Liquid-Cooled Screw Compressor

There is known a liquid-cooled screw compressor that includes a screw rotor and a casing for storing the screw rotor and forming working spaces together with the screw rotor, and cools a gas in the working spaces by supplying a liquid into the working spaces. It is to be noted that the liquid supplied into the working spaces is used also for, besides cooling, sealing of internal gaps made between the screw rotor and the casing and lubrication of sliding portions.

Patent document 1 has proposed a technology for turning liquids to minute particles by causing collision of the liquids supplied to a working space with each other for the purpose of improving the performance of a compressor.

In a compressor described in patent document 1, an oil feed nozzle insertion hole is made in a casing, and an oil feed nozzle internally having a plurality of oil feed paths for a colliding jet flow is inserted into the oil feed nozzle insertion hole. The oil feed path is composed of a main oil feed path and small-diameter sub-oil feed paths that branch from the main oil feed path and are arranged to form a reverse-tapered shape. In the compressor described in patent document 1, the oil feed nozzle is detachable. Thus, the maintenance performance is high as compared with the case in which the oil feed path for the colliding jet flow is directly processed in the casing.

Patent document 1 discloses the oil feed nozzle in which a plurality of oil feed paths are formed in order to supply a larger amount of liquid into the working spaces to improve the cooling efficiency (refer toof patent document 1). However, with this oil feed nozzle, the plurality of oil feed paths composed of the main oil feed path and the sub-oil feed paths arranged to form a reverse-tapered shape need to be formed inside the oil feed nozzle. Thus, a lot of labor and time is required for processing and a concern about increase in the processing cost arises.

An object of the present invention is to provide a liquid-cooled screw compressor that is excellent in the processability and the maintenance performance, and can improve the cooling performance for a gas in working spaces.

A liquid-cooled screw compressor according to an aspect of the present invention is a liquid-cooled screw compressor that takes in a gas and generates a compressed gas. The liquid-cooled screw compressor includes a screw rotor, a casing that stores the screw rotor and forms a working space together with the screw rotor, and a cartridge that is a separate member from the casing. A liquid feed path that supplies a liquid to the working space is formed by the casing and an outer surface of the cartridge.

According to the present invention, it is possible to provide a liquid-cooled screw compressor that is excellent in the processability and the maintenance performance, and can improve the cooling performance for the gas in the working space.

Embodiments of the present invention are described below with reference to the drawings.

A liquid-cooled screw compressor (hereinafter, described also as compressor)according to a first embodiment of the present invention is described with reference to.is a plan sectional view of the compressor.is a sectional view along line II-II in. As depicted in, the compressorincludes a drive rotorand a driven rotoras a pair of screw rotors that mesh with each other and rotate, and a casingthat internally stores the drive rotorand the driven rotorrotatably. The compressortakes in air (gas) and generates compressed air (compressed gas) by rotating the screw rotorsand.

A plurality of helical male teeth are formed in the drive rotor (male rotor). A plurality of helical female teeth are formed in the driven rotor (female rotor). In the casing, a boreas a storage chamber that stores the drive rotorand the driven rotorin the state in which they mesh with each other, an intake port that takes in air, and a discharge port that discharges compressed air are formed. A plurality of working spaces (working chambers) C for compressing air are formed by the pair of screw rotorsandand the inner wall surface of the bore.

A prime mover such as an electric motor is connected to the drive rotor. When rotational motion of the drive rotoris started by the prime mover, the driven rotorthat meshes with the drive rotoralso starts rotational motion. This causes air to be sucked into the working spaces C from the intake port. The working spaces C move from the intake port side to the discharge port side in association with the rotation of the screw rotorsand, and the volume thereof decreases in association with the movement. Due to the decrease in the volume of the working spaces C, the air moves toward the discharge port side while being compressed, and is discharged from the discharge port to the external of the compressor.

In the liquid-cooled screw compressor, a liquid (for example, oil or water) for cooling is injected into the working spaces C in order to suppress a temperature rise of the air due to heat generated by generation of compressed air. The liquid for cooling injected into the working spaces C is used not only for cooling of the air in the working spaces C but also for sealing of gaps between the screw rotors,and the inner wall surface of the bore, gaps between meshing portions of the drive rotorand the driven rotor, and the like, and lubrication of sliding portions of the screw rotorsand.

As depicted in, liquid feed pathsthat supply the liquid to the working spaces C are formed in the compressor. It is to be noted that, although the liquid feed pathis made on each of the side of the drive rotorand the side of the driven rotor, the liquid feed pathon one side is described as a representative in the following because the configuration thereof is the same on both sides.

The casinghas an introduction pathto which the liquid is introduced from the external of the casing, a communication paththat causes the storage chamberand the introduction pathto communicate with each other, and an elongated holethat couples the communication pathwith the storage chamber. As depicted in, the elongated holeis an opening extending along the rotation axis direction (hereinafter, also described as axial direction simply) of the screw rotorsand. In other words, the elongated holeis an opening surface located at the boundary between the communication pathand the storage chamber, and is formed into a rectangular shape in which the longitudinal direction is the axial direction of the screw rotorsandand the short-side direction is the direction (horizontal direction) orthogonal to the axial direction. The elongated holeaccording to the present embodiment has a pair of long sides opposite to each other and a pair of semi-circular arcs that connect the pair of long sides to each other at both end portions. The elongated holeis formed for each of a male-side bore, which stores the drive rotor, in the boreand a female-side bore, which stores the driven rotor, in the bore.

The communication pathforms a space with a flattened rectangular parallelepiped shape, and a cartridgewith a flattened rectangular parallelepiped shape is disposed in the communication path. Due to this, a pair of liquid feed pathsare formed by the inner wall surface of the casingand the outer surface of the cartridge. The cartridgeis attachable and detachable to and from the casing.

A configuration of the liquid feed pathis described in detail with reference to.is an enlarged sectional view of part III in.is a perspective view of the cartridge. As depicted in, the cartridgehas a rectangular flat plate shape and has a pair of wide width surface portionsopposite to each other and a pair of small width surface portionsopposite to each other. The wide width surface portionand the small width surface portionare flat surfaces and are orthogonal to each other. The pair of wide width surface portionsare parallel to each other, and the pair of small width surface portionsare parallel to each other. When the cartridgeis disposed in the communication path, a base end portion(see) thereof is located on the side of the introduction pathand a tip portionthereof is located on the side of the bore. That is, the cartridgeextends in the vertical direction from the side of the introduction pathtoward the side of the borein the communication path. The area of the wide width surface portionis larger than the area of each of the base end surface (lower end surface) and the small width surface portionof the cartridge. The base end surface of the cartridgeis a flat surface orthogonal to each of the wide width surface portionsand the small width surface portions.

In the cartridge, a through-holethat penetrates from one wide width surface portionto the other wide width surface portionis formed. The sectional shapes of the through-holeand the introduction path(see) extending in the horizontal direction are circular shapes. It is preferable to set the opening area of the through-holeequal to or larger than the flow path sectional area of the introduction path. That is, it is preferable that the diameter of the through-holebe set identical to that of the introduction pathor set larger than that of the introduction path. The cartridgeis disposed in the communication pathsuch that the central axis of the through-holecorresponds with the central axis of the introduction path. Due to this, as viewed in the thickness direction of the cartridge, the whole of the inner circumferential surface of the introduction pathis disposed to fit into the inside of the through-hole.

The tip portionof the cartridgeis formed into a tapered shape having a pair of tapered surface portions. That is, in the tip portion, the thickness (distance between the tapered surface portionsof the pair) becomes smaller toward the tip (top portion) thereof. In the tapered surface portions, grooves (recessed portions)are formed from the upper end of the wide width surface portiontoward the top portionof the cartridge. The top portionis a flat surface parallel to the base end surface of the cartridge. The groovesare formed between axial direction end portionslocated at both ends in the axial direction in the tapered surface portion. Bottom surfaces (hereinafter, described also as tapered surfaces)of the groovesare flat surfaces, and are inclined with respect to the wide width surface portionssuch that the distance between the tapered surfacesof the pair becomes shorter as the position comes closer to the top portionfrom the wide width surface portions. The pair of tapered surfacesare connected to each other by the top portionof the cartridge.

As depicted in, the communication pathis formed with a pair of inclined surface portionsopposite to the pair of tapered surface portionsof the cartridge, a pair of first flow path wallsopposite to the pair of wide width surface portions, and a pair of second flow path walls (not depicted) opposite to the pair of small width surface portions. It is to be noted that step portionsmay be omitted although being formed between the inclined surface portionand the first flow path wallin the present embodiment. That is, the inclined surface portionmay be directly coupled with the first flow path wall

The communication pathis formed by causing an endmill having a tapered tip portion of a V-shape to protrude to the inside of the bore (storage chamber)and move in the axial direction of the screw rotorsand, for example. The length of the elongated holein the short-side direction can be adjusted by the amount of protrusion of the endmill. Moreover, the length of the elongated holein the longitudinal direction can be adjusted by the amount of movement of the endmill in the axial direction of the screw rotorsand. That is, the opening area of the elongated holeis set on the basis of the amount of protrusion and the amount of movement regarding the endmill.

When processing is executed by the endmill or the like having the tapered tip portion of the V-shape, a V groove having the pair of inclined surface portionsis formed on the upstream side of the elongated hole. The tip portionof the cartridgeis disposed along this V groove. This forms a pair of jetting flow pathsbetween the V groove of the casingand the tip portionof the cartridge.

As depicted in, the cartridgeand the communication pathare formed into a symmetrical shape in the depicted left-right direction. Due to disposing of the cartridgeat the center of the communication pathin the depicted left-right direction, the space in the communication pathis equally divided in the depicted left-right direction by the cartridge. That is, the pair of liquid feed pathsare formed into a symmetrical shape with the interposition of the cartridgetherebetween. The cartridgeis disposed such that the top portion (tip)thereof is flush with the inner circumferential surface of the bore (storage chamber). It is to be noted that the top portionof the tip portionof the cartridgemay be located on the lower side relative to the lower end surface of the borein order to surely prevent the tip portionof the cartridgefrom getting contact with the screw rotorsand.

The pair of liquid feed pathshave a pair of supplied liquid retaining spacesthat retain the liquid supplied from the introduction pathand the pair of jetting flow pathsthat jet the liquid in the pair of supplied liquid retaining spacesinto the working space C.

The pair of supplied liquid retaining spacesare formed by the pair of wide width surface portionsof the cartridgeand the pair of first flow path wallsand the pair of second flow path walls (not depicted) forming the inner surface of the communication path, through disposing of the cartridgein the communication path.

The pair of jetting flow pathsare formed by the pair of tapered surface portionsof the cartridgeand the pair of inclined surface portionsforming the inner surface of the communication path, through disposing of the cartridgein the communication path. More specifically, the jetting flow pathshaving a rectangular flow path section are formed with the groovesof the tapered surface portionsand the inclined surface portionsby the tapered surfaces of the axial direction end portionsof the cartridgebeing made to abut against the inclined surface portions

The flow path sectional area of the supplied liquid retaining spaceis larger than that of the jetting flow pathto which the liquid is supplied from the supplied liquid retaining space. The liquid is introduced from the introduction pathmade in the horizontal direction to the supplied liquid retaining space, and the liquid introduced to the supplied liquid retaining spaceflows toward the jetting flow path(that is, toward the depicted upper side). Because the flow path sectional area of the supplied liquid retaining spaceis larger than that of the jetting flow path, the speed of the liquid flowing in the supplied liquid retaining spaceis lower than that of the liquid flowing in the jetting flow path. By making the configuration such that the liquid flows in the wide space until reaching the jetting flow pathin this manner, the pressure loss can be made as low as possible. Thus, the pressure of the liquid in the jetting flow pathcan be kept at a high state, and the liquid can be vigorously jetted from the jetting flow path.

For each of the pair of jetting flow paths, a jetting openingfacing the working space C is formed by the top portionof the tip portionof the cartridgeand the elongated holeof the casing. The jetting openingis a rectangular outlet that ejects the liquid from the jetting flow pathinto the working space C, namely, an opening end surface of the jetting flow path, and is exposed to the inside of the bore (storage chamber).

The length (opening length) in the axial direction of the screw rotorsandin the jetting openingis longer than the length (opening width) in the direction orthogonal to the axial direction. The opening width and the opening length of the jetting openingare set such that the liquid is jetted in a liquid film state from the jetting opening. That is, the jetting flow pathsaccording to the first embodiment are liquid film jetting flow paths that jet liquid films. The liquid films jetted from the jetting openingsof the pair of jetting flow pathscollide with each other in the working space C.

The pair of tapered surfacesare formed such that the angle formed by them is equal to or larger than 30 degrees. Moreover, the pair of inclined surface portionsare formed such that the angle formed by them is equal to or larger than 30 degrees. The tapered surfaceand the inclined surface portionare disposed in parallel to each other. The liquid is jetted into the working space C along the tapered surfaceand the inclined surface portionThat is, the jetting flow pathsare formed such that an angle (collision angle) θ formed by the jet directions of the liquids each jetted from the respective jetting flow paths, which make the pair, is equal to or larger than 30 degrees.

As depicted in, the base end portionof the cartridgeis located on the lower side relative to the introduction pathextending in the horizontal direction. Although not depicted, the communication pathextends to the lower end surface of the casing, and an insertion port for inserting the cartridgeinto the communication pathis formed in the lower end surface of the casing. It is to be noted that a closing member (not depicted) is mounted in the insertion port and the insertion port is closed by the closing member.

is a diagram depicting a result of numerical value analysis of liquids (liquid films) jetted from the jetting flow pathsformed by the cartridge. A blacked-out rectangular plane in the diagram is a virtual plane indicating the pressure state of the liquid films, and is not actually disposed for a product.

The flow path shape of the pair of jetting flow pathsformed by the inclined surface portionsof the casingand the groovesof the cartridgeis a thin gap shape. Thus, oils are jetted in a liquid film state from the pair of jetting flow paths. The thin liquid film jetted from one of the pair of jetting flow pathsand the thin liquid film jetted from the other of the pair of jetting flow pathscollide with each other in the working space C. By the result of the numerical value analysis, it has been confirmed that turning of the liquid to the thin film is promoted and the surface area of the liquid enlarges due to the collision of the liquids, which are jetted in the liquid film state, with each other. The liquid films that have collided with each other diffuse in a planar manner and are turned to minute particles. This promotes cooling of compressed air in the working space C.

As above, in the present embodiment, the space (communication path) that can house the cartridgefor flow path formation is made on the upstream side of the elongated holeof the casing, and the pair of liquid feed pathsare formed by disposing the cartridgehaving a flattened shape in the communication pathof the casing. The liquid passes through the liquid feed pathformed by the outer surface of the cartridgeand the casing, and is ejected into the working space C. It is to be noted that the present embodiment has the configuration in which the jetting openingsextending along the axial direction of the screw rotorsandare formed and thin liquid films are jetted from the jetting openings.

Here, a compressoraccording to a comparative example of the present embodiment is described with reference to. As depicted in, in the compressoraccording to the comparative example of the present embodiment, jetting flow pathsare formed by execution of drilled hole processing for the casing. The jetting flow pathsare small-diameter circular openings that penetrate from an introduction path to the inside of the bore. A liquid is jetted into a cylindrical shape from this jetting flow path. However, with such a jetting flow path (drilled hole), the liquid does not diffuse, and thus it is difficult to promote cooling.

In contrast, in the compressoraccording to the present embodiment depicted in, the length in the axial direction of the screw rotorsandin the cartridgeand the elongated holeis set long. Thereby, oil in a thin liquid film state is jetted while the amount of supply of the liquid is ensured, and the liquid can be effectively diffused by causing the liquid films to collide with each other. This effectively promotes cooling of compressed air in the working space C.

Moreover, in the present embodiment, the groovesare formed in the outer surface of the cartridge, and the cartridgeis disposed in the communication pathformed in the casing. Due to this, the jetting flow pathsare formed by the casingand the outer surface of the cartridge, which is a separate member from the casing. Therefore, the present embodiment is excellent in the processability as compared with the configuration in which a plurality of flow paths are formed inside the cartridgein order to increase the flow rate of the liquid as in the technology described in patent document(hereinafter, described also as conventional technology).

It is to be noted that the cartridgeis attachable and detachable to and from the casing. Thus, maintenance such as cleaning of the jetting flow pathscan be easily executed by removing the cartridgefrom the casing. In addition, when the operation condition of the compressoris changed, the liquid feed pathsthat match the operation condition after the change can be formed by changing the cartridgeattached to the casing.

The above-described embodiment provides the following operation and effect.

(1) The compressoris a liquid-cooled screw compressor that takes in air (gas) and generates compressed air (compressed gas). The compressorincludes the screw rotorsand, the casingthat stores the screw rotorsandand forms the working spaces C together with the screw rotorsand, and the cartridgethat is a separate member from the casing. The liquid feed pathsthat supply a liquid to the working space C are formed by the casingand the outer surface of the cartridge.

In this configuration, by processing for the outer shape of the cartridge, the amount of liquid (cooling medium) supplied into the working space C can be adjusted, and insufficiency of the liquid can be prevented. Therefore, according to the present embodiment, it is possible to provide the compressorthat is excellent in the processability and the maintenance performance of the liquid feed pathsand can easily achieve improvement in the cooling performance for air (gas) in the working spaces C. It is to be noted that the processing cost can be suppressed as compared with the case of forming the liquid feed pathinside the cartridgebecause the shape of the liquid feed pathcan be decided by processing for the outer shape of the cartridgeas described above. As a result, the manufacturing cost of the compressorcan be suppressed.

(2) The casinghas the bore (storage chamber)that stores the screw rotorsand, the introduction pathto which the liquid is introduced from the external of the casing, and the communication paththat causes the boreand the introduction pathto communicate with each other. The pair of jetting flow pathsare formed by the tip portionof the cartridgeand the inner surface of the communication paththrough disposing of the cartridgein the communication path. The liquids jetted from the pair of jetting flow pathscollide with each other in the working space C.

According to this configuration, by causing the liquids jetted from the pair of jetting flow pathsto collide with each other, the liquid turned to minute particles can be diffused in a wide range in the working space C. This can improve the cooling performance for the air in the working space C as compared with the case in which jetted liquids are not caused to collide with each other (see).

(3) As the jetting flow pathsaccording to the present embodiment, only one pair of jetting flow pathsare formed by the pair of tapered surface portionsand the pair of inclined surface portionsthrough disposing of the cartridgein the communication path. The groovesthat can jet the liquid (cooling medium) in a liquid film state are formed in the tapered surface portions. That is, the jetting flow pathsaccording to the present embodiment are liquid film jetting flow paths that jet liquid films. The liquid films jetted from the pair of jetting flow paths (liquid film jetting flow paths)collide with each other in the working space C.

According to this configuration, turning of the liquid to the thin film is promoted by the collision of the liquid films with each other. In addition, the liquid turned to minute particles can be diffused in a wide range. Due to the turning of the liquid to the thin film and to the minute particles, the surface area (that is, heat exchange area) of the liquid becomes large. Thus, the compressed air in the working spaces C can be effectively cooled and the compressor performance can be improved.

(4) The pair of liquid feed pathshave the pair of supplied liquid retaining spacesthat retain the liquid supplied from the introduction path, and the pair of jetting flow pathsthat jet the liquid in the supplied liquid retaining spacesinto the working space C. The pair of supplied liquid retaining spacesare formed by the pair of wide width surface portionsof the cartridgeand the inner surface of the communication path. The pair of jetting flow pathsare formed by the pair of tapered surface portionsof the cartridgeand the pair of inclined surface portionsof the communication path. The flow path sectional area of the pair of supplied liquid retaining spacesformed on the upstream side of the pair of jetting flow pathsis larger than that of the pair of jetting flow paths.

In this configuration, the supplied liquid retaining spaceshaving a flow path sectional area larger than that of the jetting flow pathsare formed from the introduction pathto the jetting flow paths. Thus, the pressure loss of the liquid flowing in the liquid feed pathscan be made low. This can cause the liquid in a high pressure state to jet vigorously from the jetting openingsand diffuse in a wider range.

(5) The pair of liquid feed pathsare formed into a symmetrical shape with the interposition of the cartridgetherebetween. Due to this, the difference between the pressure of the liquid in the liquid feed pathon the upstream side of the pair of liquid feed pathsand the pressure of the liquid in the liquid feed pathon the downstream side of the pair of liquid feed pathscan be made small. Due to this, the speed of the liquid jetted from each of the pair of jetting flow pathsbecomes almost the same speed. Thus, it is easy to control the collision part between the liquids. In the present embodiment, a liquid film is equally jetted from each of the pair of jetting flow paths. Thus, the liquid films after the collision extend straight along the upward direction.

(6) Moreover, the flow path sectional shape of the introduction pathis a circular shape, and the through-holethat is disposed in the introduction pathand has a circular shape is formed in the cartridge. The opening area of the through-holeis equal to or larger than the flow path sectional area of the introduction path. If the opening area of the through-holeis smaller than the flow path sectional area of the introduction path, the pressure loss of the liquid that passes through the through-holebecomes higher. As a result, the difference between the pressure of the liquid in the liquid feed pathon the upstream side and the pressure of the liquid in the liquid feed pathon the downstream side becomes larger. In this case, a difference is generated between the speed of the liquid jetted from one of the pair of jetting flow pathsand the speed of the liquid jetted from the other of the pair of jetting flow paths. Therefore, control of the collision part between the liquids becomes difficult. In contrast, in the present embodiment, the opening area of the through-holedisposed in the introduction pathis equal to or larger than the flow path sectional area of the introduction path. Thus, the pressure loss of the liquid that passes through the through-holecan be suppressed. Due to this, the pressure difference and the speed difference between the liquids each jetted from the respective jetting openingsof the pair can be made smaller. Thus, it is easy to control the collision part between the liquids.

(7) The jetting flow pathsare formed such that the angle (collision angle) θ formed by the jet directions of the liquids each jetted from the respective jetting flow paths, which make the pair, is equal to or larger than 30 degrees. In the present embodiment, the angle formed by extended lines of the pair of jetting flow pathsis equal to or larger than 30 degrees. In this configuration, the liquid can be effectively turned to minute particles and the surface area of the liquid can be enlarged as compared with the case in which the liquids are caused to collide with each other at the collision angle θ smaller than 30 degrees.