JP7786303B2 - Oil mist separator and manufacturing method thereof - Google Patents

Description

The present invention relates to an oil mist separator and a method for manufacturing an oil mist separator.

Internal combustion engines are equipped with a PCV (Positive Crankcase Ventilation) passage that returns blow-by gas from the crankcase to the intake passage. An oil mist separator is installed midway through the PCV passage to separate oil mist contained in the blow-by gas (see, for example, Patent Document 1).

The oil mist separator disclosed in Patent Document 1 includes a case with an inlet through which blow-by gas flows and an outlet through which the blow-by gas flows. Inside the case is a separation section that separates the oil contained in the blow-by gas. At the bottom of the case is an oil discharge section that discharges the oil separated in the separation section into the interior of the cylinder head located below the case.

Japanese Patent Application Laid-Open No. 2019-127899

Incidentally, internal combustion engines with a high maximum engine output (hereinafter referred to as high-output internal combustion engines) are often operated at higher output than internal combustion engines with a low maximum engine output (hereinafter referred to as low-output internal combustion engines). For this reason, high-output internal combustion engines generate a lot of blow-by gas, which tends to increase the flow rate of the blow-by gas flowing inside the oil mist separator. As a result, if an oil mist separator used in low-output internal combustion engines is applied to a high-output internal combustion engine, the following problem occurs. Namely, the oil separated from the blow-by gas in the separation section is likely to be carried away by the blow-by gas into the intake passage before being discharged to the outside from the oil discharge section.

The oil mist separator that solves the above problem is an oil mist separator that separates oil mist from blow-by gas of an internal combustion engine, and includes: an inlet port that introduces blow-by gas into the oil mist separator, where the downstream side of the oil mist separator in the flow direction of the blow-by gas is defined as the downstream side; multiple branch passages located downstream of the inlet port and having a separation section that separates the oil mist contained in the blow-by gas and an oil discharge section that discharges the oil separated in the separation section to the outside of the oil mist separator; and an outlet port located downstream of the multiple branch passages that discharges the blow-by gas to the outside of the oil mist separator.

With this configuration, because the oil mist separator has multiple branch passages, the total cross-sectional area of the passages is larger than in a configuration that does not have multiple branch passages, i.e., a configuration in which the passages do not branch. This allows the flow speed of blow-by gas flowing through each branch passage to be reduced. As a result, the time required for blow-by gas to pass through the interior of the oil mist separator is increased. This makes it easier for the oil mist contained in the blow-by gas to be separated from the blow-by gas. Furthermore, by reducing the flow speed of the blow-by gas, it becomes less likely that the oil separated in the separation section will be carried away by the blow-by gas before it is discharged from the oil discharge section. This means that the amount of oil contained in the blow-by gas returned to the intake passage can be reduced.

FIG. 1 is a cross-sectional view of an oil mist separator according to one embodiment. FIG. 2 is a cross-sectional side view showing a state in which the first case according to the embodiment is molded. FIG. 3 is a cross-sectional side view illustrating a state in which the second case according to the embodiment is molded. FIG. 4 is a cross-sectional side view of an oil mist separator according to a comparative example.

Hereinafter, one embodiment of an oil mist separator will be described with reference to FIGS.
As shown in FIG. 1, the oil mist separator is provided midway in a PCV passage that returns blow-by gas in a crankcase of an internal combustion engine to an intake passage.

In the following description, the downstream side of the oil mist separator in the flow direction of the blow-by gas may be referred to as the downstream side.
The oil mist separator includes a first case 10 and a second case 20 .

A hose 30 is connected to the oil mist separator.
<First case 10>
As shown in FIG. 1, the first case 10 includes a first bottom wall 11 and a case body 10A.

The first bottom wall 11 extends in the left-right direction in FIG.
In the following description, the extension direction of the first bottom wall 11 will be simply referred to as the extension direction X. The up-down direction in Fig. 1 will be simply referred to as the up-down direction Y. The direction perpendicular to both the extension direction X and the up-down direction Y will be simply referred to as the width direction Z.

The case body 10A has a first top wall 12 and a first peripheral wall 13 .
The first top wall 12 is located above the first bottom wall 11 and faces the first bottom wall 11. The first peripheral wall 13 protrudes downward from the peripheral edge of the first top wall 12. The first peripheral wall 13 is provided around the entire periphery of the first top wall 12.

The lower peripheral edge of the first peripheral wall 13 is joined to the peripheral edge of the first bottom wall 11 .
The first bottom wall 11 is provided with an inlet 14 for introducing blow-by gas into the inside of the first case 10. The inlet 14 is located on one side (the left side in the figure) of the first bottom wall 11 in the extension direction X.

The first peripheral wall 13 is provided with a first exhaust port 19 that discharges blow-by gas to the outside of the first case 10. The first exhaust port 19 is located on the opposite side of the inlet port 14 in the extension direction X (the right side in the figure). The first exhaust port 19 is cylindrical and protrudes from the first peripheral wall 13 to the outside of the first case 10.

A first collision plate 17 is provided on the underside of the first top wall 12. The first collision plate 17 protrudes toward the first bottom wall 11. A gap 17a is provided between the first collision plate 17 and the first bottom wall 11, allowing blow-by gas to pass through. The first collision plate 17 is located between the inlet 14 and the first outlet 19 in the extension direction X.

The first bottom wall 11 is provided with an oil discharge section 18 that discharges oil separated by the first collision plate 17 to the outside of the first case 10. The oil discharge section 18 is located between the first collision plate 17 and the first discharge port 19 in the extension direction X.

A communication portion 15 that penetrates the first top wall 12 is provided above the inlet 14 in the first top wall 12 .
The first case 10 is made of hard resin.

<Second case 20>
1 , the second case 20 is provided above the first top wall 12. The second case 20 has a second top wall 21 and a second peripheral wall 22.

The second top wall 21 faces the first top wall 12 .
The second peripheral wall 22 protrudes downward from the peripheral edge of the second top wall 21 .
A lower peripheral edge 26 of the second peripheral wall 22 is joined to the upper surface of the first top wall 12. The communication portion 15 is located on the inner peripheral side of the peripheral edge 26. Therefore, the interior of the first case 10 and the interior of the second case 20 are in communication with each other through the communication portion 15.

The second peripheral wall 22 is provided with a second exhaust port 25 for discharging blow-by gas to the outside of the second case 20 .
The second discharge port 25 is located on the opposite side (the right side in the figure) from the communication portion 15 in the extension direction X. The second discharge port 25 is cylindrical and protrudes outward from the second peripheral wall 22 to the outside of the second case 20. The second discharge port 25 and the first discharge port 19 protrude parallel to each other.

A second collision plate 24 is provided on the underside of the second top wall 21. The second collision plate 24 protrudes toward the first top wall 12. A gap 24a is provided between the second collision plate 24 and the first top wall 12, allowing blow-by gas to pass through. The second collision plate 24 is located between the communication portion 15 and the second exhaust port 25 in the extension direction X.

The first top wall 12 is provided with an oil discharge section 27 that discharges oil separated by the second collision plate 24 into the inside of the first case 10, i.e., outside the second case 20. The oil discharge section 27 is located between the second collision plate 24 and the second discharge port 25 in the extension direction X. The oil discharge section 27 is also located at a different position from the second discharge port 25 in the width direction Z.

The second case 20 is made of hard resin.
The first collision plate 17 and the second collision plate 24 constitute a separation portion according to the present disclosure. The first case 10 constitutes a first branch passage 16 according to the present disclosure. The second case 20 constitutes a second branch passage 23. Therefore, the second branch passage 23 is connected to the first branch passage 16 by the connecting portion 15.

<Hose 30>
As shown in FIG. 1 , the hose 30 has a first connecting portion 31 , a second connecting portion 32 , and a junction portion 33 , all of which are cylindrical.

The first connection portion 31 is connected to the first outlet 19 .
The second connection portion 32 is connected to the second outlet 25 .
The confluence portion 33 is connected to the downstream side of both the first connection portion 31 and the second connection portion 32 and is connected to an intake passage (not shown).

Next, a method for manufacturing the oil mist separator will be described.
The manufacturing method includes a step of molding the first case 10, a step of molding the second case 20, and a step of joining the second case 20 to the first case 10.

<Step of molding the first case 10>
The process of forming the first case 10 includes a process of forming the case main body 10A, a process of forming the first bottom wall 11, and a process of joining the first bottom wall 11 to the case main body 10A.

First, the process of molding the case body 10A will be described.
As shown in FIG. 2, the first molding die 40 for molding the case body 10A includes a first upper die 41, a first lower die 42, and a slide die 43.

The first upper mold 41 and the first lower mold 42 are configured to be relatively movable in the up-down direction Y. The sliding mold 43 is configured to be slidable in the extension direction X.
The case body 10A is molded by injecting molten resin through the gate 41c into a cavity 44 formed by the first upper die 41, the first lower die 42, and the slide die 43.

The first top wall 12 and the first peripheral wall 13 are formed by the first upper mold 41 and the first lower mold 42. The first collision plate 17 is formed by the first lower mold 42. The inner peripheral surface and end surface of the first discharge port 19 are formed by the slide mold 43.

In this embodiment, the first upper mold 41 includes a mold body 41a and a nesting mold 41b that is detachably attached to the mold body 41a. The communicating portion 15 is formed by the nesting mold 41b.

The first case 10 is formed by joining a separately molded first bottom wall 11 to the molded case body 10A. The case body 10A and the first bottom wall 11 are joined by welding, for example.

<Step of molding second case 20>
As shown in FIG. 3 , the second molding die 50 for molding the second case 20 includes a second upper die 51 , a second lower die 52 , and a slide die 53 .

The second upper mold 51 and the second lower mold 52 are configured to be relatively movable in the up-down direction Y. The sliding mold 53 is configured to be slidable in the extension direction X.
The second case 20 is molded by injecting molten resin through the gate 51c into a cavity 54 formed by the second upper die 51, the second lower die 52, and the slide die 53.

The second top wall 21 and second peripheral wall 22 are formed by the second upper mold 51 and second lower mold 52. The second collision plate 24 is formed by the second lower mold 52. The inner peripheral surface and end surface of the second discharge port 25 are formed by the slide mold 53.

Finally, the oil mist separator is manufactured by joining the second case 20 to the first case 10. The first case 10 and the second case 20 are joined by welding, for example.

Next, the operation of this embodiment will be described.
Blow-by gas in the crankcase of the internal combustion engine is introduced into the first case 10 from the inlet 14 via a PCV passage (not shown).

A portion of the blow-by gas introduced into the first case 10 through the inlet 14 moves within the first case 10 toward the first outlet 19. As this occurs, the blow-by gas collides with the first collision plate 17, separating the oil mist contained in the blow-by gas. The separated oil travels along the first collision plate 17 onto the first bottom wall 11. The oil is then discharged below the first case 10, i.e., to the outside, through the oil discharge portion 18.

The remainder of the blow-by gas introduced into the first case 10 from the inlet 14 moves within the second case 20 toward the second outlet 25. At this time, the blow-by gas collides with the second collision plate 24, separating the oil mist contained in the blow-by gas. The separated oil travels along the second collision plate 24 onto the first top wall 12. The oil is then discharged into the interior of the first case 10 through the oil discharge portion 27, and then discharged below the first case 10, i.e., to the outside, through the oil discharge portion 18.

The blow-by gas discharged through the first discharge port 19 and the second discharge port 25 is drawn into the intake passage of the internal combustion engine via a hose 30 .
Next, the effects of this embodiment will be described.

(1) The oil mist separator includes the first branch passage 16 and the second branch passage 23 .
With this configuration, the total cross-sectional area of the passages is larger than in a configuration without multiple branch passages, i.e., a configuration without branch passages, as shown in FIG. 4 . This reduces the flow velocity of the blow-by gas flowing through the first branch passage 16 and the second branch passage 23. As a result, the time required for the blow-by gas to pass through the oil mist separator is increased. Therefore, the oil mist contained in the blow-by gas is more likely to be separated from the blow-by gas. Furthermore, the reduction in the flow velocity of the blow-by gas makes it less likely that the oil separated at the first collision plate 17 and the second collision plate 24 will be carried away by the blow-by gas before being discharged from the oil discharge portions 18 and 27. Therefore, the amount of oil contained in the blow-by gas recirculated to the intake passage can be reduced.

(2) The first branch passage 16 is formed by the first case 10, and the second branch passage 23 is formed by the second case 20. The first case 10 is provided with a communication portion 15.
With this configuration, part of the blow-by gas introduced into the first case 10 from the inlet 14 provided in the first case 10 flows toward the first collision plate 17 of the first case 10. On the other hand, the remaining blow-by gas flows toward the second collision plate 24 of the second case 20. Therefore, there is no need to provide an inlet in the second case 20. This makes it possible to simplify the configuration of the oil mist separator.

(3) The oil mist separator includes the first outlet 19 provided in the first case 10 and the second outlet 25 provided in the second case 20 .
For example, it is possible to omit the second exhaust port 25 of the second case 20 and return the blow-by gas in the second case 20 to the first case 10 through the oil exhaust portion 27. In this case, the exhaust port is provided only in the first case 10. However, in this case, there is a risk that the oil separated at the second collision plate 24 of the second case 20 will be carried into the first case 10 by the blow-by gas flowing inside the second case 20, and then carried into the intake passage by the blow-by gas flowing inside the first case 10.

In this regard, with the above configuration, the first case 10 is provided with a first exhaust port 19, and the second case 20 is provided with a second exhaust port 25. As a result, blow-by gas flowing inside the second case 20 is discharged to the outside through the second exhaust port 25, and the blow-by gas does not flow into the first case 10. This prevents the above-mentioned problem from occurring. Therefore, the amount of oil contained in the blow-by gas recirculated to the intake passage can be further reduced.

(4) The communication portion 15 is provided in the first top wall 12. The periphery 26 of the second peripheral wall 22 is joined to the first top wall 12.
With this configuration, the oil mist separator is formed by joining the peripheral edge 26 of the second peripheral wall 22 to the first top wall 12. Therefore, the first case 10 can be formed by making a simple design change such as providing the communication portion 15 in the top wall of an existing case. Furthermore, the oil mist separator can be formed by joining the second case 20, which has a simple configuration that has the second top wall 21 and the second peripheral wall 22 but no bottom wall, to the first case 10. This simplifies the configuration of the oil mist separator.

(5) The first case 10 having the communication portion 15 is molded by using the first molding die 40 in which the nesting die 41b is attached to the die body 41a.
Here, by using the first molding die 40 to which the insert die 41b is not attached, it is possible to mold a case that does not have the communication portion 15 shown in FIG.

Therefore, the first case 10 in this embodiment and a case constituting an oil mist separator that does not have multiple branch passages, i.e., a configuration in which the passages do not branch, can be manufactured using a common mold body 41a.

<Example of change>
This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

- In the above embodiment, the first case 10 and the second case 20 are arranged adjacent to each other in the vertical direction Y. However, the first case 10 and the second case 20 may also be arranged adjacent to each other in the width direction Z. In this case, the communication portion 15 may be provided in the first peripheral wall 13 of the first case 10.

The first case 10 and the second case 20 can also be spaced apart from each other. In this case, a second bottom wall can be provided to cover the lower opening of the second peripheral wall 22, and the first case 10 and the second case 20 can be connected by a hose or the like. With this configuration, the first branch passage 16 and the second branch passage 23 can be spaced apart from each other, which increases the flexibility in the shape of the oil mist separator.

The number of branch passages for the blow-by gas may be three or more. In this case, an oil mist separator can be realized by providing a case that configures the branch passages according to the number of branch passages.
The separation portion according to the present disclosure is not limited to plate portions such as the first collision plate 17 and the second collision plate 24. For example, the separation portion may be formed of a porous member through which blow-by gas can pass.

The above embodiment includes the configurations described in the following supplementary notes.
[Appendix 1] An oil mist separator that separates oil mist from blow-by gas of an internal combustion engine, comprising: an inlet for introducing blow-by gas into the oil mist separator, a plurality of branch passages located downstream of the inlet and having a separation section that separates the oil mist contained in the blow-by gas and an oil discharge section that discharges the oil separated in the separation section to the outside of the oil mist separator, where the downstream side of the oil mist separator in the flow direction of the blow-by gas is defined as the downstream side; and an outlet located downstream of the plurality of branch passages for discharging the blow-by gas to the outside of the oil mist separator.

[Appendix 2] The oil mist separator described in [Appendix 1], wherein the multiple branch passages include a first branch passage and a second branch passage, and the oil mist separator comprises a first case constituting the first branch passage and a second case constituting the second branch passage, the inlet is provided only in the first case, and the first case and the second case are provided with communication parts that connect the first branch passage and the second branch passage.

[Appendix 3] The oil mist separator described in [Appendix 2], wherein the outlets include a first outlet provided in the first case and a second outlet provided in the second case.

[Appendix 4] An oil mist separator as described in [Appendix 2] or [Appendix 3], wherein the first case has a first bottom wall, a first top wall facing the first bottom wall, and a first peripheral wall provided between the first bottom wall and the first top wall, the second case has a second top wall facing the first top wall, and a second peripheral wall provided between the first top wall and the second top wall, the communication portion is provided in the first top wall, and the peripheral edge of the second peripheral wall is joined to the first top wall.

[Appendix 5] A method for manufacturing an oil mist separator as described in any one of [Appendix 2] to [Appendix 4], comprising the steps of: molding the first case using a first molding die that is detachable from a mold body and has a nested die attached to the mold body for molding the communication portion; molding the second case using a second molding die; and joining the second case to the first case.

10... First case 10A... Case body 11... First bottom wall 12... First top wall 13... First peripheral wall 14... Inlet 15... Communication portion 16... First branch passage (branch passage)
17...First collision plate (separation part)
17a...Gap 18...Oil discharge part 19...First discharge port (discharge port)
20... Second case 21... Second top wall 22... Second peripheral wall 23... Second branch passage (branch passage)
24...Second collision plate (separation part)
24a...Gap 25...Second discharge port (discharge port)
26...Periphery 27...Oil discharge portion 30...Hose 31...First connection portion 32...Second connection portion 33...Confluence portion 40...First molding die 41...First upper die 41a...Die body 41b...Nesting die 41c...Gate 42...First lower die 43...Slide die 44...Cavity 50...Second molding die 51...Second upper die 51c...Gate 52...Second lower die 53...Slide die 54...Cavity

Claims (3)

An oil mist separator for separating oil mist from blow-by gas of an internal combustion engine, wherein the downstream side of the oil mist separator in the flow direction of the blow-by gas is defined as the downstream side:
an inlet for introducing blow-by gas into the oil mist separator;
a plurality of branch passages located downstream of the inlet, each branch passage having a separation section that separates oil mist contained in the blow-by gas and an oil discharge section that discharges the oil separated in the separation section to the outside of the oil mist separator;
an outlet located downstream of the plurality of branch passages and configured to discharge blow-by gas to the outside of the oil mist separator ,
the plurality of branch passages include a first branch passage and a second branch passage,
a first case that constitutes the first branch passage;
a second case that constitutes the second branch passage,
the inlet is provided only in the first case,
the first case is provided with a communication portion that communicates the first branch passage with the second branch passage,
the first case includes a first bottom wall, a first top wall opposite the first bottom wall, and a first peripheral wall provided between the first bottom wall and the first top wall;
the second case includes a second top wall facing the first top wall, and a second peripheral wall provided between the first top wall and the second top wall,
the communication portion is provided in the first top wall,
The periphery of the second peripheral wall is joined to the first top wall.
Oil mist separator. The exhaust port includes a first exhaust port provided in the first case and a second exhaust port provided in the second case.
2. The oil mist separator according to claim 1. A method for manufacturing the oil mist separator according to claim 1 or 2, comprising:
a step of molding the first case using a first molding die that is detachably attached to a mold body and that has a nesting die attached to the mold body, the nesting die molding the communicating portion;
molding the second case using a second mold;
and joining the second case to the first case.
Manufacturing method for oil mist separator.