JP5780385B2 - Motor drive device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a motor driving device and an image forming apparatus including the motor driving device. The image forming apparatus includes various apparatuses such as a copying machine, a printer, a facsimile machine, and a multifunction machine having these functions in combination.

  Conventionally, an image forming apparatus adopting an electrophotographic system has a plurality of rotating bodies (loads) such as a photosensitive member, a developing roller, and an intermediate transfer belt. As a driving source for driving these rotating bodies, a brushless motor having a high rotational stability and a long life is generally used. In image formation (printing), an image forming operation is started after the brushless motor is started and each rotating body reaches the rated rotation. When starting a brushless motor, a larger torque (starting torque) is required than at rated speed due to inertia, and a large starting current proportional to the starting torque flows. In view of the peak current (starting current) in the power source, a power supply device having a relatively large capacity has to be used, and the power supply device tends to increase in size.

  In this regard, Patent Document 1 discloses a technique of performing open-loop control with a fixed PWM signal duty ratio and current application time and then switching to closed-loop control when a brushless motor is started. According to this technique, the starting current flowing through the brushless motor can be suppressed, and as a result, it is possible to avoid an increase in capacity and size of the power supply device.

JP 2001-238482 A

  Incidentally, the starting torque of the brushless motor naturally changes depending on the use environment of the image forming apparatus. For example, in a low temperature environment different from the normal environment, the starting torque increases due to the influence of a load such as a frictional resistance, and accordingly, the starting current and thus the power source current also increase. However, since the configuration of Patent Document 1 does not take into account changes in the environment, when the brushless motor is started in a low temperature environment, a power supply current having a magnitude exceeding the rated current may flow (FIG. 7 ( a) (b)). If it does so, there existed a problem that the overcurrent protection (OCP) of a power supply device worked or it caused deterioration of a power supply device.

  Here, FIG. 7A, which is a conventional example, shows a waveform diagram of a motor starting current (chopping current) in a low temperature environment, and FIG. 7B shows a motor starting time in a low temperature environment. The figure explaining the change of a power supply current is shown. 7A and 7B, the rated current of the power supply device is set to 1.8A. In this case, in a low temperature environment, the average effective value of the starting current increases to 2.5 A, and it can be seen that a power supply current having a magnitude exceeding the rated current flows.

  The present invention has been made in view of the above-mentioned problems, and the object of the present invention is to drive a motor that suppresses the starting current without significantly increasing the power supply capacity and without being influenced by environmental changes. The present invention provides an apparatus and an image forming apparatus including the apparatus.

A motor driving device according to a first aspect of the present invention includes a motor for driving a load in a housing, current control means for PWM-controlling a driving current supplied from the power supply device to the motor, and a power supply current from the power supply device. Current detecting means for detecting the temperature of the housing, and temperature detecting means for detecting the temperature inside the housing, wherein the current control means is configured such that when the motor is started, the detection result of the temperature detecting means falls below a specified temperature. If the power supply current is controlled to gradually increase the duty ratio of the PWM signal until the current reaches the rated current, while the motor detection, when the detection result of the temperature detection means exceeds the specified temperature, The duty ratio is set to 100% .

  According to a third aspect of the present invention, there is provided an image forming apparatus comprising the motor driving device according to the first or second aspect.

According to the present invention, at the time of startup of the motor, when the detection result of the temperature detection means is Tsu falls below a specified temperature, because the supply current is controlled to increase gradually the duty ratio of the PWM signal to reach the rated current Even in a low-temperature environment, the start-up current flowing through the motor can be suppressed by adjusting the duty ratio, and generation of a power supply current having a magnitude exceeding the rated current can be reliably prevented. Accordingly, it is possible to avoid overcurrent protection (OCP) of the power supply device or cause deterioration of the power supply device, and to reduce the capacity and size of the power supply device without being influenced by environmental changes. There is an effect.

In addition, according to the present invention, in a normal environment, a starting current having a duty ratio of 100% is applied to the motor as usual, so that the motor can be started with a conventional starting time, and a first copy time (power supply) There is an effect that it is possible to suppress a delay in the time from the insertion to the end of the first printing.

It is a schematic sectional drawing which shows typically the internal structure of a printer. It is a functional block diagram which shows the structure of a control part. It is a flowchart explaining motor starting control. (A) is a motor startup current waveform diagram in a normal environment, and (b) is a diagram for explaining a change in power supply current at the time of motor startup in a normal environment. (A) is a motor start current waveform diagram in a low temperature environment in the first example, and (b) is a diagram for explaining a change in power supply current at the time of motor start in a low temperature environment. (A) is a motor starting current waveform diagram in a low temperature environment in the second example, and (b) is a diagram for explaining a change in power supply current at the time of motor starting in a low temperature environment. (A) is a chopping current waveform diagram of a motor under a low temperature environment in a conventional example, and (b) is a diagram for explaining a change in power supply current when the motor is started under a low temperature environment.

  Hereinafter, an embodiment in which the present invention is applied to a tandem color digital printer (hereinafter referred to as a printer), which is an example of an image forming apparatus, will be described with reference to the drawings.

  As shown in FIG. 1, the printer 1 includes an image processing unit 10 as an operation unit, a feeding unit 20, a fixing unit 30, and a control unit 60. These units 10, 20, 30, 60 are arranged in the housing 9 of the printer 1. Although not shown, the printer 1 is connected to a network such as a LAN, and is configured to execute a print job based on the print command when a print command is received from an external terminal (not shown) or the like. ing.

  The image processing unit 10 plays a role of transferring a toner image formed on a photosensitive drum 3 which is an example of an image carrier to a recording material P, and includes yellow (Y), magenta (M), cyan ( A total of four image forming units 2 corresponding to the respective colors C) and black (K), an intermediate transfer belt 11 and the like are provided. The four image forming units 2 are arranged below the intermediate transfer belt 11 along the intermediate transfer belt 11 in the order of yellow, magenta, cyan, and black from the left in FIG. Each image forming unit 2 includes a photosensitive drum 3 that is driven to rotate clockwise in FIG. Around the photosensitive drum 3, a charging unit 4, an exposure unit 5, a developing unit 6, a primary transfer roller 7, and a photoconductor cleaner 8 are arranged in this order along the rotation direction (clockwise in FIG. 1). Yes. In FIG. 1, for convenience of explanation, symbols Y, M, C, and K corresponding to reproduced colors are attached to each image forming unit 2. Further, in the image forming units 2M-2K other than the yellow image forming unit 2Y, reference numerals 3-8 of the respective components such as the photosensitive drum 3 are omitted.

  The intermediate transfer belt 11 is also an example of an image carrier, and is wound around a driving roller 12, a driven roller 13, and a tension roller 14. The intermediate transfer belt 11 is driven to rotate counterclockwise in FIG. A secondary transfer roller 25, which is a component of the feeding unit 20, is disposed outside the portion of the intermediate transfer belt 1 that is wound around the drive roller 12. A contact portion between the intermediate transfer belt 11 and the secondary transfer roller 25 is a secondary transfer position 15. A transfer belt cleaner 16 for removing untransferred toner on the intermediate transfer belt 11 is disposed outside the portion of the intermediate transfer belt 11 that is wound around the driven roller 13.

  The feeding unit 20 includes a paper feed cassette 21 that accommodates the recording material P, a pair of paper feed rollers 22 that feeds the recording material P in the paper feed cassette 21 one by one toward the conveyance path R0, and the fed recording material P. A registration roller pair 24, a secondary transfer roller 25, and the like that take timing for feeding the recording material P to the secondary transfer position 15 are provided. The recording material P from the paper feed cassette 21 is sent out to the transport path R0 by the rotational drive of the paper feed roller pair 22. Note that the inside of the housing 9 of the printer 1 is supplied with a temperature sensor 59 as temperature detecting means for detecting the ambient temperature inside the printer 1 and 50 or 60 Hz electric power fed from a commercial AC power supply (not shown). , 20 and 30 are arranged.

  The fixing unit 30 includes a fixing roller 31 including a fixing heater 33 such as a halogen lamp, and a pressure roller 32 facing the fixing roller 31. A contact portion between the fixing roller 31 and the pressure roller 32 is a fixing position. The controller 60 controls the energization of the fixing heater 33 so that the fixing heater 33 is maintained at a temperature necessary for fixing. A discharge roller pair 41 for discharging the printed recording material P is disposed on the conveyance downstream side of the fixing unit 30. A paper discharge tray 51 for the discharge roller pair 41 is provided at the top of the printer 1. The terminal end side of the transport path R0 extends toward the discharge roller pair 41. The printed recording material P is discharged onto the paper discharge tray 51 by the rotation of the discharge roller pair 41.

  The printing operation of the recording material P is performed as follows. That is, for each image forming unit 2Y-2K, the photosensitive drum 3 cleaned by the photosensitive member cleaner 8 is uniformly charged by the charging unit 4, and the surface of the photosensitive drum 3 is exposed by exposure from the exposure unit 5. An electrostatic latent image is formed on the surface. The electrostatic latent image is reversely developed with toner from the developing unit 6 and is visualized as a toner image of each color. The toner images of the respective colors are primarily transferred from the photosensitive drum 3 onto the intermediate transfer belt 11 in the order of yellow, magenta, cyan, and black by the primary transfer roller 7 and are superimposed.

  On the other hand, the recording material P is conveyed to the secondary transfer position 15 by the rotational drive of the registration roller pair 24 in accordance with the movement timing of each color toner image toward the secondary transfer position 15 by the rotational drive of the intermediate transfer belt 11. . When the recording material P passes through the secondary transfer position 15, the overlapping four color toner images are collectively transferred onto one side of the recording material P. The intermediate transfer belt 11 after the secondary transfer is cleaned by a transfer belt cleaner 12. The recording material P which has passed the secondary transfer position 15 and has an unfixed toner image on one side is heated and pressurized when passing through the fixing unit 30 to fix the unfixed toner image. The recording material P after single-sided fixing (printed) is discharged onto the paper discharge tray 52 by the rotational drive of the discharge roller pair 42.

  The control unit 60 receives an image signal transmitted from an external terminal (not shown), converts it into digitized image data for YK colors, and performs image processing unit 10 or feeding unit 20. The printing operation is executed by controlling each operation unit such as. The control unit 60 of the embodiment is disposed above the image processing unit 10 in the housing 9. As shown in FIG. 2, the control unit 60 has a controller 61 that controls the overall control of the printer 1 and main motor control that controls speed control such as activation, stop, and acceleration / deceleration of the main motor 73 that drives the image processing unit 10. And a sub-motor control unit 72 that controls speed control such as starting, stopping, and increasing / decreasing of the sub-motor 74 that drives the feeding unit 20 and the fixing unit 30.

  In addition to the CPU 62 that executes various arithmetic processes and controls, the controller 61 temporarily stores a communication interface (I / F) unit 63 for connection with an external terminal, storage means 64 such as an EEPROM or flash memory, control programs and data. RAM 65 to be stored, a counter 66 for measuring the number of conveyed recording materials P, a timer 67 for measuring time, an input / output interface, and the like. For example, a temperature sensor 59 for measuring the ambient temperature inside the housing 9, an operation panel 57 mounted on the outer surface side of the housing 9, and the like are electrically connected to the controller 61. The main motor control unit 71 and the sub motor control unit 72 are also electrically connected to the controller 61.

  The power supply device 58 is electrically connected to the controller 61 and the main and sub motor control units 71 and 72. The power supply device 58 incorporates a current detection unit 75 as current detection means for detecting a power supply current to be supplied to the controller 61 and the like. The detection result of the current detection unit 75 is transmitted to the controller 61.

  The control unit 60 (the controller 61 and the main and sub motor control units 71 and 72) serves as a current control unit that performs PWM control (pulse width modulation control) on the drive current supplied from the power supply device 58 to the motors 73 and 74. Is responsible for. Based on the command from the controller 61, the motor control units 71 and 72 drive the corresponding motors 73 and 74, respectively. In the embodiment, the main motor 73 rotates the photosensitive drum 3, the driving roller 12, and the like, and the sub motor 74 rotates the paper feed roller pair 22, the fixing roller 31, and the like. The rotation state information of the motors 73 and 74 is transmitted to the controller 61 via the corresponding motor control units 71 and 72, respectively. The photosensitive drum 3, the driving roller 12, the paper feed roller pair 22, the fixing roller 31, and the like constitute a load. In this case, the motors 73 and 74 are brushless motors.

  The control unit 60 according to the embodiment is configured such that, when the motors 73 and 74 are started, if the detection result C (atmosphere temperature in the housing 9) of the temperature sensor 59 is less than a preset specified temperature Clw (if below), the current The duty ratio of the PWM signal is set so as to limit the detection result I (effective value of the power supply current) of the detection unit 75 to be equal to or less than the rated current Irt, and the activation of the motors 73 and 74 is controlled. That is, the PWM signal of the duty ratio is transmitted from the controller 61 to the motor control units 71 and 72, and the motor control units 71 and 72 receiving the PWM signal respectively correspond to the motors 73 and 74 corresponding to the limited starting current. To start the motors 73 and 74 (see FIGS. 5A and 5B).

  In addition, when the detection result C of the temperature sensor 59 is equal to or higher than the specified temperature Clw when the motors 73 and 74 are started up, the control unit 60 sets the duty ratio to 100% and sets the motors 73 and 74. The activation of 74 is controlled. That is, a PWM signal having a duty ratio of 100% is transmitted from the controller 61 to the motor control units 71 and 72, and the motor control units 71 and 72 that have received the PWM signal start up the motors 73 and 74 corresponding thereto without restriction. A current is applied to start each of the motors 73 and 74 (see FIGS. 4A and 4B). Here, the duty ratio of the PWM signal is a ratio of on-time (energization time) in one switching cycle. The specified temperature Clw itself that is the reference value may be included on the lower side or included on the higher side. The embodiment is a case where it is included on the higher side, and specifically, Clw = 15 ° C. is adopted. The rated current of the power supply device 58 is set to 1.8 A as in the conventional example.

  In FIG. 3, the 1st example of the motor starting control by the control part 60 is shown. The algorithm shown in the flowchart disclosed below is stored in advance in the storage unit 64 of the controller 61 as a program, and is read by the RAM 65 and then executed by the CPU 62. Here, the motor start control for the main motor 73 and the motor start control for the sub motor 74 are basically executed in the same control mode. Therefore, FIG. 3 illustrates a flowchart of motor activation control for the main motor 73, which will be described below as a representative example.

  In the motor start control of the first example, for example, when the controller 61 obtains a start command from the operation panel 57 or the like, the control is started, the detection result C of the temperature sensor 59 is read (S01), and the detection result C is set in advance. It is determined whether the temperature is lower than the specified temperature Clw (S02). If the detection result C of the temperature sensor 59 is equal to or higher than the specified temperature Clw (S02: NO), the load caused by the low temperature environment is unlikely to act on the main motor 73, so the duty ratio of the PWM signal is set to 100%. The start of the main motor 73 is controlled (S03). That is, a PWM signal with a duty ratio of 100% is transmitted from the controller 61 to the main motor control unit 71, and the main motor control unit 71 that receives the PWM signal applies an unrestricted start-up current to the main motor 73. Start up.

  When step S03 is executed, the ambient temperature in the housing 9 is in a normal environment that is equal to or higher than the specified temperature Clw. According to FIGS. 4A and 4B, even when a starting current having a duty ratio of 100% is applied to the main motor 73, the average effective value of the starting current is kept at about 1.7 A, and the power source current is equal to the rated current Irt. You can see how it does not exceed.

  Returning to step S02, if the detection result C of the temperature sensor 59 is lower than the specified temperature Clw (S02: YES), there is a high possibility that the load caused by the low temperature environment will act on the main motor 73. If the motor 73 is started, there is a high possibility that a power supply current exceeding the rated current Irt flows. In step S04, the duty ratio of the PWM signal is set to 1%, and a starting current having a duty ratio of 1% is applied to the main motor 73. Next, it is determined from the rotation state information of the main motor 73 whether or not the main motor 73 has started rotating (S05). If the main motor 73 is stopped (S05: NO), the duty ratio of the PWM signal is increased by 1%, the starting current having the increased duty ratio is applied to the main motor 73 (S06), and the process returns to step S05. .

  If the main motor 73 has started rotating (S05: YES), the detection result I of the current detector 75 in the power supply device 58 is read (S07), and whether or not the detection result I has reached the rated current Irt. A determination is made (S08). If the detection result I of the current detection unit 75 does not reach the rated current Irt (S08: NO), the process proceeds to step S06, where the starting current with a duty ratio increased by 1% is applied to the main motor 73, and step S05 is performed. Return to. If the detection result I of the current detector 75 has reached the rated current Irt (S08: YES), the duty ratio of the PWM signal is fixed at this stage, and the starting current having the fixed duty ratio is applied to the main motor 73. The main motor 73 is started (S09).

  When step S09 is executed, the ambient temperature in the housing 9 is in a low temperature environment lower than the specified temperature Clw. In the first example (see FIGS. 5A and 5B), the duty ratio (fixed duty ratio) at the stage of reaching the rated current Irt is set to 10%. According to FIGS. 5 (a) and 5 (b), the average effective value of the starting current is kept at about 1.0A by applying the starting current fixed at 10% by gradually increasing the duty ratio to the main motor 73, It can be seen that the power supply current does not exceed the rated current Irt.

  According to the above configuration, even in a low temperature environment, the duty ratio is adjusted to suppress the starting current flowing through each of the motors 73 and 74, thereby preventing the generation of the power supply current having a magnitude exceeding the rated current Irt. Therefore, it is possible to avoid overcurrent protection (OCP) of the power supply device 58 and to cause deterioration of the power supply device 58, and to reduce the capacity and size of the power supply device 58 without being influenced by environmental changes. There is an effect. In a normal environment, since a starting current having a duty ratio of 100% is applied to each motor 73, 74 as usual, each motor 73, 74 can be started in the conventional starting time, and the first copy time (power supply There is also an effect that it is possible to suppress a delay in the time from the input to the end of the first printing.

  6A and 6B show a second example of motor start control by the control unit 60. FIG. In the motor start control of the first example, the ratio of the on-time (energization time) occupying one switching cycle is set as the duty ratio. In the motor start control of the second example, the ratio of the chopping time to the predetermined time over a plurality of cycles. Is the duty ratio. In this case, the predetermined time is expressed as the sum of the chopping time and the chopping stop time, and is an integral multiple of one switching period.

  In the second example (see FIGS. 6A and 6B), the duty ratio at the stage of reaching the rated current Irt is 50%. The chopping time at this stage is 5 ms, the chopping stop time is 5 ms, and the total predetermined time is 10 ms. The control mode of the second example is the same as that of the first example.

  According to FIGS. 6 (a) and 6 (b), the average effective value of the starting current is obtained by applying the starting current fixed at 50% by gradually increasing the duty ratio to the main motor 73 as in the first example. It can be seen that the power supply current is about 1.0 A and the power supply current does not exceed the rated current Irt. Therefore, even when the second example is adopted, the same operational effects as the first example are obtained.

  The present invention is not limited to the above-described embodiment, and can be embodied in various forms. For example, a printer has been described as an example of the image forming apparatus. However, the present invention is not limited to this, and a copier, a facsimile, or a multifunction machine having these functions combined may be used. The transfer method is not limited to the intermediate transfer method employed in the embodiment, and may be a direct transfer method. Further, although the tandem method is adopted in the embodiment, a multi-rotation method may be adopted. In addition, the configuration of each unit is not limited to the illustrated embodiment, and various modifications can be made without departing from the spirit of the present invention.

1 Printer (image forming device)
DESCRIPTION OF SYMBOLS 10 Image process part 20 Feed part 30 Fixing part 58 Power supply device 59 Temperature sensor (temperature detection means)
60 Control Unit 61 Controller 71 Main Motor Control Unit 72 Sub Motor Control Unit 73 Main Motor 74 Sub Motor 75 Current Detection Unit

Claims (2)

A motor for driving a load in the housing, current control means for PWM-controlling a drive current supplied from the power supply device to the motor, current detection means for detecting a power supply current from the power supply device, Temperature detecting means for detecting the temperature,
The current control means controls the duty ratio of the PWM signal to be gradually increased until the power supply current reaches a rated current when the detection result of the temperature detection means is below a specified temperature at the time of starting the motor. on the other hand,
When the detection result of the temperature detection means exceeds a specified temperature at the start of the motor,
Setting the duty ratio to 100%;
Motor drive device . The motor drive device according to claim 1 is provided.
Image forming apparatus.

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