Bearing structure

Abstract

To suppress vibration.SOLUTION: A bearing structure includes a plurality of bearings supporting each of a plurality of journal parts provided in a crank shaft. An inner diameter of at least one of the plurality of bearings is smaller than that of others of the bearings on an extension line of a movement locus of the journal part when the journal part collides with the bearing.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a bearing structure. [Background technology]

[0002] A vehicle equipped with an engine is provided with a crankshaft for transmitting power generated by the engine. The crankshaft has a number of journals, each of which is supported by a bearing. As described in Patent Document 1, various techniques have been proposed for the structure of the portion where the crankshaft and the bearings come into contact with each other. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-264465 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the crankshaft rotates in a state of elastic deformation due to centrifugal force. This causes local contact between the crankshaft and the bearings, resulting in vibration. Such vibration can cause noise and other issues, so it is desirable to suppress the vibration.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide a bearing structure capable of suppressing vibration. [Means for solving the problem]

[0006] In order to solve the above problems, a bearing structure according to one embodiment of the present invention comprises: a plurality of bearings supporting a plurality of journal portions provided on the crankshaft, An inner diameter of at least one of the plurality of bearings is smaller than other portions of the bearing on an extension line of a movement locus of the journal portion when the journal portion collides with the bearing. Effect of the Invention

[0007] According to the present invention, it is possible to suppress vibration. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing a schematic configuration of a vehicle according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing elastic deformation during rotation of a crankshaft according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a schematic diagram showing elastic deformation during rotation of the crankshaft according to the embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view showing the AA cross section of FIG. [Diagram 5] FIG. 5 is a cross-sectional view showing the cross section BB of FIG. [Figure 6] FIG. 6 is a cross-sectional view showing a cross section taken along line CC in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The specific dimensions, materials, numerical values, etc. shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are given the same reference numerals to avoid repeated explanations, and elements not directly related to the present invention are not shown.

[0010] <Vehicle configuration> The configuration of a vehicle 1 according to an embodiment of the present invention will be described with reference to FIG.

[0011] Fig. 1 is a schematic diagram showing a general configuration of a vehicle 1. The vehicle 1 is equipped with an engine such as a gasoline engine, which is a spark ignition type internal combustion engine. As shown in Fig. 1, the vehicle 1 is equipped with a plurality of cylinders 2, a plurality of pistons 3 provided for each cylinder 2, a plurality of connecting rods 4 provided for each cylinder 2, a crankshaft 5, a flywheel 6, and a bearing structure 7.

[0012] In Fig. 1, the vehicle front direction, vehicle rear direction, vehicle right direction, and vehicle left direction are respectively indicated as front, rear, right, and left. Note that, hereinafter, the vehicle front direction, vehicle rear direction, vehicle right direction, and vehicle left direction will also be simply referred to as the front direction, rear direction, right direction, and left direction, respectively.

[0013] The following mainly describes the example of Fig. 1 in which the vehicle 1 is equipped with a horizontally opposed engine. However, as described later, the configuration of the vehicle 1 is not limited to the example of Fig. 1. For example, the number and arrangement of the cylinders 2 are not limited to the example of Fig. 1.

[0014] The vehicle 1 is provided with four cylinders 2: a first cylinder 2-1, a second cylinder 2-2, a third cylinder 2-3, and a fourth cylinder 2-4. The first cylinder 2-1, the second cylinder 2-2, the third cylinder 2-3, and the fourth cylinder 2-4 are arranged in this order from front to back in the front-to-rear direction. The first cylinder 2-1 and the third cylinder 2-3 are arranged to the right of the crankshaft 5. The second cylinder 2-2 and the fourth cylinder 2-4 are arranged to the left of the crankshaft 5.

[0015] A piston 3 is slidably provided inside each cylinder 2, and a combustion chamber is formed by the piston 3. Specifically, a first piston 3-1, a second piston 3-2, a third piston 3-3, and a fourth piston 3-4 are provided in the first cylinder 2-1, the second cylinder 2-2, the third cylinder 2-3, and the fourth cylinder 2-4, respectively. A connecting rod 4 is connected to each piston 3. Specifically, a first connecting rod 4-1, a second connecting rod 4-2, a third connecting rod 4-3, and a fourth connecting rod 4-4 are connected to the first piston 3-1, the second piston 3-2, the third piston 3-3, and the fourth piston 3-4, respectively. Each connecting rod 4 is connected to a crankshaft 5.

[0016] For example, a fuel injection valve and a spark plug are provided facing the combustion chamber in each cylinder 2. A mixture containing air and fuel is formed in the combustion chamber by the fuel injected by the fuel injection valve, and the mixture is burned by ignition of the spark plug. This causes a piston 3 to perform a linear reciprocating motion, and power is transmitted to a crankshaft 5 via a connecting rod 4.

[0017] In the vehicle 1, ignition is performed in the order of the first cylinder 2-1, the third cylinder 2-3, the second cylinder 2-2, and the fourth cylinder 2-4. Therefore, when the first piston 3-1 of the first cylinder 2-1 is located at the bottom dead center as shown in FIG. 1, the second piston 3-2 of the second cylinder 2-2 is located at the bottom dead center, and the third piston 3-3 of the third cylinder 2-3 and the fourth piston 3-4 of the fourth cylinder 2-4 are located at the top dead center. On the other hand, when the first piston 3-1 of the first cylinder 2-1 is located at the top dead center, the second piston 3-2 of the second cylinder 2-2 is located at the top dead center, and the third piston 3-3 of the third cylinder 2-3 and the fourth piston 3-4 of the fourth cylinder 2-4 are located at the bottom dead center.

[0018] The crankshaft 5 extends in the front-rear direction. The crankshaft 5 rotates about a rotation axis extending along the front-rear direction. A crank pulley (not shown) is provided at the front end of the crankshaft 5. A flywheel 6 is provided at the rear end of the crankshaft 5. The rear end of the crankshaft 5 is connected to a transmission (not shown) via the flywheel 6. The flywheel 6 accumulates the rotational energy transmitted to the crankshaft 5 and stabilizes the rotation of the crankshaft 5 by inertia force.

[0019] The crankshaft 5 includes a plurality of journal portions 51, a plurality of crank pins 52, and a plurality of counterweights 53. As described later, the crankshaft 5 rotates in a state in which it is elastically deformed by centrifugal force. Fig. 1 shows the crankshaft 5 in a stopped state.

[0020] Each journal portion 51 has a cylindrical shape. When the crankshaft 5 is stopped, the central axis of each journal portion 51 is coaxial with the rotation axis of the crankshaft 5. The crankshaft 5 is provided with five journal portions 51, namely, a first journal portion 51-1, a second journal portion 51-2, a third journal portion 51-3, a fourth journal portion 51-4, and a fifth journal portion 51-5. The first journal portion 51-1, the second journal portion 51-2, the third journal portion 51-3, the fourth journal portion 51-4, and the fifth journal portion 51-5 are arranged in this order from front to back in the front-rear direction. As described later, each journal portion 51 is rotatably supported by a bearing 71 of the bearing structure 7.

[0021] Each crankpin 52 has a cylindrical shape. When the crankshaft 5 is stopped, the central axis of the crankpin 52 is eccentric with respect to the rotation axis of the crankshaft 5. The crankshaft 5 is provided with four crankpins 52, namely, a first crankpin 52-1, a second crankpin 52-2, a third crankpin 52-3, and a fourth crankpin 52-4. The first crankpin 52-1, the second crankpin 52-2, the third crankpin 52-3, and the fourth crankpin 52-4 are arranged from front to back in this order in the front-to-rear direction. Each crankpin 52 is inserted into an end of the connecting rod 4 and connected to the connecting rod 4. Specifically, the first crank pin 52-1, the second crank pin 52-2, the third crank pin 52-3 and the fourth crank pin 52-4 are connected to the first connecting rod 4-1, the second connecting rod 4-2, the third connecting rod 4-3 and the fourth connecting rod 4-4, respectively.

[0022] The journal portions 51 and the crank pins 52 are arranged alternately in the front-rear direction. Specifically, the first crank pin 52-1 is provided between the first journal portion 51-1 and the second journal portion 51-2, and connects the first journal portion 51-1 and the second journal portion 51-2. The second crank pin 52-2 is provided between the second journal portion 51-2 and the third journal portion 51-3, and connects the second journal portion 51-2 and the third journal portion 51-3. The third crank pin 52-3 is provided between the third journal portion 51-3 and the fourth journal portion 51-4, and connects the third journal portion 51-3 and the fourth journal portion 51-4. The fourth crank pin 52-4 is provided between the fourth journal portion 51-4 and the fifth journal portion 51-5, and connects the fourth journal portion 51-4 and the fifth journal portion 51-5.

[0023] In the circumferential direction of the crankshaft 5, the position of the first crankpin 52-1 and the position of the fourth crankpin 52-4 are aligned with each other. In addition, in the circumferential direction of the crankshaft 5, the position of the second crankpin 52-2 and the position of the third crankpin 52-3 are aligned with each other, and are shifted by 180° from the positions of the first crankpin 52-1 and the fourth crankpin 52-4. In this way, in the circumferential direction of the crankshaft 5, the positions of the first crankpin 52-1 and the fourth crankpin 52-4 are shifted by 180° from the positions of the second crankpin 52-2 and the third crankpin 52-3. For example, as shown in FIG. 1, when the first crankpin 52-1 and the fourth crankpin 52-4 are positioned to the left of the crankshaft 5, the second crankpin 52-2 and the third crankpin 52-3 are positioned to the right of the crankshaft 5.

[0024] The counterweight 53 is provided on the journal portion 51 on the side of the adjacent crank pin 52, and protrudes in the opposite direction to the direction of the crank pin 52 relative to the journal portion 51. The counterweight 53 is a weight for balancing the crank pin 52 when the crankshaft 5 rotates. Eight counterweights 53 are provided on the crankshaft 5: a first counterweight 53-1, a second counterweight 53-2, a third counterweight 53-3, a fourth counterweight 53-4, a fifth counterweight 53-5, a sixth counterweight 53-6, a seventh counterweight 53-7, and an eighth counterweight 53-8. The first counterweight 53-1, the second counterweight 53-2, the third counterweight 53-3, the fourth counterweight 53-4, the fifth counterweight 53-5, the sixth counterweight 53-6, the seventh counterweight 53-7, and the eighth counterweight 53-8 are arranged in this order from the front to the back in the front-rear direction.

[0025] The first counterweight 53-1 is provided at the rear end of the first journal portion 51-1. The second counterweight 53-2 is provided at the front end of the second journal portion 51-2. The third counterweight 53-3 is provided at the rear end of the second journal portion 51-2. The fourth counterweight 53-4 is provided at the front end of the third journal portion 51-3. The fifth counterweight 53-5 is provided at the rear end of the third journal portion 51-3. The sixth counterweight 53-6 is provided at the front end of the fourth journal portion 51-4. The seventh counterweight 53-7 is provided at the rear end of the fourth journal portion 51-4. The eighth counterweight 53-8 is provided at the front end of the fifth journal portion 51-5.

[0026] The bearing structure 7 is a structure for supporting the crankshaft 5. The bearing structure 7 includes a plurality of bearings 71. Each bearing 71 is provided in a crankcase (not shown). Each bearing 71 rotatably supports each journal portion 51 of the crankshaft 5. Specifically, each bearing 71 is a sliding bearing that supports the journal portion 51 at least in the radial direction. Each bearing 71 is arranged coaxially with one another. The central axis of the bearing 71 and the rotation axis of the crankshaft are coaxial.

[0027] The bearing structure 7 is provided with five bearings 71, namely, a first bearing 71-1, a second bearing 71-2, a third bearing 71-3, a fourth bearing 71-4, and a fifth bearing 71-5. The first bearing 71-1, the second bearing 71-2, the third bearing 71-3, the fourth bearing 71-4, and the fifth bearing 71-5 are arranged in this order from front to back in the front-rear direction. The first bearing 71-1, the second bearing 71-2, the third bearing 71-3, the fourth bearing 71-4, and the fifth bearing 71-5 support the first journal portion 51-1, the second journal portion 51-2, the third journal portion 51-3, the fourth journal portion 51-4, and the fifth journal portion 51-5, respectively.

[0028] 1, the first bearing 71-1, the second bearing 71-2, the third bearing 71-3, and the fourth bearing 71-4 have radial surfaces and radially support the journal portion 51. On the other hand, the fifth bearing 71-5 has a thrust surface in addition to the radial surface, and radially supports the journal portion 51 and axially supports the crankshaft 5.

[0029] <Operation of crankshaft and bearing structure> The operation of the crankshaft 5 and the bearing structure 7 according to the embodiment of the present invention will be described with reference to FIGS.

[0030] As described above, the crankshaft 5 rotates in a state in which it is elastically deformed by centrifugal force. Hereinafter, the elastic deformation of the crankshaft 5 during rotation will be described with reference to Figs. 2 and 3.

[0031] 2 and 3 are schematic diagrams showing elastic deformation of the crankshaft 5 during rotation. Specifically, FIG. 2 shows the crankshaft 5 in the case where the first piston 3-1 and the second piston 3-2 are located at the bottom dead center, and the third piston 3-3 and the fourth piston 3-4 are located at the top dead center, as in FIG. 1. Meanwhile, FIG. 3 shows the crankshaft 5 in the case where the first piston 3-1 and the second piston 3-2 are located at the top dead center, and the third piston 3-3 and the fourth piston 3-4 are located at the bottom dead center. Note that FIGS. 2 and 3 show the rotation axis AR of the crankshaft 5.

[0032] When the crankshaft 5 rotates, the journal portion 51 is pulled by centrifugal force in a direction toward the crank pin 52 adjacent to the journal portion 51. Specifically, the first journal portion 51-1 is pulled by centrifugal force in a direction toward the first crank pin 52-1. The second journal portion 51-2 is not easily pulled in either direction by centrifugal force because the direction toward the first crank pin 52-1 is opposite to the direction toward the second crank pin 52-2. The third journal portion 51-3 is pulled by centrifugal force in a direction toward the second crank pin 52-2 and the third crank pin 52-3. The fourth journal portion 51-4 is not easily pulled in either direction by centrifugal force because the direction toward the third crank pin 52-3 is opposite to the direction toward the fourth crank pin 52-4. The fifth journal portion 51-5 is pulled by centrifugal force in a direction toward the fourth crank pin 52-4.

[0033] Therefore, as shown in Figures 2 and 3, the crankshaft 5 rotates in a bow-like elastically deformed state. For example, in the state of Figure 2 where the third piston 3-3 of the third cylinder 2-3 is located at top dead center, if an explosion occurs in the third cylinder 2-3, the third piston 3-3 moves to bottom dead center, resulting in the state of Figure 3. Next, in the state of Figure 3, if an explosion occurs in the second cylinder 2-2, the second piston 3-2 moves to bottom dead center, resulting in the state of Figure 2. Next, in the state of Figure 2, if an explosion occurs in the fourth cylinder 2-4, the fourth piston 3-4 moves to bottom dead center, resulting in the state of Figure 3.

[0034] As described above, the flywheel 6 is provided at the rear end of the crankshaft 5. Furthermore, the rear end of the crankshaft 5 is connected to a transmission (not shown) via the flywheel 6. In this way, a heavier member is present near the rear portion of the crankshaft 5 compared to the front portion of the crankshaft 5. As a result, centrifugal force acts largely on the rear portion of the crankshaft 5. Therefore, when the crankshaft 5 rotates, a large deformation occurs mainly in the rear portion of the crankshaft 5. Specifically, the main deformation occurs in which the third journal portion 51-3 and the fifth journal portion 51-5 are pulled in opposite directions starting from the fourth journal portion 51-4.

[0035] As described above, the crankshaft 5 rotates in a state where it is elastically deformed by centrifugal force. This causes local contact between the crankshaft 5 and the bearing 71, which generates vibrations. In this embodiment, by implementing some improvements in the bearing structure 7, it is possible to suppress vibrations caused by the crankshaft 5 rotating in a state where it is elastically deformed by centrifugal force. Hereinafter, such improvements will be described with reference to Figs. 4 to 6.

[0036] In the example of Figs. 4 to 6 described below, the rotation direction RD of the crankshaft 5 is counterclockwise when viewed from the rear of the vehicle.

[0037] Fig. 4 is a cross-sectional view showing a cross section taken along line AA in Fig. 1. Specifically, Fig. 4 shows the shape of the inner peripheral surface of the fifth bearing 71-5 as viewed from the rear of the vehicle.

[0038] 4, the inner diameter of the fifth bearing 71-5 is smaller at a right-side portion P1 than at other portions of the fifth bearing 71-5. Also, the inner diameter of the fifth bearing 71-5 is smaller at a portion P3 on the rotational direction RD side than the portion P1 and on the opposite side to the rotational direction RD than the portion P2 on the left-side portion than at other portions of the fifth bearing 71-5.

[0039] Here, the fifth journal portion 51-5 collides particularly strongly with the fifth bearing 71-5 when an explosion occurs in the fourth cylinder 2-4, which is close to the fifth journal portion 51-5 among the multiple cylinders 2. When an explosion starts in the fourth cylinder 2-4, as shown in FIG. 2, the fourth piston 3-4 of the fourth cylinder 2-4 is located near the top dead center, and the fifth journal portion 51-5 is eccentrically located on the upper left side in the fifth bearing 71-5. Therefore, the movement trajectory of the fifth journal portion 51-5 when an explosion occurs in the fourth cylinder 2-4 and the fifth journal portion 51-5 collides with the fifth bearing 71-5 is a trajectory from the portion P3 to the portion P1, as shown by the arrow A1 in FIG. 4.

[0040] As described above, in the bearing structure 7, the portion P1 and the portion P3 are located on an extension of the movement trajectory of the fifth journal portion 51-5 when the fifth journal portion 51-5 collides with the fifth bearing 71-5. Therefore, the movement distance of the fifth journal portion 51-5 when the fifth journal portion 51-5 collides with the fifth bearing 71-5 can be shortened. Therefore, the impact when the fifth journal portion 51-5 collides with the fifth bearing 71-5 can be weakened. Therefore, vibration can be suppressed.

[0041] As described above, centrifugal force acts largely on the rear portion of the crankshaft 5. Therefore, among the contacts between the journal portion 51 and the bearing 71, the collision of the fifth journal portion 51-5 with the fifth bearing 71-5 has a large effect on the generation of vibration. Therefore, by weakening the impact when the fifth journal portion 51-5 collides with the fifth bearing 71-5, it is possible to effectively suppress vibration.

[0042] Fig. 5 is a cross-sectional view showing the cross section BB of Fig. 2. Specifically, Fig. 5 shows the shape of the inner peripheral surface of the fourth bearing 71-4 when viewed from the rear of the vehicle.

[0043] 5, the inner diameter of the fourth bearing 71-4 is larger at a portion P4 on the right side than at other portions of the fourth bearing 71-4. As described above, when the crankshaft 5 rotates, the main deformation that occurs is that the third journal portion 51-3 and the fifth journal portion 51-5 are pulled in opposite directions from the fourth journal portion 51-4. The collision of the fifth journal portion 51-5 with the fifth bearing 71-5 has a significant effect on the generation of vibration.

[0044] Here, the greater the deformation of the fifth journal portion 51-5 starting from the fourth journal portion 51-4 during the period from the explosion of the second cylinder 2-2 to the explosion of the fourth cylinder 2-4, the stronger the impact of the collision of the fifth journal portion 51-5 with the fifth bearing 71-5 due to the explosion of the fourth cylinder 2-4. The deformation of the fifth journal portion 51-5 starting from the fourth journal portion 51-4 starts when the fourth journal portion 51-4 comes into contact with a portion P4 on the right side of the fourth bearing 71-4.

[0045] In the bearing structure 7, the inner diameter of the fourth bearing 71-4 is made larger in the right-side portion P4 than in other portions of the fourth bearing 71-4, so that the timing at which the fourth journal portion 51-4 comes into contact with the right-side portion P4 of the fourth bearing 71-4 can be delayed. Therefore, the start of deformation of the fifth journal portion 51-5 starting from the fourth journal portion 51-4 can be delayed. As a result, the deformation of the fifth journal portion 51-5 starting from the fourth journal portion 51-4 can be reduced during the period from when the second cylinder 2-2 explodes until when the fourth cylinder 2-4 explodes, and the impact of the collision of the fifth journal portion 51-5 with the fifth bearing 71-5 due to the explosion of the fourth cylinder 2-4 can be weakened. Therefore, vibration can be more effectively suppressed.

[0046] Fig. 6 is a cross-sectional view showing a cross section taken along line CC in Fig. 3. Fig. 6 shows the inner peripheral surface of the inner diameter of the third bearing 71-3 as viewed from the rear of the vehicle.

[0047] As shown in Fig. 6, the inner diameter of the third bearing 71-3 is smaller at a portion P5 on the left side than at other portions of the third bearing 71-3. As described above, explosion in the second cylinder 2-2 starts in the state shown in Fig. 3. As the explosion in the second cylinder 2-2 occurs, the third journal portion 51-3 moves from the left side to the right side within the third bearing 71-3.

[0048] In the bearing structure 7, the inner diameter of the third bearing 71-3 is made smaller at the left side portion P5 than at other portions of the third bearing 71-3, so that the timing at which the third journal portion 51-3 comes into contact with the third bearing 71-3 can be advanced when the second cylinder 2-2 explodes. Therefore, before the deformation of the fifth journal portion 51-5 starting from the fourth journal portion 51-4 starts, the elastic deformation can be generated starting from the third journal portion 51-3. This can reduce the deformation of the fifth journal portion 51-5 starting from the fourth journal portion 51-4 during the period from when the second cylinder 2-2 explodes to when the fourth cylinder 2-4 explodes, and can weaken the impact of the collision of the fifth journal portion 51-5 with the fifth bearing 71-5 due to the explosion of the fourth cylinder 2-4. Therefore, vibration can be suppressed more effectively.

[0049] An example of the vehicle 1 has been described above with reference to Figures 1 to 6. However, it is only necessary that the inner diameter of at least one of the multiple bearings 71 is smaller than that of other parts of the bearing 71 on the extension line of the movement locus of the journal portion 51 when the journal portion 51 collides with the bearing 71, and the configuration of the vehicle 1 may be modified in various ways from the above example.

[0050] For example, in the above, an example has been described in which the vehicle 1 is equipped with a horizontally opposed engine having four cylinders 2. However, the configuration of the engine of the vehicle 1 is not limited to the above example. For example, the engine of the vehicle 1 does not have to be of the horizontally opposed type. In other words, the arrangement of the cylinders 2 is not limited to the above example. Also, for example, the number of cylinders 2 may be other than four.

[0051] Also, for example, in the above, examples have been described in which vibration suppression is realized by each of the innovations in the inner diameter of the fifth bearing 71-5 described with reference to Fig. 4, the innovation in the inner diameter of the fourth bearing 71-4 described with reference to Fig. 5, and the innovation in the inner diameter of the third bearing 71-3 described with reference to Fig. 6. However, of the above three types of innovations, at least one of the innovation in the inner diameter of the fourth bearing 71-4 described with reference to Fig. 5 and the innovation in the inner diameter of the third bearing 71-3 described with reference to Fig. 6 may be omitted.

[0052] <Effects of bearing structure> The effects of the bearing structure 7 according to the embodiment of the present invention will be described.

[0053] The bearing structure 7 according to this embodiment includes a plurality of bearings 71 supporting a plurality of journal portions 51 provided on the crankshaft 5, and the inner diameter of at least one of the plurality of bearings 71 is smaller than that of other portions of the bearing 71 on an extension line of the movement locus of the journal portion 51 when the journal portion 51 collides with the bearing 71. This makes it possible to shorten the movement distance of the journal portion 51 when the journal portion 51 collides with the bearing 71. This makes it possible to weaken the impact when the journal portion 51 collides with the bearing 71. This makes it possible to suppress vibration.

[0054] In addition, in the bearing structure 7 of this embodiment, the multiple journal portions 51 include a first journal portion 51-1, a second journal portion 51-2 located rearward of the first journal portion 51-1, a third journal portion 51-3 located rearward of the second journal portion 51-2, a fourth journal portion 51-4 located rearward of the third journal portion 51-3, and a fifth journal portion 51-5 located rearward of the fourth journal portion 51-4, and the multiple bearings 71 include a first bearing 71-1 supporting the first journal portion 51-1, a second bearing 71-2 supporting the second journal portion 51-2, a third bearing 71-3 supporting the third journal portion 51-3, a fourth bearing 71-4 supporting the fourth journal portion 51-4, and a fifth bearing 71-5 supporting the fifth journal portion 51-5, and it is preferable that at least one of the bearings 71 is the fifth bearing 71-5. This makes it possible to weaken the impact of the collision of the fifth journal portion 51-5 with the fifth bearing 71-5, which has a large influence on the generation of vibration among the contacts between the journal portions 51 and the bearings 71, in the case where the crankshaft 5 has five journal portions 51 as described above, and thus makes it possible to effectively suppress vibration.

[0055] In the bearing structure 7 according to the present embodiment, the crankshaft 5 includes a first crank pin 52-1 connecting the first journal portion 51-1 and the second journal portion 51-2, a second crank pin 52-2 connecting the second journal portion 51-2 and the third journal portion 51-3, a third crank pin 52-3 connecting the third journal portion 51-3 and the fourth journal portion 51-4, and a fourth crank pin 52-4 connecting the fourth journal portion 51-4 and the fifth journal portion 51-5. In the circumferential direction of the crankshaft 5, the positions of the first crank pin 52-1 and the fourth crank pin 52-4 are shifted by 180° from the positions of the second crank pin 52-2 and the third crank pin 52-3. The first crank pin 52-1 is provided with a first crank pin for the first cylinder 2-1 arranged in the first direction relative to the crankshaft 5. The fifth bearing 71-5 has a first piston 3-1 connected to it, a second piston 3-2 of a second cylinder 2-2 arranged in a second direction opposite to the first direction with respect to the crankshaft 5 connected to the second crankpin 52-2, a third piston 3-3 of a third cylinder 2-3 arranged in the first direction with respect to the crankshaft 5 connected to the third crankpin 52-3, and a fourth piston 3-4 of a fourth cylinder 2-4 arranged in the second direction with respect to the crankshaft 5 connected to the fourth crankpin 52-4. It is preferable that the inner diameter of the fifth bearing 71-5 is smaller than other portions of the fifth bearing 71-5 at a portion P1 on the first direction side, and at a portion P3 on the side of the rotational direction RD of the crankshaft 5 relative to the portion P1 on the first direction side, and on the opposite side of the rotational direction RD of the crankshaft 5 relative to the portion P2 on the second direction side. As a result, when the vehicle 1 is equipped with a horizontally opposed engine having four cylinders 2 as described above, the impact of the collision of the fifth journal portion 51-5 with the fifth bearing 71-5, which has a large influence on the generation of vibration among the contacts between the journal portion 51 and the bearing 71, can be appropriately weakened. Therefore, the vibration can be effectively suppressed. In the above example, the right direction corresponds to the first direction, and the left direction corresponds to the second direction.

[0056] In addition, in the bearing structure 7 according to this embodiment, it is preferable that the inner diameter of the fourth bearing 71-4 is larger in the portion P4 on the first direction side than in other portions of the fourth bearing 71-4. This can delay the start of deformation of the fifth journal portion 51-5 starting from the fourth journal portion 51-4. Therefore, during the period from when the second cylinder 2-2 explodes until when the fourth cylinder 2-4 explodes, the deformation of the fifth journal portion 51-5 starting from the fourth journal portion 51-4 can be reduced, and the impact of the collision of the fifth journal portion 51-5 with the fifth bearing 71-5 due to the explosion of the fourth cylinder 2-4 can be weakened. Therefore, vibration can be suppressed more effectively. In the above example, the right direction corresponds to the first direction.

[0057] In addition, in the bearing structure 7 according to this embodiment, it is preferable that the inner diameter of the third bearing 71-3 is smaller in the portion P5 on the second direction side than in other portions of the third bearing 71-3. This allows elastic deformation to occur starting from the third journal portion 51-3 before deformation of the fifth journal portion 51-5 starting from the fourth journal portion 51-4 begins. Therefore, deformation of the fifth journal portion 51-5 starting from the fourth journal portion 51-4 can be reduced between the explosion of the second cylinder 2-2 and the explosion of the fourth cylinder 2-4, and the impact of the collision of the fifth journal portion 51-5 with the fifth bearing 71-5 due to the explosion of the fourth cylinder 2-4 can be weakened. Therefore, vibration can be suppressed more effectively. In the above example, the left direction corresponds to the second direction.

[0058] The above describes a preferred embodiment of the present invention with reference to the attached drawings. However, it goes without saying that the present invention is not limited to the above-described embodiment, and various modified or altered examples within the scope of the claims also fall within the technical scope of the present invention. [Explanation of symbols]

[0059] 1 vehicle 2-cylinder 2-1 No. 1 cylinder 2-2 No. 2 cylinder 2-3 3rd cylinder 2-4 4th cylinder 3 Piston 3-1 First piston 3-2 Second piston 3-3 3rd piston 3-4 4th piston 4 Connecting rod 4-1 First connecting rod 4-2 Second connecting rod 4-3 Third connecting rod 4-4 4th connecting rod 5 Crankshaft 6 Flywheel 7 Bearing structure 51 Journal Section 51-1 First Journal Section 51-2 2nd Journal Section 51-3 3rd Journal Section 51-4 4th Journal Section 51-5 5th Journal Section 52 Crank pin 52-1 No. 1 crank pin 52-2 No. 2 crank pin 52-3 3rd crank pin 52-4 4th crank pin 53 Counterweight 53-1 First counterweight 53-2 Second counterweight 53-3 3rd counterweight 53-4 4th counterweight 53-5 5th counterweight 53-6 6th counterweight 53-7 7th Counterweight 53-8 8th Counterweight 71 Bearings 71-1 First bearing 71-2 No. 2 bearing 71-3 3rd bearing 71-4 Fourth bearing 71-5 Fifth bearing P1 part P2 part P3 part P4 part P5 part RD Rotation direction

Claims

1. a plurality of bearings supporting a plurality of journal portions provided on the crankshaft, an inner diameter of at least one of the plurality of bearings is smaller than that of other portions of the bearing on an extension line of a movement locus of the journal portion when the journal portion collides with the bearing; Bearing structure.

2. the plurality of journal units include a first journal unit, a second journal unit located rearward of the first journal unit, a third journal unit located rearward of the second journal unit, a fourth journal unit located rearward of the third journal unit, and a fifth journal unit located rearward of the fourth journal unit, the plurality of bearings include a first bearing supporting the first journal portion, a second bearing supporting the second journal portion, a third bearing supporting the third journal portion, a fourth bearing supporting the fourth journal portion, and a fifth bearing supporting the fifth journal portion, The at least one bearing is the fifth bearing. The bearing structure according to claim 1 .

3. the crankshaft includes a first crank pin connecting the first journal portion and the second journal portion, a second crank pin connecting the second journal portion and the third journal portion, a third crank pin connecting the third journal portion and the fourth journal portion, and a fourth crank pin connecting the fourth journal portion and the fifth journal portion, In a circumferential direction of the crankshaft, the positions of the first crank pin and the fourth crank pin are shifted by 180° from the positions of the second crank pin and the third crank pin, a first piston of a first cylinder disposed in a first direction relative to the crankshaft is connected to the first crank pin; a second piston of a second cylinder disposed in a second direction opposite to the first direction with respect to the crankshaft is connected to the second crank pin; a third piston of a third cylinder disposed in the first direction with respect to the crankshaft is connected to the third crank pin, a fourth piston of a fourth cylinder disposed in the second direction with respect to the crankshaft is connected to the fourth crank pin, an inner diameter of the fifth bearing is smaller in a portion on the first direction side and a portion on a rotational direction side of the crankshaft with respect to the first direction side and on an opposite side to the rotational direction of the crankshaft with respect to the second direction side than other portions of the fifth bearing; The bearing structure according to claim 2.

4. The inner diameter of the fourth bearing is larger in a portion on the first direction side than in other portions of the fourth bearing. The bearing structure according to claim 3.

5. The inner diameter of the third bearing is smaller in a portion on the second direction side than in other portions of the third bearing. The bearing structure according to claim 3 or 4.

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