JPH0648100Y2 - Piston cooling system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a piston cooling device, and more particularly to a piston cooling device that cools a piston with oil mixed with air.

[Conventional technology]

Since the piston receives compression pressure and explosion pressure in the cylinder, the head of the piston is constantly exposed to high temperature and high pressure. Then, as the temperature of the piston rises, the piston ring provided to keep the cylinder airtight may burn. Therefore, conventionally, an annular through hole is formed inside the head of the piston, and oil is circulated in the annular through hole to prevent the temperature of the piston from rising.

[Problems to be solved by the device]

Here, in the piston cooling device as described above, the cooling capacity is determined by the flow rate of oil supplied into the annular through hole and the filling rate of oil with respect to the volume of the annular through hole.
However, at the time of high speed rotation of the engine in which the piston temperature rises most, both the oil flow rate and the oil filling rate decrease, so the cooling capacity also decreases, and a sufficient cooling effect cannot be obtained.

The present invention has been made in view of the above points, and when both the flow rate of oil supplied into the annular through hole and the oil filling rate with respect to the volume of the annular through hole decrease at the time of high speed rotation of the engine, An object of the present invention is to provide a piston cooling device capable of preventing a decrease in cooling capacity.

[Means for Solving the Problems]

In order to achieve the above object, the piston cooling device according to the present invention is configured such that oil injected from an oil injection nozzle passes through a vertical hole formed in a wall surface of a piston and is annularly formed inside a cylinder portion of the piston. In a piston cooling device that is supplied to a through hole to cool the piston, a throttle part that prevents backflow is provided in a part of the vertical hole, and further has a diameter smaller than at least the minimum diameter part of the throttle part. It is configured such that pores for supplying air are formed in the vicinity of the minimum diameter portion and the air supplied from the pores is mixed when the oil passes through the throttle portion.

[Action]

According to the above configuration, the oil jetted from the oil jet nozzle increases the flow velocity when passing through the throttle portion provided in a part of the vertical hole, and is supplied from the fine hole by the pressure difference generated thereby. Air is mixed in. This allows
Air bubbles are generated in the oil that has passed through the throttle portion, and the oil is divided into thin films. When this thin-film oil is supplied to the annular through hole, the contact area between the oil and the annular through hole increases and heat exchange is promoted, so that the cooling capacity can be improved.

〔Example〕

Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
In FIG. 1 (a), a ring groove is formed on the outer peripheral portion of the piston 1.
101 is formed, and a piston ring (not shown) is provided in the ring groove 101. Inside the head of the piston 1, a tunnel-shaped annular through hole (hereinafter referred to as a cooling channel) 2 is formed coaxially with the ring groove 101. The axial cross-sectional shape of this cooling channel 2 is
It may have any shape such as a rectangle, a circle, and an ellipse, and is not particularly limited. In the wall surface of the piston 1, there is provided an oil inlet port 30 that opens downward in the figure and has a vertical hole 3 for introducing oil into the cooling channel 2.
Further, an oil outlet port 4 for discharging the oil supplied to the cooling channel 2 via the oil inlet port 3 is formed. Immediately below the oil inlet port 30, an oil injection nozzle (oil jet) 5 is arranged at a position where it does not interfere with the oil inlet port 30 even when the piston 1 reciprocates.

Here, an enlarged view of the oil inlet port 30 is shown in FIG.

In FIG. 1 (b), the oil inlet port 30 has a throttled portion.
301 is formed, and the narrowed portion 301 is configured by a smooth curved surface, and the inner diameter is changed exponentially. In addition to this, the shape of the throttle portion 301 may be, for example, as shown in FIGS. 2 (a) and 2 (b). 2 (a) and 2 (b) shows that the inner diameter is exponentially exponentially (logarithm in the example of (a)) by a smooth curved surface from the inlet portion x side toward the smallest diameter portion of the narrowed portion y. (Functionally), it is made smaller, and at the same time when it exceeds the minimum diameter portion of the throttle portion y, its inner diameter becomes equal to the inner diameter of the outlet portion Z. FIG. 2 (c) shows that the inner diameter decreases linearly from the inlet portion x side toward the smallest diameter portion of the throttle portion y, and from the smallest diameter portion to the outlet portion Z side. It is configured to linearly increase in size. What is shown in FIG. 2 (d) is that in which the minimum diameter portion of the example shown in FIG. 2 (c) is slightly elongated. The one shown in FIG. 2 (e) is such that the inner diameter becomes linearly smaller toward the minimum diameter portion of the narrowed portion y with respect to the entire vertical hole on the inlet portion x side of the example shown in FIG. 2 (d). It is configured.

Although the shape of the narrowed portion 301 has been described above, the shape of the narrowed portion 301 is not limited to the above example, and for example, the inner diameter may be changed stepwise.

Further, in FIG. 1B, the narrowed portion 301 communicates with the fine hole 302 so that the oil passing through the narrowed portion 301 is mixed with air. At least one or more of the pores 302 communicate with the narrowed portion 301, and also, as shown in FIG.
As shown in (b), in order to prevent the oil from flowing into the pores 302, they are provided at least vertically to the vertical holes 3 or inclined toward the port inlet side toward the outer diameter. .

Next, FIGS. 4A and 4B show an example of a joint interference state between the oil inlet port 30 and the cooling channel 2. It is to be noted that FIGS. 4 (a) and 4 (b) show FIGS. 2 (a) and 2 (b).
The oil inlet port 30 having the throttle portion 301 in which the change in the inner diameter from the port inlet side to the minimum diameter portion of the throttle portion 301 is linearly formed is shown in the example shown in FIG.

As shown in FIGS. 4 (a) and 4 (b), the upper end portion of the oil inlet port 30 does not contact the upper surface 400 of the cooling channel 2 and the oil inlet port 3 is
The minimum opening area between the upper end of 0 and the upper surface 400 of the cooling channel 2 is attached at a position not smaller than the cross-sectional area of the throttle portion 301. At this time, the oil inlet port 30 is joined to the cooling channel 2 by using members such as hammering, bonding, screwing, welding or saclip.

The operation of the first embodiment configured as described above will be described with reference to FIGS. 1 (a) and 1 (b).

In FIG. 1 (a), as the engine speed increases and the engine output increases, the heat load on the piston 1 increases and the temperature of the piston 1 increases.

Here, according to the experiments conducted by the present inventors, it is apparent that the amount of oil flowing into the cooling channel 2 decreases at the time of high-speed rotation of the engine in which the temperature of the piston rises most, and thus a sufficient cooling effect cannot be obtained. Became. This is because the relative speed difference between the flow velocity of the oil jetted from the oil jet 5 and the ascending / descending velocity of the piston 1 increases as the engine speed increases. That is, when the engine rotates at a low speed, oil flows into the cooling channel 2 regardless of whether the piston 1 is moving up or down.
However, when the engine rotates at high speed, the ascending speed of the piston 1 exceeds the oil flow rate, and the oil can flow into the cooling channel 2 only when the piston 1 is descending. Moreover, since the above-mentioned relative speed is large, most of the oil that has reached the inlet of the cooling channel 2 is repelled, and only the remaining small amount of oil can flow into the cooling channel 2.

Therefore, in this embodiment, as shown in FIGS. 1 (a), (b) and FIG. 2, the throttle portion 30 is provided in the oil inlet port 30.
Forming a one. This throttle portion is particularly shown in FIG.
As represented by (b), (e), etc., a shape is provided in which the oil easily flows in the oil supply direction for supplying the oil into the cooling channel 2 and does not easily flow in the opposite direction. That is, as described above, when the engine is rotating at high speed, the oil flows into the cooling channel 2 only when the piston 1 is descending. Here, if the throttle portion 301 is not provided, not only the oil flows backward while the piston 1 is descending, but also the oil reverse flow is promoted by the inertial force while the piston 1 is rising. The throttle portion 301 has an effect of preventing such backflow of oil, and can increase the amount of oil flowing into the cooling channel 2 when the engine rotates at high speed. At this time, if the oil inlet port 30 and the cooling channel 2 are joined so that the upper end of the oil inlet port 30 projects into the cooling channel 2 as shown in FIG. The oil that has flowed in is blocked by this protrusion and can be prevented from flowing into the oil inlet port 30 again.

Next, there will be described a method capable of exhibiting a sufficient cooling effect with a small amount of oil when the temperature of the piston 1 rises during high speed rotation of the engine.

The oil supplied into the cooling channel 2 shifts from a state in which it is attached to the lower surface side of the cooling channel 2 to a state in which it is attached to the upper surface side due to inertial force when the piston 1 reverses from the ascending motion to the descending motion, for example. To do. As a result, oil flows through the wall surface of the cooling channel 2 and heat exchange is promoted. Therefore, when the cooling channel 2 is filled with oil, the operation of the oil flowing through the wall surface is suppressed, and the efficiency of heat exchange deteriorates. Further, when the amount of oil is very small, for example, when the filling rate of the oil with respect to the volume of the cooling channel 2 is about 20%, the range of the wall surface of the oil does not reach the entire cooling channel 2 and the heat exchange is also sufficient. Can't get The experiments conducted by the present inventors have revealed that the heat exchange is most promoted and the amount of oil that can be expected to have a cooling effect is about 60%.

From this result, when the filling rate of the oil with respect to the volume of the cooling channel 2 is less than about 60%, the oil film of the supplied oil is made thin so that the oil contacts the entire inner wall surface of the cooling channel 2. It can be seen that a more effective cooling effect can be obtained.

Therefore, in this embodiment, as shown in FIGS. 3A and 3B, the outside of the oil inlet port 30 and the throttle portion 301 are communicated with each other by the pores 302. As a result, when the oil passes through the throttle portion 301, its flow velocity increases, and due to the pressure difference caused by the increase in this flow velocity, the pores 30
Intake air from outside via 2. Therefore, the diaphragm 3
Air bubbles are mixed with the oil that has passed 01, and the oil is divided into thin films.

The effect of cooling the piston temperature by the oil divided into thin films is shown in FIG.

In Fig. 5, when the oil divided into a thin film is supplied into the cooling channel, the piston temperature is reduced by 45 ° C compared to the case where the piston is cooled only by the oil jet without the cooling channel. The piston temperature is reduced by 15 ° C as compared with the case where the oil inlet port has a cooling channel which is simply a straight vertical hole.

Next, a second embodiment of the present invention will be described.

In the first embodiment described above, the throttle portion 301 is provided in the oil inlet port 30, but in the second embodiment, the reverse flow of the oil flowing into the cooling channel 2 via the oil inlet port 30 is further improved. In order to surely prevent it, as shown in FIG. 6, a check ball is used together with the throttle portion 301.

In FIG. 6, the check ball 500 may be a standard hard ball used for bearings or the like, or a resin ball such as Teflon which is lightweight and has excellent engine oil resistance. The check ball 500 has a diameter larger than the inner diameter of the throttle portion 301 and smaller than the inner diameter of the oil inlet port 30 on the outlet side. However, the opening area of the gap between the ball diameter and the inner diameter of the oil inlet port 30 on the outlet side is
It is set so that it does not fall below the minimum cross-sectional area of 1.

In addition, the opening area between the upper end of the oil inlet port 30 and the upper surface 400 of the cooling channel 2 is larger than the cross-sectional area of the throttle portion 301, and the check ball 500 does not flow out into the cooling channel 2. Entrance port
A large protrusion 600 of the 30 into the cooling channel 2 is formed, and the protrusion 600 prevents the check ball 500 from flowing out.

Examples of the shape of the oil inlet port 30 when the other check balls 50 are built in are shown in FIGS. 7 (a), (b) and (c).

As shown in the front view and the top view of FIGS. 7 (a) and 7 (b), respectively, a slit is provided in the protrusion 600a to secure an opening area larger than the cross-sectional area of the throttle 301, and at the same time, the wall surface of the cooling channel. The check wall 500 may be prevented from flowing out by the wall surface 601a on which the protrusion 600a is left. Further, as shown in FIG. 7 (c), the protrusion 600b
Alternatively, a through hole may be formed in the opening to secure the opening area. However, the diameter of this through hole is the check ball 500.
Needless to say, it is smaller than the diameter of.

The narrowed portion in the first and second embodiments may be formed by driving a taper ring into a straight vertical hole or adhering it.

In the second embodiment, a check valve structure may be provided by disposing a return spring together with the check ball.

[Effect of device]

As described above, according to the present invention, since the thin film oil is supplied to the annular through hole formed inside the head of the piston, the contact area between the oil and the annular through hole increases. Therefore, even when the flow rate of oil supplied into the annular through hole and the filling rate of oil with respect to the volume of the annular through hole both decrease during high-speed rotation of the engine, the cooling capacity is prevented from decreasing and the piston temperature is reduced. The rise can be prevented.

[Brief description of drawings]

1 (a) and 1 (b) are cross-sectional views showing the structure of the first embodiment of the present invention, and FIGS. 2 (a) to 2 (e) are cross-sectional views showing another example of the diaphragm portion of the first embodiment. FIGS. 3 (a) and 3 (b) are sectional views showing the structure of pores, and FIGS. 4 (a) and 4 (b) are sectional views showing the joining state of the oil inlet port and the annular through hole. FIG. 5 is an explanatory view for explaining the effect of the first embodiment, FIG. 6 is a sectional view showing the structure of the second embodiment, and FIGS. 7 (a), (b), (c).
FIG. 8 is an explanatory view illustrating another shape of the oil inlet port of the second embodiment. 1 …… Piston, 2 …… annular through hole, 3 …… vertical hole, 4 …… oil outlet port, 5 …… oil injection nozzle, 30 …… oil inlet port, 101 …… ring groove.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Imatake 14 Iwatani, Shimohakaku-cho, Nishio-shi, Aichi Japan Auto Parts Research Institute (72) Inventor Hitoshi Hashioka 1-cho, Toyota-cho, Aichi Prefecture Toyota Auto Car Co., Ltd. (56) Bibliography Sho 62-36214 (JP, U) Patent 87991 (JP, C2)

Claims (1)

[Scope of utility model registration request] Claim: What is claimed is: 1. Oil injected from an oil injection nozzle passes through a vertical hole formed in the wall surface of the piston and is supplied to a through hole formed annularly inside the cylindrical portion of the piston to cool the piston. In the piston cooling device, a throttle portion for preventing backflow is provided in a part of the vertical hole, and a pore having a diameter smaller than at least the minimum diameter portion of the throttle portion and supplying air to the vicinity of the minimum diameter portion. And the air supplied from the pores when the oil passes through the throttle portion is mixed therein.