Screw Compressor Technical Field The present application relates to a compressor, particularly to a screw compressor with a pressure regulating device. Background Art A screw compressor is a component commonly used in a refrigeration unit. In a screw compressor, a pair of screw rotors are meshed with each other by virtue of volumes of their tooth spaces to cause volume changes of elements formed by tooth-shaped spaces so as to implement gas suction, compression and exhaust processes. In a body of the screw compressor, a pair of screw rotors meshed with each other are disposed in parallel. One end of the screw rotor is a gas suction end communicating with a gas suction opening of the body, and the other end of the screw rotor is an exhaust end communicating with an exhaust opening of the body. With rotation of the screw rotor, gas is sucked via the gas suction end and is exhausted via the exhaust end after being compressed. During running of a screw compressor, an actual working condition may be inconsistent with an ideal setting working condition. Therefore, a specific regulation means is required for enabling the screw compressor to work under the ideal setting working condition. Summary of the Invention During running of screw compressor, over-compression may occur. The compressor in the present application can realize automatic regulation of the over-compression in the compressor. A screw compressor in the present application includes: a housing, where the housing has a rotor cavity; a pair of rotors, where the pair of rotors are located in the rotor cavity, teeth of the pair of rotors are capable of forming a compression cavity with the housing, each of the pair of rotors has a gas suction end and an exhaust end, and the exhaust end has an exhaust end surface extending in a radial direction; a pressure release channel, where the pressure release channel is disposed in the housing, the pressure release channel has a pressure release channel inlet and a pressure release channel outlet, the pressure release channel inlet is capable of communicating with the compression cavity, and the pressure release channel outlet communicates with an exhaust side of the compressor; and a regulating device, where the regulating device is movably installed on the housing and is configured to controllably open or close the pressure release channel inlet so as to achieve communication or non-communication between the compression cavity and the pressure release channel. According to the above screw compressor, the regulating device is configured to: open the pressure release channel inlet to enable the compression cavity to communicate with the exhaust side of the compressor when a pressure in the compression cavity of the screw compressor is greater than a pressure at the exhaust side of the compressor; and close the pressure release channel inlet so as to achieve non-communication between the compression cavity and the exhaust side of the compressor when the pressure in the compression cavity of the screw compressor is less than the pressure at the exhaust side of the compressor. According to the above screw compressor, the housing further includes a connection channel, and the connection channel has a connection channel inlet and a connection channel outlet, where the connection channel inlet is close to the exhaust ends of the pair of rotors and is capable of communicating with the compression cavity, and the connection channel outlet communicates with the pressure release channel inlet. According to the above screw compressor, the housing further includes a regulating device cavity, one end of the regulating device cavity forms the connection channel, and the pressure release channel inlet is located on a side wall of the regulating device cavity. According to the above screw compressor, the regulating device has an outer side surface extending along a circumferential direction; the outer side surface is capable of forming a sealing side surface; and the regulating device is movable in the regulating device cavity so that the sealing side surface is capable of opening or closing the pressure release channel inlet. According to the above screw compressor, the regulating device has a head portion and a body portion. In a radial direction of the regulating device, the head portion has a larger size than the body portion, and the sealing side surface is located at a far end of the body portion. The regulating device cavity includes a first section and a second section, where the second section has a larger diameter than the first section, the first section is closer to the pair of rotors than the second section, the body portion is accommodated in the first section, the head portion is accommodated in the second section, and the head portion and a side wall of the second section are sealed in a circumferential direction. According to the above screw compressor, the head portion has a far end surface and a near end surface. The body portion is connected to the near end surface. The second section is divided into a first region and a second region by the head portion, where the first region is enclosed by the far end surface and the side wall of the second section, and the second region is enclosed by the near end surface, an outer surface of the body portion, and the side wall of the second section. The first region communicates with the exhaust side of the compressor, and the second region communicates with the compression cavity. Volumes of the first region and the second region change with movement of the regulating device. According to the above screw compressor, the housing further includes a pressure regulation channel, and the pressure regulation channel has a pressure regulation channel inlet and a pressure regulation channel outlet, where the pressure regulation channel outlet communicates with the second region, the pressure regulation channel inlet communicates with the compression cavity, and in an axial direction of the pair of rotors, the pressure regulation channel inlet is closer to the gas suction ends of the pair of rotors than the connection channel inlet. According to the above screw compressor, the housing has a housing fitting surface disposed facing the exhaust end surfaces of the exhaust ends of the pair of rotors; the connection channel inlet is located on the housing fitting surface and is capable of overlapping with the exhaust end surfaces; the housing fitting surface is provided with an exhaust cavity opening; and on a radial section, a specific distance is kept between the connection channel inlet and the exhaust cavity opening. According to the above screw compressor, the rotor cavity has a rotor cavity side wall; the pressure regulation channel inlet overlaps with the rotor cavity side wall; and in an axial direction of the pair of rotors, a specific distance is kept between the pressure regulation channel inlet and the exhaust end surfaces. The compressor in the present application has the regulating device, the pressure regulation channel, the pressure release channel, and a pressure balance channel. The regulating device is pushed by pressure changes of the pressure regulation channel and the pressure balance channel to open or close the pressure release channel, so as to regulate a gas pressure in the compression cavity, thereby regulating over-compression of the compressor. The regulating device in the present device does not require manual intervention. The regulating device is simple in structure, and easy to manufacture and maintain. Brief Description of the Drawings FIG. 1A is a three-dimensional diagram of a screw compressor according to a first embodiment of the present application; FIG. 1B is an exploded view of the screw compressor in FIG. 1A; FIG. 1C is an axial sectional view of the screw compressor in FIG. 1A sectioned along a direction indicated by a line A-A and viewed along a direction indicated by an arrow; FIG. 2A is a three-dimensional diagram of a rotor base in FIG. 1B; FIG. 2B is a side view of a rotor base in FIG. 2A; FIG. 2C is a sectional view of a rotor base in FIG. 2B sectioned along a line B-B; FIG. 3A is a three-dimensional diagram of an exhaust base in FIG. 1B; FIG. 3B is a view of the exhaust base in FIG. 3B viewed from an exhaust end surface; FIG. 3C is a sectional view of the exhaust base in FIG. 3B sectioned along a line C-C; FIG. 4 is a three-dimensional diagram of a regulating device in FIG. 1B; FIG. 5A is a side view of the screw compressor in FIG. 1A; FIG. 5B is a sectional view of the screw compressor in FIG. 5A sectioned along a line D-D; FIG. 5C is a sectional view of the screw compressor in FIG. 5A sectioned along a line F-F; FIG. 5D is another sectional view of the screw compressor in FIG. 5A sectioned along the line D-D; FIG. 5E is another sectional view of the screw compressor in FIG. 5A sectioned along the line F-F; FIG. 6 is a sectional view of a rotor base of a screw compressor according to a second embodiment of the present application; FIG. 7A is a side view of the screw compressor according to the second embodiment of the present application; FIG. 7B is a sectional view of the screw compressor in FIG. 7A sectioned along a line G-G; and FIG. 7C is another sectional view of the screw compressor in FIG. 7A sectioned along the line G-G. Detailed Description of the Invention The following describes various specific implementations of the present application with reference to the accompanying drawings that constitute a portion of this specification. It should be understood that although in the present application, the terms such as "front", "back", "up", "down", "left", "right", "inside", "outside", "top", "bottom", "reverse", "backward", "near end", "far end", "horizontal", and "longitudinal" for indicating directions are used for describing structural portions and elements in various examples of the present application, these terms used herein are merely for ease of description and are determined based on exemplary orientations shown in the accompanying drawings. Embodiments disclosed by the present application can be disposed in different directions. Therefore, these terms for indicating directions are merely for description rather than limitation. FIG. 1A is three-dimensional diagram of a screw compressor according to an embodiment of the present application, FIG. 1B is an exploded view of the screw compressor in FIG. 1A, and FIG. 1C is an axial sectional view of the screw compressor in FIG. 1A sectioned along a direction indicated by a line A-A and viewed along a direction indicated by an arrow. FIG. 1A to FIG. 1C shows some components of the screw compressor. As shown in FIG. 1A to FIG. 1C, the screw compressor includes a housing 101, a pair of screw rotors 110, and regulating devices 108 and 109. The housing 101 includes a rotor base 131 and an exhaust base 132. The rotor base 131 has a rotor cavity 105 for accommodating the pair of screw rotors 110. The rotor base 131 has an exhaust cavity 180, where the exhaust cavity 180 communicates with an exhaust opening 181 of the compressor. The screw rotor 110 includes a pair of a male rotor 121 and a female rotor 122 meshed with each other, where the male rotor 121 and the female rotor 122 can be driven to rotate. The screw rotor 110 includes a tooth portion 160, and shaft portions 161 and 162 that are respectively connected to two ends of the tooth portion 160. At the tooth portion 160 of the screw rotor 110, the male rotor 121 has a plurality of helical teeth, where a groove is formed between adjacent two of the teeth; and the female rotor 122 also has a plurality of helical teeth, where a groove is formed between adjacent two of the teeth as well. The male rotor 121 and the female rotor 122 form a mutually-meshed structure by the teeth and corresponding grooves, and form a compression cavity 150 with the housing 101. In an axis direction of the screw rotor 110, the tooth portion 160 of the screw rotor 110 has a gas suction end 112 and an exhaust end 113. Gas is sucked into the compression cavity 150 via the gas suction end 112, and gradually moves toward the exhaust end 113 with rotation of the screw rotor 110. Meanwhile, volume of the compression cavity 150 gradually decreases with rotation of the screw rotor 110, and accordingly the gas in the compression cavity 150 is gradually compressed. The compressed gas enters the exhaust cavity 180 of the compressor from the exhaust end 113, and is then exhausted via the exhaust opening 181 of the compressor. The exhaust end 113 has an exhaust end surface 118. FIG. 2A is a three-dimensional diagram of a rotor base in FIG. 1B, FIG. 2B is a side view of a rotor base in FIG. 2A, and FIG. 2C is a sectional view of a rotor base in FIG. 2B sectioned along a line B-B. As shown in FIG. 2A to FIG. 2C, the rotor base includes a front end 211 and a rear end 212. The front end 211 is close to the gas suction end 112 of the screw rotor 110, and the rear end 212 is close to the exhaust end 113 of the screw rotor 110. The rear end 212 is connected to the exhaust base 132, and the rear end 212 has a rear end surface 207. The rotor cavity 105 extends to run through the rear end surface 207 to form a rotor cavity opening 215. The rotor cavity 105 has a rotor cavity side wall 188, where the rotor cavity side wall 188 and the tooth portions 160 of the pair of rotors can be sealed. The rotor base 131 has a rotor base pressure regulation channel 240. The rotor base pressure regulation channel 240 has an inlet 241 and an outlet 242, where the inlet 241 is located on the rotor cavity side wall 188, and has a specific distance from the rear end surface 207. The outlet 242 is located on the rear end surface 207. The distance between the inlet 241 and the rear end surface 207 may be regulated according to specific configuration of the screw compressor. In an embodiment of the present application, the distance between the inlet 241 and the rear end surface 207 is less than half of length of the tooth portion 160 of the screw rotor 110 in an axial direction. FIG. 3A is a three-dimensional diagram of an exhaust base in FIG. 1B, FIG. 3B is a view of an exhaust base in FIG. 3B viewed from an exhaust end surface, and FIG. 3C is a sectional view of the exhaust base in FIG. 3B sectioned along a line C-C. As shown in FIG. 3A to FIG. 3C, the exhaust base 132 has a first end 311 and a second end 312, where the first end 311 is connected to the rotor base 131. An end surface of the first end 311 forms a housing fitting surface 341, and the housing fitting surface 341 fits the rear end surface 207 of the rotor base 131. The exhaust base 132 has a rotor shaft cavity 361, a rotor shaft cavity 362, an exhaust cavity 180, a regulating device cavity 310, a regulating device cavity 320, a pressure release channel 328, and a pressure release channel 329. The rotor shaft cavity 361 and the rotor shaft cavity 362 are configured to accommodate shafts of the screw rotors 110, and the rotor shaft cavity 361 and the rotor shaft cavity 362 are provided with a rotor shaft opening 371 and a rotor shaft opening 372 on the housing fitting surface 341. The exhaust cavity 180 is provided with an exhaust cavity opening 366 on the housing fitting surface 341. The regulating device cavity 310 and the regulating device cavity 320 are provided with a regulating device cavity opening 367 and a regulating device cavity opening 368 on the housing fitting surface 341. The exhaust cavity opening 366 has a specific distance from the regulating device cavity opening 367 and the regulating device cavity opening 368. The regulating device cavity 320 communicates with the exhaust cavity 180 through the pressure release channel 328. The housing fitting surface 341 has a rotor projection region 382, where the rotor projection region 382 is a projection region formed on the housing fitting surface 341 by the pair of screw rotors 110 in an axial direction during rotation. The rotor projection region 382 is approximately in a shape of "8" and is disposed around the rotor shaft opening 371 and the rotor shaft opening 372. During rotation of the pair of screw rotors 110, the exhaust end surface 118 passes over the housing fitting surface 341 within a range defined by the rotor projection region 382. The rotor projection region 382 has a sealing region 326, a first opening region 337, a second opening region 338, and a second opening region 339. Overlapping portions of the exhaust cavity opening 366 and the rotor projection region 382 form the first opening region 337. Overlapping portions of the regulating device cavity openings 367 and 368 and the rotor projection region 382 form the second opening region 338 and the second opening region 339, and the remaining portions form the sealing region 326. The second opening region 338 and the second opening region 339 are respectively located downstream rotating directions of the respective screw rotors with respect to the first opening region 337. In other words, during rotation, the screw rotors first pass through the second opening regions 338 and 339 and then reach the first opening region 337. A tail end of the compression cavity 150 can be sealed by the sealing region 326, so that the compression cavity 150 can form a sealing space. During rotation of the pair of screw rotors 110, when the tail end of the compression cavity 150 is aligned with the sealing region 326, the compression cavity 150 is disconnected from the exhaust cavity 180, and a refrigerant gas in the compression cavity 150 can be compressed; when the tail end of the compression cavity 150 is aligned or partially aligned with the first opening region 337, the compression cavity 150 can communicate with the exhaust cavity 180, and the gas in the compression cavity 150 can be exhausted; and when the tail end of the compression cavity 150 is aligned or partially aligned with the second opening regions 338 and 339, selective communication or non-communication is provided between the compression cavity 150 and the pressure release channels 328 and 329. A selective communication or non-communication relationship between the compression cavity 150 and the pressure release channels 328 and 329 is described in detail below. In the present application, the regulating device cavity 310 and the regulating device cavity 320 are similar in structure and different in location, and the pressure release channel 328 and the pressure release channel 329 are similar in structure and different in location. The following uses the regulating device cavity 320 and the pressure release channel 329 of the exhaust base as an example to describe the structures thereof. As shown in FIG. 3C, the regulating device cavity 320 is formed by the regulating device cavity opening 368 extending into the exhaust base. The far end (that is, an end far away from the regulating device cavity opening 367) of the regulating device cavity 320 has a bottom wall 383. The regulating device cavity 320 has a first section 321 and a second section 322, where the first section 321 is close to the regulating device cavity opening 367, and the second section 322 is close to the bottom wall 383. The second section 322 has a larger diameter than the first section 321, so that a step surface 335 is formed at a joint of the first section 321 and the second section 322. A shape of the regulating device cavity 320 is set to fit the regulating device 109 so as to make sure that the regulating device 109 is movable in the regulating device cavity 320. In the present application, in order to facilitate assembly of the regulating devices 108 and 109, the exhaust base 132 includes a separable sleeve 357 and a separable sleeve 358. The sleeves 357 and 358 are fixedly connected to an exhaust base body after the regulating devices 108 and 109 are installed in the exhaust base body. The sleeves 357 and 358 are approximately cylindrical, and the first section 321 is enclosed by side walls of the sleeves 357 and 358. The side walls of the sleeves 357 and 358 have an opening, so as to form a connection channel outlet. The step surface 335 is formed by an end surface of one end of the sleeve 358. One end of the regulating device cavity 320 has a connection channel 398. The connection channel 398 is formed by a portion, close to the regulating device cavity opening 367, of the first section 321 of the regulating device cavity 320. In other words, the connection channel 398 is a section of the first section 321. In this embodiment, the connection channel 398 is a portion, below a dotted line, of the regulating device cavity 320 in FIG. 3C. The connection channel 398 has a connection channel inlet 396 and a connection channel outlet 397, where the connection channel inlet 396 is formed by a portion of the regulating device cavity opening 368, and the connection channel inlet 396 overlaps with the second opening region 338. The connection channel outlet 397 is located on a side wall of the first section 321 of the regulating device cavity 320. The pressure release channel 329 of the exhaust base has an inlet 316 and an outlet 317, where the inlet 316 is located on the side wall of the first section 321 of the regulating device cavity 320 and overlaps with the connection channel outlet 397. The connection channel outlet 397 is located on a side wall of the exhaust cavity 180 and communicates with the exhaust cavity 180. The exhaust base 132 further includes an exhaust base pressure regulation channel 334 and a pressure balance channel 355. An inlet 332 of the exhaust base pressure regulation channel 334 communicates with the rotor base pressure regulation channel outlet 242, and an outlet 333 of the exhaust base pressure regulation channel 334 communicates with the second section 322 of the regulating device cavity 320. The outlet 333 of the exhaust base pressure regulation channel 334 is located on the side wall of the second section 322 and is close to the first section 321. A first end of the pressure balance channel 355 communicates with the second section 322 of the regulating device cavity 310, and a second end of the pressure balance channel 355 communicates with the exhaust cavity 180. A joint of the first end of the pressure balance channel 355 and the regulating device cavity 310 is located on the side wall of the regulating device cavity 310 and is close to the bottom wall 383 of the regulating device cavity 310. In another embodiment of the present application, the joint is located on the bottom wall 383 of the regulating device cavity 310. FIG. 4 is a three-dimensional diagram of a regulating device 109 in FIG. 1B. As shown in FIG. 4, the regulating device 109 is a piston, where the piston has a head portion 411 and a body portion 412. The head portion 411 has a larger diameter than the body portion 412. An outer diameter of the head portion 411 matches an inner diameter of the second section 322 of the regulating device cavity 320. An outer diameter of the body portion 412 matches an inner diameter of the first section 321 of the regulating device cavity 320. The head portion 411 is accommodated in the second section 322, and the body portion 412 is accommodated in the first section 321. In an axial direction, the length of the second section 322 of the regulating device cavity 320 is greater than the length of the head portion 411 of the regulating device 109, and the length of the first section 321 of the regulating device cavity 320 is less than the length of the body portion 412 of the regulating device 109, so that the regulating device 109 can move in the axial direction within a specific range in the regulating device cavity 320. The head portion 411 has a far end surface 441 and a near end surface 442, and the body portion 412 is connected to the near end surface 442. The body portion 412 has an outer side surface 401 extending along a circumferential direction, and the outer side surface 401 can form a sealing side surface 423. When the regulating device 109 moves in the regulating device cavity 320, the sealing side surface 423 can open or close the pressure release channel inlet 316. The far end (that is, an end far away from the head portion 411) of the body portion 412 has a regulating device sealing end surface 455. A shape of the regulating device sealing end surface 455 matches with a shape of the regulating device cavity opening 368, so that the regulating device sealing end surface 455 can seal the regulating device cavity opening 368. A circumferential outer side of the head portion 411 may be sleeved with a sealing ring so as to enhance sealing between the head portion 411 and the side wall of the second section 322. FIG. 5A is a side view of a screw compressor in FIG. 1A; FIG. 5B is a sectional view of the screw compressor in FIG. 5A sectioned along a line D-D; FIG. 5C is a sectional view of the screw compressor in FIG. 5A sectioned along a line F-F; FIG. 5D is another sectional view of the screw compressor in FIG. 5A sectioned along the line D-D; and FIG. 5E is another sectional view of the screw compressor in FIG. 5A sectioned along the line F-F. FIG. 5B and FIG. 5C shows a state of a pressure release channel at a closing position. FIG. 5D and FIG. 5E shows a state of the pressure release channel at an opening position. As shown in FIG. 5B, the length of the body portion 412 of the regulating device 109 is greater than the length of the first section 321 of the regulating device cavity 320, and the body portion 412 has a smaller diameter than the second section 322 of the regulating device cavity 320. A distance is kept between the head portion 411 and the step surface 335. The second section 322 is divided into a first region 551 and a second region 552 by the head portion 411. The first region 551 is enclosed by the far end surface 441 and the side wall of the second section 322, and the second region 552 is enclosed by the near end surface 442, an outer surface of the body portion 412, and the side wall of the second section 322. The first region 551 communicates with the exhaust side of the compressor, and the second region 552 communicates with the compression cavity 150. Volumes of the first region 551 and the second region 552 change with movement of the regulating device 109. The housing 101 has a pressure regulation channel 540, where the pressure regulation channel 540 is formed by connecting the rotor base pressure regulation channel 240 and the pressure regulation channel 334. A pressure regulation channel inlet 541 is formed by the rotor base pressure regulation channel inlet 241, and a pressure regulation channel outlet 542 is formed by the outlet 333 of the exhaust base pressure regulation channel 334. The pressure regulation channel outlet 542 is located on a side wall of the second region 552. The pressure balance channel 355 communicates with the first region 551. A gas pressure in the second region 552 is equal to a gas pressure at the pressure regulation channel inlet 541. A gas pressure in the first region 551 is equal to a gas pressure in the exhaust cavity 180. When the gas pressure in the exhaust cavity 180 is greater than the gas pressure at the pressure regulation channel inlet 541, the regulating device is subjected to a leftward pressure as shown in FIG. 5B to enter the connection channel 398 so as to close the pressure release channel. When the tail end of the compression cavity 150 of the screw rotor 110 communicates with the exhaust cavity opening 366, the gas in the compression cavity is exhausted. When the gas pressure in the exhaust cavity 180 is less than the gas pressure at the pressure regulation channel inlet 541, the regulating device is subjected to a rightward pressure as shown in FIG. 5B to leave the connection channel 398 so as to open the pressure release channel. The tail end of the compression cavity 150 first rotates to communicate with the regulating device cavity opening 368, and before the tail end rotates to reach the exhaust cavity opening 366, the gas in the compression cavity is exhausted in advance through the pressure release channel 329. As shown in FIG. 5B and FIG. 5C, when the pressure release channel is at a closing position, the regulating device 109 abuts against the rear end surface 207 of the rotor base. At this moment, the body portion 412 of the regulating device 109 is located in the connection channel 398 and fully fills the connection channel 398, such that the connection channel 398 is closed. The regulating device cavity opening 368 is closed by the regulating device sealing end surface 455. The inlet 316 of the pressure release channel 329 is closed by the sealing side surface 423. When the pressure release channel is at a closing position, the rotor cavity 105 needs to rotate to a position communicating with the exhaust cavity opening 366, and the gas in the rotor cavity 105 is exhausted to the exhaust cavity 180. As shown in FIG. 5D and FIG. 5E, when the pressure release channel is at an opening position, the regulating device 109 leaves the rear end surface 207 of the rotor base. At this moment, the body portion 412 of the regulating device 109 leaves the connection channel 398, such that the connection channel 398 is opened. The regulating device cavity opening 368 communicates with the compression cavity 150. The inlet 316 of the pressure release channel 329 communicates with the connection channel 398. When the pressure release channel is at an opening position, and the compression cavity 150 rotates to a position communicating with the regulating device cavity opening 368 and has not reached the position of the exhaust cavity opening 366, the gas in the rotor cavity 105 can be exhausted to the exhaust cavity 180 through the pressure release channel 329. In other words, when the pressure release channel is at an opening position, the gas in the compression cavity 150 is exhausted in advance, so as to reduce a pressure in the compression cavity 150, thereby preventing over-compression caused when the pressure in the compression cavity 150 is greater than a pressure at the exhaust side. The regulating device 109 realizes automatic regulation by pressure changes of the pressure regulation channel 540 and the pressure balance channel 355 without manual intervention. The regulating device 109 is simple in structure, and easy to manufacture and maintain. FIG. 6 is a sectional view of a rotor base of a screw compressor according to a second embodiment of the present application; FIG. 7A is a side view of the screw compressor according to the second embodiment of the present application; FIG. 7B is a sectional view of the screw compressor in FIG. 7A sectioned along a line G-G; and FIG. 7C is another sectional view of the screw compressor in FIG. 7A sectioned along the line G-G, where FIG. 7B shows a state of a pressure release channel at a closing position, and FIG. 7C shows a state of the pressure release channel at an opening position. As shown in FIG. 6, a rotor base includes a regulating device cavity 610, a pressure regulation channel 640, a pressure release channel 629, and a pressure balance channel 655. The regulating device cavity 610 has a regulating device cavity opening 668, where the regulating device cavity opening 668 is located on a side wall of the rotor cavity. The regulating device cavity 610 has a first section 611, a second section 612, and a third section 613. Diameters of the first section 611, the second section 612 and the third section 613 increase gradually. An inlet 641 of the pressure regulation channel 640 communicates with the compression cavity, and the inlet 641 of the pressure regulation channel 640 is closer to the gas suction ends of the pair of rotors than the regulating device cavity 610. As shown in FIG. 6, the inlet 641 of the pressure regulation channel 640 is located on a left side of the pressure regulation channel 610. An outlet of the pressure release channel 629 communicates with the exhaust cavity, and an inlet 616 of the pressure release channel 629 communicates with the first section 611 and is located on a side wall of the first section 611. The inlet 616 of the pressure release channel 629 has a specific spacing with the side wall of the rotor cavity. One end of the pressure balance channel 655 communicates with the second section 612, and the other end of the pressure balance channel communicates with the exhaust cavity. One end, close to the rotor cavity, of the first section of the regulating device cavity 610 is provided with a connection channel 698. The connection channel 698 communicates with the pressure release channel 629. The regulating device cavity 610 has a regulating device cavity opening 668. The embodiments shown in FIG. 6 and FIG. 7C are similar to the embodiment shown in FIG. 1A except that the regulating device 709 is disposed in the rotor base 131 and arranged in a direction approximately perpendicular to the pair of screw rotors 110. As shown in FIG. 7B and FIG. 7C, the regulating device 709 has a body portion 712, a head portion 711, and an extension portion 713, where the head portion 711 is located in the second section 612 of the regulating device cavity 610, and the body portion 712 is located in the first section 611 of the regulating device cavity 610. The head portion has a near end surface 742 and a far end surface 741, the body portion is connected to the near end surface 742, and the extension portion 713 is connected to the far end surface 741. The extension portion 713 is connected to the head portion 711 to facilitate assembly and position limitation. The extension portion 713 and the body portion 712 both have a smaller diameter than the head portion 711. The length of the body portion 712 of the regulating device 709 is greater than the length of the first section 611 of the regulating device cavity 610, and the body portion 712 has a smaller diameter than the second section 612 of the regulating device cavity 610. The second section 612 is divided into a first region 751 and a second region 752 by the head portion 711. The first region is enclosed by the far end surface 741 of the head portion, an outer wall of the extension portion 713 and a side wall of the second section 612. The second region 752 is enclosed by the near end surface 742, an outer surface of the body portion 712 and the side wall of the second section 612. The first region 751 communicates with the exhaust side of the compressor through the pressure regulation channel 640, and the second region 752 communicates with the compression cavity 750 through the pressure balance channel 655. Volumes of the first region 751 and the second region 752 change with movement of the regulating device 109. As shown in FIG. 7B, when the pressure release channel is at a closing position, an end surface of the body portion 712 of the regulating device 709 is flush with the regulating device cavity opening 668. At this moment, the body portion 712 of the regulating device 709 is located in the connection channel 698 and fully fills the connection channel 698, such that the connection channel 698 is closed. The regulating device cavity opening 668 is closed by the end surface of the body portion 712 of the regulating device 709. The inlet 616 of the pressure release channel 629 is closed by a side surface of the body portion of the regulating device 709. When the pressure release channel is at a closing position, the compression cavity needs to rotate to a position communicating with the exhaust cavity opening, and the gas in the compression cavity can be exhausted to the exhaust cavity 180. As shown in FIG. 7C, when the pressure release channel is at an opening position, the regulating device 709 leaves the regulating device cavity opening 668. At this moment, the body portion 712 of the regulating device 709 leaves the connection channel 698, such that the connection channel 698 is opened, and the inlet 616 of the pressure release channel 629 communicates with the compression cavity through the connection channel 698. When the pressure release channel is at an opening position, and the compression cavity rotates to a position communicating with the regulating device cavity opening 668 and has not reached the position of the exhaust cavity opening, the gas in the rotor cavity can be exhausted to the exhaust cavity through the pressure release channel. In other words, when the pressure release channel is at an opening position, the gas in the compression cavity is exhausted in advance, so as to reduce a pressure in the compression cavity, thereby preventing over-compression caused when the pressure in the compression cavity is greater than a pressure at the exhaust side. The embodiments shown in FIG. 6 to FIG. 7C can achieve the same technical effects as the embodiment shown in FIG. 1A. Although the present disclosure has been described in combination with examples of the embodiments summarized above, various alternatives, modifications, variations, improvements and/or substantial equivalents, whether known or now or foreseeable in the near future, may be apparent to those of at least ordinary skill in the art. In addition, the technical effects and/or technical problems described in this specification are exemplary rather than restrictive. Therefore, the disclosure in this specification may be used for resolving other technical problems and has other technical effects, and/or can resolve other technical problems. Therefore, the examples of the embodiments in the present disclosure described above are intended to be illustrative rather than restrictive. Various changes can be made without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is intended to include all known or early-developed alternatives, modifications, variations, improvement, and/or substantial equivalents.