CN1420291A - Arc block lower pair overrun clutch - Google Patents

Abstract

An arc block type unidirectional overrun clutch with lower pair is an improvement on prior unidirectional overrun clutch, that is, an additional arc block is used for connecting the external ring, arc block, wedge and internal ring with lower pair. Its advantages are high fatigue limit, high transferred torque, less deformation, high efficiency and long service life.

Description

The arc block type lower pair overrun clutch

Research and development to impulse stepless gear box have been focus＜1 at present 〉, but its vital part is to adopt existing overrun, because its life-span, efficient are low, transmitting torque is little, and make this existing decades of historical up-and-coming production development is slowly always.Improve its performance, it is the problem that adopts higher pair or lower pair in free wheel device after all.The unidirectional wedge-typed overrunning clutch that the existing common interior ring of 1 existing mono-directional overrun clutch introduction is the dome arc as shown in Figure 1.<2>

1) pressure＜2 of voussoir on point of contact〉point of contact a Point of contact b $F_{\mathrm{nb}}=\frac{T_e}{\mathrm{RZtg\&theta;}}---N\&lsqb;2\&rsqb;$ T in the formula _e---the calculating torque N.mm of clutch

R, R ₀---outer shroud inside radius and interior ring outer radius mm

Z---voussoir quantity

The angle of wedge of , θ---inner and outer rings point of contact is in [1] and [2], because R＞R ₀So, F _Na＞F _NbBe to reduce the pressure that a order, encircle in available for the unidirectional wedge-typed overrunning clutch of concave circular arc as shown in Figure 2.B point on a on Fig. 1, b point and Fig. 2 be voussoir under the spring tension effect, constitute the higher pair Line of contact with inner and outer rings respectively, and obtain certain initial friction.With can transmitting torque and non-slip condition is ° of-5 ° θ=3, =4 °-4 °.A on Fig. 1,2, b point all is subjected to unidirectional pulsation circuit extrusion stress and shearing stress.

2) intensity calculates＜2 〉

The contact strength condition that a is ordered

Get $r=\frac{R_0}{4}$ E＝200×10 ³N/mm ²

Behind the abbreviation

Z in the formula---voussoir number

B---high by-pass contact length mm is when outer shroud clockwise rotates, and initial friction makes voussoir and inner and outer rings self-locking, and the three rotates synchronously.When the outer shroud inhour was rotated, outer shroud and voussoir were thrown off, and interior ring does not rotate.

Owing to be that higher pair increases unidirectional pulsation circuit extrusion stress and shearing stress, fatigue limit is reduced, transmitting torque is little.Because area of contact is little, resiliently deformable is big, and the idle running angle increases, and efficient is low.Not only shock resistance is poor, and when the folding number of times increased, the life-span was low.Therefore can only be used in common workplace.The structure of 2 arc block type lower pair overrun clutch and calculating

In order to satisfy impulse stepless gear box the requirement of free wheel device is proposed ideamonger, on the structure of Fig. 2, only increase the arc piece, and connecting with revolute pair between outer shroud, arc piece, voussoir, the interior ring.Then become the arc block type lower pair overrun clutch as shown in Figure 3.

Have half through being one of the revolute pair of R on Fig. 3, half through being r ₀Two of revolute pairs, totally three revolute pairs, its friction garden radius is respectively ρ and ρ ₀The pulling force of spring [3] always makes voussoir [1], arc piece [4] that the trend that clockwise rotates is arranged, and makes three revolute pairs obtain certain initial frictional force.

1) condition of self-locking of three revolute pairs

When outer shroud [5] condition that three equal self-lockings of revolute pair can not be rotated when clockwise rotating is

Force action line ca and O ₁Rubbing, it is tangent to examine the garden, with O and O ₂Cut mutually in the friction garden.During the i.e. equal self-locking of three revolute pairs, could self-locking.

On the slip surface of revolute pair, if having a latching point then this revolute pair get final product self-locking.

Get: ρ=μ R ρ ₀=μ r ₀

Then: $\sin \mathrm{\&theta;}=\frac{\mathrm{\&mu;R}}{R}=\mathrm{\&mu;}$

Because ＞θ so self-locking is to wipe under the identical situation of condition three revolute pairs, only need make

≤arcsinμ

One removes the desirable μ of friction factor=0.14, i.e. =8 °

With can transmitting torque and non-slip condition is ≤5 °, one moves to take =4 °～5 °, θ=3 °～4 °,

Three revolute pairs show that all the condition of self-locking is O when outer shroud [5] inhour is rotated ₂The friction garden outside the af line left side.

Because revolute pair O ₂Not self-locking, remaining two revolute pair can not self-locking.

In real work, outer shroud [5] is three equal self-lockings of revolute pair when clockwise rotating.Owing to exist resisting moment to make part produce resiliently deformable, voussoir [1] pressurized and shortening makes outer shroud [5], arc piece [4], voussoir [1] clockwise rotate a small idle running angle.Internal stress in voussoir [1] is increased to and can makes interior ring [2] rotation or voussoir [1] when no longer shortening, and interior ring [2] ability and outer shroud [5] rotate synchronously.When outer shroud [5] inhour is rotated, three all not self-lockings of revolute pair, interior ring [2] does not rotate.When the stress in the voussoir [1] was zero, three revolute pairs had obtained initial frictional force again.

2) arc piece [4], voussoir [1] are derived by [1] at the suffered extruding force F of ac direction in Fig. 3 Because the ac line is between c, d point, arc piece [4] is stable on the R arc.

3) arc piece [4], voussoir [1] are at the crushing strength σ of ac direction _p ${\mathrm{\&sigma;}}_p=\frac{F}{S}---J/m{m}^2\&lsqb;5\&rsqb;$ The net sectional area mm of S-voussoir [1] in the formula ²Get the net sectional area mm of S-voussoir [1] in the formula by [4] and [5] ²Get by [4] and [5]

When forwards 4 ° to by 5 °, σ _pIncrease 1.26 times.

4) a, b, c cross section shearing stress τ $\mathrm{\&tau;}=\frac{Q}{S}---N/m{m}^2\&lsqb;7\&rsqb;$ Q in the formula---the shearing Na point on the cross section is a dangerous spot,

Get by [8] and [7] formula Owing to be revolute pair, three shear planes are circular shape, have increased shear resistance, and actual value is bigger than calculated value.

5) σ in same lower pair _pWith the ratio of τ be K by [6] ÷ [9]: $\frac{{\mathrm{\&sigma;}}_p}{\mathrm{\&tau;}}=\frac{2}{\sin 2\mathrm{\&alpha;}}=K$ When Φ=5 °, K=11.62 and commaterial one is removed $\frac{{\&lsqb;\mathrm{\&sigma;}\&rsqb;}_p}{\&lsqb;\mathrm{\&tau;}\&rsqb;}=1.96~3.2$ So the lower pair strength check should be with σ _p≤ [σ] _pBe as the criterion.

6) ratio of the high and low secondary τ that parameter is identical is that K is got by [3] ÷ [9]:

Can find out by [1O]:

When 1. only increasing the S in the lower pair, τ reduces in [9], so K increases.

When 2. only increasing the B in the higher pair, τ reduces in [3], so K reduces.

When 3. only increasing Z, because the Z in [3] is in radical sign, τ is increased, so the K value increases.

4. only reduce T _eThe time, higher pair makes τ increase in [3] by the line contact, so the K value increases.Only increase T _eThe time, higher pair transforms to lower pair owing to be out of shape, and the τ in [3] is reduced, so K reduces.

When 5. only reducing , extrusion stress increases in the higher pair, makes τ increase in [3], so K increases.

Example: establish Z=15 S=30 * 40=1200mm ²B=30mm =5 ° T _e=8 * 10 ⁶Nmm brings [10] K=145 into

Promptly higher pair is bigger 145 times than lower pair shearing stress when this identical parameters

During 7) in =5 °, the ac length computation:

In Fig. 3, ac is arc piece [4], voussoir [1] length sum.With the cosine formula of Δ aoc, Δ cof, Δ acf, get quadratic equation with one unknown after the arrangement.Obtain the length (process omission) of ac with radical formula.[11]

If R=200mm is R ₀Ac=100.18mm ° is obtained by [11] in=100mm =5.Ac=100.11mm when =4 °.Be that ac shortening amount Δ L=0.07mm accounts for total length 0.069%.

Ac distortion Δ L when 8) working also can be obtained by Hooke's law $\mathrm{\&Delta;L}=\frac{\mathrm{FL}}{\mathrm{ES}}---\mathrm{mm}\&lsqb;12\&rsqb;$

By [4] and [12]

Ac length when L is unloaded in the formula during =5 °

9) ask fatigue limit ^{＜3 〉}By the empirical correlation of fatigue limit fatigue limit: only get tension and compression σ to the fluctuating circulating stress of structural steel ₀=1.42 σ _-1=1.42 * 0.23 (σ _b+ σ _s)=0.32 (σ _b+ σ _s) σ in the formula ₀-be pulsation circuit endurance limit under pull compression

As adopt steel normalizing σ No. 45 _b=623Mpa σ _s=376Mpa is σ then ₀=0.32 * 999=319Mpa promptly gets σ ₀=319Mpa belongs to design infinite life by the S-N curve

Δ L=0.06mm when 10) inefficacy of free wheel device forwards 4 ° by [11] and [6] known ac to by 5 °, and σ _pIncrease 1.26 times.If σ at this moment _p＜[σ] _p, can be stabilized on 4 ° from the locking angle, if this moment σ _p＞[σ] _p, also can diminish from the locking angle, reach the balance on the stress.If higher pair angle diminishes, voussoir can overturn.Efficient is reduced, and abrasion increases, and clutch was lost efficacy.

11) life-span of the super interesting clutch of more high and low pair

Under the condition of identical torque, lower pair is littler than higher pair contact stress, and abrasion is little, so lower pair is longer than the higher pair life-span.

12) mechanical efficiency of more high and low secondary free wheel device

The principal element that influences mechanical efficiency is the idle running angle, and it belongs to the loss merit.The lower pair contact stress is little under the identical condition of torque, is out of shape for a short time, and the idle running angle is little, so lower pair is than higher pair efficient height, and concrete numerical value is by measuring.3 conclusions:

1) replacing higher pair with lower pair is a leap on the performance of free wheel device.

2) making complexity is more or less the same.

3) created condition for the exploitation impulse stepless gear box

Reference: 1. the design of Ruan Zhong Tang mechanical stepless transmission is rolled up 11-59 Beijing Machinery Industry publishing house 1998 with selecting 19992. Xu Hao mechanical design handbook Volume Four 29-372 Beijing Machinery Industry publishing houses of guide Beijing Chemical Industry Press, 19983. Xu Hao mechanical design handbooks second for use

Claims (5)

1. the arc block type lower pair overrun clutch is made up of voussoir [1], interior ring [2], spring [3], arc piece [4], outer shroud [5], it is characterized in that connecting with three revolute pairs between outer shroud [5], arc piece [4], voussoir [1], the interior ring [2]; When outer shroud [5] three equal self-lockings of revolute pair when clockwise rotating, interior ring [2], outer shroud [5] rotate synchronously; Three all not self-lockings of revolute pair when outer shroud [5] inhour is rotated, interior ring [2] does not rotate.

2. according to claim 1 when outer shroud [5] three equal self-lockings of revolute pair when clockwise rotating, it is characterized in that force action line ca and O ₁The friction garden is tangent, with O, O ₂Cut mutually in the friction garden; Three all not self-lockings of revolute pair when outer shroud [5] inhour is rotated is characterized in that O ₂Rub Cha Yuan outside the af line left side.

3. force action line ca according to claim 2 is characterized in that ca line and af wire clamp angle are and oc line angle theta, is respectively the angle of wedge that a, b are ordered; Three revolute pair self-lockings and non-slip condition are =4 °～5 °, θ=3 °～4 °

4. force action line ca according to claim 3 is characterized in that the c point is between ed; R arc end at arc piece [4] has angle, garden r.

5. arc block type lower pair overrun clutch according to claim 1 is characterized in that changing system into arc block type lower pair double rolling key clutch.

Images