JP2018074746A - Motor control device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent the malfunction due to the abnormal excessive current while dealing with the change in the inrush current and stationary current with the lapse of time.SOLUTION: A motor control device includes a current fuse 75 which has the rating current larger than the maximum value of the inrush current generated to the end of the service life of a motor 73 as a load; a transistor 76 which is inserted to a power supply line L1; and a current adjustment part 101 which adjusts the collector current by controlling the base voltage of the transistor 76. The current adjustment part 101 controls the base voltage so as to be a cut-off region of the transistor 76 in a first period in which the motor 73 is stopped, controls the base voltage so as to be a saturation region of the transistor 76 in a second period in which the inrush current is generated, and suppresses the collector current within a range where the stationary current can flow in the power supply line L1 by controlling the base voltage in a third period other than the first period and second period.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a motor control device and an image forming apparatus.

  As one of the methods for protecting each component constituting the motor control device, it is well known to insert a fuse into a power supply line for supplying power from a power source to the motor. For example, when an abnormality such as a short circuit occurs somewhere in the apparatus and an overcurrent flows through the power supply line, the fuse is blown. Thereby, supply of electric power is interrupted, and a malfunction due to an abnormal overcurrent flowing is prevented.

  Therefore, when an abnormality occurs in the apparatus, it is important to surely blow the fuse, and various proposals have been made. For example, Patent Document 1 below describes that when a motor abnormality is detected, a fuse is blown using a transistor. Patent Document 2 below describes providing a transistor for switching the presence or absence of a current flowing through a fuse.

JP 09-322388 A JP 2010-278124 A

  As the fuse used in the motor control device, a fuse having a rated current equal to or greater than the value of the motor drive current flowing as a steady current in the power supply line is selected. Since the steady current preferably satisfies the condition that it is about 50 to 60% of the rated current, the fuse needs to satisfy this condition. In addition to the above conditions, in addition to the above conditions, a fuse having a rated current capable of withstanding the inrush current needs to be adopted in order to avoid the fuse from being blown by an instantaneous overcurrent such as an inrush current generated at the start of the motor. is there.

  Further, the inrush current and the steady current flowing through the power supply line may increase or decrease depending on the environmental change or aging of the motor as a load. For example, when dust and debris tend to accumulate on the motor shaft and bearings, the starting torque and the steady torque become heavier as time passes, and the inrush current and the steady current increase accordingly. Conversely, if the motor shaft or bearing is used for a long time, it may melt, and in such a case, the starting torque and steady torque become lighter as time passes. As the time elapses, the inrush current and the steady current become smaller.

  Therefore, it is not sufficient to select a fuse based on the inrush current at a fixed value. If no consideration is given to the fact that the magnitude of the inrush current changes with the passage of time, even if there is no problem in the initial stage of use, there will be a situation where the fuse cannot properly cope with the inrush current when it is near the end of its life. However, the above Patent Documents 1 and 2 do not disclose a technique corresponding to a change in inrush current or steady current with time.

  In addition, if a fuse is selected based on the inrush current, a fuse having a rated current much larger than the steady current is required. In this case, an abnormality occurs in the device when the steady current is flowing. Even if an overcurrent flows in the power supply line, if the overcurrent is smaller than the rated current, the fuse is not blown, so that it may not be possible to prevent a malfunction due to an abnormal overcurrent flowing.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to reliably prevent problems due to abnormal overcurrent while responding to changes in inrush current and steady current with time.

  A motor control device according to an aspect of the present invention is inserted into a motor driver that supplies power from a power source to a motor and controls driving of the motor, and a power supply line that supplies power from the power source to the motor. In addition, a fuse having a predetermined maximum inrush current generated when the motor is started and a rated current larger than the driving current of the motor, and a fuse connected in series with the fuse, and a collector and an emitter connected to the power supply line And a current adjusting unit that adjusts a collector current of the transistor by controlling a base voltage of the transistor, and the current adjusting unit stops the motor in a first period. Then, the base voltage is controlled so as to be a cutoff region of the transistor, and the inrush power The base voltage is controlled so as to be in a saturation region of the transistor in the second period in which occurrence occurs, and in the third period other than the first period and the second period, the base voltage is controlled to control the base voltage. The collector current is controlled within a range in which the driving current of the motor can flow through the power supply line.

  An image forming apparatus according to an aspect of the present invention uses the motor control device, a drum motor that rotates a photosensitive drum as the motor, and a latent image formed on the surface of the photosensitive drum. An image forming unit that generates a toner image and forms the toner image on a recording medium.

  According to the present invention, since the fuse having the rated current larger than the maximum value of the inrush current and the drive current of the motor is inserted into the power supply line that supplies power to the motor, the inrush current becomes large until the life of the motor. Even if it becomes, it can prevent the fuse from being blown by the inrush current.

  Further, in the first period in which the motor is stopped, the base voltage is controlled so as to be in the transistor cutoff region (the state where the collector current does not flow), so no current flows through the power supply line. Therefore, in the first period, since no overcurrent flows through the power supply line, there is no problem due to overcurrent due to the fuse not fusing.

  In the second period when the inrush current occurs, the base voltage is controlled so as to be in the saturation region of the transistor (the transistor is in a conductive state). Therefore, the magnitude of the current flowing through the power supply line is not suppressed, but it exceeds the rated current. When the overcurrent flows through the power supply line, the fuse is blown, so that there is no problem due to the overcurrent. On the other hand, if an overcurrent less than the rated current flows to the power supply line, the fuse will not blow, but the inrush current will flow for a short period of time, so the second period can be set to a short time, causing problems due to overcurrent. Can be reduced.

  In the third period, the collector current is suppressed in a range in which the steady current can flow through the power supply line, so the steady current flows through the power supply line, but a much larger overcurrent does not flow. There is no problem due to overcurrent.

  Therefore, it is possible to reliably prevent a malfunction due to an abnormal overcurrent regardless of changes in the inrush current and the steady current with time.

1 is a schematic partial cross-sectional front view showing the structure of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a functional block diagram schematically illustrating a main internal configuration of the image forming apparatus according to the first embodiment. It is a block diagram which shows the structure of a motor control apparatus. It is the graph which showed typically the rush current and steady current which change with progress of time, (A) shows the state which becomes large with progress of time, (B) becomes small with progress of time. It shows the state of going. It is the graph which showed typically the current waveform which flows into an electric power supply line before and after the start-up of a motor when an inrush current and a steady-state current become large with progress of time, and (A) shows a current waveform in the initial stage of use. , (B) show current waveforms at the time of life. It is the graph which showed typically the current waveform which flows into an electric power supply line before and after the start-up of a motor when an inrush current and a steady-state current become small with progress of time, and (A) shows a current waveform in the initial stage of use. , (B) show current waveforms at the time of life. It is explanatory drawing for demonstrating the period when the adjustment method of the collector current of a transistor switches. 5 is a flowchart illustrating an example of processing operations performed by a control unit in the image forming apparatus. 5 is a flowchart illustrating an example of processing operations performed by a control unit in the image forming apparatus. 5 is a flowchart illustrating an example of processing operations performed by a control unit in the image forming apparatus.

  Hereinafter, a motor control device and an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic partial cross-sectional front view showing the structure of the image forming apparatus according to the first embodiment of the present invention. The image forming apparatus 1 is a multifunction machine having a plurality of functions such as a copy function, a printer function, a scanner function, and a facsimile function, for example, and the motor control device (FIG. 3) according to an embodiment of the present invention. In addition, the apparatus main body 11 includes an operation unit 47, a display unit 473, a document feeding unit 6, a document reading unit 5, an image forming unit 12, a fixing unit 13, and a paper feeding unit 14.

  A case where a document reading operation is performed in the image forming apparatus 1 will be described. The document reading unit 5 optically reads an image of the document fed by the document feeding unit 6 or the document placed on the document placing glass 161, and generates image data. The image data generated by the document reading unit 5 is stored in a built-in HDD (Hard Disk Drive), a network-connected computer, or the like.

  A case where an image forming operation is performed in the image forming apparatus 1 will be described. The image forming unit 12 is fed from the paper feeding unit 14 based on image data generated by the document reading operation, image data stored in the built-in HDD, image data received from a computer connected to the network, and the like. A toner image is formed on a sheet P as a recording medium.

  The image forming unit 12 includes photosensitive drums 121 for black, yellow, cyan, and magenta. The photosensitive drum 121 is driven to rotate counterclockwise in the drawing.

  The transfer unit 120 includes an intermediate transfer belt 125, a driving roller 125a, a driven roller 125b, and a primary transfer roller 126 on which a toner image is transferred to the outer peripheral surface thereof.

  The intermediate transfer belt 125 is stretched between the driving roller 125a and the driven roller 125b, is driven by the driving roller 125a in a state of being in contact with the peripheral surface of the photosensitive drum 121, and is synchronized with the photosensitive drum 121. Travel endlessly.

  Next, a case where color printing is performed will be described. The periphery of the photosensitive drum 121 is uniformly charged (charging process), and the surface of the charged photosensitive drum 121 is irradiated with laser light based on image data to form a latent image (exposure process). The latent image is visualized with toner (development process), and the toner image formed by the visualization is transferred onto the intermediate transfer belt 125 by the primary transfer roller 126.

  The toner images of the respective colors (black, yellow, cyan, and magenta) transferred onto the intermediate transfer belt 125 are superimposed on the intermediate transfer belt 125 with the transfer timing adjusted to form a color toner image.

  The secondary transfer roller 210 passes a color toner image formed on the surface of the intermediate transfer belt 125 from the paper supply unit 14 through the conveyance path 190 at a nip N between the intermediate transfer belt 125 and the driving roller 125a. This is transferred onto the conveyed paper P.

  The fixing unit 13 includes a fixing roller pair 131 and fixes the toner image on the paper P by thermocompression. The paper P on which the color image has been subjected to the fixing process is discharged to the discharge tray 151.

  FIG. 2 is a functional block diagram schematically showing the main internal configuration of the image forming apparatus 1. The image forming apparatus 1 includes a control unit 10, a document feeding unit 6, a document reading unit 5, an image forming unit 12, an operation unit 47, a fixing unit 13, and a paper feeding unit 14. Components similar to those of the image forming apparatus 1 shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted here.

  The motor drive circuit 72 controls the drive of the motor 73 in accordance with an instruction from the control unit 100 of the control unit 10. The motor 73 supplies rotational driving force to the photosensitive drum 121, the driving roller 125a, the primary transfer roller 126, the secondary transfer roller 210, the fixing roller pair 131, the pickup roller 145, the transport roller pair 19, the discharge roller pair 159, and the like. Drive source Each of the rollers may have a motor as a drive source, and a motor drive circuit 72 may be provided for each motor.

  The control unit 10 includes a processor, a RAM (Random Access Memory), a ROM (Read Only Memory), and a dedicated hardware circuit. The processor is, for example, a central processing unit (CPU), an application specific integrated circuit (ASIC), or a micro processing unit (MPU). The control unit 10 includes a control unit 100 and a current adjustment unit 101.

  The control unit 10 functions as the control unit 100 and the current adjustment unit 101 by the operation of the processor according to a control program stored in an HDD (not shown) built in the image forming apparatus 1. However, the control unit 100 and the current adjustment unit 101 can be configured by a hardware circuit regardless of the operation of the control unit 10 according to the control program. The same applies to each embodiment unless otherwise specified.

  The control unit 100 governs overall operation control of the image forming apparatus 1. The control unit 100 is connected to the document feeding unit 6, the document reading unit 5, the image forming unit 12, the operation unit 47, the fixing unit 13, and the sheet feeding unit 14, and performs drive control of these units.

  The current adjustment unit 101 adjusts the collector current of the transistor 76 by controlling the base voltage of the transistor 76 (FIG. 3) constituting the motor drive circuit 72.

  FIG. 3 is a block diagram illustrating a configuration of the motor control device according to the embodiment of the present invention. The motor control device 71 includes a motor drive circuit 72, a control unit 100, and a current adjustment unit 101. The motor drive circuit 72 includes a motor driver IC 74, a current fuse 75, a transistor 76, and a digital-analog converter (DAC) 77. The motor 73 is, for example, a brushless motor.

  The motor driver IC 74 supplies power to the motor 73 and controls driving of the motor 73. The power supply terminal 74 a is connected to the power supply VCC through a current fuse 75. The ground terminal 74b is grounded and connected. The input terminal 74 c is connected to the control unit 100. The output terminals 74e and 74f are connected to the motor 73 by power supply lines.

  The motor driver IC 74 controls the driving of the motor 73 in accordance with a command signal for instructing the start and stop of the motor 73 and the rotation speed, which is output from the control unit 100 and taken in by the input terminal 74c.

  The power supply line L1 is a line that supplies power from the power supply VCC to the motor 73. The current that flows through the motor 73 flows from the power terminal 74a of the motor driver IC 74 to the output terminal 74e, the motor 73, and the output terminal 74f, and then flows to the ground terminal 74b.

  In the transistor 76, the collector (C) is connected to the power supply VCC, the emitter (E) is connected to one end of the current fuse 75, and the transistor 76 is inserted into the power supply line L1 via the collector and the emitter. Connected in series. The base (B) of the transistor 76 is connected to the current adjustment unit 101 via the digital-analog conversion unit 77.

  The inrush current that flows through the power supply line L1 when the motor 73 is started up and the current that constantly flows through the power supply line L1 (steady current) have elapsed over time due to the performance of the motor 73 and the influence of the surrounding environment on the motor 73. At the same time, it becomes larger or smaller.

  FIG. 4 is a graph schematically showing an inrush current and a steady current that change with the passage of time. FIG. 4A shows a state in which the inrush current and the steady current increase with the passage of time. (B) shows a state in which the inrush current and the steady current become smaller with the passage of time. The time TF indicates the initial use of the motor 73, and the time TE indicates the life point of the motor 73.

  As shown in FIG. 4A, when the inrush current and the steady current increase with the passage of time, the inrush current Ib at the time of the life of the load is more than the inrush current Ia at the initial use. large. On the other hand, as shown in FIG. 4B, when the inrush current and the steady-state current become smaller with time, the inrush current Ic at the initial use of the load is more inrush current Id at the time of life. Bigger than.

  FIG. 5 is a graph schematically showing a waveform of a current flowing through the power supply line L1 before and after the start of the motor 73 when the inrush current and the steady current increase with time. FIG. 5A shows a current waveform in the initial stage of use. FIG. 5B shows the current waveform at the end of the life. The convex part shows a state where an inrush current flows, and the part with a gentle slope shows a state where a steady current flows.

  As shown in FIG. 5A, the peak value of the inrush current at the initial use of the motor 73 is Ia, and as shown in FIG. 5B, the peak value of the inrush current at the end of the life of the motor 73 is Ib. As described above, when the inrush current of the motor 73 increases with time, a current fuse 75 having a rated current larger than the peak value Ib of the inrush current at the time of the life of the motor 73 is selected.

  FIG. 6 is a graph schematically showing a waveform of a current flowing through the power supply line L1 before and after the start of the motor 73 when the inrush current and the steady current become smaller with time. FIG. 6A shows a current waveform in the initial stage of use. FIG. 6B shows a current waveform at the time of life.

  As shown in FIG. 6 (A), the peak value of the inrush current at the initial use of the motor 73 is Ic, and as shown in FIG. 6 (B), the peak value of the inrush current at the end of the life of the motor 73 is Id. It becomes. As described above, when the inrush current of the motor 73 decreases with time, a current fuse 75 having a rated current larger than the peak value Ic of the inrush current in the initial use of the motor 73 is selected.

  The peak values Ib and Ic are specifically peak values predicted by experiments or the like. Furthermore, it is desirable to select a current fuse 75 having a rated current that is about twice the predicted peak values Ib and Ic.

  As shown in FIG. 7, the collector current IC of the transistor 76 is adjusted by the current adjusting unit 101 in three periods P1 to P3. The first period P1 is a time zone in which the motor 73 is stopped. The second period P2 is a period set in advance as a period during which an inrush current occurs. The third period P3 is a period other than the first period P1 and the second period P2.

  For example, the second period P2 is a period from when the motor 73 is activated until a predetermined set time elapses, and is a predetermined time period in which an inrush current may flow. The third period P3 is a period in which the drive current of the motor 73 is supplied as a steady current.

  The current adjustment unit 101 controls the base voltage VB so as to be a cutoff region of the transistor 76 in the first period P1. Further, the current adjustment unit 101 controls the base voltage VB so as to be in the saturation region of the transistor 76 in the second period P2.

  Further, the current adjustment unit 101 suppresses the collector current IC by controlling the base voltage VB of the transistor 76 in the third period P3. For example, the current adjusting unit 101 sets the collector current IC with an upper limit of about 50% of the steady current. Further, as shown in FIGS. 4A and 4B, the steady current increases or decreases with time, so the upper limit IC_MAX (FIG. 7) of the collector current IC is determined by the motor 73. In the case where the steady current increases with the passage of time according to the characteristics of the motor, the steady current of the motor 73 decreases with the passage of time by increasing it by a predetermined value every time the predetermined time passes. Is reduced by a predetermined value every time a predetermined time elapses. As described above, the current adjustment unit 101 changes the base voltage VB and the upper limit IC_MAX of the collector current IC in the third period P3 according to the characteristics of the motor 73 with the passage of time.

  Next, an example of the processing operation performed in the control unit 10 will be described based on the flowchart shown in FIG. The processing operation is started when the control unit 100 outputs a start command signal for the motor 73 to the motor driver IC 74. That is, the current adjustment unit 101 controls the base voltage VB so as to be in the blocking region of the transistor 76 as the first period P1 during which the motor 73 is stopped until the start command signal for the motor 73 is output.

  When the start command signal for the motor 73 is output, the current adjustment unit 101 starts the second period P2, and sets the base voltage VB of the transistor 76 to a predetermined set voltage so that the transistor 76 is in a saturation region. Raise to VB1 (S1). That is, in the second period P2, the state is the same as when the collector and emitter of the transistor 76 are short-circuited. The set voltage VB1 is a value that does not increase the collector current IC even if the base voltage VB is further increased, and is calculated and determined in advance by experiments or the like. As described above, the second period P2 is a period in which the timer T is predetermined as a period in which the inrush current occurs.

  The current adjustment unit 101 executes the above S1 and resets and activates the timer T to 0 (S2), and determines whether or not the time measured by the timer T has reached the set time T1 as the second period P2. (S3).

  The current adjustment unit 101 continues the second period P2 (continues execution of S1) until the time measured by the timer T reaches the set time T1 (NO in S3).

  Then, when the current adjustment unit 101 determines that the time measured by the timer T has reached the set time T1 (that is, the end timing of the second period P2 and the start timing of the third period P3) (in S3) YES), the current adjustment unit 101 lowers the base voltage VB of the transistor 76 to a predetermined set voltage VB2 (S4), and suppresses the collector current IC. That is, in the third period P3, the current flowing through the power supply line L1 is suppressed. As described above, the set voltage VB2 is set such that the upper limit IC_MAX of the collector current IC is about 50% higher than the steady current IS.

  Subsequently, the current adjustment unit 101 determines whether or not a stop command signal for the motor 73 is output from the control unit 100 to the motor driver IC 74 (S5). The current adjustment unit 101 continues to execute S4 until a stop command signal for the motor 73 is output (NO in S5).

  Then, the current adjustment unit 101 outputs a stop command signal for the motor 73 to the motor driver IC 74 by the control unit 100 (that is, the end timing of the third period P3 and the start timing of the first period P1). (YES in S5), the current adjustment unit 101 sets the base voltage VB of the transistor 76 to 0 V so as to be in the cut-off region of the transistor 76 (S6). That is, the first period P1 is reached, and no current flows through the power supply line L1.

  According to the above embodiment, since the current fuse 75 having a rated current larger than the maximum value of the inrush current is inserted into the power supply line L1 that supplies power to the motor 73, the current fuse 75 is blown by the inrush current. do not do.

  Moreover, since the maximum value of the inrush current is the maximum value of the inrush current generated until the life of the motor 73 as a load, the current fuse 75 is not limited by the inrush current, not only in the initial use but also near the end of the life. Do not blow.

  Further, in the first period P1 during which the motor 73 is stopped, the base voltage VB is controlled so that the transistor 76 is in the cut-off region (the state where the collector current IC does not flow), so no current flows through the power supply line L1. For this reason, in the first period P1, no overcurrent flows through the power supply line L1, and a problem due to the overcurrent does not occur.

  In addition, since the base voltage VB is controlled so that the transistor 76 is in the saturation region (the transistor 76 is conductive) during the second period P2 in which the inrush current is generated, the magnitude of the current flowing through the power supply line L1 is Although not suppressed, when an overcurrent greater than or equal to the rated current flows through the power supply line L1, the current fuse 75 is blown, so that a malfunction due to the overcurrent does not occur.

  On the other hand, when an overcurrent less than the rated current flows through the power supply line L1, the current fuse 75 is not blown, but since the time during which the inrush current flows is short, the second period P2 can be set to a very limited time. Therefore, it is possible to reduce the occurrence of problems due to overcurrent.

  In the third period P3, the collector current IC is suppressed within a range in which the steady current can flow through the power supply line L1, so the steady current flows through the power supply line L1, but an overcurrent much larger than that is Since it does not flow, there will be no problems due to overcurrent.

  Therefore, according to the present embodiment, it is possible to reliably prevent a malfunction due to an abnormal overcurrent regardless of changes in inrush current and steady current with time.

  Next, an example of the processing operation performed in the control unit 10 will be described based on the flowchart shown in FIG. This processing operation is a processing operation for increasing the set voltage VB2 over time. This processing operation is performed when the steady torque of the motor 73 increases with time and the drive current of the motor 73 increases with time.

  First, the current adjustment unit 101 sets the set voltage VB2 to an initial value V1 that has been determined in advance by experiments or the like (S11), and sets the value of the counter C that counts the number of print processing sheets to 0 (S12). The current adjustment unit 101 determines from the result of the image forming process by the image forming unit 12 whether the printing process has been performed for one sheet of paper P (S13).

  When the current adjusting unit 101 determines that the printing process has been performed for one sheet (YES in S13), the current adjusting unit 101 adds 1 to the counter C (S14).

  Subsequently, the current adjusting unit 101 determines whether or not the counter C has reached a predetermined set value C1 (for example, 1000) (S15), and the counter C has reached the set value C1 (the number of printed sheets is (S16: YES), a predetermined addition value α is added to the set voltage VB2 (S16), and the set voltage VB2 is increased by the addition value α. That is, the drive current of the motor 73 is increased by an amount corresponding to the added value α. Thereafter, the process returns to S12. In this way, the current adjustment unit 101 increases the base voltage VB in accordance with the passage of time by increasing the base voltage VB in the third period P3 every time a predetermined number of sheets are printed. .

  Note that if the current adjustment unit 101 determines that the counter C has not reached the set value C1 (NO in S15), the process is repeated from S13.

  Next, still another example of the processing operation performed by the control unit 10 will be described based on the flowchart shown in FIG. This processing operation is a processing operation for reducing the set voltage VB2 as time passes. This processing operation is an operation performed when the steady torque of the motor 73 decreases with time.

  First, the current adjusting unit 101 sets the set voltage VB2 to an initial value V2 that is predetermined by experiment or the like (S21), and sets the value of the counter C that counts the number of print processed sheets to 0 (S22). The current adjustment unit 101 determines from the result of the image forming process by the image forming unit 12 whether the printing process has been performed for one sheet of paper P (S23).

  When the current adjusting unit 101 determines that one printing process has been performed (YES in S23), the current adjusting unit 101 adds 1 to the counter C (S24).

  Subsequently, the current adjusting unit 101 determines whether or not the counter C has reached a predetermined set value C1 (for example, 1000) (S25), and the counter C has reached the set value C1 (the number of printed sheets is If it is determined that the number has reached 1000 (YES in S25), a predetermined subtraction value β is subtracted from the set voltage VB2 (S26), and the set voltage VB2 is reduced by the subtraction value β. That is, the drive current of the motor 73 is reduced by an amount corresponding to the subtraction value β. Thereafter, the process returns to S22. In this way, the current adjustment unit 101 decreases the base voltage VB in accordance with the passage of time by decreasing the base voltage VB in the third period P3 every time a predetermined number of sheets are printed. .

  Note that if the current adjustment unit 101 determines that the counter C has not reached the set value C1 (NO in S25), the process is repeated from S23.

  In the embodiment shown in FIG. 9 and FIG. 10, the current adjusting unit 101 performs the base voltage VB (the driving current of the motor 73) every time a predetermined number of sheets (set value C1) are printed. ), But using the timer T instead of the counter C, the current adjustment unit 101 changes the base voltage VB (the driving current of the motor 73) every time the timer T measures a predetermined time. It is good to do.

  According to the embodiment shown in FIGS. 9 and 10 described above, the upper limit IC_MAX of the collector current IC is changed in accordance with the drive current (steady current) of the motor 73 that changes with time, so that the added value α And the subtraction value β is set in accordance with the increase / decrease of the drive current of the motor 73 that changes with the passage of time, so that the value of the current flowing through the power supply line of the motor 73 can be changed. The drive current can be suppressed within a certain range. As a result, (1) even if the level of the driving current of the motor 73 changes with time, the driving current of the motor 73 is stably sent to the power supply line, and (2) the motor is supplied to the power supply line. Even when a current larger than the drive current of 73 flows, the large current flowing in this way can always be suppressed within a certain range from the drive current of the motor 73. For this reason, it becomes possible to avoid the generation | occurrence | production of the malfunction by an overcurrent flowing into a power supply line as much as possible.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. In the above-described embodiment, a multifunction peripheral is used as an embodiment of the image forming apparatus according to the present invention. However, this is only an example, and other images such as a copier, a scanner, and a printer are used. It may be a forming apparatus or other electrical equipment.

  Moreover, in the said embodiment, the structure and process which were shown by the said embodiment using FIG. 1 thru | or FIG. 10 are only one Embodiment of this invention, and are not the meaning which limits this invention to the said structure and process.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Control unit 12 Image forming part 71 Motor control apparatus 73 Motor 74 Motor driver IC
75 Current fuse 76 Transistor 100 Control unit 101 Current adjustment unit

Claims (7)

A motor driver that supplies power from the power source to the motor and controls the driving of the motor;
A fuse inserted in a power supply line for supplying power from the power source to the motor, and having a predetermined maximum inrush current generated at the start of the motor and a rated current larger than a drive current of the motor; ,
A transistor connected in series with the fuse and inserted into the power supply line via a collector and an emitter;
A current adjusting unit that adjusts a collector current of the transistor by controlling a base voltage of the transistor;
The current adjusting unit is
In the first period in which the motor is stopped, the base voltage is controlled so as to be a cutoff region of the transistor,
In the second period in which the inrush current occurs, the base voltage is controlled so as to be in a saturation region of the transistor,
In the third period other than the first period and the second period, a motor that controls the collector current within a range in which the driving current of the motor can flow in the power supply line by controlling the base voltage. Control device. The motor is such that the starting torque of the motor increases with time,
The motor control device according to claim 1, wherein the value of the inrush current is a predicted peak value of the inrush current at the time of life of the motor.   3. The motor control device according to claim 2, wherein the current adjustment unit increases the collector current in the third period by a predetermined value as time elapses. The motor is such that the starting torque of the motor decreases with time,
The motor control device according to claim 1, wherein the value of the inrush current is a predicted peak value of the inrush current at the initial use of the motor.   5. The motor control device according to claim 4, wherein the current adjustment unit reduces the collector current in the third period by a predetermined value as time passes. A plurality of the motors coupled to each of the plurality of motors;
2. The current adjusting unit adjusts a collector current of the transistor inserted in the power supply line that supplies power from the power source to each of the motors according to the motor connected to the motor. The motor control device according to claim 5. The motor control device according to any one of claims 1 to 6,
A drum motor that rotates the photosensitive drum as the motor;
An image forming apparatus comprising: an image forming unit that generates a toner image using a latent image formed on a surface of the photosensitive drum and forms the toner image on a recording medium.