JPS591083Y2 - piston - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to improvements in pistons for internal combustion engines.

The structure of a conventional piston is shown in FIGS. 1 to 4.

FIG. 1 is a side view of the piston in the direction of the pin axis, and FIG. 2 is a side view of the piston in the direction perpendicular to the pin axis.

FIG. 3 is a side view showing a state in which a portion of the surface of the piston skirt in the axial direction of the piston pin is hollowed out, and FIG. 4 is a cross-sectional view showing a portion taken along the line IV--IV in FIG.

In the figure, 01 is the piston crown, 02 is the piston ring, 03 is the oil scraper ring, 04 is the piston pin, 05
is a piston skirt, and 06 is a hollowed out portion, and the hollowed out portion 06 is formed by thinly cutting a part of the outer peripheral surface of the piston skirt 05 into a concave shape.

Note that 07 in FIG. 1 and 08 in FIG. 2 indicate locations where scuffing occurs on the outer periphery of conventional piston scars 1 to o5.

In general, important issues for internal combustion engine pistons have been (a) eliminating piston scuffing, and (b) reducing lubricant consumption from the standpoint of resource conservation and economic efficiency for users. .

In addition, recent internal combustion engines have become significantly faster and more supercharged, and the lubrication conditions have accordingly become more severe, so improvements in (a) and (b) are more necessary than ever.

In the conventional piston shown in Figs. 1 and 2, from the viewpoint of preventing piston scuffing, 1) the outer circumference of the piston is machined into an oval shape during piston processing, so that the piston becomes a perfect circle during engine operation; 2. Countermeasures have been taken, such as increasing the piston clearance.

However, countermeasure 1 to make the piston a perfect circle while the engine is running
There was a case where an oil film was not formed on the piston sliding part and there was local metal contact at the outer periphery of the piston skirt 05, resulting in scuffing at that part.

In addition, as shown in Figs. 3 and 4, the piston skirt 05
Countermeasure 2, in which a hollowed out part 06 was provided in a part of the outer circumference to increase the piston clearance, was effective in preventing scuffing, but a large amount of lubricating oil entered the hollowed out part 06, leading to consumption of lubricating oil. The disadvantage was that the amount increased.

As mentioned above, the conventional pistons shown in Figs. 1 to 4 lack reliability because they do not have the conditions to reduce both piston scuffing and lubricant consumption. .

Additionally, in order to obtain the appropriate value for the clearance of the piston sliding part, experimental engines were used to determine the appropriate value through trial and error, but this method had drawbacks such as requiring a long period of time and expense. there were.

The purpose of the present invention is to provide a piston that eliminates the above-mentioned drawbacks, minimizes piston lubricating oil consumption, and prevents scuffing of the piston skirt. The axial profile is shaped to be optimal for oil film formation, and grooves with good oil film formation and oil retention performance are partially provided on the outer peripheral surface of the piston skirt, where scuffing has often occurred in the past.

This can reduce piston scuffing and lubricant consumption.

The present invention can be widely applied to pistons of internal combustion engines, reciprocating compressors, reciprocating hydraulic equipment, etc.

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

5 to 9 show a piston according to an embodiment of the present invention.

Fig. 5 is a side view in the axial direction of the piston pin, Fig. 6 is a longitudinal sectional view showing the barrel-shaped bulge forming the profile of the piston skirt in Fig. 5, and Fig. 7 is a side view of the screw I in the direction perpendicular to the pin axis. Side view, Figure 8 is Vllll-Vllll of Figure 7
9 is a sectional view taken along the line IX-IX in FIG. 7.

In the figure, 1 is the piston crown, 2 is the piston ring, and 3
is an oil scraper ring, 4 is a piston pin, 5 is a screw l-
It is a ciscart, and has almost the same structure as the conventional piston shown in FIGS. 1 and 2.

The difference from the conventional example is that a bulge 9 and a groove 10 that form part of the outer periphery of the piston skirt 5 are provided.

A bulge 9 on the outer periphery of the piston skirt 5 shown in FIGS. 5 and 6 is provided near the outer periphery of the piston skirt 5 through which a longitudinal section passing through the piston axis and perpendicular to the axis of the piston pin 4 passes through.

In FIG. 6, L is the length of the piston skirt 5, E is the amount of bulge in the bulge 9, and E is (1 to 2
) X 10-' times the value.

Groove 1 on the outer periphery of piston skirt 5 shown in FIGS. 5 and 7
0 is approximately halfway between the outer circumferential surface of the piston skirt 5, through which the longitudinal section passing through the piston axis and perpendicular to the axis of the piston pin 4 passes, and the outer circumferential surface of the piston skirt 5, through which the longitudinal section of the piston including the 4th axis of the piston pin passes. There are four locations on the same circumference of the piston skirt 5.

As shown in FIG. 8, the cross section of the groove 1o has a convex portion 11 and a concave portion 12, and when the pitch of the groove 10 is P and the depth of the groove 10 is H, H is (1 to 2 ) X 10-
The value has tripled.

In this embodiment, a case has been described in which both the bulge 9 and the groove 10 are used on a part of the outer periphery of the piston skirt 5, but the present invention can also be applied to only one of the bulge 9 or the groove 10.

The functions and effects of the above configuration will be described.

Since the piston skirt 5 has a bulge 9 on the outer periphery,
Even when the piston makes decimal motion or oscillates, it is possible to form an oil film on the piston sliding part, and stable lubrication is possible.

The oil film thickness hpmin on the outer circumference of the piston skirt 5 is calculated by taking the ratio of the bulge E of the bulge 9 provided on the outer circumference of the piston skirt 5 to the length L of the piston skirt 5, as shown in FIG. 10.

In addition, in the same figure, the oil film thickness hpmin (μ
m), the horizontal axis shows the bulge E and the piston skirt length L.
The ratio is taken as follows.

As can be seen from the figure, when the value of E/L is (1 to 2) x 10-4, the oil film thickness hpmin is best formed and there is a great effect in preventing scuffing of the piston skirt 5 portion.

In addition, the piston clearance can be selected smaller than before, and lubricating oil consumption is also reduced.

Further, in the groove 10 provided on the outer periphery of the piston skirt 5, the oil film thickness hmin is calculated by taking the depth H of the gap 10 and the pitch P of the gap 10, as shown in FIG. 11.

In the same figure, the oil film thickness hmin (μm) is plotted on the vertical axis.
The ratio between the depth H and the pitch P of the groove 10 is plotted on the horizontal axis.

It can be seen from the figure that there is an H/P value at which the formation of an oil film is favorable, and it is H/P value of (1 to 2) x 10-3.

Fig. 12 shows a comparison of the experimental results of the surface pressure at the limit of occurrence of scuffing for the presence/absence and shape of the groove 10 provided on the outer circumference of the piston skirt 5, and the vertical axis is the seizure of the piston skirt 5. The limit surface pressure P*kg/cm2 is taken as the ratio H/P of the depth H of the groove 10 and the pitch P on the horizontal axis.

In the figure, the bar A is the experimental condition without the groove 10, and the horizontal lines B and C are the ratio H/P of the groove depth H and pitch P of 2.5 x 10-3 and 5 x 10-3, respectively. This figure shows the experimental results when the grooves are as shown in FIG.

From FIG. 12, the seizure limit surface pressure on the outer circumference of the piston skirt 1 is higher when the piston skirt 5 has a groove 10 on the outer circumference than when there is no groove 10, and even when it has the groove 10, it is shown in FIG. Bar line B is higher than bar line C.

From the above, the entire outer circumference of the piston skirt 5 has grooves 10.
It is also possible to increase the limit surface pressure for scuffing by providing a lubricant, but in this case, the amount of oil retained in the recess 12 shown in FIG. 8 increases, which tends to increase the cost of lubricating oil.

Therefore, as shown in FIGS. 5 and 7, by providing grooves 10 at four locations on the same circumference on the outer periphery of the piston skirt 5, the amount of oil consumed can be reduced, and an oil film can be formed at locations where metal contact is likely to occur. Since the load capacity of the piston is increased, there is an advantage that scuffing of the piston is less likely to occur.

As mentioned above, the screw I of the bulge 9 shown in FIGS.
If the piston is provided with a profile and a groove 10 as shown in Figs. 5 and 7, the piston clearance can be selected to be relatively small, which not only reduces the consumption of lubricating oil but also reduces the Scuffing is also less likely to occur.

Furthermore, there is no need to select a piston profile using the conventional trial-and-error method, so there is an advantage that the cost of piston development can be reduced.

FIG. 13 is a longitudinal sectional view showing a groove on the outer periphery of a piston skirt in another embodiment of the present invention, and FIGS. 14 and 15 are transverse sectional views respectively showing the shape of a recessed part of the groove in another embodiment. .

In FIG. 13, the convex portion 11 in FIG. 8 is replaced with a flat portion 113.

Note that 110 is a groove and 105 is a piston skirt.

FIG. 14 shows a groove 210 with the same depth in cross section, and FIG. 15 shows a groove 310 with a cross section shaped into an arc.

In addition, 205.305 is a piston skirt.

The functions and effects of the embodiments shown in FIGS. 13, 14, and 15 are almost the same as those of the embodiments described above.

[Brief explanation of the drawing]

Figure 1 is a side view of a conventional piston in the pin axis direction, Figure 2 is a side view of the piston in Figure 1 in the direction perpendicular to the pin axis, and Figure 3 is a partially hollowed out surface of the piston skirt in the piston pin axis direction. Figure 4 is a side view showing the state in which the
■■ A cross-sectional view showing a part of the arrow, FIG. 5 is a side view of a piston according to an embodiment of the present invention in the axial direction of the piston pin, and FIG. 6 is a barrel forming the profile of the piston skirt shown in FIG. 5. 7 is a side view of the piston in the direction perpendicular to the piston pin axis of the piston in FIG. 5, FIG. 8 is a sectional view taken along the Vllll-vut arrow in FIG. 7
10 is a diagram showing the relationship between oil film thickness and the shape of the bulge, FIG. 11 is a diagram showing the relationship between oil film thickness and groove shape, and FIG. 13 is a diagram showing the relationship between the seizure limit surface pressure and the shape of the groove, FIG. 13 is a longitudinal sectional view showing the groove on the outer circumference of the piston skirt of another embodiment of the present invention, and FIGS. 14 and 15 are FIG. 7 is a cross-sectional view showing the shape of a recessed portion of a groove in another example. 1... Piston crown, 4... Piston pin, 5...
Piston skirt, 9...Bulge, 10...Groove, E...Bulge amount, L...Piston skirt length, P...Groove pitch, H...Groove depth.

Claims (1)

[Scope of utility model registration request] In a screw for an internal combustion engine, a barrel-shaped bulge provided near the outer circumferential surface of the screw skirt passes through the piston axis and a longitudinal section perpendicular to the piston pin axis passes through the piston axis. On the same circumference of the piston skirt outer circumferential surface, which is located approximately halfway between the piston skirt outer circumferential surface through which the longitudinal section perpendicular to the pin axis passes and the piston skirt outer circumferential surface through which the piston longitudinal section including the piston pin axis passes. A piston characterized by having grooves provided at four locations.