JP2006194109A - Piston structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piston structure which can prevent occurrence of abnormal noise resulting from collision of a piston against a cylinder bore at the time of cold start of an engine and further which can reduce friction between the piston and the cylinder bore after warming-up of the engine, so as to prevent fuel consumption from being increased by the friction. <P>SOLUTION: The piston structure includes a piston body 1 which is inclined toward the anti-thrust side in the rotational direction around a piston pin in a cylinder at the the time of stop of the engine. In the piston structure, an annular cooling channel 70 into which oil for cooling the piston body 1 is introduced, is arranged in the interior 1n of the piston body 1. A flow path area of the cooling channel 70 on the thrust side is larger than a flow path area of the cooling channel 70 on the anti-thrust side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a piston structure including a piston body that tilts to one side in a rotational direction with a piston pin as a fulcrum in a cylinder when the engine is stopped.

  In recent years, pistons, such as pistons for gasoline engines, tend to be required to be lighter and thinner for the purpose of reducing the friction of the piston with respect to the bore of the cylinder in which the piston is disposed.

  However, when the engine is cold started, the gap between the piston and the cylinder bore is large, so if the piston is reduced in weight and thickness, when the piston moves near top dead center, The piston swings larger than usual in the direction of rotation with the piston pin as a fulcrum (hereinafter referred to as the thrust direction and the anti-thrust direction), and the skirt portion violently collides with the cylinder bore.

  As a result, there is a problem that the collision noise of the piston skirt portion with respect to the cylinder bore increases, and the collision noise becomes abnormal and the driver feels uncomfortable.

  In view of such problems, when the piston receives a force that rotates in the thrust direction with the piston pin as a fulcrum, the center of the piston pin that fixes the piston is decentered (offset) in the thrust direction, and the thrust direction of the piston Generally, the side skirt is kept in contact with the cylinder bore when the engine is stopped.

  In this way, by offsetting the center of the piston pin toward the thrust direction, the collision of the skirt portion of the piston on the thrust side with the cylinder bore at the time of engine cold start can be moderated and noise can be reduced.

  Further, for example, in Patent Document 1, when the piston receives a force that rotates in the thrust direction with the piston pin as a fulcrum, a pin boss portion that supports the piston pin is formed with a jaw portion that extends only in the anti-thrust direction, A technique has been proposed in which the skirt portion on the thrust side of the piston is brought into contact with the cylinder bore when the engine is stopped by shifting the center of gravity of the piston to the anti-thrust side.

In this way, by providing a jaw portion that extends to the anti-thrust side, the collision of the piston skirt on the thrust side piston against the cylinder bore at the time of engine cold start is made gentler than the piston pin offset, effectively Abnormal noise can be reduced.
JP 2002-317692 A

  However, in Patent Document 1, even after the engine warm-up is completed and the piston expands and the gap between the piston and the cylinder liner becomes small, the piston is always inclined to the anti-thrust side. In addition, there is a problem in that friction due to side pressure is generated between the skirt portion of the piston on the thrust side and the cylinder bore, thereby reducing fuel consumption.

  The object of the present invention has been made in view of the above problems, and can prevent the generation of abnormal noise caused by the collision of the piston with the cylinder bore during the cold start of the engine. It is an object of the present invention to provide a piston structure that can prevent a reduction in fuel consumption due to friction by reducing friction with a cylinder bore.

  In order to achieve the above object, a piston structure according to the present invention includes a piston structure that includes a piston body that tilts toward the first direction of the rotational direction with the piston pin as a fulcrum in the cylinder when the engine is stopped. An annular cooling channel into which oil for cooling the piston body is introduced is disposed inside the piston body, and the rotation direction is opposite to the first direction side of the cooling channel and the piston pin as a fulcrum. The channel area on the second direction side is larger than the channel area on the first direction side.

  According to the piston structure of the present invention, it is possible to prevent the generation of noise due to the collision of the piston with the cylinder bore during the cold start of the engine, and further reduce the friction between the piston and the cylinder bore after the engine is warmed up. By doing so, it is possible to prevent a reduction in fuel consumption due to friction.

Embodiments of the present invention will be described below with reference to the drawings.
1 is a view showing the inside of an engine cylinder provided with a piston according to an embodiment of the present invention, and FIG. 2 is a view showing the inside of the engine cylinder with the piston shown in FIG. 3 is a front view of the piston of FIG. 1 as viewed from below, FIG. 4 is a sectional view taken along line IV-IV in FIG. 3, and FIG. 5 is a sectional view taken along line V-V in FIG.

  As shown in FIGS. 1 and 2, a cylinder liner 5 is cast on the inner periphery of an engine cylinder 4, and a cylinder bore 5 n is formed by the inner peripheral surface of the cast cylinder liner 5. Also, a piston 10 that reciprocates in the cylinder bore 5n is provided in the cylinder 4 within a range where the cylinder liner 5 is provided.

  The main body of the piston body 1 of the piston 10 is composed of a head portion 1h, a pin boss portion 1p (see FIG. 4), and a skirt portion 1s. A cylinder bore 5n is formed in a groove formed on the outer periphery of the head portion 1h. A piston ring 2 and an oil ring 3 that are in sliding contact with each other are supported.

  Further, a small end portion 15s of a known connecting rod 15 having a large end portion 15d connected to the crankshaft 20 is connected to the pin boss portion 1p via a piston pin 60, and thereby, to the small end portion 15s. Thus, the piston body 1 is rotatable.

  Hereinafter, of the directions in which the piston body 1 rotates with the piston pin 60 as a fulcrum, the side opposite to the rotation direction of the crankshaft 20, that is, the first direction rotating to the left in FIG. The side that coincides with the rotational direction of 20, that is, the second direction that rotates to the right in FIG. 1, will be referred to as the thrust side. Further, the piston main body 1 will be described below as receiving a force that rotates to the thrust side with the piston pin 60 as a fulcrum by the rotation of the crankshaft 20.

  As shown in FIGS. 2 and 4, the inside 1n of the head portion 1h of the piston body 1 is formed to have a prescribed thickness, and the thickness 1nh on the anti-thrust side is larger than the thickness 1ns on the thrust side. 4 is formed so as to have a predetermined thickness from a two-dot chain line to a solid line. Further, the thickness of 1 nh on the anti-thrust side is set to such a thickness that the piston is balanced when the oil 51 is filled in the cooling channel 70. That is, the thickness of the inside 1 n of the head portion 1 h of the piston main body 1 has a shape that is asymmetric with respect to the central axis of the piston main body 1.

  In the step of making the thickness on the anti-thrust side thicker than the thickness on the thrust side, the thickness of the inside 1n of the head portion 1h of the piston main body 1 is symmetrical about the central axis of the piston main body 1. After the formation, the thick portion may be separately formed on the anti-thrust side.

  Since the thickness on the anti-thrust side is thicker than the thickness on the thrust side, the center of gravity of the piston body 1 is located on the anti-thrust side, and the weight balance is biased toward the anti-thrust side. The main body 1 tilts to the anti-thrust side in the cylinder 4 (see FIG. 6). In this case, the skirt portion 1s on the thrust side of the piston body 1 is in contact with the cylinder bore 5n (see FIG. 6).

  Further, for example, as shown in FIG. 5, an annular cooling channel (oil pipe) 70 is connected to the piston pin 60 in the inside 1 n of the head portion 1 h of the piston body 1. It arrange | positions so that it may become substantially parallel.

  As shown in FIGS. 3 and 5, the cooling channel 70 is formed with a hole 1 a for introducing the oil 51 and a hole 1 b for discharging the introduced oil. The tip of the oil jet 30 is opposed to the hole 1a, and the oil jet 30 ejects oil 51 pumped up by, for example, the pump 40 from the oil pan 50 toward the hole 1a. Oil 51 is introduced into 70.

  The oil 51 introduced into the cooling channel 70 is discharged from the hole 1b after cooling the piston body 1 in the flow process. The oil jet 30 is disposed in the vicinity of the base end portion of the cylinder 4 on the crankshaft 20 side, for example.

  2 to 5, the cooling channel 70 has a thrust-side volume that is larger than the area of the thrust-side flow path 70h than the area of the anti-thrust-side flow path 70h. It is formed larger than the volume. That is, the cooling channel 70 has a shape that is asymmetric with respect to the central axis of the piston body 1.

  Therefore, when a large amount of oil 51 is continuously supplied from the oil jet 30 and the oil 51 is filled in the entire area of the cooling channel 70, the oil 51 is present more on the thrust side than on the anti-thrust side. ing. As described above, when the oil 51 is unequally filled in the cooling channel 70, the center of gravity of the piston body 1 moves in the direction of the central axis of the piston body 1.

  Next, the operation of the piston of the present embodiment configured as described above will be described with reference to FIGS. 6 is a cross-sectional view showing a state in which the piston body of FIG. 2 is tilted to the opposite thrust side when the engine is stopped, and FIG. 7 shows a state in which the cooling channel of FIG. 2 is filled with oil after the engine is started. It is sectional drawing.

  First, when the engine is stopped, as shown in FIG. 6, the inner 1n of the head portion 1h of the piston body 1 is thicker on the anti-thrust side than on the thrust side. Since the position exists and the weight balance is biased toward the anti-thrust side, that is, when the engine is not filled with the oil 51 in the cooling channel 70, the position of the center of gravity is defined by the weight balance of the piston body 1 itself. Therefore, the piston body 1 is positioned in the cylinder 4 in an unbalanced state inclined to the anti-thrust side. With this inclination, the thrust side skirt portion 1s of the piston body 1 comes into contact with the cylinder bore 5n.

  Next, when the engine is cold-started, the piston body 1 reciprocates within the cylinder bore 5n in a state where the piston liner 1 is inclined to the anti-thrust side within the range where the cylinder liner 5 is disposed. At the time of this cold start, the viscosity of the oil is high and the oil 51 injected from the oil jet 30 is not introduced into the cooling channel 70, so that the tilt of the piston body 1 toward the anti-thrust side is maintained.

  Accordingly, immediately after the cold start of the engine, as shown in FIG. 6, since the thrust side skirt portion 1s of the piston body is in contact with the thrust side cylinder bore 5n, the thrust side skirt portion 1s of the piston body 1 is Due to the reciprocating motion of the piston body 1, the piston body 1 gently collides with the cylinder bore 5 n on the thrust side.

  Next, when the engine is warmed up, as shown in FIG. 7, the piston main body 1 expands, and the gap between the outer periphery of the piston main body 1 and the cylinder bore 5n is reduced. Further, the viscosity of the oil becomes sufficiently low, and a large amount of oil 51 is ejected from the oil jet 30 to the hole 70a of the cooling channel 70, whereby sufficient oil 51 is supplied into the cooling channel 70, and thereafter Oil 51 is filled.

  At this time, the cooling channel 70 is formed such that the area of the thrust-side flow path 70s is larger than the area of the anti-thrust-side flow path 70h, so that the oil 51 is filled more on the thrust side than on the anti-thrust side. Is done. That is, the amount of oil 51 filled differs between the thrust side and the anti-thrust side.

  As a result, the center of gravity of the piston body 1 that has moved to the anti-thrust side is positioned on the central axis of the piston body 1 due to the thickness on the anti-thrust side. Therefore, after the engine is warmed up, as shown in FIG. 7, the thrust side skirt portion 1s of the piston body 1 that has been in contact with the thrust side cylinder bore 5n does not come into contact with the cylinder bore 5n. In the cylinder bore 5n, the weight balance is achieved.

  This reduces the friction between the thrust side skirt portion 1s of the piston body 1 and the thrust side cylinder bore 5n, which is caused by a decrease in the gap between the outer periphery of the piston body 1 and the cylinder bore 5n. .

  Thus, in the piston structure showing an embodiment of the present invention, when the engine is stopped, the center of gravity of the piston body 1 is moved to the anti-thrust side, and the weight balance is biased to the anti-thrust side. The piston body 1 is tilted to the opposite thrust side so that the thrust side skirt 1s of the piston body 1 is in contact with the cylinder bore 5n on the thrust side.

  Further, the flow passage area of the cooling channel 70 filled with the oil 51 is formed so that the area of the thrust flow passage 70s is larger than the area of the anti-thrust flow passage 70h. The amount of oil 51 to be filled in was increased on the thrust side than on the anti-thrust side.

  Thus, at the time of engine cold start, the thrust side skirt portion 1s of the piston body 1 and the cylinder bore 5n caused by the gap between the thrust side skirt portion 1s of the piston body 1 and the cylinder bore 5n The occurrence of abnormal noise due to the collision can be prevented.

  Further, after the engine is warmed up, the center of gravity of the piston body 1 that has moved to the anti-thrust side returns to the position of the central axis of the piston body 1 by filling the cooling channel 70 with the oil 51. In the reciprocal movement of 1, the thrust side skirt portion 1s of the piston body 1 does not come into contact with the thrust side cylinder bore 5n.

  Therefore, the gap between the thrust side skirt portion 1s of the piston body 1 and the cylinder bore 5n is reduced, resulting in a gap between the thrust side skirt portion 1s of the piston body 1 and the thrust side cylinder bore 5n. Therefore, a reduction in fuel consumption due to the friction can be prevented.

  That is, the generation of noise due to the collision between the thrust side skirt portion 1s of the piston body 1 immediately after the engine start and the cylinder bore 5n, the thrust side skirt portion 1s of the piston body 1 after engine warm-up, and the thrust side skirt portion 1s It is possible to provide a piston structure capable of simultaneously preventing a reduction in fuel consumption due to friction with the cylinder bore 5n.

Hereinafter, a modification is shown.
In the present embodiment, in order to deviate the weight balance of the piston body 1 toward the anti-thrust side, the thickness of the inside 1n of the head portion 1h of the piston body 1 is made thicker on the anti-thrust side than on the thrust side. It was shown to be done.

  Not limited to this, the internal 1n thickness of the head portion 1h of the piston body 1 is kept the same on the thrust side and the anti-thrust side, and the center of the piston pin 60 is offset to the thrust side as in the prior art. It goes without saying that the present embodiment can be applied even when the position is set. Note that the method of biasing the weight balance of the piston body 1 to the anti-thrust side is not limited to the above-described method.

  Further, in the present embodiment, it has been shown that the flow channel area of the cooling channel 70 is formed so that the area of the thrust flow channel 70s is larger than the area of the anti-thrust flow channel 70h. According to this, the volume on the thrust side of the cooling channel 70 increases, that is, the weight on the thrust side of the piston body 1 is relatively light.

  Therefore, the thickness balance on the anti-thrust side of the interior 1n of the head portion 1h of the piston main body 1 is increased, or the piston pin 60 is offset to the thrust side, so that the weight balance of the piston main body 1 is intentionally anti-thrust side. Even if it is not biased, the structure of the cooling channel 70 alone can somewhat prevent the thrust side skirt portion 1s of the piston body 1 from colliding with the cylinder bore 5n when starting the engine.

  Furthermore, in the present embodiment, the thickness of the inside 1n of the head portion 1h of the piston body 1 on the anti-thrust side is increased, and the area of the flow path 70s of the cooling channel 70 on the thrust side is increased.

  Not limited to this, when the piston body 1 receives a force that rotates to the anti-thrust side with the piston pin 60 as a fulcrum, the thickness of the inside 1n of the head portion 1h of the piston body 1 on the thrust side is increased. Thus, if the weight balance of the piston body 1 is biased toward the thrust side and the area of the flow path 70h of the cooling channel 70 on the anti-thrust side is made larger than that on the thrust side, the same effect as in the present embodiment can be obtained.

The figure which shows the inside of the cylinder of the engine by which the piston which shows one embodiment of this invention was arrange | positioned. The figure which shows the inside of the cylinder of the engine which showed the piston of FIG. 1 in cross section. The front view which looked at the piston of FIG. 1 from the downward direction. Sectional drawing which follows the IV-IV line of FIG. Sectional drawing which follows the VV line | wire of FIG. Sectional drawing which shows the state which the piston main body of FIG. 2 inclines to the anti-thrust side at the time of an engine stop. Sectional drawing which shows the state with which the oil was filled in the cooling channel of FIG. 2 after an engine start.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Piston main body 1n ... Inside piston main body 4 ... Cylinder 10 ... Piston 60 ... Piston pin 70 ... Cooling channel 70h ... Anti-thrust side flow path 70s ... Thrust side flow path agent Patent attorney Susumu Ito

Claims (3)

When the engine is stopped, in the piston structure including a piston body that tilts in the first direction side of the rotation direction with the piston pin as a fulcrum in the cylinder,
An annular cooling channel into which oil for cooling the piston body is introduced is disposed inside the piston body,
The flow path area on the first direction side of the cooling channel and on the second direction side opposite to the rotation direction with the piston pin as a fulcrum is formed larger than the flow path area on the first direction side. Piston structure characterized by   2. The piston structure according to claim 1, wherein an inner portion of the piston body on the first direction side is formed thicker than an inner portion on the second direction side.   The piston pin is disposed such that a center of the piston pin is eccentrically positioned on the second direction side from a central axis of the piston body parallel to an axis of the cylinder. Item 3. The piston structure according to Item 1 or 2.

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