JPH05171964A - Variable compression ratio device for internal combustion engine - Google Patents

Abstract

PURPOSE:To attain a variable compression ratio device provided with a buffering device which has such a structure as maintaining proper buffering characteristics in the buffering device and a stable positional relation necessary for the engagement of an eccentric sleeve with a connecting rod and the traveling stroke of pistons necessary for buffering all the time. CONSTITUTION:A buffering device 20 for decelerating the rotation of a rotatable eccentric sleeve 4 which is positioned at, the larger end part of a connecting rod 3 is constituted of pistons 21 which are slidable in the tangential direction of the eccentric sleeve 4 and a casing 20A which is formed at the wall part, of the guide holes 20A1 of the pistons 21. A pair of pistons 21 are integratedly disposed at relative positions with regard to the center line which is common in the eccentric sleeve 4 and the connecting rod 3 centered, and a return spring 22 is disposed on the facing side to support outward, and there is provided an oil chamber 20B where an orifice 23 is connected at a position on the surface side facing the piston 21 in a casing 20A.

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 device for an internal combustion engine.

[0002]

2. Description of the Related Art Generally, in an automobile engine, which is one of internal combustion engines, it is necessary to prevent knocking during operation in a high load range higher than a medium load range or in a high speed rotation range of the engine. A structure capable of changing the compression ratio has been proposed for the purpose of increasing the thermal efficiency and improving the fuel consumption rate during operation in a low load region.

As the structure of this variable compression ratio device, there is one described in the specification of Japanese Patent Application No. 2-125166, which is a prior application by the present applicant. The structure described in the above specification will now be described as follows. That is, in FIG. 2, the connecting rod 3 pivotally supported at the large end by the crankpin 2 of the crankshaft 1 is rotatable between the bearing hole at the large end and the crankpin 2 at the pivotal support. The eccentric sleeve 4 is interposed. The center of the eccentric sleeve 4 is eccentric to the center of the crank pin 2, and the centrifugal force generated by the rotation of the crank pin 2 causes the crank pin 2 to rotate.
When rotating upward, the center position of the piston pin 6 on the piston 5 side can be switched between a maximum eccentric position for raising the center position of the piston pin 6 on the side of the connecting rod 3 and a minimum eccentric position for lowering the center position of the piston pin 6 on the side of the connecting rod 3. Is becoming

The eccentric sleeve 4 has flanges 4A and 4B at both ends along the axial direction of the crankpin 2.
Are provided on the outer circumference of these flanges, for example, 1
Engagement portions 4A1 and 4B1 made of notches are formed at alternating positions with a phase of 60 degrees, and the outer peripheral surface between these engagement portions is for engaging pins of a shock absorber described later. A notch for guide 4C formed in a stepped shape is provided. The guide notch 4C is provided on the crankshaft 1
When the flange 4A and the flange 4B are viewed from the front and back directions with respect to the rotation direction, the rotation directions are opposite to each other. The direction of the uneven part is set so that it can hit the pin.

On the other hand, an eccentric sleeve lock mechanism 7 for switching the connection with the eccentric sleeve 4 is provided inside the connecting rod 3 sandwiched by the flange of the eccentric sleeve 4. Eccentric sleeve lock mechanism 7
Is provided with a piston 7A that is slidable along the axial direction of the crankshaft 1 while facing the engaging portion formed on the flange of the eccentric sleeve 4. This piston 7A
Is inserted into a hydraulic chamber provided inside the connecting rod 3 and is disposed between a collar formed in a part in the sliding direction and a cap 7B fixed to one side of the hydraulic chamber. As shown in FIG. 2, the return spring 7C is normally urged toward the engaging portion of one of the flanges so as to engage it. And in the hydraulic chamber,
Oil passages 8 and 9 are connected at positions on both sides of the flange in the sliding direction, and the sliding direction of the piston 7A can be set by controlling the supply of oil from the oil passages 8 and 9. .. In FIG. 2, the piston 7A slides to the left by the bias of the return spring 7C by setting the pressure of the oil in the oil passages 8 and 9 to the standard pressure, and the engaging portion 4A1 formed on the flange 4A. The position where the eccentric sleeve 4 and the connecting rod 3 are integrated with each other is set. Further, in FIG. 4, the oil supply pressure in the oil passage 8 is set to a value equal to or higher than a value obtained by adding the biasing pressure of the return spring 7C to the standard pressure, thereby making the piston 7A
Slides to the right against the bias of the return spring 7C, engages with the engaging portion 4B1 formed on the flange 4B, and sets the position in which the eccentric sleeve 4 and the connecting rod 3 are integrated. It is supposed to be done. In the engagement state of the piston 7A described above, for example, in the case of the state shown in FIG. 2, as shown in FIG. 3, the position of the piston pin 6 is the minimum eccentric position with respect to the center of the bearing surface of the connecting rod 3. Can be set (the amount of eccentricity indicated by symbol L1 in FIG. 3), and in the case of the position shown in FIG. 4, the position of the piston pin 6 is the bearing of the connecting rod 3 as shown in FIG. It is assumed that the maximum eccentric position can be set with respect to the center of the surface (the eccentric amount shown by reference symbol L2 in FIG.
2> L1). In the former position, it is possible to realize a low compression ratio state in the most contracted state, and in the latter position, it is possible to realize a high compression ratio state in the most expanded state. ing. At low compression,
A compression ratio that does not cause knocking in the engine is obtained, and is usually equivalent to the compression ratio set in the engine,
On the other hand, in the high compression ratio state, it is usually possible to set a compression ratio higher than the compression ratio set in the engine. In addition, these positions may be set by the controller of the engine (not shown) by determining the sliding direction of the piston of the eccentric sleeve lock mechanism in response to the input of information on the engine load and the engine speed. When the engine is in the medium load range or below, the piston 7A as shown in FIG.
If the sliding direction of the engine is a high load range or a high rotation range of the engine which is equal to or higher than the medium load range, the sliding direction of the piston 7A as shown in FIG. 4 is set. ..

On the other hand, a shock absorber 10 is provided at the bottom position of the large end of the connecting rod 3. When the piston 7A of the eccentric sleeve lock mechanism 7 is engaged with the rotating eccentric sleeve 4, the shock absorbing device 10 buffers the rotational force of the eccentric sleeve 4 to damp the rotation, and the moving direction is different. This is for facilitating engagement of the related piston 7A. As shown in FIGS. 3 and 5, the shock absorber 10 is provided with a hydraulic chamber inside the casing 10A located at the bottom of the connecting rod 3 and slides in the tangential direction of the eccentric sleeve 4 inside the hydraulic chamber. Direction piston 11 is inserted and fitted, and the piston 11 is urged by the return springs 12 arranged between the end surfaces on both sides in the sliding direction and the inner wall of the hydraulic chamber. It is designed to be held in position. In addition, a pin 11A extending in a direction perpendicular to the sliding direction is fixed to the piston 11 at a position that radially opposes the pin 11A.
It protrudes outward from the elongated guide hole 10B formed in 0A. This shock absorber 10 includes an eccentric sleeve 4
When the piston 11 moves in a direction in which the return spring 12 is contracted by abutting the end edge portion of the guide notch 4C on the side and the pin 11A, the piston 11 is contracted in addition to the contracting force for the return spring 12. The displacement of the eccentric sleeve 4 is reduced by damping the movement of the piston 11 by the discharge resistance when the oil in the hydraulic chamber in which the return spring 12 on the side is arranged flows out from the orifice 10C. And
When the piston 11 is sufficiently decelerated in the hydraulic chamber and the urging force of the return spring 12 exceeds the sliding force, the urging force of the return spring 12 causes the eccentric sleeve 4 to return to its neutral position. The engagement portion provided on the flange and the piston 7A of the eccentric sleeve lock mechanism 7 can be engaged with each other.

[0007]

In the structure of the shock absorber described above, the return spring 12 holds the piston 11 in the neutral position in the hydraulic chamber. Since the floating state is maintained in the reciprocating direction corresponding to the sliding direction, the following problems may occur. That is, by increasing the cushioning effect on the eccentric sleeve 4, the eccentric sleeve 4 is sufficiently decelerated, thereby facilitating the engagement between the engagement portion on the eccentric sleeve 4 side and the piston on the eccentric sleeve locking mechanism side. If it is desired to do so, it is conceivable to increase the movement stroke of the piston 11 required for buffering. But,
If the guide hole 10B is lengthened in order to satisfy such a requirement, the position of the rear end portion of the piston 11 sliding in the cushioning direction, that is, the forward and backward movement direction of the reciprocating movement, is set in this direction. May pass through the end edge of the guide hole 10B extending in the backward direction on the opposite side to the guide hole 10B. In this case, the rear end of the piston 11 in the sliding direction and the guide hole 1 may be passed.
There is a possibility that a part of the oil pressure chamber 0B is opened, the hydraulic chamber communicates with the outside, and the oil in the hydraulic chamber leaks to the outside.
Therefore, when the guide hole 10B is made long, the oil shortage occurs due to the oil leakage from the hydraulic chamber, and the stroke for moving the piston necessary for buffering cannot be set. Therefore, the length is naturally set. There are limits, which also mean that the cushioning effect has to be compromised to some extent.

Further, since the piston 11 is held in the neutral position to maintain a floating state in which it can move in any of the so-called reciprocating directions, the return spring 12 is provided.
Must be fairly weakly elastic so that the piston can move in either direction. This kind of
When the spring 12 is used, as shown in FIG. 6, due to the inertia force when the eccentric sleeve 4 is rotating,
One of the return springs 12 is easily contracted, it becomes difficult to hold the piston 11 in the neutral position of the piston 11, and the piston 11 vibrates in the sliding direction. Therefore, in such a case, the engagement position between the decelerated eccentric sleeve 4 side engaging portion and the eccentric sleeve lock mechanism 7 side piston becomes uncertain, and the engaging portion and the piston have an appropriate engaging relationship. Not only is not set, but the sliding start position for obtaining the stroke of piston movement required for cushioning will be displaced,
The movement stroke of the piston required for buffering becomes unstable.

Therefore, in view of the problem in the variable compression ratio device having the above-described shock absorber, the object of the present invention is to maintain proper shock absorbing characteristics in the shock absorber, and further, to engage the eccentric sleeve and the connecting rod. The object of the present invention is to obtain a variable compression ratio device equipped with a shock absorber having a structure capable of keeping constant the positional relationship required for the above and the stroke of movement of the piston necessary for shock absorption.

[0010]

In order to achieve this object, the present invention provides a piston that slides in a cylinder of an internal combustion engine, and one end of which is pivotally supported by the piston and the other end of which is pivotally supported by a crankshaft. In an internal combustion engine having a connecting rod that converts the reciprocating motion of the piston into a rotary motion of the crankshaft, the internal combustion engine is arranged between the other end of the connecting rod and the crankshaft, and the axial direction of the connecting rod. A pair of flanges that are located so as to sandwich the connecting rod at both ends along the eccentric sleeve, in which the center position of the outer peripheral surface and the inner peripheral surface are eccentric, and the outer periphery of the eccentric sleeve have different phases. First and second engaging portions that are alternately formed and a guide notch that is notched only in a predetermined section between these engaging portions, and the above-mentioned connector. A cushioning device that engages with the guide notch of the eccentric sleeve to decelerate the rotation of the eccentric sleeve. The device is composed of a piston slidable in a tangential direction of the eccentric sleeve, and a casing into which the piston is inserted and a guide hole of the piston is formed in a wall portion,
The piston is provided in a pair at a relative position with a common center line of the eccentric sleeve and the connecting rod as a boundary, and a structure in which a return spring is arranged on the opposing surface side is urged outward. The casing has a structure in which an oil chamber having an orifice connected to the piston is provided at a position on the opposite side of the piston.

[0011]

According to the present invention, the piston of the shock absorber slides by acting only on the movement in the so-called forward direction with respect to the moving direction of the guide notch on the eccentric sleeve side, and in the return direction. Since it does not act on the movement to, the length of the guide hole can be shortened because only the movement amount in one direction can be set.

Further, according to the present invention, the amount of movement of the piston is reduced because it is intended for only one direction.
As a result, the length of the return spring can be shortened, and a return spring having a strong elastic force that reduces the amount of bending can be used.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a sectional view showing a shock absorber which is a main part of a variable compression ratio device according to this embodiment using the structure shown in FIGS. 2 to 4. feature is,
This is because the piston provided in the shock absorber has a paired structure. It should be noted that the same components as those shown in FIGS. 2 to 4 are designated by the same reference numerals. That is, the shock absorber 20 includes the casing 20A located at the bottom of the connecting rod 3 as in the case shown in FIGS. 2 to 4, and the connecting rod 3 and the eccentric sleeve are provided in the casing 20A. A pair of pistons 21 that are slidable in the tangential direction of the eccentric sleeve 3 are respectively inserted at positions facing each other with the common center line C of 4 as a boundary. Further, the piston 21 is normally biased toward the inner wall surface of the casing 20A by disposing the return spring 22 on the surface on the opposite side, and the movement due to this bias is caused by the casing 20A.
The back surface of the piston 21 abuts against the inner wall surface of the piston 21 to prevent it. Therefore, the piston 21 in the normal position can be moved toward the opposing piston 21 side, in other words, the common center line C side by applying a force against the bias of the return spring 22. This force is generated when the pin 21A extending in the direction perpendicular to the sliding direction and the end of the guide notch 4C on the side of the eccentric sleeve 4 come into contact with each other.

On the other hand, in the wall portion of the casing 20A,
The pin 21A fixed to the piston 21 is attached to the wall portion of the piston 21 on the side where the pin 21A is extended.
Guide hole 20A for guiding the sliding direction by inserting through
1 (a hole indicated by a chain double-dashed line in FIG. 1) is formed, and this guide hole 20A1 has a length in the longitudinal direction that is required when the piston 21 moves only in one direction. It is said that. Therefore, the length of the guide hole 20A1 is not the center of the reciprocating direction of the piston 21 as compared with the case shown in FIGS. 2 to 4 in which the length of the guide hole is set to reciprocate. Since the initial position is set on one side, the length is shortened by the length of only one side in the reciprocating direction. The length of the guide hole 20A1 is set so that the rear end thereof does not protrude from the hole edge when the piston 21 slides, so that the rear end position of the piston passes the hole edge of the guide hole 20A1. It goes without saying that we try not to do this.

In the interior of the casing 20A, the oil chamber 20B is provided between the end portions of the piston 21 which face each other.
This oil chamber 20B is connected to an orifice 23 provided at the center of the hydraulic chamber in the sliding direction of the piston, and the oil stored inside via the orifice 23 is, for example, the connecting rod 3 It can be discharged toward the bearing surface of.

Since this embodiment has the structure as described above,
Normally, the piston 21 is pressed against the wall portion of the casing 20A by the urging force of the return spring 22 and is prevented from moving. Then, from this normal position, when the edge portion of the guide notch 4C of the eccentric sleeve 4 abuts the piston 21, the piston 21 moves toward the opposite piston 21 side in accordance with the rotation direction of the eccentric sleeve 4. Is pushed toward. Therefore, the return spring 22
Is contracted, and the repulsive force against the contracting action force on the return spring 22 at this time is used as one of the buffering forces as the piston 2
1 is transmitted to the eccentric sleeve 4 and the eccentric sleeve 4 is decelerated by the discharge resistance of the oil flowing into the orifice 23 from the oil chamber 20B.

According to this embodiment, since the orifice is provided at a position common to the sliding of the piston 21, the oil passage structure can be simplified.

Further, according to this embodiment, since the return spring 22 of the piston 21 need only have a function of allowing the piston to move only in one direction, the conventional structure, that is, the reciprocating direction of the piston. The length of the return spring 22 can be shortened as compared with the structure in which the return spring 22 can be moved to. Therefore, it is possible to select a spring having a large elastic force that can reduce the amount of bending, and it is possible to improve the cushioning capacity required for decelerating the eccentric sleeve. Further, according to the present embodiment, since the elastic force of the spring described above can be increased, the force for urging the piston 21 can be strengthened, so that the piston 21 is effective against the inertial force generated when the eccentric sleeve 4 rotates. Displacement can be suppressed and vibration can be suppressed.

According to this embodiment, the casing 2
The guide hole 20B formed in 0A is the piston 21
Since it only has to function for movement in one direction, the length in the longitudinal direction can be shortened as compared with the case where the piston is guided over the entire stroke of reciprocating movement as in the conventional structure, and it can be simply In other words, the length can be halved. Therefore, only by setting the sliding start position of the piston 21 to one end in the longitudinal direction of the guide hole 20B in consideration of the movement in only one direction, there is no length in the longitudinal direction that enables the movement in the opposite direction. Therefore, it is possible to prevent the situation in which the rear end portion of the piston 21 located rearward of this one end passes through a part of the guide hole 20B, thereby preventing oil leakage from the oil chamber. It can be prevented. In addition, the casing 20 in this embodiment
The guide hole 20B of A can be shortened because it is intended for sliding of the piston in only one direction as compared with the conventional structure. Therefore, if it is desired to expand the movement stroke of the piston for cushioning, Compared with the conventional one, the length can be easily extended based on the half length. Furthermore, according to the present embodiment, the size of the piston 21 in the sliding direction can be reduced corresponding to the movement in only one direction, so that the weight of the piston alone can be reduced, which contributes to the reduction of vibration when inertia occurs. can do.

[0021]

As described above, according to the present invention, the pistons provided in the shock absorber are provided in a state of facing each other, the return spring is disposed between the facing surfaces, and the oil chamber is provided. The piston needs to function only for sliding in one direction, so that the length of the guide hole on the casing side provided for guiding the piston is the length for guiding the entire reciprocating direction. It can be shorter than. Therefore, as compared with the conventional guide hole for a reciprocating piston, by omitting a length commensurate with one movement, it is possible to prevent the rear end of the piston from passing over the guide hole when the piston slides.
This prevents a situation in which the oil in the oil chamber leaks out through the guide hole, and it is possible to avoid a change in the cushioning characteristic due to an oil shortage during cushioning.

Further, according to the present invention, since the moving stroke of the piston described above can be shortened, it is possible to use the return spring whose length is shortened and elastic force is increased accordingly. Therefore, it is possible to prevent the piston from inadvertently moving with respect to the inertial force generated when the eccentric sleeve rotates, thereby maintaining the sliding start position of the piston for cushioning at a predetermined position. Therefore, the moving stroke of the piston and the engaging relationship with the connecting rod side, which are necessary for the cushioning set on the basis of this position, can be made constant at all times.

[Brief description of drawings]

FIG. 1 is a sectional view showing a main part of a variable compression ratio device according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view for explaining one aspect of a conventional structure of a variable compression ratio device.

FIG. 3 is a view in the direction of the arrow shown in FIG.

FIG. 4 is a partial cross-sectional view for explaining another aspect of the conventional structure of the variable compression ratio device.

FIG. 5 is a view in the direction of the arrow shown in FIG.

FIG. 6 is a schematic diagram for explaining a problem in the conventional structure shown in FIGS. 2 to 4.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 crankshaft 2 crankpin 3 connecting rod 4 eccentric sleeve 4A, 4B flange 4A1, 4B1 engaging part 4C notch for guide 7 eccentric sleeve block mechanism 7A eccentric sleeve block piston 20 shock absorber 20A casing 20A1 Guide hole 20B Oil chamber 21 Piston 22 Return spring

Claims (1)

[Claims] 1. A piston that slides in a cylinder of an internal combustion engine,
An internal combustion engine having a structure in which one end of the piston is pivotally supported and the other end is pivotally supported by a crankshaft, and the reciprocating motion of the piston is converted into rotational motion of the crankshaft. A pair of flanges, which are arranged between the other end and the crankshaft, are located at both ends along the axial direction of the connecting rod so as to sandwich the connecting rod, and the center position between the outer peripheral surface and the inner peripheral surface is provided. And an eccentric sleeve which is eccentric, first and second engaging portions which are alternately formed with different phases on the outer circumference of the flange, and a guide which is notched only in a predetermined section between these engaging portions. Notch, a lock member provided so as to alternately project from the inside of the connecting rod toward the flange portion, and the eccentric sleeve. A shock absorber for decelerating the rotation of the eccentric sleeve by engaging with the guide notch, wherein the shock absorber is a piston slidable in the tangential direction of the eccentric sleeve, and the piston is inserted and fitted to the piston. And a casing having a guide hole formed in a wall portion thereof, the pistons are provided at a relative position with a common center line of the eccentric sleeve and the connecting rod with respect to the tangential direction as a boundary, and are provided as a pair and face each other. The structure is urged outward by disposing a return spring on the surface side of the casing, and the casing has a structure in which an oil chamber having an orifice connected at a position of the surface side where the pistons face each other is provided. And a variable compression ratio device for an internal combustion engine.