A piston-type axial force balancing structure and centrifugal pump

Abstract

The present invention provides a piston-type structure for balancing axial force and a centrifugal pump, comprising first and second strain gauge pressure sensors, an axial force detection system connected to the strain gauge pressure sensor signals, and an actuator installed between the through hole on the rear end face of the pump body and the rotor shaft. The actuator comprises a piston rear cover plate, a piston disc, a screw and a through-type stepping motor. The piston rear cover plate is assembled on the rear end cover of the pump body, and its inner and outer annular protrusions together with the impeller hub form an annular pressure chamber. The piston disc is located in the pressure chamber to divide the front and rear pressure chambers. One end of the screw is connected to the piston disc, and the other end is connected to the stepping motor. The present invention utilizes the first and second strain gauge pressure sensors to detect the magnitude of the impeller axial force, and uses the actuator to reduce the pressure difference between the front and rear sides of the impeller to achieve axial force balance. Since the actuator in the present invention is stationary relative to the pump body, the actuator can avoid leakage while balancing the axial force.

Description

Technical Field

[0001] The present invention relates to the technical field of centrifugal pumps, and in particular to a piston-type axial force balancing structure and a centrifugal pump. Background Art

[0002] For vane-type fluid machinery, especially single-stage centrifugal pumps, axial force is generated as the impeller rotates. The root cause is the imbalance in liquid pressure before and after the impeller. When the pump is operating, the impeller drives the liquid. During this process, the liquid passes through the impeller, and the axial forces acting on the front and rear ends of the impeller are unbalanced, resulting in a total axial force. Balancing the axial force in the pump has become crucial to its universal application. If the axial force is not eliminated or balanced, it will pull the rotor axially, causing contact with fixed parts, causing damage and even malfunction. Therefore, both in pump structural design and practical application, it is imperative to eliminate or balance the axial force to ensure reliable pump operation.

[0003] Currently, the most common balancing methods are the use of rear sealing rings, balancing drums, and balancing disc structures. The rear sealing ring balancing method uses the rear sealing ring as a barrier and opens a balancing hole to connect the inner side of the impeller rear sealing ring with the inlet, thereby reducing the axial force acting on the impeller rear cover plate pointing towards the impeller inlet. For multi-stage pumps, the last-stage impeller uses the rear sealing ring to generate a force that is close in magnitude and opposite in direction to the axial force generated by all impellers pointing towards the impeller inlet to balance the axial force; the balancing drum and balancing disc both generate a force on the balancing structure that is opposite in direction to the axial force to balance the axial force. The complexity of these three balancing methods increases. Because all three structures belong to the rotor part and need to rotate with the shaft, there are gaps between them and the pump body, which will cause leakage. Therefore, there is an urgent need to develop an axial force balancing component that can be assembled on a centrifugal pump so that it can balance the axial force without causing fluid leakage. Summary of the Invention

[0004] In response to the problem that existing axial force balancing components are prone to causing fluid leakage while balancing the axial force, the present invention provides a piston-type axial force balancing structure and a centrifugal pump, which uses a strain gauge pressure sensor to detect the magnitude of the impeller axial force in real time, and uses an actuator to reduce the pressure difference between the front and rear sides of the impeller to achieve axial force balance. Since the actuator in the present invention is stationary relative to the pump body, the actuator can avoid leakage while balancing the axial force.

[0005] The present invention achieves the above technical objectives through the following technical means.

[0006] A piston-type structure for balancing axial force, characterized in that it includes a front deep groove ball bearing and a front shaft sleeve respectively installed on the rotor shaft at the front and rear ends of the impeller hub, a first strain type pressure sensor installed between the front end of the impeller hub and the front deep groove ball bearing, a second strain type pressure sensor installed between the rear end of the impeller hub and the front shaft sleeve, an axial force detection system connected to the signals of the first strain type pressure sensor and the second strain type pressure sensor, and an actuator; a through hole with an inner diameter larger than the outer diameter of the rotor shaft is opened on the rear end face of the pump body, and the actuator is installed between the through hole on the rear end face of the pump body and the rotor shaft.

[0007] The actuator includes a piston rear cover plate, a piston disc, a screw and a through-type stepping motor; the front end surface of the piston rear cover plate is provided with an inner annular protrusion and an outer annular protrusion, and the piston rear cover plate is installed on the rear end cover of the pump body, the inner annular protrusion and the outer annular protrusion penetrate the rear end cover of the pump body and cooperate with each other on the rear end surface of the impeller hub to form an annular pressure chamber, and a gap is left between the outer annular protrusion and the impeller hub; the piston disc is located in the annular pressure chamber, dividing the pressure chamber into a front pressure chamber and a rear pressure chamber that are not connected to each other, and a number of screw through holes are opened between the inner annular protrusion and the outer annular protrusion; one end of the screw is rotatably connected to the bearing embedded in the piston disc, and the other end passes through the screw through hole and is connected to the through-type stepping motor fixed behind the piston rear cover plate; the screw can drive the piston disc to move in the pressure chamber along the axial direction of the rotor shaft under the drive of the through-type stepping motor.

[0008] The axial force detection system is used to drive the through-type stepper motor according to the magnitude of the axial force detected by the first strain gauge pressure sensor and the second strain gauge pressure sensor, and then reduce the pressure difference between the front and rear sides of the impeller by adjusting the size of the front pressure chamber to achieve axial force balance.

[0009] Furthermore, the axial force detection system includes a multi-channel analog signal collector, a signal conditioning circuit, a D / A converter, a single-chip microcomputer, an LED display and a host computer; the input end of the multi-channel analog signal collector is connected to the first strain type pressure sensor and the second strain type pressure sensor signal; the output end of the multi-channel analog signal collector is connected to the input end signal of the signal conditioning circuit; the output end of the signal conditioning circuit is connected to the input end signal of the D / A converter; the output end of the D / A converter is connected to the I / O interface signal of the single-chip microcomputer; one of the output ends of the single-chip microcomputer is connected to the input end signal of the LED display, and the other output end of the single-chip microcomputer is connected to the host computer signal through a serial communication interface; the host computer is used to transmit the control signal to the through-type stepping motor, so that it drives the piston disk to move in the pressure chamber along the axial direction of the rotor shaft through the screw.

[0010] Furthermore, the through-type stepper motor includes a motor housing, a stator, a rotor, a support sleeve and an external nut; the support sleeve is installed in the motor housing along the axial direction of the rotor shaft using a ball bearing; the rotor is sleeved on the outer surface of the support sleeve and rotates synchronously with the support sleeve; the stator is installed on the inner wall of the motor housing around the outer side of the rotor, and is used to provide a magnetic field to the rotor to drive its rotation according to the control signal sent by the upper computer; the lead screw passes through the front end cover, the support sleeve and the rear end cover of the motor housing in sequence and is then sleeved with the external nut; the external nut is fixedly connected to the motor housing, and is used to make the lead screw move along the axial direction of the rotor shaft while rotating.

[0011] Furthermore, a sealing ring body is sleeved on the impeller hub near the rear end cover of the pump body. The sealing ring body and the rear end cover of the pump body are respectively provided with annular labyrinth sealing teeth that are staggered with each other, and the two cooperate with each other to form an annular labyrinth sealing structure.

[0012] Furthermore, grooves with an H-shaped cross section are provided on both end surfaces of the inner annular protrusion and the outer annular protrusion that are in contact with the piston disc, and cylindrical sealing rubber rings are embedded in the grooves.

[0013] Furthermore, a plurality of threaded holes are provided on the piston rear cover plate, which is fixedly connected to the rear end cover of the pump body via bolts, and an anti-loosening washer is provided between the nut of the bolt and the piston rear cover plate; a wear-resistant washer is provided on the piston rear cover plate at the contact position with the screw rod, and a gap is left between the wear-resistant washer and the screw rod.

[0014] Furthermore, the through-type stepping motor is arranged on a mounting seat, which is sleeved on the rotor shaft and connected to the rear end surface of the piston rear cover plate, and a cavity is left between the mounting seat and the rotor shaft.

[0015] Furthermore, the first strain type pressure sensor is embedded in a groove on the end face of the impeller hub close to the front deep groove ball bearing and directly abuts against the rear end face of the front deep groove ball bearing; the second strain type pressure sensor is embedded in a groove on the end face of the impeller hub close to the front sleeve and directly abuts against the front end face of the front sleeve, and a gap is left between the front sleeve and the inner annular protrusion; the gap between the outer annular protrusion and the impeller hub is 0.2mm-0.8mm.

[0016] A centrifugal pump comprising a piston-type axial force balancing structure as described in any one of the above items is characterized in that it further comprises a pump body, an impeller, a rotor shaft, and a shaft seal assembly disposed in a cavity between the mounting seat and the rotor shaft; the shaft seal assembly comprises a stationary ring, a first sealing ring, a first mechanical seal locking sleeve, a graphite ring, a dynamic ring, a second sealing ring, a push ring, a transmission seat, a wave spring, a second mechanical seal locking sleeve, a rear deep groove ball bearing, and a rear shaft sleeve, which are sequentially sleeved on the rotor shaft;

[0017] The stationary ring is detachably mounted on the rear end face of the piston rear cover plate, with a gap between it and the rear end face of the front shaft sleeve and the rotor shaft; the first sealing ring is mounted between the stationary ring and the piston rear cover plate; the first mechanical seal locking sleeve is clamped between the mounting seat and the stationary ring; the graphite ring is detachably mounted on the rear end face of the stationary ring, with a gap between it and the rotor shaft; the dynamic ring is connected to the rotor shaft and rotates synchronously therewith, and the dynamic ring is tightly attached to the rear end face of the graphite ring; the second sealing ring is mounted between the rear end portion of the dynamic ring and the rotor shaft; the push ring is detachably mounted on the rear end face of the dynamic ring to prevent the second sealing ring from falling off; the transmission seat is mounted on the rotor shaft and rotates synchronously therewith, the wave spring is connected to the transmission seat, and the rear end portion of the push ring is inserted into a plurality of wave springs, which press it toward the side of the dynamic ring; the rear deep groove ball bearing is positioned by a shaft shoulder of the rotor shaft; the second mechanical seal locking sleeve is mounted on the rotor shaft and tightly attached to the front end face of the rear deep groove ball bearing.

[0018] Furthermore, the cross-section of the static ring is in the shape of three steps, wherein the front end face of the first step is close to the rear end face of the front sleeve with a gap, the second step is detachably connected to the piston rear cover plate, and a first sealing ring is installed between the front end face of the third step and the piston rear cover plate; the cross-section of the dynamic ring is in the shape of a "T", the front end part of the dynamic ring extends toward the end face of the graphite ring away from the rotor shaft with a gap, the middle part of the dynamic ring is tightly attached to the rear end face of the graphite ring, and the graphite ring and the dynamic ring cooperate with each other to form a accommodating cavity for collecting debris generated by the graphite ring during wear; the connection design between the static ring and the piston rear cover plate, the graphite ring and the static ring, and the push ring and the dynamic ring all adopt mutually matching card hole and bayonet structure, and realize detachable connection by embedding and locking.

[0019] The present invention utilizes a first strain gauge pressure sensor and a second strain gauge pressure sensor to capture and accurately monitor the changes in the axial force during the operation of the impeller in real time, and sends the changes to the axial force detection system. After the axial force detection system optimizes and processes the received signal, the host computer transmits the control instructions to the through-type stepping motor, which drives the screw to rotate, and with the cooperation of the external nut, the screw can drive the piston disk to move back and forth in the pressure chamber along the axial direction of the rotor shaft. When the axial component force F2 on the rear end face of the impeller hub is greater than the axial component force F1 on the front end face of the impeller hub, an axial total force F offset toward the water inlet of the pump body will be applied to the impeller and the first strain gauge pressure sensor 7 will be squeezed. At this time, the through-type stepping motor drives the screw to move toward the side close to the rear end face of the impeller hub. Part of the fluid filled in the front pressure chamber will be discharged from the entrance of the labyrinth seal along the gap between the outer annular protrusion and the impeller hub. At this time, the volume of the front pressure chamber decreases, and the pressure at each radius in the front pressure chamber decreases, resulting in a decrease in the force F2 exerted by the fluid in the front pressure chamber on the rear end face of the impeller hub. Since the axial total force F and the axial component force F2 are in the same direction at this time, the value of F also gradually decreases during the process of F2 reduction until the axial force balance at both ends is achieved. When the axial component force F2 on the rear end face of the impeller hub is less than the axial component force F1 on the front end face of the impeller hub, the impeller will be given an axial total force F that is offset toward the rear end face of the pump body and squeeze the second strain gauge pressure sensor 41. At this time, the through-type stepper motor drives the screw to move toward the side away from the rear end face of the impeller hub. The front pressure chamber will absorb fluid from the pump body through the labyrinth seal and the gap between the outer annular protrusion and the impeller hub due to the suction force. At this time, the volume of the front pressure chamber increases, and the pressure at each radius in the front pressure chamber increases, resulting in an increase in the force F2 exerted by the fluid in the front pressure chamber on the rear end face of the impeller hub. Since the axial total force F is in opposite directions to the axial component force F2 at this time, the value of F gradually decreases during the increase of F2.

[0020] The beneficial effects of the present invention are as follows:

[0021] 1. The present invention drives the piston disc to move back and forth in the pressure chamber through a screw rod, thereby adjusting the volume of the front pressure chamber, and then changing the force of the fluid in the front pressure chamber on the rear end face of the impeller hub by adjusting the pressure at each radius in the front pressure chamber, thereby achieving dynamic balance of the axial forces on the front and rear sides of the impeller, effectively reducing the impact of the axial force on the bearings and other components, extending the service life of the equipment, and ensuring that the centrifugal pump can operate smoothly and efficiently under high load conditions.

[0022] 2. In the present invention, an annular labyrinth seal structure is provided between the rear end cover of the pump body and the impeller hub, and a shaft seal assembly is provided between the mounting seat and the rotor shaft. The multiple seals can effectively prevent leakage of high-pressure liquid in the pump, thereby ensuring the sealing performance and operational safety of the pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic structural diagram of the piston-type balanced axial force according to an embodiment of the present invention.

[0024] Figure 2 This is a schematic structural diagram of the piston rear cover plate according to an embodiment of the present invention.

[0025] Figure 3 This is a partial enlarged view of the cylinder sealing rubber ring described in an embodiment of the present invention.

[0026] Figure 4 Schematic diagram of the structure of the through-type stepping motor according to an embodiment of the present invention.

[0027] Figure 5 Schematic diagram of the labyrinth sealing structure according to an embodiment of the present invention.

[0028] Figure 6 Schematic diagram of the structure of the shaft sealing assembly according to an embodiment of the present invention.

[0029] Figure 7 Schematic diagram of the structure of the static ring according to an embodiment of the present invention.

[0030] The reference numerals are as follows:

[0031] 1- Pump body; 2- Rotor shaft; 3- Impeller; 4- Front deep groove ball bearing; 5- Rear deep groove ball bearing; 6- Front bushing; 7- First strain gauge pressure sensor; 8- Piston rear cover plate; 9- Piston disc; 10- Screw; 11- Through-type stepper motor; 12- Mounting seat; 13- Axial force detection system; 14- Rear bushing; 15- Inner annular protrusion; 16- Outer annular protrusion; 17- Screw through hole; 18- Front pressure chamber; 19- Rear pressure chamber; 20- Motor housing; 21- Stator; 22-rotor; 23-support sleeve; 24-external nut; 25-ball bearing; 26-stationary ring; 27-graphite ring; 28-dynamic ring; 29-push ring; 30-first mechanical seal locking sleeve; 31-second mechanical seal locking sleeve; 32-first sealing ring; 33-second sealing ring; 34-transmission seat; 35-wave spring; 36-cylinder sealing rubber ring; 37-sealing ring body; 38-threaded hole; 39-bolt; 40-anti-loosening washer; 41-second strain gauge pressure sensor. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0033] The piston-type axial force balancing structure described in this embodiment includes a front deep groove ball bearing 4 and a front bushing 6 mounted on the rotor shaft at the front and rear ends of the impeller hub 3, respectively; a first strain gauge pressure sensor 7 mounted between the front end of the impeller hub 3 and the front deep groove ball bearing 4; a second strain gauge pressure sensor 41 mounted between the rear end of the impeller hub 3 and the front bushing 6; an axial force detection system 13 signal-connected to the first strain gauge pressure sensor 7 and the second strain gauge pressure sensor 41; and an actuator. A through hole with an inner diameter larger than the outer diameter of the rotor shaft is defined on the rear end face of the pump body 1, and the actuator is mounted between the through hole on the rear end face of the pump body 1 and the rotor shaft. Figure 1 This is a schematic diagram of the structure of the piston-type balanced axial force described in this embodiment.

[0034] The actuator includes a piston rear cover plate 8, a piston disc 9, a screw 10, and a through-type stepper motor 11. The front end surface of the piston rear cover plate 8 has an inner annular protrusion 15 and an outer annular protrusion 16. Several threaded holes 38 are provided in the piston rear cover plate 8, which is fixedly connected to the rear end cover of the pump body 1 via bolts 39. A lock washer 40 is provided between the nuts of the bolts 39 and the piston rear cover plate 8. The inner and outer annular protrusions 15 and 16 on the piston rear cover plate 8 penetrate the rear end cover of the pump body 1 and cooperate with the rear end surface of the impeller 3 hub to form a non-sealed annular pressure chamber. A 0.5 mm gap is left between the outer annular protrusion 16 and the impeller 3 hub. The piston disc 9 is placed in the pressure chamber, dividing the pressure chamber into a front pressure chamber and a rear pressure chamber 19 that are not connected to each other. A plurality of screw holes 17 are opened between the inner annular protrusion 15 and the outer annular protrusion 16. A shaft hole for sleeved on the rotor shaft 2 is opened in the middle of the piston rear cover plate 8. Figure 2 The diagram is a structural diagram of the piston rear cover plate 8 in this embodiment. The inner annular protrusion 15 and the outer annular protrusion 16 are provided with grooves with an H-shaped cross section on both end surfaces in contact with the piston disc 9. The cylindrical sealing rubber ring 36 is embedded in the groove. Figure 3 This is a partial enlarged view of the cylinder sealing rubber ring 36 of this embodiment. One end of the screw rod 10 is rotatably connected to the bearing embedded in the piston plate 9, and the other end passes through the screw rod through hole 17 and is connected to the through-type stepping motor 11 fixed behind the piston rear cover plate 8. A wear-resistant washer is provided at the contact position of the piston rear cover plate 8 with the screw rod 10, and a gap is left between the wear-resistant washer and the screw rod 10. The through-type stepping motor 11 includes a motor housing 20, a stator 21, a rotor 22, a support sleeve 23 and an external nut 24. Figure 4Schematic diagram of the structure of the through-type stepper motor 11 described in this embodiment. The support sleeve 23 is mounted in the motor housing 20 along the axial direction of the rotor shaft 2 using a ball bearing 25. The rotor 22 is sleeved on the outer surface of the support sleeve 23 and rotates synchronously with the support sleeve 23. The stator 21 is mounted on the inner wall of the motor housing 20 around the outer side of the rotor 22 and is used to provide a magnetic field to the rotor 22 to drive its rotation according to the control signal sent by the host computer. The screw rod 10 passes through the front end cover of the motor housing 20, the support sleeve 23 and the rear end cover of the motor housing 20 in sequence and is then sleeved with an external nut 24. The external nut 24 is fixedly connected to the motor housing 20 and is used to move the screw rod 10 along the axial direction of the rotor shaft 2 while the screw rod 10 rotates. Driven by the through-type stepper motor 11, the screw rod 10 can drive the piston disc 9 to move along the axial direction of the rotor shaft 2 in the pressure chamber.

[0035] The axial force detection system 13 includes a multi-channel analog signal collector, a signal conditioning circuit, a D / A converter, a single-chip microcomputer, an LED display and a host computer. The input end of the multi-channel analog signal collector is signal-connected to the first strain type pressure sensor 7 and the second strain type pressure sensor 41, and is used to collect the analog signals output by the first strain type pressure sensor 7 and the second strain type pressure sensor 41. The output end of the multi-channel analog signal collector is signal-connected to the input end of the signal conditioning circuit. The output end of the signal conditioning circuit is signal-connected to the input end of the D / A converter, and is used to perform pre-processing such as filtering, amplification, and linearization on the original analog signals collected by the first strain type pressure sensor 7 and the second strain type pressure sensor 41, so as to facilitate subsequent accurate digitization. The output end of the D / A converter is signal-connected to the I / O interface of the single-chip microcomputer, and is used to convert the conditioned analog signals into digital signals. One of the microcontroller's output terminals is signal-connected to the input terminal of an LED display. Another output terminal of the microcontroller is signal-connected to a host computer via a serial communication interface. The microcontroller receives the digital signal after D / A conversion, displays the axial force value on the LED display, and simultaneously transmits the axial force data to the host computer via the serial communication interface. The host computer analyzes and makes decisions based on the data, transmitting control signals to the through-type stepper motor 11 to control its operation. This control, in turn, reduces the pressure differential between the front and rear sides of the impeller 3 by adjusting the size of the front pressure chamber, thereby achieving axial force balance.

[0036] Furthermore, a sealing ring 37 is sleeved on the impeller 3 hub near the rear end cover of the pump body 1. The inner diameter of the mating surface of the sealing ring 37 is slightly smaller than the inner diameter of the mating surface of the impeller 3, and the two are fixedly connected by an interference fit. The sealing ring 37 and the rear end cover of the pump body 1 are respectively provided with an annular labyrinth sealing teeth that are staggered and arranged with each other. The cross-section of the annular labyrinth sealing teeth is trapezoidal, and the two cooperate with each other to form an annular labyrinth sealing structure. Figure 5Schematic diagram of the structure of the labyrinth seal described in this embodiment.

[0037] The first strain gauge pressure sensor 7 is embedded in a groove on the end face of the impeller 3 hub near the front deep groove ball bearing 4 and directly abuts the rear end face of the front deep groove ball bearing 4. The depth of the groove is 0.2-0.3 mm. The second strain gauge pressure sensor 41 is embedded in a groove on the end face of the impeller 3 hub near the front sleeve 6 and directly abuts the front end face of the front sleeve 6. A gap is left between the front sleeve 6 and the inner annular protrusion 15. The through-type stepper motor 11 is mounted on a mounting seat 12, which is sleeved on the rotor shaft 2 and connected to the rear end face of the piston rear cover plate 8. A cavity is left between the mounting seat 12 and the rotor shaft 2.

[0038] This embodiment also relates to a centrifugal pump including the above-mentioned piston-type axial force balancing structure. In addition to the above-mentioned piston-type axial force balancing structure, the centrifugal pump also includes a pump body 1, an impeller 3, a rotor shaft 2, and a shaft seal assembly disposed in a cavity between the mounting seat 12 and the rotor shaft 2. The shaft seal assembly includes a stationary ring 26, a first sealing ring 32, a first mechanical seal locking sleeve 30, a graphite ring 27, a dynamic ring 28, a second sealing ring 33, a push ring 29, a transmission seat 34, a wave spring 35, a second mechanical seal locking sleeve 31, a rear deep groove ball bearing 255, and a rear shaft sleeve 14, which are sequentially mounted on the rotor shaft 2. Figure 6 Schematic diagram of the structure of the shaft seal assembly described in this embodiment.

[0039] The cross section of the stationary ring 26 is in a three-stepped shape, wherein the front end face of the first step is close to the rear end face of the front sleeve 6 and a gap is left between the rear end face of the front sleeve 6 and the rotor shaft 2; the second step is detachably connected to the piston rear cover plate 8; and a first sealing ring 32 is installed between the front end face of the third step and the piston rear cover plate 8. Figure 7The figure is a schematic diagram of the structure of the stationary ring 26 described in this embodiment. The first mechanical seal locking sleeve 30 is clamped between the mounting seat 12 and the stationary ring 26. The graphite ring 27 is removably mounted on the rear end face of the stationary ring 26, with a gap between it and the rotor shaft 2. The dynamic ring 28 is connected to the rotor shaft 2 and rotates synchronously therewith. The dynamic ring 28 has a T-shaped cross-section. The front end of the dynamic ring 28 extends toward the end face of the graphite ring 27 away from the rotor shaft 2, with a gap. The middle portion of the dynamic ring 28 is tightly attached to the rear end face of the graphite ring 27. The two graphite rings 27 and the dynamic ring 28 cooperate to form a receiving cavity for collecting debris generated by the wear of the graphite ring 27. The second sealing ring 33 is mounted between the rear end of the dynamic ring 28 and the rotor shaft 2. The push ring 29 is removably mounted on the rear end face of the dynamic ring 28 to prevent the second sealing ring 33 from falling off. The transmission seat 34 is mounted on the rotor shaft 2 and rotates synchronously therewith. The wave springs 35 are connected to the transmission seat 34, and the rear end of the push ring 29 is inserted into the wave springs 35, which press it toward the dynamic ring 28. The rear deep groove ball bearing 255 is positioned by the shoulder of the rotor shaft 2. The second mechanical seal locking sleeve 31 is mounted on the rotor shaft 2 and tightly abuts the front end face of the rear deep groove ball bearing 255.

[0040] The connection designs between the above-mentioned stationary ring 26 and the piston rear cover plate 8, the graphite ring 27 and the stationary ring 26, and the push ring 29 and the dynamic ring 28 all adopt mutually matching card hole and bayonet structures, and realize detachable connection through embedding and locking, which is convenient for later maintenance and replacement.

[0041] The specific working process of the present invention is as follows: when the impeller 3 is working, the fluid is sucked in from the water inlet of the impeller 3 and discharged from the water outlet after the impeller 3 rotates. In this process, the axial component forces F1 and F2 acting on the front and rear end surfaces of the impeller 3 cannot be balanced, generating a total axial force F. When the axial component force F2 on the rear end face of the impeller 3 hub is greater than the axial component force F1 on the front end face of the impeller 3 hub, an axial total force F will be applied to the impeller 3 that is offset toward the water inlet of the pump body 1. At this time, the through-type stepping motor 11 drives the screw 10 to move toward the side close to the rear end face of the impeller 3 hub. Part of the fluid filled in the front pressure chamber 18 will be discharged from the labyrinth seal entrance along the gap between the outer annular protrusion 16 and the impeller 3 hub. At this time, the volume of the front pressure chamber 18 is reduced, and the pressure at each radius in the front pressure chamber 18 is reduced, resulting in a decrease in the force F2 exerted by the fluid in the front pressure chamber 18 on the rear end face of the impeller 3 hub. Since the axial total force F and the axial component force F2 are in the same direction at this time, the value of F also gradually decreases during the process of F2 decreasing, thereby achieving a dynamic balance of the axial force of the impeller 3. When the axial component force F2 on the rear end face of the impeller 3 hub is smaller than the axial component force F1 on the front end face of the impeller 3 hub, an axial total force F offset toward the rear end face of the pump body 1 will be applied to the impeller 3. At this time, the through-type stepping motor 11 drives the screw 10 to move toward the side away from the rear end face of the impeller 3 hub. The front pressure chamber 18 will absorb fluid from the pump body 1 through the labyrinth seal and the gap between the outer annular protrusion and the impeller hub due to the suction force. At this time, the volume of the front pressure chamber 18 increases, and the pressure at each radius in the front pressure chamber 18 increases, resulting in an increase in the force F2 exerted by the fluid in the front pressure chamber 18 on the rear end face of the impeller 3 hub. Since the axial total force F is in opposite directions to the axial component force F2 at this time, the value of F also gradually decreases during the increase of F2, thereby achieving a dynamic balance of the axial force of the impeller 3.

[0042] The embodiments described are preferred implementations of the present invention, but the present invention is not limited to the above implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention are within the scope of protection of the present invention.

Claims

1. A centrifugal pump with a piston-type axial force balancing structure, characterized in that: The invention comprises a pump body (1), an impeller (3), a rotor shaft (2), a shaft sealing assembly arranged in a cavity between a mounting seat (12) and the rotor shaft (2), a front deep groove ball bearing (4) and a front shaft sleeve (6) respectively mounted on the rotor shaft at the front and rear ends of the impeller (3) hub, a first strain gauge pressure sensor (7) mounted between the front end of the impeller (3) hub and the front deep groove ball bearing (4), a second strain gauge pressure sensor (41) mounted between the rear end of the impeller (3) hub and the front shaft sleeve (6), an axial force detection system (13) connected to the signals of the first strain gauge pressure sensor (7) and the second strain gauge pressure sensor (41), and an actuator; a through hole with an inner diameter larger than the outer diameter of the rotor shaft is opened on the rear end face of the pump body (1), and the actuator is mounted between the through hole on the rear end face of the pump body (1) and the rotor shaft; The actuator comprises a piston rear cover plate (8), a piston disc (9), a screw rod (10) and a through-type stepping motor (11); the front end surface of the piston rear cover plate (8) is provided with an inner annular protrusion (15) and an outer annular protrusion (16); the piston rear cover plate (8) is mounted on the rear end cover of the pump body (1); the inner annular protrusion (15) and the outer annular protrusion (16) penetrate the rear end cover of the pump body (1) and cooperate with the rear end surface of the impeller (3) hub to form an annular pressure chamber, and a gap is left between the outer annular protrusion (16) and the impeller (3) hub; the piston disc (9) is located in the annular pressure chamber, dividing the pressure chamber into a front pressure chamber (18) and a rear pressure chamber (19) which are not connected to each other. , a plurality of screw through holes (17) are provided between the inner annular protrusion (15) and the outer annular protrusion (16); one end of the screw (10) is rotatably connected to the bearing embedded in the piston disc (9), and the other end passes through the screw through hole (17) and is connected to the through-type stepping motor (11) fixed behind the piston rear cover (8); the screw (10) can drive the piston disc (9) to move in the pressure chamber along the axial direction of the rotor shaft (2) under the drive of the through-type stepping motor (11); the two end surfaces of the inner annular protrusion (15) and the outer annular protrusion (16) in contact with the piston disc (9) are provided with grooves with an H-shaped cross section, and a cylindrical sealing rubber ring (36) is embedded in the groove; The axial force detection system (13) is used to drive the through-type stepping motor (11) according to the magnitude of the axial force detected by the first strain gauge pressure sensor (7) and the second strain gauge pressure sensor (41), thereby reducing the pressure difference between the front and rear sides of the impeller (3) by adjusting the size of the front pressure chamber (18) to achieve axial force balance; The axial force detection system (13) includes a multi-channel analog signal collector, a signal conditioning circuit, a D / A converter, a single-chip microcomputer, an LED display and a host computer; the input end of the multi-channel analog signal collector is signal-connected to the first strain gauge pressure sensor (7) and the second strain gauge pressure sensor (41); the output end of the multi-channel analog signal collector is signal-connected to the input end of the signal conditioning circuit; the output end of the signal conditioning circuit is signal-connected to the input end of the D / A converter; the output end of the D / A converter is signal-connected to the I / O interface of the single-chip microcomputer; one of the output ends of the single-chip microcomputer is signal-connected to the input end of the LED display, and the other output end of the single-chip microcomputer is signal-connected to the host computer via a serial communication interface; the host computer is used to transmit a control signal to the through-type stepping motor (11), so that it drives the piston disc (9) to move in the pressure chamber along the axial direction of the rotor shaft (2) through the screw rod (10).

2. The centrifugal pump with a piston-type axial force balancing structure according to claim 1, characterized in that: The through-type stepping motor (11) comprises a motor housing (20), a stator (21), a rotor (22), a support sleeve (23) and an external nut (24); the support sleeve (23) is mounted in the motor housing (20) along the axial direction of the rotor shaft (2) using a ball bearing (25); the rotor (22) is sleeved on the outer surface of the support sleeve (23) and rotates synchronously with the support sleeve (23); the stator (21) is mounted on the inner wall of the motor housing (20) around the outer side surface of the rotor (22) and is used to provide a magnetic field to the rotor (22) to drive the rotor (22) to rotate according to a control signal sent by a host computer; the screw rod (10) passes through the front end cover of the motor housing (20), the support sleeve (23) and the rear end cover of the motor housing (20) in sequence and is then sleeved with the external nut (24); the external nut (24) is fixedly connected to the motor housing (20) and is used to make the screw rod (10) move along the axial direction of the rotor shaft (2) while rotating.

3. The centrifugal pump with a piston-type axial force balancing structure according to claim 1, characterized in that: A sealing ring body (37) is sleeved on the hub of the impeller (3) near the rear end cover of the pump body (1). The sealing ring body (37) and the rear end cover of the pump body (1) are respectively provided with annular labyrinth sealing teeth that are staggered with each other, and the two cooperate with each other to form an annular labyrinth sealing structure.

4. The centrifugal pump with a piston-type axial force balancing structure according to claim 1, characterized in that: The piston rear cover plate (8) is provided with a plurality of threaded holes (38) and is fixedly connected to the rear end cover of the pump body (1) via bolts (39). An anti-loosening washer (40) is provided between the nut of the bolt (39) and the piston rear cover plate (8). A wear-resistant washer is provided at the contact position between the piston rear cover plate (8) and the screw rod (10), and a gap is left between the wear-resistant washer and the screw rod (10).

5. The centrifugal pump with a piston-type axial force balancing structure according to claim 1, characterized in that: The through-type stepping motor (11) is arranged on a mounting seat (12), which is sleeved on the rotor shaft (2) and connected to the rear end surface of the piston rear cover plate (8), with a cavity left between the mounting seat (12) and the rotor shaft (2).

6. The centrifugal pump with a piston-type axial force balancing structure according to claim 1, characterized in that: The first strain gauge pressure sensor (7) is embedded in a groove on the end face of the impeller (3) hub close to the front deep groove ball bearing (4) and directly abuts against the rear end face of the front deep groove ball bearing (4); the second strain gauge pressure sensor (41) is embedded in a groove on the end face of the impeller (3) hub close to the front shaft sleeve (6) and directly abuts against the front end face of the front shaft sleeve (6), with a gap between the front shaft sleeve (6) and the inner annular protrusion (15); the gap between the outer annular protrusion (16) and the impeller (3) hub is 0.2 mm to 0.8 mm.

7. The centrifugal pump with a piston-type axial force balancing structure according to any one of claims 1 to 6, characterized in that: The shaft seal assembly comprises a stationary ring (26), a first sealing ring (32), a first mechanical seal locking sleeve (30), a graphite ring (27), a dynamic ring (28), a second sealing ring (33), a push ring (29), a transmission seat (34), a wave spring (35), a second mechanical seal locking sleeve (31), a rear deep groove ball bearing (5) and a rear shaft sleeve (14), which are sequentially sleeved on the rotor shaft (2); The stationary ring (26) is detachably mounted on the rear end face of the piston rear cover (8) and a gap is left between the rear end face of the front shaft sleeve (6) and the rotor shaft (2); the first sealing ring (32) is mounted between the stationary ring (26) and the piston rear cover (8); the first mechanical seal locking sleeve (30) is clamped between the mounting seat (12) and the stationary ring (26); the graphite ring (27) is detachably mounted on the rear end face of the stationary ring (26) and a gap is left between the rotor shaft (2); the dynamic ring (28) is connected to the rotor shaft (2) and rotates synchronously therewith, and the dynamic ring (28) is tightly attached to the rear end face of the graphite ring (27); the second sealing ring (33) is mounted on the dynamic ring ( 28) between the rear end portion and the rotor shaft (2); the push ring (29) is detachably mounted on the rear end face of the dynamic ring (28) to prevent the second sealing ring (33) from falling off; the transmission seat (34) is mounted on the rotor shaft (2) and rotates synchronously therewith, the wave spring (35) is connected to the transmission seat (34) and the rear end portion of the push ring (29) is inserted into a plurality of wave springs (35), and is pressed toward the side of the dynamic ring (28) by the plurality of wave springs (35); the rear deep groove ball bearing (5) is positioned by the shaft shoulder of the rotor shaft (2); the second mechanical seal locking sleeve (31) is mounted on the rotor shaft (2) and is tightly attached to the front end face of the rear deep groove ball bearing (5).

8. The centrifugal pump with a piston-type axial force balancing structure according to claim 7, characterized in that: The cross section of the static ring (26) is in a three-stepped shape, wherein the front end face of the first step is close to the rear end face of the front shaft sleeve (6) with a gap, the second step is detachably connected to the piston rear cover plate (8), and a first sealing ring (32) is installed between the front end face of the third step and the piston rear cover plate (8); the cross section of the dynamic ring (28) is in a "T" shape, and the front end portion of the dynamic ring (28) extends to the end face of the graphite ring (27) away from the rotor shaft (2) with a gap, and the dynamic ring (28) is in a "T" shape. The middle portion of the ring (28) is tightly attached to the rear end face of the graphite ring (27), and the graphite ring (27) and the dynamic ring (28) cooperate with each other to form a receiving cavity for collecting debris generated by the graphite ring (27) during the wear process; the connection design between the static ring (26) and the piston rear cover plate (8), the graphite ring (27) and the static ring (26), and the push ring (29) and the dynamic ring (28) all adopt mutually matching card hole and card socket structures, and realize detachable connection by embedding and locking.

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