CN103603802A - External gear pump with offset gear pair - Google Patents

Abstract

The invention discloses an external gear pump with an offset gear pair. According to the gear pump, by horizontally shifting a central connection line of the offset gear pair from a position coinciding with the central line of the pump body to an oil discharge chamber side by a tiny distance, a tooth crest convergence oil wedge structure with a maximum tooth crest clearance on the oil absorption and a minimum tooth crest clearance on the oil discharge side can be formed. The convergence oil wedge can give full play to a dynamic lubrication effect in the tooth crest clearance, improve the lubrication performance, and enhance the volumetric efficiency, thus being especially suitable for high speed light load working conditions.

Description

A kind of external gear pump with biased teeth wheel set

Technical field

The present invention relates to a kind of external gear pump, particularly relate to a kind of external gear pump with biased teeth wheel set.

Background technique:

External gear pump is a kind of power tool of pumping work fluid, because having the aspect advantages such as price, reliability, life-span and suction capacity, applies quite extensive.

Mainly in external gear pump have four pairs of friction pairs, wherein, the failure probability of the friction pair of pump housing internal surface and the end-surface friction pair of driving and driven gear is the highest, and the internal leakage amount of the gap width in these two friction pairs while having determined this pump running.

Radial distance between pump tooth top and pump case, claims again tip clearance.During this time in gap, liquid is on the one hand under the effect of pressure difference between two teeth groove, generation from the high pressure side of force feed to the leakage of the low voltage side of oil suction, the viscous friction being caused by the peripheral velocity of top circle on the other hand, small part liquid is with to high pressure side from low voltage side again.Tip clearance increases leakage loss compared with conference, and volumetric efficiency declines; Gap is too small makes frictional loss increase, and mechanical efficiency declines.By being conceived to the relation in mechanical efficiency, volumetric efficiency and gap, can derive theoretic best tip clearance, but owing to not considering the aspect factor such as biasing, deflection of pump body of axle, actual operation is poor.In fact, scrape the frequent generation of shell phenomenon for fear of tooth top, the assemblage gap of tooth top is generally at 0.1mm～0.15mm, unsuitable too small, and the caused volumetric efficiency of assemblage gap declines thus, rather obvious.

When pump is when moving, owing to inhaling, pressing the poor caused lateral thrust of pressure at both sides, the concentricity of gear shaft and bearing is inadequate, and the factor such as pump housing stress deformation, by making, the radial clearance of each tooth top is also unequal, and near inlet port place, forming minimum value, pressing oil port to form maximum value, containing the moving lubricating effect of pump housing internal surface friction pair.

Summary of the invention

The object of the present invention is to provide a kind of external gear pump with biased teeth wheel set, this gear pump can make the moving lubricating effect in tip clearance be not fully exerted, and greasy property improves, and volumetric efficiency is improved.

The external gear pump with biased teeth wheel set provided by the invention, comprise driving gear, driven gear, the pump housing, axle, bearing, front cover and rear end cover, driving gear and the driven gear formation gear pair that is meshed, the line of centres of described gear pair moves a slight distance from the position overlapping with the center line of the pump housing to oil-discharging cavity one lateral deviation, with form maximum tip clearance in intake side and minimum tip clearance the tooth top convergence oil film wedge structure in oil extraction side, to be Offset calculated by the minimal condition formula of tooth top leakage flow described offset distance.

The gear pair place system of coordinates x of existing external gear pump _co _cy _ccenter o _cwith housing place system of coordinates x _ko _ky _kcenter o _koverlap, (note: the outlet pressure p that supposes the force feed side of pump as shown in Figure 1 ₂inlet pressure p with intake side ₁, on arbitrary position within it, be continuous distributed), the oil clearance h at inlet port place before pump operation ₁with the oil clearance h that presses oil port ₂gap h with initial setting ₀equate, as shown in a in Fig. 1, after pump operation, due to the impact of the factors such as deflection of pump body of pressurised oil side, make the gap h at inlet port place ₁with the gap h that presses oil port ₂no longer equal, as shown in b in Fig. 1.Now, h ₂> h ₁, fail to form the oil film wedge that effectively derives from convergence gap in the friction pair of pump housing internal surface, do not meet the essential condition that produces moving lubricating effect.

As when pump designs, in advance by gear pair center o _cat pump case center o _kbasis on, along x _kaxially force feed lateral deviation is moved one section of slight distance e, makes the gap h near inlet port place ₁, by minimum value originally, become maximum value, press the gap h of oil port ₂, by maximum value originally, become minimum value, as shown in Figure 2.Now, h ₁> h ₂, in the friction pair of pump housing internal surface, formed the oil film wedge that effectively derives from convergence gap, meet to produce the essential condition of moving lubricating effect, the moving lubricating effect in the friction pair of pump housing internal surface can be effectively played.

To sum up, the present invention is owing to adopting the line of centres of gear pair from original position to force feed side Parallel offset one slight distance, thereby can form maximum tip clearance and at the tooth top of oil extraction side, restrain oil film wedge structure at intake side and minimum tip clearance, this convergence oil film wedge can make the moving lubricating effect in tip clearance be not fully exerted, thereby the greasy property of external gear pump is improved, and volumetric efficiency is improved.The working condition that is particularly useful for high speed light loading.

Accompanying drawing explanation

Fig. 1 is that gear pair is without the tip clearance distribution schematic diagram before and after the external gear pump pump operation of biasing.

Fig. 2 is the postrun tip clearance distribution schematic diagram of external gear pump after gear pair biasing.

Fig. 3 is endless inclined plane slide block schematic diagram.

Fig. 4 is for moving front and back and having the postrun tooth top leakage flow schematic diagram of biasing without biasing.

Fig. 5 is that the leakage flow of the external gear pump after gear pair biasing is with the variation schematic diagram of rotating speed and outlet pressure.

In figure: 1-driving gear, 2-driven gear, 3-pump housing

Embodiment

The external gear pump of embodiment's tip clearance internal pressure linear distribution

The present invention includes driving gear 1, driven gear 2, axle, bearing, the pump housing 3, front cover and rear end cover, driving gear 1 and the driven gear 2 formation gear pair that is meshed, the present invention adopts gear pair is offset to a slight distance e(along the axial force feed side of xk (being oil-discharging cavity) is Offset), as shown in Figure 2, this Offset e adopts with the following method and calculates.

Biasing oil film wedge structure shown in Fig. 2, along the circumferential direction launches, and formation ，Gai plane of inclination, oil film wedge plane of inclination as shown in Figure 3 meets the relevant tribology theory of endless inclined plane slide block.In figure, U represents the travelling speed of tooth top, is gear angular velocity of rotation ω and Outside radius r _aproduct; The length l of inclined plane slide block is the angle in Fig. 1

with Outside radius r _awith the lubricated length factor K of tooth top _aproduct, wherein,

for the angle of the tip clearance between pump suction, force feed mouth corresponding to the driving wheel center of circle, N is

the corresponding number of teeth,

for the center of circle angle of wheel top circle, as shown in Figure 1.

According to the relevant tribology theory of endless inclined plane slide block, the leakage flow Q that must flow to intake side by tip clearance by force feed side is

$Q=Q_p-Q_{\mathrm{\&omega;}}=\frac{\mathrm{<figure-callout\; id="2"\; label="B\; h"\; filenames="HDA0000432063700000011.png,HDA0000432063700000022.png"\; state="\{\{state\}\}">B</figure-callout>}{h}_{}^{}{}_2^3{(K+1)}^2}{6\mathrm{\&mu;l}(K+2)}(p_2-p_1)-r_a\mathrm{\&omega;B}{h}_2\frac{K+1}{K+2}---\left(1\right)$

In formula, K=h ₁/ h ₂-1 is convergence ratio; Q _pfor by pressure reduction (p ₂-p ₁) differential pressure flow that causes; Q _ωfor the shearing flow that has ω to cause; B is the width of gear; μ is the viscosity of fluid.

As the initial value of pump tip clearance is made as h ₀, for before the operation shown in a in Fig. 1 without bias conditions, have h ₁=h ₀; h ₂=h ₀; h ₁+ h ₂=2h ₀; K=0.

For after the operation shown in b in Fig. 1 without bias conditions, establish the deflection of pump body of force feed side at force feed mouth oil clearance h ₂the changing value at place is K _bh ₀, wherein, K _bfor deformation coefficient, this coefficient can draw by pump housing mechanical analysis or through finite element analysis.If axle causes force feed mouth oil clearance h to intake side biasing in bearing ₂the changing value at place is K _ph ₀, wherein, K _pfor the biasing coefficient of axle, this coefficient can be drawn by the Gap Analysis of axle and bearing.As measure-alike in inlet port and the force feed mouth of establishing pump,, h ₁=(1-K _p) h ₀; h ₂=(1+K _b+ K _p) h ₀; h ₁+ h ₂=2h ₀+ K _bh ₀; K=-(2K _p+ K _b)/(1+K _p+ K _b).

For bias conditions after the operation shown in Fig. 2, as it is measure-alike to establish inlet port and the force feed mouth of pump, has

h ₁+ h ₂=2h ₀+ K _bh ₀.If e=K _eh ₀, K _efor the biasing coefficient of gear pair,

If K _e,ebiasing COEFFICIENT K _ecLV ceiling limit value, it is defined as follows

In formula, h ₂₀the h determining for the processing roughness by Topland and shell inner surface ₂the minimum value in gap.

As take modulus as 3mm, and the number of teeth is 10, and pitch circle pressure angle is 20 °, and pitch circle working pressure angle is 25 °, h ₀=0.13mm, p ₂=1MPa, p ₁=0.1MPa, rotating speed 3000rpm, viscosity 0.0262Pa.s, gets K _b=0.15, K _p=0.1, B=20mm, n=7, h ₂₀=0.01mm is example.

Corresponding to the correlation computations result in b in a, 1 in Fig. 1 and tri-kinds of situations of Fig. 2, as shown in Figure 4.Now, as get just bias COEFFICIENT K _e=0.77, that is, Offset e=0.77 * 0.13 ≈ 0.1mm, the leakage flow before and after biasing is by 6.973 * 10 before setovering so ^-6m ³/ s reduces to after biasing-1.313 * 10 ^-5m ³/ s, has reduced (6.973+1.313)/6.973 ≈ 118.8% from the leakage rate of tip clearance, not only there is no leakage flow, and by the flow of increasing export, volumetric efficiency has been greatly enhanced.

In addition, in different rotating speeds and different outlet pressure situation, leakage flow Q is with biasing COEFFICIENT K _esituation of change, as shown in Figure 5, can find out, rotating speed is higher, just bias coefficient is less, leakage flow is less, is even negative value; Outlet pressure is larger, and just bias coefficient more approaches CLV ceiling limit value, and leakage flow is larger.

For have such as 1～2 tooth sealing isoequilibrium groove improve radial force measure time, except N=1～2 and h ₁or h ₂calculating location slightly outside difference, other can calculate according to this method.

Offset value is less, in practice, need consider deflection of pump body, and axle-bearing is to the biasing of inlet port, and the factor of processing, manufacture equal error aspect.In addition, due to the biasing of gear pair, therefore the present invention is only applicable to ratchet pump.

Claims (1)

1. an external gear pump with biased teeth wheel set, comprise driving gear (1), driven gear (2), the pump housing (3), axle, bearing, front cover and rear end cover, driving gear (1) and driven gear (2) the formation gear pair that is meshed, it is characterized in that: the position that the line of centres of gear pair overlaps from the center line with the pump housing (3), to oil-discharging cavity one side translation one slight distance, is restrained oil film wedge structure at intake side and minimum tip clearance at the tooth top of oil extraction side to form maximum tip clearance.

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