JP6740984B2 - Motor driving device, image forming device, and motor driving method - Google Patents

Description

The present invention relates to a motor driving device, an image forming apparatus including the motor driving device, and a motor driving method executed by the motor driving device.

An image forming apparatus such as a printer includes a motor that drives a load member such as a conveyance roller that conveys a sheet. For example, the motor is a stepping motor. Here, in order to prevent out-of-step of the stepping motor, a configuration in which the excitation phase of the stepping motor is switched based on a detection signal output from an encoder provided on the drive shaft of the stepping motor is known as a conventional technique. (See Patent Document 1).

JP-A-61-210897

In the above-mentioned conventional technique, the excitation phase of the stepping motor is switched after waiting for the input of the detection signal output from the encoder, so that a deviation occurs between the rotation of the rotor and the switching timing of the excitation phase. This deviation increases as the rotation speed of the stepping motor increases. When the deviation becomes large, the ratio of the period in which the rotor receives a force along the rotation direction from the magnetic field generated between the magnetic poles and the excitation phase of the stator in the rotation cycle of the rotor decreases, The torque of the stepping motor drops. Therefore, in the above-mentioned conventional technique, the stepping motor cannot be rotated at high speed.

It is an object of the present invention to provide a motor drive device, an image forming apparatus, and a motor drive method that can prevent a stepping motor from being out of step and can rotate the stepping motor at high speed.

A motor drive device according to one aspect of the present invention includes a stepping motor, a switching unit, a detection signal output unit, a first signal output unit, and a second signal output unit. The stepping motors are arranged at equal intervals along the rotation direction of the rotor and have a plurality of electromagnets that rotate the rotor. The switching unit sequentially switches excitation of the plurality of electromagnets along the rotation direction each time a predetermined electric signal is input. The detection signal output unit outputs a detection signal indicating the fact that the rotor rotates every unit angle corresponding to the arrangement interval of the plurality of electromagnets. The first signal output unit outputs the electric signal to the switching unit every time the detection signal is input. The second signal output unit is configured to output the electric signal within the output interval of the electric signal by the first signal output unit when the rotation speed of the stepping motor is equal to or higher than a first speed lower than a predetermined target speed. The electric signal is output to the switching unit a predetermined number of times.

An image forming apparatus according to another aspect of the present invention includes the motor drive device and a load member. The load member is driven by the driving force supplied from the stepping motor.

A motor driving method according to another aspect of the present invention is a stepping motor having a plurality of electromagnets arranged at equal intervals along a rotation direction of a rotor and having a plurality of electromagnets for rotating the rotor, and a predetermined electric motor. Each time a signal is input, a switching unit that sequentially switches excitation of the plurality of electromagnets along the rotation direction, and that effect every time the rotor rotates by a unit angle corresponding to the arrangement interval of the plurality of electromagnets. The detection signal output part which outputs the detection signal which shows is performed by the motor drive device provided with, and includes the following 1st steps and 2nd steps. In the first step, the electric signal is output to the switching unit every time the detection signal is input. In the second step, when the rotation speed of the stepping motor is equal to or higher than a first speed lower than a predetermined target speed, the electric signal is output within the output interval of the electric signal in the first step. The predetermined number of times is output to the switching unit.

According to the present invention, it is possible to prevent stepping out of the stepping motor and to rotate the stepping motor at high speed.

FIG. 1 is a diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing the configurations of the driving force generation unit and the control unit of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a diagram showing a configuration of a stepping motor of the image forming apparatus according to the embodiment of the present invention. FIG. 4 is a diagram showing the configuration of the stepping motor of the image forming apparatus according to the embodiment of the present invention. FIG. 5 is a diagram showing a configuration of a stepping motor of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is a flowchart showing an example of drive control processing executed by the image forming apparatus according to the embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. The following embodiments are examples of embodying the present invention and do not limit the technical scope of the present invention.

[Schematic Configuration of Image Forming Apparatus 10]
First, a schematic configuration of an image forming apparatus 10 according to an exemplary embodiment of the present invention will be described with reference to FIGS. 1 to 3. Here, FIG. 1 is a schematic cross-sectional view showing the configuration of the image forming apparatus 10. FIG. 3 is a schematic sectional view showing the structure of the stepping motor 51. The two-dot chain line in FIG. 2 is for showing the driving force generation unit 5.

The image forming apparatus 10 is a multi-function peripheral having a scan function for reading image data from a document, a print function for forming an image based on the image data, and a plurality of functions such as a facsimile function and a copy function. The image forming apparatus 10 may be a printer device, a facsimile device, a copier, or the like.

As shown in FIGS. 1 and 2, the image forming apparatus 10 includes an ADF (automatic document feeder) 1, an image reading unit 2, an image forming unit 3, a paper feeding unit 4, a driving force generating unit 5, and a control unit. 6 is provided.

The ADF 1 includes a document setting unit, a plurality of transport rollers, a document retainer, and a paper discharge unit, and transports a document read by the image reading unit 2.

The image reading unit 2 includes a document table, a light source, a plurality of mirrors, an optical lens, and a CCD (Charge Coupled Device), and can read image data from a document.

The image forming unit 3 forms an image in an electrophotographic system based on image data read by the image reading unit 2 or image data input from an information processing device such as an external personal computer (printing process). ) Can be performed. As shown in FIG. 1, the image forming unit 3 includes a photosensitive drum 31, a charger 32, an optical scanning device 33, a developing device 34, a transfer roller 35, a cleaning device 36, a fixing roller 37, a pressure roller 38, and A paper discharge tray 39 is provided.

The paper feeding unit 4 supplies the sheet to the image forming unit 3. As shown in FIG. 1, the sheet feeding unit 4 includes a sheet feeding cassette 41, a pickup roller 42, a feed roller 43, a sheet conveyance path 44, a conveyance roller 45, and a registration roller 46.

In the image forming section 3, an image is formed on the sheet supplied from the sheet feeding section 4 by the following procedure, and the sheet after the image formation is discharged to the sheet discharge tray 39. The sheets supplied from the paper feeding unit 4 are sheet members such as paper, coated paper, postcards, envelopes, and OHP sheets.

First, the surface of the photosensitive drum 31 is uniformly charged to a predetermined potential by the charger 32. Next, the light scanning device 33 irradiates the surface of the photosensitive drum 31 with light based on the image data. As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 31. Then, the electrostatic latent image on the photosensitive drum 31 is developed (visualized) as a toner image by the developing device 34. The toner image formed on the photoconductor drum 31 is conveyed by the photoconductor drum 31 to the transfer position of the transfer roller 35 onto the sheet. The developing device 34 is replenished with toner (developer) from a toner container 34A that is detachable from the image forming unit 3.

On the other hand, in the sheet feeding unit 4, the uppermost sheet of the sheet bundle stored in the sheet feeding cassette 41 is conveyed to the sheet conveying path 44 by the pickup roller 42 and the feed roller 43. The sheet conveyed to the sheet conveying path 44 is conveyed by the conveying roller 45 to the position where the registration roller 46 is arranged. The registration roller 46 supplies the sheet to the transfer position in synchronization with the conveyance timing of the toner image by the photosensitive drum 31 to the transfer position. As a result, the toner image formed on the photoconductor drum 31 is transferred to the sheet supplied by the registration roller 46. The toner remaining on the surface of the photosensitive drum 31 is removed by the cleaning device 36.

After that, the toner image transferred onto the sheet is heated and fused and fixed by the fixing roller 37 when the sheet passes between the fixing roller 37 and the pressure roller 38. The sheet on which the toner image is fixed is conveyed to the sheet discharge tray 39 by the conveying roller 45.

The driving force generation unit 5 generates driving force that drives a load member provided in the image forming apparatus 10. For example, the load member is the transport roller 45 of the paper feeding unit 4. The load member may be a transport roller of ADF1. Further, the load member may be a conveying screw that is rotatably provided in the toner container 34A and conveys toner. Further, the load member may be a roller-shaped cleaning member that is rotatably provided in the cleaning device 36 and cleans the surface of the photosensitive drum 31.

As shown in FIG. 2, the driving force generation unit 5 includes a stepping motor 51, a power supply unit 52, a switching unit 53, and a detection signal output unit 54.

The stepping motor 51 has, for example, two phases and is driven by a one-phase excitation method. As shown in FIG. 3A, the stepping motor 51 includes a rotor 511 and a stator 512. The number of phases of the stepping motor 51 is not limited to two and may be three or more. Further, the excitation method of the stepping motor 51 is not limited to the one-phase excitation method, and other excitation methods may be used.

The rotor 511 is rotatably supported by the housing of the stepping motor 51. The rotor 511 includes a drive shaft 511A protruding from the housing in a direction perpendicular to the paper surface of FIG. Further, the rotor 511 includes a permanent magnet having four magnetic poles M1 to M4. As shown in FIG. 3A, the magnetic poles M1 and M3 are N poles, and the magnetic poles M2 and M4 are S poles. The rotor 511 is rotated by the stator 512 in the rotation direction D1 shown in FIG. The magnetic poles M1 to M4 are arranged at equal intervals along the rotation direction D1.

The stator 512 is provided around the rotor 511 in the housing. The stator 512 includes eight electromagnets 512A to 512H, which is twice the number of the magnetic poles M1 to M4 of the rotor 511. As shown in FIG. 3A, the electromagnets 512A to 512H are arranged at equal intervals along the rotation direction D1 of the rotor 511. Hereinafter, any one of the electromagnets 512A to 512H will be referred to as an electromagnet 512X. The electromagnets 512A to 512H rotate the rotor 511 in the rotation direction D1. In the stepping motor 51, four electromagnets 512X of the same number as the number of magnetic poles M1 to M4 among the eight electromagnets 512A to 512H are excited.

The number of magnetic poles in the rotor 511 is not limited to four, and may be three or less, or five or more. Further, the number of electromagnets 512X in the stator 512 is not limited to twice the number of magnetic poles in the rotor 511, and may be three times or more. Further, the number of electromagnets 512X in the stator 512 is not limited to eight, and may be seven or less, or nine or more. Further, the number of electromagnets 512X excited in the stepping motor 51 is not limited to four, and may be three or less, or five or more.

The power supply unit 52 supplies drive power to the stepping motor 51. For example, the power supply unit 52 is a switching power supply that increases or decreases the drive power according to the PWM (pulse width modulation) signal Sig1 (see FIG. 2) input from the control unit 6.

The switching unit 53 energizes the electromagnets 512A to 512H of the stepping motor 51 along the rotation direction D1 (see FIG. 3A) every time a predetermined electric signal Sig2 (see FIG. 2) is input. Switch sequentially. For example, the electric signal Sig2 is a pulse signal.

As shown in FIG. 2, the switching unit 53 is provided on the supply path of the drive power from the power supply unit 52 to the stepping motor 51. Each time the switching unit 53 inputs the electric signal Sig2, the excitation target is changed from the currently excited electromagnet 512X to another electromagnet 512X adjacent on the downstream side in the rotation direction D1 (see FIG. 3A). Switch. For example, the switching unit 53 is an electronic circuit including a plurality of transistors capable of switching between conduction and interruption of power supply paths corresponding to the electromagnets 512A to 512H.

For example, when the electric signal Sig2 is input in the state shown in FIG. 3A, the switching unit 53 switches the excitation target excited by the S pole from the electromagnets 512A, 512E to the electromagnets 512B, 512F, and The excitation target excited by the N pole is switched from the electromagnets 512C and 512G to the electromagnets 512D and 512H.

Thus, as shown in FIG. 3B, the magnetic pole M1 is magnetically attracted to the electromagnet 512B by the magnetic field generated between the electromagnet 512H and the electromagnet 512B and the magnetic pole M1. Further, the magnetic pole M2 is magnetically attracted to the electromagnet 512D by the magnetic field generated between the electromagnet 512B and the electromagnet 512D and the magnetic pole M2. Further, the magnetic pole M3 is magnetically attracted to the electromagnet 512F by the magnetic field generated between the electromagnet 512D and the electromagnet 512F and the magnetic pole M3. The magnetic pole M4 is magnetically attracted to the electromagnet 512H by the magnetic field generated between the electromagnet 512F and the electromagnet 512H and the magnetic pole M4. The force received by each of the magnetic poles M1 to M4 becomes a torque, and the rotor 511 rotates in the rotation direction D1 (see FIG. 3A).

The detection signal output unit 54 outputs a detection signal Sig3 (see FIG. 2) indicating that the rotor 511 rotates every unit angle corresponding to the arrangement interval of the electromagnets 512A to 512H. For example, in the stepping motor 51, eight electromagnets 512X are arranged at equal intervals along the rotation direction D1 (see FIG. 3A). Therefore, the unit angle is 360 degrees/8=45 degrees. For example, the detection signal output unit 54 is a rotary encoder attached to the drive shaft 511A of the rotor 511. For example, the detection signal output unit 54 outputs the detection signal Sig3 at the timing when the magnetic poles M1 to M4 of the rotor 511 rotating in the rotation direction D1 and the electromagnet 512X face each other (see FIGS. 3A and 3C). ).

By the way, in order to prevent the stepping motor 51 from being out of step, a configuration is known as a prior art in which the excitation target in the stator 512 is switched based on the detection signal Sig3 output from the detection signal output unit 54. Specifically, in the configuration of this conventional technique, the control unit 6 outputs the electric signal Sig2 to the switching unit 53 in response to the input of the detection signal Sig3 output from the detection signal output unit 54.

In the above-described conventional technique, the electromagnet 512X to be excited in the stator 512 is switched after waiting for the detection signal Sig3 output from the detection signal output unit 54 to be input to the control unit 6. Therefore, the rotation of the rotor 511 and the excitation target There is a deviation from the switching timing of the electromagnet 512X. This deviation increases as the rotation speed of the stepping motor 51 increases. When the deviation becomes large, in the rotation cycle of the rotor 511, the rotor 511 follows the magnetic field generated between the magnetic poles M1 to M4 and the electromagnet 512X to be excited along the rotation direction D1 (see FIG. 3A). The ratio of the period during which the force is applied decreases, and the torque of the stepping motor 51 decreases.

Specifically, in the state shown in FIG. 3(C), the rotor 511 moves from the magnetic field generated between the magnetic poles M1 to M4 and the excited electromagnets 512B, 512D, 512F, 512H in the rotation direction D1. I have not received the force along. Therefore, the rotor 511 rotates in the rotation direction D1 by inertia until the electromagnet 512X to be excited in the stator 512 is switched from when the detection signal Sig3 is output from the detection signal output unit 54 (FIG. 3(D )reference). The amount of rotation of the rotor 511 due to inertia increases as the rotation speed of the stepping motor 51 increases. Therefore, as the rotation speed of the stepping motor 51 increases, the force along the rotation direction D1 is generated from the magnetic field generated by the rotor 511 between the magnetic poles M1 to M4 and the electromagnet 512X to be excited in the rotation cycle of the rotor 511. The ratio of the period received is reduced, and the torque of the stepping motor 51 is reduced.

For the above reasons, the above-described conventional technique cannot rotate the stepping motor 51 at high speed. On the other hand, in the image forming apparatus 10 according to the embodiment of the present invention, as described below, it is possible to prevent the stepping motor 51 from being out of step and to rotate the stepping motor 51 at a high speed.

The control unit 6 includes control devices such as a CPU, a ROM, and a RAM (not shown). The CPU is a processor that executes various arithmetic processes. The ROM is a non-volatile storage device in which information such as a control program for causing the CPU to execute various processes is stored in advance. The RAM is a volatile storage device used as a temporary storage memory (work area) for various processes executed by the CPU. In the control unit 6, the CPU executes various control programs stored in the ROM in advance. As a result, the image forming apparatus 10 is comprehensively controlled by the control unit 6. Note that the control unit 6 may be configured by an electronic circuit such as an integrated circuit (ASIC), and is a control unit provided separately from the main control unit that integrally controls the image forming apparatus 10. May be.

The control unit 6 also includes a first signal output unit 61, a second signal output unit 62, and an input limiting unit 63, as shown in FIG. Specifically, the control unit 6 uses the CPU to execute the control program stored in the ROM. As a result, the control unit 6 functions as the first signal output unit 61, the second signal output unit 62, and the input limiting unit 63. The device including the driving force generation unit 5 and the control unit 6 is an example of the motor drive device of the present invention.

The first signal output unit 61 outputs the electric signal Sig2 to the switching unit 53 every time the detection signal Sig3 is input from the detection signal output unit 54.

The second signal output unit 62, within the output interval of the electric signal Sig2 by the first signal output unit 61, when the rotation speed of the stepping motor 51 is equal to or higher than a first speed lower than a predetermined target speed, The electric signal Sig2 is output to the switching unit 53 a preset number of times.

For example, the second signal output unit 62 determines, based on the input interval of the detection signal Sig3 output from the detection signal output unit 54, whether the rotation speed of the stepping motor 51 is equal to or higher than the first speed. The first speed may be an arbitrarily set speed.

For example, the second signal output unit 62 switches the electric signal Sig2 within the output interval of the electric signal Sig2 by the first signal output unit 61 when the rotation speed of the stepping motor 51 is equal to or higher than the first speed. Output once to 53. The number of times of setting may be two or more.

Here, the operation of the stepping motor 51 when the electric signal Sig2 is input to the switching unit 53 by the second signal output unit 62 will be described with reference to FIGS. Note that in FIG. 4A, it is assumed that the stepping motor 51 is rotating at the first speed.

In the state shown in FIG. 4A, the detection signal output unit 54 outputs the detection signal Sig3. When the detection signal Sig3 output from the detection signal output unit 54 is input, the first signal output unit 61 outputs the electric signal Sig2 to the switching unit 53. The second signal output unit 62 rotates the stepping motor 51 based on the input interval of the detection signal Sig3 input from the detection signal output unit 54 and the detection signal Sig3 input immediately before the detection signal output unit 54. It is determined whether the speed is equal to or higher than the first speed. Here, it is assumed that the second signal output unit 62 determines that the rotation speed of the stepping motor 51 is equal to or higher than the first speed. In this case, the second signal output unit 62 outputs the electric signal Sig2 to the switching unit 53 once immediately before or after the output of the electric signal Sig2 by the first signal output unit 61. As a result, the electric signal Sig2 is input to the switching unit 53 twice. The switching unit 53 switches the excitation target excited to the S pole from the electromagnets 512B and 512F to the electromagnets 512D and 512H in accordance with the input of the electric signal Sig2 twice, and the excitation target excited to the N pole. The electromagnets 512D and 512H are switched to the electromagnets 512F and 512B.

FIG. 4B shows a state after the electromagnet 512X to be excited is switched by the switching unit 53 from the state shown in FIG. 4A. Here, in the state shown in FIG. 4(A), the rotor 511 rotates from the magnetic field generated between the magnetic poles M1 to M4 and the electromagnets 512B, 512D, 512F, 512H to be excited in the rotation direction D1 (FIG. 3). (See (A)). Therefore, in the state shown in FIG. 4B, the rotor 511 is rotating in the rotation direction D1 from the state shown in FIG. 4A by inertia.

In the state shown in FIG. 4B, the magnetic pole M1 is magnetically attracted to the electromagnet 512D by the magnetic field generated between the magnetic pole M1 and the electromagnets 512B and 512D. Further, the magnetic pole M2 is magnetically attracted to the electromagnet 512F by the magnetic field generated between the magnetic pole M2 and the electromagnets 512D and 512F. Further, the magnetic pole M3 is magnetically attracted to the electromagnet 512H by the magnetic field generated between the magnetic pole M3 and the electromagnet 512F and the electromagnet 512H. Further, the magnetic pole M4 is magnetically attracted to the electromagnet 512B by the magnetic field generated between the magnetic pole M4 and the electromagnet 512H and the electromagnet 512B. The force received by each of the magnetic poles M1 to M4 becomes a torque, and the rotor 511 rotates in the rotation direction D1.

FIG. 4(C) shows a state in which the rotor 511 has rotated from the state shown in FIG. 4(B). In the state shown in FIG. 4C, the detection signal output unit 54 outputs the detection signal Sig3. When the detection signal Sig3 output from the detection signal output unit 54 is input, the first signal output unit 61 outputs the electric signal Sig2 to the switching unit 53. The switching unit 53 switches the excitation target excited by the S pole from the electromagnets 512D, 512H to the electromagnets 512E, 512A according to the input of the electric signal Sig2, and changes the excitation target excited by the N pole by the electromagnet 512F, Switch from 512B to electromagnets 512G and 512C.

FIG. 4D shows a state after the switching unit 53 switches the electromagnet 512X to be excited from the state shown in FIG. 4C. Here, in the state shown in FIG. 4C, unlike the state shown in FIG. 4A, the rotor 511 has magnetic poles M1 to M4 and electromagnets 512B, 512D, 512F, 512H to be excited. A force along the rotation direction D1 (see FIG. 3A) is received from the magnetic field generated between the two. Therefore, in the state shown in FIG. 4D, the rotor 511 is rotating in the rotation direction D1 from the state shown in FIG. 4C by the force received from the magnetic field instead of inertia.

In the state shown in FIG. 4D, the magnetic pole M1 is magnetically attracted to the electromagnet 512E by the magnetic field generated between the magnetic pole M1 and the electromagnets 512C and 512E. The magnetic pole M2 is magnetically attracted to the electromagnet 512G by the magnetic field generated between the magnetic pole M2 and the electromagnets 512E and 512G. Further, the magnetic pole M3 is magnetically attracted to the electromagnet 512A by the magnetic field generated between the magnetic pole M3 and the electromagnet 512G and the electromagnet 512A. Further, the magnetic pole M4 is magnetically attracted to the electromagnet 512C by the magnetic field generated between the magnetic pole M4 and the electromagnets 512A and 512C. The force received by each of the magnetic poles M1 to M4 becomes a torque, and the rotor 511 rotates in the rotation direction D1.

As described above, the second signal output unit 62 outputs the electric signal Sig2 to the switching unit 53 once, so that the period in which the rotor 511 rotates due to inertia can be eliminated in the rotation cycle of the rotor 511. Become. As a result, the rotor 511 can receive a force along the rotation direction D1 from the magnetic field generated between the magnetic poles M1 to M4 and the electromagnet 512X to be excited during the entire rotation cycle of the rotor 511. Become. Therefore, it is possible to suppress a decrease in torque when the rotation speed of the stepping motor 51 is increased.

Note that when the amount of rotation of the rotor 511 due to inertia in the state shown in FIG. 4B is small, the rotation of the stepping motor 51 may become unstable. For example, in the state shown in FIG. 4B, when the rotation amount due to inertia of the rotor 511 is small, the magnetic pole M1 receives a force from both the electromagnet 512H and the electromagnet 512D, and the rotation becomes unstable. May be. Therefore, it is desirable that the first speed be higher than the speed at which the rotor 511 rotates due to inertia.

The input limiting unit 63 outputs an electric signal to the switching unit 53 when the rotation speed of the stepping motor 51 becomes equal to or higher than the first speed and then becomes lower than the second speed that is equal to or lower than the first speed. The input of Sig2 is limited to the set number of times. The second speed may be an arbitrarily set speed.

For example, the input restriction unit 63 prohibits the first signal output unit 61 from outputting the electric signal Sig2 for the set number of times. When each of the first signal output unit 61, the second signal output unit 62, and the input limiting unit 63 is configured by an electronic circuit, the input limiting unit 63 includes the detection signal output unit 54 and the first signal output unit 61. The input of the detection signal Sig3 to the first signal output unit 61 may be blocked between and. Further, the input restriction unit 63 may prevent the electric signal Sig2 from being input to the switching unit 53 between the first signal output unit 61 and the switching unit 53.

Here, the operation of the stepping motor 51 when the input of the electric signal Sig2 to the switching unit 53 is restricted by the input limiting unit 63 will be described with reference to FIGS. In addition, in FIG. 5A, it is assumed that the stepping motor 51 is rotating at a speed lower than the second speed after the second signal output unit 62 outputs the electric signal Sig2 to the switching unit 53.

In the state shown in FIG. 5A, the magnetic pole M1 is magnetically attracted to the electromagnet 512D by the magnetic field generated between the magnetic pole M1 and the electromagnets 512B and 512D. Further, the magnetic pole M2 is magnetically attracted to the electromagnet 512F by the magnetic field generated between the magnetic pole M2 and the electromagnets 512D and 512F. Further, the magnetic pole M3 is magnetically attracted to the electromagnet 512H by the magnetic field generated between the magnetic pole M3 and the electromagnet 512F and the electromagnet 512H. Further, the magnetic pole M4 is magnetically attracted to the electromagnet 512B by the magnetic field generated between the magnetic pole M4 and the electromagnet 512H and the electromagnet 512B. The force received by each of the magnetic poles M1 to M4 becomes a torque, and the rotor 511 rotates in the rotation direction D1.

FIG. 5(B) shows a state in which the rotor 511 has rotated from the state shown in FIG. 5(A). In the state shown in FIG. 5B, the detection signal output unit 54 outputs the detection signal Sig3. The input limiting unit 63 determines the rotation speed of the stepping motor 51 based on the input interval of the detection signal Sig3 input from the detection signal output unit 54 and the detection signal Sig3 input immediately before the detection signal output unit 54. Judge whether the speed is less than 2 speeds. Here, it is assumed that the input limiting unit 63 determines that the rotation speed of the stepping motor 51 is lower than the second speed. In this case, the input restriction unit 63 restricts the input of the electric signal Sig2 to the switching unit 53 by the first signal output unit 61 once. Therefore, in the state shown in FIG. 5B, the switching unit 53 does not switch the electromagnet 512X to be excited. Further, in the state shown in FIG. 5B, the rotor 511 is rotated in the rotation direction D1( by the force received from the magnetic field generated between the magnetic poles M1 to M4 and the electromagnets 512B, 512D, 512F, 512H to be excited. 3A) (see FIG. 3A).

FIG. 5C shows a state in which the rotor 511 has rotated from the state shown in FIG. 5B. In the state shown in FIG. 5C, the detection signal output unit 54 outputs the detection signal Sig3. When the detection signal Sig3 output from the detection signal output unit 54 is input, the first signal output unit 61 outputs the electric signal Sig2 to the switching unit 53. The switching unit 53 switches the excitation target excited by the S pole from the electromagnets 512D, 512H to the electromagnets 512E, 512A in response to the input of the electric signal Sig2, and changes the excitation target excited by the N pole by the electromagnet 512F, Switch from 512B to electromagnets 512G, 512C.

FIG. 5D shows a state after the electromagnet 512X to be excited is switched by the switching unit 53 from the state shown in FIG. 5C. Here, in the state shown in FIG. 5C, unlike the state shown in FIG. 5B, the rotor 511 has electromagnets 512B, 512D, 512F, 512H that are excited with the magnetic poles M1 to M4. A force along the rotation direction D1 (see FIG. 3A) is not received from the magnetic field generated between and. Therefore, in the state shown in FIG. 5(D), the rotor 511 is rotating in the rotation direction D1 from the state shown in FIG. 5(C) by inertia.

In this way, the input limiting unit 63 regulates the input of the electric signal Sig2 to the switching unit 53, so that the state of the stepping motor 51 is changed by the second signal output unit 62 before the electric signal Sig2 is output to the switching unit 53. It is possible to return to the state of. As a result, for example, when the transport load on the transport roller 45 increases and the rotation speed of the stepping motor 51 decreases, the rotation of the stepping motor 51 is prevented from becoming unstable. Specifically, the rotation amount of the rotor 511 decreases from the time when the detection signal output unit 54 outputs the detection signal to the time when the electromagnet 512X to be excited is switched, so that each of the magnetic poles M1 to M4 rotates in the rotation direction D1 ( It is possible to prevent the rotation of the stepping motor 51 from becoming unstable due to the force applied in the opposite direction to that in FIG.

[Drive control processing]
Hereinafter, with reference to FIG. 6, a motor driving method according to the present invention will be described together with an example of a procedure of drive control processing executed by the controller 6 in the image forming apparatus 10. Here, steps S11, S12,... Show numbers of processing procedures (steps) executed by the control unit 6. For example, the drive control process is executed when the sheet is conveyed by the sheet feeding unit 4.

<Step S11>
First, in step S11, the control unit 6 starts driving the stepping motor 51.

For example, the control unit 6 outputs the electric signal Sig2 to the switching unit 53 once. As a result, the rotor 511 of the stepping motor 51 rotates by the unit angle. Therefore, the detection signal output unit 54 outputs the detection signal Sig3. After that, the control unit 6 outputs the electric signal Sig2 to the switching unit 53 every time the detection signal Sig3 is input from the detection signal output unit 54. As a result, the stepping motor 51 is driven.

Further, the control unit 6 drives the stepping motor 51 by the power supply unit 52 so that the rotation speed of the stepping motor 51 corresponding to the frequency of the detection signal Sig3 output from the detection signal output unit 54 becomes the target speed. Control the amount of power supply. For example, the control unit 6 inputs the PWM signal Sig1 generated based on the phase difference between the clock signal having the frequency corresponding to the target speed and the detection signal Sig3 to the power supply unit 52. As a result, the rotation speed of the stepping motor 51 increases. Here, the process of outputting the electric signal Sig2 to the switching unit 53 every time the detection signal Sig3 is input from the detection signal output unit 54 in step S11 is an example of the first step in the present invention.

<Step S12>
In step S12, the control unit 6 determines whether the sheet feeding by the sheet feeding unit 4 is completed.

Here, when the control unit 6 determines that the sheet conveyance by the paper feeding unit 4 is completed (Yes in S12), the process proceeds to step S121. If the sheet conveyance by the sheet feeding unit 4 is not completed (No side of S12), the control unit 6 shifts the processing to step S13.

<Step S13>
In step S13, the control unit 6 determines whether or not the rotation speed of the stepping motor 51 has become equal to or higher than the first speed.

Here, when the control unit 6 determines that the rotation speed of the stepping motor 51 has become equal to or higher than the first speed (Yes in S13), the process proceeds to Step S14. If the rotation speed of the stepping motor 51 is not equal to or higher than the set speed (No in S13), the control unit 6 shifts the processing to step S12.

<Step S14>
In step S14, the control unit 6 outputs the electric signal Sig2 to the switching unit 53 the set number of times within the output interval of the electric signal Sig2 corresponding to the input of the detection signal Sig3 from the detection signal output unit 54. Here, the process of step S14 is an example of the second step of the present invention, and is executed by the second signal output unit 62 of the control unit 6.

For example, the control unit 6 outputs the electric signal Sig2 to the switching unit 53 once. This makes it possible to further increase the rotation speed of the stepping motor 51.

<Step S15>
In step S15, the control unit 6 determines whether or not the sheet conveyance by the paper feeding unit 4 is completed, as in step S12.

Here, when the control unit 6 determines that the sheet conveyance by the sheet feeding unit 4 is completed (Yes in S15), the process proceeds to step S151. If the sheet feeding by the sheet feeding unit 4 is not completed (No side of S15), the control unit 6 shifts the processing to step S16.

<Step S16>
In step S16, the control unit 6 determines whether or not the rotation speed of the stepping motor 51 is lower than the second speed. For example, when the transport load on the transport roller 45 increases due to double feeding of sheets or the like, the rotation speed of the stepping motor 51 may decrease below the second speed.

Here, when the control unit 6 determines that the rotation speed of the stepping motor 51 has become less than the second speed (Yes in S16), the process proceeds to Step S17. If the rotation speed of the stepping motor 51 is not lower than the second speed (No side of S16), the control unit 6 shifts the processing to step S15.

<Step S17>
In step S17, the control unit 6 regulates the input of the electric signal Sig2 to the switching unit 53 by the set number of times. Here, the process of step S17 is executed by the input limiting unit 63 of the control unit 6.

For example, the control unit 6 regulates the input of the electric signal Sig2 to the switching unit 53 once. As a result, it is possible to prevent the rotation speed of the stepping motor 51 from decreasing due to an increase in the transportation load, and the rotation of the stepping motor 51 from becoming unstable.

<Step S121>
On the other hand, when it is determined in step S12 that the sheet feeding by the paper feeding unit 4 is completed, the control unit 6 executes the process of step S121. In step S121, the control unit 6 starts deceleration control for gradually decelerating the rotation speed of the stepping motor 51 and stopping it. For example, the control unit 6 gradually reduces the duty ratio in the PWM signal Sig1 output to the power supply unit 52, and gradually reduces the rotation speed of the stepping motor 51.

<Step S151>
When it is determined in step S15 that the sheet feeding by the sheet feeding unit 4 is completed, the control unit 6 executes the process of step S151. In step S151, the control unit 6 starts the deceleration control as in step S121.

<Step S152>
In step S152, the control unit 6 determines whether the rotation speed of the stepping motor 51 is less than the second speed, as in step S16.

Here, when the control unit 6 determines that the rotation speed of the stepping motor 51 has become lower than the second speed (Yes in S152), the process proceeds to step S153. If the rotation speed of the stepping motor 51 is not lower than the second speed (No side of S152), the control unit 6 determines that the rotation speed of the stepping motor 51 is lower than the second speed in step S152. Wait.

<Step S153>
In step S153, the control unit 6 limits the input of the electric signal Sig2 to the switching unit 53 to the set number of times, as in step S17. Here, the process of step S17 is executed by the input limiting unit 63 of the control unit 6.

This prevents the stepping motor 51 from becoming unstable in rotation during the deceleration control.

As described above, in the image forming apparatus 10, every time the detection signal Sig3 is input from the detection signal output unit 54, the electric signal Sig2 is output to the switching unit 53. Further, in the image forming apparatus 10, when the rotation speed of the stepping motor 51 is equal to or higher than the first speed lower than the target speed, the electric signal Sig2 corresponding to the input of the detection signal Sig3 from the detection signal output unit 54 is output. The electric signal Sig2 is output to the switching unit 53 the set number of times within the output interval. This makes it possible to eliminate the period in which the rotor 511 rotates due to inertia in the rotation cycle of the rotor 511. Therefore, it is possible to prevent the stepping motor 51 from being out of step and to rotate the stepping motor 51 at a high speed.

1 ADF
2 image reading unit 3 image forming unit 4 paper feeding unit 5 driving force generating unit 6 control unit 10 image forming apparatus 51 stepping motor 52 power supply unit 53 switching unit 54 detection signal output unit 61 first signal output unit 62 second signal output unit 63 Input limiter 511 Rotor 512 Stator 512A to 512H Electromagnet

Claims (4)

A stepping motor having a plurality of electromagnets arranged at equal intervals along the rotation direction of the rotor and rotating the rotor;
Every time a predetermined electric signal is input, a switching unit that sequentially switches excitation of the plurality of electromagnets along the rotation direction,
Each time the rotor rotates a unit angle corresponding to the arrangement intervals of the plurality of electromagnets, a detection signal output unit that outputs a detection signal indicating that,
A first signal output unit that outputs the electric signal to the switching unit every time the detection signal is input;
When the rotation speed of the stepping motor is equal to or higher than a first speed lower than a predetermined target speed, the electric signal is previously output to the switching unit within an output interval of the electric signal by the first signal output unit. A second signal output section for outputting a predetermined number of times,
A motor drive device. When the rotation speed of the stepping motor becomes less than the first speed and is less than the second speed that is less than or equal to the first speed, the input of the electric signal to the switching unit is performed the set number of times. Equipped with an input limiting unit to limit,
The motor drive device according to claim 1. A motor drive device according to claim 1 or 2;
A load member driven by a driving force supplied from the stepping motor,
An image forming apparatus including. A stepping motor having a plurality of electromagnets arranged at equal intervals along the rotation direction of the rotor and having a plurality of electromagnets for rotating the rotor, and exciting the plurality of electromagnets each time a predetermined electric signal is input. And a detection signal output unit that outputs a detection signal indicating that each time the rotor rotates by a unit angle corresponding to the arrangement intervals of the plurality of electromagnets. A method for driving a motor executed by a motor driving device, comprising:
A first step of outputting the electric signal to the switching unit every time the detection signal is input;
When the rotation speed of the stepping motor is equal to or higher than a first speed lower than a predetermined target speed, the electric signal is predetermined by the switching unit within an output interval of the electric signal by the first step. The second step of outputting the set number of times,
Driving method including a motor.

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