Screw compressor having a plurality of branch paths with intersects and central axes

Provided is a liquid supply mechanism including: a plurality of liquid supply sections each including a plurality of branch paths whose central axes intersect with each other, and a supply path having a side surface to which the plurality of branch paths of the plurality of liquid supply sections are directly connected, respectively, and supplying liquid, which is supplied from an upstream, to the branch paths.

TECHNICAL FIELD

The present invention relates to a liquid supply mechanism.

BACKGROUND ART

There is a liquid supply mechanism which has a function of causing jet streams of liquid to collide with each other so as to be thinned or atomized before supply.

There is a conventional technique of atomizing liquid before supply, in which a water supply section is formed in a wall surface of a casing corresponding to a compression chamber in a compressor, and water is injected from the section into the compression chamber. In the conventional technique, the water supply section includes a bottom having a blind hole at a central part, in which a plurality of small holes are formed at an angle of θ so as to communicate with the outside. The water guided to the blind hole is extensively injected through the small holes into the compression chamber. Patent Literature 1 is an example of the conventional technique.

CITATION LIST

Patent Literatures

Patent Literature 1: Japanese Patent Application Publication No. 2003-184768

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

In the screw compressor described in Patent Literature 1 using the conventional technique described above, the number of blind holes increases in proportion to the number of water supply sections (liquid supply sections). Therefore, the number of processing steps increases in proportion to the number of liquid supply sections, so that a manufacturing cost increases. Further, the number of paths increases by the number of blind holes, so that the number of joints and sealing members in the paths increases. As a result, there is an increasing risk that the liquid is leaked outside the compressor.

The present invention is intended to provide a liquid supply mechanism which allows for reducing a manufacturing cost and preventing joints and sealing members from increasing in number even in a case where a plurality of liquid supply sections are present.

Means to Solve the Problems

In order to solve the above problems, a liquid supply mechanism of the present invention includes a plurality of liquid supply sections each including a plurality of branch paths whose central axes intersect with each other, and a supply path through which liquid supplied from upstream is supplied to the branch paths. The plurality of branch paths of the plurality of liquid supply sections are directly connected to a side surface of the supply path, respectively.

Further, a screw compressor of the present invention includes the liquid supply mechanism, a screw rotor, a casing in which the screw rotor is accommodated. The liquid supply mechanism supplies liquid into a compression chamber defined in the casing.

Advantageous Effects of the Invention

According to the present invention, even in the case where the plurality of liquid supply sections are present, the manufacturing cost is reduced, and joints and sealing members are prevented from increasing in number.

EMBODIMENTS OF THE INVENTION

Descriptions will be given of embodiments of the present invention in detail with reference to the accompanying drawings as appropriate.

Note that, in the drawings, common components or similar components are denoted by the same reference numerals, and duplicate descriptions thereof are omitted appropriately.

First Embodiment

A first embodiment of the present invention will be described with reference toFIG. 1andFIG. 2.

FIG. 1is a cross-sectional view of a liquid supply mechanism10according to the first embodiment of the present invention.FIG. 2is a cross-sectional view taken along a line II-II inFIG. 1. Note that, inFIG. 2, a background is not shown.

The liquid supply mechanism10of the present embodiment has a function of causing jet streams of lubricant to collide with each other as liquid to be thinned or atomized before supply.

As shown inFIG. 1, the liquid supply mechanism10includes a plurality of liquid supply sections1(two in this case). The liquid supply sections1include a first liquid supply section3and a second liquid supply section4located downstream of the first liquid supply section3in a supply path5. Thus, the liquid supply sections1are used as a general term of the first liquid supply section3and second liquid supply section4.

The first liquid supply section3includes a plurality of branch paths3a,3b(a pair in this case) whose central axes intersect with each other at an angle of θ. The second liquid supply section4includes a plurality of branch paths4a,4b(a pair in this case) whose central axes intersect with each other at an angle of Ψ. The branch path3aand branch path3bare symmetrical with respect to a plane3crunning through an intersection of the central axes of the branch paths3aand3band being orthogonal to a central axis9of the supply path5. Further, the branch path4aand branch path4bare symmetrical with respect to a plane4crunning through an intersection of the central axes of the branch paths4a,4band being orthogonal to the central axis9of the supply path5. As shown inFIG. 1andFIG. 2, the branch paths3a,3band the branch paths4a,4bare directly connected to a side surface of the supply path5for communication.

As shown inFIG. 1, the supply path5, and the branch paths3a,3b,4a, and4bare formed in a casing2. The supply path5has an upstream end6thereof connected to a pump (not shown), and a downstream end7thereof forming an end surface as a dead-end surface.

With the liquid supply mechanism10thus configured, when the pump is activated, the lubricant flowing into the supply path5through the upstream end6flows into the branch paths3a,3b,4a,4b, respectively. The lubricant flowing out as a jet flow from the branch paths3a,3b, respectively, collides with each other at the angle of θ so as to be thinned and atomized to diffuse into a space8as a supply destination. The same applies to the lubricant flowing out from the branch paths4a,4b, respectively.

As described above, the liquid supply mechanism10according to the present embodiment includes the liquid supply sections1, each including the branch paths3aand3b, or4aand4bhaving the central axes to intersect with each other, and the supply path5through which the lubricant supplied from upstream is supplied to the branch paths3a,3b,4a,4b. The branch paths3a,3b,4a,4bof the liquid supply sections1are directly connected to the side surface of the supply path5, respectively.

Therefore, in the present embodiment, even in a case where the liquid supply sections1increase in number, the supply path5can be used in common as a path introducing the liquid to each of the branch paths3a,3b,4a,4b, which leads to reduction in the number of processing steps and in the manufacturing cost. Further, even if the branch paths3a,3b,4a,4bincreases in number, the openings to the outside do not increase in number, except communicating sections between the branch paths3a,3b,4a,4band the space8as a supply destination. Therefore, the paths connecting to the openings do not increase in number, so that an increase of joints and sealing members in the paths is prevented. Accordingly, a risk of lubricant leakage to the outside is reduced in a device provided with the liquid supply mechanism10, and the liquid supply sections1can be increased in number while reliability is improved.

Thus, according to the present embodiment, even in the case where the plurality of liquid supply sections1are present, the manufacturing cost is reduced, and the increase of joints and sealing members is prevented.

Second Embodiment

Next, a description will be given of a second embodiment with reference toFIGS. 3 and 4, focusing on differences from the first embodiment described above and the duplicate descriptions are omitted.

FIG. 3is a cross-sectional view of the liquid supply mechanism10according to the second embodiment of the present invention.FIG. 4is a cross-sectional view taken along a line IV-IV inFIG. 3. Note that inFIG. 4, a background is not shown.

As shown inFIG. 3andFIG. 4, the inner diameter of each of the branch paths3a,3b,4a,4bis identical and denoted by d, and the inner diameter of the supply path5is denoted by D.

The present embodiment differs from the first embodiment in that the inner diameter D of the supply path5at a connecting section C between the supply path5and the branch paths3a,3b,4a,4bis larger than the inner diameter d of each of the branch paths3a,3b,4a,4b.

In the present embodiment, the inner diameter D of the supply path5and the inner diameter d of each of the branch paths3a,3b,4a,4bhas a relationship shown by the following expression, for example.
D=6.3d(1)

In general, flow resistance at a branch section (connecting section), where branch pipes are branched from a main pipe, is known to be smaller when an angle, which is defined by an upstream of a main stream and the branch path, is an obtuse angle, than when the angle is an acute angle.

In the first liquid supply part3of the present embodiment, an angle defined by the branch path3aand the central axis9of the supply path5is an obtuse angle of (π+θ)/2, and an angle defined by the branch path3band the central axis9of the supply path5is an acute angle of (π−θ)/2. Accordingly, in the first liquid supply section3, the flow resistance at the connecting section C between the supply path5and the branch path3bis larger than the flow resistance at the connecting section C between the supply path5and the branch path3a. Therefore, there is a risk that a flow rate of the lubricant flowing through the branch path3ais larger than that flowing through the branch path3b. In this case, in the first liquid supply section3, there is a risk that a deviation in the flow rate between the branch paths3a,3bgives a negative influence on uniform diffusion of the thinned or atomized lubricant, or the very characteristics of thinning and atomization.

In the present embodiment, as described above, the inner diameter D of the supply path5and the inner diameter d of each of the branch paths3a,3b,4a,4bare set to have the relationship shown by the expression (1). Thus, a relationship shown in the following expression is established between an average flow velocity V of the lubricant in the supply path5and an average flow velocity v of the lubricant in each of the branch paths3a,3b,4a,4b, based on the continuity equation of incompressible fluid (cross-sectional area×flow rate=constant).
v=10V(2)

In this case, a dynamic pressure PD in the supply path5and an average dynamic pressure Pd in each of the branch paths3a,3b,4a,4bis derived from the expression (2), as follows.

In the first liquid supply section3of the present embodiment, the total flow resistance from the upstream end6of the supply path5up to the space8as a supply destination is referred to as R. Further, the flow resistance in the supply path5is referred to as R1, the flow resistance at the connecting sections C between the supply path5and the branch paths3a,3bis referred to as R2, the flow resistance in the branch paths3a,3bis referred to as R3, and the flow resistance at an enlarged section from the branch paths3a,3bto the space8is referred to as R4. In this case, the total flow resistance R is obtained by: R=R1+R2+R3+R4. Here, the flow resistance R2 is defined by the average flow velocity V of the lubricant in the supply path5. Further, the flow resistance R4 is defined by the average flow velocity v of the lubricant in the branch paths3a,3b.

The flow resistance is proportional to the dynamic pressure. Therefore, a ratio of the flow resistance R2, at the connecting sections C between the supply path5and the branch paths3a,3b, to the total flow resistance R is about 1%, based on the expressions (3) and (4). Consequently, the flow resistance R3 in the branch path3a,3bis overwhelmingly dominant in the total flow resistance R. Accordingly, influence of the flow resistance at the connecting sections C due to the angles defined by the supply path5and each branch path3a,3b, on the flow rate of the lubricant through each branch path3a,3b, is extremely small. This allows for reducing deviation of the flow rate of the lubricant in each branch path3a,3b. The same advantageous effect is obtained in the second liquid supply section4.

Therefore, according to the second embodiment, a diffusion range of the lubricant after jet collision is unified, and deterioration of characteristics of thinning and atomization is prevented, in addition to the advantageous effect obtained by the first embodiment described above.

Third Embodiment

Next, a description will be given of a third embodiment of the present invention with reference toFIG. 5, focusing on differences from the first embodiment described above, and the duplicate descriptions are omitted.

FIG. 5is a cross-sectional view of the liquid supply mechanism10according to a third embodiment of the present invention.

As shown inFIG. 5, an inner diameter of each of the branch path3aand branch path4ais referred to as da, and an inner diameter of the branch path3band branch path4bis referred to as db. Further, a plane, which runs through the intersection of the central axes of the branch paths3a,3band is orthogonal to the central axis9of the supply path5, is referred to as3c, and a plane, which runs through the intersection of the central axes of the branch paths4a,4band is orthogonal to the central axis9of the supply path5, is referred to as4c.

The present embodiment differs from the first embodiment in that the inner diameter db of the branch path3blocated downstream of the supply path5with respect to the plane3cis larger than the inner diameter da of the branch path3alocated upstream of the supply path5with respect to the plane3c. The same applies to the branch paths4a,4b. That is, in each of the liquid supply sections1, the branch path3bor4b, which is located downstream, has a larger inner diameter.

That is, the inner diameter da of the branch path3aand branch path4aand the inner diameter db of the branch path3band branch path4bhave a relationship shown by the following expression.
db>da(5)

As described in the second embodiment, the flow resistance at the connecting section C between the supply path5and the branch path3ais smaller than the flow resistance at the connecting section C between the supply path5and the branch path3b. Therefore, the flow rate of the lubricant in the branch path3amay be larger than that in the branch path3b. Then, in the present embodiment, the inner diameter db of the branch path3bis made larger than the inner diameter da of the branch path3a, so that the flow velocity of the lubricant in the branch path3bis made slower than that in the branch path3a. Therefore, as described in the expression (4), the dynamic pressure in the branch path3bis lower than that in the branch path3a. The flow resistance in the branch paths3a,3bis proportional to the dynamic pressure, so that, as a result, the flow resistance in the branch path3bis lower than that in the branch path3a, based on the expression (5). Therefore, the difference between the flow resistance at the connecting section between the supply path5and the branch path3aand the flow resistance at the connecting section between the supply path5and the branch path3bis lessened. Thus, the deviation in flow rate of the lubricant in the branch paths3a,3bis reduced. The same advantageous effect is obtained in the second liquid supply section4.

Therefore, according to the third embodiment, a diffusion range of the lubricant after jet collision is unified, and deterioration of characteristics of thinning and atomization is prevented, in addition to the advantageous effect obtained by the first embodiment described above.

Fourth Embodiment

Next, a description will be given of a fourth embodiment of the present invention with reference toFIG. 6, focusing on differences from the first embodiment described above, and the duplicate descriptions are omitted.

FIG. 6is a cross-sectional view of the liquid supply mechanism10according to the fourth embodiment of the present invention.

As shown inFIG. 6, the plane, which runs through the intersection of the central axes of the branch paths3a,3band is orthogonal to the central axis9of the supply path5, is referred to as3c, and the plane, which runs through the intersection of the central axes of the branch paths4a,4band is orthogonal to the central axis9of the supply path5, is referred to as4c. An angle defined by the central axis of the branch path3a, located upstream of the supply path5with respect to the plane3c, and the plane3c, is referred to as ea, and an angle defined by the central axis of the branch path3b, located downstream of the supply path5with respect to the plane3c, and the plane3c, is referred to as θb. An angle defined by the central axis of the branch path4a, located upstream of the supply path5with respect to the plane4c, and the plane4c, is referred to as Ψa, and an angle defined by the central axis of the branch path4b, located downstream of the supply path5with respect to the plane4c, and the plane4c, is referred to as Ψb. The angles θa, θb, Ψa, Ψb each are a crossing angle defined on a side of a branch path closer to the supply path5and an acute angle.

The present embodiment differs from the first embodiment in that the angle θb is larger than the angle θa, and the angle Ψb is larger than the angle Ψa. That is, in each of the liquid supply sections1, the branch path3bor4blocated downstream has a larger angle defined by the central axis and the plane3cor4c.

That is, the angles θa, θb, Ψa, Ψb have relationships shown in the following expressions.
θa<θb(6)
Ψa<Ψb(7)

As described in the second embodiment, the flow resistance at the connecting section C between the supply path5and the branch path3ais smaller than that at the connecting section C between the supply path5and the branch path3b. Therefore, the flow rate of the lubricant in the branch path3amay be larger than that in the branch path3b. The lubricant injected from the branch path3aand branch path3bcollides with each other, and normally diffuses to be thin on the plane3c. An oil film spreads in the width direction with progression, to become gradually thinner and then is broken into pieces and atomized. However, in a case where the flow rate of the lubricant in the branch path3ais larger than that in the branch path3b, the oil film formed by the collision of the jet is directed toward the branch path3b. Then, in the present embodiment, the angle θb defined by the central axis of the branch path3band the plane3cis made larger than the angle θa defined by the central axis of the branch path3aand the plane3c, to reduce the oil film from directing toward the branch path3b. This reduces influence due to deviation of the flow rate of the lubricant in the branch paths3a,3b. The same advantageous effect is obtained in the second liquid supply section4.

Therefore, according to the fourth embodiment, a diffusion range of the lubricant after jet collision is unified, and deterioration of characteristics of thinning and atomization is prevented, in addition to the advantageous effects obtained by the first embodiment described above.

Next, a description will be given of a screw compressor100provided with the liquid supply mechanism10of the embodiments described above, with reference toFIG. 7andFIG. 8.

The screw compressor100shown inFIG. 7andFIG. 8is a so-called oil-feeding air compressor. The configuration of the liquid supply mechanism10provided in the screw compressor100has the same as that shown inFIG. 1, denoted by the same reference numerals, and the duplicate descriptions are omitted. Note that the screw compressor100may be configured to include the liquid supply mechanism10shown inFIG. 3,FIG. 5orFIG. 6.

FIG. 7is a schematic diagram showing a supply flow path of the lubricant supplied to the liquid supply mechanism10provided in the screw compressor100.

As shown inFIG. 7, the supply flow path of the lubricant includes the screw compressor100, a centrifugal separator11, a cooler12, an auxiliary element13such as a filter or a check valve, and pipes14to connect said elements with each other. Compressed air delivered from the screw compressor100is mixed with the lubricant injected from the outside into the screw compressor100. The lubricant mixed with the compressed air is separated from the compressed air by the centrifugal separator11, is cooled by the cooler12, and passes through the auxiliary element13, and then is supplied again via a liquid supply hole15to the screw compressor100. Note that an object to be compressed by the screw compressor100is not limited to air and may be other gases such as nitrogen.

FIG. 8shows the configuration of the screw compressor100inFIG. 7.

As shown inFIG. 8, the screw compressor100includes a screw rotor16and a casing18to accommodate the screw rotor16. The screw rotor16includes a male rotor and a female rotor each having helical lobes to mesh with each other from rotation.

The screw compressor100includes a suction bearing19and a delivery bearing20each rotatably supporting the male rotor and female rotor of the screw rotor16, and a shaft seal member21such as an oil seal and a mechanical seal. The “suction” refers to a suction side, for the air, in the axial direction of the screw rotor16, and the “delivery” refers to a delivery side, for the air, in the axial direction of the screw rotor16.

In general, the male rotor of the screw rotor16has a suction end connected to a motor22, as a rotation drive source, via a rotor shaft. The male rotor and female rotor of the screw rotor16are each accommodated in the casing18so as to keep a clearance of several tens to several hundreds μm with respect to the inner wall surface of the casing18.

The male rotor of the screw rotor16driven to rotate by the motor22drives to rotate the female rotor, so that the volume of a compression chamber23, defined by grooves of the male rotor and female rotor and the inner wall surface of the casing18surrounding the rotors, is expanded and contracted. Thus, the air is sucked through a suction port24, is compressed to a predetermined pressure, and then is delivered through a delivery port25.

Further, the lubricant is injected from outside the screw compressor100to the compression chamber23via the liquid supply hole15.

One of the purposes to supply the lubricant into the compression chamber23is to cool the air in a compression process. In the present embodiment, in order to have a large heat transfer area between the compressed air and the lubricant to promote a cooling effect on the compressed air, a jet impingement type nozzles are provided in the two liquid supply sections1. The first liquid supply section3includes the branch path3aand branch path3bwhose central axes intersect with each other, and the second liquid supply section4includes the branch path4aand branch path4bwhose central axes intersect with each other.

The branch paths3a,3b,4a,4bare all connected to the supply path5which communicates with the liquid supply hole15, so that the lubricant flowing through the liquid supply hole15is supplied into the compression chamber23. If paths for introducing the lubricant which flows in the supply path5to each branch path3a,3b,4a,4bwere respectively formed in the casing18, holes processed therefor would communicate outside the screw compressor100, requiring sealing sections such as joints and plugs. The more the branch paths increase in number, the more the processed holes would also increase in number. Therefore, the number of processing steps would increase, and a risk of lubricant leak would increase.

In contrast, in the present embodiment, the branch paths3a,3b,4a,4bare all directly connected to the side surface of the supply path5for communication. Thus, no portions through which the oil supply path communicates with outside the screw compressor100are present other than the liquid supply hole15. Accordingly, the number of processing steps is reduced so that the manufacturing cost is reduced, and the risk of lubricant leak to the outside the screw compressor100is eliminated.

Further, in the present embodiment, the pressure at the space8(seeFIG. 1), as a supply destination, to communicate with the branch paths3a,3bof the first liquid supply section3is higher than the pressure at the space8(seeFIG. 1), as a supply destination, to communicate with the branch paths4a,4bof the second liquid supply section4. That is, in the oil supply path, the first liquid supply section3on the upstream is formed in a region closer to the air delivery port25to have higher air pressure, and the second liquid supply part4on the downstream is formed in a region closer to the suction port24to have lower air pressure. Thus, the supply path5communicates with the first liquid supply section3on the high pressure side where the pressure of the lubricant is higher in the supply path5, so that the air in the compression chamber23is prevented from flowing back into the supply path5via the liquid supply section3.

The present invention has been described above based on the embodiments, but the present invention is not limited thereto and includes various modifications. For example, the embodiments described above have been described in detail for the purpose of illustrating the present invention and are not necessarily limited to those including all of the configurations described above. The configurations of the embodiments may partly be added or replaced with other configurations, or deleted.

For example, in the embodiments described above, the lubricant is used as the liquid supplied by the liquid supply mechanism10, but the liquid is not limited thereto, and other liquid such as water, coolant, fuel may be used, for example.

Further, in the embodiments described above, the liquid supply mechanism10includes the two liquid supply sections1, but is not limited thereto, and the three liquid supply sections1or more may be formed.

Still further, in the embodiments described above, the case has been described where the pair of branch paths is formed in the every liquid supply section1, but is not limited thereto, and three branch paths or more may be formed in the every liquid supply section1, for example.

Yet further, in the embodiments described above, the case has been described where the liquid supply mechanism10is provided in the screw compressor100, but is not limited thereto, and may be provided in another device such as a fuel injection device.

REFERENCE NUMERALS