Geared Hydraulic Apparatus Noise Reduction via Curved Tooth Profiles
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Solution Overview
Problem
Conventional geared hydraulic pumps experience noise issues due to fluid encapsulation and ripple noise caused by discontinuous volume variations during gear meshing, which are difficult to address with existing solutions, especially at high pressure differentials.
Innovation Solution
The design incorporates helical gearwheels with a significant helix angle and undercuts on the lateral abutment means to minimize noise and pulsation, allowing for a higher number of teeth and improved sealing without by-pass between intake and delivery, achieving reduced noise and increased volumetric output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional spur gearwheels with involute tooth profile are used, then the structure is simple and easy to manufacture, but fluid is trapped and compressed in the meshing zone causing harmful local stress peaks and direct operating noise
Solution Approach 1:
The patent applies curved tooth profiles instead of conventional straight involute profiles. The tooth flanks are designed with specific curvature radii (R1, R2, R3, R4) to control the meshing process, eliminating closed fluid entrapment zones while maintaining manufacturing feasibility through standardized gear cutting processes
Solution Approach 2:
The patent modifies the tooth profile parameters by defining specific curvature radii and pressure angle variations along the tooth flank. These parameter changes transform the meshing characteristics to prevent fluid encapsulation, reducing direct noise while preserving the basic gear manufacturing process
2Device complexity
If conventional gearwheels are used, then the structure is simple, but irregularity in fluid transfer causes ripple noise and pressure pulsation in the user circuit
Solution Approach 1:
The curved tooth profiles ensure continuous and smooth fluid transfer from inlet to outlet. The meshing process maintains constant volumetric displacement without discontinuities, eliminating the root cause of ripple noise and pressure pulsation while keeping the gear pump structure simple
3Object-generated harmful factors
If helical gearwheels are used to reduce ripple noise, then fluid entrapment areas extend helically creating potential by-pass routes between intake and delivery, requiring complex solutions
Solution Approach 1:
The patent uses curved tooth profiles on spur gearwheels that achieve smooth continuous fluid transfer without extending entrapment areas helically. This eliminates by-pass routes while maintaining simple spur gear construction, avoiding the complexity of helical gear solutions
4Object-generated harmful factors
If the number of teeth is increased to reduce pulsation, then the gearwheels become larger and more complex, increasing manufacturing difficulty
Solution Approach 1:
The curved tooth profiles with optimized curvature radii enable smooth fluid transfer with fewer teeth. The parameter optimization allows achieving low pulsation and ripple noise without increasing the number of teeth or gear dimensions, maintaining manufacturing simplicity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution significantly reduces noise and pulsation while maintaining high volumetric output, providing reliable and economical operation even at high pressure differentials, with improved sealing characteristics and simpler manufacturing compared to conventional solutions.
Implementation Method 1
the pumped fluid is encapsulated, i.e. trapped, and compressed or in any case subjected to volume variations in the spaces enclosed between the profiles of the teeth in the meshing zone
Implementation Method 2
there is also a known problem arising from the phenomenon of irregularity, or 'ripple', in the transfer of the fluid which entails an indirect operating noise, known as ripple noise, linked to the flow rate pulsation
Data Source
Figure 1~3
Figure 2
Figure 4~5
AI summary
An improved geared hydraulic apparatus, comprising a pair of meshing gearwheels, mounted to be reciprocally rotatable in a casing between an inlet side and an outlet side for a fluid having, in use, a substantially transverse flow with respect to the axes of rotation of the gearwheels. The meshing gearwheels create, during their reciprocal rotation, progressive meshing configurations between respective co- operating teeth. In at least one of said progressive meshing configurations is defined, in at least one cross- section of the gearwheels, at least one closed area between respective fluid entrapment teeth. The closed area decreases until it is substantially cancelled out at and around at least one other, separate progressive meshing configuration between the aforesaid respective co-operating teeth.