Showing papers on "Gear pump published in 2019"

Hydraulic control systems

Abstract: Preface. Introduction. I. FUNDAMENTALS. 1 Fluid Properties. 1.1 Introduction. 1.2 Fluid Mass Density. 1.3 Fluid Bulk Modulus. 1.4 Thermal Fluid Properties. 1.5 Fluid Viscosity. 1.6 Vapor Pressure. 1.7 Chemical Properties. 1.8 Fluid Types and Selection. 1.9 Conclusion. 1.10 References. 1.11 Homework Problems. 2 Fluid Mechanics. 2.1 Introduction. 2.2 Governing Equations. 2.3 Fluid Flow. 2.4 Pressure Losses. 2.5 Pressure Transients. 2.6 Hydraulic Energy and Power. 2.7 Lubrication Theory. 2.8 Conclusion. 2.9 References. 2.10 Homework Problems. 3 Dynamic Systems and Controls. 3.1 Introduction. 3.2 Modeling. 3.3 Linearization. 3.4 Dynamic Behavior. 3.5 State-Space Analysis. 3.6 Block Diagrams and the Laplace Transform. 3.7 Stability. 3.8 Compensation. 3.9 Conclusion. 3.10 References. 3.11 Homework Problems. II HYDRAULIC COMPONENTS. 4 Hydraulic Control Valves. 4.1 Introduction. 4.2 Valve Flow Coefficients. 4.3 Two-Way Spool Valves. 4.4 Three-Way Spool Valves. 4.5 Four-Way Spool Valves. 4.6 Poppet Valves. 4.7 Flapper Nozzle Valves. 4.8 Conclusion. 4.9 References. 4.10 Homework Problems. 5 Hydraulic Pumps. 5.1 Introduction. 5.2 Pump Efficiency. 5.3 Gear Pumps. 5.4 Axial-Piston Swash-Plate Pumps. 5.5 Conclusion. 5.6 References. 5.7 Homework Problems. 6 Hydraulic Actuators. 6.1 Introduction. 6.2 Actuator Types. 6.3 Linear Actuators. 6.4 Rotary Actuators. 6.5 Conclusion. 6.6 References. 6.7 Homework Problems. III HYDRAULIC CONTROL SYSTEMS. 7 Valve-Controlled Hydraulic Systems. 7.1 Introduction. 7.2 Four-Way Valve Control of a Linear Actuator. 7.3 Three-Way Valve Control of a Linear Actuator. 7.4 Four-Way Valve Control of a Rotary Actuator. 7.5 Conclusion. 7.6 References. 7.7 Homework Problems. 8 Pump-Controlled Hydraulic Systems. 8.1 Introduction. 8.2 Fixed-Displacement Pump Control of a Linear Actuator. 8.3 Variable-Displacement Pump Control of a Rotary Actuator. 8.4 Conclusion. 8.5 References. 8.6 Homework Problems. INDEX.

Theoretical Investigation into the Ripple Source of External Gear Pumps

Abstract: External gear pumps are among the most popular fluid power positive displacement pumps, however they often suffer of excessive flow pulsation transmitted to the downstream circuit. To meet the increasing demand of quiet operation for modern fluid power system, a better understanding of the ripple source of gear pumps is desirable. This paper presents a novel approach for the analysis of the ripple source of gear pumps based on decomposition into a kinematic component and a pressurization component. The pump ripple can be regarded as the superposition of the displacement solution and the pressurization solution. The displacement solution is driven by the kinematic flow, and it can be derived from the kinematic flow theory; instead, the pressurization solution can be approximated by overlapping the pressurization flow for a single displacement chamber. Furthermore, in this way the changes of these two components with modification of the delivery circuit are determined in both analytical and numerical ways. The result of this analysis provides a good interpretation of the pulsation simulated by a detailed lumped-parameter simulation model, thus showing its validity. The result also indicates that the response of two ripple sources to the change of the loading in the downstream hydraulic circuit is very different. These findings reveal the limitation of the traditional experimental method for determining the pump ripple, that new experimental methods which are more physics-based can be potentially formulated based on this work.

Evaluation of the Hydro—Mechanical Efficiency of External Gear Pumps

Abstract: This paper proposes and describes a model for evaluating the hydro-mechanical efficiency of external gear machines. The model is built considering and evaluating the main friction losses in the machines, including the viscous friction losses at the tooth tip gap, at the bearing blocks-gears gaps, at the journal bearings, and the meshing loss. To calculate the shear stress at each gap interface, the geometry of the gap has to be known. For this reason, the actual position of the gears inside the pump casing and consequent radial pressure distribution are numerically calculated to evaluate the gap height at the tooth tips. Moreover, the variation of the tilt and reference height of the lateral gaps between the gears and the pump bushings are considered. The shear stresses within the lateral gaps are estimated, for different lateral heights and tilt values. At the journal bearings gaps, the half Sommerfeld solution has been applied. The meshing loss has been calculated according to the suggestion of the International Standards. The hydro-mechanical efficiency results are then discussed with reference to commercial pumps experimentally characterized by the authors in a previous work. The average percentage deviation from experimental data was around 2%, without considering the most critical operating conditions (high delivery pressure, low rotational speed). The limits of this approach are also explained. Finally, the role of each source of loss is discussed, considering different operating conditions and two values of fluid viscosity. Lateral gap losses and meshing loss are much more relevant in determining the hydro-mechanical efficiency variation in the pump’s operating range, especially at a low delivery pressure. Moreover, while lateral gap losses increase with the rotational speed, the meshing loss shows the opposite behavior. The tooth tip gap losses are never as relevant, but they increase at high pressure. The journal bearings losses become comparable with the lateral and meshing ones at high delivery pressure values. Considering the pumps analyzed and the operating range of delivery pressure values and rotational speed values, the meshing loss made the mechanical efficiency vary in a percentage range of ±7%, with lateral losses in the range of about the ±15%, when also considering the extreme operating points (low speed, high pressure; high speed, low pressure). The weight of the lateral losses slightly reduced when we analyzed the higher temperature results, while the meshing losses slightly increased.

Investigation of leakage within an external gear pump with new decompression slots: numerical and experimental study

Abstract: Gear pumps are amongst the most common types of positive displacement pumps. Having advantages such as small size, continuous and smooth output flow and high performance, these pumps are mainly used for handling high pressure fluids and flow metering. But the most important weakness of these pumps is the severe radial leakage at high pressures. Hence, it is important to study the leakage types and the methods of eliminating them in order to decrease any performance lost. In this study, a simple external gear pump has been studied numerically, analytically and experimentally. Using a commercial software, the pump leakage, volumetric efficiency and power consumption are studied numerically with respect to cavitation modeling. The numerical result shows good agreement with the experimental and analytical data. A new set of decompression slots on the gears teeth is introduced which eliminates the weakness of the prior methods. The results show that it has eliminated high pressure pulsations and catastrophic cavitation during the meshing process of the gears without increasing the radial leakage. As a result, the pump overall performance increases with smoother outflow. Also, the effect of gear teeth radius/teeth tip length on the pump performance has been studied in various working pressures within a case study. This investigation can be an essential and simple tool to design high performance gear pumps.

Pressure Pulsation and Cavitation Phenomena in a Micro-ORC System

Abstract: Micro-ORC systems are usually equipped with positive displacement machines such as expanders and pumps. The pumping system has to guarantee the mass flow rate and allows a pressure rise from the condensation to the evaporation pressure values. In addition, the pumping system supplies the organic fluid, characterized by pressure and temperature very close to the saturation. In this work, a CFD approach is developed to analyze from a novel point of view the behavior of the pumping system of a regenerative lab-scale micro-ORC system. In fact, starting from the liquid receiver, the entire flow path, up to the inlet section of the evaporator, has been numerically simulated (including the Coriolis flow meter installed between the receiver and the gear pump). A fluid dynamic analysis has been carried out by means of a transient simulation with a mesh morphing strategy in order to analyze the transient phenomena and the effects of pump operation. The analysis has shown how the accuracy of the mass flow rate measurement could be affected by the pump operation being installed in the same circuit branch. In addition, the results have shown how the cavitation phenomenon affects the pump and the ORC system operation compared to control system actions.

Effects of complex graphite-like carbon coating on gear vibration noise

Abstract: In this paper, the effects of substrate surface roughness and the addition of yttrium, cerium and tantalum on thickness uniformity of graphite-like carbon (GLC) coatings on gears were studied by magnetron sputtering method using mosaic targets. And noise reduction effects of gear pump deposited with complex GLC coatings were evaluated at different rotate speeds. The results showed that target-substrate distance, sputtering angle and surface roughness had influences on thickness uniformity of GLC coatings on gear. The introduction of elements Y, Ce and Ta into GLC coatings could effectively improve their thickness uniformity. The complex GLC coating with optimal thickness uniformity on gear exhibited significantly reduction effect for gear noise and the reduction effect for axial vibration was better than that of radial vibrations. Compared with uncoated gears, the noise for the coated gears was decreased by 10 dB at 2000 rpm. Good high-frequency noise reduction was obtained, which could be decreased by 19 dB in the range of 4000–10,000 Hz.

Experimental and theoretical studies on the pressure fluctuation of an internal gear pump with a high pressure

Abstract: In this paper, the flow ripple equation is derived to analyze the effect of working condition on pressure pulsations of an internal gear pump. Results indicate that working pressure has a significa...

Numerical and experimental studies on flow performances and hydraulic radial forces of an internal gear pump with a high pressure

Abstract: Unbalanced radial force is one of the most urgent issues for internal gear pumps (IGPs) working at high working pressures. A numerical model for the prediction of the unbalanced radial force is ess...

Theoretical Analysis and Design of a Variable Delivery External Gear Pump for Low and Medium Pressure Applications

Abstract: This paper describes a unique design concept that is capable of electronically controlling the flow delivered by an external gear pump (EGP). The principle used for varying the flow relies on the variable timing concept which has been previously demonstrated by the author's research team for EGP's operating at high pressures (HPs) (p > 100 bar). This principle permits to vary the flow within a certain range, without introducing additional sources of power loss. In this paper, the above concept has been applied to formulate a design for a variable delivery EGP for low pressure (LP) applications (p < 30 bar), suitable for direct electric actuation. Specific design principles for the gear and the flow variation mechanisms are introduced to limit the force required by the electric actuation, and for maximizing the flow variation range. Also, the low target pressure allows the variable timing principle to be realized with an asymmetric solution, with only one variable timing element present at one side of the gears. A detailed analysis concerning the relationship between the electrically commanded position of the flow varying element and the theoretical flow delivered by the pump is also presented. This analysis is used to formulate analytical expressions for the instantaneous flow rate and the flow nonuniformity of the pump. The paper details the design principle of the proposed variable flow pump and describes the multi-objective optimization approach used for sizing the gears and flow variation mechanism. The paper also discusses the experimental activity performed on a prototype of the proposed unit, able to achieve a flow variation of 31%.

Wind Energy Usage for Building Heating Applying Hydraulic System

Abstract: The most ordinary way to use wind energy for building heating needs is to convert mechanical wind energy into electrical energy and to use electrical energy for heating. Though there are ways to convert mechanical wind energy into thermal energy without transitional energy conversion – hydraulic systems can be implemented for this purpose. Wind rotor gives rotational motion to the pump of hydraulic system and it creates fluid circulation in the hydraulic system. A part of liquid mechanical energy due to hydraulic resistance of the system converts into the thermal energy when the liquid circulates in the close hydraulic loop and it heats up the liquid that can be used for heating purposes. Different hydraulic valves can be integrated in the hydraulic system and they can work as the load-regulating component of the system. The purpose of the study was to adjust the hydraulic load to the optimal value in order to generate a maximum amount of thermal energy. During the study, the work of a wind rotor was simulated by an electric motor, rotated at different frequencies (without feedback). The hydraulic system consisted of a gear pump, an adjustable load regulation valve, pipes, oil tank, sensors for measuring motor shaft rotational speed, oil temperature and pressure. The experiments were carried out at different electromotor speeds: 12.5, 17.5 and 22.5 Hz, and for different oil temperatures in the range of 20 to 50 °C. The relationship between the opening degree of the valve and the amount of generated thermal energy was determined. The study showed that wind energy usage can cover a significant part of the building's thermal energy needs at the same time reducing pollution and the usage of the fossil fuel for heating purposes.

Device and method for preparing low-density polymeric foam beads by utilizing extrusion and foaming of supercritical mixed fluid

Abstract: The invention discloses a device and a method for preparing low-density polymeric foam beads by utilizing extrusion and foaming of supercritical mixed fluid. The device comprises an extruding and mixing unit, a supercritical fluid injection unit, a static mixing unit, a gear pump, a melt cooler, an extruding mold head and an underwater granulating system and the like, wherein the main body of theextruding and mixing unit is a double-screw extruder, screws and a charging barrel are respectively equipped with a special temperature control unit, and the charging barrel is provided with two gas-injecting holes; the static mixing unit is arranged at the downstream of the extruding and mixing unit so as to enhance the mixing effect; the gear pump is arranged at the downstream of the static mixing unit so as to regulate the system pressure; the melt cooler is connected at the downstream of the gear pump so as to regulate the system temperature. The device and method disclosed by the invention have the advantages that the process is stable, the production efficiency is high, and the prepared polymeric foam beads are low in density and uniform in structure.

A Control Algorithm for Improving the Ratio Precision of Solventless Laminating

Abstract: In order to reduce the influence of gear pump flow fluctuation on the mixing ratio precision of the solventless laminator mixing unit, this paper establishes a mathematical model of the instantaneous flow fluctuation of the gear pump, then the theoretical analysis and calculation are carried out. Based on the analysis of the relationship between the flow fluctuation of the gear pump and the angle change, a sinusoidal acceleration and deceleration speed compensation control algorithm is proposed. Through the use of optimization model with the smallest flow fluctuation, and the relevant parameters of the optimal compensation algorithm are determined by the least squares method. Finally, this paper establishes a gear pump flow analysis experimental platform and carry out a flow analysis experiment. Through the measurement and analysis of the sinusoidal acceleration and deceleration speed compensation control algorithm and the gear pump flow without applying the compensation algorithm, the results show that the proposed control algorithm can relative reduce the gear pump flow fluctuation by 62.6%, and the mixing ratio can be controlled within 5 %.

Design of a High Speed Internal Gear Pump to Increase the Power Density of Electro Hydraulic Actuators (EHA) in Mobile Applications

Abstract: Increasing the rotational speed of the internal gear pump entails addressing topics such as cavitation, overheating and filling problems of the tooth spaces. Besides the development of a tooth geometry and flow optimization, using CFD simulation is necessary. This paper discusses the design of the newly developed high speed internal gear pump. This includes a detailed description of the different parts as well as the dimensioning of the pump by using CFD simulations. The geometry of the pressure build-up groove has a significant effect of pressure build up inside the pump. Therefore, three different geometries are investigated. The calculation of the journal bearings for the internal gear as well as for the driving shaft is shown. To avoid cavitation problems, the suction pressure of the pump will be increased up to 25 bar. This paper will show the technical arrangements to reach this high suction pressure level whilst still using a radial shaft seal ring. In order to determine the efficiency of the newly developed high speed pump, a test rig was built up. The test rig allows the measurement of the volumetric efficiency as well as the hydraulic-mechanical efficiency at different operation points up to 10 000 rpm and 250 bar.

Study on Acoustic Performance of a Water Muffler for Gear Pump

Abstract: A water muffler is used for the noise control of a hydraulic pipeline with an external gear pump. An experimental system is established to investigate the acoustic performance of the water muffler, in which the gear pump is utilized as the sound source and power supply. Comparisons between the experimental results of the reference tube, rubber tube, and water mufflers with different inner structures have been made. Numerical simulations on the rubber tube and different water mufflers with various inner structures have been conducted. Simulation results have been compared with the experimental results. These comparison results show that the rubber tube with a compliant wall substantially contributes to the reduction of the noise generated by the gear pump, especially at the high frequency band and relatively low rotate speed of the gear pump. The water muffler results in the enhancement of the noise reduction effect on the rubber tube. With the speed of the gear pump increasing from 1172 r/min to 2344 r/min, the effect of the noise reduction becomes much weaker, since the flow-induced noise gets more intensified. For the rubber tube, in particular, the sound pressure level gets close to that of the reference tube at the speed of 2344 r/min. Moreover, it has been proven by another important experimental result that the length of the inner structure can play a critical role to the flow noise generation.

Deep sea buoy hydraulic system

Abstract: The invention provides a deep sea buoy hydraulic system. The system comprises an inner oil bag, an oil outlet of the inner oil bag is connected with a bidirectional gear pump, the bidirectional gear pump is respectively connected with an oil tank and an oil inlet of an outer oil bag through a supercharging unit, an oil outlet of the outer oil bag is connected with the bidirectional gear pump to form a closed hydraulic oil path, the bidirectional gear pump is matched with the supercharging unit for using, so that the problem that self-suction capacity is insufficient due to a plunger pump is solved, the energy consumption is reduced by the low-pressure bidirectional gear pump and the supercharging unit, and the underwater working time is prolonged; a double-action booster pump is adopted, the interior of the double-action booster pump adopts a mechanical structure mode to achieve supercharging, and the floating and diving flexibility is high, the problem that the occupied space is too large and the load is too large due to the fact that an air pump and an auxiliary structure such as a driving air pump are installed is avoided.

Preliminary testing of the internal gear pump with modifications of the sickle insert

Abstract: This paper presents the modifications that have been made to the sickle insert of the gear pump with internal gearing. This procedure allowed the obtainment of radial compensation. The test stand to plot the characteristics of the pump before, as well as after the first and second modification is discussed. The results of the measurements from the tests conducted are presented. The results obtained confirmed the achievement of radial compensation by cutting the appropriate channel in the sickle insert. As a result, it will be possible to obtain a higher discharge pressure for this type of pump and to increase its efficiency.

Electric gear pump

Abstract: An electric gear pump comprising a gerotor that may rotate about an axis of rotation A, comprising an external spur rotor and an internal spur rotor arranged outside the external spur rotor; a stator having electrical windings arranged outside the internal spur rotor; at least one magnet at least partially housed in the internal spur rotor in such a way as to cause the gerotor to rotate when the electrical windings of the stator are supplied with current; in which the internal spur rotor comprises a cylindrical external surface centred on the axis of rotation A; the magnet comprises an external surface separated from the external surface of the internal spur rotor; the external surface of the magnet is shaped in such a way as to define a constant radial distance d between the magnet and the corresponding portion of the external surface of the internal spur rotor.

Analysis of the Comparative Advantages of Gear Pumps Indicators

Abstract: Hydraulic pumps belong to the basic devices of each hydraulic system, because they convert mechanical energy to the pressure of the working fluid. As a significant number of drive solutions are realized by gear pumps, special attention will be dedicated to them in this paper. Their basic comparative advantage is in the simplicity of conservative solutions as well as relatively simple production. This implies, for the buyer, an acceptable price and not a negligible or favorable mass ratio and the achieved strength. For this reason, the authors of this paper will define all the indicators of this conclusion. In support of this assertion, we will analyze the gears of production of the famous Serbian manufacturer, PPT-HIDRAULIKA ad from Trstenik. The same will show tabs and diagrams.

Study on wear mechanism of gear pump end plate of combined harvester based on CFD fluid analysis

Abstract: Aiming at the floating end plate wear of the high pressure gear pump of combine harvester, the key factors that lead to overturning moment of the end plate and the dynamic equilibrium mechanism of the end plate were studied emphatically. The internal flow field of gear pump with a model of gear pump of a certain type combine harvester was analyzed using CFD software, and according to the characteristics of the end plate structure, the differential equation about the compression force and the anti – thrust was established, and the overturning moment change rules of the end plate in the meshing period of 1 wheel tooth can be obtained. Meanwhile, the experimental system was established to verify the theoretical analysis results. The experimental data show that the error of the overturning moment test and the theoretical value is 4.18% under rated condition and when the gear angle φ = 14°, the overturning moment reaches the maximum value Ms = 82.16 N·m. The research provides theoretical basis and technical support for the structural optimization design to reduce the wear of end plates.

A Study on Noise Reduction of Gear Pumps of Wheel Loaders Based on the ICA Model.

Abstract: In order to reduce the noise level of wheel loaders caused by gear pumps and realize environmentally sustainable development, the noise generation mechanism of a gear pump was studied, and the influence of flow pulsation and gear impact on noise was analyzed. In order to reduce the interference of other noise sources on the noise level of the gear pump, a noise test rig was established. The mixed noise signals obtained from the rig test were separated using the ICA model. The ICA model includes the following algorithms: The fast Fourier transform (FFT), independent component analysis (ICA) and inverse fast Fourier transform (IFFT). Some theories about the influence of the teeth number and teeth profile on noise were analyzed by theory and simulation. A noise reduction strategy was proposed by increasing the teeth numbers and modifying the teeth profile of the gear pump. The tests results showed that the noise values of the external and the driver’s ear of the wheel loader were reduced to 1 and 2.2 dB (A), respectively. This proves the effectiveness of the optimization scheme of gear pump noise reduction.

PERFORMANCE PREDICTION AND DESIGN OPTIMIZATION OF A kW-SIZE RECIPROCATING PISTON EXPANDER WORKING WITH LOW-GWP FLUIDS

Abstract: Micro-ORC systems represent a promising technology in the field of the energy conversion from lowgrade temperature sources. However, nowadays the working efficiency are still relatively low, resulting from the lack of appropriate expander machines but also from the need of optimal working fluid. The ideal working fluid should maximize the performance of the system for given operating conditions (as the hot source temperature) and, at the same time, it must respect the environmental impact restrictions, linked to the fluid ozone depletion potential (ODP) and global warming potential (GWP). In this study, low-GWP fluids, as R1234yf and R1234ze(E) have been compared with R134a, as working fluid of a kW-size reciprocating piston expander and the optimization of the built-in volume ratio has been performed for each analyzed fluid in design conditions. To this purpose, a previously calibrated and validated semi-empirical model of the expander has been integrated with a new gear pump model, in order to simulate the volumetric machines into the real operation of the ORC system. The comprehensive model is conceived to accommodate the change of the working fluid: model parameters taking into account the thermo-fluid-dynamic properties of the fluid are updated compared to the original values calibrated over R134a by means of an extensive experimental campaign.

Intelligent heat dissipation method and device for generator of wind driven generator set

Abstract: The invention discloses an intelligent heat dissipation method for a generator of a wind driven generator set. When the generator temperature is not larger than the set threshold value and the outputpower is larger than the rated power or the generator temperature is larger than the set threshold value, an electric grid is used for supplying electricity, and a gear pump drive motor is driven to drive a gear blade pump to conduct heat dissipation; and when the generator temperature is not larger than the set threshold value and the output power is not large than the rated power, a gearbox output counter shaft is used for driving the gear blade pump to conduct heat dissipation. The invention further discloses a heat dissipation device which comprises a temperature detection unit, a controlunit and a switch unit. The switch unit is used for switching the gear blade pump to be connected with the gear pump drive motor or the gearbox output counter shaft. The temperature detection unit isused for detecting the generator temperature and sending the generator temperature to the control unit, and the control unit controls the switch unit according to the generator temperature and the output power. The intelligent heat dissipation method and device for the generator of the wind driven generator set have the beneficial effects that heat dissipation is reliable, and the power generationamount is increased.

Influence of Addendum Modification Factor on Root Stresses in Normal Contact Ratio Asymmetric Spur Gears

Abstract: Tooth root crack is considered as one of the crucial causes of failure in the gearing system and it occurs at the tooth root due to an excessive bending stress developed in the root region. The modern power transmission gear drives demand high bending load capacity, increased contact load capacity, low weight, reduced noise and longer life. These subsequent conditions are satisfied by the aid of precisely designed asymmetric tooth profile which turns out to be a suitable alternate for symmetric spur gears in applications like aerospace, automotive, gear pump and wind turbine industries. In all step up and step down gear drives (gear ratio > 1), the pinion (smaller in size) is treated as a vulnerable one than gear (larger in size) which is primarily due to the development of maximum root stress in the pinion tooth. This paper presents an idea to improve the bending load capacity of asymmetric spur gear drive system by achieving the same stresses between the asymmetric pinion and gear fillet regions which can be accomplished by providing an appropriate addendum modification. For this modified addendum the pinion and gear teeth proportion equations have been derived. In addition, the addendum modification factors required for a balanced maximum fillet stress condition has been determined through FEM for different parameters like drive side pressure angle, number of teeth and gear ratio. The bending load capacity of the simulated addendum modified asymmetric spur gear drives were observed to be prevalent (very nearly 7%) to that of uncorrected asymmetric gear drives.

Gear mesh geometry effect on performance improvement for external gear pumps

Abstract: The parameters of the involute and cycloidal gearing which influence on fluid volume at the tooth space are analysed. It is established that to a greater extent on the flow rate of the pump with involute gearing is influenced by the radial clearance coefficient and the profile shift coefficient. The radii ratio of the auxiliary and pitch circles, as well as the radial clearance coefficient, mainly affect the flow rate of the pump with cycloidal gearing. Since the gear module is determined for reasons of pump flow rate, the teeth has a significant safety factor for contact stress and especially bending stress. This allows a wide variation of the gearing parameters in greater limits than in transmissions. The dependences of the fluid volume at the tooth space in the cycloidal gearing on the radial clearance coefficient, on the radii ratio of the auxiliary and pitch circles, on the fillet radius coefficient, is found. The boundaries of the variation of the gearing parameters were established taking into account the bending strength of the teeth. The analysis is carried out using the finite element method. Recommendations for the use of cycloidal gearing in external gear pumps have been developed.