JPS6348691B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a temperature control device for a heating cylinder for heating, melting, and kneading resin in an injection molding machine. Injection molding machines supply resin into a heating cylinder, heat it, melt it, and knead it before injecting it.At this time, the properties of the resin change depending on the amount of heating. It is necessary to keep the temperature of the resin constant. Conventionally, heating cylinder temperature control for injection molding machines is
The temperature of the heating cylinder was measured and the power supplied to the heating source such as a band heater was turned on and off to maintain the heating cylinder at a constant temperature. However, this temperature control measures the temperature of the outer surface of the heating cylinder and does not take into account the heat lag in the radial direction of the heating cylinder. I couldn't control it. In addition, for example, by using the method described in Japanese Patent Application No. 57-68704 filed by the present inventor on April 26, 1982, under the title "Temperature pattern detection method for injection molding machines, etc." Although it is possible to accurately detect the temperature of the resin, it does not take into account the diffused heat flow of the heating cylinder, so it only controls the power supplied to the band heater, and is not sufficient to accurately control the temperature of the resin. Nakatsuta. SUMMARY OF THE INVENTION An object of the present invention is to provide a heating cylinder temperature control device for an injection molding machine that can solve the above-mentioned conventional drawbacks and accurately control the temperature of resin. According to the present invention, in a device for controlling the temperature of a heating cylinder of an injection molding machine, m (m2) of means are provided in the axial direction of the heating cylinder and detect the temperature of the resin in the heating cylinder; means for receiving m outputs of the temperature detection means and executing calculations based on a non-interference control algorithm; and means for supplying electric power to the heating source of the injection molding machine, controlled by the m outputs of the calculation means. A non-interference control device for an injection molding machine heating cylinder is obtained. In the present invention, the influence of heat exchange within the heating cylinder layer, heat flow according to the movement of the molten resin fed in while being heated, and shear heat generated in the resin as the kneading screw rotates is controlled by a mutual interference system. The power of the heating source is controlled by making the mutual interference system non-interfering. The characteristics of the injection molding machine system will be explained below with reference to FIG. In the figure, 1 is a cylinder, 2 is a heater, 3 is a resin, and 4 is a screw. When the injection molding machine is divided into zones in the axial direction as shown in FIG. 1, the cylinder temperature θ _ci [°C] and the resin temperature θ _ri [°C] in zone i are expressed by the following differential equation. θ〓 _ci =B ₁ /ΔxA ₁ w _c c _c qhi−B1α _i /ΔxA ₁ w _c c _c (
θ _c1 −θ _a )−λ/(Δx) ² w _c c _c (θ _c1 −θ _ci-1 )− λ/(Δx) ² w _c c _c (θ _ci −θ _ci+1 )−B ₀ β _i /
ΔxA ₁ w _c c _c (θ _ci −θ _ri )=K _h q _hi −K〓 _i (θ _c1 −θ _a )
− K〓 _i (θ _ci −θ _ci-1 )−K〓 _i (θ _ci −θ _ci+1 )
−K〓 _i (θ _c1 −θ _ri )(1) θ〓 _ri = −B ₀ β _i ／ΔxA ₀ w _r c _r (θ _ri −θ _ci )−A _v
v/ΔxA ₀ (θ _ri −θ _ri-1 ) + Q _di /w _{r cr} = −K〓 _ri (θ _ri −θ _ci )−K _vi (θ _ri −θ _ri-1
)＋q _di (2) K _h =B ₁ /ΔxA ₁ w _c c _c , K〓 _i =B ₁ α _i /ΔxA ₁ w _c c _c , K
〓 _i = λ / (Δx) ² w _c c _c , Kβ _i = B ₀ β _i /ΔxA ₁ w _p c _p , K〓 _ri = B ₀ B _i /ΔxA ₀
w _{r cr} , K _vi = A _v v / ΔxA ₀ , q _di = Q _di / w _{r cr} (3) Here, each symbol is A ₀ : Screw groove cross-sectional area [m ² ], A ₁ : Cylinder cross-sectional area [m ² ], B ₀ : Cylinder inner surface area [m ² ], B ₁ : Cylinder outer surface area [m ² ],
Δx: Axial length of one zone [m], w _c : Cylinder density [Kg/m ³ ], c _c : Cylinder specific heat [J/
Kg・℃], λ: Cylinder thermal conductivity [W/m・
°C], α _i : Heat radiation coefficient [W/m ² · °C], β _i : Heat transfer coefficient between cylinder and resin [W/m ² · °C], q _hi : Amount of heat supplied from heater per area [ J/m ² ], θ _a : Ambient temperature [°C], A _v : Screw groove cross-sectional area perpendicular to resin flow [m ² ] ² w _r : Resin density [Kg/m ² ],
c _r : Specific heat of resin [J/Kg・℃], v: Flow velocity of resin [m/s] (v=2πr ⁿ ₆₀ ), n: Screw rotation speed [rpm], r: Screw radius [m], Q _di : represents the shear calorific value per volume [W/m ³ ]. Therefore, in the case of three zones, if the differential equations of equations (1) and (2) are found for i = 1, 2, and 3, and expressed as a state equation corresponding to the system diagram shown in Figure 2, x = = _{Ax ＋ Bu ＋ w y = Cx _ _ _} θ′ _r3 )′

【formula】

【formula】

[Formula] W = (000q〓 ₁ q〓 ₂ q〓 ₃ )', and each element of matrix A is a ₁₁ = - (K〓 ₁ +K〓 ₁ +K〓 ₁ ), a ₁₂ =K〓 ₁ , a ₁₄ =K〓 ₁
, a ₂₁ =K〓 ₂ , a ₂₂ =−(K〓 ₂ +2K〓 ₂ +K〓 ₂ ), a ₂₃ =K〓 ₂ , a ₂₅ =K〓 ₂
(6) a ₃₂ =K〓 ₃ , a ₃₃ =−(K〓 ₃ +K〓 ₃ +K〓 ₃ ), a ₃₆ =K〓 ₃ a
₄₁ = K〓 _r1 , a ₄₄ = −K〓 _r1 a ₅₂ = K〓 _r2 , a ₅₄ = K _v2 , a ₅₅ = −(K〓 _r2 +K _v2 ) a ₆₃ = K
〓 _r3 , a ₆₅ = K _v3 , a ₆₆ = -(K〓 _r3 + K _v3 ). Here, ( )′ indicates the transposed matrix, θ′ _c1 = θ _c1 −θ _a , θ′ _c2 = θ _c2 −θ _a , θ′ _c3 = θ _c3
−θ _a (7) θ′ _r1 =θ _r1 −θ _a , θ′ _r2 =θ _r2 −θ _a , θ′ _r3 =θ _r3
−θ _a . The conditions for non-interference to be possible for such a system are Each element of D is expressed as K〓 _ri by referring to equation (6).
It consists of _K〓ri is a coefficient related to heat transfer between the cylinder 1 and the resin 3, and since it satisfies the condition of equation (8), non-interference is always possible. As shown in Figure 3 for the above system, u=Kx+Lv v=(v ₁ v ₂ v ₃ )′ (9) Non-interference is performed by applying the state feedback shown in . Here, each element of the feedback matrix K is calculated using the elements of A, k ₁₂ = −a ₁₂ , k ₂₁ = −(a ₅₄ a ₄₁ /a ₅₂ ) −a ₂₁ , k ₂₃ = −a ₂₃ k ₂₄ = a ₅₄ (a ₂₂ + K ₂₂ − a ₄₄ ) / a ₅₂ , k ₃₂ = − ( a ₅₂ a ₆₅ / a ₆₃ ) − a ₃₂ k ₃₄ = − a ₅₄ a ₆₅ / a ₆₃ , k ₃₅ = a ₆₅ ( It is expressed as a ₃₃ + k ₃₃ − a ₅₅ )/a ₆₃ (11). In addition, k ₁₁ , k ₂₂ , k ₃₃ ,
k ₁₄ , k ₂₅ , and k ₃₆ are set to obtain predetermined characteristics. By applying non-interference as described above,
One input v _i (1
i3) will affect only one output θ' _ri (1i3) of the output vector y, and one output θ' _ri will be influenced by only one input v _i . As a result, in the injection molding machine, the control system can be configured in accordance with the state of the resin for each zone, making it possible to improve the accuracy of temperature control. In the present invention, the new vector v is set as V=r−y r=(r ₁ r ₂ r ₃ )′ (12) as shown in FIG. Here, r indicates the target value of the system, that is, the set temperature. FIG. 5 is a block diagram showing an embodiment of the present invention to which the above-mentioned non-interference is applied. In the figure, 1 is a heating cylinder of an injection molding machine, which is made of thick iron and has a cylindrical shape. Three band heaters 2 serving as heating sources are installed outside this heating cylinder 1.
1 to 23 are wound. sr ₁ to _{sr 3} are temperature detection ends for detecting the temperatures θ' _r1 to θ' _r3 of the resin 3, and S _c1 to S _c3 are temperature detection ends for detecting the temperatures θ' _c1 to θ' _c3 of the cylinder 1. Among these, the temperature detection terminals S _r1 to _{S r3} are, for example, the above-mentioned Japanese Patent Application No. 57-68704 filed by the present inventor.
It consists of a thermocouple inserted deeply toward the heating cylinder 1 based on the description in No. 1, and outputs an electromotive force commensurate with the temperature θ' _ri (1i3), which is approximately close to the resin temperature. This X _A = (θ′ _c1 θ′ _c2 θ′ _c3 θ′ _r1 θ′ _r2 θ′ _r3 )
The electromotive force is
Digital quantity X _D by analog-to-digital converter 5
and is input to the arithmetic circuit 6. This calculation circuit 6 executes calculations based on the above-mentioned non-interference control algorithm. That is, X _D is input to matrix calculation units 61 and 62. Matrix calculator 3
2 executes the calculation of Cx _D to find the detected temperature y _D = (θ′ _r1 θ′ _r2
θ′ _r3 )′ is output. This detected temperature _yD is displayed on the display 7 and is input to the subtracter 63.
On the other hand, the digital quantity corresponding to the set temperature r _D input from the input device 8 is input to the subtracter 63, and the subtracter 63 executes r _D −y _D , V _D = v ₁ v ₂ v ₃ )' Output. V _D is input to the matrix calculator 64 .
Kx _D and Lv _D output from the matrix calculators 61 and 64, respectively, are added by an adder 65, and
It is output from the arithmetic circuit 6 as _uD . Arithmetic circuit 6
The digital quantity u _D outputted from is input to the digital-to-analog converter 9, which outputs the analog quantity U _A. This u _A is input as a control signal to the power control devices 101 to 103, and
3, power according to this control signal _uA is supplied to the band heaters 21 to 23, respectively. Here, power control devices 101 to 103, band heaters 21 to 2
3 and the heating cylinder 1, etc., are:
It corresponds to the part surrounded by the dotted line in Figure 3, and u _A
Input the temperature detection terminals S _r1 ~ S _r3 , S _c1 ~ _{S c3}
Output. Note that when a microcomputer is used as the arithmetic circuit 6, the value of K of the matrix arithmetic unit 61 may be calculated by this microcomputer, and the determined constant value may be stored internally.
Calculate the value of K in advance using another calculator,
Only the constant value may be stored in the microcomputer's storage device. In any case, during operation, these constant values are used for on-line control by a microcomputer. Furthermore, even if the heating cylinder 1 of the injection molding machine is replaced, there is sufficient room in the storage device of the microcomputer, so the above constant values for the scheduled heating cylinders can be stored in the storage device in advance. You can also do it. As is clear from the above description, according to the present invention, the resin temperature can be accurately controlled by collecting resin temperature information from at least two temperature detection points and skillfully applying non-interference. be.

[Brief explanation of the drawing]

Figure 1 is a diagram for explaining the characteristics of the system of an injection molding machine to which the present invention is applied, Figure 2 is a system diagram of an injection molding machine using the state space method, and Figure 3 is an injection molding machine using the state space method. Figure 4 is a diagram of a non-interference control system to which the present invention is applied for an injection molding machine using the state space method, and Figure 5 is an implementation of the present invention to which the non-interference of Figure 4 is applied. FIG. 2 is a block diagram showing an example. 1... Heating cylinder, 2, 21-23... Band heater, 3... Resin, 4... Screw, 5...
...Analog-digital converter, 6... Arithmetic circuit, 6
1, 62, 64...matrix calculator, 63...
Subtractor, 65... Adder, 7... Display, 8...
Input device, 9...Digital-analog converter, 10
1 to 103...Power control device.

Claims (1)

[Claims] 1. In a device for controlling the temperature of a heating cylinder of an injection molding machine, m in the axial direction of the heating cylinder.
(m2) means for detecting the temperature of the resin in the heating cylinder; a means for receiving the m outputs of the temperature detecting means and executing calculations based on a non-interference control algorithm; and means for supplying power to a heating source of the injection molding machine.