JP6716161B2 - Lubrication structure of piston support - Google Patents

Description

The present invention relates to a lubrication structure for a piston support part.

As shown in FIG. 5, in a general reciprocating engine used in an automobile or the like, a piston 2 housed in a cylinder 1 is swingably supported by a small end 4a of a connecting rod 4 via a piston pin 3. The large end 4b of the connecting rod 4 is connected to the crankshaft 6 via the crankpin 5.

The crank pin 5 is supported by the crank arm 6a at a position displaced from the center of the crank shaft 6, and the crank pin 5 moves around the center of the crank shaft 6 in a circular path. The piston 2 moves up and down in the cylinder 1 while the connecting rod 4 swings around the piston pin 3.

Here, as shown in FIG. 6, both ends of the piston pin 3 are rotatably supported by a pin boss portion 7 formed on the back surface of the piston 2, and the small end portion 4a of the connecting rod 4 is The central portion of the piston pin 3 sandwiched between the pin boss portions 7 is rotatably supported.

In order to lubricate the support portion of the piston 2 as described above, the lubricating oil is forcibly supplied through the oil passage 8 inside the connecting rod 4, or the lubricating oil is supplied from the oil injection nozzle (not shown) provided under the cylinder 1 to the rear surface of the piston 2. To the upper side of the crankshaft 6 or by utilizing the splashing of the lubricating oil on the crankshaft 6.

Prior art document information relating to this type of piston support lubrication structure includes the following Patent Documents 1 and 2.

JP 2006-258194 A JP, 2011-149444, A

Nowadays, it is widely practiced to reduce friction by lowering the rotation speed in order to save fuel consumption of an engine and to combine high supercharging to compensate for the reduction in power due to the low rotation speed. In such a case, the in-cylinder pressure in the engine is greatly increased in all the strokes, and the piston 2 is always kept in the depressed state, while the inertial force acting on the piston 2 near the exhaust top dead center is reduced. There is a concern that the lubricating oil may not spread well to the moving part and the risk of seizure between the piston 2, the piston pin 3, and the connecting rod 4 may increase.

That is, in the prior art, no matter how much the cylinder pressure depresses the piston 2, the force that the piston 2 floats up due to the inertial force near the exhaust top dead center is greater, and the small end 4a of the connecting rod 4 and the piston 4 2 is a sliding portion of the piston pin 3 pressed against each pin boss portion 7 (for the small end portion 4a of the connecting rod 4, the lower portion of the central portion of the piston pin 3 and each pin boss portion 7 of the piston 2). On the other hand, there was a gap in the upper part of both ends of the piston pin 3), and lubricating oil entered into this gap for lubrication and cooling. When both the supply and the supply are compatible, it becomes difficult to allow the lubricating oil to enter the sliding portion even near the exhaust top dead center.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a lubrication structure for a piston support portion capable of suppressing seizure among a piston, a piston pin, and a connecting rod.

The present invention provides a lubrication structure for a piston support portion in which the piston is swingably supported by a small end portion of a connecting rod through a piston pin whose both ends are pivotally supported by a pin boss portion formed on the back surface of the piston. And forming a housing space inside the piston pin and arranging a weight in the housing space so as to be vertically movable, and the weight collides with the upper side of the housing space by inertial force near the top dead center. It is characterized in that it is configured to generate an impact load.

Thus, in this way, near the exhaust top dead center, the weight collides with the upper side of the accommodation space due to the inertial force to generate an impact load, and the impact load of the weight is added to the force of lifting the piston due to the inertial force. Thus, the force that lifts the piston is greater than the force that pushes down the piston due to the in-cylinder pressure, and there is a gap in the sliding end where the piston pin is pressed against the small end of the connecting rod and each pin boss of the piston. Lubricating oil enters to achieve good lubrication and cooling.

Here, since the impact load by the weight momentarily acts as a very large upward force, even if the weight is large enough to be accommodated inside the piston, it is expected to have a sufficient effect by setting the specific gravity appropriately. In addition, since the gap in the sliding part that is momentarily generated by applying this impact load is in a state of very low pressure close to vacuum, the surrounding lubricating oil is effectively sucked in and the It will spread to the sliding parts.

Further, in carrying out the present invention more specifically, the piston pin is formed of a circular tube, the penetrating portion forms a storage space, and the weight having a cylindrical shape with a diameter smaller than the inner diameter of the storage space is stored in the storage space. It is preferably housed in a space, and openings at both ends of the housing space are closed by plugs.

According to the above-described lubrication structure of the piston support portion of the present invention, the weight is made to collide with the upper side of the accommodation space by the inertial force in the vicinity of the top dead center of the exhaust gas to generate an impact load, and the piston is against the force of pushing down the piston due to the cylinder internal pressure. So that the floating force of the piston is superior, a gap is created in the sliding part where the piston pin is pressed against the small end part of the connecting rod or each pin boss part of the piston, and lubricating oil is allowed to enter into this gap and the sliding part Since excellent lubrication and cooling can be achieved, it is possible to effectively prevent seizure between the piston, the piston pin, and the connecting rod.

It is a front sectional view showing an example of a mode for carrying out the present invention. It is a side surface sectional view regarding the piston support part of FIG. It is a side sectional view which shows the detail of the piston pin of FIG. It is a graph explaining the load which acts on the piston of FIG. It is a front sectional view showing a conventional example. FIG. 6 is a side sectional view of the piston support portion of FIG. 5.

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

As shown in FIGS. 1 to 3, in the present embodiment, both ends are rotatably supported by a pin boss portion 7 formed on the back surface of the piston 2 in the same manner as in the case of FIGS. 5 and 6 described above. The piston 2 is swingably supported by the small end portion 4a of the connecting rod 4 via the formed piston pin 3, and further, the accommodation space 9 is formed in the piston pin 3 and is accommodated in the accommodation space 9. The weight 10 is arranged so as to be movable in the vertical direction, and the weight 10 collides with the upper side of the accommodation space 9 by an inertial force in the vicinity of the top dead center so that an impact load can be generated.

More specifically, the piston pin 3 is formed of a circular tube, and the penetrating portion forms a housing space 9, and a cylindrical weight 10 having a diameter smaller than the inner diameter of the housing space 9 is housed in the housing space 9. The openings at both ends of the accommodation space 9 are closed by the plugs 11 and 12. For example, the weight 10 may be made of lead having a large specific gravity.

here,
Cylinder pressure: P
Cylinder bore area: S
Weight of piston 2 + piston pin 3: W
Acceleration of piston 2: a
Impact load: F
In such a case, the piston 2 at the top dead center of the exhaust gas receives the pushing-down force PS due to the in-cylinder pressure and the lifting force Wa due to the inertial force.
Maximum cylinder pressure: P _max
Minimum cylinder pressure: P _min
When
P _max S>F+Wa>P _min S
It is sufficient to set F so that

still,
Crank radius: r
Angular velocity: ω (converted from rotation speed)
Time: t
And the acceleration a of the piston 2 is
a=−rω ² sin ωt
Required by.

Also,
Weight of weight 10: m
Maximum piston movement speed: v _max
And the impact load F is
F=mv _max /Δt
Given in. At this time, Δt is Δt=1/v _max , assuming that the velocity of the weight 10 can be absorbed at a short distance l.
You can give it at.

Thus, in this way, as shown in the graph of FIG. 4, the weight 10 collides with the upper side of the accommodation space 9 due to the inertial force near the exhaust top dead center (near the crank angle of 450° in FIG. 4). A force that lifts the piston 2 with respect to a force that pushes down the piston 2 due to in-cylinder pressure (see curve A in FIG. 4) by generating an impact load and adding the impact load of the weight 10 to the force that lifts the piston 2 due to inertial force. (Refer to the curve B in FIG. 4), a gap is created in the sliding portion where the piston pin 3 is pressed against the small end portion 4a of the connecting rod 4 and each pin boss portion 7 of the piston 2, and the lubricating oil is provided in this gap. Will be introduced, and good lubrication and cooling will be achieved.

Here, since the impact load by the weight 10 momentarily acts as an extremely large upward force, even if the weight 10 is large enough to be housed inside the piston 2, a sufficient effect can be obtained by appropriately setting the specific gravity. It is possible to expect, and since the gap in the sliding part that is instantaneously generated by applying this impact load is in a state of very low pressure close to vacuum, the surrounding lubricating oil is effectively sucked in. Will surely reach the sliding parts.

The impact load of the weight 10 is also generated near the compression top dead center (near the crank angle of 90° in FIG. 4), but the in-cylinder pressure at this time is extremely high. The impact load generated near the top dead center does not contribute to the improvement of lubrication of the piston pin 3 with respect to the small end portion 4a of the connecting rod 4 and each pin boss portion 7 of the piston 2.

Therefore, according to the above-described embodiment, the weight 10 collides with the upper side of the accommodation space 9 by the inertial force in the vicinity of the top dead center of the exhaust gas to generate an impact load, and the piston 2 floats up against the force of pushing down the piston 2 due to the cylinder internal pressure. As the force is overcome, a gap is formed in the sliding portion where the piston pin 3 is pressed against the small end portion 4a of the connecting rod 4 and each pin boss portion 7 of the piston 2, and the lubricating oil is introduced into this gap to allow the above-mentioned Since good lubrication and cooling of the sliding portion can be achieved, seizure between the piston 2, the piston pin 3, and the connecting rod 4 can be effectively suppressed.

Incidentally, the lubrication structure of the piston support portion of the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the scope of the present invention.

2 Piston 3 Piston Pin 4 Connecting Rod 4a Small End 7 Pin Boss 9 Storage Space 10 Weight 11 Plug 12 Plug

Claims (2)

A lubrication structure of a piston support part in which the piston is swingably supported by a small end part of a connecting rod via a piston pin whose both ends are rotatably supported by a pin boss part formed on the back surface of the piston, An accommodating space is formed inside the piston pin, and a weight is arranged in the accommodating space so as to be movable in the vertical direction, and the weight collides with the accommodating space due to an inertial force near the top dead center to cause an impact load. A lubricating structure for a piston support portion, characterized in that The piston pin is formed of a circular tube and the penetrating portion forms a storage space, a cylindrical weight having a diameter smaller than the inner diameter of the storage space is stored in the storage space, and openings at both ends of the storage space are formed. The lubrication structure for a piston support portion according to claim 1, wherein the lubrication structure is closed by a plug.

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