JPH09195848A - Piston for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston for an engine by which impact noise at the time of collision against a cylinder due to its swinging movement caused by explosive combustion in the engine can be lowered. SOLUTION: The direction of force FP generated by expansion pressure P due to explosive combustion is shifted to an anti-thrust side 1a from the direction of reciprocating movement of a piston by forming a tilting angle θin a pressure receiving top land face 11 of a piston 2. Consequently, the swinging moment Mf in the counterclockwise direction affecting the piston 2 near an upper dead point immediate after explosive combustion and the suppressing moment MP in the clockwise direction by the force FP generated by expansion pressure P due to explosive combustion are well balanced. As a result, a phenomenon that the piston 2 which contacts the anti-thrust side 1a of a cylinder during compressing process swings to the thrust side 1b immediate after explosive combustion is suppressed and the impact noise generated by collision of the piston 2 against the thrust side 1b can be lowered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine piston for various engines such as a gasoline engine, a diesel engine, a gas engine, etc., which is characterized by a top land pressure receiving surface of the piston.

[0002]

2. Description of the Related Art As shown in FIG. 4, a piston 2 slidably fitted in a cylinder 1 has a crank arm integrated with a crank shaft 5 via a connecting rod 4 connected by a piston pin 3. Pin-coupled to 6. There is a slight gap 7 between the cylinder 1 and the piston 2.
There is. In the figure, this gap 7 is shown for ease of explanation.
Is greatly represented.

The piston 2 which was in contact with the anti-thrust side 1a of the cylinder 1 in the compression stroke shown in FIG.
Immediately after the explosive combustion shown in (B), that is, near the top dead center (top dead center), a reaction centered on the piston pin 3 due to the frictional force F _f between the piston and the cylinder acting upward on the piston 2. A clockwise swinging moment M _f causes a swinging motion in the gap 7. Further, as shown in (C), the explosion pressure acts on the piston 2 from above, and the load from the vehicle body and the road surface acts diagonally along the connecting rod 4 from below, so that the piston 2 contacts the thrust side 1b. Contact.

[0004]

As described above, in the conventional piston, as shown in FIG. 4B, when the piston is lowered by the expansion pressure at the time of explosive combustion, the thrust side of the cylinder 1 is near the top dead center. Although a swinging motion to 1b occurs, at this time, there is a problem that the upper part 2a of the piston 2 collides with the thrust side 1b, and an impact sound (slap sound) generated by the impact force as a vibration source is generated as noise.

The present invention has been made in view of the above point, and by changing the pressure receiving surface of the piston, it is possible to reduce the impact noise between the piston and the cylinder generated at the time of explosive combustion of the engine. The purpose is to provide a piston for use.

[0006]

According to the first aspect of the present invention,
In the engine piston that is reciprocally movable in the cylinder, the pressure receiving surface that receives the expansion pressure due to explosive combustion is provided with a moment canceling means that directs the force generated from the expansion pressure in the direction against the swinging moment during explosive combustion. It is a piston for the engine of the constitution.

Then, when the expansion pressure due to the explosive combustion acts on the pressure receiving surface, the force received by the expansion pressure is shifted by the moment offsetting means in a direction different from the piston reciprocating direction, so that the vicinity of the top dead center during the explosive combustion is reached. A rotational force is applied to the piston in the direction opposite to the direction of the swinging motion of the piston. That is, the restraining moment is applied in the direction opposite to the swinging moment to restrain the swinging motion of the piston, and the impact sound resulting from this motion is reduced.

According to a second aspect of the present invention, there is provided a moment canceling means for the engine piston according to the first aspect.
An inclination angle is set on the pressure receiving surface with respect to a surface perpendicular to the reciprocating direction of the piston.

Then, the force generated from the expansion pressure at the time of explosive combustion is displaced in the direction different from the reciprocating direction of the piston on the pressure receiving surface of the piston having the inclination angle set, so as to be opposite to the swinging moment generated in the piston. Apply a restraining moment in the direction of.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIG.
2 and another embodiment will be described with reference to FIG. The same parts as those of the conventional one shown in FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 1, the topland pressure receiving surface 11 which receives the expansion pressure due to the explosive combustion in the piston 2
In addition, as a moment offsetting means, an inclination angle θ is set with respect to a plane perpendicular to the piston reciprocating direction.

By setting this inclination angle θ, the anti-thrust side
Top land pressure receiving surface 11 of piston 2 so that the upper edge of piston 1a is slightly higher than the upper edge of the piston on thrust side 1b.
To form

Inclination angle θ as means for canceling the moment
Is the force F _p (= P × pressure receiving area) generated by receiving the expansion pressure P at the time of engine explosion combustion on the topland pressure receiving surface 11.
It has the function of pointing diagonally downward, which is different from the piston reciprocating direction.

That is, in the state shown in FIGS. 2B and 2C immediately after the combustion stroke from the compression stroke shown in FIG. 2A through the top dead center, the piston 2
When the expansion pressure P due to the explosive combustion acts on the topland pressure receiving surface 11, the direction of the force F _p generated from the expansion pressure P is the piston reciprocal movement. It shifts to the anti-thrust side 1a from the moving direction.

As a result, in the vicinity of the top dead center immediately after the explosion and combustion shown in FIG. 2B, the force is applied in the direction opposite to the counterclockwise swinging moment M _f that causes the swinging motion of the piston 2. A clockwise restraining moment M _p caused by F _p is applied to restrain the swinging motion of the piston 2 shown in FIG. 4 (B).

At this time, as shown in FIG. 1, the swinging moment M _f generated around the piston pin 3 and the force F _p that receives the expansion pressure P near the top dead center cause the piston pin 3 to move.
And restraining moment M _p of the distance L _p which occurs around so equal, i.e., in FIG. 1, M _f = _{F p}
The tilt angle θ and the like are determined so that the equilibrium conditional expression of L _p = M _p is satisfied.

By suppressing the swinging motion of the piston 2 in this manner, when the upper portion 2a of the piston 2 collides with the cylinder 1 near the top dead center at the time of engine explosion combustion shown in FIG. 4 (B). By mitigating the impact force of, it is possible to reduce the impact sound (slap sound) generated.

Next, the moment canceling means of the invention described in claim 1 is not limited to the setting of the tilt angle θ.

For example, as shown in FIG. 3, by providing a step 12 on the top land pressure receiving surface 11, a force F _px is generated in a direction orthogonal to the piston reciprocating direction due to the expansion pressure P generated near the top dead center. to since, by the orthogonal force F _px and the piston reciprocating direction of the force F _pz generates a resultant force F _p directed obliquely downward by restraining moment M _p which occurs on the basis of the force F _p, near the top dead center The swinging moment M _f generated in step S1 is canceled.

Further, instead of the step 12, a partially inclined surface may be provided so that the force generated from the expansion pressure at the time of explosive combustion is directed obliquely downward.

Finally, conventionally, there is also an offset piston in which noise is reduced by offsetting the fitting position of the piston pin 3 to the piston 2 to one side from the center. The moment offsetting means on the topland pressure receiving surface 11 according to the present invention is advantageous over the conventional offset piston in the following points.

(1) Manufacturing Method Since the pressure receiving surface of the piston top land is merely provided with an inclination angle, the manufacturing is relatively easy.

(2) Tuning (Adjustment) Method The offset amount of the piston pin in the offset piston is about a comma number mm to 2 mm. In this range, it is necessary to adjust the offset amount so as to be optimal for reducing the piston slap, and thus extremely high processing accuracy is required.

On the other hand, in the piston of the present invention, the moment generated in the piston can be easily adjusted by partially changing the inclination angle of the top land pressure receiving surface or providing a step.

[0025]

According to the first aspect of the present invention, the moment canceling means provided on the pressure receiving surface applies a restraining moment in a direction opposite to the swinging motion generated in the piston near the top dead center during engine explosion combustion. It is possible to suppress the swinging motion of the piston, reduce the impact force of the piston colliding with the cylinder by the swinging motion, and reduce the noise due to the impact sound (slap sound).
The durability of the piston can be improved.

According to the second aspect of the present invention, as the moment canceling means, the neck generated on the piston at the time of explosive combustion is obtained by the simple processing of setting the inclination angle on the pressure receiving surface with respect to the surface perpendicular to the piston reciprocating direction. It is possible to obtain a restraining moment against the swinging moment, and it is possible to reduce the impact noise caused by the swinging motion of the piston and improve the durability of the piston by simple means.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an embodiment of an engine piston according to the present invention.

FIG. 2 is an explanatory view showing the action of the piston of the above.

FIG. 3 is an explanatory view showing another embodiment of the same piston.

FIG. 4 is an explanatory view showing the operation of a conventional engine piston.

[Explanation of symbols]

 1 Cylinder 2 Piston 11 Pressure receiving surface θ Inclination angle

Claims (2)

[Claims] 1. A piston for an engine reciprocally provided in a cylinder, wherein a force generated from the expansion pressure is directed to a pressure receiving surface receiving expansion pressure due to explosive combustion in a direction against a swinging moment during explosive combustion. An engine piston, which is provided with a canceling means. 2. The piston for an engine according to claim 1, wherein, as the moment offsetting means, an inclination angle is set on the pressure receiving surface with respect to a surface perpendicular to the piston reciprocating direction.