JP2000237615A - Control method of shredder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the number of paper sheets possible to be shredded within an allowable range of input electric current and shorten the time to shred paper sheets per a paper sheet in a control method of a shredder constituted as to shred paper sheets by driving a shredding mechanism by a motor. SOLUTION: This shredder is provided with a motor 4 having a characteristic that the motor torque is lowered approximately linearly with respect to the increase of rotation speed in the case the supplied voltage is used as a parameter and a control means 3 installed between the motor 4 and a commercial power source for applying electric power to the motor 4. Consequently, the shredder control is so carried out as to keep the electric power source to be supplied from the commercial power source within a prescribed level by lowering the rotation speed of the motor 4 following the prescribed increase of the torque of a shredding mechanism 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shredder for cutting unnecessary paper sheets by driving a shredding mechanism by a motor, and more particularly to a shredder control method capable of shredding a small number to a large number of sheets. is there.

[0002]

2. Description of the Related Art A general shredder is composed of an induction motor having a commercial power supply (single-phase 100 V, 50 or 60 Hz) as an input, and a motor connected to an output side of the motor to reduce the rotation of the motor to a predetermined number of rotations. And a high-torque output, and a shredding mechanism such as a rotary cutter device coupled to the output side of the speed reducer.

FIG. 6 shows the rotational speed-torque characteristics of the induction motor. The stable rotation range of the induction motor is between the point P6 of the synchronous speed and the point P7 of the stop torque, and therefore, the motor is used in a line between P6 and P7. When the load of the motor increases, the slip of the motor increases, and the current value increases. As a result, a large torque is generated and shredding is performed.

[0004]

When the number of paper sheets to be cut at one time increases and the load on the motor increases, the operation of the motor shifts from the synchronous speed P6 to the stop P7, and the current is reduced. The value rises exponentially. Since the voltage applied to the motor is constant at the commercial power supply voltage, the input power sharply increases in proportion to the current. In order to prepare for such a state, the lead-in line from the commercial power supply to the shredder needs to be configured to have a sufficient thickness for a large current.

If the load is too heavy, if the load is left as it is, it exceeds the rated input power of the shredder or the motor stalls beyond the stop torque point P7, and the shredding function is lost. In addition, a power outlet or the like exceeds a current value specified by the Electrical Appliance and Material Control Law, and a breaker may fly to protect power supply to other electric products other than the shredder.

[0006] In order to avoid the above situation, usually,
Means are provided in which the motor is stopped before reaching the stop torque P7, for example, a reverse rotation operation is performed to discharge the sheet caught in the shredding mechanism to the insertion side. When such a reverse rotation operation is performed, there is a problem that the crushed pieces of the paper sheet in the middle of the shredding are scattered in the shredding mechanism or in the vicinity of the charging port, so that cleaning is forced.

Further, if a large number of paper sheets are piled in at a time, a state in which the shredding function is lost occurs as described above. However, in the case of a large number of unspecified persons, not only those who fully understand the functions are provided, and thus, the stoppage of shredding occurs repeatedly, which makes the handling of the shredder very complicated.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method for controlling a shredder configured to cut a sheet by driving a shredding mechanism by a motor. A motor having a characteristic that a motor torque droops substantially linearly with an increase, and control means for outputting power to the motor interposed between the motor and a commercial power supply; The present invention is characterized in that the number of revolutions of the motor is reduced as the required torque increases, and control is performed so that the electric power input from the commercial power supply does not exceed a predetermined value.

In the above control method, a current detecting means is provided between the control means and the commercial power supply to monitor a current value at an input from the commercial power supply. Alternatively, current and voltage detecting means may be provided between the control means and the motor to estimate the current value at the input from the commercial power supply.

According to the above control method, when the power input from the commercial power supply to the control means rises and approaches the limit value in accordance with the increase in the required torque of the shredding mechanism, the control means reduces the rotation speed of the motor. By reducing the power, the power supplied from the control means to the motor decreases while maintaining the required motor torque, and as a result, the power input from the commercial power supply to the control means also decreases. When the input power approaches the limit value again, the rotation speed is further reduced to maintain the same operation as described above. When reducing the number of revolutions, mainly the voltage component of the power supplied from the control means to the motor is reduced, so there is room for the motor current to increase, and the allowable motor torque within the limit value of the input power from the commercial power supply is It will increase as the rotational speed decreases.

[0011]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating an outline of a method for controlling a shredder according to the present invention. Motor 4
Is constituted by a motor having a characteristic that a motor torque droops substantially linearly with an increase in the number of rotations when a supplied voltage is used as a parameter, such as a brushed or brushless type DC motor or the like. A reluctance motor or the like is applied. A shredding mechanism 5 such as a rotary cutter device is connected to the output side of the motor 4 via a speed reducer that reduces the rotation of the motor at a fixed rate and outputs a high torque.

The current detecting means 2 comprises an AC current transformer or the like,
It detects an input current from a commercial power supply and outputs a signal to the control means 3. For example, in the case of a brushless DC motor or the like, the control unit 3 includes a power supply circuit that rectifies a commercial power supply and outputs power to the motor 4 via an inverter circuit. Control is performed so that the power input from the commercial power supply does not exceed a predetermined value by comparing and discriminating with a preset allowable level. When a large number of paper sheets 10 are stacked and fed into the shredding mechanism 5 and the input current exceeds the allowable level, for example, the link voltage of the inverter circuit is reduced,
The voltage supplied to the motor is reduced by means such as narrowing the duty width of the WM wave, thereby reducing the rotation speed of the motor.

FIG. 2 shows an example in which the control device 1 of FIG. Current / voltage detecting means 8
Is for detecting, for example, a phase current and a phase voltage supplied to the motor 4 by a current transformer or a transformer and outputting those signals to the input estimating means 9. The input estimating means 9 multiplies the signal representing the current by the signal representing the voltage, estimates an input power value or an input current value from the commercial power supply, and outputs the signal to the control means 7. Since the power consumption of the control means 7 is small, the above estimation can be made relatively easily without causing a large error. The control means 7 compares and determines the estimated input power or the estimated input current with a preset allowable level according to the output signal of the input estimating means 9,
Other functions are the same as those of the control means 2 in FIG. 1, and control is performed so that the electric power input from the commercial power supply does not exceed a predetermined value.

FIG. 3 illustrates the relationship between the rotational speed and the torque of the motor 4 shown in FIGS. T1-T
Line 6 is a rotation speed-torque characteristic using the supply voltage to the motor as a parameter, and the supply voltage increases from T6 to T1. The line connecting the points P2 and P4 is a current limiting line, and represents the maximum motor torque with respect to the rotational speed at the allowable upper limit of the input current value from the commercial power supply. For example, by lowering the rotation speed from the point P2 to the point P3, the supply voltage to the motor decreases, and the operation of the motor changes from the line T1 to the line T4. , The input current value from the commercial power supply decreases. Therefore, the motor torque can be increased by increasing the input current value to the allowable upper limit value. As a result, the current limiting lines P2 to P4 increase as the rotation speed decreases.

As a control method in the present invention, for example, P
Operation control of the motor along the line 1-P2-P4 is conceivable. The point P1 is set near the synchronous speed of the conventional induction motor, but this is an effective method when there is a possibility that noise or deterioration of the shredding mechanism may occur when the rotation speed is further increased. In the operating range of P1-P2, by controlling the supply voltage to the motor in accordance with the load of the shredding mechanism, control is performed so that the normal shredding operation of the shredder is performed at high speed and constant speed.

Now, when a large number of paper sheets are put into the shredding mechanism and input current exceeds an allowable level, the operation range along the P1-P2 line is changed to P2-P.
Control is performed so as to shift to an operation range along four lines.
That is, when the supply voltage to the motor is reduced and the number of revolutions is reduced, the operation state of the motor is changed from the line T1 to, for example, the line T2. Then, there is a margin in the input current value, so that operation can be performed in this state until the input current again reaches the allowable level. In this way, the operating state of the motor gradually changes in the low speed direction along the current limiting lines P2-P4.

When the cutting speed is not required, the operation of the motor may be controlled, for example, along the line P1-P3-P4. In this case, voltage adjustment between P1-P3 is unnecessary. In the case where noise and deterioration of the shredding mechanism do not cause a problem at high speed, for example, P5-
Operation control of the motor along the line P2-P4 may be performed. In this case, the cutting speed can be increased within a range not exceeding the current limit line between P5 and P2.

[0018]

FIG. 4 shows the input current from the commercial power source with respect to the number of cut pieces, where A is the case of operation by the control method of the present invention, A50 is A60 in the case of 50 Hz operation using the conventional induction motor. Indicates the case of the 60 Hz operation. According to the present invention, it is possible to always obtain the maximum torque by reducing the rotation speed within the limit value of the input current from the commercial power supply. Therefore, as shown in FIG. 4, the number of pieces that can be shredded is increased within the limit value of the input current, and the frequency of shredding stop due to overload can be greatly reduced.

FIG. 5 shows the relationship between the number of pieces to be shredded and the time for shredding.
In the case of the Hz operation, B60 indicates the case of the 60 Hz operation. According to the present invention, the combination of the maximum number of revolutions and the maximum torque is selectively controlled within the limit value of the input current from the commercial power supply.
The shredding time can be significantly reduced. Further, since the number of revolutions can be increased to the maximum within the limit value of the input current from the commercial power supply according to the required torque, the shredding speed can be further increased beyond the conventional synchronous speed.

Further, according to the present invention, the shredding speed can be set in advance irrespective of the difference in the frequency of the commercial power supply, so that there is no need to replace the shredding mechanism in accordance with the frequency, and the constant shredding regardless of the frequency. It has the feature of obtaining fine shredding characteristics.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a control method according to the present invention.

FIG. 2 is a block diagram showing another embodiment of the control method of the present invention.

FIG. 3 is a characteristic diagram illustrating the relationship between the number of rotations of a motor and torque according to the present invention.

FIG. 4 is a characteristic diagram showing a relationship between the number of cut pieces and an input current.

FIG. 5 is a characteristic diagram showing a relationship between the number of pieces and the cutting time.

FIG. 6 is a characteristic diagram showing a relationship between a rotation speed and a torque of a conventional motor.

Continued on the front page (72) Inventor Takashi Hori 2nd Aichi-cho, Kasugai-shi, Aichi F-term (reference) in Aichi-Mason Electric Co., Ltd. 4D065 CA12 CB02 CC01 CC08 DD08 EB12 ED35 EE07 EE15

Claims (3)

[Claims] In a shredder control method configured to cut a paper sheet by driving a shredding mechanism by a motor, when a supplied voltage is used as a parameter, a motor torque substantially increases with an increase in the number of rotations. A motor having a characteristic of drooping linearly, and control means for outputting electric power to the motor interposed between the motor and a commercial power supply, and as the required torque of the shredding mechanism increases, A method for controlling a shredder, comprising reducing the number of revolutions of a motor and controlling power input from a commercial power supply not to exceed a predetermined value. 2. The method of controlling a shredder according to claim 1, wherein a current detecting means is provided between said control means and a commercial power supply. 3. The method of controlling a shredder according to claim 1, further comprising detecting current and voltage between said control means and said motor and estimating a current value at an input from a commercial power supply.