Noise reduction circuit control method for paper shredder

Abstract

A noise reduction circuit control method for a shredder, comprising the following steps: S10: setting the current range of the motor in the shredder to I‑0~I‑max, where I‑0 represents zero current, and I‑max represents the current corresponding to the motor overload protection value; S20: setting the current I‑a corresponding to the full power output threshold value of the motor within the current range; S30: setting multiple current gears within the current range I‑0~I‑a, as: I‑a1, I‑a2, ..., I‑an; and setting multiple different output powers corresponding to the multiple current gears; S40: the current detection module detects the current signal I‑b of the motor, and matches the corresponding output power as the motor working power output. A noise reduction circuit control method for a shredder in the present invention can detect the current delivered to the motor through the improvement of the circuit structure on the main control board of the shredder, thereby realizing the control of the motor speed and achieving the purpose of noise reduction.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic control circuits for paper shredders, and in particular relates to a noise reduction circuit control method for a paper shredder. Background Art

[0002] Paper shredders are commonly used equipment in the office field. Among the conventional paper shredder products currently on the market, their circuits are DC or series-excited induction motors according to the motor type. The AC power supply is rectified into pulsating DC and then supplied to the motor. No power control is performed on the motor's current and voltage. During operation, the voltage on the motor is always equal to the power supply voltage, causing the motor to have high speed and high noise when it is idling, and slow speed when it is heavily loaded. The paper feeding speed and noise level are inconsistent when counting a small number of sheets and a large number of sheets. The sound of the paper shredder is louder when idling than when feeding paper, but the noise becomes smaller when shredding paper, resulting in excessive machine noise and a poor user experience.

[0003] To address this problem, some paper shredders on the market currently install magnets or porous gratings at the tail of the motor rotor shaft, and install a Hall detector or infrared receiving tube next to it. When the motor rotates, the Hall or infrared receiving tube outputs pulse signals of different lengths and timings depending on the speed. The control circuit adjusts the power supplied to the motor according to the length of the pulse signal timing corresponding to the speed of the motor to control the motor speed. When the speed is high, the voltage power supplied to the motor becomes smaller, which reduces the motor speed. When the speed is low, the voltage power supplied to the motor becomes larger, which increases the motor speed. The motor speed is fixed and controlled within the set range. When the motor shreds different papers, the speed and paper passing sound are constant. Although this method is feasible, the motor needs to be specially processed and customized, the product structure is complex and the cost is high, and there are disadvantages such as troublesome production and assembly.

[0004] In view of the above shortcomings, the present application proposes a noise reduction circuit control method for a shredder by improving the circuit structure. Summary of the invention

[0005] In view of the above deficiencies in the prior art, the present invention provides a noise reduction circuit control method for a shredder. By improving the circuit structure on the main control board of the shredder, the current delivered to the motor can be detected, thereby realizing the control of the motor speed and achieving the purpose of noise reduction.

[0006] The present invention is solved by the following technical solutions.

[0007] A noise reduction circuit control method for a shredder comprises the following steps: S10: setting the current range of the motor in the shredder to be I-0~I-max, wherein I-0 represents zero current and I-max represents the current corresponding to the motor overload protection value; S20: setting the current Ia corresponding to the full power output threshold value of the motor within the current range; S30: setting a plurality of current gears within the current range I-0~Ia, namely: I-a1, I-a2, ..., I-an; and setting a plurality of different output powers corresponding to the plurality of current gears; S40: a current detection module detects the current signal Ib of the motor, and matches the corresponding output power as the motor working power output.

[0008] In a preferred embodiment, step S40 also specifically includes the following steps: the analysis and processing module compares Ib and Ia, if Ib≥Ia, the motor maintains full power output; if Ib<Ia, the current level I-an closest to Ib is matched, and the output power corresponding to the current level I-an is used as the motor working power output.

[0009] In a preferred embodiment, the current detection module includes a current sampling resistor, and the current passing through the shredder motor flows back to the power supply through the current sampling resistor. The voltage drop across the current sampling resistor increases with the increase of the motor current. After rectification and filtering, a voltage value is provided to the analysis and processing module, and the real-time operating current parameters are obtained through the voltage value.

[0010] In a preferred implementation, in step S40, when Ib<Ia, the corresponding output power is output at different current levels, and the rotation speed of the motor of the shredder is ensured to remain unchanged.

[0011] Compared with the prior art, the present invention has the following beneficial effects: it provides a noise reduction circuit control method for a shredder, and by improving the circuit structure on the main control board of the shredder, it is possible to detect the current delivered to the motor, thereby realizing the control of the motor speed and achieving the purpose of noise reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a circuit diagram of the analysis and processing module (main control MCU) in the present invention.

[0013] Figure 2 It is a circuit diagram of the power module and the trash can extraction detection module in the present invention.

[0014] Figure 3 It is a schematic diagram of the circuit related to the motor in the present invention.

[0015] Figure 4 It is a circuit diagram of the paper entrance sensing module in the present invention.

[0016] Figure 5 It is a circuit diagram of the CD entrance sensing module in the present invention.

[0017] Figure 6 Schematic diagram of the circuit of the full barrel sensing module in the present invention. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0019] In the following embodiments, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0020] The shredders in the prior art all have a current detection circuit. When the current exceeds the specified value, the motor power supply will be disconnected to protect the motor. This circuit is only applicable to motor overcurrent protection. In addition, according to the conventional method of detecting the motor speed, the motor speed is set to a fixed standard value, and the speed is adjusted according to the fixed standard reference value. When the speed is high, the voltage power provided to the motor becomes smaller, so that the motor speed is reduced. When the speed is low, the voltage power provided to the motor becomes larger, so that the motor speed is increased, so that the motor speed is fixed.

[0021] Moreover, in the motor current detection method in the prior art, when the motor is idling, whether it is using full power or half power, the motor speed is high and a small current is detected. When paper is added, the current will increase. The more paper, the greater the current. This current parameter is a variable that changes in real time and cannot be used as a fixed value to adjust the motor output power. For this reason, this patent uses the following unique control method for control to achieve the purpose of adjusting speed and reducing noise.

[0022] See also Figures 1 to 6 The present invention relates to a noise reduction circuit control method for a shredder, comprising the following steps.

[0023] S10: The current range of the motor in the shredder is set to be I-0~I-max, where I-0 represents zero current and I-max represents the current corresponding to the motor overload protection value.

[0024] S20: setting the current Ia corresponding to the motor's full power output threshold value within the current range.

[0025] S30: Within the current range I-0~Ia, multiple current gears are set, namely: I-a1, I-a2, ..., I-an; and multiple different output powers corresponding to the multiple current gears are set.

[0026] S40: The current detection module detects the current signal Ib of the motor, and matches the corresponding output power as the motor working power output. Specifically, the analysis and processing module compares Ib with Ia. If Ib≥Ia, the full power output of the motor is maintained; if Ib<Ia, the current gear I-an closest to Ib is matched, and the output power corresponding to the current gear I-an is used as the motor working power output.

[0027] Furthermore, in step S40, when Ib<Ia, the corresponding output power is output at different current levels, and the rotation speed of the motor of the shredder is ensured to remain unchanged.

[0028] In the present application, the current detection module includes a current sampling resistor, and the current passing through the shredder motor flows back to the power supply through the current sampling resistor. The voltage drop across the current sampling resistor increases with the increase of the motor current. After rectification and filtering, a voltage value is provided to the analysis and processing module, and the real-time operating current parameters are obtained through the voltage value.

[0029] The following is a description of the circuit diagram involved in this application in conjunction with the accompanying drawings. Figure 2 J1 and Figure 3 Connect to J1 in.

[0030] The power supply L is divided into three paths after the electromagnetic compatibility circuit is formed by the fuse F1, varistor VR1, EMC_C1 and common mode inductor T1. The first path is rectified by resistor R1 and diodes D1_1 and D1_2, and filtered by EC1 and EC2 to be high voltage. After passing through the power supply circuit such as U1 switching power supply chip, it becomes 24V DC power to directly supply the relay for operation. The 24V is then stabilized to 5V by U2, and filtered by capacitors EC4 and C4 to supply the control chip and other circuits for operation.

[0031] After the second route comes out of R1, it enters the control chip pin 19 (interrupt pin) as the chip zero-crossing voltage detection circuit after voltage reduction and current limiting by R35, R36, and R37. It detects both the rising and falling edge signals of the power supply voltage, and can provide the chip with a zero-crossing pulse signal of the power supply voltage regardless of the positive or negative cycle of the power supply.

[0032] The third voltage is connected to the AC input pin 2 of the rectifier bridge DB1 after passing through the trash can detection safety switch SW1. The AC input pin 2 of DB1 is connected to the thyristor TR1 (bidirectional thyristor) power regulation circuit (the control chip adjusts the power of the thyristor through the optocoupler U2), wherein the C_TR resistor and the C_TR capacitor are connected in series and connected in parallel to the thyristor T1 and T2 pins together with the surge absorption varistor TR_VDR to protect the thyristor. The circuit is controlled by the motor temperature, then to the PTC insurance, and the current sampling resistor R21 to the ground, that is, the input power supply N forms a complete AC path, and the rectifier bridge DB1 outputs the adjusted DC power between the DC output pins 1 and 4, with pin 4 being positive and pin 1 being negative. Then the double-pole switching relay RELAY_REV (Q2 is controlled by the chip to control the on and off) controls the DC current direction to achieve the forward and reverse functions of the motor, so that the machine can shred and reverse paper normally.

[0033] The current sampling resistor R21 is connected in series in the AC path of DB1. The current passing through the motor flows back to the power supply through R21. The voltage drop across R21 increases with the increase of the motor current. After rectification and filtering by R13, D8, and C6 (the maximum input voltage is adjusted by the voltage divider R14 and R15), the voltage value, i.e. the current parameter of the real-time operation of the motor, is provided to the control chip pin 12 through R16.

[0034] The principle of motor output regulation of different powers is as follows: when the mains zero-crossing detection pin at pin 19 of the chip has a rising edge signal in the positive half cycle and a falling edge signal in the negative half cycle, it is judged as a zero-crossing signal. After the delay setting time, the control chip pin 25 outputs a low level, causing U2 to turn on and trigger the thyristor TR1. Only then will voltage and current be added to the motor, and the motor will have power output at this time. Because the thyristor is not turned on at the beginning of the positive or negative half cycle of the power supply, the voltage and current of the thyristor turned off during the delay period are not added to the motor, so the output power of the motor becomes smaller during this cycle, achieving the goal of regulating the output power of the motor. The longer the delay time between the start of zero crossing and the turn-on of the thyristor by the chip output, the larger the thyristor phase shift trigger angle, the shorter the turn-on time of the thyristor in half a cycle of the mains, the lower the working voltage of the motor, the less current passes through, and the smaller the motor power will be.

[0035] The mains frequency in different countries is divided into 50Hz and 60Hz. At 60Hz, the positive to negative half cycle time of the power supply is 8.3ms, which is shorter than 10ms at 50Hz. For example, when the power output is 50%, the delay time of interrupting zero crossing to open the thyristor is half of 8.3ms at 60Hz and half of 10ms at 50Hz. Therefore, the machine needs to detect the mains power frequency. The positive and negative pulse times of the zero crossing detection foot are different. The AC frequency of the mains is detected by the length of the timing time, corresponding to different frequencies. Outputting different interrupts after opening the thyristor delay time ensures that the output power is the same at different frequencies.

[0036] The specific operation of this noise reduction circuit is to set a full-power output threshold value between 0 current and overload current value. When it is detected that the actual operating current of the motor is above the threshold value, the optocoupler U4 is always turned on, the thyristor is always in the on state, and the AC power is output at full power. When the current is below the threshold current value during the actual operation of the motor, as mentioned above, there are many gears for setting the current. The actual current is compared with the set current gear value. The corresponding gear outputs the interrupt 0 point that has been set for this gear and the fixed delay time parameters for opening the thyristor (that is, different parameters for the motor output power percentage) for adjustment. That is, by adjusting the conduction angle of the thyristor (dual thyristor) to control the current passing time of the motor, thereby controlling the input power of the motor, so that the motor power output outputs different powers synchronously according to the set gear current. The larger the current, the higher the gear, and the greater the power output to the motor by the circuit. Because the more paper, the greater the current, the greater the gear power provided to the motor to maintain the balance of the motor speed.

[0037] Therefore, although the load on the motor changes, the real-time current detection will detect the changing voltage. The chip will select different current gears based on different voltages to output a power to the motor that can balance the motor speed, thereby increasing or decreasing the motor input power and reaching a stable speed.

[0038] When the motor current exceeds the threshold value, the motor needs to run at full power to balance the speed. If the current continues to increase and exceeds the maximum gear of the blade protection current, the output pin of the control chip turns off the thyristor to stop the motor from working, protecting the shredder blade and structure from damage. The panel overload LED indicator lights up to remind the user to pay attention.

[0039] Other auxiliary functions of the shredder are as follows.

[0040] The trash can pull-out detection circuit is connected to the safety switch SW1. During normal operation, the mains power is stepped down and limited by R22, R23, and R24, rectified by D10, and the maximum clamping input voltage of ZD3 is within the normal working range of the chip. The voltage after filtering by C11 is provided to the chip trash can detection pin 15 through R25 with a high level. When the trash can is pulled out, the safety switch SW1 is disconnected, there is no mains power before R22, and the chip detection pin 15 is 0 voltage. Then the voltage can be used to determine whether the trash can is pulled out.

[0041] The overheat protection function of the machine is that the thermostat is tied to the motor housing. When the working temperature of the motor rises and reaches or exceeds the protection temperature of the thermostat, the thermostat is disconnected, and the AC voltage is reduced and limited by R17, R18, and R19, rectified by D7 and filtered by C8, and the maximum chip working voltage is clamped by ZD2. A high-level motor overheat signal is provided to the chip at pin 17 through R20, and the chip turns off the thyristor and relay to stop the motor.

[0042] See also Figure 6 The machine's trash can full paper detection function is that the control chip sends a pulse signal to the infrared transmitting tube LD for full bin detection. When the trash can is full of paper, the infrared light of the transmitting tube is reflected back to the infrared receiving tube by the full bin of paper scraps. The receiving tube signal passes through capacitor C11 and is amplified by transistor Q3 and then provided to the control chip. Due to the existence of C11, the signal passing through it can only be the fixed pulse AC signal emitted by the transmitting tube. The control chip only considers it as a paper full signal of the trash can when it detects this signal. Other external non-modulated pulse infrared signals such as sunlight cannot pass through C11, or the signal will not be considered as a paper full signal if it does not meet the requirements. The control chip will not act, effectively avoiding external interference.

[0043] See also Figure 4 and Figure 5 When the paper inlet and the CD shredded disc induction port are normal, each receiving tube can receive the signal of the transmitting tube when nothing is put into the paper inlet or the CD slot, and it is considered that there is no paper or CD in the paper inlet or the CD slot, and the machine will not operate. When paper or CD is put in, the paper or CD blocks the light from the transmitting tube to the receiving tube, and the receiving tube cannot receive the signal. The receiving foot of the control chip 2 senses that there is paper or CD in, and the motor starts to operate. After the paper is shredded, it stops working.

[0044] In addition, the control panel on the shredder has three touch keys KEY1, KEY2, and KEY3, which are used for turning the machine on and off and manually clearing paper in both directions. There are 8 LEDs (LED1-LED8), in addition to the three touch display lights, five abnormal lights, which indicate current overload, motor overtemperature, full trash can, and abnormal trash can extraction. The machine will stop and light up to remind users.

[0045] It can be seen from the above description that a noise reduction circuit control method for a shredder in the present invention can detect the current delivered to the motor by improving the circuit structure on the main control board of the shredder, thereby realizing the control of the motor speed and achieving the purpose of noise reduction.

[0046] The protection scope of the present invention includes but is not limited to the above embodiments. The protection scope of the present invention shall be based on the claims. Any replacement, deformation, and improvement of the technology that can be easily thought of by technicians in this field shall fall within the protection scope of the present invention.

Claims

1. A noise reduction circuit control method for a paper shredder, characterized in that: The following steps are involved: S10: Setting the current range of the motor in the shredder to be I-0~I-max, where I-0 represents zero current and I-max represents the current corresponding to the motor overload protection value; S20: setting the current Ia corresponding to the motor full power output threshold value within the current range; S30: setting a plurality of current gears within the current range I-0~Ia, namely: I-a1, I-a2, ..., I-an; and setting a plurality of different output powers corresponding to the plurality of current gears; S40: The current detection module detects the current signal Ib of the motor, and matches the corresponding output power as the motor working power output; Step S40 also specifically includes the following steps: the analysis and processing module compares Ib with Ia, if Ib≥Ia, the motor is kept at full power output; if Ib<Ia, the current gear I-an closest to Ib is matched, and the output power corresponding to the current gear I-an is used as the motor working power output; In step S40, when Ib<Ia, the corresponding output power is output at different current levels, and the rotation speed of the motor of the shredder is ensured to remain unchanged.

2. A noise reduction circuit control method for a paper shredder according to claim 1, characterized in that: The current detection module includes a current sampling resistor. The current passing through the shredder motor flows back to the power supply through the current sampling resistor. The voltage drop across the current sampling resistor increases with the increase of the motor current. After rectification and filtering, a voltage value is provided to the analysis and processing module, and the real-time operating current parameters are obtained through the voltage value.

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