JP2007028786A - Motor controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor controller for protecting a drive section for driving a DC motor against an abnormal overcurrent. <P>SOLUTION: A copier 1 is provided with the motor controller of the invention. A toner motor 17 is driven by a drive circuit section 18. When a current of a current reference value or more flows in the drive circuit section 18, a duration of a high-level current detection signal S2 outputted from a current detecting section 16 is counted as a count value T by a CPU 10, and compared with a count setting value A for determining an abnormal overcurrent state in the drive circuit section 18. If the count value T is smaller than the count setting value A, the toner motor 17 is continuously driven, and a new count setting value A is calculated from the count value T and stored in a memory section 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a motor control device that controls a DC motor, and more particularly to a technique for protecting a drive unit that drives a DC motor from abnormal overcurrent.

  2. Description of the Related Art Conventionally, in image forming apparatuses such as printers, facsimiles, and copiers, DC motors (for example, DC brushless motors) are used for various movable parts. For example, a DC motor is provided in an image forming apparatus as a drive source for opening and closing a shutter for supplying toner from a toner container to a developing device. Further, the image forming apparatus includes an output transistor and the like, and a drive unit for driving the DC motor is electrically connected to the DC motor.

  By the way, when an abnormally large overcurrent (hereinafter referred to as an abnormal overcurrent) flows through the drive unit due to some cause (for example, the toner becomes hard and the shutter cannot move and the DC motor becomes difficult to operate). In such a case, the output transistor of the driving unit may be damaged by an abnormal overcurrent. Further, when the DC motor is driven in an abnormal overcurrent state, the apparatus main body mechanism side (for example, the shutter opening / closing mechanism) may be damaged.

  For this reason, in order to protect the drive unit and the apparatus main body mechanism, for example, an image forming apparatus provided with a motor control device equipped with a current fuse that interrupts the flow of abnormal overcurrent to the drive unit is known. .

  Further, when the current flowing through the DC motor is detected and the current exceeds a reference value, it is possible to perform control to determine that the drive unit is in an abnormal overcurrent state and stop the operation of the DC motor. An image forming apparatus provided with a motor control device is known.

In addition, as a prior art document related to the above contents, a gaming machine having a drive unit for operating an electrical component, wherein an overcurrent is detected as a current exceeding a predetermined value flowing through the drive unit. Detected by the detection means, the abnormal overcurrent determination means for determining the overcurrent as an abnormal overcurrent when the overcurrent has flowed through the drive unit for a predetermined time or longer, and detected by the overcurrent detection means When the overcurrent is determined as an abnormal overcurrent by the abnormal overcurrent means, the energization to the drive unit is limited, while the overcurrent is not determined as an abnormal overcurrent by the abnormal overcurrent determination means. There has been disclosed and proposed a gaming machine provided with driving unit protection means for continuing energization of the driving unit (see, for example, Patent Document 1).
JP 2001-170339 A

  Certainly, in the case of an image forming apparatus equipped with a motor control device equipped with a current fuse, when an abnormal overcurrent flows through the current fuse, the current fuse is disconnected due to the abnormal overcurrent and the drive unit is abnormally overloaded. Since no current flows, it is possible to protect the drive unit and the apparatus main body mechanism.

  Further, in the case of an image forming apparatus provided with the latter motor control device, when the current flowing through the DC motor is detected and the current exceeds a reference value, the drive unit is in an abnormal overcurrent state. Since the determination is made and the operation of the DC motor is stopped, an abnormal overcurrent does not flow through the drive unit, so that the drive unit and the apparatus main body mechanism can be protected.

  However, in an image forming apparatus including a motor control device equipped with a current fuse, replacement work when the current fuse is disconnected due to an abnormal overcurrent becomes complicated.

  In the image forming apparatus provided with the latter motor control device, a starting current is generated in the DC motor due to its load characteristics at the moment when the driving of the DC motor is started. This starting current is about 2 to 3 of a steady current. Since the starting current exceeds the reference value of the current that is determined to be in an abnormal overcurrent state, the drive unit is in an abnormal overcurrent state even though the DC motor is not in an abnormal overcurrent state. There is a case where it is erroneously detected as a state.

  In order to prevent these problems, when the gaming machine disclosed in Patent Document 1 is applied to an image forming apparatus equipped with a motor control device, the time when the current flowing through the DC motor becomes equal to or greater than a reference value is counted. By comparing with the preset count setting value, it is possible to determine whether the current flowing through the DC motor is the starting current when starting the DC motor or an abnormal overcurrent It is.

  However, the count setting value that serves as a reference for performing the above comparison determination is determined by taking into account variations in the generation time of the DC motor start-up current (for example, DC motor mounting position, DC motor manufacturing error, etc.) It is necessary to set the motor starting current when the generation time is the longest. For this reason, even when a DC motor with a short start-up current generation time is mounted, the count setting value is set in advance so that the start-up current generation time of the DC motor is the longest. However, there is a problem in that it takes a long time to be determined as an abnormal overcurrent state, and the drive unit cannot be protected from the abnormal overcurrent.

  In view of the above problems, an object of the present invention is to provide a motor control device capable of protecting a drive unit for driving a DC motor from abnormal overcurrent.

  In order to achieve the above object, a motor control device according to the present invention detects a drive unit that drives a DC motor and a current flowing through the drive unit or the DC motor, and a current that is equal to or greater than a predetermined current reference value is detected. When flowing through the drive unit or the DC motor, a current detection unit that outputs a predetermined current detection signal and a time setting value for determining whether or not the drive unit is in an abnormal overcurrent state are stored in advance. A memory unit that counts, a count unit that counts an output time of the predetermined current detection signal output from the current detection unit, and a magnitude of the output time and the latest time setting value stored in the memory unit When the overcurrent detection means for performing the comparison determination and the overcurrent detection means determine that the output time is smaller than the latest time set value, the drive unit continues to drive the DC motor. And, a new time set value is calculated based on the output time, the new time set value is stored in the memory unit, and the output time is larger than the latest time set value by the overcurrent detecting means. In the case where it is determined, the control unit is configured to have the drive unit stop the DC motor.

  By adopting such a configuration, it becomes possible to optimize the time set value corresponding to the variation in the starting time of the DC motor, so when an abnormal overcurrent flows in the DC motor, the overcurrent detection means As a result, the time until it is determined that the output time is larger than the latest time set value is shortened, and the drive unit can be reliably protected from abnormal overcurrent.

  As described above, the motor control device according to the present invention can protect the drive unit for driving the DC motor from abnormal overcurrent.

  In the following, the present invention will be described with reference to the drawings, taking as an example a copying machine equipped with a motor control device according to the present invention. FIG. 1 is a block diagram showing a main part configuration of a copying machine equipped with a motor control device according to the present invention. FIG. 2 schematically shows a main part structure of a copying machine equipped with a motor control device according to the present invention. It is a longitudinal cross-sectional view. As shown in both figures, the copier 1 of this embodiment includes a central processing unit 10 (hereinafter referred to as a CPU [Central Processing Unit] 10) that controls the operation of the entire apparatus, and a document transport that automatically transports a document. Unit 11, a document take-in unit 12 that takes in a document transported from document transport unit 11 and generates image data, and an operation display unit 13 that includes operation means (such as a numeric keypad or touch panel) and display means (such as a liquid crystal display). An image forming unit 15 that forms a toner image on a sheet based on the image data, a sheet feeding unit 14 that feeds the image forming unit 15, and a toner image formed on the sheet by the image forming unit 15. A fixing unit 19 for fixing to a sheet, a ROM [Read Only Memory] in which various control programs are stored, a RAM [Random Access Memory] used as a work area, data and the like are stored. When the toner 153a is replenished from the toner container 153 to the developing device 152 as will be described later, a DC motor (DC) as a driving source that opens and closes the shutter 152a provided in the developing device 152, as will be described later. A toner motor 17 composed of a brush motor, a drive circuit unit 18 that drives the toner motor 17 by supplying a motor current I1 to the toner motor 17 based on a remote signal S1 from the CPU 10, and a drive circuit unit 18 (drive circuit unit) An output stage current I2 flowing in the output stage 18), and a current detection signal S2 having a predetermined potential based on a comparison between a preset current reference value and the output stage current I2 is input to the CPU 10; , Comprising. The current detection unit 16 detects an output stage current I2 flowing through an output stage of an output transistor (not shown) disposed between the ground in the output stage of the drive circuit unit 18 and a predetermined potential.

  Further, the copying machine 1 of the present embodiment includes a power switch (not shown) for turning on / off power supply to each part of the apparatus, a plurality of openable / closable covers (not shown) that cover the apparatus main body 100, and A cover sensor (not shown) is provided for each cover (not shown) and inputs a detection signal corresponding to opening / closing of the cover (not shown) to the CPU 10.

  The CPU 10 controls the operation of the entire apparatus and performs processing related to drive control of the toner motor 17. Further, the CPU 10 counts the output time of the predetermined current detection signal S2 output from the current detection unit 16 when the output stage current I2 is equal to or greater than the current reference value, and the output time and the memory unit 20 It plays a role of overcurrent detection means for comparing the size with the latest stored time setting value (in this embodiment, the count setting value A).

  As shown in FIG. 2, the sheet feeding unit 14 includes a plurality of (three in this embodiment) sheet storage units 141 a to 141 c serving as a sheet supply source to the image forming unit 15, and each sheet storage unit 141 a to 141 c. A sheet conveyance unit 142 serving as a common sheet conveyance path from the image forming unit 15 to the image forming unit 15.

As shown in FIG. 2, the image forming unit 15 uniformly charges the photosensitive drum 151 of the latent image carrier on which the toner image is formed on the drum surface based on the image data, and the surface of the photosensitive drum 151 to a predetermined potential. A charging device 155 for irradiating a laser beam based on image data, an exposure unit 154 for forming an electrostatic latent image on the surface of the photosensitive drum 151, and a toner image from the electrostatic latent image on the surface of the photosensitive drum 151. The developing device 152 formed on the surface of the drum 151, the toner container 153 storing the toner 153a supplied to the developing device 152, and the toner image formed on the surface of the photosensitive drum 151 are electrostatically applied to the sheet that has been conveyed. Transfer roller 158 for transferring automatically,
A cleaning unit 157 that removes toner remaining on the surface of the photosensitive drum 151 and a static eliminator 156 that neutralizes the surface of the photosensitive drum 151 are provided.

  Further, when the toner 153a is supplied from the toner container 153, the developing device 152 detects the toner concentration in the developing device 152 and the shutter 152a that is opened / closed by the driving force of the toner motor 17, and the CPU 10 determines the toner concentration. And a toner sensor 152b for inputting a corresponding toner density signal.

  Here, FIG. 3 shows the relationship among the remote signal S1, the current detection signal S2, and the output stage current I2 when the drive circuit unit 18 is not in an abnormal overcurrent state (that is, when the toner motor 17 is driven normally). FIG. The graph shown in FIG. 3 shows the relationship between the output stage current I2 of the drive circuit unit 18 and time. As shown in the graph of FIG. 3, the characteristic of the output stage current I2 when the driving of the toner motor 17 is normal is instantaneously large due to the load characteristic of the toner motor 17 after the driving of the toner motor 17 is started. Then, the current value in a steady state is shown. In the output stage current I2, the current value of the output stage current I2 increases from the start of driving of the toner motor 17 due to the load characteristics of the toner motor 17 until the steady state is reached. The output stage current I2 is a steady current I4. In addition, the time from when the output stage current I2 is output after the start of the driving of the toner motor 17 until when the output stage current I2 is in a steady state is defined as a startup time Ts. Further, the motor current I1 flowing through the toner motor 17 shows a tendency of current characteristics similar to the output stage current I2.

  In detail, as shown in FIGS. 1 and 3, the drive circuit unit 18 receives toner from the output stage of its output transistor (not shown) when a high level remote signal S <b> 1 is input from the CPU 10. A predetermined voltage is applied to the motor 17, and an output stage current I 2 is supplied to the output stage, and a motor current I 1 is supplied from the output stage to the toner motor 17. In addition, when a low level remote signal S1 is input from the CPU 10, the drive circuit unit 18 does not apply a voltage to the toner motor 17 from the output stage of its output transistor (not shown). The output stage current I2 does not flow, and the motor current I1 does not flow to the toner motor 17 from the output stage.

  The current reference value set in advance in the current detection unit 16 is a current value at which an output transistor (not shown) in the output stage of the drive circuit unit 18 is not destroyed or a shutter of the developing device 152 based on a result of an experiment performed in advance. The current value is set so that the 152a mechanism is not destroyed. For example, the current reference value is set to about 80 [mA] when the maximum value of the starting current I3 is 150 [mA]. The current reference value is usually set to about 1.5 to 3 times the above-described steady current I4.

  Further, in detail, as shown in FIGS. 1 and 3, the current detection unit 16 detects an output stage current I2 flowing through the output stage of an output transistor (not shown) in the output stage of the drive circuit unit 18, The detected output stage current I2 is compared with the current reference value. Furthermore, the current detection unit 16 inputs a high level current detection signal S2 to the CPU 10 when the output stage current I2 is greater than or equal to the current reference value, and when the output stage current I2 is less than the current reference value, the current detection unit 16 A level current detection signal S 2 is input to the CPU 10.

  In the memory unit 20, the output stage current I2 flowing through the output stage of an output transistor (not shown) in the output stage of the drive circuit unit 18 is in an abnormal overcurrent state (that is, the drive circuit unit 18 An initial value of the count setting value A serving as a reference for determining whether or not the current state is present is stored in advance in a predetermined storage area. Note that the initial value of the count setting A is determined in consideration of time variations of the starting current I3 (for example, the mounting position of the toner motor 17, the manufacturing error of the toner motor 17, etc.) when the toner motor 17 is normal. Is set to the one with the longest time. Further, the count set value A is set so that the output stage current I2 is not erroneously detected from the starting current I3 that the drive circuit unit 18 (that is, the toner motor 17) is in an abnormal overcurrent state when the driving of the toner motor 17 is started. The time is set longer than the activation time Ts. Further, as will be described later, when a new count setting value A is set by the CPU 10, the initial value of the count setting value A stored in advance in the memory unit 20 is stored without being overwritten.

  The memory unit 20 stores a table indicating the relationship between the toner density signal and an appropriate toner density value in the developing device 152.

  Next, the document copying operation in the copying machine 1 configured as described above will be described. In the document copying operation of the copying machine 1 of this embodiment, when a document is first transported from the document transport unit 11 to the document capture unit 12, the document capture unit 12 captures the document and generates image data. Is done. The generated image data is temporarily stored in the memory unit 20, read again, and sent to the image forming unit 15. Subsequently, the image forming unit 15 starts image forming processing, and an electrostatic latent image is formed on the surface of the photosensitive drum 151 uniformly charged to a predetermined potential by the charger 155 by the exposure unit 154 based on the image data. Made. Subsequently, a toner image is formed on the surface of the photosensitive drum 151 from the electrostatic latent image by the developing device 152. The toner image formed on the surface of the photosensitive drum 151 is transferred onto the paper conveyed from the paper supply unit 14 by the transfer roller 158.

  Thereafter, the sheet carrying the unfixed toner image is sent to the fixing unit 19 where the toner image is fixed on the sheet by being heated and pressurized by the fixing unit 19 and discharged. Further, after the toner remaining on the surface of the photosensitive drum 151 is removed by the cleaning unit 157, the surface of the photosensitive drum 151 is neutralized by the static eliminator 156. A solid line arrow in FIG. 2 indicates a sheet conveyance path.

  Further, in the copying machine 1 of this embodiment, the number of times the toner motor 17 is driven after the power switch (not shown) is turned on or the cover (not shown) covering the apparatus main body 100 is opened and closed is stored in the memory unit as toner motor history information. 20 is stored.

  Note that the copying machine 1 including the motor control device according to the present embodiment is characterized by controlling the toner motor 17 for protecting the drive circuit unit 18 that drives the toner motor 17 from abnormal overcurrent.

  Therefore, hereinafter, the control of the toner motor 17 for protecting the drive circuit unit 18 that drives the toner motor 17 in the copying machine 1 including the motor control device of the present embodiment from an abnormal overcurrent will be described with reference to the drawings. In detail. FIG. 4 is a flowchart for explaining the control of the toner motor 17 in the copying machine 1 of the present embodiment. FIG. 5 is a diagram illustrating a relationship among the remote signal S1, the current detection signal S2, and the output stage current I2 when the drive circuit unit 18 is in an abnormal overcurrent state.

  In the copying machine 1 of the present embodiment, as shown in FIG. 4, the toner density signal input from the toner sensor 152 b of the developing device 152 by the CPU 10 and the toner density stored in the memory unit 20 in step 4-1. A comparison is made with a table showing the relationship between the signal and the appropriate toner density value in the developing device 152. When the CPU 10 determines that the toner density in the developing device 152 is lower than an appropriate toner density value, the toner motor 17 is requested to be driven from the toner container 153 to the developing device 152. In (S4-1 YES), the process proceeds to step S4-2.

  If it is determined in step 4-1 that the toner motor 17 is not required to be replenished from the toner container 153 to the developing device 152 (NO in S4-1), the process returns to step S4-1 and the toner motor 17 is turned on. Until the drive is requested, the toner motor 17 is in a standby state.

  Subsequently, in step S4-2, the toner motor 17 has been driven once by the CPU 10 when the power switch (not shown) of the copying machine 1 is turned on or when the cover (not shown) covering the apparatus main body 100 is opened and closed. The toner motor history information is read from the memory unit 20 in order to determine whether or not the When the CPU 10 determines that the toner motor 17 has never been driven from when the power switch (not shown) of the copying machine 1 is turned on or when a cover (not shown) covering the apparatus main body 100 is opened or closed (see FIG. In S4-2 YES), in step S4-3, the CPU 10 causes the CPU 10 to determine whether or not the drive circuit unit 18 stored in advance in the memory unit 20 is in an abnormal overcurrent state. Are read, and the count setting value A is set to the initial value.

  The reason why the count setting value A is set to the initial value in this way is, for example, replacement of the toner motor 17 (toner when the power switch (not shown) is turned off or when the cover (not shown) is opened). The load of the toner motor 17 is changed due to a gear (not shown) attached to the rotating shaft of the motor 17 and the gear (not shown) of the shutter 152a is changed), and the starting time Ts is increased, and As will be described later, when the count setting A is reset at a time shorter than the initial value, the possibility of erroneous detection as an abnormal overcurrent state is eliminated.

  In step S4-2, the toner motor 17 has been driven by the CPU 10 when the power switch (not shown) of the copying machine 1 is turned on or when the cover (not shown) covering the apparatus main body 100 is opened or closed. When it determines (S4-2 NO), it progresses to step S4-4.

  Subsequently, in step S4-4, as shown in FIGS. 1, 3, and 5, the CPU 10 inputs the high level remote signal S1 to the drive circuit unit 18. Based on the inputted high level remote signal S1, the motor current I1 is supplied from the drive circuit unit 18 to the toner motor 17, and the driving of the toner motor 17 is started (timing 31, 51). When the driving of the toner motor 17 is started (timing 31, 51), as shown in FIG. 3 and FIG. 5, the output stage current I2 is less than the current reference value. The signal S2 is input to the CPU 10. Further, as shown in FIGS. 3 and 5, it can be seen that the starting current I3 is generated when the driving of the toner motor 17 is started.

  Subsequently, in step S4-5, when the output stage current I2 becomes equal to or higher than the current reference value due to the load at the start of the toner motor 17, a high-level current detection signal S2 is input from the current detection unit 16 to the CPU 10. The Then, the CPU 10 starts counting with the time when the current detection signal S2 is at the high level (that is, the time when the output stage current I2 is equal to or greater than the current reference value) as the count value T (timing 32, 52).

  Subsequently, in step S4-6, when step S4-6 is passed for the first time or when the previous step S4-3 is passed, the CPU 10 reads the initial value of the count setting value A into the memory unit 20. Then, the count setting value A is set to the initial value. Then, the CPU 10 compares the count set value A set as the initial value with the count value T being counted. In addition, it returns to step S4-1 from below-mentioned step S4-11, and the case where it passes newly step S4-6 is mentioned later.

  Then, as shown in FIG. 4, a low level current detection signal S2 is input from the current detection unit 16 to the CPU 10 (timing 33), and the CPU 10 determines that the count value T is smaller than the count set value A. In (S4-6 YES), in step S4-7, the CPU 10 determines that the drive circuit unit 18 is in a normal state (that is, no abnormal overcurrent flows through the drive circuit unit 18 and the toner motor 17). The memory unit 20 stores a count value T (a time during which the current detection signal S2 is at a high level). The startup time Ts is on the order of about several hundreds [ms], although it varies depending on the torque and the rotational speed of the toner motor 17.

  In step S4-6, as shown in FIG. 5, the low-level current detection signal S2 is not input to the CPU 10 from the current detection unit 16 even after the time of the count setting value A, and the CPU 10 counts the count value. When it is determined that T is greater than the count setting value A (NO in S4-6, timing 53), in step S4-8, the CPU 10 determines that the drive circuit unit 18 is in an abnormal overcurrent state. That is, the abnormal overcurrent I5 flows through the drive circuit unit 18 (the abnormal overcurrent also flows through the toner motor 17). In step S4-9, the low-level remote signal S1 is immediately input from the CPU 10 to the drive circuit unit 18 (timing 54), and the toner motor 17 is stopped. At this time, the output stage current I2 becomes zero, and the low-level current detection signal S2 is input from the current detection unit 16 to the CPU 10 (timing 55).

  Subsequently, in step S4-10, the CPU 10 uses a calculation formula or a table obtained from an experiment or the like stored in advance in the memory unit 20 based on the count value T obtained in step S4-7. A new count setting value A is calculated and stored in the memory unit 20. For example, based on the count value T, a new count setting value A that is twice the time of the count value T is calculated and stored in the memory unit 20. The initial value of the count setting value A is always stored in the memory unit 20 without being overwritten with the new count setting value A.

  In step S 4-11, the shutter 152 a is opened by the driving force of the toner motor 17, and the toner 153 a is supplied from the toner container 153 to the developing device 152. The CPU 10 develops the toner based on the toner density signal input from the toner sensor 152b and a table indicating the relationship between the toner density signal stored in the memory unit 20 and the appropriate toner density value in the developing device 152. When it is determined that the toner density in the device 152 has reached an appropriate value, the low-level remote signal S1 is input from the CPU 10 to the drive circuit unit 18 (timing 34). Then, the toner motor 17 stops.

  Subsequently, returning to step S4-1, this flowchart is repeated, but if the count set value A is set to the initial value in step S4-3, the count set value A is set in step S4-6. The initial value is set. In step S4-2, the CPU 10 may have driven the toner motor 17 when the power switch (not shown) of the copying machine 1 is turned on or when a cover (not shown) covering the apparatus main body 100 is opened or closed (S4). -2NO), in step S4-6, the CPU 10 sets the count setting value A to the new count setting value A stored in the memory unit 20 in the previous step S4-10. Then, as described above, the toner motor 17 is controlled.

  Here, the characteristic of the setting of the count setting value A in the copying machine 1 of the present embodiment described above (when not passing through steps S4-3, S4-8, and S4-9) will be described below. FIG. 6 is a diagram for explaining the feature of setting the count setting value A in the copying machine 1 of the present embodiment. FIG. 6A is a diagram showing a current detection signal in a flow two before the current current detection signal shown in FIG. 6C, and FIG. 6B is a diagram showing the current detection signal shown in FIG. FIG. 6C is a diagram showing the current detection signal in the flow immediately before the current detection signal, and FIG. 6C is a diagram showing the current current detection signal. The flow means the flowchart shown in FIG.

  In the copying machine 1 of the present embodiment, as shown in FIG. 6A, in the flow two steps before the present time, the count value T1 is counted by the CPU 10 in steps S4-5 and S4-6 as described above. Further, in step S4-10, the count setting value A2 used in the previous flow shown in FIG. 6B is obtained and set based on the count value T1.

  Subsequently, as shown in FIG. 6B, in the flow immediately before the current time, as described above, the count value T2 is counted by the CPU 10 in steps S4-5 and S4-6, and further in step S4- 10, the count setting value A3 used in the current flow shown in FIG. 6C is obtained and set based on the count value T2. For example, as shown in FIG. 6, when the count value T2 becomes shorter, the count setting value A3 calculated and set based on the count value T2 becomes shorter than the count setting value A2.

  Therefore, as described above, the copying machine 1 provided with the motor control device of the present embodiment has a function of the toner motor 17 even if the load state of the toner motor 17 changes due to variations due to various factors as described above. The start time is configured such that a new count setting value A for determining an abnormal overcurrent state of the drive circuit unit 18 is set based on the count value T obtained in the previous flow. Since the count set value A corresponding to the variation of 17 can be optimized, when the abnormal overcurrent flows through the drive circuit unit 18 and the toner motor 17, the CPU 10 assumes that the drive circuit unit 18 is in an abnormal overcurrent state. The time until the determination is shortened, and it becomes possible to reliably protect the drive circuit unit 18 (the output transistor at the output stage of the drive circuit unit 18) from an abnormal overcurrent. Therefore, the copying machine 1 equipped with the motor control device according to the present invention can perform the optimum overcurrent detection of the drive circuit unit 18.

  Further, in the copying machine 1 equipped with the motor control device of the present embodiment, the CPU 10 in step S4-2 sets a cover (not shown) that covers the apparatus main body 100 when the power switch (not shown) of the copying machine 1 is turned on. When it is determined that the toner motor 17 has never been driven since opening / closing (YES in S4-2), the initial value of the count setting value A for the longest time considering the variation of the toner motor is the count setting value. Therefore, even when the toner motor 17 is replaced, it is possible to detect the optimum overcurrent of the drive circuit unit 18.

  In the above-described embodiment, the output stage current I2 flowing through the drive circuit unit 18 (the output stage of the drive circuit unit 18) is detected by the current detection unit 16, but the motor current I1 flowing through the toner motor 17 is The structure detected by the electric current detection part 16 may be sufficient. Even in such a configuration, the same effect as described above can be obtained.

  In the case where there is no possibility that the load of the toner motor 17 is changed due to replacement or re-installation of the toner motor 17 in the copying machine 1 equipped with the motor control device of the present embodiment, it is shown in FIG. 4 described above. A flowchart excluding steps S4-2 and S4-3 may be used.

  In the above embodiment, the control of the toner motor 17 (DC brushless motor) has been described as an example. However, the configuration of the present invention is not limited to the toner motor 17 (DC brushless motor). It can be widely applied to DC motors.

  Further, in the above embodiment, the configuration in the case where the motor control device according to the present invention is mounted on a copying machine has been described as an example, but the configuration of the present invention is not limited to this, The present invention can be widely applied to devices equipped with a DC motor.

  The configuration of the present invention can be variously modified within the scope of the present invention in addition to the above embodiment.

  The present invention is a useful technique for protecting a drive circuit unit that drives a DC motor from abnormal overcurrent.

These are the block diagrams which show the principal part structure of the copying machine provided with the motor control apparatus based on this invention. These are the longitudinal cross-sectional views which show typically the principal part structure of the copying machine provided with the motor control apparatus which concerns on this invention. These are figures which show the relationship between the remote signal S1, the current detection signal S2, and the output stage current I2 when the drive circuit unit 18 is not in an abnormal overcurrent state. These are flowcharts for explaining the control of the toner motor 17 in the copying machine 1 of the present embodiment. These are figures which show the relationship between the remote signal S1, the current detection signal S2, and the output stage current I2 when the drive circuit unit 18 is in an abnormal overcurrent state. FIG. 6 is a diagram for explaining the feature of setting the count setting value A in the copying machine 1 of the present embodiment.

Explanation of symbols

1 Copier 10 Central processing unit (CPU)
DESCRIPTION OF SYMBOLS 100 Main unit 11 Document transport unit 12 Document take-in unit 13 Operation display unit 14 Paper feed unit 141a to 141c Paper storage unit 142 Paper transport unit 15 Image forming unit 151 Photosensitive drum 152 Developer 152a Shutter 152b Toner sensor 153 Toner container 153a Toner 16 Current detector 17 Toner motor 18 Drive circuit unit 19 Fixing unit 20 Memory unit I1 Motor current I2 Output stage current I3 Starting current I4 Steady current I5 Abnormal overcurrent S1 Remote signal S2 Current detection signal

Claims (1)

  A drive unit for driving a DC motor and a current flowing through the drive unit or the DC motor are detected, and when a current exceeding a predetermined current reference value flows through the drive unit or the DC motor, a predetermined current detection is performed. A current detection means for outputting a 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 the predetermined current output from the current detection means Counting means for counting the output time of the detection signal, overcurrent detection means for comparing the output time with the latest time setting value stored in the memory unit, and the overcurrent detection means If it is determined that the output time is smaller than the latest time set value, the drive unit continues to drive the DC motor, and a new time set value is calculated based on the output time, The new time setting value is stored in the memory unit, and when the output time is determined to be larger than the latest time setting value by the overcurrent detecting means, the driving unit stops the DC motor. And a motor control device.

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