Noise reduction oil pump

Abstract

The invention relates to the technical field of power-assisted steering, in particular to a noise reduction oil pump. Noise reduction grooves are formed in an inlet section outside a liquid inlet channel and a liquid outlet channel in a pump core cavity, a middle section in a liquid outlet groove within a first distance range from a meshing end point of a driving gear and a driven gear, and an outlet section in the liquid outlet groove within a second distance range from a liquid outlet hole in a honeycomb array. The obvious noise reduction effect is achieved, meanwhile, vibration of the oil pump is reduced, and the service life is prolonged. The novel noise reduction oil pump has remarkable advantages in the aspects of reducing environmental noise pollution, improving driving comfort and the like, and has important significance in promoting sustainable development and environmental protection of the automobile industry.

Description

Technical Field

[0001] This invention relates to the field of power steering technology, specifically a noise-reducing oil pump. Background Technology

[0002] The power steering pump is a core component of a car's hydraulic power steering system. Connected to the engine, it converts mechanical energy into hydraulic energy, powering the steering gear for precise and agile steering. Its functions include power supply, hydraulic energy conversion, and system pressure maintenance. The main structural types include gear-type, vane-type, and rotor-type. Existing gear-type power steering pumps suffer from high noise levels, reducing driving comfort. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the purpose of this invention is to provide a noise-reducing oil pump.

[0004] The technical solution adopted by this invention to solve its technical problem is:

[0005] A noise-reducing oil pump includes: a base, a pump housing, and a pump core; the pump housing is disposed on the base, and a pump cavity is formed between the pump housing and the base, and an inlet pipe communicating with the pump cavity is disposed on the pump housing; a pump core seat is disposed on the base, a through hole is disposed in the middle of the pump core seat, an inlet groove is disposed on one side of the through hole and an outlet groove is disposed on the other side of the pump core seat, and an outlet hole communicating with the outside of the base is disposed on the side wall of the outlet groove;

[0006] The pump core is located inside the pump cavity. The pump core includes a pump core body, through which the pump core cavity is axially oriented. A driving gear and a driven gear mesh with each other inside the pump core cavity. The driving shaft of the driving gear extends a certain length through a through hole from the base and is rotatably and sealingly connected to the through hole. An inlet channel is axially oriented on one side of the pump core cavity opposite to the meshing surfaces of the driving and driven gears, and an outlet channel is axially oriented on the other side. An inlet hole is located on the side of the pump core body opposite to the inlet channel. A pump core cover is located on the top surface of the pump core body, and the bottom surface is connected to the pump core seat. A special-shaped sealing ring is installed between the pump core body and the pump core cover, and between the pump core body and the pump core seat. These special-shaped sealing rings isolate the inlet hole, inlet groove, and inlet channel into an inlet chamber, and the outlet channel, outlet groove, and outlet hole into an outlet chamber.

[0007] Noise reduction grooves are arranged in a honeycomb array at the inlet section outside the inlet and outlet channels in the pump core cavity, the middle section within the first distance range from the end of the meshing of the driving gear and the driven gear in the outlet groove, and the outlet section within the second distance range from the outlet hole in the outlet groove.

[0008] As a preferred embodiment, a further technical solution of the present invention is:

[0009] Preferably, the cross-section of the noise reduction groove is a regular hexagon.

[0010] Preferably, the distance between opposite sides of the noise reduction groove in the middle section gradually decreases from the neck to the bottom of the groove.

[0011] Preferably, the noise reduction channel in the outlet section has a double-layer stepped hexagonal structure.

[0012] Preferably, an adapter plate is connected to the lower surface of the base.

[0013] Preferably, a detection hole is provided on the side wall of the liquid tank parallel to the liquid outlet, and a pressure sensor is installed on the opening of the detection hole.

[0014] This invention also discloses a design method for a noise-reducing oil pump, the specific steps of which are as follows:

[0015] S1: Determine the structure and dimensions of each component according to the design requirements. The components include: base, pump housing and pump core.

[0016] S2: Determine the characteristic range of the noise spectrum generated by the noise-reducing oil pump based on the pump speed and the number of gear teeth of the noise-reducing oil pump;

[0017] S3: Divide the feature range into low-frequency noise, mid-frequency noise and high-frequency noise in sequence, and determine the distribution location of the noise reduction slots based on the causes of low-frequency noise, mid-frequency noise and high-frequency noise.

[0018] S4: Guided by Helmholtz resonance theory, acoustic impedance matching principle and viscous loss mechanism, inversion calculations and optimization of the size of noise reduction slots at each distribution location are performed.

[0019] Preferably, the feature range is determined in S2 using the following expression:

[0020]

[0021] Where n represents the oil pump speed and N represents the number of gear teeth.

[0022] Preferably, S3 specifically includes: low-frequency noise covering the fundamental frequency and its second harmonic, ranging from 100 to 800 Hz; mid-frequency noise covering high-energy harmonics, ranging from 800 to 3000 Hz; and high-frequency noise covering higher-order harmonics and broadband turbulence noise, ranging from 3000 to 20000 Hz.

[0023] Low-frequency noise mainly includes oil filling pulsation noise generated by gear disengagement cavity, fluid separation noise caused by pressure fluctuation in inlet pipeline, and cavitation noise caused by bubble collapse. Accordingly, noise reduction tanks for low-frequency noise are set in the inlet section outside the inlet and outlet channels in the pump core cavity.

[0024] The main types of mid-frequency noise include pulsating pressure noise generated by gear meshing, fluid burst noise from oil compression and release, and turbulent noise caused by eddies in the high-pressure zone. The noise reduction tank for mid-frequency noise is set in the middle section of the outlet tank within the first distance range from the end point of meshing of the driving gear and the driven gear.

[0025] High-frequency noise mainly includes cavitation noise from oil cavitation and collapse, whistling noise from metal contact friction, and ultrasonic oscillation caused by sudden pressure drop. The noise reduction tank for high-frequency noise is set in the outlet section within the second distance range from the outlet hole in the outlet tank.

[0026] Preferably, S4 specifically includes:

[0027] The noise reduction slots in the inlet section are configured using a mix of slots with different side distances. The size optimization process is as follows:

[0028] Using low-frequency noise as the characteristic frequency of the target noise reduction band, the basic volume of the noise reduction groove is determined by comprehensively considering the physical boundary of the pump core cavity design size and the structural strength. The range of the physical depth of the neck of the noise reduction groove is set by combining the feasibility of the processing technology. Based on the characteristic frequency, the basic volume and the range of the physical depth of the neck, the Helmholtz resonance theory formula is used for iterative calculation to determine the range of the edge distance of the noise reduction groove in the inlet section.

[0029] The noise reduction groove in the middle section adopts a structure in which the distance between the edges gradually decreases from the neck to the bottom of the groove. The size optimization process is as follows:

[0030] Using mid-frequency noise as the characteristic frequency of the target frequency band for noise reduction, the physical depth of the neck opening is set to a fixed value. The acoustic impedance matching principle is introduced as a constraint condition to limit the neck opening to the optimal setting value. The recommended value of the edge distance of the noise reduction groove is determined by combining the Helmholtz resonance theory.

[0031] The noise reduction channel at the outlet section adopts a double-layer stepped hexagonal structure, and the size optimization process is as follows:

[0032] To maximize the frictional effect between the sound wave and the hole wall, the neck size was determined based on the principle of viscosity-heat loss. The distance between the upper and lower edges was directly set to 1.0 mm and 0.8 mm, respectively. High-frequency noise was used as the characteristic frequency of the noise reduction target frequency band. The cavity structure of the noise reduction groove was solved by inversion using Helmholtz resonance theory. The layer spacing was optimized and determined using acoustic simulation to construct an impedance transition region between the two layers, thereby improving the coupling and dissipation efficiency of high-frequency sound waves.

[0033] The present invention, which adopts the above technical solution, has the following prominent features compared with the prior art:

[0034] Through innovative structural design, the flow characteristics and pressure distribution of the fluid within the gear pump are altered, effectively suppressing the generation and propagation of noise. Furthermore, this optimized solution not only provides new insights into noise reduction design for external gear pumps but also offers significant reference value for research on sound insulation and noise reduction in external gear pumps. Attached Figure Description

[0035] Figure 1 This is an exploded structural diagram of the noise-reducing oil pump in an embodiment of the present invention;

[0036] Figure 2 This is a cross-sectional view of the noise-reducing oil pump in an embodiment of the present invention;

[0037] Figure 3 This is a schematic diagram of the internal structure of the noise-reducing oil pump in an embodiment of the present invention. Figure 1 ;

[0038] Figure 4 This is a schematic diagram of the internal structure of the noise-reducing oil pump in an embodiment of the present invention. Figure 2 ;

[0039] Figure 5 This is a schematic diagram of the pump core cavity structure of the noise-reducing oil pump in an embodiment of the present invention;

[0040] Figure 6 This is a schematic diagram of the pump core seat structure of the noise-reducing oil pump in an embodiment of the present invention. Figure 1 ;

[0041] Figure 7 This is a schematic diagram of the pump core seat structure of the noise-reducing oil pump in an embodiment of the present invention. Figure 2 ;

[0042] Figure 8 This is a detailed view of the noise reduction groove at the inlet section in an embodiment of the present invention;

[0043] Figure 9 These are detailed diagrams of the noise reduction grooves in the middle and outlet sections of this invention.

[0044] Figure 10 This is a pressure comparison diagram from an embodiment of the present invention;

[0045] Figure 11 This is a comparison chart of simulation results in the embodiments of the present invention;

[0046] Figure 12 This is a comparison chart of experimental verification results in the embodiments of the present invention.

[0047] Explanation of reference numerals in the attached drawings: 1. Base; 2. Pump housing; 3. Pump chamber; 4. Inlet pipe; 5. Pump core seat; 6. Through hole; 7. Inlet groove; 8. Outlet groove; 9. Outlet hole; 10. Pump core body; 11. Drive gear; 12. Driven gear; 13. Inlet channel; 14. Outlet channel; 15. Inlet hole; 16. Pump core cover; 17. Special-shaped sealing ring; 18. Inlet section; 19. Intermediate section; 20. Outlet section; 21. Adapter plate; 22. Weight reduction groove; 23. Detection hole; 24. Pressure sensor; 25. Figure-eight housing; 26. Bearing. Detailed Implementation

[0048] The present invention will be further illustrated below with reference to specific embodiments. The purpose of this illustration is solely to provide a better understanding of the invention. Therefore, the examples given do not limit the scope of protection of the present invention.

[0049] like Figures 1 to 9 As shown in the figure, this embodiment provides a noise reduction oil pump including: a base 1, a pump housing 2, and a pump core; the pump housing 2 is disposed on the base 1, and a pump chamber 3 is formed between the pump housing 2 and the base 1, and an inlet pipe 4 communicating with the pump chamber 3 is disposed on the pump housing 2; a pump core seat 5 is disposed on the base 1, a through hole 6 is disposed in the middle of the pump core seat 5, an inlet groove 7 is disposed on one side of the through hole 6 and an outlet groove 8 is disposed on the other side of the pump core seat 5, and an outlet hole 9 communicating with the outside of the base 1 is disposed on the side wall of the outlet groove 8;

[0050] The pump core is housed within the pump chamber 3. The pump core includes a pump core body 10, with a pump core cavity axially extending through its center. A driving gear 11 and a driven gear 12 mesh within the pump core cavity. The driving shaft of the driving gear 11 extends a certain length through a through hole 6 from the base and is rotatably and sealingly connected to the through hole 6. An inlet channel 13 is axially arranged on one side of the pump core cavity opposite the meshing surfaces of the driving gear 11 and the driven gear 12, and an outlet channel 14 is axially arranged on the other side. A liquid inlet hole 15 is provided on the side of the body 10 opposite to the liquid inlet channel 13. A pump core cover 16 is provided on the top surface of the pump core body 10 and the bottom surface is connected to the pump core seat 5. A special-shaped sealing ring 17 is provided between the pump core body 10 and the pump core cover 16, and between the pump core body 10 and the pump core seat 5. Thus, the special-shaped sealing ring 17 isolates the liquid inlet hole 15, the liquid inlet groove 7 and the liquid inlet channel 13 into a liquid inlet chamber, and isolates the liquid outlet channel 14, the liquid outlet groove 8 and the liquid outlet hole 9 into a liquid outlet chamber.

[0051] Noise reduction grooves are arranged in a honeycomb array at the inlet section 18 outside the inlet channel 13 and outlet channel 14 in the pump core cavity, the middle section 19 within the first distance range from the end of meshing of the drive gear 11 and driven gear 12 in the outlet groove 8, and the outlet section 20 within the second distance range from the outlet hole 9 in the outlet groove 8.

[0052] In practice, the noise reduction channel has a regular hexagonal cross-section. The inlet section 18 uses a mix of noise reduction channels with different side-to-side distances. The side-to-side distance of the noise reduction channel in the middle section 19 gradually decreases from the neck to the bottom of the channel. The noise reduction channel in the outlet section 20 has a double-layer stepped hexagonal structure.

[0053] In practice, the oil enters the pump chamber 3 from the inlet pipe 4 on the pump casing 2. The oil in the pump chamber 3 enters the inlet tank 7 through the inlet hole on the pump core body 10 and then flows into the inlet channel 13. It then enters the gear inlet area inside the pump core cavity. After being pressurized by the driving gear 11 and driven gear 12 inside the pump core cavity, it enters the outlet tank 8 through the outlet channel 14 from the outlet area and flows out through the outlet hole 9 on one side. During the flow process, the oil passes through the noise reduction grooves set at the inlet section 18, the intermediate section 19 and the outlet section 20, which changes the flow characteristics and pressure distribution of the fluid inside the gear pump and effectively suppresses the generation and propagation of noise.

[0054] In practice, noise reduction grooves can also be provided on the inner sidewall of the base 1. When setting the liquid outlet 9, a boss can be set close to the sidewall of the liquid outlet trough 8. The liquid outlet 9 starts from the top surface of the boss and extends downwards for a certain distance before turning towards the sidewall of the liquid trough 8 and finally connecting to the outside of the base 1. Multiple weight reduction grooves 22 are provided on the pump core 10 opposite to the liquid outlet trough 8. The two ends of the driving gear 11 and the driven gear 12 can be rotated through the figure-eight shell 25 set in the pump core cavity and the bearing 26 set in the shell.

[0055] During implementation, an adapter plate 21 is connected to the lower surface of the base 1.

[0056] In existing hydraulic steering systems, the low standardization of the interface between the oil pump and the drive motor has become a key factor restricting equipment compatibility and maintenance efficiency. Major motor brands on the market use different mounting interface standards, with significant differences in the number, distribution, diameter, and positioning of mounting holes. This difference leads to serious compatibility issues for users when replacing motors or performing repairs, often requiring custom adapters or replacing the entire pump unit, resulting in high maintenance costs and long downtime.

[0057] This invention's adapter plate structure transforms the traditional fixed interface into a configurable modular interface by introducing a replaceable adapter plate module between the oil pump body and the drive motor. The oil pump body maintains a standardized interface, while compatibility with different motor brands is achieved by replacing the corresponding adapter plate. This design not only solves the multi-brand compatibility problem but also significantly improves the equipment's maintainability and emergency response capabilities.

[0058] The adapter plate 21 adopts a double-layer composite design. The oil pump side connection interface uses a three-point positioning screw connection system, with three M6 high-strength internal hexagon screws evenly distributed at 120 degrees. The screw strength grade is 12.9, ensuring connection reliability. The positioning system adopts a precision stop design with a tolerance grade of H7 / h6, ensuring radial positioning accuracy is controlled within 0.05 mm, ensuring sealing reliability under high-pressure conditions.

[0059] The motor-side interface is designed differently according to the standards of mainstream brands. Special adapter plates are provided for motors of different brands. In addition, a universal adapter plate is also designed with multiple sets of mounting holes to support the customized needs of special motor models.

[0060] The application of adapter 21 brings significant economic benefits. Spare parts inventory costs are reduced by more than 60%, and users only need to keep a small number of adapters to adapt to various motor models. The average maintenance time is shortened from the traditional 45 minutes to 8 minutes, greatly improving equipment availability. Different motor models can be quickly adapted on-site, and oil pump replacement can be completed within 10 minutes in emergencies. Especially in the event of sudden equipment failure, resources can be allocated across brands, greatly improving the flexibility of emergency maintenance.

[0061] Market feedback shows that this adapter panel structure is particularly popular with after-sales service departments and emergency repair teams, as it not only reduces the skill requirements for technicians but also significantly improves the standardization of repair operations.

[0062] During implementation, a detection hole 23 is provided on the side wall of the liquid outlet tank 8, parallel to the liquid outlet hole 9, and a pressure sensor 24 is installed on the opening of the detection hole 23.

[0063] Pressure sensor 24 employs a fiber optic Bragg pressure sensor (high-pressure pulsation monitoring), capable of real-time monitoring of pressure fluctuations within the pump chamber. Unlike the installation location of traditional oil pump pressure sensors, this invention allows the pressure sensor probe to be directly inserted into the pump chamber through a detection hole for detection, enabling faster and more accurate acquisition of oil pressure fluctuation data. See [link to relevant documentation]. Figure 10 This graph compares the pressure monitored internally by the pressure sensor of this invention with the pressure monitored externally by a traditional pressure sensor. It shows that the pressure fluctuation value monitored externally is 2.25%, while the pressure fluctuation value monitored internally is 3.75%, an increase of 66.6%. The monitored data is more accurate and more timely, allowing the control system to adjust the oil pump more quickly and accurately.

[0064] During oil pressure monitoring using pressure sensor 24, fault tree analysis (FTA) can be employed to establish a database. An alarm is triggered when the oil bubble pressure fluctuation frequency exceeds 500Hz and the viscosity reading decreases by more than 20%. Combined with bearing wear warnings, specifically, an alarm is triggered when the increase in the 2×BPFO frequency component in the vibration signal envelope spectrum exceeds a threshold. This allows the driver to obtain the oil pump's health status more promptly, enabling timely maintenance and replacement to prevent more serious accidents.

[0065] One aspect provided by the embodiments of the present invention is a design method for a noise-reducing oil pump, the specific steps of which are as follows:

[0066] S1: Determine the structure and dimensions of each component according to the design requirements. The components include: base, pump housing and pump core.

[0067] S2: Determine the characteristic range of the noise spectrum generated by the noise-reducing oil pump based on the pump speed and the number of gear teeth of the noise-reducing oil pump;

[0068] S3: Divide the feature range into low-frequency noise, mid-frequency noise and high-frequency noise in sequence, and determine the distribution location of the noise reduction slots based on the causes of low-frequency noise, mid-frequency noise and high-frequency noise.

[0069] S4: Guided by Helmholtz resonance theory, acoustic impedance matching principle and viscous loss mechanism, inversion calculations and optimization of the size of noise reduction slots at each distribution location are performed.

[0070] In practice, this invention is based on the Helmholtz resonance principle: the design aims to capture and dissipate acoustic energy. When noise of a specific frequency enters the neck of the noise reduction tank, it excites the oil inside the cavity to produce a violent resonance. The key is that the hydraulic oil has high viscosity, and during the resonance process, huge internal friction is generated between oil molecules and between the oil molecules and the tank wall, thereby irreversibly converting and dissipating the ordered acoustic vibration energy into disordered heat energy.

[0071] Therefore, the essence of noise reduction is not to prevent resonance, but to use the resonance effect to introduce more sound energy into such an efficient "viscous dissipation trap" and convert it into heat energy, so as to achieve the purpose of noise attenuation.

[0072] Its resonant frequency is determined by the formula:

[0073]

[0074] Where A represents the cross-sectional area of ​​the groove opening, V represents the cavity solvent of the noise reduction groove, and L eff represents the effective diameter depth, and c represents the speed of sound in the oil;

[0075] In gear pumps, by designing a noise-reducing groove array of a specific size, noise of different frequencies (such as gear meshing pulsation and oil flow noise) can be selectively absorbed, achieving selective attenuation of sound energy.

[0076] The operating noise of a gear pump mainly originates from flow pulsation and mechanical impact during gear meshing, with its acoustic energy concentrated at the meshing frequency and its higher harmonics. Specifically, the characteristic range is determined using the following expression:

[0077]

[0078] Where n represents the oil pump speed and N represents the number of gear teeth.

[0079] Based on this formula and measured spectrum, in order to systematically design noise reduction structures, it is necessary to scientifically divide the target frequency band according to the spectral characteristics. The noise spectrum exhibits obvious characteristics: the low-frequency region (100-800Hz) concentrates the highest energy discrete tone components such as the meshing fundamental frequency and its second harmonic, which is the most prominent source of roaring sound in subjective hearing; the mid-frequency region (800-3000Hz) is densely distributed with high-energy line spectra caused by meshing high-order harmonics and bearing vibration, which constitute the main body of mechanical noise; while in the high-frequency region (3000-20000Hz), although the line spectrum energy is weakened, broadband turbulent noise is significant, and the physical mechanism of sound waves gradually transforms from macroscopic resonance to microscopic viscous-thermal effects as the wavelength shortens. Based on the differences in energy distribution and acoustic mechanisms, the total frequency band is clearly divided into three sub-domains for targeted processing: the entry segment (100-800Hz), the middle segment (800-3000Hz), and the exit segment (3000-20000Hz), thus laying the foundation for the differentiated design of subsequent resonant units. The dimensions of each segment are determined based on the above division, and inversion calculations and optimizations are performed guided by Helmholtz resonance theory, acoustic impedance matching principles, and viscous loss mechanisms. The specific divisions are as follows:

[0080] Low-frequency noise covers the fundamental frequency and its second harmonic, ranging from 100 to 800 Hz; mid-frequency noise covers high-energy harmonics, ranging from 800 to 3000 Hz; and high-frequency noise covers higher-order harmonics and broadband turbulence noise, ranging from 3000 to 20000 Hz.

[0081] Low-frequency noise mainly includes oil filling pulsation noise generated by gear disengagement cavity, fluid separation noise caused by pressure fluctuation in inlet pipeline, and cavitation noise caused by bubble collapse. Accordingly, noise reduction tanks for low-frequency noise are set in the inlet section outside the inlet and outlet channels in the pump core cavity.

[0082] The main types of mid-frequency noise include pulsating pressure noise generated by gear meshing, fluid burst noise from oil compression and release, and turbulent noise caused by eddies in the high-pressure zone. The noise reduction tank for mid-frequency noise is set in the middle section of the outlet tank within the first distance range from the end point of meshing of the driving gear and the driven gear.

[0083] High-frequency noise mainly includes cavitation noise from oil cavitation and collapse, whistling noise from metal contact friction, and ultrasonic oscillation caused by sudden pressure drop. The noise reduction tank for high-frequency noise is set in the outlet section within the second distance range from the outlet hole in the outlet tank.

[0084] In practice, the Helmholtz resonance frequency formula is the theoretical basis for size inversion. The sound velocity c (1400 m / s) is a known quantity, the target frequency f0 is determined, and the unknown quantities are the neck cross-sectional area A, the groove volume V, and the effective diameter depth L. eff This is a problem with multiple solutions, and a decision needs to be made in conjunction with engineering constraints (such as the internal space of the pump body and the manufacturing process).

[0085] Specifically, the inversion calculation follows this approach: First, the cavity volume V is qualitatively determined based on the target frequency band (a large cavity is needed for low frequencies, and a small cavity is needed for high frequencies). Then, a feasible effective neck depth L is set. eff Finally, the required neck-to-side distance D is obtained by iteratively solving the formula.

[0086] The noise reduction slots in the inlet section employ a mixed configuration of noise reduction slots with different side distances. The size optimization process is as follows:

[0087] Using low-frequency noise as the characteristic frequency of the target noise reduction band, the basic volume of the noise reduction groove is determined by comprehensively considering the physical boundary of the pump core cavity design size and the structural strength. The range of the physical depth of the neck of the noise reduction groove is set by combining the feasibility of the processing technology. Based on the characteristic frequency, the basic volume and the range of the physical depth of the neck, the Helmholtz resonance theory formula is used for iterative calculation to determine the range of the edge distance of the noise reduction groove in the inlet section.

[0088] During implementation, the primary consideration is the physical boundary of the gear cavity within the pump body. For example, measurements from the drawings show a radius of 9.8 mm and a depth of 37.3 mm. To ensure structural strength and accommodate oil flow channels, the maximum depth suitable for arranging the noise-reducing cavity is much less than 37.3 mm. After comprehensive evaluation, a cylindrical cavity with a diameter of 12.0 mm (radius 6.0 mm) and a depth of 10.0 mm was determined to be a safe and effective design. Its basic volume is as follows:

[0089] V1=π×(6.0×10 -3 ) 2 ×10.0×10 -3 ≈1.13×10 -6

[0090] After determining the cavity volume, the characteristic frequencies (250Hz and 800Hz) of the noise reduction target frequency band are used as the design frequencies (f0). The unknowns in the Helmholtz formula are simplified to the neck area (A) and the effective neck depth (L). eff Based on the depth of the noise reduction groove and the feasibility of the manufacturing process, the physical depth (L) of the neck was initially set to a range of 1.0-1.5 mm. Using this parameter as input, iterative calculations were performed, and the required neck offset (D) to meet the two target frequencies was determined to be approximately 1.8 mm and 1.2 mm, respectively. Therefore, this section was ultimately designed as an array of holes with an offset gradually decreasing from 1.8 mm to 1.2 mm and a depth finely adjusted between 1.0 and 1.5 mm, as shown in Table 1. This design, under strict space constraints, still achieved coverage of the target low-frequency band through optimization of geometric parameters.

[0091] Table 1 Structural parameters of the noise reduction groove in the inlet section

[0092]

[0093] In a specific implementation, the noise reduction groove in the inlet section is designed to be located between the non-load-bearing side wall of the pump core (opposite to the surface of gear meshing force) and the gear top circle clearance (which must be greater than the gear radial runout tolerance), and terminates 3-5mm before the gear begins to mesh to prevent interference with the gear oil filling process.

[0094] The noise reduction groove in the middle section adopts a structure in which the distance between the edges gradually decreases from the neck to the bottom of the groove. The size optimization process is as follows:

[0095] Using mid-frequency noise as the characteristic frequency of the target noise reduction band, the physical depth of the neck opening is set to a fixed value. The acoustic impedance matching principle is introduced as a constraint condition to limit the neck opening to the optimal setting value of 0.62. The recommended value of the edge distance of the noise reduction groove is determined by combining the Helmholtz resonance theory.

[0096] Specifically, to ensure consistency in acoustic characteristics, the physical depth (L) of the neck is preferentially set to a fixed value of 1.5 mm. The target frequency (f0) is set to cover this frequency band. Subsequently, acoustic impedance matching theory is introduced as a second constraint, limiting the neck-to-cavity narrowing ratio to approximately the theoretically optimal value of 0.62. Thus, for a cavity with a diameter of 10 mm, its optimal neck hydraulic diameter D... h =10×0.62=6.2mm, corresponding to a recommended side-to-side distance of approximately 1.6mm for a regular hexagon. To expand the working bandwidth, the neck opening size was ultimately designed as a gradient sequence starting from this value and ending at 1.2mm, thereby achieving wideband suppression of core mid-frequency noise while ensuring the peak sound absorption coefficient, as shown in Table 2.

[0097] Table 2 Structural parameters of the middle section noise reduction groove

[0098]

[0099] In a specific implementation, the noise reduction groove in the middle section is designed to be located on the base extending 5-8mm backward from the end point of gear meshing.

[0100] The noise reduction channel at the outlet section adopts a double-layer stepped hexagonal structure, and the size optimization process is as follows:

[0101] To maximize the frictional effect between the sound wave and the hole wall, the neck size was determined based on the principle of viscosity-heat loss. The distance between the upper and lower edges was directly set to 1.0 mm and 0.8 mm, respectively. High-frequency noise was used as the characteristic frequency of the noise reduction target frequency band. The cavity structure of the noise reduction groove was solved by inversion using Helmholtz resonance theory. The layer spacing was optimized and determined using acoustic simulation to construct an impedance transition region between the two layers, thereby improving the coupling and dissipation efficiency of high-frequency sound waves.

[0102] Specifically, given the changing wavelength scale and energy dissipation mechanism of high-frequency sound waves, and the extremely short wavelengths of high-frequency and ultrasonic waves, small resonators are required. This invention prioritizes determining the neck size based on the principle of viscosity-heat loss. To maximize the frictional effect between the sound wave and the hole wall, the distance between the edges of the micro-holes (D) of 1.0 mm in the upper layer and 0.8 mm in the lower layer is directly set, thereby locking the neck area (A). The target frequency (f0) is set in the high-frequency region. Based on this, the micro-cavity structure necessary to achieve the target resonant frequency is solved by inversion using the Helmholtz formula. The 0.3 mm interlayer spacing is determined through acoustic simulation optimization and is used to construct an impedance transition region between the two layers, improving the coupling and dissipation efficiency of high-frequency sound waves. The hole size of 0.8 mm in the lower layer is extremely small, and its mechanism of action goes beyond macroscopic resonance, relying more on the viscosity-heat effect: when the sound wave propagates in such a tiny channel, the friction (viscous loss) and heat exchange (heat conduction loss) with the hole wall are extremely intense, thus directly converting sound energy into heat energy and dissipating ultrasonic energy extremely efficiently. The 0.3 mm interlayer spacing creates a micro-interference space, which further optimizes impedance matching, as shown in Table 3.

[0103] Table 3. Structural Design of Noise Reduction Groove at the Outlet Section

[0104]

[0105]

[0106] In a specific implementation, the noise reduction groove at the outlet section is designed to be located on the base 5-6mm before the oil pump outlet.

[0107] After the design was completed, the internal flow field characteristics of the gear pump were simulated and analyzed using the Fluent simulation software, such as... Figure 11The simulation clearly demonstrates the significant improvement effect of the noise reduction groove structure on oil pressure fluctuations. Simulation results show that the gear pump with the noise reduction groove exhibits more stable pressure characteristics during operation, and the internal pressure pulsation of the gear pump is effectively suppressed. This improvement mainly stems from the guiding and dispersing effect of the noise reduction groove structure on fluid pressure waves, disrupting the coherence of pressure pulsations and reducing pressure peak values. The simulation results verify the effectiveness of the noise reduction groove design from a fluid dynamics perspective, providing a sufficient theoretical basis for product noise optimization.

[0108] Once the design and parameters of the noise-reducing oil pump are completed, it can be manufactured in its entirety according to the following steps:

[0109] Step 1: Preparation of Powder Metallurgy Blanks

[0110] Raw material formulation and mixing: AlSi10Mg aluminum alloy powder with a particle size of 15-45μm was used as the matrix material, and 5wt% nano-alumina (Al2O3, particle size 50nm) was added as the reinforcing phase, along with 3wt% zinc stearate as a lubricant. The powders were three-dimensionally mixed under inert gas protection for 2 hours to ensure uniform distribution of each component.

[0111] Cold isostatic pressing: The mixed powder is loaded into a flexible mold and cold isostatically pressed at 600 MPa for 3 minutes. The resulting blank has a density of over 95% of the theoretical density and includes a pre-formed hole structure. The noise reduction groove size is 0.5 mm larger than the design value as a machining allowance.

[0112] Segmented sintering process: The pressed blank is placed in a vacuum sintering furnace and sintered according to the following temperature curve: the temperature is increased from room temperature to 350°C at a rate of 2°C / min, and held for 1 hour to completely remove the lubricant.

[0113] Solid-state sintering was carried out by increasing the temperature from 350°C to 580°C at a rate of 5°C / min.

[0114] Liquid phase sintering was carried out by increasing the temperature from 580℃ to 620℃ at a rate of 1℃ / min and holding for 30 minutes.

[0115] Remove it after it has cooled to 200°C in the furnace.

[0116] During the sintering process, the oxygen content in the furnace is controlled below 100 ppm, and the porosity of the final blank does not exceed 3%.

[0117] Step 2: Precision machining at a machining center

[0118] Reference positioning and clamping: The pre-forming groove of the powder metallurgy blank is used as the reference, and a three-jaw hydraulic clamp is used for positioning and clamping. The laser centering system ensures that the positioning accuracy reaches ±0.01mm.

[0119] Step-by-step processing:

[0120] Rough machining stage: using Carbide drill bits can quickly remove excess material at a speed of 8000 rpm and a feed rate of 0.1 mm / rev, leaving a finishing allowance of 0.2 mm.

[0121] Semi-finishing stage: Replacement Diamond-coated end mills are used to perform groove contour forming at a speed of 12000 rpm and a radial depth of cut of 0.5 mm, achieving a surface roughness of Ra≤3.2μm.

[0122] Finishing stage: using Polycrystalline diamond (PCD) micro-end milling cutters are used for precision machining at a speed of 20,000 rpm and an axial depth of cut of 0.05 mm to ensure that the final groove diameter tolerance is controlled within ±0.02 mm and the surface roughness reaches Ra≤0.8 μm.

[0123] Real-time detection and compensation: During the machining process, a pneumatic measuring instrument is used for online measurement, and the measurement data is fed back to the CNC system in real time to automatically compensate for dimensional deviations caused by tool wear.

[0124] Step 3: Surface Strengthening Treatment

[0125] Micro-shot peening: Ceramic shot with a diameter of 0.1 mm is used to strengthen the surface of the tank under a pressure of 0.3 MPa, with a coverage of 200%, resulting in a residual compressive stress of -150 MPa on the surface.

[0126] Micro-arc oxidation treatment: Micro-arc oxidation is carried out in a silicate electrolyte, using a constant current mode of 450V and 8A for 30 minutes to form a ceramic coating with a thickness of 50μm and a porosity of 15%.

[0127] Step 4: Quality Inspection and Verification

[0128] Dimensional inspection: A coordinate measuring machine is used to randomly check the hole position accuracy, and the groove center distance tolerance is controlled within ±0.03mm.

[0129] Acoustic performance verification: The natural frequency of each slot is detected by an ultrasonic resonator. Slots that deviate from the design value by more than 5% are marked and reworked.

[0130] Durability test: The finished product is subjected to a pulse pressure test and 500,000 cycles at a working pressure of 25MPa to confirm that the tank structure has no deformation or cracks.

[0131] After fabrication, experimental verification can be performed. Sound pressure level tests were conducted on external gear pump samples with and without noise reduction groove structures. The tests were conducted in a semi-anechoic noise laboratory. The oil tank was placed at least 2 meters away from the test point of the external gear pump, and the oil pipeline was ensured to be without bends. The overflow valve was placed outside the semi-anechoic noise laboratory. The microphone was positioned directly opposite the external gear pump, perpendicular to the pump's axis and at the same horizontal plane as the pump's center. The microphone was 15 cm away from the pump. Before the noise test, venting was performed. After filling the oil tank, the pump was allowed to run at a constant speed of 3000 rpm under no-load until no more gas overflowed.

[0132] Both the external gear pumps with and without noise-reducing grooves use the same motor and controller; the only difference is the inner wall of the gear pump body. Under test conditions, sampling was recorded continuously for 100 seconds, and the time history of the sound pressure level was analyzed. The time span was from the 2nd second to the 100th second of sampling. Since it was a stationary signal, the full 1-second time history was used. The sound pressure level history results are as follows... Figure 12 As shown.

[0133] In the experiment studying the acoustic pressure characteristics of an external gear pump, Figure 12 The sound pressure level curves reveal a significant advantage in noise reduction for the external gear pump with the optimized internal wall noise reduction groove structure. From the 2nd to the 100th second of the test cycle, the sound pressure level of the optimized structure was consistently lower than that of the conventional external gear pump, and the sound pressure level at its noise peak was also significantly reduced. Specifically, the average A-weighted sound pressure level of the external gear pump with the optimized noise reduction groove structure during the test was 51.6 dB(A), compared to 57.7 dB(A) of the conventional structure, a reduction of 6.1 dB(A), or approximately 11%.

[0134] The technical solution of this invention, through innovative structural design, alters the flow characteristics and pressure distribution of the fluid within the gear pump, effectively suppressing the generation and propagation of noise. Furthermore, this optimized solution not only provides a new approach to noise reduction design for external gear pumps but also offers significant reference value for research on sound insulation and noise reduction in external gear pumps.

[0135] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. All equivalent changes made based on the description and drawings of the present invention are included within the scope of the present invention.

Claims

1. A noise-reducing oil pump, comprising: A base, a pump housing, and a pump core; characterized in that the pump housing is disposed on the base, and a pump cavity is formed between the pump housing and the base, and an inlet pipe communicating with the pump cavity is disposed on the pump housing; a pump core seat is disposed on the base, a through hole is disposed in the middle of the pump core seat, an inlet groove is disposed on one side of the through hole and an outlet groove is disposed on the other side of the pump core seat, and an outlet hole communicating with the outside of the base is disposed on the side wall of the outlet groove. The pump core is located inside the pump cavity. The pump core includes a pump core body, through which the pump core cavity is axially oriented. A driving gear and a driven gear mesh with each other inside the pump core cavity. The driving shaft of the driving gear extends a certain length through a through hole from the base and is rotatably and sealingly connected to the through hole. An inlet channel is axially oriented on one side of the pump core cavity opposite to the meshing surfaces of the driving and driven gears, and an outlet channel is axially oriented on the other side. An inlet hole is located on the side of the pump core body opposite to the inlet channel. A pump core cover is located on the top surface of the pump core body, and the bottom surface is connected to the pump core seat. A special-shaped sealing ring is installed between the pump core body and the pump core cover, and between the pump core body and the pump core seat. These special-shaped sealing rings isolate the inlet hole, inlet groove, and inlet channel into an inlet chamber, and the outlet channel, outlet groove, and outlet hole into an outlet chamber. Noise reduction grooves are arranged in a honeycomb array at the inlet section outside the inlet and outlet channels in the pump core cavity, the middle section within the first distance range from the end of the meshing of the driving gear and the driven gear in the outlet groove, and the outlet section within the second distance range from the outlet hole in the outlet groove.

2. The noise-reducing oil pump according to claim 1, characterized in that, The cross-section of the noise reduction groove is a regular hexagon.

3. The noise-reducing oil pump according to claim 2, characterized in that, The distance between opposite sides of the noise reduction groove in the middle section gradually decreases from the neck to the bottom of the groove.

4. The noise-reducing oil pump according to claim 2, characterized in that, The noise reduction channel at the outlet section has a double-layered stepped hexagonal structure.

5. The noise-reducing oil pump according to claim 1, characterized in that, An adapter plate is connected to the lower surface of the base.

6. The noise-reducing oil pump according to claim 1, characterized in that, A detection hole is provided on the side wall of the liquid tank, parallel to the liquid outlet, and a pressure sensor is installed on the opening of the detection hole.

7. A design method for a noise-reducing oil pump, characterized in that, The specific steps for using the noise-reducing oil pump according to any one of claims 1 to 6 are as follows: S1: Determine the structure and dimensions of each component according to the design requirements. The components include: base, pump housing and pump core. S2: Determine the characteristic range of the noise spectrum generated by the noise-reducing oil pump based on the pump speed and the number of gear teeth of the noise-reducing oil pump; S3: Divide the feature range into low-frequency noise, mid-frequency noise and high-frequency noise in sequence, and determine the distribution location of the noise reduction slots based on the causes of low-frequency noise, mid-frequency noise and high-frequency noise. S4: Guided by Helmholtz resonance theory, acoustic impedance matching principle and viscous loss mechanism, inversion calculations and optimization of the size of noise reduction slots at each distribution location are performed.

8. The design method according to claim 7, characterized in that, The feature range is determined in S2 using the following expression: Where n represents the oil pump speed and N represents the number of gear teeth.

9. The design method according to claim 7, characterized in that, S3 specifically includes: low-frequency noise covering the fundamental frequency and its second harmonic, ranging from 100 to 800 Hz; mid-frequency noise covering high-energy harmonics, ranging from 800 to 3000 Hz; and high-frequency noise covering higher-order harmonics and broadband turbulence noise, ranging from 3000 to 20000 Hz. Low-frequency noise mainly includes oil filling pulsation noise generated by gear disengagement cavity, fluid separation noise caused by pressure fluctuation in inlet pipeline, and cavitation noise caused by bubble collapse. Accordingly, noise reduction tanks for low-frequency noise are set in the inlet section outside the inlet and outlet channels in the pump core cavity. The main types of mid-frequency noise include pulsating pressure noise generated by gear meshing, fluid burst noise from oil compression and release, and turbulent noise caused by eddies in the high-pressure zone. The noise reduction tank for mid-frequency noise is set in the middle section of the outlet tank within the first distance range from the end point of meshing of the driving gear and the driven gear. High-frequency noise mainly includes cavitation noise from oil cavitation and collapse, whistling noise from metal contact friction, and ultrasonic oscillation caused by sudden pressure drop. The noise reduction tank for high-frequency noise is set in the outlet section within the second distance range from the outlet hole in the outlet tank.

10. The design method according to claim 7, characterized in that, S4 specifically includes: The noise reduction slots in the inlet section are configured using a mix of slots with different side distances. The size optimization process is as follows: Using low-frequency noise as the characteristic frequency of the target noise reduction band, the basic volume of the noise reduction groove is determined by comprehensively considering the physical boundary of the pump core cavity design size and the structural strength. The range of the physical depth of the neck of the noise reduction groove is set by combining the feasibility of the processing technology. Based on the characteristic frequency, the basic volume and the range of the physical depth of the neck, the Helmholtz resonance theory formula is used for iterative calculation to determine the range of the edge distance of the noise reduction groove in the inlet section. The noise reduction groove in the middle section adopts a structure in which the distance between the edges gradually decreases from the neck to the bottom of the groove. The size optimization process is as follows: Using mid-frequency noise as the characteristic frequency of the target frequency band for noise reduction, the physical depth of the neck opening is set to a fixed value. The acoustic impedance matching principle is introduced as a constraint condition to limit the neck opening to the optimal setting value. The recommended value of the edge distance of the noise reduction groove is determined by combining the Helmholtz resonance theory. The noise reduction channel at the outlet section adopts a double-layer stepped hexagonal structure, and the size optimization process is as follows: To maximize the frictional effect between the sound wave and the hole wall, the neck size was determined based on the principle of viscosity-heat loss. The distance between the upper and lower edges was directly set to 1.0 mm and 0.8 mm, respectively. High-frequency noise was used as the characteristic frequency of the noise reduction target frequency band. The cavity structure of the noise reduction groove was solved by inversion using Helmholtz resonance theory. The layer spacing was optimized and determined using acoustic simulation to construct an impedance transition region between the two layers, thereby improving the coupling and dissipation efficiency of high-frequency sound waves.

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