Oil separator

Abstract

An oil separator comprises: a case (10) having inlets (11, 12), a gas outlet (14), and an oil discharge port (13); and a separation wall (21) provided inside the case (10). Inside the case (10), a first communication passage (23) and a second communication passage (24) are provided, which are defined by the separation wall (21) and communicate between an upstream flow path (15) and a downstream flow path (16). The first communication passage (23) has a smaller passage cross-sectional area than the second communication passage (24), and is provided at a position closer to a first side wall (33) than the second communication passage (24). Below the separation wall (21), a rib (43) is provided that has a fixed end connected to the first side wall (33) and a free end having a gap between itself and the second side wall (34), and that covers the first communication passage (23) from below.

Description

Oil Separator

[0001] The present disclosure relates to an oil separator.

[0002] Conventionally, there has been known an oil separator that is attached to a cylinder block of an internal combustion engine and separates oil from blow-by gas. As shown in FIG. 10, an oil separator 100 described in Patent Document 1 includes a case 110, and a first separation wall 111 and a second separation wall 112 provided inside the case 110. The interior of the case 110 is divided by the first separation wall 111 into an upstream flow path 110a located on the upstream side in the flow direction of blow-by gas, and a downstream flow path 110b located downstream of and above the upstream flow path 110a. The second separation wall 112 is provided in the downstream flow path 110b. Inflow ports 121 and 122 and an oil discharge port 123 communicate with the upstream flow path 110a. A gas outflow port 124 communicates with the downstream flow path 110b.

[0003] The case 110 forms the upstream flow path 110a and the downstream flow path 110b, and has a first side wall 113 and a second side wall 114 facing each other. A gap G is provided between the first separation wall 111 and the first side wall 113. A communication path 115 that communicates the upstream flow path 110a and the downstream flow path 110b is provided between the first separation wall 111 and the second side wall 114.

[0004] Blow-by gas that has flowed into the upstream flow path 110a from the inflow ports 121 and 122 collides with the lower surface of the first separation wall 111, then flows into the downstream flow path 110b through the communication path 115 and collides with the lower surface of the second separation wall 112. When the blow-by gas collides with the first separation wall 111 and the second separation wall 112, oil contained in the blow-by gas is separated. The oil separated in the upstream flow path 110a flows out of the case 110 through the oil discharge port 123. The oil separated in the downstream flow path 110b drops onto the upper surface of the first separation wall 111, then drops into the upstream flow path 110a through the gap G, and flows out of the case 110 through the oil discharge port 123. The blow-by gas from which oil has been separated flows out of the case 110 through the gas outflow port 124.

[0005] Japanese Patent Publication No. 2022-151029

[0006] In the oil separator 100, the upstream passage 110a and the downstream passage 110b are in communication via a gap G. Therefore, if the flow rate of blow-by gas flowing into the upstream passage 110a or the amount of oil contained in the blow-by gas is large, there is a risk that some of the blow-by gas may flow into the downstream passage 110b via the gap G without passing through the communication passage 115. In this case, the amount of oil flowing into the downstream passage 110b will increase, which may increase the amount of oil that flows out of the case 110 along with the blow-by gas from the gas outlet 124. Therefore, there is room for improvement in improving the oil separation performance of the oil separator.

[0007] An oil separator according to one aspect of the present disclosure comprises a case having an inlet for blow-by gas to flow in, a gas outlet for blow-by gas to flow out, and an oil outlet, and a separation wall provided inside the case, wherein the oil contained in the blow-by gas is separated by the separation wall and the separated oil is discharged to the outside of the case through the oil outlet, and when the upper and lower in the vertical direction are simply referred to as upper and lower, respectively, the inside of the case is divided by the separation wall into an upstream flow path located upstream of the blow-by gas flow direction and a downstream flow path located downstream of the upstream flow path and above the upstream flow path, and the upstream flow path The inlet and the oil outlet are in communication with each other, and the gas outlet is in communication with the downstream passage. The case has a first side wall and a second side wall that constitute the upstream passage and the downstream passage and are opposite to each other. Inside the case, there is a first connecting passage and a second connecting passage that are partitioned by the separation wall and connect the upstream passage and the downstream passage. The first connecting passage has a smaller cross-sectional area than the second connecting passage and is located closer to the first side wall than the second connecting passage. Below the separation wall, there is a rib that covers the first connecting passage from below, having a fixed end connected to the first side wall and a free end facing the second side wall.

[0008] Figure 1 is a perspective view showing an oil separator according to one embodiment. Figure 2 is a perspective view showing the inner case of the oil separator in Figure 1. Figure 3 is a front view showing the inner case of the oil separator in Figure 1. Figure 4 is an enlarged view of the inner case in Figure 3, centered on the ribs. Figure 5 is a cross-sectional view of the oil separator along line 5-5 in Figure 3. Figure 6 is a perspective view showing the outer case of the oil separator in Figure 1. Figure 7 is a cross-sectional perspective view showing the interior of the oil separator in Figure 1. Figure 8 is a cross-sectional view of the oil separator along line 8-8 in Figure 3. Figure 9 is a front view showing the inner case of a modified oil separator. Figure 10 is a front view showing a conventional oil separator.

[0009] An embodiment of the oil separator will be described below with reference to Figures 1 to 8. The oil separator of this embodiment is attached to the side of the cylinder block that constitutes the engine body of an internal combustion engine and separates the oil contained in the blow-by gas into liquid and gas.

[0010] (Case 10) As shown in Figure 1, the oil separator includes a case 10 that is attached to the side of the cylinder block (not shown).

[0011] Hereafter, the direction of blow-by gas flow will simply be referred to as the flow direction. The direction in which the case 10 faces the side of the cylinder block will be referred to as the opposing direction. The direction perpendicular to both the vertical direction and the opposing direction will be referred to as the width direction. Furthermore, the upper and lower parts of the vertical direction will simply be referred to as the upper and lower parts, respectively. Of the opposing directions, the side closer to the cylinder block will be referred to as the inner side, and the side further away from the cylinder block will be referred to as the outer side.

[0012] The case 10 comprises an inner case 30 attached to the side of the cylinder block and an outer case 50 provided on the opposite side of the cylinder block from the inner case 30. The inner case 30 and the outer case 50 are joined to each other. The inner case 30 and the outer case 50 are formed of, for example, a resin material.

[0013] Next, the internal structure of case 10 will be described with reference to Figures 2 and 3, which show the internal structure of the inner case 30, for convenience. As shown in Figures 2 and 3, case 10 has a first inlet 11 and a second inlet 12 into which blow-by gas flows, an oil outlet 13 from which oil is discharged, and a gas outlet 14 from which blow-by gas flows out. The first inlet 11, the second inlet 12, and the oil outlet 13 are located at the bottom of case 10. The gas outlet 14 is located at the top of case 10. The first inlet 11, the second inlet 12, and the oil outlet 13 are arranged in this order in a direction that intersects vertically.

[0014] Inside the case 10, there are a first separation wall 21 and a second separation wall 22 for separating oil contained in the blow-by gas. The first separation wall 21 is located above the second inlet 12. The second separation wall 22 is located above the oil outlet 13. The second separation wall 22 is located higher than the first separation wall 21.

[0015] As shown in Figure 3, the interior of the case 10 is divided into an upstream flow path 15 and a downstream flow path 16 by a first separation wall 21. The upstream flow path 15 is located on the upstream side in the flow direction within the interior of the case 10. The downstream flow path 16 is located downstream and above the upstream flow path 15. The upstream flow path 15 is connected to the inlets 11 and 12 and the oil outlet 13.

[0016] Inside the case 10, there are a first connecting passage 23 and a second connecting passage 24, which are partitioned by a first separation wall 21 and connect the upstream flow path 15 and the downstream flow path 16. The first connecting passage 23 has a smaller cross-sectional area than the second connecting passage 24. The first connecting passage 23 is located closer to the first side wall 33 (described later) than the second connecting passage 24. The first connecting passage 23 is formed by the gap between the first separation wall 21 and the first side wall 33. The first connecting passage 23 is located directly above the second inlet 12. The second connecting passage 24 is formed by the gap between the first separation wall 21 and the second side wall 34 (described later). The second connecting passage 24 is located directly above the oil outlet 13. The second separation wall 22 is located directly above the second connecting passage 24.

[0017] The downstream channel 16 is divided into a first downstream channel 16a and a second downstream channel 16b by a second separation wall 22. The first downstream channel 16a is located upstream in the flow direction within the downstream channel 16. The second downstream channel 16b is located downstream and above the first downstream channel 16a in the flow direction. The gas outlet 14 is connected to the second downstream channel 16b.

[0018] Inside case 10, a third connecting passage 25 is provided, which is partitioned by a second separation wall 22 and connects the first downstream channel 16a and the second downstream channel 16b. The third connecting passage 25 is formed by the gap between the second separation wall 22 and the first side walls 33 and 53, which will be described later. The third connecting passage 25 is located directly above the first separation wall 21. The first connecting passage 23 and the third connecting passage 25 are aligned vertically. The second connecting passage 24 and the third connecting passage 25 are not aligned vertically. The second connecting passage 24 and the third connecting passage 25 are located on opposite sides in the width direction.

[0019] (Inner Case 30) As shown in Figures 2 and 3, the inner case 30 has an inner opposing wall 31 and a peripheral wall 32. The inner opposing wall 31 faces the side surface of the cylinder block. The peripheral wall 32 protrudes outward from the periphery of the inner opposing wall 31 over its entire circumference. On the surface of the peripheral wall 32 facing the outer case 50, a joint portion (not shown) that is joined to the outer case 50 is provided over its entire circumference.

[0020] The inner opposing wall 31 has a first portion 31a and a second portion 31b. The first portion 31a is a roughly rectangular shape that is elongated in the vertical direction. The second portion 31b extends from the lower part of the first portion 31a to one side in the width direction. The inner opposing wall 31 as a whole has a roughly L-shape.

[0021] The peripheral wall 32 has a first side wall 33 and a second side wall 34 that face each other in the width direction. The first side wall 33 and the second side wall 34 constitute both the upstream channel 15 and the downstream channel 16.

[0022] The first side wall 33 has an upper first side wall 33a and a lower first side wall 33b. The upper first side wall 33a protrudes outward from the first end in the width direction of the first portion 31a. The lower first side wall 33b protrudes outward from the first end in the width direction of the second portion 31b.

[0023] The second side wall 34 protrudes outward from the second end of the first portion 31a opposite to the first end in the width direction. The second side wall 34 faces the upper first side wall 33a and the lower first side wall 33b in the width direction.

[0024] The peripheral wall 32 has a connecting wall 35 that connects the upper first side wall 33a and the lower first side wall 33b. The connecting wall 35 extends in the width direction and faces the portion of the peripheral wall 32 that constitutes the bottom surface of the inner case 30.

[0025] As shown in Figure 3, a first inlet 11, a second inlet 12, and an oil outlet 13 are provided at intervals from each other at the lower part of the inner opposing wall 31. The first inlet 11, the second inlet 12, and the oil outlet 13 are provided in this order from the first side wall 33 toward the second side wall 34. The second inlet 12 is located below the first inlet 11. The oil outlet 13 is located below the second inlet 12.

[0026] A gas outlet 14 is provided at the top of the inner opposing wall 31. The gas outlet 14 communicates with a passage (not shown) of the internal combustion engine. The gas outlet 14 is located above the oil outlet 13.

[0027] (First partition plate 41) A first partition plate 41 is provided between the first side wall 33 and the second side wall 34, above the second inlet 12. The first partition plate 41 protrudes outward from the first portion 31a of the inner opposing wall 31. The first partition plate 41 is provided between the upper first side wall 33a and the second side wall 34. The first partition plate 41 extends inclined with respect to the horizontal direction such that it is positioned lower as it moves from the side where the second side wall 34 is located toward the side where the first side wall 33 is located.

[0028] The interior of the inner case 30 is divided into an upstream flow path 15 and a first downstream flow path 16a by a first partition plate 41. The first partition plate 41 constitutes a part of the first separation wall 21. As shown in Figure 4, the first partition plate 41 has a first end and a second end that face the first side wall 33 and the second side wall 34, respectively, in the width direction. A gap is provided between the first end of the first partition plate 41 and the first side wall 33, forming a first connecting passage 23. A gap is provided between the second end of the first partition plate 41 and the second side wall 34, forming a second connecting passage 24. The second end of the first partition plate 41 is located above the portion between the second inlet 12 and the oil outlet 13 (see Figure 3).

[0029] (Rib 43) Below the first partition plate 41, a rib 43 is provided that covers the first connecting passage 23 from below. The rib 43 is separated downward from the first partition plate 41. The rib 43 is flat. The rib 43 protrudes outward from the first portion 31a of the inner opposing wall 31. The rib 43 is located between the upper first side wall 33a and the second side wall 34, and is provided directly above the second inlet 12.

[0030] The rib 43 has a fixed end 43a and a free end 43b. The fixed end 43a is connected to the upper first side wall 33a. The free end 43b faces the second side wall 34 in the width direction. The free end 43b is located below the first partition plate 41. A gap is provided between the free end 43b and the second side wall 34. The rib 43 extends inclined with respect to the horizontal direction such that it is located lower as it moves from the side where the first side wall 33 is located towards the side where the second side wall 34 is located.

[0031] As shown in Figure 2, the amount of protrusion of the rib 43 from the inner opposing wall 31 is greater than the amount of protrusion of the peripheral wall 32 from the inner opposing wall 31. For this reason, as shown in Figure 5, the rib 43 extends from the inner opposing wall 31 beyond the first connecting passage 23 to a position below the first partition plate 61 of the outer case 50, which will be described later. A gap is provided between the tip of the rib 43 in the opposing direction and the inner surface of the outer opposing wall 51 of the outer case 50.

[0032] (Second partition plate 42) As shown in Figure 3, a second partition plate 42 is provided above the first partition plate 41 and above the oil discharge port 13. The second partition plate 42 protrudes outward from the first portion 31a of the inner opposing wall 31. The second partition plate 42 extends inclined with respect to the horizontal direction such that it is positioned lower as it moves from the second side wall 34 toward the side where the first side wall 33 is located.

[0033] The interior of the inner case 30 is divided into a first downstream channel 16a and a second downstream channel 16b by a second partition plate 42. The second partition plate 42 constitutes part of the second separation wall 22.

[0034] The second partition plate 42 has an end portion 42a that faces the first side wall 33 in the width direction. A gap is provided between the end portion 42a and the first side wall 33, which forms part of the third connecting passage 25. The end portion 42a is located above the portion between the second inlet 12 and the oil outlet 13.

[0035] The surface of the second partition plate 42 facing the outer case 50 is provided with a joint portion (not shown) that is joined to the outer case 50. Therefore, the inner case 30 is joined to the outer case 50 at the peripheral wall 32 and the second partition plate 42.

[0036] (First shielding plate 44) The second downstream channel 16b is provided with a first shielding plate 44 that protrudes outward from the first portion 31a of the inner opposing wall 31. The first shielding plate 44 extends vertically. The first shielding plate 44 is connected to the upper portion of the second partition plate 42 of the peripheral wall 32.

[0037] As shown in Figure 2, the amount of protrusion of the first shielding plate 44 from the inner opposing wall 31 is greater than the amount of protrusion of the peripheral wall 32 from the inner opposing wall 31. Therefore, as shown in Figure 8, the tip of the first shielding plate 44 is located inside the outer case 50. A gap is provided between the tip of the first shielding plate 44 in the opposing direction and the inner surface of the outer case 50.

[0038] (Fixing parts 36) As shown in Figure 3, a plurality of fixing parts 36 are provided on the periphery of the inner case 30. The plurality of fixing parts 36 protrude outward from the outer circumference of the inner case 30 and are fixed to the cylinder block. Each fixing part 36 has an insertion hole 36a. Bolts (not shown) for fixing the inner case 30 to the cylinder block are inserted into the insertion holes 36a.

[0039] (Outer case 50) As shown in Figure 6, the outer case 50 has an outer opposing wall 51 and a peripheral wall 52. The outer opposing wall 51 faces the inner opposing wall 31 of the inner case 30. The peripheral wall 52 protrudes inward from the periphery of the outer opposing wall 51 all the way around.

[0040] The outer opposing wall 51 has a first portion 51a and a second portion 51b. The first portion 51a is a roughly rectangular shape that is elongated in the vertical direction. The second portion 51b extends from the lower part of the first portion 51a to one side in the width direction. The outer opposing wall 51 as a whole has a roughly L-shape.

[0041] The peripheral wall 52 has a first side wall 53 and a second side wall 54 that face each other in the width direction. The first side wall 53 and the second side wall 54 constitute both the upstream channel 15 and the downstream channel 16.

[0042] Some of the components of the outer case 50 have shapes that correspond to the components of the inner case 30. For this reason, in the following, for components of the outer case 50 that correspond to the components of the inner case 30, we may omit redundant explanations by adding the symbols "5*" and "6*", which are obtained by adding "20" to the symbols "3*" and "4*" that indicate the components of the inner case 30.

[0043] (First partition plate 61) Between the first side wall 53 and the second side wall 54, a first partition plate 61 is provided that divides the inside of the outer case 50 into an upstream channel 15 and a first downstream channel 16a. The first partition plate 61 faces the first partition plate 41 of the inner case 30 in the opposing direction. The first partition plate 61 connects the first side wall 53 and the second side wall 54.

[0044] The first partition plate 61 forms a part of the first separation wall 21. From the above, in the present embodiment, the first separation wall 21 is configured by the first partition plate 41 of the inner case 30 and the first partition plate 61 of the outer case 50. Further, as shown in FIG. 7, the second communication passage 24 is formed by the gap between the first partition plate 41 of the inner case 30 and the second side wall 34, and the first partition plate 61 of the outer case 50.

[0045] (Second partition plate 62) As shown in FIG. 6, above the first partition plate 61, a second partition plate 62 that partitions the interior of the outer case 50 into the first downstream flow path 16a and the second downstream flow path 16b is provided. The second partition plate 62 is entirely joined to the second partition plate 42 of the inner case 30 in the opposing direction.

[0046] The second partition plate 62 forms a part of the second separation wall 22. From the above, in the present embodiment, the second separation wall 22 is configured by the second partition plate 42 of the inner case 30 and the second partition plate 62 of the outer case 50.

[0047] Between the end 62a of the second partition plate 62 opposing the upper first side wall 53a and the upper first side wall 53a, there is provided a gap that forms a part of the third communication passage 25. From the above, the third communication passage 25 is configured by the gap between the end 42a of the second partition plate 42 in the inner case 30 and the first side wall 33, and the gap between the end 62a of the second partition plate 62 in the outer case 50 and the first side wall 53.

[0048] (Second shielding plate 63 and third shielding plate 64) In the second downstream flow path 16b, a second shielding plate 63 and a third shielding plate 64 protruding inward from the first portion 51a of the outer opposing wall 51 are provided. The second shielding plate 63 and the third shielding plate 64 are provided spaced apart from each other in the width direction. The third shielding plate 64 is provided further downstream in the flow direction than the second shielding plate 63.

[0049] The second shielding plate 63 and the third shielding plate 64 extend vertically. The second shielding plate 63 and the third shielding plate 64 are connected to the upper portion of the peripheral wall 52 above the second partition plate 62. The amount of protrusion of the second shielding plate 63 and the third shielding plate 64 from the outer opposing wall 51 is greater than the amount of protrusion of the peripheral wall 52 from the outer opposing wall 51. The amount of protrusion of the second shielding plate 63 is greater than the amount of protrusion of the third shielding plate 64. Therefore, as shown in Figure 8, the respective ends of the second shielding plate 63 and the third shielding plate 64 are located inside the inner case 30. A gap is provided between the respective ends of the second shielding plate 63 and the third shielding plate 64 in the opposing direction and the inner surface of the inner case 30.

[0050] The first shielding plate 44 of the inner case 30 is located between the second shielding plate 63 and the third shielding plate 64. As a result, in the second downstream flow path 16b, the shielding plates 63, 44, and 64 form a flow path in which the blow-by gas flows in a meandering manner.

[0051] <Operation of this embodiment> As shown by the solid arrows in Figure 3, the blow-by gas flowing into the upstream flow path 15 inside the case 10 from each inlet 11, 12 collides with the lower surface of the connecting walls 35, 55 located above each inlet 11, 12, or with the lower surface of the first separation wall 21. As a result, as shown by the dashed arrows in Figure 3, mainly liquid oil with relatively large particle sizes is separated from the blow-by gas. The oil separated from the blow-by gas falls due to its own weight and accumulates at the bottom of the case 10, and is discharged to the outside of the case 10 through the oil outlet 13.

[0052] After the blow-by gas strikes the lower surface of the connecting walls 35, 55 or the lower surface of the first separation wall 21, it flows into the first downstream passage 16a through the second connecting passage 24. The blow-by gas that flows into the first downstream passage 16a strikes the lower surface of the second separation wall 22, which is located above the second connecting passage 24. As a result, mist-like oil particles, which have smaller particle sizes than liquid oil, are separated from the blow-by gas from the oil that was not separated from the blow-by gas by the first separation wall 21.

[0053] After impacting the second separation wall 22, the blow-by gas flows into the second downstream passage 16b through the third connecting passage 25. The blow-by gas flowing into the second downstream passage 16b then impacts the shielding plates 63, 44, and 64. This separates the mist-like oil from the blow-by gas. Subsequently, the blow-by gas flows out of the case 10 through the gas outlet 14.

[0054] As shown by the dashed arrows in Figure 4, the oil separated in the downstream channel 16 falls onto the upper surface of the first separation wall 21, then through the first connecting passage 23 onto the upper surface of the rib 43 located in the upstream channel 15. The oil then flows down the upper surface of the rib 43 to the bottom of the case 10 and is discharged to the outside of the case 10 through the oil outlet 13.

[0055] <Effects of this embodiment> (1) Inside the case 10, a first connecting passage 23 and a second connecting passage 24 are provided, which are partitioned by a first separation wall 21 and connect the upstream flow path 15 and the downstream flow path 16. Below the first separation wall 21, a rib 43 is provided that covers the first connecting passage 23 from below.

[0056] According to the above configuration, the first connecting passage 23 is covered from below by the rib 43. As a result, blow-by gas flowing into the upstream passage 15 from each inlet 11, 12 can easily flow into the downstream passage 16 via the second connecting passage 24 without passing through the first connecting passage 23. This prevents oil contained in the blow-by gas from flowing from the upstream passage 15 to the downstream passage 16 through the first connecting passage 23.

[0057] Furthermore, oil is separated from the blow-by gas when the blow-by gas collides with the lower surface of the rib 43 in addition to the lower surface of the first separation wall 21. This increases the amount of oil separated from the blow-by gas in the upstream passage 15.

[0058] As a result of the above, the amount of oil contained in the blow-by gas flowing into the downstream passage 16 is less likely to increase, and therefore the amount of oil flowing out of the case 10 is less likely to increase. Consequently, the oil separation performance of the oil separator can be improved.

[0059] Furthermore, for example, if the vertical size of the oil separator is reduced due to design changes, reducing the volume of the downstream passage 16 may decrease the separation efficiency of mist-like oil. In this case, it is possible to reduce the volume of the upstream passage 15 by reducing its vertical dimensions without changing the volume of the downstream passage 16. When such a design change is made to the conventional oil separator 100 shown in Figure 10, the vertical distance between the gap G and the inlet 122 becomes shorter. As a result, blow-by gas flowing from the inlet 122 into the upstream passage 110a can more easily flow into the downstream passage 110b via the gap G.

[0060] In this respect, in the separator of this embodiment, the first communication passage 23 is covered from below by the rib 43. Therefore, even when the vertical distance between the first communication passage 23 and the second inlet 12 becomes shorter, it is possible to suppress the flow of blow-by gas from the upstream passage 15 through the first communication passage 23 to the downstream passage 16. As a result, even when the volume of the upstream passage 15 is reduced without changing the volume of the downstream passage 16, it is possible to suppress a decrease in the oil separation performance in the downstream passage 16. Therefore, the design flexibility of the oil separator can be improved.

[0061] (2) The first connecting passage 23 is formed by the gap between the first partition plate 41 and the first side wall 33 that constitute the first separation wall 21. With the above configuration, since the first connecting passage 23 is formed by the first side wall 33, it is possible to suppress the length of the rib 43 extending from the first side wall 33 from becoming excessively long. For this reason, it is possible to suppress the increase in the amount of material required for manufacturing the oil separator that occurs when the rib 43 is provided on the oil separator.

[0062] (3) The first separation wall 21 extends inclined with respect to the horizontal direction such that it is located lower as it moves from the side where the second side wall 34 is located toward the side where the first side wall 33 is located. The rib 43 extends inclined with respect to the horizontal direction such that it is located lower as it moves from the side where the first side wall 33 is located toward the side where the second side wall 34 is located.

[0063] With the above configuration, the oil separated in the downstream flow path 16 and falling onto the upper surface of the first separation wall 21 is more likely to move towards the first connecting passage 23 due to its own weight. Furthermore, the oil that falls from the first connecting passage 23 onto the upper surface of the rib 43 is more likely to fall to the bottom of the case 10 due to its own weight. Therefore, the oil discharge performance of the oil separator can be improved.

[0064] (4) The rib 43 is located directly above the second inlet 12. With the above configuration, blow-by gas flowing into the upstream passage 15 from the second inlet 12 is more likely to collide with the lower surface of the rib 43. This makes it easier to separate oil from the blow-by gas through the collision between the blow-by gas and the rib 43.

[0065] <Examples of Modifications> This embodiment can be implemented with the following modifications. This embodiment and the following examples of modifications can be combined with each other to the extent that they do not contradict each other technically.

[0066] - The second inlet 12 may be located directly below the connecting wall 35. In this case, the rib 43 does not have to be located directly above the second inlet 12. - As shown in Figure 9, the first partition plate 41 may have a first inclined portion 41a and a second inclined portion 41b. The first inclined portion 41a is connected to the first side wall 33. The second inclined portion 41b is located at a distance from the first inclined portion 41a towards the side where the second side wall 34 is located. The first inclined portion 41a extends inclined with respect to the horizontal direction such that it is located lower as it moves from the side where the first side wall 33 is located towards the side where the second side wall 34 is located. The second inclined portion 41b extends inclined with respect to the horizontal direction such that it is located lower as it moves from the side where the second side wall 34 is located towards the side where the first side wall 33 is located. The first connecting passage 23 is formed by the gap between the first inclined portion 41a and the second inclined portion 41b. The rib 43 covers the first inclined portion 41a and the second inclined portion 41b from below. Even with this configuration, oil that falls onto the upper surface of the first separation wall 21 is more likely to be directed towards the first connecting passage 23 by its own weight.

[0067] - The first separation wall 21 may extend horizontally. - The rib 43 may extend horizontally. - The first connecting passage 23 may be formed by through holes formed in the first separation wall 21.

[0068] - The case 10 may be provided with one or more inlets. - The oil separator may be mounted on the cylinder block in a position where it is located lower as it moves from the outer case 50 towards the inner case 30. In this case, the oil separated from the blow-by gas in the downstream passage 16 and falling onto the upper surface of the first separation wall 21 is more easily guided toward the first connecting passage 23.

Claims

1. An oil separator comprising: a case having an inlet for blow-by gas to flow in, a gas outlet for blow-by gas to flow out, and an oil outlet; a separation wall provided inside the case, wherein the oil contained in the blow-by gas is separated by the separation wall and the separated oil is discharged to the outside of the case through the oil outlet, wherein when the upper and lower directions in the vertical direction are simply referred to as upper and lower, respectively, the inside of the case is divided by the separation wall into an upstream passage located upstream of the blow-by gas flow direction and a downstream passage located downstream and above the upstream passage in the flow direction, the inlet and the oil outlet are in communication with the upstream passage, the gas outlet is in communication with the downstream passage, and the case has a first side wall and a second side wall that constitute the upstream passage and the downstream passage and are opposite to each other. An oil separator is provided, inside the case, which is partitioned by the separation wall and has a first connecting passage and a second connecting passage that connect the upstream passage and the downstream passage, the first connecting passage having a smaller cross-sectional area than the second connecting passage and being located closer to the first side wall than the second connecting passage, and below the separation wall, there is a rib that covers the first connecting passage from below, having a fixed end connected to the first side wall and a free end facing the second side wall.

2. The oil separator according to claim 1, wherein the first connecting passage is formed by the gap between the separation wall and the first side wall.

3. The oil separator according to claim 1 or claim 2, wherein the separation wall extends inclined with respect to the horizontal direction such that it is located lower as it moves from the side where the second side wall is located toward the side where the first side wall is located, and the rib extends inclined with respect to the horizontal direction such that it is located lower as it moves from the side where the first side wall is located toward the side where the second side wall is located.

4. The oil separator according to any one of claims 1 to 3, wherein the rib is provided directly above the inlet.

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