JPH0338426Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The invention is a method of varying the compression ratio of an internal combustion engine by interposing an eccentric bearing between a piston pin and a connecting rod and rotating the eccentric bearing. The present invention relates to a structure for engaging a lock pin with an eccentric bearing for locking or freeing rotation of the eccentric bearing in an eccentric bearing type variable compression ratio mechanism.

[Prior Art] A mechanism for varying the compression ratio using an eccentric bearing has been disclosed in Japanese Utility Model Application No. 58-137832, Japanese Utility Model Application No. 59-11132, etc. by the applicant of this utility model registration. Proposed.

In the conventional variable compression ratio mechanism, as shown in FIGS. 4 to 6, a piston 2 is fitted into a cylinder 1 so as to be able to reciprocate and is connected to a connecting rod 3 via a piston pin 4. Between the piston pin insertion hole 5 of the connecting rod 3 and the piston pin 4, an eccentric bearing 6 whose inner circumference and outer circumference are eccentric from each other is rotatably interposed, and the eccentric bearing 6 is rotated. By changing the relative position of the piston 2 with respect to the connecting rod 3, the compression ratio can be made variable. In order to fix the compression ratio, one lock pin engagement hole 7 extending in the radial direction is bored in the thick part of the eccentric bearing 6, and a lock pin engagement hole 7 is formed on the connecting rod 3 side. A lock pin storage hole is provided to retractably store the lock pin 8 that can be connected to the lock pin, and by switching the hydraulic pressure to the lock pin locking hydraulic passage 10 and the lock pin unlocking hydraulic passage 11 provided in the connecting rod 3, the lock pin 8 can be removed from the lock pin. Storage hole 9
The rotation of the eccentric bearing 6 was locked by engaging the lock pin 8 with the lock pin engagement hole 7. Hydraulic passage 10 for lock pin lock
When the hydraulic pressure is applied, the lock pin 8 comes out of the lock pin storage hole 9 and engages with the lock pin engagement hole 7, and when the eccentric bearing 6 is fixed with the thickest part facing down, the piston 2 is inserted into the connecting groove. It maintains a high position relative to 3rd position, resulting in a high compression ratio. Further, when pressure builds up in the lock pin unlocking hydraulic passage 11 and the lock pin 8 sinks into the lock pin storage hole 9 and disengages from the lock pin engagement hole 7,
The eccentric bearing 6 can rotate freely, and at the top dead center of the compression stroke, the thinnest part of the eccentric bearing 6 comes down due to the compressed gas pressure and explosion pressure, automatically creating a low compression ratio state. It was starting to happen.

[Problems to be solved by the invention] However, in the conventional variable compression ratio mechanism, as shown in an enlarged view in FIG. A lock pin 8 consisting of a cylindrical pin is slidably inserted, and the lock pin 8 is controlled by increasing or decreasing hydraulic pressure to the bottom surface.

If the lock pin engaging hole 7 came into contact with the lock pin 8 at a relatively high speed while the lock pin 8 was protruding, there was a risk that deformation would occur near the top of the pin, as shown by the broken line in FIG. As a result, some portions of the lock pin 8 protrude in the radial direction, and there is a risk that the lock pin 8 may not be able to move freely within the lock pin storage hole 9.

SUMMARY OF THE INVENTION An object of the present invention is to provide a lock pin engagement structure in an eccentric bearing type variable compression ratio mechanism that prevents the lock pin from malfunctioning even if the lock pin is deformed at its tip.

[Means for solving the problem] The lock pin engagement structure of the eccentric bearing type variable compression ratio mechanism of the present invention in accordance with this purpose includes an eccentric bearing interposed between the piston pin and the connecting rod, and The compression ratio is changed by changing the relative position of the piston to the connecting rod according to the amount of rotation of the bearing, and the piston can slide freely into the lock pin engagement hole provided in the eccentric bearing and into the lock pin storage hole provided in the connecting rod. In an eccentric bearing type variable compression ratio mechanism in which rotation of an eccentric bearing is locked or free by inserting and removing a lock pin inserted into the eccentric bearing, the gap between the outer periphery of the lock pin and the lock pin storage hole is made larger on the tip side of the lock pin. Consists of structure.

[Function] By configuring the lock pin engagement structure as described above, even if the lock pin tip portion is slightly deformed, when the lock pin enters the lock pin storage hole, the deformed portion will fill the enlarged gap. Since the deformed portion does not come into contact with the circumferential surface of the lock pin storage hole due to the gap, the lock pin does not stick to the lock pin storage hole, and smooth sliding is always ensured.

[Embodiments] Hereinafter, preferred embodiments of the lock pin engagement structure of the eccentric bearing type variable compression ratio mechanism according to the present invention will be described with reference to the drawings. In addition, among the structures shown in FIGS. 5 and 6, the structure of the parts other than the lock pin and the lock pin storage hole can be applied to the present invention, so a description of the structure of the applicable parts will be omitted, and only the characteristic structure of the present invention will be described. Only the and effects will be explained below.

First Embodiment FIG. 1 shows a first embodiment of the present invention. In FIG. 1, reference numeral 6 indicates an eccentric bearing, and the eccentric bearing 6 is rotatably interposed between the piston pin 4 of the piston 2 and the connecting rod 3. The eccentric bearing 6 is made of a cylindrical body whose inner and outer circumferences are eccentric, and has a lock pin engagement hole 7 extending radially through the inner and outer circumferences. A lock pin storage hole 9 is provided on the connecting rod 3 side so as to be located on an extension of the radius of the eccentric bearing 6, and a lock pin 8 is slidably inserted into the lock pin storage hole 9. The lock pin storage hole 9 consists of a cylindrical hole, and the lock pin 8 consists of a cylindrical pin. At the bottom of the lock pin storage hole 9, there is a hydraulic passage 1 for a lock pin that drives the lock pin 8 in the direction of the eccentric bearing 6.
0 is open. Hydraulic passage 10 for locking the lock pin 8 in the lock pin storage hole 9
On the opposite side, hydraulic pressure from a hydraulic passage 11 for unlocking the lock pin can be applied. The hydraulic load on the lock pin locking hydraulic passage 10 and the lock pin unlocking hydraulic passage 11 can be switched by a switching valve. Pressure is applied to the lock pin locking hydraulic passage 10 during light loads, and the lock pin is released under medium and high loads. Pressure is applied to the lock hydraulic passage 11.

The tip of the lock pin 8 on the eccentric bearing 6 side is
It constitutes a reduced diameter part 12 whose outer diameter is smaller than that of other parts, and the other part is a sliding part 13. In this case, since the diameter of the lock pin storage hole 9 is the same, the radial gap D between the lock pin 8 and the lock pin storage hole 9 in the reduced diameter part 12 is the same as the radial gap D between the lock pin 8 and the lock pin storage hole 9 in the sliding part 13. greater than d.

Next, the operation of the first embodiment configured as described above will be explained. Lock pin 8 is
It is driven by pressurization of the lock pin locking hydraulic passage 10 or the lock pin unlocking hydraulic passage 11. When the engine is under light load, pressure is applied to the lock pin lock hydraulic passage 10, driving the lock pin 8 in the direction of the eccentric bearing 6. and,
The eccentric bearing 6 rotates and the lock pin engagement hole 7
When the lock pin 8 comes to a position facing the lock pin 8, the lock pin 8 driven in the direction of the eccentric bearing 6 enters the lock pin engagement hole 7 and locks the rotation of the eccentric bearing 6. At this time, since the rotation of the eccentric bearing 6 is locked when the thickest part is at the bottom, the relative position of the piston 2 with respect to the connecting rod 3 is high, and the piston 2 is locked in a high compression ratio state. This improves fuel efficiency and shaft torque. When the lock pin 8 hits the eccentric bearing 6 when the lock pin 8 is engaged with the lock pin engagement hole 7, the part that hits the eccentric bearing 6, that is, the tip of the lock pin 8 on the eccentric bearing 6 side, is as shown by the broken line in FIG. Slightly transformed into
A partially radially protruding portion 14 may be formed. However, this does not impede the movement of the locking pin 8, as will be described below.

When the engine is under high load, hydraulic pressure is applied to the lock pin unlocking hydraulic passage 11, and the lock pin 8 is driven in the direction of entering the lock pin storage hole 9, and is disengaged from the lock pin engagement hole 7, causing the eccentric bearing The rotation of 6 becomes free. In this state, the eccentric bearing 6 receives the compressed gas load and explosion load from the piston 2 near the compression top dead center of the piston, and automatically moves to the position that minimizes the relative position of the piston 2 to the connecting rod 3. The engine rotates and a low compression ratio state is obtained. Therefore, even when the degree of gas compression is at its highest and the load is high, knocking is less likely to occur, the compression ratio can be increased accordingly, and fuel efficiency and shaft torque can be improved.

When the lock pin 8 is moved into the lock pin storage hole 9, even if the protruding portion 14 is located at the tip of the lock pin 8, the lock pin 8
The tip part becomes a diameter-reduced part 12 and the gap with the lock pin storage hole 9 is large, so the protruding part 14 does not come into contact with the lock pin storage hole 9 and the lock pin 8 is inside the lock pin storage hole 9. movement is not obstructed. Therefore, the movement of the lock pin 8 is always maintained normally, and the compression ratio switching operation is performed with high reliability.

Second Embodiment FIG. 2 shows a second embodiment of the present invention. In this embodiment, a structure in which the gap between the tip of the lock pin and the lock pin housing hole is increased is achieved by making the diameter of the vicinity of the exit of the lock pin housing hole larger than that of other parts.

In other words, the vicinity of the exit of the lock pin storage hole 9 is
The stroke (lx) of the portion 14 of the lock pin 8 that may protrude + the distance α (lx'=lx
The large diameter portion 15 has a larger diameter than the other sliding portions 13 by +α). The outer diameters of the lock pins 8 are the same, and the large diameter portion 1 of the lock pin storage hole 9
The gap D between the lock pin 5 and the outer diameter of the lock pin 8 is larger than the gap d in the sliding portion. Since the other configurations are similar to those of the first embodiment, the same parts are given the same reference numerals as those of the first embodiment.

In the second embodiment as well, even if a protruding portion 14 appears as shown by the broken line in FIG. 2 due to the tip of the lock pin 8 hitting the eccentric bearing 6, it is absorbed by the large gap D. The protruding portion 14 does not come into contact with the lock pin storage hole 9, and the movement of the lock pin 8 is not inhibited.

Third Embodiment FIG. 3 shows a third embodiment of the present invention. In this embodiment, the reduced diameter portion of the lock pin is achieved by a tapered structure. That is, a taper 16 is formed at the tip of the lock pin 8 so that the diameter decreases to a greater degree in the direction of the eccentric bearing 6. Therefore, the gap D between the outer diameter of the taper 16 portion of the lock pin 8 and the inner circumference of the lock pin storage hole 9 is:
It is larger than the gap d of the sliding part 13. Since the other configurations are similar to those of the first embodiment, corresponding parts are given the same reference numerals as those of the first embodiment.

Even in the third embodiment, even if a protruding portion 14 is formed as shown by the broken line in FIG. 3 due to the tip of the lock pin 8 hitting the eccentric bearing 6, the protruding portion 14 is absorbed by the large gap D. Part 1
4 does not hit the lock pin storage hole 9, and the movement of the lock pin 8 is not inhibited.

[Effect of the invention] As explained above, in the present invention, the gap between the lock pin and the lock pin storage hole is made larger at the tip of the lock pin on the eccentric bearing side, so that the lock pin contacts the eccentric bearing and the gap between the lock pin and the lock pin storage hole is increased. Even if deformation occurs in the lock pin storage hole, sliding performance with the lock pin storage hole is not inhibited, and stable compression ratio switching can be performed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the lock pin engagement structure of the eccentric bearing type variable compression ratio mechanism according to the first embodiment of the present invention, and FIG. 2 is a sectional view of the eccentric bearing type variable compression ratio mechanism according to the second embodiment of the present invention. 3 is a sectional view of the lock pin engagement structure of the eccentric bearing type variable compression ratio mechanism according to the third embodiment of the present invention, and FIG. 4 is a sectional view of the conventional lock pin engagement structure. , FIG. 5 is a cross-sectional view of a conventional eccentric bearing type variable compression ratio mechanism, and FIG. 6 is a cross-sectional view of the mechanism shown in FIG. 5 in a direction perpendicular to FIG.
It is. 3...Connecting rod, 4...Piston pin, 6...Eccentric bearing, 7...Lock pin engagement hole, 8...Lock pin, 9...Lock pin storage hole, 12...Reduced diameter portion, 13... Sliding part, 14...
...protruding portion, 15...large diameter portion, 16...tapered portion.

Claims (1)

[Scope of utility model registration request] An eccentric bearing is interposed between the piston pin and the connecting rod, and the compression ratio is changed by changing the relative position of the piston to the connecting rod in accordance with the amount of rotation of the eccentric bearing.
Eccentric bearing type variable compression that locks or frees rotation of the eccentric bearing by inserting and removing the lock pin that is slidably inserted into the lock pin storage hole provided in the connecting rod and into the lock pin engagement hole provided in the eccentric bearing. A lock pin engagement structure for an eccentric bearing type variable compression ratio mechanism, characterized in that the gap between the outer periphery of the lock pin and the lock pin storage hole is made larger on the tip side of the lock pin.