CN110687941A - System and method for synchronously controlling temperatures of upper die and lower die of 3D cover plate glass - Google Patents

Abstract

A system and a method for synchronously controlling the temperature of an upper mold and a lower mold of 3D cover plate glass comprise an upper mold main loop, an upper mold auxiliary loop, a lower mold main loop and a lower mold auxiliary loop, the temperature of an upper mold heating wire and the temperature of a lower mold heating wire are detected, difference is made according to the temperatures, then the obtained temperature deviation signal is used as a power compensation signal of the upper mold heating wire and the lower mold heating wire to adjust the power of the heating wires in real time, and the difference between the output temperature of the upper mold and the lower mold and the target set temperature of the mold is used as an input regulating quantity, so that the effective control and adjustment. The invention solves the problem of large temperature overshoot of the product, thereby improving the temperature control precision of the die. The control precision of the upper die and the lower die is guaranteed, the effect of high-precision synchronous temperature control of the upper die and the lower die is achieved, the dynamic performance of the system in the temperature transferring process is improved, the problem of synchronous control and precision of the upper die and the lower die of the 3D cover plate glass is solved, and the yield and quality of the 3D cover plate glass in forming are improved.

Description

A 3D cover glass upper and lower mold temperature synchronization control system and method

technical field

The invention belongs to the technical field of 3D cover glass temperature control, in particular to a method for controlling the temperature synchronization of upper and lower molds on a 3D cover plate.

Background technique

With the wide application of wireless charging technology and flexible OLED, the cover glass needs to be matched into a curved shape, which is called 3D cover glass in the industry. At present, many flagship models of mobile phone manufacturers have launched 3D cover models. The 3D glass cover can be smoothly connected to the middle frame at 180°, which is more ergonomic, thus greatly improving the feel of the sliding screen. Glass materials are superior to metal and plastic materials in terms of anti-electromagnetic shielding, machinability, and aesthetics. Mobile phone manufacturers also use 3D glass to replace metal or plastic back covers for product differentiation and wireless charging technology needs. The hot bending forming process is currently the mainstream forming process of 3D glass.

The performance of hot bending die material requires that the material should have the characteristics of fine grain, dense and uniform structure, high thermal stability, easy processing, good thermal conductivity, and small thermal expansion. Generally, alloys, ceramics and graphite can be selected, but the excellent characteristics of graphite are more in line with the requirements of 3D cover glass hot bending molds. Most of the industry uses graphite as the mold raw material. In order to improve the uniformity of the product, the graphite mold for 3D glass is generally For use, that is, the concave and convex dies are used together.

The concave and convex molds of graphite molds are independently controlled, but the problem of poor product uniformity is not effectively solved in practice. This is because the heat flux density in each area is different. In the process of independent temperature control of the concave and convex molds, the temperature rise and fall are not synchronized, and the temperature control of the concave and convex molds is coupled with each other. Concave and convex mold temperature temperature difference phenomenon.

3D glass hot bending forming process:

Preheating stage: After the original glass is put into the graphite mold, it enters the preheating zone, where the mold is heated, and the temperature of the glass is gradually increased after the heat conduction of the mold, and the temperature transitions to the hot bending stage smoothly and stably.

Hot bending forming stage: After the glass enters this area, the temperature reaches the working temperature, deforms under the action of external force, and finally reaches the same curvature as the mold. This stage should be combined with the glass deformation point and softening point to set the temperature.

Annealing stage: The residual stress of the glass is eliminated in this area, and the temperature should be set according to the annealing point and strain point of the glass.

Cooling stage: Under the action of the cooling device, the glass is cooled and shaped, and the temperature is set according to the heat conduction of the mold, so as to avoid the glass warping exceeding the standard.

In the process of hot bending, temperature and pressure are the most important control parameters. A slight change in temperature and pressure near the critical point of hot bending will cause significant changes in hot bending. If the temperature is set too low, it is easy to cause the glass to fail to reach the The temperature of the deformation point is crushed under pressure; the temperature of the upper and lower molds of the mold is inconsistent, resulting in inconsistent heating rates on the upper and lower surfaces of the glass, which will cause the glass to bend, and in severe cases, crack under stress. It is of great significance to study the temperature synchronization control technology of the upper and lower molds in the hot bending forming process to improve the yield and quality of 3D cover glass forming.

The traditional upper and lower mold temperature control structure is parallel control, that is, the temperature target value of each area is the same, and the upper and lower mold temperatures are independently controlled by themselves. The speed is different, which causes the temperature and surface temperature of the upper and lower molds to be out of sync.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned technical problems, the present invention provides a temperature synchronization control system and method for the upper and lower molds of the 3D cover glass.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical solutions:

A 3D cover glass upper and lower mold temperature synchronization control system, comprising an upper mold main circuit, an upper mold sub-circuit, a lower mold main circuit and a lower mold sub-circuit;

The main circuit of the upper mold has the main controller of the upper mold and the heating wire of the upper mold, and the auxiliary circuit of the upper mold has the sub-controller of the upper mold. The lower die main circuit has a lower die main controller and a lower die heating wire, and the lower die sub circuit has a lower die sub controller, and the output ends of the lower die main controller and the lower die sub controller are respectively connected to the lower die heating wire input connection;

The difference between the output temperature of the upper die heating wire and the target setting temperature of the die is used as the input adjustment amount of the upper die main controller, and the output temperature of the upper die heating wire and the output temperature of the lower die heating wire are used as the upper die pair control. The input adjustment amount of the upper mold controller, the output of the upper mold main controller and the output of the upper mold sub-controller are superimposed as the input adjustment amount of the upper mold heating wire;

The difference between the output temperature of the heating wire of the lower die and the target setting temperature of the die is used as the input adjustment amount of the main controller of the lower die. The input adjustment amount of the lower mold main controller and the output of the lower mold sub-controller are superimposed together as the input adjustment amount of the lower mold heating wire.

The upper mold main controller, upper mold sub-controller, lower mold main controller and lower mold sub-controller are all PID controllers.

A 3D cover glass upper and lower mold temperature synchronous control method, comprising the following steps:

Given the target setting temperature Sv(t) of the mold, the output temperature of the heating wire of the upper die is detected as v _u (t), and the output temperature of the heating wire of the lower die is recorded as v _d (t);

Calculate each temperature difference

e _u (t)=Sv(t)-v _u (t), _{ed (t)=Sv(t)-v d (t), e ud ( t} )=v _u (t)-v _d (t ), e _du (t)=v _d (t)-v _u (t),

Calculated u _u (t), u _d (t), u _ud (t), u _du (t) control variables, where u _u (t) is the output of the main loop control value of the upper die, and u _d (t) is the lower The output of the control value of the main loop of the mold, u _ud (t) is the output when the upper mold sub-circuit is controlled, and u _du (t) is the output of the control value of the lower mold sub-circuit;

The superposition of u _u (t) and u _ud (t) is used as the input control value of the heating wire of the upper die, and the superposition of _ud (t) and u _du (t) is used as the input control value of the heating wire of the lower die.

Described u _u (t), u _d (t), u _ud (t), u _du (t) control quantities are controlled by PID controller, adopt PID control algorithm to calculate and obtain: PID controller is made up of proportional unit (P), The integral unit (I) and the differential unit (D) are composed, and the relationship between the input e _u (t) and the output u _d (t) is:

In the formula,

分别为误差，误差积分，误差微分项；

are error, error integral, and error differential term respectively;

k _p , k _i , k _d are proportional coefficient, integral coefficient, differential coefficient, respectively,

u _d (t)=PID( _ed (t))

u _u (t)=PID(e _u (t))

u _ud (t)=PID(e _ud (t))

u _du (t)=PID(e _du (t)).

The present invention introduces a cross-coupling structure, which not only controls the temperature of the heating wire of the upper die and the lower die separately, but also uses the temperature difference between the heating wire of the upper die and the heating wire of the lower die as a control input adjustment value, which effectively improves the temperature synchronization performance of the upper and lower die. , so as to realize the temperature synchronization of the upper and lower molds while ensuring its own control accuracy, so as to achieve the effect of high-precision synchronous temperature control of the upper and lower molds. Dynamic performance, solve the problem of synchronization and accuracy of 3D cover glass upper and lower mold control, and improve the yield and quality of 3D cover glass molding.

Description of drawings

Accompanying drawing 1 is the system connection schematic diagram of the present invention;

Figure 2 is a schematic diagram of a cascade PID mold temperature control structure.

Detailed ways

In order to further understand the features, technical means, and specific goals and functions of the present invention, the present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in accompanying drawing 1, the present invention discloses a kind of 3D cover glass upper and lower mould temperature synchronous control system, including upper mould main circuit, upper mould auxiliary circuit, lower mould main circuit and lower mould auxiliary circuit;

The main circuit of the upper mold has the main controller of the upper mold and the heating wire of the upper mold, and the auxiliary circuit of the upper mold has the sub-controller of the upper mold. The lower die main circuit has a lower die main controller and a lower die heating wire, and the lower die sub circuit has a lower die sub controller, and the output ends of the lower die main controller and the lower die sub controller are respectively connected to the lower die heating wire input connection.

The difference between the output temperature of the upper die heating wire and the target setting temperature of the die is used as the input adjustment amount of the upper die main controller, and the output temperature of the upper die heating wire and the output temperature of the lower die heating wire are used as the upper die pair control. The input adjustment amount of the upper mold controller, the output of the upper mold main controller and the output of the upper mold sub-controller are superimposed together as the input adjustment amount of the upper mold heating wire.

The difference between the output temperature of the heating wire of the lower die and the target setting temperature of the die is used as the input adjustment amount of the main controller of the lower die. The input adjustment amount of the lower mold main controller and the output of the lower mold sub-controller are superimposed together as the input adjustment amount of the lower mold heating wire.

The upper mold main controller, upper mold sub-controller, lower mold main controller and lower mold sub-controller are all PID controllers.

By making the output temperature difference between the heating wire of the upper die and the heating wire of the lower die, and then using the obtained temperature deviation signal as the power compensation signal of the heating wire of the upper and lower die to adjust the power of the heating wire in real time, so as to ensure the control accuracy of itself, and to adjust the power of the heating wire in real time. It can take into account the temperature synchronization of the upper and lower molds, so as to achieve the effect of high-precision synchronous temperature control of the upper and lower molds. It does not affect the control accuracy of the system, but also improves the dynamic performance of the system during the temperature transfer process.

A 3D cover glass upper and lower mold temperature synchronous control method, comprising the following steps:

Given the target setting temperature Sv(t) of the mold, the output temperature of the heating wire of the upper die is detected as v _u (t), and the output temperature of the heating wire of the lower die is recorded as v _d (t);

Calculate each temperature difference

e _u (t)=Sv(t)-v _u (t), _{ed (t)=Sv(t)-v d (t), e ud ( t} )=v _u (t)-v _d (t ), e _du (t)=v _d (t)-v _u (t),

Calculated u _u (t), u _d (t), u _ud (t), u _du (t) control variables, where u _u (t) is the output of the main loop control value of the upper die, and u _d (t) is the lower The output of the control value of the main loop of the mold, u _ud (t) is the output when the upper mold sub-circuit is controlled, and u _du (t) is the output of the control value of the lower mold sub-circuit;

The superposition of u _u (t) and u _ud (t) is used as the input control value of the heating wire of the upper die, and the superposition of _ud (t) and u _du (t) is used as the input control value of the heating wire of the lower die.

Described u _u (t), u _d (t), u _ud (t), u _du (t) control quantities are controlled by PID controller, adopt PID control algorithm to calculate and obtain: PID controller is made up of proportional unit (P), The integral unit (I) and the differential unit (D) are composed, and the relationship between the input e _u (t) and the output u _d (t) is:

In the formula,

分别为误差，误差积分，误差微分项；

are error, error integral, and error differential term respectively;

k _p , k _i , k _d are proportional coefficient, integral coefficient, differential coefficient, respectively,

通过该控制量，实现输入量的调节，保证上模 加热丝和下模加热丝的温度的同步性，从而确保上模和下模的加热温度。

Through this control amount, the adjustment of the input amount is realized, and the synchronization of the temperature of the heating wire of the upper die and the heating wire of the lower die is ensured, thereby ensuring the heating temperature of the upper die and the lower die.

It can be seen from the above that the upper die main loop control variable output u _u (t) and the lower die main loop control variable output u _d (t), while conventionally adjusting their own errors, also use the auxiliary loop to adjust the upper The temperature difference between the die heating wire and the lower die heating wire is used to adjust the input quantity, which can effectively solve the problem that the temperature of the upper and lower dies is not synchronized due to the uneven heat flow density caused by excessive temperature rise in some areas.

In the present invention, the measured output temperature of the heating wire of the upper mold and the output temperature of the heating wire of the lower mold are respectively made difference, and used as the input adjustment amount, which is a cross-coupling structure, which can effectively improve the synchronization of the temperature of the upper mold and the lower mold. .

In addition, in order to avoid the steady-state oscillation of the system, the system adopts the control strategy of automatic switching of sub-region PID parameters. A single PID parameter does not apply to all temperature zones. According to the debugging experience, the system divides the temperature range into low temperature zone, medium temperature zone and high temperature zone according to the temperature zone, and debugs separately according to the set value of the temperature and the actual value at the current moment, so as to select the appropriate PID parameters to achieve accurate temperature control. Effect. As shown in Figure 2, on the loop, through two PIDs, the output temperature of the heating wire temperature control of the mold is v'(t), the output of the mold temperature control is v(t), and the output of the mold temperature control is the same as that of the mold. The difference between the target set temperature and the input of the first-stage PID, the temperature control output of the heating wire and the output of the first-stage PID are made difference and used as the input of the second PID, and the output of the second PID u(t) is used as the heating wire input volume.

In addition, when implementing the application,

(1) Set Sv(t) according to the 3D cover glass process, and set the PID parameters of the low temperature zone, the medium temperature zone and the high temperature zone respectively;

(2) The temperature v _d (t) and v _u (t) of the upper and lower molds of 3D cover glass forming are respectively measured by thermocouple sensors;

(3) Calculate the following error values respectively,

e _u (t)=Sv(t)-v _u (t), _{ed (t)=Sv(t)-v d (t), e ud ( t} )=v _u (t)-v _d (t ), e _du (t)=v _d (t) -v _u (t),

(4) Calculate u _u (t), u _d (t), u _ud (t), u _du (t) control variables by PID algorithm and cascade structure.

(5) The output value of the control quantity is output to the heating wire of the upper and lower molds to realize the synchronous temperature control of the upper mold and the lower mold.

It should be noted that the above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art can still understand the above-mentioned implementations. Modifications are made to the technical solutions described in the examples, or some technical features thereof are equivalently replaced, but any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (4)

1. A temperature synchronous control system for upper and lower molds of 3D cover plate glass is characterized by comprising an upper mold main loop, an upper mold auxiliary loop, a lower mold main loop and a lower mold auxiliary loop;

the upper die main loop is provided with an upper die main controller and an upper die heating wire, the upper die auxiliary loop is provided with an upper die auxiliary controller, the output ends of the upper die main controller and the upper die auxiliary controller are respectively connected with the input end of the upper die heating wire, the lower die main loop is provided with a lower die main controller and a lower die heating wire, the lower die auxiliary loop is provided with a lower die auxiliary controller, and the output ends of the lower die main controller and the lower die auxiliary controller are respectively connected with the input end of the lower die heating wire;

the difference between the output temperature of the upper die heating wire and the target set temperature of the die is used as the input regulating variable of the upper die main controller, the difference between the output temperature of the upper die heating wire and the output temperature of the lower die heating wire is used as the input regulating variable of the upper die sub-controller, and the output quantity of the upper die main controller and the output quantity of the upper die sub-controller are superposed and used as the input regulating variable of the upper die heating wire;

and the difference between the output temperature of the lower die heating wire and the target set temperature of the die is used as the input regulating quantity of the lower die main controller, the difference between the output temperature of the lower die heating wire and the output temperature of the upper die heating wire is used as the input regulating quantity of the lower die sub controller, and the output quantity of the lower die main controller and the output quantity of the lower die sub controller are superposed and used as the input regulating quantity of the lower die heating wire.

2. The system for synchronously controlling the temperature of the upper die and the lower die of the 3D cover glass according to claim 1, wherein the upper die main controller, the upper die sub-controller, the lower die main controller and the lower die sub-controller are PID controllers.

3. A method for synchronously controlling the temperature of an upper mold and a lower mold of 3D cover glass comprises the following steps:

setting a target set temperature Sv (t) of the die, and detecting the output temperature of the upper die heating wire as v_u(t), the output temperature of the lower die heating wire is recorded as v_d(t)；

Calculating each temperature difference

e_u(t)＝Sv(t)-v_u(t)，e_d(t)＝Sv(t)-v_d(t)，e_ud(t)＝v_u(t)-v_d(t)，e_du(t)＝v_d(t)-v_u(t)，

U is obtained by calculation_u(t)、u_d(t)、u_ud(t)、u_du(t) control amount, wherein u_u(t) is the output of the control quantity of the upper die main loop, u_d(t) output of control quantity of main loop of lower die, u_ud(t) is the output of the upper die auxiliary loop control, u_du(t) outputting the control quantity of the lower die secondary loop;

will u_u(t)、u_ud(t) as the input control quantity of the upper die heating wire after superposition, u_d(t)、u_duAnd (t) after superposition, the control quantity is used as the input control quantity of the lower die heating wire.

4. The method for synchronously controlling the temperature of the upper die and the lower die of the 3D cover glass according to claim 3, wherein u is the same as u_u(t)、u_d(t)、u_ud(t)、u_du(t) the control quantity is controlled by a PID controller, and is calculated by adopting a PID control algorithm to obtain: the PID controller is composed of a proportional unit (P), an integral unit (I) and a differential unit (D), and the input e of the PID controller is_u(t) and output u_dThe relationship of (t) is:

in the formula (I), the compound is shown in the specification,

e(t),

error, error integral, error differential terms,

k_p,k_i,k_dproportional coefficient, integral coefficient, differential coefficient,

u_d(t)＝PID(e_d(t))

u_u(t)＝PID(e_u(t))

u_ud(t)＝PID(e_ud(t))

u_du(t)＝PID(e_du(t))。

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