JPH065046B2 - Eccentric bearing locking mechanism - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a variable compression ratio mechanism for an internal combustion engine in which an eccentric bearing is provided between a small end of a connecting rod and a piston pin, and more particularly to a lock mechanism for the eccentric bearing. It is about.

[Prior Art] Conventionally, an eccentric bearing is interposed between a small end of a connecting rod and a piston pin, and the compression ratio is changed by changing the relative position of the piston and the connecting rod by the eccentric bearing. The variable compression ratio mechanism of the
137832).

This conventional variable compression ratio mechanism is constructed, for example, as shown in FIGS. 10 and 11.

In the figure, 1 is a cylinder block, 2 is a piston, 3 is a connecting rod, and 4 is a piston pin.

A cylindrical body in which the wall thickness varies in the circumferential direction between the piston pin insertion hole 5 at the small end of the connecting rod 3 and the outer circumference of the piston pin 4, and the inner circumference circle and the outer circumference circle are eccentric to each other. An eccentric bearing 6 consisting of is rotatably interposed.

A lock pin housing hole 7 extending on a radial extension line of the eccentric bearing 6 is formed at a position of the connecting rod 3 corresponding to the eccentric bearing 6, and a lock pin 8 as a lock member is slidable in the hole 7. It is housed in the eccentric bearing 6 through the hole 7 so as to be retractable. On the other hand, the eccentric bearing 6 is formed with a lock pin engaging hole 9 having a diameter with which the lock pin 8 can be projected and retracted in a portion having a large radial thickness, and the lock pin 8 is inserted into the lock pin engaging hole 9. When engaged, the piston 2 is kept at a high position with respect to the connecting rod 3 to achieve a high compression ratio, and the lock pin 8
When the engagement is released, the eccentric bearing 6 freely rotates, and the piston is in the low position at the compression top dead center, so that the low compression ratio state can be realized.

The lock pin 8 is driven by hydraulic pressure between a lock pin lock hydraulic passage 10 that is opened at a position that biases the lock pin 8 toward the eccentric bearing 6 and a lock pin unlock hydraulic passage 11 that applies hydraulic pressure in the opposite direction. This is done by switching. Pressure oil is sent to the respective hydraulic passages 10 and 11 from the crankshaft 12 side.

In such a lock mechanism of the eccentric bearing 6,
When the lock pin 8 is biased by the hydraulic pressure from the hydraulic passage 10, the lock pin 8 is inserted into the lock pin engagement hole 9 without jumping over the lock pin engagement hole 9.
As shown in the figure, there is also known one in which a guide groove 13 is provided on the upstream side of the lock pin engagement hole 9 in the rotational direction (actually disclosed in Japanese Utility Model Laid-Open No. 58-58-
137832).

[Problems to be Solved by the Invention] In the lock mechanism of the type described above, the oil chamber 14 is formed immediately before the lock pin 8 is engaged with the lock pin engagement hole 9, as shown in FIG. Due to the oil damping action of this portion, the collision force between the lock pin 8 and the stopper portion 9a of the lock pin engagement hole 9 is weakened.

However, when the hydraulic pressure from the hydraulic passage 10 that drives the lock pin 8 is insufficient, the biasing force of the lock pin 8 toward the eccentric bearing 6 is weak, so that the oil from the oil chamber 14 toward the upstream side in the rotational direction is prevented. The leakage resistance is small, and sufficient oil damping action cannot be obtained. Therefore, the lock pin 8 may violently collide with the stopper portion 9a of the lock pin engagement hole 9, causing wear and deformation of the head portion of the lock pin 8 and burr of the eccentric bearing 6. Further, a large shearing force is applied to the lock pin 8 from the eccentric bearing 6 in shock, and there is a possibility that sufficient durability of the lock pin 8 cannot be ensured. When such a situation occurs, the movement of the lock pin 8 and the eccentric bearing 6 becomes uncertain, and there is a possibility that switching of a predetermined compression ratio cannot be performed.

In order to increase the hydraulic pressure that drives the lock pin 8,
When the capacity of the oil pump is increased, the energy consumption of the oil pump increases correspondingly, which causes a problem that the output performance of the engine deteriorates.

In order to solve the above problems, the present invention reduces the collision force between the lock member and the eccentric bearing to reduce the durability of the lock member and the eccentric bearing regardless of the magnitude of the hydraulic pressure for urging the lock member. An object is to provide a highly reliable locking mechanism that can be sufficiently secured.

[Means for Solving the Problems] In order to achieve this object, the lock mechanism of the eccentric bearing of the present invention is different from the conventional mechanism for inserting and removing the lock pin in the radial direction of the eccentric bearing. Is configured to be engaged with a lock hole formed in the tangential direction of. That is, in the lock mechanism of the present invention, the eccentric bearing groove is provided on the outer circumference of the eccentric bearing, and the eccentric bearing groove is provided on the inner circumference of the small end of the connecting rod so as to cooperate with the eccentric bearing groove. A connecting rod groove that forms a lock hole with a dead end is provided, and a locking member that can enter and exit the locking hole and that locks the eccentric bearing with the connecting rod by entering the locking hole is provided in the connecting rod groove. Has been.

[Operation] In such a lock mechanism, the lock member is driven by hydraulic pressure as in the conventional mechanism, but the lock hole engaged by the lock member is provided when the eccentric bearing groove is rotated to the position of the connecting rod groove. , The eccentric bearing groove and the connecting rod groove cooperate with each other, and the lock hole is formed as a tangential hole of the eccentric bearing. Since it is a tangential lock hole, the lock member engages in a wedge shape, and in the process of forming the lock hole by the cooperation of the eccentric bearing groove and the connecting rod groove, the lock member is formed along with the rotation of the eccentric bearing. The eccentric bearing will eventually lock onto the connecting rod as it gradually engages the locking hole. Therefore, since the rotation stopping force is gradually applied to the eccentric bearing as the lock member is inserted into the lock hole, a violent collision between the lock member and the eccentric bearing does not occur. As a result of keeping the collision force small, the durability of the lock member and the eccentric bearing is improved. And
The hydraulic pressure for driving the lock member has no relation to the collision force in the locking process, and a predetermined operation can be reliably obtained even with a small drive hydraulic pressure.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to the drawings.

1 to 4 show a lock mechanism for an eccentric bearing according to a first embodiment of the present invention. In the figure, 2
Reference numeral 0 indicates a connecting rod, and 21 indicates a piston pin. An eccentric bearing 2 composed of a cylindrical body in which an inner circumference circle and an outer circumference circle are eccentric to each other between an inner circumference 23 of the small end portion 22 of the connecting rod 20 and an outer circumference of the piston pin 21.
4 is rotatably interposed with respect to the connecting rod small end portion 22.

On the outer circumference of the eccentric bearing 24, an eccentric bearing groove 25 extending in the tangential direction of the outer circumference circle is provided. The eccentric bearing groove 25 is formed such that one end of the eccentric bearing, that is, the downstream end of the eccentric bearing 24 with respect to the rotation direction A is notched in the cross-sectional shape of the groove 25, and the other end thereof is formed. The side is formed in a quarter-sphere shape so that the groove 25 is dammed. Therefore, the eccentric bearing groove 25
The cross-sectional shape of is substantially semi-circular on the tip side of the groove 25 in the rotation direction A, and the arc length becomes shorter toward the downstream side in the rotation direction A. This eccentric bearing groove 25 has a third
As shown in the figure, the groove 25 is provided at a position in the direction 1 (eccentricity e) in which the inner circumference circle and the outer circumference circle of the eccentric bearing 24 are eccentric.
The position is determined so that the center of the 1/4 spherical shape of the tip portion comes.

The inner periphery 23 of the connecting rod small end portion 22 extends in the tangential direction of the inner peripheral surface, and the connecting rod small end portion 22 is formed.
Connecting rod groove 26 extending in the shape of a hole within the thickness of the
Is provided. The tip shape of the eccentric bearing rotation direction A side of the connecting rod groove 26 is formed in a 1/4 spherical shape like the tip shape of the eccentric bearing groove 25. Therefore, the cross-sectional shape of the connecting rod groove 26 is a substantially semi-circular shape on the tip side in the rotation direction A, and the arc length becomes longer toward the downstream side with respect to the rotation direction A, and within the wall thickness of the small end portion 22 of the connecting rod. It is a circle when entering. Then, the connecting rod groove 26 and the eccentric bearing groove 25 cooperate with each other when the eccentric bearing 24 rotates and the eccentric bearing groove 25 comes to the position of the connecting rod groove 26 as shown in FIG. 5B. A circular lock hole 27 having a circular cross section and a dead end is formed.

A lock member 28 is provided in the connecting rod groove 26. The lock member 28 is formed of a spherical lock ball in this embodiment. The rock ball 28 is
When the lock hole 27 is not formed, the connecting rod groove 26 is accommodated in the lock member accommodating hole (lock member accommodating portion) 29 that is a portion extending to the inside thickness of the connecting rod small end portion 22, and the lock hole 27 is accommodated. When formed, it is inserted into the lock hole 27 and engages both the connecting rod groove 26 and the eccentric bearing groove 25 so that the eccentric bearing 24 can lock its rotation with respect to the connecting rod 20. Has become.

The lock member receiving hole 29 of the connecting rod groove 26 communicates with a lock hydraulic passage 30 that supplies a hydraulic pressure for urging the lock ball 28 toward the lock hole 27 through a hydraulic passage for high compression ratio. An unlocking hydraulic passage 31 for a low compression ratio that supplies hydraulic pressure for pushing the lock ball 28 from the lock hole 27 to the lock member accommodating hole 29 is connected to an end portion on the opposite side of the connecting rod groove 26. The mechanism for supplying and switching the hydraulic pressure to the lock hydraulic passage 30 and the unlock hydraulic passage 31 is the same as or similar to the conventional mechanism shown in FIG.

In this embodiment, the lock hole 27 is formed at the lowermost portion of the inner periphery 23 of the connecting rod small end portion 22 so as to extend in a substantially horizontal direction, that is, in a direction perpendicular to the axis of the connecting rod 20. The inner circumference 23 can be provided at any suitable position in the circumferential direction. However, in order to eliminate the influence of the inertial force due to the movement of the lock ball 28, it is advantageous to make the lock hole 27 in a direction close to horizontal as in this embodiment.

Further, in the present embodiment, one lock hole 27 and one lock ball 28 are used, but if space allows, for example, a plurality of lock holes 27 and lock balls 28 are arranged in parallel in a direction perpendicular to the paper surface of FIG. It is also possible to provide a plurality of them in series in the circumferential direction of the inner circumference 23 of the connecting rod.

The operation of the embodiment apparatus configured as described above will be described below.

First, when the compression ratio is low, the lock ball 28 serving as the lock member is retracted into the lock member accommodation hole 29, and the piston position with respect to the connecting rod near the compression top dead center is lowered to reveal the low compression ratio state.

At the time of switching to high compression, hydraulic pressure is applied to the lock hydraulic passage 30, and the lock ball 28 is urged to the left in FIG. Since the eccentric bearing 24 rotates in the clockwise direction (same as the rotation direction of the crank) in FIG.
As shown in FIG. 9A, when the eccentric bearing groove 25 is rotated on the connecting rod groove 26, the biased lock ball 28 is also inserted into the eccentric bearing groove 25, and the insertion is performed by the eccentric bearing 24. Progresses with the rotation of. Then, when the eccentric bearing groove 25 is aligned with the connecting rod groove 26, as shown in FIG. 5B, the lock hole 27 is formed by cooperation, and the lock ball 28 urged by the hydraulic pressure is locked by the lock hole 27. Of the lock hole 27 and is locked at the tip position of the lock hole 27.
In this state, since the lock ball 28 is in contact with both the connecting rod 20 side and the eccentric bearing 24 side, the eccentric bearing 24 is locked to the connecting rod 20 via the lock ball 28,
The rotation is locked.

Since the lock ball 28 gradually engages in the lock hole 27 during the process of forming the lock hole 27, the eccentric bearing 2
Since the rotation stopping force of No. 4 is gradually applied and the lock hole forming direction is formed tangential to the rotation of the eccentric bearing 24, the lock ball 28 gradually wedges into the lock hole 27. The biting state is reached, and the rotational energy of the eccentric bearing 24 is gradually absorbed via the lock balls 28. Therefore, the shocking stopping force is
Neither the lock ball 28 nor the eccentric bearing 24 is applied, and no shocking shearing force is applied to the lock ball 28.

Further, in this embodiment, the lock hole 27 of the lock ball 28 is
Since the lock ball 28 rolls during the engagement process with the eccentric bearing 2
4 Energy for stopping is absorbed.

To switch from the high compression ratio to the low compression ratio, as shown in FIG. 5C, the lock ball 28 is pushed out to the lock member accommodation hole 29 by the hydraulic pressure from the unlock hydraulic passage 31, and the eccentric bearing 24 is moved. The rotation stop of is released.

Next, FIG. 6 shows a second embodiment of the present invention. In this embodiment, the lock member accommodating portion 41 of the connecting rod groove 40 is directed toward the connecting rod large end (not shown) side with respect to the lock hole forming portion 42. By thus directing the lock member accommodating portion 41 downward,
When the lock of the eccentric bearing 24 is released, the lock ball 28 easily falls into the lock member housing portion 41 due to gravity, and the smoothness of operation is improved. Other configurations,
The operation is similar to that of the first embodiment.

Next, FIG. 7 shows a third embodiment of the present invention. In this embodiment, the lock member 50 is a lock pin made of a columnar body. Therefore, the eccentric bearing 5
The eccentric bearing groove 52 and the connecting rod groove 54 of the connecting rod 53 are also formed in a groove having a width corresponding to the length of the lock pin 50 in the direction perpendicular to the paper surface of FIG. 7. Since the lock member 50 has the pin structure as described above, the longitudinal dimension of the pin can be reduced, and thus the shear stress applied to the lock member 50 can be reduced accordingly. Then, by using the lock pin 50 of a cylindrical body, the eccentric bearing 51 can be rolled by the rolling.
It is possible to reduce the shear stress while absorbing the stop energy. Other configurations and operations are similar to those of the first embodiment.

Next, FIG. 8 shows a fourth embodiment of the present invention. In this embodiment, the lock member 60 is formed into a columnar body having an oval cross section. Therefore, the eccentric bearing groove 62 of the eccentric bearing 61 and the connecting rod groove 64 of the connecting rod 63 are also formed in a groove shape corresponding to the shape of the lock member 60. In this way, by increasing the cross-sectional area of the lock member 60, the shear stress applied to the lock member 60 is further reduced, and the lock member 60
The durability of is further improved. Other configurations and operations are first
According to the example.

Next, FIG. 9 shows a fifth embodiment of the present invention. In the present embodiment, the eccentric bearing groove 7 of the eccentric bearing 70.
The circumferential position where 1 is formed is a position deviated from the eccentric direction 1 of the eccentric bearing 70 by an angle θ.

As shown in FIGS. 5B and 3, when the lock hole is formed at the position of the eccentric bearing in the eccentric direction, the center of the connecting rod inclines with respect to the sliding direction of the piston during combustion, so that the locking member is locked. A force acts in the direction of pushing the lock member out of the lock hole, but the action of the force is easily prevented by slightly shifting the position of the eccentric bearing groove 71 as described above. Other configurations and operations are similar to those of the first embodiment.

[Effects of the Invention] As described above, according to the lock mechanism of the eccentric bearing of the present invention, the lock hole is formed in the tangential direction of the eccentric bearing, and the lock member is wedge-shaped in the lock hole as the eccentric bearing rotates. It is possible to prevent the impact force from acting on the lock member and the eccentric bearing, so that the durability of these members can be improved and a reliable compression ratio switching operation can be performed. The effect is obtained.

Further, in the past, a material excellent in compression resistance, bending resistance, and shear resistance was required for the lock member, whereas in the present invention, a large shocking force is not applied to the lock member. Since it is only necessary to select a strong material, it is possible to easily select the material, and it is possible to obtain a highly reliable locking mechanism that is low in cost and functionally durable. In particular, when a lock ball is used for the lock member, the shearing force received from the eccentric bearing can be made extremely weak structurally, and the durability of the lock member can be greatly enhanced.

Furthermore, since the hydraulic pressure for driving the lock member has nothing to do with the force that the lock member and the eccentric bearing receive when the eccentric bearing stops rotating, there is no need to increase the capacity of the oil pump, and a small oil As the pump, the energy consumption of the oil pump can be reduced, and the performance of the engine can be improved.

[Brief description of drawings]

1 is a longitudinal sectional view of a lock mechanism for an eccentric bearing according to a first embodiment of the present invention, FIG. 2 is a partial sectional view taken along the line II-II of FIG. 1, and FIG. 3 is the apparatus of FIG. Of the eccentric bearing of FIG. 4, FIG. 4 is a bottom view of the eccentric bearing of FIG. 3, and FIGS. 5 (a), (b), and (c) are sectional views of the eccentric bearing showing the movement of the lock member, and FIG. FIG. 7 is a vertical sectional view of an eccentric bearing locking mechanism according to a second embodiment of the present invention, FIG. 7 is a vertical sectional view of an eccentric bearing locking mechanism according to a third embodiment of the present invention, and FIG. FIG. 9 is a vertical sectional view of an eccentric bearing locking mechanism according to a fourth embodiment, FIG. 9 is a sectional view of an eccentric bearing portion according to a fifth embodiment of the present invention, and FIG. 10 is a vertical sectional view of a conventional eccentric bearing locking mechanism. FIG. 11 is a partially enlarged sectional view taken along the line XI-XI in FIG. 20, 53, 63 ... Connecting rod 21 ... Piston pin 22 ... Connecting rod small end 23 ... Inner circumference 24, 51, 61, 70 ... Eccentric bearing 25, 52, 62, 71 ... Eccentric bearing groove 26, 40, 54, 64 ... connecting rod groove 27 ... lock hole 28, 50, 60 ... lock member 29, 41 ... lock member accommodating portion 30 ... lock hydraulic passage 31 ... unlock hydraulic passage 42: Lock hole forming part l: Eccentric direction A: Eccentric bearing rotation direction

Claims (8)

[Claims] 1. A cylindrical eccentric bearing, in which an inner circumference circle and an outer circumference circle are eccentric to each other, is interposed between an inner circumference of a small end portion of a connecting rod and an outer circumference of a piston pin, and the eccentric bearing is connected. In a variable compression ratio mechanism using an eccentric bearing of an internal combustion engine that changes the compression ratio by stopping and releasing rotation of the rod, an eccentric bearing groove extending tangentially is provided on the outer periphery of the eccentric bearing, and the connecting rod small A connecting rod groove, which extends tangentially and forms a deadlock-like lock hole in cooperation with the eccentric bearing groove, is provided on the inner circumference of the end portion, and the lock hole is capable of entering and leaving the connecting rod groove. Providing a lock member that locks the eccentric bearing with respect to the connecting rod by entering the lock hole The lock mechanism of the eccentric bearing, characterized in that. 2. The lock mechanism for an eccentric bearing according to claim 1, wherein the lock member has a spherical shape. 3. The lock mechanism for an eccentric bearing according to claim 1, wherein the lock member has a cylindrical shape. 4. The lock mechanism for an eccentric bearing according to claim 1, wherein the shape of the lock member is a columnar body having an oval cross section. 5. The lock mechanism for an eccentric bearing according to claim 1, wherein the extending direction of the lock hole is a direction perpendicular to the axis of the connecting rod. 6. The lock mechanism for an eccentric bearing according to claim 1, wherein the lock member accommodating portion of the connecting rod groove faces the connecting rod large end side with respect to the lock hole forming portion. 7. The eccentric bearing groove is formed on the outer periphery of the eccentric bearing in the eccentric direction.
An eccentric bearing locking mechanism described in the paragraph. 8. The lock mechanism for an eccentric bearing according to claim 1, wherein the eccentric bearing groove is formed at an outer peripheral position offset from the eccentric direction of the eccentric bearing.