JP2008069753A - Variable stroke characteristics engine - Google Patents

Abstract

A variable stroke characteristic engine capable of realizing a sufficient improvement in durability reliability around a control link without causing an increase in the weight of the engine or the like.
In a variable stroke characteristic engine in which a piston (3) and a crankshaft (6) are connected by a plurality of links (4, 5, 12), a direction L axis parallel to a central axis Y of the cylinder (2) is used. The direction orthogonal to the central axis Y and L axis is the X axis, the center of the crankpin is A, the connection center of the second link and the control link is B, and the connection center of the first link and the second link is D The distance ΔD in the X-axis direction between point D and point A on the L-axis and the distance ΔB in the X-axis direction between point B and point A on the L-axis The link geometry is set so that the relationship is ΔD <ΔB over the entire rotation range of the crankshaft.
[Selection] Figure 6

Description

  The present invention relates to a variable stroke characteristic engine, and more particularly to a variable stroke characteristic engine configured to reduce a load applied to a control link during an expansion stroke.

  An upper connecting rod (4) (first link) and a lower connecting rod (7) (second link) for connecting the piston (3) and the crankshaft (10), and a shaft supported by the lower connecting rod and the engine body ( 11) It has a swing arm (8) (control link) for connecting (eccentric shaft), and the piston stroke is changed by changing the position of the connecting portion of the swing arm with respect to the engine body. A variable stroke characteristic engine is known (see Patent Document 1).

Reference 1 describes that the center of rotation of the crankshaft is the origin, the axis of motion of the piston and the direction perpendicular to the crankshaft is the x-axis, and the cylinder of the swing arm when the crankshaft rotates counterclockwise (clockwise) A variable compression ratio mechanism is described in which the x-coordinate of the rocking fulcrum in the block is positive (negative) and the x-coordinate of the piston pin reciprocating axis is negative (positive).
JP 2001-317383 A

  According to the technique described in Document 1, since the load applied to the swing arm increases particularly when an explosion load is applied to the piston during the expansion stroke, in order to ensure the durability reliability of these connecting portions, Longer diameters, larger diameters, and consequently larger shaft diameters are unavoidable, leading to an increase in engine weight.

  The present invention has been devised to solve such problems of the prior art, and its main purpose is a stroke characteristic capable of ensuring sufficient durability and reliability without causing an increase in the weight of the engine. It is to provide a variable engine.

In order to solve such a problem, claim 1 of the present invention provides the first and second links 4 and 5 that connect the piston 3 and the crankshaft 6, and the second link and the engine body. In a variable stroke characteristic engine having a control link 12 for connecting the control link 12 and changing the position of the connecting portion of the control link with respect to the engine body, the direction parallel to the motion axis Y of the piston Is the L axis, the direction orthogonal to the L axis when viewed from the axial direction of the crankshaft is the X axis, the center of the crankpin is A, the connection center of the second link and the control link is B, The distance in the X-axis direction between point D that changes during rotation of the crankshaft and point A on the L-axis, where D is the connection center with the second link. The relationship between ΔD and the distance ΔB in the X-axis direction between point B changing during rotation of the crankshaft and point A on the L-axis is such that ΔD <ΔB in the entire rotation range of the crankshaft. The link geometry was set to.
According to a second aspect of the present invention, a lubricating oil supply path to the connecting portion between the second link and the control link is provided in the second link or the control link. In this case, in particular, a bifurcated portion sandwiching the second link and a pin that spans the bifurcated portion and pivotally attaches the second link is provided in the control link, and the lubricating oil supply path 23 faces the pivotal portion with the pin. It is good to install in the 2nd link (Claim 3).

According to such a configuration of the first aspect of the present invention, since the swing angle of the second link is smaller than the rotation angle of the crankshaft, the moment around the point A is substantially balanced over the entire rotation range of the crankshaft. ing. In other words, if the L-axis direction load at point D is FDL and the L-axis direction load at point B is FBL, then ΔD · FDL≈ΔB · FBL holds, so the link geometry is always set so that ΔD <ΔB. By doing so, the point B load can be made lower than the point D load over the entire rotation range of the crankshaft.
Due to the decrease in the load at point B, the surface pressure of the pin portion provided at point B is reduced, so that the length and diameter of the pin portion provided at point B can be further reduced. Since the shape around the point B becomes compact, the mass of the rotating / swinging portion is reduced, so that the load at the point B is further reduced. By reducing the point B load, the load transmitted to the connection portion between the control link and the engine body is reduced, and the drive mechanism for moving the connection portion between the control link and the engine body can be reduced in size and weight. That is, according to the first aspect of the present invention, it is possible to achieve a great effect in improving durability reliability and realizing a compact stroke characteristic variable mechanism.
Further, according to the second and third aspects, the lubricating oil can be easily supplied to the connecting portion between the second link and the control link.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

  1 to 4 are schematic configuration diagrams in which the upper part is omitted from a cylinder head of a variable compression ratio / displacement engine as an example of a variable stroke characteristic engine to which the present invention is applied. The piston 3 slidably engaged with the cylinder 2 of the engine 1 is connected to the crankshaft 6 through two links, a first link 4 and a second link 5. Note that the valve operating mechanism, the intake system, and the exhaust system provided in the cylinder head are not different from the conventional four-cycle engine, and are omitted.

  The crankshaft 6 basically has the same configuration as that of a normal fixed compression ratio engine, and includes a crankpin 9 that is eccentric from a crank journal 8 (a center of rotation of the crankshaft) supported in the crankcase 7. An intermediate portion of the second link 5 that swings in a seesaw manner is supported by the crankpin 9. The large end portion 4b of the first link 4 having the small end portion 4a connected to the piston pin 10 is connected to one end 5a of the second link 5. The crankshaft 6 is provided with a counterweight mainly for reducing the rotational primary vibration component of the piston motion, which is also the same as that of a conventional reciprocating engine and is omitted.

  The other end 5b of the second link 5 is pin-coupled with a small end portion 12a of the control link 12 having substantially the same configuration as a connecting rod for connecting a piston and a crankshaft in a normal engine. The large end portion 12 b of the control link 12 is connected to the eccentric portion 13 a of the eccentric shaft 13 that is rotatably supported by the crankcase 7 and extends parallel to the crankshaft 6, with a two-part bearing hole 14. Has been.

  The eccentric shaft 13 supports the large end portion 12b of the control link 12 so as to be movable within a predetermined range (about 90 degrees in the present embodiment) within the crankcase 7, and an appropriate type of rotary actuator (not shown). Therefore, the rotation angle is continuously changed according to the operation state of the engine 1 and is held at an arbitrary angle.

  According to this engine 1, by rotating the eccentric shaft 13, the position of the large end portion 12b of the control link 12 is changed to the position shown in FIGS. 1 and 2 (horizontal inward / minimum compression ratio state or maximum exhaust). 3) and the position shown in FIGS. 3 and 4 (vertically downward / maximum compression ratio state or minimum displacement amount state), the swing angle of the second link 5 accompanying the rotation of the crankshaft 6 changes. Change. As a result, the apparent length of the connecting rod connecting the piston 3 and the crankshaft 6 exhibits an action as if it changes continuously according to the movement of the piston 3, and the rotation of the eccentric shaft 13 By changing the position of the support end of the control link 12 with respect to the crankcase 7 by movement, the compression ratio or the displacement can be arbitrarily changed.

  That is, the first and second links 4 and 5, the control link 12, and the eccentric shaft 13 constitute a piston stroke characteristic variable mechanism, which provides a stroke characteristic variable function for continuously changing the compression ratio or the displacement. It is.

  In this way, the stroke range of the piston 3 in the cylinder 2, that is, the top dead center position and the bottom dead center position of the piston 3 are represented by the range indicated by the symbol A in FIG. 2 and the range indicated by the symbol B in FIG. It will change continuously between.

  In the above embodiment, the driving force for moving the large end portion 12b, which is the engine side coupling portion of the control link 12, is provided by rotating the eccentric shaft 13 having the eccentric portion 13a. However, as long as the position of the engine side connecting portion of the control link 12 can be changed, this may be moved linearly by other means, such as a hydraulic cylinder.

  In the engine 1 configured as described above, when the crankshaft 6 is rotated by the piston pressing force due to the combustion pressure of the fuel during the expansion stroke, a large tensile force is applied to the control link 12 via the second link 5 supported by the crankpin 9. Works. In order to ensure the durability and reliability of the connecting portion between the second link 5 and the control link 12 against this, in the past, it has been unavoidable to increase the length and diameter of the connecting pin, and consequently the diameter of the eccentric shaft. An increase in engine weight was inevitable.

  Therefore, in the present invention, as shown in FIG. 5, the direction parallel to the center axis Y of the cylinder 2 (movement axis of the piston pin 10) Y is defined as the L axis, and is orthogonal to the L axis when viewed from the axial direction of the crankshaft 6. When the direction is the X axis, the center of the crankpin 9 is A, the connection center of the second link 5 and the control link 12 is B, and the connection center of the first link 4 and the second link 5 is D, A distance ΔD in the X-axis direction between point D changing during rotation of the crankshaft 6 and point A on the L-axis, and point B changing during rotation of the crankshaft 6 and A on the L-axis The link geometry is set so that the relationship between the point and the distance ΔB in the X-axis direction satisfies ΔD <ΔB in the entire rotation range of the crankshaft 6. FIGS. 6 and 7 show that ΔD <ΔB is always maintained during rotation of the crankshaft 6.

  According to such a configuration of the present invention, since the swing angle of the second link 5 is smaller than the rotation angle of the crankshaft 6, the moment around the point A is substantially balanced over the entire rotation range of the crankshaft 6. ing. In other words, if the L-axis direction load at point D is FDL and the L-axis direction load at point B is FBL, then ΔD · FDL≈ΔB · FBL holds, so the link geometry is always set so that ΔD <ΔB. By doing so, the point B load can be made lower than the point D load over the entire rotation range of the crankshaft 6.

  Since the load acting on the connection point between the second link 5 and the control link 12 is reduced at point B, the surface pressure of the pin portion provided at point B is reduced, so the length of the pin portion provided at point B The sheath diameter can be further reduced. Since the shape around the point B becomes compact, the mass of the rotating / swinging portion is reduced, so that the load at the point B is further reduced. By reducing the load at point B, the load transmitted to the eccentric shaft 13 via the control link 12 is reduced, so that the diameter of the eccentric shaft 13 can be reduced and the bearing can be reduced in size and weight.

  Next, an embodiment considering the supply of lubricating oil to the connecting portion between the small end portion 12a of the control link 12 and the other end 5b of the second link 5 will be described with reference to FIGS. In the present embodiment, the small end portion 12a of the control link 12 is formed in a bifurcated manner so as to sandwich the other end 5b of the second link 5, and a pin 21 spanned between the bifurcated portions causes the first end 12a. The other end 5b of the two links 5 is pivotally supported.

  On the other hand, in the second link 5, a lubricating oil supply path 23 that communicates with a lubricating oil supply path 22 provided in the crankshaft 6 is formed from a pivot portion with respect to the crank pin 9 toward a pivot portion with respect to the pin 21. Has been.

  As described above, according to the configuration of the present invention in which the link geometry is set so that ΔD <ΔB in the entire rotation range of the crankshaft 6, the distance between the point A and the point B, that is, the crank link 9 in the second link 5 is determined. Although the dimension between the pivot part and the pivot part with respect to the pin 21 tends to increase, the lubricating oil supply path to the connection part (point B) between the second link 5 and the control link 12 extends from the crank pin 9. When branched, the centrifugal force acting on the point B is increased by the swinging of the second link 5, and the lubricating oil is likely to go around the point B, that is, the pivot portion with respect to the pin 21. Thereby, the supply of the lubricating oil to the connecting portion between the second link 5 and the control link 12 becomes easy.

It is a longitudinal cross-sectional view which shows the piston top dead center position in the minimum compression ratio state or the maximum displacement amount state of the engine to which the present invention is applied. It is a longitudinal cross-sectional view which shows the piston bottom dead center position in the minimum compression ratio state or the maximum displacement amount state of the engine to which the present invention is applied. It is a longitudinal cross-sectional view which shows the piston top dead center position in the maximum compression ratio state or the minimum displacement amount state of the engine to which the present invention is applied. It is a longitudinal cross-sectional view which shows the piston bottom dead center position in the maximum compression ratio state or the minimum displacement amount state of the engine to which the present invention is applied. It is explanatory drawing which shows an example of the link geometry concerning this invention. It is explanatory drawing which shows the relationship between the rotation angle of a crankshaft, and the motion state of a link. It is a diagram which shows the relationship between (DELTA) D and (DELTA) B, and the rotation angle of a crankshaft. It is an enlarged view of the connection part of a 2nd link and a control link. It is the IX-IX arrow line view in FIG.

Explanation of symbols

2 Cylinder 3 Piston 4 First link 5 Second link 6 Crankshaft 8 Crank journal 9 Crankpin 10 Piston pin 12 Control link 13 Eccentric shaft 23 Lubricating oil supply path

Claims (3)

A first link and a second link connecting the piston and the crankshaft; a control link connecting the second link and the engine body; and a position of the connecting portion of the control link with respect to the engine body. A variable stroke characteristic engine that changes the piston stroke by changing
The direction parallel to the movement axis Y of the piston is the L axis, the direction orthogonal to the L axis when viewed from the axial direction of the crankshaft is the X axis, the center of the crankpin is A, the second link and the control When the connection center with the link is B and the connection center between the first link and the second link is D,
A distance ΔD in the X-axis direction between the point D that changes during the rotation of the crankshaft and the point A on the L-axis, and the point B and the L-axis that change during the rotation of the crankshaft The variable stroke characteristic engine is characterized in that the link geometry is set such that the relationship between the point A and the distance ΔB in the X-axis direction is ΔD <ΔB in the entire rotation range of the crankshaft. .   The variable stroke characteristic engine according to claim 1, wherein a lubricating oil supply path to a connecting portion between the second link and the control link is provided in the second link or the control link.   The control link includes a portion formed to be bifurcated so as to sandwich the second link, and a pin that spans the bifurcated portion and pivotally attaches the second link, and the lubricating oil supply path includes the pin and The variable stroke characteristic engine according to claim 2, wherein the engine is installed in the second link toward the pivotally attached portion.

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