vicinity of the ring treger, and prevents troubles such as sticking of the ring stick.

In both the diesel and gasoline combustion systems, the ring position can be further provided above the piston by the cooling effect of the ring portion, and as a result, the gap volume between the piston and the cylinder is reduced and the air utilization rate is improved. At the same time, the amount of unburned hydrocarbons (THC) discharged by the quenching action (quenching) of the flame in this gap decreases.

Further, the effect of suppressing the piston temperature is effective in improving the air supply efficiency, and the specific output of the engine is improved by improving the air charging efficiency.

Further, the control of the piston temperature suppresses the thermal expansion of the piston, the piston distortion is also reduced, and the clearance between the cylinder and the piston can be designed to be small. The piston fluttering noise is reduced, and the piston durability is improved along with the quietness.

Since the piston temperature becomes a barrier to the improvement of the compression ratio of the flame ignition engine and is a major factor of the end gas knocking, according to the present technique which can arbitrarily control the piston temperature, the piston cooling action can be improved. Due to the improvement, the compression ratio can be increased as compared with the conventional method. As a result, thermal efficiency is improved even in the spark ignition engine, and CO ₂ emission can be reduced.

According to the present invention, a heat conduction area is formed by a high heat conduction material having a copper core on the piston head, and its end portion is extended to a low temperature portion to promote heat conduction due to a change in upper and lower heat transfer mass, and lower heat in a lower temperature area. A piston cooling method in which this area is directly cooled by oil or the like by increasing the transmission area, and a cooling technology in which the lower portion of the heat conduction ring is used as an oil cooling ring (8) to further enhance the cooling action. It is a feature of the present technology that the piston high temperature range can be maintained at an arbitrary temperature depending on the cooling oil amount and temperature.

[0019]

[Operation] In a reentrant or squish lip type combustion chamber engine, the temperature in the end region of the combustion chamber opening is farther than the coolable region, and it has the property of receiving the combustion heat most. How to control the temperature has been an important issue for this type of engine.

On the other hand, according to the present invention, the high thermal conductivity material is brought close to the vicinity of the opening where the temperature becomes high to form the heat induction region due to the temperature difference, so that the heat in the high temperature region is quickly transferred to other low temperature regions. The action of moving is performed by the high heat conduction ring, and the heat induction cooling action by the high heat conduction material can be performed in the vicinity of the piston ring portion requiring cooling other than the combustion chamber opening.

Further, a part of the high thermal conductive material is exposed on the rear surface of the piston, and an oil jet stream (9) cooled on this exposed portion
It is a piston cooling technology that can forcibly and quickly control the temperature of the high heat conduction part by injecting.

Further, the integral structure of the heat receiving part (3) and the cooling ring (8) made of a copper plate is a structure that satisfies the heat transfer cooling condition with a small amount of heat transfer material.

[0023]

[Effects] This technology can be applied to piston engines regardless of the fuel used and the combustion method, that is, LPG / LNG as well as liquid fuels such as gasoline, light oil, heavy oil, and methanol.
It is effective for all combustion systems that use gaseous fuel such as, and the piston temperature control effect of the present invention is to increase the output by improving the filling efficiency, improve the thermal efficiency by improving the compression ratio, and reduce the noise and durability by suppressing the coefficient of thermal expansion. The effect such as the improvement of reliability is great.

[0024]

[Brief description of drawings]

FIG. 1 is an example showing a cooling structure of a piston in a sub-chamber combustion system, in which a collision area of high-temperature gas ejected from the sub-chamber is subjected to a heat treatment with alumite, and a high-thermal-conductivity material is provided on the back surface thereof. It is a figure.

FIG. 2 is a cross-sectional explanatory view showing a configuration in which a cooling ring and a heat conduction ring are shared in the piston head as a means for cooling the lip portion of the squish lip cavity and the piston ring portion. B = A cross-sectional explanatory view in which a heat conduction ring is integrally configured from a high temperature portion to a low temperature portion.

FIG. 3 is a cross-sectional explanatory view of a structure example in which a lip portion and a ring portion of a reentrant cavity can be forcibly cooled, and a cooling action is mainly performed by an oil flow from an oil pump.

FIG. 4 is a cross-sectional explanatory view showing an example of a forced cooling structure of a piston for a spark ignition engine. In the figure, the high thermal conductive material portion is indicated by diagonal lines, and the dot portion indicates the recess and the window-shaped opening.

[0025]

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Combustion sub-chamber of head part, 2 ... Piston cavity lip end, 3 ... High thermal conductive material part, 4 ... Piston bottom part, 5 ... Thermal conductive ring, 6 ... Ring hole part, 7 ... Ring part, 8 ... Cooling ring Road, 9
... oil jet, 10 ... heat-resistant alloy part or alumite treatment part.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area F02F 3/22 F02F 3/22 A

Claims (7)

[Claims] 1. A heat transfer ring, which is made of a copper plate and has a short cylindrical ring shape, whose upper end is squeezed or whose lower end is a flange-shaped structure having a curved portion, and whose upper end is in the high temperature range of the piston. A piston for an internal combustion engine, characterized in that it has an aluminum alloy cast-in structure in which the lower end is in close proximity to the back surface of the low temperature piston, and the piston temperature is controlled. 2. A heat conducting ring is positioned between the piston cavity wall and the piston ring groove, and an oil cooling ring surface portion is formed by utilizing a curved flange portion at the lower end of the ring. Internal combustion engine piston. 3. A unilateral heat flow enhancement of the heat conducting ring by punching a short annular heat conducting ring or changing the thickness of the heat conducting ring so that the lower end mass increases from the upper end mass. The piston according to claim 2, which is intended. 4. A copper plate is formed as a short ring-shaped heat conductor by press working, and when it is cast into the piston head, it is subjected to pickling and water washing, and then only a temporary antioxidation treatment with oil for casting. A method for producing a copper core casting of an aluminum alloy, which comprises performing the casting. 5. The method according to claim 1 or 2, wherein the copper surface is subjected to a surface treatment with another metal as a means for suppressing the diffusion phenomenon of the copper surface when the heat conduction ring of copper is cast into the aluminum alloy. Piston manufacturing method. 6. An aluminum piston casting method in which an oil cooling ring structure and a heat transfer cooling structure are simultaneously formed by casting a salt core attached to the lower part of a heat conduction ring formed by processing a copper plate. 7. A plurality of recesses are provided on the inner wall surface of the piston,
The piston according to claim 1 or 2, wherein a partial thin region is formed and a plurality of window-shaped openings are formed in the skirt to reduce the weight of the piston and promote the cooling action.