JP5036604B2 - Crankshaft bearing structure - Google Patents

Description

  The present invention relates to a bearing structure that supports a crankshaft of a multi-cylinder internal combustion engine (also referred to as an engine).

  Generally, the journal part of the crankshaft is rotatably supported by the cylinder block, and the connecting rod is swingably supported by the crankpin of the crankshaft. Metals as slide bearings are interposed between the support portion and the swing support portion of the connecting rod.

  Here, a description will be given focusing on the rotation support portion in the journal portion of the crankshaft.

  That is, the journal portion of the crankshaft is sandwiched between a pedestal having a substantially U-shaped recess provided on the lower side of the cylinder block and a crank cap having a substantially U-shaped recess attached to the base with a bolt or the like. It is designed to be supported in a freely rotating state.

  A metal as a slide bearing is interposed between the outer peripheral surface of the journal portion of the crankshaft and the concave inner surface of the pedestal and the concave inner surface of the crank cap.

  This metal is generally shaped like a cylinder divided into two parts and used in pairs. Of these two metals, the metal disposed on the pedestal side of the cylinder block is generally referred to as an upper metal, and the metal disposed on the crank cap side is generally referred to as a lower metal.

  Conventionally, the upper metal and the lower metal are generally set to have the same overall width in the axial direction, but an oil groove is provided in an intermediate region in the axial direction of the inner peripheral surface of the upper metal. For example, the oil groove has a constant depth, that is, the groove bottom surface is concentric with the outer diameter surface.

  Due to the relationship in which such oil grooves are provided, the upper metal and the lower metal have an effective bearing width of the upper metal that is smaller than the effective bearing width of the lower metal even if the entire axial width is set to be the same.

  In recent years, for example, although there is no designation of the journal portion, it has been considered that the effective bearing width of the lower metal is made smaller than the effective bearing width of the upper metal with an oil groove (see, for example, Patent Document 1).

  For reference, the larger the effective bearing width for each metal, the more advantageous it is to increase the oil film thickness, but the friction tends to increase.

In addition, in the in-line four-cylinder engine, the outer diameter of the first journal part and the outer diameter of the metal used therefor are set larger than others (for example, refer to Patent Document 2), and the cylinder block side that supports a specific journal part It is also conceivable to set the section modulus of the lens to be larger than others (for example, see Patent Document 2).
JP-A-8-28570 Japanese Utility Model Publication No. 2-51711 JP 59-93509 A

  In the above-described conventional examples, all of these are techniques that deal with only that point in consideration of local problems. However, the present inventor has considered that it is preferable to optimally design each part in consideration of the pressure acting on each journal part according to the movement of the crankshaft, and has proposed the present invention.

  In view of such circumstances, the present invention provides a bearing structure that supports a large number of journal portions in a crankshaft of a multi-cylinder internal combustion engine via an upper metal and a lower metal. The objective is to achieve both optimization and reduction of friction in a balanced manner.

The present invention is a bearing structure for supporting a large number of journal portions in a crankshaft of an in- line four- cylinder internal combustion engine via an upper metal and a lower metal, and an oil groove is provided in an axial intermediate region of the concave surface of the upper metal. And the effective bearing width of the upper metal of the first, third, and fifth journal portions is set to be larger than the effective bearing width of the lower metal .

  The effective bearing width is an axial width of a surface that slides and guides the outer peripheral surface of the journal portion in each metal.

  Incidentally, when an oil groove is provided in the center of the concave surface of the upper metal or the lower metal in the axial direction, an effective bearing width is obtained by subtracting the oil groove from the entire axial width of the metal. Further, when there is no oil groove as described above on the concave surface of the upper metal or the lower metal and the entire axial direction is flush, the entire axial width of the metal is the effective bearing width.

  Here, as the effective bearing width is increased, the pressure receiving area is increased, so that the oil film is easily retained and the seizure resistance is improved, but the friction tends to be increased. On the other hand, the smaller the effective bearing width, the smaller the pressure receiving area, so that the friction tends to decrease, but the seizure resistance tends to decrease.

  In general, in the case of a multi-cylinder internal combustion engine, excessive pressure is applied to each journal portion of the crankshaft in the compression stroke at which the cylinder internal pressure becomes maximum. Differences in rotational eccentricity occur in each part. Therefore, in the journal part with a large amount of rotational eccentricity, the oil film thickness with the upper metal is thinner than that on the lower metal side, whereas in the journal part with a small amount of rotational eccentricity, the oil film thickness with the upper metal is smaller than that on the lower metal side. Thickness can be afforded.

  Based on such knowledge, the above configuration is adopted. In the above configuration, for example, the effective bearing width of the upper metal used for the journal part having a large amount of rotational eccentricity is set large so as to ensure a sufficient oil film thickness, while the lower metal used for the journal part having a large amount of rotational eccentricity is set. The effective bearing width can be set small so as to reduce friction. In addition, the effective bearing width of the upper metal used for the journal portion having a small amount of rotational eccentricity is set to be small so as to reduce friction, while the effective bearing width of the lower metal used for the journal portion having a small amount of rotational eccentricity is sufficient for an oil film. It becomes possible to set large so as to ensure the thickness.

  For example, in an in-line four-cylinder internal combustion engine, the rotational eccentricity of the first, third, and fifth journal portions is large, and the rotational eccentricity of the second and fourth journal portions is small. Due to this relationship, the No. 1, No. 3, and No. 5 journals with large rotational eccentricity have a thinner oil film between the upper metal and the No. 2 and No. 4 journals with lower rotational eccentricity. Then, the oil film thickness between the upper metal and the lower metal side has a sufficient margin.

In this knowledge, it is important to optimally design the effective bearing width of the upper metal and the lower metal used for at least the first, third, and fifth journal portions. In the present invention, the internal combustion engine is an in-line four-cylinder type. The effective bearing width of the upper metal of the first, third, and fifth journal portions is set larger than the effective bearing width of the lower metal .

  In the above configuration, the effective bearing width of the upper metal for No. 1, No. 3, No. 5 and No. 5 tends to be large in the journal part of the crankshaft is set large to ensure a sufficient oil film thickness. On the other hand, the effective bearing width of the first, third, and fifth lower metals is set to be small in order to reduce the friction.

  As a result, it is possible to balance the improvement in seizure resistance and the reduction of friction in the first, third, and fifth journal portions.

  More preferably, the effective bearing width of the upper metal of the second and fourth journal portions can be set smaller than the effective bearing width of the lower metal.

  Here, in addition to optimally designing the effective bearing width of the upper metal and lower metal used for the first, third, and fifth journal parts described above, the upper used for the second and fourth journal parts having a small amount of rotational eccentricity. The effective bearing width of metal and lower metal is designed optimally.

  The magnitude relationship shown in the above configuration is achieved, for example, by reducing the effective bearing width of the No. 2 and No. 4 upper metal having a sufficient oil film thickness. In that case, it is possible to reduce the friction between the 2nd and 4th journal parts and the upper metal, and to secure the necessary and sufficient oil film thickness between the 2nd and 4th journal parts and the lower metal. It becomes possible to do.

As a result, it is possible to balance the improvement of seizure resistance and the reduction of friction in the second and fourth journal portions in a balanced manner . Therefore, it is possible to achieve both the improvement of seizure resistance and the reduction of friction in a balanced manner in all journal portions of the crankshaft of the in-line four-cylinder internal combustion engine .

  According to the crankshaft bearing structure of the present invention, it is possible to balance the optimization of the oil film thickness and the reduction of the friction in a balanced manner for each journal portion of the crankshaft. This is advantageous in improving the fuel efficiency and output characteristics of the multi-cylinder internal combustion engine.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best embodiment according to the present invention will be described in detail based on the drawings. 1 to 7 show an embodiment of the present invention.

  First, an outline of a crankshaft bearing structure according to an embodiment of the present invention will be described with reference to FIGS.

  In the embodiment shown in the figure, an in-line four-cylinder internal combustion engine is taken as an example. In the figure, 1 is a cylinder block, 2 is a crankshaft, 3 is a connecting rod, and 4 is a piston.

  The crankshaft 2 has four crankpins 21 and five journal portions 22A to 22E because of the relationship for the in-line four-cylinder type.

  The journal portions 22A to 22E of the crankshaft 2 are rotatably supported in a state of being sandwiched between a pedestal 11 on the lower side of the cylinder block 1 and a crank cap 5 coupled thereto with a bolt (not shown). The

  The pedestal 11 is provided with a recess 12 that is recessed in a substantially U-shaped cross section toward the upper side of the cylinder block 1. The crank cap 5 is provided with a recess 51 that is recessed in a substantially U-shaped cross section toward the cylinder block 1 side.

  And the rotation support part of each journal part 22A-22E of the crankshaft 2, specifically, the outer peripheral surface of the journal parts 22A-22E of the crankshaft 2, and the inner surface of the recessed part 12 of the base 11 and the inner surface of the recessed part 51 of the crank cap 5 are opposed. In the meantime, metals 7A to 7E and 8A to 8E as slide bearings are interposed.

  The crank journal metals 7A to 7E, 8A to 8E are generally shaped like a cylinder divided into two parts, and are used in pairs.

  Of these two types of metals, one metal 7A to 7E is fitted and attached to the inner surface of the recess 12 of the base 11, and the other metal 8A to 8E is fitted and attached to the inner surface of the recess 51 of the crank cap 5. In accordance with this mounting relationship, hereinafter, the metals 7A to 7E disposed on the base 11 side of the cylinder block 1 are referred to as an upper metal, and the metals 8A to 8E disposed on the crank cap 5 side are referred to as a lower metal.

  The upper metals 7A to 7E are of a type in which an oil groove 71 having a constant depth is provided in the axially intermediate region of the concave surface, and two circumferential directions at the bottom of the oil groove 71 are arranged in the thickness direction. A penetrating oil hole 72 (only shown in FIGS. 3 to 5) is provided.

  Engine oil in an oil pan (not shown) attached to the lower side of the cylinder block 1 is supplied to the oil holes 72 of the upper metals 7A to 7E via an appropriate oil passage (not shown). ing.

  The lower metals 8A to 8E are generally of a type in which the oil grooves 71 and the oil holes 72 are not provided as in the upper metals 7A to 7E.

  The connecting rod 3 is swingably attached to the crankpin 21 of the crankshaft 2, and the swinging support portion of the connecting rod 3 is also used as a slide bearing in the same manner as the journal portions 22A to 22E. Metal (not shown) is interposed.

  In general, the oil passages 12 and 13 (only shown in FIGS. 4 and 5) of the cylinder block 1 and the oil grooves 71 of the upper metals 7A to 7E with respect to the rotation support portions of the journal portions 22A to 22E of the crankshaft 2 are provided. The engine oil is supplied through the oil hole 72 and the engine oil supplied to the rotation support portion is also supplied to the swing support portion of the crank pin 21.

  In the embodiment shown in FIG. 1 and FIG. 2, the five journal portions 22A to 22E of the crankshaft 2 are numbered from No. 1 to No. 5 from the front (Fr) side to the rear (Rr) side, From the first journal portion 22A to the first crankpin 21, from the second journal portion 22B to the second crankpin 21, from the fourth journal portion 22D to the third crankpin 21, and from the fifth journal portion 22E to the fourth crank A passage for enabling supply of engine oil to the pin 21 is provided.

  This engine oil passage penetrates through four journal portions 22A, 22B, 22D, and 22E in the radial direction except for the third journal portion 22C in the axial center of the five journal portions 22A to 22E of the crankshaft 2. The radial hole 24 provided, the inclined hole 25 provided penetrating from each end face side to the outer peripheral surface of all four crank pins 21, and the radial hole 24 and the inclined hole 25 communicate with each other in the above-described relationship. A corresponding balance weight 23 is combined with an inclined communication hole 26 provided so as to penetrate in the thickness direction. No radial hole 24 is provided in the third journal portion 22 </ b> C of the crankshaft 2.

  The engine oil supplied to the oil holes 72 of the crank journal upper metals 7A to 7E through such an engine oil passage first has four journal portions 22A, 22B, 22D, 22E of the crankshaft 2 and each metal 7A, The connecting rod 3 is supplied between 7B, 7D, 7E, 8A, 8B, 8D, and 8E or between the crankpin 21 and the crankpin metal (not shown) and lubricates and cools the connecting rod 3. Is jetted from the oil jet nozzle (not shown) to the back surface of the piston 4 and the inner circumferential surface of the cylinder.

  Next, portions to which the features of the present invention are applied will be described in detail with reference to FIGS.

  In the first place, in the in-line four-cylinder internal combustion engine exemplified in this embodiment, as shown in FIG. 1, the rotational eccentricity of the first, third, fifth journal portions 22A, 22C, 22E is large, The rotational eccentricity of the second and fourth journal portions 22B and 22D is reduced.

  From this relationship, if all of the upper grooves 7A to 7E with oil grooves and the lower metals 8A to 8E without oil grooves are set to have the same width in the axial direction, the first, third, and fifth with large rotational eccentricity In the second journal portion 22A, 22C, 22E, the oil film thickness between the upper metal 7A, 7C, 7E is relatively stricter than that of the lower metal 8A, 8C, 8E side, and the rotation eccentricity amount No. 2, 4 is small. In the numbering journal portions 22B and 22D, the oil film thickness between the upper metals 7B and 7D is relatively thicker than the lower metals 8B and 8D.

  For reference, in the case where all the upper grooves 7A to 7E with oil grooves and the lower metals 8A to 8E without oil grooves have the same overall width in the axial direction as described above, the compression top dead center ( Since the thickness of the oil film held between each of the journal portions 22A to 22E and the upper metal 7A to 7E or the lower metal 8A to 8E in TDC) is examined, the result will be described with reference to FIGS.

  The data shown in FIGS. 8 to 11 is obtained by operating, for example, an in-line four-cylinder type diesel engine in a vehicle non-mounted state. The engine displacement is 1400 cc, the engine oil is 10 W / 30, and the combustion order is 1 → 3 → 4 → 2. In the figure, data indicated by a solid line indicates a full load state, and data indicated by a one-dot chain line indicates a motoring state.

  The full load state is a state where the accelerator is fully opened (for example, 4500 rpm). The motoring state is a state in which the crankshaft 2 is cranked by external force without fuel injection, and corresponds to a state in which the accelerator is switched from the accelerator-on state to the accelerator-off state while the vehicle is traveling.

  First, as shown in FIG. 8, on the upper metal 7C side of the third journal portion 22C, when the third cylinder and the second cylinder are at the compression top dead center (TDC), the oil film is in both the full load state and the motoring state. When the thickness is reduced and the first and fourth cylinders are at compression top dead center (TDC), there is a margin in the oil film thickness in both the full load state and the motoring state.

  Further, as shown in FIG. 9, on the side of the lower metal 8C of the third journal portion 22C, when the third cylinder or the second cylinder is at the compression top dead center (TDC), the full load state and the motor are reversed. The oil film thickness is sufficient in both the ring state, and when the first cylinder and the fourth cylinder are at compression top dead center (TDC), the oil film thickness becomes thin in both the full load state and the motoring state.

  The upper metal 7A, 7E side and the lower metal 8A, 8E side of the first and fifth journal portions 22A, 22E are substantially the same as the case of the third journal portion 22C.

  On the other hand, as shown in FIG. 10, for the upper metal 7B side of the second journal portion 22B, when the first cylinder, the third cylinder, and the second cylinder are at compression top dead center (TDC), No. 3 upper metal 7C, although there is a margin in the oil film thickness in the ring state, and when the No. 4 cylinder is compression top dead center (TDC), the oil film thickness is slightly reduced in both the full load state and the motoring state. Compared to the side, it has a sufficient thickness.

  Further, as shown in FIG. 11, on the side of the lower metal 8B of the second journal portion 22B, when the third cylinder, the fourth cylinder, and the second cylinder are at the compression top dead center (TDC), as opposed to the above, The oil film thickness is relatively large in both the load state and the motoring state, and the oil film thickness becomes thin in both the full load state and the motoring state when the first cylinder is at the compression top dead center (TDC).

  Note that the upper metal 7D side and the lower metal 8D side of the fourth journal portion 22D are substantially the same as the case of the second journal portion 22B.

  In this knowledge, it is important to optimally design the effective bearing widths Wu1, Wu2, Wr1, and Wr2 of the upper metals 7A to 7E and the lower metals 8A to 8E used for all the journal portions 22A to 22E. I have a lot of ingenuity.

  Since the oil grooves 21 are provided in all the upper metals 7A to 7E, the effective bearing widths Wu1 and Wu2 (not shown in FIGS. 6 and 7) are different from each upper as shown in FIGS. It is obtained by subtracting the axial width Wg of the oil groove 21 from the total axial width W of the metals 7A to 7E.

  Specifically, first, among all the journal portions 22A to 22E of the crankshaft 2, the upper metals 7A, 7C for the first, third, fifth journal portions 22A, 22C, 22E, which tend to have large rotational eccentricity, While setting the effective bearing width Wu1 of 7E large, the effective bearing width Wu2 of the lower metal 8A, 8C, 8E for the first, third, fifth journal portions 22A, 22C, 22E is set small.

  Further, while setting the effective bearing width Wu2 of the upper metal 7B, 7D for the second and fourth journal portions 22B, 22D having a small rotational eccentricity, the lower metal 8B for the second, fourth journal portion 22B, 22D. , 8D effective bearing width Wu2 is set large.

  By setting in this way, as shown in FIG. 6, the effective bearing width Wu1 of the upper metal 7A, 7C, 7E of the first, third, fifth journal portions 22A, 22C, 22E is reduced to the lower metal 8A, 8C, As shown in FIG. 7, the effective bearing width Wu2 of the upper metal 7B, 7D of the second and fourth journal portions 22B, 22D is larger than the effective bearing width of the lower metal 8B, 8D. The magnitude relationship of smaller than Wr2 is established. In this size relationship, it is preferable to set the larger effective bearing width to 1.2 to 1.5 times the smaller one.

  By the way, as the effective bearing widths Wu1, Wu2, Wr1, and Wr2 of the upper metals 7A to 7E and the lower metals 8A to 8E are increased, the pressure receiving area is increased, so that the oil film is easily held and seizure resistance is improved. On the other hand, friction tends to increase. On the other hand, as the effective bearing widths Wu1, Wu2, Wr1, and Wr2 are reduced, the pressure receiving area is reduced, so that friction tends to be reduced, but seizure resistance tends to be reduced.

  From this, since the effective bearing width Wu1 of the upper metal 7A, 7C, 7E for the first, third, fifth journal portions 22A, 22C, 22E is set large, a sufficient oil film thickness is secured. Since the effective bearing width Wu2 of the lower metal 8A, 8C, 8E for the first, third, fifth journal portions 22A, 22C, 22E is set small, it is possible to reduce the friction. Become. Further, since the effective bearing width Wu2 of the upper metal 7B, 7D for the second and fourth journal portions 22B, 22D having a small rotational eccentricity is set small, it becomes possible to reduce the friction, and the second, Since the effective bearing width Wu2 of the lower metal 8B, 8D for the fourth journal portions 22B, 22D is set large, it is possible to ensure a sufficient oil film thickness.

  As a result, for the first, third, and fifth journal portions 22A, 22C, and 22E, the seizure resistance is improved when viewed on the upper metal 7A, 7C, and 7E side and the lower metal 8A, 8C, and 8E side in total. In addition, the reduction of friction can be achieved in a balanced manner. In addition, as for the second and fourth journal portions 22B and 22D, when viewed in total on the upper metal 7B and 7D side and the lower metal 8B and 8D side, improvement in seizure resistance and reduction of friction can be achieved in a balanced manner. become.

  Therefore, according to the embodiment to which the features of the present invention are applied, in an in-line four-cylinder internal combustion engine, improvement in seizure resistance and reduction of friction in all the journal portions 22A to 22E of the crankshaft 2 are balanced. As a result, it is advantageous in improving the fuel efficiency and output characteristics of the internal combustion engine.

  In addition, this invention is not limited only to the said embodiment, All the deformation | transformation and application included in the range equivalent to the claim and the said range are possible. Examples are given below.

  (1) In the above embodiment, an in-line four-cylinder internal combustion engine is described as an example. However, the present invention is not particularly limited to the number of cylinders or the arrangement of cylinders. The present invention can also be applied to an internal combustion engine such as a mold. The present invention can also be applied to all types of internal combustion engines such as gasoline engines and diesel engines.

  (2) In the said embodiment, in order to support each of several journal part 22A-22E with which the crankshaft 2 is equipped, the example which couple | bonds the individual crank cap 5 with the base 11 of the cylinder block 1 is given. However, in the present invention, a crankcase having a so-called ladder beam structure in which the crank caps 5 are integrally connected can be used instead of the plurality of crank caps 5.

  (3) In the above embodiment, an example in which the oil grooves 71 are provided in the upper metals 7A to 7E is described. However, the present invention may be a type in which the oil grooves 71 are not provided as the upper metals 7A to 7E. It is.

  (4) In the above embodiment, even when the effective bearing width of the upper metal 7B, 7D of the second and fourth journal portions 22B, 22D of the crankshaft 2 and the effective bearing width of the lower metal 8B, 8D are set to be the same, It is included as another embodiment of the present invention.

In one embodiment of the bearing structure of a crankshaft concerning the present invention, while showing a schematic structure typically, it is a figure showing the amount of rotation eccentricity for every journal part. It is a figure which shows the external appearance of the crankshaft of FIG. It is a disassembled perspective view of the bearing structure of FIG. FIG. 3 is a cross-sectional view taken along line (4)-(4) in FIG. 2. FIG. 3 is a cross-sectional view taken along line (5)-(5) in FIG. 2. It is a perspective view which shows the upper metal and lower metal for 1st, 3rd, 5th journal part shown in FIG. It is a perspective view which shows the upper metal and lower metal for 2nd and 4th journal parts shown in FIG. In a reference example, it is a graph which shows the relationship between the crank angle of the 3rd journal part, and the oil film thickness of the upper metal side. In a reference example, it is a graph which shows the relationship between the crank angle of the 3rd journal part, and the oil film thickness of the lower metal side. In a reference example, it is a graph which shows the relationship between the crank angle of the 2nd journal part, and the oil film thickness of the upper metal side. In a reference example, it is a graph which shows the relationship between the crank angle of the 2nd journal part, and the oil film thickness of the lower metal side.

Explanation of symbols

1 Cylinder block
2 Crankshaft
3 Connecting rod
5 Crank cap 7A-7E Upper metal 8A-8E Lower metal
11 Cylinder block base 22A to 22E Crankshaft journal
51 Crank cap recess

Claims (2)

A bearing structure that supports a number of journal portions in a crankshaft of an in- line four- cylinder internal combustion engine via an upper metal and a lower metal,
An oil groove is provided in the axially intermediate region of the concave surface of the upper metal,
A bearing structure for a crankshaft , wherein the effective bearing width of the upper metal of the first, third, and fifth journal parts is set to be larger than the effective bearing width of the lower metal . The crankshaft bearing structure according to claim 1,
A bearing structure for a crankshaft, characterized in that the effective bearing width of the upper metal of the second and fourth journal portions is set smaller than the effective bearing width of the lower metal .

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