A combined shafting structure for measuring axial force of a pump impeller

Abstract

The application discloses a combined shaft structure for measuring axial force of a pump impeller, which comprises a driving shaft, a bearing shaft, a tensile and compressive force sensor and a hole-cylinder key; the driving shaft and the bearing shaft are connected in a sleeved mode, and the axial length of the driving shaft and the bearing shaft in cooperation satisfies that the center lines of the driving shaft and the bearing shaft can be coaxial, only one axial degree of freedom of the bearing shaft and the driving shaft is realized, and the structural strength requirement under the driving torque is satisfied; the tensile and compressive force sensor is located at the axial gap after the driving shaft and the bearing shaft are nested, and the two ends of the tensile and compressive force sensor are connected with the driving shaft and the bearing shaft respectively; the bearing shaft and the driving shaft are provided with a waist-shaped mounting hole in cooperation in the circumferential direction, the driving shaft is provided with a key groove at the corresponding position, and the hole-cylinder key is installed in the key groove through the waist-shaped mounting hole, so that the driving shaft is tightly matched with the hole-cylinder key, and the bearing shaft and the hole-cylinder key have a certain movement space in the axial direction. The application can realize more accurate real-time measurement of the axial force of the pump.

Description

Technical Field

[0001] This invention relates to the field of measuring the excitation force of rotating equipment impellers, and more specifically, to a combined shaft system structure for measuring the axial force of the pump impeller on a rotating drive shaft during pump operation. Background Technology

[0002] During operation, the main shaft of a water pump generates axial force. Under the action of this axial force, the rotor undergoes axial displacement, causing grinding and collision between the moving and stationary parts. This leads to excessive vibration of the pump and damage to components such as mechanical seals and bearings, reducing its service life and overall performance. In severe cases, it can even endanger the safety of operators. Compared to centrifugal pumps, the axial force generated by axial flow pumps and mixed flow pumps often has a more serious impact, thus requiring accurate measurement.

[0003] Currently, commonly used industrial axial force measuring devices for water pumps suffer from problems such as complex structure, high cost, insufficient installation space, and cumbersome procedures, making it difficult to determine the axial force of water pumps. Patent document CN112302963A discloses a testing device for the axial force of a centrifugal pump. However, to ensure that the axial force on the outer ring of the bearing is evenly transmitted to each pressure sensor, this patent requires multiple pressure sensors to be set at equal intervals, which is cumbersome to install and prone to errors. Furthermore, this measuring device cannot effectively isolate the interference from bending moments and torques on the rotating shaft on the axial force measurement.

[0004] Therefore, there is a need for a simpler and more effective way to measure the axial force generated by the pump during operation without affecting the original installation method of the impeller. It is necessary to design an accurate and easy-to-install pump impeller axial force measuring device. Summary of the Invention

[0005] To address the problems of inaccurate axial force measurement, complex structure, and difficult installation of existing measuring devices, this invention proposes a combined shaft system structure for measuring the axial force of a pump impeller. The specific technical solution is as follows:

[0006] A combined shaft system structure for measuring the axial force of a pump impeller, the combined shaft system structure includes a drive shaft, a load-bearing shaft, a tension / compression sensor, and a perforated cylindrical key;

[0007] The drive shaft and the bearing shaft are assembled in a set manner; one end of the drive shaft is embedded in the hollow section of the bearing shaft, and the axial length of the drive shaft and the bearing shaft are such that the center lines of the drive shaft and the bearing shaft are coaxial, so that the bearing shaft and the drive shaft have only one degree of freedom in the axial direction, and the structural strength requirements under the driving torque are met.

[0008] The tension / compression sensor is located in the axial gap after the drive shaft and the bearing shaft are nested, and both ends of the tension / compression sensor are connected to the drive shaft and the bearing shaft respectively;

[0009] The bearing shaft and the drive shaft are provided with a waist-shaped mounting hole in the circumference. The drive shaft is provided with a keyway at the corresponding position. The cylindrical key with a hole passes through the waist-shaped mounting hole and is installed in the keyway, so as to achieve a tight fit between the drive shaft and the cylindrical key with a hole. There is a certain amount of axial movement space between the bearing shaft and the cylindrical key with a hole.

[0010] Furthermore, there are four waist-shaped mounting holes and keyways, which are evenly distributed circumferentially, and a perforated cylindrical key is installed in each waist-shaped mounting hole and keyway; the waist-shaped mounting holes and keyways are arranged away from the edges of the bearing shaft and the drive shaft.

[0011] Furthermore, the perforated cylindrical key is recessed radially into the waist-shaped mounting hole of the bearing shaft.

[0012] Furthermore, the bearing shaft has a stepped through hole with a coaxial axis. The tension / compression sensor is a miniature tension / compression sensor made of stainless steel with a double-ended stud. The tension / compression sensor is placed in the stepped through hole and is threaded to the bearing shaft and the drive shaft respectively through the double-ended stud. The cable of the tension / compression sensor passes through the stepped through hole and exits the bearing shaft.

[0013] The beneficial effects of this invention are as follows:

[0014] (1) The combined shaft system structure for measuring the axial force of the pump impeller of the present invention can realize the real-time measurement of the axial force of the pump impeller. The measuring device is modified based on the original pump shaft and will not affect the normal operation of the axial flow pump or mixed flow pump being measured.

[0015] (2) The present invention leaves a certain axial contact length between the drive shaft and the bearing shaft, the radial contact surface is a small clearance fit, and the center lines of the two shafts are coaxial; the drive shaft and the bearing shaft are connected to the tension and compression sensors by thread at the center line, and the drive shaft and the bearing shaft are connected by a circular key with holes evenly distributed on the circumference to establish line contact between the drive shaft and the bearing shaft so as to transmit only the rotational torque. This avoids the problems of inaccurate installation position and uneven force caused by setting multiple sensors. The connection cable between the sensor and the external equipment is also located at the center line position, which better isolates the interference of bending moment and torque on the measuring device from the rotating shaft.

[0016] (3) The present invention adopts a cylindrical key with holes instead of a flat key structure design, which realizes the relative position fixation between the drive shaft and the bearing shaft. The cylindrical key with holes is located in the waist hole of the bearing shaft and achieves line contact, which not only gives the measuring device a certain amount of axial movement space, but also greatly reduces the axial friction force on the cylindrical key with holes, and significantly reduces the interference of axial friction force on the measurement results.

[0017] (4) The combined shaft system structure of the present invention can be modified and designed according to the object being measured, and can be applied to various impeller axial force measurement occasions such as centrifugal pumps and fans.

[0018] (5) Compared with traditional industrial axial force measuring devices, the combined shaft system structure of the present invention is simpler in structure, lower in cost, easier to install and does not occupy additional space. Attached Figure Description

[0019] Figure 1 A schematic diagram of the assembly cross-sectional structure of a combined shaft system for measuring the axial force of a pump impeller, as provided in an embodiment of the present invention, mounted on a mixed-flow pump;

[0020] Figure 2 A schematic diagram of the surface structure of a combined shaft system for measuring the axial force of a pump impeller provided in an embodiment of the present invention;

[0021] Figure 3 Embodiments of the present invention Figure 2 A schematic diagram of the half-section structure extending from direction A in the middle;

[0022] Figure 4 Embodiments of the present invention Figure 2 A schematic diagram of the cross-sectional structure extending from the B direction in the middle;

[0023] Figure 5 Embodiments of the present invention Figure 1 A magnified schematic diagram of the structure at point C.

[0024] Figure label:

[0025] 1. Pump front cover; 2. Impeller nut; 3. Impeller; 4. Round-headed plain key; 5. Guide vane; 6. Pump body; 7. Drive shaft; 8. Sliding bearing bushing; 9. Sliding bearing; 10. Sliding bearing housing; 11. Perforated round key; 12. Tension / compression sensor; 13. Bearing shaft; 14. Mechanical seal; 15. Deep groove ball bearing; 16. Radial bearing end cover; 17. Bearing retaining ring; 18. Thrust cylindrical roller bearing; 19. Axial bearing end cover. Detailed Implementation

[0026] The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. The purpose and effects of the present invention will become clearer. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0027] Figure 1 An example is a schematic diagram of the assembly cross-sectional structure of a pump axial force measuring device mounted on a mixed-flow pump, as shown below. Figure 1 As shown, a pump front cover 1 is provided at one end of the pump body 6, and the pump front cover 1 is fixed by double-ended studs; an axial bearing end cover 19 is provided at the other end of the pump body 6, and the axial bearing end cover 19 is fixed by hexagonal head bolts. The drive shaft 7 and the bearing shaft 13 are modified designs of the original pump shaft, which are installed and fixed on the mixed flow pump under test in the same way as the original pump shaft.

[0028] The front half of the pump body 6 contains an impeller nut 2, an impeller 3, a round-headed key 4, a guide vane 5, a sliding bearing sleeve 8, a sliding bearing 9, and a sliding bearing housing 10, all related to the installation of the drive shaft 7. The threaded connection at the front end of the drive shaft 7 is to the impeller nut 2. A retaining washer abuts between the impeller nut 2 and the impeller 3. A keyway is provided at the front end of the drive shaft 7. The impeller 3 is connected to the drive shaft 7 via the round-headed key 4. The sliding bearing 9 is fitted onto the outer circumference of the drive shaft 7. The drive shaft 7 mates with the guide vane 5 via the sliding bearing sleeve 8, the sliding bearing 9, and the sliding bearing housing 10. The sliding bearing sleeve 8 and the sliding bearing 9 have a radial clearance fit. The sliding bearing housing 10 is connected to the guide vane 5 via an internal hexagon head screw.

[0029] The rear half of the pump body 6 contains a mechanical seal 14, a deep groove ball bearing 15, a radial bearing end cap 16, a bearing retaining ring 17, a thrust cylindrical roller bearing 18, and an axial bearing end cap 19, all related to the installation of the bearing shaft 13. The front end of the bearing shaft 13 is connected to the rear end of the drive shaft 7. The deep groove ball bearing 15 is fitted onto the outer circumference of the bearing shaft 13. The outer ring of the deep groove ball bearing 15 is fitted with the radial bearing end cap 16, which is connected to the axial bearing end cap 19 via hexagonal head screws. One side of the bearing retaining ring 17 abuts against a shoulder of the deep groove ball bearing 15 and the bearing shaft 13, and the other side abuts against one side of the thrust cylindrical roller bearing 18. The other side of the thrust cylindrical roller bearing 18 abuts against the axial bearing end cap 19. The mechanical seal 14 is positioned via the shoulder of the bearing shaft 13 using a mechanical seal retaining ring and a locating nut, and is connected to the pump body 6 via hexagonal head screws.

[0030] Figure 2 This example illustrates a surface structure diagram of a combined shaft system for measuring the axial force of a pump impeller. The testing device includes: a drive shaft 7, a perforated cylindrical key 11, a tension / compression sensor 12, and a bearing shaft 13. The tension / compression sensor 12 is mounted on the inner side of the mating end face of the drive shaft 7 and the bearing shaft 13, and is not shown. Figure 2In the surface structure shown, the perforated cylindrical key 11 is used to fix the circumferential relative position of the drive shaft 7 and the bearing shaft 13. The outer diameter of the part where the drive shaft 7 and the bearing shaft 13 are connected is smaller than the outer diameter of the original pump shaft, and the outer diameter of the part where the bearing shaft 13 and the drive shaft 7 are connected is equal to the outer diameter of the original pump shaft. The drive shaft 7 is inserted into the hollow section of the bearing shaft 13 and fixed by the perforated cylindrical key 11, which is a simple detachable structure.

[0031] It should be noted that, in addition to the connection structure between the drive shaft 7, the perforated cylindrical key 11, the tension / compression sensor 12, and the bearing shaft 13, Figure 2 The axial lengths of each segment, the position of the shoulder, and the keyways and threads in the surface structures of the drive shaft 7 and the bearing shaft 13 shown are only used to match the mixed-flow pump in this embodiment of the invention. For axial-flow pumps and mixed-flow pumps in other embodiments, those skilled in the art can make corresponding designs according to specific needs.

[0032] Figure 3 Example Figure 2 A schematic diagram of the half-section structure extending from direction A in the middle, as shown below. Figure 3 As shown, the connection between the drive shaft 7 and the bearing shaft 13 has a certain length in the axial direction so that the center lines of the drive shaft 7 and the bearing shaft 13 can be well aligned; however, the length of the connection should not be too long, the drive shaft 7 has a sufficient outer diameter in the connection part, and the hollow part of the bearing shaft 13 has sufficient wall thickness to prevent the structural strength of the drive shaft 7 and the bearing shaft 13 from being affected during normal operation.

[0033] Furthermore, the specific connection scheme involves keyways and oblong mounting holes on the circumference of the drive shaft 7 and the bearing shaft 13 to match the perforated cylindrical key 11. The perforated cylindrical key 11 is used for torque transmission between the drive shaft 7 and the bearing shaft 13. The keyway on the drive shaft 7 needs to fit tightly with the perforated cylindrical key 11, while the oblong mounting hole on the bearing shaft 13 provides a certain amount of axial movement. That is, the drive shaft 7 and the perforated cylindrical key 11 are in surface contact, while the bearing shaft 13 and the perforated cylindrical key 11 are in line contact. On the one hand, torque transmission of the drive shaft 7 is achieved through line contact; on the other hand, the oblong mounting hole arrangement does not bear axial force. The advantage of adopting the line contact design is that it greatly reduces the axial friction force on the perforated cylindrical key 11, significantly reducing the interference of axial friction force on the axial force measurement results.

[0034] The tension and compression sensor 12 is located at the axial gap after the drive shaft 7 and the bearing shaft 13 are nested together. It is used to detect the axial interaction force between the drive shaft 7 and the bearing shaft 13. It is set at the center line position and connected to the drive shaft 7 and the bearing shaft 13 by a thread.

[0035] Figure 4 Example Figure 2 A schematic diagram of the cross-sectional structure extending from the B direction is shown below. Figure 4As shown, four perforated cylindrical keys 11 are evenly distributed on the circumference and connect the drive shaft 7 and the bearing shaft 13 via keyways to further ensure accurate alignment of the centerlines of the drive shaft 7 and the bearing shaft 13. The radial height of the perforated cylindrical keys 11 does not exceed that of the drive shaft 7 and the bearing shaft 13; that is, it is recessed into the waist-shaped mounting hole of the bearing shaft and does not affect the installation of the drive shaft 7 and the bearing shaft 13 on the mixed-flow pump under test in this embodiment of the invention. To ensure the alignment of the centerlines of the drive shaft 7 and the bearing shaft 13, the number of perforated cylindrical keys 11 and corresponding keyways should be at least four, but not too many, otherwise it will increase the error caused by inaccurate installation position. Furthermore, the perforated cylindrical keys 11 and keyways should be arranged far from the edges of the drive shaft 7 and the bearing shaft 13, maintaining sufficient distance from each other to prevent affecting the structural strength of the drive shaft 7 and the bearing shaft 13 during normal operation.

[0036] Figure 5 Example Figure 1 A magnified schematic diagram of the local structure at point C, as shown below. Figure 5 As shown, a tension / compression sensor 12 is installed only at the centerline position between the drive shaft 7 and the bearing shaft 13. Threaded holes are provided at the centerline position on both the drive shaft 7 and the bearing shaft 13 to match the tension / compression sensor 12. The external threads at the front and rear ends of the tension / compression sensor 12 are connected to the rear threaded hole of the drive shaft 7 and the front threaded hole of the bearing shaft 13, respectively. A through hole is provided at the centerline position on the bearing shaft 13 for the cable of the tension / compression sensor 12 to pass through, connecting the sensor power supply and external processing equipment.

[0037] The connection cables between the tension / compression sensor 12 and the external device are all located at the centerline, effectively isolating the measuring device from interference from bending moments and torques on the rotating shaft. The tension / compression sensor 12 bears all the axial force alone, avoiding problems such as inaccurate installation positions and uneven force distribution that occur when multiple sensors are used. It can directly obtain the axial force when the mixed-flow pump in this embodiment of the invention is working.

[0038] Furthermore, the tension / compression sensor 12 should possess basic characteristics such as small size, fatigue resistance, tensile strength, and compressive strength. A miniature tension / compression sensor made of stainless steel can be used, containing a double-threaded design to connect the drive shaft 7 and the bearing shaft 13. Preferably, the tension / compression sensor 12 can be a DYMH-106 type miniature tension / compression sensor, which has advantages such as high sensitivity, high signal-to-noise ratio, good operational reliability, simple structure, and small footprint, making it suitable for applications with limited internal space in axial flow pumps and mixed flow pumps.

[0039] Furthermore, regarding the matching of the tension / compression sensor 12 with external processing equipment, the preferred solution is to connect the signal output terminal of the tension / compression sensor 12 to the signal input terminal of the signal amplifier. The transmitter outputs various standard analog signals and is powered by 24V. The signal amplifier can be connected to various secondary instruments to achieve long-distance signal transmission.

[0040] It will be understood by those skilled in the art that the above descriptions are merely preferred examples of the invention and are not intended to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. All modifications and equivalent substitutions made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A combined shaft system structure for measuring the axial force of a pump impeller, characterized in that, This combined shaft system structure includes a drive shaft, a load-bearing shaft, a tension / compression sensor, and a perforated cylindrical key; The drive shaft and the bearing shaft are assembled in a set manner; one end of the drive shaft is embedded in the hollow section of the bearing shaft, and the axial length of the drive shaft and the bearing shaft are such that the center lines of the drive shaft and the bearing shaft are coaxial, so that the bearing shaft and the drive shaft have only one degree of freedom in the axial direction, and the structural strength requirements under the driving torque are met. The tension / compression sensor is located in the axial gap after the drive shaft and the bearing shaft are nested, and both ends of the tension / compression sensor are connected to the drive shaft and the bearing shaft respectively; The bearing shaft and the drive shaft are provided with a waist-shaped mounting hole in the circumference. The drive shaft is provided with a keyway at the corresponding position. The cylindrical key with a hole passes through the waist-shaped mounting hole and is installed in the keyway, so as to achieve a tight fit between the drive shaft and the cylindrical key with a hole. There is a certain amount of axial movement space between the bearing shaft and the cylindrical key with a hole.

2. The combined shaft system structure for measuring the axial force of the pump impeller according to claim 1, characterized in that, There are four waist-shaped mounting holes and four keyways, which are evenly distributed circumferentially. A perforated cylindrical key is installed in each waist-shaped mounting hole and keyway. The waist-shaped mounting holes and keyways are located away from the edges of the bearing shaft and the drive shaft.

3. The combined shaft system structure for measuring the axial force of the pump impeller according to claim 2, characterized in that, The perforated cylindrical key is recessed radially into the waist-shaped mounting hole of the bearing shaft.

4. The combined shaft system structure for measuring the axial force of the pump impeller according to claim 1, characterized in that, The bearing shaft has a stepped through hole with a coaxial axis. The tension and compression sensor is a miniature tension and compression sensor made of stainless steel with a double-ended stud. The tension and compression sensor is placed in the stepped through hole and is threaded to the bearing shaft and the drive shaft respectively through the double-ended stud. The cable of the tension and compression sensor passes through the stepped through hole and exits the bearing shaft.

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