JP2015034572A - Bearing structure of rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing structure of a rotor which reduces rotational friction.SOLUTION: A bearing structure of a rotor includes: a bearing 12 rotatably supporting a rotor 2; a lubrication oil supply passage 21 which supplies a lubrication oil to a bearing surface 11a of the bearing 12 which faces the rotor 2; a communication hole 30 which is formed at the bearing 12 and allows a bearing surface opening 30a opening on the bearing surface 11a to communicate with an outer surface opening 30b opening on an outer surface of the bearing 12; and an air introduction mechanism 40 which is provided at the communication hole 30 and circulates air from the outer surface opening 30b side to the bearing surface opening 30a side to introduce the air to the inner side of the bearing surface 11a. When a negative pressure is generated in a bearing gap, air is introduced from the communication hole 30.

Description

  The present invention relates to a bearing structure including a bearing that rotatably supports a rotating body and a lubricating oil supply mechanism that supplies lubricating oil to a bearing surface facing the rotating body.

  A crankshaft of an internal combustion engine rotatably supports a journal by a journal bearing including a cylinder block (upper block or crankcase upper) and a bearing cap (or lower block) fastened thereto. A journal bearing generally has a cylinder block and a bearing cap as bearing support portions, and a bearing surface is formed by a half bearing plate (bearing metal) attached to each. Lubricating oil is supplied to the bearing surface in order to reduce rotational friction of the crankshaft. The large end of the connecting rod is rotatably connected to the pin of the crankshaft, and the oil passage formed inside the crankshaft is also formed on the bearing surface of the pin bearing of the large end pivoted by this pin. Lubricating oil is supplied from

  As a crankshaft lubrication system, lubricating oil is supplied to each journal bearing from an oil passage formed in the cylinder block, and for the adjacent pin bearing, it opens to the outer peripheral surface of the pin and the outer peripheral surface of the adjacent journal. There is a type in which lubricating oil is supplied through an in-shaft oil passage formed in the crankshaft (hereinafter referred to as a block oil supply system). In this block lubrication method, in the journal bearing that lubricates the pin bearing, the oil is fed over the entire length in the circumferential direction on the inner surface of the upper bearing, which is the bearing half on the cylinder block side, so that the lubrication to the pin bearing does not stagnate. A plain bearing with a groove formed with a groove is used, and a plain bearing without a groove is used for a lower bearing which is a bearing half on the bearing cap side.

  As another lubrication method, lubricating oil is supplied from one end in the direction of the crankshaft to the oil passage in the shaft formed inside the crankshaft, and lubricating oil is supplied to each pin and each journal by applying pressure by centrifugal force. A center oiling system (for example, Patent Document 1) and a fueling system (for example, Patent Document 2) in which a journal that is lubricated from the cylinder block side and a journal that is lubricated from this journal through an oil passage in the shaft are mixed. There is (hereinafter referred to as an in-shaft oiling system). In these in-shaft oil supply systems, plain bearings without grooves can be used for both the upper and lower bearing halves of the journal bearing that is supplied from the oil passage in the shaft. For this reason, the amount of lubricating oil leaked from the gap between the bearing surface and the journal outer surface (hereinafter referred to as the bearing gap) can be reduced compared to the above-described method using a plain bearing with a groove in the upper bearing. The oil pump can be downsized, and the agitation resistance caused by the scattering of the lubricating oil by the crankshaft and the collision of the scattered lubricating oil with the crankshaft can be reduced.

JP 2009-204001 A Japanese Patent No. 4399263

  However, there is still room for reducing rotational friction in the conventional crankshaft oiling system.

  The present invention has been made in view of such a background, and an object of the present invention is to provide a bearing structure for a rotating body that can reduce rotational friction.

  As a result of intensive research, the inventors of the present application have adopted a conventional crankshaft oiling system, a block oiling crankshaft 101 as shown in FIG. 12, and an in-shaft oiling system as shown in FIG. It has been found that in the crankshaft 102, the surface pressure of the lower bearing may be negative. Here, the crankshaft is used for an in-line four-cylinder internal combustion engine, and the arrows in FIGS. 12 and 13 indicate the direction of refueling. In the block oil supply type crankshaft 101 shown in FIG. 12, a plain bearing with a groove is used for the upper bearing in all of the first to fifth journal bearings in order from the left. On the other hand, in the crankshaft 102 of the in-shaft oil supply system shown in FIG. 13, among the first to fifth journal bearings in order from the left, in the second and fourth journal bearings, a plain bearing with a groove in the upper bearing. On the other hand, the first, third, and fifth journal bearings are configured so that there is no groove over the entire circumference by using plain bearings without grooves in both the upper and lower.

  FIG. 14 shows the surface pressure of the lower bearing in the third journal (shaft center portion) of the crankshafts 101 and 102 of both oil supply systems shown in FIGS. 12 and 13 when the rotational speed is 2000 rpm and the supply hydraulic pressure is 300 kPa. It shows the transition. As can be seen from the figure, the surface pressure of the lower bearing shows a waveform that repeatedly increases and decreases, and the surface pressure has a negative value in a predetermined section (period) in which the surface pressure is lowest. In this section, the journal rotation center is swung away from the lower bearing, and it is considered that negative pressure is generated by increasing the volume of the bearing gap.

  Further, the inventors of the present application reduced the supply hydraulic pressure from an external electric oil pump to 250 kPa, and changed the rotational speed while keeping the supply hydraulic pressure constant, so that the internal combustion engine using both crankshafts 101 and 102 was used. The motoring friction of was measured. As a result, as shown in FIG. 15, the crankshaft 102 of the in-shaft oil passage lubrication system shown in FIG. 13, which can use a plain bearing without a groove as the upper bearing, is better than the crankshaft 101 of the block lubrication system shown in FIG. 12. It has been found that the friction is lower than that.

  In any of the oil supply type crankshafts 101 and 102, the leakage oil agitation resistance decreases due to a decrease in the supply oil pressure, but the block oil supply method shown in FIG. Is considered large. However, as shown in FIG. 15, there is a difference in friction from the low rotation range, and it is necessary to use a grooved upper bearing. In the journal bearing of the block oil supply type crankshaft 101 shown in FIG. It can be considered that a larger effect than the effect of the decrease occurs in the journal bearing of the crankshaft 102 of the in-shaft oil supply system shown in FIG. For the crankshaft 102 of the in-shaft oil supply system shown in FIG. 13, plain bearings without a circumferential groove are applied to the three journal bearings. Therefore, this influence is applied to the three journal bearings in the image diagram of FIG. 16. As shown in FIG. 5, it can be presumed that an air film layer having a low viscosity is formed in the bearing gap due to a decrease in the supply hydraulic pressure, and the viscous drag resistance is reduced.

  As described above, the volume of the bearing gap changes due to the rotation of the rotation center of the journal and negative pressure is generated on the bearing surface of the plain bearing. The conventional internal combustion using a plain bearing without a groove on one bearing half body It is presumed that it had also occurred in the organization. However, the fluid sucked by the negative pressure is considered to be the lubricating oil supplied from the cylinder block to the grooved plain bearing side or the peripheral oil immediately after leaking sideways from the plain bearing. If the fluid mainly composed of such a viscous fluid is filled in the negative pressure portion, the effect of reducing a large bearing friction loss cannot be expected.

  Similarly, in an in-shaft internal combustion engine that can use plain bearings without grooves in both bearing halves, the fluid filled by negative pressure is less than that of plain bearings with grooves, but on the side of the plain bearings. It is expected that the peripheral oil re-entering from the area will account for the majority. Therefore, it is considered that bearing friction loss occurs due to the viscosity of the lubricating oil even in the section where the rotation center of the journal is separated and no load is applied.

  Although there are air bearing technologies classified as static pressure bearings, this technology is a technology that floats the rotating body by supplying compressed air made by a dedicated high-pressure air generator to the bearing gap. Equipment such as a compressor, surge tank, and pressure piping are required. Therefore, although it is possible to reduce bearing friction, it is disadvantageous in terms of weight, cost, and energy consumption.

  This invention is made | formed based on such knowledge of this inventor. According to one aspect of the present invention, the above-described problem of reducing rotational friction is a bearing (12) that rotatably supports a rotating body (2) and the bearing (12) that faces the rotating body (2). ) For supplying lubricating oil to the bearing surface (11a), the bearing surface opening (30a) formed in the bearing (12) and opening in the bearing surface (11a) A communication hole (30) that communicates with the outer surface opening (30b) that opens to the outer surface of the bearing (12), and the communication surface (30) are provided in the communication hole (30), and the bearing surface opening (30a) from the outer surface opening (30b) side. This is achieved by providing a bearing structure for a rotating body having an air introduction mechanism (40, 50) for introducing air into the bearing surface (11a) by circulating air to the side.

  Thus, by providing an air introduction mechanism that introduces air into the bearing surface between the bearing surface of the bearing that pivotally supports the rotating body and the external space, the air is efficiently taken into the bearing gap so that the bearing surface Since the air layer is formed on the surface, the viscous resistance of the rotating body can be reduced as compared with the conventional configuration in which the lubricating oil is taken in.

  Further, according to one aspect of the present invention, the bearing surface opening (30a) is located at a position where a bearing gap is enlarged when the rotation center of the rotating body (2) starts to move away from the bearing surface (11a). The rotating body (2) can be provided at a position downstream of the rotating direction.

  By providing the bearing surface opening at such an angular position on the circumference of the bearing surface, it is possible to easily form an air layer in a circumferential section where the gap between the bearing surface and the rotating shaft is widened, The effect of reducing rotational friction can be further increased.

  According to another aspect of the present invention, the rotating body is a crankshaft (2) of an internal combustion engine (1), and the bearing is fastened to the cylinder block (7) and the cylinder block (7). A bearing support portion (10) constituted by a bearing cap (9), a block side bearing half (11U) and a cap side bearing half which are respectively mounted on the cylinder block (7) and the bearing cap (9). (11L) is a crank journal bearing (12) having a bearing metal (11), and the bearing surface opening (30a) of the communication hole (30) is formed on the cap side bearing half (11L). The outer circumferential opening (30b) of the communication hole (30) is formed on the downstream side in the rotation direction of the crankshaft (2) with respect to the circumferential center of the bearing surface. There may be a configuration that is formed downward in the vertical direction than the bearing surface opening (30a).

  According to this configuration, since the bearing surface opening is not formed on the upstream side in the rotational direction of the block side bearing half and the cap side bearing half, the lubricating oil is applied during the expansion stroke of the internal combustion engine when applied to the journal bearing of the crankshaft. It is possible to prevent backflow through the communication hole. Further, since the outer surface opening is formed below the bearing surface opening in the vertical direction, the lubricating oil in the communication hole can be easily discharged.

  Further, according to one aspect of the present invention, the lubricating oil supply passage is formed in the crankshaft (2) and opens in the outer surface of the journal (3) of the crankshaft (2). (24), both the block side bearing half (11U) and the cap side bearing half (11L) can be configured as plain bearings having a flat bearing surface in a longitudinal section.

  According to this configuration, since plain bearings are used for both bearing halves, the negative pressure generated between the crankshaft and the bearing surface increases, and more air can flow into the bearing gap.

  Also, according to one aspect of the present invention, the block side bearing half (11U) and the cap side bearing half (11L) are each formed in the same shape having a through hole (11d), and the lubricating oil The supply path is formed in the cylinder block (7), and the lubricating oil supplied from an oil pump provided in the internal combustion engine (1) is supplied to the through hole (11d) of the block side bearing half (11U). It can be set as the structure containing the main oil path (22) supplied to.

  According to this configuration, the number of types of bearings incorporated in the assembly process of the internal combustion engine is reduced (in the least case, a grooved plain bearing in which a large-diameter oil hole is opened in the oil groove and a single small-diameter oil hole are provided. Therefore, it is possible to prevent erroneous assembly by an operator and to reduce the part management cost.

  Further, according to one aspect of the present invention, the air introduction mechanism (40) can include a spiral orifice (43) that allows air to flow at a larger flow rate than the lubricating oil.

  According to this configuration, by using a spiral orifice for the air introduction mechanism, high-pressure lubricating oil on the crankshaft side can be prevented from leaking through the spiral orifice, and the function as a hydrodynamic bearing can be impaired. There is no. Further, when the bearing gap is enlarged and negative pressure is generated, low-viscosity air can be sucked from the external space and supplied through the spiral orifice to the bearing gap.

  Further, according to one aspect of the present invention, the air introduction mechanism (50) is closed when the pressure on the bearing surface (11a) side is positive, and the pressure on the bearing surface (11a) side is predetermined. A one-way valve (52) that opens when the negative pressure is exceeded may be included.

  According to this configuration, since the air introduction mechanism includes the one-way valve, the high-pressure lubricating oil on the crankshaft side can be prevented from leaking to the external space side by the closed one-way valve, There is no loss of functionality. In addition, when a negative pressure exceeding the specified negative pressure is generated due to the expansion of the bearing gap, the one-way valve opens to suck in low-viscosity air from the external space and supply air to the bearing gap. Can do.

  Thus, according to this invention, the bearing structure of the rotary body which can reduce rotational friction can be provided.

1 is a longitudinal sectional view of a bearing structure of a rotating body according to a first embodiment. II-II sectional view in FIG. III-III sectional view in FIG. Part IV enlarged view in FIG. The graph which shows the pressurization test result of the lubricating oil by the orifice shown in FIG. The graph which shows the pressure reduction test result of the air by the orifice shown in FIG. The graph which shows the flow volume of lubricating oil and air according to the dimension of the orifice shown in FIG. Graph showing the friction torque of the bearing structure and the comparative example shown in FIG. A graph showing the minimum hydraulic pressure of the lower bearing shown in FIG. Sectional drawing corresponding to FIG. 3 of the bearing structure of the rotary body which concerns on 2nd Embodiment. XI section enlarged view in FIG. Explanatory drawing of a conventional crank bearing with a block lubrication system Explanatory drawing of a conventional crank bearing with a shaft oiling system Time chart of the surface pressure of the lower bearing in a crank bearing with a conventional double lubrication system Graph showing the friction torque of a crank bearing with a conventional double lubrication system Image diagram showing the mechanism by which the agitation resistance is reduced in a conventional crank bearing with a shaft oiling system

  Hereinafter, an embodiment in which the present invention is applied to an automobile internal combustion engine 1 will be described in detail with reference to the drawings.

<< First Embodiment >>
First, the bearing structure of the rotating body according to the first embodiment will be described with reference to FIGS. As shown in FIG. 1, the bearing structure is applied to a crankshaft 2 of an in-line four-cylinder internal combustion engine (hereinafter simply referred to as the internal combustion engine 1). The crankshaft 2 is composed of five journals 3 provided at positions coaxially and spaced apart in the axial direction, and a pair of webs 4 connected to the shaft end of each journal 3 between two adjacent journals 3. And four crankpins 5 arranged at positions separated from the center of rotation. The web 4 constitutes a crank arm, and includes a counterweight 6 integrally formed at an appropriate position on the side opposite to the crankpin 5. At the left end of the crankshaft 2 in the figure, a sprocket for driving the camshaft of the internal combustion engine 1 and a crank pulley for driving an auxiliary machine are attached. On the other hand, a flywheel coupled to a transmission including a transmission is attached to the right end of the crankshaft 2 in the drawing.

  The internal combustion engine 1 has an upper block 7 (cylinder block) constituting four cylinders arranged in series, and a lower part of the upper block 7 supports a crankshaft 5 together with a skirt constituting an upper part of a crankcase. Two support walls 8 are integrally formed. A bearing cap 9 is fastened to the lower part of each support wall 8, and five journal support portions 10 are configured by the support wall 8 and the bearing cap 9. In the present embodiment, the internal combustion engine 1 is described as being in an upright state with the cylinder axis extending in the vertical direction, but the mounting angle of the internal combustion engine 1 is not necessarily limited to this.

  In each journal support portion 10, a cylindrical hole having a substantially circular cross section is formed by the support wall 8 and the bearing cap 9, and a halved bearing metal 11 (11 </ b> U, 11 </ b> U) constituting the bearing surface 11 a of the journal 3 is formed in the cylindrical hole. 11L) is installed, thereby forming a journal bearing 12 that rotatably supports the journal 3 of the crankshaft 2. Hereinafter, a half body of the bearing metal 11 attached to the semicircular cutout formed in the support wall 8 is referred to as an upper bearing 11U, and the bearing attached to the semicircular cutout formed in the bearing cap 9 is referred to as an upper bearing 11U. A half of the metal 11 is referred to as a lower bearing 11L. Further, the five journal bearings 12 and the elements constituting the journal bearing 12 and the corresponding elements such as the journal 3 are first, second, fifth from the left side of FIG. The description will be made in order from the left as first, second,.

  As shown in FIGS. 2 and 3, in the present embodiment, the five bearing caps 9 are integrally formed with the lower block 13 fastened to the lower surface of the upper block 7. In other embodiments, the bearing caps 9 may be configured separately from each other, or may be configured separately from the lower block 13 as an integral ladder frame.

  Water jackets 14 are formed on the intake side and the exhaust side of the upper block 7. An oil gallery 21 extending in the cylinder row direction is formed in parallel with the crankshaft 2 at a portion above the crankshaft 2 between the water jackets 14. Lubricating oil is supplied to the oil gallery 21 from an oil pump attached to the internal combustion engine 1.

  As shown in FIGS. 1 and 2, in the second and fourth journal bearings 12, main oil for supplying lubricating oil to the second and fourth journal bearings 12 on the support wall 8 integral with the upper block 7, respectively. The passage 22 is formed so as to extend downward from the oil gallery 21 through the center in the thickness direction of the support wall 8. In the second and fourth journal bearings 12, an oil supply groove 23 extending in the circumferential direction is formed on the outer surface of the upper bearing 11U, that is, on the inner peripheral surface of the semicylindrical cutout of the support wall 8.

  In the present embodiment, the lubricating oil in the oil gallery 21 is supplied to the second and fourth journal bearings 12 through the main oil passage 22 formed in the second and fourth support walls 8 as indicated by the arrows in FIG. The lubricating oil supplied to the second and fourth journals 3 is supplied to the adjacent crank pins 5 and journals 3 through an in-shaft oil passage 24 formed in the crankshaft 2.

  The shaft internal oil passage 24 includes a journal oil passage 26 formed in the journal 3 so as to open to the outer surface of each journal 3, and a pin formed in the crank pin 5 so as to open to the outer surface of each crank pin 5. The oil passage 27 is constituted by a communication oil passage 28 extending in the axial direction and the radial direction of the crankshaft 2 so as to communicate the journal oil passage 26 and the pin oil passage 27 adjacent to each other. The communication oil passage 28 (28A, 28B, 28C, 28D) extends from the journal oil passage 26 of the second journal 3 to the journal oil passage 26 of the first journal 3 via the pin oil passage 27 of the first crankpin 5. A first branch oil passage 28A, a second branch oil passage 28B extending from the journal oil passage 26 of the second journal 3 to the journal oil passage 26 of the third journal 3 via the pin oil passage 27 of the second crankpin 5; The third branch oil passage 28C from the journal oil passage 26 of the fourth journal 3 to the pin oil passage 27 of the third crankpin 5 and the pin oil passage of the fourth crank 3 from the journal oil passage 26 of the fourth journal 3 27 and a fourth branch oil passage 28 </ b> D that reaches the journal oil passage 26 of the fifth journal 3.

  In the second and fourth journal bearings 12, two oil supply holes 11 b that open to the outer peripheral surface and the inner peripheral surface, respectively, in the center in the axial direction of the upper bearing 11 U aligned with the oil supply groove 23 and at different positions in the circumferential direction. Is formed. In the second and fourth journal bearings 12, the upper bearing 11U forms the bearing surface 11a in order to continuously supply the lubricating oil to the other bearing portions via the communication oil passages 28 in the crankshaft 2. It is a plain bearing with a groove in which an oil supply groove 11c extending over the entire length in the circumferential direction is formed at the center in the axial direction of the inner peripheral surface, and the journal oil passage 26 is 180 degrees different in the circumferential direction of the journal 3. It is formed by a through hole that opens to the outer surface at a position. On the other hand, the lower bearing 11L of the second and fourth journal bearings 12 is a plain bearing without grooves having a flat bearing surface 11a in the longitudinal section.

  As shown in FIGS. 1 and 3, in the first, third, and fifth journal bearings 12, since the lubricating oil is supplied from the first, second, and fourth branch oil passages 28A, 28B, 28D, the support wall 8, the main oil passage 22 is not formed, and both the upper bearing 11U and the lower bearing 11L are groove-free plain bearings in which the oil supply groove 11c is not formed on the bearing surface 11a. Unlike the second and fourth journals 3, the journal oil passage 26 is formed so as to extend from the center of the journal 3 in one of the radial directions and open to the outer surface of the journal 3.

  On the other hand, in the first, third and fifth journal bearings 12, as shown in FIGS. 3 and 4, the bearing cap 9 and the lower bearing 11 </ b> L are provided with a bearing surface opening 30 a which opens to the bearing surface 11 a and the bearing cap 9. A communication hole 30 is formed that communicates with an outer surface opening 30b that opens to the outer surface (the surface that defines the oil sump rather than the water jacket 14). The communication hole 30 includes a through hole 9a formed in the bearing cap 9 and a through hole 11d formed in the lower bearing 11L so as to be connected thereto. The through hole 11d formed in the lower bearing 11L. The inner end of the bearing is a bearing surface opening 30a. The through hole 11d of the lower bearing 11L has a smaller diameter than the oil supply hole 11b formed in the upper bearing 11U of the second and fourth journal bearings 12 (FIG. 2).

  The communication hole 30 is provided with an air introduction mechanism 40 that introduces air into the bearing surface 11a by flowing air from the outer surface opening 30b side to the bearing surface opening 30a side. As shown in FIG. 4, the air introduction mechanism 40 of the present embodiment includes a screw hole 41 formed at an end portion on the lower bearing 11 </ b> L side in the through hole 9 a of the bearing cap 9, and a stop screwed into the screw hole 41. It is a spiral orifice 43 between the two formed by a screw 42 (potato screw). The set screw 42 is a hexagon socket set screw 42 in which a hexagon hole is formed on the end surface on the lower bearing 11L side. In order to ensure communication between the spiral orifice 43 and the first through hole, the end surface on the side opposite to the hexagonal hole of the set screw 42 may be formed obliquely or unevenly.

  In addition to the gap formed between the top of the thread and the bottom of the thread groove, the spiral orifice 43 is provided between the follower side flank 42a of the set screw 42 and the advance side flank 41a of the screw hole 41 opposed thereto. And is provided at a position adjacent to the back surface of the lower bearing 11L. Although illustration is omitted, in order to stabilize the gap formed between the flank, an elastic member is interposed between the lower bearing 11L and the set screw 42 so that the set screw 42 is always on the outer surface opening 30b side. Energize.

  Alternatively, the spiral orifice 43 may be formed by a gap formed between the advance side flank 42b of the set screw 42 and the follower side flank 41b of the screw hole 41 opposed thereto. In this case, in order to stabilize the gap formed between the flank, an elastic member such as a disc spring is interposed between the bottom of the screw hole 41 and the set screw 42 so that the set screw 42 is inserted into the bearing surface opening 30a. Always energize the side.

  The size of the spiral orifice 43 is set so that air flows from the outer surface opening 30b side to the bearing surface opening 30a side, while the flow of the lubricating oil from the bearing surface opening 30a side to the outer surface opening 30b side is hindered. Yes. Thereby, when negative pressure is generated in the bearing gap, the air flowing through the spiral orifice 43 is introduced into the bearing gap through the communication hole 30. The dimensions and performance of the spiral orifice 43 will be described in detail later.

  As shown in FIG. 3, the crankshaft 2 rotates clockwise in the figure as indicated by the arrow, and the journal 3 swings greatly in the vertical direction due to the influence of the reciprocating motion of the piston. The communication hole 30 forms a bearing surface opening 30a at a position on the left side, that is, on the downstream side in the rotation direction of the crankshaft 2, with respect to the lowest end (center in the middle direction) of the bearing surface 11a of the lower bearing 11L. That is, the bearing surface opening 30a is provided at a position on the downstream side in the rotation direction of the journal 3 with respect to a portion where the bearing gap expands when the rotation center of the journal 3 starts to move away from the bearing surface 11a at the lowermost end of the lower bearing 11L. It has been.

  Further, the communication hole 30 extends obliquely downward to the left from the bearing surface opening 30 a and forms an outer surface opening 30 b on the outer surface of the bearing cap 9. That is, the outer surface opening 30b of the communication hole 30 is formed below the bearing surface opening 30a in the vertical direction. Therefore, a small amount of lubricating oil that has passed through the spiral orifice 43 descends through the communication hole 30 and is discharged from the outer surface opening 30b to the oil sump, and the bearing clearances of the first, third, and fifth journal bearings 12 become negative pressure. The air is preferentially circulated to introduce the air into the bearing surface 11a.

  The lower bearing 11L of the second and fourth journal bearings 12 (FIG. 2) and the upper bearing 11U of the first, third and fifth journal bearings 12 (FIG. 3) are provided with through holes 11d. Those having the same shape as the lower bearings of the first, third and fifth journal bearings 12 (FIG. 3) are used.

  Next, the dimension and performance of the spiral orifice 43 will be described. The inventors change the dimension of the set screw 42 forming the spiral orifice 43 (including the dimension of the screw hole 41) to apply positive pressure to the lubricating oil charged on the bearing surface 11a side, and thereby the spiral orifice 43 An experiment was conducted to measure the flow rate of the lubricating oil passing through. As the dimensions of the set screw 42, there are prepared two screw diameters M4 and M8, two lengths of 5 mm and 10 mm for M4, lengths of 4.4 mm and 8.8 mm for M8, and Three lengths of 17.6 mm were prepared, and experiments were conducted on a total of five different dimensions. The result was as shown in FIG.

  For the set screw 42 of four different dimensions excluding the nominal thread M8 and length of 17.6 mm, negative pressure is applied to the air charged on the bearing surface 11a side, and the flow rate of the air passing through the spiral orifice 43 is measured. An experiment was conducted. The result was as shown in FIG. FIG. 7 is a graph comparing the flow rate of the lubricating oil and the flow rate of air by the set screws 42 having these four dimensions. As shown in FIG. 7, the ratio of the air flow rate to the lubricating oil flow rate is the largest in the nominal screw M4 and the set screw 42 having a length of 5 mm, and the characteristics suitable for the present invention are shown. A set screw 42 having a length of M4 and a length of 5 mm was adopted for the air introduction mechanism 40, and motoring friction was measured.

  The motoring friction is measured by changing the rotation speed while keeping the same conditions as those for the conventional oil supply crankshafts 101 and 102 described above, that is, the oil pressure supplied from the oil pump is constant at 250 kPa. I went. The result is as shown in FIG. 8, and in the bearing structure according to the present invention, the friction torque is reduced as compared with the conventional crankshafts 101 and 102 of both oil supply systems. In particular, the amount of reduction in friction torque is large at a low rotational speed range.

  This is a diagram showing the relationship between the rotational speed of the crankshaft 2 and the minimum pressure (hydraulic pressure) on the bearing surface 11a of the lower bearing 11L when the supply hydraulic pressure is constant at various values in the bearing structure according to the present invention. As shown in the graph of FIG. 9, it is in harmony with the fact that the surface pressure of the lower bearing 11L is minimized in the low rotational speed range. That is, it is considered that the oil film viscous resistance is reduced by the low-viscosity air mixed into the bearing gap due to the negative pressure generated on the bearing surface 11a of the lower bearing 11L.

  In this way, in the first, third and fifth journal bearings 12 (FIGS. 3 and 4), the bearing clearance from the outside to the communication hole 30 that communicates the bearing clearance (bearing surface 11a) and the outside (oil sump). By providing the spiral orifice 43 for preferentially circulating air on the side, when a negative pressure is generated in the bearing gap, air is efficiently taken into the bearing gap and an air layer is formed on the bearing surface 11a. Therefore, the rotational friction of the crankshaft 2 is reduced as compared with the conventional configuration in which the lubricating oil is taken in.

  Further, the bearing surface opening 30a of the communication hole 30 is located downstream of the lowermost end of the lower bearing 11L in the rotation direction of the crankshaft 2, that is, the rotation center of the journal 3 is the expansion stroke of the internal combustion engine 1 at the lower bearing 11L. Is provided at a position downstream of the journal 3 in the rotational direction of the journal 3 with respect to a portion where the bearing gap expands when starting to move away from the bearing surface 11a at the end of the piston moving direction in An air layer is easily formed in a circumferential section where the gap is widened, and the rotational friction (viscous resistance) of the crankshaft 2 is more effectively reduced.

  Further, since the bearing surface opening 30a of the communication hole 30 is formed on the downstream side in the rotation direction of the crankshaft 2 with respect to the lowermost end of the lower bearing 11L, the lubricating oil passes through the communication hole 30 in the expansion stroke of the internal combustion engine 1. Backflow is prevented. Further, since the outer surface opening 30b of the communication hole 30 is formed below the bearing surface opening 30a in the vertical direction, the lubricating oil in the communication hole 30 can be easily discharged, and the bearing gap becomes negative pressure. Air is preferentially introduced into the bearing surface 11a.

  In the present embodiment, as shown in FIG. 1, an in-shaft oil passage 24 that opens to the outer surface of the journal 3 is formed inside the crankshaft 2. In the first, third, and fifth journal bearings 12, the upper bearing 11 </ b> U. Since both the lower bearing 11L and the lower bearing 11L are plain bearings having a flat bearing surface 11a in the longitudinal section, the negative pressure generated between the journal 3 and the bearing surface 11a is increased, and more air is removed from the bearing gap. And the rotational friction of the crankshaft 2 can be more effectively reduced.

  A first through hole 11d is formed in the lower bearing 11L of the second and fourth journal bearings 12 (FIG. 2) and the upper bearing 11U of the first, third and fifth journal bearings 12 (FIG. 3). Since the same shape as the lower bearings of the third and fifth journal bearings 12 (FIG. 3) is used, only two types of bearing halves are used for the five journal bearings 12. Prevent the wrong assembly by the user and reduce the part management cost.

  Further, in the present embodiment, the air introduction mechanism 40 is configured by the spiral orifice 43 provided at a predetermined position of the communication hole 30, so that high-pressure lubricating oil on the crankshaft 2 side passes through the spiral orifice 43. Leakage is prevented and the function as a hydrodynamic bearing is not impaired. Further, when the bearing gap is expanded and negative pressure is generated, it is possible to suck in low-viscosity air from the external space and supply the sucked air to the bearing gap through the spiral orifice 43. .

<< Second Embodiment >>
Next, the bearing structure of the rotating body according to the second embodiment will be described with reference to FIGS. 10 and 11. In addition, the same code | symbol is attached | subjected to the element which is the same or the same as that of 1st Embodiment, or a function, and the overlapping description is abbreviate | omitted.

  In the bearing structure of this embodiment, the air introduction mechanism 50 provided in the first, third and fifth journal bearings 12 (see FIG. 1) is different from that of the first embodiment. The air introduction mechanism 50 of the present embodiment is accommodated in the valve accommodating portion 51 formed by expanding the diameter of the end of the through hole 9a formed in the bearing cap 9 on the lower bearing 11L side, and the valve accommodating portion 51. And a one-way valve 52 for allowing fluid to flow only from the outer surface opening 30b side to the bearing surface opening 30a side.

  The valve accommodating part 51 has a valve seat 51a formed at the center of the bottom surface where the communication hole 30 opens, and the open surface is covered with the lower bearing 11L. A through hole 11d of the lower bearing 11L is disposed at the center of the open surface. The one-way valve 52 is interposed between the housing 53, the check ball 54 seated on the valve seat 51a, and the check ball 54 and the housing 53, and constantly biases the check ball 54 toward the valve seat 51a. A compression coil spring 55 as means. Accordingly, the one-way valve 52 is closed when the pressure on the bearing surface 11a side is positive, and is opened when the pressure on the bearing surface 11a side exceeds a predetermined negative pressure.

  By configuring the air introduction mechanism 50 in this way, the high-pressure lubricating oil on the crankshaft 2 side is prevented from leaking to the external space side by the closed one-way valve 52, and the function as a dynamic pressure bearing is achieved. It will not be damaged. Further, when the bearing gap is enlarged and a negative pressure exceeding a predetermined negative pressure is generated, the one-way valve 52 is opened to suck in low-viscosity air from the external space and supply air to the bearing gap. The

  Although the description of the specific embodiment is finished as described above, the present invention is not limited to the above embodiment and can be widely modified. For example, in the above-described embodiment, the bearing structure has been described as a crank bearing of the internal combustion engine 1 for an automobile as an example. However, the present invention is naturally applicable to a crankshaft of an internal combustion engine used for other purposes or a bearing other than the crankshaft. Is possible. In addition, when applied to a crankshaft, the present invention is not limited to in-line 4-cylinders, but can be applied to in-cylinder types such as 2-cylinder, 3-cylinder, or 5-cylinder or more, in-line cylinder type, V type, and horizontally opposed type. . In addition, the specific configuration, arrangement, quantity, and angle of the lubricating oil supply path, the air introduction mechanism 40, the communication hole 30, and other members and parts can be changed as appropriate without departing from the spirit of the present invention. On the other hand, all the components of the bearing structure shown in the above embodiment are not necessarily essential, and can be appropriately selected.

1 Internal combustion engine 2 Crankshaft (rotary body)
3 Journal 7 Upper block (Cylinder block)
9 Bearing cap 10 Journal support (bearing support)
11 Bearing metal 11L Lower bearing (Cap side bearing half)
11U upper bearing (block side bearing half)
11a Bearing surface 11d Through hole 12 Journal bearing 21 Oil gallery 22 Main oil passage 23 Oil supply groove 24 Oil passage in shaft 30 Communication hole 30a Bearing surface opening 30b Outer surface opening 40 Air introduction mechanism 43 Spiral orifice 50 Air introduction mechanism 52 One direction valve

Claims (7)

A bearing that rotatably supports the rotating body;
A lubricating oil supply path for supplying lubricating oil to the bearing surface of the bearing facing the rotating body;
A communication hole that is formed in the bearing and communicates with a bearing surface opening that opens to the bearing surface and an outer surface opening that opens to the outer surface of the bearing;
A bearing structure for a rotating body, comprising: an air introduction mechanism that is provided in the communication hole and introduces air into the bearing surface by allowing air to flow from the outer surface opening side to the bearing surface opening side.   The bearing surface opening is provided at a position on the downstream side in the rotation direction of the rotating body with respect to a portion where the bearing gap expands when the rotation center of the rotating body starts to move away from the bearing surface. The bearing structure for a rotating body according to claim 1. The rotating body is a crankshaft of an internal combustion engine;
The bearing includes a bearing support portion configured by a cylinder block and a bearing cap fastened to the cylinder block, and a block side bearing half and a cap side bearing half mounted on the cylinder block and the bearing cap, respectively. A crank journal bearing having a bearing metal configured,
The bearing surface opening of the communication hole is formed on the downstream side in the rotational direction of the crankshaft with respect to the center in the circumferential direction of the bearing surface of the cap-side bearing half.
The bearing structure for a rotating body according to claim 1, wherein the outer surface opening of the communication hole is formed below the bearing surface opening in a vertical direction. The lubricating oil supply path includes an in-shaft oil path that is formed inside the crankshaft and opens to an outer surface of a journal of the crankshaft.
The bearing structure for a rotating body according to claim 3, wherein both the block side bearing half and the cap side bearing half are plain bearings having a flat bearing surface in a longitudinal section. The block side bearing half and the cap side bearing half are each formed in the same shape having a through-hole,
The lubricating oil supply path includes a main oil path that is formed in the cylinder block and supplies the lubricating oil supplied from an oil pump provided in the internal combustion engine to the through hole of the block side bearing half. The bearing structure for a rotating body according to claim 3 or 4, characterized in that:   The bearing structure for a rotating body according to any one of claims 1 to 5, wherein the air introduction mechanism includes a spiral orifice that allows air to flow at a larger flow rate than the lubricating oil.   The air introduction mechanism includes a one-way valve that closes when the pressure on the bearing surface side is positive and opens when the pressure on the bearing surface side exceeds a predetermined negative pressure. The bearing structure for a rotating body according to any one of claims 1 to 5.

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