Gap self-compensation axial force balance shield pump based on heterogeneous material thermal matching

Abstract

The invention relates to the technical field of shield pumps, and discloses a gap self-compensation axial force balance shield pump based on heterogeneous material thermal matching, which comprises a pump body, a pump cover assembly and a motor shell assembly which are enclosed to form a closed cavity for mounting a rotor part; the rotor component comprises an impeller, the impeller is arranged in an inner cavity of the pump body, a rear cover plate of the impeller is provided with an annular rear opening ring extending in the axial direction, the motor shell assembly comprises a motor shell, the end, facing the pump body, of the motor shell is provided with an annular opening ring, the annular opening ring and the annular rear opening ring are oppositely arranged in the radial direction, and a rear opening ring radial gap is formed between the annular opening ring and the annular rear opening ring. The impeller is made of a first polymer-based composite material, the motor shell is made of a second polymer-based composite material, and the thermal expansion coefficient of the first polymer-based composite material is larger than that of the second polymer-based composite material. According to the invention, the situation that the main thrust bearing liquid film bears too high load at high temperature can be avoided, and a dynamic and self-adaptive axial force compensation system is formed.

Description

Technical Field

[0001] This invention relates to the field of shielded pump technology, and more specifically to a shielded pump with gap self-compensation and axial force balance based on thermal matching of heterogeneous materials. Background Technology

[0002] As a fully sealed, leak-free fluid transport device, the canned motor pump is widely used in industries with stringent requirements for media sealing, such as chemical, pharmaceutical, nuclear power, HVAC, and water treatment, due to its core advantages of safety, environmental friendliness, and low operating noise. Among these, canned motor pumps made of engineering plastics have been widely adopted and applied in the transport of corrosive and clean media due to their excellent acid and alkali corrosion resistance, lightweight characteristics, and manufacturing cost advantages. In the overall design of plastic canned motor pumps, the precise balance of rotor axial force and the stable and reliable operation of the thrust bearing are the core technical points determining the pump's service life, adaptability to operating conditions, and operational safety. In existing conventional technologies, the axial force balance of plastic canned motor pumps often adopts a throttling self-balancing structure with an impeller rear ring and balancing holes, while relying on a hydrodynamic lubrication type thrust bearing to bear the residual axial force during pump operation, thereby achieving control of the rotor axial force.

[0003] Existing conventional plastic canned motor pumps often use homogeneous engineering plastic materials for their impellers, rear rings, and mating casings, or combinations of dissimilar materials without precise matching of thermal expansion coefficients. The radial clearance of the rear ring is typically designed as a fixed value based on a single rated operating temperature, failing to adapt to changes in medium characteristics and bearing performance fluctuations under wide temperature ranges, resulting in significant technical limitations. On one hand, when the pump operates at high temperatures, the dynamic viscosity of the pumped medium decreases significantly with increasing temperature. This change directly leads to a substantial reduction in the throttling effect of the impeller rear ring clearance, causing an imbalance in pressure distribution on the impeller rear cover side. This results in irregular and significant drift of the axial force within the pump, exceeding the design controllable range. Simultaneously, the decrease in medium viscosity also significantly reduces the liquid film carrying capacity of the hydrodynamic lubrication thrust bearing. The abnormal increase in axial force at this point directly triggers bearing overload, easily leading to serious failures such as lubricant film rupture, bearing end face friction wear, and even burning failure. This drastically shortens the service life of the canned motor pump and severely restricts its operational reliability under high-temperature conditions.

[0004] To alleviate the problems of insufficient throttling capacity and axial force imbalance at the rear inlet ring under high-temperature conditions, existing technologies often employ a method of reducing the radial design clearance of the rear inlet ring in the cold state at room temperature, thereby reserving a margin for throttling capacity under high-temperature conditions. However, this approach has consistently failed to resolve the performance contradiction between cold and hot conditions. An excessively small ring design clearance in the cold state at room temperature not only significantly increases the machining precision requirements and assembly difficulty of pump components, making it highly susceptible to ring jamming during assembly, but also leads to friction and wear between the impeller's rear inlet ring and the mating housing during cold starts and low-temperature operation. As the ring wears, the mating clearance further widens, exacerbating the axial force imbalance problem during long-term pump operation. This approach cannot simultaneously meet the safety requirements of cold assembly and start-up and the stability requirements of axial force balance under high-temperature conditions.

[0005] Furthermore, in existing conventional plastic canned motor pumps, the radial bearings and mating bushings, bearing mounting seats and related mating components are mostly not designed with matching coefficients of thermal expansion, material hardness, and self-lubricating properties. Differences in the coefficients of thermal expansion between different components can cause irregular changes in the radial clearances within the pump as the operating temperature fluctuates. This not only further exacerbates abnormal fluctuations in axial force and internal leakage parameters within the pump, affecting the pump's hydraulic efficiency and media transport performance, but may also lead to rubbing failures between the radial bearings and bushings. Simultaneously, it negatively impacts the flow stability of the motor cooling circulation channel, failing to guarantee the long-term stable operation of the pump's cooling and bearing lubrication systems. At the same time, the bearing seats, main thrust bearings, and other components in existing conventional plastic canned motor pumps are mostly assembled and fixed separately using fasteners. This not only requires numerous threaded connections, increasing the number of parts and assembly steps, but also makes the threads prone to corrosion and connections susceptible to damage under corrosive media conditions. This increases the difficulty of daily maintenance and the risk of failure, and is also detrimental to the integrated and miniaturized design of the canned motor pump's overall structure.

[0006] In summary, among the existing technologies related to plastic canned pumps, there is still no perfect technical solution that can achieve dynamic self-compensation of the rear ring clearance through the matching design of the thermal expansion coefficients of heterogeneous materials, while simultaneously decoupling the axial force balance requirements and internal cooling and lubrication requirements of the pump unit. It cannot simultaneously solve a series of technical pain points such as large axial force drift under wide temperature range variable temperature conditions, insufficient thrust bearing load capacity under high temperature conditions, easy jamming and wear of the rear ring under cold conditions, and poor thermal stability of the internal fitting clearance of the pump. These issues severely restrict the application range and long-term operational reliability of engineering plastic canned pumps under harsh conditions such as complex temperature variations and strong corrosion. Summary of the Invention

[0007] In view of this, the present invention provides a gap self-compensating axial force balancing shielded pump based on heterogeneous material thermal matching, which can avoid excessive load on the main thrust bearing liquid film at high temperature, forming a dynamic and adaptive axial force compensation system.

[0008] To achieve the above objectives, the present invention provides a gap self-compensating axial force balancing shielded pump based on heterogeneous material thermal matching, comprising a pump body, a pump cover assembly, and a motor housing assembly. The two ends of the pump body are respectively fixedly connected to the pump cover assembly and the motor housing assembly, and the three together form a sealed chamber for the installation of the rotor components. The rotor component includes an impeller, which is disposed in the inner cavity of the pump body. The rear cover plate of the impeller is provided with an annular rear end ring extending axially. The motor housing assembly includes a motor housing, which is provided with an annular end ring at one end facing the pump body. The annular end ring and the annular rear end ring are arranged radially opposite to each other and a radial gap is formed between them. The pump cover assembly is equipped with a main thrust bearing on the side facing the impeller. The front cover plate of the impeller is fixed with a wear-resistant ring. The wear-resistant ring is axially opposite to the main thrust bearing and forms a paired friction pair that bears the axial force of the rotor. The impeller is made of a first polymer-based composite material, and the motor housing is made of a second polymer-based composite material. The coefficient of thermal expansion of the first polymer-based composite material is greater than that of the second polymer-based composite material, so that the radial clearance of the rear inlet ring decreases as the operating temperature of the shielded pump increases. This is to compensate for the attenuation of the throttling effect and the decrease in the thrust bearing capacity caused by the decrease in medium viscosity, and to maintain the axial force balance of the impeller.

[0009] Preferably, the first polymer-based composite material is carbon fiber reinforced polypropylene, and the second polymer-based composite material is carbon fiber reinforced polyphenylene sulfide.

[0010] Preferably, the motor housing assembly further includes a stator core, and the motor housing and the stator core are an integral fixed structure.

[0011] Preferably, a front radial bearing and a rear radial bearing are fixed on the inner side of the motor housing, and the front radial bearing and the rear radial bearing are respectively disposed on the axial sides of the stator core; the rotor component also includes a motor rotor core and its plastic cover, a front bushing and a rear bushing, the front bushing and the rear bushing are both fixedly sleeved on the radial outer side of the motor rotor core and its plastic cover, the front bushing is radially paired with the front radial bearing, and the rear bushing is radially paired with the rear radial bearing.

[0012] Preferably, the motor rotor core and its plastic cover have a hollow shaft hole that extends axially through the rotor core, and the hollow shaft hole connects the inlet side of the impeller with the rear chamber of the rear radial bearing.

[0013] Preferably, the front radial bearing, rear radial bearing, front bushing, and rear bushing are all fixed to the corresponding base using a heat-shrinking process. The heat-shrinking temperature is higher than the maximum operating temperature of the shielded pump and lower than the heat deformation temperature of the corresponding material.

[0014] Preferably, the end face of the main thrust bearing facing the impeller is provided with a plurality of circumferentially arranged thrust bearings and flow channels.

[0015] Preferably, the rear cover plate of the impeller has at least one balance hole near the hub, and the balance hole connects the inlet side of the impeller with the inner chamber of the rear ring.

[0016] Preferably, the motor housing has several circumferentially distributed axial through holes, one end of which is connected to the inner cavity of the pump body's volute, and the other end of which is connected to the rear chamber of the front radial bearing.

[0017] Preferably, the internal circulation flow of the shielded pump is divided into three paths: the first path passes through the radial gap of the impeller rear inlet ring and returns to the impeller inlet through the impeller balance hole; the second path passes through the axial through hole on the motor housing and returns to the impeller inlet sequentially through the annular gap of the front radial bearing and the impeller balance hole; the third path passes through the shielding sleeve gap between the motor stator and rotor and returns to the impeller inlet sequentially through the annular gap of the rear radial bearing and the hollow shaft hole of the motor rotor.

[0018] As can be seen from the above technical solution, compared with the prior art, the self-compensating axial force balancing shielded pump based on heterogeneous material thermal matching provided by the present invention has the following beneficial effects: 1. This invention uses two polymer-based composite materials with different coefficients of thermal expansion to prepare the impeller and motor housing respectively. This allows the radial clearance of the rear ring formed by the rear ring of the impeller and the extended annular ring of the motor housing to decrease systematically as the operating temperature of the canned pump increases. This can dynamically compensate for the attenuation of the throttling effect caused by the decrease in medium viscosity under high-temperature conditions, stabilize the pressure distribution on the side of the impeller rear cover plate, accurately control the residual axial force of the pump set, compensate for the decrease in the dynamic pressure lubrication bearing capacity of the thrust bearing under high-temperature conditions, keep the thrust bearing load within the design safety range, effectively ensure the safe operation of the thrust bearing, achieve dynamic adaptive balance of rotor axial force under wide temperature range variable temperature conditions, and significantly improve the operational reliability of the pump set under variable temperature conditions. 2. This invention uses a preferred material combination of carbon fiber reinforced polypropylene and carbon fiber reinforced polyphenylene sulfide to prepare the impeller and motor housing, which enables the core flow components of the pump set to have excellent acid and alkali corrosion resistance, making it suitable for conveying highly corrosive media and effectively expanding the application scenarios of the pump set. At the same time, the material matching design can maintain a large initial safety clearance of the rear ring during cold assembly and low temperature start-up, avoiding assembly jamming problems and eliminating the wear and tear of the ring during cold operation. It fully considers the convenience and safety of cold assembly and start-up of the pump set and the axial force balance performance under high temperature conditions. 3. This invention, through the integrated fixing structure of the motor housing and stator core, eliminates the need for separately set bearing seats and a large number of connecting fasteners, significantly reducing the number of parts in the whole machine, simplifying the assembly process, reducing the difficulty of daily maintenance of the equipment, and effectively improving the coaxiality of the whole machine structure, ensuring the stability of the rotor components during high-speed operation, avoiding vibration and rubbing problems caused by coaxiality deviation, adapting to the structural layout of the motor-integrated single-stage mixed flow shielded pump, and realizing the integrated and miniaturized design of the whole machine; 4. This invention utilizes circumferentially distributed axial through holes on the motor housing and hollow shaft holes penetrating the motor rotor core and its plastic sheath, along with balance holes on the impeller rear cover, to form three independent internal circulation flows. This achieves a decoupling design between the pump unit's axial force balance circuit and the motor and bearing cooling and lubrication circuits. The design of the rear ring radial clearance can be optimized solely for axial force balance requirements without considering cooling flow constraints, significantly expanding the range of clearance design values. Simultaneously, the three independent circulation flows provide continuous and stable cooling and lubrication for the front and rear radial bearings and the motor stator and rotor, ensuring the pump unit's operational stability under all temperature range conditions and preventing excessive motor temperature rise under high-temperature conditions. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0020] Figure 1 This is a schematic cross-sectional view of the self-compensating axial force balancing shielded pump based on heterogeneous material thermal matching of the present invention. Figure 2 This is a diagram of the internal circulation flow path of the self-compensating axial force balancing shielded pump based on heterogeneous material thermal matching according to the present invention, where A, B, and C are the three paths of the internal circulation flow of the shielded pump.

[0021] Explanation of reference numerals in the attached drawings: 1-Pump cover, 2-Main thrust bearing, 3-Wear ring, 4-Impeller nut, 5-Locking nut, 6-Impeller, 7-Pump body, 8-Front radial bearing, 9-Front shaft sleeve, 10-Motor rotor core and its plastic cover, 11-Motor housing, 12-Stator core, 13-Rear shaft sleeve, 14-Pump inlet, 15-Pump outlet, 16-Rear radial bearing. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of an exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] like Figure 1 As shown, this invention discloses a gap-self-compensating axial force-balancing shielded pump based on heterogeneous material thermal matching. It is a single-stage mixed-flow shielded pump with a front-mounted motor, including a pump body 7, a pump cover assembly, and a motor housing assembly. The first axial end of the pump body 7 is sealed and fixedly connected to the pump cover assembly, and the second axial end of the pump body 7 is sealed and fixedly connected to the motor housing assembly. The three together enclose a sealed chamber for the installation of the rotor components, realizing a fully sealed and leak-free structural design for the entire pump unit, which is suitable for various conveying conditions with strict requirements for media sealing. The pump cover assembly includes a pump cover 1 and a main thrust bearing 2. A pump inlet 14 is located at the center of the pump cover 1. The main thrust bearing 2 is fixedly installed on the side of the pump cover 1 facing the pump body 7 via a heat-shrink fitting process. The end face of the main thrust bearing 2 facing the impeller 6 has several circumferentially evenly arranged thrust bearings and flow grooves. The thrust bearings can form a stable dynamic pressure lubricating film during pump operation, bearing the residual axial force of the rotor components. The flow grooves ensure smooth flow of the lubricating medium, avoiding the risk of dry friction between the friction pairs and improving the stability and service life of the bearing. A rotor component, including an impeller 6, is installed in the sealed chamber. The impeller 6 is located within the inner cavity of the pump body 7. A wear-resistant ring 3 is embedded and fixed on the side of the front cover plate of the impeller 6 facing the pump cover assembly. The wear-resistant ring 3 and the main thrust bearing 2 are axially opposite each other, forming a paired friction pair capable of bearing the axial force of the rotor. The wear-resistant ring 3 rotates synchronously with the impeller 6, forming a stable dynamic pressure lubrication pair with the main thrust bearing 2, ensuring stable bearing of the rotor's axial force. The impeller 6 has a rear cover plate with an annular rear end ring extending axially toward the motor housing assembly. Near the hub, the rear cover plate of the impeller 6 has at least one balancing hole. This balancing hole connects the inlet side of the impeller 6 with the inner chamber of the rear end ring, allowing for basic self-balancing of the axial force of the impeller 6 in conjunction with the throttling effect of the rear end ring, providing a fundamental guarantee for axial force control of the pump unit. The motor housing assembly includes a motor housing 11. An annular end ring extends integrally from one end of the motor housing 11 toward the pump body 7. This annular end ring is fitted radially outward of the annular rear end ring of the impeller 6, with the two arranged radially opposite each other to form an annular radial gap, providing a structural basis for dynamic self-compensation of axial force.

[0024] The impeller 6 is integrally made of a first polymer-based composite material, and the motor housing 11 is integrally made of a second polymer-based composite material. The coefficient of thermal expansion of the first polymer-based composite material is greater than that of the second polymer-based composite material, so that the radial clearance of the rear inlet ring decreases systematically as the operating temperature of the shielded pump increases. In this embodiment, the first polymer-based composite material is preferably carbon fiber reinforced polypropylene (PP+CF), and the second polymer-based composite material is preferably carbon fiber reinforced polyphenylene sulfide (PPS+CF). Both are engineering plastics resistant to acid or alkali corrosion, which can be adapted to the conveying conditions of highly corrosive media, greatly expanding the application scenarios of the pump set. This material matching design can maintain a large initial safety at the rear inlet ring when the pump set is cold-assembled and started at low temperature. The clearance effectively avoids jamming during assembly and eliminates the risk of friction and wear between the impeller 6 rear ring and the motor housing 11 annular ring during cold starts. When the pump unit enters high-temperature operating conditions, the thermal expansion of the impeller 6 is significantly greater than that of the motor housing 11 as the operating temperature rises, causing the radial clearance of the rear ring to gradually decrease with increasing temperature. This enhances the throttling capacity of the rear ring, dynamically compensates for the attenuation of the throttling effect caused by the decrease in medium viscosity at high temperatures, stabilizes the pressure distribution on the side of the impeller 6 rear cover plate, and reduces the residual axial force of the pump unit pointing towards the inlet. This perfectly compensates for the decrease in the dynamic pressure lubrication bearing capacity of the thrust bearing under high-temperature conditions, ensuring that the load of the thrust bearing is always within the design safety range. This fundamentally avoids the risk of bearing overload and friction failure, forming a dynamic and adaptive axial force compensation system.

[0025] The motor housing assembly also includes a stator core 12. The motor housing 11 and the stator core 12 are an integral fixed structure. This design eliminates the need for separately set bearing seats and a large number of connecting fasteners in traditional canned motor pumps, greatly reducing the number of parts in the whole machine, simplifying the assembly process, reducing the difficulty of daily maintenance of the equipment, and effectively improving the coaxiality of the whole machine structure, ensuring the stability of the rotor components during high-speed operation, and avoiding vibration and rubbing problems caused by coaxiality deviation. The inner side of the motor housing 11 is fixed with a front radial bearing 8 and a rear radial bearing 16. The front radial bearing 8 and the rear radial bearing 16 are respectively located on both sides of the stator core 12. The rotor component also includes a motor rotor core and its plastic cover 10, a front bushing 9 and a rear bushing 13. The front bushing 9 and the rear bushing 13 are both fixedly sleeved on the radial outer side of the motor rotor core and its plastic cover 10 by interference fit. The front bushing 9 and the front radial bearing 8 are radially paired to form an annular lubrication gap, and the rear bushing 13 and the rear radial bearing 16 are radially paired to form an annular lubrication gap, providing stable radial support for the rotor component. The front radial bearing 8, the rear radial bearing 16 and the paired front bushing 9 and rear bushing 13 are made of engineering plastics with similar coefficients of thermal expansion, different hardness, and self-lubricating properties. This can effectively avoid large fluctuations in the radial fit clearance with the working temperature, ensure the dimensional stability of the radial clearance, and fundamentally avoid the risk of radial rubbing of the rotor component. At the same time, the self-lubricating material can further improve the reliability of bearing operation and extend service life. The front radial bearing 8, rear radial bearing 16, front bushing 9, and rear bushing 13 are all fixed to the corresponding base using a heat-shrinking process. The heat-shrinking temperature is higher than the maximum operating temperature of the canned pump and lower than the heat deformation temperature of the corresponding material. This process ensures that the mating surfaces can maintain a stable interference fit when the pump unit is running at the maximum operating temperature, and there will be no problem of parts loosening. It also ensures the processability of disassembly and maintenance of the parts at high temperatures.

[0026] The rotor component also includes an impeller nut 4 and a locking nut 5. The hub of the impeller 6 extends rearward and axially connects with the front shaft sleeve 9. The impeller nut 4 and the locking nut 5 cooperate with each other to axially lock and fix the impeller 6 to the motor rotor core and its plastic cover 10. The double-nut locking structure can effectively ensure the axial positioning accuracy of the impeller 6 under high-speed rotation and variable temperature conditions, avoid axial movement of the impeller 6 that causes abnormal changes in the radial clearance of the rear end ring, and ensure the long-term stability of the dynamic compensation effect of axial force. The motor housing 11 has several circumferentially distributed axial through holes. One end of each axial through hole connects to the inner cavity of the volute of the pump body 7, and the other end connects to the rear chamber of the front radial bearing 8. The motor rotor core and its plastic cover 10 have hollow shaft holes that extend axially. These hollow shaft holes connect the inlet side of the impeller 6 to the rear chamber of the rear radial bearing 16, thus forming three independent circulating flows within the pump unit. This achieves a decoupling design between the axial force balance problem and the internal cooling and lubrication problem of the shielded pump, allowing the design of the radial clearance of the rear inlet ring to be optimized only for the axial force balance requirement without having to consider the cooling flow constraint, thus greatly expanding the range of clearance design values.

[0027] like Figure 2 As shown, the internal circulation flow of the canned pump is divided into three paths: the first path (A) passes through the radial clearance of the impeller 6's rear annular ring and returns to the impeller 6's inlet through the balance hole of the impeller 6. This path is the main circuit for axial force balance of the pump set, specifically used to achieve self-balancing of the impeller 6's axial force, and is not affected by the cooling and lubrication circuit; the second path (B) passes through the axial through hole on the motor housing 11, sequentially through the annular clearance of the front radial bearing 8 and the balance hole of the impeller 6, and returns to the impeller 6's inlet. This path is the dedicated cooling and lubrication circuit for the front radial bearing 8, and can be used for the front radial shaft... The bearing 8 provides a continuous and stable cooling and lubrication medium to ensure the reliability of bearing operation; the third path (C) passes through the shielding sleeve gap between the motor stator and rotor, and sequentially through the annular gap of the rear radial bearing 16, the motor rotor core and the hollow shaft hole of its plastic cover 10, returning to the impeller 6 inlet. This path can simultaneously achieve heat dissipation and cooling of the motor stator and rotor and lubrication and cooling of the rear radial bearing 16, ensuring that the motor and the rear radial bearing 16 can obtain a stable cooling effect under the full temperature range, avoiding the problem of excessive motor temperature rise under high temperature conditions.

[0028] In this embodiment, during operation, the pump medium enters from the pump inlet 14 at the center of the pump cover 1, is pressurized by the impeller 6, enters the volute flow channel of the pump body 7, and finally flows out from the pump outlet 15 on the pump body 7, completing the medium transportation process. Under cold start and low-temperature operation conditions, the radial clearance between the impeller 6 and the motor housing 11 remains relatively large initially, ensuring ease of assembly and preventing wear and tear of the impeller ring during cold operation. At this time, the residual axial force of the pump unit is stably borne by the main thrust bearing 2. As the operating temperature of the pump unit increases, the viscosity of the pump medium gradually decreases, and the hydrodynamic lubrication bearing capacity of the main thrust bearing 2 decreases accordingly. Due to the difference in thermal expansion coefficients between the impeller 6 and the motor housing 11, the radial clearance of the rear end ring decreases systematically with increasing temperature, gradually enhancing the throttling capacity of the rear end ring. Consequently, the pressure on the outer side of the impeller 6 rear cover plate decreases, and the residual axial force of the pump unit decreases synchronously. This perfectly compensates for the decrease in the thrust bearing's load-bearing capacity at high temperatures, ensuring that the main thrust bearing 2 remains within a safe liquid film thickness and load range. This achieves dynamic self-compensation of axial force under variable temperature conditions. During the full-condition operation of the pump unit, three independent internal circulation flows continuously provide stable cooling and lubrication for the radial bearing and motor, unaffected by the axial force balance circuit, ensuring the stability and reliability of the pump unit's long-term operation.

[0029] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A self-compensating axial force balancing shielded pump based on thermal matching of heterogeneous materials, characterized in that, It includes a pump body (7), a pump cover assembly and a motor housing assembly. The two ends of the pump body (7) are fixedly connected to the pump cover assembly and the motor housing assembly, respectively. The three together form a sealed chamber for the installation of the rotor components. The rotor component includes an impeller (6), which is located in the inner cavity of the pump body (7). The rear cover plate of the impeller (6) is provided with an annular rear end ring extending axially. The motor housing assembly includes a motor housing (11), which is provided with an annular end ring at one end facing the pump body (7). The annular end ring and the annular rear end ring are arranged radially opposite to each other and a radial gap is formed between them. The pump cover assembly is equipped with a main thrust bearing (2) on the side facing the impeller (6). The front cover plate of the impeller (6) is fixed with a wear-resistant ring (3). The wear-resistant ring (3) is axially opposite to the main thrust bearing (2) and forms a pair of friction pairs that bear the axial force of the rotor. The impeller (6) is made of a first polymer-based composite material, and the motor housing (11) is made of a second polymer-based composite material. The thermal expansion coefficient of the first polymer-based composite material is greater than that of the second polymer-based composite material, so that the radial clearance of the rear end ring decreases as the operating temperature of the shielded pump increases, in order to compensate for the attenuation of the throttling effect and the decrease in the thrust bearing capacity caused by the decrease in medium viscosity, and to maintain the axial force balance of the impeller (6).

2. The self-compensating axial force balancing shielded pump based on heterogeneous material thermal matching according to claim 1, characterized in that, The first polymer-based composite material is carbon fiber reinforced polypropylene, and the second polymer-based composite material is carbon fiber reinforced polyphenylene sulfide.

3. The self-compensating axial force balancing shielded pump based on heterogeneous material thermal matching according to claim 1, characterized in that, The motor housing assembly also includes a stator core (12), and the motor housing (11) and the stator core (12) are an integral fixed structure.

4. The self-compensating axial force balancing shielded pump based on heterogeneous material thermal matching according to claim 3, characterized in that, The inner side of the motor housing (11) is fixed with a front radial bearing (8) and a rear radial bearing (16), which are respectively located on the axial sides of the stator core (12); the rotor component also includes a motor rotor core and its plastic cover (10), a front bushing (9) and a rear bushing (13), which are both fixedly sleeved on the radial outer side of the motor rotor core and its plastic cover (10). The front bushing (9) is radially paired with the front radial bearing (8), and the rear bushing (13) is radially paired with the rear radial bearing (16).

5. The self-compensating axial force balancing shielded pump based on heterogeneous material thermal matching according to claim 4, characterized in that, The motor rotor core and its plastic cover (10) have a hollow shaft hole that runs through the axis. The hollow shaft hole connects the inlet side of the impeller (6) with the rear chamber of the rear radial bearing (16).

6. The self-compensating axial force balancing shielded pump based on heterogeneous material thermal matching according to claim 4, characterized in that, The front radial bearing (8), rear radial bearing (16), front bushing (9) and rear bushing (13) are all fixed to the corresponding base by a heat-shrinking process. The heat-shrinking temperature is higher than the maximum operating temperature of the shielded pump and lower than the heat deformation temperature of the corresponding material.

7. The self-compensating axial force balancing shielded pump based on heterogeneous material thermal matching according to claim 1, characterized in that, The main thrust bearing (2) has several circumferentially arranged thrust bearings and flow channels on the end face facing the impeller (6).

8. The self-compensating axial force balancing shielded pump based on heterogeneous material thermal matching according to claim 1, characterized in that, The impeller (6) has at least one balance hole near the hub on its rear cover plate. The balance hole connects the inlet side of the impeller (6) with the inner chamber of the rear ring.

9. The self-compensating axial force balancing shielded pump based on heterogeneous material thermal matching according to claim 4, characterized in that, The motor housing (11) has several circumferentially distributed axial through holes. One end of the axial through hole is connected to the inner cavity of the volute of the pump body (7), and the other end of the axial through hole is connected to the rear cavity of the front radial bearing (8).

10. The self-compensating axial force balancing shielded pump based on heterogeneous material thermal matching according to claim 4, characterized in that, The internal circulation flow of the shielded pump is divided into three paths: The first path passes through the radial clearance of the impeller (6) back to the impeller (6) inlet through the balance hole of the impeller (6); The second path passes through the axial through hole on the motor housing (11), and then through the annular gap of the front radial bearing (8) and the balance hole of the impeller (6) to return to the inlet of the impeller (6); The third path passes through the gap between the shielding sleeve between the motor stator and rotor, and then through the annular gap of the rear radial bearing (16), the hollow shaft hole of the motor rotor core and its plastic covering (10), before returning to the impeller (6) inlet.

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