JPS6246834Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving the performance of liquid-cooled pistons for reciprocating engines.

The piston of a reciprocating engine, especially an internal combustion engine, must maintain sufficient strength to withstand the high gas pressure and combustion temperature within the combustion chamber, and a well-balanced design is required in terms of both pressure resistance and heat resistance. be.

Recently, pistons for high-output engines that take this into consideration have been proposed and put into practical use.

A typical example of the prior art is a so-called multi-hole piston (or bore-cooled piston).

This type aims to further improve the pressure resistance and heat resistance compared to conventional pistons with radial ribs, and as shown in Figures 1 and 2 a and b, there are many cooling units inside the piston. This type has a hole 6 or 6'. The cross-section (perpendicular to the piston axis) of each cooling hole is circular or oval (if the circular hole is inclined to the piston axis)
Or it is a modified quadrilateral or triangle (with rounded corners). With this type, there is a lot of extra wall 7 inside the piston.
Or, since 7' can be left, its pressure resistance is greatly improved. Furthermore, since the inner surfaces of the large number of cooling holes 6 or 6' serve as cooling surfaces, the cooling surface area increases and heat resistance is improved due to improved cooling effect.

However, it has the following drawbacks.

(1) Since the cross section of the cooling hole 6 or 6' is close to circular, the ratio L/B of its radial length L to circumferential average width B is close to 1.0, so the cooling fluid at the bottom of the hole is close to 1.0. It is difficult to distinguish between the inlet and the outlet, making it impossible to supply new low-temperature coolant to the tip of the cooling hole 6 or 6', which reduces the cooling effect per cooling area. In particular, when the depth d of the cooling hole is large, this amount of decrease cannot be ignored.

(2) If a cooling liquid supply nozzle or the like is provided for each cooling hole, the structure becomes extremely complicated.

The purpose of this invention is to focus on the above points, and to
In particular, the objective is to provide a comprehensively balanced liquid-cooled piston that maintains the advantages and compensates for the disadvantages of the multi-hole piston of the prior art. In a liquid-cooled piston having a plurality of cooling holes opening into a space, the cooling hole is formed by two cylindrical holes whose lower portions overlap each other, and one of the two cylindrical holes is This is because the coolant inlet is oriented toward the small diameter hole.

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

FIG. 3 is a cross-sectional view showing essential parts of a piston according to an embodiment of the present invention, FIG. 4 is a cross-sectional view taken along the - arrow in FIG. 3, and FIG. 5 is a cross-sectional view taken in the - arrow direction in FIG.

In the figure, 100 is a piston, 101 is a piston top wall, 102a and 102b are cooling holes, 10
3a and 103b are the main cylinders, 104a and 104
b is a liquid supply cylinder, and 105 is a drainage reservoir. 110
111 is the internal hardware, 111 is the liquid supply reservoir, 112a and 1
12b is a liquid supply nozzle.

A plurality of cooling holes 1 open downward inside the piston 100 and reach near the piston top wall 101.
02a or 102b, and these cooling holes 1
02a or 102b are formed by mutually overlapping cylindrical holes.

Cooling hole 102 as a typical example of cooling hole shape
a has a smaller diameter than the main cylinder 103a;
It is formed by a liquid supply cylinder 104a whose axis is substantially parallel to the axis of the main cylinder 103a.

Cooling hole 102 as another representative example of cooling hole shape
b is formed by a main cylinder 103b and a liquid supply cylinder 104b having a smaller diameter and whose axis intersects with the main cylinder 102b.

The internal hardware 110 is provided with a liquid supply reservoir 111 therein, and is provided with liquid supply nozzles 112a, 112b, that is, cooling liquid inlet openings into the liquid supply cylinders 104a or 104b of the cooling holes 102a or 102b.

Furthermore, the inside side of the piston 100 and the internal hardware 11
A drainage reservoir 105 is formed in the space on the outside of the tank 0.

Note that two of each cooling hole 102a or 102b
The overlapping portions of the two cylinders shall extend at least to a depth of 1/3 or more from the lower opening of each cooling hole. This makes it possible to further ensure the functions and effects described below.

Furthermore, the diameter of the liquid supply cylinder relative to the diameter of the main cylinder is at least equal to or smaller than the diameter of the main cylinder.

The operation in the case of the above configuration will be described.

The cooling liquid is supplied from the liquid supply reservoir 111 built into the internal hardware 110 through the liquid supply nozzles 112a and 112b into the liquid supply cylinder 104a or 104b of the cooling hole 102a or 102b, macroscopically speaking, the liquid supply cylinder 104a Alternatively, it flows out from the 104b side to the main cylinder 103a or 103b side, and flows out into the drainage reservoir 105.

In addition, within the cooling hole 102a or 102b, a flow due to the vibration of the cooling liquid is added due to the vertical acceleration caused by the vertical movement of the piston 100.
Re-entry of the coolant into 2a or 102b occurs.

The above case has the following effects.

(1) By providing the liquid supply cylinder 104a or 104b in the cooling hole 102a or 102b, the low temperature cooling liquid (new liquid) is reliably supplied into the cooling hole through the liquid supply nozzle 112a or 112b. Therefore, the coolant (old liquid) whose temperature has increased will not remain in the cooling hole for a long time.

(2) Furthermore, as shown in FIGS. 4 and 5, the axis of each cooling hole 102a on the outermost circumferential side and the axis of the piston 106
If the main cylinder 103 is formed at an angle, the main cylinder 103
Compared to a conventional multi-hole piston in which only the pistons a are arranged, the liquid supply nozzle 11 is increased by the fact that the liquid supply cylinder 104a is additionally installed on the side closer to the piston axis 106.
Since it can be made higher than the tip position of the piston 2a and closer to the piston top wall 101, the cooling effect is further ensured.

Note that the outermost cooling hole (for example, 102a)
The liquid supply nozzle 112a for the piston 100
A condition is required that the liquid supply nozzle 112a is located inside the cylindrical mating surface D with the lower internal hardware 110 and does not come into contact with the wall surface of the cooling hole 102a on the side closer to the piston axis 106, which limits the height of the liquid supply nozzle 112a. .

As a result of the above, it is possible to realize a liquid-cooled piston that is comprehensively balanced and has excellent pressure resistance and heat resistance.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the main parts of a conventional multi-hole piston, Figures 2a and b are cross-sectional views taken along the - arrow in Figure 1 when the cross-sectional shapes of the cooling holes are different, and Figure 3 is a cross-sectional view showing the main parts of a conventional multi-hole piston. FIG. 4 is a cross-sectional view taken along the - arrow in FIG. 3, and FIG. 5 is a cross-sectional view taken along the - arrow in FIG. 3. 100... Piston, 101... Piston top wall, 1
02a, 102b...cooling hole, 103a, 103b
...Main cylinder, 104a, 104b...Liquid supply cylinder, 10
5...Drainage reservoir, 110...Internal hardware, 111...Liquid supply reservoir, 112a, 112b...Liquid supply nozzle.

Claims (1)

[Scope of utility model registration request] In a liquid-cooled piston of a reciprocating engine, the piston has a plurality of cooling holes that open into the space inside the piston in the upper part of the piston, and each of the cooling holes is formed by two cylindrical holes whose lower portions overlap each other. A liquid-cooled piston characterized in that the cooling liquid inlet is directed to the smaller diameter hole of the two cylindrical holes.