Closed-loop control method for material level of jaw crusher

Abstract

The invention relates to the field of jaw crusher feeding. According to the material level closed-loop control method for the jaw crusher, a support 2 extending in the direction of the jaw crusher 4 is installed on the side portion of a draw shaft 1, and a radar material level indicator 3 which can completely measure the surface of mineral aggregate in an inner cavity of the jaw crusher 4 and has a surface measurement function is installed on the support above an opening of the jaw crusher 4. The heavy plate ore feeder 5 is connected with a discharging port in the bottom of the draw shaft 1 and a feeding port of an inner cavity of the jaw crusher 4, and the heavy plate ore feeder 5 and the radar level gage 3 are in electric signal connection with the PLC. According to the implementation of the invention, the accuracy of measuring the material level in the machine cavity of the jaw crusher can be improved, and the material level signal is used for performing closed-loop control on the frequency (variable frequency motor) of the heavy plate feeder, so that the full feeding of the crusher is realized, the mineral crushing granularity is improved, the entering of strip-shaped ores into the next process is reduced, and the unattended operation of the crusher is realized.

Description

Technical Field

[0001] The invention relates to the field of jaw crusher feeding. Background Art

[0002] A jaw crusher, commonly known as a jaw crusher or tiger's mouth, consists of two jaw plates, a movable jaw and a stationary jaw, forming a crushing chamber that simulates the movement of an animal's jaws to crush materials. It is widely used to crush various ores and bulk materials in industries such as mining and smelting, building materials, highways, railways, water conservancy, and the chemical industry. The working parts of a jaw crusher are its two jaw plates: a fixed jaw plate (fixed jaw), vertically fixed (or with its upper end slightly tilted outward) to the front wall of the machine body; and a movable jaw plate (moving jaw), tilted, forming a crushing chamber (working chamber) with the fixed jaw plate. The movable jaw plate periodically reciprocates against the fixed jaw plate, alternately moving apart and approaching. When moving apart, material enters the crushing chamber, and the finished product is discharged from the bottom. When moving together, the material contained between the two jaw plates is squeezed, bent, and split, causing it to break.

[0003] When a jaw crusher is fed through a heavy plate feeder, the material is irregular, with strips and lumps, and the largest single-side size can reach over 1 meter. The smallest is powder ore. This causes significant variations in the height of each point on the material surface. Existing material level meters measure the height of one or several points on the material surface to reflect the material surface height. If the measurement point is aligned with a high point, the feed rate will be reduced. If the measurement point is aligned with a low point, the feed rate will increase, resulting in the crusher's movable jaw being unable to move, which may cause the "garlic crushing" equipment to malfunction. Current heavy plate feeders can only feed at a constant rate. However, the jaw crusher crushes large and small materials at different rates, which can result in slow material crushing or jaw crusher malfunction.

[0004] Chinese patent number CN202411214995.1 discloses a variable frequency control device for a jaw crusher feeder. The device uses a material retaining mechanism to achieve quantitative material discharge, thereby improving the operating efficiency of the crusher and indirectly increasing the service life of the crusher. However, when feeding the ore, it is not entirely certain where the ore will land in the crusher cavity. As a result, the material retaining mechanism cannot accurately obtain the material level in some cases (when the high point of the ore deviates from the retaining mechanism). Summary of the Invention

[0005] The technical problem to be solved by the present invention is: how to overcome the defects of the material level measurement of the jaw crusher in the background technology, accurately and automatically measure the actual height of the material level in the machine cavity, and how to link it with the feeding frequency (variable frequency motor) of the heavy-duty plate feeder to achieve closed-loop control, so as to achieve full feeding of the crusher and improve the crushing effect.

[0006] The technical solution adopted by the present invention is: a closed-loop control method for the material level of a jaw crusher, wherein a bracket (2) extending toward the jaw crusher (4) is installed on the side of a chute (1), and a radar material level meter (3) with a surface measurement function capable of completely measuring the surface of the ore material in the inner cavity of the jaw crusher (4) is installed on the bracket above the mouth of the jaw crusher (4), a heavy plate feeder (5) is connected to the discharge port at the bottom of the chute (1) and the feed port of the inner cavity of the jaw crusher (4), and the heavy plate feeder (5) and the radar material level meter (3) are electrically connected to a PLC; a PID control system is installed in the PLC, and the input quantity of the PID control system is the average value of the surface height of the ore material measured by the radar material level meter (3). Deviation, the output of the PID control system is the feed amount of the jaw crusher (4), and the PLC converts the feed amount of the jaw crusher (4) into the speed of the variable frequency motor of the heavy plate feeder (5) to adjust the speed of the variable frequency motor; the PLC controls the variable frequency motor of the heavy plate feeder (5) by switching between manual and automatic modes. When the jaw crusher (4) is debugged or the material level meter fails, the PLC switches to manual mode. In manual mode, the speed of the variable frequency motor is directly adjusted according to the observed surface height of the ore in the inner cavity of the jaw crusher (4) to feed the material. In automatic mode, the PLC automatically controls the speed of the variable frequency motor of the heavy plate feeder (5) through the PID control system to feed the material.

[0007] The proportional coefficient Kp of the PID control system is 1.5-1.8, the integral time constant Ti of the PID control system is 0.6-0.9 minutes, and the Td of the PID control system is 0.3-0.5 minutes.

[0008] The PID control system is set with a maximum height of the ore surface. When the PLC detects that the average value of the ore surface height is greater than or equal to the maximum height, the variable frequency motor of the heavy plate feeder (5) is controlled to stop feeding for 1-2 minutes, and Kp takes the minimum value. When the PLC detects that the average value of the ore surface height is less than or equal to 1 / 2 of the maximum height, Kp takes the maximum value. When the PLC detects that the average value of the ore surface height is greater than 1 / 2 of the maximum height and less than the maximum height, the Kp value decreases linearly with the increase of the average value of the ore surface height.

[0009] The beneficial effects of the present invention are as follows: the implementation of the present invention can improve the accuracy of material level measurement in the jaw crusher cavity, use the material level signal to perform closed-loop control on the frequency of the heavy plate feeder (variable frequency motor), realize full feeding of the crusher, improve the mineral crushing particle size, reduce the number of strip ores entering the next process, and realize unmanned operation of the crusher. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a structural schematic diagram of the present invention; Among them, 1. chute, 2. bracket, 3. radar level meter, 4. heavy plate feeder, 5. heavy plate feeder. DETAILED DESCRIPTION

[0011] like Figure 1 As shown, the device used in the present invention is partially improved based on the existing technology. The purpose is to improve the accuracy of material level measurement, thereby improving the working efficiency of the jaw crusher and reducing the probability of equipment failure.

[0012] A closed-loop control method for the material level of a jaw crusher is disclosed. A bracket 2 extending toward the jaw crusher 4 is installed on the side of a chute 1. A radar level meter 3 with a surface measurement function that can fully measure the surface of the ore material in the inner cavity of the jaw crusher 4 is installed on the bracket above the mouth of the jaw crusher 4. A heavy plate feeder 5 is connected to the discharge port at the bottom of the chute 1 and the feed port of the inner cavity of the jaw crusher 4. The electrical signals of the heavy plate feeder 5 and the radar level meter 3 are connected to a PLC.

[0013] A chute is a tunnel through which ore is discharged downward by gravity. In this embodiment, an existing chute is used. The bracket 2 in this embodiment is a rod welded to the side (sidewall) of the chute 1, with the head of the rod positioned directly above the feed port of the jaw crusher 4. The radar level meter 3, which has a surface measurement function, has its detector head mounted on the bracket 2. In this embodiment, a KERD-800 / 900 series radar level meter is used. In this embodiment, the heavy plate feeder 5 is manufactured by Jiangsu Tianpeng Electromechanical Manufacturing Co., Ltd., a company specialized in serving jaw crushers. After ore exits the chute's lower outlet under the action of gravity, it falls directly onto the conveyor belt (chain belt) of the heavy plate feeder 5. The heavy plate feeder 5 then feeds the jaw crusher 4. Therefore, the feeding speed of the jaw crusher 4 can be controlled by controlling the speed of the conveyor belt of the heavy plate feeder 5. In the present invention, the conveyor belt of the heavy plate feeder 5 is driven by a variable frequency motor, so the feeding speed of the jaw crusher 4 can be controlled by simply controlling the variable frequency motor.

[0014] The present invention is controlled by a program. In this embodiment, overall control is performed by a PLC system. In one embodiment, the designed PLC system uses a Siemens S7-200smart PLC, including a CPU SR40 and an expansion module EMAM06. These are installed on an electrical rail and connected together to form a PLC hardware system, which is then installed in a control box named "Material Level Control." The control box is installed next to the heavy-duty plate feeder operating box. The material level signal output by the material level meter (radar material level meter) is an RS485 communication signal. A TD-3104 RS485 to 4-20mA conversion module is used to connect the RS485 communication output of the material level meter to the input terminal, and the output terminal is connected to the AI3 terminal of the PLC expansion module below.

[0015] Purchase a toggle switch (installed on the heavy plate feeder operation box), connect it to the I0.0 terminal of the CPU module, select a 3kΩ potentiometer (used for the material level setting signal, installed on the heavy plate feeder operation box), connect it to the analog input AI0 of the expansion module, connect the manual given frequency signal to the analog input AI2 of the PLC expansion module, convert the RS485 signal output by the material level meter into a 4-20mA signal through the conversion module and connect it to the input AI3 of the PLC expansion module, and connect the analog output AQ0 of the expansion module to the frequency setting terminal of the inverter.

[0016] The control logic of this embodiment is as follows: when the switch is disconnected, the given output (AQ0) output to the frequency converter is equal to the manual given frequency (AI2), which means the control is switched to manual control. When the switch is closed, the PLC program switches the PID computer to automatic control, uses the signal given by the material level adjustment potentiometer (AI0) as the target value, and uses the material level feedback signal AI3 as the feedback value for calculation. After calculation, the given frequency (AQ0) is output to the weight plate frequency converter (variable frequency motor).

[0017] A PID control system is installed in the PLC. The input of the PID control system is the average deviation of the surface height of the ore material measured by the radar level meter 3. The output of the PID control system is the feed amount of the jaw crusher 4. The PLC converts the feed amount of the jaw crusher 4 into the speed of the variable frequency motor of the heavy plate feeder 5 and adjusts the speed of the variable frequency motor.

[0018] In industrial process control, a control system that controls the object by comparing the real-time data collected with the given value based on the proportion, integration and differentiation of the error generated is called PID (Proportional Integral Derivative) control system for short.

[0019] The differential equation of PID control is: u(t)=K p ⋅e(t)+ K i ⋅∫0 t e(t)dt+K d ⋅de(t) / d(t).

[0020] u(t) is the output of the control; K p ⋅e(t) is the proportional link, which adjusts the output proportionally according to the instantaneous value of the current error e(t) and responds quickly to the deviation. The proportional coefficient K p A larger value results in faster response but may cause overshoot or oscillation.

[0021] K i ⋅∫0 t e(t)dt is the integral link, the cumulative historical error ∫0t e(t)dt eliminates the system steady-state error, the integral time constant K i Determines the accumulation speed. Too long will lead to response lag, and too short will easily cause oscillation.

[0022] K d ⋅de(t) / d(t) is the differential link, which predicts the error change trend de(t) / d(t)to suppress overshoot and improve system stability. The differential time constant K d Adjust the prediction sensitivity. Too high a value will amplify noise interference.

[0023] In the present invention, the proportional coefficient Kp of the PID control system is 1.5-1.8, the integral time constant Ti of the PID control system is 0.6-0.9 minutes, and the Td of the PID control system is 0.3-0.5 minutes. In the present invention, the proportional coefficient Kp of the PID control system is within a limited range. During operation, the value is determined according to the surface height of the ore, which can improve the feeding speed and the feeding accuracy. i and the differential time constant K d The same is true.

[0024] The PID control system is provided with a maximum height (i.e., a warning height) and a minimum height of the ore surface. When the PLC detects that the average value of the ore surface height is greater than or equal to the maximum height, the variable frequency motor of the heavy plate feeder 5 is controlled to stop feeding for 1-2 minutes, and Kp takes the minimum value. When the PLC detects that the average value of the ore surface height is less than or equal to 1 / 2 of the maximum height, Kp takes the maximum value. When the PLC detects that the average value of the ore surface height is greater than 1 / 2 of the maximum height and less than the maximum height, the value of Kp decreases linearly with the increase of the average value of the ore surface height. In one embodiment, when the PLC detects that the average value of the ore surface height is greater than 1 / 2 of the maximum height and less than the maximum height, Kp = 1.5 + 0.3 (maximum height of the ore surface - average value of the ore surface height) / maximum height of the ore surface. When the PLC detects that the average value of the ore surface height is less than the minimum height, Kp is 1.8. Integral time constant K i and the differential time constant K d Directly take the constant.

[0025] In one embodiment, the control logic of the program is as follows: manual mode and automatic mode are switched by a switch. In manual mode, the adjustment is made directly on the monitoring machine through the position. In automatic mode, the target material level is adjusted by a potentiometer, and the material level value fed back by the material level meter is compared. When the material level is higher than the target material level, the frequency is reduced (variable frequency motor), and when the material level is lower than the target material level, the frequency is increased. The calculation method is the PID (proportional integral differential) calculation method, and the closed-loop control of the material level is achieved through PID calculation. In one embodiment, at a certain time, the value range of Kp value is 1.6 times of the change amount, K i The value range is 0.8 minutes, K d The value range is 0.4 minutes. In one embodiment, when the material level feedback value exceeds 7 meters (the highest height of the ore surface), the given frequency output by the PLC is immediately reset to zero.

[0026] After on-site debugging, it was found that the crusher's material level could be adjusted through a potentiometer, provided that the discharge port met the requirements. When the potentiometer was adjusted to 4V output, the crusher's material level could be controlled between one-quarter and two-thirds of the full material level. The crushing effect was significantly improved, and the amount of strip ore with a particle size greater than 800mm could be reduced by more than 50%.

Claims

1. A closed-loop control method for material level of a jaw crusher, characterized by: A bracket (2) extending toward the jaw crusher (4) is installed on the side of the chute (1). A radar level meter (3) with a surface measurement function capable of completely measuring the surface of the ore in the inner cavity of the jaw crusher (4) is installed on the bracket above the mouth of the jaw crusher (4). A heavy plate feeder (5) is connected to the discharge port at the bottom of the chute (1) and the feed port of the inner cavity of the jaw crusher (4). The heavy plate feeder (5) and the radar level meter (3) are electrically connected to a PLC; a PID control system is installed in the PLC. The input of the PID control system is the average deviation of the ore surface height measured by the radar level meter (3). The output of the PID control system is the average deviation of the ore surface height measured by the radar level meter (3). In order to feed the jaw crusher (4), the PLC converts the feed amount of the jaw crusher (4) into the speed of the variable frequency motor of the heavy plate feeder (5) and adjusts the speed of the variable frequency motor; the PLC controls the variable frequency motor of the heavy plate feeder (5) by switching between manual and automatic modes. When the jaw crusher (4) is debugged or the material level meter fails, the PLC switches to the manual mode. In the manual mode, the speed of the variable frequency motor is directly adjusted according to the observed surface height of the ore in the inner cavity of the jaw crusher (4) to feed the material. In the automatic mode, the PLC automatically controls the speed of the variable frequency motor of the heavy plate feeder (5) through the PID control system to feed the material.

2. A closed-loop control method for material level of a jaw crusher according to claim 1, characterized in that: The proportional coefficient Kp of the PID control system is 1.5-1.8, the integral time constant Ti of the PID control system is 0.6-0.9 minutes, and the Td of the PID control system is 0.3-0.5 minutes.

3. A closed-loop control method for material level of a jaw crusher according to claim 1, characterized in that: The PID control system is set with a maximum height of the ore surface. When the PLC detects that the average value of the ore surface height is greater than or equal to the maximum height, the variable frequency motor of the heavy plate feeder (5) is controlled to stop feeding for 1-2 minutes, and Kp takes the minimum value. When the PLC detects that the average value of the ore surface height is less than or equal to 1 / 2 of the maximum height, Kp takes the maximum value. When the PLC detects that the average value of the ore surface height is greater than 1 / 2 of the maximum height and less than the maximum height, the Kp value decreases linearly with the increase of the average value of the ore surface height.

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