Oil separator

In an oil separator that separates mist oil contained in target gas from the gas, the present disclosure is aimed to easily mount the oil separator to various targets and to increase its versatility. An oil separator according to the present disclosure includes: a nozzle that injects oil from an injection hole to rotate a spindle around an axis; a housing having a gas communicating portion and an oil communicating portion on its bottom; and a joint member that is removably mounted to the housing, and that includes a gas introducing portion and an oil discharge portion, the gas introducing portion introducing blow-by gas and transferring the gas to the gas communicating portion, the oil discharge portion receiving oil from the oil communicating portion and discharging the oil to outside.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 371 U.S. National Stage of International Application No. PCT/JP2014/054630, filed Feb. 26, 2014. The disclosures of the above application are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an oil separator that separates mist oil contained in target gas from the gas.

BACKGROUND ART

There has been known an oil separator that separates mist oil contained in target gas from the gas. For example, an oil separator described in Patent Literature 1 includes a cylindrical stationary housing, a cylindrical stationary casing with a ceiling, and a conical partition with an opening on the top surface. These components define a lower chamber and an upper chamber. The lower chamber includes a centrifugal rotor to clean oil. The upper chamber includes a gas cleaning device to clean gas. A lower end of the stationary housing is coupled to a base. The lower chamber is communicated with an internal space of the tubular base.

This tubular base is communicated with a combustion engine. Oil after being cleaned is returned to the combustion engine and gas from a crankcase is introduced to the combustion engine. In the internal space of the tubular base, a tubular fixing member is disposed which fixes the lower end of the shaft. Through the fixing member, oil to be cleaned is supplied.

The centrifugal rotor and the gas cleaning device are coupled with a tubular supporting member and are rotatable around a stationary shaft inserted through the supporting member. The centrifugal rotor internally includes a separation chamber. The oil is supplied to this separation chamber through a clearance between the supporting member and the stationary shaft and through an opening open at the supporting member. After the cleaning in the separation chamber, the supplied oil is discharged to a side portion through discharge ports disposed at a bottom surface of the centrifugal rotor. Discharging the oil generates a driving power to rotate the centrifugal rotor and the gas cleaning device.

CITATION LIST

Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2005-515065

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

In the foregoing oil separator, the lower chamber is coupled to the tubular base, and therefore is not versatile. That is, the lower chamber is needed to be prepared for each engine to which an oil separator is to be mounted. In addition, a supply passage for oil is restricted because oil is supplied through the fixing member disposed inside the tubular base. This also worsens the versatility of the oil separator. In addition, it is difficult to mount the oil separator to a target object other than an engine, for example, a vehicle body.

The present invention has been made under these circumstances, and an object of the present invention is to provide a highly versatile oil separator which is easy to mount to various targets.

Summary of Invention

To achieve the above-described object, the present invention is an oil separator for separating mist oil contained in target gas, the oil separator including: a rotor that are rotatable together with a spindle and separates the mist oil by rotation; a nozzle that is projected from a part of a peripheral surface of the spindle, the part being located below the rotor, and that injects oil from an injection hole to rotate the spindle around an axis; a housing including: an oil supply portion that supplies oil to be injected from the injection hole; an oil communicating portion for discharging oil injected from the injection hole; and a gas communicating portion for introducing the target gas; and a joint member that is removably mounted to the housing, and that includes a gas introducing portion and an oil discharge portion, the gas introducing portion introducing the target gas from outside and transferring the target gas to the gas communicating portion, the oil discharge portion receiving oil from the oil communicating portion and discharging the oil to outside.

According to the present invention, the gas introducing portion introducing the target gas from outside and the oil discharge portion discharging the oil to outside are disposed of a joint. In addition, the joint is removably mounted to the housing. Accordingly, it is possible to easily mount the oil separator to various target by preparing an appropriate type of the joint for each target object.

In the above-described oil separator, it is preferable that the joint member includes a common chamber communicating with each of the oil communicating portion, the gas communicating portion, the gas introducing portion, and the oil discharge portion and that the oil communicating portion and the gas communicating portion communicate an upper portion of the common chamber, and that the gas introducing portion communicates a side portion of the common chamber, and that the oil discharge portion communicates a lower portion of the common chamber. In such a configuration, in the common chamber, the target gas introduced the gas introducing portion come into contact with the oil which is flowing down from the oil communicating portion. Accordingly, oil mist contained in the target gas is partially taken into the oil, and this can increase the removal efficiency of oil in the target gas.

In the above-described oil separator, it is preferable that the oil communicating portion is composed of a through-opening formed on a bottom of the housing and penetrating the bottom in a thickness direction and that the gas communicating portion is composed of a tubular portion projecting upward from the bottom of the housing. In such a configuration, the tubular portion constituting the gas communicating portion defines a passage for the target gas. Accordingly, even if oil accumulates at the bottom of the housing, the gas communicating portion ensures a passage for the target gas. Consequently, a large amount of flowing target gas pushes back oil upward, and this can prevent a failure of deterioration of the removal efficiency of oil in blow-by gas.

In the above-described oil separator, it is preferable that an opening of a gas outlet of the gas communicating portion is located on an inner peripheral side with respect to a path of the injection hole. In such a configuration, it is possible to efficiently introduce the target gas.

In the above-described oil separator, it is preferable that the oil separator further comprises a bracket, and that the bracket is mounted to the housing and serves as a section on which the oil separator is mounted to a supporting body. In such a configuration, it is possible to mount the oil separator to a target object other than an engine. For example, the oil separator can be mounted to a vehicle body. In addition, since the mounting position of the bracket to be close to the center of gravity of each rotator (a separation disk, a nozzle, and a spindle), vibration and wobble of the oil separator can be prevented.

Advantageous Effects of Invention

According to the present invention, in an oil separator that separates mist oil contained in target gas from the gas, it is possible to easily mount the oil separator to various targets and to increase its versatility.

DETAILED DESCRIPTION

The following describes embodiments of the present invention with reference to the drawings. The following describes with an example of a closed crankcase ventilation system1(hereinafter referred to as a ventilation system1) illustrated inFIG. 1.

As illustrated inFIG. 1, the ventilation system1includes an oil separator2and a breather pipe3. The oil separator2processes blow-by gas (equivalent to target gas containing mist oil) discharged from an engine4to separate the mist oil. In this embodiment, the oil separator2is mounted at a side surface of an engine4, which is a target object. The breather pipe3constitutes a return flow passage, through which the processed blow-by gas discharged from the oil separator2returns to an intake-side flow passage5of the engine4.

In this ventilation system1, the blow-by gas discharged from the engine4is introduced to the oil separator2through a gas introduction pipe6a. The oil separated by the oil separator2is returned to the engine4through an oil discharge pipe6b. On the other hand, the processed blow-by gas is discharged from an upper end portion of the oil separator2and then is returned to the intake-side flow passage5through the breather pipe3. Specifically, the processed blow-by gas is returned to a part at which an air filter7is coupled to a turbocharger8in the intake-side flow passage5. The returned blow-by gas is mixed with fresh air from the air filter7and is compressed by the turbocharger8. Afterwards, the blow-by gas is cooled by a charge cooler9and is supplied to the engine4.

The following describes the oil separator2. As illustrated inFIGS. 2 and 3, this oil separator2includes a housing11, which includes a lower case12and an upper case13. The housing11houses various components such as a rotor unit21and a PCV valve24in an internal space (a chamber) (described later).

The lower case12is a part that partitions a lower side part of the housing11. The lower case12is constituted of a saucer-shaped member having a bottom and an opened top surface. The side portion of the lower case12has a cylindrical shape and a fitted portion is disposed at the upper end portion thereof. This fitted portion is fitted to a lower end portion of the upper case13. A joint member14is removably mounted to the lower surface of the lower case12. In this embodiment, the lower case12, the communication tube portion, and the like are manufactured by casting; however, the lower case12, the joint member14, and the like may be manufactured by molding a resin.

The upper case13is a member mounted to the lower case12from above. The upper case13and the lower case12separate a chamber that houses components such as the rotor unit21. An O-ring15is mounted to a coupling part at which the upper case13is coupled to the lower case12(seeFIG. 5), and this ensures air tightness and liquid tightness. The upper case13includes a cylindrical body cover16and a disk-shaped top surface cover17.

The top surface cover17is mounted in an airtight manner to the upper end portion of the body cover16. A tubular gas discharge portion18is oriented upward at a center of the top surface cover17. This gas discharge portion18is a part from which the processed blow-by gas is discharged. The breather pipe3is coupled to the gas discharge portion18via an outlet pipe19.

The following describes an internal structure of the oil separator2. As illustrated in the exploded perspective view ofFIG. 4, a chamber formed by the lower case12and the upper case13accommodates the rotor unit21, a partition member22and a stationary frame23. As illustrated in the cross-sectional view inFIG. 5, a PCV valve24is mounted to the inside of the top surface cover17.

First, the following describes the rotor unit21. This rotor unit21is a mechanism to separate the mist oil contained in the blow-by gas. As illustrated inFIG. 5, the rotor unit21includes a rotor25, a spindle26, and a spindle shaft27.

The rotor25is a part that condenses the mist oil by rotation and separates the mist oil from the blow-by gas. The rotor25includes a plurality of separation disks28, an upper holder29, and a lower holder30. The separation disks28are ring-shaped plates that incline downward toward the outer peripheral side, in other words, plates having a side surface of a truncated cone shape. The separation disk28of this embodiment has a thickness of 1 mm or less, and is manufactured by molding resin. These separation disks28are laminated in an axial direction of the spindle26. For convenience of explanation, the separation disks28are illustrated providing intervals from one another; however, the actual intervals are defined to be extremely narrow (for example, less than 1 mm).

The upper holder29is a member that holds the plurality of laminated separation disks28from above. Similarly, the lower holder30is a member that holds the separation disks28from below. In the outer peripheral edge of the lower holder30, a plurality of coupling arms30afor coupling to the upper holder29are disposed (seeFIG. 4). In this embodiment, the four coupling arms30aare provided circumferentially at intervals of 90 degrees. The upper ends of the coupling arms30aare joined to the upper holder29so that the plurality of separation disks28, the upper holder29, and the lower holder30are integrated to constitute the rotor25.

This rotor25has a cylindrical appearance. On the inner peripheral side of the rotor25, there is a hollow part, and the hollow part vertically extends through. The spindle26is inserted into this hollow part and the spindle26and the rotor25are joined to one another. Accordingly, the rotor25rotates, together with the spindle26, around the axis of the spindle26.

Nozzles31project from a part of a peripheral surface of the spindle26located below the rotor25. Each of the nozzles31is a part from which the oil supplied through the spindle shaft27is injected to generate a driving power to rotate the spindle26and the rotor25.

The nozzles31of this embodiment include cylindrical nozzle bodies32and injection holes33disposed at distal end portions of the nozzle bodies32. Base ends of the nozzle bodies32are coupled to the spindle26, and the distal ends of the nozzle bodies32are closed. The nozzle bodies32are mounted at an angle of 45 degrees obliquely downward with respect to the axial direction of the spindle26. The three nozzle bodies32are circumferentially disposed at intervals of 120 degrees. The injection hole33is disposed on a side surface at the distal end portion of the nozzle body32. More specifically, the injection hole33is disposed in a direction perpendicular to the axial direction of the nozzle body32so that oil is injected horizontally.

The spindle shaft27is a pillar member serving as a bearing of the spindle26, and supports the spindle26in a rotatable manner. The spindle shaft27internally includes an oil supply passage27ato supply the oil. A lower end portion of the spindle shaft27is coupled to an upper end portion of a support tube portion34disposed in the lower case12. The support tube portion34corresponds to the oil supply portion, and supplies the oil supply passage27awith oil which has injected from the injection holes33. And, the oil supply pipe6cillustrated inFIG. 1is coupled to the support tube portion34. Accordingly, the oil supplied through the oil supply pipe6cpasses through the support tube portion34, and then flows into the spindle shaft27. Thereafter, the oil flows into the nozzle bodies32, and then is injected from the injection holes33.

As described above, the injection hole33is disposed at the distal end portion of the nozzle body32in a direction in which oil is injected horizontally. At the three nozzles31disposed at intervals of 120 degrees, formation positions for the injection holes33are matched. Accordingly, when the oil is injected from the respective injection holes33, the rotor25and the spindle26rotate about the spindle shaft27as the axis.

The following describes the partition member22. As illustrated inFIG. 5, the partition member22is a member that partitions the internal space (the chamber) of the housing11into a lower chamber35(a primary separation chamber) and an upper chamber36(a secondary separation chamber). And the partition member22forms a communication port37. The blow-by gas in the lower chamber35is guided by the communication port37to the upper chamber36. The partition member22has an outer peripheral portion41and a tapered portion42. The outer peripheral portion41is a short cylindrical part and has a collar portion43projecting outwardly at the middle in the height direction. The tapered portion42is disposed on the inner peripheral side with respect to the outer peripheral portion41, and has a tapered shape in which the diameter is gradually reduced from the lower end of the outer peripheral portion41toward the top. The tapered portion42of this embodiment has an inclined surface that inclines downward toward an outer peripheral side. an upper end opening of the tapered portion42forms the communication port37.

The partition member22is fitted to the inner peripheral side of the fitted portion in the lower case12. The collar portion43abuts on an upper end of the fitted portion from above to be positioned. Consequently, the tapered portion42is disposed immediately below the lower holder30included in the rotor25. The chamber is partitioned into the lower chamber35and the upper chamber36, which are bordered by the partition member22. These lower chamber35and upper chamber36are communicated through the communication port37.

When the rotor25rotates at a high speed, oil film, which is turning at high speed, is formed on the outer peripheral side with respect to the turning paths of the injection holes33. When the blow-by gas contacts this oil film, the mist oil contained in the blow-by gas is taken in the oil film and is centrifuged. This makes it possible to reduce the mist oil content in the blow-by gas. Thus, in the lower chamber35, the mist oil content in the blow-by gas can be reduced by the injection of the oil, which functions as the driving source for the spindle26and the rotor25. Therefore, the lower chamber35functions as the primary separation chamber for the mist oil.

The following describes the PCV valve24. As illustrated inFIG. 5, the PCV valve24includes a diaphragm45, upper springs46, and lower springs47.

The diaphragm45is a valve element and is manufactured by molding rubber and resin. The diaphragm45is composed of a disk-shaped member. The upper springs46and the lower springs47are members to support the diaphragm45in such a manner that the diaphragm45can move vertically. The PCV valve24is placed on a pedestal portion at a position immediately below the top surface cover17. The diaphragm45covers this pedestal portion in an airtight manner. a space defined by the pedestal portion and the diaphragm45is open to open air through an air communicating portion.

The diaphragm45vertically moves according to intake-side pressure of the engine4and internal pressure of the crankcase, to adjust the flow of the blow-by gas. That is, under an excessively large intake pressure (negative pressure) of the engine4, the diaphragm45moves toward the gas discharge portion18(upward), and under a high pressure of the side close to the crankcase, the diaphragm45moves toward the opposite side (downward).

Accordingly, when the pressure in the upper chamber36becomes higher than a PCV-set pressure, the diaphragm45moves downward to increase a flow rate of the blow-by gas. On the contrary, when the pressure in the upper chamber36is lower than the PCV-set pressure, the diaphragm45moves upward to reduce the flow rate of the blow-by gas. Thus, the flow rate of the blow-by gas is appropriately adjusted, and thereby the crankcase-side pressure of the engine4maintains within a constant range.

An outer periphery of the pedestal portion on which the PCV valve24is placed is defined by a sidewall portion, the sidewall portion having a circular shape as viewed from above. a communicating window48is disposed at this sidewall portion. Through this communicating window48, an upper part of the upper chamber36with respect to the diaphragm45and a part of the upper chamber36on the rotor25side communicate.

A cylindrical rib49is disposed at the lower side of the sidewall portion. This cylindrical rib49is a ring-shaped projection disposed at a position higher than the rotor unit21and lower than the diaphragm45, and the cylindrical rib49is integrated with the body cover16. In the upper end part of the body cover16, the cylindrical rib49guides downwards fluid (oil and blow-by gas) which is flowing along the inner surface of the body cover16from the outer peripheral side to the inner peripheral side. Since this cylindrical rib49can also reduce the amount of oil, it is possible to surely restrain an attachment of the oil to the PCV valve24.

The lower case12and the joint member14will be described below. As illustrated inFIGS. 6A and 6B, the lower case12has a disk-shaped bottom51. A cylindrical-shaped side portion52is disposed upright from an outer peripheral edge of the bottom51. On the center of the bottom51, an outlet-side part of the support tube portion34, which is the side on which oil is discharged, is disposed upright. As illustrated inFIG. 5, an upper end of the support tube portion34, which is a flow-in side to the oil supply passage27a, is fitted to the stationary frame23. This stationary frame23is a metallic frame (seeFIG. 4) disposed to increase the rigidity of the support tube portion34. As illustrated inFIGS. 6A and 6B, the inlet-side part of the support tube portion34, which is the flow-in side of oil, extends along the bottom51toward the side. In addition, an end portion of the inlet-side part is open to outside at the side surface of the lower case12.

In addition, a gas communicating portion53is disposed along the outlet-side part of the support tube portion34. This gas communicating portion53introduces the blow-by gas from the inside of the joint member14to the inside of the lower case12. The gas communicating portion53according to the present invention is a cylinder portion that penetrates the bottom51of the lower case12and that projects upward. An upper end (a gas outlet) of the gas communicating portion53is positioned on the inner peripheral side with respect to the paths of the injection holes33provided with the nozzles31. Oil communicating portions54for discharging oil are disposed at the bottom51of the lower case12. These oil communicating portions54are openings that penetrate the bottom51of the lower case12in the thickness direction. In the present invention, the oil communicating portions54are disposed at positions that surround the support tube portion34and the gas communicating portion53.

The joint member14is a member mounted to the bottom51of the lower case12from the lower side. The joint member14includes a joint body55, a mounting flange56, a gas introducing portion57, and an oil discharge portion58.

The joint body55is a rectangular parallelepiped hollow member whose top surface is open. The internal space of the joint body55serves as a common chamber. The mounting flange56is a part used to mount the joint member14to the lower case12. The mounting flange56is composed of plates which projects laterally from an upper end of the joint body55. The mounting flange56includes screw openings provided respectively in its four corners. A fixing male screw is inserted into each screw opening, and is tightened into a female screw part formed on the bottom51of the lower case12. Thereby, the joint member14is mounted to the lower case12. Between the joint member14and the lower case12, a rectangular ring-shaped packing59is mounted to ensure liquid tightness.

The gas introducing portion57is a part that introduces the blow-by gas to the inside of the oil separator2, the blow-by gas being flowing in through the gas introduction pipe6a. The gas introducing portion57is a cylindrical member laterally projecting from a sidewall of the joint body55. The gas introducing portion57communicates an internal space55a(the common chamber) of the joint body55on the side of the joint body55. An end portion of the gas introduction pipe6ais coupled to the projection part of the gas introducing portion57.

The oil discharge portion58is a part for discharging to the engine4the oil which flows down from the oil communicating portions54of the lower case12. The oil discharge portion58is a cylindrical member projecting downward from the bottom51of the joint body55. The oil discharge portion58communicates the internal space55aof the joint body55on the lower side of the joint body55. To the projection part of the oil discharge portion58, an end portion of the oil discharge pipe6bis coupled.

FIG. 7is a drawing of the lower case12, to which the joint member14is mounted, as viewed in a planar direction. As illustrated inFIG. 7, when the joint member14is mounted to the lower case12, the oil discharge portion58is positioned immediately below the oil communicating portions54. Accordingly, the oil flowing down from the oil communicating portions54is smoothly discharged from the oil discharge portion58.

Here, the separation of the mist oil from the blow-by gas in the oil separator2having the foregoing configuration will be described.

As illustrated inFIG. 8, the oil which has been supplied to the support tube portion34flows into the spindle shaft27as indicated by a path of reference symbol F1. The oil flows from the spindle shaft27to the nozzle bodies32and is injected from the injection holes33. By the injection of the oil from each injection hole33, the rotor25and the spindle26rotate around the spindle shaft27.

The oil which has been injected from the injection holes33moves along the path indicated by reference symbol F2. That is, the injected oil is sprayed to the tapered portion42of the partition member22. And then, the oil is guided obliquely below toward the outer peripheral side along the inclined surface of the tapered portion42. Accordingly, a mixture of oil spray to the blow-by gas is restrained. Afterwards, the oil flows down on the inner surface of the lower case12, and flows into the internal space55aof joint member14from the oil communicating portion54. And, the oil flows into the oil discharge portion58and is returned to the engine4through the oil discharge pipe6b.

On the other hand, blow-by gas introduced from the engine4through the gas introduction pipe6amoves along the path indicated by the arrow of reference symbol F3. That is, the blow-by gas flows into the gas introducing portion57of the joint member14. The blow-by gas which has passed the gas introducing portion57flows into the gas communicating portion53from the internal space55aof the joint body55. The blow-by gas which has passed the gas communicating portion53flows into the hollow part of the rotor25through an area inside the motion paths of the injection holes33.

The blow-by gas flowing into the hollow part of the rotor25moves through the clearances between the separation disks28to the outer peripheral direction of the rotor25due to a centrifugal force which is generated by the rotation of the rotor25. Thus, when the blow-by gas moves to the outer peripheral direction of the rotor25due to the centrifugal force, the pressure at the inner peripheral side of the rotor25becomes lower than the pressure at the outer peripheral side. Due to the pressure difference, the blow-by gas which has passed the gas communicating portion53becomes more likely to flow into the hollow part at the rotor25, and thereby the flow efficiency of the blow-by gas increases.

When the blow-by gas comes into contact with the separation disks28, the mist oil contained in this blow-by gas attaches to the surfaces of the separation disks28. The attached mist oil and additional mist oil coalesce, and thus the oil condenses on the surfaces of the separation disks28. That is, the oil undergoes secondary separation. As described above, in the lower chamber35, the mist oil is separated from the blow-by gas by primary separation. Accordingly, by the secondary separation at the separation disks28, the mist oil is separated from the blow-by gas at a high level. Thus, the upper chamber36corresponds to the secondary separation chamber in which the secondary separation of the remaining mist oil is performed to separate the remaining mist oil from the blow-by gas which has undergone primary separation of the mist oil.

As shown inFIG. 5, a clearance SP is formed between the spindle26and the spindle shaft27. This clearance SP serves as an oil guiding passage and is filled with the oil which is supplied to be injected from the nozzles31. Since the oil supply pressure is sufficiently high, some oil filling the clearance passes through the upper end of the clearance and is discharged from the upper end portion of the spindle26to the hollow part of the rotor25. Similar to the blow-by gas, due to the centrifugal force of the rotor25, the oil discharged to the hollow part of the rotor25moves through the clearances between the separation disks28to the outer peripheral direction of the rotor25.

The oil condensed on the surfaces of the separation disks28coalesces with the oil discharged to the hollow part of the rotor25. This cleans the surfaces of the separation disks28, and therefore simplifies maintenance for the separation disks28.

The oil which has been condensed on the surfaces of the separation disks28and the oil which has coalesced move along the path indicated by reference symbol F4inFIG. 8. That is, the oil is discharged from the outer peripheral edges of the separation disks28, and collides with the inner surface of the body cover16, and then flows down along this inner surface. And, the oil joins the oil injected from the nozzles31in the lower case12, and passes the oil communicating portion54, the oil discharge portion58, and the oil discharge pipe6b. Finally, the oil is returned to the engine4.

The blow-by gas that has passed through the rotor25and from which the mist oil has been separated moves along a path indicated by reference symbol F5inFIG. 8. That is, the blow-by gas that has passed through the rotor25becomes a turning flow and moves up inside the upper case13. Thus, the blow-by gas is introduced to a top-surface-side space of the PCV valve24. Afterwards, the blow-by gas moves through the outlet pipe19and is introduced to the breather pipe3.

In the oil separator2according to the present embodiment which operates as described above, the oil communicating portions54and the gas communicating portion53communicate the upper portion of the internal space55a(the common chamber) of the joint body55. The gas introducing portion57communicates the internal space55aof the joint body55on the side of the joint body55. The oil discharge portion58communicates the internal space55aof the joint body55on the lower side of the joint body55. Accordingly, in the internal space55aof the joint body55, the blow-by gas introduced from the gas introducing portion57come into contact with the oil which is flowing down from the oil communicating portions54. Thus, oil mist contained in the blow-by gas is partially taken into the oil, and this can increase the removal efficiency of oil in the blow-by gas.

The oil communicating portions54are composed of through-openings, which are formed on the bottom51of the lower case12and which penetrate through the bottom51in the thickness direction. The gas communicating portion53is composed of a tubular portion projecting upward from the bottom51of the lower case12. That is, the tubular portion constituting the gas communicating portion53defines a passage for blow-by gas extending vertically. Accordingly, a large amount of oil flows in through a path indicated by reference symbol F6inFIG. 9. Even if the oil accumulates at the bottom51of the lower case12, the gas communicating portion53ensures a passage for blow-by gas, as indicated by reference symbol F7. Consequently, a large amount of flowing blow-by gas pushes back the oil upward, and this can prevent a failure of deterioration of the removal efficiency of oil in the blow-by gas. Additionally, the gas outlet of the gas communicating portion53is disposed on the inner peripheral side with respect to the paths of the injection holes33. This makes it possible to efficiently introduce the blow-by gas to the hollow part of the rotor25.

Here, a bracket61for mounting the oil separator2to the engine4will be described. The bracket61illustrated inFIG. 10includes a mounting base61aand forks61b. The mounting base61ais a part mounted to the engine4and is composed of a trapezoidal-shaped metal plate. The forks61bare two elongated plate-shaped portions extending from both lower ends of the mounting base61ain a direction perpendicular to the mounting base61a. A plurality of screw holes are disposed in each of the mounting base61aand forks61b. Fixing screws are inserted into the screw holes and are tightened. Thereby, the mounting base61ais mounted to a side surface of the engine4, and the forks61bis fixed to the bottom surface of the lower case12.

The use of this bracket61allows a mounting position of the bracket61to be close to the center of gravity of each rotator (the separation disks28, the nozzles31, and the spindle26). This can prevent vibration and wobble of the oil separator2. In addition, this also makes it possible to mount the oil separator2to a target object other than the engine4. For example, the oil separator2can be mounted to a vehicle body.

The following describes variations of the joint member14. First, the first modification illustrated inFIG. 11differs from the above-described embodiment in that the gas introducing portion57provided with the joint member14is composed of an elbow member. In the first modification, the gas introducing portion57is composed of the elbow member being capable of nodding. Therefore, even if the position of the gas introduction pipe6a, which introduces the blow-by gas, is restricted, this restriction can be dealt with relatively easily.

The second modification illustrated inFIG. 12differs from the above-described embodiment in that the gas introducing portion57and the oil discharge portion58include flanges57aand58a. In the second modification, the flanges57aand the flange58aare respectively disposed of the gas introducing portion57and the oil discharge portion58. This makes it possible to couple easy to the gas introduction pipe6aand the oil discharge pipe6b, which include these flanges.

The third modification illustrated inFIG. 13differs from the above-described embodiment in that the third modification uses a joint member14A where the gas introducing portion57and the oil discharge portion58are integrated.

As apparent from the above-described embodiment and these first modification to third modification, in this oil separator2, the gas introducing portion57and the oil discharge portion58are disposed of the joint, and this joint is removably mounted to the lower case12. Accordingly, it is sufficient to prepare the joint member14or14A according to a vehicle type to which the oil separator2is to be mounted. This makes it possible to easily mount the oil separator2to various targets. Other components can be shared, and mass production of the oil separator can be achieved, which results in cost reduction.

The description of the above-described embodiment is for ease of understanding of the present invention and does not limit the present invention. The present invention may be modified or improved without departing from the gist and includes the equivalents.

REFERENCE SIGNS LIST