Internal Gear Pump Resin Casing and Sintered Metal Rotors
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Solution Overview
Problem
Internal gear pumps face challenges with high manufacturing costs due to complex machining processes and metal abrasion issues, particularly when pumping liquids with poor wetting effects, leading to reduced durability and performance.
Innovation Solution
The internal gear pump features a casing injection-molded from a resin composition with a metal bottom face, sintered metal rotors, and a sintered metal cover, eliminating the need for machining and reducing metal abrasion through improved frictional abrasion characteristics and sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the casing is made from cast iron or aluminum and machined to form the trochoid-receiving recess, then dimensional precision and sealing performance are improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The casing is constructed as a composite structure combining cast iron or aluminum base material with resin material (epoxy resin, polyurethane resin, or polyester resin) applied to the inner surface. This composite construction allows the use of cost-effective casting processes while achieving the dimensional precision and surface quality required for the trochoid-receiving recess through the resin layer, thereby reducing manufacturing cost while maintaining precision.
Solution Approach 2:
Instead of machining the entire casing surface, the resin material is applied locally to the inner surface where the trochoid-receiving recess is formed. This localized treatment provides the necessary dimensional precision and sealing performance only where required, reducing overall manufacturing complexity and cost while maintaining critical precision.
2Strength
If metal rotors are used, then structural strength is improved, but metal abrasion increases particularly when pumping liquids with poor wetting effects, reducing reliability
Solution Approach 1:
The rotors are constructed as composite structures with metal base material (providing structural strength) and resin material (providing abrasion resistance). The resin coating on the rotor surfaces prevents direct metal-to-metal contact and reduces abrasion when pumping liquids with poor wetting effects, while the metal core maintains the required structural strength.
Solution Approach 2:
The resin material acts as an intermediary layer between the metal rotor surface and the pumped liquid. This intermediate layer prevents direct contact between the metal and abrasive liquids, reducing metal abrasion while allowing the metal structure to provide mechanical strength.
3Reliability
If machining processes are used to form the trochoid-receiving recess, then sealing performance is improved, but manufacturing time and device complexity increase
Solution Approach 1:
The traditional mechanical machining process is replaced with a chemical/resin-based process. The resin material is applied to the casing inner surface and cured to form the trochoid-receiving recess, eliminating the need for complex machining operations while achieving adequate sealing performance and reducing manufacturing time.
Solution Approach 2:
The manufacturing approach changes from mechanical removal of material (machining) to chemical/resin-based formation of the recess. This parameter change in the manufacturing process reduces time and complexity while maintaining the functional requirements for sealing.
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
This configuration reduces manufacturing costs, minimizes metal abrasion, enhances sealing, and maintains performance consistency across various liquids, including those with poor wetting effects, while preventing liquid leakage and maintaining dimensional precision.
Implementation Method 1
at least some of the casing (5) in which is formed a recess (5a) for receiving the trochoid (4) is a body injection-molded from a resin composition
Implementation Method 2
The outer rotor (2), inner rotor (3), and cover (6) are sintered metal bodies
Implementation Method 3
improves the frictional abrasion characteristics of the outer rotor (2) and inner rotor (3)
Implementation Method 4
enhances sealing, and maintains performance consistency across various liquids, including those with poor wetting effects, while preventing liquid leakage
Implementation Method 5
The inner rotor (23) and outer rotor (22), which is fixed to a drive shaft, rotate along with the rotation of the drive shaft and act to suction and discharge liquids
Implementation Method 6
The rotation of the rotors increases the volume, and suctions liquid from an inlet into the suction-side chamber, which is under negative pressure. This suction-side chamber decreases in volume as a result of rotation of the trochoid 24 and is converted to a discharge-side chamber with increased internal pressure
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Provided is an internal gear pump requiring fewer machining steps, allowing inexpensive manufacture, and offering high safety from the standpoint of function. The internal gear pump 1 comprises: a trochoid 4 in which an inner rotor 3 having a plurality of outer teeth is eccentrically and rotatably accommodated in an outer rotor 2 having a plurality of inner teeth, the outer teeth meshing with the inner teeth, and in which a suction-side chamber for suctioning liquid and a discharge-side chamber for discharging liquid that has been suctioned into the suction-side chamber are formed in between the inner teeth and outer teeth; a casing 5 in which is formed a recess 5a for accommodating the trochoid 4; and a cover 6 for closing off the recess 5a of the casing 5. At least some of the casing 5 is a body injection-molded from a resin composition. The invention also comprises a groove 5d in a portion of the recess 5a of the casing 5 in which the outer periphery is sealed, with a sealing ring 13 installed therein, and bushings 7 made from sintered metal that are provided integrally during injection molding in bolt fixing hole portions.