Crankshaft

Abstract

To restrain deflection of a crankshaft.SOLUTION: A crankshaft 10 provided in an engine includes a plurality of crank journals J1-J5 positioned at a rotation center CR, a plurality of crank pins P1-P4 eccentric with respect to the crank journals J1-J5, and a plurality of crank webs W1-W8 connecting the crank journals J1-J5 and the crank pins P1-P4 with each other. A plurality of thin webs W2, W3, W6, W7 and a plurality of thick webs W1, W4, W5, W8 having a thickness dimension larger than the thin webs are used as the plurality of crank webs W1-W8.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a crankshaft provided in an engine. [Background technology]

[0002] A crankshaft provided in an engine has a crank journal located at the center of rotation and a crank pin that is eccentric with respect to the center of rotation. A piston is connected to the crank pin via a connecting rod, and loads such as inertial force and centrifugal force act on the crank pin when the crankshaft rotates. For this reason, a counterweight is provided on a crank web that connects the crank journal and the crank pin, and the load acting on the crank pin is cancelled by the centrifugal force of this counterweight. In this way, by providing a counterweight on the crankshaft, the load acting on the crank pin can be cancelled, and the runout of the crankshaft can be suppressed (see Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6443546 [Patent Document 2] JP 2010-144804 A [Patent Document 3] JP 2005-42837 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to achieve a compact engine, it is necessary to shorten the crankshaft in the axial direction. However, shortening the crankshaft in the axial direction leads to a thinner crank web on which the counterweight is formed, which leads to a smaller and lighter counterweight. In this way, when the crankshaft is shortened in the axial direction, the centrifugal force generated in the counterweight is reduced, making it difficult to sufficiently counteract the load acting on the crank pin, and therefore difficult to suppress the runout of the crankshaft.

[0005] An object of the present invention is to suppress runout of a crankshaft. [Means for solving the problem]

[0006] A crankshaft according to one embodiment of the present invention is a crankshaft provided in an engine, and includes a plurality of crank journals located at the center of rotation, a plurality of crank pins eccentric to the crank journals, and a plurality of crank webs connecting the crank journals and the crank pins to each other. do. The crank webs include a plurality of thin webs and a plurality of thick webs having a thickness larger than that of the thin webs. The crank journals include a first journal, a second journal, a third journal, a fourth journal, and a fifth journal in axial order. The thin web is connected to the second journal and the fourth journal. The thick web is connected to the first journal, the third journal, and the fifth journal. Effect of the Invention

[0007] According to the present invention, the multiple crank webs are provided in the form of multiple thin webs and multiple thick webs having a thickness dimension greater than that of the thin webs, thereby making it possible to cancel out much of the load acting on the crankshaft and suppress vibration of the crankshaft. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing an engine equipped with a crankshaft according to an embodiment of the present invention; [Diagram 2]2 is a cross-sectional view showing a cylinder block and a crankshaft of the engine taken along line AA in FIG. 1. [Diagram 3] 1 is a diagram showing a crankshaft according to an embodiment of the present invention; [Figure 4] FIG. 4 is a diagram showing a load acting on a crankshaft. [Diagram 5] FIG. 4 is a diagram showing a crankshaft of a comparative example. [Figure 6] FIG. 11 is a diagram showing a load acting on a crankshaft of a comparative example. [Figure 7A] FIG. 4 is a diagram showing the relationship between friction loss of a crank journal and engine speed. [Figure 7B] FIG. 13 is a diagram showing the relationship between an improvement effect value and an engine rotation speed. [Figure 8] FIG. 2 is a diagram showing a crankshaft of an embodiment and a crankshaft of a comparative example side by side. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0010] [Engine structure] Fig. 1 is a schematic diagram showing an engine 11 equipped with a crankshaft 10 according to an embodiment of the present invention. Fig. 2 is a cross-sectional view showing cylinder blocks 14, 16 and the crankshaft 10 of the engine 11 along the line AA in Fig. 1.

[0011] 1 and 2, engine 11, which is a horizontally opposed engine, has a pair of cylinder banks 12, 13. One cylinder bank 12 is provided with a cylinder block 14 and a cylinder head 15, and the other cylinder bank 13 is provided with a cylinder block 16 and a cylinder head 17. Engine 11 also has a crankshaft 10 that is rotatably supported by the pair of cylinder blocks 14, 16. Crankshaft 10 has a plurality of crank journals J1-J5 provided at a rotation center CR, and a plurality of crank pins P1-P4 that are eccentric with respect to the rotation center CR.

[0012] As shown in Fig. 2, a pair of cylinder blocks 14, 16 are formed with semicircular journal bores 21 each having a bearing metal 20, and crank journals J1-J5 of the crankshaft 10 are rotatably supported by the opposing journal bores 21. The cylinder blocks are also formed with cylinder bores B1-B4, and pistons Pi1-Pi4 are housed in the cylinder bores B1-B4 so as to be capable of reciprocating freely. The pistons Pi1-Pi4 are connected to the crank pins P1-P4 of the crankshaft 10 via connecting rods 22. As shown in Fig. 1, the crank pins P1, P4 and the crank pins P2, P3 are attached at positions shifted by 180° from each other.

[0013] [Crankshaft structure] Fig. 3 is a diagram showing a crankshaft 10 according to one embodiment of the present invention. As shown in Fig. 3, an accessory drive shaft 23 is provided at one end of the crankshaft 10, and an output flange 24 is provided at the other end of the crankshaft 10. When the engine 11 is mounted on a vehicle as a power source, a crank pulley (not shown) or the like is connected to the accessory drive shaft 23, and a torque converter (not shown) or the like is connected to the output flange 24.

[0014] As described above, the crankshaft 10 has a plurality of crank journals J1-J5 located at the center of rotation CR. As the crank journals J1-J5, the crankshaft 10 is provided with a crank journal (first journal) J1, a crank journal (second journal) J2, a crank journal (third journal) J3, a crank journal (fourth journal) J4, and a crank journal (fifth journal) J5, in that order from one end to the other end in the axial direction.

[0015] The crankshaft 10 also has a number of crank pins P1 to P4 that are eccentric with respect to the crank journals J1 to J5. As the crank pins P1 to P4, the crankshaft 10 is provided with a crank pin P1 disposed between the crank journals J1 and J2, a crank pin P2 disposed between the crank journals J2 and J3, a crank pin P3 disposed between the crank journals J3 and J4, and a crank pin P4 disposed between the crank journals J4 and J5.

[0016] Furthermore, the crankshaft 10 has a plurality of crank webs W1-W8 that connect the crank journals J1-J5 and the crank pins P1-P4 to one another. As the crank webs W1-W8, the crankshaft 10 is provided with the crank web W1 connected to the crank journal J1, the crank webs W2 and W3 connected to the crank journal J2, the crank webs W4 and W5 connected to the crank journal J3, the crank webs W6 and W7 connected to the crank journal J4, and the crank web W8 connected to the crank journal J5.

[0017] Each of the crank webs W1-W8 includes a crank arm (arm portion) 1a-8a that connects the crank journals J1-J5 and the crank pins P1-P4 to each other, and a counterweight (weight portion) 1b-8b that is connected to the crank arm 1a-8a and extends to the opposite side of the crank pins P1-P4. As the crank webs W1-W8, the crankshaft 10 is provided with a plurality of thin webs having a thickness dimension "T1", and a plurality of thick webs having a thickness dimension "T2" larger than "T1".

[0018] That is, the crankshaft 10 is provided with crank webs W2, W3, W6, and W7 connected to the crank journals J2 and J4 as a plurality of thin webs. The crankshaft 10 is also provided with crank webs W1, W4, W5, and W8 connected to the crank journals J1, J3, and J5 as a plurality of thick webs. In this manner, the crankshaft 10 is provided with the thick webs W1, W4, W5, and W8 and the thin webs W2, W3, W6, and W7 having different thickness dimensions, and the counterweights 1b, 4b, 5b, and 8b of the thick webs W1, W4, W5, and W8 are heavier than the counterweights 2b, 3b, 6b, and 7b of the thin webs W2, W3, W6, and W7.

[0019] [Load acting on the crankshaft] Next, the load acting on the rotating crankshaft 10 will be described. FIG. 4 is a diagram showing the load acting on the crankshaft 10. As described above, the crankshaft 10 is provided with the crankpins P1 to P4 at positions away from the rotation center CR, and the pistons are connected to the crankpins P1 to P4 via the connecting rods 22. As a result, when the crankshaft 10 rotates, loads such as centrifugal force and inertial force act on each of the crankpins P1 to P4. That is, the loads L1a and L1b act on the crankpin P1, the loads L2a and L2b act on the crankpin P2, the loads L3a and L3b act on the crankpin P3, and the loads L4a and L4b act on the crankpin P4. In the example shown in FIG. 4, the loads acting on the crankpins P1 to P4 are conveniently divided into two and described in order to facilitate understanding of the invention.

[0020] In addition, the crankshaft 10 is provided with counterweights 1b-8b at positions away from the rotation center CR. As a result, when the crankshaft 10 rotates, a load such as a centrifugal force acts on each of the counterweights 1b-8b. As described above, the counterweights 1b, 4b, 5b, and 8b of the thick webs W1, W4, W5, and W8 are heavier than the counterweights 2b, 3b, 6b, and 7b of the thin webs W2, W3, W6, and W7. Therefore, the loads Lw1, Lw4, Lw5, and Lw8 acting on the counterweights 1b, 4b, 5b, and 8b are larger than the loads Lw2, Lw3, Lw6, and Lw7 acting on the counterweights 2b, 3b, 6b, and 7b.

[0021] As shown by hatched arrows in Fig. 4, the crank pins P1 and P4 located at both ends of the crank pins P1 to P4 are subjected to loads L1a, L1b, L4a, and L4b in the direction of the arrow D1, while the crank pins P2 and P3 located in the center are subjected to loads L2a, L2b, L3a, and L3b in the direction of the arrow D2 opposite to the direction of the arrow D1. Therefore, the crank journal J2 located between the crank pins P1 and P2 is less likely to vibrate because the loads acting on the crank pins P1 and P2 cancel each other out. Similarly, the crank journal J4 located between the crank pins P3 and P4 is less likely to vibrate because the loads acting on the crank pins P3 and P4 cancel each other out.

[0022] On the other hand, the crank journal J1 located between the crank pin P1 and the accessory drive shaft 23 is easily vibrated because the load of the crank pin P1 acts mainly in one direction. Similarly, the crank journal J5 located between the crank pin P4 and the output flange 24 is easily vibrated because the load of the crank pin P4 acts mainly in one direction. Furthermore, the crank journal J3 located between the crank pins P2 and P3 is easily vibrated because the load of the crank pins P2 and P3 acts mainly in one direction.

[0023] In this way, the crankshaft 10 has a structure in which the crank journals J2 and J4 are less likely to vibrate, while the crank journals J1, J3 and J5 are more likely to vibrate. As described above, the crank journals J2 and J4 that are less likely to vibrate are connected to thin webs W2, W3, W6 and W7 equipped with light counterweights 2b, 3b, 6b and 7b, while the crank journals J1, J3 and J5 that are more likely to vibrate are connected to thick webs W1, W4, W5 and W8 equipped with heavy counterweights 1b, 4b, 5b and 8b. This makes it possible to increase the centrifugal force of the counterweights 1b, 4b, 5b and 8b for the crank journals J1, J3 and J5 that are more likely to vibrate, thereby suppressing the vibration of the crank journals J1, J3 and J5.

[0024] That is, for the crank journal J1, the load Lw1 acting on the counterweight 1b is increased so as to cancel the load L1a acting on the crank pin P1. For the crank journal J5, the load Lw8 acting on the counterweight 8b is increased so as to cancel the load L4a acting on the crank pin P4. Furthermore, as indicated by the reference symbol X3, for the crank journal J3, the loads Lw4 and Lw5 acting on the counterweights 4b and 5b are increased so as to cancel the loads L2a and L3a acting on the crank pins P2 and P3. This makes it possible to reduce many of the loads acting on the crank journals J1, J3, and J5, and suppress the runout of the crank journals J1, J3, and J5.

[0025] As for the crank journal J2, as indicated by the reference symbol X2, the load L1b acting on the crank pin P1 and the load Lw3 acting on the counterweight 3b can cancel out the load L2b acting on the crank pin P2 and the load Lw2 acting on the counterweight 2b. As for the crank journal J4, as indicated by the reference symbol X4, the load L4b acting on the crank pin P4 and the load Lw6 acting on the counterweight 6b can cancel out the load L3b acting on the crank pin P3 and the load Lw7 acting on the counterweight 7b. This can reduce many of the loads acting on the crank journals J2 and J4, and suppress runout of the crank journals J2 and J4.

[0026] As described above, by providing thick and thin webs as the crank webs W1-W8, it is possible to cancel out much of the load acting on the crankshaft 10. This makes it possible to suppress runout of each of the crank journals J1-J5, thereby reducing friction loss between each of the crank journals J1-J5 and the bearing metal 20. Moreover, since the thin crank webs W2, W3, W6, and W7 are connected to the crank journals J2 and J4, which are less susceptible to runout, it is possible to shorten the overall length of the crankshaft 10 while suppressing runout of each of the crank journals J1-J5.

[0027] [Comparative Example] Next, the load acting on the crankshaft 100 of the comparative example will be described. Fig. 5 is a diagram showing the crankshaft 100 of the comparative example, and Fig. 6 is a diagram showing the load acting on the crankshaft 100 of the comparative example. Note that in Figs. 5 and 6, the same parts and loads as those shown in Figs. 3 and 4 are denoted by the same reference numerals, and the description thereof will be omitted.

[0028] As shown in FIG. 5, the crankshaft 100 of the comparative example has a plurality of crank webs W1x-W8x formed at a common thickness dimension "T3". When the crank webs W1x-W8x have the same thickness dimension, the masses of the counterweights 1bx-8bx provided on the crank webs W1x-W8x are also common. Therefore, as shown in FIG. 6, the counterweights 1bx-8bx are subjected to substantially the same loads Lw1x-Lw8x. The only difference between the crankshaft 10 of the embodiment and the crankshaft 100 of the comparative example is the thickness dimensions of the crank webs W1-W8, W1x-W8x. The crankshaft 10 of the embodiment and the crankshaft 100 of the comparative example have the same positions of the crank journals J1-J5.

[0029] As described above, when the common loads Lw1x to Lw8x act on the counterweights 1bx to 8bx, the centrifugal force of the counterweights 1bx, 4bx, 5bx, and 8bx cannot be sufficiently increased, and it is difficult to suppress the vibration of the crank journals J1, J3, and J5. That is, for the crank journal J1, it is difficult to increase the load Lw1x acting on the counterweight 1bx, and it is therefore impossible to sufficiently cancel the load L1a acting on the crank pin P1. That is, since the load L1a of the crank pin P1 remains, the load acts on the crank journal J1 in the direction of the arrow α1. Also, for the crank journal J5, it is difficult to increase the load Lw8x acting on the counterweight 8bx, and it is therefore impossible to sufficiently cancel the load L4a acting on the crank pin P4. That is, since the load L4a of the crank pin P4 remains, the load acts on the crank journal J5 in the direction of the arrow α5. Furthermore, as for the crank journal J3, since it is difficult to increase the loads Lw4x, Lw5x acting on the counterweights 4bx, 5bx as indicated by the reference symbol X3, it is impossible to sufficiently cancel the loads L2a, L3a acting on the crank pins P2, P3. In other words, since the loads L2a, L3a on the crank pins P2, P3 remain, a load acts on the crank journal J3 in the direction of the arrow α3.

[0030] In this way, if the thickness dimensions of the crank webs W1x to W8x are the same, the load acts on the crank journal J1 in the direction of the arrow α1, the load acts on the crank journal J3 in the direction of the arrow α3, and the load acts on the crank journal J5 in the direction of the arrow α5. As a result, in the crankshaft 100 of the comparative example, it is difficult to suppress the runout of the crank journals J1 to J5, and it is difficult to reduce the friction loss between each of the crank journals J1 to J5 and the bearing metal 20. In contrast, in the crankshaft 10 of the embodiment, thick webs and thin webs are provided as the crank webs W1 to W8, so that most of the load acting on the crankshaft 10 can be canceled. As a result, it is possible to suppress the runout of each of the crank journals J1 to J5, and it is possible to reduce the friction loss between each of the crank journals J1 to J5 and the bearing metal 20.

[0031] Here, FIG. 7A is a diagram showing the relationship between the friction loss of the crank journal and the engine speed, and FIG. 7B is a diagram showing the relationship between the improvement effect value and the engine speed. As described above, when the crankshaft 10 of the embodiment is used, the crankshaft 10 is less likely to vibrate, whereas when the crankshaft 100 of the comparative example is used, the crankshaft 100 is more likely to vibrate. Therefore, as shown in FIG. 7A, when the crankshaft 10 of the embodiment is used, the friction loss between the crank journals J1 to J5 and the bearing metal 20 can be reduced compared to when the crankshaft 100 of the comparative example is used. As shown by the symbol X in FIG. 7A, the friction loss when the crankshaft 10 of the embodiment is used and the friction loss when the crankshaft 100 of the comparative example is used are more divergent as the engine speed increases. That is, as shown in FIG. 7B, in the crankshaft 10 of the embodiment, the improvement effect value of the friction loss is increased as the engine speed increases. The improvement effect value shown in FIG. 7B is a value obtained by subtracting the friction loss when the crankshaft 10 of the embodiment is used from the friction loss when the crankshaft 100 of the comparative example is used.

[0032] [Engine downsizing] By using the crankshaft 10 of the embodiment, the bank offset of the engine 11 can be reduced, and the engine 11 can be made more compact. The reduction in size of the engine 11 will be described below. Here, Fig. 8 is a diagram showing the crankshaft 10 of the embodiment and a crankshaft 100 of the comparative example side by side.

[0033] First, as shown in Fig. 2, one cylinder block 14 is formed with two cylinder bores B1, B3. A piston Pi1 is accommodated in the cylinder bore B1, and a crank pin P1 is connected to the piston Pi1. A piston Pi3 is accommodated in the cylinder bore B3, and the piston Pi3 is connected to the crank pin P3. Therefore, the cylinder pitch Sp, which is the distance between the central axes of the cylinder bores B1, B3, corresponds to the distance between the crank pins P1, P3, i.e., the distance between the center lines C1, C3 that pass through the centers of the crank pins P1, P3.

[0034] Similarly, two cylinder bores B2, B4 are formed in the other cylinder block 16. A piston Pi2 is accommodated in the cylinder bore B2, and this piston Pi2 is connected to the crank pin P2. Furthermore, a piston Pi4 is accommodated in the cylinder bore B4, and this piston Pi4 is connected to the crank pin P4. Therefore, the cylinder pitch Sp, which is the distance between the central axes of the cylinder bores B2, B4, corresponds to the distance between the crank pins P2, P4, that is, the distance between the center lines C2, C4 that pass through the centers of the crank pins P2, P4.

[0035] As shown in Fig. 8, when comparing the crankshaft 10 of the embodiment and the crankshaft 100 of the comparative example, the intervals between the crank journal J1 and the crank journal J5 are the same. In addition, in the crankshaft 10 of the embodiment, thick webs W1, W4, W5, and W8, which are crank webs formed to a thickness dimension of "T2", are connected to the crank journals J1, J3, and J5. On the other hand, in the crankshaft 100 of the comparative example, crank webs W1x, W4x, W5x, and W8x, which are formed to a thickness dimension of "T3" smaller than "T2", are connected to the crank journals J1, J3, and J5.

[0036] In this way, in the crankshaft 10 of the embodiment, a thick web W1 is provided between the crank journal J1 and the crank pin P1, and a thick web W5 is provided between the crank journal J3 and the crank pin P3. Therefore, in the crankshaft 10 of the embodiment, the crank pins P1 and P3 are shifted by a predetermined distance g1 in the direction of the arrow D3 compared to the crankshaft 100 of the comparative example. Also, in the crankshaft 10 of the embodiment, a thick web W4 is provided between the crank journal J3 and the crank pin P2, and a thick web W8 is provided between the crank journal J5 and the crank pin P4. Therefore, in the crankshaft 10 of the embodiment, the crank pins P2 and P4 are shifted by a predetermined distance g1 in the direction of the arrow D4 compared to the crankshaft 100 of the comparative example.

[0037] As described above, in the crankshaft 10 of the embodiment, the crank pins P1, P3 are offset by a predetermined distance g1 in the direction of the arrow D3, so that the cylinder block 14 can be offset by a predetermined distance g1 in the direction of the arrow D3, as shown in Fig. 2. Also, the crank pins P2, P4 are offset by a predetermined distance g1 in the direction of the arrow D4, so that the cylinder block 16 can be offset by a predetermined distance g1 in the direction of the arrow D4, as shown in Fig. 2. In other words, by using the crankshaft 10 of the embodiment, the bank offset of the cylinder blocks 14, 16 can be reduced, so that the engine 11 can be made more compact.

[0038] The present invention is not limited to the above embodiment, and can be modified in various ways without departing from the gist of the present invention. In the above description, the thickness dimension of all the thin webs W2, W3, W6, and W7 is "T1", and the thickness dimension of all the thick webs W1, W4, W5, and W8 is "T2", but the present invention is not limited to this. For example, the thickness dimensions of the thin webs W2, W3, W6, and W7 may be different from each other, and the thickness dimensions of the thick webs W1, W4, W5, and W8 may be different from each other. In this way, even if the thickness dimensions are different from each other, the thickness dimensions of the thick webs W1, W4, W5, and W8 are set to be larger than the thickness dimensions of all the thin webs W2, W3, W6, and W7.

[0039] In the above description, a four-cylinder horizontally opposed engine is exemplified as the engine 11, but the present invention is not limited thereto. For example, the crankshaft of the present invention may be incorporated into a V-type engine having a pair of cylinder banks. In the illustrated example, the crank arms 1a-8a are formed while maintaining a constant thickness dimension, but the present invention is not limited thereto. As long as the rigidity required for the crankshaft 10 can be ensured, the ends of the crank arms 1a-8a may be chamfered. [Explanation of symbols]

[0040] 10. Crankshaft 11 Engine (horizontally opposed engine) 12,13 Cylinder bank J1 Crank journal (first journal) J2 Crank journal (second journal) J3 Crank journal (third journal) J4 Crank journal (4th journal) J5 Crank journal (5th journal) P1~P4 Crank pins W1, W4, W5, W8 Crank web (thick web) W2, W3, W6, W7 Crank web (thin web) 1a~8a Crank arm (arm part) 1b~8b Counterweight (weight part)

Claims

1. A crankshaft provided in an engine, A plurality of crank journals located at a rotation center; A plurality of crank pins that are eccentric with respect to the crank journal; a plurality of crank webs connecting the crank journals and the crank pins to each other; having The crank webs include a plurality of thin webs and a plurality of thick webs having a thickness dimension larger than that of the thin webs, the plurality of crank journals include, in an axially arranged order, a first journal, a second journal, a third journal, a fourth journal and a fifth journal, the thin web is connected to the second journal and the fourth journal; the thick web is connected to the first journal, the third journal, and the fifth journal; Crankshaft.

2. 2. The crankshaft according to claim 1, the thin web and the thick web each include an arm portion that connects the crank journal and the crank pin to each other, and a weight portion that is continuous with the arm portion; Crankshaft.

3. 3. The crankshaft according to claim 1 or 2, The engine comprises a pair of cylinder banks. Crankshaft.

4. The crankshaft according to any one of claims 1 to 3, The engine is a horizontally opposed engine. Crankshaft.

Images