Vibration damping structure for in-line six-cylinder engine

Abstract

To provide a vibration damping structure for an engine capable of effectively damping vibration in a multi-cylinder reciprocating engine.SOLUTION: An in-line six-cylinder engine 1 includes: six pistons 11-16; a crank shaft 30; a flywheel 52 fixed to a rear end of the crank shaft 30; a lower cylinder block 60 having seven crank journal parts 61-67 that journal the crank shaft 30; and a dynamic damper 80 mounted to at least one of lower parts between #2 to #4 cylinders 1b-1d in the lower cylinder block 60.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a vibration damping structure for an in-line six-cylinder engine, and particularly to a vibration damping structure for a reciprocating engine.

Background Art

[0002] In a reciprocating in-line six-cylinder engine (hereinafter sometimes simply referred to as "engine") mounted vertically in a vehicle engine room, vibration occurs during driving. The vibration generated by the engine is propagated as radiated sound into the vehicle interior through a transmission or the like. From the viewpoint of ensuring the comfort of passengers, it is required to suppress the propagation of radiated sound into the vehicle interior. In an in-line six-cylinder engine, since the radiation area is larger than that of an in-line four-cylinder engine, a large amount of radiated sound is propagated.

[0003] As a measure for suppressing the propagation of radiated sound into the vehicle interior, it is conceivable to cover the entire engine with a sound insulation material. By covering the entire engine with a sound insulation material, it is possible to reduce the sound radiated to the outside of the engine at all frequencies in the entire range. However, simply covering the engine with a sound insulation material makes it difficult to achieve sound insulation up to the target level at some resonance frequencies.

[0004] As a measure for reducing the level at some resonance frequencies as described above, for example, Patent Document 1 proposes the following structure.

[0005] Patent Document 1 discloses a structure in which a plurality of main bearing caps are integrally coupled by an integral beam, and an inertia mass is attached to the integral beam via an elastic member. In Patent Document 1, by attaching the inertia mass to the integral beam as described above, it is said that engine vibration can be effectively reduced without increasing the dimensions and weight of the integral beam itself.

Prior Art Documents

Patent Documents

[0006] Japanese Utility Model Publication No. 63-126611 (JP-U-63-126611) SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] However, in the vibration damping structure disclosed in Patent Document 1, vibrations generated by an in-line 6-cylinder engine cannot be sufficiently damped, and radiated noise may be transmitted into the passenger compartment. That is, in the structure disclosed in Patent Document 1, an inertia mass is attached below the integral beam, but since the attachment location is not specified, it is considered that it may be difficult to sufficiently damp vibrations.

[0008] The present invention has been made to solve the above problems, and an object thereof is to provide a vibration damping structure for an in-line 6-cylinder engine that can effectively damp vibrations in an in-line 6-cylinder reciprocating engine vertically mounted in an engine room. MEANS FOR SOLVING THE PROBLEMS

[0009] The vibration damping structure of an in-line six-cylinder engine according to one aspect of the present invention is a vibration damping structure of an in-line six-cylinder engine mounted vertically on a vehicle and having six cylinders arranged in series, comprising pistons reciprocally fitted to each of the six cylinders, a crankshaft disposed below the pistons in the vertical direction of the vehicle and connected to the pistons via connecting rods to rotate, a cylinder block disposed below the crankshaft in the vertical direction and having a plurality of crank journal portions for pivotally supporting the crankshaft between adjacent cylinders of the crankshaft, a flywheel fixed to the rear end of the crankshaft in the front-rear direction of the vehicle, and, for the six cylinders, when arranged in the order of #1 cylinder, #2 cylinder, #3 cylinder, #4 cylinder, #5 cylinder, #6 cylinder from the front side to the rear side in the front-rear direction of the vehicle, a dynamic damper attached to at least one location between the #2 cylinder and the #4 cylinder in the lower part of the cylinder block.

[0010] In the vibration damping structure of the in-line six-cylinder engine according to the above aspect, a dynamic damper is attached to at least one lower part between the #2 to #4 cylinders in the lower part of the cylinder block. Such a configuration is adopted due to the fact that a flywheel is fixed to the rear end of the crankshaft. That is, since the flywheel is fixed to the rear end of the crankshaft, the crankshaft vibrates with a larger amplitude on the front end side than on the rear end side in the longitudinal direction.

[0011] Here, as a result of intensive studies on the vibration during the driving of the in-line six-cylinder engine by the inventors of the present application, it has been found that the crankshaft vibrates with a large amplitude at the portion between the #2 to #4 cylinders. For this reason, in the vibration damping structure of the in-line six-cylinder engine according to the above aspect, by attaching a dynamic damper to at least one location in the lower part between the #2 to #4 cylinders in the front-rear direction of the cylinder block, it is possible to effectively consume the vibration energy at the location with a large amplitude in the dynamic damper.

[0012] In the vibration damping structure of the in-line six-cylinder engine according to the above aspect, the dynamic damper is attached to the lower part of the crank journal portion, and has a fixed portion extending downward from the lower part, a beam portion connected to the lower part of the fixed portion and extending in the front-rear direction, and two mass portions connected to respective connection portions on one side and the other side in the front-rear direction of the rib and each extending in the left-right direction of the vehicle while being spaced apart from each other in the front-rear direction, and may be integrally formed.

[0013] In the vibration damping structure of the in-line six-cylinder engine according to the above aspect, a configuration is provided in which a dynamic damper having a fixed portion, a beam portion, and two mass portions integrally is attached to a cylinder block. The two mass portions are connected at respective connection portions of the beam portion and are formed to extend in the left-right direction. Therefore, even when the crankshaft vibrates in a manner having amplitudes in the vertical direction and the left-right direction along with the driving of the in-line six-cylinder engine, vibration energy is input to the dynamic damper via the crank journal portion and consumed by the dynamic damper. Specifically, when vibration energy is input to the dynamic damper, the beam portion is deformed in the vertical direction by the vibration of the two mass portions to consume vibration energy in the vertical direction (cylinder axis direction), and is also deformed in the left-right direction to consume vibration energy in the left-right direction (intake / exhaust direction).

[0014] Therefore, in the vibration damping structure of the in-line six-cylinder engine according to the above aspect, not only vibration energy in the vertical direction as in the structure disclosed in Patent Document 1 is consumed, but also vibration energy in both the vertical direction and the left-right direction can be consumed. Thus, in the vibration damping structure of the in-line six-cylinder engine according to the above aspect, a resonance peak caused by vibration of the crankshaft due to driving can be more effectively suppressed to a lower level.

[0015] In the vibration damping structure of the in-line six-cylinder engine according to the above aspect, the fixed portion has a column shape, and when assuming a virtual plane passing through the column center in the fixed portion and orthogonal to the front-rear direction, the dynamic damper may have a shape symmetric with respect to the virtual plane.

[0016] In the vibration damping structure of the in-line six-cylinder engine according to the above aspect, since the dynamic damper is configured to be symmetric with respect to the virtual plane, the beam portion and the mass portion can be vibrated in antiphase with respect to torsional and bending deformations, which is effective in suppressing the resonance peak associated with the vibration of the crankshaft.

[0017] In the vibration damping structure of the in-line six-cylinder engine according to the above aspect, when the beam portion and the two mass portions are viewed from one side in the left-right direction in side view, the beam portion may be formed such that the thickness dimension of the beam portion in the up-down direction is smaller than the thickness dimension of each of the two mass portions in the up-down direction.

[0018] In the vibration damping structure of the in-line six-cylinder engine according to the above aspect, since the thickness dimension of the beam portion in the dynamic damper is made smaller than the thickness dimension of the mass portion, when vibration energy from the crankshaft is input to the dynamic damper via the crank journal portion of the cylinder block, both mass portions are likely to deform with the connection portion as a base point. Therefore, in the vibration damping structure of the in-line six-cylinder engine according to the above aspect, the vibration of the crankshaft can be more effectively consumed by the dynamic damper, which is more effective in suppressing the resonance peak.

[0019] In the vibration damping structure of the in-line six-cylinder engine according to the above aspect, in both cases when the beam portion and the two mass portions are viewed from one side in the left-right direction in side view and when viewed from one side in the up-down direction in plan view, the beam portion and the two mass portions may both form an H shape.

[0020] In the vibration damping structure of the in-line six-cylinder engine according to the above aspect, when the beam portion and the mass portion are viewed in side view and plan view, the dynamic damper is configured to have an H shape in both cases. Therefore, when vibration energy is input from the crankshaft, the mass portion can be easily deformed with the connection portion as a fulcrum. For this reason, in the vibration damping structure of the in-line six-cylinder engine according to the above aspect, the vibration of the crankshaft can be more effectively consumed by the dynamic damper, and it is more effective in suppressing the resonance peak to a low level.

[0021] In the vibration damping structure of the in-line six-cylinder engine according to the above aspect, the dynamic damper may be formed using cast iron.

[0022] In the vibration damping structure of the in-line six-cylinder engine according to the above aspect, since the dynamic damper is formed using cast iron, vibration energy can be effectively consumed even with a small occupied volume. This is because the specific gravity of cast iron is significantly higher, about 7.0, compared to the specific gravity of about 2.7 of the aluminum alloy used as the forming material for the cylinder block and the like. Therefore, in the vibration damping structure of the in-line six-cylinder engine according to the above aspect, while realizing high space efficiency, the vibration of the crankshaft can be more effectively consumed by the dynamic damper.

Effect of the Invention

[0023] In the vibration damping structure of the in-line six-cylinder engine according to each of the above aspects, the vibration in the in-line six-cylinder reciprocating engine mounted vertically in the engine room can be effectively attenuated.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Mode for Carrying Out the Invention

[0025] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below exemplify the present invention, and the present invention is not limited to the following embodiments except for its essential configuration.

[0026] In addition, in the drawings used in the following description, "FR" indicates the front side in the vehicle longitudinal direction, "RR" indicates the rear side, "LH" indicates the left side in the vehicle lateral direction, "RH" indicates the right side, "UP" indicates the upper side in the vehicle vertical direction, and "LO" indicates the lower side.

[0027] 1. Configuration of Vehicle V The configuration of a vehicle V equipped with an in-line six-cylinder reciprocating engine 1 (hereinafter simply referred to as "engine 1") according to an embodiment of the present invention will be described with reference to FIG. 1.

[0028] As shown in FIG. 1, the vehicle V has an engine room R1 at the front, and a passenger compartment R2 at the rear separated from the engine room R1 by a dash panel DP. The engine 1 is mounted longitudinally in the engine room R1. That is, the #1 cylinder 1a to #6 cylinder 1f of the engine 1 are arranged in order from the front side to the rear side.

[0029] A transmission TM is joined to the rear part of the engine 1. A part of the transmission TM is inserted into a floor tunnel (not shown).

[0030] Although detailed illustration is omitted, the cylinder axes of the respective cylinders 1a to 1f of the engine 1 are not arranged along the vertical direction, but are arranged in a state where the cylinder axes are inclined with respect to the vertical direction. That is, the engine 1 is a slant engine.

[0031] 2. Structure of Engine 1 The configuration of the engine 1 according to the present embodiment will be described with reference to FIGS. 1 and 2. Note that in FIG. 1, illustrations of the upper cylinder block, cylinder head, head cover, and oil pan in the engine 1 are omitted.

[0032] As shown in FIG. 1, the engine 1 is an in-line six-cylinder reciprocating engine, and six cylinders 1a to 1e are provided along the front-rear direction. Hereinafter, the six cylinders 1a to 1f will be referred to as #1 cylinder 1a, #2 cylinder 1b, #3 cylinder 1c, #4 cylinder 1d, #5 cylinder 1e, and #6 cylinder 1f in order from the front side.

[0033] The engine 1 includes pistons 11 to 16 that reciprocate in the vertical direction in each cylinder 1a to 1f. Connecting rods 21 to 26 are connected to the respective pistons 11 to 16.

[0034] The connecting rods 21 to 26 are pivotally supported by crank pins 43 to 48 of a crankshaft 30 so as to be rotatable at their lower portions. Crank webs 33 to 42 are disposed on the front side and the rear side of each crank pin 43 to 48.

[0035] The crankshaft 30 is rotatably supported by a combination of crank journal portions 61 to 67 disposed below the crankshaft 30 and bearing caps 71 to 77 attached to the respective crank journal portions 61 to 67.

[0036] The crank journal portions 61 to 67 and the bearing caps 71 to 77 are disposed on the front side of the #1 cylinder 1a and the rear side of the #6 cylinder 1f, and between each of the cylinders 1a to 1e, respectively. Hereinafter, the crank journal portions 61 to 67 will be referred to as #1 crank journal portion 61, #2 crank journal portion 62, #3 crank journal portion 63, #4 crank journal portion 64, #5 crank journal portion 65, #6 crank journal portion 66, and #7 crank journal portion 67 in order from the front side.

[0037] Here, in the engine 1 of the present embodiment, the seven crank journal portions 61 to 67 are integrally formed with the lower cylinder block 60.

[0038] For the crankshaft 30, a pulley 51 is fixed to the front end, and a flywheel 52 is fixed to the rear end. Note that as described above, since the engine 1 according to the present embodiment is mounted vertically in the engine room R1, the crankshaft 30 is arranged such that the front end side where the pulley 51 is fixed is the front side of the vehicle, and the rear end side where the flywheel 52 is fixed is the rear side of the vehicle.

[0039] As shown in FIGS. 1 and 2, a dynamic damper 80 is attached to the lower part of the #3 crank journal portion 63 in the lower cylinder block 60. The attachment of the dynamic damper 80 to the lower cylinder block 60 is, for example, made by fastening using bolts 81.

[0040] Note that the center position of the lower cylinder block 60 in the front-rear direction is the location where the #4 crank journal portion 64 is arranged, but the dynamic damper 80 is attached to the lower part of the #3 crank journal portion 63 on the front side of the #4 crank journal portion 64. However, the attachment position of the dynamic damper 80 to the lower part of the lower cylinder block 60 is not limited to this as long as it is a location between the #2 cylinder 1b to the #4 cylinder 1d. Also, the number of dynamic dampers 80 attached to the lower part of the lower cylinder block 60 is not limited to one, and it is also possible to attach a plurality of dynamic dampers 80.

[0041] Here, in the present embodiment, the dynamic damper 80 is attached to the lower part of the #3 crank journal 63 because the flywheel 52 is fixed to the rear end of the crankshaft 30. That is, when the engine 1 is driven, the amplitude of the shaft runout on the rear end side of the crankshaft 30 where the flywheel 52 is fixed is smaller than that on the front end side (the side where the pulley 51 is fixed). Conversely, when the engine 1 is driven, the part on the front end side of the crankshaft 30 vibrates with a larger amplitude than the part on the rear end side with respect to the center position in the front-rear direction of the crankshaft 30. Therefore, in the engine 1, the dynamic damper 80 is attached below the front end side part of the crankshaft 30 that vibrates with a large amplitude when the engine 1 is driven. Thereby, vibration can be effectively suppressed by the dynamic damper 80.

[0042] 3. Structure of the dynamic damper 80 The structure of the dynamic damper 80 will be described with reference to FIGS. 4 to 6.

[0043] The dynamic damper 80 is formed using cast iron as an example, and as shown in FIGS. 4 to 6, it has a fixing part 800, a beam part 801, and two mass parts 802 and 803. The fixing part 800 is attached to the lower part of the #3 crank journal part 63 in the lower cylinder block 60 and is formed to extend in the vertical direction. The fixing part 800 has a column shape with an outer peripheral surface formed as a curved surface. And the fixing part 800 has a through hole 800a through which the threaded part of the bolt 81 (see FIGS. 1 and 2) can be inserted, and a pin hole 800b for receiving the insertion of a pin for preventing rotation with respect to the lower cylinder block 60.

[0044] The beam part 801 is connected to the lower side of the fixing part 800 and is formed to extend in the front-rear direction. The beam part 801 has a flat plate shape or a prism shape and is formed to protrude more than the fixing part 800 on both the front side and the rear side.

[0045] The two mass portions 802 and 803 each have a prismatic shape and are formed to extend in the left - right direction. The mass portion 802 is connected to the beam portion 801 by the connecting portion 801a. The mass portion 803 is connected to the beam portion 901 by the connecting portion 801b. That is, the mass portion 802 and the mass portion 803 are arranged to be separated by the length of the beam portion 801 in the front - rear direction. Note that each of the mass portions 802 and 803 is formed so as to have substantially the same mass (allowing a difference of about 8 g) from each other in the left - right direction from the connecting portions 801a and 801b.

[0046] Here, as shown in FIGS. 4 to 6, assume a virtual plane VP passing through the column center in the fixing portion 800 and orthogonal to the front - rear direction. In this case, as shown in FIGS. 5 and 6, the dynamic damper 80 has a shape symmetric with respect to the virtual plane VP. And, as shown in FIG. 5, when the beam portion 801 and the mass portions 802 and 803 are viewed from the - Y side in side view, the beam portion 801 and the mass portions 802 and 803 are formed to form an H - shaped configuration.

[0047] Also, as shown in FIG. 6, when the beam portion 801 and the mass portions 802 and 803 are viewed from below in plan view, the beam portion 801 has a shape symmetric with respect to the virtual plane VP in the front - rear direction, and the mass portion 802 and the mass portion 803 have shapes symmetric with respect to each other in the front - rear direction with respect to the virtual plane VP. And, as shown in FIG. 6, also in the plan view from below, the beam portion 801 and the mass portions 802 and 803 are formed to form an H - shaped configuration.

[0048] 4. Sizes of the beam portion 801 and the mass portions 802 and 803 The sizes of the beam portion 801 and the mass portions 802 and 803 in the dynamic damper 80 will be described with reference to FIG. 7. Note that in FIG. 7, only the mass portion 803 of the two mass portions 802 and 803 is shown, but the size relationship of the mass portion 802 with respect to the beam portion 801 is the same.

[0049] As shown in FIG. 7, the beam portion 801 is connected to the mass portion 803 at the connection portion 801b. The connection portion 801b is arranged to include the center-of-gravity position of the mass portion 802 in the left-right direction. The beam portion 801 is formed with a size (width) of W in the left-right direction and a size (height) of H in the up-down direction.

[0050] On the other hand, the mass portion 803 is formed with a size of W0 in the left-right direction and a size of H0 in the up-down direction. The mass of the mass portion 803 is set based on the magnitude of the amplitude at the resonance frequency. As an example, the mass of the mass portion 802 is set within the range of 250 g to 350 g. More specifically, the mass of the mass portion 802 is set within the range of 275 g to 300 g.

[0051] In the dynamic damper 80, the sizes H, W of the beam portion 801 with respect to the sizes H0, W0 of the mass portion 803 are set based on the frequency of the resonance peak to be reduced. As an example, the ratio of W / WO is set within the range of 1 / 10 to 1 / 3, and more specifically within the range of 1 / 5 to 1 / 4.

[0052] Also, the ratio of H / H0 is set within the range of 1 / 5 to 1 / 2, and more specifically within the range of 1 / 4 to 2 / 5.

[0053] 5. Bottom Surface Shape of Dynamic Damper 80 and Peripheral Members The relationship between the shape of the bottom surface 80a of the dynamic damper 80 and the peripheral members will be described with reference to FIG. 8. Note that FIG. 8 is a rear view of the dynamic damper 80 and the peripheral members as viewed from the rear side, and the illustration of the beam portion 801 and the mass portion 802 of the dynamic damper 80 is omitted.

[0054] First, the engine 1 according to the present embodiment is mounted vertically in an engine room R1 provided at the front part of a vehicle V. The vehicle V targeted is a four-wheel drive vehicle and includes a front drive shaft 91 extending in the left-right direction in the engine room R1. Therefore, the oil pan 90 has a shaft insertion portion 90a through which the front drive shaft 91 is inserted. The axis Ax91 of the front drive shaft 91 inserted through the shaft insertion portion 90a is arranged along the left-right direction.

[0055] Next, the engine 1 is arranged to be inclined such that the intake side (left side) is positioned above the exhaust side (right side). Therefore, the upper surface of the oil pan 90 attached to the lower part of the lower cylinder block 60 (see FIG. 1 etc.) is also inclined (inclination line LN90).

[0056] As shown in FIG. 8, the dynamic damper 80 is arranged above the shaft insertion portion 90a formed in the oil pan 90. Therefore, the lower surface 80a of the dynamic damper 80, that is, the lower surface of the mass portions 802, 803 (in FIG. 8, the illustration of the mass portion 802 is omitted) in the dynamic damper 80 is arranged to be substantially parallel to the upper outer surface of the shaft insertion portion 90a so as to avoid interference with the outer surface of the shaft insertion portion 90a. Therefore, when a virtual line LN80 is drawn along the lower surface 80 of the dynamic damper 80, the virtual line LN80 is substantially parallel to the axis Ax91 of the front drive shaft 91 and is arranged in a direction intersecting the inclination line LN90 at an acute angle.

[0057] 6. Control according to the operating state of the engine 1 The control according to the operating state of the engine 1 will be described with reference to FIG. 9.

[0058] The engine 1 according to the present embodiment is drive-controlled by a PCM (Power Control Module). The PCM has a microprocessor that executes arithmetic processing and a memory in which maps for each operating region are stored in advance. FIG. 9 is a diagram showing an operating map for explaining the difference in combustion control according to the rotational speed and load of the engine 1.

[0059] As shown in FIG. 9, the operating region of the engine 1 is roughly divided into two operating regions A1 and A2 according to the difference in combustion modes. Assuming the first operating region A1 and the second operating region A2 respectively, the second operating region A2 is a high-speed region where the rotational speed of the engine 1 exceeds the first rotational speed N1, and the first operating region A1 is a low- and medium-speed region where the rotational speed of the engine 1 is equal to or less than the first rotational speed N1. The outline of combustion control in each operating region A1 and A2 is as follows.

[0060] (1) First operating region A1 In the first operating region A1 (low- and medium-speed region) where the rotational speed of the engine 1 is equal to or less than the first rotational speed N1, partially premixed charge compression ignition (SPCCI) combustion, which combines spark ignition (SI) combustion and compression ignition (CI) combustion, is executed.

[0061] SI combustion is a combustion mode in which an air-fuel mixture is ignited by a spark generated from a spark plug, and the air-fuel mixture is forcibly burned by flame propagation that expands the combustion region from the ignition point to the surroundings.

[0062] CI combustion is a combustion mode in which an air-fuel mixture is burned by self-ignition in an environment that has been sufficiently heated and pressurized by the compression of pistons 11 to 16.

[0063] SPCCI combustion, which combines SI combustion and CI combustion, is a combustion mode in which a part of the air-fuel mixture in the combustion chamber is burned by spark ignition performed in an environment just before the air-fuel mixture self-ignites, and then the other air-fuel mixture in the combustion chamber is burned by self-ignition (CI combustion) (due to further heating and pressurization accompanying the SI combustion).

[0064] In SPCCI combustion, heat generation by SI combustion and heat generation by CI combustion occur successively in this order. At this time, due to the property that the combustion speed of CI combustion is faster, the rise of heat generation during CI combustion becomes steeper than that during SI combustion. Therefore, the waveform of the heat generation rate in SPCCI combustion has an inflection point that appears at the timing of switching from SI combustion to CI combustion.

[0065] The crank angle corresponding to the inflection point that appears at the timing of switching from the above SI combustion to CI combustion is defined as the start timing of CI combustion. When the engine 1 is driven in the first operation region A1, the PCM that executes the drive control of the engine 1 controls the injection amount and injection timing of combustion by the injector, and the ignition timing by the spark plug so that the start timing of this CI combustion becomes an appropriate timing considering thermal efficiency and the output of the engine 1 becomes the required value.

[0066] (2) Second operation region A2 In the second operation region A2 (high-speed region) where the rotational speed of the engine 1 is higher than the first rotational speed N1, control is executed to burn the air-fuel mixture by SI combustion. For example, the PCM controls the injector so that the required amount of fuel is mainly injected during the intake stroke, and causes the spark plug to perform spark ignition near top dead center of compression. Then, SI combustion is started triggered by the spark ignition, and all of the air-fuel mixture in the combustion chamber burns by flame propagation.

[0067] 7. Contribution of each of cylinders 1a to 1f to the in-vehicle noise Regarding the noise radiated from the engine 1 and propagated into the vehicle interior, the contribution of each of cylinders 1a to 1f will be described with reference to FIG. 10. FIG. 10 is a graph showing the partial pressures of each of cylinders 1a to 1f in the engine 1.

[0068] As shown in FIG. 10, the partial pressure in the #6 cylinder 1f had the lowest measurement result among the six cylinders 1a to 1f. This is presumably because the flywheel 52 was fixed to the rear end of the crankshaft 30 extending in the front-rear direction, suppressing the vibration at the rear end side portion of the crankshaft 30. Regarding the partial pressure of each of the #1 to #5 cylinders 1a to 1e, it will be described based on the partial pressure of the #6 cylinder 1f.

[0069] The partial pressure in the #1 cylinder 1a had a measurement result about 40% higher than the partial pressure in the #6 cylinder 1f. Similarly, the partial pressure in the #2 cylinder 1b had a measurement result about 67% higher, the partial pressure in the #3 cylinder 1c had a measurement result about 140% higher, the partial pressure in the #4 cylinder 1d had a measurement result about 67% higher, and the partial pressure in the #5 cylinder 1e had a measurement result about 87% higher.

[0070] From the above, in the in-line six-cylinder engine 1, it can be seen that the contribution of the #3 cylinder 1c located at a position offset forward from the center positions of the cylinders 1a to 1f in the front-rear direction (cylinder row direction) is high. Therefore, in the present embodiment, as described above, the dynamic damper 80 is attached to the lower part of the #3 crank journal portion 63 located at a position offset forward (the side where the pulley 51 is fixed to the crankshaft 30) with respect to the center position in the front-rear direction in the lower cylinder block 60.

[0071] 8. Vibration mode of the dynamic damper 80 during driving of the engine 1 The vibration mode of the dynamic damper 80 during driving of the engine 1 will be described with reference to FIG. 11. FIG. 11(a) is a diagram showing the vibration mode in the vertical direction (cylinder axis direction), and FIG. 11(b) is a diagram showing the vibration mode in the left-right direction (intake and exhaust direction).

[0072] As shown in FIG. 11(a), when vibration energy is input from the crankshaft 30 to the dynamic damper 80 via the lower cylinder block 60 as the engine 1 is driven, the mass portions 802 and 803 vibrate vertically as indicated by the dashed arrow Vz. As a result, the beam portion 801 vibrates in the vertical direction (cylinder axis direction) mode.

[0073] Also, as shown in FIG. 11(b), when vibration energy from the crankshaft 30 is input, the ends of the mass portions 802 and 803 vibrate as indicated by the dashed-line arrow Vy in the directions of approaching each other and moving away from each other. As a result, the beam portion 801 vibrates in a mode in the left-right direction (intake and exhaust direction).

[0074] 9. Reduction of Engine Radiated Noise for Each Frequency The effect of attaching the dynamic damper 80 having the above structure to the lower part of the #3 crank journal portion 63, that is, the reduction of engine radiated noise, will be described for each frequency with reference to FIG. 12. In the graph of FIG. 12, the engine radiated noise of the engine 1 with the structure of the present embodiment is shown by a solid line, and the engine radiated noise of the engine with a structure in which the dynamic damper 80 is not attached to the engine 1 is shown by a dashed line.

[0075] As shown in FIG. 12, in the case of the comparative example shown by the dashed line, the largest resonance peak was measured in the vicinity of a frequency of 1600 Hz. Also, in the case of the comparative example, a resonance peak was measured also in the vicinity of 4000 Hz.

[0076] On the other hand, in the case of the example, the component in the vicinity of 1600 Hz in the engine radiated noise became about 2 dB lower than that of the comparative example. Also, the component in the vicinity of 4000 Hz became about 3 dB lower than that of the comparative example, and no peak appeared.

[0077] 10. ERP in the #3 and #4 Crank Journal Portions 63 and 64 The ERP (Equivalent Radiated Power) at 1600 Hz in the #3 and #4 crank journal portions 63 and 64 in each of an example in which the dynamic damper 80 having the above structure is attached to the lower part of the #3 crank journal portion 63 and a comparative example in which it is not attached will be described with reference to FIG. 13. FIG. 13(a) shows the ERP of the example, and FIG. 13(b) shows the ERP of the comparative example.

[0078] As shown in FIG. 13(b), in the comparative example where the dynamic damper 80 having the above structure was not attached to the lower part of the #3 crank journal portion 63, the ERP in the left-right direction (#3_Y) of the #3 crank journal portion 63 was 55 dBA, and the ERP in the up-down direction (#3_Z) was 62 dBA. The total ERP of the #3 and #4 crank journal portions 63 and 64 was 63.5 dBA.

[0079] On the other hand, as shown in FIG. 13(a), in the embodiment where the dynamic damper 80 having the above structure was attached to the lower part of the #3 crank journal portion 63, the ERP in the left-right direction (#3_Y) of the #3 crank journal portion 63 was 35 dBA, and the ERP in the up-down direction (#3_Z) was 42 dBA. The total ERP of the #3 and #4 crank journal portions 63 and 64 was 55.6 dBA. Comparing FIG. 13(a) and FIG. 13(b), in the embodiment where the dynamic damper 80 was attached to the lower part of the #3 crank journal portion 63, the ERP in the left-right direction and the up-down direction of the #3 crank journal portion 63 was significantly lower than that in the comparative example. Specifically, in the embodiment, a 20 dBA decrease was observed in both the left-right direction and the up-down direction compared to the comparative example.

[0080] 11. Effects In the engine 1 according to the present embodiment, as described with reference to FIG. 9, in the first operation region A1 (low and medium speed region) where the rotational speed of the engine 1 is equal to or less than the first rotational speed N1, SPCCI combustion is executed. As a result of intensive studies by the inventors of the present application, it was concluded that knock sound propagation from the engine 1 into the passenger compartment via the transmission becomes a problem with the execution of SPCCI combustion. Then, in order to suppress this knock sound propagation, the engine 1 according to the present embodiment adopted the vibration damping structure as described above.

[0081] In the vibration damping structure of the engine 1 according to the present embodiment, a dynamic damper 80 is attached to at least one lower portion between the #2 to #4 cylinders 1b to 1d at the lower portion of the lower cylinder block 60. Specifically, the structure includes a dynamic damper 80 attached to the lower portion of the #3 crank journal 63 in the lower cylinder block 60. The dynamic damper 80 is attached to the lower portion of the position between the #2 to #4 cylinders 1b to 1d on the front side of the center position in the front-rear direction in the lower cylinder block 60 (in this embodiment, the #3 crank journal 63 as an example) because, as described above, the flywheel 52 is fixed to the rear end of the crankshaft 30, and it vibrates with a larger amplitude on the front end side than on the rear end side.

[0082] Therefore, in the vibration damping structure of the engine 1, by attaching a dynamic damper to at least one lower portion between the #2 to #4 cylinders in the front-rear direction of the lower cylinder block 60, the vibration energy at the location with a large amplitude can be effectively consumed by the deformation of the dynamic damper 80.

[0083] Further, in the vibration damping structure of the engine 1 according to the present embodiment, the structure includes a dynamic damper 80 integrally having a fixing portion 800, a beam portion 801, and two mass portions 802, 803 attached to the lower portion of the lower cylinder block 60. The two mass portions 802, 803 are connected at the respective connection portions 801a, 801b of the beam portion 801 and are formed to extend in the left-right direction. Therefore, even when the crankshaft 30 vibrates in a mode having amplitudes in the vertical and left-right directions as the engine 1 is driven, the vibration energy is input to the dynamic damper 80 via the #3 crank journal portion 63 and consumed by the dynamic damper 80. Specifically, when the vibration energy is input to the dynamic damper 80, the beam portion 801 deforms in the vertical direction due to the vibration of the two mass portions 802, 803, consuming the vibration energy in the vertical direction (cylinder axis direction), and also deforms in the left-right direction, consuming the vibration energy in the left-right direction (intake / exhaust direction).

[0084] Therefore, in the vibration damping structure of the engine 1, not only the vertical vibration energy is consumed as in the structure disclosed in the above Patent Document 1, but also the vibration energy in both the vertical and horizontal directions can be consumed. Thus, in the vibration damping structure of the engine 1, the resonance peak caused by the vibration of the crankshaft 30 due to driving can be more effectively suppressed to a lower level.

[0085] Also, in the vibration damping structure of the engine 1 according to the present embodiment, since the dynamic damper 80 is configured to be symmetric with respect to the virtual plane VP shown in FIGS. 4 to 6, the beam portion 801 and the mass portions 802, 803 can be vibrated in antiphase with respect to torsional and bending deformations, which is effective in suppressing the resonance peak associated with the vibration of the crankshaft 30 to a lower level.

[0086] Also, in the vibration damping structure of the engine 1 according to the present embodiment, since the thickness dimension H in the vertical direction of the beam portion 801 in the dynamic damper 80 is made smaller than the thickness dimension H0 of the mass portions 802, 803, when the vibration energy from the crankshaft 30 is input to the dynamic damper 80 via the #3 crank journal portion 63 of the lower cylinder block 60, the two mass portions 802, 803 are likely to deform with the connection portions 801a, 801b as the fulcrums. Thus, in the vibration damping structure of the engine 1, the vibration of the crankshaft 30 can be more effectively consumed by the dynamic damper 80, which is even more effective in suppressing the resonance peak to a lower level.

[0087] Also, in the vibration damping structure of the engine 1 according to the present embodiment, as shown in FIGS. 5 and 7, when the beam portion 801 and the mass portions 802, 803 are viewed in side view and plan view, the dynamic damper 80 is configured to form an H shape in both cases. Therefore, when the vibration energy is input from the crankshaft 30, the mass portions 802, 803 can be easily deformed with the connection portions 801a, 801b as the fulcrums. For this reason, in the vibration damping structure of the engine 1, the vibration of the crankshaft 30 can be more effectively consumed by the dynamic damper 80, which is even more effective in suppressing the resonance peak to a lower level.

[0088] Further, in the vibration damping structure of the engine 1 according to the present embodiment, since the dynamic damper 80 is formed using cast iron, vibration energy can be effectively consumed even with a small occupied volume. That is, as described above, the specific gravity of cast iron is significantly higher, about 7.0, compared to the specific gravity of about 2.7 of the aluminum alloy used as the forming material such as the lower cylinder block 60. Therefore, in the vibration damping structure of the engine 1, while realizing high space efficiency, the vibration of the crankshaft 30 can be more effectively consumed by the dynamic damper.

[0089] As described above, in the vibration damping structure of the engine 1 according to the present embodiment, vibration in a 6-cylinder reciprocating engine can be effectively attenuated.

[0090] [Modification Example] A vibration damping structure of an in-line 6-cylinder reciprocating engine according to a modification example (hereinafter simply referred to as "engine") will be described with reference to FIGS. 14 and 15. Note that the in-line 6-cylinder engine according to this modification example is different only in the configuration of the dynamic damper 82 from the above embodiment, and the other configurations are the same as those of the above embodiment. Therefore, the description of the same configurations as those of the above embodiment will be omitted below.

[0091] In the engine according to this modification example, a dynamic damper 82 is attached at at least one location between the #2 to #4 cylinders 1b to 1d, which is the lower part of the lower cylinder block 60 (see FIG. 1 etc.). The attachment of the dynamic damper 82 to the lower cylinder block 60 is made by fastening bolts 81, similar to the above embodiment.

[0092] As shown in FIG. 14, the dynamic damper 82 has a fixed portion 820 and one mass portion 821. The fixed portion 810 is attached to the lower part of the lower cylinder block 60 and is formed to extend in the vertical direction. The fixed portion 820 has a columnar shape with an outer peripheral surface formed as a curved surface, similar to the above-described embodiment. The fixed portion 820 has a through hole 820a through which the threaded portion of the bolt 81 (see FIGS. 1 and 2) can be inserted, and a pin hole 820b for receiving the insertion of a pin for preventing rotation with respect to the lower cylinder block 60.

[0093] The mass portion 821 is connected to the fixed portion 820 in a state of hanging downward. The mass portion 821 has a prismatic shape and is formed to protrude more than the fixed portion 820 in a direction orthogonal to the vertical direction. Note that the shape of the mass portion 821 is not limited to the shape shown in FIG. 14, and for example, a cylindrical shape or a spherical shape can also be adopted.

[0094] Next, with reference to FIG. 15, the ERP at 1600 Hz in each of the crank journal portions 63 and 64 when the dynamic damper 82 of this modification is attached to the lower part of the #3 crank journal portion 63 and when it is attached to both lower parts of the #3 crank journal portion 63 and the #4 crank journal portion 64 will be described. In FIGS. 15(a) and 15(b), the broken line indicates the value of the ERP (ERP in the comparative example) in FIG. 13(b).

[0095] As shown in FIG. 15(a), in the embodiment where the dynamic damper 82 is attached to the lower part of the #3 crank journal portion 63, the ERP in the vertical direction (#3_Z) of the #3 crank journal portion 63 is 42 dBA, and the total of the #3 and #4 crank journal portions 63 and 64 is 58.3 dBA. Compared with the comparative example in FIG. 13(b), in the embodiment where the dynamic damper 82 is attached to the lower part of the #3 crank journal portion 63, the ERP in the vertical direction of the #3 crank journal portion 63 is significantly lower than that in the comparative example. Specifically, in the embodiment, a decrease of 20 dBA in the vertical direction is observed compared with the comparative example.

[0096] Next, as shown in FIG. 15(b), in the embodiment where the dynamic damper 82 is attached to the lower part of the #3 crank journal portion 63, the ERPs in the vertical direction (#3_Z, #4_Z) of the #3 crank journal portion 63 and the #4 crank journal portion 64 are 42 dBA and 35 dBA respectively, and the total at the #3 and #4 crank journal portions 63 and 64 is 55.6 dBA. Compared with the comparative example in FIG. 13(b), in the embodiment where the dynamic damper 82 is attached to the lower part of each of the #3 crank journal portion 63 and the #4 crank journal portion 64, the ERPs in the vertical direction at the #3 crank journal portion 63 and the #4 crank journal portion 64 are significantly lower than those in the comparative example. Specifically, in the embodiment, a 20 dBA decrease is observed in each of the #3 crank journal portion 63 and the #4 crank journal portion 64 compared with the comparative example.

[0097] As described above, also in the vibration damping structure of the engine according to this modification, even when the dynamic damper 82 having the structure shown in FIG. 14 is attached to the lower part of the lower cylinder block 60 and between the #2 to #4 cylinders 1b to 1d, vibration attenuation in the vertical direction can be achieved. That is, due to the flywheel 52 being fixed to the rear end of the crankshaft 30, the crankshaft 30 vibrates with a large amplitude at the portion on the front end side rather than the center position in the front-rear direction. Therefore, by attaching the dynamic damper 82 to the lower part of the lower cylinder block 60 between the #2 to #4 cylinders 1b to 1d, the vibration generated by the crankshaft 30 can be effectively consumed by the dynamic damper 82, and the propagation of sound into the vehicle interior can be suppressed.

[0098] Although detailed description is omitted, for the dynamic damper 82 of this modification as well, the fixing portion 820 and the mass portion 821 are integrally formed using cast iron. The effect thereof is the same as that of the above-described embodiment.

[0099] [Other Modifications] In the above-described embodiment, although the applicable ranges of H / H0 and W / W0 in the dynamic damper 80 were described as examples, they can be variously changed according to the resonance peak frequency of the vibration generated with the rotation of the engine's crankshaft. Also, regarding the mass of the mass portion, it can be variously changed according to the frequency to be consumed by the dynamic damper.

[0100] Further, in the above-described embodiment, the dynamic damper 80 having two mass portions 802 and 803 was adopted, but in the present invention, three or more mass portions may be connected to the beam portion.

[0101] Also, in the above-described embodiment, only one dynamic damper 80 was attached to the lower part of the #3 crank journal portion 63 in the lower cylinder block 60, and in the above-described modification, the dynamic damper 82 was attached to the lower parts of the #3 crank journal portion 63 and the #4 crank journal portion 64. However, in the present invention, one or more of the above-described dynamic dampers 80 and 82 may be attached to the lower part between the #2 to #4 cylinders 1b to 1d in the cylinder block.

[0102] Also, regarding the position where the dynamic dampers 80 and 82 are attached, it is not necessarily required to include the #3 crank journal portion 63. That is, according to the characteristics of the engine, the location where the amplitude of the vibration is the largest can be determined, and a high vibration damping property can be ensured by attaching a dynamic damper having the same configuration as above to that location.

[0103] In the above-described embodiment and the above-described modification, the lower cylinder block 60 having a bottom wall with an opening between the crank journal portions 61 to 67 is adopted as an example. However, the present invention is not limited thereto. It is also possible to adopt a lower cylinder block having a bottom wall with a structure in which the space between the crank journal portions is closed. In this case, it is not always necessary to attach the dynamic damper to the lower part of the crank journal portions 63 and 64. It is also possible to attach it to a position shifted in the front-rear direction with respect to the crank journal portions 63 and 64 as long as it is in the lower part between the #2 to #4 cylinders 1b to 1d in the cylinder block.

[0104] In the above-described embodiment, the dynamic dampers 80 and 82 integrally formed using cast iron are adopted. However, in the present invention, it is not always necessary to adopt cast iron as the constituent material of the dynamic damper. By forming the dynamic damper using a material having a higher specific gravity than the constituent material of the lower cylinder block or the like, the same effects as described above can be achieved. Further, the dynamic damper does not necessarily have to be of an integral structure, and it is also possible to adopt a dynamic damper formed by combining a plurality of members.

Explanation of Reference Numerals

[0105] 1 Engine 1a - 1f Cylinders 30 Crankshaft 51 Pulley 52 Flywheel 60 Lower Cylinder Block 61 - 67 Crank Journal Portions 80, 82 Dynamic Dampers 81 Bolt 800, 820 Fixing Portions 801 Beam Portion 801a, 801b Connection Portions 802, 803, 821 Mass Portions V Vehicle R1 Engine Room TM Transmission

Claims

1. A vibration damping structure for an in-line six-cylinder engine mounted vertically in a vehicle and having six cylinders arranged in series, pistons reciprocally fitted to each of the six cylinders, a crankshaft disposed below the piston in the vertical direction of the vehicle and connected to the piston via a connecting rod to rotate, a cylinder block disposed below the crankshaft in the vertical direction and having a plurality of crank journal portions that support the crankshaft between adjacent cylinders of the crankshaft, a flywheel fixed to the rear end of the crankshaft in the front-rear direction of the vehicle, When the six cylinders are arranged in the order of #1 cylinder, #2 cylinder, #3 cylinder, #4 cylinder, #5 cylinder, and #6 cylinder from the front side to the rear side in the front-rear direction of the vehicle, a dynamic damper attached to at least one location between the #2 cylinder and the #4 cylinder at the lower part of the cylinder block, comprising, A vibration damping structure for an in-line six-cylinder engine.

2. The dynamic damper, is attached to the lower part of the crank journal portion and has a fixing portion extending downward from the lower part, a beam portion connected to the lower part of the fixing portion and extending in the front-rear direction, and two mass portions that are connected to respective connection portions on one side and the other side in the front-rear direction of the rib and extend in the left-right direction of the vehicle while being separated from each other in the front-rear direction, integrally having, The vibration damping structure for an in-line six-cylinder engine according to Claim 1.

3. The fixing portion has a column shape, When assuming a virtual plane passing through the center of the column in the fixing portion and orthogonal to the front-rear direction, the dynamic damper has a shape symmetric with respect to the virtual plane. The vibration damping structure of the in-line six-cylinder engine according to claim 2.

4. When the beam portion and the two mass portions are viewed from one side in the left-right direction, in a side view, the beam portion is formed such that the thickness dimension in the up-down direction of the beam portion is smaller than the thickness dimension in the up-down direction of each of the two mass portions. The vibration damping structure of the in-line six-cylinder engine according to claim 2.

5. In both cases where the beam portion and the two mass portions are viewed from one side in the left-right direction and in a plan view from one side in the up-down direction, the beam portion and the two mass portions both form an H shape. The vibration damping structure of the in-line six-cylinder engine according to any one of claims 1 to 4.

6. The dynamic damper is formed using cast iron. The vibration damping structure of the in-line six-cylinder engine according to any one of claims 1 to 4.

Images