JP4259214B2 - Variable compression ratio mechanism of internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable compression ratio mechanism capable of changing an engine compression ratio of an internal combustion engine, and more particularly to improvement of an upper link and a pin connection structure thereof.
[0002]
[Prior art]
Patent Document 1 describes a multi-link variable compression ratio mechanism that changes and controls the engine compression ratio. This variable compression ratio mechanism has a lower link that is rotatably attached to a crankpin of a crankshaft, and an upper link that links the lower link and the piston, and changes the movement restraint condition of the lower link. The engine compression ratio can be changed and controlled.
[0003]
The upper link and the lower link are rotatably connected by a connecting pin. Typically, in order to ensure lubricity in a high-speed and high-load region or the like, a full float pin connection structure is used in which both the upper link and the lower link rotatably support and support the connection pin.
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2002-47955
[Problems to be solved by the invention]
In the full-float type pin connection structure as described above, in order to prevent the connection pin from falling off, for example, it is necessary to fit a snap ring into an engagement groove formed and formed in the connection pin. Cost increases.
[0006]
Further, in the full float pin coupling structure, the frictional force for supporting the component force acting in the coupling pin axial direction is extremely small. For this reason, for example, when the pin bearing boss of the upper link has a bifurcated shape or a clevis shape that sandwiches the pin bearing boss of the lower link in the axial direction, the moment acting on the bifurcated root portion of the upper link increases, and this In order to secure the rigidity against various moments, there is a risk of increasing the size and weight of the upper link.
[0007]
The present invention has been made in view of such problems, and has as its main object to reduce the cost and weight of the variable compression ratio mechanism.
[0008]
[Means for Solving the Problems]
A variable compression ratio mechanism for an internal combustion engine according to the present invention includes a lower link rotatably attached to a crankpin of a crankshaft, an upper link that links the lower link and a piston, and the upper link and the lower link connected to each other. And a compression ratio changing means for changing the engine compression ratio by changing the motion constraint condition of the lower link. A connecting pin bearing boss through which the connecting pin is rotatably passed is formed in the lower link. A pair of connecting pin fixing bosses are formed in the upper link so as to sandwich the connecting pin bearing boss in the axial direction. Both ends of the connecting pin are fixed to the connecting pin fixing boss.
[0009]
【The invention's effect】
According to the present invention, since both ends of the connecting pin are fixed to the pair of connecting pin fixing bosses of the upper link, bearing members such as a snap ring are omitted as compared with the above-described full float type pin connecting structure. Thus, weight reduction and cost reduction can be achieved. In addition, since the load acting in the axial direction of the connecting pin with respect to the upper link can be supported on the connecting pin side, the moment acting on the upper link can be effectively reduced, and it is easy to ensure the strength and rigidity. The size and weight of the upper link can be reduced.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of a variable compression ratio mechanism for an internal combustion engine according to the present invention will be described in detail with reference to the drawings.
[0011]
First, the basic configuration of the variable compression ratio mechanism of this embodiment will be described with reference to FIGS. 1 and 2 do not show or reflect specific shapes and structures of an upper link and its pin connection structure which will be described later.
[0012]
The variable compression ratio mechanism includes a lower link 6 rotatably attached to a crankpin 5 of a crankshaft 4 extending in the cylinder row direction, an upper link 3 that links the lower link 6 and the piston 1 of each cylinder, and a lower link 6. Compression ratio changing means for changing and controlling the engine compression ratio by changing the motion constraint condition of the link 6. The piston 1 and one end of the upper link 3 are connected by a piston pin 2, and the other end of the upper link 3 and the lower link 6 are connected by a connecting pin 9.
[0013]
The compression ratio changing means includes a control shaft 7 extending obliquely below the crankshaft 4 in the cylinder row direction, an eccentric shaft portion 7a provided eccentric to the control shaft 7, and the eccentric shaft portion 7a and the lower link 6 And a control link 8 that cooperates with each other. The lower link 6 and the control link 8 are connected by a control pin 10. When the rotational position of the control shaft 7 is changed by an actuator such as a motor (not shown), the position of the eccentric shaft portion 7a that is the swing fulcrum of the control shaft 7 is changed, and the motion constraint condition of the lower link 6 is changed. The engine compression ratio will change.
[0014]
Such a multi-link variable compression ratio mechanism can change the engine compression ratio continuously according to the vehicle operating conditions, and brings the piston stroke characteristics closer to ideal characteristics (for example, characteristics close to single vibration). In addition, since the control shaft 7 and the control link 8 are disposed on the lower side of the engine having a relatively large space, there are advantages such as excellent engine mountability.
[0015]
Hereinafter, with reference to FIGS. 3 to 8, the upper link 3 and the connecting structure thereof, which are the main part of the present embodiment, will be described in detail.
[0016]
As shown in FIG. 5, the lower link 6 is formed with a substantially cylindrical connection pin bearing boss 20 through which the connection pin 9 is rotatably passed, and the connection pin 9 is rotatably supported and supported.
[0017]
The upper link 3 has a piston pin 2 rotatably passing therethrough, and a substantially cylindrical piston pin bearing boss 21 for supporting and bearing the piston pin 2 rotatably, and a connecting pin bearing boss 20 of the lower link 6 as a connecting pin. A pair of substantially cylindrical connection pin fixing bosses 22 that are positioned on both sides in the axial direction of the connection pin bearing boss 20 so that both ends of the connection pin 9 are fixedly fitted, and a piston pin bearing boss 21. And an arm body 23 that connects the connecting pin fixing bosses 22 and is integrally formed with each part of a metal material.
[0018]
The arm body 23 includes a main arm 24 that is integrally connected to the outer periphery of the piston pin bearing boss 21, and an outer periphery of the connecting pin fixing boss 22 that is bifurcated and clevised from the main arm 24 to form a substantially cylindrical shape. And a bifurcated arm 25 integrally connected to each other.
[0019]
When assembling, for example, in a state where the connection pin bearing boss 20 is coaxially disposed and positioned between the pair of connection pin fixing bosses 22, the connection pin 9 is press-fitted into one of the connection pin fixing bosses 22 and connected. By inserting the pin bearing boss 20 into the other connecting pin fixing boss 22 while press-fitting, the connecting pin 9 is fixed to the pair of connecting pin fixing bosses 22 and the connecting pin 9 is rotated by the piston pin bearing boss 21. Possible support or bearing.
[0020]
FIG. 7A shows a comparative example in which the pin boss 22 ′ of the upper link forms a bearing structure in which the connecting pin 9 is rotatably supported and supported. FIG. 7B shows the connecting pin fixing boss of the upper link. This embodiment shows a fixing structure in which both ends of the connecting pin 9 are fixed by press-fitting.
[0021]
A load F1 acting on the upper link 3 from the piston pin 2 side of the piston due to a combustion load or the like acts from the piston pin boss 21 toward the connecting pin boss 22 side. As a reaction force of this load F1, the upper link 3 is connected from the connecting pin 9 side. The load F <b> 2 acting on the piston acts from the connecting pin boss 22 toward the piston pin boss 21. When these loads F1 and F2 are displaced in the axial direction, a component force in the axial direction is generated, and a base portion (connecting portion) 29 where the arm body 23 of the upper link 3, particularly the bifurcated arm 25 is connected to the main arm 24. The moment M acts intensively in the vicinity of.
[0022]
In the comparative example, since the contact portion between the connecting pin bearing boss 22 ′ and the connecting pin is configured as a bearing, the axial friction coefficient is extremely low and the axial component force cannot be received. The acting moment M tends to increase.
[0023]
On the other hand, when the connecting pin is fixedly fitted to the connecting pin fixing boss 22 of the upper link and both are substantially integrated as in this embodiment, the connecting pin acts on the connecting pin fixing boss 22. Since the axial component force F3 is supported by the connecting pin, the moment M acting on the base portion 29 of the bifurcated arm 25, which is particularly difficult and important in securing the strength and rigidity of the arm body, is reduced. It is easy to ensure the strength and rigidity of the upper link, and the upper link can be reduced in size and weight.
[0024]
Further, when the connecting pin boss 22 ′ has a bearing structure as in the comparative example, in order to prevent the connecting pin from falling off, for example, it is necessary to fit the snap ring into the engaging groove of the connecting pin. However, when the connecting pin is fixed to the connecting pin fixing boss 22 as in this embodiment, there is no need for a bearing member such as a snap ring for the bearing. Cost reduction can be achieved.
[0025]
As in the comparative example, when the connecting pin boss 22 ′ has a bearing structure, if the contact pressure distribution is non-uniform, wear may progress locally and the durability may be impaired. On the other hand, in the case of the fixing structure in which the connecting pin is fixed to the connecting pin fixing boss 22 as in this embodiment, even if the contact pressure distribution is not uniform, the durability is reduced as in the comparative example. There is no.
[0026]
Rather, in this embodiment, as shown in FIG. 8 (b), the connecting pin 9 bends due to non-uniform contact pressure distribution, and the load F2 acting from the connecting pin side concentrates on the inner side in the axial direction of the connecting pin boss 22. Thus, as shown in FIG. 8A, compared to the case where the contact pressure distribution is uniform, the load F2 described above, and the load F1 acting on the axially outer end of the piston pin boss 21 from the piston pin side, Since the displacement in the axial direction is reduced and the moment M acting on the root portion 29 is reduced, this is advantageous in terms of rigidity. In FIG. 8 and the like, the bending of the connecting pin is exaggerated for easy understanding.
[0027]
In addition, in this embodiment, various improvements as described below are added so that the improvement in strength and rigidity of the upper link 3 and the reduction in size and weight can be achieved at a high level.
[0028]
As shown in FIGS. 4 to 6, the arm body 23 is set to have the largest axial width of the base portion 29 of the bifurcated arm 25. The arm body 23 is set so that the cross-sectional area perpendicular to the link center line connecting the pin center of the piston pin and the connecting pin is maximized in the vicinity of the root portion 29. Therefore, the strength and rigidity of the bifurcated arm 25 can be effectively secured. Further, the main arm 24 has a shape in which an intermediate portion in the longitudinal direction of the pin is smoothly constricted in order to reduce the weight while ensuring rigidity.
[0029]
The arm body 23 has a main rib 26 for reinforcement, which is partially thickened and continuously extends from the piston pin bearing boss 21 to the connecting pin fixing boss 22 so as to follow a portion where the loads F1 and F2 are concentrated. They are formed on both sides in the direction (see the hatched portion in FIG. 4). Each main rib 26 extends from the axially outer end of the piston pin bearing boss 21 along the axially outer edge of the main arm 24, and the axially inner edge of the bifurcated arm 25 (the side where the pair of bifurcated arms 25 face each other). ) And is connected to the axially inner end of each connecting pin fixing boss 22. In other words, a first concave portion 27 that is partially thinned (thin) is formed in the central portion of the main arm 24 in the axial direction, and a thin portion is formed in the axially outer portion of the bifurcated arm 25. The second recesses 28 are formed to reduce the weight.
[0030]
The main rib 26 is locally widened at the root portion 29 in order to ensure the rigidity of the root portion 29, and the axial width gradually increases from the root portion 29 toward the connecting pin fixing boss 22. It is narrower. In addition, the base portion 29 is formed with auxiliary ribs 31 for reinforcement that are partially thickened to connect and bridge the main ribs 26 on both sides. The auxiliary rib 31 has a partially thickened central portion in the axial direction.
[0031]
As shown in FIG. 6, the load 30 acts on the portion 30 along the inner side in the axial direction of the bifurcated arm 25 as described above. The wall thickness is further increased. That is, the inner peripheral edge portions 30 and 31 having a substantially U shape of the bifurcated arm 25 are most thickened.
[0032]
As shown in FIG. 5, the cylindrical inner surface, that is, the bearing surface of the piston pin bearing boss 21, and the cylindrical inner surface, that is, the press-fit contact surface, of each connecting pin fixing boss 22 overlap (overlap) by a predetermined width E in the axial direction. Is set to The main rib 26 for reinforcement against the loads F1 and F2 is connected to the axially outer end of the piston pin bearing boss 21 at a position corresponding to the range of the predetermined width E in the axial direction, and the connecting pin fixing boss 22 It is designed to be connected to the axially inner end. Therefore, there is almost no axial displacement of the loads F1 and F2, and the moment M acting on the root portion 29 is sufficiently suppressed.
[0033]
The press-fitting contact surface of each connecting pin fixing boss 22 has a shape in which the axial width differs in the circumferential direction. Specifically, the axial direction near the piston pin bearing boss 21 to which a large load F2 acts (rightward in FIG. 5). The width A is the longest and the axial width B on the opposite side, that is, the side far from the piston pin bearing boss 21 (left side in FIG. 5) is set to be the shortest. Correspondingly, the cylindrical inner surface, that is, the bearing surface of the connecting pin bearing boss 20 of the lower link 6 also has a shape having a different axial width in the circumferential direction, and the upper link 3 and the lower link 6 during actual engine operation. The portion D having the shortest axial width is positioned closer to the piston pin bearing boss 21 and the portion C having the longest axial width is positioned farther from the piston pin bearing boss 21. Is set to In this way, the connecting pin fixing boss 22 of the upper link 3 and the connecting pin bearing boss 20 of the lower link 6 that are relatively rotated within a predetermined rotation angle range are set to partially overlap in the axial direction. Therefore, it is possible to effectively ensure the contact width of the pin boss with respect to the load while suppressing the axial width of the entire pin boss.
[0034]
As described above, in the bifurcated arm 25, the load is concentrated on the inner end in the axial direction, so that the axial width of the bifurcated arm 25 is larger than the axial (maximum) width A of the connecting pin fixing boss 22 as shown in FIG. The bifurcated arm 25 is retracted and recessed toward the inner side in the axial direction with respect to the connecting pin fixing boss 22. In other words, the connecting pin fixing boss 22 protrudes outward in the axial direction with respect to the bifurcated arm 25. Thereby, weight reduction can be achieved, ensuring the rigidity with respect to a load effectively.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a basic configuration of a variable compression ratio mechanism according to an embodiment of the present invention.
FIG. 2 is a perspective view of the variable compression ratio mechanism.
FIG. 3 is a perspective view showing an upper link and a connecting pin according to the present embodiment.
4 is a perspective view showing the upper link of FIG. 3 alone. FIG.
FIG. 5 is a front view showing a pin connection structure between an upper link and a lower link.
FIG. 6 is a front view (a), a side view (b) and a sectional view (c) taken along line XX of the upper link.
FIG. 7 is an operation explanatory diagram corresponding to a comparative example (a) and a working example (b).
FIG. 8 is an operation explanatory diagram of the present embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Piston 2 ... Piston pin 3 ... Upper link 4 ... Crankshaft 5 ... Crankpin 6 ... Lower link 7 ... Control shaft (compression ratio changing means)
8. Control link (compression ratio changing means)
DESCRIPTION OF SYMBOLS 9 ... Connecting pin 20 ... Connecting pin bearing boss 21 ... Piston pin bearing boss 22 ... Connecting pin fixing boss 23 ... Arm body 24 ... Main arm 25 ... Forked arm 26 ... Main rib 29 ... Base part 31 ... Auxiliary rib

Claims (8)

A lower link that is rotatably attached to a crank pin of the crankshaft, an upper link that links the lower link and the piston, a connecting pin that connects the upper link and the lower link, and the piston and the upper link. A piston pin, and compression ratio changing means for changing the engine compression ratio by changing the motion constraint condition of the lower link,
The lower link has a connecting pin bearing boss through which the connecting pin is rotatably passed,
The above upper link is
A pair of connecting pin fixing bosses disposed so as to sandwich the connecting pin bearing boss in the axial direction, and both ends of the connecting pin being fixed by press fitting;
A substantially cylindrical piston pin bearing boss through which the piston pin penetrates rotatably;
An arm body connecting the piston pin bearing boss and the connecting pin fixing boss,
This arm body
A main arm integrally connected to the outer periphery of the piston pin bearing boss;
Branches from the main arm forked, have a, a bifurcated arm integrally connected to the outer periphery of the connecting pin fixed boss,
The arm body is formed with a partially thickened main rib extending continuously from the piston pin bearing boss to the connecting pin fixing boss,
The main rib is connected to the axially outer end portion of the piston pin bearing boss and is connected to the axially inner end portion of the connecting pin fixing boss . A lower link that is rotatably attached to a crank pin of the crankshaft, an upper link that links the lower link and the piston, a connecting pin that connects the upper link and the lower link, and the piston and the upper link. A piston pin, and compression ratio changing means for changing the engine compression ratio by changing the motion constraint condition of the lower link,
The lower link has a connecting pin bearing boss through which the connecting pin is rotatably passed,
The above upper link is
A pair of connecting pin fixing bosses disposed so as to sandwich the connecting pin bearing boss in the axial direction, and both ends of the connecting pin being fixed by press fitting;
A substantially cylindrical piston pin bearing boss through which the piston pin penetrates rotatably;
An arm body connecting the piston pin bearing boss and the connecting pin fixing boss,
This arm body
A main arm integrally connected to the outer periphery of the piston pin bearing boss;
Branches from the main arm forked, have a, a bifurcated arm integrally connected to the outer periphery of the connecting pin fixed boss,
The arm body is formed with a partially thickened main rib extending continuously from the piston pin bearing boss to the connecting pin fixing boss,
In addition, a variable compression ratio of the internal combustion engine in which a partially thickened auxiliary rib connecting the main ribs provided on each of the bifurcated arms is formed at a base portion where the bifurcated arm is connected to the main arm. mechanism. The variable compression ratio mechanism for an internal combustion engine according to claim 1 or 2 , wherein the connecting pin fixing boss has the longest axial width on the piston pin bearing boss side. A lower link that is rotatably attached to a crank pin of the crankshaft, an upper link that links the lower link and the piston, a connecting pin that connects the upper link and the lower link, and the piston and the upper link. A piston pin, and compression ratio changing means for changing the engine compression ratio by changing the motion constraint condition of the lower link,
The lower link has a connecting pin bearing boss through which the connecting pin is rotatably passed,
The above upper link is
A pair of connecting pin fixing bosses disposed so as to sandwich the connecting pin bearing boss in the axial direction, and both ends of the connecting pin being fixed by press fitting;
A substantially cylindrical piston pin bearing boss through which the piston pin penetrates rotatably;
An arm body connecting the piston pin bearing boss and the connecting pin fixing boss,
This arm body
A main arm integrally connected to the outer periphery of the piston pin bearing boss;
Branches from the main arm forked, have a, a bifurcated arm integrally connected to the outer periphery of the connecting pin fixed boss,
The connecting pin fixing boss is a variable compression ratio mechanism for an internal combustion engine in which the axial width on the piston pin bearing boss side is set to be the longest . The variable compression ratio mechanism for an internal combustion engine according to claim 4 , wherein the arm body is formed with a partially thickened main rib continuously extending from the piston pin bearing boss to the connecting pin fixing boss. The variable internal combustion engine according to any one of claims 1 to 5 , wherein the axially outer end of the piston pin bearing boss and the axially inner end of the connecting pin fixing boss partially overlap in the axial direction. Compression ratio mechanism.   The variable compression ratio mechanism for an internal combustion engine according to any one of claims 1 to 6, wherein the arm body is set so that a cross-sectional area is maximized at a base portion where the bifurcated arm is connected to the main arm.   The variable compression ratio mechanism for an internal combustion engine according to any one of claims 1 to 7, wherein the bifurcated arm is recessed inward in the axial direction with respect to the connecting pin fixing boss.

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