JPH08277831A - Crank lubricating device for internal combustion engine - Google Patents

Abstract

PURPOSE: To achieve both improvement on the requirement for lubrication in high rotation region and the reduction of frictional loss in a low and medium rotation regions in a crank lubricating device for internal combustion engine. CONSTITUTION: A path 9 in a crank for guiding lubricating oil to a crank pin 2 is formed to be offset from the rotary center of a crankshaft, and an overlay layer having the thermal conductivity higher than that of the crank pin 2 is formed over the whole periphery on the bearing surface of respective bearing metals 7, 8 interposed in connecting rod bearings.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a crank lubrication device for an internal combustion engine.

[0002]

2. Description of the Related Art The sliding surface of a crank pin and a connecting rod is
As the engine speeds up and the output power increases, it slides at high speed and under a large load, so that the temperature rises due to shearing heat generation of the lubricating oil, resulting in extremely severe lubrication conditions.

In order to solve such a problem, the applicant of the present invention, in order to alleviate the lubricating condition of the sliding surface of the crank pin, the thermal conductivity of the overlay layer, which is the bearing surface of the connecting rod bearing, from the crank pin over the entire circumference. We have developed a connecting rod bearing structure made of high-quality material.

In this connecting rod bearing structure, the minimum oil film portion that raises the temperature and pressure under an instantaneous load in a high rotational speed region where the inertial force of the piston, connecting rod, etc. is dominant as the load suspended from the connecting rod bearing to the crank pin The heat from the main is quickly flowed mainly to the connecting rod bearing side. Next, the part that absorbed heat from the minimum oil film moves in the circumferential direction due to the rotation of the crank pin and is exposed to the lubricating oil in the part with a large oil film thickness, and the heat once absorbed by the connecting rod bearing is absorbed. Flows into the lubricating oil again (this is also done quickly due to the high thermal conductivity of the overlay layer), and is released to the outside of the connecting rod bearing together with the lubricating oil. That is, the heat generated in the minimum oil film portion can be largely suppressed from flowing into a specific portion of the inner region of the crankpin where cooling with the lubricating oil is difficult because it constantly faces the minimum oil film portion.

By suppressing the temperature rise in the vicinity of the minimum oil film portion of the crankpin in this manner, it is possible to prevent the viscosity of the lubricating oil in the vicinity of the minimum oil film portion from decreasing, and to secure the oil film thickness of the minimum oil film portion, It is possible to prevent the shear rate of the liquid film in step (1) from becoming extremely high and the friction loss from rapidly increasing.

On the other hand, as a crank lubrication device for an automobile engine, for example, there is a conventional one as shown in FIG. 7 (reference material: Preprints for Academic Lecture Meeting of Automotive Engineering Society 921 19).
92-5 117th to 120th tribute).

To explain this, the crankshaft provided in the engine has a journal portion 1 supported by a main bearing of the engine body and a crank pin 2 supported by a connecting rod bearing of a connecting rod.

Upper and lower bearing metals 5 and 6 which are in sliding contact with the journal portion 1 are interposed in each main bearing.

Upper and lower bearing metals 7 and 8 slidingly contacting the crank pin 2 are interposed in each connecting rod bearing.

Inside the crankshaft 3, a crank internal passage 9 connecting each journal portion 1 and the crankpin 2 is formed. Lubricating oil discharged from the oil pump is shunted from the main gallery of the engine body and supplied to each main bearing, and the half-circumferential groove 11 formed only on the upper bearing metal 5 is formed.
Is supplied to each crank pin 2 through each crank internal passage 9.

A so-called H type internal crank passage 9
Has a through hole 38 whose both ends are open to the journal portion 1,
Both ends thereof are formed by a through hole 36 opened to the crank pin 2 and a through hole 37 connecting the through holes 38 and 36.

The bearing metal 7, 8 interposed in the connecting rod bearing is generally made of an anti-friction alloy containing lead (Pb) and tin (Sn) as its main components on the surface of the bearing that is in sliding contact with the crankpin 2 of the crankshaft. A general overlay layer is formed.

It should be noted that the opening end 30 must be sufficiently chamfered so that the corner portion formed at the outlet of the through hole 36 does not damage the relatively soft overlay layer. Since it is processed in a direction orthogonal to the outer peripheral surface of No. 2, sufficient chamfering can be easily performed.

[0014]

Since the H-type crank internal passage 9 has a structure in which lubricating oil is guided to the crank pin 2 through the center of rotation of the crankshaft, centrifugal force due to the rotation of the crankshaft is generated in the crank internal passage 9. It works against the lubricating oil that is about to flow. Therefore, the amount of lubricating oil supplied to the crankpin 2 has a characteristic shown by a broken line in FIG. 4, that is, a characteristic that is not significantly affected by the engine speed.

By the way, in the connecting rod bearing structure in which the overlay layer serving as the bearing surface is formed of a material having a higher thermal conductivity than the crankpin 2 over the entire circumference, not only in the high rotation range but also in the low and medium rotation range to some extent. Since it has the effect of suppressing the bearing temperature, the combination of such a connecting rod bearing structure and the conventional lubrication system described above is used to improve the discharge pressure characteristics of the oil pump to ensure the cooling performance of the connecting rod bearing in the output range (high rotation range). If set, the amount of lubricating oil in the fuel consumption range (low to middle speed range) becomes excessive, the temperature of the connecting rod bearing drops too much, and the viscosity of the lubricating oil increases, causing an increase in friction loss.

An object of the present invention is to solve the above problems and to improve the lubrication conditions in the high rotation speed range and reduce the friction loss in the low and middle rotation speed range.

[0017]

According to another aspect of the present invention, there is provided a crank lubrication device for an internal combustion engine, which rotatably supports a connecting rod for converting a reciprocating motion of a piston into a rotary motion of a crankshaft and a journal part of the crankshaft. A main bearing, a connecting rod bearing that rotatably supports a crankshaft crankpin on the connecting rod, and a crank internal passage that supplies lubricating oil discharged from an oil pump from the crankshaft main bearing to the connecting rod bearing through the inside of the crankshaft. In the internal combustion engine including, the crank internal passage is formed offset from the rotation center of the crankshaft, and an overlay layer having a higher thermal conductivity than the crankpin is formed on the bearing surface of the connecting rod bearing over the entire circumference.

According to a second aspect of the present invention, in the crank lubrication device for an internal combustion engine according to the first aspect of the present invention, the sliding surface of the crank pin with respect to the connecting rod bearing is formed from the main shaft side region close to the journal part and the journal part. When divided into the distant main spindle side regions, the open end of the crank internal passage with respect to the crank pin is arranged in the counter main spindle side region.

According to a third aspect of the present invention, in the crank lubrication device for an internal combustion engine according to the first or second aspect, the overlay layer of the connecting rod bearing is formed on the bearing surface with an alloy containing aluminum and tin as main components.

A crank lubrication device for an internal combustion engine according to a fourth aspect is the crank lubrication device for an internal combustion engine according to any one of the first to third aspects, in which a main bearing is formed with a half-circumferential groove communicating with the main gallery, and a crank internal passage is formed. , Two openings for the journal portion and one opening for the crankpin are formed.

According to a fifth aspect of the present invention, there is provided a crank lubrication device for an internal combustion engine according to any one of the first to third aspects, in which a main bearing is formed with an entire circumferential groove communicating with the main gallery, One opening for the journal portion and one opening for the crankpin are formed in the passage.

[0022]

In the lubricating system for the internal combustion engine according to the first aspect, the lubricating oil discharged from the oil pump is supplied from the main bearing through the crank internal passage to the bearing gap between the connecting rod bearing and the crank pin. This lubricating oil lubricates the sliding contact part between the connecting rod bearing and the crank pin,
Cooled.

At high engine speed, the inertial force of the piston, connecting rod, etc. increases in proportion to the square of the number of revolutions.
The load is always applied to the inner region of the sliding surface of the crank pin located on the center side of the crank shaft, and the frequency of the minimum oil film thickness of the lubricating oil increases at a specific portion of the inner region. When the oil film thickness of the minimum oil film portion is, for example, about 1 to 2 microns, the viscosity of the lubricating oil is significantly increased due to the increase in pressure, the shear rate of the liquid film is increased, and the friction loss (friction heat generation) is rapidly increased. To do.

The crankpin always faces the minimum oil film portion at a specific portion in its inner region, while the portion where the connecting rod bearing faces the minimum oil film portion extends in the circumferential direction over substantially the entire circumference as the crankpin rotates. Move to.

Since the overlay layer serving as the bearing surface of the connecting rod bearing is formed of a material having a higher thermal conductivity than the crank pin over the entire circumference, the inertia force of the piston, connecting rod, etc. is dominant as the load suspended from the connecting rod bearing to the crank pin. In the high rotation speed range, the heat from the minimum oil film portion that heats up and pressurizes under an instantaneous load is mainly rapidly flowed into the connecting rod bearing side. Next, the part that absorbed heat from the minimum oil film moves in the circumferential direction due to the rotation of the crank pin and is exposed to the lubricating oil in the part with a large oil film thickness, and the heat once absorbed by the connecting rod bearing is absorbed. Flows into the lubricating oil again (this is also done quickly due to the high thermal conductivity of the overlay layer), and is released to the outside of the connecting rod bearing together with the lubricating oil. That is, the heat generated in the minimum oil film portion can be largely suppressed from flowing into a specific portion of the inner region of the crankpin where cooling with the lubricating oil is difficult because it constantly faces the minimum oil film portion.

By suppressing the temperature rise in the vicinity of the minimum oil film portion of the crankpin in this way, it is possible to prevent the viscosity of the lubricating oil in the vicinity of the minimum oil film portion from decreasing, to secure the oil film thickness of the minimum oil film portion, and to reduce the minimum oil film portion. It is possible to prevent the shear rate of the liquid film in step (1) from becoming extremely high and the friction loss from rapidly increasing.

The crank internal passage formed offset from the center of rotation of the crankshaft reduces the centrifugal force acting against the lubricating oil flowing from the main bearing into the through hole, and at the same time, lubricating oil flowing out to the connecting rod bearing. The centrifugal force that acts on is increased. For this reason, the amount of lubricating oil supplied to the crankpin greatly increases as the engine speed increases.

In an operating range where the engine speed is low and the frictional heat generated in the connecting rod bearing is small, the discharge pressure of the oil pump is low and the centrifugal force acting on the lubricating oil flowing in the crank internal passage is small, so Is supplied with a small amount of lubricating oil, but heat is radiated from the overlay layer, which has a higher thermal conductivity than the crankpin, to the lubricating oil, and the temperature of the lubricating oil intervening in the connecting rod bearings is maintained properly. The viscosity is reduced to reduce friction loss.

In an operating range where the engine speed is high and frictional heat generated in the connecting rod bearing is large, a large amount of lubricating oil is supplied to the connecting rod bearing because the centrifugal force acting on the lubricating oil flowing through the crank internal passage is large, and the crankpin Dissipation of heat from the overlay layer, which has a higher thermal conductivity, to the lubricating oil is promoted, and the large amount of frictional heat that is generated is sufficiently carried away by the lubricating oil, which prevents overheating of the connecting rod bearings and prevents seizures. To prevent.

In the crank lubrication device for an internal combustion engine according to a second aspect of the present invention, the opening end of the crank internal passage, which is open in the anti-spindle side region of the sliding surface of the crank pin, has a piston,
Without reducing the bearing area in the main shaft side region where the inertial force of the connecting rod or the like acts, the surface pressure can be suppressed to a low level and the lubricating oil film constituent capacity can be secured.

While the main shaft side region of the crank pin always faces the minimum oil film portion, the lubricating oil sent from the crank internal passage is supplied to the anti-spindle side region, so that the minimum oil film portion carried away by the lubricating oil Although the amount of heat generated is reduced, heat dissipation from the overlay layer, which has a higher thermal conductivity than the crankpin, to the lubricating oil is promoted, and the frictional oil that is generated in large quantities in the high rpm range is sufficiently carried away by the lubricating oil.
The connecting rod bearing can be prevented from being overheated and seizure can be prevented.

In the crank lubrication device for an internal combustion engine according to claim 3, since the overlay layer of the connecting rod bearing has a structure in which the bearing surface is made of an alloy containing aluminum and tin as a main component, the heat from the lubricating oil film to the overlay layer is increased. Even if the amount of conduction is secured, the hardness of the bearing surface is sufficiently secured, and even if the chamfering process at the open end of the crank internal passage opening to the crank pin is simplified, the overlay layer is not scraped off.

In the crank lubrication device for an internal combustion engine according to a fourth aspect, a part of the lubricating oil supplied to the main bearing flows into the crank chamber from the bearing gap between the main bearing and the journal portion, and the rest flows to the main bearing. The formed half-circumferential groove is supplied to each crank pin through each crank internal passage.

By forming the crank internal passage connecting the journal portion and the crank pin by offsetting from the center of rotation of the crankshaft, the centrifugal force acting against the lubricating oil flowing from the main bearing into the through hole is reduced. With
Since the centrifugal force that acts on the lubricating oil that flows out to the crankpin increases, the amount of lubricating oil that is supplied to the crankpin greatly increases as the engine speed increases.

In the crank internal passage, either one of the two openings opened in the journal portion is always in communication with the half-circumferential groove, and the supply of lubricating oil to the crank pin is not interrupted.

In the crank lubrication device for an internal combustion engine according to a fifth aspect, a part of the lubricating oil supplied from the main gallery to the main bearing flows out into the crank chamber from the bearing gap between the main bearing and the journal portion, and the rest is left. It is supplied to each crank pin from each half-circle groove formed in the main bearing through each crank internal passage.

By forming the crank internal passage connecting the journal portion and the crank pin by offsetting from the center of rotation of the crankshaft, the centrifugal force acting against the lubricating oil flowing from the main bearing into the through hole is reduced. With
Since the centrifugal force that acts on the lubricating oil that flows out to the crankpin increases, the amount of lubricating oil that is supplied to the crankpin greatly increases as the engine speed increases.

In the crank internal passage, one opening opening in the journal portion is always in communication with the entire circumferential groove, and the supply of lubricating oil to the crank pin is not interrupted.

In the crank internal passage having one opening in the journal, the amount of lubricating oil supplied to the crank pin is reduced as compared with the structure having a plurality of openings in the journal. However, heat dissipation from the overlay layer, which has a higher thermal conductivity than the crankpin, to the lubricating oil is promoted, and the large amount of frictional heat that is generated is sufficiently carried away by the lubricating oil, which prevents the connecting rod bearing from overheating and seizing. To prevent the occurrence of

Further, the productivity can be improved by forming the crank internal passage with a single through hole.

[0041]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 3, a crankshaft 3 provided in a four-cylinder engine has five journal portions 1 supported by main bearings of the engine body and four crankpins 2 supported by connecting rod bearings of connecting rods. Have.

As shown in FIG. 1, upper and lower bearing metals 5 and 6 slidably contacting the journal portion 1 are interposed in each main bearing.

Upper and lower bearing metals 7 and 8 slidably contacting the crank pin 2 are interposed in each connecting rod bearing.

Inside the crankshaft 3, a crank internal passage 9 connecting each journal 1 and the crankpin 2 is formed. Lubricating oil discharged from the oil pump is shunted from the main gallery of the engine body and supplied to each main bearing, and the half-circumferential groove 11 formed only on the upper bearing metal 5 is formed.
Is supplied to each crank pin 2 through each crank internal passage 9.

As shown in FIG. 2, the bearing metals 7 and 8 provided in the connecting rod bearing are mainly formed of a cylindrical back metal 15 having a half shape. The back metal 15 is made of steel. On the other hand, the crankshaft 3 is made of steel or cast iron.

In FIG. 2, reference numeral 16 is a metal layer formed on the bearing surface side of the backing metal 15 of the bearing metals 7 and 8. The metal layer 16 is made of a Kelmet alloy containing copper (Cu) and lead (Pb) as main components and is formed into a layer having a thickness of 300 μm. The thermal conductivity of this metal layer 16 is 1
It is set to about 30 W / mK.

An overlay layer 17 made of a softer material than the metal layer 16 is formed on the bearing surface of the bearing metal 7, 8 which is in sliding contact with the crank pin 2 to secure the initial conformability to the crank pin 2 and the burying property of foreign matter. To be done.

The overlay layer 17 is formed of an alloy containing aluminum (Al) and tin (Sn) as main components, which has a higher thermal conductivity than the crankpin 2. Iron (F
The thermal conductivity of the crankpin 2 whose main component is e) is 50W.
/ MK, whereas the thermal conductivity of the overlay layer 17 is set to about 120 W / mK.

The overlay layer 17 is formed in layers in a thickness of about 20 microns over the entire circumference of the upper and lower bearing metals 7, 8.

The material of the overlay layer 17 is not limited to the aluminum-tin based aluminum alloy, and in another embodiment, aluminum-tin is used as a material having a higher thermal conductivity than iron used as the material of the crank pin 2. It is also conceivable to use an aluminum alloy such as tin-lead based metal, or a nickel based or copper based metal. Further, if the production cost is not taken into consideration, it is possible to use silver (Ag) having a higher thermal conductivity than an aluminum alloy.

The bearing metal 7, 8 interposed in the connecting rod bearing is such that the metal layer formed on the bearing surface side of the backing metal 15 is formed of an alloy containing aluminum and tin as main components, and the overlay layer is eliminated. Good.

On the other hand, the sliding surface of the crank pin 2 is microfinished to reduce its surface roughness as compared with the ordinary lapping finish.
The roundness is raised.

The sliding surface of the crank pin 2 is microfinished so that its surface roughness can be suppressed sufficiently small. The oil film supported on the smooth surface of the crankpin 2 that has been subjected to the microfinishing finish is kept in a fluid lubrication state even if it becomes thin under high temperature and high pressure.

As shown in FIG. 1, the so-called Vorl type crank internal passage 9 has a through hole 18 whose both ends open to the journal portion 1, and one end of which is connected to the end of the through hole 18 and the other end thereof. Through hole 1 opened in the crank pin 2
9 and 9.

The through hole 19 connecting the journal portion 1 and the crank pin 2 is formed offset from the center of rotation of the crank shaft 3.

When the sliding surface of the crank pin 2 with respect to the connecting rod bearing is divided into a main shaft side region close to the journal part 1 and an anti-spindle side region distant from the journal part 1, the opening of the crank internal passage 9 for the crank pin 2 is formed. Edge 20
Are arranged in the area opposite to the main spindle.

The opening end 20 of the crank inner passage 9 which is opened in the anti-spindle side area of the sliding surface of the crank pin 2 can reduce the bearing area in the spindle side area where the inertial force of the piston, connecting rod or the like acts. The surface pressure can be kept small,
The constituent ability of the lubricating oil film can be secured.

Since the open end 20 of the crank internal passage 9 is machined in an oblique direction with respect to the outer peripheral surface of the crank pin 2, it is difficult to sufficiently perform chamfering. For this reason,
When the bearing metal is provided with an overlay layer made of an alloy mainly composed of lead and tin, the edge portion of the opening end 20 may scrape off the overlay layer during operation. However, the bearing metal 7, 8 has a relatively high hardness of the aluminum alloy overlay layer 1
7 is applied, it is possible to prevent the edge portion of the open end 20 from scraping off the overlay layer 17 during operation.

With the above construction, the operation will be described below.

The aluminum-tin overlay layer 17 is formed on the bearing metals 7 and 8 of the connecting rod bearing, and the thermal conductivity of the bearing surface is higher than that of the crankpin 2, so that the crankpin 2 passes through the lubricating oil and overlays. As the heat flow velocity transmitted to the layer 17 increases, the heat flow velocity transmitted to the lubricating oil flowing from the overlay layer 17 to the lubricating oil increases while the load is reduced due to the rotation of the crankshaft 3 to improve the cooling effect of the crank pin 2. To be enhanced.

The cooling action of the crankpin 2 by the aluminum-tin overlay layer 17 will be described in detail below.

The friction loss applied to the crankpin supported by the conventional bearing metal in which the overlay layer is formed of an alloy containing lead and tin as the main components having low thermal conductivity causes the temperature of the shaft surface to rise. Along with that, there is a characteristic that it decreases until it reaches about 100 ° C, but conversely increases after it exceeds about 100 ° C.

The phenomenon that the friction loss changes according to the lubricating oil temperature generally means that the viscosity of the lubricating oil decreases and the friction loss decreases until the lubricating oil temperature rises to about 100 ° C. After the temperature of the lubricating oil exceeds 100 ° C, the viscosity of the lubricating oil further decreases and the thickness of the oil film decreases, and the lubricating state changes from fluid lubrication to contact between solid surfaces and liquid film shearing (fluid lubrication). ) Was considered to shift to mixed coexistence (reference material: Papers of the Japan Society of Mechanical Engineers, Preprint, 71st 1993, 332-334).

However, the applicant of the present invention has found that the temperature of the lubricating oil is 10
Under high temperature and high load lubrication conditions such that the temperature rises above 0 ° C, the thinnest oil film thickness becomes 1 to 2 microns, and the increase in pressure increases the viscosity of the lubricating oil, and We believe that the shear rate of the film will increase and the friction loss will increase rapidly.

Under a large load condition, friction loss increases as the oil temperature rises. The reason for this is that at high temperature, the minimum oil film thickness becomes small, so the oil film pressure becomes large, and considering the viscosity increase due to the pressure, the lubricating oil viscosity of the minimum oil film part becomes higher on the contrary at high temperature conditions, Since the oil film thickness is thin, the shear rate is high, and the friction loss tends to increase in the bearing as a whole.

Therefore, in order to reduce friction loss under such a high temperature and high load lubrication condition, from a thin oil film portion (hereinafter referred to as a minimum oil film portion) where the viscosity is increased by raising the temperature and pressure under an instantaneous load. It is necessary to quickly release the heat and suppress the temperature rise of the lubricating oil.

The lubricating oil supplied to the bearing gap between the crankpin 2 and the upper and lower bearing metals 7, 8 cools the crankpin 2. The upper and lower bearing metals 7 and 8 are formed of aluminum alloy having a higher thermal conductivity than that of the crankpin 2 in the overlay layers 17, so that the overlay layers are made of an alloy mainly containing lead and tin having a low thermal conductivity. The heat dissipation to the overlay layer of the lubricating oil film can be improved as compared with the formed conventional bearing metal.

The crankpin 2 always faces the minimum oil film portion in its main shaft side area. On the other hand, the part where the bearing metals 7 and 8 face the minimum oil film part moves around the entire circumference moment by moment as the crank pin 2 rotates.

The minimum oil film portion is a phenomenon that occurs instantaneously when viewed from the bearing side, and the position changes moment by moment, and friction torque is generated due to oil film shearing due to relative rotation between the shaft and the bearing, but The heat generated in the oil film portion quickly flows into the overlay layer 17 having a higher thermal conductivity than the crankpin 2,
The portion facing the minimum oil film portion moves in the circumferential direction with the rotation of the crank pin 2 and comes off the minimum oil film portion, so that the heat absorbed by the bearing metals 7 and 8 becomes lubricant oil that intervenes again in the bearing gap. Inflow. As a result, the heat dissipation from the (minimum) lubricating oil film is improved as compared with the bearing metal formed of a lead alloy having a low thermal conductivity in the overlay layer.

Although the overlay layer 17 has a thickness of only about 20 μm, the minimum oil film portion has a thickness of about several μm and has a sufficient heat capacity for absorbing the heat generated in the minimum oil film portion. ing. Furthermore, since the minimum oil film portion is an instantaneous phenomenon that moves, even if most of the heat generated in the minimum oil film portion flows into the overlay layer 17, the temperature does not rise sharply and is not thermally saturated, and is 20 μm. The overlay layer 17 having only a certain thickness has a great influence on the temperature of the lubricating oil.

In the conventional bearing metal in which the overlay layer is made of a lead alloy, the overlay layer has a thermal conductivity of 30 W.
/ MK, which is significantly lower than the thermal conductivity of the crankpin mainly composed of iron of 50 W / mK, so most of the friction heat generated in the minimum oil film portion flows into the crankpin, This causes a local temperature rise in the main shaft side region of the crankpin, raises the temperature of the oil film, and causes a vicious circle in which the friction heat generated in the minimum oil film portion increases.

The oil is supplied to each main bearing through each supply passage branched from the main gallery to lubricate the sliding portions of the upper and lower bearing metals 5 and 6 and the journal 1.

A part of the lubricating oil supplied to the main bearing flows out from the bearing gap between the main bearing and the journal portion 1 into the crank chamber, and the rest is fed from the half-circumferential groove 11 formed in the upper bearing metal 5 of the main bearing to the crank. It is supplied to each crank pin 2 through the internal passage 9 to lubricate and cool the sliding portions of the upper and lower bearing metals 7, 8 and the crank pin 2.

A half-circumferential groove 11 is formed only in the upper bearing metal 5 of the main bearing, and a groove is formed in the lower bearing metal 6 on which combustion pressure mainly acts through the crankshaft 3, so that the bearing area is reduced. Therefore, the surface pressure on the journal portion 1 can be reduced.

Since the both ends of the through hole 18 of the crank internal passage 9 are open to the journal portion 1, the crank internal passage 9 is always communicated with the half-circumferential groove 11 and from the through hole 18 to the crank pin 2 through the through hole 19. The supply of lubricating oil is not interrupted.

The Vorl type internal crank passage 9 is
Since the through hole 19 connecting the journal portion 1 and the crank pin 2 is formed offset from the center of rotation of the crankshaft 3, the centrifugal force that works against the lubricating oil flowing from the main bearing into the through hole 19 is reduced. At the same time, the centrifugal force acting on the lubricating oil flowing out from the through hole 19 to the crank pin 2 increases. Therefore, as shown by the solid line in FIG. 4, the amount of lubricating oil supplied to the crankpin 2 greatly increases as the engine speed increases, becomes small in the fuel consumption range, and becomes large in the output range. The fuel consumption range is a low / medium speed range in which the fuel consumption rate is suppressed to a low level, the output range is a high speed range where the engine output is maximized, and the red zone is a higher speed range than the output range.

In the fuel consumption range where the engine speed is low and the frictional heat generated in the connecting rod bearing is small, the discharge pressure of the oil pump is low and the Vorl type crank internal passage 9 is used.
Since the centrifugal force acting on the lubricating oil flowing through the bearing is small, the amount of lubricating oil supplied to the connecting rod bearing is greatly reduced. But,
As described above, since the heat dissipation from the aluminum alloy overlay layer 17 of each bearing metal 7, 8 to the lubricating oil is promoted, the temperature of the lubricating oil interposed in the connecting rod bearing is properly maintained and the viscosity of the lubricating oil is lowered. Therefore, the friction loss can be reduced.

In the output region where the engine speed is high and the frictional heat generated in the connecting rod bearing is large, the discharge pressure of the oil pump is increased and the Voll type crank internal passage 9 is used.
Since a large centrifugal force acts on the lubricating oil flowing through the lubricating oil, a large amount of lubricating oil is supplied to the connecting rod bearings, and heat dissipation from the aluminum alloy overlay layer 17 of each bearing metal 7 and 8 to the lubricating oil is promoted. The generated frictional heat is sufficiently carried away by the lubricating oil, the overheating of the connecting rod bearing is suppressed, and the occurrence of seizure or the like is prevented.

Hereinafter, the relationship between the surface temperature of the crank pin 2 and the friction loss will be described in detail with reference to the characteristic diagram shown in FIG.

In the case of the conventional system in which an overlay layer containing lead and tin as the main components, the thermal conductivity of which is smaller than that of the crankpin 2, is formed on each bearing metal interposed in the connecting rod bearing,
When the amount of oil supplied to the crank pin 2 in the fuel consumption range decreases due to the change of the internal crank passage 9 from the H type to the Voll type, the heat flow rate from the crank pin 2 to the overlay layer mainly composed of lead and tin is small. There is a problem that the pin surface temperature rises excessively as indicated by arrow a, and the friction loss increases beyond its minimum point as indicated by arrow b.

Also in the output region, the internal crank passage 9 is changed from the H type to the Vorl type, so that from the open end 20 located on the opposite main spindle side of the crank pin 2 to the minimum oil film portion generated on the main spindle side of the crank pin 2. Since the amount of oil supply decreases and the heat flow velocity from the crank pin 2 to the overlay layer mainly composed of lead and tin is small, the pin surface temperature rises as indicated by arrow c and the friction loss as indicated by arrow d. There is a problem of increase.

On the other hand, in the case of the present system in which the bearing metal 7, 8 is formed with the aluminum alloy overlay layer having a large thermal conductivity, the crank internal passage 9
Even if the amount of oil supplied to the crank pin 2 decreases due to the change from H type to Vorl type, the heat flow velocity from the crank pin 2 to the aluminum alloy overlay layer 17 is large, so the pin surface temperature is as shown by arrow A. It is possible to obtain the effect that the friction loss is reduced as shown by the arrow B without increasing excessively.

Even in the output region, since the crank internal passage 9 is changed from the H type to the Vorl type, the heat flow velocity from the crank pin 2 to the aluminum alloy overlay layer 17 is large, so that the pin surface temperature is as shown by an arrow C. It is possible to obtain the effect that the friction loss is reduced as shown by the arrow D without increasing excessively.

In FIG. 4, among the Vorl type characteristics, those shown by a thin solid line are those in which the discharge pressure characteristics of the oil pump are set so as to secure the same oil amount in the output range as the characteristics of the conventional system of the H type shown by the broken line. It was done. Voll
The type indicated by a thick solid line is that the discharge amount of the oil pump is reduced so that the amount of oil supplied to the crank pin 2 in the output region is reduced because the heat flow rate from the crank pin 2 to the aluminum alloy overlay layer 17 is large in the output region. It is a characteristic that the pressure is lowered.

As shown by the thick solid line in FIG. 5, by reducing the discharge pressure of the oil pump, the friction loss is reduced in both the fuel consumption range and the output range as indicated by arrows E and F, respectively. Is obtained.

Even in the red zone where the number of revolutions further rises from the output range, the action of increasing the amount of oil supplied to the crank pin 2 via the Vorl type crank internal passage 9 and the overlay layer 17 made of aluminum alloy from the crank pin 2
Combined with the effect of a large heat flow rate to the connecting rod bearing, the durability of the connecting rod bearing can be improved.

Next, another embodiment shown in FIG. 6 will be described. It should be noted that the same parts as those in FIG.

The crank internal passage 9 is constituted by a single through hole 19 having one end opened to the journal portion 1 and the other end opened to the crank pin 2.

A part of the lubricating oil supplied from the oil pump to the main bearing flows out from the bearing gap between the main bearing and the journal portion 1 into the crank chamber, and the rest is the upper and lower bearing metal 5 of the main bearing.
It is supplied to each crank pin 2 through each crank internal passage 9 from all the circumferential grooves 12 and 13 formed in 6.

In the crank internal passage 9, one end of the through hole 19 is always in communication with the entire circumferential grooves 12 and 13, and the supply of lubricating oil to the crank pin 2 through the through hole 19 is not interrupted.

In the present embodiment, the crank internal passage 9 in which one end of the through hole 19 is opened to the crank pin 2 has two openings for the crank pin 2 as compared with the above embodiment, in which the crank pin 2 and the connecting rod are connected. The amount of lubricating oil supplied to the bearing clearance of the bearing is reduced.

However, due to the structure in which the crankpin 2 is supported by the overlay layer 17 containing aluminum and tin as the main components, sufficient cooling of the crankpin 2 is ensured and the amount of lubricating oil supplied to the crankpin 2 is increased. It can prevent shortage.

Further, the crank internal passage 9 is provided with one through hole 1
By being formed by 9, the productivity can be increased.

[0095]

As described above, the crank lubrication device for an internal combustion engine according to claim 1 enhances lubricity in a high rotation range, downsizes an oil pump to reduce a drive loss, and low-medium rotation. Friction loss in the area can be reduced.

According to a second aspect of the present invention, there is provided a crank lubrication device for an internal combustion engine according to the first aspect of the present invention, wherein the sliding surface of the crank pin with respect to the connecting rod bearing is formed from the main shaft side region close to the journal part and the journal part. When divided into the distant main spindle side regions, the opening end of the crank internal passage for the crank pin is arranged in the anti-spindle side region, so that the surface pressure of the main spindle side region is suppressed to be small and the constituent ability of the lubricating oil film is ensured. It is possible to sufficiently secure the cooling performance of the connecting rod bearing by the lubricating oil.

In the crank lubrication device for an internal combustion engine according to a third aspect of the present invention, the amount of heat conduction from the lubricating oil film to the overlay layer is ensured, and the bearing surface is prevented from being scraped off by the open end of the crank internal passage. Durability is secured.

In the crank lubrication device for an internal combustion engine according to a fourth aspect of the present invention, there is provided a crank lubrication device which is open at the journal portion of the crank internal passage.
One of the two openings is always in communication with the half-circle groove, and the supply of lubricating oil to the crankpin is not interrupted, and sufficient lubricity can be ensured.

In the crank lubrication device for an internal combustion engine according to a fifth aspect of the present invention, the crank lubrication device having the opening 1 at the journal portion of the crank internal passage is provided.
One opening always communicates with the entire circumference groove, and the supply of lubricating oil to the crank pin is not interrupted. Moreover, productivity is improved by forming the crank internal passage with a single through hole.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a crank internal passage, a bearing metal and the like showing an embodiment of the present invention.

FIG. 2 is a sectional view of the bearing metal taken along the line BB of FIG.

FIG. 3 is a side view of the same crankshaft.

FIG. 4 is a characteristic diagram showing the relationship between the engine speed and the amount of oil supplied to the crankpin.

FIG. 5 is a characteristic diagram showing the relationship between the surface temperature of the crank pin and friction loss.

FIG. 6 is a configuration diagram of a crank internal passage, a bearing metal and the like showing another embodiment.

FIG. 7 is a configuration diagram of a crank internal passage, a bearing metal, and the like showing a conventional example.

[Explanation of symbols]

 1 Journal part 2 Crank pin 3 Crank shaft 7 Bearing metal 8 Bearing metal 9 Crank internal passage 11 Half circumference groove 12 Groove 13 Groove 15 Back metal 16 Metal layer 17 Overlay layer 18 Through hole 19 Through hole 20 Open end

Claims (5)

[Claims] 1. A connecting rod for converting a reciprocating motion of a piston into a rotational movement of a crankshaft, a main bearing for rotatably supporting a journal portion of a crankshaft, and a connecting rod for rotatably supporting a crankpin of a crankshaft on the connecting rod. In an internal combustion engine that includes a bearing and a crank internal passage that supplies lubricating oil discharged from an oil pump to the connecting rod bearing from the main bearing of the crankshaft through the inside of the crankshaft, offset the crank internal passage from the center of rotation of the crankshaft. A crank lubrication device for an internal combustion engine, wherein an overlay layer having a higher thermal conductivity than a crank pin is formed on the bearing surface of a connecting rod bearing over the entire circumference. 2. When the sliding surface of the crank pin with respect to the connecting rod bearing is divided into a main shaft side region close to the journal part and an anti-spindle side region distant from the journal part, the open end of the crank internal passage for the crank pin is The crank lubrication device for an internal combustion engine according to claim 1, wherein the crank lubrication device is arranged in an area opposite to the main spindle. 3. The crank lubrication device for an internal combustion engine according to claim 1, wherein the overlay layer of the connecting rod bearing is formed on the bearing surface with an alloy containing aluminum and tin as main components. 4. The main bearing is formed with a half-circumferential groove that communicates with the main gallery, and the crank internal passage is formed with two openings for the journal and one opening for the crank pin. The crank lubrication device for an internal combustion engine according to any one of 1 to 3. 5. A main bearing is formed with an entire circumference groove communicating with the main gallery, and one opening for a journal portion and one opening for a crank pin are formed in the crank internal passage. Item 4. A crank lubrication device for an internal combustion engine according to any one of items 1 to 3.