Internal combustion engine

Abstract

To ensure vibration reduction of a front cover for an internal combustion engine.SOLUTION: An internal combustion engine 1 includes a balancer shaft 14 disposed in parallel with a crank shaft 18, and a front cover 7 that covers an end surface on one end side of an internal combustion engine body 8 in a cylinder row direction thereof. The front cover 7 comprises a thick part 11 having a relatively thicker portion which overlaps the balancer shaft 14 when viewed in a shaft direction of the crank shaft. The internal combustion engine 1 can effectively suppress occurrence of membrane vibration (oscillation) of the front cover 7, with mass added to the front cover 7 through the thick part 11.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an internal combustion engine having a front cover. [Background technology]

[0002] For example, Patent Document 1 discloses a chain cover (front cover) for an internal combustion engine that is provided to cover the front surface of a timing chain that is hung between a crank timing sprocket and a cam timing sprocket via an idler sprocket.

[0003] The chain cover of Patent Document 1 reduces resonance of the chain cover caused by impact noise caused by engagement between the timing chain and the sprocket by increasing the thickness of the front surface of the cylinder head cover.

[0004] However, in Patent Document 1, when reducing resonance of the chain cover, nothing is taken into consideration other than the impact noise caused by the engagement between the timing chain and the sprocket.

[0005] That is, there is room for further improvement in the internal combustion engine in order to reduce vibrations of the chain cover (front cover). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 9-209774 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in Patent Document 1, when reducing resonance of the chain cover, nothing is taken into consideration other than the impact noise caused by the engagement between the timing chain and the sprocket.

[0008] That is, there is room for further improvement in the internal combustion engine in order to reduce vibrations of the chain cover (front cover). [Means for solving the problem]

[0009] The internal combustion engine of the present invention includes a balancer shaft arranged parallel to the crankshaft, and a front cover covering one end face of the internal combustion engine body in the direction of cylinder row. The front cover has a thick portion that is relatively thick at a portion that overlaps with the balancer shaft as viewed in the axial direction of the crankshaft. [Effects of the Invention]

[0010] In an internal combustion engine, the occurrence of membrane vibration (vibration) of the front cover can be suppressed by adding mass to the front cover by using a thick portion. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is an explanatory diagram that schematically shows the general configuration of an internal combustion engine according to the present invention; [Figure 2] FIG. 2 is a rear view of the front cover of the internal combustion engine according to the present invention. [Figure 3] 3 is a cross-sectional view of one end of the internal combustion engine taken along line AA in FIG. 2. [Figure 4] 3 is a cross-sectional view of one end of the internal combustion engine taken along line BB in FIG. 2. [Figure 5] 3 is a cross-sectional view of one end of the internal combustion engine taken along line CC in FIG. 2. [Figure 6] 3 is a cross-sectional view of one end of the internal combustion engine taken along line DD in FIG. 2. [Figure 7] FIG. 3 is a cross-sectional view of the front cover taken along line EE in FIG. 2. [Figure 8] FIG. 4 is a front view of the front cover showing the cover members overlapped with each other. [Figure 9] FIG. 10 is an explanatory diagram schematically illustrating a part of a runner and a gate when casting a front cover. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment of the present invention will be described in detail below with reference to the drawings. In each drawing, the X-axis indicates an axis along the longitudinal direction of the internal combustion engine 1 (an axis parallel to the central axis of the crankshaft 18 of the internal combustion engine 1), the Y-axis indicates an axis along the left-right direction (width direction of the internal combustion engine) of the internal combustion engine 1, and the Z-axis indicates an axis along the vertical direction of the internal combustion engine 1 (an axis parallel to the cylinder axis L of the internal combustion engine 1). In other words, the X-axis is an axis along the direction in which the cylinders of the internal combustion engine 1 or the internal combustion engine main body 8 (described later) are aligned. The Y-axis is an axis along the width direction of the internal combustion engine main body 8. The internal combustion engine 1 is mounted on, for example, a vehicle.

[0013] 1 is an explanatory diagram showing a schematic configuration of an internal combustion engine 1 according to the present invention. The internal combustion engine 1 is, for example, an in-line multi-cylinder internal combustion engine, and has a cylinder head 2, a cylinder block 3 attached to the bottom of the cylinder head 2, a cam bracket 4 attached to the top of the cylinder head 2, an upper oil pan 5 attached to the bottom of the cylinder block 3, a lower oil pan 6 attached to the bottom of the upper oil pan 5, and a front cover 7 that covers the front of an internal combustion engine body 8. The cylinder head 2, cylinder block 3, cam bracket 4, and upper oil pan 5 together constitute the internal combustion engine body 8.

[0014] The cylinder head 2 is a casting made of a metal material such as an aluminum alloy, and is formed with an intake port (not shown) that supplies intake air to a combustion chamber (not shown), and an exhaust port (not shown) that discharges exhaust gas from the combustion chamber (not shown).

[0015] The cylinder block 3 is a casting made of a metal material such as an aluminum alloy, and has a number of cylinders (not shown) corresponding to the number of cylinders. As will be described later, in this embodiment, a balancer shaft arranged parallel to the crankshaft is supported by the cylinder block 3.

[0016] The cam bracket 4 is made of a metal material such as an aluminum alloy, and supports a camshaft (not shown) together with the cylinder head 2 so that the camshaft can rotate.

[0017] The oil pan upper 5 is made of a metal material such as an aluminum alloy, and together with the cylinder block 3 constitutes a crankcase (not shown) that houses the crankshaft 18 (see FIG. 2).

[0018] The oil pan lower 6 is made of a synthetic resin material such as polyamide, and stores oil for lubrication.

[0019] The front cover 7 is a casting made of a metal material such as aluminum alloy, and is attached liquid-tight to the internal combustion engine body 8 so as to cover the front surface of the internal combustion engine body 8. More specifically, the front cover 7 is attached to the front surfaces of the cylinder block 3, the cylinder head 2, the cam bracket 4, and the oil pan upper 5 with bolts (not shown). In other words, the front cover 7 is attached to the internal combustion engine body 8 so as to cover one end surface of the cylinder block 3 and the cylinder head 2 in the crankshaft axial direction (X-axis direction), i.e., one end surface of the internal combustion engine body 8 in the cylinder row direction. The front cover 7 has a shallow dish shape, and forms a space between the front surface of the internal combustion engine body 8 and the front surface of the internal combustion engine body 8 that communicates with the oil pans 5 and 6.

[0020] As shown in FIG. 2, which is a rear view of the front cover 7, the balancer shaft 14 of this embodiment is disposed parallel to the crankshaft 18 and is supported by the cylinder block 3 at a position slightly above the crankshaft 18 in the cylinder axial direction. As viewed in the crankshaft axial direction, the cylinder block 3 of this embodiment supports the balancer shaft 14, making the engine width dimension (length in the intake and exhaust directions) larger than when no balancer shaft is provided. Specifically, in FIG. 2, the area near the balancer shaft 14 at the front end of the engine of the cylinder block 3 protrudes to the right of the balancer shaft 14 in a substantially circular shape centered on the balancer shaft 14 to accommodate the rotating member attached to the front end of the balancer shaft. The front of the engine, including the cylinder block 3 whose dimension in the engine width direction is thus increased, is covered by the front cover 7.

[0021] As shown in Figures 2 to 7, the front cover 7 is formed with a thick portion 11 having an increased thickness. Figure 3 is a cross-sectional view of one end of the internal combustion engine 1 taken along line AA in Figure 2. Figure 4 is a cross-sectional view of one end of the internal combustion engine 1 taken along line BB in Figure 2. Figure 5 is a cross-sectional view of one end of the internal combustion engine 1 taken along line CC in Figure 2. Figure 6 is a cross-sectional view of one end of the internal combustion engine 1 taken along line DD in Figure 2. Figure 7 is a cross-sectional view of the front cover 7 taken along line EE in Figure 2.

[0022] The front cover has a thick portion 11 that is relatively thick in at least a part of the portion that overlaps with the balancer shaft when viewed in the crankshaft axial direction (when viewed through). Specifically, the thick portion 11 in this embodiment is formed in a predetermined first region 12 and a predetermined second region 13 of the front cover 7. The thick portion 11 is set so as to be able to add mass that suppresses membrane vibration of the front cover 7.

[0023] The first region 12 is a circular region that faces the balancer shaft gear 15 and balance weight 16 attached to one end of the balancer shaft 14 of the front cover 7 when viewed in the crankshaft axial direction. More specifically, the first region 12 is a portion that faces the balancer shaft gear 15 and balance weight 16 when they rotate. When viewed in the crankshaft axial direction, the first region 12 protrudes to the side of the internal combustion engine body 8 to cover the balancer shaft gear 15 and balance weight 16. The front cover 7 has a thick portion 11 in the first region 12 where the thickness is increased.

[0024] The second region 13 is a semicircular region with a radius extending from the center of the crankshaft axis to the outer circumferential edge of the front cover. That is, the front cover 7 has a thickened portion 11 formed in a portion facing the crank pulley 19 of the crankshaft 18. The second region 13 is designed to include a portion of the front cover 7 where membrane vibration is likely to occur, and is also designed to largely cover the side of the front cover 7 where the balancer shaft gear 15 and balance weight 16 are located, as viewed in the crankshaft axial direction. That is, the second region 13 is designed on the side of the front cover 7 where the balancer shaft gear 15 and balance weight 16 are located, as viewed in the crankshaft axial direction. The second region 13 has a portion that overlaps with the balancer shaft gear 15 and balance weight 16, as viewed in the crankshaft axial direction. That is, the second region 13 has a portion that overlaps with the first region 12.

[0025] The balancer shaft 14 is disposed parallel to the crankshaft 18. As shown in FIG. 5, a first bolt 20 for fixing a balancer shaft gear 15 and a balance weight 16 is attached to one axial end of the balancer shaft 14. The balancer shaft gear 15 and the balance weight 16 correspond to rotating members. One end of the balancer shaft 14 is located at one end side of the internal combustion engine body 8 in the cylinder row direction.

[0026] As shown in Figures 5 and 6, the balancer shaft gear 15 and the balance weight 16 are arranged on one end side of the internal combustion engine body 8 in the cylinder row direction. The balancer shaft gear 15 and the balance weight 16 are arranged between the front cover 7 and one end of the internal combustion engine body 8. The balancer shaft gear 15 is a disk-shaped member and is arranged closer to the internal combustion engine body 8 than the balance weight 16. The balancer shaft gear 15 meshes with a crankshaft gear 21 attached to one end of the crankshaft 18 and rotates in the opposite direction to the crankshaft 18. The balance weight 16 is a fan-shaped member with a radius smaller than the radius of the balancer shaft gear 15 and is arranged closer to the front cover 7 than the balancer shaft gear 15. One end of the crankshaft 18 is located on one end side of the internal combustion engine body 8 in the cylinder row direction.

[0027] As shown in Figures 5 and 6, the crankshaft gear 21 is disposed between the front cover 7 and one end of the internal combustion engine body 8. Furthermore, a crank pulley 19 is disposed on the outside of the crankshaft gear 21 at one end of the crankshaft 18. As shown in Figures 5 and 6, the crank pulley 19 is located on the outside of the front cover 7. As shown in Figure 6, the crank pulley 19 is fixed to the crankshaft 18 by a second bolt 22. The second bolt 22 is attached to the axial end of one end of the crankshaft 18.

[0028] The front cover 7 has a recess 24 formed by thinning the wall thickness at a position facing the head of the first bolt 20 on the rear surface of the front cover that faces one end face of the internal combustion engine body 8 in the cylinder row direction, the recess 24 being slightly larger than the head of the first bolt 20 so as to avoid interference with the head of the first bolt 20. In other words, in the first region 12 of the front cover 7, the position where the recess 24 is formed is not part of the thick wall portion 11, as shown in Figures 2 and 5.

[0029] As shown in Figures 2 and 5, the front cover 7 has a first rib 25 formed on the outer peripheral edge of the recess 24, which is continuous in an annular shape and protrudes toward one end face of the internal combustion engine body 8 in the cylinder row direction.

[0030] 2, the front cover 7 has one end connected to the first rib 25 and formed with a plurality of radial ribs, the second ribs 26, which extend radially from the recess 24 on the outside of the first rib 25. The other end of the second ribs 26 is connected to a bolt boss 27 into which a bolt (not shown) is inserted for fixing the front cover 7 to the internal combustion engine body 8. The second ribs 26 are ridges that protrude toward one end face of the internal combustion engine body 8 in the cylinder row direction.

[0031] Similarly to the second ribs 26, the front cover 7 is also provided with third ribs 28, which are multiple radial ribs that are connected at one end to the first rib 25 and extend radially from the recess 24 on the outside of the first rib 25. The other end of each of the third ribs 28 is not connected to the bolt boss 27.

[0032] The first rib 25, the second rib 26, and the third rib 28 protrude further toward the internal combustion engine body 8 than the thick portion 11. That is, the front cover has a rib portion where the ribs are provided, a portion other than the ribs that has a thickness within the normal range, and a thick portion that has a thickness smaller than the thickness (height) of the ribs but greater than the normal range.

[0033] 3 to 7, the front cover 7 is formed so that, in the area where the thick-walled portion 11 is formed, the front cover surface side is curved and the back surface side of the front cover facing one end face of the internal combustion engine body 8 in the cylinder row direction is flat. Here, the curved surface on the front cover surface side is set to have a gentle curvature without a sudden change in thickness so that the thickness of the front cover 7 does not decrease suddenly and porosity does not occur during casting. In other words, in the thick-walled portion 11 of the front cover 7, the curved surface on the front cover surface side is set to a gentle curve so that porosity does not occur during casting.

[0034] In the area where the thick portion 11 is formed, the curved surface on the front cover surface side is formed so that, as viewed in the crankshaft axial direction, the thickness increases from the balancer shaft axial center toward the radially outward side and then decreases. That is, in the first region 12, the front cover 7 is formed so that the thickness increases from the balancer shaft axial center toward the radially outward side and then decreases. More specifically, on the back side, the front cover 7 has a portion on the outer periphery of the recess 24 where the thick portion 11 is particularly thick and is concentrically connected to the recess 24. The dashed circle r1 in FIG. 2 indicates the thick portion of the thick portion 11 on the outer periphery of the recess 24 in the first region 12.

[0035] In addition to the portion indicated by circle r1, front cover 7 also has a portion where the thickness is particularly thick within thick portion 11. More specifically, front cover 7 has, on the back surface side, a portion on the outer periphery of crankshaft 18 where the particularly thick portion within thick portion 11 continues in an arc shape concentric with crankshaft 18. Arcs r2 and r3 indicated by dashed lines in Fig. 2 indicate the particularly thick portions within thick portion 11 at positions on the outer periphery of crankshaft 18 in second region 13.

[0036] As shown in Fig. 8, the internal combustion engine 1 has a cover member 31 with a substantially rectangular outer shape that covers the thick-walled portion 11 from the outside of the front cover 7. The cover member 31 is formed using, for example, nonwoven fabric. Fig. 8 is a front view of the front cover 7 showing the cover member 31 in a stacked state.

[0037] As shown in Fig. 9, the portion of the front cover 7 that was in contact with the gate 32 during casting is set on the side of the balancer shaft 14 relative to the crankshaft 18 when viewed in the axial direction of the crankshaft. Fig. 9 is an explanatory diagram that schematically shows a portion of the runner 33 and the gate 32 when the front cover 7 is cast.

[0038] When the balancer shaft gear 15 and balance weight 16 are arranged, the outer shape of the front cover 7 changes (expands) so that it protrudes to the side (outer periphery) to cover the balancer shaft gear 15 and balance weight 16 when viewed in the crankshaft axial direction, compared to when the balancer shaft gear 15 and balance weight 16 are not arranged, which could make the membrane more susceptible to vibration.

[0039] Therefore, in the internal combustion engine 1 of the above-described embodiment, in response to such a change (expansion) in the outer shape of the front cover 7, the thick portion 11 is formed in the front cover 7, where the thickness increases.

[0040] As a result, the internal combustion engine 1 can effectively suppress the occurrence of membrane vibration (vibration) of the front cover 7 by adding mass to the front cover 7 with the thick portion 11.

[0041] In the internal combustion engine 1, the thick portion 11 is also formed in the second region 13 of the front cover 7. Compared to when the thick portion 11 is formed only in the first region 12, the area in which the thick portion 11 is formed in the front cover 7 is wider, making it possible to distribute the added mass for suppressing membrane vibration over a wide area. As a result, in the internal combustion engine 1, the thickness of the thick portion 11 of the front cover 7 can be made relatively thin, which suppresses changes in the thickness of the front cover 7 due to the formation of the thick portion 11 and makes it possible to suppress the occurrence of porosity during casting of the front cover 7. In other words, in the internal combustion engine 1, the thickness of the thick portion 11 throughout the first region 12 and the second region 13 is set to a predetermined thickness (thickness) that prevents porosity from occurring during casting.

[0042] Furthermore, if the second region 13 of the front cover 7 of the internal combustion engine 1 is set to include an area of ​​the front cover 7 where membrane vibration is likely to occur, the occurrence of voids during casting of the front cover 7 can be suppressed while more effectively suppressing the occurrence of membrane vibration.

[0043] When forming the thick portion 11 in the front cover 7 of the internal combustion engine 1, no unevenness is provided on the back side of the front cover, and the front surface side of the front cover is made curved. This avoids interference with other components on the back side of the front cover, while suppressing sudden changes in thickness in the area where the thick portion 11 of the front cover 7 is formed, and makes it possible to suppress the occurrence of voids when casting the front cover 7.

[0044] The front cover 7 is formed so that the thickness increases from the axial center of the balancer shaft toward the radially outward side and then decreases in thickness in the first region 12. In other words, the thickness of the front cover 7 gradually changes in the first region 12 between before and after the thickest part of the thick-walled portion 11.

[0045] Therefore, a sudden change in thickness is suppressed in the portion of the front cover 7 where the thick portion 11 is formed, and the occurrence of voids during casting of the front cover 7 can be suppressed.

[0046] In the internal combustion engine 1, a recess 24 is formed on the rear surface side of the front cover 7 at the position where the balancer shaft 14 is arranged, and the thickness of the head of the first bolt 20 is absorbed by utilizing the thickness of the front cover 7.

[0047] This makes it possible to prevent the length of the internal combustion engine 1 along the crankshaft axial direction from becoming too long at the position where the balancer shaft 14 is arranged.

[0048] The front cover 7 of the internal combustion engine 1 is formed with a first rib 25 around the portion where the thickness is reduced by forming the recess 24. As a result, the outer peripheral edge of the recess 24 of the front cover 7 of the internal combustion engine 1 is protected by the first rib 25, and fragility and stress concentration at the outer peripheral edge of the recess 24 of the front cover 7 can be reduced.

[0049] The front cover 7 of the internal combustion engine 1 is formed with a second rib 26 around the portion where the thickness is reduced by forming the recess 24. As a result, the periphery of the recess 24 of the front cover 7 of the internal combustion engine 1 is protected by the second rib 26, and the strength of the periphery of the recess 24 can be increased.

[0050] The front cover 7 of the internal combustion engine 1 can improve the circulation of the molten metal by pouring the molten metal from the side where the thickness needs to be relatively thick to form the thick part 11.

[0051] Since the cover member 31 is attached to the internal combustion engine 1, the NVH (Noise, Vibration, Harshness) performance can be improved.

[0052] Although specific embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention.

[0053] For example, even if the thick portion 11 is provided only in the first region 12 of the front cover 7, the effect of suppressing membrane vibration can be obtained by appropriately setting the thickness of the thick portion 11.

[0054] For example, when the thickness of the thick portion 11 of the front cover 7 is set to a predetermined thickness that will not cause porosity during casting throughout the first region 12 and the second region 13, the thickness of the thick portion 11 may be made constant throughout the first region 12 and the second region 13.

[0055] The front cover 7 has the thick portions 11 whose thicknesses are constant throughout the first region 12 and the second region 13, thereby distributing the added mass of the thick portions 11 over a wide area. Therefore, the front cover 7 has reduced thickness variations in the thick portions 11, which can reduce the occurrence of porosity during casting.

[0056] In addition, when the thickness of the thick portion 11 of the front cover 7 is set to a predetermined thickness that will not cause porosity during casting throughout the first region 12 and the second region 13, the thickness of the thick portion 11 may be constant throughout either the first region 12 or the second region 13.

[0057] For example, the entire area of ​​the front cover 7 facing the crank pulley 19 of the crankshaft 18 may be the thick portion 11 . [Explanation of symbols]

[0058] 1...Internal combustion engine 2...Cylinder head 3...Cylinder block 4...Cam bracket 5...Oil pan upper 6...Oil pan lower 7...Front cover 8...Internal combustion engine body 11...Crankshaft 12...First area 13…Second area 14...Balancer shaft 15...Balancer shaft gear 16...Balance weight 18...Crankshaft 19...Crank pulley 20...First bolt 21...Crankshaft gear 22...Second bolt 24...recess 25...First rib 26...Second rib 27...Bolt boss 28...Third rib 31...Cover member 32...Gate 33...Runner

Claims

1. a balancer shaft arranged parallel to the crankshaft; a front cover that covers an end face on one end side of the internal combustion engine body in the cylinder row direction, The internal combustion engine is characterized in that the front cover has a thick portion that is relatively thick at a portion that overlaps with the balancer shaft when viewed in the axial direction of the crankshaft.

2. a rotating member attached to one end of the balancer shaft and arranged on the one end side in the cylinder row direction of the internal combustion engine body, 2. The internal combustion engine according to claim 1, wherein the thick portion is formed in a first region that faces the rotary member and is thicker than other portions.

3. 3. The internal combustion engine according to claim 2, wherein the balancer shaft is supported by a cylinder block.

4. 4. The internal combustion engine according to claim 3, wherein the second region has a semicircular shape with a radius extending from the center of the crankshaft axis to the outer peripheral edge of the front cover as viewed in the axial direction of the crankshaft, and is set to cover the side where the rotating member is located, and further includes a thick portion.

5. 2. The internal combustion engine according to claim 1, wherein the front cover is formed by casting.

6. 6. The internal combustion engine according to claim 5, wherein the thick portion is formed so that the front cover surface side is curved and the rear surface side of the front cover is flat.

7. 7. The internal combustion engine according to claim 6, wherein the thick portion is set so that a change in thickness is suppressed to a predetermined value that does not cause porosity during casting.

8. 7. The internal combustion engine according to claim 6, wherein the thick-walled portion has a curved surface formed on the front surface side of the front cover such that the thickness increases from the axial center of the balancer shaft toward the radially outward direction and then decreases.

9. A bolt for fixing the rotating member is attached to the shaft end of the balancer shaft, 3. The internal combustion engine according to claim 2, wherein the front cover has a recess formed on the rear surface of the front cover at a position facing the bolt, the recess being able to avoid interference with the bolt.

10. 10. The internal combustion engine according to claim 9, wherein the front cover has an annular first rib formed on an outer peripheral edge of the recess on the back surface of the front cover, the first rib being convex toward an end face on one end side of the internal combustion engine body in the cylinder row direction.

11. 11. The internal combustion engine according to claim 10, wherein the front cover is formed with a plurality of radial ribs that are connected to the first rib, extend radially from the recess on the outside of the first rib, and are convex toward an end face on one end side of the internal combustion engine body in the cylinder row direction.

12. 2. The internal combustion engine according to claim 1, wherein the front cover is cast, and a portion of the front cover that was in contact with a gate during casting is set on a side of the crankshaft where the balancer shaft is located, as viewed in the axial direction of the crankshaft.

13. 2. The internal combustion engine according to claim 1, wherein a cover member is attached to the outside of the front cover so as to cover the thick portion.

14. 2. The internal combustion engine according to claim 1, wherein the thick portion is formed in a portion of the front cover facing the crankshaft.

15. 5. The internal combustion engine according to claim 4, wherein the front cover is cast, and the change in thickness of the thick portion throughout the first region and the second region is set to be suppressed to a predetermined thickness change that does not cause porosity during casting.

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