Lubrication oil supply structure

Abstract

A main journal 25a of a crank-shaped swinging shaft 25 which swings in a range of a predetermined angle is supported by bearing metals 51 and 52 each divided into two pieces. In supplying a lubrication oil through an oil bore 51b in the bearing metal 51 to a sliding surface of the main journal 25a and to inlet openings of lubrication oil passages P1 and P2 of the swinging shaft 25 open to the sliding surface, the inlet openings of the lubrication oil passages P1 and P2 of the swinging shaft 25 are designed so that they do not move past division portions 55 of the bearing metals 51 and 52 upon swing of the swinging shaft 25 in the range of the predetermined angle. Therefore, it is possible to prevent the lubrication oil to be supplied to the lubrication oil passages P1 and P2 from leaking from the division portions 55 of the bearing metals 51 and 52, thereby reliably lubricating a pin journal 25b of the swinging shaft 25 by the lubrication oil supplied from the lubrication oil passages P1 and P2.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lubrication oil supply structure in which a lubrication oil passage formed within a rotary shaft or a swinging shaft is open to a journal which is supported by a bearing member divided into a plurality of pieces, and relates to a lubrication oil supply structure which is applied to a control shaft of an engine.

2. Description of the Related Art

There is a variable compression ratio engine known from Japanese Patent Application Laid-open No. 2003-322036, which comprises a crankshaft whose main journal is rotatably supported in an engine block, a control shaft whose main journal is supported in the engine block so as to swing in a range of a predetermined angle, a lower link swingably supported at its intermediate portion on a pin journal of the crankshaft, an upper link connecting one end of the lower link to a piston, and a control link which connects the other end of the lower link to a pin journal of the control shaft.

With this variable compression ratio engine, the control shaft is swung by an actuator to move the control link vertically, thereby changing the motion-restraining condition of the lower link to change the stroke characteristic including the position of a top dead center of a piston, thereby controlling the compression ratio of the engine as desired.

When a journal of a shaft is supported by a bearing metal divided into a plurality of pieces, and a portion of a lubrication oil for lubricating a sliding surface of the journal is supplied to other portions to be lubricated through a lubrication oil passage formed within the shaft, the pressure on portions in the vicinity of division portions of a bearing metal divided into a plurality of pieces is reduced due to the leakage of the lubrication oil. Therefore, there is a possibility that when an inlet opening of the lubrication oil passage moves to face the division portions, the amount of the lubrication oil supplied from an inner peripheral surface of the bearing metal to the lubrication oil passage is decreased, so that it is impossible to sufficiently lubricate the other portions to be lubricated.

Especially in the case where the opening of the lubrication oil passage stops for a certain period of time at a location opposed to the division portions of the bearing metal, there is a possibility that a state of the decreased amount of lubrication oil continues to cause a lubrication deficiency.

SUMMARY OF THE INVENTION

The present invention has been accomplished with the above circumstance in view, and it is an object of the present invention to ensure that lubrication oil can be reliably supplied to a journal of a rotary shaft or a swinging shaft supported by a bearing member divided into a plurality of pieces.

In order to achieve the above object, according to a first feature of the present invention, there is provided a lubrication oil supply structure in which a lubrication oil passage formed within a rotary shaft is open to a journal which is supported by a bearing member divided into a plurality of pieces, wherein an opening of the lubrication oil passage of the rotary shaft is designed so that the opening does not stop at division portions of the bearing member.

With the above arrangement, in the lubrication oil supply structure in which the journal, to which the lubrication oil passage formed within the rotary shaft is open, is supported by the bearing member divided into the plurality of pieces, the opening of the lubrication oil passage of the rotary shaft is designed so that the opening does not stop at the division portions of the bearing member. Therefore, it is possible to prevent by the simple arrangement the lubrication oil from leaking from the division portions to cause the lubrication deficiency.

Further, according to a second feature of the present invention, there is provided a lubrication oil supply structure in which a lubrication oil passage formed within a swinging shaft, which swings in a range of a predetermined angle, is open to a journal which is supported by a bearing member divided into a plurality of pieces, wherein an opening of the lubrication oil passage of the swinging shaft is designed so that the opening does not stop at division portions of the bearing member.

With the above arrangement, in the lubrication oil supply structure in which the journal, to which the lubrication oil passage formed within the swinging shaft which swings in the range of the predetermined angle is open, is supported by the bearing member divided into the plurality of pieces, the opening of the lubrication oil passage of the swinging shaft is designed so that the opening does not stop at the division portions of the bearing member. Therefore, it is possible to prevent by the simple arrangement the lubrication oil from leaking from the division portions to cause the lubrication deficiency.

Furthermore, according to a third feature of the present invention, there is provided a lubrication oil supply structure comprising: a crankshaft whose main journal is rotatably supported in an engine block; a control shaft whose main journal is supported in the engine block so as to swing in a range of a predetermined angle; a lower link swingably supported on a pin journal of the crankshaft; an upper link connecting the lower link to a piston; and a control link which connects the lower link or the upper link to a pin journal of the control shaft, the main journal of the control shaft being supported by a bearing metal divided into a plurality of pieces, a lubrication oil being supplied through the bearing metal to a sliding surface of the main journal of the control shaft and to an inlet opening of a lubrication oil passage which is formed within the control shaft and open to the sliding surface of the main journal of the control shaft, wherein the range of swing of the control shaft is determined so that the inlet opening of the lubrication oil passage of the control shaft does not move past division portions of the bearing metal divided into the plurality of pieces.

With the above arrangement, the lower link is swingably supported on the pin journal of the crankshaft and connected to the piston through the upper link, and the lower link or the upper link is connected to the pin journal of the control shaft through the control link. Therefore, it is possible to change the motion-restraining condition of the lower link to change the stroke characteristic of the piston by swinging the control shaft in the range of the predetermined angle about the main journal to move the control link vertically.

The main journal of the control shaft is supported by the bearing metal divided into the plurality of pieces, and when the lubrication oil is supplied through the bearing metal to the sliding surface of the main journal and to the inlet opening of the lubrication oil passage in the main journal opening to the sliding surface, the inlet opening of the lubrication oil passage of the control shaft is designed so that the opening does not move past the division portions of the bearing metal upon swing of the control shaft in the range of the predetermined angle. Therefore, it is possible to prevent the lubrication oil to be supplied to the lubrication oil passage from leaking from the division portions of the bearing metal to cause the lubrication deficiency. Especially, it is possible to excellently maintain the supply of the lubrication oil to the pin journal of the control shaft to which a large load is applied by a combustion pressure, leading to a smooth movement of each link.

According to a fourth feature of the present invention, in addition to the third feature, the lubrication oil passage of the control shaft is divided into a first lubrication oil passage open to the main journal of the control shaft, and a second lubrication oil passage open to the pin journal of the control shaft, the first and second lubrication oil passages being formed to intersect each other at a predetermined angle as viewed in an axial direction of the control shaft.

With the above arrangement, the lubrication oil passage of the control shaft is comprised of the first and second oil passages intersecting each other at the predetermined angle, the first lubrication oil passage is formed to be open to the main journal, and the second lubrication oil passage is formed to be open to the pin journal. Therefore, it is possible to easily design the inlet opening so that the opening does not stop at the division portions of the first and second bearing metals, while connecting together the main journal and the pin journal by the first and second lubrication oil passages.

A control shaft 25 in embodiments corresponds to the rotary shaft or the swinging shaft of the present invention; a main journal 25a in the embodiments corresponds to the journal of the present invention; first and second bearing metals 51 and 52 in the embodiments correspond to the bearing metal or the bearing member of the present invention; and first and second lubrication oil passages P1 and P2 in the embodiments correspond to the lubrication oil passage of the present invention.

The above and other objects, features and advantages of the invention will become apparent from the preferred embodiments which will be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 9 show a first embodiment of the present invention, wherein FIG. 1 is a vertical sectional view of a variable compression ratio engine (in a state of a high compression ratio); FIG. 2 is a view taken along a line 2-2 in FIG. 1; FIG. 3 is a view taken along a line 3-3 in FIG. 1; FIG. 4 is a view taken in a direction of an arrow 4 in FIG. 1; FIG. 5 is a vertical sectional view of the variable compression ratio engine (in a state of a low compression ratio); FIG. 6 is an enlarged sectional view of an area indicated by 6 in FIG. 1 (in the state of the high compression ratio); FIG. 7 is a sectional view taken along a line 7-7 in FIG. 6; FIG. 8 is an exploded perspective view of a bearing metal; and FIG. 9 is an enlarged sectional view of Part 9 in FIG. 5 (in the state of the low compression ratio).

FIGS. 10 and 11 show a second embodiment of the present invention, wherein FIG. 10 is a view similar to FIG. 6 (in a state of a high compression ratio); and FIG. 11 is a view similar to FIG. 9 (a state of a low compression ratio).

DESCRIPTION OF PREFERRED EMBODIMENTS

A first embodiment of the present invention will now be described with reference to FIGS. 1 to 9.

First, a variable compression ratio engine which is one example of a variable stroke characteristic engine in which positions of a top dead center and a bottom dead center of a piston are changeable, will be described as the first embodiment of the present invention.

As shown in FIGS. 1 to 4, the variable compression ratio engine E includes an engine block 13 to which a cylinder block 11 and a crankcase 12 are coupled. A cylinder head 14 and a head cover 15 are coupled to an upper portion of the cylinder block 11. An oil pan 16 is formed in a lower portion of the crankcase 12. A main journal 17a of a crankshaft 17 is rotatably supported on parting faces of the cylinder block 11 and the crankcase 12. An intermediate portion of a substantially triangular lower link 18 is pivotally supported so as to swing on a pin journal 17b eccentric from the main journal 17a.

A piston 21 is slidably received in a cylinder sleeve 20 mounted in the cylinder block 11. An upper link 22 (a connecting rod) is pivotally supported at its upper end on the piston 21 through a piston pin 23, and at its lower end on one end of the lower link 18 through a first pin 24. A main journal 25a of a crank-shaped control shaft 25 is pivotally supported, via a cap 27 fastened to the crankcase 12 by bolts 26, 26 so as to swing, on a lower surface of the crankcase 12 laterally eccentric from the position of the crankshaft 17. A control link 28 includes a body 28a and a cap portion 28b fastened to a lower end of the body 28a by bolts 29, 29. The body 28a is pivotally supported at its upper end on the other end of the lower link 18 through a second pin 30. A pin journal 25b of the control shaft 26 is pivotally supported between a lower end of the body 28a and the cap portion 28b. The control shaft 25 swings in a range of a predetermined angle (for example, 120°) by an actuator (not shown) mounted at one end of the control shaft 25.

An intake port 32 and an exhaust port 33 are open into a combustion chamber 14a formed in a lower surface of the cylinder head 14. An intake valve 34 for opening and closing the intake port 32 and an exhaust valve 35 for opening and closing the exhaust port 33 are mounted in the cylinder head 14. The intake valve 34 is opened and closed by an intake camshaft 36 through an intake rocker arm 37. The exhaust valve 35 is opened and closed by an exhaust camshaft 38 through an exhaust rocker arm 39.

As shown in FIGS. 6 and 8, half-cylindrical first and second bearing metals 51 and 52 are mounted on parting faces 50 of the crankcase 12 and the cap 27, respectively, which clamp the main journal 25a of the control shaft 25. Oil grooves 51a and 52a for spreading a lubrication oil to an outer peripheral sliding surface of the main journal 25a are formed in inner peripheral surfaces of the first and second bearing metals 51 and 52. An oil bore 51b is formed in the first bearing metal 51 supported on the side of the crankcase 12. An oil reservoir 12a is formed in the crankcase 12 so as to face the oil bore 51b in the first bearing metal 51, and is connected to a lubrication oil pump (not shown) through oil passages 12b and 12c.

On the other hand, a first lubrication oil passage P1 and a second lubrication oil passage P2 are formed in the control shaft 25. The first lubrication oil passage P1 is open to the outer peripheral sliding surface of the main journal 25a, and the second lubrication oil passage P2 is formed to intersect the first lubrication oil passage P1 and open to an outer peripheral sliding surface of the pin journal 25b. Half-cylindrical first and second bearing metals 53 and 54 are mounted respectively to the body 28a and the cap portion 28b of the control link 28 supporting the pin journal 25b of the control shaft 25. The second lubrication oil passage P2 is open into oil grooves 53a and 54a circumferentially formed in inner peripheral surfaces of the first and second bearing metals 53 and 54.

The operation of the first embodiment of the present invention having the above-described arrangement will be described below.

The actuator is driven in accordance with the operational state of the engine E, whereby the control shaft 25 connected to the actuator is rotated to any position between a position shown in FIG. 1 and a position shown in FIG. 5. In the position shown in FIG. 1, the pin journal 25b is located below the main journal 25a of the control shaft 25. Therefore, the control link 28 is pulled down, so that the lower link 18 is swung in a clockwise direction about the pin journal 17b of the crankshaft 17, whereby the upper link 22 is pushed up to raise the position of the piston 21, thereby bringing the engine E into a state of a high compression ratio.

On the other hand, in the position shown in FIG. 5, the pin journal 25b is located above the main journal 25a of the control shaft 25. Therefore, the control link 28 is pushed up, so that the lower link 18 is swung in a counterclockwise direction about the pin journal 17b of the crankshaft 17, whereby the upper link 22 is pulled down to lower the position of the piston 21, thereby bringing the engine E into a state of a low compression ratio.

In this way, the control link 28 is moved up and down by the swing of the control shaft 25, thereby changing the motion-restraining condition of the lower link 18 to change the stroke characteristic including the position of the top dead center of the piston 21. In this manner, the compression ratio of the engine E is controlled as desired.

As shown in FIGS. 6 to 9, the lubrication oil is supplied to the oil reservoir 12a through the oil passages 12c and 12b in the crankcase 12 in order to lubricate the main journal 25a and the pin journal 25b of the control shaft 25 during operation of the engine E, and flows from the oil bore 51b of the first bearing metal 51 among the first and second bearing metals 51 and 52 supporting the main journal 25a of the control shaft 25 into the oil grooves 51a and 52a in the inner peripheral surface of the first and second bearing metals 51 and 52, thereby lubricating the sliding surface of the main journal 25a.

A portion of the lubrication oil supplied to the oil bore 51b in the first bearing metal 51 flows from the first lubrication oil passage P1 formed in the control shaft 25 via the second lubrication oil passage P2 to reach the sliding surface of the pin journal 25b, and then flows into the oil grooves 53a and 54a in the inner peripheral surfaces of the first and second bearing metals 53 and 54 supporting the pin journal 25b, thereby lubricating the sliding surface of the pin journal 25b.

A portion of the lubrication oil supplied to the oil grooves 51a and 52a in the inner peripheral surfaces of the first and second bearing metals 51 and 52 leaks from division portions 55, 55 of the first and second bearing metals 51 and 52 via the parting surfaces 50 of the crankcase 12 and the cap 27. Therefore, a reduction of hydraulic pressure is inevitable in the vicinity of the division portions 55, 55. Therefore, there is a possibility that when an inlet opening of the first lubrication oil passage P1 moves past the division portions 55, 55 in the process of the swing of the control shaft 25, or when the inlet opening of the first lubrication oil passage P1 stops at the division portions 55, 55, the amount of the lubrication oil supplied to the first lubrication oil passage P1 is decreased to cause a lubrication deficiency to the pin journal 25b.

In the present embodiment, however, even if the control shaft 25 is swung between a high compression ratio position shown in FIG. 6 and a low compression ratio position shown in FIG. 9, the position of the inlet opening of the first lubrication oil passage P1 of the main journal is determined so that the opening is not aligned with the division portions 55, 55 of the first and second bearing metals 51 and 52, namely, the inlet opening of the first lubrication oil passage P1 cannot stop at the division portions 55, 55 of the first and second bearing metals 51 and 52 in the process of the reciprocal swing of the control shaft 25. Therefore, it is possible to minimize the leakage of the lubrication oil from the division portions 55, 55 and supply the lubrication oil having a sufficient pressure to the first lubrication oil passage P1, thereby reliably lubricating the pin journal 25b. Especially, it is possible to excellently maintain the supply of the lubrication oil to the pin journal 25b of the control shaft 25 to which a large load is applied by a combustion pressure, leading to a smooth movement of each link.

To ensure a sufficient vertical stroke of the control link 28, the pin journal 25b is required to move vertically in Figures across the parting faces 50 of the crankcase 12 and the cap 27. Therefore, if the first and second lubrication oil passages P1 and P2 are replaced by a single straight lubrication oil passage, an inlet opening of such a lubrication oil passage inevitably moves past the division portions 55, 55 of the first and second bearing metals 51 and 52 for the main journal 25a. In the present embodiment, however, it is possible to easily prevent the inlet opening of the first lubrication oil passage P1, into which the lubrication oil flows, from moving past the division portions 55, 55 of the first and second bearing metals 51 and 52, by forming the first and second lubrication oil passages P1 and P2 intersecting each other at a predetermined angle in the control shaft 25.

A second embodiment of the present invention will now be described with reference to FIGS. 10 and 11.

In the above-described first embodiment, the oil reservoir 12a and the lubrication oil passages 12b and 12c for supplying the lubrication oil to the main journal 25a of the control shaft 25 are formed in the crankcase 12, but in the second embodiment, an oil reservoir 27a and lubrication oil passages 27b and 27c are formed in the cap 27, and the arrangement of the other components is the same as that of the first embodiment.

Also in the second embodiment, when the control shaft 25 is located between the high compression ratio position shown in FIG. 10 and the low compression ratio position shown in FIG. 11, the inlet opening of the first lubrication oil passage P1 cannot move past the division portions 55, 55 of the first and second bearing metals 51 and 52, thereby achieving an effect same as that of the first embodiment.

Although the embodiments of the present invention have been described, various modifications in design may be made without departing from the subject matter of the invention.

For example, the variable compression ratio engine has been described in the embodiments, but one or both of the compression ratio and the displacement of the engine can be changed by changing the dimensions of various portions in the same structure. The present invention is applicable to this kind of variable stroke characteristic engine.

The application of the present invention is not limited to a swinging shaft such as the control shaft 25, and the present invention is also applicable to a rotary shaft rotatable at a rotational angle exceeding 360°. Also in this case, the leakage of lubrication oil can be minimized by arranging the rotary shaft so that the inlet opening of the first lubrication oil passage P1 does not stop at the division portions 55, 55 of the first and second bearing metals 51, 51.

Further, in the embodiments, the control link 28 is connected to the lower link 18, but the present invention is also applicable to a variable stroke characteristic engine in which the control link 28 is connected to the upper link 22.

Furthermore, in the embodiments, the opening of the first lubrication oil passage P1 is the inlet for the lubrication oil, but may be an outlet for the lubrication oil.

Claims

1. A lubrication oil supply structure in which a lubrication oil passage formed within a rotary shaft is open to a journal which is supported by a bearing member divided into a plurality of pieces, wherein an opening of the lubrication oil passage of the rotary shaft is designed so that the opening does not stop at division portions of the bearing member.

2. A lubrication oil supply structure in which a lubrication oil passage formed within a swinging shaft, which swings in a range of a predetermined angle, is open to a journal which is supported by a bearing member divided into a plurality of pieces, wherein an opening of the lubrication oil passage of the swinging shaft is designed so that the opening does not stop at division portions of the bearing member.

3. A lubrication oil supply structure comprising: a crankshaft whose main journal is rotatably supported in an engine block; a control shaft whose main journal is supported in the engine block so as to swing in a range of a predetermined angle; a lower link swingably supported on a pin journal of the crankshaft; an upper link connecting the lower link to a piston; and a control link which connects the lower link or the upper link to a pin journal of the control shaft, the main journal of the control shaft being supported by a bearing metal divided into a plurality of pieces, a lubrication oil being supplied through the bearing metal to a sliding surface of the main journal of the control shaft and to an inlet opening of a lubrication oil passage which is formed within the control shaft and open to the sliding surface of the main journal of the control shaft, wherein the range of swing of the control shaft is determined so that the inlet opening of the lubrication oil passage of the control shaft does not move past division portions of the bearing metal divided into the plurality of pieces.

4. A lubrication oil supply structure according to claim 3, wherein the lubrication oil passage of the control shaft is divided into a first lubrication oil passage open to the main journal of the control shaft, and a second lubrication oil passage open to the pin journal of the control shaft, the first and second lubrication oil passages being formed to intersect each other at a predetermined angle as viewed in an axial direction of the control shaft.