Patent Application
20190265624
The entire disclosure of Japanese patent Application No. 2018-033241, filed on Feb. 27, 2018, is incorporated herein by reference in its entirety.
The present invention relates to an image forming apparatus.
An image forming apparatus such as a printer, copying machine, or multifunction machine includes various rotating bodies such as rollers for conveying sheets, and motors that drive these rotating bodies. In this type of image forming apparatus, it is known that a state of a rotating body is determined by measuring torque generated by a motor.
JP 2014-2233 A discloses that, in an electrophotographic image forming apparatus, an image is formed plural times by changing temperature of a photoconductor, and torque of a motor that drives the photoconductor is measured by a torque sensor at that time, and a degradation state of the photoconductor is determined on the basis of a change in torque.
JP 2011-102853 A discloses that, in a multifunction machine including an automatic document conveying apparatus, torque of a motor that drives a document conveying roller is detected on the basis of a motor current supplied to the motor, and on the basis of the torque detected, it is determined whether or not a loose-leaf document is being conveyed.
On the other hand, as a prior art for suppressing temperature rise of a motor accompanying rotational driving, there are techniques described in JP 2007-62250 A and JP H9-138531 A. JP 2007-62250 A discloses that, to prevent overheating of a motor during continuous printing, temperature of the motor is predicted on the basis of the number of fed sheets, and a conveying speed of the sheet is changed depending on the predicted temperature. JP 2011-102853 A discloses that, a motor is provided with a temperature sensor, and a rotational speed of the motor is lowered when temperature detected by the temperature sensor is equal to or higher than a threshold value.
When the torque sensor is used for measurement of the torque as in the technique of the above-described JP 2014-2233 A, it is necessary to secure a space for arranging the torque sensor, so that problems occur that downsizing of the image forming apparatus is difficult and cost of components is increased.
Such problems can be solved by measuring the motor current as torque as in the technique of JP 2011-102853 A.
However, since the torque of the motor depends on the temperature, there has been a problem that an error occurs in the measurement of the torque depending on the temperature at the time of measurement, so that the state of the rotating body may be erroneously determined. The techniques of JP 2007-62250 A and JP H9-138531 A prevent excessive temperature rise of the motor but do not keep the temperature constant, so that this problem cannot be solved.
The present invention has been made in view of the above-described problems, and it is an object to provide an image forming apparatus capable of accurately determining a state of a rotating body driven by a motor more than before without using a torque sensor.
To achieve the abovementioned object, according to an aspect of the present invention, an image forming apparatus that forms an image on a sheet, reflecting one aspect of the present invention comprises: a rotating body that forms the image; a motor that rotationally drives the rotating body; a current measurer that measures a motor current flowing through a current supply path including a winding of the motor at a measurement timing that is a timing after the motor is started; a torque acquisitor that acquires a torque value of the motor, based on a measured value of the motor current; and a corrector that performs correction to cancel a current change amount based on a characteristic change depending on a temperature state of the motor at the measurement timing, in acquisition of the torque value by the torque acquisitor.
The advantages and features provided by one or more embodiments of the invention will become more fully understood from the detailed description given hereinbelow and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention:
Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments.
In
The printer engine 1A includes four imaging stations 4y, 4m, 4c and 4k arranged in the horizontal direction. Each of the imaging stations 4y to 4k includes a photoconductor 5 having a cylindrical shape, a charging roller 6, a print head 7, a developing device 8, a cleaner 9 of a blade-type, and the like.
In a color printing mode, the four imaging stations 4y to 4k form toner images of four colors of yellow (Y), magenta (M), cyan (C), and black (K), respectively in parallel. The four color toner images are primarily transferred sequentially to an intermediate transfer belt 15 being rotated. First, the toner image of Y is transferred, and the toner image of M, the toner image of C, and the toner image of K are sequentially transferred to overlap with the toner image of Y.
When the toner image primarily transferred faces a secondary transfer roller 14, the toner image is secondarily transferred to a sheet (recording sheet) 2 taken out and conveyed from a storage cassette 1B below. After the secondary transfer, the toner image is fed to a sheet ejection tray 19 above through the inside of a fixing device 16. When passing through the fixing device 16, the toner image is fixed to the sheet 2 by heating and pressing.
Referring to
The image forming apparatus 1 includes the plurality of motors 3a, 3b, and 3c that are rotational driving sources. The motor 3a is mainly used as a photoconductor motor that drives the photoconductor 5 of the imaging station 4k. The motor 3b is a driving source common to the pickup roller 11, the sheet feeding roller 12, the registration roller 13, the secondary transfer roller 14, and the intermediate transfer belt 15. The motor 3c is a driving source common to the fixing roller 17 and the sheet ejection rollers 18A and 18B.
Rotational driving force of the motor 3b is transmitted to the pickup roller 11 and the sheet feeding roller 12 via a clutch 51, and to the registration roller 13 via a clutch 52. By turning on and off the clutches 51 and 52, control of rotation/stop of these rollers is performed independently of drive control of the secondary transfer roller 14.
Hereinafter, these motors 3a to 3c are sometimes referred to as “motor 3” without distinction.
The image forming apparatus 1 includes a plurality of motors besides the motors 3a to 3c. For example, there are a development motor that drives a roller in the developing device 8 of each of the imaging stations 4y to 4k, and a toner replenishing motor that drives a mechanism that replenishes toner from a toner bottle to the developing device 8.
The motor 3 is a DC brushless motor, that is, a permanent magnet synchronous motor (PMSM) in which a rotor using a permanent magnet rotates. A stator of the motor 3 includes U-phase, V-phase, and W-phase cores arranged at intervals of an electrical angle of 120°, and three windings (coils) connected together, for example, by Y-connection. Three-phase AC currents of U-phase, V-phase, and W-phase are caused to flow through the windings, and the cores are excited in order, whereby a rotating magnetic field is generated. The rotor rotates in synchronization with the rotating magnetic field.
The number of magnetic poles of the rotor may be 2, 4, 6, 8, 10 or more. The rotor may be an outer type or an inner type. In addition, the number of slots of the stator may be 3, 6, 9 or more.
In any case, to the motor 3, vector control is performed that determines a direction and magnitude of magnetic flux of the rotating magnetic field by using a control model based on a d-q coordinate system. In the vector control of the motor 3, the control is simplified by converting the AC currents of three phases flowing through the windings of the motor 3 into DC currents flowing through the windings of two phases rotating in synchronization with the rotor.
The image forming apparatus 1 has a function of measuring (detecting) torque generated by the motor 3 and determining states of various rotating bodies that are driving targets of the motor 3. The state of the rotating body includes a state of aging such as wear, alteration, or dirt, and a contact state with another member, such as sticking or wrapping of a sheet, curling of a blade for cleaning, or the like.
Hereinafter, the configuration and operation of the image forming apparatus 1 will be described focusing on this function.
As the motor 3, a motor unit 30 can be used that is integrated with an electric circuit 31 for driving the motor 3 and is commercially available. In the motor unit 30, supply of driving power to the motor 3 and input of a control signal are performed via a connector 32 fixed to a circuit board 30A including the electric circuit 31. The electric circuit 31 includes an inverter that drives the motor 3, an integrated circuit component for the vector control, and the like.
To the motor unit 30, a drive current Im is supplied from a power supply circuit 60 that outputs power of a voltage (for example, 24 volts) for driving. The drive current Im is an example of a motor current flowing through a current supply path 63 including the inverter in the electric circuit 31 and a winding group 3C in the motor 3.
To the motor unit 30, a control signal S3 indicating commands such as start, stop, a target speed, and the like is input from the control circuit 20. The electric circuit 31 controls driving of the motor 3 by the inverter in accordance with a command by the control signal S3.
The control circuit 20 includes a motor control command device 210, a current measurer 211, a measured value corrector 212, and a state determiner 213. Functions of these devices are implemented by a hardware configuration of the control circuit 20, the control program being executed by a CPU, or a combination thereof.
The motor control command device 210 gives the control signal S3 to each of a plurality of the motor units 30. The rotating bodies driven by the motors 3a to 3c need to rotate at a constant speed in image formation. Specifically, the photoconductor 5 needs to rotate at a constant speed at least from the start of formation of an electrostatic latent image to the end of primary transfer of a toner image, and the intermediate transfer belt 15 needs to rotate at a constant speed at least from the start of the first primary transfer to the end of secondary transfer. In addition, the fixing roller 17 needs to rotate at a constant speed at least in a period during which the sheet 2 passes through the fixing device 16.
For this reason, the motor control command device 210 gives a command of starting of the motor 3 at an appropriate time so that rotation is stabilized by a timing at which the motor 3 should be rotated at a constant speed. An operation pattern applied to the motor 3 is basically an acceleration/deceleration pattern that performs so-called trapezoidal driving. That is, driving is started from a stopped state and accelerated to a target speed, and maintained at the target speed for a predetermined time, and then decelerated and stopped.
However, the target speed is switched depending on a process speed. The process speed is an image forming condition that defines a rotational speed of the photoconductor, a conveying speed of the sheet 2, and the like. For example, when a thick sheet is used as the sheet 2, the process speed is made lower than that in a case where a regular sheet is used. That is, a rotational speed of the motor 3 is lowered. Thus, time for the sheet 2 to pass through the fixing device 16 becomes longer, so that the sheet 2 can be sufficiently heated to improve the fixing property of a toner image.
The current measurer 211 measures the drive current Im flowing from the power supply circuit 60 to the motor unit 30 at a predetermined measurement timing that is a timing after the motor 3 is started. A current detector 250 that detects the drive current Im is provided between the power supply circuit 60 and the motor unit 30 in the current supply path 63 through which the drive current Im flows, and a detection signal SIm by the current detector 250 is input to the current measurer 211. The current measurer 211 quantizes the detection signal SIm and outputs the signal quantized as a measured value DIm of the motor current.
The measured value corrector 212 corrects the measured value DIm to cancel a current change amount based on a characteristic change depending on a temperature state of the motor 3 at the measurement timing. Note that, when the motor 3 is driven, temperature rise occurs, and a temperature rise state at this time is an example of the “temperature state” in the present invention. Correction by the measured value corrector 212 will be described later in detail.
The measured value corrector 212 is provided with a current corrector 212A and a torque conversion device 212B. The current corrector 212A corrects the measured value DIm from the current measurer 211 on the basis of correction information 70. The torque conversion device 212B converts a measured value DAIm corrected by the current corrector 212A into a torque value DT and acquires the torque value DT. That is, the torque conversion device 212B converts the motor current into the torque.
The measured value corrector 212 of the present embodiment converts the corrected measured value DAIm into the torque value DT, but conversely, the measured value corrector 212 may be configured to perform correction to the torque value depending on the temperature rise state, after converting the measured value DIm from the current measurer 211 into the torque value.
The state determiner 213 determines the state of the rotating body driven by the motor 3 on the basis of the torque value DT from the measured value corrector 212. Determination based on the torque value DT is equivalent to determination based on the measured value DAIm.
As illustrated in
R=Rs[1+α1(TC−Ts)]
Rs: Resistance value at reference temperature
Ts: Reference temperature
TC: Temperature of winding
α1: Temperature coefficient
In addition, as illustrated in
When the resistance value R increases, the current flowing through the winding decreases, so that the torque of the motor 3 decreases and the rotational speed decreases. The vector control therefore increases a voltage applied to the winding and increases the drive current Im. Thus, the decrease of the torque is compensated, and the rotational speed is kept at a constant target speed.
As a result of such constant speed rotation control, even when a load of the motor 3 is constant and the torque of the motor 3 is not different from that before the temperature rise of the winding, the drive current Im is larger than before the temperature rise. There is therefore a possibility that an error occurs in the determination if it is assumed that the state of the rotating body is determined by using the measured value DIm of the drive current Im as it is as the measured value of the torque.
In the image forming apparatus 1 of the present embodiment, the measured value DIm is therefore corrected by the measured value corrector 212.
Due to heat generation of the winding group 3C, temperature rise of the permanent magnet also occurs inside the motor 3. When the temperature rise of the permanent magnet occurs, the magnetic flux linkage decreases and the torque decreases. That is, when the temperature rise of the permanent magnet occurs, the drive current Im increases with the vector control that rotates the motor 3 at a constant speed, similarly to a case where the temperature rise of the winding occurs. The measured value corrector 212 corrects the measured value DIm to reduce influence of the characteristic change due to a change of the temperature state such as the temperature rise, such as the resistance value of the winding and the magnetic flux of the permanent magnet.
The correction information 70a is obtained by an experiment in which a drive current Im is measured by applying a predetermined load (for example, 100 mNm) to the motor 3 using an experimental machine having a configuration in which a use condition is similar to that of the motor 3 of the image forming apparatus 1, and indicates the relationship between the current change amount Δ and the elapsed time Y during the experiment for each of a plurality of operation conditions each having a different target speed ω*.
In
When the correction is based on the correction information 70a, the measured value corrector 212 corrects the measured value DIm as follows.
Referring to
Then, a difference between the measured value DIm (y1) taken in for the first time and a reference value (DIm0) stored in advance together with the correction information 70a is calculated as a current change amount Δy1 at the timing y1.
Next, in comparison with data corresponding to the notified target speed ω* in the correction information 70a, the elapsed time Y during the experiment corresponding to the calculated current change amount Δy1, that is, the initial timing y1 is identified.
In the example of
After that, the measured value corrector 212 corrects the measured value DIm to be measured next time and later, assuming that the current change amount Δ changes (in this example, increases) along the curve L from the point P1. The measured value corrector 212 therefore measures the elapsed time Y from the timing y1.
For example, when a measurement timing y2 of the next drive current Im is a timing when a time Y1 has elapsed from the initial timing y1, a point P2 is identified corresponding to the measurement timing y2 in the curve L, and a current change amount Δy2 is obtained corresponding to the point P2 in the current change amount Δ on the vertical axis. Then, the corrected measured value DAIm is calculated by using the following equation.
DAIm=DIm−Δy2
After that, it is only necessary to further perform measurement at the measurement timing after the next measurement timing and correct the measured value DIm similarly.
Unlike during the experiment, the initial starting described above means that the motor 3 has been started not in the reference temperature Ts but in a temperature state higher than the reference temperature Ts. This happens, for example, when a job is started again this time before the motor 3 is cooled in which temperature rise has occurred in the previous job.
That is, in a case where the motor 3 is started in an arbitrary temperature state, the initial measured value DIm (y1) described above is necessary to identify the timing y1 on the horizontal axis of the graph of
In a case where the motor 3 is started at the same temperature state as that of when the correction information 70a illustrated in
Next, another example will be described of the method of correcting the measured value DIm.
As described above, temperature rise of the winding of the motor 3 occurs due to current supply, but the temperature eventually settles to a substantially constant temperature (saturation temperature). As illustrated in the graph on the right side of
The drive current Im0 is therefore measured at the starting and the saturation temperature of the motor 3 is identified. That is, a temperature rise characteristic of the winding of the motor 3 is identified. Thereafter, at the arbitrary measurement timing y3 during rotation, the temperature TC (y3) of a present winding is identified in comparison with the identified temperature rise characteristic.
Then, a change rate β is calculated of the resistance value R between the reference temperature Ts and the present temperature TC (y3) on the basis of a relationship between the temperature TC and the resistance value R in the winding illustrated in
β=(resistance value R at present temperature TC(y3))/(resistance value Rs at reference temperature Ts)
In the case of this example, the measured value corrector 212 calculates the corrected measured value DAIm by using the following equation.
DAIm=DIm×β
Further, there is also a method of using a feedback signal or another signal in the vector control for the correction of the measured value DIm as follows.
The motor 3 is driven by the motor controller 21 and is subjected to sensorless vector control. In this vector control, proportional-integral-derivative control (PID control) is performed that causes a rotational speed (ωm) of the motor 3 to coincide with the target speed ω* by feedback.
The motor controller 21 includes a motor drive unit 26 that supplies power to the motor 3, a current detection unit 27 that detects a current flowing through the motor 3, and a vector control unit 25 that indirectly controls the rotation of the motor 3 by controlling the motor drive unit 26.
The motor drive unit 26 is an inverter circuit for driving a rotor by causing currents to flow through the windings 33 to 35 of the motor 3. The motor drive unit 26 controls the drive current Im flowing from a DC power supply line 60A to a ground line via the windings 33 to 35 by turning on and off a plurality of transistors in accordance with control signals U+, U−, V+, V−, W+, and W− from the vector control unit 25. Specifically, a current Iu flowing through the winding 33 is controlled in accordance with the control signals U+ and U−, a current Iv flowing through the winding 34 is controlled in accordance with the control signals V+ and V−, and a current Iw flowing through the winding 35 is controlled in accordance with the control signals W+ and W−.
The current detection unit 27 detects the currents Iu and Iv respectively flowing through the windings 33 and 34. Since Iu+Iv+Iw=0, the current Iw can be calculated from values of the detected currents Iu and Iv. Note that, a W-phase current detection unit may be provided.
The current detection unit 27 performs A/D conversion of a signal obtained by a voltage drop due to a shunt resistor inserted in a flow path of the currents Iu and Iv, and outputs converted signals as detected values of the currents Iu and Iv. That is, two-shunt type detection is performed. A resistance value of the shunt resistor is a small value of the order of 1/10Ω.
The vector control unit 25 includes a speed control unit 41, a current control unit 42, an output coordinate conversion unit 43, a PWM conversion unit 44, an input coordinate conversion unit 45, and a speed and position estimation unit 46. The target speed (speed command value) ω* is given to the vector control unit 25 from the control circuit 20 by the control signal S3.
The speed control unit 41 performs calculation for proportional-integral control (PI control) that brings a difference between the target speed ω* from the control circuit 20 and an estimated speed (rotational speed) ωm from the speed and position estimation unit 46 close to zero, and determines current command values Id* and Iq* of the d-q coordinate system. The estimated speed mm is periodically input. The speed control unit 41 determines the current command values Id* and Iq* each time the estimated speed ωm is input.
The current control unit 42 performs calculation for proportional-integral control that brings a difference between the current command value Id* and an estimated current value (d-axis current value) Id from the input coordinate conversion unit 45, and a difference between the current command value Iq* and an estimated current value (q-axis current value) Iq also from the input coordinate conversion unit 45 close to zero. Then, voltage command values Vd* and Vq* in the d-q coordinate system are determined.
On the basis of an estimated angle ωm from the speed and position estimation unit 46, the output coordinate conversion unit 43 converts the voltage command values Vd* and Vq* into U-phase, V-phase, and W-phase voltage command values Vu*, Vv*, and Vw*. That is, conversion is performed of the voltage from two phases to three phases.
On the basis of the voltage command values Vu*, Vv*, and Vw*, the PWM conversion unit 44 generates patterns of control signals U+, U−, V+, V−, W+, and W− depending on the amplitude of a pseudo sinusoidal voltage to be applied to the windings 33 to 35, and outputs the patterns to the motor drive unit 26. The control signals U+, U−, V+, V−, W+, and W− are signals for controlling the frequency and amplitude of three-phase AC power to be supplied to the motor 3 by pulse width modulation (PWM).
The input coordinate conversion unit 45 calculates a value of the W-phase current Iw from values of the U-phase current Iu and the V-phase current Iv detected by the current detection unit 27. Then, on the basis of the estimated angle θm from the speed and position estimation unit 46 and the values of the three-phase currents Iu, Iv, and Iw, the d-axis current value Id and the q-axis current value Iq is calculated that are estimated current values of the d-q coordinate system. That is, conversion is performed of the current from three phases to two phases. The q-axis current value Iq is an example of the measured value of the motor current flowing through the windings 33 to of the motor 3 to generate torque of rotation.
On the basis of the estimated current values (Id, Iq) from the input coordinate conversion unit 45 and the voltage command values Vd* and Vq* from the current control unit 42, the speed and position estimation unit 46 obtains the estimated speed value ωm and the estimated angle θm in accordance with a so-called voltage current equation. The obtained estimated speed value ωm is input to the speed control unit 41. The obtained estimated angle θm is input to the output coordinate conversion unit 43 and the input coordinate conversion unit 45.
The control signals U+, U−, V+, V−, W+, and W− output from the vector control unit 25 can be measured as the drive current Im. For example, the control signals U+ and U− are input to the current measurer 211b of the control circuit 20.
The current measurer 211b obtains a voltage to be applied to the motor 3 from the pattern of one period of the PWM modulation of the control signals U+ and U−. Then, from the voltage and the known resistance value Rs at the reference temperature Ts of the winding through which the current Iu flows when the voltage is applied, a value of the current Iu is obtained and output as the measured value DIm of the drive current Im.
The measured value corrector 212b of the control circuit 20 acquires, for example, the estimated speed value ωm from the vector control unit 25, and corrects the measured value DIm of the drive current Im depending on a deviation amount Δω between the estimated speed value tom and the target speed ω* in accordance with the correction information 70b illustrated in
In this example, it is assumed that the load of the motor 3 is constant, and speed change in a constant speed control period is caused by the characteristic change accompanying the temperature rise of the motor 3.
In
In the case of this example, the measured value corrector 212b calculates the corrected measured value DAIm by using the following equation.
DAIm=DIm+ΔIm
For example, when the deviation amount Δω is “−2”, since the current correction amount ΔIm is “−0.02”, the corrected measured value DAIm becomes “DIm−0.02” and is a value smaller than the measured value DIm before correction.
Regarding
When the sheet ejection rollers 18A and 18B become slippery, the load is reduced with respect to the motor 3c, so that control for reducing the torque is performed for the motor 3c. That is, the torque of the motor 3c changes in accordance with the degree of wear of the roller. The state of the roller can therefore be determined from the measured value of the torque.
In
On the basis of the torque values DT1 and DT2, a change rate is obtained of the torque value DT in a period from the measurement timing when the travel distance M is M1 to the measurement timing when the travel distance M is M2. The change rate is expressed by (DT2−DT1)/(M2−M1).
Assuming that the torque value DT changes (in this case, decreases) at the obtained change rate thereafter, a travel distance Me is calculated at a timing at which the torque value DT will be a predetermined threshold value DTth. Then, a difference between Me and M2 is calculated as the life expectancy ΔM.
Predetermined processing can be performed depending on the life expectancy ΔM, and for example, a message is displayed recommending replacement of the roller when the life expectancy ΔM is less than a set value.
Regarding
When the frictional force between the photoconductor 5 and the blade increases, the load is increased with respect to the motor 3a, so that control for increasing the torque is performed for the motor 3a. That is, the torque of the motor 3a changes depending on the frictional force with the blade. The contact state of the photoconductor 5 with the blade can therefore be determined from the measured value of the torque. This also applies to the intermediate transfer belt 15.
In
On the basis of the torque values DT1 and DT2, a change rate is obtained of the torque value DT in a period from the measurement timing when the number of printed sheets N is N1 to the measurement timing when the number of printed sheets N is N2. This change rate is expressed by (DT2−DT1)/(N2−N1).
Assuming that the torque value DT changes (in this case, increases) at the obtained change rate thereafter, the number of printed sheets Ne is calculated at a timing at which the torque value DT will be a predetermined threshold value DTth. Then, a difference between Ne and N2 is calculated as the life expectancy ΔN.
Predetermined processing can be performed depending on the life expectancy ΔN, and for example, a message is displayed recommending replacement of the photoconductor 5 and the blade when the life expectancy ΔN is less than a set value.
As illustrated in
In the example of
Each time printing is performed, a count value is updated of the number of printed sheets N after the previous measurement (#401). When the updated number of printed sheets N is checked (#402), and the number of printed sheets N reaches a predetermined number of sheets n (YES in #402), it is checked whether or not it is defined that the measurement is to be performed for a rotating body to be subjected to state determination at the end of a job (#403).
When it is not defined that the measurement is to be performed at the end of the job (NO in #403), a measurement permission flag is set as processing to permit the measurement (#405). When it is defined that the measurement is to be performed at the end of the job (YES in #403), waiting is performed for the end of the job (#404), and the measurement permission flag is set (#405).
The predetermined number of sheets n is selected depending on the rotating body to be subjected to the state determination and a purpose of the state determination. For example, when the state determination is performed for the purpose of predicting the lifetime of the sheet ejection rollers 18A and 18B, the predetermined number of sheets n can be set to 5000 to 10000, for example. In continuous printing exceeding several hundred sheets, when the state determination is performed as an operation check during job execution, the predetermined number of sheets n may be set to 100, for example.
In the torque detection processing as illustrated in
In the state determination processing as illustrated in
When the change amount of the torque value DT is equal to or greater than the threshold value (YES in #602), it is determined that the lifetime of the rotating body is exhausted (lifetime arrival) (#604). In this case, the subsequent image formation may be prohibited.
When the change amount of the torque value DT is less than the threshold value (NO in #602), the number of printable sheets until the lifetime arrival, that is, the life expectancy is calculated (#603). When the calculated life expectancy is equal to or greater than a set value (YES in #605), it is determined that the rotating body can continue to be used (#606). When the life expectancy is less than the set value (NO in #605), a user or a service person is notified that the life expectancy is short (#607).
According to the above embodiment, the measured value DIm of the motor current measured as the torque of the motor 3 is corrected to cancel the current change amount based on the characteristic change depending on the temperature state of the motor 3, so that the state of the rotating body can be determined with higher accuracy than before on the basis of the corrected measured value. In addition, there is no need to use a torque sensor.
In the above-described embodiment, an actual rotational speed ω of the motor 3 may be detected by a speed detector such as an encoder or a resolver. In this case, the measured value corrector 212 obtains the current change amount based on the characteristic change depending on the temperature state of the motor 3, depending on a difference between the rotational speed ω of the motor 3 at the measurement timing and the target speed ω*, and performs correction by using the current change amount.
In the above-described embodiment, an example has been described in which the measured value DIm is corrected in accordance with the deviation amount Δω between the target speed ω* and the estimated speed value mm or the actual rotational speed ω, and it can be performed as follows.
That is, a rotational angle position θ of the motor 3 is detected or measured by a rotational angle position detector such as a Hall element or an encoder. Then, the measured value DIm is corrected depending on a deviation amount Δθ between the rotational angle position θ and a position command θ*. That is, in this case, the measured value corrector 212 obtains the current change amount based on the characteristic change of the motor 3 depending on a difference between an actual measured value (rotational angle position θ) of the rotational position of the motor 3 at the measurement timing and a target position (position command θ*), and performs correction by using the current change amount. In the correction of this case, it is only necessary to store correction information 70d illustrated in
The measured value DIm may be corrected depending on a difference between the target position (position command θ*) and a measured value of the rotational position of the motor 3 detected or measured by a method different from the above-described method or an estimated value.
In this case, the motor 3 only needs to be subjected to the vector control in the vector control unit 25 similarly as described above.
In the above-described embodiment, the correction information 70a illustrated in
The motor 3 incorporates a temperature sensor for detecting a motor temperature that is a temperature inside the motor 3, and the measured value DIm of the motor current may be corrected depending on the detected motor temperature on the basis of the correction information 70 indicating a relationship between the motor temperature and the current change amount.
When the motor current is measured at the end of a job, on the basis of the number of sheets of image formation of the job, a difference between the reference temperature Ts and the motor temperature is estimated and the current change amount Δ is identified, and the measured value DIm may be corrected.
In the above-described embodiment, when a circuit component for the vector control capable of taking out the q-axis current value Iq is mounted unlike the electric circuit 31 of the motor unit 30, the q-axis current value Iq or q-axis current command value Iq* may be used as the measured value DIm of the motor current indicating the torque of the motor 3. In that case, it is preferable to correct the measured value DIm in consideration of a possibility that a change amount due to the temperature rise of the motor 3 is included in the q-axis current value Iq.
In the above-described embodiment, the vector control is not limited to the sensorless vector control. It may be vector control that causes the rotational speed ω measured by using a sensor such as a Hall element, an encoder, or a resolver to coincide with the target speed ω*.
Besides, the configuration of the whole or each part of the image forming apparatus 1, the details, order, or timing of the processing, the configuration of the motor 3, the configuration of the motor controller 21, and the like can be appropriately changed in accordance with the spirit of the present invention.
Although embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are made for purposes of illustration and example only and not limitation. The scope of the present invention should be interpreted by terms of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-033241 | Feb 2018 | JP | national |
