Practice of Mechanical Design - APS

五维生物

2015-12-01

APS, ME

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V belt convertor and its Helical tooth cylindrical gear speed reducer Design

Requirement

V belt

use Y112M-4 motor
blower speed 750 r/min
work 16 h eveyday

Gear

3 axis
2 class
work precondition

Aim

V Belt

motor calculation
v-belt design
component design
key choose and check

Gear

motor choose
gear design
axis design
bearing choose
key and coupling choose
assembly and component drawing
design calculation sheet

V Belt Design

motor calculation

In reality need to choose, in this task, assume the motor is Y112M-4

4 Kw
1440 r/min

v-belt design

$i\rightarrow P_{ca}\rightarrow d_{d1}\rightarrow v_1\rightarrow d_{d2} \rightarrow L_{d} \rightarrow a\rightarrow \alpha_1\rightarrow z\rightarrow F_0\rightarrow F_p$

Transmission ratio $i=\dfrac{n_1}{n_2}=\dfrac{1440}{750}=1.92$
calculate power $P_{ca}=K_AP$
- $K_A$ work hour and load type
- blower : fluid
$P_{ca}, n_1$$\rightarrow$ Type A : $d_d=75-100$mm
decide $d_{d1}$– trail and error method
1. choose $d_{d1}$, if $v_1\in [5,25]$m/s
2. then $d_{d2}=id_{d1}$
  
  round up according to table
$a\approx 2d_{d2}, \in [0.7,2](d_{d1}+d_{d2})$
get $\alpha_1\approx 180-(d_{d2}-d_{d1})$, should$\ge 120^\circ$
number of belt
Initial $F_0$
Axis $F_p=2zF_0 \sin\frac{\alpha_1}{2}=1081N$

component design

belt wheel
- small$\rightarrow$motor
  - $\Phi$28mm
  - long 60mm
  - HT150

key choose and check

Gear Reducer Design

motor choose

from main axis to motor axis

$P_w$$\rightarrow$$\eta$$\rightarrow$ $P_d$ $\rightarrow$ $n_d$

Final choose Y112M-4 with 4 kw power and speed 1440 r/min

Y for continuous work

Overall ratio

$i=\dfrac{n_m}{n_w}=31$

$i_1=(1.1-1.5)i_2=6.35$
$i_2=4.89$

Dynamic Calculation

Gear design

Low speed pair

material, tooth number, precision
- helical angle $\beta=15^\circ$
- pressure angle $\alpha=20^\circ$
- 7 class
- small
  - 40Cr
  - tempering and surface quenching
  - surface 48-55HRC
  - inner 260-280 HBS
- big
  - 45
  - tempering and quenching
  - surface 40-50 HRC
  - inner 230-250HBS
Tooth surface contact fatigue strength

trail and error method, set $z_3=23, z_4=z_3i_2=113$
1. get pitch circle diameter from
  - face width $\phi_d$
  - transmission ratio $u$
  so
2. change pitch circle
Root bending fatigue strength
1. trail and error method, get modulus
  
  when
2. modulus modify
  
  $m_n=2$
$z_3=\dfrac{d_3\cos\beta}{m_3}=18.338$, no root cutting $z_3=21$

$z_4=uz_3=103$, prime number to each other
other calculation
2 strength check
- tooth surface for 1
- root surface for 2

High speed Pair

design part the same

first choose $z_1=23, z_2=z_1i_1=146$
Tooth Surface fatigue strength
- $d_1=21.794$mm
- $m_n=0.915$mm
Root bending fatigue strength
- $m_n$=2mm
- $z_1=20$
- $z_2=uz_1$=127
other calculation
strength check

Interference check

do intervene

$z_1=20, z_2=127, z_3=26,z_4=127$

Recheck Low Speed

center distance
pitch circle
strength check

Axis design

dmin Calculation

interference check fail, change again

Axis I

Basic
Force
- circumferential force : $F_t$
- radial force : $F_r$
- axial force : $F_a$
Design
- Angular contact ball bearings
Force Calculation
bending twist combination check

$\sigma_{ca}=\dfrac{\sqrt{M_2^2+(\alpha T_1)^2}}{W}\ge [\sigma_{-1}]$
Dangerous cross section check
- round corner stress concentration influence
- interference fit influence
- key influence

Axis II

the same

Basic

Force

Design
- Tapered Roller Bearings
Force Calculation
Bending twist check
Dangerous section check

Axis III

basic
force
design
force calculation
Bending twist check
Dangerous section check

Gear Design

Type

low speed
- small : solid
- big
  - B
  - $D_0$
  - $c$
  - $D_1$
  - $D_3$
  - $D_4$
high speed
- big : like above

Bearing lifetime check

Axis I 70000C

$F_{r1}F_{r2}\rightarrow F_d\rightarrow F_a\rightarrow P\rightarrow L_h$

Axis II 30306

Axis III 30212