JP2012200062A - Motor control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor control device that can quickly detect the application of excessive torque to a DC motor and stop rotary drive of the DC motor.SOLUTION: The motor control device for supplying a rotation enabling signal permitting rotary drive of a DC motor to a motor unit comprising the DC motor and a drive circuit includes an overcurrent detection section for detecting a supply current to the motor unit to detect an overcurrent, and a rotation enabling signal generation section for generating a rotation enabling signal according to the result of overcurrent detection. The rotation enabling signal generation section outputs the rotation enabling signal irrespective of the result of overcurrent detection for a constant period after the start of the DC motor, and stops outputting the rotation enabling signal when an overcurrent is detected after the lapse of the constant period.

Description

  The present invention relates to a motor control device, and more particularly to a motor control device that supplies a rotation enable signal for permitting rotation driving of a DC motor to a motor unit including a DC motor and a drive circuit.

  Printers, copiers, and FAX (facsimile) apparatuses are provided with a transport device for transporting recording paper in a paper feed cassette to an image forming unit, and the transport device is provided with various rollers such as paper feed rollers. . The image forming unit is also provided with a photosensitive drum, a transfer roller, a fixing roller, and the like. These rollers are rotationally driven by a DC motor, and the rotation of a rotor is transmitted via a reduction gear. In such an apparatus, when a paper jam called a paper jam occurs, the rotation of the roller stops despite being energized by the DC motor. For this reason, excessive rotational torque is added to the reduction gear of the roller stopped due to a paper jam.

  In particular, in the case of a motor unit including a DC motor and a drive circuit that performs feedback control so that the rotor rotates at a constant speed, the larger the rotation of the rotor deviates from the target speed, the larger the rotation torque increases. Current is supplied. For this reason, there has been a problem that a larger rotational torque is applied to the reduction gear of the roller stopped due to a paper jam.

  Further, when a plurality of rollers are rotationally driven by a single DC motor, a DC motor that generates a larger rotational torque is required than when each roller is rotationally driven individually. In such a drive system, if a paper jam occurs at one location, the rotational torque of the DC motor concentrates on the roller stopped by the paper jam, and an excessive rotational torque is added to the reduction gear of the roller. There was also. In the case of a resin reduction gear, if excessive torque is applied, it may be damaged.

  Therefore, a paper sensor for detecting the presence or absence of the recording paper is provided in the recording paper conveyance path, the occurrence of the paper jam is detected based on the output of the paper sensor, and if the occurrence of the paper jam is detected, the DC motor is driven to rotate. It is conceivable to stop. However, with such a configuration, there is a problem that the time lag from when the roller stops due to a paper jam until the occurrence of the paper jam is detected by the output of the paper sensor is large, and the reduction gear cannot be damaged. It was.

  Patent Document 1 discloses a DC motor control technique for monitoring the current flowing through the armature in order to detect that the rotational speed of the rotor exceeds the speed limit. Patent Document 2 discloses a control technique for detecting a current flowing through a DC motor and adjusting a duty ratio of a PWM (Pulse Width Modulation) signal in order to prevent the brush and commutator from being worn. Yes. The techniques described in these patent documents do not detect the occurrence of a paper jam and cannot prevent the reduction gear from being damaged.

  In particular, the motor unit is packaged with a DC motor and a drive circuit that controls the DC motor based on a speed control signal that indicates a target speed, a rotation enable signal that permits rotation drive, and a direction signal that indicates the rotation direction. There is something that is. Conventionally, regarding such a packaged motor unit, there is no known technique for detecting the addition of excessive torque due to a paper jam or the like and stopping the rotational drive of the DC motor.

JP 2000-22902 A JP-A-8-275573

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a motor control device that can quickly detect the addition of excess torque in a DC motor and stop the rotational drive of the DC motor. . It is another object of the present invention to provide a motor control device that can correctly detect the application of excessive torque due to a paper jam or the like and stop the rotational drive of a DC motor.

  A motor control device according to a first aspect of the present invention is a motor control device that supplies a rotation enable signal for permitting rotation of the DC motor to a motor unit comprising a DC motor and a drive circuit. An overcurrent detection unit that detects supply current and detects an overcurrent, and a rotation enable signal generation unit that generates the rotation enable signal based on the detection result of the overcurrent, and the rotation enable signal generation unit includes: The rotation enable signal is output within a certain period after the DC motor is started regardless of the detection result of the overcurrent, and the rotation enable signal is detected when an overcurrent is detected after the lapse of the certain period. Configured to stop the output of.

  According to such a configuration, the overcurrent is detected by the supply current to the motor unit, and the output of the rotation enable signal is stopped. Therefore, the addition of excess torque in the DC motor is detected immediately, and the rotation of the DC motor is driven. Can be stopped. Also, even if an overcurrent is detected during a certain period after the DC motor is started, the output of the rotation enable signal is not stopped. Therefore, it is possible to correctly detect the addition of excessive torque due to a paper jam or the like to drive the rotation of the DC motor. Can be stopped.

  A motor control device according to a second aspect of the present invention includes, in addition to the above configuration, a timer that outputs a time-up signal after a predetermined time has elapsed since the start of the DC motor, and the rotation enable signal generation unit includes the time-up The rotation enable signal is configured to be generated based on the signal.

  According to such a configuration, by appropriately specifying in advance the time until the timer expires, it is possible to suppress erroneous detection of excessive torque due to overcurrent immediately after the DC motor is started. it can.

  According to a third aspect of the present invention, in the motor control device according to the present invention, the overcurrent detection transistor is turned on when the current flowing through the ground line between the motor unit and the ground exceeds a certain level. And an overcurrent signal generation circuit for generating an overcurrent detection signal whose voltage level is switched from a high level to a low level when the overcurrent detection transistor is turned on, the rotation enable signal generation unit and the timer Is constituted by a single processor in which the overcurrent detection signal is input to the input port.

  According to such a configuration, the overcurrent detection unit can be configured by hardware, and the rotation enable signal generation unit and the timer can be configured by software. Also, since an overcurrent detection signal that switches the voltage level to a low level when an overcurrent is detected is input, the input port for detecting excess torque is not an I / O port for analog signals, but a general-purpose I / O ports can be used.

  According to a fourth aspect of the present invention, there is provided a motor control device comprising: a speed control signal indicating a target speed of the DC motor; and a rotation enable signal for permitting the rotational drive of the DC motor to a motor unit including a DC motor and a drive circuit. A motor control device that receives a rotation abnormality signal indicating that a difference between a rotation speed of the DC motor and a target speed is equal to or greater than a threshold, detects a supply current to the motor unit, and detects an overcurrent. An overcurrent detection unit for detecting, an activation period determination unit for determining an activation period from when the DC motor is activated until the rotation speed reaches a target speed, based on the rotation abnormality signal; A rotation enable signal generating unit that generates the rotation enable signal based on a current detection result, and the rotation enable signal generating unit The rotation enable signal is output regardless of the detection result of the overcurrent, and the output of the rotation enable signal is stopped when an overcurrent is detected after the start-up period. .

  According to such a configuration, the overcurrent is detected by the supply current to the motor unit, and the output of the rotation enable signal is stopped. Therefore, the addition of excess torque in the DC motor is detected immediately, and the rotation of the DC motor is driven. Can be stopped. Also, even if an overcurrent is detected during the start-up period of the DC motor, the output of the rotation enable signal is not stopped. Therefore, the rotation drive of the DC motor is stopped by correctly detecting the addition of excessive torque due to a paper jam or the like. Can do. In particular, since the activation period is determined based on the rotation abnormality signal received from the motor unit, it is possible to suppress erroneous detection of excessive torque due to an overcurrent immediately after activation of the DC motor.

  A motor control device according to a fifth aspect of the present invention includes, in addition to the above configuration, a speed control signal generation unit that generates the speed control signal, and the overcurrent detection unit has a current flowing through a ground line between the motor unit and the ground. An overcurrent detection transistor that turns on when the voltage exceeds a certain level, and an overcurrent detection signal that generates an overcurrent detection signal that switches the voltage level from a high level to a low level when the overcurrent detection transistor is turned on. A generation circuit, and the start period determination unit includes a period end signal generation circuit that generates a period end signal for switching a voltage level from a high level to a low level at the end of the start period, and the speed control signal generation unit And the rotation enable signal generator generates a logical sum of the overcurrent detection signal and the period end signal. Configured such that a single processor to be input to.

  According to such a configuration, the overcurrent detection unit and the activation period determination unit can be configured by hardware, and the speed control signal generation unit and the rotation enable signal generation unit can be configured by software. The processor input port also includes a period end detection signal for switching the voltage level to a low level when the DC motor start-up period ends, and an overload for switching the voltage level to a low level when an overcurrent is detected. A logical sum with the current detection signal is input. Therefore, a general-purpose input / output port can be used as an input port for detecting excess torque, instead of an input / output port for analog signals.

  In the motor control device according to the present invention, the overcurrent is detected by the supply current to the motor unit, and the output of the rotation enable signal is stopped. Therefore, the addition of excess torque in the DC motor is detected immediately to drive the rotation of the DC motor. Can be stopped. Also, even if an overcurrent is detected during a certain period after the DC motor is started, the output of the rotation enable signal is not stopped. Therefore, it is possible to correctly detect the addition of excessive torque due to a paper jam or the like to drive the rotation of the DC motor. Can be stopped.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view illustrating an example of a multifunction machine 1 including a motor control device 100 according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view illustrating an example of a cut surface when the multifunction machine 1 of FIG. 1 is cut along a vertical plane, and shows a state inside the main body 13. FIG. 2 is a block diagram illustrating a configuration example of a roller driving unit 6 disposed in the multifunction machine 1 of FIG. 1, in which a motor control device 100 and a motor unit 200 are illustrated. FIG. 4 is a block diagram showing an example of a detailed configuration in the motor unit 200 of FIG. 3. FIG. 4 is a block diagram illustrating a configuration example in a main part of the motor control device 100 in FIG. 3, illustrating an example of a functional configuration in a CPU 110. It is explanatory drawing which showed typically an example of the rotational torque Rt at the time of starting in the DC motor 220 of FIG. It is the flowchart which showed an example of the operation | movement at the time of DC motor starting in CPU110 of FIG. It is the block diagram which showed the structural example of the roller drive unit 6 containing the motor control apparatus 100 by Embodiment 2 of this invention. FIG. 9 is a block diagram illustrating a configuration example in a main part of the motor control device 100 in FIG. 8, illustrating an example of a functional configuration in the CPU 110. FIG. 9 is a timing chart showing an example of an operation when the DC motor 220 is started in the roller drive unit 6 of FIG. 8. FIG. It is the block diagram which showed the other structural example of the motor control apparatus 100 by this invention.

Embodiment 1 FIG.
<Multifunction machine 1>
FIG. 1 is a perspective view illustrating an example of a multifunction machine 1 including a motor control device 100 according to Embodiment 1 of the present invention. The multifunction device 1 is an image processing apparatus that has a scanner function, a printer function, a FAX transmission / reception function, and a copying function, and can selectively execute these functions, and includes a document reading unit 11, an operation panel 12, and a main body unit. 13.

  The document reading unit 11 is a reading unit that optically reads a document, and includes a manual tray that stores the document, an ADF (auto document feeder) that transports the document in the manual tray to a reading position, and illumination light to the document at the reading position. It consists of an illumination device for irradiating, an image sensor for receiving reflected light from a document, and the like.

  The operation panel 12 is provided with a display for displaying operation information and various operation keys such as a start key. The main body unit 13 is an image forming unit that prints image data on a recording sheet, and includes a conveyance device, a printing unit, and the like. A paper feed cassette 14 for storing recording paper before printing is provided below the main body 13. In addition, a discharge tray 15 for storing the recording paper after printing is provided on the upper part of the main body 13. A front cover 21 is provided on the front surface of the main body 13, and a jam access cover 22 is provided on the right side surface.

  If a print request is received from an external device such as a PC (Personal Computer), or image data is received by FAX, or if the start key is pressed when the copy function is selected, the inside of the paper cassette 14 The recording paper is conveyed to the printing unit, and printing processing is executed. The printed recording paper is discharged into the paper discharge tray 15.

<Roller group driven by DC motor>
FIG. 2 is a cross-sectional view showing an example of a cut surface when the multi-function device 1 of FIG. 1 is cut along a vertical plane, and shows the inside of the main body 13. The main body 13 includes a paper feed cassette 14, a paper discharge tray 15, a transport path 16, a paper feed roller 18, a separation roller 19, a registration roller 20, a development transfer unit 3, a fixing unit 4, a transport roller 51, and a paper discharge roller 52. Is arranged.

  The recording paper 2 accommodated in the paper feed cassette 14 is lifted by the flapper 17, and the recording paper 2 arranged at the uppermost stage is picked up into the conveyance path 16 by the paper feed roller 18, and the separation roller 19 and the registration roller 20 is conveyed to the developing and transferring unit 3 via 20.

  The development transfer unit 3 includes a photosensitive drum 31, a charger 32, an exposure unit 33, a development unit 34, a developer carrier 35, a transfer roller 36, and a cleaner 37, and recorded on the charged photosensitive drum 31. The electrostatic latent image is developed with toner.

  The fixing unit 4 includes a heat roller 41 heated by a halogen heater, a press roller 42, and a separation claw 43. The unfixed toner image transferred to the recording paper 2 is heated and applied by the heat roller 41 and the press roller 42. Press and fix. The printing unit described above includes such a development transfer unit 3 and a fixing unit 4.

  The printed recording paper 2 is transported in the transport path 16 by the transport roller 51 and discharged into the paper discharge tray 15 by the paper discharge roller 52. Among various rollers arranged in the main body 13, a plurality of rollers are driven by one DC motor. For example, the paper feed roller 18, the separation roller 19, the registration roller 20, the photosensitive drum 31, the heat roller 41, the transport roller 51, and the paper discharge roller 52 are rotationally driven by one DC motor via a reduction gear.

<Roller drive unit 6>
FIG. 3 is a block diagram illustrating a configuration example of the roller driving unit 6 disposed in the multifunction machine 1 of FIG. 1, in which the motor control device 100 and the motor unit 200 are illustrated. The roller drive unit 6 includes a motor control device 100 and a motor unit 200, and rotationally drives various rollers in the main body unit 13.

  The motor unit 200 is an electric motor unit including an external terminal unit 201, a drive circuit 210, and a DC motor 220. The DC motor 220 is a DC motor that is rotationally driven by a DC voltage supplied from the drive circuit 210. The drive circuit 210 performs feedback control of the DC motor 210 so that the DC motor 220 rotates at a constant speed based on a predetermined speed control signal indicating the target speed.

The external terminal unit 201 includes a power supply terminal for supplying DC power (power supply voltage V ₁ ) to the drive circuit 210 and a plurality of input / output terminals for inputting / outputting various control signals such as a speed control signal. The motor unit 200 is packaged such that various control signals are input / output to / from the drive circuit 210 via the external terminal unit 201.

  The motor control device 100 is a control unit that supplies a DC power source, a speed control signal, a rotation enable signal, and a direction signal to the motor unit 200. The motor control device 100 includes a circuit board 101, an external terminal unit 102, a CPU 110, and an overcurrent detection unit 120. Composed. The external terminal unit 102 includes a power supply terminal and a plurality of input / output terminals for inputting / outputting various control signals.

  The CPU 110 is a single processor that generates a speed control signal, a rotation enable signal, and a direction signal, and an overcurrent detection signal is input from the overcurrent detection unit 120 to an input port for detecting excess torque. The CPU 110 operates based on an instruction from another control unit in the main body unit 13, for example, a printing unit.

  The speed control signal is a speed instruction signal for instructing a target speed of the DC motor 220, and includes, for example, a clock pulse signal (CLK) whose frequency corresponds to the target speed. The direction signal is a rotation direction instruction signal for instructing the rotation direction of the DC motor 220.

  The rotation enable signal is a drive permission signal for permitting rotation driving of the DC motor 220, and is output during a period during which rotation driving is permitted. As such a rotation enable signal, for example, a state signal in which the voltage level is switched from the high level to the low level at the start of the permission period and the voltage level is switched from the low level to the high level at the end of the permission period is used. it can.

Overcurrent detection unit 120 detects a current supplied to the motor unit 200, the detection circuit for outputting a detection result to the CPU110 detects an overcurrent, for example, an overcurrent detection transistor T _r1, overcurrent It consists of a signal generation circuit 121.

Overcurrent detection transistor T _r1 is a switching element for detecting the current I ₁ flowing through the ground line between the motor unit 200 and the ground as the supply current to the motor unit 200. The transistor T _r1 is turned on when the current I ₁ that flows to ground from the power supply terminal via a resistor element R ₁ exceeds a predetermined level. That is, the transistor T _r1, the voltage obtained by the current I ₁ flows through the resistor element R ₁ is applied to the gate terminal, is turned on by the voltage value exceeds a predetermined value.

Overcurrent signal generation circuit 121 includes a DC power supply (power supply voltage V ₂₎ and a resistor element R _2, by overcurrent detection transistor T _r1 is turned on, the overcurrent voltage level is switched from the high level to the low level A detection signal is generated and output to the CPU 110. Excess torque detecting input port, the input of the overcurrent detection signal, when the overcurrent is detected, is driven from the potential V ₂ to the voltage 0. Such external terminal unit 102, CPU 110, and overcurrent detection unit 120 are arranged on the circuit board 101.

<Motor unit 200>
FIG. 4 is a block diagram showing an example of a detailed configuration in the motor unit 200 of FIG. In the motor unit 200, the DC motor 220 is a three-phase brushless motor. Specifically, the drive circuit 210 includes a PWM circuit 211, a DC voltage output circuit 212, an excitation control circuit 213, and an FG sensor 214, and the DC motor 220 includes a rotor 221 and a stator (stator) coil 222. .

  The rotor 221 is a rotating body that rotates about a predetermined rotation axis with respect to the stator coil 222, and a reduction gear for transmitting rotational torque to various rollers is fixed. A magnet for the FG sensor is disposed on the peripheral portion of the rotor 221. The FG (frequency power generation) sensor 214 is arranged to face the circumferential surface of the rotor 221 and includes a magnetic detection element that generates a pulse signal (FG pulse signal) having a frequency corresponding to the rotational speed of the rotor 221.

  The PWM circuit 211 receives the FG pulse signal from the FG sensor 214, generates a PWM signal based on the clock pulse signal input from the motor control device 100, and outputs the PWM signal to the DC voltage output circuit 212. The PWM circuit 211 compares the target speed indicated by the clock pulse signal with the rotational speed of the rotor 221 and adjusts the duty ratio of the PWM signal so that they match.

The DC voltage output circuit 212 is supplied with the DC power supply V ₁ from the motor control device 100, and switches the switching element by the PWM signal input from the PWM circuit 211, thereby supplying a predetermined DC voltage Vs to the excitation control circuit 213. Output. The excitation control circuit 213 receives the rotation enable signal and the direction signal from the motor control device 100 and switches the current flowing through the stator coil 222 by the DC voltage Vs input from the DC voltage output circuit 212. The rotational speed of the rotor 221 is controlled by the DC voltage Vs.

In the excitation control circuit 213, when the rotation drive is permitted by the rotation enable signal, the rotor 221 is driven to rotate based on the DC voltage Vs. On the other hand, when the rotational drive is not permitted, the rotor 221 is not rotationally driven. The current I ₁ detected in the motor control device 100 is output from the excitation control circuit 213 to the ground line.

<CPU 110 in Motor Control Device 100>
FIG. 5 is a block diagram illustrating a configuration example of a main part of the motor control device 100 in FIG. 3, and illustrates an example of a functional configuration in the CPU 110. The CPU 110 includes a speed control signal generator 111, a rotation enable signal generator 112, a direction signal generator 113, and a timer 114.

  The speed control signal generation unit 111, the rotation enable signal generation unit 112, and the direction signal generation unit 113 generate a clock pulse signal, a rotation enable signal, and a direction signal, respectively, based on instructions from the printing unit and the like, and send them to the motor unit 200. Output.

  Here, the target speed indicated by the clock pulse signal (CLK) is constant during the output period of the rotation enable signal. In addition, with respect to the rotation enable signal, by driving the output port potential from the high level to the low level, the motor unit 200 is instructed to start the rotation drive, and by driving the output port potential from the low level to the high level. The end of the rotation drive is instructed.

  The rotation enable signal generation unit 112 generates a rotation enable signal based on the detection result of the overcurrent by the overcurrent detection unit 120 and the timer 114 time-up signal. That is, the rotation enable signal generation unit 112 outputs a rotation enable signal within a certain period (starting period) after starting the DC motor 220 regardless of the detection result of the overcurrent. On the other hand, after the start-up period has elapsed, when an overcurrent is detected, an operation for stopping the output of the rotation enable signal is performed.

  The timer 114 outputs a predetermined time-up signal to the rotation enable signal generation unit 112 after a predetermined time Th1 has elapsed since the DC motor 220 was started. The activation of the DC motor 220 can be detected by, for example, a rotation enable signal.

  The rotation enable signal generation unit 112 detects the end of the activation period based on the time-up signal input from the timer 114. During the start-up period of the DC motor 220, the overcurrent detection signal input from the overcurrent signal generation circuit 121 is ignored and a rotation enable signal is output. On the other hand, if the overcurrent detection signal is input after the start-up period ends, the output of the rotation enable signal is stopped.

<Rotational torque at startup>
FIG. 6 is an explanatory view schematically showing an example of the rotational torque Rt at the start-up of the DC motor 220 in FIG. When the DC motor 220 is started when a predetermined load such as a roller is applied to the rotor 221, a rotational torque Rt having a large peak (peak value = R _t1 ) is generated immediately after the start.

That is, the rotational torque Rt applied to the rotor 221 increases rapidly from 0 after the starting time 0 and reaches the peak value R _t1 at time t ₁ . Torque Rt, the time _{t 1} and later gradually decreases, are stable after reaching the torque value _{R t2} at time _{t 2.}

DC motor 220, the time _{t 2} after a state where the rotor 221 is rotated at a constant speed (steady state). In general, the current I ₁ supplied to the motor unit 200 varies in proportion to such rotational torque. Therefore, it is determined that the starting time 0 to the time t ₂ is the starting period of the DC motor 220, and the timer 114 that times up by a time Th1 longer than the starting period is used. By configuring in this way, it is possible to prevent erroneous detection of addition of excess torque due to overcurrent during the startup period.

If it is overcurrent detected after the timer 114 has timed at time t _3, the output of the rotary enable signal is stopped, the rotational driving of the rotor 221 is also stopped. Here, the time Th1 may be a fixed value, or may be varied according to the target speed or load state of the rotor 221, that is, the torque value _Rt2 .

  Steps S101 to S106 in FIG. 7 are flowcharts showing an example of the operation when the DC motor is started in the CPU 110 in FIG. First, when an instruction to start driving the DC motor 220 is given from the printing unit or the like, the CPU 110 generates a rotation enable signal and outputs it to the motor unit 200 (step S101). At this time, the CPU 110 activates the timer 114 (step S102).

  Next, when a time-up signal is input from the timer 114 after a predetermined time has elapsed, the CPU 110 shifts to an excessive torque detection mode and monitors an overcurrent detection signal input to the input port for excessive torque detection (step). S103). Then, if an overcurrent is detected by the input of the overcurrent detection signal, the CPU 110 immediately stops outputting the rotation enable signal and ends this processing (steps S104 and S105).

  On the other hand, when the CPU 110 is instructed to end the driving of the DC motor 220, the CPU 110 stops outputting the rotation enable signal and ends this processing (steps S104 and S106).

  According to the present embodiment, the overcurrent is detected by the supply current to the motor unit 200 and the output of the rotation enable signal is stopped. Therefore, the addition of excess torque in the DC motor 220 is detected immediately, and the DC motor 220 The rotational drive can be stopped. Further, even if an overcurrent is detected during a certain period after the start of the DC motor 220, the output of the rotation enable signal is not stopped. Therefore, the rotation of the DC motor 220 is detected by correctly detecting the addition of excessive torque due to a paper jam or the like. The driving can be stopped.

  Furthermore, by appropriately specifying in advance the time until the timer 114 times out, it is possible to suppress erroneous detection of excessive torque due to an overcurrent immediately after the DC motor 220 is started. Further, the overcurrent detection unit 120 can be configured by hardware, and the rotation enable signal generation unit 112 and the timer 114 can be configured by software. In addition, since an overcurrent detection signal that switches the voltage level to a low level when an overcurrent is detected is input, the overtorque detection input port is not an input / output port for analog signals, but a general-purpose input. An output port can be used.

Embodiment 2. FIG.
In the first embodiment, in order to prevent erroneous addition of excessive torque due to overcurrent during the start-up period of DC motor 220, the detection result of overcurrent until a certain time has elapsed since the start-up of DC motor 220. An example of ignoring was described. On the other hand, in the present embodiment, a description will be given of a case where the startup period of the DC motor 220 is determined using a rotation abnormality signal indicating that the difference between the rotation speed of the DC motor 220 and the target speed is greater than or equal to a threshold value. To do.

  FIG. 8 is a block diagram showing a configuration example of the roller drive unit 6 including the motor control device 100 according to Embodiment 2 of the present invention. In this roller drive unit 6, the motor unit 200 outputs a rotation abnormality signal when the difference between the rotation speed of the DC motor 220 and the target speed is greater than or equal to a predetermined threshold value. Further, the motor control device 100 includes a period end signal generation circuit 131 and an excessive torque determination circuit 132 as compared with the motor control device 100 of FIG.

  The drive circuit 210 compares the rotation speed of the DC motor 220 with the target speed indicated by the clock pulse signal (CLK), and generates a rotation abnormality signal based on the comparison result. Here, if the difference between the rotational speed and the target speed is 5% or more of the target speed, an abnormal rotation signal is output. Further, such a rotation abnormality signal is referred to as a motor lock signal.

  When the DC motor 220 is activated, a motor lock signal having a high voltage level is output until the rotational speed of the DC motor 220 reaches the target speed, and when the target speed is reached, the voltage level is switched to a low level. It is done.

  The period end signal generation circuit 131 determines an activation period from when the DC motor 220 is activated until the rotation speed reaches the target speed, based on the rotation enable signal and the motor lock signal received from the motor unit 200. It is a starting period determination part.

The period end signal generation circuit 131 is composed of a D flip-flop circuit having a Vcc terminal, a D terminal, a CLK terminal, a / CLR terminal, a Q terminal, and a / Q terminal, and the voltage level is changed from a high level at the end of the activation period. generating a period end signal X ₂ is switched to a low level. The Vcc terminal is a power supply terminal and is supplied with a DC power supply (power supply voltage V ₃ ).

The D terminal, the power supply voltage V ₃ is applied via a resistor element. An inverted signal of the motor lock signal is input to the CLK terminal, and an inverted signal of the rotation enable signal is input to the / CLR terminal. Period end signal X ₂ is a control signal indicating the end of the starting period, is output from the / Q terminal.

In the period end signal generation circuit 131, the input signal of the D terminal is output from the Q terminal in synchronization with the rise of the signal input to the CLK terminal. That is, the output signal of the / Q terminal is switched from the high level to the low level in synchronization with the switching of the motor lock signal to the low level at the end of the activation period. In this way, the period end signal X ₂ is generated.

Excess torque determining circuit 132 generates a logical sum of the overcurrent detection signal X ₁ inputted from the over-current signal generation circuit 121, and the period end signal X ₂ inputted from period end signal generating circuit 131, the excess torque It is a logic circuit for outputting as a detection signal Y. The excessive torque detection signal Y is input to the excessive torque detection input port of the CPU 110.

  By configuring in this way, the excessive torque detection input port is prevented from going to a low level due to overcurrent during the startup period from when the DC motor 220 is started until the rotational speed reaches the target speed. it can. Further, once the output of the motor lock signal once becomes low level, the overcurrent can be detected correctly regardless of the logic of the motor lock signal thereafter.

  FIG. 9 is a block diagram illustrating a configuration example in a main part of the motor control device 100 in FIG. 8, and illustrates an example of a functional configuration in the CPU 110. In the CPU 110, the rotation enable signal generation unit 112 generates a rotation enable signal based on the starting period of the DC motor 220 and the overcurrent detection result by the overcurrent detection unit 120.

  That is, the rotation enable signal generation unit 112 outputs a rotation enable signal within the start-up period of the DC motor 220 regardless of the overcurrent detection result, and rotates when an overcurrent is detected after the start-up period has elapsed. Stop outputting the enable signal.

  Specifically, the rotation enable signal is output while the excessive torque detection signal Y input to the excessive torque detection input port is at a high level, and if the excessive torque detection signal Y is switched to a low level, the rotation enable signal is output. The operation to stop the output is performed.

  FIG. 10 is a timing chart showing an example of the operation at the time of starting the DC motor 220 in the roller drive unit 6 of FIG. 8, and an overcurrent is detected due to a paper jam after the DC motor 220 is started. Signal waveforms up to are shown.

First, the CPU 110 generates a rotation enable signal and outputs the rotation enable signal to the motor unit 200 when an instruction to start driving the DC motor 220 is given from the printing unit or the like. That is, the rotation enable signal at time t _11, is switched from the high level to the low level, permission period of the driving rotation is initiated.

On the other hand, the motor lock signal at time t _14, until switched to the low level by the rotational speed of the DC motor 220 reaches the target speed, the high level is maintained. Overcurrent detection transistor _{T r1} is turned on at time _{t 12} a slight delay from the start of the authorization period, turns off at time _{t 13.} Between the time t ₁₂ to t ₁₃ is the overcurrent is detected, the motor lock signal is high, it is ignored.

The period end signal / CLR terminal of the generator 131, since the inverted signal of the rotation enable signal is input, the internal state of the generator 131 is cleared released at time t _11. On the other hand, the CLK terminal, since the inverted signal of the motor lock signal is input, the voltage level of the input signal are switched at time t ₁₄ from a low level to a high level. The voltage level of the / Q terminal is switched from the high level to the low level in synchronization with the rising edge of the input signal.

In this example, at time _{t 15,} the rotation abnormality of the DC motor 220 has occurred. At this time, the motor locking signal is output, at time t ₁₆ to the rotational speed returns to normal, the high level is maintained.

At time t _17, the overcurrent is generated, the transistor T _r1 is if turned on, the overcurrent detection signal X ₁ is switched to the low level. Excess torque detection signal Y in synchronization with the falling of the overcurrent detection signal X _1, is switched from the high level to the low level. CPU110 an excess torque detection signal Y by being switched to the low level, and detects the addition of excess torque, stops the output of the rotation enable signal at time t _18.

The voltage level of the / CLR terminal is switched to the low level by switching the rotation enable signal to the high level, and the / Q output is fixed to the high level. Motor lock signal is output at time t ₁₉ with a slight delay from the end of the grant period (time t _18).

  According to the present embodiment, since the activation period is determined by the motor lock signal received from motor unit 200, it is possible to suppress erroneous detection of addition of excess torque due to overcurrent immediately after activation of DC motor 220. .

  Further, the overcurrent detection unit 120, the period end signal generation circuit 131, and the excessive torque determination circuit 132 are configured by hardware, and the speed control signal generation unit 111, the rotation enable signal generation unit 112, and the direction signal generation unit 113 are configured by software. can do. Further, since the excessive torque detection signal Y is input to the excessive torque detection input port of the CPU 110, a general-purpose input / output port can be used instead of the analog signal input / output port.

  In the first embodiment, the CPU 110 outputs a rotation enable signal within the startup period of the DC motor 220 regardless of the detection result of the overcurrent, and rotates if an overcurrent is detected after the startup period has elapsed. An example of stopping the output of the enable signal has been described. However, the present invention is not limited to such a configuration. For example, the CPU 110 is configured to generate the rotation enable signal based on the detection result of the overcurrent regardless of whether the DC motor 220 is within the startup period or after the startup period has elapsed. Also good.

  FIG. 11 is a block diagram showing another configuration example of the motor control device 100 according to the present invention. The motor control device 100 is different from the motor control device 100 of FIG. 3 in that an AND gate circuit 141 is provided. The CPU 110 generates a rotation enable signal 142 based on the overcurrent detection signal input from the overcurrent detection unit 120 and outputs the rotation enable signal 142 to the AND gate circuit 141 from the output port. That is, the CPU 110 outputs the rotation enable signal 142 based on an instruction from the printing unit or the like, and stops outputting the rotation enable signal 142 when an overcurrent is detected.

  The timer in the CPU 110 outputs a predetermined time-up signal 143 from the output port to the AND gate circuit 141 when a certain time Th1 has elapsed since the DC motor 220 was started. The AND gate circuit 141 is a logic circuit that generates a logical product of the rotation enable signal 142 and the time-up signal 143 and outputs the logical product to the motor unit 200. Even with such a configuration, it is possible to correctly detect the addition of excess torque due to a paper jam or the like and stop the rotation drive of the DC motor 220.

  In the second embodiment, an example in which the overcurrent detection unit 120 and the activation period determination unit (period end signal generation circuit 131) are configured by hardware has been described. However, the present invention is not limited to such a configuration. It is not something that can be done. For example, the overcurrent detection unit 120 or the activation period determination unit may be configured by software.

DESCRIPTION OF SYMBOLS 1 Multifunction machine 11 Document reading part 12 Operation panel 13 Main body part 14 Paper feed cassette 15 Paper discharge tray 16 Carriage path 18 Paper feed roller 19 Separation roller 20 Registration roller 2 Recording paper 3 Development transfer part 31 Photosensitive drum 36 Transfer roller 4 Fixing Unit 41 Heat roller 42 Press roller 51 Transport roller 52 Paper discharge roller 6 Roller drive unit 100 Motor controller 101 Circuit board 102 External terminal unit 110 CPU
111 Speed control signal generation unit 112 Rotation enable signal generation unit 113 Direction signal generation unit 114 Timer 120 Overcurrent detection unit 121 Overcurrent signal generation circuit 131 Period end signal generation circuit 132 Excess torque determination circuit 141 And gate circuit 200 Motor unit 201 External Terminal unit 210 Drive circuit 211 PWM circuit 212 DC voltage output circuit 213 Excitation control circuit 214 FG sensor 220 DC motor 221 Rotor 222 Stator coil

Claims (5)

In a motor control device for supplying a rotation enable signal for permitting rotation of the DC motor to a motor unit comprising a DC motor and a drive circuit,
An overcurrent detection unit that detects supply current to the motor unit and detects overcurrent;
A rotation enable signal generation unit that generates the rotation enable signal based on the detection result of the overcurrent;
The rotation enable signal generation unit outputs the rotation enable signal regardless of the detection result of the overcurrent within a certain period after starting the DC motor, and the overcurrent is detected after the lapse of the certain period. And a motor control device that stops the output of the rotation enable signal in the event of a failure. A timer for outputting a time-up signal after a predetermined time has elapsed from the start of the DC motor;
The motor control device according to claim 1, wherein the rotation enable signal generation unit generates the rotation enable signal based on the time-up signal. The overcurrent detection unit includes an overcurrent detection transistor that is turned on when a current flowing through the ground line between the motor unit and the ground exceeds a certain level, and a voltage level that is set when the overcurrent detection transistor is turned on. Consists of an overcurrent signal generation circuit that generates an overcurrent detection signal that is switched from high level to low level,
3. The motor control apparatus according to claim 2, wherein the rotation enable signal generation unit and the timer include a single processor in which the overcurrent detection signal is input to an input port. A speed control signal indicating the target speed of the DC motor and a rotation enable signal for permitting rotation driving of the DC motor are supplied to a motor unit including a DC motor and a drive circuit, and the rotation speed of the DC motor and the target In the motor control device that receives the rotation abnormality signal indicating that the difference from the speed is equal to or greater than the threshold value,
An overcurrent detection unit that detects supply current to the motor unit and detects overcurrent;
An activation period determination unit that determines an activation period from when the DC motor is activated until the rotation speed reaches a target speed based on the rotation abnormality signal;
A rotation enable signal generating unit that generates the rotation enable signal based on the detection period and the detection result of the overcurrent;
The rotation enable signal generation unit outputs the rotation enable signal within the start-up period regardless of the detection result of the overcurrent, and the rotation enable signal is detected when an overcurrent is detected after the start-up period. A motor control device that stops output of a signal. A speed control signal generator for generating the speed control signal;
The overcurrent detection unit includes an overcurrent detection transistor that is turned on when a current flowing through the ground line between the motor unit and the ground exceeds a certain level, and a voltage level that is set when the overcurrent detection transistor is turned on. Consists of an overcurrent signal generation circuit that generates an overcurrent detection signal that is switched from high level to low level,
The activation period determination unit includes a period end signal generation circuit that generates a period end signal in which the voltage level is switched from a high level to a low level at the end of the activation period.
5. The speed control signal generation unit and the rotation enable signal generation unit include a single processor in which a logical sum of the overcurrent detection signal and the period end signal is input to an input port. The motor control apparatus described.

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