Driving device and image forming apparatus

Abstract

To provide a driving device that can accurately predict service lives of a driving source and driving components and identify an abnormal portion.SOLUTION: A driving device comprises: a stepping motor 130 that has pieces of winding; a plurality of driving components for transmitting driving force output from the stepping motor 130 to loads; a current detection unit 152 that detects a first driving current flowing in first winding by using a first low-pass filter with a first cut-off frequency, and detects a second driving current flowing in second winding by using a second low-pass filter with a second cut-off frequency higher than the first cut-off frequency; and a CPU 150 that determines a service life of the stepping motor 130 on the basis of the first driving current, determines the presence or absence of an abnormality in the stepping motor 130 on the basis of the first driving current and second driving current, and determines the presence or absence of an abnormality in the driving components on the basis of the second driving current.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a drive device including a stepping motor and a drive mechanism driven by the stepping motor, such as an image forming apparatus, and to an image forming apparatus including this drive device. [Background technology]

[0002] Image forming devices such as printers, copiers, and multifunction machines include a transport roller for transporting paper in order to print an image on the paper, a photosensitive drum on which an image is formed, and a transfer roller for transferring the image formed on the photosensitive drum to the paper. The transfer roller forms a nip between itself and an image carrier that carries the image when transferring the image, and transfers the image from the image carrier to the paper at the nip. The transfer roller can perform contact / separation operations with respect to the image carrier in order to form the nip. For example, the transfer roller waits at a position separated from the image carrier except during transfer, thereby preventing deterioration of the image carrier.

[0003] Stepping motors are often used as the drive source for drive devices that rotate the transport roller, rotate the photosensitive drum, and drive the transfer roller into contact / separation, etc. Replacement of drive parts that make up the drive device, such as the stepping motor, is carried out from the following perspectives: (1) The life of a part has expired due to use exceeding the specified number of sheets or the specified cumulative operating time. (2) Detection of abnormalities such as malfunction of parts

[0004] In part replacement due to part life, parts are replaced before they reach their expected life and become unable to operate normally. Part life is set taking into consideration the installation environment of the image forming apparatus, the type of paper used for printing, and the characteristic variations of parts. Usually, a certain margin is added to the part life. Therefore, even when parts are replaced according to the set part life, it is rare that the part actually reaches the end of its life. However, in order to reduce the running cost of the image forming apparatus, it is preferable to replace parts infrequently. Patent Document 1 discloses an image forming apparatus that reduces running costs by measuring the drive current of a motor that drives a driving part, predicting the part life from the measured drive current, and replacing parts at an appropriate timing.

[0005] In part replacement due to abnormality detection, parts are replaced when they are unable to operate normally due to an unexpected event. Abnormalities in parts are detected by monitoring the operation of the parts using an abnormality detection sensor such as an optical sensor such as a photointerrupter. In this case, it is difficult to distinguish whether the detected abnormal state is an abnormality in the abnormality detection sensor itself, an abnormality in the parts, or an abnormality in the control board that controls the abnormality detection sensor or the parts. Therefore, it takes time to identify the abnormal part when an abnormality is detected, and the downtime of the image forming apparatus increases. In addition, unnecessary part replacement may increase the running cost. Patent Document 2 discloses an apparatus that detects abnormalities by changing the detection method of the drive current of a motor that drives a drive mechanism according to the drive conditions. This apparatus detects abnormalities in parts without using sensors or the like. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2007-309980 A [Patent Document 2] JP 2014-176273 A Summary of the Invention [Problem to be solved by the invention]

[0007] In order to reduce the increase in running costs due to unnecessary part replacement and the downtime of the device when an abnormality occurs, it is necessary to accurately predict the lifespan of the parts and identify the abnormal part of the parts. If both the configuration of Patent Document 1 and the configuration of Patent Document 2 are adopted for this purpose, the circuit scale becomes large and the initial cost increases. Furthermore, with the configuration of Patent Document 2, it is difficult to identify abnormalities such as breaks in the windings of the motor itself.

[0008] In view of the above-mentioned problems, a main object of the present invention is to provide a drive device that can accurately predict the life span of a drive source and drive components and identify abnormal locations. [Means for solving the problem]

[0009] The drive device of the present invention comprises a drive source having a plurality of windings, a plurality of drive components for transmitting a drive force output from the drive source to a load, a current detection means for detecting a drive current flowing through the windings, and a control means for determining the lifespan and the presence or absence of an abnormality of the drive source and the plurality of drive components based on the drive current, wherein the current detection means detects a first drive current flowing through a first winding using a first low-pass filter having a first cutoff frequency, and detects a second drive current flowing through a second winding using a second low-pass filter having a second cutoff frequency higher than the first cutoff frequency, and the control means determines the lifespan of the drive source based on the first drive current, the control means determines the presence or absence of an abnormality of the drive source based on the first drive current and the second drive current, and determines the presence or absence of an abnormality of the drive components based on the second drive current.

[0010] The image forming apparatus of the present invention comprises an image forming means for forming an image on paper, a load used in image formation, and a driving means for driving the load, wherein the driving means comprises a driving source having a plurality of windings, a plurality of driving components for transmitting a driving force output from the driving source to the load, a current detection means for detecting a driving current flowing through the windings, and a control means for determining the life and presence or absence of an abnormality of the driving source and the plurality of driving components based on the driving current, wherein the current detection means detects a first driving current flowing through a first winding by a first low-pass filter having a first cutoff frequency, and detects a second driving current flowing through a second winding by a second low-pass filter having a second cutoff frequency higher than the first cutoff frequency, and the control means determines the life of the driving source based on the first driving current, the control means determines the presence or absence of an abnormality of the driving source based on the first driving current and the second driving current, and determines the presence or absence of an abnormality of the driving components based on the second driving current. Effect of the Invention

[0011] According to the present invention, it is possible to accurately predict the life span of a motor and driving components and identify abnormal locations. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing the configuration of an image forming system. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] FIG. 4 is a specific circuit configuration diagram of a drive control unit and a current detection unit. [Diagram 5] 1 is a diagram illustrating voltage values ​​of voltages VA and VB. [Figure 6] 4 is a flowchart showing a life prediction process and an abnormality detection process. [Figure 7] FIG. 4 is a diagram illustrating the relationship between the driving torque and driving current of a stepping motor. [Figure 8] 11 is a flowchart showing a life prediction process. [Figure 9]FIG. 4 is a waveform diagram of the drive current IB and voltage VB when the drive torque increases. [Figure 10] FIG. 4 is a waveform diagram of the drive current IB and voltage VB when the drive torque is reduced. [Figure 11] 13 is a flowchart showing an abnormality detection process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The configurations and circuits of the devices described in the present embodiment are examples for explaining the proposed contents, and the present invention is not limited to the described contents.

[0014] 1 is a configuration diagram of an image forming system according to the present embodiment. The image forming system 1000 includes an image forming apparatus 10 including a drive device according to the present embodiment, a sheet processing apparatus 500, a reader 200, an original feeding device 100, and an operation unit 400. The image forming apparatus 10 according to the present embodiment is configured to form monochrome images, but the drive device according to the present embodiment can also be adopted in a configuration to form color images.

[0015] Reader 200 is an original reading device that reads an image from an original on which the image is formed. Reader 200 generates a video signal based on the read image and transmits it to image forming apparatus 10. Reader 200 can read an image from an original placed on an original table (not shown), and can also read an image from an original fed from original feeder 100. Original feeder 100 can transport multiple originals continuously to a position where the originals are read by reader 200.

[0016] The operation unit 400 is a user interface having an input interface and an output interface. The input interface is, for example, various key buttons, a touch panel, etc. The output interface is, for example, a display, a speaker, etc. A user can input instructions, various settings, etc. through the input interface of the operation unit 400. A user can check the status of the image forming system 1000 and various notifications, etc. through the output interface of the operation unit 400. Notifications include, for example, notifications to encourage replacement of parts that have reached the end of their life or that require replacement due to the occurrence of an abnormality.

[0017] The image forming apparatus 10 includes an exposure control unit 110, a photosensitive drum 111, a developing unit 113, a transfer unit 116, and a fixing unit 117 as an image forming unit 11 for paper. The image forming apparatus 10 also includes paper feed cassettes 114 and 115 and a manual feed tray 125 for storing paper on which an image is to be printed. Paper is fed one sheet at a time from either the paper feed cassettes 114, 115 or the manual feed tray 125.

[0018] The exposure control unit 110 modulates and outputs a laser beam based on a video signal acquired from an external device such as the reader 200. The exposure control unit 110 has a rotating polygon mirror 110a, and the laser beam is reflected by the rotating polygon mirror 110a to irradiate the photosensitive drum 111. The laser beam scans the photosensitive drum 111 in one direction by changing the reflection angle due to the rotation of the rotating polygon mirror 110a.

[0019] The photosensitive drum 111 is a drum-shaped photoconductor having a charged layer on its surface. The photosensitive drum 111 is scanned by a laser beam while rotating around the drum axis, with the surface being uniformly charged. An electrostatic latent image corresponding to a video signal is formed on the surface of the photosensitive drum 111 by the scanning of the laser beam. The developing device 113 contains a developer, and develops the electrostatic latent image formed on the photosensitive drum 111 with the developer. By developing the electrostatic latent image, a developer image is formed on the surface of the photosensitive drum 111. The photosensitive drum 111 conveys the developer image to a transfer unit 116 by rotating.

[0020] Depending on the timing at which the developer image is formed on the photosensitive drum 111, the paper is fed from either the paper feed cassettes 114, 115 or the manual feed tray 125, and is transported to a nip portion formed by the photosensitive drum 111 and the transfer unit 116. The transfer unit 116 transfers the developer image carried on the photosensitive drum 111 to the transported paper. The paper to which the developer image has been transferred is transported to a fixing unit 117. The fixing unit 117 heats, melts and pressurizes the developer image to fix the developer image to the paper. In this manner, an image is printed on the paper.

[0021] Discharge rollers 118, a flapper 121, and an inversion path 122 are provided downstream of the fixing unit 117 in the paper transport direction. A double-sided transport path 124 is connected to the inversion path 122. The flapper 121 transports the paper on which an image has been printed to either the discharge rollers 118 or the inversion path 122. In the case of single-sided printing, or in the case of double-sided printing in which images are printed on both sides, the paper is transported to the sheet processing device 500 by the discharge rollers 118.

[0022] When double-sided printing is performed, a sheet of paper with an image printed on one side (first side) is transported to double-sided conveying path 124 via inversion path 122. When the sheet of paper is transported to double-sided conveying path 124 via inversion path 122, the side on which the image is printed is inverted. The sheet of paper is transported to transfer unit 116 via double-sided conveying path 124, and an image is printed on the other side (second side) by the same process as for the first side.

[0023] The sheet processing apparatus 500 can perform various post-processing operations on the paper on which an image has been printed. The post-processing operations include, for example, bookbinding and stapling. The sheet processing apparatus 500 ejects the paper after the post-processing operations to the outside of the apparatus. The sheet processing apparatus 500 can also eject the paper as is without performing post-processing operations on the paper.

[0024] (Drive unit) The image forming apparatus 10 includes a drive device for controlling the transport of paper and the rotation of the photosensitive drum 111. The drive device includes a drive source and drive components for transmitting the driving force output from the drive source to a rotating body (load) such as a transport roller that transports paper and the photosensitive drum 111. Here, the drive device that drives the transport roller that transports paper will be described. Figure 2 is a configuration diagram of such a drive device.

[0025] The driving device 300 of this embodiment uses a stepping motor 130 as a driving source, and rotates and drives a transport roller 135, which is a rotating body (load). The transport roller 135 transports paper. The stepping motor 130 is press-fitted into a pulley 131. The pulley 131 is connected via a belt 133 to a transport roller shaft 134, which serves as a drive shaft for the transport roller 135. The pulley 131, the belt 133, the transport roller shaft 134, and gears (not shown) are driving parts.

[0026] Rotation of the stepping motor 130 rotates a belt 133 connected to a pulley 131. The belt 133 rotates to transmit a driving force to a conveying roller shaft 134, causing the conveying roller shaft 134 to rotate. The rotation of the conveying roller shaft 134 rotates a conveying roller 135 to convey the paper. A plurality of such conveying rollers 135 are provided on a conveying path from the paper feed cassettes 114, 115 and the manual feed tray 125 to the paper being discharged outside the image forming apparatus 10.

[0027] For this purpose, a plurality of drive devices 300 are provided in the image forming apparatus 10. Also, a configuration in which a single drive device 300 drives and controls a plurality of loads may be used. For example, it may be better for two transport rollers arranged adjacent to each other on a transport path to operate synchronously when transporting paper. In such a case, a single drive device 300 drives and controls the two adjacent transport rollers. Also, when a plurality of photosensitive drums are provided in the image forming apparatus 10, such as when forming a color image, the rotation of two or more photosensitive drums may be driven and controlled by a single drive device 300.

[0028] 3 is a configuration diagram of a control device that drives and controls the stepping motor 130. This control device is capable of communicating with a main control device that controls the overall operation of the image forming apparatus 10, and controls the drive of the stepping motor 130 according to instructions from the main control device. The control device may be provided within the drive device 300, or may be provided independently of the drive device 300.

[0029] The control device includes a CPU (Central Processing Unit) 150, a memory 151, an ASIC (Application Specific Integrated Circuit) 140, a drive control unit 141, and a current detection unit 152. The CPU 150 executes a predetermined computer program to control the drive of the stepping motor 130. The ASIC 140 is a dedicated semiconductor device for controlling the drive of the stepping motor 130. The memory 151 stores a conversion formula and a conversion table for acquiring a current value (drive current value) of a drive current flowing through the stepping motor 130. In this embodiment, the ASIC 140 and the CPU 150 are described separately, but they may be configured as an integrated control unit. In other words, the control device may be equipped with a control unit capable of executing both the processing of the ASIC 140 and the processing of the CPU 150 instead of the ASIC 140 and the CPU 150.

[0030] The CPU 150 transmits drive conditions and a drive start command for the stepping motor 130 to the ASIC 140. The drive conditions include the drive speed (rotation speed) and rotation direction of the stepping motor 130. The ASIC 140 generates a drive control signal for the stepping motor 130 based on the drive conditions and drive start command acquired from the CPU 150. The ASIC 140 transmits the generated drive control signal to the drive control unit 141. The drive control unit 141 supplies a drive current to the stepping motor 130 based on the drive control signal. The stepping motor 130 is driven by the flow of the drive current.

[0031] The current detection unit 152 detects the drive current flowing through the stepping motor 130, converts it to a voltage, and generates a detection signal by amplifying and smoothing the converted voltage. The current detection unit 152 transmits the generated detection signal to the ASIC 140. The ASIC 140 includes an A / D converter and a memory area (not shown). The ASIC 140 A / D converts the detection signal acquired from the current detection unit 152 using the A / D converter, and stores the conversion result in the memory area as current detection data.

[0032] The CPU 150 acquires the current detection data from the ASIC 140 at a predetermined timing, and converts the current detection data into a drive current value using a conversion formula and a conversion table stored in the memory 151. The CPU 150 calculates the life span of the stepping motor 130 and drive components and detects abnormal states, etc., based on the drive current value, as will be described later.

[0033] 4 is a specific circuit configuration diagram of the drive control unit 141 and the current detection unit 152. The stepping motor 130 of this embodiment is a two-phase stepping motor having two pairs of windings, phase A and phase B. Note that the stepping motor 130 may be a multi-phase motor having multiple windings.

[0034] The drive control unit 141 includes H-bridge driving units 143 and 144 for controlling the currents of the A phase and the B phase, a control unit 142, and shunt resistors 148 and 149. The control unit 142 controls the H-bridge driving units 143 and 144 in response to a drive control signal acquired from the ASIC 140. The H-bridge driving unit 143 controls the current to the A phase of the stepping motor 130. The H-bridge driving unit 144 controls the current to the B phase of the stepping motor 130. The shunt resistor 148 is used to detect the current value of the driving current flowing through the A phase of the stepping motor 130. The shunt resistor 149 is used to detect the current value of the driving current flowing through the B phase of the stepping motor 130.

[0035] The current detection unit 152 includes an A-phase current detection unit 146 that amplifies and smoothes the voltage generated by the shunt resistor 148, and a B-phase current detection unit 147 that amplifies and smoothes the voltage generated by the shunt resistor 149. The A-phase current detection unit 146 transmits a voltage VA generated by amplifying and smoothing the voltage of the shunt resistor 148 to the ASIC 140 as a detection signal. The B-phase current detection unit 147 transmits a voltage VB generated by amplifying and smoothing the voltage of the shunt resistor 149 to the ASIC 140 as a detection signal.

[0036] The A-phase current detection unit 146 is a non-inverting amplifier circuit equipped with a low pass filter (hereinafter referred to as "LPF: Low Pass Filter") using an operational amplifier OPA. The cutoff frequency fA of the LPF is determined by the resistance value of resistor RA4 and the capacitance value of capacitor CA1. The A-phase current detection unit 146 converts the drive current IA flowing through the A-phase into a voltage VA using the following conversion formula, amplifies it, and smoothes it at the cutoff frequency fA. "RSA" is the resistance value of the shunt resistor 148. "RA3" is the resistance value of resistor RA3. "RA4" is the resistance value of resistor RA4. "CA1" is the capacitance value of capacitor CA1. VA = (IA x RSA) x (1 + RA4 / RA3) fA = 1 / (2π × RA4 × CA1)

[0037] The drive current IA when the stepping motor 130 is driven contains high-frequency components. Therefore, it is preferable that the resistance value of the resistor RA4 and the capacitance value of the capacitor CA1 are constants that can filter out the high-frequency components and sufficiently smooth the drive current IA. Specifically, the resistance value of the resistor RA4 and the capacitance value of the capacitor CA1 are set so that the cutoff frequency fA is a frequency that is 10 to 20 times higher than the drive frequency of the stepping motor 130.

[0038] Similarly, the B-phase current detection unit 147 is a non-inverting amplifier circuit equipped with an LPF using an operational amplifier OPB. The cutoff frequency fB of the LPF is determined by the resistance value of resistor RB4 and the capacitance value of capacitor CB1. The B-phase current detection unit 147 converts the drive current IB flowing through the B-phase into a voltage VB using the following conversion formula, amplifies it, and smoothes it at the cutoff frequency fB. "RSB" is the resistance value of the shunt resistor 149. "RB3" is the resistance value of resistor RB3. "RB4" is the resistance value of resistor RB4. "CB1" is the capacitance value of capacitor CB1. VB = (IB × RSB) × (1 + RB4 / RB3) fB=1 / (2π×RB4×CB1)

[0039] The resistance value of resistor RB4 and the capacitance value of capacitor CB1 are set so that cutoff frequency fB is higher than cutoff frequency fA (fB>fA). Specifically, the resistance value of resistor RB4 and the capacitance value of capacitor CB1 are set so that cutoff frequency fB is about 1 / 3 to 1 / 10 of the drive frequency of stepping motor 130. Setting these values ​​makes it possible to filter out sudden changes in the drive current.

[0040] 5 is a diagram illustrating the voltage values ​​of the detection signals (voltages VA, VB) when driving the stepping motor 130. Here, the voltage values ​​of the voltages VA and VB are illustrated when the drive currents IA and IB based on a drive clock of four pulses are smoothed and amplified at cutoff frequencies fA and fB that are 10 times and 1 / 4 the drive frequency, respectively.

[0041] The drive currents IA and IB detected by the current detection unit 152 fluctuate at high frequency within one drive clock pulse period. For this reason, if the drive currents IA and IB are converted into voltages without smoothing, completely different current values ​​will be detected depending on the sampling point, making accurate voltage conversion difficult.

[0042] However, as shown in Figure 5, the voltage VA is converted to a constant voltage value regardless of the timing of sampling because the high frequency components of the drive current IA are smoothed at the cutoff frequency fA. Also, the voltage VB smooths the drive current IB at a cutoff frequency fB that is higher than the voltage VA. Therefore, although the high frequency components of the drive current IB within one drive clock pulse period are roughly smoothed, it is more responsive to changes in the drive current IB than the voltage VA.

[0043] For example, the current values ​​of the drive current in each drive clock period of the four drive clock pulses in Fig. 5 are detected as approximately the same current value when sampling the voltage VA. However, when sampling the voltage VB, it is easily determined that the current value of the fourth pulse is larger than the first, second, and third pulses.

[0044] 6 is a flowchart showing the life prediction process and abnormality detection process for each driving part of the driving device 300 configured as described above. This process is executed when the user inputs an instruction to execute a print job through the operation unit 400.

[0045] The image forming apparatus 10 starts a print job in response to an instruction to execute the print job (S300). The image forming apparatus 10 first performs a warm-up process for each component (S301). In the warm-up process, the driving device 300 drives the motor, controls the sensors, adjusts the various components, and so on. During the warm-up process, the image forming apparatus 10 instructs the driving device 300 to perform a life prediction process for the stepping motor 130 and the driving components (S302). The life prediction process for the stepping motor 130 and the driving components will be described in detail later.

[0046] When the warm-up process is completed, the image forming device 10 prints an image on paper in accordance with the print job (S303). If the warm-up process or the print process is completed normally without causing a jam, error, alarm, or the like (S304: Y), the image forming device 10 ends the operation of the print job.

[0047] If a jam, error, alarm, or the like occurs during the warm-up process or printing operation and the operation ends abnormally (S304: N), the image forming apparatus 10 judges whether the abnormality is within the scope of the abnormality diagnosis (S305). If the abnormality is not within the scope of the abnormality diagnosis (S305: N), the image forming apparatus 10 issues an error according to the nature of the abnormality and ends the process (S307). The image forming apparatus 10 issues an error by notifying the error via the operation unit 400, for example. If the image forming apparatus 10 is capable of communicating with an external device via a network, the image forming apparatus 10 may notify the external device of the nature of the abnormality.

[0048] If the abnormal part is to be diagnosed (S305: Y), the image forming apparatus 10 instructs the driving device 300 to perform abnormality detection processing on the stepping motor 130 and the driving parts (S306). Details of the abnormal state detection processing will be described later. When the abnormal state detection processing is completed, the image forming apparatus 10 notifies the abnormal state detection result and ends the processing (S308). The image forming apparatus 10 notifies the detection result, for example, by the operation unit 400. If the image forming apparatus 10 is capable of communicating with an external device via a network, the image forming apparatus 10 may notify the external device of the detection result.

[0049] (Life expectancy prediction) The process of predicting the life span of the stepping motor 130 and the driving parts in S302 will be described below. Here, the process of predicting the life span of the stepping motor 130 will be described.

[0050] 7 is an example diagram showing the relationship between the driving torque and driving current of the stepping motor 130. In general, as the accumulated value of the time that the driving device 300 has been driven (accumulated driving time) increases, the driving torque of the stepping motor 130 increases due to wear of the pulley 131 and the belt 133, etc. When the driving torque exceeds the upper limit of the torque that the stepping motor 130 can output, the stepping motor 130 loses synchronization and cannot operate normally.

[0051] A conversion table, a conversion formula, etc. showing the relationship between the drive torque and the drive current shown in FIG. 7 are stored in advance in the memory 151. The CPU 150 that controls the stepping motor 130 can derive the drive torque from the drive current using the conversion table or the conversion formula. As described above, the drive current is calculated from the sampled value of the voltage VA. The ASIC 140 derives the drive current from the voltage VA acquired as appropriate. The CPU 150 can detect the current drive torque of the stepping motor 130 based on the drive current derived by the ASIC 140. The CPU 150 can detect the life of the stepping motor 130 based on the detected drive torque. The life of driving parts can also be detected in a similar manner.

[0052] 8 is a flowchart showing a life prediction process. Here, the life prediction is performed for the stepping motor 130. The life prediction is performed using the voltage VA calculated by the A-phase current detection unit 146, which is less affected by high-frequency noise.

[0053] The ASIC 140 samples the voltage VA at a predetermined timing when the stepping motor 130 moves at a constant speed, such as at the start of a print job (S100). The ASIC 140 averages the acquired voltages VA to acquire an average VA value (S101). The ASIC 140 calculates the drive current IA (detected current data) of the stepping motor 130 from the average VA value using a conversion formula prepared in advance (S102). The CPU 150 derives the drive torque of the stepping motor 130 according to the drive current IA calculated by the ASIC 140, using the conversion table and conversion formula described in FIG. 7 (S103).

[0054] The CPU 150 judges whether the derived drive torque is equal to or less than a prescribed value of the drive torque that is the life limit of the stepping motor 130 (S104). If the derived drive torque is equal to or less than the prescribed value (S104: Y), the CPU 150 judges that the derived drive torque is within a normal range (S105). In this case, the CPU 150 judges that the stepping motor 130 has not reached the end of its component life.

[0055] If the derived drive torque is greater than the specified value (S104: N), the CPU 150 determines that the stepping motor 130 has reached the end of its component life (S106). Because the stepping motor 130 has reached the end of its component life, the CPU 150 issues a notification of component replacement via the operation unit 400. As described above, the voltage VA detected by the A-phase current detection unit 146 is used to predict the lifetime of the stepping motor 130 and the drive components.

[0056] (Abnormal condition detection) The process of detecting an abnormal state in S306 will now be described. Here, the process of detecting an abnormal state of the stepping motor 130 will be described.

[0057] 9 is a waveform diagram of the driving current IB and the voltage VB when the driving torque of the stepping motor 130 increases instantaneously. For example, if a foreign object or the like adheres to any of the multiple driving components that transmit the driving force output from the stepping motor 130 to the conveying roller 135, an abnormality occurs in the combination of the pulley 131. In this case, the driving torque of the stepping motor 130 increases instantaneously at the timing of the combination of the pulley 131. The instantaneous increase in the driving torque increases the driving current IB. The increase in the driving current IB also increases the voltage VB generated by converting and smoothing the driving current IB.

[0058] If a foreign object adheres to a location of a driving part that transmits the driving force output from stepping motor 130 to conveyor roller 135, the driving torque increases instantaneously just once during one rotation period of pulley 131 due to the influence of the adhered foreign object. By detecting the fluctuation period of such driving torque, if the fluctuation period coincides with one rotation period of pulley 131, it is determined that some abnormality exists in pulley 131.

[0059] The fluctuation period of the driving torque is calculated by integrating the voltage VB during one pulse period of the driving clock of the stepping motor 130, for example, as shown in Fig. 9. The period of the driving clock generation timing at which the integral value of the voltage VB falls outside a preset range is the fluctuation period of the driving torque. Whether or not the fluctuation period of the driving torque matches the one rotation period of the pulley 131 can be determined by referring to a period table specific to the driving component that is prepared in advance.

[0060] 10 is a waveform diagram of the driving current IB and the voltage VB when the driving torque of the stepping motor 130 is momentarily reduced. For example, when any of the multiple driving parts that transmit the driving force output from the stepping motor 130 to the conveying roller 135 is damaged, the driving torque of the stepping motor 130 is reduced by the parts rotating freely when meshed. The reduction in driving torque reduces the driving current IB. The reduction in driving current IB reduces the voltage VB generated by converting and smoothing the driving current IB. When the driving part is damaged in one place, the driving torque is reduced momentarily only once per one rotation period of the belt 133.

[0061] The fluctuation period of the driving torque is detected in the same manner as above, and if the fluctuation period coincides with one rotation period of the belt 133, it is determined that there is some abnormality in the belt 133. Whether or not the fluctuation period coincides with one rotation period of the belt 133 can be determined by referring to a part-specific period table prepared in advance.

[0062] Incidentally, when the driving torque of the stepping motor 130 changes instantaneously, the driving current IA does not change. This is because the cut-off frequency fA of the A-phase current detection unit 146 is set to a frequency lower than the cut-off frequency fB of the B-phase current detection unit 147. In the A-phase current detection unit 146, instantaneous fluctuations in the driving current IA and the voltage VA are smoothed. Therefore, the voltage VA detected by the A-phase current detection unit 146 is not used for determining abnormalities in the driving components. Incidentally, when the relationship between the cut-off frequency fA of the A-phase current detection unit 146 and the cut-off frequency fB of the B-phase current detection unit 147 is reversed (fB < fA), the voltage VA detected by the A-phase current detection unit 146 is used for determining abnormalities in the driving components. In this case, the voltage VB detected by the B-phase current detection unit 147 will be used for life prediction.

[0063] In addition, damage such as a broken wire or abnormal resistance value may occur in the stepping motor 130 itself. In this case, the driving current when the stepping motor 130 is driven becomes an abnormal value that is always larger or smaller than the normal value, rather than instantaneously. The driving currents IA and IB of the A-phase and B-phase of the stepping motor 130 can be calculated from the voltages VA and VB, respectively. When at least one of the current values of the driving currents IA and IB is outside the specified range and the current value outside the specified range is continuously detected, it can be determined that an abnormality has occurred in the stepping motor 130.

[0064] Figure 11 is a flowchart showing the abnormal detection process of the driving components.

[0065] The CPU 150 drives the stepping motor 130 of the drive device 300. The ASIC 140 samples the voltage VA at a predetermined timing when the stepping motor 130 is moving at a constant speed (S200). The ASIC 140 performs an averaging process on the acquired plurality of voltages VA to obtain an average value of VA (S201). The ASIC 140 calculates the driving current IA of the stepping motor 130 using a conversion formula prepared in advance from the average value of VA (S202).

[0066] The CPU 150 judges whether the drive current IA calculated by the ASIC 140 is within a specified range (S203). If the drive current IA is outside the specified range (S203: N), the CPU 150 judges that a winding abnormality has occurred in the A phase of the stepping motor 130 (S204). The CPU 150 notifies the operation unit 400 that a part replacement is necessary due to the occurrence of a winding abnormality in the A phase of the stepping motor 130.

[0067] If the drive current IA is within the specified range (S203: Y), the ASIC 140 samples the voltage VB at a predetermined timing when the stepping motor 130 moves at a constant speed (S205). The ASIC 140 averages the acquired voltages VB to obtain the VB average value (S206). The ASIC 140 calculates the drive current IB of the stepping motor 130 from the VB average value using a conversion formula prepared in advance (S207).

[0068] The CPU 150 judges whether the drive current IB calculated by the ASIC 140 is within a specified range (S208). The specified range in this case may be the same as the specified range in the process of S203. If the drive current IB is outside the specified range (S208:N), the CPU 150 judges that a winding abnormality has occurred in the B phase of the stepping motor 130 (S204). The CPU 150 notifies the operation unit 400 that a winding abnormality has occurred in the B phase of the stepping motor 130 and that part replacement is necessary. In this way, the presence or absence of an abnormality in the stepping motor 130 itself is judged.

[0069] If the drive current IB is within the specified range (S208:Y), the CPU 150 judges whether or not there is an abnormality in drive parts other than the stepping motor 130. First, the CPU 150 samples the voltage VB at a sampling period that is sufficiently faster than the period of the drive clock while the stepping motor 130 is moving at a constant speed by the ASIC 140 (S209). The CPU 150 integrates the acquired voltage VB within one pulse period of the drive clock (S210). The CPU 150 and the ASIC 140 repeatedly sample the voltage VB and integrate the voltage VB until a predetermined number of clocks are completed (S211:N). Here, the predetermined number of clocks is a clock number that can rotate drive parts such as the pulley 131 and the belt 133 driven by the stepping motor 130 at least a predetermined number of times.

[0070] When the calculation of the integral values ​​for the predetermined number of clocks is completed (S211: Y), CPU 150 judges whether or not each of the calculated integral values ​​for the predetermined number of clocks is within a specified range (S212). The specified range in this case is different from the specified range in the processing of S203 and S208. If all the integral values ​​are within the specified range (S212: N), CPU 150 judges that there is no abnormality in stepping motor 130 and all of the multiple driving parts that transmit the driving force output from stepping motor 130 to conveyor roller 135 (S218).

[0071] If at least one integral value falls outside the specified range (S212: Y), CPU 150 calculates the generation period of the clock that calculated the integral value (S213). CPU 150 compares the calculated generation period of the clock with a rotation period table of each driving component that has been prepared in advance (S214).

[0072] If there is a rotation period that matches the generation period of the clock (S215: Y), the CPU 150 determines that an abnormality has occurred in the driving part with the matching rotation period (S216). The CPU 150 notifies the operation unit 400 that the driving part determined to have an abnormality needs to be replaced.

[0073] If there is no rotation period that matches the generation period of the clock (S215: N), the CPU 150 determines that an abnormality has occurred in either the stepping motor 130 or the driving parts, or in two or more driving parts (S217). The CPU 150 notifies the operation unit 400 that the stepping motor 130 and / or the driving parts in which the abnormality has occurred, or in two or more driving parts, need to be replaced.

[0074] As described above, the drive device 300 can predict the life span of the drive source and drive components in the drive device 300 and determine whether or not an abnormality has occurred, using the current detection unit 152, ASIC 140, and CPU 150. The drive device 300 can detect the life span of the drive components and stepping motor 130 with a minimum configuration. Furthermore, the drive device 300 can identify the component in which the abnormality has occurred when an abnormality occurs.

Claims

1. A drive source having a first winding and a second winding; a plurality of driving components for transmitting the driving force output from the driving source to a load; a first current detection means for detecting a first drive current flowing through the first winding using a first low-pass filter having a first cutoff frequency; a second current detection means for detecting a second drive current flowing through the second winding using a second low-pass filter having a second cutoff frequency higher than the first cutoff frequency; and a control means for determining whether the drive source has reached the end of its life based on the first drive current, determining whether there is an abnormality in the drive source based on the first drive current and the second drive current, and determining whether there is an abnormality in the drive components based on the second drive current. Drive unit.

2. The control means derives a drive torque from the first drive current and determines the life of the drive source based on the drive torque. The drive device according to claim 1.

3. The control means determines that the drive source has reached the end of its life when the derived drive torque is greater than a specified value of drive torque that is the life limit of the drive source. The drive device according to claim 2.

4. The control means determines that the drive source is abnormal when at least one of the first drive current and the second drive current is outside a specified range. The drive device according to claim 1.

5. the control means samples and integrates the second drive current for a predetermined period, and if the integrated value is within a specified range, does not determine that there is an abnormality in the drive source and the plurality of drive components. The drive device according to claim 1.

6. The control means determines which driving part has an abnormality based on the occurrence cycle of a period in which the integrated value falls outside the specified range. The drive device according to claim 5.

7. The control means determines that a driving part having a rotation cycle that matches the occurrence cycle is a driving part in which an abnormality has occurred. The drive device according to claim 6.

8. The control means determines that an abnormality has occurred in either the drive source or the plurality of drive parts when there is no drive part having a rotation cycle that matches the generation cycle. The drive device according to claim 6.

9. The drive source is a stepping motor. The drive device according to any one of claims 1 to 8.

10. the first cutoff frequency is 10 to 20 times higher than the driving frequency of the stepping motor; The second cutoff frequency is 1 / 3 to 1 / 10 of the drive frequency of the stepping motor. The drive device according to claim 9.

11. an image forming means for forming an image on a sheet; a load used in image formation; and the drive device according to any one of claims 1 to 10, The driving device drives the load. Image forming device.

Images