JPH0324859Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a piston for an internal combustion engine, and particularly to a piston used in an internal combustion engine equipped with a hydraulic injection type piston cooling device.

[Prior Art] As the output of internal combustion engines increases, the top wall of the piston, which is located inside the cylinder bore and forms part of the wall of the combustion chamber, is exposed to a severe thermal load and requires forced cooling. It is coming.

As a piston cooling device that forcibly cools the top wall of the piston, engine lubricating oil is injected from inside the piston to the top wall of the piston, and the oil injection cools the top wall of the piston with the engine lubricating oil. A type piston cooling device has already been proposed, and in order to more effectively cool the piston top wall with such an oil injection type piston cooling device, the lubricating oil injected toward the piston top wall is once received. In order to stop the oil and spray the oil toward the top wall of the piston again as the piston reciprocates, an oil reservoir was constructed facing the top wall of the piston.
Publication No. 58-96037, Publication No. 58-96037
This method has been proposed in Publication No. 34282, Publication of Utility Model Publication No. 54-26424, and the earlier application, Publication No. 185184-1984 (Kokai Publication No. 90055-1987).

By configuring the oil reservoir facing the top wall of the piston body as described above, the lubricating oil injected from the inside of the piston toward the top wall of the piston body from the oil injection device is directed toward the top wall of the piston body. Once cooled, the oil is caught in the oil reservoir, and when the piston reaches its top dead center again, the inertial force acting on the oil causes it to be sprayed again onto the inner surface of the top wall of the piston, causing the lubricating oil to be re-sprayed. Better cooling of the piston top wall is achieved by spraying or re-spraying.

As described above, by arranging the oil reservoir to face the top wall of the piston body from inside and supplying oil between them, when the piston reaches the top dead center, the oil accumulated in the oil reservoir is transferred to the top wall of the piston. Oil can be sprayed from the inner surface of the navel, but if we look at each molecule of oil sprayed on the inner surface of the top wall of the piston at this time,
Compared to the case where the object simply hits only one place on the inner surface and immediately leaves the inner surface, the case where it hits one place on the inner surface and then moves to some extent while contacting the inner surface and then leaves the inner surface. It is thought that the cooling effect of the piston top wall by spraying oil is further increased. That is, spraying oil onto the inner surface of the piston top wall is more effective in improving the cooling effect if the oil sprayed onto the inner surface flows along the inner surface. .

One effective method for causing oil to flow along the inner surface of the top wall of the piston when the oil that is splashed up by inertia from the oil reservoir when the piston reaches top dead center is sprayed onto the inner surface of the top wall of the piston. The inner surface of the top wall of the piston is inclined with respect to a plane perpendicular to the direction of movement of the piston, that is, the longitudinal axis of the piston. In the pistons shown in the above-mentioned publications and the drawings of the earlier application, the inner surface of the piston top wall has an inclination more or less as described above; It has a favorable configuration for cooling the parts.

[Problem to be solved by the invention] However, as mentioned above, the increase in the cooling effect obtained by the oil sprayed from the oil reservoir flowing along the inclined inner surface of the piston top wall, In order to obtain a larger value for the unit amount of oil sprayed, the sloped inner surface of the piston top wall should be uniformly distributed over the entire unit area from the lower part to the higher part. Rather than spraying a large amount of oil, it is effective to spray a relatively larger amount of oil on lower parts than on higher parts. This is because, even if oil sprayed at a high point on a slope flows along the slope, it reaches the end of the slope after flowing a very small distance and cannot flow any further along the slope. This is because oil sprayed at a low point on a slope can form a flow along the slope over the entire length from the low point to the high point if it is sprayed with sufficient momentum. However, if all the oil is sprayed at a low point on the slope, it is not possible to spread the oil well over the slope and make contact over a wide area, and in order to store a certain amount of oil, it is necessary to Recesses are undesirable because they have a small planar dimension and a large depth. Therefore, assuming that the slope has a uniform angle of inclination, the amount of oil sprayed toward a higher point on the slope is different from the amount of oil sprayed toward a lower point on the slope due to the difference in height. Preferably, it is increased approximately in inverse proportion to .

The present invention focuses on the above-mentioned circumstances regarding the amount of oil sprayed to each part of the slope when spraying cooling oil to the sloped inner surface of the piston top wall.
An object of the present invention is to provide a piston for an internal combustion engine in which the cooling effect of cooling the top wall of the piston by spraying oil from the inner surface is further improved.

[Means for Solving the Problem] According to the present invention, the problem is solved by forming a top wall portion and a peripheral wall portion facing each other inwardly, each having an inner surface that is concave so as to become gradually deeper from the periphery toward the center. A piston body having a pair of protruding boss parts and a piston pin hole formed in the boss parts, and an oil sump recess inserted into the inner space of the piston body and facing the inner surface of the top wall part. an oil sump component including a shelf board and a pair of leg parts bent from both side edges of the shelf board; A cylindrical engaging member whose diameter is reduced in steps around the inner end of the boss portion is engaged in the engaging hole provided in the piston body, and the piston body is prevented from rotating around the boss portion. The oil sump recess is a recess that is recessed from an edge in a plane perpendicular to the central axis of the piston body, and The depth from the inner surface of the top wall of the piston body is gradually increased from a portion facing a portion near the center of the inner surface to a portion facing a portion near the peripheral edge of the inner surface. This is achieved by a piston for an internal combustion engine characterized by:

[Operation of the device] As described above, the oil sump depression provided opposite to the inner surface of the piston top wall, which is recessed upward so that the height gradually increases from the periphery toward the center, is folded away from the shelf plate and its both side edges. The oil reservoir component is provided in the shelf plate portion of the oil reservoir component having a pair of bent leg pieces, and the oil reservoir recess is a recess that is recessed from the edge of the piston body in a plane perpendicular to the central axis of the piston body. The depth of the recess from the edge is gradually increased from the portion facing the inner surface of the top wall of the piston body near the center to the portion facing the inner surface near the peripheral edge. By locking the shelf board providing the oil reservoir recess to the boss section of the piston body with a pair of leg pieces and fixedly attaching the oil reservoir component to the piston, the piston can be raised. The oil stored in the oil sump recess before it reaches the dead center is drained along its edges, so there is a portion of the oil sump recess that faces the inner surface of the top wall of the piston near the center. An amount of oil is stored that gradually increases toward the part that is closer to the periphery of the inner surface, and when the piston reaches top dead center, the inertia force of the oil stored in this quantitative distribution increases. The oil jumps up from the oil sump depression and is sprayed toward the sloping inner surface of the piston top wall, and the inner surface sprays a larger amount of oil toward the periphery than toward the center. This results in the desired cooling enhancement effect as described above.

Regarding this point, in the pistons described in the specifications and drawings of the above-mentioned publications and earlier applications, the amount of oil sprayed against the inclined inner surface of the top wall of the piston is compared to the amount of oil sprayed against the lower position. No consideration is given to increasing the amount of oil relative to the higher position.

In Utility Model Publication No. 52-11810 and Utility Model Publication No. 58-34282, it is true that the cross-sectional shape of the oil reservoir is such that the part corresponding to the lower position of the inclined inner surface of the piston top wall is the part corresponding to the higher position. Although it is somewhat deeper, the oil reservoir in these publications is formed as a cavity whose periphery is closed together with the inner surface of the piston top wall, and an oil drain port is opened in the center of the oil reservoir. It has a structure that In a cavity like this, which is virtually closed all around except for a very small port in the center, a liquid such as oil injected into the cavity will certainly flow if the piston is at rest. This creates a liquid level that matches the opening height of the port, and stores more oil in the lower part of the sloped inner surface of the piston top wall than in the higher part. When the piston is in motion, no such liquid level is formed in this cavity, so in these pistons, a larger amount of oil is applied to the lower part of the inner surface of the piston top wall than to the higher part. It is thought that no spraying effect will occur.

In Utility Model Application Publication No. 58-96037, the oil reservoir is provided at the end of the connecting rod, and its depth is almost uniform except for the rounded portions at both ends. be. Also, if an oil sump recess is provided in the connecting rod like this,
The connecting rod tilts considerably as the piston reciprocates, so even if the depth changes slightly, the piston will reach top dead center and the oil will flow from the oil sump recess toward the top wall of the piston. It can be seen that the distribution of the amount of oil stored in the oil reservoir at the moment when the oil jumps up due to inertia does not necessarily correspond to changes in depth, and that the influence of dynamic changes in the liquid level is far greater. It will be done.

In addition, in Utility Model Publication No. 54-26424, the change in the depth of the oil sump recess is opposite to that proposed by the present invention, and the oil sump recess is located at a high position on the inner surface of the top wall of the piston. A larger amount of oil can be stored in the area corresponding to the lower position than in the area corresponding to the lower position.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 to 3 show one embodiment of a piston for an internal combustion engine according to the present invention. The piston for an internal combustion engine according to the present invention is composed of a piston body 1 and an oil reservoir forming member 10.

The piston body 1 is cast into a cup shape having a cylindrical peripheral wall part 2 and a top wall part 3 provided at one end of the peripheral wall part so as to close the one end. The inner surface 3a of the top wall portion 3, ie, the ceiling surface of the inner space of the piston body 1, is inclined upward from the side circumferential portion toward the center, and is formed in a substantially conical shape. Note that the inner surface 3a may be formed into a substantially hemispherical shape. A pair of boss portions 4 are formed on the inside of the peripheral wall portion 2 to face each other and bulge toward the inner space of the piston body 1, and each of the pair of boss portions 4 is provided with a piston pin hole on the same axis. 5 is provided. A piston pin that connects the piston body 1 to a connecting rod (not shown) is inserted into the piston pin hole 5. Two piston ring grooves 6 and one oil ring groove 7 are provided on the outer periphery of the top wall 3 and the side peripheral wall 2, and the oil ring groove 7 passes through a slit hole 8 into the inner space of the piston body 1. It's communicating.

Each of the boss parts 4 has a stepped part on the outer periphery of the tip part, which consists of a cylindrical engaging part 9a having a smaller diameter than the outer periphery of the root part, and an annular end surface 9b located at the end of the cylindrical engaging part on the root side. It has 9. On the inner circumferential surface of the piston body 1, the parts facing each other in the direction orthogonal to the axis of the piston pin hole 5, that is, the skirt parts, each have a relatively wide guide groove extending from the tip end thereof along the axis of the piston body 1. 2a is formed.

As clearly shown in FIG. 4, the oil reservoir component 10 includes a substantially rectangular shelf section 12 having two oil reservoir recesses 11a and 11b, and one side from both side edges of the shelf section 12. It has a pair of leg pieces 13 which are bent to form a shape, and a pair of engagement pieces 14 which are bent from both end edges of the shelf board part 12 to one side and engage with the guide groove 2a. The entire structure is press-formed from a metal plate having appropriate elasticity, such as spring steel.

The oil reservoir recesses 11a and 11b are integrally formed with the shelf plate part 12 by drawing, and the bottom surfaces 20a and 20b of each are inclined so that they become shallower from the outer circumferential side toward the center.

In the free state before installation, the pair of leg portions 13 are spread apart toward each other as shown in FIG. An overhanging cylindrical portion 15 is formed by bulge overhang press molding to protrude toward the other leg portion, that is, toward the inside, and an engagement hole 16 is formed by the overhanging cylindrical portion. The hole is adapted to be externally engaged with the cylindrical engagement portion 9a of the boss portion 4.

In the oil reservoir component 10, the shelf plate part 12 is located on the side closer to the piston main body 1, the pair of leg pieces 13 correspond to the boss part 4, and the pair of engagement pieces 14 correspond to the guide groove 2.
By inserting the pair of leg portions 13 toward the inner space of the piston body 1 in a direction posture corresponding to a and with the pair of leg portions 13 being elastically deformed in the direction toward each other, the piston body 1 is pressed into the piston body 1 with a single touch due to the spring action. Installed.

When the pair of leg portions 13 are inserted between the boss portions 4 and the engagement hole 16 is aligned with the cylindrical engagement portion 9a of the boss portion 4, the pair of leg portions 13 are separated from each other by their own spring force. It is elastically deformed in this direction, and is pressed against the annular end surface 9b of the boss portion 4 on the outer surface of the leg portion 13 around the engagement hole 16, and at the same time, on the inner circumferential surface of the overhanging cylindrical portion 15 over its entire surface. It is joined to the outer peripheral surface of the cylindrical engaging portion 9a. As a result, the engagement hole 16 circumscribes the cylindrical engagement portion 9a, and the oil reservoir component 10 is fixedly connected to the piston body 1 by its own spring action.

When the oil reservoir component 10 is fixed in the inner space of the piston body 1 as described above, the shelf plate portion 12 is a plane (horizontal plane) perpendicular to the axis of the piston body 1.
An oil sump depression 1 is provided near the top wall 3 extending along the
1a and 11b constitute an oil reservoir, and the bottom surfaces 20a and 20b of each of the oil reservoir recesses 11a and 11b extend inclined in the same direction as the inner surface 3a. As a result, the depth of the oil sump depressions 11a and 11b from the edge is gradually deepened from the periphery toward the center toward the high part of the inner surface 3a of the top wall of the piston body near the center. It gradually increases toward the part facing the lower part near the peripheral edge of the inner surface 3a than the part where they meet.

As clearly shown in FIGS. 3 and 4, the shelf portion 12 of the oil reservoir component 10 has wing portions 17 extending from the side edges in the vicinity of both ends, and the wing portions hold the oil. It acts to receive the air, and is provided only on one side near one end, and only on the other side near the other end. As a result, as better shown in Figure 3,
A relatively large opening 18 is formed between the piston body 1 and the piston body 1 on the other side near the one end of the oil reservoir component 10, and a relatively large opening 18 is formed on the other side near the other end. A relatively large opening 19 is provided between the piston body 1 and the piston body 1, one of which is used as an oil supply passage and the other as an oil discharge passage.

Next, the behavior of the lubricating oil for cooling the piston in the piston configured as described above will be explained.
Lubricating oil for cooling the piston is injected toward the inner surface 3a of the piston body 1 through the opening 18 from a nozzle (not shown) fixedly disposed on the side of the crank chamber. The lubricating oil sprayed from the nozzle is sprayed onto the inner surface 3a, and then the oil reservoir forming member 10
falls onto the shelf board 12 of the oil reservoir 11a and 1
It accumulates in 1b. When the piston reaches the top dead center position, the lubricating oil accumulated in the oil reservoir depressions 11a and 11b jumps up due to inertia and is sprayed onto the inner surface 3a of the piston body 1. Lubricating oil is on the inner surface 3a
The oil sump depressions 11a and 11b are inclined upwardly from the side periphery toward the center.
The bottom surfaces 20a and 20b of the oil sump recesses are inclined, and the amount of oil stored in each of the oil sump recesses is larger at the side circumference of the piston than at the center of the piston.
Since the amount of oil that jumps up from 1a and 11b and is sprayed onto the inner surface 3a is larger at the side circumference of the piston than at the center of the piston, a larger amount of oil can be sprayed without concentrating on one spot. The lubricating oil is sprayed onto the lower part of the inclined inner surface 3a, and from this point, the lubricating oil flows along the inclined surface from the side periphery toward the center while cooling the top wall 3. As a result, the oil that jumps up from the oil sump recesses 11a and 11b is effectively used for cooling the piston. The oil splashed up from the oil sump recesses 11a and 11b collides with each other at the center of the piston, creating a flow in a direction perpendicular to this, so that the inner surface 3a near the pin boss rib portion is effectively cooled. become.

During the downward movement of the piston, the relative speed of the lubricating oil from the nozzle to the inner surface 3a is large, so that the lubricating oil injected from the nozzle is directed to the inner surface 3a.
The lubricating oil that has already adhered to the inner surface is pushed away toward the opening 19 while cooling the inner surface. As a result, the heat-receiving oil is exchanged with new supplied oil. When the piston reaches the bottom dead center position, the lubricating oil adhering to the inner surface 3a is separated from the inner surface 3a due to inertia and falls onto the shelf plate 12 of the oil reservoir component 10. The shelf board portion 12 has oil reservoir recesses 11a and 1 recessed on the side opposite to the inner surface 3a.
1b, the lubricating oil is accumulated in the oil sump recesses 11a and 11b, and when the piston reaches the top dead center position, the lubricating oil then jumps toward the inner surface 3a and returns to the top wall. Section 3 is cooled.

[Effect of the invention] Thus, according to the invention, by providing an oil reservoir recess facing the inner surface of the top wall of the piston, the lubricating oil injected between the two is absorbed by the inertia of the piston as it reciprocates. When cooling the piston top wall by repeatedly spraying the lubricating oil onto the inner surface of the piston top wall, the lubricant is not only sprayed onto the inner surface of the piston top wall; The oil sprayed on the inner surface is made to flow over as long a distance as possible along the inner surface while avoiding excessive concentration in one spot, thereby further enhancing the cooling effect of the oil spray on the top wall of the piston. can be increased.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing one embodiment of a piston for an internal combustion engine according to the present invention, FIG. 2 is a sectional view taken along the line - of FIG. 1, and FIG. 3 is a sectional view taken along the line - of FIG.
FIG. 4 is a perspective view of an oil reservoir component incorporated in the piston for an internal combustion engine according to the present invention shown in FIGS. 1 to 3. 1... Piston body, 2... Surrounding wall portion, 2a...
Guide groove, 3...Top wall portion, 3a...Ceiling surface, 4...
Boss part, 5... Piston pin hole, 6... Piston ring groove, 7... Oil ring groove, 8... Slit hole, 9... Stepped part, 9a... Cylindrical engaging part, 9
b...Annular end surface, 10...Oil reservoir constituent member, 11
a, 11b...Oil sump depression, 12...Shelf board part, 1
3...Leg piece part, 14...Engagement piece part, 15...Extruding cylindrical part, 16...Engagement hole, 17...Wing part, 1
8, 19...opening, 20a, 20b...bottom surface.

Claims (1)

[Scope of utility model registration request] The top wall has a concave inner surface that is gradually deepened from the periphery toward the center, and the peripheral wall has a pair of bosses protruding inwardly facing each other, and the boss has a piston pin hole. a piston body, a shelf plate portion inserted into the inner space of the piston body and forming an oil reservoir recess facing the inner surface of the top wall portion, and a pair of shelf plate portions bent from both side edges of the shelf plate portion. and an oil reservoir component having leg pieces, and the oil reservoir component includes a pair of leg pieces arranged in a stepped manner around an inner end of the boss portion at an engagement hole formed in the pair of leg pieces. It is fixedly attached to the piston body by being engaged with the diameter-reduced cylindrical engagement part and being locked from rotating around the boss part with respect to the piston body, and the oil The reservoir depression is a depression recessed from the edge in a plane perpendicular to the central axis of the piston body, and the depth of the depression from the edge is equal to the center of the inner surface of the top wall of the piston body. A piston for an internal combustion engine, characterized in that the piston is gradually increased in size from a portion facing a nearer portion toward a portion facing a portion closer to a peripheral edge of the inner surface.