JP2007306673A - Counter-electromotive force eliminating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a counter-electromotive force eliminating device capable of eliminating a counter-electromotive force generated due to an inertial force of a motor by operating a load in an earlier stage, even if power supply is unexpectedly interrupted such as cover open, and having a simple circuit configuration. <P>SOLUTION: In order to eliminate a counter-electromotive force of a printer engine provided with a motor 26 connected to a power source line 36 for supplying power from a power source and a load 18 other than the motor 26 connected to the power source line 36, the eliminating device is provided with a detecting section 24 for outputting an alarm signal when the number of revolutions of the motor 26 is reduced from a usual number of revolutions to not more than a predetermined number of revolutions. When the alarm signal is inputted from the detecting section 24, a CPU 12 operates the load 18 so that the load 18 consumes the counter-electromotive force generated in the motor 26. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a back electromotive force removing apparatus that removes a back electromotive force generated by a motor connected to a power supply line that supplies power from a power source.

  Conventionally, processing devices such as printers have been provided with an interlock switch in a power supply line that supplies power to a drive system such as a motor, and when the user opens the cover, the interlock switch is turned off and the motor or the like A mechanism that cuts off the power supply to the drive system is installed. Thereby, even if the cover suddenly opens, the drive system such as a motor can be stopped, and safety can be ensured.

  For example, a ROS motor that rotates a polygon mirror of a ROS (light exposure apparatus) is also driven by a 24V power source and is ON / OFF controlled by an interlock switch. However, since the ROS motor rotates at high speed, even if the drive of the motor is stopped, the motor does not stop immediately due to the inertial force, but causes the action of the generator, and electrical energy that does not require the rotational energy (back electromotive force) Is generated.

  The opening / closing of the interlock switch is recognized by reading the divided voltage value of the resistor with a voltage detection circuit on the MCU connected to the power supply line and detecting the voltage level. Specifically, when the interlock switch is opened, the power supply is cut off and a voltage drop occurs in the power supply line. By detecting this, it can be detected that the cover is opened. However, since the potential level rises due to the electric energy generated by the motor described above, the voltage drop is delayed until the voltage drops below the threshold for detecting the low level voltage in the CPU constituting the MCU. Takes time.

  Therefore, the interlock switch is opened by opening the cover and the power supply to the ROS motor is cut off, but the detection voltage does not drop immediately, the detection of the switch opening is delayed, and the control at the time of opening the cover is delayed. There is a case. In addition, the power supply of the other logic system (5V / 3.3V) that is converted from the 24V power supply by dividing the voltage becomes unstable, and the accuracy of engine control is lowered.

  Generally, in inductive loads such as motors and solenoids, the current due to back electromotive force generated by switching is looped by a flywheel diode, etc., or the FET or transistor prepared for power removal is switched to consume the current. This increases the cost due to the addition of elements and hinders the integration of the substrate.

In addition, a back electromotive force removing device using a MOS-FET has also been proposed (see, for example, Patent Document 1). In addition, a method of increasing the load amount in advance in accordance with the DC motor stop timing has been devised (see, for example, Patent Document 2).
JP-A-6-343291 JP 2001-150755 A

  However, in the conventional technology, there are many additional mounting parts and the circuit becomes complicated. In addition, it cannot respond to unexpected motor stops such as cover open.

  In addition, it is possible to connect a dedicated switch open / close detection line independent of the power supply line to the MCU to detect the opening of the interlock switch, and to expedite the switch open detection, but this additional function increases the cost. It leads to accumulation inhibition.

  The present invention has been made in order to solve the above-described problems. The counter electromotive force generated by the inertial force of the motor can be removed by operating the load earlier and the circuit configuration is simple. An object is to provide a removal device.

  In order to achieve the above object, a back electromotive force removing device according to a first aspect of the present invention includes a motor connected to a power supply line for supplying power from a power supply and a load other than the motor connected to the power supply line. A back electromotive force removing device for removing back electromotive force generated in the processing device, and a detection means for outputting a detection signal when it is detected that the rotational speed of the motor has decreased from a normal rotational speed to a predetermined rotational speed or less. And a control means for operating the load so that the counter electromotive force generated by the motor is consumed when the detection signal is inputted from the detection means.

  The back electromotive force removing device according to the second aspect of the present invention includes a motor connected to a power supply line that supplies power from a power supply, a load other than the motor connected to the power supply line, and a power supply line connected to the power supply line. A back electromotive force removing device that operates when a cover is opened and removes a back electromotive force generated in a processing device having a switch that cuts off power supply from the power source to the motor and a load other than the motor. A detection means for outputting a detection signal when it is detected that the rotational speed of the motor has decreased from a normal rotational speed to a predetermined rotational speed or less after power to the motor is interrupted; and Control means for operating the load so as to consume the counter electromotive force generated by the motor when a signal is input.

  As described above, the detection signal is output when the rotation speed of the motor is reduced from the normal rotation speed to a predetermined rotation speed or less, and the counter electromotive force generated by the inertia force of the motor is consumed when the detection signal is output. Since the load is operated as described above, it is possible to remove the back electromotive force by operating the load earlier, to prevent element destruction due to the back electromotive force of the motor, and to remove unstable elements of engine control.

  Further, by speeding up the voltage drop of the power supply line, necessary processing can be executed more quickly, especially when the power supply is suddenly shut down such as when the cover is open.

  Moreover, since the load pre-installed in the processing device is used to remove the back electromotive force, an additional part, for example, an ON / OFF circuit using a transistor or FET, and two systems for detecting a cover open are provided. It can be realized by an inexpensive circuit configuration without mounting electronic parts such as a microswitch and a diode.

  The processing apparatus may include an optical exposure apparatus, and the motor may be a motor that drives the optical exposure apparatus.

  The processing apparatus includes a plurality of motors connected to the power supply line, the first or second back electromotive force removing apparatus is provided with a plurality of detection means corresponding to the plurality of motors, and the control is performed. The means may operate the load when a detection signal input earliest among a plurality of detection signals input from the plurality of detection means.

  In addition, it is preferable that the control unit operates a load unrelated to the process being executed in the processing device when the detection signal is input from the detection unit.

  As a result, the greatest effect can be expected in shortening the power down time.

  As described above, according to the present invention, it is possible to reduce the number of additional mounting parts, and to operate the load more quickly with a simple circuit configuration to remove the counter electromotive force generated by the inertial force of the motor. There is an excellent effect of being able to.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a printer engine including a back electromotive force removing device according to an embodiment of the present invention.

  A power supply device 30 that supplies power from a 24V power supply 32; a ROS unit 16 that includes a ROS motor 26 that rotates a polygon mirror of a light exposure device (ROS); a load 18 that is a load other than the ROS motor 26; An MCU (Main Computer Unit) 10 that performs logic control of ON / OFF of the load 18 is provided. The load 18 is a load that is pre-installed in the printer engine, and can be an inductive load such as a clutch or a solenoid disposed in a feeder portion that supplies print paper.

  Although the printer engine is provided with various motors in addition to the ROS motor 26, the illustration is omitted in this example.

  The ROS motor 26 and the load 18 are connected to a power supply line 36 connected to a 24V power supply 32, and power from the 24V power supply is supplied via the power supply line 36.

  An interlock switch 34 is disposed between the 24V power supply 32 and the MCU 10. The interlock switch 34 turns off the power supply line 36 when the rear or front cover of the printer on which the printer engine is mounted is opened to cut off the power supply from the 24V power supply 32 to the ROS motor 26 and the load 18. When closed, the power supply from the 24V power source 32 to the ROS motor 26 and the load 18 is maintained in the ON state.

  The MCU 10 is disposed after the interlock switch and includes a CPU 12 and a voltage dividing circuit 14.

  The potential level of the voltage from the power supply line 36 to the CPU 12 is converted to a logic voltage (5 V / 3.3 V) that can be input to the CPU 12 by the voltage dividing resistors 20 and 22 constituting the voltage dividing circuit 14. The open / close state of the interlock switch 34 is determined by the CPU 12 detecting the voltage from the power supply line 36 at the potential level converted by the voltage dividing circuit 14.

  Generally, a threshold value for determining whether an input voltage is a high level voltage (VIH: Input High Voltage) or a low level voltage (VIL: Input Low Voltage) is set in the CPU. For example, when a voltage having a level lower than the VIL threshold is input from the power supply line 36 via the voltage dividing circuit 14, the CPU 12 recognizes the low level voltage and determines that the interlock switch 34 is opened.

  The ROS unit 16 includes a detection unit 24 that monitors the rotation of the ROS motor 26. The detection unit 24 detects that the power line 36 is turned off and the power supply to the ROS motor 26 is cut off, or an error occurs in the ROS motor 26, and the rotation speed of the ROS motor 26 decreases from the normal rotation speed to a predetermined rotation speed or less. Sometimes, an alarm signal is output to the CPU 12.

  The configuration of the detection unit 24 that outputs an alarm signal is not particularly limited. For example, an encoder that is generally used for controlling the number of rotations of the motor may be used as the detection unit 24.

  FIG. 2 shows a flowchart of the back electromotive force removal control executed by the CPU 12.

  In step 100, it is determined whether an alarm signal is input from the detection unit 24. When an alarm signal is input, in step 102, the load 18 that does not affect the operation of the printer engine is turned on and operated.

  For example, when an alarm signal is output to the CPU 12 due to the interruption of the power supply line 36 due to the opening of the interlock switch 34 (or an error of the ROS motor 26), it is connected to the power supply line 36 so as not to affect the conveyance of the printing paper. A load 18 such as a clutch or solenoid is driven. Thereby, the counter electromotive force generated by the rotation of the ROS motor 26 can be generated.

  Even if the alarm signal input to the CPU 12 is a signal output with the interlock switch 34 opened as a trigger, the voltage level of the voltage input to the CPU 12 via the voltage dividing circuit 14 at this time is the ROS motor 26. The voltage drop is not recognized because it is not sufficiently lowered by the electric energy (back electromotive force) generated by the inertial force. On the other hand, the detection unit 24 outputs an alarm signal when the rotation speed of the ROS motor falls below a predetermined rotation speed regardless of the counter electromotive force, so that the voltage input to the CPU 12 via the voltage dividing circuit 14 is VIL threshold. An alarm signal can be output before reaching a level below the hold. Thus, even during a period when the CPU 12 cannot recognize the voltage drop, the alarm signal from the detection unit 24 is used as a trigger to operate the load 18 that does not affect the operation of the printer engine, and the electric power generated by the inertia of the ROS motor 26 Since energy (back electromotive force) can be consumed by the load 18, the potential level of the voltage input to the CPU 12 via the voltage dividing circuit 14 falls quickly.

  For example, when there are a plurality of feeders that feed paper to the printer engine, the load to be operated here is to cause the solenoid or clutch of a feeder other than the feeder being used by the printer engine to consume back electromotive force. It can be used as a load to be operated. In this way, the maximum effect can be expected to shorten the voltage drop time by operating a load unrelated to the process being executed.

  In step 104, the interlock open / close detection is performed until a predetermined (but extremely short) time elapses after the load 18 is turned on, and the voltage level of the power supply line 36 input via the voltage dividing circuit 14 is changed to the VIL threshold. It is determined whether or not a level below the hold has been reached and the level has become Low.

  When it is recognized in step 104 that the voltage level of the power supply line 36 input via the voltage dividing circuit 14 has reached a level below the VIL threshold and has become low level, the rear or front cover is opened. In step 106, it is determined that the power supply has been cut off because the interlock switch 34 has been opened, and in step 106, the driving of all the motors including the ROS motor 26 is stopped to notify the cover open. Etc.).

  On the other hand, if the voltage detection level is high even at the time of step 104, the 24V power supply is not cut off and it is determined that there is an error in the ROS motor 26, and motor error processing (for example, all including the ROS motor 26). The process of notifying the error of the ROS motor and the like is stopped).

  FIG. 3 is a graph showing an example of a measurement result obtained by measuring the voltage level when the interlock switch 34 is opened at the contact 28 connecting the voltage dividing circuit 14 and the CPU 12.

  When the interlock switch 34 is opened at the timing of T1, a back electromotive force is generated and the voltage level is increased as shown by a solid line L1 (see T2). On the other hand, the rotational speed of the ROS motor is decreased. , An alarm signal is output from the detection unit 24 at the timing of T3. When the CPU 12 receives the alarm signal, the CPU 12 turns on an inductive load clutch or the like (load 18) so as to consume the generated back electromotive force. As a result, the fall of the voltage drop is accelerated, and the voltage level reaches the VIL threshold at time T4.

  If the voltage level reaches the VIL threshold without operating the load, the voltage level changes as shown by the dotted line L2, and the voltage level reaches the VIL threshold at the timing of T5. Become.

  Therefore, the voltage drop time can be shortened by Δt by operating the load using the alarm signal from the detection unit 24 as a trigger before the voltage level reaches the VIL threshold.

  The voltage drop time can be controlled by the capacity of the inductive load, and the voltage drop time can be further shortened by turning on many loads and supplying a current.

  In this way, the alarm signal is output when the motor rotation speed falls below the predetermined rotation speed from the normal rotation speed, and the load is operated so that the counter electromotive force is consumed when the alarm signal is output. Therefore, with a simple circuit configuration, even when the power supply is suddenly interrupted, such as when the cover is open, the load can be operated earlier to remove the back electromotive force. As a result, the voltage can be quickly lowered, so that the power supply interruption can be detected earlier by the CPU, and the necessary processing can be executed earlier. Furthermore, instability that occurs in the logic system due to a delay in voltage drop and destruction of other elements can be prevented.

  In the above-described embodiment, the example in which the load is operated using the alarm signal output due to the decrease in the rotation speed of the ROS motor 26 as a trigger has been described. The detection unit 24 can also be installed in each of the other motors driven by the power supplied from the power supply line 36. Then, among the alarm signals output from the plurality of detection units 24, the load may be operated when the alarm signal input to the CPU 12 earliest is input. As a result, the load can be operated more quickly, which is effective in removing the counter electromotive force.

  Also, with regard to loads that consume back electromotive force, it is effective to use all loads that do not affect print control because more current can be consumed more quickly by simultaneously controlling (ON) multiple loads. is there.

It is a figure which shows the structure of the printer engine containing the back electromotive force removal apparatus which concerns on this Embodiment. It is a flowchart of the back electromotive force removal control performed by CPU. It is a graph which shows an example of the measurement result which measured the voltage level when the interlock switch was opened in the contact which connects a voltage dividing circuit and CPU.

Explanation of symbols

10 MCU
12 CPU
14 Voltage Divider 18 Load 24 Detector 26 ROS Motor 30 Power Supply 32 24V Power Supply 34 Interlock Switch 36 Power Supply Line

Claims (5)

A back electromotive force removing device that removes a back electromotive force generated in a motor connected to a power supply line that supplies power from a power supply and a processing device including a load other than the motor connected to the power supply line,
Detection means for outputting a detection signal when detecting that the rotational speed of the motor has decreased from a normal rotational speed to a predetermined rotational speed or less;
Control means for operating the load so as to consume back electromotive force generated by the motor when the detection signal is input from the detection means;
A back electromotive force removing device. A motor connected to a power supply line for supplying power from a power supply, a load other than the motor connected to the power supply line, and a motor connected to the power supply line and operating when the cover is opened, from the power supply to the motor And a back electromotive force removing device that removes back electromotive force generated in a processing device having a switch that cuts off the supply of power to a load other than the motor,
Detection means for outputting a detection signal when it is detected that the rotational speed of the motor has decreased from a normal rotational speed to a predetermined rotational speed or less after power to the motor is interrupted;
Control means for operating the load so as to consume back electromotive force generated by the motor when the detection signal is input from the detection means;
A back electromotive force removing device. The processing apparatus includes a light exposure device,
3. The back electromotive force removing apparatus according to claim 1, wherein the motor is a motor that drives an optical exposure apparatus. The processing apparatus includes a plurality of motors connected to the power line,
A plurality of the detection means are provided corresponding to the plurality of motors,
3. The back electromotive force removal apparatus according to claim 1, wherein the control unit operates the load when a detection signal input earliest among a plurality of detection signals input from the plurality of detection units.   5. The back electromotive force according to claim 1, wherein when the detection signal is input from the detection unit, the control unit operates a load irrelevant to a process being executed in the processing device. 6. Removal device.

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