JP2017067011A - Oil injection type screw compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable displacement oil injection type screw compressor that can be manufactured in relative easy manner without increasing a ratio power.SOLUTION: A casing 12 of an oil injection type screw compressor is formed with a releasing hole 21 communicating between a compression action space and an intake passage and at the same time there is provided a releasing valve 23 having a piston 232 for opening or closing the releasing hole through insertion or removal of its extremity end. A piston extremity end surface 232a of the releasing valve is formed as a flat surface forming a right angle crossing in respect to an advancing or retracting direction and at the same time the surface is opened at the extremity end surface, an oil supply flow passage 237 opened at the extremity end surface and communicated with a closing valve pressure receiving chamber 233 is arranged at the piston and when the releasing hole is closed by the releasing valve, working oil in the closing valve pressure receiving chamber 233 is fed into the compression action space through this oil supply flow passage.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an oil-cooled screw compressor, and more specifically, by changing the length (effective length) of a portion of a compression working space used for compressing compressed gas, the intake air amount and the compression ratio. The present invention relates to a variable-capacity oil-cooled screw compressor that can be made variable.

  An oil-cooled screw compressor accommodates a pair of male and female screw rotors in a rotor chamber formed in a casing so as to be able to rotate. The screw rotors engage with each other and rotate between the teeth of both screw rotors. Compress the suction gas introduced into the compression space through the suction passage by gradually reducing the volume of the compression space defined by the inner wall of the casing containing the gas from the suction side to the discharge side. However, it can be discharged from the discharge channel.

  In the oil-cooled screw compressor constructed in this way, the effective length, which is the length of the portion used for compression, in the compression working space can be varied to vary the intake air amount and compression ratio of the compressed gas. A variable capacity oil-cooled screw compressor has been proposed.

  As such a variable capacity type oil-cooled screw compressor, as shown in FIGS. 11 (A) to 11 (C), an unload that communicates with the compression working space at a position closer to the discharge side than the suction closed position is provided. A hole 921 is formed in the wall surface of the casing 912 and moves forward and backward in the unload hole 921, and closes the unload hole 921 at a position advanced toward the inside of the casing 912, so that the front end surface 923 a An unload valve that functions as a part of the inner peripheral surface and opens the unload hole 921 in the retracted position, thereby communicating the compression working space to the suction passage 916 through the unload hole 921 and the communication path 922. An oil-cooled screw compressor 900 with 923 has been proposed.

  In the oil-cooled screw compressor 900 configured as described above, in a state where the unload hole 921 is closed by the unload valve 923, the compressed gas taken into the compression working space via the suction passage 916 is sucked into the suction side. The compression is performed using substantially the entire length of the compression working space extending from the discharge side to the discharge side. However, when the unload valve 923 opens the unload hole 921, the compression is performed via the unload hole 921 and the communication path 922. Since the working space communicates with the suction passage 916, the compression working space on the suction side from the unload hole 921 is not used for compressing the compressed gas, and the compression action on the discharge side from the unload hole 921. Since the compressed gas is compressed only in the space, the effective length of the compression working space is shortened, and compared with the case of operating with the unload hole 921 closed, In an open state unload hole 921, thereby making it possible to reduce the intake air amount and the compression ratio of the oil-cooled screw compressor 900.

JP 59-131790 A

  In the oil-cooled screw compressor 900 described in Patent Document 1 configured as described above, the tip end surface 923a of the unload valve 923 described above is moved when the unload valve 923 is moved to the forward position as described above. The rotor chamber 913 is formed in a part of the inner wall surface.

  And in patent document 1, in order to process the shape of the front end surface 923a of the unload valve 923 into the shape which makes a part of inner wall surface of the rotor chamber 913, "co-processing" is carried out at the time of processing the inner surface of the rotor chamber 913. In addition, the unloading valve 923 is inserted into the unloading hole 921 so as to be in the above-described advance position in order to process the tip end surface 923a of the unloading valve 923 with the inner wall surface of the rotor chamber 913. The unload valve 923 is fixed so as not to rotate by a pin 930 provided on the casing 912 (Patent Document 1, page 3, lower right column, lines 11 to 16).

  Here, if further processing is performed on the unload valve 923 and the unload hole 921 after co-processing, and the shapes of the unload valve 923 and the unload hole 921 change even slightly, Therefore, even if the tip end surface 923a of the unload valve 923 is made to exactly match the inner wall surface shape of the rotor chamber 913, the shapes of the two at the time of final assembly are displaced.

  Therefore, when the front end surface 923a of the unload valve 923 is co-processed with the inner wall surface of the rotor chamber 913, each part other than the front end surface 923a of the unload valve 923 (the flange, outer periphery, It is necessary to precisely finish the holes and grooves for inserting the rotation-preventing pins and the respective parts of the unloading hole 921 until the final finished state that does not require subsequent adjustment is achieved. It is necessary to fix the valve 923 so as not to move in the unload hole 921 so as to be in the forward position, and the setup work before processing is complicated.

  In addition, after performing the co-processing in this way, when the main assembly of the oil-cooled screw compressor 900 is performed, the unload valve 923 fixed to the unload hole 921 is removed, and a spring, an O-ring, etc. After installing the necessary parts, it is necessary to assemble the product again in the correct orientation and orientation, which requires twice the work.

  Moreover, since the unload valve 923 manufactured by such co-processing is manufactured as a single product, the shape of the inner wall of the rotor chamber 913 of the co-processed casing 912 is exactly the same, but other The shape of the inner wall surface of the rotor chamber 913 of the casing 912 does not exactly match, and it becomes difficult to obtain the replacement unload valve 923.

  For this reason, when the unload valve 923 needs to be replaced for maintenance or the like, the replacement parts cost becomes high, such as not only the unload valve 923 but also the casing 912 must be replaced at the same time.

  In view of the above, it is conceivable to process the unload valve 923 independently without co-processing the inner wall surface of the rotor chamber 913.

  However, when the unload valve 923 is machined alone, it is extremely difficult to machine the tip surface 923a of the unload valve 923 so as to exactly match the curved shape of the inner wall surface of the rotor chamber 913.

  As a result, the shape of the tip end surface 923a of the unload valve 923 and the shape of the inner wall surface of the rotor chamber 913 do not coincide with each other, and the tip of the unload valve 923 reaches the rotor chamber from the unload hole 921 at the advanced position of the unload valve 923. When protruding inside 913, the tooth tip of the rotating screw rotor 911 may collide with the tip of the unload valve 923 and be damaged.

  On the other hand, in order to avoid contact with the tooth tip of the screw rotor 911, the tip of the unload valve 923 is more peripheral than the inner wall surface of the rotor chamber 913 even when the unload valve 923 is formed short and disposed at the forward position. In the case of machining so as to be positioned on the side, contact with the tooth tip of the screw rotor 911 can be avoided, but the tip surface 923a of the unload valve 923 is formed in the bottom surface of the unload hole 921 on the inner wall surface of the rotor chamber 913. Therefore, the space between the inner wall surface of the rotor chamber 913 and the tooth tip of the screw rotor 911 is increased in the recessed portion as compared with the other portions.

  Therefore, when the tooth tip of the screw rotor passes through this recess, the compression working space on the high pressure side and the compression working space on the low pressure side adjacent to this communicate with each other, and the compression working space on the high pressure side is connected to the low pressure side. As the compressed fluid leaks toward the compression working space, the specific power of the compressor (power consumption per intake amount) increases.

  In particular, as described in Patent Document 1, the inner wall surface of the rotor chamber of the male screw rotor and the inner wall surface of the rotor chamber of the female screw rotor overlap with each other toward the tip portion of the ridge 934. In the configuration in which the load hole 921 is provided and the unload valve 923 having a tip shape corresponding to the tip shape of the ridge 934 is provided, the male and female screw rotors start to engage at the top of the ridge 934. For this reason, if a depression occurs in this portion and leakage of compressed gas occurs, the specific power of the oil-cooled screw compressor 900 increases further.

  Therefore, the present invention was made to eliminate the above-mentioned drawbacks of the prior art, and is used for compressing compressed gas in the compression working space, like the oil-cooled screw compressor introduced as the above-mentioned Patent Document 1. The variable capacity oil-cooled screw compressor with variable length (effective length) can be manufactured relatively easily without performing the above-mentioned co-processing. An object of the present invention is to provide an oil-cooled screw compressor capable of preventing leakage of compressed gas to a compression working space to prevent an increase in specific power.

  Hereinafter, means for solving the problem will be described together with reference numerals used in the embodiment for carrying out the invention. This code is used to clarify the correspondence between the description of the scope of claims and the description of the mode for carrying out the invention. Needless to say, it is used in a limited manner for the interpretation of the technical scope of the present invention. It is not a thing.

In order to achieve the above object, the oil-cooled screw compressor 10 of the present invention includes:
A cylinder 13 formed in the casing 12 and a pair of male and female screw rotors 11 (11a, 11b) that mesh with each other and rotate in the cylinder 13 are provided, and an inner wall surface of the cylinder 13 and the screw rotor 11 (11a, 11b) 11b), a compression working space is formed between the teeth, and the compression working space is formed from one end side of the screw rotor 11 (11a, 11b) via the suction passage 16 by the rotation of the screw rotor 11 (11a, 11b). In the oil-cooled screw compressor 10 which compresses the compressed gas introduced therein together with the cooling oil and discharges it through the discharge passage 18 communicating with the other end side of the screw rotor 11 (11a, 11b).
In the casing 12,
An escape hole 21 is formed near the discharge passage 18 with respect to the suction closed position and in communication with the compression working space before communicating with the discharge passage 18.
An escape passage 22 for communicating the escape hole 21 and the suction passage 16;
When the relief hole 21 is opened, the compression working space and the relief passage 22 are communicated with each other, and when the relief hole 21 is closed, the compression working space and the relief passage 22 are connected to each other. And a relief valve 23 for blocking the communication of
In the relief valve 23,
An axis orthogonal to the axis a of the male or female screw rotor (11a or 11b) and orthogonal to the tangent t to the arc of the inner wall surface of the cylinder 13 at the contact point p between the arc and the tangent t A piston chamber 231 having a center c;
A piston 232 that moves forward and backward in the piston chamber 231 between a forward position that closes the escape hole 21 and a retracted position that opens the escape hole 21, and is biased toward the retracted position;
A valve closing pressure receiving chamber 233 for moving the piston 232 in the retracted position to the advanced position by introducing hydraulic oil is provided;
In the piston 232,
A flat front end surface 232a that is orthogonal to the advancing / retreating direction of the piston 232;
An oil supply passage 237 having one end opened at the tip end surface 232a and the other end opened by the valve-closing pressure receiving chamber 233 is provided.
The front end surface 232a of the piston 232 in the forward movement position is located on the outer periphery of the cylinder 13 more than the position (α1) that is separated from the rotational locus of the tooth tip of the screw rotor 11 (11a, 11b) by a predetermined allowable rotation interval δ. The relief valve 23 is formed so as to be disposed on the side [the lower side in FIG. 6A] (Claim 1).

  In the oil-cooled screw compressor 10 configured as described above, when the piston 232 is in the forward movement position, the front end surface 232a of the piston 232 has a position substantially the same as the tangent t, for example, β1 and The relief valve 23 may be formed so as to be disposed in a range of an allowable error ± Δ in manufacturing for β 1 (Claim 2).

  Furthermore, in the oil-cooled screw compressor 10 of the present invention, when the piston 232 is in the forward position, the tip end surface 232a of the piston 232 is the farthest point from the tangent t among the opening edges of the escape hole 21. The relief valve 23 may be formed so as to be disposed between the position of f and the tangent t [between γ1 and γ2 in FIG. 6C] (Claim 3).

  With the configuration of the present invention described above, in the oil-cooled screw compressor 10 of the present invention, the effective length of the compression working space is made variable by opening and closing the relief hole 21 by the relief valve 23, thereby reducing the amount of compressed gas. In addition to being able to change the intake air amount and compression ratio, the following remarkable effects could be obtained.

  Since the piston 232 of the relief valve 23 has a simple shape having a flat front end surface 232a, the piston 232 can be compared without performing complicated work such as co-processing with the inner wall surface of the cylinder 13 of the casing 12. Therefore, it is easy to manufacture, and it is easy to manufacture only the piston 232 as a replacement part.

  In addition, since the front end surface 232a of the piston 232 is a flat surface, the piston 232 can be formed into a rotating body shape, thereby preventing the piston 232 from rotating in the piston chamber 231 and rotating. It is not necessary to provide a pin, pin hole, pin groove or the like for stopping, and the manufacturing and assembling work of the relief valve 23 can be simplified.

  On the other hand, in the configuration in which the escape hole 21 formed in the curved surface is closed by the distal end portion of the piston 232 having the flat distal end surface 232a as described above, the distal end surface of the piston 232 when the escape hole 21 is closed by the piston 232 A step is formed between 232a and the opening edge of the escape hole 21, and the step forms a minute recess D (see FIG. 4) on the inner wall surface of the cylinder 13.

  However, by providing the piston 232 with the oil supply passage 237 that communicates with the valve closing pressure receiving chamber 233 and opens at the tip end surface 232a, the hydraulic oil introduced into the valve closing pressure receiving chamber 233 of the relief valve 23 is supplied to the oil supply flow. Through the passage 237, it is introduced into the compression action space from the tip end surface 232a, and thereby the working oil sufficient to fill the recess D is supplied to the portion where the escape hole 21 is formed.

  As a result, by providing such an oil supply passage 237, it is possible to prevent the compressed gas from leaking from the high pressure side compression action space to the adjacent low pressure side compression action space even when the above-described depression D is generated, It was possible to prevent the specific power of the oil-cooled screw compressor 10 from increasing.

  In the configuration in which the relief valve 23 is formed so that the front end surface 232a of the piston 232 is disposed at substantially the same position as the tangent t when the piston 232 is in the forward position, the inner side of the inner wall surface of the cylinder 13 is formed. The tip of the piston 232 does not protrude and the tip of the piston 232 and the tooth tip of the screw rotor 11 (11a, 11b) can be reliably prevented from contacting each other. By disposing, the depression D formed on the inner wall surface of the cylinder 13 can be minimized in an arrangement in which the front end surface 232a of the piston 232 does not protrude from the inner wall surface of the cylinder 13, and the increase in specific power is further increased. I was able to prevent it.

  On the other hand, when the piston 232 is in the forward position, the tip end surface 232a of the piston 232 is located between the position of the farthest point f from the tangent line t of the opening edge of the escape hole 21 and the tangent line t. When the relief valve 23 is formed so as to be arranged [between γ1 and γ2 in FIG. 6C], the recess D formed on the inner wall surface of the cylinder 13 is further reduced to prevent an increase in specific power. It was possible to improve further.

Explanatory drawing which shows the example of 1 structure of the compressed air supply apparatus provided with the oil-cooled screw compressor of this invention. The principal part sectional drawing of the oil-cooled screw compressor of this invention. The expanded view of the cylinder in the oil-cooled screw compressor of this invention. The expanded sectional view of the relief valve part in the oil-cooled screw compressor of this invention. The expanded sectional view of the relief valve part in the oil-cooled screw compressor of this invention which showed the modification of the piston. It is explanatory drawing for demonstrating the arrangement position of a piston front end surface, (A) is Claim 1, (B) is Claim 2, (C) is arrangement explanatory drawing of Claim 3. Explanatory drawing which shows the example of 1 structure of the compressed air supply apparatus provided with the oil-cooled screw compressor of this invention. The principal part sectional drawing which shows another modification of the oil-cooled screw compressor of this invention. The principal part sectional drawing which shows another modification of the oil-cooled screw compressor of this invention. The principal part sectional drawing which shows another modification of the oil-cooled screw compressor of this invention. It is explanatory drawing of the conventional oil-cooled screw compressor, (A) is sectional drawing cut | disconnected in the orthogonal direction with respect to the rotor axis | shaft, (B) is a perspective view of an unloading valve, (C) is parallel to a rotor axis | shaft. Sectional drawing cut in various directions.

  Hereinafter, an oil-cooled screw compressor 10 of the present invention will be described with reference to the accompanying drawings.

[Overall structure of oil-cooled screw compressor]
Reference numeral 10 in FIG. 1 denotes an oil-cooled screw compressor according to the present invention. The oil-cooled screw compressor 10 includes a pair of screw rotors 11 including a male screw rotor 11a and a female screw rotor 11b. A cylinder 13 for accommodating the screw rotor 11 is provided with a casing 12 formed therein.

  As shown in FIG. 2, the cylinder 13 formed in the casing 12 includes a cylindrical portion that serves as a housing portion for the male screw rotor 11 a and a cylindrical portion that serves as a housing portion for the female screw rotor 11 b. Are arranged in parallel so as to overlap with each other, and are formed in a substantially horizontal 8-shape in the cross-section in the direction perpendicular to the axis of the screw rotor 11, and engage the male screw rotor 11a and the female screw rotor 11b. Both can be accommodated in the cylinder 13 in a combined state.

  In the illustrated example, the accommodating portion of the male screw rotor 11a is accommodated with respect to the accommodating portion of the female screw rotor 11b so that the male screw rotor 11a having a large diameter with respect to the female screw rotor 11b can be accommodated. However, like the conventional oil-cooled screw compressor described with reference to FIG. 11, the female screw rotor 11b and the male screw rotor 11a are formed to have the same diameter. The configuration of the present invention may be applied to the oil-cooled screw compressor 10 formed to have the same diameter with respect to the housing portion of the male screw rotor 11a and the housing portion of the female screw rotor 11b.

  As shown in FIG. 1, the male screw rotor 11a and the female screw rotor 11b housed in the cylinder 13 can rotate in opposite directions while being engaged with each other, as shown in FIG. Each of the rotor shafts provided at both ends is rotatably supported by bearings 14 and 15 provided in the casing 12, and one of the male screw rotor 11a and the female screw rotor 11b is illustrated as an example in the figure. In this case, an output shaft of a drive source 40 such as an engine or a motor can be connected to a suction-side rotor shaft of the male screw rotor 11a to input a rotational driving force.

  In this way, the suction side end of the cylinder 13 that meshes with the male screw rotor 11a and the female screw rotor 11b and is rotatably accommodated communicates with the suction passage 16 and is introduced through the suction passage 16. The compressed gas can be compressed by the meshing rotation of the screw rotor 11 together with the cooling oil injected through the cooling oil injection hole 17, and the discharge passage provided at the discharge side end of the cylinder 13 The compressed gas, which is a gas-liquid mixed fluid compressed together with the cooling oil, can be discharged via 18.

[Variable capacity mechanism]
In the oil-cooled screw compressor 10 of the present invention, which is a variable capacity oil-cooled screw compressor, compression formed between the teeth of the screw rotor 11 (11a, 11b) and the inner wall surface of the cylinder 13 is performed. A variable capacity mechanism is provided in which the effective length of the working space is variable, and the intake amount of the oil-cooled screw compressor 10 and the compression ratio with respect to the sucked compressed gas are variable.

  As such a variable capacity mechanism, in the oil-cooled screw compressor 10 shown in the figure, the compression working space before the communication with the discharge passage 18 in the casing 12 is close to the discharge passage 18 with respect to the suction closed position. A relief hole 21 that communicates with the suction passage 16 is provided, and a relief passage 22 that communicates between the relief hole 21 and the suction passage 16 is provided, and the relief hole 21 is opened and closed to open the relief hole 21 when the relief hole 21 is opened. A relief valve 23 is provided to connect the compression working space and the escape passage 22 through the air and to block communication between the compression working space and the escape passage 22 when the relief hole 21 is closed.

  As shown in FIG. 4, the relief valve 23 includes a piston chamber 231 provided in the casing 12, a piston 232 that moves back and forth in the piston chamber 231 to open and close the relief hole 21, and the piston 232. A valve-closing pressure receiving chamber 233 into which hydraulic oil that moves to an advance position that closes the escape hole 21 is introduced is provided.

  In the illustrated embodiment, the above-described escape hole 21 is provided on the rotor chamber side that accommodates the male screw rotor 11a, and an escape passage 22 that communicates with the escape hole 21 is formed, and the outer periphery of the escape passage 22 is formed. A piston chamber 231 having the same axis c as the above-described escape hole 21 is formed on the side, and the piston 232 accommodated in the piston chamber 231 is moved forward and backward, so that the escape hole 21 is formed at the tip of the piston 232. It is comprised so that can be opened and closed.

  As shown in FIG. 4, the axis C of the escape hole 21 and the piston chamber 231 is provided in a direction perpendicular to the tangent t at a contact point p between the arc drawn by the inner wall of the cylinder 13 and the tangent t. As shown in FIG. 1, it is provided in a direction orthogonal to the axis a of the rotor shaft of the screw rotor 11 (in the example shown, the axis of the male screw rotor 11a).

  In the embodiment shown in FIG. 4, the piston chamber 231 includes a narrow-diameter portion 231 a formed to have the same diameter as the escape hole 21 on the escape hole 21 side, and is opposite to the escape hole 21 side. On the side, a spring accommodating portion 231b formed to have a large diameter, and a larger diameter than the spring accommodating portion 231b, with an interval capable of accommodating a coil spring 234 described later with respect to the small diameter portion 231a, A large-diameter portion 231c that opens toward the outside of the casing 12 is provided, and the piston 232 is accommodated in the piston chamber 231 so as to be movable back and forth.

  The above-described piston 232 accommodated in the piston chamber 231 has a flat front end surface 232a formed in a direction orthogonal to the advancing / retreating movement direction of the piston 232, and the relief hole 21 and the small diameter portion of the piston chamber 231. A cylindrical portion 232b formed to have a diameter corresponding to 231a, and a flange portion 232c formed to a diameter corresponding to the large-diameter portion 231c of the piston chamber 231 at the rear end of the cylindrical portion 232b. With the coil spring 234 fitted to the 232b, the front end surface 232a is inserted into the escape hole 21 into the piston chamber 231 and, after the piston 232 is inserted, the open end of the piston chamber 231 is closed with the end plate 235. Thus, the relief valve 23 described above is formed in the casing 12.

  The aforementioned cylindrical portion 232b of the piston 232 moves the piston 232 to a forward position where the flange portion 232c of the piston 232 collides with a step portion 231d provided at the boundary portion between the spring accommodating portion 231b and the large diameter portion 231c of the piston chamber 231. When the piston 232 is advanced, the tip of the cylindrical portion 232b of the piston 232 is formed in such a length that it can be inserted into the escape hole 21 to close the escape hole 21, and when the piston 232 is retracted, the escape hole 21 is formed. The end of the cylindrical portion 232b of the piston 232 is extracted from the inside so as to open the escape hole 21 and to communicate with the escape passage 22.

  The aforementioned coil spring 234 fitted on the cylindrical portion 232b of the piston 232 is a compression spring, and the piston 232 is constantly urged toward the retracted position where the escape hole 21 is opened, and the large-diameter portion 231c. Among them, a valve closing pressure receiving chamber 233 is formed between the end plate 235 and the flange portion 232 c of the piston 232, and hydraulic oil is supplied to the valve closing pressure receiving chamber 233 through an oil filling port 236 provided in the end plate 235. The piston 232 can be advanced to the advanced position against the biasing force of the coil spring 234 by the pressure of the injected hydraulic oil.

  Since the front end surface 232a of the piston 232 is formed in a simple shape as a flat surface orthogonal to the advancing / retreating movement direction of the piston 232 as described above, like the oil-cooled screw compressor described as the prior art, The piston 232 can be easily machined independently without performing a complicated operation of co-working with the inner wall surface of the cylinder so that the tip of the piston has a shape corresponding to the inner wall surface of the cylinder 13.

  Also, as explained in the prior art, in the configuration in which the piston tip is co-machined with the cylinder inner wall, when the piston rotates, the piston tip protrudes from the inner wall surface of the cylinder in the inner circumferential direction and contacts the tooth tip of the screw rotor. In order to prevent the rotation of the piston, it is necessary to adopt a configuration such as pinning. However, as described above, the tip surface 232a of the piston 232 is a flat surface. In the configuration, the piston 232 can be formed in the shape of a rotating body, and when it is formed in such a rotating body shape, the position of the front end surface 232a of the piston 232 varies even if the piston 232 rotates in the piston chamber 231. In order to prevent such contact, the piston 232 does not come into contact with the tooth tip of the screw rotor 11. There is no need to provide a structure of a pinned to prevent rotation of the down 232, and can be simplified device configuration.

  As described above, since the front end surface 232a of the piston 232 is formed as the above-described flat surface, when the escape hole 21 formed in the inner wall surface of the arc-shaped cylinder 13 is closed by the front end portion of the piston 232, the cylinder 13 A step is formed between the opening edge of the relief hole in the inner wall surface of the cylinder and the outer peripheral edge of the tip end surface 232a of the piston 232, and a recess D is formed at the corner of the step.

  As described above, when the recess D is formed on the inner wall surface of the cylinder 13, the distance between the tooth tip of the screw rotor 11 and the inner wall of the cylinder 13 in the recess D is larger than that in the other portions. When the tooth tip of the screw rotor 11 passes through the portion where the depression D is generated, the compressed gas in the compression working space on the high pressure side is likely to leak into the adjacent compression working space on the low pressure side. Specific power may increase due to pressure loss due to leakage.

  Therefore, in the oil-cooled screw compressor of the present invention, in order to prevent an increase in specific power even if such a depression D is generated, oil is supplied into the compression working space at the position where the relief hole 21 is formed. Thus, when the tooth tip of the screw rotor passes over the above-mentioned recess D, the amount of cooling oil that seals between the tooth tip of the screw rotor and the recess D is increased, and the tooth of the screw rotor is increased by high-pressure oil supply. The gap between the tip and the recess D is shielded, and the presence of the recess D prevents the compressed gas in the compression working space on the high pressure side from leaking into the compression working space on the low pressure side.

  In order to enable such oil supply to the compression space, in the oil-cooled screw compressor 10 of the present invention, one end is opened at the front end surface 232a and the other end is opened at the above-described piston 232. An oil supply passage 237 that opens in the valve closing pressure receiving chamber 233 is provided, and when the hydraulic oil is introduced into the valve closing pressure receiving chamber 233, the hydraulic oil is provided on the front end surface 232a of the piston 232 via the oil supply passage 237. It is configured to be introduced into the compression action space through the opening.

  In the illustrated embodiment, the piston 232 is formed hollow except for the tip portion, and the portion extending from the hollow portion to the end plate 235 is formed as the valve closing pressure receiving chamber 233 and the piston 232 is formed. An oil supply passage (oil supply hole) 237 that penetrates the tip end surface 232 a and communicates with the valve closing pressure receiving chamber 233 formed inside the piston 232 is provided.

  In the embodiment shown in FIGS. 1 to 4, only one oil supply passage 237 is provided at the center of the front end surface 232 a of the piston 232. This oil supply passage is shown in FIG. 5. In this case, as shown in FIG. 5, in the cross-section perpendicular to the axial direction of the screw rotor 11, the position is symmetrical with respect to the axis of the piston 232. Each may be provided with an oil supply passage 237.

  As described above, in the configuration in which the two oil supply passages 237 are provided, the above-described depression D can be filled with the hydraulic oil more efficiently.

  That is, in the configuration of the oil-cooled screw compressor 10 of the present invention in which the front end surface 232a of the piston 232 is flat, the recess D generated on the inner wall surface of the cylinder 13 when the piston 232 is in the forward movement position is formed on the screw rotor 11. It occurs at both end portions in the width direction of the front end surface 232a of the piston 232 in the cross section perpendicular to the axial direction, or becomes deepest at this portion.

  Therefore, as shown in FIG. 5, in the configuration in which the oil supply passages 237 are provided at both ends in the width direction of the front end surface 232a of the piston 232, the efficiency is higher than the formation portion of the recess D or the deepest portion of the recess D. Therefore, it is possible to more effectively prevent leakage of compressed gas.

  In the oil-cooled screw compressor 10 of the present invention, as described above, the oil supply flow path 237 is provided in the piston 232, thereby preventing the compressed gas from leaking even when the recess D is formed. In order to more effectively prevent leakage of compressed gas due to the generation of the recess D, in addition to this configuration, the above-described recess D formed on the inner wall surface of the cylinder 13 should be made as small as possible. In this configuration, when the piston 232 is in the forward position, the front end surface 232a of the piston 232 is substantially at the same position as the tangent t [for example, β1 in FIG. It is preferable to form the relief valve 23 so as to be disposed within a range of an allowable error ± Δ.

  In this configuration, the generated dent D can be minimized within a range in which the front end surface 232a of the piston 232 does not protrude from the inner wall surface of the cylinder 13.

  Further, when the piston 232 is in the forward position, the tip end surface 232a of the piston 232 is located between the position of the farthest point f from the tangent t in the opening edge of the escape hole 21 and the tangent t [FIG. The relief valve 23 may be formed so as to be disposed between [gamma] 1- [gamma] 2 of 6 (C). In this configuration, the above-described depression D generated on the inner wall surface of the cylinder 13 is made even smaller. The increase in specific power described above can be prevented more effectively.

  However, even when the tip surface 232a is disposed in the above range [range between γ1 and γ2 in FIG. 6C], the tip surface 232a of the piston 232 is the tip of the screw rotor 11 (11a, 11b). It is necessary to configure such that it is located on the outer peripheral side [the lower side of the sheet in FIG. 6 (A)] from the position (α1) that is separated from the rotation locus by a predetermined allowable rotation interval δ.

[Operation of oil-cooled screw compressor]
In the oil-cooled screw compressor 10 of the present invention described above, when the hydraulic oil is not introduced into the valve closing pressure receiving chamber 233 provided in the relief valve 23, the piston 232 of the relief valve 23 has the coil spring 234. Due to this urging force, the escape hole 21 is opened, and the compression working space communicates with the suction passage 16 through the escape hole 21 and the escape passage 22.

  As a result, in the compression working space defined by the space between the teeth of the screw rotor 11 and the inner wall surface of the cylinder 13, the portion from the suction side to the communicating portion of the escape hole 21 is not used for compression. , It is performed only in the portion on the discharge side from the escape hole 21, and the length actually used for compression (effective length) in the compression working space is shortened, so that the oil-cooled screw compressor 10 is covered. As the intake amount of the compressed gas decreases, the compression ratio with respect to the sucked compressed gas decreases, and accordingly, the power necessary for driving the oil-cooled screw compressor 10 can also be reduced.

  This point will be described with reference to FIG. 3 which is an exploded view of the cylinder of the oil-cooled screw compressor 10 of the present invention. In the configuration example shown in FIG. 3, the above-described escape hole 21 is substantially omitted from the suction closed position. In this example, when the relief hole 21 is opened by the relief valve 23, it is compressed in the compression working space for about one pitch after the suction is closed. Since the compressed air is discharged to the suction passage 16 side through the escape hole 21, it is not compressed.

  Therefore, compared with the case where the escape hole 21 is closed, the intake amount and compression ratio per cycle of the screw rotor 11 are reduced by one pitch, and the screw rotor 11 of the oil-cooled screw compressor 10 is correspondingly reduced. The power required to rotate the motor is reduced so that it can be rotated with a smaller force.

  On the other hand, in a state where hydraulic oil is introduced into the valve closing pressure receiving chamber 233 of the relief valve 23, the piston 232 moves forward toward the relief hole 21 toward the axial center a of the rotor shaft of the screw rotor 11 by introduction of the hydraulic oil. Then, when it moves to the forward movement position, the tip of the piston 232 closes the escape hole 21 and the communication between the escape hole 21 and the suction passage 16 via the escape passage 22 is released.

  As a result, when the piston 232 of the relief valve 23 is in the forward position, the entire length of the compression working space from the suction side to the discharge side is used for compression, and when operating with the relief hole 21 opened. In comparison, the intake amount of the compressed gas to the oil-cooled screw compressor 10 and the compression ratio to the sucked compressed gas can be increased.

  At this time, the hydraulic oil introduced into the valve closing pressure receiving chamber 233 is introduced into the compression working space from the front end surface 232a of the piston 232 via the oil supply passage 237 provided in the piston 232, and thus as described above. By adopting a piston 232 having a flat tip surface 232a, a recess D is formed on the inner wall surface of the cylinder 13 due to a step formed between the opening edge of the escape hole 21 and the peripheral edge of the tip surface 232a of the piston 232. , Hydraulic oil is surely injected into the recess D.

  As a result, when the tooth tip of the screw rotor passes over the recess D described above, the amount of cooling oil that seals between the tooth tip of the screw rotor and the recess D increases, and the tooth of the screw rotor is increased by high-pressure oil supply. The gap between the tip and the recess D is shielded, and the presence of the recess D can suppress the leakage of the compressed gas from the compression working space on the high pressure side to the adjacent compression working space on the low pressure side. An increase in the specific power of the compressor 10 can be prevented.

  In addition, as the working oil to be introduced into the valve closing pressure receiving chamber 233 of the relief valve 23, the cooling oil that is introduced and circulated for lubrication, cooling, and sealing in the compression working space of the oil-cooled screw compressor 10 is used. In this case, when the cooling oil is introduced through the suction passage 16, the compressed gas in the suction passage 16 is heated and expanded by the temperature of the cooling oil, and the intake amount of the cooling oil and the compression action are expanded. The amount of intake air that is introduced into the space is reduced.

  However, this cooling oil is used as the working oil introduced into the valve closing pressure receiving chamber 233 of the above-described relief valve 23, and when the relief hole 21 is closed, the oil is supplied through the oil supply passage 237 provided in the piston 232 of the relief valve 23. By adopting a configuration in which cooling oil is supplied into the compression working space, it is possible to supply cooling oil to the working space that is not in communication with the suction passage after the suction is closed. The cooling oil is supplied to the compression space via the oil supply passage 237 provided in the piston 232 of the relief valve 23 without reducing the intake air amount accompanying the supply of the cooling oil. Thus, the specific power of the compressor body can be further improved.

[Usage example of oil-cooled screw compressor of the present invention]
An example of use of the oil-cooled screw compressor 10 of the present invention configured as described above will be described with reference to FIG.

(1) Example of starting load reduction type device configuration FIG. 1 shows a configuration example of a compressed air supply device 1 using an oil-cooled screw compressor 10 of the present invention. In the illustrated embodiment, FIG. The use of the oil-cooled screw compressor 10 of the present invention can reduce the starting load of the compressed air supply device 1.

  In this compressed air supply device 1, an engine for rotating the screw rotor 11 around the rotor shaft of the screw rotor 11 of the oil-cooled screw compressor 10 (in the illustrated example, the suction side rotor shaft of the male screw rotor 11a). The output shaft of the drive source 40 consisting of a motor and the like is connected.

  Further, the suction passage 16 of the oil-cooled screw compressor 10 removes a suction valve 51 for controlling intake air to the oil-cooled screw compressor 10 and foreign matters in the air introduced into the suction valve 51. The air filter 52 is communicated, and the screw rotor 11 is rotated by the drive source 40 described above so that air corresponding to the opening degree of the suction valve 51 can be sucked through the air filter 52. ing.

  Further, the discharge passage 18 of the oil-cooled screw compressor 10 has a receiver tank 60 for introducing compressed air discharged as a mixed fluid with cooling oil, and cooling oil contained in the compressed gas in the form of mist. A separator 61 for removing the air is communicated, and compressed air discharged as a gas-liquid mixed fluid from the oil-cooled screw compressor 10 is introduced into the receiver tank 60, so that the compressed air is received in the receiver tank 60. And the cooling oil are primarily separated, the compressed air after the primary separation is introduced into the separator 61, and the cooling oil still mixed in the mist state is removed and then supplied to the consumer side. It is configured as follows.

  On the other hand, the cooling oil collected in the receiver tank 60 is introduced again into the compression working space of the oil-cooled screw compressor 10 and circulated for use. The cooling oil recovered by the receiver tank 60 is passed through an oil filter 72 to remove impurities, cooled by an oil cooler 73, and then introduced into the oil-cooled screw compressor 10 to cool the compression working space. , Sealing and lubrication, and lubricating oil for bearings 14 and 15.

  In the illustrated embodiment, the above-described suction valve 51 is always open, and the compressed air from the receiver tank 60 introduced through the control pipe 53 is used as the closed valve receiving pressure of the suction valve 51. The suction valve 51 can be closed or throttled by being introduced into a chamber (not shown).

  By providing the pressure adjusting valve 54 in the control pipe 53, when the pressure of the compressed air supplied to the consumption side rises above the set pressure of the pressure adjusting valve 54, the introduction of the operating pressure to the intake valve 51 is started. Thus, the intake valve 51 is closed or throttled to perform intake control on the oil-cooled screw compressor 10, and the pressure of the compressed air supplied to the consumption side is set to a certain range corresponding to the set pressure of the pressure adjustment valve 54. It is the same as the structure of the compressed air supply apparatus constructed | assembled using the general oil-cooled screw compressor in the point comprised so that it can maintain.

  In the illustrated compressed air supply apparatus 1 using the oil-cooled screw compressor 10 of the present invention which is a variable capacity type, the branch pipe 74 branched from the oil supply pipe 71 connected to the receiver tank 60 is provided. One end of the branch pipe 74 communicates with a valve closing pressure receiving chamber 233 provided in the relief valve 23.

  In this way, in the compressed air supply device 1 shown in FIG. 1, by adopting a configuration in which the branch pipe 74 branched from the oil supply pipe 71 communicated with the receiver tank 60 is connected to the valve closing pressure receiving chamber 233 of the valve 23. , The starting load can be reduced.

  That is, when the drive source 40 is stopped and the operation of the oil-cooled screw compressor 10 is stopped, the pressure in the receiver tank 60 is reduced to the atmospheric pressure, so that the valve-closing pressure receiving chamber of the relief valve 23 is closed. No hydraulic oil is introduced into the valve 233, and the piston 232 of the relief valve 23 is retracted in the outer circumferential direction of the cylinder 13 by the urging force of the coil spring 234, and the tip of the piston 232 comes out of the relief hole 21. Thus, the escape hole 21 is opened.

  Accordingly, when the compressed air supply device 1 is started, the compression working space communicates with the escape passage 22 and the suction passage 16 via the escape hole 21, and therefore reaches the escape hole 21 from the suction side in the compression working space. The portion is not used for compression, and the effective length of the compression working space is shortened. As a result, the intake air amount of the oil-cooled screw compressor 10 is reduced and the compression is reduced as compared with the case where the escape hole 21 is closed. The ratio decreases.

  As a result, the power required for driving the oil-cooled screw compressor 10 is also reduced, so that the load on the engine and motor immediately after startup can be reduced, the engine can be started without causing a stall, or the start-up congestion. The compressed air supply device 1 can be started smoothly by automatically reducing the load at the start of the drive source 40, such as by starting the motor without causing any problems.

  In this way, when the operation of the drive source 40 started with the starting load reduced is continued and the drive source 40 enters a stable operation state, the compressed air discharge from the oil-cooled screw compressor 10 continues. As a result, the pressure in the receiver tank 60 rises, and due to this pressure rise, the lubricating oil in the receiver tank 60 is introduced into the valve closing pressure receiving chamber 233 of the relief valve 23 through the oil supply pipe 71 and the branch pipe 74, and the coil spring 234. The piston 232 is advanced to the advance position toward the axis a of the rotor shaft of the screw rotor 11 against the urging force.

  As the piston 232 advances, the tip of the piston 232 is inserted into the escape hole 21 to close the escape hole 21, and the entire length of the compression working space from the suction side to the discharge side is used for compression. Generation of compressed air is started, and cooling oil is injected into the compression working space from the oil supply passage 237 that opens at the front end surface 232a of the piston 232, thereby lubricating, cooling, and sealing the compression working space. In addition, by introducing the cooling oil at the position where the escape hole 21 is formed, a fine recess D is generated on the inner wall surface of the cylinder 13 by using the piston 232 having the tip surface 232a formed flat as described above. However, it is possible to prevent the compressed air from leaking out from the compression working space on the high pressure side to the compression working space on the low pressure side adjacent to the compression working space, and an increase in specific power is prevented.

(2) Apparatus configuration of variable supply pressure type In contrast to the configuration of the compressed air supply apparatus 1 described above with reference to FIG. 1, a compressed air supply apparatus in which the pressure setting of the compressed air supplied to the consumer side is variable. A configuration example of 1 will be described with reference to FIG.

  In this supply pressure variable type compressed air supply apparatus 1, as shown in FIG. 7, the branch pipe 74 is opened and closed with respect to the branch pipe 74 branched from the oil supply pipe 71 with respect to the apparatus configuration described with reference to FIG. An electromagnetic on-off valve 75 is provided.

  In addition to the apparatus configuration described with reference to FIG. 1, a bypass pipe 55 that bypasses the pressure adjustment valve 54 ′ is provided in the control pipe 53, and the low-pressure pressure adjustment valve 56 and the bypass pipe 55 are provided in the bypass pipe 55. An electromagnetic on-off valve 57 that opens and closes the bypass pipe 55 is provided, and a high-pressure pressure adjustment valve 54 that operates a pressure adjustment valve 54 ′ provided on the control pipe 53 at a relatively high operating pressure with respect to the low-pressure adjustment valve 56. It's different in that

  The electromagnetic on-off valve 57 provided in the bypass pipe 55, the switch 81 for controlling the opening / closing of the electromagnetic on-off valve 75 provided on the branch pipe 74, and the electromagnetic on-off valve 57, When a low pressure is selected by switching the switch 81, the electromagnetic on / off valve 57 opens the bypass pipe 55 and the electromagnetic on / off valve 75 opens the branch pipe 74. When the switch 81 is opened and “high pressure” is selected, the electromagnetic switching valve 57 closes the bypass pipe 55 and the electromagnetic switching valve 75 closes the branch pipe 74.

  In the present embodiment, as the electromagnetic on / off valves provided in the bypass pipe 55 and the branch pipe 74, a normally open type electromagnetic on / off valve is used, and the control device 82 is connected to the branch pipe 74 when “high pressure” is selected. A valve closing signal is output to both the electromagnetic open / close valve 75 provided and the electromagnetic open / close valve 57 provided in the bypass pipe 55.

  In the compressed air supply device 1 configured as described above, when the switch 81 is set to “low pressure”, the control signal is not output by the control device 82, and the electromagnetic on-off valve 75 provided in the branch pipe 74 and the bypass pipe Both electromagnetic open / close valves 57 provided at 55 are maintained in an open state.

  Therefore, when the drive source 40 is started up with the switch 81 set to “low pressure” and the rotation of the screw rotor 11 of the oil-cooled screw compressor 10 is started, the inside of the receiver tank 60 is stopped when the oil-cooled screw compressor 10 is stopped. Since the pressure of the valve has decreased to atmospheric pressure, the branch pipe 74 is opened by the electromagnetic on-off valve 75, but hydraulic oil is not introduced into the valve-closing pressure receiving chamber 233 of the relief valve 23, and the relief pipe is released. Since the piston 232 of the valve 23 is in the retracted position and the escape hole 21 is open, the starting load of the oil-cooled screw compressor 10 can be reduced at the time of starting to reduce the starting load of the driving source 40. .

  When the pressure in the receiver tank 60 rises by continuing the operation of the oil-cooled screw compressor 10, the cooling oil in the receiver tank 60 is introduced into the closed pressure receiving chamber 233 of the relief valve 23, and the relief valve 23. The piston 232 moves forward toward the axis a of the rotor shaft of the screw rotor 11 against the biasing force of the coil spring 234 due to the pressure increase in the receiver tank 60, and the flange portion 232c of the piston 232 It advances until it collides with the step 231d in the chamber 231.

  As a result, the entire end of the compression working space extending from the suction side to the discharge side is used for compressing the intake air by inserting the tip of the piston 232 into the escape hole 21 and closing the escape hole 21. Compared with the setting of “high pressure” described later, the intake air amount to the oil-cooled screw compressor increases and the compression ratio of the compressed air to be discharged increases to generate compressed air efficiently. Can do.

  On the other hand, when the above-described switch 81 is switched to “high pressure”, the control device 82 outputs a close signal to both the electromagnetic on-off valve 57 provided on the bypass pipe 55 and the electromagnetic on-off valve 75 provided on the branch pipe 74. Both the bypass pipe 55 and the branch pipe 74 are closed.

  In this way, the communication between the receiver tank 60 and the valve closing pressure receiving chamber 233 of the relief valve 23 is blocked, so that even if the pressure in the receiver tank 60 increases due to the operation of the oil-cooled screw compressor 10, The operating pressure is not introduced into the valve closing pressure receiving chamber 233 of the relief valve 23, and the piston 232 of the relief valve 23 is arranged on the outer peripheral side of the cylinder 13 by the biasing force of the coil spring 234 regardless of the pressure fluctuation in the receiver tank 60. Maintain the retracted state.

  As a result, the compression working space communicates with the escape passage 22 and the suction passage 16 at the position where the escape hole 21 is formed, and a portion of the compression working space that is on the suction side with respect to the escape hole 21 is not used for compression. Since only the compression working space from 21 to the discharge passage 18 is used for compression, the amount of intake air of the oil-cooled screw compressor 10 is smaller than that in the case where “low pressure” is selected. Along with the decrease, the compression ratio of the compressed air to be discharged decreases, and accordingly, the power necessary for driving the oil-cooled screw compressor decreases.

  On the other hand, until the above-described bypass pipe 55 is closed, the pressure of the compressed air supplied to the consumption side is equal to or higher than the operating pressure of the pressure regulating valve (high pressure regulating valve) 54 ′ provided in the control pipe 53. Since the compressed air is not introduced into the closed pressure receiving chamber of the intake valve 51, the pressure of the compressed air supplied to the consumption side becomes a high pressure corresponding to the set pressure of the high pressure adjusting valve 54 ′. .

  As described above, when the setting of “high pressure” is selected with respect to the setting of “low pressure” described above, the power consumption consumed for driving the oil-cooled screw compressor 10 can be reduced. Even if the set pressure of the high pressure adjustment valve 54 ′ is set higher than the set pressure of the low pressure adjustment valve 56 and the pressure of the compressed air supplied to the consumption side is increased by the margin generated by the decrease, The driving source 40 such as an engine or a motor can be operated with a predetermined margin lower than the rated output, and the pressure of the compressed air supplied to the consuming side is increased without causing the driving source 40 to stall. Is possible.

[Others / variations, etc.]
As described above, in the configuration of the oil-cooled screw compressor 10 described with reference to FIGS. 1 to 7, the above-described relief hole 21 and the relief valve 23 that opens and closes the relief hole 21 are provided at the bottom of the cylinder 13. Although the case where it is provided has been described as an example, the relief hole 21 and the relief valve 23 may be provided in a portion other than the bottom of the cylinder 13.

  Moreover, in the oil-cooled screw compressor 10 described with reference to FIGS. 1 to 7, with respect to the oil-cooled screw compressor 10 in which the male screw rotor 11a and the female screw rotor 11b are arranged in the horizontal direction, Although the configuration in which the relief hole 21 and the relief valve 23 are provided has been described, the oil-cooled screw compressor 10 of the present invention is configured so that a male screw rotor 11a and a female screw rotor 11b are vertically moved as shown in FIG. It may be applied to the oil-cooled screw compressor 10 having a configuration arranged side by side. In the example shown in the figure, a relief hole 21 is opened at the bottom of the cylinder 13, and the piston vertically extends toward the axis of the cylinder 13. The relief valve 23 is configured so that 232 moves forward and backward.

  In this configuration, all the cooling oil supplied to the male screw rotor 11a side and the female screw rotor 11b side is collected at the bottom of the cylinder 13 so that the cooling oil can be more easily concentrated on the portion where the relief hole 21 is formed. As a result, a sufficient amount of lubricating oil for sealing the gap between the inner wall surface of the cylinder 13 and the tooth tip of the screw rotor 11 can be introduced into the position where the relief hole 21 is formed. In addition, it is possible to prevent the compressed fluid in the high pressure side working space from being blown into the adjacent low pressure side working space, thereby preventing an increase in the specific power of the compressor body.

  Furthermore, in the embodiment described above, the case where the above-described escape hole 21 and the relief valve 23 are provided in the cylinder 13 on the side that accommodates the male screw rotor 11a has been described as an example. The relief valve 23 may be provided on the female screw rotor 11b side as shown in FIG. 9, or may be provided on either the female side or the male side as shown in FIG.

  In particular, in the configuration in which the relief holes 21 are provided on both the male side and the female side as shown in FIG. 10, when the relief hole 21 is opened, the compressed fluid in the compression working space is smoothly allowed to escape to the suction passage 16. And the effect of reducing the operating power can be enhanced.

  In addition, since the diameter of each escape hole 21 can be reduced by providing a plurality of escape holes 21, the formed depression D can also be reduced, and the adjacent working spaces are sealed, The effect of preventing the compressed gas in the working space on the high-pressure side from blowing into the working space on the low-pressure side is further enhanced, and the specific power of the compressor body can be further improved.

DESCRIPTION OF SYMBOLS 1 Compressed air supply apparatus 10 Oil-cooled screw compressor 11 Screw rotor 11a Male screw rotor 11b Female screw rotor 12 Casing 13 Cylinder 14, 15 Bearing 16 Suction passage 17 Injection hole 18 Discharge passage 21 Relief hole 22 Relief passage 23 Relief Valve 231 Piston chamber 231a Small diameter portion 231b Spring accommodating portion 231c Large diameter portion 231d Step portion 232 Piston 232a Tip surface 232b Cylindrical portion 232c Flange portion 233 Pressure receiving chamber (valve closing pressure receiving chamber)
234 Coil spring 235 End plate 236 Oil supply port 237 Oil supply passage 238 O-ring 40 Drive source 51 Suction valve 52 Air filter 53 Control piping 54 Pressure adjustment valve 54 ′ Pressure adjustment valve (for high pressure)
55 Bypass piping 56 Pressure regulating valve (for low pressure)
57 On-off valve (electromagnetic on-off valve)
60 Receiver Tank 61 Separator 71 Oil Supply Pipe 72 Oil Filter 73 Oil Cooler 74 Branch Pipe 75 On-off Valve (Electromagnetic On-off Valve)
81 Switch 82 Control device a Rotor axis c C axis (relief hole and piston chamber)
t tangential line p contact point 900 oil-cooled screw compressor 911 screw rotor 912 casing 913 rotor chamber 916 suction passage 921 unload hole 922 communication passage 923 unload valve 923a distal end surface 930 pin 934 ridge

Claims (3)

A cylinder formed in the casing and a pair of male and female screw rotors that mesh and rotate with each other in the cylinder are provided, and a compression working space is formed between the inner wall surface of the cylinder and the teeth of the screw rotor. The compressed gas introduced into the compression working space from one end side of the screw rotor via the suction passage by the rotation of the rotor is compressed together with the cooling oil, and is connected to the other end side of the screw rotor via the discharge passage. Oil-cooled screw compressor
In the casing,
Forming a relief hole close to the discharge passage with respect to the suction closed position and communicating with the compression working space before communicating with the discharge passage;
An escape passage for communicating the escape hole and the suction passage;
When the relief hole is opened, the compression working space and the escape passage are communicated with each other, and when the relief hole is closed, the communication between the compression working space and the relief passage is blocked. A relief valve,
The relief valve,
A piston chamber having an axis perpendicular to the axis of the male or female screw rotor and perpendicular to the tangent to the arc of the inner wall surface of the cylinder;
A piston that moves forward and backward in the piston chamber between a forward position that closes the escape hole and a backward position that opens the escape hole, and is biased toward the backward position;
Providing a valve-closing pressure receiving chamber that moves the piston in the retracted position to the advanced position by introducing hydraulic oil;
The piston,
A flat tip surface perpendicular to the direction of movement of the piston;
An oil supply passage having one end opened at the tip surface and the other end opened by the valve-closing pressure receiving chamber is provided.
A configuration in which the relief valve is formed so that the front end surface of the piston is disposed at the outer peripheral side of the cylinder at a position where the tip end surface of the piston is spaced a predetermined rotation-permissible interval with respect to the rotation locus of the tooth tip of the screw rotor at the forward position. An oil-cooled screw compressor characterized by that.   2. The oil-cooled screw compressor according to claim 1, wherein when the piston is in the forward movement position, the relief valve is formed so that a front end surface of the piston is disposed at substantially the same position as the tangent. .   The relief valve is formed such that when the piston is in the forward position, the tip surface of the piston is disposed between the tangent and the position of the farthest point with respect to the tangent of the opening edge of the escape hole. The oil-cooled screw compressor according to claim 1.

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