JPH0426672Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention involves interposing an eccentric bearing between a piston pin and a connecting rod, and rotating the eccentric bearing to vary the compression ratio of an internal combustion engine. The present invention relates to a locking mechanism for eccentric bearing rotation 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. 9 to 11, a piston 2 is reciprocatably fitted into a cylinder 1 and connected to a connecting rod 3 via a piston pin 4. An eccentric bearing 6 whose inner and outer circumferences are eccentric from each other is inserted between the piston pin insertion hole 5 of the connecting rod 3 and the piston pin 4, and the eccentric bearing 6 is rotated to connect the piston 2. By changing the relative position to the bearing rod 3,
The compression ratio was made variable. and,
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. Obtain lock pin 8
The lock pin 8 can be removed from the lock pin storage hole 9 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 rotation of the eccentric bearing 6 was locked by inserting and removing the eccentric bearing 6 and engaging the lock pin 8 with the lock pin engagement hole 7. When hydraulic pressure is applied to the lock pin lock hydraulic passage 10, 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 maintains a high position relative to the connecting rod 3, resulting in a high compression ratio. Furthermore, 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 becomes free to rotate, and during the compression stroke. Near the dead center, the thinnest part of the eccentric bearing 6 comes down under the pressure of compressed gas and explosion pressure, and a low compression ratio state is automatically created.

[Problem that the invention attempts to solve]

However, in conventional variable compression ratio mechanisms, the axis of the lock pin engagement hole provided in the eccentric bearing lies on a plane that includes the center of the inner circumference and the center of the outer circumference of the eccentric bearing. It was set up. Therefore, when the lock pin enters the lock pin engagement hole of the eccentric bearing and fixes the eccentric bearing in a high compression ratio state, the piston pin will receive a large inertia force of the piston or inertia force + gas pressure near the vertical dead center. , no external force acts on the lock pin. However, during the explosion stroke, an explosive force greater than the inertia force at suction top dead center acts on the piston pin, and this generates a large rotational moment in the eccentric bearing due to the angle between the connecting rod centerline and the cylinder bore centerline. This causes a shearing force to act on the lock pin, causing problems such as breakage, deformation, and wear of the lock pin.

The present invention not only solves these problems, but also prevents the lock pin, which is pressurized into the lock pin engagement hole of the eccentric bearing, from coming out due to its own inertia at bottom dead center when the compression ratio is high. The purpose of the present invention is to provide a more reliable compression ratio switching mechanism.

[Means for solving problems]

The eccentric bearing locking mechanism of the variable compression ratio mechanism of the present invention, which meets this purpose, interposes an eccentric bearing whose inner and outer circumferences are mutually eccentric between the piston pin and the connecting rod, and adjusts the amount of rotation of the eccentric bearing. The compression ratio is changed accordingly, a lock pin engagement hole is formed in the eccentric bearing, a lock pin storage hole is formed in the connecting rod, and the lock pin is inserted into the lock pin storage hole so that it can be moved in and out of the lock pin engagement hole. In the eccentric bearing mechanism of the variable compression ratio mechanism, in which the rotational position of the eccentric bearing can be locked by engagement between the lock pin and the lock pin engagement hole, the lock pin storage hole and the lock pin engagement hole are connected to the inner circumferential circle of the eccentric bearing. From the one provided at a position where the axis of the lock pin storage hole and the axis of the lock pin engagement hole coincide when the plane passing through the center and the center of the outer circumference is inclined from the plane containing the longitudinal axis of the connecting rod. Become.

[Effect]

In the eccentric bearing lock mechanism having the above configuration, the longitudinal axis of the connecting rod is not in a plane passing through the center of the inner circumferential circle and the center of the outer circumferential circle of the eccentric bearing, or in a plane parallel to that plane, and is deviated from the plane by an angle θ. Since it is located in the same plane, the moment applied to the eccentric bearing is reduced, and the shear force applied to the lock pin is reduced.

Further, since the axis of the lock pin is inclined from the axis of the cylinder bore, the lock pin can be prevented from coming off due to its own inertia, and the compression ratio can be changed more reliably.

〔Example〕

Hereinafter, preferred embodiments of the eccentric bearing lock mechanism for the variable compression ratio mechanism according to the present invention will be described with reference to the drawings. Of the structures shown in FIGS. 9 and 11, the lock pin, lock pin engagement hole,
Since the structure of the parts other than the arrangement position of the lock pin storage hole can be applied to the present invention, a description of the structure of the applicable parts will be omitted, and only the characteristic structure and operation of the present invention will be described below.

First Embodiment FIGS. 1 to 4 show a first embodiment of the present invention. In the figure, reference numeral 6 indicates an eccentric bearing, which is rotatably interposed between the piston pin 4 of the piston 2 and the connecting rod 3.
is made of a cylindrical body whose inner and outer circumferences are eccentric, and has a lock pin engagement hole 7 that penetrates between the inner and outer circumferences and extends in the radial direction of the outer circumference. The lock pin storage hole 9 on the connecting rod 3 side accommodates the eccentric bearing 6.
The 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. A lock pin lock hydraulic passage 10 for driving the lock pin 8 in the direction of the eccentric bearing 6 is opened at the bottom of the lock pin storage hole 9.
Hydraulic pressure from a lock pin unlocking hydraulic passage 11 can be applied to the side of the lock pin storage hole 9 opposite to the lock pin locking hydraulic passage 10 with respect to the lock pin 8. 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 medium to light loads, and the lock pin is released under high loads. Pressure is applied to the lock hydraulic passage 11.

When the axes of the lock pin storage hole 9 and the lock pin engagement hole 7 are aligned, the lock pin 8 can move in and out of the lock pin engagement hole 7, but the positions of the lock pin storage hole 9 and the lock pin engagement hole 7 are The relationship is that the center 1 of the inner circumferential circle 12 of the eccentric bearing 6
A plane 16 passing through 3 and the center 15 of the outer circumferential circle 14 is
It is arranged so that the axis of the lock pin storage hole 9 and the axis of the lock pin engaging hole 7 coincide when the lock pin is tilted at an angle θ with respect to the longitudinal axis 17 of the connecting rod 3.

For example, in the example shown in FIG.
A plane 16 passing through the centers 13 and 15 of the outer circumferential circle
includes a line passing through the thickest part of the eccentric bearing 6, the lock pin engagement hole 7 is inclined at an angle θ from this plane 16, and extends in the longitudinal direction of the connecting rod 3 in the lock pin storage hole 9. When the axes of the lock pin engaging hole 7 and the lock pin housing hole 9 coincide, the axes are inclined from the plane 16 by an angle θ.

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 locking hydraulic passage 10, driving the lock pin 8 in the direction of the eccentric bearing 6. Then, the eccentric bearing 6 rotates to lock 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 (the state shown in FIG. 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 to the connecting rod 3 is high.
Locked at high compression ratio.

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
is driven in the direction of entering the lock pin storage hole 9,
When the eccentric bearing 6 is disengaged from the lock pin engagement hole 7 (the state shown in FIG. 6), the eccentric bearing 6 receives the compressed gas load and the explosion load from the piston 2 near the compression top dead center of the piston. It is automatically rotated to the position where the relative position with respect to the connecting rod 3 is the lowest, and a low compression ratio state is obtained. Therefore, even under high load conditions when the degree of gas compression is greatest, knocking is less likely to occur, the compression ratio can be increased accordingly, and fuel efficiency and shaft torque can be improved.

The moment applied to the eccentric bearing 6 and the shear force applied to the lock pin 8 while the eccentric bearing 6 is in operation are as follows.

First, in FIGS. 1 and 2, the point where the combustion gas pressure reaches its maximum is located approximately 20 degrees in crank angle from the top dead center of the piston (see FIG. 5). Here, let the angle between the center line 17 of the connecting rod 3 and the center line of the cylinder bore 1 be α, and the crank angle at that time be θ ₂ (see FIG. 4). in this case,
Combustion gas pressure F is applied downwardly to the center 13 of the piston pin 4 via the piston 2. A reaction force F from the connecting rod 3 is applied upward to the center 15 of the outer circumference 14 of the eccentric bearing 6. When the center of the outer circumference and the center of the inner circumference of the eccentric bearing are on the axis of the lock pin engagement hole as in the conventional case shown in FIG. 9, the center of the piston pin 4 is located at P as shown in FIG. Since it is at the position of , both centers 1
If the distance between 3 and 15 is e, an arm with a moment of esinα appears, and a moment of Fesinα acts on the eccentric bearing. The maximum of this moment is on the lagging side of the crank angle at which the combustion gas pressure becomes maximum, and as shown in FIG. 5, it is around the crank angle θ ₂ =30 degrees. (Here, let α at this time be α ₀ )
Approximately α ₀ =10 degrees. This moment exerts a shearing force on the lock pin 8. However, in the present invention, since the lock pin engagement hole 7 is inclined by θ from the plane 16 passing through the centers 13 and 15 of the inner and outer circumferential circles of the eccentric bearing 6, by setting this θ to α ₀ (approximately 10 degrees), As shown in Figure 2, the moment arm is near 0 (the downward force applied to point 13 and the upward force applied to point 15 are on the same line),
The moment applied to the eccentric bearing 6 is reduced to 0 when the inclination α of the connecting rod 3 is around α ₀ .
It can be done. However, in reality, α=α ₀
Then, at the top and bottom dead centers of the piston, piston 2
When the maximum inertial force G (G is usually smaller than F) is applied to the eccentric bearing 6, a moment of Gesin θ is applied to the eccentric bearing 6, so we want to reduce this moment as well, so if θ is a value other than α ₀ and the piston 2 The moment is set to a value that makes the moment as small as possible when it is at the top or bottom dead center compared to when θ = α ₀ , and when θ = α ₀ , the moment is made smaller than the conventional case (θ = θ ₀ ). .

Figure 5 shows a comparison of the force acting on the piston pin 4 with respect to the crank angle and the moment acting on the crank angle and the eccentric bearing 6 in the case of θ = α ₀ (curve A) and the conventional case (curve B). There is. The case of the present invention (curve C) is approximately midway between curves A and B. As shown in the figure, in the conventional case (curve B), the crank angle from top dead center (TDC) is approximately
The maximum combustion load occurs at 20 degrees, the maximum moment occurs at approximately 30 degrees of crank angle from top dead center, and the moment is 0 at top dead center and bottom dead center (BDC). On the other hand, in the present invention (curve C), the moment at α=α ₀ is reduced compared to the conventional case, and the absolute values of the positive and negative values of the moment are overall smaller than in the conventional case (curve B).

Second Embodiment FIG. 8 shows a second embodiment of the present invention. In this embodiment, the position of the lock pin storage hole 9A is different from that in the first embodiment. Also in the second embodiment, the lock pin storage hole 9A and the lock pin engagement hole 7
The relationship between the positions is as follows: a plane 16 passing through the center 13 of the inner circumferential circle and the center 15 of the outer circumferential circle 14 of the eccentric bearing 6;
is arranged so that when the lock pin housing hole 9A is tilted at an angle θ with respect to the longitudinal axis of the connecting rod 3, the axis of the lock pin storage hole 9A and the axis of the lock pin engaging hole 7 are aligned.

For example, in the example shown in FIG.
A plane 16 passing through the centers 13 and 15 of the outer circumferential circle
includes a line passing through the thickest part and the thinnest part of the eccentric bearing 6, the lock pin engagement hole 7 is inclined at an angle (θ+θ ₁ ) from this plane 16, and the lock pin storage hole 9A is connected to the connecting groove. When the axes of the lock pin engagement hole 7 and the lock pin engagement hole 9A are aligned, the connecting rod axis 17 is inclined by an angle θ from the plane ₁₆ . ing.

Other configurations and operations are similar to those of the first embodiment, so similar parts are given the same reference numerals as those of the first embodiment and their explanations will be omitted.

[Effect of idea]

As explained above, according to the eccentric bearing lock mechanism of the variable compression ratio mechanism of the present invention, the moment applied to the eccentric bearing is reduced, and the shear force applied to the lock pin is reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an eccentric bearing lock mechanism of a variable compression ratio mechanism according to a first embodiment of the present invention;
The figure is an enlarged sectional view of the eccentric bearing in the mechanism in Figure 1, Figure 3 is a front view of the eccentric bearing in Figure 1, Figure 4 is a schematic diagram of the piston crank mechanism in Figure 1, and Figure 5 is a schematic diagram of the piston crank mechanism in Figure 1. A diagram of the relationship between the crank angle and the force acting on the piston pin and the moment acting on the eccentric bearing in the present invention. Figure 6 is a sectional view of the variable compression ratio mechanism in Figure 1 in a low compression ratio state.
The figure is a cross-sectional view of the variable compression ratio mechanism in the high compression ratio state of FIG. 1, FIG. A sectional view of the vicinity of the eccentric bearing of the variable compression ratio mechanism, FIG. 10 is a sectional view of the conventional variable compression ratio mechanism, and FIG. 11 is the first section of the variable compression ratio mechanism of FIG.
2 is a sectional view taken in a direction perpendicular to FIG. 3...Connecting rod, 4...Piston pin, 6...Eccentric bearing, 7...Lock pin engagement hole, 8...Lock pin, 9,9A...Lock pin storage hole, 13...Eccentric bearing inner circumference Center, 15... Center of eccentric bearing outer circumference, 16...
... A plane passing through the centers 13 and 15, 17 ... the longitudinal axis of the connecting rod.

Claims (1)

[Scope of utility model registration request] An eccentric bearing whose inner and outer circumferences are eccentric with respect to each other is interposed between the piston pin and the connecting rod, the compression ratio is changed according to the amount of rotation of the eccentric bearing, and a lock pin engagement hole is formed in the eccentric bearing. A lock pin storage hole is formed in the connecting rod, a lock pin is inserted into the lock pin storage hole so as to be removable from the lock pin engagement hole, and the rotational position of the eccentric bearing is locked by engagement between the lock pin and the lock pin engagement hole. In the eccentric bearing lock mechanism of the variable compression ratio mechanism,
The axis of the lock pin housing hole and the lock pin engaging hole are aligned when the plane passing through the center of the inner circumferential circle and the center of the outer circumferential circle of the eccentric bearing is inclined from a plane containing the longitudinal axis of the connecting rod. An eccentric bearing lock mechanism for a variable compression ratio mechanism characterized by being provided at a position where the axes of the core and the lock pin engagement hole coincide.