JP7041549B2 - Double link type piston crank mechanism of internal combustion engine - Google Patents

Description

The present invention relates to a double link type piston crank mechanism of an internal combustion engine, and more particularly to an improvement of a lubricating structure for supplying lubricating oil to a connecting portion between a lower link and an upper link through the inside of a crankshaft.

Patent Document 1 and the like previously proposed by the present applicant are known as a conventional technique in which a piston pin and a crank pin of a reciprocating internal combustion engine are connected by a double-link type piston crank mechanism. This is an upper link connected to the piston pin of the piston, a lower link connecting the upper link and the crank pin of the crankshaft, one end swingably supported toward the engine body side, and the other end of the lower end. It has a control link that is linked to the link. The upper link and the lower link are rotatably connected to each other via the upper pin, and the control link and the lower link are rotatably connected to each other via the control pin.

The upper link in such a double-link type piston crank mechanism has a configuration in which an annular pin boss portion is provided at both ends of a rod-shaped rod, and one piston pin pin boss portion is connected to the piston pin. The other pin boss portion for the upper pin is connected to the upper pin. Both ends of the upper pin are supported by a pair of lower link side pin bosses formed in a bifurcated shape at one end of the lower link, and the upper pin pin boss portion of the upper link is rotatably fitted in the central portion in the axial direction. It fits.

In order to lubricate the fitting portion between the upper pin pin boss portion and the upper pin, that is, the sliding surface, Patent Document 1 describes a crankpin oil passage formed radially through the crankpin and a penetration formed through the lower link. A lubrication structure is disclosed in which pressurized lubricating oil is ejected toward a pin boss portion for an upper pin through a lower link oil passage. Specifically, the crankpin oil passage and the lower link oil passage communicate with each other at the crank angle at the top dead point of the piston, and the lubricating oil pumped from the lubricating oil passage inside the crankshaft to the crankpin oil passage is the lower link oil passage. It is configured to eject toward the pin boss part for the upper pin through. As a result, the upper pin is lubricated near the compression top dead center where the lubrication requirement becomes strict due to the combustion load.

Japanese Unexamined Patent Publication No. 2010-185329

In the above Patent Document 1, the crank pin oil passage and the lower link oil passage are set to communicate with each other when the crank angle is at the top dead point position of the piston, but the lubricating oil has a relatively large mass and has a relatively large mass. Due to its viscosity, there is a delay between the opening of the oil passage and the actual ejection of the lubricating oil. That is, there is a relatively large delay between the timing when the communication area of the oil passage becomes maximum and the timing when the amount of lubricating oil actually supplied near the upper pin peaks. Patent Document 1 discloses that such a delay in transfer is not taken into consideration, and that the crankpin oil passage and the lower link oil passage are matched at a necessary timing for lubrication (that is, near the top dead center of the piston). I'm just there. However, even if the communication area is maximized at the top dead center position of the piston, the amount of lubricating oil is actually sufficient for the crank angle (for example, 10 ° to 20 ° after top dead center) where the combustion load is maximum. I can't get it.

In particular, between the upper pin to which the lubricating oil is supplied and the pin boss portion for the upper pin, the mode of the minute gap between the two is changed by receiving the combustion load after the top dead point of the piston and reversing the load acting direction. A pumping action is obtained that sucks the lubricating oil into the minute gaps that become the oil film surface from the surroundings, but if the lubricating oil does not reach the vicinity of the upper pin by the time the load action direction is reversed, the lubricating oil will be minute due to this pumping action. Unable to get introduction into the gap.

The present invention is a double link type piston crank mechanism of an internal combustion engine including an upper link, a lower link and a control link.
A crankpin oil passage that is formed inside the crankpin so that one end opens to the outer peripheral surface of the crankpin and is supplied with lubricating oil pressurized from the crank journal.
Lower link oil formed on the lower link, one end of which opens toward the upper pin pin boss portion of the upper link, and the other end of which opens on the crank pin bearing surface of the lower link corresponding to the crank pin oil passage. With a road,
The crankpin oil passage and the lower link oil passage are aligned with each other near the top dead center of the piston, and the lubricating oil is supplied toward the pin boss portion for the upper pin. The crank angle that maximizes the communication area with the lower link oil passage is set before the top dead center of the piston.
Specifically, the communication area between the crankpin oil passage and the lower link oil passage is maximized at 10 ° to 20 ° before top dead center, and the crankpin oil passage and the lower link oil passage are also at the top dead center. The state of communication with the oil passage is maintained.

In this way, the maximum communication area between the crankpin oil passage and the lower link oil passage is before the top dead center of the piston, so that the peak amount of lubricating oil actually supplied to the vicinity of the upper pin is delayed after this. , The timing corresponds relatively to the crank angle at which the combustion load after the top dead center of the piston becomes maximum.

Then, the lubricating oil has reached the vicinity of the minute gap between the upper pin and the pin boss portion for the upper pin by the time when the load acting direction is reversed, and the lubricating oil is oil filmed by the pumping action due to the reversing of the load acting direction. It is effectively introduced into the minute gaps that form the surface.

According to the present invention, the communication area of the oil passage is maximized at the crank angle before the top dead center of the piston in consideration of the mass of the lubricating oil and the supply delay due to the viscosity, so that the combustion load is maximized. Sufficient lubrication is possible at the crank angle.

The configuration explanatory view of the double-link type piston crank mechanism of one Example. A perspective view of the lower link. FIG. 6 is a cross-sectional view of a piston crank mechanism at BTDC 10 ° showing a lubrication structure. Explanatory drawing which shows the angular relation of three oil passages. Sectional view at top dead center position of the piston. Sectional drawing at the crank angle which maximizes a combustion load. A characteristic diagram showing the time change of the amount of lubricating oil supplied to the bearing surface of the upper pin. Explanatory drawing explaining the reversal of the load acting direction in the bearing part of an upper pin, and the pumping action of the lubricating oil accompanying this.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the components of a double link piston crank mechanism to which the present invention applies. This double-link type piston crank mechanism itself is known from Patent Document 1 and the like described above, and has an upper link 3 having one end connected to the piston 1 via a piston pin 2 and an upper pin to the other end of the upper link 3. It includes a lower link 6 connected via 4 and connected to a crankpin 5A of the crankshaft 5, and a control link 7 that regulates the degree of freedom of the lower link 6. One end of the control link 7 is swingably supported by the support pin 8 on the engine body side, and the other end is connected to the lower link 6 via the control pin 9. The double link type piston crank mechanism can also be configured as a variable compression ratio mechanism by changing the position of the support pin 8.

As shown in FIG. 2, the lower link 6 has a cylindrical crankpin bearing portion 11 fitted to the crankpin 5A in the center, and is substantially 180 ° opposite to each other with the crankpin bearing portion 11 interposed therebetween. A pin boss portion 12 for an upper pin and a pin boss portion 13 for a control pin are provided at positions on the side. The lower link 6 has a parallelogram shape close to a rhombus as a whole, and has a lower link upper 6A including a pin boss portion 12 for an upper pin and a control pin on a dividing surface 14 passing through the center of the crankpin bearing portion 11. It is formed by being divided into two parts, a lower link lower 6B including a pin boss portion 13. These lower link uppers 6A and lower link lowers 6B are fastened to each other by a pair of bolts 18 (see FIG. 3) that are inserted in opposite directions after fitting the crankpin bearing portion 11 into the crankpin 5A.

The upper pin pin boss portion 12 has a bifurcated structure so as to sandwich the upper link 3 in the axial center portion, and each of the pair of upper pin pin boss portions 12 supporting both ends in the axial direction of the upper pin 4 , Extends along the axial end face of the lower link 6. That is, between the pair of upper pin pin boss portions 12, there is a groove portion 15 having a constant width that enables the swinging motion of the upper link 3. Each upper pin pin boss portion 12 has a circular pin fitting hole 16, and the upper pin 4 is press-fitted into these pin fitting holes 16.

The control pin pin boss portion 13 has basically the same configuration, and the control link 7 is combined with the groove portion (not shown) between the pair of bifurcated control pin pin boss portions 13 to form both ends of the control pin 9. The portion is press-fitted into the pin fitting hole 17 of the pin boss portion 13 for the control pin.

The upper link 3 is configured as one part by forging or casting carbon steel, and is provided with a rod portion 21 having a rectangular cross section extending linearly and one end of the rod portion 21. It has an annular piston pin pin boss portion 22 and an annular upper pin pin boss portion 23 provided at the other end of the rod portion 21.

The piston pin pin boss portion 22 is rotatably fitted to the central portion of the piston pin 2 whose both ends are supported by the piston 1. The piston pin 2 may be press-fitted into the piston 1 to be fixed, or may be rotatably supported by the piston 1 as a so-called full float type.

The upper pin pin boss portion 23 is rotatably fitted to the central portion of the upper pin 4 whose both ends are supported by the upper pin pin boss portion 12 on the lower link 6 side. A cylindrical bearing metal (not shown) is press-fitted into the piston pin pin boss portion 22 and the upper pin pin boss portion 23.

FIG. 3 is a cross-sectional view showing a lubrication structure for lubricating the contact surface (sliding surface) between the upper pin 4 and the pin boss portion 23 for the upper pin, along a cross section passing through the center of the lower link 6 in the axial direction. Each part of the double link type piston crank mechanism is shown.

As part of the oil passages constituting the lubrication structure, the crankpin 5A includes a crankpin oil passage 33 formed by drilling in the radial direction. The crank pin oil passage 33 intersects the oil passage 34 inside the crankshaft 5 which is diagonally drilled over the crank journal 5B and the crank pin 5A, and communicates with each other.

The crank journal 5B of the crankshaft 5 is rotatably supported between the bulkhead 31a of the cylinder block 31 and the main bearing cap 32. For example, the crank journal 5B is rotatably supported from the cylinder block 31 side via an oil hole on the main bearing surface. Pressurized lubricating oil is introduced into the oil passage 34. Therefore, pressurized lubricating oil is constantly supplied to the crankpin oil passage 33.

FIG. 3 shows the position and posture of each member when the crank angle is 10 ° (BTDC 10 °) before the top dead center of the piston, and one end 33a of the crankpin oil passage 33 opened on the outer peripheral surface of the crankpin 5A. Directs the vicinity of the upper pin pin boss portion 12 of the lower link 6 at this BTDC 10 °. More specifically, it points to a position below the center of the upper pin 4.

In this way, the lower link oil passage 35 is drilled on the upper pin pin boss portion 12 side of the lower link 6 corresponding to the crank pin oil passage 33 that opens on the outer peripheral surface of the crank pin 5A. The lower link oil passage 35 penetrates the bottom surface of the groove portion 15 of the lower link 6, and one end 35a on the outer peripheral side opens toward the upper pin pin boss portion 23 of the upper link 3 and the other end 35b on the inner peripheral side. Is open to the crankpin bearing surface so as to match one end 33a of the crankpin oil passage 33. When the bearing metal does not intervene between the crankpin 5A and the lower link 6, the inner peripheral surface of the crankpin bearing portion 11 of the lower link 6 becomes the crankpin bearing surface, but when the bearing metal intervenes, it becomes the crankpin bearing surface. An oil hole that becomes a part of the lower link oil passage 35 is also formed through the bearing metal.

Further, in the upper pin pin boss portion 23 of the upper link 3, the upper link oil passage 36 is drilled in the radial direction corresponding to the lower link oil passage 35. The upper link oil passage 36 penetrates between the inner peripheral surface and the outer peripheral surface of the upper pin pin boss portion 23, and one end 36a on the outer peripheral side opens toward the lower link oil passage 35 of the lower link 6. ing. Further, the upper link oil passage 36 is located in the lower half portion of the upper pin pin boss portion 23 forming an annular shape. That is, when the pin boss portion 23 for the upper pin is divided into the upper half portion of 180 ° centered on the rod portion 21 and the lower half portion of the remaining 180 °, the upper link oil passage 36 is within the range of the lower half portion. Is located. Further, even in the lower half of 180 °, avoiding the central portion (the portion opposite to the rod portion 21) on which the load in the tensile direction of the upper link 3 acts, the direction is diagonal to the center line of the upper link 3. It is formed through at the position where.

In the illustrated example, the crankshaft 5 rotates clockwise. Then, when the crank angle is near the top dead point of the piston, the crankpin oil passage 33, the lower link oil passage 35, and the upper link oil passage 36 communicate with each other (that is, the openings at the ends of the oil passages match each other). ), And the pressurized lubricating oil is ejected from the lower link oil passage 35 toward the upper pin pin boss portion 23, and the contact surface (sliding) between the upper pin pin boss portion 23 and the upper pin 4 via the upper link oil passage 36. Introduced to the moving surface).

More specifically, as described above, FIG. 3 shows a state when the crank angle is at BTDC 10 °, and the communication area between the crankpin oil passage 33 and the lower link oil passage 35 is the maximum at this BTDC 10 °. It becomes. That is, the opening center of one end 33a of the crankpin oil passage 33 and the opening center of the other end 35b of the lower link oil passage 35 match. At the same time, the opening of one end 35a of the lower link oil passage 35 points to the opening of one end 36a of the upper link oil passage 36, and the center of the opening of one end 35a of the lower link oil passage 35 and one end 36a of the upper link oil passage 36. It almost matches the center of the opening.

Here, when the crank angle is at BTDC 10 ° as shown in FIG. 3, the crankpin oil passage 33, the lower link oil passage 35, and the upper link oil passage 36 are not aligned in a perfect straight line. , Continuous in a polygonal line. This is because the formation position of the alllink oil passage 35 in the lower link 6 is taken into consideration. Assuming that the three oil passages 33, 35, and 36 are arranged so as to be linearly aligned along the straight line connecting the center of the crankpin 5A and the center of the upper pin 4, the lower link oil passage 35 is larger than the illustrated example. It will be located near the center of the lower link 6. For example, when a downward combustion load acts on the upper pin 4 with the control pin 9 as a fulcrum, the crankpin 5A as an action point, and the upper pin 4 as a force point, a large bending load acts on a portion near the center of the upper part of the lower link 6. Therefore, it is not preferable to form the lower link oil passage 35 through the portion having a large bending load. As shown in the illustrated example, the lower link oil passage 35 is configured to form a polygonal line when the communication area of the oil passages 33 and 35 is maximized, so that the lower link oil passage 35 is located at the center of the crankpin 5A and the center of the upper pin 4. It is arranged outside the straight line connecting the two (on the left side in FIG. 3), and a portion having a large bending load of the lower link 6 can be avoided.

In the figure, the crankpin oil passage 33 and the lower link oil passage 35 are almost linearly aligned, but the lower link oil passage 35 is on the radius line of the crankpin 5A (in other words, the crankpin oil passage 33). On the other hand, it is slightly tilted. Specifically, one end 35a on the upper link 3 side is located offset upward (in other words, closer to the center of the lower link 6) with respect to the radius line of the crankpin 5A passing through the opening center of the other end 35b on the crankpin 5A side. is doing. FIG. 4 is an explanatory diagram schematically showing the angular relationship of the three oil passages 33, 35, and 36 having a polygonal line shape with some exaggeration, and connects the center O1 of the crankpin 5A and the center O2 of the upper pin 4. Three oil passages 33, 35, and 36 are arranged so as to project outward (left side) with respect to the straight line L, and the angles θ1 and θ2 having less than 180 ° are all configured on the side closer to the straight line L.

FIG. 5 shows a state at a position where the crank angle is advanced by 10 ° from the state of FIG. 3, that is, a state at the top dead center position of the piston. At the top dead center position of the piston, the communication area of the oil passages 33 and 35 has already passed the maximum, and the communication area of the oil passages 33 and 35 has begun to decrease.

Further, FIG. 6 shows a state at a crank angle position where the combustion load is maximized, for example, 20 ° after the top dead center of the piston. At the crank angle where the combustion load is maximum, the communication area of the oil passages 33 and 35 is further reduced.

As described above, in the above embodiment, the communication area of the oil passages 33 and 35 is maximized at an appropriate crank angle position before the top dead point of the piston, for example, BTDC 10 °, and the communication is performed at the crank angle where the combustion load with high lubrication requirement is maximum. Although the area is relatively reduced, there is a relatively large delay due to the mass and viscosity of the lubricating oil in the transfer of the lubricating oil through the oil passages 33 and 35, so that there is a relatively large delay to the vicinity of the upper pin 4. Appropriate characteristics can be obtained as the actual supply amount of lubricating oil.

FIG. 7 is a characteristic diagram showing the time change of the amount of lubricating oil supplied to the bearing surface of the upper pin 4, and the time t1 corresponds to the BTDC 10 ° at which the communication areas of the oil passages 33 and 35 are maximum, and the time. t2 corresponds to the piston top dead center (TDC). Further, the time t3 corresponds to ATDC 20 ° at which the combustion load is maximized. In the above embodiment, as shown by the solid line, the amount of lubricating oil actually supplied increases from the time t1 when the communication area of the oil passages 33 and 35 is maximum, and lubrication is performed at the time t3 when the combustion load is maximum. The amount of oil peaks. Therefore, it is possible to reliably lubricate the bearing surface that receives the combustion load.

On the other hand, as shown by the broken line as a comparative example, if the communication area of the oil passages 33 and 35 is set to be the maximum at the time t2 corresponding to the top dead center of the piston, the lubrication that actually reaches the upper pin 4 is achieved. The peak amount of oil is delayed from the timing t3 at which the combustion load is maximized. Therefore, effective lubrication cannot be achieved.

If the engine rotation speed and viscosity (in other words, oil temperature) are different, the crank angle corresponding to the transfer delay of the lubricating oil changes. Therefore, it is possible to set the crank angle that maximizes the communication area of the oil passages 33 and 35 so that the peak of the lubricating oil amount and the timing of the maximum combustion load coincide with each other under the target engine operating conditions. desirable. For example, the crank angle that maximizes the communication area of the oil passages 33 and 35 is set within the range of 10 ° to 20 ° (BTDC 10 ° to BTDC 20 °) before the top dead center of the piston.

FIG. 8 is an explanatory diagram illustrating the reversal of the load acting direction in the bearing portion of the upper pin 4 and the accompanying pumping action of the lubricating oil. Between the upper pin 4 and the inner peripheral surface of the pin boss portion 23 for the upper pin, there is a minute gap 41 (exaggerated and enlarged in FIG. 8) for securing a lubricating oil film. FIG. 8A shows an aspect of the minute gap 41 at the top dead center position of the piston, and the pin boss portion 23 for the upper pin is moved upward by the inertial force of the piston 1 and the upper link 3 at the top dead center of the piston. The cylindrical microgap 41 expands at the top and shrinks at the bottom. FIG. 8B shows an aspect of the minute gap 41 at the crank angle where the combustion load is maximized. At this time, the upper pin pin boss portion 23 is pushed downward by the combustion load, so that the minute gap is cylindrical. The gap 41 shrinks at the top and expands at the bottom. That is, while the crank angle advances from the top dead center of the piston to the crank angle where the combustion load is maximized, the load acting direction is reversed, and the volume of the lower region of the minute gap 41 through which the upper link oil passage 36 communicates changes. do. This gives a pumping action.

Specifically, when changing from the aspect of FIG. 8 (a) to the aspect of FIG. 8 (b), the pressure decreases as the volume of the lower portion of the minute gap 41 increases, and the pressure decreases from the upper link oil passage 36. Lubricating oil is sucked into the gap 41. Here, in the above embodiment, as described above, the communication area of the oil passages 33 and 35 is maximized before the piston top dead center, so that the crank angle period from the piston top dead center to the maximum combustion load is reached. Therefore, the lubricating oil is surely present in the vicinity of the opening of one end 36a, which is the inlet of the upper link oil passage 36. Therefore, when the pumping action occurs due to the reversal of the load acting direction, the lubricating oil is surely introduced into the minute gap 41, that is, the bearing surface through the upper link oil passage 36.

In addition, instead of the upper link oil passage 36 in the upper pin pin boss portion 23, or in addition to the upper link oil passage 36, an oil groove along the radial direction may be provided on the end surface of the upper pin pin boss portion 23. In this case as well, the lubricating oil can be introduced by the pumping action.

1 ... Piston 2 ... Piston pin 3 ... Upper link 4 ... Upper pin 5 ... Crankshaft 5A ... Crankpin 6 ... Lower link 7 ... Control link 23 ... Upper pin pin boss 33 ... Crankpin oil passage 35 ... Lower link oil passage 36 ... Upper link oil passage 41 ... Small gap

Claims (3)

An upper link with one end connected to the piston via a piston pin,
The lower link connected to the other end of the upper link via the upper pin and connected to the crank pin of the crankshaft,
One end is swingably supported on the engine body side, and the other end is connected to the lower link via a control pin.
It is a double-link piston crank mechanism of an internal combustion engine equipped with
A crankpin oil passage formed inside the crankpin so that one end opens on the outer peripheral surface of the crankpin and to which the lubricating oil pressurized from the crank journal is supplied.
Lower link oil formed on the lower link, one end of which opens toward the upper pin pin boss portion of the upper link, and the other end of which opens on the crank pin bearing surface of the lower link corresponding to the crank pin oil passage. With a road,
The crankpin oil passage and the lower link oil passage are aligned with each other near the top dead center of the piston, and the lubricating oil is supplied toward the pin boss portion for the upper pin. The crank angle that maximizes the communication area with the lower link oil passage is set before the top dead center of the piston .
The communication area between the crankpin oil passage and the lower link oil passage is maximized at 10 ° to 20 ° before top dead center, and the communication between the crankpin oil passage and the lower link oil passage is also at the top dead center. A double-link piston crank mechanism for an internal combustion engine that is kept in good condition . Further, an upper link oil passage formed through between the inner peripheral surface and the outer peripheral surface of the pin boss portion for the upper pin is further provided.
At the crank angle where the communication area between the crankpin oil passage and the lower link oil passage is maximized, the opening at one end of the lower link oil passage directs the opening of the upper link oil passage on the outer peripheral surface of the pin boss portion for the upper pin. is doing,
The double link type piston crank mechanism of an internal combustion engine according to claim 1 . An upper link with one end connected to the piston via a piston pin,
The lower link connected to the other end of the upper link via the upper pin and connected to the crank pin of the crankshaft,
One end is swingably supported on the engine body side, and the other end is connected to the lower link via a control pin.
It is a double-link piston crank mechanism of an internal combustion engine equipped with
A crankpin oil passage formed inside the crankpin so that one end opens on the outer peripheral surface of the crankpin and to which the lubricating oil pressurized from the crank journal is supplied.
Lower link oil formed on the lower link, one end of which opens toward the upper pin pin boss portion of the upper link, and the other end of which opens on the crank pin bearing surface of the lower link corresponding to the crank pin oil passage. With a road,
The crankpin oil passage and the lower link oil passage are aligned with each other near the top dead center of the piston, and the lubricating oil is supplied toward the pin boss portion for the upper pin. The crank angle that maximizes the communication area with the lower link oil passage is set before the top dead center of the piston.
Further, an upper link oil passage formed through the inner peripheral surface and the outer peripheral surface of the pin boss portion for the upper pin is further provided.
At the crank angle where the communication area between the crankpin oil passage and the lower link oil passage is maximized, the opening at one end of the lower link oil passage directs the opening of the upper link oil passage on the outer peripheral surface of the pin boss portion for the upper pin. And
An internal combustion engine in which the crankpin oil passage, the lower link oil passage, and the upper link oil passage are continuous in a broken line at a crank angle at which the communication area between the crankpin oil passage and the lower link oil passage is maximized. Double link type piston crank mechanism.

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