JPH1162648A - Variable compression ratio mechanism of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable compression ratio mechanism for internal combustion engine which is precluded from poor performance of operations, in which a change of the compression ratio is prevented by hindering an eccentric bearing from dislocation from the long stroke setting position or short stroke setting position. SOLUTION: The locked condition of an eccentric bearing 2 in the bearing lock position is generated by putting a lock pin 10 in engagement with a first oil pressure chamber 19 or second oil pressure chamber 21 furnished in the eccentric bearing 2 using only an energizing means, and the hydraulic force of an oil pump is allowed to act only for release of this engagement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable compression ratio mechanism for an internal combustion engine, and more particularly to a variable compression ratio mechanism capable of changing a compression ratio by changing a piston stroke.

[0002]

2. Description of the Related Art When the operating state of an internal combustion engine is in a high load range or a high speed range, the compression ratio is reduced so as not to cause knocking, and when the internal combustion engine is in a middle load range or a low speed range, the thermal efficiency is increased. A variable compression ratio mechanism capable of increasing the compression ratio to increase the output of the engine is disclosed in, for example, Japanese Unexamined Patent Publication No. 8-283.
No. 14 discloses this.

[0003] As is well known, the compression ratio is a numerical value indicating how much the piston is compressing the air sucked by the cylinder in the compression stroke, and is indicated by the multiple of the cylinder volume of the combustion chamber. If the piston stroke can be lengthened in the compression process, the compression ratio becomes higher because the volume of the combustion chamber becomes smaller (hereinafter referred to as “high compression ratio state”). Conversely, if the piston stroke can be shortened in the compression step, the volume of the combustion chamber will increase accordingly, and thus decrease (hereinafter referred to as “low compression ratio state”).

An eccentric bearing is a component of the variable compression ratio mechanism that changes the compression ratio. FIG. 5 shows an application example of such an eccentric bearing, in which the eccentric bearing a is interposed between the large end b1 of the connecting rod b and the crankpin c1 of the crankshaft c.

[0005] As shown in FIG. 5, the center axis L1 of the rotary hole f of the eccentric bearing a is shifted by a distance l in the radial direction with respect to the center axis L2 of the outer peripheral wall d of the eccentric bearing a. Referring to FIG. 5, the central axis L1 is shifted upward by a distance 1 with respect to the stop axis L2. Therefore, the thickness of the eccentric bearing a is not uniform, and in FIG. 5, the thinnest portion g located at the uppermost portion of the eccentric bearing a and the thickest portion h located at the lowermost portion of the eccentric bearing a. Face each other. That is, the thinnest portion g and the thickest portion h are shifted by 180 ° in the circumferential direction. Therefore, the portion from the thinnest portion g to the thickest portion h gradually increases in thickness in the circumferential direction. It's getting thinner. The arrow indicated by A in the drawing indicates the rotation direction of the crankshaft c, and the point indicated by O indicates the center of rotation of the crankshaft c.

[0006]

In order to extend the piston stroke using the eccentric bearing a having such a structure, that is, to obtain a high compression ratio state, as shown in FIG. When it is at the top dead center, the thickest portion h of the eccentric bearing a may be located on the cylinder s side. Conversely, in order to shorten the piston stroke, that is, to obtain a low compression ratio state, as shown in FIG. 7, when the piston i is at least at the top dead center, the thinnest portion g of the eccentric bearing a is It should just be located on the side.

The state in which the thickest portion h is located on the cylinder s side when the piston i is at the top dead center is called that the eccentric bearing a is at the "long stroke setting position". The thinnest part g is cylinder s
The state located on the side means that the eccentric bearing a is at the “short stroke setting position”.

When the operating state of the internal combustion engine is in a high-load range or a high-speed range, the eccentric bearing a is automatically placed at the short stroke setting position.
Therefore, in this case, the compression ratio is low, and a low compression ratio state is set.
Also, when the engine is in the middle load range or lower or in the low / medium rotation range,
The eccentric bearing a is automatically placed at the long stroke setting position. Therefore, in this case, the compression ratio is high, and the compression ratio is high.

In order to secure a low compression ratio state or a high compression ratio state, the eccentric bearing a is connected to the crank pin c.
By locking _one or the connecting rod big end b _1, the locking means j for setting the eccentric bearing a at or long stroke set position a short-stroke setting position is adapted to hydraulically actuated. The locking means j releases the locked state before the operating state of the internal combustion engine changes, so that the eccentric bearing a can freely rotate. By doing so, the eccentric bearing a is automatically placed at the long stroke setting position or the short stroke setting position in accordance with the operation state of the internal combustion engine. When the eccentric bearing a is at the long stroke setting position or at the short stroke setting position, the locking means j automatically locks the eccentric bearing a at those positions by hydraulic pressure.

In such a locking means j, the connecting rod b extends radially from the center of the crank pin c1.
Lock pin m which is a component of the axial oil path k the locking means j extending coaxially receives a hydraulic force against the urging force of the spring n from the base end k ₁ side of the oil path k, the oil pressure of It reciprocates according to the height. When the piston i is at the bottom dead center, the lock pin m stops at a predetermined position of the oil path k, and depending on the stop position, the eccentric bearing a locks with the connecting rod large end b1 or the crank pin c1. And integrated. When the eccentric bearing a is integrated with the large end b1 of the connecting rod, the eccentric bearing a is placed at the short stroke setting position and the crankpin c
When integrated with 1, it is placed at the long stroke setting position.

However, the lock pin m of the eccentric bearing a
The lock state is maintained by the hydraulic pressure, so if the hydraulic pressure is higher or lower than a predetermined value, the balance between the urging force of the spring n and the hydraulic pressure is lost. There is a possibility that the lock pin m is shifted from a predetermined position of the oil path k. Then, since the locked state is released, the integrated state of the eccentric bearing a and the large end b1 of the connecting rod or the crankpin c1 is released, and the eccentric bearing a is moved to the long stroke setting position or the short stroke setting position. It may be difficult to keep it. As a result, a desired compression ratio corresponding to the operating state of the internal combustion engine cannot be obtained, and the variable compression ratio mechanism may malfunction.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to solve the problem that the eccentric bearing does not deviate from a long stroke setting position or a short stroke setting position to change the compression ratio. It is a technical object to prevent the malfunction of the variable compression ratio mechanism from occurring due to this.

[0013]

In order to solve the above-mentioned problems, a variable compression ratio mechanism of an internal combustion engine according to the present invention connects a piston and a crankshaft, and converts a reciprocating motion of the piston in the cylinder into a rotational motion of the crankshaft. The connecting rod to be converted is interposed between the connecting rod large end, which is a ring-shaped portion located on the crankshaft side, and the crankshaft crankpin fitted inside the connecting rod large end. An eccentric bearing rotatably mounted between an inner peripheral surface of the crank pin and an outer peripheral surface of the crankpin; and locking the eccentric bearing at a predetermined position in the circumferential direction thereof by using an urging force of urging means. Lock means for releasing the lock by applying hydraulic pressure against the pressure by hydraulic means. A variable compression ratio of an internal combustion engine in which a compression ratio represented by a multiple of a cylinder volume of a combustion chamber can be changed by changing a piston stroke according to a difference in the predetermined position at which the eccentric bearing is locked by locking means. The mechanism has the following configuration.

That is, the locking means maintains the locked state of the eccentric bearing by only the urging force of the urging means, and the hydraulic pressure by the hydraulic means acts only to release the locked state. It is characterized by the following.

In the variable compression ratio mechanism for an internal combustion engine according to the present invention,
The maintenance of the locked state in which the eccentric bearing provided between the large end of the connecting rod and the crank pin is locked at a predetermined position is performed only by the urging force of the urging means, and the hydraulic pressure by the hydraulic means is used to release the locked state. In this state, the hydraulic pressure does not act in the locked state based only on the mechanical acting force of the urging means such as a spring. Therefore, the lock state to be realized has high reliability and is hard to be released. For this reason, the lock of the eccentric bearing is released due to the oil pressure being too high or too low than a predetermined value, as in the case where the lock state has been dependent on the oil pressure until now. There is no such thing. As a result, the eccentric bearing does not shift with respect to the large end of the connecting rod or the crankpin. Therefore, a change in the compression ratio can be reliably prevented, so that operation failure of the variable compression ratio mechanism can be prevented.

The predetermined position refers to a position where the eccentric bearing is locked to a specific object, for example, a connecting rod to integrate the two. The urging means is, for example, a spring, and uses the urging force.

Further, the locking means locks the eccentric bearing by engaging with a specific hole provided on a peripheral wall surface of the eccentric bearing at a predetermined position in a circumferential direction of the eccentric bearing. You may. Also, if this specific hole is provided, for example, in the outer surface of the eccentric bearing by drilling in the radial direction of the eccentric bearing, in order for the specific hole and the locking means to engage, the locking means must also have its axial direction. It must be arranged to coincide with the radial direction of the eccentric bearing, in which case the locking means will be provided, for example, in the longitudinal direction of the connecting rod. For this reason, compared with the case where the locking means is provided in the thickness direction of the connecting rod, the thickness dimension of the connecting rod and thus the length of the crankshaft can be reduced, so that the internal combustion engine can be made compact.

Further, the specific hole is a hole which engages with the locking means when the operation state of the internal combustion engine is in a high load range or a high rotation range, and the operation state is lower than a middle load range or a low middle rotation range. It is desirable that there be at least two of the holes that engage with the locking means in the case of (1). This makes it possible to reliably change the compression ratio in accordance with the operating state of the internal combustion engine. The hole that engages with the locking means may be a through hole or a recess that does not penetrate.

Further, the hydraulic pressure is supplied to the specific hole via a first hydraulic passage provided in the crankpin and a second hydraulic passage provided in the eccentric bearing. Preferably, when the eccentric bearing is at the predetermined position in the circumferential direction, the first and second hydraulic paths are connected to each other.

By doing so, unless the eccentric bearing is at a predetermined position, the connection between the first hydraulic passage and the second hydraulic passage is not established. Therefore, the hydraulic pressure is supplied to the specific hole only when the eccentric bearing is at a predetermined position, and when the eccentric bearing is located at other positions, the locked state of the eccentric bearing is maintained by the biasing means. And this will not be solved. In other words, when the eccentric bearing is not at the predetermined position, the hydraulic pressure does not act in the direction of weakening the urging force of the urging means, so that the compression ratio may fluctuate under the influence of the hydraulic pressure. Absent. As a result, fluctuations in the compression ratio can be reliably prevented, so that malfunction of the variable compression ratio mechanism can be prevented.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION

<Overall Configuration of Apparatus> Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

As shown in FIGS. 1 to 4, an eccentric bearing 2, which is one of the components of the variable compression ratio mechanism 1, is externally fitted on a crank pin 4 of a crankshaft 3 and a ring of a connecting rod 6. Base hole 7 of large end 7 shaped
a. That is, the eccentric bearing 2
It is mounted between the outer peripheral surface of the crank pin 4 and the inner peripheral surface of the connecting rod large end portion 7, and lubricating oil is put between them. Therefore, the eccentric bearing 2 is rotatably mounted between the crank pin 4 and the connecting rod large end 7. Although the connecting rod large end portion 7 and the eccentric bearing 2 have a two-part structure, they are shown as one body in the drawings for convenience.

As shown in FIGS. 2 and 4, the right side 2a and the left side 2b of the eccentric bearing 2 in these figures are respectively connected to the inner surface 8a of the right crank arm 8 and the left crank arm 9 in the same figure. Is mounted so as to face the inner surface 9a. Further, the eccentric bearing 2 is basically pulled by the crankshaft 3 and rotates in the rotation direction of the crankshaft 3. However, although it is dragged by the crankshaft 3, the crankshaft 3
It does not necessarily rotate in the same cycle as the rotation of.

The eccentric bearing 2 is fixed at a predetermined circumferential position on the outer peripheral surface of the eccentric bearing 2, that is, at a long stroke setting position and a short stroke setting position, so that the rotating eccentric bearing 2 is integrated with the connecting rod 6. Is a lock pin 10 as a lock means for making the lock state or the anti-lock state with respect to the connecting rod 6.

The variable compression ratio mechanism 1 basically includes the eccentric bearing 2 and the lock pin 10. The eccentric bearing 2 is a cylindrical body in which a difference T between an outer diameter and an inner diameter, which is a thickness thereof, differs depending on a portion in a circumferential direction.

More specifically, the inner peripheral wall surface 1 of the eccentric bearing 2
The center axis 3 of the eccentric bearing 2, that is, the stop axis L 1 of the rotary hole 15 of the eccentric bearing 2, is shifted in parallel with the center axis L 2 of the outer peripheral wall surface 17 of the eccentric bearing 2 by a distance l in the radial direction. For this reason, the thickness of the eccentric bearing 2, that is, the difference T between the inner diameter and the outer diameter is not uniform, and the thinnest portion T19 and the thickest portion T21 of the eccentric bearing 2 are shifted by 180 ° in the circumferential direction. I have. Therefore, the thinnest portion T19
From the thickest portion T21 to the thinnest portion T21, the thickness gradually increases as it advances in the circumferential direction.
From 19, it becomes thinner as it moves in the circumferential direction.

A first hydraulic chamber 19 and a second hydraulic chamber 21 as specific holes are formed in the thinnest portion T19 and the thickest portion T21, respectively. As can be seen from FIGS. 1 to 4, inner oil passages 22 a and 22 b and outer oil passages 23 a and 23 b are respectively formed on the inner peripheral wall surface 13 and the outer peripheral wall surface 17 of the eccentric bearing 2 along their circumferential directions. Is formed.

The inner oil passages 22a and 22b are formed around the entire circumference of the inner peripheral wall 13 so as to be parallel to the entire circumference, whereas the outer oil passages 23a and 23b are
a and 23b are formed along the entire circumference of the outer peripheral wall surface 17, but the thinnest portion T19 and the thickest portion T21 in which the first hydraulic chamber 19 and the second hydraulic chamber 21 are provided.
And the thickest portion T21 and the thinnest portion T19
1 or 3, an outer oil passage 23a is located on the left side of FIG. 1 or 3, and an outer oil passage 23b is located on the right side.
Is located.

The inner oil passages 22a and 22b are in communication with the first hydraulic passages 25a and 25b, respectively. Most of the first hydraulic passages 25a and 25b are provided in the crank arm 9 and the crank arm 8, respectively. However, the distal ends of the hydraulic passages 25a and 25b pass through a part of the crank pin 4 respectively. I have.

The first hydraulic passages 25a and 25b
Are connected to an oil gallery 29 provided on the crank journal 27. Oil is supplied to the oil gallery 29 from an oil pump (not shown) as hydraulic means. This oil is used as lubricating oil,
Is used as oil for releasing the locked state of the eccentric bearing 2 with respect to the connecting rod 6 due to the above.

The first hydraulic chamber 19 and the second hydraulic chamber 21
Are oil reservoirs 30a which are both opened radially outward on the outer peripheral surface of the eccentric bearing 2, and leg-shaped passages as second hydraulic passages extending straight from the oil reservoir 30a toward the inner oil passage 22a or 22b. 30b. The leg-shaped passage 30b of the second hydraulic chamber 21 provided in the thickest portion T21 is longer. When the eccentric bearing 2 is at the long stroke setting position or the short stroke setting position, the leg-shaped passages 30b serving as the second hydraulic passages are connected to the first hydraulic passages 25a and 25b and the inner oil guide respectively. They are connected via roads 22a and 22b.

The inner oil passage 22 of the eccentric bearing 2
a between the eccentric bearing 2 and the base hole 7a of the connecting rod large end 7 from the oil pump, and between the eccentric bearing 2 and the crankpin 4 via the outer oil passages 23a and 23b. Lubricating oil is supplied.

The lock pin 10 is arranged together with a spring 39 in a hole 35 provided inside the rod portion 6a of the connecting rod 6. The hole 35 is located on the axis of the rod portion 6a, and is opened in the base hole 7a of the large end portion 7 of the connecting rod. The spring 39 disposed inside the hole 35
The locking pin 10 receives the urging force of
The hole 35 is kept in a state of always facing the base hole 7a from the hole 5a.
It is stored so that it can appear and disappear. For this reason, the lock pin 10 is movable in the axial direction of the connecting rod 6, and fits into the oil sump 30a when the eccentric bearing 2 is at the long stroke setting position or the short stroke setting position depending on the operation state of the internal combustion engine. As a result, the eccentric bearing 2 and the connecting rod 6, which have been separate bodies, are integrated.
Since the eccentric bearing 2 is fixed to the connecting rod 6 at the long stroke setting position and the short stroke setting position, the two stroke setting positions are collectively referred to as a bearing lock position.

The movement of the lock pin 10 is controlled by a lock pin retracting member described below. The member for retracting the lock pin is configured such that the lock pin 10
5a, the component members are composed of a member for projecting the lock pin 10 from the hole 35 and a member for pushing the lock pin 10 into the hole 35, The former is a spring 39, and the latter is a first hydraulic chamber 19, a second hydraulic chamber 21, an oil guide passage 22a,
22b, first hydraulic passages 25a and 25b, an oil gallery 29, and an oil pump (not shown).

When the operating state of the internal combustion engine changes, for example, when the eccentric bearing 2 is changed from the long stroke setting position to the short stroke setting position or when the eccentric bearing 2 is changed from the short stroke setting position to the long stroke setting position, the change is made. Prior to this, the lock state between the eccentric bearing 2 and the connecting rod 6 by the lock pin 10 is released, the eccentric bearing 2 is automatically placed in the anti-lock state, and the eccentric bearing 2 becomes rotatable.

Then, from an oil pump (not shown), an oil gallery 29, a first hydraulic passage 25a, an inner oil passage 22a, a leg-shaped passage 30b of the second hydraulic chamber 21, which is a second hydraulic passage, and a second hydraulic chamber 21. And from the oil pump to the oil gallery 29 -the first hydraulic passage 25b -the inner oil passage 22b -the first hydraulic passage which is the second hydraulic passage.
The first hydraulic chamber 19 via the leg-shaped passage 30b of the hydraulic chamber 19
The oil is supplied to the oil sump 30a.

The first hydraulic chamber 19 or the second hydraulic chamber 2
The oil entering 1 then supplies lubricating oil from the oil reservoir 30a to between the outer peripheral wall surface 17 of the eccentric bearing 2 and the base hole 7a of the large end 7 of the connecting rod. In addition, when the eccentric bearing 2 rotates, the outer peripheral wall 17 of the eccentric bearing 2 and the base hole 7a of the connecting rod large end 7 are formed through the outer oil passages 23a and 23b provided on the outer peripheral wall 17 of the eccentric bearing 2. Promotes lubrication between. <Function and Effect of Embodiment> Next, the function and effect of the variable compression ratio mechanism 1 will be described.

When the operating state of the internal combustion engine is lower than the middle load range or in the low / medium rotation range, the eccentric bearing 2 is moved to the position shown in FIG.
As shown in FIG. 4, the thinnest portion T19 is located at the short stroke setting position that comes to the cylinder side, and the first hydraulic chamber 1
The tip of the lock pin 10 fits into the oil sump 30a of No. 9.

When the operating state of the internal combustion engine is below the high load range or in the high or low rotation range, the eccentric bearing 2
However, as shown in FIGS. 1 and 2, the thickest portion T21 is placed at the long stroke setting position where the thickest portion T21 comes to the cylinder side.
The tip of the lock pin 10 fits into the oil reservoir 30a of the hydraulic chamber 21.

More specifically, when the operating state of the internal combustion engine falls below the medium load range or in the low-medium rotation range, the eccentric bearing 2 is automatically placed at the short stroke setting position as shown in FIGS. Become like Accordingly, when the tip of the lock pin 10 corresponds to the first hydraulic chamber 19 provided in the thinnest portion T19, the lock pin 10 is pushed toward the first hydraulic chamber 19 by the spring force of the spring 39, and the tip of the lock pin 10 Fits in the oil sump 30 a of the first hydraulic chamber 19. Therefore, the eccentric bearing 2 is locked and cannot move, so that the state at the short stroke setting position where the thinnest portion T19 is located on the cylinder side is maintained.

On the other hand, when the operating state of the internal combustion engine is in a high load range or a high rotation range, the eccentric bearing 2 is automatically placed at the long stroke setting position. As a result, when the tip of the lock pin 10 corresponds to the second hydraulic chamber 21 provided in the thickest part T21, the lock pin 10 is pushed toward the second hydraulic chamber 21 by the spring force of the spring 39, and The tip fits into the oil reservoir 30a of the second hydraulic chamber 21. For this reason, the eccentric bearing 2 is locked and cannot move, so that the state at the long stroke setting position where the thickest portion T21 is located on the cylinder side is maintained.

When the operating state changes from a state of lower than the middle load range or a state of low to middle rotation to a state of high load or high rotation, as shown in FIG. Hydraulic passage 25b-inner oil passage 22
b—Leg passage 3 of first hydraulic chamber 19 as second hydraulic passage
If oil is supplied to the oil sump 30a of the first hydraulic chamber 19 via 0b, the oil pressure of the oil sump 30a of the first hydraulic chamber 19 increases, so that the lock pin 10 resists the spring force of the spring 39. It is pushed into the hole 35.

On the other hand, when the operating state changes from the state of the high load region or the high rotation region to the state of the middle load region or lower or the low rotation region, as shown in FIG. 1 hydraulic passage 25a-inner oil passage 2
2a—If the oil is supplied to the oil reservoir 30a of the second hydraulic chamber 21 via the leg-shaped passage 30b of the second hydraulic chamber 21, which is the second hydraulic passage, the oil pressure of the oil reservoir 30a of the second hydraulic chamber 21 Is increased, the lock pin 10 is pushed into the hole 35 against the spring force of the spring 39.

As described above, when the operating state of the internal combustion engine changes, the locked state of the eccentric bearing 2 by the lock pin 10 is released prior to the change. In addition, since the eccentric bearing 2 receives the rotational force from the crankshaft 3, the lock pin 10 is moved to the first hydraulic chamber 19 or the second
When it comes out of each oil sump 30a of the hydraulic chamber 21 and becomes an unlocked state in which the locked state is released, at the same time, the eccentric bearing 2 is pulled by the crankshaft 3 and rotates in the same rotational direction as the crankshaft 3. .

The eccentric bearing 2 rotates by being dragged by the crankshaft 3 and moves 180 degrees from the short stroke set position.
と こ ろ で After the rotation, that is, when the lock pin 10
When the lock pin 10 comes to the long stroke setting position corresponding to the hydraulic chamber 21, the lock pin 10 is pushed toward the second hydraulic chamber 21 by the spring force of the spring 39. Thereafter, if the lock pin 10 enters the second hydraulic chamber 21 and the operating state is not changed and remains in the high load region or the high rotation region, the lock pin 10 is moved to the second
The fitting state of the hydraulic chamber 21 with the oil sump 30a is maintained. That is, the eccentric bearing 2 maintains the state in which the thickest portion T21 is located at the long stroke setting position where the thickest portion T21 is located on the cylinder side as shown in FIGS. 1 and 2 until the operation state changes next. .

Further, the eccentric bearing 2 is rotated by being pulled by the crankshaft 3 and rotated 180 ° from the long stroke setting position, that is, the lock pin 10
Comes to the short stroke setting position corresponding to the first hydraulic chamber 19, the lock pin 10 is pushed toward the first hydraulic chamber 19 by the spring force of the spring 39. Then, the lock pin 10 is moved to the first hydraulic chamber 1.
9 and if the operating state remains unchanged and is in the middle load range or below or in the low / medium rotation range, the lock pin 10
Keeps the first hydraulic chamber 19 fitted to the oil sump 30a. That is, the eccentric bearing 2 has its thickest portion T
19 maintains the state where it is located at the short stroke setting position, which is located on the cylinder side as shown in FIGS. 3 and 4, until the operation state changes next.

As described above, to achieve a high compression ratio state using the variable compression ratio mechanism 1, the thickest portion T21 of the eccentric bearing 2
However, the connecting rod 6 only needs to enter the compression stroke while being located on the cylinder side (upper side) as shown in FIGS. Conversely, to achieve a low compression ratio state, use the eccentric bearing 2
The connecting rod 6 only needs to enter the compression stroke while the thinnest portion T19 is located on the cylinder side as shown in FIGS.

The lock state of the eccentric bearing 2 at the bearing lock position is based on the mechanical action using only the urging force of the spring 39 (ie, no hydraulic pressure is applied), and the lock pin 10 is moved to the first position. Since the locking is performed by engaging each oil reservoir 30a of the hydraulic chamber 19 or the second hydraulic chamber 21, the maintenance of the locked state of the eccentric bearing 2 is extremely reliable. For this reason, the lock of the eccentric bearing 2 will not be released unlike the case where the locked state has been dependent on the hydraulic pressure. Therefore, the eccentric bearing 2 does not shift with respect to the connecting rod large end 7 or the crank pin 4.
Therefore, since the fluctuation of the compression ratio can be reliably prevented, the operation failure of the variable compression ratio mechanism 1 can be prevented.

Furthermore, since the lock pin 10 which engages with the first hydraulic chamber 19 or the second hydraulic chamber 21 is provided in the axial direction of the connecting rod 6, when the locking means 10 is provided in the thickness direction of the connecting rod 6, Since the thickness of the connecting rod 6 and the length of the crankshaft 3 can be reduced, the internal combustion engine can be made compact.

Further, the position where the lock pin 10 engages with the eccentric bearing 2 is the second hydraulic chamber 21 used when the operation state of the internal combustion engine is in a high load range or a high rotation range.
And the first hydraulic chamber 19 used when the operating state is lower than the medium load range or in the low-medium rotation range, so that the compression ratio can be reliably changed according to the operating state of the internal combustion engine. .

The anti-lock state is established by releasing the engagement of the lock pin 10 with the first hydraulic chamber 19 or the second hydraulic chamber 21 by the hydraulic pressure of an oil pump. First hydraulic passage 25 provided
a, 25b and leg-like passages 30b, 30b as second hydraulic passages provided in the eccentric bearing 2, and are supplied to the respective oil sumps 30a of the first hydraulic chamber 19 or the second hydraulic chamber 21. These supplies are provided when the eccentric bearing 2 is in the bearing lock position.
5a and the leg-shaped passage 30b of the second hydraulic chamber 21, which is the second hydraulic path, is connected to the leg-shaped passage 30b of the first hydraulic chamber 19, which is the first hydraulic path 25b and the second hydraulic path. It is realized by being done. Therefore, when the eccentric bearing 2 is not at the bearing lock position, the hydraulic pressure does not act in a direction to weaken the urging force of the spring 39, and when the eccentric bearing 2 is not at the bearing lock position,
The compression ratio does not fluctuate under the influence of the oil pressure. Therefore, the variation of the compression ratio can be reliably prevented by this, so that the operation failure of the variable compression ratio mechanism 1 can be prevented.

[0052]

As described above, according to the present invention, in the locked state of the eccentric bearing at the bearing locked position, the locking means is engaged with a specific hole provided in the eccentric bearing by the urging means. The anti-lock state is achieved by releasing the engagement by hydraulic pressure of hydraulic means, so that a change in compression ratio can be reliably prevented. Therefore, it is possible to prevent operation failure from occurring in the variable compression ratio mechanism.

[Brief description of the drawings]

FIG. 1 is a partially cutaway side view showing an application example of a variable compression ratio mechanism for an internal combustion engine according to the present invention and showing a case where a compression ratio is high.

FIG. 2 is a partially cutaway side view of FIG. 1;

FIG. 3 is a partially cutaway side view showing an application example of the variable compression ratio mechanism of the internal combustion engine according to the present invention and showing a case where the compression ratio is low.

FIG. 4 is a partially cutaway side view of FIG. 3;

FIG. 5 is a view for explaining a conventional variable compression ratio mechanism.

FIG. 6 is a partially cutaway side view showing a case where a compression ratio is high in a conventional variable compression ratio mechanism.

FIG. 7 is a partially cutaway side view showing a case where the compression ratio is low in the conventional variable compression ratio mechanism.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Variable compression ratio mechanism 2 Eccentric bearing 2a Right side of eccentric bearing 2b Left side of eccentric bearing 3 Crankshaft 4 Crank pin 6 Connecting rod 6a Connecting rod rod part 7 Large connecting rod end 7a Base hole of large connecting rod end 8 Crank arm 8a Crank Arm inner surface 9 Crank arm 9a Crank arm inner surface 10 Lock pin (locking means) 13 Inner peripheral wall surface of eccentric bearing 15 Rotation hole of eccentric bearing L1 Rotation hole stop shaft of eccentric bearing 17 Outer peripheral wall surface of eccentric bearing L2 Outer peripheral wall center of eccentric bearing Shaft 1 Amount of deviation between suspension axis L1 and suspension axis L2 T Thickness of eccentric bearing 19 First hydraulic chamber (specific hole) 21 Second hydraulic chamber (specific hole) 22a, 22b Oil guide path 23a, 23b Oil guide Roads 25a, 25b First hydraulic passage 29 Le gallery 30a Oil reservoir 30b Leg-shaped passage (second hydraulic passage) 35 Hole in connecting rod part 39 Spring (biasing means) T19 Thinnest part T21 Thickest part

Claims (4)

[Claims] A connecting rod for connecting a piston to a crankshaft and converting a reciprocating motion of the piston in the cylinder into a rotary motion of the crankshaft; a connecting rod large end which is a ring-shaped portion located on the crankshaft side; An eccentric bearing interposed between the crankpin of the crankshaft fitted to the large end and rotatably mounted between the inner peripheral surface of the connecting rod large end and the outer peripheral surface of the crankpin; Locking means for locking the eccentric bearing at a predetermined position in the circumferential direction using the urging force of the urging means and releasing the lock by applying hydraulic pressure against the urging force by the hydraulic means. The difference in the predetermined position at which the eccentric bearing is locked by the locking means. A variable compression ratio mechanism of the internal combustion engine, wherein the compression ratio represented by the multiple of the combustion chamber volume can be changed by changing the piston stroke. Is maintained only by the urging force of the urging means,
A variable compression ratio mechanism for an internal combustion engine, wherein the hydraulic pressure by the hydraulic means acts only on the release of the locked state. 2. The eccentric bearing according to claim 1, wherein said locking means locks said eccentric bearing by engaging with a specific hole provided in a peripheral wall surface of said eccentric bearing at a predetermined position in a circumferential direction of said eccentric bearing. The variable compression ratio mechanism for an internal combustion engine according to claim 1. 3. The specific hole formed in the peripheral wall surface of the eccentric bearing includes a hole that engages with the locking means when the operation state of the internal combustion engine is in a high load range or a high rotation range, and the operation state is 3. The variable compression ratio mechanism for an internal combustion engine according to claim 1, wherein there are at least two holes that engage with the locking means when the engine is in a middle load region or lower or in a low to middle rotation region. 4. The hydraulic pressure is supplied to the specific hole through a first hydraulic passage provided in the crankpin and a second hydraulic passage provided in the eccentric bearing.
The supply according to any one of claims 1 to 3, wherein the supply is performed by connecting the first and second hydraulic paths when the eccentric bearing is at the predetermined position. Variable compression ratio mechanism for internal combustion engines.