US2006145379A1PendingUtilityA1
Method and device for pressure control of electric injection molding machine
Est. expirySep 17, 2023(expired)· nominal 20-yr term from priority
Inventors:Yoshinori Okazaki
B29C 45/77B29C 2945/76006B29C 2945/76013B29C 2945/7602B29C 2945/7612B29C 2945/7621B29C 2945/76498B29C 2945/76605B29C 2945/76665B29C 2945/76859
48
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Claims
Abstract
A rotational angle of a motor operative to propel forward a screw in an injection molding machine is detected at an encoder. An output from the encoder is employed to obtain an angular velocity ω of the motor. From the obtained angular velocity ω, an estimated melt pressure value δˆ that contains no differential term is derived using a certain observer theory. The estimated melt pressure value δˆ is employed to calculate a torque command value T CMD for the motor, which is fed back to the motor. Thus, precise propelling power control unaffected by noises can be executed without the use of a pressure sensor such as a load cell.
Claims
exact text as granted — not AI-modified1 . A method of controlling pressure in an electric injection molding machine, comprising:
detecting an angular velocity X of a motor operative to propel forward a screw in an injection molding machine; deriving an estimated melt pressure value δˆ, based on an observer, from said detected angular velocity ω of said motor and a torque command value T CMD given to said motor; and controlling said motor such that said estimated melt pressure value δˆ follows a melt pressure setting δ REF .
2 . The method of controlling pressure in an electric injection molding machine according to claim 1 , wherein said observer is represented by the following Expression 1.
ⅆ
ⅆ
t
(
ω
^
δ
^
)
=
(
d
1
1
/
J
d
2
0
)
(
ω
^
δ
^
)
+
(
1
/
J
0
)
T
CMD
+
(
1
/
J
0
)
F
(
ω
)
-
(
d
1
d
2
)
ω
[
Expression
1
]
where ωˆ: Estimated value of Angular velocity of Motor
d 1 , d 2 : Certain coefficients
J: Inertia moment over Injection mechanism
F(ω): Dynamic frictional resistance and Static frictional resistance over Injection mechanism
3 . The method of controlling pressure in an electric injection molding machine according to claim 1 , wherein said observer is represented by the following Expression 2.
[Expression 2] ωˆ=ωˆ −1 +{d 1 (ωˆ −1 −ω)+(1 /J ) ( T CMD −1 +δˆ −1 +F (ω))} d t δˆ=δˆ −1 +{d 2 (ωˆ −1 −ω)} d t where ωˆ: Estimated value of Angular velocity of Motor d 1 , d 2 : Certain coefficients J: Inertia moment over Injection mechanism F(ω): Dynamic frictional resistance and Static frictional resistance over Injection mechanism x −1 : Value of x at Immediately preceding processing period
4 . The method of controlling pressure in an electric injection molding machine according to claim 1 ,
wherein said screw in said injection molding machine and said motor are coupled together via a belt suspended around pulleys mounted on respective rotation shafts, and wherein said observer is represented by the following Expression 3. ⅆ ⅆ t ( ω ^ M ω ^ L F ^ δ ^ σ ^ ) = ( d 1 0 - R M J M 0 0 d 2 0 R L J L 1 J L 0 d 3 + K b R M - K b R L 0 0 0 d 4 K w K wd R L J L K wd J L 1 d 5 0 0 0 0 ) ( ω ^ M ω ^ L F ^ δ ^ σ ^ ) + ( 1 J M 0 0 0 0 ) T CMD + ( 0 1 J L 0 K wd J L 0 ) F d ( ω L ) - ( d 1 d 2 d 3 d 4 d 5 ) ω M [ Expression 3 ] where d 1 -d 5 : Certain coefficients J M : Inertia moment at Motor side ω M : Angular velocity of Motor R M : Pulley radius at Motor side F: Tension of Belt K b : Spring constant of Belt J L : Inertia moment at Screw side ω L : Angular velocity at Screw side R L : Pulley radius at Screw side F d (ω L ): Dynamic frictional resistance at Screw side K w : Elastic modulus of Resin K wd : Coefficient of Viscosity of Resin σ: Force of Screw pushing Resin
5 . The method of controlling pressure in an electric injection molding machine according to claim 1 ,
wherein said screw in said injection molding machine and said motor are coupled together via a belt suspended around pulleys mounted on respective rotation shafts, and wherein said observer is represented by the following Expression 4. ω ^ M = ω ^ - 1 M + { d 1 ( ω ^ - 1 M - ω M ) + 1 J M ( T - 1 CMD - R M F ^ - 1 ) } dt
ω ^ L = ω ^ - 1 L + { d 2 ( ω ^ - 1 M - ω M ) + 1 J L ( R L F ^ - 1 + δ ^ - 1 + F d ( ω L ) ) } dt
F ^ = F ^ - 1 + { d 3 ( ω ^ - 1 M - ω M ) + K b ( R M ω ^ - 1 M - R L ω ^ - 1 L ) } dt
δ ^ = δ ^ - 1 + { d 4 ( ω ^ - 1 M - ω M ) + K w ω ^ - 1 L + K wd J L ( R L F ^ - 1 + δ ^ - 1 + F d ( ω L ) ) + σ ^ - 1 } dt
σ ^ = σ ^ - 1 + d 5 ( ω ^ - 1 M - ω M ) dt [ Expression 4 ] where d 1 -d 5 : Certain coefficients J M : Inertia moment at Motor side ω M : Angular velocity of Motor R M : Pulley radius at Motor side F: Tension of Belt K b : Spring constant of Belt J L : Inertia moment at Screw side ω L : Angular velocity at Screw side R L : Pulley radius at Screw side F d (ω L ): Dynamic frictional resistance at Screw side K w : Elastic modulus of Resin K wd : Coefficient of Viscosity of Resin σ: Force of Screw pushing Resin x −1 : Value of x at Immediately preceding processing period
6 . The method of controlling pressure in an electric injection molding machine according to claim 1 ,
wherein said screw in said injection molding machine and said motor are coupled together via a belt suspended around pulleys mounted on respective rotation shafts, and wherein said observer is represented by the following Expression 5. ⅆ ⅆ t ( ω ^ M ω ^ L F ^ δ ^ ) = ( d 1 0 - R M J M 0 d 2 0 R L J L 1 J L d 3 + K b R M - K b R L 0 0 d 4 0 0 0 ) ( ω ^ M ω ^ L F ^ δ ^ ) + ( 1 J M 0 0 0 ) T CMD + ( 0 1 J L 0 0 ) F d ( ω L ) - ( d 1 d 2 d 3 d 4 ) ω M [ Expression 5 ] where d 1 -d 4 : Certain coefficients J M : Inertia moment at Motor side ω M : Angular velocity of Motor R M : Pulley radius at Motor side F: Tension of Belt K b : Spring constant of Belt J L : Inertia moment at Screw side ω L : Angular velocity at Screw side R L : Pulley radius at Screw side F d (ω L ): Dynamic frictional resistance at Screw side
7 . The method of controlling pressure in an electric injection molding machine according to claim 1 ,
wherein said screw in said injection molding machine and said motor are coupled together via a belt suspended around pulleys mounted on respective rotation shafts, and wherein said observer is represented by the following Expression 6. ω ^ M = ω ^ - 1 M + { d 1 ( ω ^ - 1 M - ω M ) + 1 J M ( T - 1 CMD - R M F ^ - 1 ) } dt
ω ^ L = ω ^ - 1 L + { d 2 ( ω ^ - 1 M - ω M ) + 1 J L ( R L F ^ - 1 + δ ^ - 1 + F d ( ω L ) ) } dt
F ^ = F ^ - 1 + { d 3 ( ω ^ - 1 M - ω M ) + K b ( R M ω ^ - 1 M - R L ω ^ - 1 L ) } dt
δ ^ = δ ^ - 1 + d 4 ( ω ^ - 1 M - ω M ) dt [ Expression 6 ] where d 1 -d 4 : Certain coefficients J M : Inertia moment at Motor side ω M : Angular velocity of Motor R M : Pulley radius at Motor side F: Tension of Belt K b : Spring constant of Belt J L : Inertia moment at Screw side ω L : Angular velocity at Screw side R L : Pulley radius at Screw side F d (ω L ): Dynamic frictional resistance at Screw side x −1 : Value of x at Immediately preceding processing period
8 . The method of controlling pressure in an electric injection molding machine according to claim 3 , 5 or 7 , further comprising:
calculating said torque command value T CMD for said motor based the following Expression 7; and feeding back said torque command value to said motor. [Expression 7] T CMD =k p (δ REF −δˆ)+α where kp: Certain constant α: Certain function or constant
9 . An apparatus for controlling pressure in an electric injection molding machine, comprising:
an observer arithmetic unit operative to derive an estimated melt pressure value δˆ, based on an observer, from an angular velocity ω of a motor operative to propel forward a screw in an injection molding machine and a torque command value T CMD given to said motor; and a torque arithmetic unit operative to calculate said torque command value T CMD for said motor using said estimated melt pressure value δˆ derived at said observer arithmetic unit and feed back said torque command value to said motor.
10 . The method of controlling pressure in an electric injection molding machine according to claim 1 , further comprising deriving a dynamic frictional resistance F(ω) from a relation between a velocity or position and a torque or current value associated with said motor at the time of injection with no resin loaded.
11 . The method of controlling pressure in an electric injection molding machine according to claim 1 , further comprising:
defining a dynamic frictional resistance F(w) as a sum of a velocity-dependent component and a load-dependent component; deriving said velocity-dependent component of said dynamic frictional resistance from a relation between a velocity or position and a torque or current value associated with said motor at the time of injection with no resin loaded; and deriving said load-dependent component of said dynamic frictional resistance from a relation between a torque or current value and a pressure value at the time of injection with a plugged nozzle.Join the waitlist — get patent alerts
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