Motor driving device, image processing apparatus, and motor driving method

Abstract

To provide a motor driving device, an image processing apparatus, and a motor driving method that can easily improve the responsiveness of driving current.SOLUTION: A motor driving device 100 comprises a current supply unit 101, an adjustment unit 102, and a changing unit 104. The current supply unit 101 drives a stepping motor 110 by supplying driving current to the stepping motor 110. The adjustment unit 102 can adjust the driving current within a variable range equal to or more than a lower limit current value. The changing unit 104 changes the lower limit current value.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a motor driving device, an image processing device, and a motor driving method. [Background technology]

[0002] As a related technique, an image processing device (image forming device) that uses a stepping motor as a motor for driving components of the image processing device (image forming device) is known (see, for example, Patent Document 1). This image processing device includes a determination means for determining a drive current value of the stepping motor. The determination means forms two or more toner patches on an image carrier, detects the toner patches with a sensor, and determines a drive current value of the stepping motor based on the detected value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-42416 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the configuration of the related art described above, since it is necessary to generate a toner patch in order to set the drive current, the responsiveness of the drive current may be reduced.

[0005] An object of the present invention is to provide a motor drive device, an image processing device, and a motor drive method that can easily improve the responsiveness of the drive current. [Means for solving the problem]

[0006] A motor drive device according to one aspect of the present invention includes a current supply unit, an adjustment unit, and a change unit. The current supply unit drives a stepping motor by supplying a drive current to the stepping motor. The adjustment unit is capable of adjusting the drive current within a variable range equal to or greater than a lower limit current value. The change unit changes the lower limit current value.

[0007] An image processing device according to another aspect of the present invention includes the motor drive device described above and a movable member driven by the stepping motor.

[0008] A motor driving method according to another aspect of the present invention includes driving a stepping motor by supplying a drive current to the stepping motor, adjusting the drive current within a variable range equal to or greater than a lower limit current value, and changing the lower limit current value. Effect of the Invention

[0009] According to the present invention, it is possible to provide a motor drive device, an image processing device, and a motor drive method that can easily improve the responsiveness of the drive current. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing the external appearance and internal configuration of an image processing device according to a first embodiment. [Diagram 2] FIG. 2 is a schematic block diagram of the image processing device according to the first embodiment. [Diagram 3] FIG. 3 is a schematic diagram showing an image forming unit and a developing device of the image processing apparatus according to the first embodiment. [Figure 4] FIG. 4 is a graph showing an example of a current flowing through a stepping motor in the developing device according to the first embodiment. [Diagram 5] FIG. 5 is a graph showing an example of a current flowing through a stepping motor in the developing device according to the first embodiment. [Figure 6] FIG. 6 is a flowchart showing an example of a motor driving method according to the first embodiment. [Figure 7] FIG. 7 is a flowchart showing an example of a motor driving method according to the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The following embodiment is an example of the present invention, and is not intended to limit the technical scope of the present invention.

[0012] (Embodiment 1) [1] Overall configuration of image processing device First, the overall configuration of an image processing device 10 according to this embodiment will be described with reference to FIGS.

[0013] For ease of explanation, the vertical direction in the installed state (as shown in FIG. 1) in which the image processing device 10 can be used is defined as the up-down direction D1. Also, the left side of the image processing device 10 shown in FIG. 1 is defined as the front (front face) as the front direction D2. Also, the left-right direction D3 is defined based on the front face of the image processing device 10 in the installed state.

[0014] The image processing device 10 according to the present embodiment is, for example, a multifunction device having multiple functions such as a scanning function for acquiring image data from an original, a printing function for forming an image based on image data, a facsimile function, and a copy function. The image processing device 10 only needs to have an image processing function including at least one of a function for forming an image and a function for acquiring image data, and may be a printer, a scanner, a facsimile machine, a copy machine, or the like.

[0015] 1 and 2, an image processing device 10 includes an automatic document feeder 1, an image reading unit 2, an image forming unit 3, a developing unit 4, a paper feeder 5, an operation display unit 6, a general control unit 7, and a storage unit 8. The automatic document feeder 1 is an ADF (Auto Document Feeder), and will be referred to as "ADF1" in the following description.

[0016] The ADF 1 transports an original document whose image is to be read by the image reading unit 2. The ADF 1 includes an original document setting unit, a plurality of transport rollers, an original document pressing unit, and a paper ejection unit.

[0017] The image reading unit 2 reads an image from a document and outputs image data corresponding to the read image. The image reading unit 2 includes a document table, a light source, a plurality of mirrors, an optical lens, a CCD (Charge Coupled Device), and the like.

[0018] The image forming unit 3 realizes a printing function by forming a color or monochrome image on a sheet by an electrophotographic method. The image forming unit 3 forms an image on a sheet based on image data output from the image reading unit 2. The image forming unit 3 also forms an image on a sheet based on image data input from an information processing device external to the image processing device 10, such as a personal computer.

[0019] The developing device 4 executes a developing process to develop the electrostatic latent images formed on the surfaces of the photoconductor drums 311, 321, 331, and 341 (see FIG. 3) of the image forming unit 3. In particular, in this embodiment, the developing device 4 performs development using a two-component developer containing a toner and a carrier.

[0020] The paper feed unit 5 supplies a sheet to the image forming unit 3. The paper feed unit 5 has a paper feed cassette, a manual feed tray, a sheet transport path, a plurality of transport rollers, etc. The image forming unit 3 forms an image on the sheet supplied from the paper feed unit 5.

[0021] The operation display unit 6 is a user interface in the image processing device 10. The operation display unit 6 has a display unit such as a liquid crystal display that displays various information in response to control instructions from the overall control unit 7, and an operation unit such as a switch or a touch panel that inputs various information to the overall control unit 7 in response to user operations.

[0022] The overall control unit 7 performs overall control of the image processing device 10. The overall control unit 7 mainly comprises a computer system having one or more processors and one or more memories. In the image processing device 10, the one or more processors execute a program to realize the functions of the overall control unit 7. The program may be recorded in advance in the memory, or may be provided via a telecommunication line such as the Internet, or may be recorded and provided on a non-transitory recording medium readable by a computer system, such as a memory card or an optical disk.

[0023] The storage unit 8 includes one or more non-volatile memories, and stores information such as control programs for causing the general control unit 7 to execute various processes in advance.

[0024] The image processing device 10 further includes a communication unit etc. The communication unit is an interface that executes data communication between the image processing device 10 and an external device connected via a communication network such as the Internet or a LAN (Local Area Network).

[0025] [2] Image forming unit and developing device configuration Next, the configurations of the image forming unit 3 and the developing device 4 will be described in more detail with reference to FIGS.

[0026] 1, the image forming section 3 has an optical scanning device 30, four image forming units 31-34, an intermediate transfer device 36, a secondary transfer roller 37, a fixing device 38, and a paper discharge tray 39. The developing device 4 has four developing units 41-44 corresponding to the four image forming units 31-34.

[0027] The image forming unit 31 forms a Y (yellow) toner image. As shown in Fig. 3, the image forming unit 31 has a photoconductor drum 311, a charging roller 312, a primary transfer roller 314, and a drum cleaning unit 315. The image forming unit 31 further has a toner container 316 (see Fig. 1). The developing unit 41 corresponding to the image forming unit 31 has a developing roller 411, a magnet roller 412, and the like.

[0028] The image forming unit 32 forms a C (cyan) toner image. As shown in Fig. 3, the image forming unit 32 has a photoconductor drum 321, a charging roller 322, a primary transfer roller 324, and a drum cleaning unit 325. The image forming unit 32 further has a toner container 326 (see Fig. 1). The developing unit 42 corresponding to the image forming unit 32 has a developing roller 421, a magnet roller 422, and the like.

[0029] The image forming unit 33 forms a toner image of M (magenta). As shown in Fig. 3, the image forming unit 33 has a photoconductor drum 331, a charging roller 332, a primary transfer roller 334, and a drum cleaning unit 335. The image forming unit 33 further has a toner container 336 (see Fig. 1). The developing unit 43 corresponding to the image forming unit 33 has a developing roller 431, a magnet roller 432, etc.

[0030] The image forming unit 34 forms a Bk (black) toner image. As shown in Fig. 3, the image forming unit 34 has a photoconductor drum 341, a charging roller 342, a primary transfer roller 344, and a drum cleaning unit 345. The image forming unit 34 further has a toner container 346 (see Fig. 1). The developing unit 44 corresponding to the image forming unit 34 has a developing roller 441, a magnet roller 442, etc.

[0031] In this way, the multiple (four in this embodiment) image forming units 31-34 correspond to four colors, Y (yellow), C (cyan), M (magenta) and Bk (black), respectively, and basically adopt a common configuration. In other words, the image processing device 10 according to this embodiment is a tandem type device having multiple photoconductors (photoconductor drums) corresponding one-to-one to the multiple colors. Therefore, in the following, unless otherwise specified, the configuration described for the image forming unit 31 also has the same configuration as the other image forming units 32-34. Furthermore, unless otherwise specified, the configuration described for the development unit 41 also has the same configuration as the other development units 42-44.

[0032] An electrostatic latent image is formed on the photoconductor drum 311. The photoconductor drum 311 is supported rotatably about a rotation axis extending in the left-right direction D3 by a unit housing that houses the photoconductor drum 311, the charging roller 312, and the drum cleaning unit 315. The photoconductor drum 311 receives a driving force supplied from a motor, for example, and rotates in a rotation direction D5 shown in FIG.

[0033] The charging roller 312 charges the surface (outer circumferential surface) of the photoconductor drum 311 to a positive polarity. Specifically, the charging roller 312 is electrically connected to a power supply circuit, and charges the surface of the photoconductor drum 311 by receiving a high voltage from the power supply circuit. However, the charging roller 312 is not limited to a configuration in which the surface of the photoconductor drum 311 is positively charged, and may charge the surface of the photoconductor drum 311 to a negative polarity.

[0034] The surface of the photoconductor drum 311 charged by the charging roller 312 is irradiated with light beams based on image data from the optical scanning device 30 (see FIG. 1). As a result, an electrostatic latent image is formed on the surface of the photoconductor drum 311. That is, in this embodiment, the photoconductor drum 311 is an example of an "image carrier" on which an electrostatic latent image is formed by the light beams output from the optical scanning device.

[0035] The developing unit 41 develops the electrostatic latent image formed on the surface of the photoconductor drum 311. In addition to the developing roller 411 and the magnet roller 412, the developing unit 41 has a container 45, a first stirring screw 401, and a second stirring screw 402. The container 45 supports each of the developing roller 411, the magnet roller 412, the first stirring screw 401, and the second stirring screw 402 so that they can rotate about a rotation axis extending in the left-right direction D3. The container 45 also contains a two-component developer including a Y (yellow) toner and a carrier.

[0036] The first stirring screw 401 and the second stirring screw 402 stir the developer contained in the container 45 to charge the toner. In this embodiment, the toner is positively charged. However, the charged polarity of the toner is not limited to positive polarity and may be negative polarity. The magnet roller 412 picks up the developer stirred by the first stirring screw 401 and the second stirring screw 402, and supplies the toner therein to the surface (outer circumferential surface) of the developing roller 411.

[0037] The developing roller 411 uses the charged toner to develop the electrostatic latent image formed on the photoconductor drum 311. Specifically, a high-voltage developing bias is applied between the developing roller 411 and the photoconductor drum 311 by a power supply circuit, forming a developing electric field, and the charged toner moves from the developing roller 411 to the photoconductor drum 311. A toner image is formed on the surface of the photoconductor drum 311 by such a developing process.

[0038] The primary transfer roller 314 transfers the toner image formed on the surface of the photosensitive drum 311 by the developing device 4 (developing unit 41) onto the outer circumferential surface of the intermediate transfer belt 361 (see FIG. 3). Specifically, a high-voltage transfer bias is applied between the photosensitive drum 311 and the primary transfer roller 314 by a power supply circuit, forming a transfer electric field, and the toner having a charge moves from the photosensitive drum 311 to the intermediate transfer belt 361. As a result, the toner image is formed (transferred) on the outer circumferential surface of the intermediate transfer belt 361.

[0039] Drum cleaning unit 315 cleans the surface of photoconductor drum 311 after the toner image is transferred by primary transfer roller 314. For example, drum cleaning unit 315 has a blade-shaped cleaning member and a transport member. The cleaning member comes into contact with the surface of photoconductor drum 311 to remove toner adhering to the surface. The transport member transports the toner removed by the cleaning member to a toner storage container.

[0040] The toner container 316 supplies toner to the container 45 of the developing unit 41. In the image forming unit 31 that forms a Y (yellow) toner image, the toner container 316 supplies Y (yellow) toner.

[0041] The toner images of each color formed by each of the multiple (four in this example) image forming units 31-31 are transferred in a superimposed manner onto the outer circumferential surface of the intermediate transfer belt 361. As a result, a color image (toner image) is formed on the outer circumferential surface of the intermediate transfer belt 361.

[0042] 3, the intermediate transfer device 36 includes an intermediate transfer belt 361, a tension roller 362, a drive roller 363, a belt cleaning unit 364, and a density detection unit 365. The intermediate transfer device 36 uses the intermediate transfer belt 361 to transport the toner images formed by the image forming units 31 to a transfer position P1 (see FIG. 3) by the secondary transfer roller 37.

[0043] The intermediate transfer belt 361 is an endless belt onto which the toner images of each color are transferred from the photosensitive drums 311, 321, 331, and 311. As shown in FIG. 3, the intermediate transfer belt 361 is stretched around a tension roller 362 and a drive roller 363 that are spaced apart from each other in the front-rear direction D2 of the image processing device 10. The drive roller 363 rotates by receiving a driving force supplied from a motor. This causes the intermediate transfer belt 361 to rotate in a rotation direction D4 shown in FIG. 3. The toner images transferred onto the outer peripheral surface of the intermediate transfer belt 361 are transported to a transfer position P1 by the secondary transfer roller 37 as the intermediate transfer belt 361 rotates. The belt cleaning unit 364 cleans the outer peripheral surface of the intermediate transfer belt 361 after the toner images are transferred at the transfer position P1.

[0044] The secondary transfer roller 37 transfers the toner image formed on the outer peripheral surface of the intermediate transfer belt 361 to a sheet supplied by the paper feed unit 5. As shown in FIG. 3, the secondary transfer roller 37 is disposed in a position facing the driving roller 363 across the intermediate transfer belt 361 so as to contact the outer peripheral surface of the intermediate transfer belt 361. The secondary transfer roller 37 is pressed against the driving roller 363 by a biasing member. The secondary transfer roller 37 is electrically connected to a power supply circuit, and when a high voltage is applied from the power supply circuit, the secondary transfer roller 37 transfers the toner image formed on the outer peripheral surface of the intermediate transfer belt 361 to a sheet passing through a transfer position P1 where the secondary transfer roller 37 and the intermediate transfer belt 361 contact each other.

[0045] The fixing device 38 melts and fixes the toner image transferred to the sheet by the secondary transfer roller 37 to the sheet. For example, the fixing device 38 includes a fixing roller and a pressure roller. The fixing roller is disposed so as to come into contact with the pressure roller, and heats the toner image transferred to the sheet to fix it to the sheet. The pressure roller pressurizes the sheet passing through the contact portion formed between the fixing roller and the pressure roller.

[0046] The sheet on which the image has been formed is discharged to a discharge tray 39 .

[0047] [3] Configuration of developing device Next, the configuration of the developing device 4 will be described in more detail with reference to Figures 2, 4, and 5. In the following, the configuration of the developing device 4 will be described using the developing unit 41 as an example, but unless otherwise specified, the configuration described for the developing unit 41 is the same for the other developing units 42 to 44.

[0048] In this embodiment, the developing device 4 (developing unit 41) is a trickle type developing device in which the developer is replenished to the container 45 while an excess amount of the developer is discharged from the container 45. This developing device 4 includes the container 45, and a first stirring screw 401 and a second stirring screw 402 that circulate the developer while stirring it in the container 45. Furthermore, as shown in FIG. 2, this developing device 4 includes a stepping motor 110, a T / C sensor 112, a motor driving device 100, and the like.

[0049] The stepping motor 110 generates a driving force for driving the movable member 111. The stepping motor 110 rotates in synchronization with the pulse. The movable member 111 of the developing device 4 driven by the stepping motor 110 includes, for example, a first stirring screw 401, a second stirring screw 402, or a developing roller 411. In this embodiment, the movable member 111 includes the first stirring screw 401 and the second stirring screw 402. Here, as an example, one stepping motor 110 is provided for the first stirring screw 401 and the second stirring screw 402. In other words, both the first stirring screw 401 and the second stirring screw 402 as the movable member 111 are driven by one stepping motor 110.

[0050] The T / C sensor 112 detects the mixture ratio of the toner and carrier contained in the developer. Specifically, the T / C sensor 112 outputs a detection value corresponding to the ratio (proportion) of the toner in the developer to, for example, the general control unit 7. The T / C sensor 112 is a sensor that detects the developer in the developing device 4 and changes its output value according to the ratio of the toner and carrier in the developer. During image formation (printing), the carrier remains in the developing device 4 and only the toner is consumed. Therefore, when the toner is consumed during image formation, the ratio of the carrier in the developer in the developing device 4 increases and the ratio of the toner in the developer decreases. Since the carrier is a magnetic material, the magnetic permeability of the developer increases when the ratio of the carrier in the developer increases. Taking advantage of this, for example, a magnetic permeability sensor whose output changes according to the magnetic permeability is used as the T / C sensor 112. In this case, the T / C sensor 112 includes a coil.

[0051] The motor driving device 100 drives the stepping motor 110. The motor driving device 100 drives the stepping motor 110 by supplying a driving current to the stepping motor 110. The motor driving device 100 is a so-called motor driver for the stepping motor 110. In particular, in this embodiment, the motor driving device 100 is a driver IC (integrated circuit) in which multiple circuits (functions) related to rotation control of the stepping motor 110 are integrated into a single chip (integrated circuit). As an example, the motor driving device 100 drives a stepping motor 110 having an A-phase and a B-phase as motor coils (windings).

[0052] The motor driving device 100 according to this embodiment includes a current supply unit 101, an adjustment unit 102, a switching unit 103, and a change unit 104, as shown in FIG.

[0053] The current supply unit 101 supplies a drive current for driving the stepping motor 110 to the stepping motor 110. In other words, the current supply unit 101 drives the stepping motor 110 by supplying a drive current to the stepping motor 110. Therefore, the stepping motor 110 is driven by receiving a power supply from the current supply unit 101.

[0054] The adjustment unit 102 is configured to be able to adjust the driving current Id1 (see FIG. 5). That is, the magnitude (current value) of the driving current Id1 supplied by the current supply unit 101 to the stepping motor 110 is not constant but is adjustable (variable) by the adjustment unit 102. Specifically, the adjustment unit 102 is configured to be able to adjust the driving current within a variable range equal to or greater than a lower limit current value I2 (see FIG. 5).

[0055] More specifically, when the magnitude of the drive current Id1 is constant, the drive current Id1 is set to an upper limit current value I1 (=Ip1+M1) obtained by adding a margin M1 to the peak current value Ip1, as shown in Fig. 4. Fig. 4 is a graph in which the horizontal axis represents time and the vertical axis represents the current supplied to the stepping motor 110.

[0056] Here, the peak current value Ip1 is the value of the required current In1 that needs to be supplied to the stepping motor 110 when driving the stepping motor 110 at maximum torque, and is equal to the maximum value of the required current In1. In other words, when the drive current Id1 is constant, as illustrated in Fig. 4, the drive current Id1 is fixed to an upper limit current value I1 obtained by adding a margin M1 to the required current In1 (=Ip1) when driving the stepping motor 110 at maximum torque.

[0057] On the other hand, when the adjustment unit 102 adjusts the magnitude of the driving current Id1, the driving current Id1 can vary within a range (variable range) between a lower limit current value I2 and an upper limit current value I1 (>I2), as illustrated in Fig. 5. Fig. 5 is a graph in which the horizontal axis represents time and the vertical axis represents the current supplied to the stepping motor 110.

[0058] Here, the lower limit current value I2 is a current value that is set so that the drive current Id1 does not become too low, and is equal to the minimum value of the required current In1 or a value slightly larger than the minimum value. That is, when the drive current Id1 is adjusted by the adjustment unit 102, the drive current Id1 can vary within a range equal to or greater than the lower limit current value I2 and equal to or less than the upper limit current value I1, as illustrated in FIG.

[0059] When using the stepping motor 110, if the driving force is insufficient and so-called "torque loss" occurs, step-out may occur. Here, "step-out" means that the stepping motor 110, which is originally driven in synchronization with the pulse, loses synchronization due to a sudden speed change, overload, or the like, and becomes out of synchronization with the pulse. In order to avoid such step-out, when the magnitude of the driving current Id1 is kept constant, as described above, the driving current Id1 is set to the upper limit current value I1 obtained by adding a margin M1 to the peak current value Ip1.

[0060] However, when the drive current Id1 is fixed to the upper limit current value I1 in this way, the drive current Id1 becomes larger overall than the required current In1, and a large amount of surplus power is wasted by the stepping motor 110. The wasteful power consumption by the stepping motor 110 also increases the amount of heat generated, so there is a need to suppress such wasteful power consumption. Particularly in recent years, the performance of the image processing device 10 has improved, such as the paper linear speed (the linear speed of the sheet during image formation), and the like, and the operating speed of the stepping motor 110 has improved, but the demand for energy conservation has also become stricter.

[0061] Here, since the stepping motor 110 is controlled by open loop control, the motor driving device 100 is required to output an optimal driving current Id1 by itself. Specifically, the motor driving device 100 monitors the voltage of the output final stage of the current supply unit 101 to perform feedback control, detects fluctuations in the load (load due to the stepping motor 110), and adjusts the magnitude of the driving current Id1 by the adjustment unit 102 as shown in FIG. 5 so that the optimal driving current Id1 is obtained. In this case, since the feedback loop is completed within the motor driving device 100, no additional sensors or the like are required, and it is possible to achieve power saving and low heat generation with a relatively simple configuration. That is, in the example of FIG. 5, the adjustment unit 102 adjusts the driving current Id1 to a current value slightly larger than the required current In1, thereby reducing power consumption corresponding to the hatched area (diagonal line area) in the figure compared to the case where the driving current Id1 is fixed to the upper limit current value I1.

[0062] That is, the adjustment unit 102 adjusts the drive current Id1 according to the torque required by the stepping motor 110. In other words, the drive current Id1 is automatically adjusted within a variable range (a range of not less than the lower limit current value I2 and not more than the upper limit current value I1) according to the torque required by the stepping motor 110. This makes it possible to efficiently suppress unnecessary power consumption in the stepping motor 110. As a result, by supplying the drive current Id1 according to the required torque, highly efficient drive control of the stepping motor 110 can be achieved.

[0063] The switching unit 103 has a function of switching between enabled and disabled states of the adjustment unit 102. In other words, the function of the adjustment unit 102 is not always enabled, and the function of the adjustment unit 102 can be disabled by the switching unit 103. When the adjustment unit 102 is enabled, the magnitude of the drive current Id1 supplied by the current supply unit 101 to the stepping motor 110 is adjusted (varied) by the adjustment unit 102, as illustrated in FIG. 5. On the other hand, when the adjustment unit 102 is disabled, the magnitude of the drive current Id1 supplied by the current supply unit 101 to the stepping motor 110 is fixed to an upper limit current value I1 (=Ip1+M1), as illustrated in FIG.

[0064] That is, the current supply unit 101 fixes the drive current Id1 to a predetermined maximum current value when the adjustment unit 102 is disabled. In this embodiment, the upper limit current value I1 is an example of the "maximum current value." With this configuration, even when the adjustment unit 102 is disabled, it is possible to suppress loss of synchronism of the stepping motor 110.

[0065] Furthermore, in this embodiment, the switching unit 103 switches between enabled and disabled states of the adjustment unit 102 in accordance with a switching instruction from the control unit. In this embodiment, the general control unit 7 is an example of a "control unit." That is, the switching unit 103 of the motor driving device 100 receives a switching instruction from the general control unit 7, and switches between enabled and disabled states of the adjustment unit 102 in accordance with the switching instruction. With this configuration, it is possible to freely set the enable / disable state of the adjustment unit 102 in accordance with a switching instruction from the control unit. The "control unit" that issues the switching instruction may be provided separately from the general control unit 7, and may or may not be included in the motor driving device 100.

[0066] The change unit 104 has a function of changing the lower limit current value I2. That is, the magnitude (current value) of the lower limit current value I2, which is the minimum value (lower limit value) of the drive current Id1 when the adjustment unit 102 adjusts the drive current Id1, is not constant but can be changed (variable) by the change unit 104. On the other hand, the upper limit current value I1 is not changed but is constant (=Ip1+M1).

[0067] In this embodiment, the change unit 104 changes the lower limit current value I2 according to a change instruction from the control unit. In this embodiment, the general control unit 7 is an example of a "control unit." That is, the change unit 104 of the motor driving device 100 receives a change instruction from the general control unit 7 and changes the lower limit current value I2 according to the change instruction. With this configuration, it is possible to freely set the lower limit current value I2 according to the change instruction from the control unit. The "control unit" that issues the change instruction may be provided separately from the general control unit 7, and may or may not be included in the motor driving device 100.

[0068] The motor driving device 100 described above, together with the movable member 111 and the like, constitutes an image processing device 10. That is, the image processing device 10 according to this embodiment has the motor driving device 100 and the movable member 111 driven by a stepping motor 110.

[0069] [4] Motor drive method Next, an example of the operation of the switching unit 103 will be described with reference to Fig. 6 and Fig. 7. Here, steps S1, S2, etc. in Fig. 6 and Fig. 7 indicate the numbers of processing procedures (steps) executed by the motor driving device 100 and the control unit (general control unit 7).

[0070] As a first related technique, a motor drive device suitable for an image processing device is known. This motor drive device includes a temperature detection means for detecting the temperature state of a load mechanism, a storage means, and a current setting means. The storage means stores drive current value setting data created from data on motor drive torque and drive current value and load fluctuation data due to temperature state. The current setting means reads out the drive current value setting data corresponding to the temperature information output from the temperature detection means from the storage means and sets the drive current of the stepping motor.

[0071] However, in the configuration of the first related art, since the temperature of the load mechanism is measured, the structure and control become complicated, leading to an increase in costs. Also, since the drive current is set according to the temperature, the drive current has low responsiveness to actual load fluctuations, making it difficult to achieve high efficiency.

[0072] In contrast, in this embodiment, the configuration described below allows the stepping motor 110 to be driven with a simpler structure and control, and provides a motor drive device 100, an image processing device 10, and a motor drive method that make it easier to achieve high efficiency.

[0073] That is, the motor driving device 100 according to this embodiment includes a current supply unit 101, an adjustment unit 102, and a switching unit 103. The current supply unit 101 drives the stepping motor 110 by supplying a driving current Id1 to the stepping motor 110. The adjustment unit 102 is capable of adjusting the driving current Id1. The switching unit 103 switches the adjustment unit 102 between enabled and disabled states.

[0074] According to this configuration, for example, it is possible to disable the adjustment unit 102 when the load of the stepping motor 110 is unstable, and to enable the adjustment unit 102 when the load of the stepping motor 110 is stable. As a result, when the load is stable, the adjustment unit 102 adjusts the drive current Id1, thereby making it possible to conserve energy while suppressing loss of synchronism of the stepping motor 110. On the other hand, when the load is unstable, the adjustment unit 102 is disabled, making it possible to drive the stepping motor 110 stably even against load fluctuations. Moreover, since there is no need to measure the temperature of the load mechanism, it is possible to provide a motor drive device 100, an image processing device 10, and a motor drive method that can drive the stepping motor 110 with a simpler structure and control, and that can easily achieve high efficiency.

[0075] More specifically, the switching unit 103 disables the adjustment unit 102 at least during the acceleration control period of the stepping motor 110. The "acceleration control period" here is a period during which the motor driving device 100 performs "acceleration control" to increase the number of rotations (rotation speed) of the stepping motor 110 at an acceleration equal to or greater than a threshold. The "threshold" here may include zero (0). During acceleration control of the stepping motor 110, the stepping motor 110 often has high torque and the load may become unstable, so that adjustment of the drive current Id1 by the adjustment unit 102 may lead to loss of synchronization. Therefore, in this embodiment, by disabling the adjustment unit 102 during the acceleration control period, it is possible to realize stable driving of the stepping motor 110 even against a sudden load change that occurs during acceleration.

[0076] Furthermore, the switching unit 103 disables the adjustment unit 102 at least during a transitional period from the start of the constant speed control of the stepping motor 110 until the driving of the stepping motor 110 becomes stable. The "transient period" here refers to a period from when the motor driving device 100 performs acceleration control and the stepping motor 110 reaches its maximum torque until the load becomes stable. In such a transitional period, the fluctuation range of the required current In1 also increases with torque fluctuation, so that if the driving current Id1 is adjusted by the adjustment unit 102, there is a possibility that the driving will become unstable. Therefore, in this embodiment, by disabling the adjustment unit 102 during the transitional period, it is possible to realize stable driving of the stepping motor 110 even if the required current In1 fluctuates greatly.

[0077] On the other hand, in periods other than the acceleration control period and the transition period, the load is likely to be stable in a steady state. Therefore, in a period in which the stepping motor 110 is in a steady state, the switching unit 103 enables the adjustment unit 102. As a result, in the steady state, it is possible to suppress unnecessary power consumption.

[0078] In this embodiment, the switching unit 103 switches between enabled and disabled states of the adjustment unit 102 in accordance with a switching instruction from a control unit (as an example, the general control unit 7). Therefore, the general control unit 7 outputs a switching signal for switching the adjustment unit 102 from enabled to disabled at the start of the acceleration control period as described above, and outputs a switching signal for switching the adjustment unit 102 from disabled to enabled at the end of the transition period.

[0079] FIG. 6 is a flowchart showing an example of a motor driving method for switching between enabling and disabling the adjustment unit 102 (adjustment function).

[0080] <Steps S1 and S2> First, in step S1, the switching unit 103 enables the adjustment unit 102. As a result, the drive current Id1 is adjusted according to the torque required by the stepping motor 110. Then, in step S2, the central control unit 7 determines whether or not an acceleration control period has started. When acceleration control of the stepping motor 110 starts, the central control unit 7 determines that the acceleration control period has started (S2: Yes), and shifts the process to step S3. On the other hand, if acceleration control of the stepping motor 110 has not started, the central control unit 7 determines that the acceleration control period has not started (S2: No), and repeatedly executes step S2.

[0081] <Steps S3 and S4> In step S3, the switching unit 103 disables the adjustment unit 102. As a result, the drive current Id1 is fixed to the maximum current value (upper limit current value I1). Then, in step S4, the central control unit 7 determines whether the transition period has ended. If the drive of the stepping motor 110 becomes stable, the central control unit 7 determines that the transition period has ended (S4: Yes), and moves the process to step S5. On the other hand, if the drive of the stepping motor 110 does not become stable, the central control unit 7 determines that the transition period has not ended (S4: No), and repeatedly executes step S4.

[0082] <Step S5> Then, in step S5, the switching unit 103 enables the adjustment unit 102. As a result, the drive current Id1 is adjusted in accordance with the torque required by the stepping motor 110.

[0083] The processes of steps S1 to S5 are repeatedly executed. The procedure of the motor driving method described above is merely an example, and the order of the processes shown in the flowchart of Fig. 6 may be changed as appropriate, or processes may be added.

[0084] As a second related technique, an image processing device using a stepping motor as a motor for driving components of the image processing device is known. This image processing device includes a determination unit that determines a drive current value of the stepping motor. The determination unit forms two or more toner patches on an image carrier, detects the toner patches with a sensor, and determines a drive current value of the stepping motor based on the detected value.

[0085] However, in the configuration of the second related art, since it is necessary to generate a toner patch in order to set the drive current, the responsiveness of the drive current may decrease.

[0086] In contrast, in this embodiment, the motor drive device 100, the image processing device 10, and the motor drive method are provided that make it easy to improve the responsiveness of the drive current Id1 by using the configuration described below.

[0087] That is, the motor driving device 100 according to this embodiment includes a current supply unit 101, an adjustment unit 102, and a change unit 104. The current supply unit 101 drives the stepping motor 110 by supplying a drive current Id1 to the stepping motor 110. The adjustment unit 102 is capable of adjusting the drive current Id1 within a variable range equal to or greater than a lower limit current value I2. The change unit 104 changes the lower limit current value I2.

[0088] According to this configuration, the adjustment unit 102 adjusts the drive current Id1 within a variable range equal to or greater than the lower limit current value I2, thereby making it possible to conserve energy while suppressing step-out of the stepping motor 110. Here, since the lower limit current value I2 of the drive current Id1 adjusted by the adjustment unit 102 can be changed, for example, by reducing the lower limit current value I2 under light load, it becomes possible to further reduce the drive current Id1, resulting in a significant energy-saving effect. Moreover, it is not necessary to generate a toner patch to set the drive current Id1, and it is possible to provide a motor drive device, an image processing device, and a motor drive method that can easily improve the responsiveness of the drive current Id1.

[0089] More specifically, the stepping motor 110 drives a movable member 111 of the developing device 4 that performs development using a developer containing toner and carrier. The change unit 104 changes the lower limit current value I2 according to the mixture ratio of the toner and carrier. In the present embodiment, as an example, the movable member 111 is a first stirring screw 401 and a second stirring screw 402. That is, the load of the movable member 111 (the first stirring screw 401 and the second stirring screw 402) of the developing device 4 differs depending on the mixture ratio of the toner and carrier in the developer, and by changing the lower limit current value I2 according to the mixture ratio, it becomes easier to set an appropriate lower limit current value I2.

[0090] Here, the change unit 104 increases the lower limit current value I2 as the toner ratio increases. As the toner ratio in the developer increases, the load on the movable members 111 (first stirring screw 401 and second stirring screw 402) of the developing device 4 increases, and as the carrier ratio in the developer increases, the load on the movable members 111 of the developing device 4 decreases. Therefore, by increasing the lower limit current value I2 as the toner ratio increases, it becomes easier to set an appropriate lower limit current value I2 that takes into account load fluctuations according to variations in the mixture ratio. In other words, by decreasing the lower limit current value I2 as the toner ratio decreases, it becomes easier to suppress unnecessary power consumption.

[0091] Moreover, the change unit 104 determines the lower limit current value I2 based on a correspondence relationship between the mixing ratio and the lower limit current value I2 that is stored in advance. The correspondence relationship between the mixing ratio and the lower limit current value I2 is stored in advance, for example, in the storage unit 8. This configuration can reduce the calculation load for determining the changed lower limit current value I2.

[0092] Specifically, in this embodiment, the change unit 104 changes the lower limit current value I2 according to a change instruction from a control unit (for example, the general control unit 7). For this purpose, the general control unit 7 acquires a detection value of the T / C sensor 112 from the developing device 4, and changes the lower limit current value I2 based on the detection value (mixture ratio of toner and carrier). Here, since the correspondence relationship between the mixture ratio and the lower limit current value I2 is stored in advance in an appropriate format such as a table in the storage unit 8, the general control unit 7 refers to the storage unit 8 and outputs a change instruction including information on the lower limit current value I2 corresponding to the mixture ratio. For this reason, the change unit 104 that receives the change instruction can change the lower limit current value I2 to the lower limit current value I2 corresponding to the mixture ratio.

[0093] In addition, in comparison with the second related art, the motor driving device 100 according to the present embodiment does not need to generate a toner patch to set the driving current, and can change the lower limit current value I2 in real time during normal T / C control. Therefore, no special detection control or external circuit for current detection is required, and an appropriate lower limit current value I2 can be realized, making it easy to suppress wasteful power consumption. Furthermore, even if the load suddenly increases due to toner replenishment, etc., there is no need to generate a toner patch, and the lower limit current value I2 is updated in real time, making it possible to suppress loss of synchronism and drive the stepping motor 110 stably. Furthermore, for the user, waiting time for generating a toner patch, as in the second related art, is unlikely to occur, and the user is unlikely to feel annoyed by the waiting time.

[0094] FIG. 7 is a flowchart showing an example of a motor driving method related to switching between enabling and disabling of the adjustment unit 102 (adjustment function).

[0095] <Step S11> First, in step S1, the central control unit 7 acquires the mixture ratio of toner and carrier from the T / C sensor 112 of the developing device 4 (the T / C detection value).

[0096] <Step S12> In the next step S12, the central control unit 7 judges whether the mixture ratio of toner and carrier (T / C detection value) is the same as the previous mixture ratio. If the mixture ratio has changed by a predetermined value or more (S12: Yes), the central control unit 7 shifts the process to step S13. On the other hand, if the mixture ratio has changed by less than the predetermined value, the central control unit 7 judges that the mixture ratio has not changed (S12: No) and repeats step S12.

[0097] <Step S13> In step S13, the central control unit 7 reads out the lower limit current value I2 corresponding to the changed mixture ratio from the storage unit 8, and outputs a change instruction including the lower limit current value I2. As a result, the change unit 104 that has received the change instruction changes the lower limit current value I2 in accordance with the change instruction.

[0098] The processes of steps S11 to S13 are repeatedly executed. The procedure of the motor driving method described above is merely an example, and the order of the processes shown in the flowchart of Fig. 7 may be changed as appropriate, or processes may be added.

[0099] [5] Variations The multiple components included in the motor drive device 100 may be distributed across multiple housings. For example, the adjustment unit 102, the switching unit 103, and the change unit 104 may be provided in different housings. Conversely, for example, the general control unit 7 may be integrated with the switching unit 103 or the change unit 104.

[0100] Moreover, the movable member 111 driven by the stepping motor 110 is not limited to the first stirring screw 401 and the second stirring screw 402. Furthermore, the movable member 111 is not limited to a component of the developing device 4.

[0101] Moreover, it is not essential that the motor driving device 100 includes both the switching unit 103 and the change unit 104, and the motor driving device 100 may include only one of the switching unit 103 and the change unit 104. In other words, one of the switching unit 103 and the change unit 104 may be omitted.

[0102] Furthermore, the configuration of the developing device 4 according to the first embodiment is not limited to the tandem image processing device 10 having a plurality of photoconductors (photoconductor drums) corresponding one-to-one to a plurality of colors, but can also be applied to a monochrome image processing device.

[0103] [Appendix to the invention] The following will provide an overview of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0104] <Appendix 1> a current supply unit that supplies a drive current to the stepping motor to drive the stepping motor; an adjustment unit capable of adjusting the drive current within a variable range equal to or greater than a lower limit current value; A change unit that changes the lower limit current value. Motor drive unit.

[0105] <Appendix 2> The change unit changes the lower limit current value in accordance with a change instruction from a control unit. 2. A motor drive device as claimed in claim 1.

[0106] <Appendix 3> the adjusting unit adjusts the driving current according to a required torque of the stepping motor. 3. The motor drive device according to claim 1 or 2.

[0107] <Appendix 4> the stepping motor drives a movable member of a developing device that performs development using a developer containing a toner and a carrier; the changing unit changes the lower limit current value in accordance with a mixture ratio of the toner and the carrier. 4. The motor drive device according to claim 1,

[0108] <Appendix 5> the change unit increases the lower limit current value as the ratio of the toner increases; 5. The motor drive device according to claim 4.

[0109] <Appendix 6> the change unit determines the lower limit current value based on a correspondence relationship between the mixing ratio and the lower limit current value that is stored in advance. 6. The motor drive device according to claim 4 or 5.

[0110] <Appendix 7> A motor drive device according to any one of appendix 1 to 6, A movable member driven by the stepping motor. Image processing device. [Explanation of symbols]

[0111] 3. Image forming section 4. Developing device 7 General control section (control section) 10 Image processing device 100 Motor Drive Unit 101 Current supply section 102 Adjustment part 104 Changes 110 Stepping motor 111 Movable parts Id1 Drive current I2 Lower limit current value

Claims

1. a current supply unit that supplies a drive current to the stepping motor to drive the stepping motor; an adjustment unit capable of adjusting the drive current within a variable range equal to or greater than a lower limit current value; A change unit that changes the lower limit current value. Motor drive unit.

2. The change unit changes the lower limit current value in accordance with a change instruction from a control unit.

2. The motor drive device according to claim 1.

3. the adjusting unit adjusts the driving current according to a required torque of the stepping motor.

3. The motor drive device according to claim 1 or 2.

4. the stepping motor drives a movable member of a developing device that performs development using a developer containing a toner and a carrier; the changing unit changes the lower limit current value in accordance with a mixture ratio of the toner and the carrier.

3. The motor drive device according to claim 1 or 2.

5. the change unit increases the lower limit current value as the ratio of the toner increases; 5. The motor drive device according to claim 4.

6. the change unit determines the lower limit current value based on a correspondence relationship between the mixing ratio and the lower limit current value that is stored in advance.

5. The motor drive device according to claim 4.

7. The motor drive device according to claim 1 or 2; A movable member driven by the stepping motor. Image processing device.

8. supplying a drive current to a stepping motor to drive the stepping motor; adjusting the driving current within a variable range equal to or greater than a lower limit current value; Changing the lower limit current value. Motor drive method.

Images