Crankshaft and engine

Abstract

To provide a crank shaft which enables reduction of vibration etc. of an engine without increasing friction.SOLUTION: In a crank shaft 1, five main journals 131 to 135 and four crank pins 111 to 114 are arranged on the same plane so as to be located adjacent to each other. A center axis of the third main journal 133 from the front end side is eccentric in an axial direction of the first crank pin 111 from the front end side relative to center axes of the other main journals 131, 132, 134, 135. An outermost diameter of the fourth main journal 134 from the front end side is formed so as to be identical to diameters of the other main journals 131 to 133 and 135 and an outer peripheral surface of the fourth main journal 134 is formed into an arc shape along the axial direction. A diameter of a front end of the fifth main journal 135 from the front end side is formed so as to be identical to the diameters of the other main journals 131 to 134 and the fifth main journal 135 is formed into a taper shape so that its diameter gradually reduces along the axial direction toward the rear end side.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a crankshaft and an engine equipped with the crankshaft. [Background technology]

[0002] An engine is equipped with a crankshaft to convert the reciprocating motion of pistons into rotational motion. The crankshaft has multiple main journals supported by bearings and multiple crankpins connected to connecting rods (conrods). Because the centers of the main journals and crankpins are eccentric when viewed from the axial direction, when the pistons are pushed down by the combustion pressure of the air-fuel mixture, the reciprocating linear motion of the pistons is converted into rotational motion via the connecting rods, causing the crankshaft to rotate around the central axis of the main journals. Such crankshafts are required to rotate smoothly with little vibration.

[0003] Incidentally, it has been known for some time that engine vibration and noise (hereinafter also referred to as "vibration, etc.") can be reduced by reducing the clearance (oil clearance) between the main journal and the main bearing. For example, Patent Document 1 discloses a technology for improving vibration and noise by reducing the oil clearance of the end-side journal bearings (main bearings) closest to both front and rear ends of the crankshaft compared to the oil clearance of journal bearings other than the end-side journal bearings. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-27126 Summary of the Invention [Problem to be solved by the invention]

[0005] However, reducing the clearance (oil clearance) between the main journal and main bearing causes a problem of increased friction (which in turn worsens fuel consumption rate (fuel economy)).

[0006] The present invention has been made to solve the above problems, and aims to provide a crankshaft that can reduce engine vibrations and the like without increasing friction, and an engine equipped with such a crankshaft. [Means for solving the problem]

[0007] After extensive research into the above-mentioned problems, the inventors discovered that the inertial force caused by the movement of the piston and connecting rod causes the crankshaft to deform into a bow shape within the oil clearance and rotate while the combustion pressure acting on the piston moves the crankshaft, causing the main journal to hit the main bearing, resulting in vibrations, etc. The inventors also discovered that the inertial force causes the crankshaft to rotate while deforming into a bow shape around the third main journal from the front end.

[0008] Therefore, the crankshaft according to the present invention is characterized in that, in a crankshaft in which a plurality of main journals and a plurality of crankpins are arranged adjacent to each other and on the same plane, the central axis of the main journal that is third from the front end side among the plurality of main journals is eccentric in the axial direction of the crankpin that is first from the front end side relative to the central axes of the other main journals.

[0009] In the crankshaft according to the present invention, the central axis of the third main journal from the front end is eccentric relative to the central axes of the other main journals in the axial direction of the first crankpin from the front end, thereby suppressing deformation of the crankshaft due to inertial forces during rotation. Furthermore, the load when the main journals strike the main bearings due to movement of the crankshaft caused by combustion pressure is reduced, thereby suppressing engine vibrations and the like. Furthermore, engine vibrations and the like can be suppressed without changing (reducing) the total oil clearance. [Effects of the Invention]

[0010] As a result, according to the present invention, it is possible to reduce engine vibrations and the like without increasing friction. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a horizontal cross-sectional view showing an engine (cylinder block) incorporating a crankshaft according to an embodiment. [Figure 2] FIG. 1 is a cross-sectional view showing a configuration of a crankshaft according to an embodiment. [Figure 3] FIG. 2 is a cross-sectional view schematically showing only a main journal of the crankshaft according to the embodiment. [Figure 4] 1 is a diagram showing a schematic diagram of deformation of a crankshaft incorporated in an engine when it rotates; DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts will be designated by the same reference numerals. In addition, the same elements will be designated by the same reference numerals in each drawing, and redundant explanations will be omitted.

[0013] First, the configuration of a crankshaft 1 according to an embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a horizontal cross-sectional view showing an engine 3 (cylinder block 31) incorporating the crankshaft 1. FIG. 2 is a cross-sectional view showing the configuration of the crankshaft 1. FIG. 3 is a cross-sectional view schematically showing only the main journals 131 to 135 of the crankshaft 1. Note that in FIGS. 1 to 3, the shapes of the main journals 131 to 135 are exaggerated for ease of understanding. Hereinafter, the present embodiment will be described taking as an example a case where the crankshaft 1 is applied to a horizontally opposed four-cylinder engine 3.

[0014] When mounted on the engine 3, the crankshaft 1 converts the reciprocating motion of the pistons 32 into rotational motion via the connecting rods 33. The crankshaft 1 includes five main journals (crank journals) 131-135 that are arranged in a straight line at intervals from one another and that are supported by the cylinder block 31 via main bearings 34 when mounted on the engine 3, and four crank pins (pin journals) 111-114 that are located between adjacent main journals 131-135 and to which the big ends of the connecting rods 33 are attached.

[0015] That is, the five main journals 131 to 135 and the four crank pins 111 to 114 are arranged adjacent to each other. Furthermore, the five main journals 131 to 135 (center axes) and the four crank pins 111 to 114 (center axes) are arranged in the same plane.

[0016] The crankshaft 1 also includes eight crank arms 12 connecting the crank pins 111-114 and the main journals 131-135, and eight counterweights 14 formed continuously from the crank arms 12. In the crankshaft 1, the centers of the main journals 131-135 and the crank pins 111-114 are eccentric when viewed from the axial direction, so when a piston 32 is pushed down by the combustion pressure of the air-fuel mixture, the reciprocating linear motion of the piston 32 is converted into rotational motion via a connecting rod 33, and the crankshaft 1 rotates around the central axis of the main journals 131-135. In the crankshaft 1, the centers of the main journals 131-135 and the crank pins 111-114 are eccentric when viewed from the axial direction, so that counterweights 14 are provided on the crank arms 12 on the opposite side of the crank pins 111-114 relative to the main journals 131-135 to maintain balance during rotation.

[0017] The crankshaft 1 including the counterweight 14 is preferably made of a material such as cast iron. Cast iron is an alloy of iron and carbon with a content of 1.7 to 6.7%. Cast iron also contains silicon, manganese, phosphorus, sulfur, and other elements with a content of 0.5 to 7.0% and has high castability.

[0018] A crank pulley can be attached to a front end (tip end) 16 of the crankshaft 1. On the other hand, a rear end (base end) 15 of the crankshaft 1 is provided with a flange to which a flywheel is fastened.

[0019] Here, the five main journals 131 to 135 are, in order from the front end 16 side (front end side), the first (first main journal 131), the second (second main journal 132), the third (third main journal 133), the fourth (fourth main journal 134), and the fifth (fifth main journal 135).

[0020] Similarly, the four crankpins 111 to 114 are, in order from the front end 16 side (front end side), the first (first crankpin 111), the second (second crankpin 112), the third (third crankpin 113), and the fourth (fourth crankpin 114).

[0021] In particular, the crankshaft 1 has the function of reducing engine vibrations and the like without increasing friction. Therefore, in the crankshaft 1, the central axis of the third main journal 133 from the front end 16 side (front end side) is eccentric in the axial direction of the first crankpin 111 from the front end 16 side (front end side) relative to the central axes of the other main journals 131, 132, 134, and 135.

[0022] More specifically, as shown in Fig. 3, the central axis of the third main journal 133 is eccentric in the axial direction of the first crankpin 111 by, for example, 10 μm. Note that Fig. 3 shows a state in which the crankshaft 1 (main journals 131-135) is shifted to one side of the oil clearance (the right side of the drawing). The crankshaft 1 (main journals 131-135) is supported within the oil clearance so that it can move and deform. Also, in Fig. 3, the shape of a conventional main journal is shown by a dashed line.

[0023] The fourth main journal 134 from the front end 16 side (front end side) has an outermost diameter that is the same as the diameters of the other main journals 131 to 133, 135, and an outer peripheral surface that is arcuate (curved) along the axial direction. That is, the fourth main journal 134 is formed so that its diameter is smaller at both ends and larger in the center.

[0024] More specifically, as shown in FIG. 3, the outer peripheral surface of the fourth main journal 134 is formed in an arc shape along the axial direction, and the diameters at the front and rear ends are, for example, -20 (μm) smaller than the diameter at the center (i.e., are smaller).

[0025] Furthermore, the fifth main journal 135 from the front end 16 side (front end side) is formed in a tapered shape so that the diameter at the front end is the same as the diameters of the other main journals 131 to 134 and the diameter decreases linearly along the axial direction toward the rear end 15 side (rear end side).

[0026] More specifically, as shown in FIG. 3, the fifth main journal 135 is formed so that the diameter at its rear end is, for example, −10 μm smaller than the diameter at its front end (that is, so that it is smaller).

[0027] When the crankshaft 1 configured as described above is incorporated into the engine 3 and rotates, it deforms into a bow shape within the oil clearance and rotates on the same plane due to the inertial forces caused by the movements of the piston 32 and the connecting rod 33, as shown by the solid lines in Figure 4. At that time, the crankshaft 1 rotates while deforming into a bow shape around the third main journal 133 from the front end side.

[0028] Then, as the crankshaft 1 is moved by the combustion pressure acting on the piston 32, the main journals 131-135 strike the main bearings 34. As a result, the fourth main journal 134 from the front end strikes the edges at both ends. The fifth main journal 135 from the front end strikes the edges at the rear end. Here, the solid lines in FIG. 4 are diagrams that schematically show deformation when the crankshaft 1 incorporated in the engine 3 rotates. Note that the shape (deformation) is exaggerated in FIG. 4 (solid lines) to make it easier to understand. Also, in FIG. 4, the shape of the crankshaft 1 when stationary is shown by dashed lines.

[0029] In contrast, by configuring the crankshaft 1 as described above, that is, by making the central axis of the third main journal 133 eccentric in the axial direction of the first crankpin 111, deformation of the crankshaft 1 due to inertial force during rotation is suppressed. Furthermore, the load when the main journals 131-135 hit the main bearing 34 due to movement of the crankshaft 1 caused by combustion pressure is reduced.

[0030] In addition, the outer peripheral surface of the fourth main journal 134 from the front end is formed in an arc shape (curved) along the axial direction, thereby increasing the area of ​​contact with the main bearing 34 and supporting the crankshaft 1 (main journals 131 to 135) in a fluid lubricated state.

[0031] Furthermore, the fifth main journal 135 from the front end is tapered in the axial direction so that the diameter decreases toward the rear end, thereby increasing the contact area with the main bearing 34 and reducing the load when the crankshaft 1 hits the main bearing 34.

[0032] As described above, according to this embodiment, the central axis of the third main journal 133, which can be the center of bow-shaped deformation, is eccentric in the axial direction of the first crankpin 111 relative to the central axes of the other main journals 131, 132, 134, and 135, thereby suppressing deformation of the crankshaft 1 due to inertial forces during rotation. Furthermore, the load applied when the main journals 131-135 strike the main bearing 34 due to movement of the crankshaft 1 caused by combustion pressure is reduced, thereby suppressing engine vibrations and the like. Furthermore, engine vibrations and the like can be suppressed without changing (reducing) the total oil clearance.

[0033] Furthermore, according to this embodiment, the outer peripheral surface of the fourth main journal 134, which may cause edge contact at both ends, is formed in an arc shape (curved) along the axial direction, thereby increasing the contact area with the main bearing 34 and supporting the crankshaft 1 (main journals 131 to 135) in a fluid lubricated state, thereby suppressing engine vibrations, etc.

[0034] Furthermore, according to this embodiment, the fifth main journal 135, which may cause edge strike at its rear end, is tapered so that its diameter decreases toward the rear end. This increases the area of ​​contact with the main bearing 34 and reduces the load when the crankshaft 1 strikes the main bearing 34, thereby suppressing engine vibrations and the like.

[0035] As a result, according to this embodiment, it is possible to reduce engine vibrations and the like without increasing friction.

[0036] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and various modifications are possible. For example, in the above embodiments, the crankshaft 1 is incorporated into (applied to) a horizontally opposed four-cylinder engine 3, but the present invention can also be applied to, for example, an in-line four-cylinder engine or a V-type four-cylinder engine.

[0037] Furthermore, the dimensions, materials, and other specific numerical values ​​shown in the above embodiments are examples to facilitate understanding of the present invention, and do not limit the present invention unless otherwise specified. [Explanation of symbols]

[0038] 1 crankshaft 3 Engine 111 No. 1 crank pin 112 No. 2 crank pin 113 No. 3 crank pin 114 No. 4 crank pin 12 crank arms 131 No. 1 Main Journal 132 No. 2 Main Journal 133 No. 3 Main Journal 134 No. 4 Main Journal 135 No. 5 Main Journal 14 Counterweight 15 Rear end 16 Front end 31 Cylinder block 32 piston 33 Connecting rod 34 Main bearing

Claims

1. A crankshaft assembled to a four-cylinder engine, in which a plurality of main journals and a plurality of crank pins are arranged adjacent to each other and in the same plane, a center axis of the third main journal from the front end side among the plurality of main journals is eccentric in the axial direction of the first crankpin from the front end side with respect to the center axes of the other main journals.

2. 2. The crankshaft according to claim 1, wherein the fourth main journal from the front end side of the plurality of main journals has an outermost diameter that is the same as the diameters of the other main journals, and an outer peripheral surface that is formed in an arc shape along the axial direction.

3. 3. The crankshaft according to claim 1, wherein the fifth main journal from the front end side of the plurality of main journals is tapered so that its front end diameter is the same as that of the other main journals and its diameter decreases axially toward its rear end side.

4. An engine comprising the crankshaft according to any one of claims 1 to 3.

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