JP2022179039A - MOTOR DRIVE AND IMAGE FORMING APPARATUS INCLUDING THE SAME - Google Patents

Abstract

A motor driving device and an image forming apparatus equipped with the motor driving device are provided, which can reduce the convergence time of the actual rotation speed to the target rotation speed when starting to rotate a DC servomotor. .
A motor driving device that rotationally drives a DC servomotor includes a control section. In the frequency control, the control unit performs slow-up control in which the control frequency is gradually increased until a predetermined target frequency, which is the target of the control frequency, is reached when the rotation of the DC servo motor is started. It has a reset mode for resetting the accumulated phase difference, which is the difference between the control accumulated phase and the actual accumulated phase, when phase control is executed during the operation of .
[Selection drawing] Fig. 5A

Description

The present invention relates to a motor driving device for rotationally driving a DC servomotor and an image forming apparatus such as a copying machine, a multi-function machine, a facsimile machine, and a printer having the same.

A DC servomotor is used, for example, in an image forming apparatus to rotate rotating members such as an image carrier (for example, a photoreceptor) and an intermediate transfer member (for example, a driving roller wound around an intermediate transfer belt). be. A motor driving device for rotationally driving a DC servomotor generally controls the rotation speed of the DC servomotor based on a pulsed actual rotation signal having a real frequency corresponding to the actual rotation speed of the DC servomotor. Control the rotational speed to match the target rotational speed.

For example, the control unit of the motor drive device detects the actual frequency, which is the frequency of the detected actual rotation signal, and performs frequency control and phase control on the DC servomotor. In frequency control, the detected actual frequency is compared with the control frequency of the control signal input to the DC servomotor, and the actual frequency is controlled to match the control frequency. In phase control, for example, in order to prevent the detected actual frequency from being controlled by being offset from the control frequency during frequency control, the detected actual frequency is set to a predetermined value based on the control frequency. It is determined that the phase control effective range has been entered, and the control cumulative phase and the actual cumulative phase of the control phase from the reference time are calculated, and the actual cumulative phase matches the control cumulative phase. Phase control the DC servo motor.

In such a motor driving device, for example, when rotating a rotating member such as an image bearing member or an intermediate transfer member whose rotational load is greater than a predetermined rotational load, the DC servomotor starts rotating at a frequency of Slow-up control is performed to gradually increase the control frequency until it reaches a predetermined target frequency, which is the target of the control frequency in control (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2006-106506

However, the conventional motor driving device that performs slow-up control has the following problems.

FIG. 9 shows temporal changes in the actual frequency Fr and the actual accumulated phase Sr of the actual rotation signal FG at the time when the rotation of the DC servomotor is started in the rotation speed control of the DC servomotor in the conventional motor drive device. It is a graph which shows an example. In FIG. 9, Fc indicates the control frequency of the control signal CLK. The control signal CLK is a pulse waveform signal having a control frequency Fc corresponding to the target rotational speed of the DC servomotor. Here, E indicates the effective phase control range for the control frequency Fc, Ea indicates the lower limit of the effective phase control range E, and Eb indicates the upper limit of the effective phase control range E. Both Ea and Eb are set with respect to the frequency of the control signal CLK. Also, Ft indicates the target frequency of the control signal CLK, Sc indicates the control cumulative phase, and N is an arbitrary integer.

In the conventional rotation speed control of a DC servo motor shown in FIG. Control the rotation speed. Specifically, the actual frequency Fr and the actual phase Pr are respectively detected from the actual rotation signal FG, and frequency control and phase control are performed on the DC servomotor. Note that the actual rotation signal FG is a pulse feedback signal, and the frequency of the pulse waveform corresponds to the actual rotation speed. Therefore, it can be said that the period of the pulse waveform corresponds to the actual rotational speed.

In frequency control, the actual frequency Fr detected from the actual rotation signal FG (pulse waveform) is compared with the control frequency Fc of the control signal CLK input to the DC servomotor, and the actual frequency Fr is matched with the control frequency Fc. Control the DC servo motor to

Further, the phase control is performed at the time λ (see FIG. 9) when the detected actual frequency Fr enters a predetermined range (phase control effective range E) based on the control frequency Fc while the frequency control is being performed. ), the DC servomotor is controlled based on the actual phase Pr detected from the actual rotation signal FG and the control phase Pc of the control signal CLK input to the DC servomotor.

Here, the actual phase Pr and the control phase Pc represent the phase of each falling position of the repeated pulse waveform in each signal. Phase control counts the number of successively repeated falls (number of repetitions of falling position) for each signal from the reference time, and also calculates the accumulated time by integrating the time from the previous falling position to the current falling position. Calculate each. Then, the accumulated time of the actual phase Pr and the accumulated time of the control phase Pc at the same count number match, in other words, the difference between the accumulated time of the control phase Pc and the accumulated time of the actual phase Pr (accumulated phase The DC servo motor is controlled so that the phase difference ΔS) becomes zero.

More specifically, in the phase control executed from the time when the actual frequency Fr enters the phase control effective range E, the cumulative control phase Sc from the reference time Ts and the cumulative control phase Sc at the falling timing of each signal. The actual accumulated phase Sr of the actual phase is detected, and the actual accumulated phase Sr is controlled to be the same as the control accumulated phase Sc. Specifically, in the phase control, the elapsed time Tc (accumulated control phase Sc) of each phase of the control signal CLK from the reference time Ts and the progress of each phase of the actual rotation signal FG from the reference time Ts at the timing of the fall of each signal Time Tr (actual cumulative phase Sr) is counted, and the elapsed time Tr of each phase of the actual rotation signal FG is controlled to be the same as the elapsed time Tc of each phase of the control signal CLK.

As described above, when the rotation speed of the rotation shaft of the DC servo motor approaches the target rotation speed (control frequency Fc), the frequency control is switched to the phase control. The rotational speed is controlled more finely so that it is not offset with respect to the target rotational speed.

Further, slow-up control is performed to gradually increase the control frequency Fc until it reaches a predetermined target frequency Ft, which is the target of the control frequency Fc, in frequency control when the DC servomotor is started to rotate.

In the rotation speed control of the DC servo motor described above, as shown in FIG. 9, it is determined that the detected actual frequency Fr has entered the phase control effective range E (λ ), since the control frequency Fc is gradually increased when the phase control is started, the load driven by the DC servomotor momentarily fluctuates, resulting in the control cumulative phase Sc (elapsed time Tc) and the actual There is a case where the accumulated phase difference ΔS (elapsed time difference ΔT), which is the difference from the accumulated phase Sr (elapsed time Tr), increases (see α in FIG. 9). Then, in an attempt to eliminate this increased cumulative phase difference ΔS, the actual rotational speed of the DC servomotor is corrected with a larger correction value (see β1 in FIG. 9), which in turn causes an unexpectedly large overshoot. (See γ1 in FIG. 9) There is a possibility. As a result, there is a problem that the convergence time required for the actual rotation speed to converge to the target rotation speed becomes longer.

SUMMARY OF THE INVENTION Accordingly, the present invention provides a motor driving device and an image forming apparatus having the same capable of shortening the convergence time of the actual rotation speed to the target rotation speed when starting to rotate the DC servomotor. intended to provide

In order to solve the above-described problems, a motor driving device according to the present invention is a motor driving device for rotationally driving a DC servomotor, wherein pulses having a real frequency corresponding to the actual rotational speed of the DC servomotor are provided. a controller for controlling the actual rotation speed of the DC servomotor so as to match the target rotation speed based on the actual rotation signal in the form of a real rotation signal, wherein the controller detects the actual frequency of the actual rotation signal; The frequency detection means, the actual frequency detected by the actual frequency detection means, and the frequency of the control signal input to the DC servomotor, which corresponds to the target rotation speed of the DC servomotor. A frequency control means for comparing the control frequency with the control frequency and controlling the actual frequency so as to match the control frequency; real phase detection means; control phase detection means for detecting a control phase indicating a position in a cycle repeated at the control frequency in the control signal; and a difference value between the control frequency and the actual frequency. a real accumulated phase calculating means for calculating a real accumulated phase by accumulating a detection cycle of the real phase repeatedly detected by the real phase detecting means from a reference time within a predetermined value; and the control phase from the reference time. a control cumulative phase calculating means for calculating a control cumulative phase by accumulating a detection cycle of the control phase repeatedly detected by the detecting means; phase control means for controlling the phase of the DC servo motor toward the next detection cycle so as to match the control cumulative phase calculated by the control cumulative phase calculating means; When starting rotational driving of the motor, a slow-up control is performed to gradually increase the control frequency until the control frequency reaches a predetermined target frequency, and the control unit performs the slow-up control. A reset mode is provided for resetting a cumulative phase difference, which is a difference between the control cumulative phase and the actual cumulative phase, when the phase control means executes the phase control during operation. do. Further, an image forming apparatus according to the present invention includes the motor driving device according to the present invention.

According to the present invention, it is possible to shorten the convergence time of the actual rotation speed to the target rotation speed when starting to rotate the DC servomotor.

1 is a front view perspectively showing a schematic configuration of an image forming apparatus according to an exemplary embodiment; FIG. FIG. 2 is a perspective view of a belt driving roller portion of an intermediate transfer belt device in the image forming apparatus shown in FIG. 1 as viewed obliquely from the upper right; 3 is a block diagram showing a drive circuit for a DC servomotor of a controller in the motor drive device; FIG. A graph showing an example of temporal changes in the actual frequency and the actual accumulated phase of the actual rotation signal when the rotation of the DC servomotor is started in the rotation speed control of the DC servomotor by the motor drive device according to the present embodiment. is. 7 is a graph showing another example of rotation speed control of the DC servo motor by the motor drive device according to the embodiment; 7 is a graph showing another example of rotation speed control of the DC servo motor by the motor drive device according to the embodiment; 9 is a graph showing still another example of rotation speed control of the DC servo motor by the motor drive device according to the present embodiment; 9 is a graph showing still another example of rotation speed control of the DC servo motor by the motor drive device according to the present embodiment; 9 is a graph showing still another example of rotation speed control of the DC servo motor by the motor drive device according to the present embodiment; 4 is a flowchart showing an example of rotation speed control of a DC servomotor by the motor drive device according to the present embodiment; 7 is a graph showing an example of temporal changes in the actual frequency and the actual accumulated phase of the actual rotation signal when the rotation of the DC servomotor is started in the rotation speed control of the DC servomotor by the conventional motor drive device.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments according to the present invention will be described below with reference to the drawings. In the following description, the same parts are given the same reference numerals. Their names and functions are also the same. Therefore, a detailed description thereof will not be repeated.

[Description of Entire Image Forming Apparatus]
FIG. 1 is a front view perspectively showing a schematic configuration of an image forming apparatus 100 according to the present embodiment. In FIG. 1, the symbol X indicates the left-right direction, the symbol Y indicates the front-rear direction, and the symbol Z indicates the vertical direction.

The image forming apparatus 100 is a multifunction machine having a copy function, a scanner function, a facsimile function, and a printer function, and transmits the image of the document G read by the image reading device 102 to the outside. Further, the image forming apparatus 100 forms an image of the document G read by the image reading apparatus 102 or an image received from the outside on a sheet P such as paper in color or monochrome.

Above the image reading section 130, a document feeder 160 supported to be openable and closable with respect to the image reading section 130 is provided. The document feeder 160 sequentially conveys one or a plurality of documents G one by one. The image reading device 102 reads a document G conveyed one by one out of one or a plurality of documents by the document feeder 160 . The image reading device 102 includes a document placement table 130a (document setting table) on which a document G is placed, and a placed document reading function for reading the document G placed on the document placement table 130a. In the image forming apparatus 100, when the document feeder 160 is opened, the document table 130a above the image reading section 130 is opened so that the document G can be manually placed. The document feeder 160 also includes a document placement tray 161 on which the document G is placed, and a document ejection tray 162 on which the document G ejected to the outside is stacked. The image reading device 102 has a conveyed document reading function of reading the document G conveyed by the document feeder 160 . The document feeding device 160 conveys the document G placed on the document placing tray 161 onto the document reading section 130 b of the image reading section 130 . The image reading unit 130 scans the scanning optical system 130c to read the document G placed on the document table 130a or reads the document G conveyed by the document feeder 160 to obtain image data.

The image forming apparatus main body 101 includes an optical scanning device 1, a developing device 2, a photosensitive drum 3 (an example of an image carrier), a drum cleaning device 4, a charger 5, an intermediate transfer belt device 70 (belt device), a secondary transfer A device 11 , a fixing device 12 , a sheet conveying path H, a paper feed cassette 18 and a sheet discharge tray 141 are provided.

The image forming apparatus 100 forms an image corresponding to a color image using black (K), cyan (C), magenta (M), and yellow (Y), or a monochrome image using a single color (for example, black). data is handled. The image transfer unit 50 of the image forming apparatus 100 is provided with four developing devices 2, four photosensitive drums 3, four drum cleaning devices 4, and four chargers 5 for forming four types of toner images. Corresponding to cyan, magenta and yellow, four image stations Qa, Qb, Qc and Qd are configured.

The optical scanning device 1 exposes the surface of the photosensitive drum 3 to form an electrostatic latent image. The developing device 2 develops the electrostatic latent image on the surface of the photoreceptor drum 3 to form a toner image on the surface of the photoreceptor drum 3 . The drum cleaning device 4 removes and collects residual toner on the surface of the photosensitive drum 3 . The charger 5 uniformly charges the surface of the photosensitive drum 3 to a predetermined potential. A toner image of each color is formed on the surface of each photosensitive drum 3 by the series of operations described above.

The intermediate transfer belt device 70 includes a primary transfer roller 6 (intermediate transfer roller), an endless intermediate transfer belt 71 , a belt driving roller 72 , a belt driven roller 73 and a belt cleaning device 9 . Four primary transfer rollers 6 are provided inside the intermediate transfer belt 71 so as to form four types of toner images corresponding to each color. The primary transfer roller 6 transfers the toner image of each color formed on the surface of the photosensitive drum 3 onto the intermediate transfer belt 71 rotating in the circumferential direction C. As shown in FIG.

The intermediate transfer belt 71 is stretched around rollers including a belt driving roller 72 and a belt driven roller 73 . In the image forming apparatus 100 , the toner images of each color formed on the surface of each photosensitive drum 3 are sequentially transferred and superimposed to form a color toner image on the surface of the intermediate transfer belt 71 . Remove and recover residual toner.

The secondary transfer device 11 forms a transfer nip area TN (nip area) between the secondary transfer roller 11a and the intermediate transfer belt 71, and transfers the sheet P conveyed through the sheet conveying path H to the transfer nip area. It is sandwiched between TNs and transported. When the sheet P passes through the transfer nip area TN, the toner image on the surface of the intermediate transfer belt 71 is transferred to the sheet P, and the sheet P is conveyed to the fixing device 12 .

The fixing device 12 includes a fixing roller 31 and a pressure roller 32 that rotate with the sheet P therebetween. The fixing device 12 fixes the toner image to the sheet P by sandwiching the sheet P having the toner image transferred between the fixing roller 31 and the pressure roller 32 and applying heat and pressure.

The paper feed cassette 18 is a cassette for storing sheets P used for image formation, and is provided below the optical scanning device 1 . The sheet P is pulled out from the paper feed cassette 18 by the pickup roller 16 and conveyed to the sheet conveying path H. As shown in FIG. The sheet P conveyed to the sheet conveying path H passes through the secondary transfer device 11 and the fixing device 12 , is conveyed to the discharge roller 17 , and is discharged to the sheet discharge tray 141 in the discharge section 140 . Conveyance rollers 13 , registration rollers 14 and discharge rollers 17 are arranged in the sheet conveyance path H. As shown in FIG. The conveying roller 13 encourages the sheet P to be conveyed. The registration roller 14 temporarily stops the sheet P and aligns the leading edge of the sheet P. The registration rollers 14 convey the temporarily stopped sheet P in synchronization with the timing of the color toner image on the intermediate transfer belt 71 . The color toner image on the intermediate transfer belt 71 is transferred onto the sheet P in the transfer nip area TN between the intermediate transfer belt 71 and the secondary transfer roller 11a.

When the image forming apparatus 100 forms an image not only on the front surface of the sheet P but also on the back surface of the sheet P, the image forming apparatus 100 conveys the sheet P from the discharge roller 17 to the sheet reversing path Hr in the reverse direction. The image forming apparatus 100 reverses the front and back of the sheet P conveyed in the opposite direction, and guides the sheet P again to the registration rollers 14 . Also, the image forming apparatus 100 forms an image on the back surface of the sheet P guided by the registration rollers 14 in the same manner as the front surface, and conveys the sheet P to the sheet ejection tray 141 .

[Intermediate transfer belt device]
FIG. 2 is a perspective view of the belt drive roller 72 portion of the intermediate transfer belt device 70 shown in FIG. 1, viewed diagonally from the upper right.

The DC servo motor 300 can be configured to rotate a rotating member such as the photosensitive drum 3. In this example, the configuration for rotating the belt driving roller 72 wound around the intermediate transfer belt 71 will be described below. do.

The belt driving roller 72 receives a rotational driving force from a DC servomotor 300 via a drive transmission mechanism 400 . As a result, the intermediate transfer belt 71 can rotate in the circumferential direction C. As shown in FIG.

The roller shaft 72 a of the belt driving roller 72 and the rotating shaft 300 a of the DC servo motor 300 are connected via a drive transmission mechanism 400 . The drive transmission mechanism 400 is composed of a gear train in this example. The gear train consists of a drive gear 410 fixed to the rotary shaft 300a of the DC servomotor 300 and a driven gear 420 fixed to the roller shaft 72a of the belt drive roller 72 while meshing with the drive gear 410. As shown in FIG. The drive transmission mechanism 400 may include a timing belt and pulleys instead of or in addition to the gear train.

[Motor drive device]
FIG. 3 is a block diagram showing a drive circuit for the DC servo motor 300 of the controller 210 in the motor drive device 200. As shown in FIG.

Motor driving device 200 rotationally drives DC servomotor 300 . The motor driving device 200 has a control section 210 . Control unit 210 is provided in image forming apparatus 100 .

DC servo motor 300 is a DC brushless motor in this example. However, the motor is not limited to this, and may be a motor with a DC brush. The actual rotation signal detector 310 detects the actual rotation signal FG (pulse feedback signal) of the DC servomotor 300 . The actual rotation signal detector 310 is a Hall IC in this example, and is provided in the DC servomotor 300 . Based on the actual rotation signal FG detected by the actual rotation signal detection unit 310, the control unit 210 targets the actual rotation speed (actual rotation speed of the rotation shaft 300a) of the rotation shaft of the DC servomotor 300. Control to match the rotation speed. Note that the motor drive device 200 may include the actual rotation signal detection section 310 .

As shown in FIG. 3, the control section 210 includes a power circuit 211, a current control circuit 212, a logic circuit 213, a setting comparison circuit 214, a power supply circuit 215, and a storage section 216.

Power circuit 211 controls the current flowing through the motor windings of DC servo motor 300 . More specifically, the power circuit 211 repeats turning on and off in a constant order in a transistor circuit in which three sets of transistor arrays each having two transistors connected in series (not shown) are connected in parallel, thereby controlling the motor winding of the DC servomotor 300 . Pass a current through the line.

The current flowing through the DC servomotor 300 changes depending on the size of the load. Therefore, the current control circuit 212 constantly detects the current flowing through the DC servomotor 300 and controls the rotation speed so that it does not deviate from the set rotational speed.

The logic circuit 213 receives the actual rotation signal FG of the DC servomotor 300 from the actual rotation signal detector 310, detects the position of the rotating shaft 300a of the DC servomotor 300, and determines the excitation order of the motor windings. Signals that determine the order in which the motor windings are energized are sent to the power circuit 211 to drive each transistor in the power circuit 211 in a fixed order. The logic circuit 213 detects the actual frequency Fr and the actual phase Pr output from the DC servomotor 300 based on the actual rotation signal FG detected by the actual rotation signal detection section 310 . The logic circuit 213 also controls the commands to the DC servomotor 300, start/stop, brake/run, clockwise (CW: Clock Wise), and counterclockwise (CCW: Counter Clock Wise).

The setting comparison circuit 214 compares the detected actual frequency Fr with the control frequency Fc of the control signal CLK input to the DC servomotor 300 based on the speed setting signal Vc. The current control circuit 212 performs frequency control on the DC servomotor 300 so that the actual frequency Fr matches the control frequency Fc based on the comparison result of the setting comparison circuit 214 . Specifically, the current control circuit 212 drives the DC servomotor 300 with a correction value that allows the actual frequency Fr to match the control frequency Fc. The setting comparison circuit 214 also compares the detected actual phase Pr with the control phase Pc of the control signal CLK input to the DC servomotor 300 based on the speed setting signal Vc. The current control circuit 212 performs phase control on the DC servomotor 300 so that the actual phase Pr matches the control phase Pc based on the comparison result of the setting comparison circuit 214 . Specifically, the current control circuit 212 drives the DC servomotor 300 with a correction value that allows the actual phase Pr to match the control phase Pc.

The power supply circuit 215 converts the input voltage into the voltage required to drive the DC servo motor 300 and each circuit.

The storage unit 216 includes nonvolatile memory such as ROM and volatile memory such as RAM. The control unit 210 loads a control program previously stored in the ROM of the storage unit 216 onto the RAM of the storage unit 216 and executes it, thereby controlling the operation of various components.

Specifically, the control unit 210 includes an actual frequency detection means P1, a frequency control means P2, an actual phase detection means P3, a control phase detection means P4, an actual cumulative phase calculation means P5, and a control cumulative phase calculation means. P6 and phase control means P7.

The actual frequency detection means P1 detects the actual frequency Fr, which is the frequency corresponding to the period of the actual rotation signal FG detected by the actual rotation signal detection section 310. FIG.

The frequency control means P2 performs frequency control. In the frequency control, the actual frequency Fr detected by the actual frequency detection means P1 and the frequency of the control signal CLK input to the DC servomotor 300, which is the frequency corresponding to the target rotation speed of the DC servomotor 300, are controlled. is compared with the control frequency Fc, and the actual frequency Fr is controlled to match the control frequency Fc.

The actual phase detection means P3 detects the actual phase Pr that indicates the position in the cycle repeated at the actual frequency Fr in the actual rotation signal FG detected by the actual rotation signal detection section 310. FIG.

The control phase detection means P4 detects a control phase Pc indicating a position in a cycle repeated at the control frequency Fc in the control signal CLK input to the DC servomotor 300. FIG.

FIG. 4 shows the actual frequency Fr and the actual accumulated phase of the actual rotation signal FG at the time when the rotation of the DC servo motor 300 is started in the rotation speed control of the DC servo motor 300 by the motor drive device 200 according to the present embodiment. 4 is a graph showing an example of temporal changes in Sr; In FIG. 4, Fc indicates the control frequency of the control signal CLK. E indicates the effective phase control range, Ea indicates the lower limit of the effective phase control range E, and Eb indicates the upper limit of the effective phase control range E. FIG. Also, Ft indicates the target frequency of the control signal CLK, Sc indicates the control cumulative phase, and N is an arbitrary integer.

In the actual cumulative phase calculation means P5, the control cumulative phase calculation means P6, and the phase control means P7, from the reference time when the difference value between the control frequency Fc and the actual frequency Fr is within a predetermined value, in this example, the actual frequency When it is determined that the actual frequency Fr detected by the detection means P1 has entered the predetermined phase control effective range E (in this example, the control frequency Fc ±6.25%) based on the control frequency Fc (Fig. 4), and performs phase control in addition to frequency control.

In the phase control, the actual cumulative phase calculating means P5 accumulates the detection period of the actual phase Pr repeatedly detected by the actual phase detecting means P3 from the reference time to calculate the actual cumulative phase Sr. The control cumulative phase calculating means P6 accumulates the detection period of the control phase Pc repeatedly detected by the control phase detecting means P4 from the reference time to calculate the control cumulative phase Sc. The phase control means P7 adjusts the DC phase toward the next detection cycle so that the actual cumulative phase Sr calculated by the actual cumulative phase calculating means P5 coincides with the control cumulative phase Sc calculated by the control cumulative phase calculating means P6. Servomotor 300 is phase-controlled.

Specifically, in the phase control, the control cumulative phase Sc of the control phase from the reference time Ts and the actual cumulative phase Sr of the control phase from the reference time Ts are respectively detected at the falling timing of each signal, and the actual cumulative phase Sr is detected as the control phase. It is controlled to be the same as the cumulative phase Sc. Specifically, in the phase control, the elapsed time Tc (accumulated control phase Sc) of each phase of the control signal CLK from the reference time Ts and the progress of each phase of the actual rotation signal FG from the reference time Ts at the timing of the fall of each signal Time Tr (actual cumulative phase Sr) is counted, and the elapsed time Tr of each phase of the actual rotation signal FG is controlled to be the same as the elapsed time Tc of each phase of the control signal CLK.

Further, the frequency control means P2 performs slow-up control. In the slow-up control, the control frequency Fc is gradually increased until it reaches a predetermined target frequency Ft, which is the target of the control frequency Fc when the rotation of the DC servomotor 300 is started.

As described above, in conventional rotation speed control of a DC servomotor, as shown in FIG. 9, it is determined that the detected actual frequency Fr has entered the phase control effective range E during slow-up control operation (Fig. 9), since the control frequency Fc gradually increases in the state where the phase control is started, the load driven by the DC servomotor momentarily fluctuates, resulting in the control cumulative phase Sc (elapsed time Tc) and the actual cumulative phase Sr (elapsed time Tr), that is, the accumulated phase difference ΔS (elapsed time difference ΔT) increases (see α in FIG. 9). Then, in an attempt to eliminate this increased cumulative phase difference ΔS, the actual rotational speed of the DC servomotor is corrected with a larger correction value (see β1 in FIG. 9), which in turn causes an unexpectedly large overshoot. (See γ1 in FIG. 9) There is a possibility. As a result, there is a problem that the convergence time required for the actual rotation speed to converge to the target rotation speed becomes longer.

In this regard, in the present embodiment, the control unit 210 is controlled at some timing during the operation of the slow-up control (in this example, at a preset timing, specifically when the phase control means P7 executes the phase control). (See .delta. in FIG. 4.) It has a reset mode for resetting (to zero) the cumulative phase difference .DELTA.S, which is the difference between the detected control cumulative phase Sc and the actual cumulative phase Sr.

As described above, according to the present embodiment, the cumulative phase difference ΔS is reset at some timing during the operation of the slow-up control (see β2 in FIG. 4), so that the cumulative phase difference ΔS does not increase. can be avoided, therefore, the actual rotation speed of the DC servo motor 300 can be corrected with the correction value based on the reset cumulative phase difference ΔS, and the inconvenience of causing an unexpectedly large overshoot can be effectively prevented. can be prevented (see γ2 in FIG. 4). As a result, it is possible to shorten the convergence time of the actual rotation speed to the target rotation speed when starting to rotate the DC servomotor 300 .

In the present embodiment, the reset is performed by changing the control frequency Fc to the target frequency Ft when the control frequency Fc during slow-up control reaches a state lower than the target frequency Ft by a predetermined value. implement.

As a result, the cumulative phase difference ΔS can be reset when the control frequency Fc during slow-up control reaches a state lower than the target frequency Ft by a predetermined value.

Further, in the present embodiment, the phase control means P7 is configured so that the actual frequency Fr detected by the actual frequency detection means P1 is a predetermined frequency based on the control frequency Fc in a state where the frequency control means P2 performs frequency control. By performing the phase control when it is determined that the phase control effective range E is entered, the phase control effective range E can be defined as the condition for performing the phase control.

(First embodiment)
In the first embodiment, the timing at which the reset is performed is the timing at which the control frequency Fc of the control signal CLK exceeds a predetermined determination frequency Fh. Here, the determination frequency Fh is set in advance based on the overshoot occurrence timing predicted in advance by experiments or the like, and stored in the storage unit 216 .

In this embodiment, when the phase control means P7 determines that the actual frequency Fr detected by the actual frequency detection means P1 deviates from the phase control effective range E, the phase control means P7 resets (sets to zero) the accumulated phase difference ΔS. ) configuration. The phase control means P7 can deviate the actual frequency Fr detected by the actual frequency detection means P1 from the phase control effective range E at any timing during the slow-up control operation of the frequency control means P2. The control frequency Fc is increased by a possible predetermined increment Fi (10% of the control frequency Fc at the time of resetting in this example).

In this way, by using the configuration for resetting the cumulative phase difference ΔS when it is determined that the actual frequency Fr deviates from the phase control effective range E, the reset operation for the cumulative phase difference ΔS can be easily realized. .

By the way, after entering the phase control effective range E, the actual frequency Fr is usually located between the control frequency Fc and the lower limit value Ea of the phase control effective range E in many cases.

In this regard, in the present embodiment, the increment Fi of the control frequency Fc is more than half the width Ed of the phase control effective range E (in this example, 12.5% of the control frequency Fc at the time of resetting). value (in this example, 10% of the control frequency Fc at the time of resetting).

By doing so, the actual frequency Fr detected by the actual frequency detecting means P1 can be reliably deviated from the phase control effective range E. Thereby, the cumulative phase difference ΔS can be reliably reset.

In the present embodiment, the phase control means P7 controls the elapsed time Tc (accumulated control phase Sc) of the control phase of the control signal CLK from the reference time Ts and the elapsed time Tr (actual phase) of the actual rotation signal FG. The cumulative phase Sr) is counted, and control is performed so that the elapsed time Tr of the real phase of the actual rotation signal FG is the same as the elapsed time Tc of the control phase of the control signal CLK. Then, the phase control means P7 changes the reference time Ts at any timing (preset timing in this example) during the operation of the slow-up control in the frequency control means P2, and shifts from the changed reference time Ts to The elapsed time Tc of each phase of the control signal CLK and the elapsed time Tr of each phase of the actual rotation signal FG are counted again.

By re-counting the elapsed time Tc of each phase of the control signal CLK and the elapsed time Tr of each phase of the actual rotation signal FG from the changed reference time Ts, the cumulative control phase Sc and the actual cumulative phase Sr are calculated. can be reset (to zero).

By performing the control as described above, it is possible to effectively prevent the phase control from being executed during the slow-up control in which the control frequency Fc is changing. As a result, the phase control is executed before the actual rotation speed reaches the target rotation speed, and it is possible to prevent an overshoot of the actual rotation speed due to the phase control and a longer time for the actual rotation speed to converge to the target rotation speed. . In other words, it is possible to shorten the convergence time of the actual rotation speed to the target rotation speed.

(Second embodiment)
By the way, as in the first embodiment, the determination frequency Fh may be set in advance based on the overshoot occurrence timing predicted in advance by experiments or the like and stored in the storage unit 216, but in this case, the overshoot occurrence Since the timing is a mere predicted value, overshoot may occur depending on the value of the actual frequency detected by the actual frequency detection means P1.

In this respect, in the second embodiment, the reset timing is based on the value of the real frequency Fr detected by the real frequency detection means P1.

Since the actual frequency Fr is a measured value that is detected by the actual frequency detection means P1 at any time, the accumulated phase difference ΔS can be reset at a timing that is less likely to cause overshoot.

5A and 5B are graphs showing another example of rotational speed control of DC servo motor 300 by motor drive device 200 according to the present embodiment.

In this embodiment, the timing for resetting is the timing when the actual frequency Fr detected by the actual frequency detecting means P1 exceeds the judgment frequency Fh which is smaller than the target frequency Ft and is within the phase control effective range E. is.

In the example shown in FIG. 5A, the determination frequency Fh is a value obtained by subtracting the width Ed of the phase control effective range E (12.5% of the control frequency Fc at the time of resetting) from the target frequency Ft. The increment Fi of the frequency Fc is half the width of the phase control effective range E (in this example, 6.25% of the control frequency Fc at the time of resetting).

By doing so, the possibility of causing overshoot can be further reduced by setting the reset timing based on the actual frequency Fr detected by the actual frequency detection means P1 to a value lower (smaller) than the target frequency Ft. At the same time, the actual frequency Fr detected by the actual frequency detecting means P1 can be reliably deviated from the phase control effective range E.

In the example shown in FIG. 5B, the determination frequency Fh is obtained by subtracting 1.5 times the width Ed of the phase control effective range E (18.75% of the control frequency Fc at the time of resetting) from the target frequency Ft. The increment Fi of the control frequency Fc is the width of the phase control effective range E (12.5% of the control frequency Fc at the time of resetting in this example).

By doing so, the possibility of causing overshoot can be further reduced by setting the reset timing based on the actual frequency Fr detected by the actual frequency detection means P1 to a value lower (smaller) than the target frequency Ft. At the same time, the actual frequency Fr detected by the actual frequency detecting means P1 can be more reliably deviated from the phase control effective range E.

FIG. 6 is a graph showing still another example of rotational speed control of DC servo motor 300 by motor drive device 200 according to the present embodiment.

As shown in FIG. 6, in the phase control means P7, the actual frequency Fr detected by the actual frequency detection means P1 during the frequency control by the frequency control means P2 is a predetermined value based on the control frequency Fc. If it is determined that it is not within the phase control effective range E (in this example, the control frequency Fc ±6.25%), only the frequency control is performed without performing the phase control, and the control operation is performed up to the target rotation speed. Increase the frequency Fc.

(Third embodiment)
7A and 7B are graphs showing still another example of rotational speed control of DC servo motor 300 by motor drive device 200 according to the present embodiment. FIG. 7A shows an example in which the increment Fi of the control frequency Fc is half the width of the phase control effective range E. In FIG. FIG. 7B shows an example in which the increment Fi of the control frequency Fc is the width of the phase control effective range E. In FIG.

By the way, at the initial stage when the rotation of the DC servomotor 300 is started, the possibility that the actual frequency Fr detected by the actual frequency detecting means P1 is within the phase control effective range E is low. Since the cumulative phase difference ΔS is small even if the control effective range E is entered, it is considered that the possibility of overshooting is low. Therefore, as shown in FIGS. 7A and 7B, it is desirable that the determination frequency Fh be a value close to the target frequency Ft. Therefore, as the determination frequency Fh, for example, a frequency that is lower (smaller) than the target frequency Ft and equal to or more than 1/2 of the target frequency Ft, or a frequency that is equal to or more than 2/3 of the target frequency Ft can be used.

By doing this, it is possible to reset the cumulative phase difference ΔS at the time when it is highly likely that the actual frequency Fr is within the phase control effective range E and that overshoot is highly likely to occur. .

Note that the determination frequency Fh is, for example, half the width Ed of the phase control effective range E from the target frequency Ft (in this example, 6.25% of the control frequency Fc at the time of resetting) or more, and the phase control effective It may be a frequency obtained by subtracting a value less than three times the width Ed of the range (in this example, 37.5% of the control frequency Fc at the time of resetting).

By doing this, it is possible to reset the accumulated phase difference ΔS at a time when it is considered that the possibility that the actual frequency Fr is within the phase control effective range E is higher and that the overshoot is more likely to occur. can be done.

(Control example)
FIG. 8 is a flowchart showing an example of rotational speed control of DC servo motor 300 by motor drive device 200 according to the present embodiment.

As shown in FIG. 8, the control unit 210 first starts rotational driving of the DC servomotor 300 (S1), and starts slow-up control in which the control frequency Fc is gradually increased until the target frequency Ft is reached ( S2). Next, the control unit 210 detects the actual frequency Fr and the actual phase Pr from the actual rotation signal FG output from the DC servomotor 300 (S3), and adjusts the frequency so that the actual frequency Fr matches the control frequency Fc. Control is performed (S4).

Next, control unit 210 determines whether or not actual frequency Fr is within phase control effective range E (S5). (S5: No), while proceeding to S9, if it is determined that the actual frequency Fr has entered the phase control effective range E (S5: Yes), the actual phase Pr is adjusted to match the control phase Pc. Control is performed (S6).

Next, the control unit 210 determines whether or not the actual frequency Fr exceeds the determination frequency Fh (S7). When it is determined that the actual frequency Fr has exceeded the judgment frequency Fh (S7: Yes), the control frequency Fc is increased by a predetermined increment Fi to reset the cumulative phase difference ΔS (S8). , S9.

Next, the control unit 210 determines whether or not the slow-up control has ended (S9). When finished (S9: Yes), the slow-up control is finished.

(Other embodiments)
Although the DC servo motor 300 rotates the belt drive roller 72 in this embodiment, it may rotate a rotating member such as the photosensitive drum 3 whose rotational load is larger than a predetermined rotational load.

The present invention is not limited to the embodiments described above, but can be implemented in various other forms. Therefore, the embodiment concerned is merely an example in all respects, and should not be construed in a restrictive manner. The scope of the present invention is indicated by the claims and is not restricted by the text of the specification. Furthermore, all modifications and changes within the equivalence range of claims are within the scope of the present invention.

100 Image forming apparatus 200 Motor driving device 210 Control unit 211 Power circuit 212 Current control circuit 213 Logic circuit 214 Setting comparison circuit 215 Power supply circuit 216 Storage unit 300 DC servo motor 300a Rotary shaft 310 Actual rotation signal detection unit CLK Control signal E Phase Effective control range Ea Lower limit value Eb of phase control effective range Upper limit value FG of phase control effective range Actual rotation signal Fc Control frequency Fh Judgment frequency Fi Increment Fr Actual frequency Ft Target frequency P1 Actual frequency detection means P2 Frequency control means P3 Actual phase Detection means P4 Control phase detection means P5 Actual cumulative phase calculation means P6 Control cumulative phase calculation means P7 Phase control means Pc Control phase Pr Actual phase Sc Control cumulative phase Sr Actual cumulative phase TN Transfer nip area Tc Elapsed time Tr Elapsed time Time Ts Reference time Vc Speed setting signal ΔS Accumulated phase difference ΔT Elapsed time difference

Claims (10)

A motor driving device that rotationally drives a DC servomotor,
a controller for controlling the actual rotation speed of the DC servomotor to match a target rotation speed based on a pulsed real rotation signal having an actual frequency corresponding to the actual rotation speed of the DC servomotor; prepared,
The control unit
real frequency detection means for detecting the real frequency of the real rotation signal;
The actual frequency detected by the actual frequency detecting means and the control frequency, which is the frequency of the control signal input to the DC servomotor and corresponds to the target rotation speed of the DC servomotor, frequency control means for comparing and controlling the actual frequency so as to match the control frequency;
a real phase detecting means for detecting a real phase indicating a position in a cycle repeated at the real frequency in the real rotation signal;
control phase detection means for detecting a control phase indicating a position in a cycle repeated at the control frequency in the control signal;
Real accumulation for calculating a real accumulated phase by accumulating a detection period of the real phase repeatedly detected by the real phase detecting means from a reference point in time when a difference value between the control frequency and the real frequency is within a predetermined value. phase calculation means;
an accumulated control phase calculating means for calculating an accumulated control phase by accumulating a detection period of the control phase repeatedly detected by the control phase detecting means from the reference time point;
Phase control of the DC servomotor toward the next detection cycle such that the actual cumulative phase calculated by the actual cumulative phase calculating means matches the control cumulative phase calculated by the control cumulative phase calculating means. and a phase control means for
The frequency control means performs slow-up control to gradually increase the control frequency until it reaches a predetermined target frequency, which is a target of the control frequency, when starting to rotate the DC servomotor,
The controller resets an accumulated phase difference, which is a difference between the control accumulated phase and the actual accumulated phase, when the phase control means executes the phase control during the operation of the slow-up control. A motor drive device characterized by having modes. The motor drive device according to claim 1,
The reset is performed by changing the control frequency to the target frequency when the control frequency during the slow-up control reaches a state lower than the target frequency by a predetermined value. and a motor drive device. 3. The motor driving device according to claim 1 or 2,
A motor driving device, wherein the timing for resetting is based on the value of the real frequency detected by the real frequency detecting means. A motor drive device according to any one of claims 1 to 3,
The motor driving device, wherein the phase control means performs the phase control when the actual frequency is within a predetermined phase control effective range based on the control frequency. The motor drive device according to claim 4,
The phase control means is configured to reset the accumulated phase difference when it is determined that the actual frequency detected by the actual frequency detection means deviates from the phase control effective range,
At any of the timings during the operation of the slow-up control, the control frequency is increased by a predetermined increment that allows the actual frequency detected by the actual frequency detection means to deviate from the phase control effective range. A motor drive device characterized by: The motor drive device according to claim 5,
The motor drive device according to claim 1, wherein the increment of the control frequency is a value equal to or greater than half of the width of the phase control effective range. A motor driving device according to any one of claims 4 to 6,
The resetting timing is the timing when the actual frequency detected by the actual frequency detecting means is within the phase control effective range at the time when the actual frequency exceeds the judgment frequency which is smaller than the target frequency. motor drive device. The motor drive device according to claim 7,
The motor driving device according to claim 1, wherein the determination frequency is lower than the target frequency and is equal to or greater than half the target frequency. A motor driving device according to any one of claims 1 to 8,
The phase control means counts the elapsed time of the control phase of the control signal and the elapsed time of the actual phase of the actual rotation signal from the reference time, respectively, and determines the actual phase of the actual rotation signal. controlling the elapsed time to be the same as the elapsed time of the control phase of the control signal;
The reference time is changed at any of the timings during the operation of the slow-up control, and the elapsed time of each phase of the control signal and the elapsed time of each phase of the actual rotation signal from the changed reference time. A motor drive device characterized by re-counting with. An image forming apparatus comprising the motor driving device according to any one of claims 1 to 9.

Images