Internal combustion engine

Abstract

To provide an internal combustion engine that prevents a balance weight from being directly splashed with oil and can be easily manufactured.SOLUTION: An internal combustion engine 1 includes: a balancer shaft 9 rotatably supported by a cylinder block 3; a balance weight accommodation chamber 11 formed in the cylinder block 3 to rotatably accommodate a balance weight 10 of the balancer shaft 9; a rear side oil passage 15b for causing oil to fall to the balance weight accommodation chamber 11; and a shielding wall 17 located between an opening part 16 of the rear side oil passage 15b opened in the balance weight accommodation chamber 11 and the balancer shaft 9 to cover an upper part of the balance weight 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] For example, Patent Document 1 discloses an internal combustion engine in which a pair of balancer shafts extending parallel to the crankshaft and a balancer supported by the balancer shafts are arranged so as to partially interfere with an oil return passage that returns oil downward in the lateral direction. The internal combustion engine of Patent Document 1 is provided with an oil baffle formed integrally with the cylinder block around the balancer, and the oil baffle prevents oil that drops from the oil return passage from directly contacting the balancer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 61-77448 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in Patent Document 1, an oil baffle is provided all around the balancer, which may obstruct the flow of blow-by gas from the internal combustion engine and deteriorate the ventilation performance of the blow-by gas.

[0005] That is, in order to prevent oil from coming into direct contact with the balancer (balance weight) supported by the balancer shaft, there is room for further improvement in terms of ventilation performance of blow-by gas. [Means for solving the problem]

[0006] The internal combustion engine of the present invention comprises a balancer shaft rotatably supported by a cylinder block, a balance weight accommodating chamber formed in the cylinder block for rotatably accommodating a balance weight of the balancer shaft, an oil return passage for dropping oil into the balance weight accommodating chamber, and a shielding wall located between the balancer shaft and an opening of the oil return passage that opens into the balance weight accommodating chamber. [Effects of the Invention]

[0007] According to the present invention, the shielding wall covers the upper part of the balance weight to prevent oil from directly contacting the upper part, and does not impede the flow of blow-by gas through the balance weight chamber toward the oil return passage. In other words, in the internal combustion engine of the present invention, even with the shielding wall in the balance weight chamber, a flow path for blow-by gas toward the oil return passage is secured, so that ventilation performance for blow-by gas can be secured (guaranteed). [Brief explanation of the drawings]

[0008] [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 cylinder block of the internal combustion engine according to the present invention. [Figure 3] FIG. 2 is an enlarged perspective view showing a main part of the present invention. [Figure 4] FIG. 2 is an enlarged perspective view showing a main part of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described in detail below with reference to the drawings.

[0010] An internal combustion engine 1 according to the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 is an explanatory diagram that schematically shows the general configuration of the internal combustion engine 1 according to the present invention. FIG. 2 is a rear view of the cylinder block 3 of the internal combustion engine 1 according to the present invention, showing the rear surface (rear end) of the cylinder block 3. FIGS. 3 and 4 are enlarged perspective views of essential parts of the present invention, showing the balance weight accommodating chamber 11 and the shielding wall 17 as seen from the rear surface of the cylinder block 3. The X-axis in FIG. 1 is an axis along the front-rear direction of the internal combustion engine 1 (an axis parallel to the central axis of the crankshaft 8 or the central axis of the balancer shaft 9 of the internal combustion engine 1). The Y-axis in FIG. 2 is an axis along the left-right direction of the internal combustion engine 1 (the width direction of the internal combustion engine). The Z-axis in FIGS. 1 and 2 is an axis along the up-down direction of the internal combustion engine 1 (an axis parallel to the cylinder axis L of the internal combustion engine 1). That is, the X-axis is an axis along the cylinder row direction (axial direction of the crankshaft 8 or axial direction of the balancer shaft 9) of the internal combustion engine 1 or the internal combustion engine body 7 (described later). Also, the Y-axis is an axis along the width direction of the internal combustion engine 1 or the internal combustion engine body 7.

[0011] The internal combustion engine 1 is an in-line multi-cylinder internal combustion engine and is mounted on a vehicle such as an automobile. As shown in FIG. 1, the internal combustion engine 1 has a cylinder head 2, a cylinder block 3 attached to the lower part of the cylinder head 2, an oil pan 4 attached to the lower part of the cylinder block 3, a front cover 5 covering the front of the internal combustion engine body 7 and the oil pan 4, and a rear cover 6 covering the rear of the internal combustion engine body 7 and the oil pan 4. The internal combustion engine body 7 is made up of the cylinder head 2, the cylinder block 3, etc. The front of the internal combustion engine body 7 is the surface on one end side of the internal combustion engine body 7 (internal combustion engine 1) in the X-axis direction. The rear surface of the internal combustion engine body 7 is the surface on the other end side of the internal combustion engine body 7 (internal combustion engine 1) in the X-axis direction.

[0012] 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).

[0013] 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. The cylinder block 3 has open ends at its front and rear ends in the balancer shaft axial direction (crankshaft axial direction or cylinder row direction), which are covered by other members such as a front cover 5 and a rear cover 6. The open ends of the cylinder block 3, where other members such as the front cover 5 and rear cover 6 are attached, are smoothed by machining.

[0014] The oil pan 4 is made of a metal material such as an aluminum alloy or a resin material such as a hard synthetic resin, and together with the cylinder block 3 forms a crankcase (not shown) that houses the crankshaft 8, and also stores oil for lubrication.

[0015] The front cover 5 is made of a synthetic resin material such as polyamide, and is attached to the internal combustion engine body 7 and the oil pan 4 so as to cover the front surfaces of the internal combustion engine body 7 and the oil pan 4.

[0016] The rear cover 6 is made of a synthetic resin material such as polyamide, and is attached to the internal combustion engine body 7 and the oil pan 4 so as to cover the rear surfaces of the internal combustion engine body 7 and the oil pan 4.

[0017] The internal combustion engine 1 also has a balancer shaft 9 arranged parallel to the crankshaft 8, and the balancer shaft 9 is equipped with a balance weight 10. The balancer shaft 9 is attached to the internal combustion engine 1 to suppress vibration.

[0018] The balancer shaft 9 is rotatably supported by the cylinder block 3. The balancer shaft 9 rotates when the crankshaft 8 of the internal combustion engine 1 rotates.

[0019] The balance weight 10 is attached to the rear end, which is one end of the balancer shaft 9. The balance weight 10 rotates integrally with the balancer shaft 9. The balance weight 10 is located inside the cylinder block 3. The balance weight 10 is rotatably accommodated in a balance weight accommodating chamber 11 of the internal combustion engine body 7. More specifically, the balance weight accommodating chamber 11 is formed at the rear end of the cylinder block 3, which is one end side of the balancer shaft in the axial direction.

[0020] As shown in Figures 1 to 4, the balance weight accommodating chamber 11 is formed by a recess 12 formed in the cylinder block 3 so that the balance weight 10 can be accommodated therein, and a lid member 13 attached to the tip of an outer peripheral wall 12a of the recess 12 to close the recess 12. The tip of the outer peripheral wall 12a and the lid member 13 are liquid-tightly sealed with a sealing material (not shown), such as a liquid gasket, except for a communicating passage recess 22, which will be described later. For convenience, the lid member 13 is not shown in Figures 2 to 4.

[0021] The recess 12 is a box-shaped space that is surrounded by an outer peripheral wall 12a that is generally aligned with the balancer shaft axis and a bottom wall 12b that is generally aligned with a direction intersecting the balancer shaft axis, and that opens to the rear surface of the cylinder block 3. That is, the recess 12 has the outer peripheral wall 12a and the bottom wall 12b. The recess 12 is formed so as to open to the end of the cylinder block 3 in the balancer shaft direction.

[0022] The outer peripheral wall 12a defines the outer shape of the balance weight accommodating chamber 11 and is continuous in an annular shape when viewed in the balancer shaft axial direction (when viewed in the crankshaft axial direction). The bottom wall 12b defines the bottom surface of the recess 12 and is formed with a balancer shaft through-hole 14 through which the balancer shaft 9 passes.

[0023] In the balance weight accommodating chamber 11, the tip of the outer peripheral wall 12a of the recess 12 corresponds to the open end of the cylinder block 3 in the axial direction of the balancer shaft.

[0024] The cover member 13 is a flat plate member that faces the balance weight 10 and the bottom wall 12b of the recess 12, and is located inside the rear surface of the rear cover 6 and the cylinder block 3. The cover member 13 can also be configured as a part of the rear cover 6 by being integrated with the rear cover 6.

[0025] 1, the internal combustion engine body 7 is formed with an oil passage 15 that allows oil in the cylinder head 2 to drip toward the oil pan 4. The oil passage 15 passes through the lower deck of the cylinder head 2 and also passes through the cylinder block 3 to return the oil to the oil storage space in the oil pan 4. The oil passages 15 in this embodiment include a front oil passage 15a located on the rear side of the internal combustion engine 1 in the direction of cylinder alignment, and a rear oil passage 15b located on the rear side of the internal combustion engine 1 in the direction of cylinder alignment.

[0026] Here, the rear oil passage 15b returns oil to the oil pan 4 via the balance weight accommodating chamber 11. That is, as shown in FIGS. 1 and 3, the rear oil passage 15b, which serves as an oil return passage, is connected to the balance weight accommodating chamber 11. The rear oil passage 15b opens to the inner wall surface of the balance weight accommodating chamber 11, and allows oil from the cylinder head side to fall into the balance weight accommodating chamber 11. In this embodiment, an opening 16 of the rear oil passage 15b is formed in the upper part of the outer peripheral wall 12a of the recess 12, which is on the cylinder head 2 side.

[0027] Furthermore, the balance weight accommodating chamber 11 is located between the opening 16 of the rear oil passage 15b and the balancer shaft 9 (balance weight 10) in the vertical direction of the internal combustion engine 1, i.e., the vertical direction in which oil drips, and has an eave-shaped shielding wall 17 that covers only the upper part of the balance weight 10. In other words, the internal combustion engine 1 has the shielding wall 17 that is located between the opening 16 of the rear oil passage 15b and the balancer shaft 9 (balance weight 10) and covers only the upper part of the balance weight 10.

[0028] The shielding wall 17 is formed to rise from the inner peripheral surface of the recessed portion 12 toward the inside of the accommodation chamber 11. The shielding wall 17 is formed by casting integrally with the cylinder block 3 and is connected to the outer peripheral wall 12a and bottom wall 12b of the recessed portion 12. The shielding wall 17 is formed in a shape that is curved in an arc as a whole when viewed in the axial direction of the balancer shaft so that dripping oil is guided to the side (lateral side) of the balance weight 10. Most of the oil that drips onto the shielding wall 17 heads toward the tip of the shielding wall 17, passes between the tip of the shielding wall 17 and the outer peripheral wall 12a (the gap between the tip of the shielding wall 17 and the outer peripheral wall 12a on the right side of the shielding wall 17 in Figure 3), and reaches the lower part of the accommodation chamber 11 in the direction of gravity.

[0029] Furthermore, a gap is formed between the shielding wall 17 and the cover member 13 so that the shielding wall 17 near the cover member 13 is spaced from the cover member 13. Specifically, the shielding wall 17 is formed so that the tip side, as seen from the outer peripheral wall 12a from which the shielding wall 17 stands, is spaced from the cover member 13, and the base side, as seen from the outer peripheral wall 12a from which the shielding wall 17 stands, is in contact with the cover member 13. In other words, the shielding wall 17 is made up of a first wall portion 18, the end face in the axial direction of the balancer shaft of which is a contact end face 19 that comes into contact with the cover member 13, and a second wall portion 20, the end face in the axial direction of the balancer shaft of which is a non-contact end face 21 that does not come into contact with the cover member 13. The first wall portion 18 is a portion that is continuous with the outer peripheral wall 12a of the recess 12, and is the shielding wall 17 on the base end side as seen from the outer peripheral wall 12a. The second wall portion 20 is a portion that is continuous with the outer peripheral wall 12a of the recess 12 via the first wall portion 18, and is a shielding wall 17 on the tip side when viewed from the outer peripheral wall 12a.

[0030] The first wall portion 18 has a tip end in the axial direction of the balancer shaft sealed to the cover member 13 via a sealing material (not shown) such as a liquid gasket.

[0031] The second wall portion 20 is set so that the position of its tip in the axial direction of the balancer shaft is substantially the same as the position in the axial direction of the outer end face of the balance weight 10 that faces the cover member 13. In other words, the amount of protrusion of the second wall portion 20 from the bottom wall 12b is constant along the Y-axis direction. Therefore, the gap between the second wall portion 20 and the cover member 13 is constant along the Y-axis direction.

[0032] The contact end surface 19 is a portion that protrudes from the bottom wall 12b of the outer peripheral wall 12a of the recess 12 by the same amount in the axial direction of the balancer shaft as the tip surface of the outer peripheral wall 12a of the recess 12, and is the portion that comes into contact with the cover member 13. After the cylinder block 3 is cast, the contact end surface 19, together with the tip surface of the outer peripheral wall 12a of the recess 12, is subjected to a smoothing process by machining.

[0033] The non-contact end surface 21 protrudes less from the bottom wall 12b than the tip end surface of the outer peripheral wall 12a of the recess 12 in the axial direction of the balancer shaft, and is a portion that does not come into contact with the cover member 13. The non-contact end surface 21 is a portion that does not need to be smoothed by machining after the cylinder block 3 is cast.

[0034] The gap formed between the second wall portion 20, whose tip is the non-contact end surface 21, and the cover member 13 is set so as not to overlap with the opening 16 of the rear-side oil passage 15b in the axial direction of the balancer shaft. In other words, the rear-side oil passage 15b is formed so that the opening 16 to the balance weight accommodating chamber 11 does not overlap with the gap between the tip of the shielding wall 17 and the cover member 13 in the axial direction of the balancer shaft.

[0035] The end face of the shielding wall 17 in the axial direction of the balancer shaft corresponds to the open end of the cylinder block 3.

[0036] The balance weight accommodating chamber 11 also communicates with the oil storage space in the oil pan 4. More specifically, the balance weight accommodating chamber 11 has a communication passage (not shown) on the lower side in the vertical direction of the internal combustion engine 1 that communicates with the space between the rear cover 6 and the internal combustion engine body 7.

[0037] The communication passage is formed between the tip of the outer peripheral wall 12a and the cover member 13. In this embodiment, a communication passage recess 22 is provided by recessing a part of the tip of the outer peripheral wall 12a, and a gap is formed between the outer peripheral wall 12a and the cover member 13 to serve as the communication passage. Note that the communication passage may also be formed by providing a recess on the cover member 13 side to form a gap between the outer peripheral wall 12a and the tip of the outer peripheral wall 12a.

[0038] The oil in the balance weight accommodating chamber 11 is discharged through the communication passage into the space between the rear cover 6 and the internal combustion engine body 7 and then collected in the oil pan 4.

[0039] In the internal combustion engine 1 of the above-described embodiment, the shielding wall 17 covers the upper part of the balance weight 10 to prevent oil from directly contacting the upper part, and the shielding wall 17 does not obstruct the flow of blow-by gas toward the rear oil passage 15b inside the balance weight accommodating chamber 11. In other words, even though the shielding wall 17 is present in the balance weight accommodating chamber 11, the internal combustion engine 1 ensures a flow path for blow-by gas toward the rear oil passage 15b, and therefore, can ensure (guarantee) ventilation performance for blow-by gas.

[0040] In the internal combustion engine 1, if a mold is prepared, the shielding wall 17 can be formed integrally with the cylinder block 3, which makes manufacturing easier than attaching a separate part to the balance weight accommodating chamber 11 to form the shielding wall 17.

[0041] The tip end side of the shielding wall 17 as seen from the outer peripheral wall 12a has weaker structural rigidity than the base end side of the shielding wall 17 as seen from the outer peripheral wall 12a. However, the tip end side of the shielding wall 17 as seen from the outer peripheral wall 12a has a small amount of protrusion from the bottom wall 12b of the recess 12 along the balancer shaft axial direction so that it is spaced apart from the cover member 13, and there is no need to perform smoothing by machining.

[0042] When machining the outer wall 12a of the recess 12, which is the open end of the cylinder block 3, and the end face of the shielding wall 17 in the balancer shaft axial direction to smooth the internal combustion engine 1, it is possible to prevent the tip portion of the shielding wall 17, which is on the tip side as seen from the outer wall 12a, i.e., the tip portion of the second wall portion 20 as seen from the bottom wall 12b, from chipping off or getting caught in a tool.

[0043] The non-contact end surface 21 of the shielding wall 17 is set to have a gap between it and the cover member 13. Therefore, the internal combustion engine 1 does not need to set a sealing material such as a liquid gasket between the non-contact end surface 21 and the cover member 13, and the overall area required for the sealing material can be reduced.

[0044] In the internal combustion engine 1, the rear oil passage 15b is formed so that the opening 16 to the balance weight accommodating chamber 11 does not overlap with the gap between the tip of the shielding wall 17 and the cover member 13 in the balancer shaft axial direction.

[0045] Therefore, the internal combustion engine 1 can prevent oil dripping from the rear oil passage 15b into the balance weight accommodating chamber 11 from dripping downward through the gap between the shielding wall 17 and the cover member 13 and getting onto the balance weight 10.

[0046] 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.

[0047] For example, the shielding wall 17 may be inclined along the X-axis direction.

[0048] For example, the second wall portion 20 of the shielding wall 17 may vary the amount of protrusion from the bottom wall 12b of the recess 12 along the balancer shaft axial direction along the Y-axis direction, as long as oil does not get on the balance weight 10. [Explanation of symbols]

[0049] 1...Internal combustion engine 3...Cylinder block 6...Rear cover 7...Internal combustion engine body 9...Balancer shaft 10...Balance weight 11...Balance Weight Storage Room 12...Recess 12a...Outer wall 12b…Bottom wall 13...Cover member 15...Oil passage 15b...Rear oil passage 16...Opening 17…shielding wall 18…First wall part 19...Contact end surface 20…Second wall part 21…Non-contact end face 22...Recessed portion for communication passage

Claims

1. a balancer shaft rotatably supported by the cylinder block; a balance weight accommodating chamber formed in the cylinder block for rotatably accommodating a balance weight of the balancer shaft; an oil return passage for dropping oil into the balance weight accommodation chamber; a shielding wall that is located between the balancer shaft and an opening of the oil return passage that opens into the balance weight accommodating chamber, and that covers an upper portion of the balance weight; An internal combustion engine comprising:

2. 2. The internal combustion engine according to claim 1, wherein the shielding wall is cast integrally with the cylinder block.

3. The balance weight is attached to one end of the balancer shaft, the balance weight accommodating chamber is formed by a recess formed in the cylinder block so as to open at an end of the cylinder block in the axial direction of the balancer shaft, and a cover member that closes the recess, 3. The internal combustion engine according to claim 2, wherein the shielding wall is formed so as to rise from the inner circumferential surface of the recess toward the accommodation chamber.

4. the recess has an outer peripheral wall extending substantially along the balancer shaft axis and a bottom wall extending substantially along a direction intersecting the balancer shaft axis, 4. The internal combustion engine according to claim 3, wherein the shielding wall is connected to an outer peripheral wall and a bottom wall of the recess.

5. 5. The internal combustion engine according to claim 4, wherein a gap is formed between the shielding wall and the cover member so that the shielding wall near the cover member is spaced apart from the cover member.

6. 6. The internal combustion engine according to claim 5, wherein the gap is provided on the tip end side of the shielding wall, and not on the base end side.

7. 4. The internal combustion engine according to claim 3, wherein an opening of the oil return passage to the balance weight accommodating chamber is formed at a position that does not overlap with a gap between a tip end side of the shielding wall and the cover member in the balancer shaft axial direction.

8. 2. The internal combustion engine according to claim 1, wherein the balance weight accommodating chamber communicates with an oil storage space in an oil pan attached to a lower portion of the cylinder block.

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