JP5543746B2 - Overcompression prevention device for screw compressor - Google Patents

Description

The present invention relates to equipment you prevent the excessive compression of the compressed gas at the discharge port side of the screw compressor is generated by a simple mechanism.

  A screw compressor, which is a rotary displacement compressor, has excellent advantages such as a simple structure and good durability, and is widely used in general. The screw compressor includes a suction port and a discharge port on both sides of the casing, and a male rotor and a female rotor are accommodated in the rotor casing. A space between the tooth crests of the male and female rotors and an inner wall of the rotor casing The compressed gas is compressed in the confined space formed, and the compressed gas is discharged from the discharge port.

The screw compressor has a volume ratio Vi (= suction volume V ₁ / discharge volume V ₂ ) suitable for operating conditions, and starts to discharge compressed gas at a timing corresponding to the volume ratio Vi suitable for operating conditions. In addition, the positions and shapes of the suction port and the discharge port are determined.
Therefore, a high performance can always be exhibited when operated under the designed conditions, but the efficiency decreases conversely under conditions deviating from the designed conditions. In particular, when the volume ratio Vi is operated at a value larger than the set volume ratio, “over-compression” that is compressed more than necessary occurs, and the pressure in the confined space becomes abnormally high. In this case, not only the efficiency is lowered, but also an excessive load is applied to a bearing or the like that supports the male and female rotors of the screw compressor, which causes a problem of shortening the life of the screw compressor.

Many existing screw compressors have a discharge port having a shape in which the volume ratio Vi is fixed and an average volume ratio is selected. And when the fluctuation | variation of the actual driving | running condition is estimated, it was supposed that the driving | running | working on the conditions which remove | deviate from this average volume ratio cannot help even if efficiency falls.
On the other hand, a mechanism capable of changing the volume ratio Vi has been proposed so that a single screw compressor can cope with a wide range of operating conditions. Patent Document 1 discloses this volume ratio variable mechanism. Hereinafter, this mechanism will be described with reference to FIGS.

  4 and 5, the screw compressor 100 includes a suction port 104 and a discharge port 106 in a casing 102, a Vi variable valve 108 for making the volume ratio Vi variable, a suction volume by making the suction volume variable. And a displacement control valve 110 that makes the variable. A rod 114 that is rotationally driven by a step motor 112 is provided in the longitudinal direction of the screw compressor 100. A male screw 114 a is formed at the tip of the rod 114, and the male screw 114 a is screwed into a screw hole 108 a formed in the Vi variable valve 108. The Vi variable valve 108 is movable in the longitudinal direction of the screw compressor 100 (the axial direction of the rod 114) by the rotation of the step motor 112.

  A hydraulic cylinder 116 is provided below the suction port 104, and hydraulic oil supply / discharge ports 118 and 120 are provided at both ends of the hydraulic cylinder 116. The hydraulic piston 122 is moved in the longitudinal direction of the screw compressor 100 by supplying and discharging hydraulic oil to and from the supply / discharge ports 118 and 120. The displacement control valve 110 and the hydraulic piston 122 are connected by a piston rod 124. As shown in FIG. 5, the capacity control valve 110 and the piston rod 124 are integrally connected by a bolt 126. The Vi variable valve 108 has a through hole 108b through which the piston rod 124 passes.

  A hollow hole 128 is formed in the piston rod 124 in the axial direction. A rod body 130 that is rotatably fixed to the inner wall of the hydraulic cylinder 116 is inserted into the hollow hole 128. A spiral groove 132 is formed on the peripheral surface of the rod body 130. A displacement sensor mounting hole 134 is formed in the casing 102 below the Vi variable valve 108, and a tapered groove 108 c is provided on the lower surface of the Vi variable valve 108. Note that the male and female rotors housed in the casing 102 are omitted.

In such a configuration, the compressed gas sucked from the suction port 104 enters the tooth space of the male and female rotors. The volume of the tooth space increases with the rotation of the male and female rotors, and when the volume reaches a maximum, the communication between the tooth space and the suction port is interrupted to form a sealed confined space. The confined space moves to the discharge port side in accordance with the rotation of the male and female rotors, and the volume is reduced. Therefore, the compressed gas in the confined space is compressed. When the teeth top of the rotors has reached the notch starting end 110a ₁ of the notch 110a of the displacement control valve 110 communicates with the discharge port 106 through the space narrowing Ji the closed is a discharge port Po, inclusive Ji said closed according to the rotation of the rotor The compressed gas in the space is discharged.

Wherein the maximum volume capacity V ₁ of the spatial confinement of time, the ratio of the volume V ₂ of the space confinement immediately before the discharge begins is volume ratio Vi. When it is necessary to change the volume ratio Vi, the step motor 112 is operated, the rod 114 is rotated, and the Vi variable valve 108 is moved along the rod 114. At this time, the displacement control valve 110 moves together with the Vi variable valve 108 by the hydraulic pressure in the hydraulic cylinder 116, and is fixed in a state of being in contact with the Vi variable valve 108 fixed at a new position. Thus, since the change notch position of the starting end 110a ₁ of the out portion 110a of the displacement control valve 110, changes the volume _{V 2,} you can change the volume ratio Vi.

  When it is necessary to change the suction flow rate, the displacement control valve 110 is moved by a necessary amount by moving the hydraulic piston 122 by supplying and discharging hydraulic oil to and from the hydraulic cylinder 116. Thereby, a gap is formed between the capacity control valve 110 and the Vi variable valve 108, and a part of the compressed gas is bypassed from the gap to the suction port side. Thereby, the suction flow rate can be changed.

  Note that a pin protruding from the hydraulic piston 122 is engaged with the spiral groove 132 of the rod body 130, and the magnitude of the movement stroke of the hydraulic piston 122 is detected with high accuracy by the magnitude of the rotation angle of the rod body 130. It can be done. In addition, as shown in FIG. 5, the position of the Vi variable valve 108 is detected by inserting a displacement sensor (not shown) into the displacement sensor mounting hole 134 and mounting the displacement sensor, and the displacement sensor detects the gap between the displacement sensor and the taper groove 108c. The position of the Vi variable valve 108 is specified by detecting the displacement.

  In Patent Document 2, due to the presence of lubricating oil accumulated in the confined space when the screw compressor is stopped, abnormal torque and abnormal noise are generated when the compressor is started, which causes damage, breakage, and the like of the rotor shaft. Means for preventing this are disclosed. In FIG. 1 of Patent Document 2, a relief valve 31 is provided at an appropriate position on the discharge side of the compressor casing, and the lubricating oil accumulated in the closed space when the compressor is started is opened to open the relief valve 31. A means for solving the above-mentioned problem is disclosed.

  Further, in FIG. 4 of Patent Document 2, a wall lubricating oil discharge hole 4 is provided in the lower periphery of the rotor chamber, and the position of the discharge hole 4 is changed according to the pressure difference between the rotor chamber and the discharge port. Disclosed is a means for providing a piston 1 that opens and closes the valve, opens the discharge hole 4 at the time of start-up when the discharge pressure is low, and causes the accumulated oil to flow out, and closes the outflow hole 4 during normal operation when the discharge pressure is high Has been.

  Further, in Patent Document 3, in the screw compressor, a slide valve that slides in the rotor axial direction is provided like the Vi variable valve 108 in Patent Document 1, and the slide valve is slid in the rotor axial direction to It is disclosed that the load at startup is reduced by adjusting the flow rate of the discharge gas. Furthermore, a relief valve is provided on the slide valve or the compressor casing, and when the discharge pressure rises to a specified value or more, the relief valve is operated to release the compressed gas in the rotor chamber, thereby The abnormal load on the supporting bearing is reduced.

JP-A-5-231363 Japanese Utility Model Publication No. 63-41593 (FIGS. 1 and 4) JP-A-4-43883

  As disclosed in Patent Document 1, a mechanism using a capacity control valve or a volume ratio variable valve is generally not very popular because of its complicated structure and high cost. However, if these mechanisms are not provided, as described above, "over-compression" that is compressed more than necessary occurs, the pressure in the confined space becomes abnormally high, the efficiency is lowered, and the durability of the screw compressor is reduced. The problem which impairs property arises. Since the pressure is highest in the confined space immediately before communicating with the discharge space, it is particularly necessary to eliminate “over-compression” in the confined space.

The mechanism for discharging the lubricating oil by the relief valve 31 shown in FIG. 1 of Patent Document 2 is for discharging the lubricating oil accumulated in the rotor chamber, and for preventing overcompression of the compressed gas. is not. Further, regardless of the suction pressure or the discharge pressure, the rotor chamber is opened when the pressure in the rotor chamber exceeds the threshold value, and therefore, the suction flow rate and the volume ratio Vi cannot be adjusted.
Further, the lubricating oil discharge mechanism shown in FIG. 4 of Patent Document 2 does not release the compressed gas from the confined space immediately before communicating with the discharge space as seen from the position of the liquid discharge hole 4. However, it only has a function of discharging the lubricating oil.

  Since the screw compressor disclosed in Patent Document 3 includes a slide valve that makes it possible to adjust the discharge pressure, the problem that the structure becomes complicated and the cost is high cannot be solved. In addition, the slide valve or the casing of the screw compressor is provided with a relief valve that allows the gas to be compressed in the rotor chamber to escape to the discharge port when the pressure in the rotor chamber exceeds a specified level. Since this relief valve is not provided in the confined space immediately before communicating with the discharge space, it is not possible to prevent overcompression of the confined space that is at the highest pressure. Further, this relief valve does not adjust the volume ratio Vi.

In view of the problems of the prior art, the present invention does not require a complicated mechanism such as a capacity control valve or a Vi variable valve in a screw compressor, and the excess of the discharge side confinement space where the pressure becomes high with a simpler mechanism. The purpose is to prevent compression. In particular, an object is to prevent overcompression of the discharge space immediately before communicating with the discharge space having the highest pressure.
It is another object of the present invention to make it possible to adjust the volume ratio Vi without requiring a complicated mechanism like the conventional Vi variable valve.

In order to achieve this object, a male rotor and a female rotor are accommodated in a casing having a suction port and a discharge port, and the compressed gas sucked from the suction port is separated between the male and female rotors and the casing inner wall. In the overcompression preventing device of the screw compressor that compresses in the formed confined space and discharges from the discharge port,
A pressure sensor for detecting the pressure of the compressed gas compressed in the confined space immediately before communicating with the discharge space;
An overcompression prevention valve that is provided in the confined space and opens the confined space when the pressure of the compressed gas in the confined space exceeds a threshold value, and releases the compressed gas outside the casing;
The overcompression prevention valve has a valve body loosely fitted in a recess provided in a closed space immediately before passing through the casing wall and communicating with the discharge space, and a spring force disposed in the recess to close the valve body. a spring member for adding, a flow path for communicating the the recess suction space and a discharge space, e Bei a switching valve which is interposed in the flow path, a recess by the controller is the suction space or discharge space The switching valve is controlled so as to communicate with the valve, and the overcompression prevention valve is controlled to open and close.

According to the present invention , the pressure of the compressed gas in the confined space immediately before communicating with the discharge space is detected, and when the detected value exceeds the upper limit threshold, the overcompression prevention valve provided in the confined space is opened. To do. As a result, over-compression of the confined space can be prevented, the volume ratio Vi can be prevented from becoming excessively large, and the volume ratio Vi can be adjusted to an appropriate value. Therefore, abnormally high pressure in the rotor chamber can be prevented, so that an excessive load can be prevented from being applied to the rotor bearing and the like, the durability of the screw compressor can be improved, and the operating efficiency of the screw compressor can be prevented from being lowered. it can.

According to the present invention, the pressure of the compressed gas suction space and a discharge space is respectively detected, by calculating the volume ratio of these detected values, the over-compression prevention valve when said container product ratio exceeds the upper threshold opening may be that.
As a result, the volume ratio Vi can be adjusted with respect to fluctuations in the pressure values in the suction space and the discharge space, and overcompression in the rotor chamber can be prevented. For this reason, it is possible to prevent the operating efficiency of the screw compressor from being lowered and to maintain the durability of the screw compressor.

  In the device of the present invention, the pressure sensor detects the pressure of the compressed gas compressed in the confined space immediately before communicating with the discharge space, and when the pressure detection value of the confined space exceeds the upper limit threshold, The overcompression prevention valve is opened so that the compressed gas in the confined space is released out of the casing.

  This can prevent overcompression of the confined space immediately before communicating with the discharge space having the highest pressure. Further, the volume ratio Vi can be prevented from becoming excessively large, and the volume ratio Vi can be adjusted to an appropriate value. Accordingly, abnormally high pressure in the rotor chamber can be prevented, so that an excessive load can be prevented from being applied to the rotor bearing and the like, the durability of the screw compressor can be maintained, and a decrease in operating efficiency of the screw compressor can be prevented. .

In the device of the present invention, the second pressure sensor for detecting the pressure of the compressed gas in the suction space, the third pressure sensor for detecting the pressure of the compressed gas in the discharge space, the second pressure sensor, and the third pressure. It is preferable to provide a controller that inputs sensor detection values, calculates a volume ratio from these detection values, and opens the overcompression prevention valve when the volume ratio exceeds an upper limit threshold.
As a result, over-compression in the rotor chamber can be prevented against fluctuations in the pressure values in the suction space and the discharge space, and the volume ratio Vi can be adjusted so as not to become an excessive volume ratio Vi. Therefore, the durability of the screw compressor can be maintained, and a decrease in operating efficiency can be prevented.

In the apparatus of the present invention, in particular, the overcompression prevention valve is loosely fitted in a recess provided in a confined space immediately before passing through the casing wall and communicating with the discharge space, and the valve body disposed in the recess. A spring member that applies a spring force in a closing direction, a flow path that communicates the recess with the suction space and the discharge space, and a switching valve that is interposed in the flow path. by controlling the switching valve so as to communicate with the suction space or discharge space you configured to open and close control the over-compression valve.

  As a result, the over-compression prevention valve can be opened and closed using the pressure difference between the suction pressure and the discharge pressure, so that no special driving force is required for opening and closing the over-compression prevention valve. Therefore, a simple and low-cost configuration can be obtained.

According to the present invention , a male rotor and a female rotor are accommodated in a casing having a suction port and a discharge port, and the compressed gas sucked from the suction port is formed by the male and female rotors and the inner wall of the casing. Detecting the pressure of the compressed gas compressed in the confined space immediately before communicating with the discharge space in the overcompression preventing method of the screw compressor that compresses in the confined space and discharges from the discharge port; Opening the overcompression prevention valve provided in the confined space and releasing the compressed gas in the confined space to the outside of the casing when the detected pressure value of the confined space exceeds the upper limit threshold; Accordingly, it is possible to prevent over-compression of the confined space and to prevent the volume ratio Vi from becoming excessively large. As a result, abnormally high pressure in the rotor chamber can be prevented, so that an excessive load can be prevented from being applied to the rotor bearings and the like, the durability of the screw compressor can be maintained, and the operating efficiency of the screw compressor can be reduced. Can be prevented.

Further, according to the apparatus of the present invention, the male rotor and the female rotor are accommodated in the casing having the suction port and the discharge port, and the compressed gas sucked from the suction port is supplied to the male and female rotors and the inner wall of the casing. In the overcompression prevention device of the screw compressor that compresses in the confined space formed by and discharges from the discharge port, the pressure of the compressed gas compressed in the confined space immediately before communicating with the discharge space is detected A pressure sensor that is provided in the confined space, and an overcompression prevention valve that opens the confined space and releases the compressed gas outside the casing when the pressure of the compressed gas in the confined space exceeds a threshold value. by comprising the said book onset Ming implementation capable ing.

It is a cross-sectional view of the rotor chamber of the screw compressor according to the present onset Ming embodiment. It is front view sectional drawing of the rotor shaft end part of the screw compressor which concerns on the said embodiment. It is a systematic diagram of the control apparatus of the screw compressor which concerns on the said embodiment. It is a front view sectional view of the screw compressor provided with the conventional capacity control function and volume ratio variable function. It is a partially expanded sectional view of the screw compressor of FIG.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention to that unless otherwise specified.

This onset Ming embodiment will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing a rotor chamber in the vicinity of a discharge port of a twin rotor type screw compressor 10. In FIG. 1, a twin cylindrical accommodation space (rotor chamber) 12 for accommodating a male rotor 14 and a female rotor 16 is provided in a rotor casing 11 of a screw compressor 10. A discharge port 18 is provided at the discharge port side end of the rotor chamber 12.

  The male rotor 14 rotates in the direction of arrow a, and the female rotor 16 rotates in the direction of arrow b opposite to the direction of arrow a. While the male and female rotors 14 and 16 are engaged with each other, a plurality of tooth space is formed between the teeth crests of the male and female rotors and the inner wall of the rotor casing 11. The tooth gap space advances from the suction port side toward the discharge port 18 side by the rotation of the male and female rotors. When the volume of the tooth space is maximized, it is blocked from the suction port to form a sealed confined space. Since the volume of the confined space decreases toward the discharge port 18 side, the compressed gas in the confined space is compressed.

  Since the confined space has a minimum volume immediately before communicating with the discharge port 18, the pressure of the gas to be compressed becomes maximum here, and the volume ratio Vi becomes maximum. When the confined space communicates with the discharge port 18, the compressed gas confined in the confined space is discharged to the discharge port 18. In the present embodiment, an overcompression prevention valve 20 is provided in a closed space immediately before communicating with the discharge port 18. Hereinafter, the configuration of the overcompression prevention valve 20 will be described with reference to FIG.

  In FIG. 2, following the rotor casing 11 that forms the rotor chamber 12, covers 30 and 32 that seal the rotor shaft end portion 17 are connected. A discharge port 34 communicating with the discharge port 18 is provided on the inner wall of the cover 30. The compressed gas compressed in the rotor chamber 12 is discharged from the discharge port 34 through the discharge port 18. The shaft end portion 17 of the male and female rotors is rotatably supported by a radial bearing 36 and a thrust bearing 38.

  Of the confined spaces formed by the male and female rotors 14, 16 and the rotor casing 11, the confined space Sc (see FIG. 3) just before communicating with the discharge port 18 and the discharge port 34 are formed on the inner wall of the cover 30. A bypass passage 40 to be connected is formed. A recess 22 is formed in the inner wall of the cover 30 facing the bypass passage 40. A valve body 24 having a cylindrical shape in the concave portion 22 and having a bottom surface on the side facing the bypass passage 40 is slidably fitted in the concave portion 22. A cylindrical coil spring 26 is provided between the valve body 24 and the back end of the recess 22.

  The elastic force of the coil spring 26 acts to urge the valve body 24 toward the bypass passage 40 and close the bypass passage 40. A compressed gas passage 42 is formed in the covers 30 and 32, and the passage 42 opens at the back end of the recess 22. The passage 42 is connected to the communication pipe 44. The communication pipe 44 is provided with a three-way valve 46, and the communication pipe 44 is connected to the connection pipe 48 or 50 via the three-way valve 46 in a switchable manner.

  Next, the control device of the screw compressor 10 according to the present embodiment will be described with reference to FIG. In FIG. 4, the connection pipe 48 is connected to a suction pipe 54 connected to the suction port 52. The suction pipe 54 is provided with a pressure sensor 56 that detects the suction pressure Ps of the compressed gas in the suction pipe 54. The connection pipe 50 is connected to a discharge pipe 58 connected to the discharge port 34. The discharge pipe 58 is provided with a pressure sensor 60 that detects the discharge pressure Pd of the compressed gas in the discharge pipe 58.

  Further, a pressure sensor 62 is provided for detecting the pressure of the compressed gas in the confined space Sc just before communicating with the discharge port 18 of the rotor chamber 12 among the confined spaces formed between the crests t of the rotor. Yes. Further, a controller 64 is provided which inputs the detection values of the pressure sensors 58, 60 and 62, switches the three-way valve 46 based on these detection values, and switches and connects the communication pipe 44 to the connection pipe 48 or 50. .

  In the present embodiment having such a configuration, during normal operation of the screw compressor 10, the controller 64 inputs and monitors the detection values of the pressure sensors 56, 60 and 62 to the controller 64, and the communication pipe 44 and the connection pipe 50 are connected. Keep in communication. Thereby, the inside of the recess 22 is in a high pressure state equivalent to the discharge pressure Pd of the discharge port 34. Therefore, the valve body 24 is urged in a direction to close the bypass passage 40 by a total force of the discharge pressure Pd and the elastic force of the coil spring 26, and the bypass passage 40 is closed by this urging force. .

  When the pressure in the confined space Sc exceeds the upper threshold, the controller 64 operates the three-way valve 46 to connect the communication pipe 44 from the connection pipe 50 to the connection pipe 48. As a result, the inside of the recess 22 is in a low pressure state equivalent to the suction port 52. Therefore, the pressure of the compressed gas in the confined space Sc overcomes the elastic force of the coil spring 26 and causes the valve body 24 to retreat into the recess 22. As a result, the bypass passage 40 is opened, the compressed gas in the confined space Sc is discharged to the discharge port 34, and the overcompression of the confined space Sc is eliminated.

Further, the pressure sensor 56 detects the suction pressure Ps of the suction port 52, the pressure sensor 60 detects the discharge pressure Pd of the discharge port 34, and the controller 64 calculates the volume ratio Vi from these detected values. That is, the suction volume V ₁ is converted from the suction pressure Ps, and the discharge volume V ₂ is converted from the discharge pressure Pd to calculate the volume ratio Vi (= suction volume V ₁ / discharge volume V ₂ ). When there is a risk that the calculated value exceeds the upper limit threshold value, the controller 64 operates the three-way valve 46 to connect the communication pipe 44 from the connection pipe 50 to the connection pipe 48. As a result, the bypass passage 40 is opened, the compressed gas in the confined space Sc is discharged to the discharge port 34, and the volume ratio Vi can be kept below the upper limit threshold.

According to this embodiment, the overcompression of the discharge pressure Pd can be prevented beforehand by providing the overcompression prevention valve 20 in the closed space Sc. Therefore, abnormally high pressure in the rotor chamber 12 can be prevented, thereby preventing an excessive load from being applied to the rotor bearings and the like, and improving the durability of the screw compressor.
Further, since the volume ratio Vi can be maintained at an appropriate value, it is possible to prevent a decrease in the operation efficiency of the screw compressor 10 and to continue a highly efficient operation.

  According to the present invention, by simply adding a simple and low-cost device to an existing screw compressor, over-compression of the rotor chamber of the screw compressor can be prevented, and the durability of the screw compressor can be maintained. Operation efficiency can be continued.

DESCRIPTION OF SYMBOLS 10 Screw compressor 11 Rotor casing 12 Rotor chamber 14 Male rotor 16 Female rotor 18 Discharge port 20 Overcompression prevention valve 22 Recessed part 24 Valve body 26 Coil spring 34 Discharge port 40 Bypass path 42 Path 44 Communication pipe 46 Three-way valve 48, 50 Connection pipe 52 Suction port 54 Suction piping 56 Pressure sensor (second pressure sensor)
58 Discharge piping 60 Pressure sensor (third pressure sensor)
62 pressure sensor 64 controller Ps suction pressure Pd discharge pressure Sc confinement space t rotor crest

Claims (2)

In a confined space formed by housing a male rotor and a female rotor inside a casing having a suction port and a discharge port, the compressed gas sucked from the suction port is formed by the male and female rotors and the inner wall of the casing. In the overcompression preventing device of the screw compressor that compresses and discharges from the discharge port,
A pressure sensor for detecting the pressure of the compressed gas compressed in the confined space immediately before communicating with the discharge space;
An overcompression prevention valve that is provided in the confined space and opens the confined space when the pressure of the compressed gas in the confined space exceeds a threshold value, and releases the compressed gas outside the casing;
The overcompression prevention valve has a valve body loosely fitted in a recess provided in a closed space immediately before passing through the casing wall and communicating with the discharge space, and a spring force disposed in the recess to close the valve body. a spring member for adding, a flow path for communicating the the recess suction space and a discharge space, e Bei a switching valve which is interposed in the flow path, a recess by the controller is the suction space or discharge space An overcompression prevention device for a screw compressor, wherein the overcompression prevention valve is controlled to be opened and closed by controlling the switching valve so as to communicate with the overcompression valve. A second pressure sensor for detecting the pressure of the compressed gas in the suction space, and a third pressure sensor for detecting the pressure of the compressed gas in the discharge space;
A controller that inputs detection values of the second pressure sensor and the third pressure sensor, calculates a volume ratio from these detection values, and opens the overcompression prevention valve when the volume ratio exceeds an upper limit threshold; The overcompression preventing device for a screw compressor according to claim 1, comprising:

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