Patent Description:
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 <NUM> 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. Accordingly, oil after the cleaning is returned to the combustion engine, and gas from a crankcase flows into the tubular base.

An example of such oil separator is disclosed in <CIT>.

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.

In this oil separator, gas cleaning device is rotating at a high speed for separating mist oil contained in target gas from the gas. Accompanying with the rotation of gas cleaning device, a turning flow of air is generated in the inner space. The separated oil is carried by the turning flow and moves an inner surface of the upper chamber.

As the gas cleaning device rotates at a higher speed, the speed of the turning flow generated in the inner space increases. The separated oil is moved upward because of the speed increase of the turning flow. Accordingly, there is a possibility that the separated oil is discharged with target gas from the oil separator. This cause a problem that the removal efficiency of the oil contained in target gas decreases.

The present invention has been made under these circumstances, and an object of the present invention is to increase the removal efficiency of the oil contained in target gas.

To achieve the above-described object, the present invention is oil separator for separating mist oil contained in target gas. The oil separator includes: a plurality of separation disks that are rotatable together with a spindle and that are laminated in an axial direction of the spindle; a nozzle that is projected from a part of a peripheral surface of the spindle, the part being located below with respect to the separation disks, and that injects oil from an injection hole to rotate the spindle around an axis; and a housing that includes a cylindrical side wall, and that defines a chamber accommodating the spindle, the separation disks, and the nozzle, wherein a plurality of longitudinal ribs extending in the vertical direction are circumferentially formed on the inner surface of the side wall.

According to the present invention, the oil moving along the inner surface of the side wall of the upper case is captured by the longitudinal ribs and condenses. Since condensation increases the weight of oil, the condensed oil flows down along the longitudinal ribs against turning flow. This makes it possible to reduce the amount of oil that is carried upward by a turning flow and is discharged with target gas. This can increase the removal efficiency of oil.

In the above-described oil separator, the housing includes a cylindrical guide rib at a position above the separation disks, and the guide rib guides downward fluid that is flowing along the inner surface of the upper case toward a center as viewed from above. In this case, the guide rib can capture the separated oil which has not been captured by the longitudinal ribs. This can further increase the removal efficiency of oil.

In the above-described oil separator, the guide rib includes a guiding nail projecting downward beyond a lower edge of the guide rib, so that the oil that has been captured by the guide rib condenses and become likely to drop. This can further increase the removal efficiency of oil.

In the above-described oil separator, if the guiding nail is composed of a plurality of small pieces disposed with a predetermined clearance from one another, the oil that has been captured by the guide rib can be captured in a clearance between a pair of adjacent small pieces. Accordingly, the oil can easily condense.

In the above-described oil separator, if the small pieces are formed tapered off downward, the force with which the guiding nail holds the oil can be reduced as the oil heads for downward. Accordingly, the oil which has captured and condensed at the guiding nail moves downward due to its own weight, and therefore the oil can be easily release from the guiding nail.

In the above-described oil separator, a projection part of the guiding nail is disposed in a range where wind generated by a rotation of the separation disks flows through. This allows the wind generated in the separation disks to assist the release of the oil from the guiding nail. It is possible to further easily release the oil from the guiding nail.

According to the present invention, in an oil separator that separates mist oil contained in target gas from the gas, it is possible to increase the removal efficiency of the oil contained in target gas.

The following describes embodiments of the present invention with reference to the drawings. The following describes with an example of a closed crankcase ventilation system <NUM> (hereinafter referred to as a ventilation system <NUM>) illustrated in <FIG>.

As illustrated in <FIG>, the ventilation system <NUM> includes an oil separator <NUM> and a breather pipe <NUM>. The oil separator <NUM> processes blow-by gas (equivalent to target gas containing mist oil) discharged from an engine <NUM> to separate the mist oil. This embodiment includes the oil separator <NUM> at a side surface of an engine <NUM>. The breather pipe <NUM> constitutes a return flow passage, through which the processed blow-by gas discharged from the oil separator <NUM> returns to an intake-side flow passage <NUM> of the engine <NUM>.

In this ventilation system <NUM>, the blow-by gas discharged from the engine <NUM> flows into to the oil separator <NUM> disposed at the side surface of the engine <NUM>. The oil separated by the oil separator <NUM> is returned to the engine <NUM>. On the other hand, the processed blow-by gas is discharged from an upper end portion of the oil separator <NUM> and then is returned to the intake-side flow passage <NUM> through the breather pipe <NUM>. Specifically, the processed blow-by gas is returned to a part at which an air filter <NUM> is coupled to a turbocharger <NUM> in the intake-side flow passage <NUM>. The returned blow-by gas is mixed with fresh air from the air filter <NUM> and is compressed by the turbocharger <NUM>. Afterwards, the blow-by gas is cooled by a charge cooler <NUM> and is supplied to the engine <NUM>.

The following describes the oil separator <NUM>. As illustrated in <FIG>, this oil separator <NUM> includes a housing <NUM>, which includes a lower case <NUM> and an upper case <NUM>. The housing <NUM> houses various components such as a rotor unit and a PCV valve in an internal space (a chamber) (described later).

The lower case <NUM> is a part that constitutes and separates a lower side part of the housing <NUM>. The lower case <NUM> is constituted of a box-shaped member having a bottom and an opened top surface. In this embodiment, the lower case <NUM>, the communication tube portion, and the like are manufactured by casting; however, the lower case <NUM>, the communication tube portion, and the like may be manufactured by molding a resin.

As illustrated in <FIG>, a circular fitted portion <NUM> is disposed on an upper end portion of the lower case <NUM>, and is fitted to a lower end portion <NUM> of the upper case <NUM>. The lower case <NUM> includes a communication tube portion <NUM> facing backward on the back surface, and the communication tube portion <NUM> communicates backward with the engine <NUM>. The communication tube portion <NUM> includes a flange <NUM> at its distal end portion, and the flange <NUM> is joined to the side surface of the engine <NUM>. As shown in <FIG>, a tubular member <NUM> is disposed immediately above the communication tube portion <NUM>, and the tubular member <NUM> is for guiding blow-by gas. The back end of the tubular member <NUM> projects backward beyond the flange <NUM>.

As shown in <FIG>, on a bottom surface of the lower case <NUM>, a lower end portion of a joint <NUM> projects downward. This joint <NUM> has a cylindrical shape and is coupled to one end of an oil supply pipe <NUM>, which is illustrated in <FIG>. As will be described later, a part of the joint <NUM> projects upward inside the lower case <NUM>. The other end of the oil supply pipe <NUM> is coupled to the side surface of the engine <NUM>. The oil is supplied to the oil supply pipe <NUM> from an oil passage (not illustrated) disposed inside the engine <NUM>. This oil is used as a power to rotate a rotor unit <NUM>.

As illustrated in <FIG>, the upper case <NUM> is a member mounted to the lower case <NUM> from above. The upper case <NUM> and the lower case <NUM> separate a chamber that houses components such as the rotor unit <NUM>. This upper case <NUM> includes a cylindrical body cover <NUM> and a disk-shaped top surface cover <NUM>. A plurality of longitudinal ribs <NUM> are formed at regular intervals in a circumferential direction on an inner surface of the body cover <NUM>. These longitudinal ribs <NUM> capture the separated oil which is flowing circumferentially along the inner surface of the body cover <NUM>, and the oil condenses and flows down. The longitudinal ribs <NUM> will be described later.

As illustrated in <FIG>, the top surface cover <NUM> is mounted in an airtight manner to the upper end portion of the body cover <NUM>. A tubular gas discharge portion <NUM> is oriented upward at a center of the top surface cover <NUM>. This gas discharge portion <NUM> is a part from which the processed blow-by gas is discharged. The breather pipe <NUM> is coupled to the gas discharge portion <NUM> via an outlet pipe <NUM>.

The following describes an internal structure of the oil separator <NUM>. As illustrated in <FIG>, the oil separator <NUM> internally includes the rotor unit <NUM> and a partition member <NUM>. As illustrated in the cross-sectional view in <FIG>, a PCV valve <NUM> is mounted to the inside of the top surface cover <NUM>.

First, the following describes the rotor unit <NUM>. This rotor unit <NUM> is a mechanism to separate the mist oil contained in the blow-by gas. As illustrated in <FIG>, the rotor unit <NUM> includes a rotor <NUM>, a spindle <NUM>, and a spindle shaft <NUM>.

The rotor <NUM> is a part that condenses the mist oil through rotation and separates the mist oil from the blow-by gas. The rotor <NUM> includes a plurality of separation disks <NUM>, an upper holder <NUM>, and a lower holder <NUM>. The separation disks <NUM> are 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 disk <NUM> of this embodiment has a thickness of <NUM> or less, and is manufactured by molding resin. These separation disks <NUM> are laminated in an axial direction of the spindle <NUM>. For convenience of explanation, the separation disks <NUM> are illustrated providing intervals from one another; however, the actual intervals are defined to be extremely narrow (for example, less than <NUM>).

The upper holder <NUM> is a member that holds the plurality of laminated separation disks <NUM> from above. Similarly, the lower holder <NUM> is a member that holds the separation disks <NUM> from below. In the outer peripheral edge of the lower holder <NUM>, a plurality of coupling arms 36a for coupling to the upper holder <NUM> are disposed (see <FIG>). In this embodiment, the four coupling arms 36a are provided circumferentially at intervals of <NUM> degrees. The upper ends of the coupling arms 36a are joined to the upper holder <NUM> so that the plurality of separation disks <NUM>, the upper holder <NUM>, and the lower holder <NUM> are integrated to constitute the rotor <NUM>.

This rotor <NUM> has a cylindrical appearance. On the inner peripheral side of the rotor <NUM>, there is a hollow part, and the hollow part vertically extends through. The spindle <NUM> is inserted into this hollow part and the spindle <NUM> and the rotor <NUM> are joined to one another. Accordingly, the rotor <NUM> rotates, together with the spindle <NUM>, around the axis of the spindle <NUM>.

Nozzles <NUM> project from a part of a peripheral surface of the spindle <NUM> located below the rotor <NUM>. Each of the nozzles <NUM> is a part from which the oil supplied through the spindle shaft <NUM> is injected to generate a driving power to rotate the spindle <NUM> and the rotor <NUM>.

The nozzles <NUM> of this embodiment include cylindrical nozzle bodies <NUM> and injection holes <NUM> disposed at distal end portions of the nozzle bodies <NUM>. Base ends of the nozzle bodies <NUM> are coupled to the spindle <NUM>, and the distal ends of the nozzle bodies <NUM> are closed. The nozzle bodies <NUM> are mounted at an angle of <NUM> degrees obliquely downward with respect to the axial direction of the spindle <NUM> indicated by reference symbol AL. The three nozzle bodies <NUM> are circumferentially disposed at intervals of <NUM> degrees. The injection hole <NUM> is disposed on a side surface at the distal end portion of the nozzle body <NUM>. More specifically, the injection hole <NUM> is disposed in a direction perpendicular to the axial direction of the nozzle body <NUM> indicated by reference symbol NL so that oil is injected horizontally.

The spindle shaft <NUM> is a pillar member serving as a bearing of the spindle <NUM>, and supports the spindle <NUM> in a rotatable manner. As illustrated in <FIG>, the spindle shaft <NUM> internally includes an oil supply passage 33a to supply the oil. A lower end portion of the spindle shaft <NUM> is coupled to an upper end portion of the joint <NUM>, disposed in the lower case <NUM>. As described above, the oil supply pipe <NUM> is coupled to the joint <NUM>. Accordingly, the oil supplied through the oil supply pipe <NUM> passes through the joint <NUM>, and then flows into the spindle shaft <NUM>. Thereafter, the oil flows into the nozzle bodies <NUM>, and then is injected from the injection holes <NUM>.

As described above, the injection hole <NUM> is disposed at the distal end portion of the nozzle body <NUM> in a direction in which oil is injected horizontally. At the three nozzles <NUM> disposed at intervals of <NUM> degrees, formation positions for the injection holes <NUM> are matched. Accordingly, when the oil is injected from the respective injection holes <NUM>, the rotor <NUM> and the spindle <NUM> rotate about the spindle shaft <NUM> as the axis.

The following describes the partition member <NUM>. As illustrated in <FIG>, the partition member <NUM> is a member that partitions the internal space (the chamber) of the housing <NUM> into a lower chamber <NUM> (a primary separation chamber) and an upper chamber <NUM> (a secondary separation chamber). And the partition member <NUM> forms a communication port <NUM>, and the blow-by gas in the lower chamber <NUM> is guided by the communication port <NUM> to the upper chamber <NUM>. The partition member <NUM> has an outer peripheral portion <NUM> and a tapered portion <NUM>. The outer peripheral portion <NUM> is a short cylindrical part and has a collar portion <NUM> projecting outwardly at the middle in the height direction. The tapered portion <NUM> is disposed on the inner peripheral side with respect to the outer peripheral portion <NUM>, and has a tapered shape in which the diameter is gradually reduced from the lower end of the outer peripheral portion <NUM> toward the top. The tapered portion <NUM> of this embodiment has an inclined surface 45a that inclines at an angle of approximately <NUM> degrees with respect to the axis of the spindle <NUM>. An upper end opening of the tapered portion <NUM> forms the communication port <NUM>.

The partition member <NUM> is fitted to the inner peripheral side of the fitted portion <NUM> in the lower case <NUM>. The collar portion <NUM> abuts on an upper end of the fitted portion <NUM> from above to be positioned. Consequently, the tapered portion <NUM> is disposed immediately below the lower holder <NUM> included in the rotor <NUM>. The chamber is partitioned into the lower chamber <NUM> and the upper chamber <NUM>, which are bordered by the partition member <NUM>. These lower chamber <NUM> and upper chamber <NUM> are communicated through the communication port <NUM>. That is, this partition member <NUM> forms the communication port <NUM> around the spindle <NUM> at a height between the nozzles <NUM> and the separation disks <NUM>, and the communication port <NUM> guides the blow-by gas in the lower chamber <NUM> to the upper chamber <NUM>.

When the rotor <NUM> rotates 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 holes <NUM>. 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 chamber <NUM>, 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 spindle <NUM> and the rotor <NUM>. Therefore, the lower chamber <NUM> functions as the primary separation chamber for the mist oil.

The following describes the PCV valve <NUM>. As illustrated in <FIG>, the PCV valve <NUM> includes a diaphragm <NUM>, upper springs <NUM>, and lower springs <NUM>.

The diaphragm <NUM> is a valve element and is manufactured by molding rubber and resin. The diaphragm <NUM> is composed of a disk-shaped member slightly inclining downward from the center to the peripheral edge portion. The upper springs <NUM> and the lower springs <NUM> are members to support the diaphragm <NUM> in such a manner that the diaphragm <NUM> can move vertically. That is, the upper springs <NUM> are disposed at the center of the diaphragm <NUM> from above, and the lower springs <NUM> are disposed at the center of the diaphragm <NUM> from below. The diaphragm <NUM> is supported in a vertically movable manner by being sandwiched between these upper springs <NUM> and lower springs <NUM>.

This PCV valve <NUM> is disposed at the upper portion of the upper case <NUM>. More specifically, the PCV valve <NUM> is placed on a pedestal portion <NUM> at a position immediately below the top surface cover <NUM>. The diaphragm <NUM> covers this pedestal portion <NUM> in an airtight manner. The lower springs <NUM> are mounted between the pedestal portion <NUM> and the diaphragm <NUM>. A space defined by the pedestal portion <NUM> and the diaphragm <NUM> is open to open air through an air communicating portion <NUM>. On the other hand, the upper springs <NUM> are mounted between the top surface cover <NUM> and the diaphragm <NUM>.

The diaphragm <NUM> vertically moves according to intake-side pressure of the engine <NUM> and 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 engine <NUM>, the diaphragm <NUM> moves toward the gas discharge portion <NUM> (upward), and under a high pressure of the side close to the crankcase, the diaphragm <NUM> moves toward the opposite side (downward).

Accordingly, when the pressure in the upper chamber <NUM> becomes higher than a PCV-set pressure, the diaphragm <NUM> moves downward to increase a flow rate of the blow-by gas. On the contrary, when the pressure in the upper chamber <NUM> is lower than the PCV-set pressure, the diaphragm <NUM> moves 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 engine <NUM> maintains within a constant range.

An outer periphery of the pedestal portion <NUM> on which the PCV valve <NUM> is placed is defined by a sidewall portion, the sidewall portion having a circular shape as viewed from above. A communicating window <NUM> is disposed at this sidewall portion. Through this communicating window <NUM>, an upper part of the upper chamber <NUM> with respect to the diaphragm <NUM> and a part of the upper chamber <NUM> on the rotor <NUM> side communicate. A cylindrical rib <NUM> is disposed at the lower side of the sidewall portion. This cylindrical rib <NUM> corresponds to the guide rib which guides downwardblow-by gas from the outer peripheral side. The cylindrical rib <NUM> will be described later with the longitudinal rib <NUM>.

Here, the internal structure of the lower case <NUM> will be described below. As shown in the cross-sectional view of <FIG>, in the internal space of the lower case <NUM>, the cylindrical joint <NUM> projecting upward is provided. A part of the tubular member <NUM> is disposed along the joint <NUM>. This tubular member <NUM> is bent into an L shape in the middle, and the remaining part is disposed parallel to the communication tube portion <NUM>. The tubular member <NUM> is disposed immediately above the communication tube portion <NUM>, and an end portion of the tubular member <NUM> projects from the flange <NUM>.

An upper end portion of the joint <NUM> is fitted to a stationary frame <NUM>. This stationary frame <NUM> is a metallic frame mounted to the fitted portion <NUM> in the lower case <NUM> (see <FIG>). In the tubular member <NUM>, the end portion on the side at which blow-by gas is discharged is disposed near the joint <NUM> and immediately below the stationary frame <NUM>. Accordingly, the blow-by gas discharged from the tubular member <NUM> flows upward through the stationary frame <NUM>, and flows into the hollow part of the rotor <NUM>.

Here, the overall operation of the oil separator <NUM> having the foregoing configuration will be described. As shown in <FIG>, the oil which has been supplied from the engine <NUM> to the joint <NUM> through the oil supply pipe <NUM> flows into the spindle shaft <NUM> as indicated by an arrow with reference symbol F1. Afterwards, the oil flows from the spindle shaft <NUM> to the nozzle bodies <NUM> and is injected from the injection holes <NUM> as indicated by an arrow with reference symbol F2. By the injection of the oil from each injection hole <NUM>, the rotor <NUM> and the spindle <NUM> rotate around the spindle shaft <NUM>.

The oil which has been injected by the nozzle <NUM> (the injection holes <NUM>) is sprayed to the tapered portion <NUM> of the partition member <NUM>. And then, as indicated by an arrow with reference symbol F3, the oil is guided obliquely below toward the outer peripheral side along the inclined surface 45a of the tapered portion <NUM>. As indicated by an arrow with reference symbol F4, the guided oil is collected, together with the oil which has been separated from blow-by gas, in the bottom of the lower chamber <NUM>. Then, the oil is returned to the engine <NUM> through the communication tube portion <NUM> as indicated by an arrow with reference symbol F5.

On the other hand, as indicated by an arrow with reference symbol F11, the blow-by gas from the engine <NUM> is guided by the tubular member <NUM>. Afterwards, as indicated by an arrow with reference symbol F12, the blow-by gas which has been discharged from the tubular member <NUM> flows into the hollow part of the rotor <NUM> through an area inside the motion paths of the injection holes <NUM>. As indicated by an arrow with reference symbol F13, the blow-by gas flowing into the hollow part moves through the clearances between the separation disks <NUM> to the outer peripheral direction of the rotor <NUM> due to a centrifugal force generated by the rotation of the rotor <NUM>.

When the blow-by gas comes into contact with the separation disks <NUM>, the mist oil contained in this blow-by gas attaches to the surfaces of the separation disks <NUM>. The attached mist oil and additional mist oil coalesce, and thus the oil condenses on the surfaces of the separation disks <NUM>. That is, the oil undergoes secondary separation. Thus, the upper chamber <NUM> corresponds 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.

A clearance SP is formed between the spindle <NUM> and the spindle shaft <NUM>. This clearance SP serves as an oil guiding passage and is filled with the oil which is supplied to be injected from the nozzles <NUM>. 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 spindle <NUM> to the hollow part of the rotor <NUM>. Similar to the blow-by gas, due to the centrifugal force of the rotor <NUM>, the oil discharged to the hollow part of the rotor <NUM> moves through the clearances between the separation disks <NUM> to the outer peripheral direction of the rotor <NUM>.

The oil condensed on the surfaces of the separation disks <NUM> coalesces with the oil discharged to the hollow part of the rotor <NUM>. The oil which has coalesced is discharged from the outer peripheral edges of the separation disks <NUM>. The oil collides with the inner surface of the body cover <NUM>, and then flows down along this inner surface. And, the oil joins the oil injected from the nozzles <NUM> in the lower chamber <NUM> and is returned to the engine <NUM>.

The blow-by gas, which has passed through the rotor <NUM> and from which the mist oil has been separated, moves upward with turning through the clearance between the inner surface of the upper case <NUM> and the rotor <NUM> in the upper chamber <NUM>. It may be considered that the separated oil is carried upward by a turning flow of the blow-by gas. However, as to be described later, the movement of the oil is blocked by the longitudinal ribs <NUM>, which are disposed at the inner surface of the body cover <NUM>, or by the cylindrical rib <NUM>, which are disposed below the pedestal portion <NUM>.

Thus, the blow-by gas from which the mist oil has been separated is introduced to the space on the top surface side of the PCV valve <NUM>, as indicated by arrows with reference symbols F14 and F15. Then, as indicated by an arrow with reference symbol F16, the blow-by gas passes through the outlet pipe <NUM> and is introduced to the breather pipe <NUM>.

Here, the longitudinal ribs <NUM> and the cylindrical rib <NUM> will be described below in detail. First, the longitudinal ribs <NUM> will be described. <FIG> is a cross-sectional view illustrating the internal structures of the upper case <NUM> and the lower case <NUM>, and the rotor unit <NUM> and the partition member <NUM> are omitted from the figure. <FIG> is a magnified view of a part of the longitudinal ribs <NUM>.

As illustrated in these figures, the plurality of longitudinal ribs <NUM> are disposed on the inner surface of the body cover <NUM> (the cylindrical side wall) constituting the upper case <NUM> throughout the entire circumference. Each of the longitudinal ribs <NUM> extends in the vertical direction (the axial direction of the spindle shaft <NUM>). In this embodiment, the height and the width of each longitudinal rib <NUM> from the inner surface are each <NUM>, and the number of the longitudinal ribs <NUM>, which are circumferentially equally spaced, is twenty four. The length of the longitudinal rib <NUM> is defined identical to or slightly longer than the height of the rotor unit <NUM>.

As described above, these longitudinal ribs <NUM> capture and condense the separated oil which is circumferentially flowing along the inner surface of the body cover <NUM> so that the oil flows downward. A high speed rotation of rotor unit <NUM> generates a highspeed turning flow around the rotor unit <NUM>. For example, a turning flow indicated by an arrow of reference symbol F21 in <FIG> is generated. The separated oil is carried by the turning flow and moves on the inner surface of the body cover <NUM>. As the speed of the turning flow increases, the oil is also affected by upward flowing of blow-by gas. Accordingly, the oil moving on the inner surface is subject to buoyancy directing obliquely upward indicated by an arrow of reference symbol F22.

In the present invention, since the plurality of longitudinal ribs <NUM> are formed on the inner surface of the body cover <NUM>, the movement of the separated oil circumferentially flowing on the inner surface is blocked by the longitudinal ribs <NUM> and the oil is captured as indicated by an arrow of reference symbol F23. The captured oil coalesces with subsequent oil and condenses. Since condensation increases the weight of oil, the condensed oil flows down along the longitudinal ribs <NUM> against a turning flow. This makes it possible to reduce the amount of oil that is carried upward by a turning flow and is discharged with blow-by gas. This can increase the removal efficiency of oil.

In the present invention, the height of the longitudinal rib <NUM> is set to <NUM>. However, in experiments, the longitudinal ribs <NUM> having a height of <NUM> to <NUM> enable the separated oil which is circumferentially flowing to flow down. Concerning the number of the longitudinal ribs <NUM>, there is no significant difference of effect in experiments using <NUM> pieces of longitudinal ribs. Accordingly, it is considered that, if the longitudinal ribs <NUM> are placed at intervals appropriate to the speed of turning flow, the mixture of oil to blow-by gas can be prevented.

In the present invention, as illustrated in <FIG>, a plurality of reinforcing ribs <NUM> are disposed on the outer surface of the body cover <NUM> through the entire circumference. Accordingly, the reinforcing ribs <NUM> ensure the necessary strength of the body cover <NUM>. This increases the degree of freedom in design of the longitudinal ribs <NUM>. That is, the longitudinal ribs <NUM> can be disposed at a height and at intervals appropriate to the speed of turning flow.

The cylindrical rib <NUM> (the guide rib) will be described below. As illustrated in a partially-cut cross-sectional view in <FIG>, the cylindrical rib <NUM> is a circular ring-shaped protrusion disposed inside the body cover <NUM> facing downward at a position below the pedestal portion <NUM>, on which the PCV valve <NUM> is placed. As apparent from the cross-sectional view in <FIG>, the diameter of the cylindrical rib <NUM> approximately matches the diameter of the rotor <NUM>. The cylindrical rib <NUM> and the rotor <NUM> are concentrically disposed as viewed in the planar direction. A predetermined clearance is defined between a lower edge of the cylindrical rib <NUM> and an outer peripheral upper edge of the rotor <NUM>.

As illustrated in <FIG>, the cylindrical rib <NUM> includes guiding nails <NUM> projecting downward beyond the lower edge of the cylindrical rib <NUM>. These guiding nails <NUM> are projections to condense the oil captured at the cylindrical rib <NUM> and to drop the oil. As illustrated in <FIG>, a projection length of the guiding nail <NUM> is defined slightly shorter than the clearance between the cylindrical rib <NUM> and the rotor <NUM>. The lower ends of the guiding nails <NUM> are positioned immediately above the outer peripheral upper edge of the rotor <NUM>.

The guiding nails <NUM> according to the present embodiment are circumferentially disposed at intervals of <NUM> degrees. That is, six pieces of the guiding nails <NUM> are disposed in total. As shown in the magnified view of <FIG>, the guiding nails <NUM> are composed of small pieces <NUM> each having an arrow shape heading downward; in other words, the small pieces <NUM> each have a shape whose lower part is tapered off like a wedge. As illustrated in <FIG>, a pair of small pieces <NUM> are laterally mounted with predetermined intervals. This mounting interval is defined to be a size at which the oil moving along the cylindrical rib <NUM> can be captured at the clearances between the adjacent small pieces <NUM>. For example, the mounting interval is defined around <NUM> to <NUM>.

Thus, the cylindrical rib <NUM> to which the guiding nails <NUM> are mounted is disposed. Accordingly, the separated oil which has failed to be fully removed by the longitudinal ribs <NUM> can be reliably captured. This feature will be described below with reference to the schematic diagrams in <FIG>, <FIG>.

For example, as indicated by arrows with reference symbols F21 to F23 in <FIG>, oil OL that has moved up to the outer surface of the cylindrical rib <NUM> flows down the outer surface of the cylindrical rib <NUM>, and the oil OL moves to the lower end of the cylindrical rib <NUM>. As illustrated in <FIG> and <FIG>, the oil OL that has moved to the lower end of the cylindrical rib <NUM> moves along the lower end of the cylindrical rib <NUM> as indicated by an arrow with reference symbol F24. Then, the oil OL attaches to the surface on a windward side of the small piece <NUM>. As the time elapses, additional oil OL also attaches to the surface of the small piece <NUM> and coalesces. Accordingly, as illustrated in <FIG>, the attached oil OL is held at the clearance formed between the respective small pieces <NUM> by surface tension.

Afterwards, when additional oil OL further coalesces, the own weight of the oil increases, and the oil OL moves downward as illustrated in <FIG> and <FIG>. As described above, the distal ends of the pair of small pieces <NUM> constituting the guiding nails <NUM> are tapered off to the lower end. Accordingly, as the oil OL moves down, a force with which the small pieces <NUM> hold the oil OL reduces. Consequently, the oil OL becomes likely to release. As indicated by an arrow with reference symbol F25, when the oil OL falls from the guiding nail <NUM>, the clearance formed by the respective small pieces <NUM> returns to a state where the new droplet of oil OL can be accumulated, as illustrated in <FIG>.

As described above, the lower ends of the guiding nails <NUM> are positioned immediately above the upper end on the outer periphery of the rotor <NUM>. Accordingly, an air current generated by the rotation of the rotor <NUM> acts on the projection portions of the guiding nails <NUM> from the cylindrical rib <NUM>. When the oil OL flowing down on the guiding nails <NUM> receives this air current, the oil OL forms droplets and is blown out the oil OL to the outer periphery direction. Consequently, the separated oil which has been turned into mist is less likely to return to the blow-by gas. This can increase the removal efficiency of oil.

Thus, the oil separator <NUM> according to the present embodiment includes the cylindrical rib <NUM>. Accordingly, the guide rib can capture the separated oil which has failed to be captured by the longitudinal ribs <NUM>. This can further increase the removal efficiency of oil. Since this cylindrical rib <NUM> has the guiding nails <NUM>, the oil that has reached the lower end of the cylindrical rib <NUM> can condense easily.

The guiding nails <NUM> are composed of the pair of small pieces <NUM>, which are disposed with the predetermined clearances from one another. This allows the clearances between the adjacent small pieces <NUM> to capture the oil which has been captured by the guide rib. Accordingly, the oil can condense easily. In addition, since these small pieces <NUM> are formed tapered off downward, the force with which the small pieces <NUM> hold the oil OL can be reduced as the oil heads for downward. Accordingly, the oil which has captured and condensed at the guiding nails <NUM> moves downward due to its own weight, and therefore the oil can be easily release from the guiding nails <NUM>.

The projection parts of the guiding nails <NUM> are disposed in the range where the wind (the turning flow) generated by the rotation of the rotor <NUM> (the separation disks <NUM>) flows through. This allows the wind generated in the separation disks <NUM> to assist the release of the oil from the guiding nails <NUM>. It is possible to further easily release the oil from the guiding nails <NUM>.

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. For example, the present invention may be configured as follows.

The height and the number of the longitudinal ribs <NUM> are not limited to the examples of the embodiment. As long as the longitudinal ribs <NUM> extend in the vertical direction, the longitudinal ribs <NUM> may not have the linear shape. For example, the longitudinal rib <NUM> may be a spiral rib which guides obliquely downward the oil that has received the turning flow.

The configuration that the upper case <NUM> includes the longitudinal ribs <NUM> is described as the example. However, the lower case <NUM> may include the longitudinal ribs <NUM>. The housing <NUM> may have a three-piece configuration composed of an upper portion, an intermediate portion and a lower portion. In this case, the intermediate portion may include the longitudinal ribs <NUM>.

The number of the guiding nails <NUM> is not limited to six. The number of the small pieces <NUM>, which constitute the guiding nails <NUM>, is not limited to two. The number of the small pieces <NUM> may be three or more, or also may be one. It is more preferable that the guiding nails <NUM> is composed of the plurality of small pieces <NUM>, because the oil can be captured in their clearances.

Claim 1:
An oil separator for separating mist oil contained in target gas, wherein the oil separator comprises:
a plurality of separation disks (<NUM>) that are rotatable together with a spindle and that are laminated in an axial direction of the spindle;
a nozzle (<NUM>) that is projected from a part of a peripheral surface of the spindle, the part being located below the separation disks, and that injects oil from an injection hole to rotate the spindle around an axis;
a housing (<NUM>) that includes a cylindrical side wall and defining a chamber accommodating the spindle, the separation disks, and the nozzle, characterized by the housing including a cylindrical guide rib (<NUM>) at a position above the separation disks, and the guide rib guides downward fluid that is flowing along an inner surface of the upper case toward a center as viewed from above, wherein the guide rib includes a guiding nail (<NUM>) projecting downward beyond a lower edge of the guide rib; and
a plurality of longitudinal ribs (<NUM>) extending in the vertical direction are circumferentially formed on the inner surface of the side wall.