JP3195062B2 - Engine piston structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a piston structure of an engine, and more particularly to a measure for improving the cooling performance of the piston.

[0002]

2. Description of the Related Art Conventionally, as a piston structure of an engine, for example, Japanese Unexamined Utility Model Publication No. 50-78804 or
As disclosed in Japanese Patent Application Laid-Open No. 8-165236 and the like, a portion of a height range in which a piston reciprocates in a cylinder inner peripheral surface of an engine is recessed by a predetermined depth over the entire circumference. A liner is arranged on the surface, a cooling water passage of a predetermined space is formed between the liner and the cylinder, and the liner is directly cooled by engine cooling water flowing through the cooling water passage. There is known a device designed to improve performance.

[0003]

When the above-mentioned wet liner is made of aluminum, which is the same material as the piston, the clearance between the liner and the piston is increased because both of them are the same material and have the same thermal expansion coefficient. In addition to the effect that aluminum itself has a soft property and the cooling water passage is located on the outer periphery of the liner, it has the effect of reducing the change in clearance from high to low temperatures. Under force, cavitation is likely to occur.

On the other hand, the reciprocating motion of the piston is generally
The characteristic that the piston does not move parallel to the liner inner peripheral surface but reciprocates while striking the liner wall by repeatedly oscillating left and right by a small angle in the direction perpendicular to the crankshaft. Have.

Therefore, when the wet liner is made of aluminum, the clearance can be reduced as described above, but cavitation occurs on the side wall surface of the cooling water passage of the liner due to the slap operation of the piston.

Therefore, the present inventors have paid attention to the following points in order to address the above problems. That is, the slap operation of the piston is caused by the inertia force of the piston and the combustion pressure of the air-fuel mixture, and is promoted when the clearance between the piston and the liner is large.Therefore, in order to reduce the inertia force of the piston, the weight of the piston must be reduced. It is possible to plan. Then, as a method, for example, instead of the large end regulation that regulates the displacement of the connecting rod of the engine in the axial direction at the large end, a small end regulation that regulates at the small end is adopted. Can be considered. That is, in the large end regulation, since the piston is required to slide on the inner peripheral surface of the liner at the same time as the regulation of the large end of the connecting rod, a gap for allowing an error in the positional accuracy between the two is formed with the small end of the connecting rod. It is necessary to provide at the engagement part with the piston,
There is a regret that the piston cannot be reduced in weight because the piston becomes larger inward by the gap. On the other hand, in the small end regulation, a gap for allowing an error in positional accuracy is provided at the large end of the connecting rod, so that there is an advantage that the piston can be reduced in weight.

Therefore, when the above-mentioned small end regulation is adopted and the slap operation is suppressed by reducing the inertia force of the piston by reducing the weight of the piston, the distance between the piston pin and the small end of the connecting rod and between the piston pin and the piston are reduced. Compared to connecting both rotatably, the former connection between the piston and the connecting rod small end is performed by press-fitting the piston pin into the connecting rod small end, and the two are integrally connected so that they cannot rotate. To that extent, it is conceivable that the movement of the piston around the piston pin can be suppressed, and the swing of the piston can be further reduced.

However, in the above-mentioned idea, since a part of the piston pin is press-fitted into the connecting rod,
The oil film area between the piston pin boss of the piston and the piston pin is reduced, and due to this relationship, when the engine is under a high load, a high combustion stimulating force per unit area acts on the oil film of the piston pin boss of the piston. Stimulation is transmitted to the boss. In this case, particularly, an aluminum piston or a wet liner has a property that the reliability with respect to strength is rapidly reduced in a region of a temperature value near 150 ° C. or higher, and therefore the piston receives a high combustion stimulating force as described above. There is regret that cracks and seizures occur.

[0009] The present invention has been made in view of mow斯, its objects are achieved by a piston which reciprocates La Inner inner peripheral surface, while preventing cracks and seizure of the piston effectively, the piston Effectively control slap motion,
Especially to effectively suppress the cavitation of the U <br/> Ettoraina a reciprocating engine with wet liners.

[0010]

In order to achieve the above-mentioned object, according to the present invention, a connecting rod is used for a liner, particularly an aluminum wet liner or a piston reciprocating on the inner peripheral surface of a surface coated with a plating. The structure is such that the piston is actively cooled while the end is regulated and the piston pin is pressed into the small end of the connecting rod.

That is, a specific solution of the invention according to claim 1 is based on a piston structure of a reciprocating engine. Then, the movement in the axial direction of the crankshaft of the connecting rod which is connected to the inner peripheral surface of the liner disposed inwardly of the cylinder to a piston reciprocates, said Konekuti
The small end of the rod is engaged with the piston without gap.
Thus, while being restricted at the small end of the connecting rod, the piston pin of the piston is pressed into the small end of the connecting rod, and is rotatable relative to the piston in the circumferential direction of the piston pin. And the connecting rod is swingably connected to the piston. Further, a cooling means for cooling the piston is arranged inside the piston.

[0012] The structure of the invention described in claim 2 is the above-described claim.
Identify the reciprocating engine described in 1.
And a predetermined space between the liner and cylinder.
Limited to engines with cooling water passages.

According to a third aspect of the present invention, the cooling means of the second aspect of the present invention is specified and has a cooling gallery formed of an aluminum pipe.

Further, according to the invention described in claim 4 , according to claim 3,
The configuration of the described invention is limited, and an oil inlet for introducing oil into a cooling gallery formed of an aluminum pipe and an oil inlet wall surrounding the oil inlet are formed on the piston.

In addition, in the fifth aspect of the invention, the shape of the cooling gallery formed by the aluminum pipe according to the third or fourth aspect of the invention is specified, and a cross section extending toward the end of the upper surface of the piston is specified. It has an elliptical shape.

The invention according to claim 6 limits the invention according to claim 3 or 4 , wherein a small-diameter portion having a smaller cross-sectional area than that of the other is provided in a cooling gallery formed of an aluminum pipe. It is configured to be formed.

[0017]

According to the above construction, in the first and second aspects of the present invention, the axial displacement of the connecting rod is restricted by its small end, so that the piston is lightened. The inertia force of the piston is reduced. Further, since the connection between the connecting rod and the piston is performed by press-fitting the piston pin into the small end of the connecting rod, the movement of the piston around the piston pin is suppressed. As a result, slap operation of the piston Ru is effectively regulated. Moreover, in particular, claim 2
Cooling water flows between the liner and cylinder as in the above-mentioned invention.
Reciprocating engine with wet liner with channel formed
In this case, the generation of cavitation on the side surface of the liner on the side of the cooling water passage is effectively suppressed.

At this time, when the engine is under a high load, a high combustion stimulating force per unit area acts on the piston pin boss portion of the piston, but the piston itself is sufficiently cooled by cooling means disposed therein. Since the allowable value of the combustion stimulating force acting on the piston becomes higher, the margin for the combustion stimulating force acting on the piston increases,
Cracks and the like hardly occur in the piston, and the reliability of the strength of the piston increases.

According to the third aspect of the present invention, since the cooling means is constituted by a cooling gallery formed of an aluminum pipe, it is possible to arrange the cooling means at the same time as casting the piston.

Further, in the invention according to claim 4 , the oil for cooling the piston is introduced into the cooling gallery from the oil inlet while being guided by the oil introduction wall, so that a large amount of the cooling oil is efficiently supplied to the cooling gallery. It can be introduced to improve the cooling performance of the piston.

In addition, according to the fifth aspect of the present invention, since the cooling gallery formed by the aluminum pipe has an elliptical cross section extending toward the end of the upper surface of the piston, which has a higher temperature than other portions, the cooling gallery can be cooled. The required high temperature part of the piston can be effectively cooled.

According to the sixth aspect of the present invention, since the small diameter portion is formed in the cooling gallery, the flow speed of the oil on the upstream side of the small diameter portion is reduced, and the cooling of the piston on the upstream side of the small diameter portion is performed. The performance is improved. Therefore, if the upstream side of the small diameter portion of the cooling gallery is specified on the exhaust port side or around the piston pin boss portion, these portions can be cooled well.

[0023]

As described above, claims 1 and 2
According to the piston structure of the engine of the invention described in Item 2 , the piston is actively cooled by the cooling means to increase the margin of the piston with respect to the combustion stimulating force, thereby effectively suppressing the occurrence of cracks and the like of the piston. , together with the weight of the piston to reduce the inertial force of the piston, the movement around the piston pin of the piston and suppressed small, Ru can effectively regulate the piston slap operation. In particular, the invention of claim 2
A cooling water passage is formed between the liner and the cylinder
Reciprocating engines with wet liners
The generation of cavitation in the wet liner can be effectively suppressed.

According to the third aspect of the present invention, in addition to the effect of the second aspect of the present invention, a cooling gallery formed of an aluminum pipe constitutes a main part of the cooling means, so that the cooling means can be cooled during casting of the piston. It is possible to arrange the means simultaneously.

Further, in the invention according to claim 4 , since the oil for cooling the piston is introduced into the cooling gallery from the oil introduction port while being guided by the oil introduction wall, a large amount of the cooling oil is efficiently supplied to the cooling gallery. As a result, the cooling performance of the piston can be improved.

In addition, according to the fifth aspect of the present invention, since the cooling gallery formed by the aluminum pipe is formed in an elliptical shape extending toward the end of the upper surface of the piston, the high temperature portion of the piston can be effectively cooled. It works.

According to the sixth aspect of the present invention, since a small diameter portion is formed in the cooling gallery, an upstream portion of the small diameter portion is specified as, for example, an exhaust port side or a piston pin boss portion, and these portions are identified. Can be cooled well.

[0028]

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2, 1 is a reciprocating engine, 2 is a plurality of cylinders formed in a line in the engine 1, and 3 is a row direction of the plurality of cylinders 2. It is a crankshaft arranged in.

Each of the cylinders 2 is provided with an aluminum liner 5. Each of the liners 5 has an inner surface coated with a plating, and an inner peripheral surface of the liner 5 is provided on the inner peripheral surface thereof. An aluminum piston 7 that reciprocates on the surface is inserted. A small end 8a of a connecting rod 8 is connected to the piston 7 so as to be swingable in a direction orthogonal to the axial direction of the crankshaft 2. A large end 8b of the connecting rod 8 is connected to the crankshaft 2. The rotational motion of the crankshaft 2 is converted into a vertical motion by a connecting rod 8, and the piston 7 is
The reciprocating motion is performed while sliding on the inner peripheral surface. The connecting rod 8, not shown, the gap error tolerance for the positional accuracy of the crank shaft 2 axially Ru provided large end 8b. That is, the small size of the connecting rod 8
The end portion 8a has an error in the positional accuracy of the crankshaft 2 in the axial direction.
No gap is provided for allowing the difference, and the small end 8a is pierced.
By engaging the ton 7 without gap, the connecting
The axial movement of the grod 8 of the crankshaft 2 is restricted by its small end 8a.

Further, in the engine 1, a combustion chamber 12 whose volume is variable according to the reciprocating motion of the piston 7 is formed in the cylinder head portion 10, and an intake port 13 and an exhaust port 14 are formed in the combustion chamber 12. An intake valve 15 is arranged at the opening of the intake port 13 of the combustion chamber 12, and an exhaust valve 16 is arranged at the opening of the exhaust port 14.

Further, on the engaging surface between the liner 5 and the cylinder 2, the cylinder 2 is recessed at a predetermined depth over the entire circumference in the height range where the piston 7 reciprocates, and Cooling water passage 2 in a predetermined space between cylinder 2
0 is formed. The cooling water passage 20 communicates with a cooling water supply port 21 to which engine cooling water is supplied from a water pump (not shown), and an upper end portion of the engine cooling water after being supplied to the cooling water passage 20. A communication passage 22 for sending water to the cylinder head 10 side communicates with the liner 5 by the engine cooling water flowing into the cooling water passage 20.
This is a wet-liner type configuration that directly cools down.

FIGS. 3, 4 and 5 show the piston 7 shown in FIGS.
As shown in FIG. 3, a piston pin boss 7a extending in the axial direction of the crankshaft 2 is formed at a lower end position thereof, and a concave portion 7b of a predetermined space is formed at a lower end position of the central portion. 7b, connecting rod 8
With the upper end portion 8at of the small end portion 8a facing, the hollow cylindrical piston pin 25 (see FIG. 2) is fitted to the piston pin boss portion 7a so as to be rotatable in the circumferential direction thereof.
The small end 8a of the connecting rod 8 is press-fitted into the small end 8a of the connecting rod 8 and the piston pin 25.
Are integrally connected so as not to rotate, and the piston pin 2
5, the connecting rod 8 is swingably connected to the piston 7.

Further, FIGS. 4 and 5
As shown in FIG. 7, an aluminum pipe 30 having a circular cross section is arranged coaxially with the piston 7 at the time of casting, and a cooling gallery 31 is formed in the piston 7. As shown in FIGS. 5 and 6, the cooling gallery 31 communicates with an oil introduction port 32 pierced from below the piston 7, and at a position radially opposed to the oil introduction port 32 from below the piston 7. A perforated oil discharge port 33 is formed.
1 and the oil is discharged from the oil discharge port 33,
A cooling means 35 for cooling the piston 7 is provided.

In addition, around the oil inlet 32, as shown in FIG. 6, an oil inlet wall 36 surrounding the oil inlet 32 is formed at a predetermined interval.

Therefore, in the above-described embodiment, the deviation of the connecting rod 8 in the axial direction of the crankshaft 2 is restricted by the small end 8a, and the gap for permitting the error in the positional accuracy is formed in the large end 8b. Since the piston 7 is provided, the weight of the piston 7 can be reduced by the gap, and the inertial force of the piston 7 can be limited to a small value. Moreover, since the connection between the piston 7 and the connecting rod 8 is performed by press-fitting the piston pin 25 into the small end 8a of the connecting rod 8, the operation of the piston 7 around the piston pin 25 can be restricted to a small extent. As a result, the weight reduction of the piston 7 and the regulation of the operation of the piston 7 around the piston pin 25 are combined,
The slap operation of the piston 7 can be suppressed small, and cavitation in the wet liner 5 is effectively suppressed as shown in FIG.

In this case, the piston pin 25 has a portion Lo of press-fitting into the connecting rod 8 out of its axial length (length L shown in FIG. 5).
The combustion stimulating force per unit area received by 5 increases. However, the piston 7 has an oil inlet 32 from below.
Is supplied to the cooling gallery 31 inside the piston 7 and is effectively cooled by the oil flowing through the gallery 31, so that the permissible limit value of the combustion stimulating force acting on the piston 7 is increased, and the margin for the combustion stimulating force is increased. The degree increases. As a result, even if a high combustion stimulating force per unit area is applied to the piston 7 during the high-load operation of the engine 1, cracks are less likely to occur in the piston 7, and the strength of the piston 7 is reliably ensured.

In addition, since the oil introduction wall 36 is present around the oil inlet 32 of the cooling gallery 31, the oil is efficiently introduced into the oil inlet 32, and a large amount of oil is removed from the cooling gallery 31. And the piston 7 can be cooled more effectively.

FIG. 7 shows a fifth embodiment of the present invention. In the above embodiment, the cooling gallery 31 has an aluminum pipe 30 'having an elliptical cross section instead of a circular cross section. 31 ', and its major axis direction is a direction extending toward the end of the upper surface of the piston 7.

Therefore, in this embodiment, the end of the upper surface of the piston, which becomes high in temperature, can be effectively cooled, and the reliability of the strength of the piston 7 can be further increased.

[0041] Figure 8 shows an embodiment of the invention described in claim 6. In the present embodiment, a narrowing portion 40 having a small diameter is formed in a cooling gallery 31 ″ made of an aluminum pipe 30 ″ having a circular cross section, and the narrowing portion 40 has a smaller cross-sectional area than the other. This is a portion corresponding to a position downstream of the position where the exhaust valve 16 is arranged.

Therefore, in the present embodiment, the oil flow speed upstream of the throttle section 40 is reduced, and the exhaust valve 1
Since the portion located below 6 is cooled well, the reliability of the strength of the piston 7 can be further increased.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view of an engine.

FIG. 2 is a vertical side view of the engine.

FIG. 3 is a view of the piston as viewed from an axial direction of a piston pin.

FIG. 4 is a sectional view of the same.

FIG. 5 is a cross-sectional view of the piston as viewed from the radial direction of the piston pin.

6 is a sectional view of the piston taken along line AA of FIG. 5;

FIG. 7 is a diagram corresponding to FIG. 5, showing an embodiment of the invention described in claim 5 ;

FIG. 8 is a diagram corresponding to FIG. 4 showing an embodiment of the invention described in claim 6 ;

FIG. 9 is an explanatory diagram of a region where cavitation occurs in a wet liner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Cylinder 5 Liner 7 Piston 8 Connecting rod 8a Small end part 20 Cooling water passage 25 Piston pin 31, 31 ', 31' 'Cooling gallery 32 Oil inlet 35 Cooling means 36 Oil inlet wall 40 Restricted part (small diameter part)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-134253 (JP, A) JP-A 62-29455 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02F 3/22 F02F 3/00

Claims (6)

(57) [Claims] 1. A connecting rod connected to a piston reciprocating on an inner peripheral surface of a liner disposed inside a cylinder, wherein the connecting rod is a piston structure of a reciprocating engine.
Clear the small end of the connecting rod to the piston
Without thereby engaged, though movement in the axial direction of the crank shaft is regulated, the piston pin of the piston is pressed into the small end of the connecting rod of the engine, and circumference of the piston pin with respect to said piston The connecting rod is swingably connected to the piston so as to be rotatable in the direction, and cooling means for cooling the piston is arranged inside the piston. Engine piston structure. 2. The engine according to claim 1, wherein the cylinder is disposed inside the cylinder of the engine.
Between the aluminum liner and the cylinder
Piping of a reciprocating engine with a cooling water passage in a constant space
It has a stone structure and is connected to a piston that reciprocates on the inner peripheral surface of the liner.
The connecting rod is
The small end of the
The movement of the shaft in the axial direction is restricted, and the piston pin of the piston is connected to the connector of the engine.
The piston is pressed into the small end of the
Is rotatably linked to the piston pin in the circumferential direction.
The connecting rod swings with respect to the piston
The piston is freely connected , and a cooling means for cooling the piston is provided inside the piston.
An engine fixie characterized by a step arrangement
Structure. 3. The cooling means comprises a cooling gallery formed of an aluminum pipe.
3. The piston structure of the engine according to 2 . 4. A piston according to claim 3, characterized in that the oil inlet for introducing the oil to the cooling gallery formed by aluminum pipes, an oil inlet wall surrounding the oil inlet is formed The piston structure of the described engine. 5. Cooling formed by aluminum pipe gallery, a piston structure according to claim 3 or claim 4, wherein the engine characterized in that it is a cross-sectional oval shape extending toward the end of the piston top surface. 6. The cooling gallery formed of aluminum pipe, a piston structure according to claim 3 or claim 4, wherein the engine, characterized in that the small diameter portion having a small cross-sectional area is formed.