JP2018053829A - Piston for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston for an internal combustion engine that can effectively cool a piston ring groove and furthermore a piston ring and inhibit heat from escaping from a piston combustion chamber at the same time, thereby improving thermal efficiency.SOLUTION: In a piston 1 for an internal combustion engine, an annular first gallery 8 supplied with cooling oil is provided between a piston combustion chamber 10 recessing at a piston top surface and a piston ring groove 1R for accommodating a piston-ring 6: and a second gallery 7 is provided between the first gallery 8 and a piston combustion chamber 10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a piston for an internal combustion engine.

  Patent Document 1 describes an example of a technique related to a conventional piston of an internal combustion engine. The piston described in Patent Document 1 includes a combustion chamber provided in a concave shape on the top surface of the piston, a gallery (annular cavity) formed on the back surface of the piston ring groove group so as to surround the combustion chamber, have.

JP 2014-206159 A

  The gallery is supplied with oil (engine oil) ejected from an oil jet provided below, and this oil circulates in the gallery, cools the piston ring groove and cools the piston ring, and then is discharged from the gallery. To return to the oil pan.

  In addition, since the piston ring that is inserted (accommodated) with a predetermined clearance in the piston ring groove of the piston is in sliding contact with the inner peripheral wall of the cylinder, there is a risk of occurrence of sticking or scuffing at a high temperature. The piston and then the piston ring's heat is taken away by the oil flowing through the gallery, cooling it to reduce the thermal load and contributing to effectively suppressing the occurrence of engine seizure.

  Gallery's contribution as a countermeasure against such heat load is high, but on the other hand, the heat of combustion gas is transferred from the combustion chamber side of the piston to the inside of the piston, but this heat is taken away by the oil in the gallery. For this reason, there has been a situation in which heat loss has increased and heat efficiency has not been sufficiently increased.

  The present invention has been made in view of such circumstances, and can effectively cool the piston ring groove and the piston ring, and at the same time, suppresses the escape of heat from the piston combustion chamber and improves the thermal efficiency. An object of the present invention is to provide a piston for an internal combustion engine.

For this reason, the present invention
A piston of an internal combustion engine,
An annular first gallery to which cooling oil is supplied is provided between the piston combustion chamber recessed in the piston top surface and the piston ring groove that houses the piston ring,
A second gallery is provided between the first gallery and the piston combustion chamber.

  In the present invention, when viewed from the horizontal direction, the bottom end of the second gallery extends below the bottom end of the first gallery, and the top of the second gallery extends above the top end of the first gallery. It can be characterized in that the upper end extends.

  In the present invention, the uppermost end of the second gallery is extended to a position intersecting with or above a straight line connecting the inlet lip portion of the piston combustion chamber and the first gallery at the shortest distance. Can be characterized.

  In the present invention, the lowermost end of the second gallery is extended to a position intersecting with a straight line connecting the R center of the bottom R portion of the piston combustion chamber and the first gallery with the shortest distance or a position below it. It can be characterized by being present.

  In the present invention, when the piston combustion chamber has two upper and lower inlet lip portions, up to a position intersecting with a straight line connecting the lower inlet lip portion and the first gallery at the shortest distance or to a position above it. The top end of the second gallery may be extended.

  According to the present invention, the piston ring groove and thus the piston ring can be cooled effectively, and at the same time, the escape of heat from the piston combustion chamber can be suppressed to improve the thermal efficiency. Can be provided.

It is sectional drawing which shows one structural example of the piston which concerns on one embodiment of this invention. It is sectional drawing which shows an example of the relationship of the arrangement | positioning position of the inlet lip part of a piston which concerns on embodiment same as the above, a 2nd gallery, and a 1st gallery. It is sectional drawing which shows an example of the relationship of R arrangement | positioning of the bottom R part of the piston which concerns on embodiment same as the above, the arrangement position of a 2nd gallery, and a 1st gallery. It is sectional drawing which shows an example of the relationship of the arrangement | positioning position of the lower stage inlet lip | rip part of a piston which concerns on embodiment same as the above, a 2nd gallery, and a 1st gallery. It is sectional drawing which shows the structural example of the conventional 1st piston with a gallery.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the accompanying drawings. The present invention is not limited to the embodiments described below.

  As shown in FIG. 1, a piston 1 according to an embodiment of the present invention is slidable (reciprocally movable) in a cylinder (cylinder) defined by a cylinder head 4 and a cylinder liner 5. It is inserted through.

  Although the piston ring 6 is single here, the present invention is not limited to this, and the present invention can also be applied to a case where a plurality of piston rings are provided in the vertical direction in FIG.

  The piston ring 6 is accommodated (inserted) in a piston ring groove 1 </ b> R provided on the outer periphery of the piston 1 with a predetermined gap, and the outer periphery thereof is in sliding contact with the inner peripheral wall of the cylinder liner 5.

  In the vicinity of the center of the cylinder 3, a fuel injection nozzle 2 is provided so as to protrude from the lower surface of the cylinder head 4, and is controlled to inject and supply fuel at a predetermined timing.

  The top surface of the piston 1 is provided with a combustion chamber (recess) (piston combustion chamber) 10 that is recessed in a rotor shape obtained by rotating the recess cross-sectional shape A of FIG. 1 around the cylinder central axis CL. The piston 1 is connected to a crankshaft (not shown) via a connecting rod (not shown) by a piston pin (not shown) and used as a component of a reciprocating linear motion-rotational motion conversion mechanism. The crankshaft is driven to rotate when 1 is pushed downward.

  A first gallery (oil cooling cavity) 8 provided near the back surface of the piston ring 6 is formed around the combustion chamber (piston combustion chamber) 10 of the piston 1. The first gallery 8 can be formed by using an annular vanishing core or the like when casting the piston 1. Note that an oil inlet hole for introducing oil ejected from an oil jet or the like into the first gallery 8, an oil discharge hole for discharging the cooled oil, and the like are provided in the circumferential direction of the annular first gallery 8. (For these holes (openings), for example, an opening formed for holding the disappearing core at the time of casting can be used. However, it is also possible to open by drilling or the like) Is).

  In the case where the piston 1 includes a plurality of piston rings, a first gallery (oil cooling cavity) 8 may be disposed in the vicinity of the back surface of the top piston ring (top ring) that is severe in terms of heat load. preferable.

Here, in the present embodiment, the second gallery 7 for functioning as a heat insulating layer is further provided between the combustion chamber 10 of the piston 1 and the first gallery 8.
Similar to the first gallery 8, the second gallery 7 is provided in an annular shape so as to surround the combustion chamber 10 of the piston 1. When the piston 1 is cast, an annular disappearing core or the like is used. Can be formed. However, oil is not supplied into the interior, but functions as a space (heat insulating layer) where air exists. Further, the core pressing hole can be closed with a plug or the like so that the splashed oil or the like does not enter.

  The second gallery 7 is for suppressing the heat of the combustion gas from being transferred from the combustion chamber 10 to the inside of the piston 1 and being taken away by the oil in the first gallery 7 (so-called heat dam). The dimension (size) in the height direction (vertical direction) can be larger than the height dimension of the first gallery 8 as shown in FIG. That is, when viewed from the horizontal direction, the bottom end of the second gallery 7 extends below the bottom end of the first gallery 8, and the second gallery 7 extends above the top end of the first gallery 8. It is preferred that the uppermost end of the

  However, when the effect as a heat dam can be expected to some extent, the height dimension of the second gallery 7 can be made smaller than the height dimension of the first gallery 8.

  By the way, although the combustion chamber 10 is exposed to a high-temperature combustion gas, since the heat transfer coefficient is high at a portion where the flow velocity is high, it is heat to suppress the transfer of heat from the portion where the flow velocity is high to the first gallery 8. Effective for reducing loss (improving thermal efficiency).

Here, as a portion where the flow velocity of the combustion gas is fast, there is an inlet lip portion (minimum diameter portion apex) 10 </ b> A to the combustion chamber 10.
Since the heat transferred from the inlet lip (vertex) 10A travels the shortest distance to the first gallery 8, in order to effectively insulate (inhibit) this, as shown in FIG. By extending the uppermost end of the second gallery 7 up to a position H1 that intersects the straight line X connecting 10A and the first gallery 8 at the shortest distance or to a position H2 that is closer to the top surface than that. Shielding the heat transfer path (suppressing heat escape from the combustion chamber 10) is effective in reducing heat loss (improving thermal efficiency).

In addition, another part having a high flow velocity is the bottom R portion 10B of the combustion chamber 10. The bottom R portion 10B is a portion that connects the lower surface of the combustion chamber 10 and the side surface of the combustion chamber 10 at a predetermined R (radius).
In such a case, as shown in FIG. 3, up to or below a position H3 that intersects a straight line Y connecting the R (radius) center of the bottom R portion 10B and the first gallery 8 with the shortest distance. Until the bottom end of the second gallery 7 is extended downward, the heat transfer path is blocked (suppressing heat escape from the combustion chamber 10) is effective in reducing heat loss (improving thermal efficiency). Is.

  Further, when the combustion chamber 10 of the piston 1 has two upper and lower inlet lip portions, the flow rate of the lower inlet lip portion (vertex) 10C is high, so that the heat transferred from the lower inlet lip portion (vertex) 10C is In order to effectively insulate (inhibit) the shortest distance to the first gallery 8, as shown in FIG. 4, the lower lip 10 </ b> C and the first gallery 8 are shortest. The upper end of the second gallery 7 is extended upward to a position that intersects with a straight line connecting at a distance or a position closer to the top surface than that to block the heat transfer path (the escape of heat from the combustion chamber 10). Suppression) is effective in reducing heat loss (improving thermal efficiency).

  As described above, in the present embodiment, the piston ring 6 and the like are effectively cooled by the first gallery 8 provided on the back surface (inside the piston 1) of the piston ring groove 1R of the piston 1 to reduce the thermal load. At the same time, since the second gallery 7 is provided between the first gallery 8 and the combustion chamber 10, the heat transferred from the combustion gas to the combustion chamber 10 is the first. Since the heat transfer path to the gallery 8 can be blocked (since the escape of heat from the combustion chamber 10 to the first gallery 8 can be suppressed), heat loss is reduced (improved thermal efficiency). be able to.

  That is, according to the present embodiment, the piston ring groove and the piston ring can be effectively cooled while the structure is relatively simple and low-cost, and at the same time, the heat from the combustion chamber of the piston can be reduced. It is possible to provide a piston for an internal combustion engine capable of suppressing escape and improving thermal efficiency.

  In the present embodiment, the second gallery 7 has been described as an air layer. However, the second gallery 7 may be filled with or provided with another heat insulating material or heat insulating material.

  The present invention is not limited to the embodiments of the invention described above, and various modifications can be made without departing from the gist of the present invention.

1 Piston 1R Piston ring groove 2 Fuel injection nozzle 3 Cylinder
4 Cylinder head 5 Cylinder liner 6 Piston ring 7 Second (air layer) gallery (heat insulation layer)
8 1st gallery (oil cooling cavity)
10 Combustion chamber (recess) (piston combustion chamber)
10A Inlet lip (vertex)
10B Bottom R part 10C Lower entry lip part (vertex)
CL Cylinder center axis

Claims (5)

A piston of an internal combustion engine,
An annular first gallery to which cooling oil is supplied is provided between the piston combustion chamber recessed in the piston top surface and the piston ring groove that houses the piston ring,
A piston for an internal combustion engine, wherein a second gallery is provided between the first gallery and the piston combustion chamber.   When viewed from the horizontal direction, the bottom end of the second gallery extends below the bottom end of the first gallery, and the top end of the second gallery extends above the top end of the first gallery. The piston of the internal combustion engine according to claim 1, wherein   The uppermost end of the second gallery is extended to a position intersecting with or above a straight line connecting the inlet lip portion of the piston combustion chamber and the first gallery at the shortest distance. The piston of the internal combustion engine according to claim 1.   The bottom end of the second gallery is extended to a position intersecting with a straight line connecting the R center of the bottom R portion of the piston combustion chamber and the first gallery with the shortest distance or a position below it. The piston of the internal combustion engine according to claim 1, wherein the piston is an internal combustion engine. When the piston combustion chamber has upper and lower two-stage inlet lip portions, the second inlet lip portion and the first gallery are crossed with a straight line connecting the shortest distances to a position intersecting with the second lip portion. The piston of the internal combustion engine according to claim 1, wherein the uppermost end of the gallery is extended.

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