Patent Application
20240035401
The present invention relates to the improvement of a lower link composing a multi-link piston crank mechanism for an internal combustion engine.
As a conventional technology in which a multi-link piston crank mechanism connects between a crank pin and a piston pin of a reciprocation type internal combustion engine, one described in a patent document 1 previously proposed by the present applicants has been publicly known. This multi-link piston crank mechanism includes an upper link connected to a piston pin of a piston, a lower link which connects the upper link with a crank pin of a crankshaft, and a control link of which one end is swingably supported on the engine body side and the other end is connected to the lower link. Then, the upper link and the lower link are rotatably connected to each other via an upper pin, and the control link and the lower link are rotatably connected to each other via a control pin.
Such a lower link in the multi-link piston crank mechanism receives combustion pressure, which is received by the piston, from the upper pin via the upper link, and transmits force to the crank pin by motion like leverage with the control pin as a fulcrum.
In the patent document 1, there is disclosed a configuration in which an oil hole for injecting lubricating oil to the outside when it meets an oil hole on the crank pin side is formed through a crank pin bearing portion, which is fitted to a crank pin, along a substantially radial direction. The lubricating oil injected from the oil hole lubricates the bearing portion between the upper pin and the upper link.
When the moving direction of the piston is up and down direction, a combustion load is input to the upper pin of one end of the lower link toward the down direction, and the reaction force of the combustion load acts on the control pin of the other end of the lower link toward the down direction similarly. Then, the reaction force of the combustion load acts on the crank pin bearing portion to which the crank pin positioned between the upper pin and the control pin is fitted, toward the substantially up direction. By such a load input, a large stress as tensile stress or bending stress is concentrated at the opening edge on the crank pin side of the oil hole formed through the crank pin bearing portion. Therefore, the opening on the crank pin side of the oil hole is a weak point on the strength of the lower link, and an increase in the output of the internal combustion engine having a multi-link piston crank mechanism is limited.
A lower link according to the present invention is provided with an oil hole for supplying lubricating oil from an oil supply hole of a crank pin toward the connecting portion between an upper pin and a upper link, and the oil hole is composed of a first oil hole linearly extending from the inner peripheral surface of a crank pin bearing portion outwardly in the radial direction, and a second oil hole linearly extending so as to intersect a distal end portion of the first oil hole and having one end opened to the outer surface of the lower link as an oil outlet.
In other words, the oil hole of the lower link is formed in a substantially L shape formed by combining the first oil hole and the second oil hole each having a liner shape. The lubricating oil supplied from the crank pin is injected and supplied to the connecting portion between the upper pin and the upper link, which is a lubrication object, through the first oil hole and the second oil hole.
In such a configuration, as compared with case where an oil hole having a simple liner shape is formed from the crank pin side toward the connecting portion between the upper pin and the upper link which is a lubrication object, the angle of the inclination of the first oil hole opened to the inner peripheral surface of the crank pin bearing portion can be relatively small (that is, it is inclined in the direction away from a piston). The circumferential distribution of stress generated at the crank pin bearing portion by the above-mentioned load input becomes mostly large in an area in a direction from the center of the crank pin toward the piston, and by reducing the inclination angle of the first oil hole, the opening position of the first oil hole becomes a part at which stress is relatively small.
Accordingly, the stress concentration at the opening edge of the oil hole in the crank pin bearing portion that becomes a weak point in the strength of the lower link is alleviated, with advantageous for securing the strength of the lower link and for increasing in output of the internal combustion engine.
In the following, one embodiment of the present invention will be explained in detail based on the drawings.
In
As shown in
Upper-pin pin boss portion 12 and control-pin pin boss portion 13 are formed in bifurcated shapes so as to sandwich upper link 3 and control link 7 in the middle part in the axial direction, and a pair of bearing flange portions 12a and a pair of bearing flange portions 13a respectively supporting upper pin 4 and control pin 9 extend along the end surfaces in the axial direction of lower link 6. That is, bearing flange portions 12a and 13a respectively forming pin boss portions 12 and 13 are connected to the end portions in the axial direction of crank pin bearing portion 11 having a cylindrical shape. Bearing flange portions 12a and 13a have circular through holes 12b and 13b respectively, and cylindrical end portions of upper pin 4 and control pin 9 are press-fitted into through holes 12b and 13b respectively. Then, upper link 3 and control link 7 are swingably moved in groove portions 17 and 18 respectively which are formed between a pair of bearing flange portions 12a and between a pair of bearing flange portions 13a respectively.
Crank pin bearing portion 11 is fitted to crank pin 5 via a pair of semi-cylindrical bearing metals 16 (see
Combustion load acts on upper-pin pin boss portion 12 from upper link 3 via upper pin 4, and lower link 6 swings with control pin 9 as a fulcrum so as to transmit force to crank pin 5 by motion like leverage. Consequently, the combustion load acts on upper-pin pin boss portion 12 in the lower direction in
In
Oil hole 30 is formed to lubricate the connecting portion of upper link 3 connected to lower link 6 in upper-pin pin boss portion 12, namely, the sliding surface between upper link 4 and upper link 3, and is formed in a substantially L shape by a first oil hole 31 and a second oil hole 32.
First oil hole 31 is a non-through hole (that is, a distal end 31a is sealed) linearly extending from an inner peripheral surface 11a of crank pin bearing portion 11 outwardly in the radial direction, and the base end is opened to inner peripheral surface 11a of crank pin bearing portion 11 as an oil inlet 31b. In one embodiment, first oil hole 31 is obliquely inclined with respect to divided surface 14, and is formed along the radial line of crank pin bearing portion 11. In this way, by arranging first oil hole 31 along the radial line of crank pin bearing portion 11, oil inlet 31b is opened in a form of substantially true circle.
In addition, the inclination angle of first oil hole 31 (for example, an inclination angle θ of first oil hole 31 with divided surface 14 set as a reference) in lower link 6 is set so as to be relatively small, to avoid being positioned in an area where stress is high in the above-mentioned circumferential distribution of stress of crankpin pin bearing portion 11. In the illustrated first embodiment, inclination angle θ of first oil hole 31 with divided surface 14 set as a reference is 10°. In this way, since inclination angle θ is small, first oil hole 31 is formed such that the extension line of the center line of first oil hole 31 extends in a direction not intersecting the outer peripheral surface of upper pin 4. Specifically, the extension line of the center line of first oil hole 31 passes through the lower side of upper pin 4 (opposite side of piston 1).
Second oil hole 32 is a non-through hole (that is, a distal end 32a is sealed) linearly extending from the outer surface of lower link 6 to the inside of lower link 6. Specifically, it extends from a bottom surface 17a of a groove portion 17 facing upper pin 4 to the inside of lower link 6, and the base end of second oil hole 32 is opened to bottom surface 17a as an oil outlet 32b. In the inside of lower link 6, the distal end portion of second oil hole 32 (that is, a portion on the distal end 32a side) and the distal end portion of first oil hole 31 (that is, a portion on the distal end 31a side) intersect each other. That is, second oil hole 32 communicates with first oil hole 31.
Second oil hole 32 is formed such that the extension line of the center line of second oil hole 32 extends in a direction intersecting the outer peripheral surface of upper pin 4, and, in the illustration, it is directed to the vicinity of the center of upper pin 4. In addition, in the illustrated embodiment, second oil hole 32 extends along the direction orthogonal to divided surface 14, so as to be parallel to the center axial line of bolt 21 adjacent thereto and screw hole 24 corresponding to bolt 21. In this way, since second oil hole 32 extends parallel to screw hole 24 adjacent thereto, the thickness therebetween is fixed in the axial direction, and it is possible to suppress the occurrence of partial thinning and partially lowering of strength.
First oil hole 31 and second oil hole 32 are formed along one plane orthogonal to the axial direction of crank pin 5. For example, first oil hole 31 and second oil hole 32 are positioned on the plane passing through the middle of the dimension in the axial direction of crank pin bearing portion 11. In addition, in the present invention, although first and second oil holes 31 and 32 may be formed in an oblique direction so as to have angles to the plane slightly, it is desirable to formed them along the plane in order to secure the strength in oil inlet 31b of first oil hole 31.
The angle formed by first oil hole 31 and second oil hole 32 intersecting each other is larger than 90°. For example, inclination angle θ of first oil hole 31 with divided surface 14 set as a reference is 10°, and when second oil hole 32 is orthogonal to divided surface 14, second oil hole 32 intersects first oil hole 31 at the angle of 100°. In this way, first oil hole 31 intersects second oil hole 32 at an obtuse angle, and consequently, the loss of flow of lubricating oil at the intersection becomes small.
First oil hole 31 and second oil hole 32 are each formed, for example, by secondary machining with a drill after forming lower link upper 6A by forging. In addition, although carburization treatment (carburization quench hardening) is conducted to lower link upper 6A for increasing surface hardness, it is desirable to perform drilling before the carburization treatment.
Here, in one preferable embodiment, the diameter of second oil hole 32 is set to be larger than that of first oil hole 31. In this way, when second oil hole 32 is formed so as to have a larger diameter, the rigidity around second oil hole 32 is lowered, and a relatively large deformation occurs, as a result of which stress around first oil hole 31 (in particular, around oil inlet 31b of first oil hole 31) where stress concentration as the largest problem arises is lowered. That is, as compared with case where the diameter of first oil hole 31 is the same as that of second oil hole 32, or case where the diameter of first oil hole 31 is smaller than that of second oil hole 32, stress at oil inlet 31b is alleviated.
In addition, by setting the diameter of second oil hole 32 so as to be larger than that of first oil hole 31, even if there is some machining error or tolerance, a communication state at the intersecting portion therebetween can be surely secured, and a predetermined passage sectional area can be stably obtained.
In addition, in the illustrated example, although distal end 32a of second oil hole 32 passes through and slightly extends from first oil hole 31 further due to drilling, such an excess passage part is not necessary if working can be performed.
In lower link 6 of the embodiment configured as above, at a predetermined crank angle, oil supply hole 29 on the crank pin 5 side meets oil inlet 31b of first oil hole 31, and, as oil jet, pressurized lubricating oil is injected from oil outlet 32b toward upper pin 4 through first oil hole 31 and second oil hole 32. By this oil jet, lubrication is performed between upper pin 4 and upper link 3.
Here, since inclination angle θ of first oil hole 31 with respect to divided surface 14 is relatively small and oil inlet 31b is opened at a position close to divided surface 14, the stress concentration at the opening edge of oil inlet 31b is alleviated. For example, when an oil hole was linearly formed penetrating in a direction intersecting upper pin 4 along the radial line of crank pin bearing portion 11, assuming that the positions of upper pin 4 and the like are the same as those shown in
Here, when, as mentioned above, inclination angle θ of first oil hole 31 with divided surface 14 set as a reference is small, the circumferential velocity of oil inlet 31b with respect to crank pin 5 becomes high during the swinging movement of lower link 6 and rotation movement of crank pin 5 (as compared with case where inclination angle θ is, for example, approximately 40°). Consequently, the time during which oil supply hole 29 on the crank pin 5 side meets oil inlet 31b becomes relatively short, and the amount of lubricating oil tends to decrease. Therefore, in one preferable embodiment, as shown in
That is, bearing metal 16 is formed by being divided into two parts by 180° so as to have a cylindrical shape as a whole, and they are assembled to respective lower link upper 6A and lower link lower 6B in a non-rotation state. Bearing metal 16 is formed with communicating hole 41 located at a position corresponding to inlet 31b, in order to communicate oil supply hole 29 on the crank pin 5 side and oil inlet 31b of lower link 6 with each other. In addition, communicating hole 41 has a long hole shape extending in the circumferential direction. Accordingly, oil supply hole 29 on the crank pin 5 side and oil inlet 31b of lower link 6 are kept in a communication state over a predetermined angle range. In other words, the time during which oil supply hole 29 on the crank pin 5 side and oil hole 31b of lower link 6 communicate with each other becomes long. Consequently, a sufficient amount of lubricating oil can be secured.
In one embodiment, as shown in
In addition, when communicating hole 41 is excessively enlarged, surface pressure as a bearing becomes high, and it is therefore not preferable.
Although, as an example, first embodiment in which inclination angle θ of first oil hole 31 with divided surface 14 set as a reference is 10° has been explained, in the present invention, inclination angle θ of first oil hole 31 is not limited to a specific angle.
In the second embodiment, the intersecting angle at the intersection portion between first oil hole 31 and second oil hole 32 is larger than that of the first embodiment, and pressure loss caused by a change in a flow direction is small. In addition, the passage length of second oil hole 32 becomes shorter than that in the first embodiment, as a result of which pressure loss also becomes small. However, oil inlet 31b of first oil hole 31 is positioned close to the area where stress is high. It is therefore preferable to set inclination angle θ while considering these matters.
In the second embodiment, although communicating hole 41 of bearing metal 16 is also formed in a long hole shape, inclination angle θ of first oil hole 31 is large as compared with the first embodiment, and oil inlet 31b of first oil hole 31 is positioned in the vicinity of the middle in the circumferential direction of communicating hole 41 having a long hole shape (see
In addition, lower link upper 6A (lower link 6) of the first embodiment and the second embodiment is provided with, in addition to oil hole 30, an oil hole 28 for supplying oil jet toward piston 1 (see
As the above, although one embodiment of the present invention has been explained in detail, the present invention is not limited to the above embodiments, and various changes can be made to the embodiments. For example, although, in the above embodiments, first oil hole 31 is formed along the radial line of crank pin bearing portion 11, it may be slightly inclined with respect to the radial line of crank pin bearing portion 11 or may be arranged so as to be slightly displaced in parallel with respect to the radial line.
In addition, second oil hole 32 may not be accurately arranged along the direction orthogonal to divided surface 14 (that is, the direction parallel to bolt 21).
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2020/000771 | 9/15/2020 | WO |
