Oil separator

An oil separator includes a plurality of separation discs rotatable together with a spindle and layered in an axis direction of the spindle, a nozzle that protrudes from a lower circumferential face of the spindle and configured to rotate the spindle by injection of an oil, a lower case has a gas inflow part into which blow-by gas flows, an oil discharge part into which an oil after separation is discharged, an upper case that sections together with the lower case a housing chamber in which spindle, separation discs and nozzle are housed, and a sectioning member that sections the housing chamber into a primary separation chamber, configured to primarily separate the oil mist, and a secondary separation chamber that secondarily separates the oil mist included in the gas after primary separation, and forms between the nozzle and the separation discs a communication opening that guides the gas being treated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 371 U.S. National Stage of International Application No. PCT/JP2013/059295, filed Mar. 28, 2013. The entire disclosures of the above application are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an oil separator that separates oil in a mist form (hereinafter oil mist) included in gas which is a target of treatment.

BACKGROUND ART

An oil separator that separates oil mist included in gas which is a target of treatment is known. For example, the oil separator disclosed in PTL1 separates oil mist using centrifugal force created by a rotating member arranged between the inlet and the outlet for the gas.

This oil separator has hermetically partitioned a separation space where a rotating member is housed and a drive space where a driving mechanism for rotating this rotating member is housed. The rotating member includes a rotary shaft and a plurality of separation discs that are layered along the axis direction of this rotary shaft. The rotary shaft is attached with the axis line being along the vertical direction and a driving mechanism for rotating the rotary shaft about the axis is attached at the lower end part of the rotary shaft. For example, a nozzle for injecting oil and a set of vanes to which oil is sprayed, or a motor is used in the driving mechanism.

CITATION LIST

Patent Literature

[PTL 1] Japanese translation of PCT International application No. 2008-501505

SUMMARY OF INVENTION

Technical Problem

The conventional oil separator has the rotary shaft attached along the vertical direction so that the drive space is arranged below the separation space. Since the drive space and the separation space are divided, the gas which is the target of treatment is introduced from above the separation space and discharged from the side of the separation space. A structure that discharges gas which is the target of treatment from the side of the separation space in this way would have the portion that discharges gas jut out sideways which would upsize the device by a corresponding amount. Additionally, there is a desire for the oil separators of this type to have the separation efficiency improved.

The present invention has been made in view of such circumstances, and an objective thereof is to allow minimization of an oil separator while improving the separation efficiency in the oil separator that separates from gas oil mist included in a gas which is a target of treatment.

Solution to Problem

One aspect of the present invention to achieve the foregoing objective is an oil separator which separates an oil mist included in a gas which is a target of treatment, including a plurality of separation discs which are provided rotatable together with a spindle and are layered in an axis direction of the spindle, a nozzle which is provided to protrude from a circumferential face of the spindle below the separation discs and configured to rotate the spindle about an axis line by injection of an oil, a lower case which is provided with a gas inflow part into which the gas being the target of treatment flows and an oil discharge part into which an oil after separation is discharged, an upper case which is attached from above the lower case and sections together with the lower case a housing chamber in which the spindle, the separation discs and the nozzle are housed, and a sectioning member which sections the housing chamber into a primary separation chamber configured to allow an oil injected from the nozzle to flow down as well as to primarily separate the oil mist included in the gas being the target of treatment which has flown in from the gas inflow part and into a secondary separation chamber in which the separation discs are arranged and which secondarily separates the oil mist included in the gas being the target of treatment from which the oil mist has been primarily separated, and at the same time forms between the nozzle and the separation discs a communication opening which guides into the secondary separation chamber the gas being the target of treatment in the primary separation chamber.

According to the present invention, the housing chamber is partitioned into a primary separation chamber and a secondary separation chamber where the primary separation chamber has introduced therein a gas which is the target of treatment as well as has injected therein an oil which becomes the driving source so that the primary separation chamber can be used for multiple purposes permitting minimization of the device. Here, in the primary separation chamber, a part of the gas being the target of treatment comes into contact with the oil which has been injected from the nozzle for the oil mist to be taken into the oil. Hereby, the oil mist is primarily separated. Then the gas being the target of treatment, after the oil mist is primarily separated, is guided to the secondary separation chamber through a communication opening. Since the secondary separation chamber only has to perform secondary separation on the remaining oil mist, the separation efficiency of the oil mist can be improved. Further, the number of separation discs can be lessened and the diameters of the separation discs can be reduced which also allows the device to be minimized.

In the aforementioned oil separator it is preferable that the sectioning member has a diameter reduced toward above and has an upper end thereof set as the communication opening, and includes a tapered part whose inner face has sprayed thereagainst the oil injected from the nozzle. In this oil separator, the oil that has been injected from the nozzle flows downward by being sprayed against the inner face of the tapered part. Hereby, the problem of the oil flowing into the upper housing chamber can be restrained.

In the aforementioned oil separator it is preferable that the gas inflow part and the oil discharge part are structured with a common tubular member. The structure of this oil separator can be simplified. Further, the oil which has been injected from the nozzle and the oil which has been separated from the gas being the target of treatment can be discharged together.

In the aforementioned oil separator it is preferable that the oil separator further includes a spindle shaft which rotatably supports the spindle and has formed on an inner side thereof an oil feeding path for feeding the oil, wherein a space between the spindle and the spindle shaft functions as an oil guide path for guiding to the separation discs a part of the oil fed to be injected from the nozzle. With this oil separator, the oil which has been guided through the oil guiding path cleans the surface of the separation discs so that the maintenance of the separation discs can be simplified.

In the aforementioned oil separator it is preferable that a gas discharge part is provided to an upper end part of the upper case and discharges a post treated gas having the oil mist separated. With this oil separator, gas after treatment is discharged from the upper end part of the upper case so that oil is restrained from mixing into the gas after treatment.

In the aforementioned oil separator it is preferable that the separation discs are annular plate materials inclined downward toward an outer circumferential side. With this oil separator, the oil which has been separated with the separation discs flows downward so that the oil can be restrain from mixing into the gas after treatment.

Advantageous Effects of Invention

According to the present invention, the separation efficiency can be improved while making the device compact in an oil separator which separates from gas oil mist included in a gas which is a target of treatment.

DESCRIPTION OF EMBODIMENTS

Description of the embodiments according to the present invention will be given in the following with reference to the drawings. Here, description will be given taking the closed type crankcase ventilation system1(hereinafter, referred to as ventilation system1) as an example.

The ventilation system1includes an oil separator2and a breather pipe3, as shown in the figure. The oil separator2treats the blow-by gas (corresponding to the gas being the target of treatment including oil mist) discharged from an engine4to separate the oil mist. The oil separator2in the present embodiment is mounted on the side face of the engine4. The breather pipe3sections the flow path for returning the post treated blow-by gas discharged from the oil separator2to an air intake side flow path5of the engine4.

In this ventilation system1, the blow-by gas discharged from the engine4is introduced into the oil separator2provided to the side face of the engine4. Then the oil separated with the oil separator2is returned to the engine4. Meanwhile, the post treated blow-by gas after being discharged from the upper end part of the oil separator2is returned to the air intake side flow path5through the breather pipe3. Specifically, the post treated blow-by gas is returned to the section which couples an air filter6and a turbo charger7in the air intake side flow path5. The returned blow-by gas is mixed with fresh air sent from the air filter6and compressed by the turbo charger7and thereafter, cooled in a charge cooler8to be fed to the engine4.

Description of the oil separator2will be given next. As illustrated inFIGS. 2 and 3, this oil separator2has a housing13including a lower case11and an upper case12. A rotor unit, a PCV valve and the like are arranged in the inner space (housing chamber) of the housing13. Description of the rotor unit and the PCV valve will be given later.

The lower case11is a section which partitions the lower section of the housing13and is structured with a box-like member having a bottom face with the upper face being open. The upper end part of the lower case11is provided with a circular fitting part11awhich fits together with the lower end part of the upper case12. A communication tube part14facing rearward and communicating with the engine4is provided on the back face of the lower case. This communication tube part14is a tubular member which functions as a gas inflow part into which blow-by gas flows as well as an oil discharge part from which oil after separation is discharged. The tip part of the communication tube part14is provided with a flange15which is to be joined to the side face of the engine4. In the present embodiment, the lower case11, the engine4and the like are made of cast metal, however, they may be made by molding resin.

The bottom face of the lower case11is provided with a connecting part16aof an elbow pipe16in a protruding manner. This connecting part16ais connected to one end of an oil feeding pipe9shown inFIG. 1. The other end of this oil feeding pipe9is connected to the side face of the engine4so that oil is fed to the oil feeding pipe9through an oil path (not shown) provided inside the engine4. This oil is used to create power for rotating the rotor unit and will be described later in detail.

As illustrated inFIGS. 2 and 3, the upper case12is a member which is mounted to the lower case11from above and sections together with the lower case11the housing chamber in which the rotor unit and the like are housed. This upper case12includes a tubular main body cover17and a disc shaped top face cover18. The lower end part of the main body cover17is hermetically mounted to the upper end part of the lower case11. The top face cover18is hermetically mounted to the upper end part of the main body cover17so as to cover the PCV valve. Additionally, the center part of the top face cover18is provided with a tubular gas discharge part19facing upward. This gas discharge part19is a section that discharges post treated blow-by gas and is connected to the breather pipe3via an outlet pipe.

Next, description of the inner structure of the oil separator2will be given. As illustrated inFIG. 4, a rotor unit21, a PCV valve22and a sectioning member23are arranged in the inner part of the oil separator2.

Firstly, description of the rotor unit21will be given. This rotor unit21is a mechanism for separating oil mist which is included in blow-by gas and has a rotor24, a spindle25and a spindle shaft26.

The rotor24is a section which agglomerates the oil mist by rotation and has a plurality of separation discs27, an upper holder28and a lower holder29. The separation discs27are annular plate materials inclined downward toward the outer circumferential side, that is, plate materials which have been worked to be shaped into the side faces of conical frustums. The separation discs27of the present embodiment have thicknesses of 1 mm or less and are manufactured by molding resin. These separation discs27are layered in the axis direction of the spindle25. For the sake of description, the separation discs27are illustrated with enlarged spaces therebetween, however, the actual spaces are defined to be extremely narrow (e.g. less than 1 mm).

The upper holder28is a member for holding the layered plurality of separation discs27from above and similarly, the lower holder29is a member for holding from below. The outer circumferential edge of the lower holder29is provided with a plurality of coupling arms29afor coupling to the upper holder28. In the present embodiment, four coupling arms29aare provided at 90 degrees intervals in the circumferential direction. The plurality of separation discs27, the upper holder28and the lower holder29are integrated by coupling the upper ends of the coupling arms29ato the upper holder28.

The outer appearance of this rotor24is tubular and the inner circumferential side is a hollow section which penetrates in the vertical direction. A spindle25is inserted into this hollow section and the spindle25and the rotor24are coupled to each other. Therefore, the rotor24rotates about the axis line of the spindle25together with the spindle25.

Nozzles31are provided to protrude from the circumferential face of the spindle25at parts below the rotor24. These nozzles31are sections which inject oil fed through a spindle shaft26and generate the driving force for rotating the spindle25and the rotor24.

As shown inFIG. 6, the nozzle31of the present embodiment has a tubular nozzle main body31aend tip of which is closed and a nozzle opening31bprovided at the tip end part of the nozzle main body31a. The base end of the nozzle main body31ais connected to the spindle25The nozzle main body31ais mounted to the spindle25, the nozzle main body31abeing inclined downward at an angle of 45 degrees with respect to the direction of the axis of the spindle25. Three nozzle main bodies31aare provided at 120 degrees intervals in the circumferential direction. The nozzle opening31bis provided to the side face at the tip end part of the nozzle main body31a. Specifically, the nozzle opening31bis provided in a direction that intersects the direction of the axis line of the nozzle main body31aas well as the direction which allows oil to be injected in the horizontal direction.

As illustrated inFIG. 4, the spindle shaft26is a cylindrical member which serves as the shaft bearing of the spindle25and supports the spindle25in a rotatable manner. As indicated inFIG. 5, an oil feeding path26afor feeding oil is formed inside the spindle shaft26. Additionally, the lower end part of the spindle shaft26is joined with the upper end part of the elbow pipe16. As mentioned above, a connecting part16aof the elbow pipe16is connected with the oil feeding pipe9. Therefore, the oil that has been fed through the oil feeding pipe9flows through the elbow pipe16and then into the spindle shaft26. Then, the oil after flowing into the nozzle main body31ais injected from the nozzle opening31b.

Description of the PCV valve22will follow. As illustrated inFIG. 4, the PCV valve22is equipped with a diaphragm32, an upper side spring33and a lower side spring34.

The diaphragm32is a valving element and is manufactured by forming rubber and resin. The exemplified diaphragm32includes a main diaphragm32a, an upper side diaphragm32band a lower side diaphragm32c. The main diaphragm32ais a disc shaped member made of rubber with a columnar projection formed at the center part thereof and is slightly inclined downward from the center part toward the circumferential edge part. The upper diaphragm32bis a disc shaped member made of resin arranged on the top face of the main diaphragm32awith an opening formed at the center part thereof through which the projection of the main diaphragm32apenetrates. The upper side diaphragm32bis also slightly inclined downward from the center part toward the circumferential edge part. The lower side diaphragm32cis a disc shaped member made of resin arranged on the lower face of the main diaphragm32aand is slightly inclined downward from the center part toward the circumferential edge part.

The upper side spring33and the lower side spring34are members for supporting the diaphragm32in a manner movable in the vertical direction. In other words, the upper side spring33is arranged above the diaphragm32and the lower side spring34is arranged below the diaphragm32. These upper and lower side springs33,34sandwich and support the diaphragm32in a movable manner.

The diaphragm32moves in the vertical direction in response to the pressure on the air intake side of the engine4and the inner pressure of the crank case, and adjusts the flow of the blow-by gas. In other words, the diaphragm32moves to the gas discharge part19side (upward) when the air intake pressure (negative pressure) of the engine4is excessively high and moves to the other side (downward) when the pressure on the crank case side is high. Hereby, the amount of flow of the blow-by gas can be adjusted appropriately.

Next, description of the sectioning member23will be given. The sectioning member23is a member which sections the inner space (housing chamber) of the housing13into a primary separation chamber (lower housing chamber) and a secondary separation chamber (upper housing chamber) as well as forms a communication opening which guides the gas being the target of treatment (blow-by gas) in the primary separation chamber to the secondary separation chamber. This sectioning member23includes an outer circumferential part36and a tapered part37. The outer circumferential part36is a section in a short annular shape and has brim part jutting out sideward at the middle part in the height direction. The tapered part37is provided on the inner circumferential side of the outer circumferential part36and is in a tapered form having the diameter reduced gradually when approaching upward from the lower end of the outer circumferential part36. And the upper end opening of the tapered part37forms the communication opening38.

As illustrated inFIG. 5, the sectioning member23is fit into the fitting part11aof the lower case11from the inner circumferential side. Hereby, the tapered part37is arranged right below the lower holder29included in the rotor24. The housing chamber41is sectioned into a lower housing chamber42and an upper housing chamber43with the sectioning member23as the boundary and these lower and upper housing chambers42,43are communicated through the communication opening38.

In the lower housing chamber42, the lower end part of the spindle25, the lower end part of the spindle shaft26, the nozzle31, the elbow pipe16, a fixing frame44and the like. Here, the fixing frame44is a member for fixing the upper end part of the elbow pipe16to a predetermined location. Meanwhile, in the upper housing chamber43, the sections above the lower end part of the spindle25and the spindle shaft26, the rotor24, the PCV valve22and the like are arranged.

In the following, the inner structure of the oil separator2will be described in the order of the lower housing chamber42, the parts proximate the rotor of the upper housing chamber43and the parts proximate the PCV valve of the upper housing chamber43.

As illustrated inFIGS. 5 and 6, the lower housing chamber42is sectioned by the lower case11and the sectioning member23. The elbow pipe16is hermetically mounted upward from the bottom part of the lower case11. The upper end of the elbow pipe16is fixed to the fixing frame44. The fixing frame44is a frame body which is mounted to the bottom part of the fitting part11a. The blow-by gas that has flown in from the communication tube part14can move upward through the fixing frame44.

Further, as illustrated inFIG. 6, a space45is provided between the spindle shaft26and the spindle25. This space45is provided for guiding the oil which has been discharged from the oil feeding path26ato the nozzles31. Here, this space45constitutes a part of the oil guiding path to guide a part of the oil which has been discharged from the oil feeding path26ato the separation discs27which will be described later in detail.

The nozzles31are arranged at positions proximate the tapered part37of the sectioning member23. As mentioned above, the nozzles31inject oil in the horizontal direction from the nozzle openings31b. Thus, the injected oil is sprayed against the inner face of the tapered part37as indicated by an arrow with the reference sign F1. Here, the inner face of the tapered part37has a conical face which is inclined from the outer circumferential side toward the center side so that the oil sprayed thereagainst would flow downward as indicated by an arrow with the reference sign F2. Hereby, the injected oil can be positively introduced to the bottom part side of the lower housing chamber42and thus can restrain the oil from flowing into the upper housing chamber43.

Here in the present embodiment, the inclination angle of the tapered part37is set to 45 degrees with respect to the axis line AL of the spindle25, however, the angle is not limited to this. The angle can be set to any angle as long as the injected oil can be made to positively flow toward the bottom part side of the lower housing chamber42. For example, the inclination angle of the tapered part37can be set to 30 degrees or to 60 degrees with respect to the axis line AL.

Further, a film of oil that circles at high speed is formed on the outer circumferential side of the circling path of the nozzle opening31bwhen the rotor24rotates at high speed. When blow-by gas contacts this film of oil, the oil mist included in the blow-by gas is taken into the film of oil and centrifugally separated. Hereby, the amount of oil mist included in the blow-by gas can be reduced. Injecting the oil which becomes the driving source of the spindle25and the rotor24in the lower housing chamber42in this way allows the amount of oil mist included in the blow-by gas to be reduced. For such reason, the lower housing chamber42functions as the primary separation chamber of the oil mist.

Furthermore, the oil injected from the nozzles31is collected at the bottom part of the lower housing chamber42together with the oil separated from the blow-by gas. As indicated with arrows with the reference sign F3, the oil flows along the bottom part of the lower housing chamber42and then flows into the communication tube part14. Thereafter, the oil is returned to the crank case from the side face of the engine4. As indicated with arrows with the reference sign F4, the communication tube part14being a section into which blow-by gas flows, this communication tube part14serves as the gas inflow part which allows the blow-by gas to flow in as well as an oil discharge part which allows oil to be discharged toward the engine4. Hereby, the structure can be simplified.

Next, description of the parts proximate the rotor of the upper housing chamber43will be given with reference toFIGS. 7 and 8. Here also in these drawings, the separation discs27are illustrated with enlarged spaces provided therebetween, however, the actual device has the separation discs27layered with much narrower spaces than those in the drawings.

As mentioned above, the rotor24is coupled to the spindle25so as to rotate integrally with this spindle25. An air through hole29bis formed at the central section of the lower holder29and thus the blow-by gas that has passed through the communication opening38flows through the air through hole29band into the hollow section of the rotor24as indicated with an arrow with the reference sign F5inFIG. 8. The blow-by gas that has flown into the hollow section of the rotor24moves through the spaces between the separation discs27toward the direction of the outer circumference of the rotor24, as indicated with arrows with the reference sign F6, by the centrifugal force created along with the rotation of the rotor24. A pressure difference is created between the outer and inner circumferential sides of the rotor24when the blow-by gas moves toward the direction of the outer circumference of the rotor24by a centrifugal force in the above manner. In other words, the pressure at the inner circumferential side becomes lower than the pressure at the outer circumferential side. With this pressure difference, the blow-by gas in the lower housing chamber42can flow easily into the hollow section of the rotor24, as indicated with an arrow with the reference sign F7inFIG. 7, thereby improving the treatment efficiency.

The oil mist included in the blow-by gas would adhere to the surface of the separation discs27when this blow-by gas contacts the separation discs27. The adhered oil mist would unite with a different oil mist so that oil is agglomerated on the surface of the separation discs27. In other words, the oil is secondarily separated. As mentioned above, the blow-by gas has the oil mist primarily separated in the lower housing chamber42. Therefore, the secondary separation at the separation discs27allows the oil mist to be separated from the blow-by gas at a high level. For such reason, the upper housing chamber43corresponds to the secondary separation chamber which secondarily separates the remaining oil mist in the blow-by gas from which oil mist has been primarily separated.

As illustrated inFIG. 8, a space45is formed between the spindle25and the spindle shaft26. This space45functions as the oil guiding path and is filled with oil fed to be injected from the nozzles31. Since the oil feeding pressure is sufficiently high, a part of the oil filled in the space45flows through the upper end of the space45, as indicated with arrows with the reference sign F8, to be emitted to the hollow section of the rotor24from the upper end of the spindle24. The oil emitted to the hollow section of the rotor24moves through the spaces between the separation discs27toward the direction of the outer circumference of the rotor24by the centrifugal force of the rotor24, as indicated with arrows with the reference sign F9, similar to the case of the blow-by gas. The oil agglomerated on the surfaces of the separation discs27at this time unites with the oil emitted to the hollow section of the rotor24.

In this oil separator2, a part of the oil fed to be injected from the nozzles31is emitted through the space45formed between the spindle25and the spindle shaft26and out to the hollow section of the rotor24. Hereby, the emitted oil is fed to the spaces between the separation discs27and then flows along the surface of the separation discs27. Thus, the surfaces of the separation discs27are cleaned which can prevent clogging caused by the agglomerated oil remaining between the separation discs27. As a result, maintenance of the separation discs27can be simplified.

The oil agglomerated or united on the surfaces of the separation discs27is emitted from the outer circumferential edges of the separation discs27and after hitting the inner wall face of the main body cover17, the oil flows down this inner wall face. Further the oil joins the oil injected from the nozzles31at the lower housing chamber42to be returned to the engine4. As mentioned above, the separation discs27are manufactured using annular plate materials which are inclined downward toward the outer circumferential side. Therefore, the agglomerated oil is emitted obliquely downward from the outer circumferential edges of the separation discs27. Hereby, the emitted oil can easily flow downward after hitting against the inner wall face of the main body cover17so that mixing of splattered oil into the blow-by gas (corresponding to the post treated gas) can be restrained. Next, description of the parts proximate the PCV valve of the upper housing chamber43will be given with reference toFIGS. 9 and 10.

The PCV valve22is arranged on the top part (corresponding to the top part of the upper case12) of the upper housing chamber43. Specifically, the PCV valve22is arranged in a state rested on the platform51at a position right under the top face cover18in the upper housing chamber43. As illustrated inFIG. 10, the platform51is hermetically covered by the diaphragm32. A lower side spring34is mounted between the platform51and the diaphragm32. Additionally, the space sectioned by the platform51and the diaphragm32is open to the atmosphere via the atmosphere communication part52. Meanwhile, an upper side spring33is mounted between the top face cover18and the diaphragm32.

With such structure, when the pressure in the upper housing chamber43becomes higher than the pressure set to the PCV, the diaphragm32moves downward to increase the amount of flow of the blow-by gas. On the other hand, when the pressure in the upper housing chamber43becomes lower than the pressure set to the PCV, the diaphragm32moves upward to decrease the amount of flow of the blow-by gas. Hereby, the pressure on the crank case side of the engine4is maintained within a predetermined range.

Since the diameter of the PCV valve22is set equal to or smaller than the diameter of the rotor24, the upper side case12need not be widened diametrically even if the PCV valve22is provided. Thus, the device is unsusceptible to constraints by the diametrical size, thereby making it possible to make the device compact.

As illustrated inFIGS. 9 and 10, the outer circumference of the platform51is sectioned by the side wall part53which is circular when seen in a planar view. This side wall part53is provided with communication openings54which communicate the section on the top face side of the diaphragm32and the section on the rotor24side, in the upper housing chamber43. A rib55is provided on the lower side of the side wall part53. This rib55is provided integral with the main body cover17, at a height lower than the rotor unit21and higher the diaphragm32. In other words, the rib55is manufactured with an annular member (short tubular member) of a diameter slightly smaller than the main body cover17.

This rib55corresponds to the tubular guiding part and guides downward the fluid (oil and blow-by gas) flowing from the outer circumferential side to the inner circumferential side along the inner surface of the main body cover17, at the upper end part of the main body cover17. Oil becomes difficult to pass through the communication openings54with this rib55so that the oil adhering to the PCV valve22can be restrained at a high level.

As it is clear from the above description, the oil separator2according to the present embodiment has the following advantages.

Firstly, since the communication tube part14is provided to introduce the blow-by gas into the lower housing chamber42, the lower housing chamber42can be used also as a drive chamber where the rotor unit21is rotated as well as an introduction chamber into which blow-by gas is introduced. Since the lower housing chamber42can be used for multiple purposes in this way, the oil separator2can be compact.

Further, the lower housing chamber42is used as the primary separation chamber for primarily separating the oil mist included in the blow-by gas and the upper housing chamber43is used as the secondary separation chamber for secondarily separating the oil mist remaining in the blow-by gas after the primary separation so that the upper housing chamber43only has to secondarily separate the remaining oil mist. Hereby, the separation efficiency of the oil mist can be improved. For example, in the example shown inFIG. 11(the particle diameter of d50 mist being 80 μm), approximately 70% of the oil mist can be separated by the primary separation at the lower housing chamber42. Further, the removal rate of oil mist after the secondary separation can reach 95% or greater by setting the number of rotor revolutions to 6000 rpm and greater.

Since the lower housing chamber42is used as the primary separation chamber in this way, the oil mist can be sufficiently separated even when the number of the required separation discs27is lessened or the diameter of the separation discs27is reduced. Thus, it is preferable for the oil separator2to be further compact by lessening the number of the separation discs27or the reducing the diameter thereof.

Further, the oil separator2according to the present embodiment has a centrifugal force created by the rotation of the rotor24(separation discs27) so that the blow-by gas flows toward the outer circumferential side of the separation discs27. In association with this, the pressure in the inner circumferential part of the rotor24becomes lower than the pressure in the outer circumferential part36. Since the lower housing chamber42and the hollow section of the rotor (upper housing chamber43) are communicated by the communication opening38, the blow-by gas in the lower housing chamber42can be easily guided to the hollow section of the rotor24. Hereby, the blow-by gas can be smoothly flown so as to improve the treatment efficiency.

Furthermore, the gas discharge part19that discharges the post treated blow-by gas is provided to the upper end part of the upper case12and the PCV valve22is provided on the top part (right below the gas discharge part19) of the upper housing chamber43. Hereby, the upper case12is unsusceptible to constraints by the diametrical size so as to be appropriate for making the device compact of the device. Additionally, the blow-by gas after having oil mist separated at the rotor unit21contacts the PCV valve22. Hereby, oil mist adhering to the PCV valve22can be restrained.

The above description of the embodiments is merely for facilitating the understanding of the present invention and is not to be interpreted as limiting the present invention. The present invention can be altered and improved without departing from the gist thereof and equivalents are intended to be embraced therein. For example, the following structures are possible.

In the aforementioned embodiment, the blow-by gas was made to flow into the lower case11as well as the oil of the lower case11made to be discharged with the communication tube part14, however, it is not limited to this structure. For example, a gas inflow part which allows blow-by gas to flow into the lower case11and an oil discharge part which discharges oil in the lower case11can be provided separately. In this case, a pipe for allowing blow-by gas to flow in just has to be joined to the side face of the lower case11. Further, the elbow pipe16and the lower case11can be provided integrally.

Further in the aforementioned embodiment, the separation discs27were annular plate materials inclined downward toward the outer circumferential side, however, it is not limited to this structure. For example, the separation discs27may be annular plate materials inclined upward toward the outer circumferential side. Further, the separation discs27may be annular plate materials deformed in corrugated forms toward the outer circumferential side.

Furthermore in the aforementioned embodiment, the structure was made such that the space45between the spindle45and the spindle shaft26was used as an oil guiding path and a part of the oil fed for injecting from the nozzles31was guided to the separation discs27, however, it is not limited to this structure. For example, all the fed oil can be injected from the nozzles31.

Even furthermore in the aforementioned embodiment, blow-by gas was exemplified as the gas as the target of treatment, however, any type of gas may be used as long as the gas includes oil mist.

REFERENCE SIGNS LIST