JP2002155769A - Variable compression ratio mechanism of reciprocation type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid a vibration deterioration in a right and left direction caused by an existence of a control link for restricting a motion. SOLUTION: The combined link type variable compression ratio mechanism is provided with an upper link 3 of which one end is connected to a piston pin 2; and a lower link 7 connected to the other end of the upper link 3 through a connection pin and connected to a crank pin 6 of a crank shaft 5. The lower link 7 is extended at an opposite side to the connection pin 4 and a motion track is restricted by engaging a slide element 22 at a tip end thereof with a guide groove 13 of a rail member 11. When a pivotable position of the rail member 11 is varied by a cam mechanism 15, a compression ration is varied. By using the rail member 11 instead of a conventional control link, an inertia mass reciprocating in a right and left direction does not exist and a vibration is reduced.

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 a reciprocating internal combustion engine in which a piston top dead center position is changed by using a double-link type piston-crank mechanism.

[0002]

2. Description of the Related Art As a conventional variable compression ratio mechanism of a reciprocating internal combustion engine, a mechanism utilizing a double-link type piston-crank mechanism as disclosed in Japanese Patent Application Laid-Open No. 9-228858 is known. ing. This is an upper link with one end connected to the piston via a piston pin, and connected to the other end of the upper link,
A lower link connected to a crankpin of the crankshaft; and a control link connecting the lower link to the internal combustion engine body to restrain movement of the lower link. The dynamic support position is controlled by the eccentric cam. In this device, the movement of the piston is transmitted to the lower link via the upper link, but as an instantaneous movement, the lower link attempts to swing around the connection point with the control link, and the lower link is moved. The movement of the piston is transmitted to the crank pin via the crank pin. Since the crankpin rotates about the main journal of the crankshaft, the connection point between the lower link and the control link tries to reciprocate in relation to the radius of rotation.
That is, the control link swings back and forth. The swing fulcrum position at the end of the control link changes according to the rotation position of the eccentric cam, and accordingly, the top dead center position of the piston and, consequently, the compression ratio change.

[0003]

As described above, in the conventional variable compression ratio mechanism using the control link as the movement restricting means of the lower link, the control link swings in the left-right direction with the rotation of the crankshaft. Therefore, due to the inertial load of the control link, a new vibration component is generated in the internal combustion engine, for example, the horizontal vibration excitation force as shown in FIG. 13 increases, and the vibration noise characteristics of the internal combustion engine deteriorate. Since the control link is usually arranged substantially along the direction of the piston reciprocating movement,
As a result of this reciprocating motion, vibration along a direction substantially perpendicular to the cylinder is deteriorated.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention is to constitute a movement restricting means for a link member without using a control link having a large reciprocating mass.

That is, according to the first aspect of the present invention, the piston pin of the piston and the crankpin of the crankshaft are connected by a link row comprising a plurality of link members rotatably connected to each other. A reciprocating internal combustion engine having a motion restricting means for restricting the motion of one link member so as to limit the motion, and wherein a compression ratio is changed by changing a mode of motion restriction by the motion restricting means. In the variable compression ratio mechanism of the above, the movement restricting means comprises a rail member having a guide groove of a predetermined shape for reciprocatingly guiding one point of the link member, and that the compression ratio changes due to the movement of the rail member. Features.

In this configuration, one point of the link member reciprocates along the guide groove of the rail member with the rotation of the crankshaft. In other words, the movement of the link member is restricted so that one point of the link member can move only along the guide groove, and the movement of the link row between the piston and the crankshaft is limited as a piston-crank mechanism. Exercise. When the link row is composed of three or more link members, additional motion restraining means for another link member is provided. Then, when the position of the rail member, that is, the guide groove in the internal combustion engine body is changed, the initial posture of each link member changes, and the piston top dead center position and thus the compression ratio change.

[0007] The second aspect of the present invention is a more specific example.
According to the invention, the guide groove is an arc or a straight line having a constant radius of curvature, and the slider provided with an arc surface or a flat sliding surface having the same radius of curvature so as to conform to the arc is linear. It is rotatably attached to the link member.

In this device, the slider comes into wide surface contact with the guide groove and smoothly reciprocates.
This is advantageous in terms of lubrication durability.

According to the third aspect of the present invention, the guide groove has a shape in which the radius of curvature is not constant or the centers of a plurality of radii of curvature are located on opposite sides of the guide groove. A slider having a cylindrical sliding surface that engages with the slider is attached to the link member.

In the conventional control link, the connection point with the link member reciprocates along a simple arc-shaped trajectory, but with the guide groove of the present invention,
The movement of a certain point of the link member can be guided along a desired trajectory without being limited to such an arc shape. In other words, the guide groove is formed into a shape whose radius of curvature is not always constant, and is engaged with the cylindrical slider, so that the degree of freedom in design becomes very large.

According to a fourth aspect of the present invention, the slider attached to the link member projects on both sides of the link member, and engages with a pair of guide grooves arranged on both sides of the link member. It is characterized by having. In this case, the link member is guided on both sides along the pair of guide grooves, so that a smooth movement can be secured while resisting a large combustion load. In particular, support from both sides is possible without increasing the size of the link member that moves with the rotation of the crankshaft. In addition, a pair of guide grooves can be provided in a pair of rail members, respectively.
It is also possible to branch the two rail members into, for example, a bifurcated shape and provide them on the inner facing surfaces.

According to a fifth aspect of the present invention, the guide groove is formed so as to penetrate the rail member in a slit shape, and both ends of a slider disposed through the guide groove are connected to the link. It is characterized by being supported by a member. In this device, the slider is supported from both sides, and a smooth movement can be ensured while also resisting a large combustion load.

Further, in the invention according to claim 6, the rail member is swingably supported by the internal combustion engine main body, and a swing position of the rail member is controlled by a cam mechanism for changing a compression ratio. It has become.

[0014]

In the variable compression ratio mechanism of the reciprocating internal combustion engine according to the present invention, the motion of the link member can be restricted without using the reciprocating swinging control link. Since the rail member does not substantially move, generation of a vibration component due to the conventional reciprocating movement of the control link can be avoided, and the vibration noise characteristics of the internal combustion engine are improved. Moreover, since the inertia load of the conventional control link is not received, it is advantageous in terms of the bearing load of each part of the piston-crank mechanism. Further, it is possible to arbitrarily set the shape of the guide groove without being restricted by the length of the arm or the center of rotation of the conventional control link.

In particular, according to the second aspect of the present invention, the guide groove and the slider come into wide surface contact with each other, so that smooth movement can be ensured and lubrication durability is advantageous.

According to the third aspect of the present invention, the degree of freedom in designing the shape of the guide groove is increased, and it is possible to obtain optimum characteristics in view of changes in the compression ratio and characteristics of the piston-crank mechanism. Become.

According to the fourth aspect of the present invention, since the link member is guided on both sides by the pair of guide grooves, a smooth movement can be ensured without any one-sided contact due to the inclination of the slider. Moreover, there is no increase in the size of the link member or increase in the inertial mass.

According to the fifth aspect of the present invention, the guide groove engages with the center of the slider supported from both sides.
As in the case of the fourth aspect, a smooth movement can be ensured without causing any one-sided contact due to the inclination of the slider. Moreover, in this case, there is an advantage that only one guide groove requiring high-precision finishing is required.

Further, according to the configuration of the sixth aspect, similarly to the conventional control link, the compression ratio can be variably controlled with a simple cam mechanism.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view of an internal combustion engine provided with a variable compression ratio mechanism according to the present invention, particularly showing a state where a piston 1 is at an intermediate position in a stroke. Also, FIG.
The main part is shown as a diagram viewed from the left side of FIG.

This variable compression ratio mechanism comprises an upper link 3 having one end connected to a piston 1 via a piston pin 2.
And a lower link 7 that is swingably connected to the other end of the upper link 3 via a connecting pin 4 and that is connected to a crank pin 6 of a crankshaft 5. That is, the piston 1 and the crankshaft 5 are connected by a link row including the upper link 3 and the lower link 7. The crankshaft 5 is rotatably supported between the bulkhead 9 of the cylinder block 8 and the main bearing cap 10.

The lower link 7 extends from a bearing portion for the crank pin 6 to a side opposite to the connecting pin 4.
The movement trajectory of the tip is restricted by the rail member 11. Specifically, the rail member 11 has a plate shape, and is arranged in a pair along both sides of the lower link 6. The rail member 11 has a slit-shaped guide groove substantially along a direction orthogonal to the center axis of the cylinder 12. An opening 13 is formed. The guide groove 13 is formed to have a constant width, and as shown in FIG. 1, has a loose arc shape having a constant radius of curvature. Further, the rail member 11 is rotatably supported by a shaft 14 at one end portion away from the crankshaft 5 and its swing position is
It is positioned by the cam mechanism 15. Shaft 1
4 is fixed between the bulkheads 9 as shown in FIG. The cam mechanism 15 uses a camshaft 16 rotatably supported by the bulkhead 9.
The camshaft 16 is linked to a motor (not shown) via a gear train 17 such as a worm gear, and has a small-diameter eccentric shaft portion 16a at a position corresponding to the rail member 11, and the eccentric shaft portion 16a , A pair of blocks 18, 18
Through the recess 30 of the rail member 11.
Therefore, when the camshaft 16 is rotated by a motor (not shown), the pair of rail members 11 swings up and down integrally.

On the other hand, a cylindrical boss 21 is formed at the end of the lower link 6, and a substantially columnar slider 22 is rotatably attached thereto. As shown in FIG. 5, the slider 22 has a cylindrical portion 22a rotatably fitted to the boss portion 21 in the middle, and has a guide groove 1 as shown in FIG.
3 are processed into a two-sided width shape, and especially, upper and lower sliding surfaces 22c, 22c
Are formed on an arc surface having the same radius of curvature as the radius of curvature of the guide groove 13. When the slider 22 is attached to the rail member 11, the end 22b protrudes to both sides, and is slidably engaged with the guide groove 13.

In the above arrangement, the lower link 7 swings up and down with the slider 22 as a swing fulcrum, and rotates the crank pin 6 as the piston 1 moves up and down. For example, FIG. 3 shows a state where the piston 1 is almost at the top dead center position. The slider 22 is provided in the guide groove 13 corresponding to the crank radius of the crank pin 6.
Slide back and forth along FIG. 4 shows a state where the rail member 11 is swung upward by the cam mechanism 15 as compared with the state shown in FIG.
Is changed, the posture of the lower link 7 changes even if the crank pin 6 is at the same position, and finally the position of the piston 1 changes, so that the top dead center position of the piston 1 and consequently the compression ratio changes. Will do.

According to the structure of this embodiment, since there is no large inertial mass swinging right and left as compared with the structure using the conventional control link, as shown in FIG. Higher-order vibration components are greatly reduced, and the vibration noise level is reduced as a whole. At the same time, since the inertial mass of the conventional control link can be removed, the bearing load on each part of the sliding portion can be reduced. FIG.
Shows the bearing load of each part of the present embodiment, and FIG. 15 shows the bearing load of each part of the conventional example. The “between L rails” in FIG. 14 refers to the lower link 7 and the rail member 11.
15 means “bearing load”, and “between LC” in FIG.
Means a bearing load between the lower link and the control link.

Further, according to the above configuration, since the radius of curvature of the guide groove 13 and the radius of curvature of the sliding surface 22c of the slider 22 are equal, it is possible to secure a sufficiently large sliding area between them. Yes, it can sufficiently withstand a large reaction force due to the combustion load, and is advantageous in lubrication durability. Further, since the lower link 7 is supported from both sides by the pair of rail members 11, the slider 22 and the guide groove 1 are supported.
There is no one-side contact on the sliding surface with the lower link 3, and the lower link 7 can be positioned in the axial direction at the same time.

FIGS. 6 to 8 show a second embodiment of the present invention. In this embodiment, the rail member 1
The guide groove 13 formed in FIG. 1 is not a simple arc, but has a complicated shape in consideration of various characteristics such as a change in compression ratio and characteristics of a piston-crank mechanism as shown in FIG. Here, the above-mentioned complex shape is a shape in which the radius of curvature is not constant, or a shape in which the center of the radius of curvature is located on the opposite side across the guide groove 13, and is a shape formed by a combination of these two shapes. You may. As shown in FIG. 8, the slider 22 guided by the guide groove 13 has an end 22b engaged with the guide groove 13 formed in a cylindrical shape having a diameter substantially equal to the width of the guide groove 13. ing. That is, the sliding surface 22c has a cylindrical surface. The slider 22 may be fixed to the boss 21 of the lower link 7 so as not to rotate. However, in order to avoid local wear, the slider 22 is rotatably supported as in the above-described embodiment. Is preferred.

According to this embodiment, the degree of freedom in designing the shape of the guide groove 13 is increased, and, for example, the characteristics of the piston-crank mechanism can be further optimized.

Next, FIGS. 9 to 11 show a third embodiment of the present invention. In this embodiment, as shown in FIG. 10, the distal end of the lower link 7 near the rail member 11 has a forked shape, and the rail member 11 is located in the central concave portion. A guide groove 13 is formed in the rail member 11 so as to penetrate in a slit shape, and a slider 22 penetrates the guide groove 13. That is, the slider 22 is supported by the lower link 7 on both sides, and the center portion is engaged with the guide groove 13. FIG.
Shows a specific configuration of the slider 22. As shown in FIG. 3B, the slider 22 has two end portions 22d, 2d.
2e has a cylindrical shape, and has a sliding surface 22f in an intermediate portion. The cylindrical ends 22d and 22e are rotatably supported by the boss 21 at the tip of the rail member 11, respectively. In this embodiment, as in the first embodiment, the guide groove 1
Reference numeral 3 denotes an arc having a constant radius of curvature, and the sliding surface 22f is formed on an arc surface having the same radius of curvature so as to conform to this. It is also possible to make the guide groove 13 a complicated shape as in the second embodiment. In this case, the sliding surface of the intermediate portion is replaced with a small-diameter cylindrical surface as in the second embodiment. I just need. In order to assemble the slider 22 into the guide groove 13, one end 22e is formed in advance as a separate member as shown in FIG. It is designed to be integrated by screwing or the like.

According to the structure of this embodiment, the guide groove 13
Is supported from both sides by the lower link 7, so that the supporting rigidity is improved, and the sliding surface between the slider 22 and the guide groove 13 may be one-sided. Absent. In particular, since there is only one guide groove 13 requiring high-precision finishing, there is an advantage that the processing is easy.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a first embodiment of an internal combustion engine provided with a variable compression ratio mechanism according to the present invention.

FIG. 2 is a cross-sectional view showing the main part from the side.

FIG. 3 is a sectional view similar to FIG. 1, showing a state where the piston is near top dead center;

FIG. 4 is a cross-sectional view showing a state where a rail member swings.

FIG. 5 is a perspective view of a slider.

FIG. 6 is a sectional view of an internal combustion engine showing a second embodiment of the present invention.

FIG. 7 is a cross-sectional view showing the main part from the side.

FIG. 8 is a perspective view of a slider according to a second embodiment.

FIG. 9 is a sectional view of an internal combustion engine showing a third embodiment of the present invention.

FIG. 10 is a cross-sectional view showing the main part from the side.

FIG. 11 is a perspective view of a slider according to a third embodiment.

FIG. 12 is a characteristic diagram showing horizontal vibration of the internal combustion engine of the first embodiment.

FIG. 13 is a characteristic diagram showing horizontal vibration of a conventional internal combustion engine.

FIG. 14 is a characteristic diagram showing a bearing load of each sliding portion in the internal combustion engine of the first embodiment.

FIG. 15 is a characteristic diagram showing a bearing load of each sliding portion in a conventional internal combustion engine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Piston 3 ... Upper link 5 ... Crank shaft 6 ... Crank pin 7 ... Lower link 11 ... Rail member 13 ... Guide groove 22 ... Slider

Claims (6)

[Claims] 1. A piston pin of a piston and a crankpin of a crankshaft are connected by a link row composed of a plurality of link members rotatably connected to each other, and the movement of the link row is limited.
In a variable compression ratio mechanism of a reciprocating internal combustion engine, comprising a motion restraining means for restraining the motion of one link member, and changing a compression ratio by changing a mode of motion restraint by the motion restraining means, The reciprocating internal combustion engine, wherein the movement restricting means comprises a rail member having a guide groove of a predetermined shape for guiding one point of the link member in a reciprocating manner, and a movement of the rail member changes a compression ratio. Variable compression ratio mechanism. 2. The slider according to claim 1, wherein the guide groove has an arc or a straight line having a constant radius of curvature, and a slider having an arc surface or a flat sliding surface having the same radius of curvature so as to coincide with the arc. 2. A variable compression ratio mechanism for a reciprocating internal combustion engine according to claim 1, wherein said variable compression ratio mechanism is rotatably attached to said link member. 3. The guide groove has a shape in which a radius of curvature is not constant or a center of a plurality of radii of curvature is located on opposite sides of the guide groove, and has a cylindrical shape engaged with the guide groove. 2. A variable compression ratio mechanism for a reciprocating internal combustion engine according to claim 1, wherein a slider having a sliding surface is attached to said link member. 4. A slider attached to the link member protrudes on both sides of the link member, and engages with a pair of guide grooves arranged on both sides of the link member. The variable compression ratio mechanism for a reciprocating internal combustion engine according to claim 1. 5. The guide groove is formed so as to penetrate the rail member in a slit shape, and both ends of a slider disposed through the guide groove are supported by the link member. The variable compression ratio mechanism for a reciprocating internal combustion engine according to any one of claims 1 to 3, wherein: 6. The rail member is swingably supported by an internal combustion engine main body, and a swing mechanism of the rail member is controlled by a cam mechanism to change a compression ratio. A variable compression ratio mechanism for a reciprocating internal combustion engine according to any one of claims 1 to 5.