JP6398892B2 - Motor control device and image forming apparatus - Google Patents

Description

  The present invention relates to a motor control device that controls a motor and an image forming apparatus including the motor control device.

  2. Description of the Related Art Conventionally, image forming apparatuses such as copiers, printers, and multifunction machines are configured to include a motor for driving a movable member in a lift-up mechanism of a paper feed cassette that stores paper and other parts.

  In the paper feeding cassette, a lift-up method using a DC brush motor is widely adopted to cope with papers having various basis weights. For example, a paper feed cassette that employs a lift-up system includes a paper placement plate and a movable member such as a lift plate, and makes one end of the lift plate abut against the paper placement plate and rotates to the other end of the lift plate. A moving shaft is attached. The rotation shaft is connected to the DC brush motor, and the rotation shaft is rotated by the DC brush motor, whereby the lift plate to which the rotation shaft is attached rotates, and the paper is loaded along with the rotation of the lift plate. The mounting plate moves up and down.

  However, there are cases where the movable member such as the lift plate of the sheet feeding cassette described above cannot be smoothly rotated (driven) due to an abnormality in its rotating mechanism (drive mechanism). In this case, the drive mechanism for driving the movable member is locked, and an overcurrent flows through the motor. Even if the motor is stopped after detecting the overcurrent flowing through the motor, parts of a rotating mechanism (drive mechanism) such as a gear connected to the motor may be damaged. Therefore, there is a motor control device that stops the motor when the drive mechanism as described above is in a locked state.

  For example, Patent Document 1 discloses a motor drive circuit (motor control device) that applies a drive voltage to a winding of a motor via a half-bridge circuit. This motor drive circuit includes a capacitor connected between the output terminal of the half bridge circuit and a DC power supply line, a drive pulse generation circuit that generates a drive pulse for turning on a switching element of another half bridge circuit, and a threshold voltage. A threshold voltage generation circuit that generates a voltage, a voltage comparison circuit that compares the terminal voltage of the capacitor with the threshold voltage, and an abnormality determination circuit that determines an abnormality of the winding based on the output signal of the voltage comparison circuit after the drive pulse is output And equipped with

  In addition, the motor control device disclosed in Patent Document 2 detects a current flowing through a drive unit that drives a DC motor and the drive unit, and a predetermined current when a current that is equal to or greater than a predetermined current reference value flows through the drive unit. Current detection means for outputting a detection signal, a memory section for preliminarily storing a time setting value for determining whether or not the drive section is in an abnormal overcurrent state, and a predetermined current detection signal output from the current detection means Counting means for counting the output time, overcurrent detection means for comparing the output time with the latest time set value stored in the memory, and the output time from the latest time set value by the overcurrent detection means And a control means for stopping the DC motor in the drive unit when it is determined that the value is larger.

  Further, the motor control device of Patent Document 3 is provided with second current limiting means having a larger limit value than the current limit value in the conventional current limiting means, in addition to the current limiting means in the conventional motor control device. . When an overcurrent is detected by the second current limiting means, the motor start signal is forcibly cut off to cut off the power supply to the motor.

JP 2009-254199 A JP 2007-28786 A JP 2002-119083 A

  The motor control device as described above uses the threshold voltage, time set value, and current limit value as threshold values, and the motor overcurrent state (drive mechanism lock state) according to the comparison result with the voltage, output time, and current. It is configured with a circuit that detects the motor and stops the motor. However, the motor cannot be stopped suddenly due to the inertia of rotation even when the current is cut off. In addition, if the circuit is configured to detect an overcurrent state, a time lag such as noise removal or a time lag from when the overcurrent state is detected until the detection signal is output will occur. After that, the motor will be instructed to stop. Therefore, parts of a rotation mechanism (drive mechanism) such as a gear connected to the motor may be damaged.

  Further, in the case of a configuration in which the drive mechanism is determined to be in the locked state when the current flowing through the motor exceeds a predetermined threshold value, the predetermined threshold value is set between the necessary current value and the abnormal current value. Here, the required current value is the maximum value of current that does not exceed during normal operation of the motor, and the abnormal current value is a current value that exceeds when the drive mechanism is abnormal. For example, when the required current value is 75 mA and the abnormal current value is 147 mA, the threshold is set between 75 mA and 147 mA, for example, 100 mA. If the current flowing through the motor is less than the abnormal current value, tooth skipping will not occur between the gears connected to the motor, but if the current flowing through the motor exceeds the abnormal current value, the gears connected to the motor Tooth skipping occurs. However, the motor and its rotation mechanism are configured without a sufficient interval between the required current value and the abnormal current value, and for example, the abnormal current value may be near the required current value. In such a case, it is difficult to set the threshold appropriately, and it becomes difficult to detect the lock state of the drive mechanism without malfunction. Therefore, for example, in a paper feed cassette, it is difficult to achieve both the securing of torque necessary for lift-up and the accurate detection of the locked state of the drive mechanism.

  In view of the above-described circumstances, an object of the present invention is to accurately detect the lock state of the drive mechanism and avoid damage to the motor and the drive mechanism.

  The motor control device of the present invention includes a motor drive unit that controls the drive of the motor by flowing a current to a motor of a drive mechanism that drives a predetermined movable member, a current detection unit that detects a current flowing through the motor, The current change within a predetermined period of the current detected by the current detection unit is compared with a first threshold having a predetermined slope indicating an increase in current per unit time, and the current change is greater than the first threshold. A lock detection unit that detects a lock state of the drive mechanism when the current change is a tendency to increase more rapidly than the first threshold; The motor driving unit stops driving the motor when the lock detecting unit detects the locked state of the driving mechanism.

  By adopting such a configuration, it is possible to stop the drive of the motor by detecting the lock state of the drive mechanism before overcurrent flows to the motor, avoiding that the current flowing to the motor exceeds the abnormal current value Is done. In this way, it is possible to accurately detect the lock state of the drive mechanism and avoid damage to the drive mechanism such as the motor and its drive gear.

  The lock detection unit may detect the current change for each predetermined period, average the current change that is repeated a predetermined number of times, and compare the average change with the first threshold value.

  By adopting such a configuration, it is possible to remove noise due to current change and to prevent a normal current such as an inrush current from being erroneously detected as an abnormal current.

  The lock detection unit compares the current change with the first threshold value and a second threshold value that has a slope of an increasing tendency that is steeper than the first threshold value, and the current change indicates the first threshold value. It is determined whether the current change is more rapid than the second threshold, and whether the current change is more rapid than the first threshold and the second threshold. In the case of a gradual increase trend, the lock state of the drive mechanism may be detected.

  By adopting such a configuration, the locked state of the drive mechanism can be detected with higher accuracy, and a normal current such as an inrush current can be prevented from being erroneously detected as an abnormal current.

  The image forming apparatus of the present invention includes any one of the fixing devices described above.

  The image forming apparatus further includes a paper feed cassette that stores a recording medium, the movable member is a lift plate of the paper feed cassette, and the motor of the drive mechanism is a lift motor that drives the lift plate. There may be.

  According to the present invention, it is possible to accurately detect the lock state of the drive mechanism and avoid damage to the motor and the drive mechanism.

1 is a schematic diagram illustrating an outline of a configuration of a printer according to an embodiment of the present invention. 1 is a block diagram illustrating a configuration of a printer according to an embodiment of the present invention. 6 is a graph showing a current flowing through a lift motor when a drive mechanism of a paper feed cassette of a printer is in a locked state. 6 is a graph showing a current flowing through a lift motor when a lift motor of a drive mechanism of a paper feed cassette of a printer operates normally. 6 is a graph showing a threshold value of a lift motor used for detecting a lock state of a drive mechanism of a paper feed cassette in a printer according to an embodiment of the present invention.

  First, the overall configuration of the printer 1 (image forming apparatus) will be described with reference to FIG.

  The printer 1 includes a box-shaped printer main body 2. A paper feed cassette 3 that stores paper S (recording medium) is stored in the lower portion of the printer main body 2, and a paper discharge is performed on the upper surface of the printer main body 2. A tray 4 is provided. An upper cover 5 is attached to the upper surface of the printer main body 2 so as to be openable and closable on the side of the paper discharge tray 4, and a toner container 6 is accommodated below the upper cover 5. Details of the paper feed cassette 3 will be described later.

  An exposure unit 7 composed of a laser scanning unit (LSU) is disposed below the paper discharge tray 4 above the printer body 2, and an image forming unit 8 is provided below the exposure unit 7. Yes. The image forming unit 8 is rotatably provided with a photosensitive drum 10 as an image carrier. Around the photosensitive drum 10, a charger 11, a developing device 12, a transfer roller 13, and a cleaning device are provided. The apparatus 14 is disposed along the rotation direction of the photosensitive drum 10 (see arrow X in FIG. 1).

  A conveyance path 15 for the paper S is provided inside the printer body 2. A paper feed unit 16 is provided at the upstream end of the conveyance path 15, and a transfer unit 17 configured by the photosensitive drum 10 and the transfer roller 13 is provided at a middle portion of the conveyance path 15. Is provided with a fixing device 18, and a paper discharge unit 20 is provided at the downstream end of the conveyance path 15. A reverse path 21 for double-sided printing is formed below the transport path 15.

  Next, an image forming operation of the printer 1 having such a configuration will be described.

  When the printer 1 is turned on, various parameters are initialized, and initial setting such as temperature setting of the fixing device 18 is executed. Then, when image data is input from a computer or the like connected to the printer 1 and an instruction to start printing is given, an image forming operation is executed as follows.

  First, after the surface of the photosensitive drum 10 is charged by the charger 11, exposure corresponding to the image data is performed on the photosensitive drum 10 by laser light from the exposure device 7 (see the two-dot chain line P in FIG. 1). The electrostatic latent image is formed on the surface of the photosensitive drum 10. Next, the electrostatic latent image is developed by the developing device 12 into a toner image with toner.

  On the other hand, the paper S taken out from the paper feed cassette 3 by the paper feed unit 16 is conveyed to the transfer unit 17 in synchronization with the image forming operation described above, and the toner image on the photosensitive drum 10 is transferred to the transfer unit 17. Transferred onto the paper S. The sheet S to which the toner image has been transferred is conveyed downstream in the conveyance path 15 and enters the fixing device 18, where the toner image is fixed on the sheet S. The paper S on which the toner image is fixed is discharged from the paper discharge unit 20 to the paper discharge tray 4. The toner remaining on the photosensitive drum 10 is collected by the cleaning device 14.

  Next, the paper feed cassette 3 will be described with reference to FIG.

  The paper feed cassette 3 is provided below the box-shaped housing 30, a paper placement plate 31 provided along the bottom plate of the housing 30 on which the paper S is placed, and the paper placement plate 31. A lift plate 32, a rotation shaft 33 attached to the lift plate 32, and a lift motor 34 (motor) connected to a drive mechanism 35 that drives the rotation shaft 33 are provided. One end of the lift plate 32 is in contact with the paper placement plate 31, and a rotation shaft 33 is attached to the other end, and the lift plate 32 is disposed to be rotatable around the rotation shaft 33. The rotation shaft 33 has an axis extending in the front-rear direction. One end side of the rotation shaft 33 is connected to the drive mechanism 35. The lift motor 34 is composed of, for example, a DC brush motor, and is driven and controlled by a motor control device 50 described later.

  Next, the control system of the printer 1 will be described with reference to FIG.

  The printer 1 is provided with a control unit 40. The control unit 40 is connected to a storage unit 41 composed of a ROM, a RAM, and the like, and is configured to control each unit of the printer 1 based on a control program and control data stored in the storage unit 41.

  The control unit 40 is connected to the operation display unit 42, the motor drive unit 43, the current detection unit 44, and the lock detection unit 45 in addition to the image forming unit 8, the paper feeding unit 16, and the fixing device 18 described above. These motor drive unit 43, current detection unit 44, and lock detection unit 45 constitute a motor control device 50 that controls the drive of the lift motor 34. The lock detection unit 45 may be configured with a control program stored in the storage unit 41.

  The control unit 40 connected to the image forming unit 8 is connected to, for example, a drive motor (not shown) that rotates the photosensitive drum 10 and the transfer roller 13. The control unit 40 controls the rotation of the photosensitive drum 10 and the transfer roller 13 by controlling the drive of the drive motor.

  The control unit 40 connected to the image forming unit 8 is connected to, for example, a charging bias application unit (not shown), a development bias application unit (not shown), or a transfer bias application unit (not shown). . These charging bias application unit, development bias application unit, and transfer bias application unit are connected to the charger 11, the developer 12 and the transfer roller 13 of the image forming unit 8, respectively. A charging bias, a developing bias, and a transfer bias are respectively applied to the roller 13. The control unit 40 controls the charging bias applying unit, the developing bias applying unit, and the transfer bias applying unit, so that the charging bias, the developing bias, and the transfer bias applied to the charger 11, the developing device 12, and the transfer roller 13, respectively. Control the bias.

  For example, the control unit 40 connected to the paper feeding unit 16 controls the paper feeding unit 16 so that the paper S is fed from the paper feeding cassette 3 to the transport path 15 in synchronization with the image forming operation described above. To do.

  The control unit 40 connected to the fixing device 18 is connected to, for example, a heater (not shown) provided in the fixing device 18, and the heater generates heat to a temperature suitable for fixing by controlling energization of the heater. To control.

  The operation display unit 42 includes, for example, operation keys such as a start key, a stop / clear key, a numeric keypad, and a touch panel. When the user operates each operation key or touch panel, the operation instruction is output to the control unit 40. It is comprised so that.

  The motor drive unit 43 is connected to the lift motor 34 of the paper feed cassette 3. The motor drive unit 43 drives the rotation of the lift motor 34 by causing a current to flow through the lift motor 34 based on a control signal from the control unit 40. The motor drive unit 43 stops driving the lift motor 34 based on a stop signal from the lock detection unit 45 described later.

  For example, when the drive of the lift motor 34 is started, the motor drive unit 43 causes a relatively high inrush current to flow through the lift motor 34 as shown in FIGS. become. 3 and 5, the current value Ia indicates a necessary current value for driving the lift motor 34, and the current value Ib indicates an abnormal current value at which an abnormality occurs in the drive mechanism 35. Thereafter, if the drive mechanism 35 connected to the lift motor 34, the rotation shaft 33, the lift plate 32 attached to the rotation shaft 33, and the like smoothly rotate (drive), the torque related to the lift motor 34 is reduced. Since the lift motor 34 can be normally driven, the current flowing through the lift motor 34 by the motor drive unit 43 converges to the rated current (see FIG. 4).

  On the other hand, when the drive mechanism 35 connected to the lift motor 34, the rotation shaft 33, the lift plate 32 attached to the rotation shaft 33, or the like is abnormal, it cannot be smoothly rotated (driven). The torque related to the lift motor 34 increases, and the current flowing through the lift motor 34 by the motor drive unit 43 increases rapidly without converging (see FIG. 3). When the current flowing through the lift motor 34 exceeds the abnormal current value Ib, for example, an abnormality such as tooth skipping occurs between the drive gears of the drive mechanism 35 connected to the lift motor 34.

  The current detection unit 44 is configured to detect a current output from the motor driving unit 43 to the lift motor 34, and outputs a current value of the detection result to the lock detection unit 45.

  The lock detection unit 45 compares the current change within a predetermined period of the current detected by the current detection unit 44 with a first threshold Th1 (see FIG. 5) having a predetermined inclination indicating an increase in current per unit time. Then, it is determined whether or not the current change has a tendency to increase more rapidly than the first threshold Th1. Further, the lock detection unit 45 detects the lock state of the drive mechanism 35 when the current change tends to increase more rapidly than the first threshold Th1, and, for example, outputs a stop signal that instructs the stop of the lift motor 34 to the motor. Output to the drive unit 43.

  For example, the lock detector 45 sets a predetermined period for obtaining a current change, that is, the sampling timing to 10 ms, and sets the first threshold Th1 to be compared with the current change to 0.2 to 0.3 A per unit time (1 ms). Set to (A / ms). The predetermined period and the first threshold Th1 are stored in the storage unit 101. The first threshold Th1 tends to increase more slowly than the slope of the current change when the drive mechanism 35 is in the locked state, and the current increases as the load on the drive mechanism 35 changes during normal use. It is set to a tendency to increase more rapidly than the slope of the current change. In the normal operation of the paper feed cassette 3, it is difficult to assume a state in which the load of the drive mechanism 35 continuously increases during the operation. Therefore, even if such a state occurs for some reason, the load increases only slightly, and the current change of the lift motor 34 does not become larger than the threshold Th1. Further, there may be a case where a large load is instantaneously generated in the drive mechanism 35 due to the influence of friction between members during normal use. However, when the load of the drive mechanism 35 fluctuates, the lift motor 34 generates only a short-time current change gradient. The lock detection unit 45 measures the current change for a predetermined period every predetermined period, for example, every 500 ms, averages the current change measured continuously a predetermined number of times, for example, 10 times, and calculates the current change of the average result. It may be compared with the first threshold Th1. Thereby, noise due to current change can be removed, and a normal current such as an inrush current is prevented from being erroneously detected as an abnormal current.

  With the configuration as described above, the operation of the lock detection unit 45 will be described with reference to FIG.

  First, before driving the lift motor 34 (section T <b> 1 shown in FIG. 5), the motor drive unit 43 does not flow current to the lift motor 34. Therefore, even if the lock detection unit 45 measures the current change for a predetermined period for the current detected by the current detection unit 44, the slope of the current change is substantially zero, and the current change is measured a predetermined number of times. Even when averaged, the slope of the current change is substantially zero. Therefore, the lock detection unit 45 does not detect the lock state of the drive mechanism 35 even if the current change with the inclination of approximately 0 is compared with the first threshold Th1.

  Next, when a steep inrush current flows from the motor drive unit 43 to the lift motor 34 (section T2 shown in FIG. 5), the lock detection unit 45 has a current with a slope of increasing tendency steeper than the first threshold Th1. The change will be measured. However, since the lock detection unit 45 averages the current change based on the inrush current with a current change with a slope measured before that, the average current change is greater than the first threshold Th1. The inclination becomes gentle. Accordingly, the lock detection unit 45 does not detect the lock state of the drive mechanism 35 even if the current change when the inrush current flows is compared with the first threshold Th1.

  After the inrush current flows to the lift motor 34 (section T3 shown in FIG. 5), the drive mechanism 35 connected to the lift motor 34, the rotating shaft 33, and the lift plate attached to the rotating shaft 33. When 32 or the like normally rotates (drives), the current I1 flowing from the motor drive unit 43 to the lift motor 34 converges normally. At this time, when the lock detection unit 45 measures the current change for a predetermined period for the current I1 detected by the current detection unit 44, the slope of the current change tends to decrease. Accordingly, the lock detection unit 45 does not detect the locked state of the drive mechanism 35 even if the current change when the current I1 during normal operation flows is compared with the first threshold Th1.

  On the other hand, when an abnormality occurs in the drive mechanism 35, the rotation shaft 33, the lift plate 32, and the like and the rotation (drive) cannot be performed smoothly, the current I2 flowing from the motor drive unit 43 to the lift motor 34 converges. It increases rapidly without. At this time, when the lock detection unit 45 measures a current change for a predetermined period with respect to the current I2 detected by the current detection unit 44, the slope of the current change tends to increase rapidly.

  And when abnormality has arisen in the drive mechanism 35, the rotating shaft 33, and the lift board 32, the electric current I2 which flows from the motor drive part 43 to the lift motor 34 continues increasing. Therefore, there are many samples of the current change of the current I2 during the abnormal operation, and when the lock detection unit 45 measures and averages the current change of the current I2 during the abnormal operation a predetermined number of times, the slope of the current change of the average result Tends to increase more rapidly than the first threshold Th1. Therefore, the lock detection unit 45 detects the lock state of the drive mechanism 35 by comparing the current change of the current I2 during the abnormal operation with the first threshold Th1. The lock detection unit 45 sets the first threshold Th1, the predetermined period, the predetermined number, and the predetermined period so that the lock state of the drive mechanism 35 is detected before the current I2 reaches the abnormal current value Ib. Configured.

  The lock detection unit 45 that has detected the lock state of the drive mechanism 35 outputs a stop signal that instructs the stop of the lift motor 34 to the motor drive unit 43. The motor drive unit 43 stops driving the lift motor 34 in response to a stop signal from the lock detection unit 45.

  Even when an abnormality occurs in the drive mechanism 35, the rotation shaft 33, and the lift plate 32, the current change of the current I2 is changed at the initial stage of flowing the current I2 from the motor drive unit 43 to the lift motor 34. The number of samples is smaller than the predetermined number. For this reason, the current change based on the current I2 is averaged with the current change whose slope measured before that is substantially zero, so that the current change of the average result has a gentler slope than the first threshold Th1. Therefore, the lock detection unit 45 does not detect the lock state of the drive mechanism 35 even if the current change when the current I2 flows at the initial stage during the abnormal operation is compared with the first threshold Th1. However, in the initial stage of abnormal operation, the current I2 is smaller than the abnormal current value Ib, and torque that damages the lift motor 34, the drive mechanism 35, the rotating shaft 33, the lift plate 32, etc. is not generated. .

  In the present embodiment, as described above, the motor control device 50 of the printer 1 includes the motor drive unit 43, the current detection unit 44, and the lock detection unit 45. The motor drive unit 43 controls the drive of the lift motor 34 by passing a current to a lift motor 34 (motor) that drives the rotary shaft 33 and the lift plate 32 (predetermined movable member) via the drive mechanism 35. The current detection unit 44 detects the current flowing through the lift motor 34. The lock detection unit 45 compares the current change within a predetermined period of the current detected by the current detection unit 44 with a first threshold Th1 having a predetermined slope indicating an increase in current per unit time, and compares the current change. Is determined to be a steep increase tendency than the first threshold Th1, and when the current change is a steep increase tendency than the first threshold Th1, the lock state of the drive mechanism 35 is detected. The motor drive unit 43 stops driving the lift motor 34 when the lock detection unit 45 detects the locked state of the drive mechanism 35.

  As a result, the lock state of the drive mechanism 35 can be detected before the overcurrent flows to the lift motor 34, and the drive of the lift motor 34 can be stopped, and the current flowing through the lift motor 34 can exceed the abnormal current value Ib. Avoided. In this way, the locked state of the drive mechanism 35 is accurately detected to avoid damage to the lift motor 34, its drive gear (not shown), the drive mechanism 35, the rotating shaft 33, the lift plate 32, and the like. Can do.

  Further, in the present embodiment, the lock detection unit 45 is configured to detect a current change at every predetermined period, average the current changes that are continued a predetermined number of times, and compare the average current change with the first threshold Th1. Thereby, noise due to current change can be removed, and a normal current such as an inrush current is prevented from being erroneously detected as an abnormal current.

  In the present embodiment, the lock detection unit 45 compares the current change within a predetermined period of the current detected by the current detection unit 44 with the first threshold Th1, and the current change is steeper than the first threshold Th1. The configuration for determining whether or not the driving mechanism 35 is in the increasing state and detecting the lock state of the drive mechanism 35 when the current change has a tendency to increase more rapidly than the first threshold Th1 has been described. The configuration is not limited to this. For example, in another different embodiment, the lock detection unit 45 causes the current change to occur not only in the first threshold value Th1, but also in the second threshold value Th2 having a slope of increasing tendency that is steeper than the first threshold value Th1 (FIG. 5), it is determined whether or not the current change has a tendency to increase more rapidly than the first threshold Th1 and is gentler than the second threshold Th2. It may be configured to detect the lock state of the drive mechanism 35 when it is in a tendency of increasing more rapidly than the threshold value Th1 and in a tendency of increasing more slowly than the second threshold value Th2. Thereby, the locked state of the drive mechanism 35 can be detected with higher accuracy, and it is possible to prevent a normal current such as an inrush current from being erroneously detected as an abnormal current.

  In the present embodiment, the configuration in which the motor control device 50 is applied to drive control of the lift motor 34 has been described, but the motor to which the motor control device 50 is applied is not limited to the lift motor 34. For example, in another different embodiment, the motor control device 50 includes a drive motor (not shown) that drives the photosensitive drum 10 and the transfer roller 13 of the image forming unit 8, the paper feeding unit 16, the fixing device 18, or the discharge device. The present invention may be applied to drive control of a motor (not shown) that drives the paper unit 20 or another motor (not shown) provided in the transport path 15.

  In the present embodiment, the case where the configuration of the present invention is applied to the printer 1 has been described. However, in another different embodiment, the configuration of the present invention is applied to other image forming apparatuses such as a copying machine, a facsimile, and a multifunction peripheral. May be. Also. In the present embodiment, the case where the motor control device of the present invention is applied to the image forming apparatus has been described. However, in another different embodiment, the present invention is applied to other devices including a motor that drives a movable member other than the image forming apparatus. You may apply the motor control apparatus of invention.

1 Printer (image forming device)
DESCRIPTION OF SYMBOLS 3 Paper feed cassette 30 Case 31 Paper mounting board 32 Lift board 33 Rotating shaft 34 Lift motor 35 Drive mechanism 40 Control part 41 Storage part 43 Motor drive part 44 Current detection part 45 Lock detection part 50 Motor control apparatus

Claims (4)

A motor drive unit for controlling the drive of the motor by passing a current through a motor of a drive mechanism that drives a predetermined movable member;
A current detection unit for detecting a current flowing in the motor;
The current change within a predetermined period of the current detected by the current detection unit is compared with a first threshold having a predetermined slope indicating an increase in current per unit time, and the current change is detected by the first threshold. A lock detection unit that determines whether or not the current change is a steep increase tendency, and detects a lock state of the drive mechanism when the current change is a steep increase tendency than the first threshold value; ,
With
The motor drive unit stops driving the motor when the lock detection unit detects the lock state of the drive mechanism ,
The lock detection unit compares the current change with the first threshold value and a second threshold value that has a slope of an increasing tendency that is steeper than the first threshold value, and the current change indicates the first threshold value. It is determined whether the current change is more rapid than the second threshold, and whether the current change is more rapid than the first threshold and the second threshold. A motor control device that detects a lock state of the drive mechanism when the tendency is a gradual increase .   2. The motor control device according to claim 1, wherein the lock detection unit detects the current change for each predetermined period, averages the current change that is repeated a predetermined number of times, and compares the average with the first threshold value. . An image forming apparatus characterized in that it comprises a motor control device according to claim 1 or 2. A paper cassette for storing the recording medium;
The movable member is a lift plate of the paper feed cassette;
The image forming apparatus according to claim 3 , wherein the motor is a lift motor of the drive mechanism that drives the lift plate.

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