Chapter 11 Selection
11–13
11-5 Motor shaft conversion load torque
The main load torque calculation expressions are shown below.
Type
Mechanism
Calculation expression
Linear
movement
W
Z
1
Z
2
F
C
F
0
η
Servo-
motor
T
L
=
F in the above expression is obtained from the lower expression
when the table is moved as shown on the left.
F = Fc +
µ
(W · g · F
0
)
Rotary
movement
Servomotor
T
LO
Z
1
Z
2
T
L
= · ·
T
LO
+ T
F
= · · T
LO
+ T
F
Vertical
movement
W
2
W
1
1/n
Servomotor
Guide
Counter-
weight
Load
When rising
T
L
= T
U
+ T
F
When lowering
T
L
= –T
U
·
η
2
+ T
F
T
U
=
T
F
=
F·
△
S
2
×
10
3
πη
V
N
F
2
×
10
3
πη
·
) =
Fc : Force applied on axial direction of moving section (N)
F
0
: Tightening force on inner surface of table guide (N)
W : Total weight of moving section
(kg)
g : Gravitational acceleration
(m/sec
2
)
µ
: Friction coefficient
T
L
: Load torque
(N· m)
F : Force in axial direction of linear motion
machine
(N)
η
: Drive system efficiency
(%)
V : Speed of linear operation object
(mm/min)
N : Motor speed
(r/min)
∆
S: Object movement amount per motor rotation (mm)
Z
1
, Z
2
: Deceleration ratio
T
L
: Load torque
(N· m)
T
LO
: Load torque on load shaft
(N)
T
F
: Motor shaft conversion load friction torque
(N· m)
η
: Drive system efficiency
Z
1
, Z
2
: Deceleration ratio
n
: Deceleration rate
T
L
: Load torque
(N· m)
T
U
: Unbalanced torque
(N· m)
T
F
: Friction torque on moving section
(N· m)
1
n
1
η
Z
1
Z
2
1
η
V
N
·
) =
(W
1
−
W
2
) ·
g
2
×
10
3
πη
(W
1
– W
2
) · g ·
△
S
2
×
10
3
πη
µ
· (W
1
+ W
2
) · g ·
△
S
2
×
10
3
πη
W
1
: Load weight
(kg)
W
2
: Counterweight weight
(kg)
η
: Drive system efficiency
g : Gravitational acceleration = 9.8
(m/sec
2
)
V : Speed of linear operation object
(mm/min)
N : Motor speed
(r/min)
△
S: Object movement speed per motor rotation
(mm)
µ
: Friction coefficient
