JP5258209B2 - Stepping motor driving apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a stepping motor driving apparatus suitable for an image forming apparatus, and more particularly to suppression of vibration of a motor shaft that occurs during acceleration / deceleration.

In an image forming apparatus that forms an image by an electrophotographic method, a stepping motor includes a conveyance roller driving motor that conveys recording paper (also referred to as a recording medium), a photosensitive member driving motor, and a rotating holder that holds a plurality of developing devices. It is used in various places such as rotary drive motors.
Here, the prior art of the stepping motor driving device will be described. As a driving method of the stepping motor, two-phase excitation, 1-2 phase excitation, microstep driving, and the like are known, and are generally put into practical use. Further, a unipolar drive circuit and a bipolar drive circuit are known as drive circuits, and a unipolar drive circuit is used when high-speed rotation is desired, and a bipolar drive circuit is used when high-torque rotation is desired. Further, there are constant voltage control and constant current control as methods for controlling the power supplied to the stepping motor. In general, constant current control is used in which stable torque is obtained in a wide frequency band. Furthermore, as a drive pattern, the motor starts to be driven at a drive frequency that does not step out (referred to as a self-starting frequency), accelerates to a target speed (target rotation angle per unit time), and steps out again at a desired rotation amount There is a pattern where the vehicle decelerates and stops within a range that does not occur. Such a driving pattern is realized by determining a pattern in advance and applying an exciting current corresponding to the pattern to the winding of the stepping motor. As an acceleration / deceleration pattern in the drive pattern, a trapezoidal pattern, an S-shaped pattern for suppressing vibration, a pattern using a quadratic function, and the like have been put into practical use.

However, if the drive pattern does not cause a step-out when the load torque becomes maximum as in the above-described method, the torque becomes excessive at low speeds regardless of the shape of the drive pattern, and the motor shaft vibrates due to the remainder of the torque. . Further, a torque margin is further required in consideration of load fluctuations and variations. As a technique for avoiding this, there is a technique (Patent Document 1) in which the drive pattern is divided into certain sections and the torque is controlled by switching the current setting value to a small value at a low speed and a large value at a high speed for each section. On the other hand, in the case of a load with large inertia, the current value is increased at startup and acceleration / deceleration, the current value is decreased at steady speed, and the current before the load change occurs when the load change timing is known. Techniques for increasing and decreasing the value (Patent Documents 2 and 3) have been proposed.
JP 2000-177194 A JP 2006-082957 A JP 2006-085153 A

  However, the methods of Patent Documents 1, 2, and 3 are essentially the same in that the current setting value is determined in advance with a margin for out-of-step with respect to the estimated load torque, and is transient. It does not deal with behavior, variation or aging.

  The present invention has been made under such circumstances, and is excellent in suppressing vibrations of the motor shaft during acceleration / deceleration, corresponding to variations in load, and having a short acceleration / deceleration time and the above-described stepping motor drive device An object of the present invention is to provide an image forming apparatus using a driving device.

  In order to solve the above-mentioned problems, the present invention comprises a stepping motor driving apparatus as described in the following (1) and an image forming apparatus as described in the following (2).

(1) Stepping motor drive means for driving the stepping motor based on a drive signal for switching the excitation phase of the stepping motor;
Rotation angle detection means for detecting the rotation angle of the motor shaft of the stepping motor;
A rotation angle command value derived from the product of an integrated value obtained by integrating the number of outputs of the drive signal from the start of driving of the stepping motor and a step angle, and a detection signal of the rotation angle detecting means from the start of driving of the stepping motor Deviation calculating means for calculating a deviation from the rotation angle of the motor shaft derived from
In the acceleration process of the stepping motor, the drive signal is output to the stepping motor drive means every time the deviation calculated by the deviation calculation means reaches a first specified value. In the constant speed process of the stepping motor, a predetermined cycle is output. And a control means for outputting the drive signal to the stepping motor drive means .
In the acceleration process, the control means has a period of the drive signal longer than a limit value of the drive signal period at which the speed or rotation angle of the stepping motor can reach the target speed or rotation angle within a specified time, And a stepping motor drive device that does not output the next drive signal when the deviation is larger than a second prescribed value that is larger than the first prescribed value .

(2) In an image forming apparatus that forms an image using a stepping motor for at least one of rotation of a photosensitive member, conveyance of a recording sheet, and rotation of a fixing device,
An image forming apparatus using the stepping motor driving device according to (1) for driving the stepping motor.

  According to the present invention, a stepping motor driving device that is excellent in suppressing vibrations of the motor shaft during acceleration / deceleration, supports load variations, and has a short acceleration / deceleration time, and an image forming apparatus including the stepping motor driving device are provided. Can be provided.

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described in detail by way of examples of embodiments.

[First Embodiment]
FIG. 1 is a block diagram showing a configuration of a stepping motor driving device used in the “image forming apparatus” according to the first embodiment. For convenience of explanation, the stepping motor driving device will be described first, and then the entire image forming apparatus will be described.

  In FIG. 1, a control device 101 includes a CPU that performs various operations, a ROM that stores various data and programs, and a RAM that functions as a work area of the CPU and stores data. The control device 101 outputs a set value (hereinafter referred to as a current set value) of a current flowing through the winding of the stepping motor 104 and a drive signal. The drive circuit 102 has a function of supplying a constant current having a value based on the current setting signal to the motor winding by performing PWM control on the power supplied from the power source 103 based on the current setting value output from the control device 101. The drive circuit 102 further has a function of switching the excitation phase of the stepping motor 104 that is a supply destination of power supplied from the power supply 103 based on the drive signal output from the control device 101. The encoder 105 is a detection device (rotation angle detection means) that is attached to the motor shaft of the stepping motor 104 and detects the rotation angle of the motor shaft, and outputs a pulse signal (detection signal) to the control device 101.

  The driving in the acceleration process of the stepping motor 104 will be described.

  A processing flow of the control apparatus 101 in the acceleration process is shown in FIG. In this processing flow, the CPU in the control device 101 is processed by a program stored in the ROM. The same applies to other processing flows.

  When an operation signal is input from a host controller (not shown), the control device 101 enters the acceleration process control mode, sets the current set value as the current set value A, and outputs the first drive signal to the drive circuit 102 (S1, S2). . The current set value A is determined in advance in consideration of the limitation on the acceleration time and the limitation on the current that can be supplied. Next, the rotation angle command value is derived from the product of the integrated value obtained by integrating the output number (pulse number) of the drive signal and the known step angle of the stepping motor 104 (rotation angle per step of the stepping motor). Further, the motor shaft rotation angle is derived from the product of the integrated value obtained by integrating the pulses of the output signal of the encoder 105 and the known pulse interval angle of the encoder. A deviation between the rotation angle command value and the motor shaft rotation angle is calculated (S3, deviation calculation means). The pulse interval angle is an angle at which the encoder 105 rotates from one pulse output from the encoder 105 until the next pulse is output. Next, it is determined whether or not the deviation obtained in step S3 is equal to the specified value a (first specified value) (S4). The specified value a is an angle defined between 0 ° and the step angle.

  When it is determined in step S4 that they are equal, it is determined whether or not the output period of the drive signal is shorter than the drive signal period (excitation phase switching period) at the target constant speed (S5).

  A method for realizing the processing in step S5 will be described. A clock generator is provided inside the control device 101, and the output period of the drive signal is derived by counting the number of clocks output between drive signals (between drive pulses). When the derived drive signal output cycle is shorter than the drive signal cycle at the constant speed, it is determined to shift to the constant speed mode.

  If it is determined in step S5 that the output period of the drive signal is longer than the drive signal period at the constant speed, the process returns to step S2 to output the next drive signal (drive pulse).

  With the above sequence, the stepping motor 104 always switches the excitation phase at the timing when the deviation between the rotation angle command value of the motor shaft and the rotation angle of the motor shaft becomes constant. Therefore, when the generated torque is larger than the friction torque, the motor rotates at an acceleration corresponding to the difference (acceleration torque) between the generated torque and the friction torque. Therefore, at low speeds where high torque can be generated, the motor rises with a large acceleration, and as the speed increases, the acceleration decreases, and a drive without vibration due to the remainder of the torque can be realized. As for torque change due to the natural vibration of the load, the acceleration when the force is applied in the rotational direction is accelerated to be greater than the acceleration when the force is applied in the direction opposite to the rotational direction, thereby reducing torque fluctuation due to the natural vibration. An adaptive acceleration pattern can be realized. In addition, the acceleration pattern is similarly adapted to variations in load variation.

  Next, driving in a constant speed process will be described. The processing flow of the control device 101 in the constant speed process is shown in FIG. The current set value is switched from the current set value A to the current set value B, and a drive signal is output (S6, S7). The current setting value B is a value that can generate a torque with a margin that takes into account variations in load and aging with respect to the torque measured in advance. The current set value B is characterized in that it can be made smaller than the current set value A in the acceleration process, but may be equal.

  The constant speed drive signal output cycle is set by counting the internal clock (S8). Next, it is confirmed whether a deceleration signal is input from a host controller (not shown) (S9). When the deceleration signal input is confirmed, the process proceeds to the deceleration process. If the input of the deceleration signal is not confirmed, the process returns to step S7 to output the next drive signal and continue the constant speed drive.

  Next, driving in the deceleration process will be described. FIG. 4 shows a control flow of the control device 101 in the deceleration process. The current set value C is output as the current set value (S10). The current setting value C is determined in consideration of the limitation of the deceleration time and the limitation of the current that can be supplied. At the time of deceleration, the stepping motor 104 is acted on in the rotational direction by the load connected to the stepping motor 104 and the inertial force of the rotor, so that a drive signal for applying the force in the rotational direction is not required. When the deviation between the rotation angle command value from the start of driving and the rotation angle of the motor shaft becomes a negative one step angle (specified value c, third specified value), that is, when the rotor position has advanced from the drive signal by one step. A drive signal is output to (S11, S12, S13). When such control is performed, force is applied to the stepping motor 104 only in the direction opposite to the rotation direction, so that the deceleration time can be shortened and useless vibration can be suppressed. However, depending on the size of the inertia and the driving speed, the rotational energy is lost before the rotor advances by one step angle, and the rotor is pulled back to the excited phase. The drive signal is output when the value is equal to or less than the prescribed value (S14). That is, in step S14, it can be determined that the encoder has sufficiently decelerated when the period of the output pulse signal of the encoder is longer than the period at which the speed becomes the specified value d, so the next drive signal is output and stopped (S15, S16). Along with the stop, the rotation command value and the motor shaft rotation angle are initialized (S17). When the output pulse signal cycle is shorter than the cycle in which the speed becomes the specified value d in step S14, the process returns to step S11.

  Even if there is a load variation by the above control sequence, it is possible to realize driving with a high vibration suppression effect.

  FIG. 9 is a schematic cross-sectional view showing the configuration of the image forming apparatus according to the present embodiment.

  In FIG. 9, the photosensitive member 1 as an image carrier is rotated in the direction of arrow A by a motor (not shown). A developing unit 10 and a cleaner device 8 are disposed around the photoreceptor 1. The developing unit 10 includes three color developing devices 10Y, 10M, 10C and a black developing device 10K for full color development. The developing devices 10Y, 10M, 10C, and 10K develop the electrostatic latent image on the photoreceptor 1 with toners of yellow (Y), magenta (M), cyan (C), and black (K), respectively. When developing each color of Y, M, C, and K, the developing unit 10 is rotated in the direction of the arrow R by a motor (not shown), and the developing device for that color is aligned so as to contact the photoreceptor 1. The toner images of the respective colors developed on the photosensitive member 1 are sequentially transferred to the belt 2 as an intermediate transfer member by the transfer device 7 and the four color toner images are superimposed. The belt 2 is stretched around rollers 20, 21, 22, and 23. Among these, the roller 20 functions as a driving roller that is coupled to a driving source (not shown) and drives the belt 2. The rollers 21 and 23 function as tension rollers for adjusting the tension of the belt 2, and the roller 22 functions as a backup roller for the transfer roller 24 as a secondary transfer device.

  A belt cleaner 9 is provided at a position facing the roller 20 with the belt 2 interposed therebetween, and residual toner on the belt 2 is scraped off by a blade.

  The recording paper drawn from the recording paper cassette 25 to the conveyance path by the pickup roller 26 is fed to the nip portion, that is, the contact portion between the secondary transfer device 24 and the belt 2 by the roller pairs 27 and 28. The toner image formed on the belt 2 is transferred onto the recording paper at this nip portion, thermally fixed by the fixing device 4 and discharged outside the device.

  In the image forming apparatus having the above-described configuration, an image is formed as follows. First, a voltage is applied to the charging device 5 to uniformly negatively charge the surface of the photoreceptor 1 with a predetermined charging portion potential. Subsequently, exposure is performed by an exposure device 6 composed of a laser scanner so that an image portion on the charged photoreceptor 1 has a predetermined exposure portion potential, and an electrostatic latent image is formed. The exposure device 6 turns on and off the laser based on the image signal, thereby forming an electrostatic latent image corresponding to the image.

  A developing bias set in advance for each color is applied to the developing roller of the developing device 10Y and the like, and the electrostatic latent image is developed with toner when passing through the position of the developing roller and visualized as a toner image. The toner image is transferred to the belt 2 by the transfer device 7 and further transferred to the recording paper by the secondary transfer device 24, and the recording paper is fed to the fixing device 4. In full-color printing, toners of four colors are superimposed on the belt and then transferred onto the recording paper. The toner remaining on the photosensitive member 1 is easily charged by a preliminary cleaning device, and is removed and collected by a cleaner device 8. Finally, the photosensitive member 1 is uniformly removed by a static eliminator (not shown) at around 0 volts. Until the next image forming cycle.

  The image formation timing is controlled with reference to a predetermined position on the belt 2. The belt 2 is stretched around rollers including a driving roller 20, tension rollers 21 and 23, and a backup roller 22, and a predetermined tension is applied by the tension rollers 21 and 23.

  Between the backup roller 22 and the tension roller 23, a reflective sensor 30 for detecting the reference position is disposed. The reflective sensor 30 detects a marking such as a reflective tape provided at the end of the outer peripheral surface of the belt 2 and outputs a reference signal I-top.

  The peripheral length of the photoreceptor 1 and the peripheral length of the belt 2 have an integer ratio represented by 1: n (n is an integer). With this setting, the photoreceptor 1 rotates an integer while the belt 2 makes one round and returns to the exact same position as before the belt. Accordingly, when the four colors are superimposed on the intermediate transfer belt 2 (the belt rotates four times), it is possible to avoid color misregistration due to rotation unevenness of the photoreceptor 1.

In the intermediate transfer type image forming apparatus as described above, after the reference signal I-top is detected, the exposure apparatus 6 starts latent image formation according to the image signal after a predetermined time has elapsed. Further, as described above, since the photoreceptor 1 rotates an integer number of times during one revolution of the belt 2 and returns to the same state as before the belt one revolution, a toner image is always formed on the belt 2 at the same position. .
The color image is copied onto the recording paper through the above process.

  In the image forming apparatus described above, there are a plurality of transport rollers for transporting the recording paper until the recording paper is discharged from the recording paper cassette 25 through the fixing device 4. In addition, there is a conveyance path (not shown) for conveying the recording paper to the conveyance roller pair 27 in order to form an image on the back surface of the recording paper once image formation is completed by the fixing device 4, and a plurality of conveyance paths are also provided in the conveyance path. There is a roller. These transport rollers start driving based on the position of the recording paper, and transfer the recording paper at a constant speed between the transport roller that transports the recording paper and the transport roller that transports the recording paper next, Stop after passing the paper. In addition, the fixing roller built in the photosensitive member 1 and the fixing device 4 is also driven at a constant speed to perform photosensitive and fixing.

  In this embodiment, the photosensitive member, the fixing device, and the various transport rollers are driven to rotate according to the processing flow shown in FIGS. 2, 3, and 4 using the stepping motor driving device shown in FIG.

  As described above, according to the present embodiment, it is possible to realize a stepping motor drive that is excellent in suppressing vibration of the motor shaft during acceleration / deceleration, supports load variations, and has a short acceleration / deceleration time. .

[Second Embodiment]
The “image forming apparatus” according to the second embodiment will be described. Since the overall configuration of the image forming apparatus according to the present embodiment is the same as that of the first embodiment, the description thereof is cited and re-explanation is omitted here.

  The configuration of the stepping motor driving apparatus used in this embodiment is the same as that shown in FIG.

The driving in the acceleration process will be described.
FIG. 5 shows a processing flow of the control device 101 in the acceleration process.

  When an operation signal is input from a host controller (not shown), the control device 101 enters a control mode in the acceleration process, sets the current set value to the current set value A, and outputs the first drive signal (drive pulse) to the drive circuit (S18, S19). The current set value A is determined in advance in consideration of the limitation on the acceleration time and the limitation on the current that can be supplied. Next, a rotation angle command value is derived from the product of the integrated value obtained by integrating the output number (number of pulses) of the drive signal and the step angle of the known stepping motor 104. Further, the motor shaft rotation angle is derived from the product of the integrated value obtained by integrating the pulses of the output signal of the encoder 105 and the known pulse interval angle of the encoder. A deviation between the rotation angle command value and the motor shaft rotation angle is calculated (S20). Next, it is determined whether or not the deviation obtained in step S20 is equal to the specified value a (S21). The specified value a is an angle defined between 0 ° and the step angle. When it is determined in step S21 that they are equal, the process proceeds to step S22 to determine whether the drive signal output cycle is shorter than the drive signal cycle at the target constant speed.

  In step S22, when the drive signal output cycle is shorter than the target drive signal cycle at the constant speed, the mode shifts to the constant speed mode. When the drive signal output cycle is longer than the target drive signal output cycle at the constant speed, the process returns to step S19 to output the next drive signal.

  When it is determined in step S21 that they are not equal, the processes in steps S23 to S25 described in detail below are performed.

  The current set value A is a value determined in consideration of the acceleration time. This is a case where parameters such as load friction and inertia are considered as representative values. Although the above-described control method can achieve acceleration while suppressing vibration against load fluctuations, when the load fluctuation is large, the above-described control method can target the speed or rotation angle of the stepping motor 104 within a specified time. There is no guarantee that the speed or rotation angle will be reached. Therefore, in step 23, it is determined whether the drive signal output cycle satisfies the condition determined within the specified time.

  Therefore, the drive signal period indicating the limit value of the drive signal output period at which the speed or rotation angle of the stepping motor 104 can reach the target speed or rotation angle within the specified time at a time point t seconds after the start of driving. Are stored in the memory unit in advance. This limit value table is a table as shown in FIG. That is, when the drive signal output period t seconds after the start of driving is smaller than the limit value at t seconds in the limit value table, the speed or rotation angle of the stepping motor 104 becomes the target speed or rotation angle within the specified time. Since it can be reached, the process returns to step S20.

  The specified value b (second specified value) is a value larger than the specified value a, a value less than the step angle, and a specified angle for preventing step-out. In the stepping motor, when the deviation between the rotation angle command value and the motor shaft rotation angle is twice or more than the step angle, the rotor cannot obtain a force in the rotation direction, and a phenomenon of step-out in which the rotor cannot rotate occurs. Therefore, when the drive signal output period t seconds after the start of driving is longer than the limit value at t seconds in the limit value table, the deviation between the rotation angle command value and the motor shaft rotation angle is larger than the specified value b. At this time, the drive signal is not switched until the deviation reaches the specified value b (S24). Further, it is determined that the acceleration cannot be maintained for a specified time, and a warning signal is returned to a host controller (not shown) (S25).

  Next, driving in the constant speed process will be described. FIG. 6 shows a processing flow of the control device 101 in the constant speed process. A drive signal is output at a constant cycle in which the motor rotates at the set speed (S26, S27). Next, the deviation between the rotation angle command value sampled immediately before the drive signal output and the motor shaft rotation angle is calculated (S28). The current set value is determined whether or not the deviation between the rotation angle command value and the rotation angle of the motor shaft is within a specified range defined by two values (S29). This specified range is a range of 0 ° or more and a step angle or less, and is a value for adjusting the excess or deficiency of the generated torque. If the specified range is determined within a range close to the step angle, the torque margin is small but the drive consumes less power. If the specified range is narrowed, torque fluctuation can be reduced. When the deviation is outside the specified range, it is first determined whether the deviation is equal to or less than the specified value b. When the deviation is equal to or greater than the specified value b, the drive signal is not switched until the deviation reaches the specified value b, thereby avoiding step-out. Further, it is determined that the current control cannot maintain a constant speed, and a warning signal is returned to a host controller (not shown) (S30, S31).

  If it is less than or equal to the specified value b, the current set value is changed (S32). The change of the current set value in step S32 is that when the current value is increased, the deviation decreases, and when the current value is decreased, the deviation increases. Therefore, the average value of the two values that define the specified range (the center value of the specified range) and Control is performed so as to be within a specified range by PI (proportional + integral) control with respect to an error from the deviation. Other control theories can be used. By the processes of S28, S29, and S32, a torque surplus due to an increase or decrease in load torque can be prevented, and driving can be performed with an appropriate torque margin. Next, it is determined whether or not the rotation angle command value is equal to (coincides with) the specified rotation angle 1 (first specified rotation angle) (S33). If they are not equal, the process returns to S26 and the constant speed driving is continued. When they are equal, control is transferred to the deceleration process. The specified rotation angle 1 is a value obtained by subtracting the rotation angle necessary for deceleration under the limit condition from the specified rotation angle 2 in order to stop at the specified rotation angle 2.

  Next, driving in the deceleration process will be described. FIG. 7 shows a processing flow of the control apparatus 101 in the deceleration process. The current set value C is output as the current set value, and the drive signal is output (S34). The current set value C is determined in consideration of the limitation on the deceleration time and the limitation on the current that can be supplied. Next, it is determined whether or not the rotation angle command value is equal to the specified rotation angle 2 (second specified rotation angle). When the rotation angle command value is equal, the driving of the stepping motor is stopped (S35, S40). Then, the rotation angle command value and the rotation angle are initialized (S41). If they are not equal in the process of step S35, when the deviation between the rotation angle command value from the start of driving and the rotation angle of the motor shaft is a negative one step angle (specified value c), that is, the rotor position is determined from the drive signal by one step. A drive signal is output when the vehicle advances (S36, S37, S39). However, depending on the size of the inertia and the driving speed, the rotational speed of the motor shaft is less than the specified value d because the rotational energy is lost before the rotor advances by one step angle and the rotor is pulled back to the excited excited phase. A drive signal is output when the value becomes (S38).

  In the image forming apparatus of the present embodiment shown in FIG. 9, the developing unit 10 rotates to the developing position by the time when the development of each color is started. In the present embodiment, the rotation time and rotation angle of the developing unit 10 are defined, and the load torque varies significantly due to increase / decrease of toner in the developing unit 10, whereas the processing shown in FIGS. 5, 6, and 7 is performed. Control by flow. In addition to the developing unit, the above-described control can be applied to a driving motor such as a conveyance roller or a fixing device in which a load torque during conveyance varies depending on a recording paper material.

  As described above, according to the present embodiment, it is possible to provide a stepping motor drive device that is excellent in suppressing vibrations of the motor shaft during acceleration / deceleration, supports load variations, and has a short acceleration / deceleration time. it can.

  In addition, the rotation angle can be specified, and it is possible to deal with abnormalities in the acceleration process and the constant speed process.

The figure which shows the structure of the stepping motor drive device used by 1st Embodiment. The flowchart which shows the process in the acceleration process in 1st Embodiment The flowchart which shows the process in the constant speed process in 1st Embodiment The flowchart which shows the process in the deceleration process in 1st Embodiment The flowchart which shows the process in the acceleration process in 2nd Embodiment The flowchart which shows the process in the constant speed process in 2nd Embodiment The flowchart which shows the process in the deceleration process in 2nd Embodiment. Limited value table Sectional view showing configuration of image forming apparatus

Explanation of symbols

101 Control Device 102 Drive Circuit 103 Power Supply 104 Stepping Motor 105 Encoder

Claims (5)

Stepping motor driving means for driving the stepping motor based on a driving signal for switching the excitation phase of the stepping motor;
Rotation angle detection means for detecting the rotation angle of the motor shaft of the stepping motor;
A rotation angle command value derived from the product of an integrated value obtained by integrating the number of outputs of the drive signal from the start of driving of the stepping motor and a step angle, and a detection signal of the rotation angle detecting means from the start of driving of the stepping motor Deviation calculating means for calculating a deviation from the rotation angle of the motor shaft derived from
In the acceleration process of the stepping motor, the drive signal is output to the stepping motor drive means every time the deviation calculated by the deviation calculation means reaches a first specified value. In the constant speed process of the stepping motor, a predetermined cycle is output. And a control means for outputting the drive signal to the stepping motor drive means.
In the acceleration process, the control means has a period of the drive signal longer than a limit value of the drive signal period at which the speed or rotation angle of the stepping motor can reach the target speed or rotation angle within a specified time, And a stepping motor drive device that does not output the next drive signal when the deviation is larger than a second prescribed value that is larger than the first prescribed value. Stepping motor driving means for driving the stepping motor based on a driving signal for switching the excitation phase of the stepping motor;
Rotation angle detection means for detecting the rotation angle of the motor shaft of the stepping motor;
A rotation angle command value derived from the product of an integrated value obtained by integrating the number of outputs of the drive signal from the start of driving of the stepping motor and a step angle, and a detection signal of the rotation angle detecting means from the start of driving of the stepping motor Deviation calculating means for calculating a deviation from the rotation angle of the motor shaft derived from
In the acceleration process of the stepping motor, the drive signal is output to the stepping motor drive means every time the deviation calculated by the deviation calculation means reaches a first specified value. In the constant speed process of the stepping motor, a predetermined cycle is output. And a control means for outputting the drive signal to the stepping motor drive means.
The control means outputs a next drive signal when the deviation reaches a third specified value in the deceleration process of the stepping motor and when the rotational speed of the motor shaft becomes equal to or lower than a fourth specified value. A stepping motor driving device characterized in that the output is output. In the stepping motor drive device according to claim 1 or 2,
The stepping motor drive means drives the stepping motor based on the drive signal and a current setting signal for setting a current value to be supplied to the excitation phase,
The stepping motor driving device characterized in that the control means changes the current setting signal so that the deviation falls within a specified range in the constant speed process. In the stepping motor drive device according to any one of claims 1 to 3 ,
The control means shifts from the constant speed process to the deceleration process of the stepping motor when the rotation angle command value matches the first specified rotation angle, and when the rotation angle command value matches the second specified rotation angle, A stepping motor driving apparatus that controls the stepping motor driving means so as to stop driving of the stepping motor. In an image forming apparatus that forms an image using a stepping motor for at least one of rotation of a photosensitive member, conveyance of a recording sheet, and rotation of a fixing device,
Wherein the drive of the stepping motor, the image forming apparatus characterized by using a stepping motor driving apparatus according to any one of claims 1 to 4.

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