Image forming device

Abstract

To suppress efficiency decline and insufficient drive torque when controlling a motor.SOLUTION: A motor control unit 14 rotates a motor 15F at 500 rpm, acquires a load torque value TRQ based on a Vref voltage and a set lead angle, updates the lead angle based on the acquired load torque value TRQ and a motor rotation speed value SPD based on the motor rotation speed command value of the motor 15F or the rotation speed detected by a rotary encoder 61, and controls a motor driver IC 60 in accordance with the rotor orientation detected by the rotary encoder 61 and the updated lead angle.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an image forming apparatus, and more particularly to a control technique for a motor provided in the image forming apparatus.

Background Art

[0002] A stepping motor is used as a drive source for an image forming apparatus. While a stepping motor can relatively easily control the desired rotational speed and rotational angle, there is a problem in that there is a possibility of out-of-step. Therefore, in order to prevent out-of-step, a method of detecting the operation of the stepping motor using a sensor such as an encoder and performing feedback control has been proposed. For example, Patent Document 1 discloses a configuration in which an encoder is provided in a stepping motor and feedback control is performed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There are the following methods for the purpose of cost reduction of the motor control circuit. For example, there is a method of driving a motor by performing on / off control (BangBang control) of the voltage applied to the coil without having a current control loop (without feedback control of the coil current value) so that the coil current value does not exceed the target value. In this case, it is necessary to adjust the timing of applying the voltage with respect to the detected electrical angle of the rotor so that current flows through the coil at an appropriate timing according to the rotor operation of the stepping motor. Hereinafter, the timing of applying the voltage with respect to the electrical angle is described as the advance angle. If the advance angle is not set appropriately, there may be problems such as a decrease in efficiency due to wasteful current flowing that does not contribute to the generation of driving torque, and a shortage of driving torque due to insufficient current flowing.

[0005] Generally, the advance angle is set such that the faster the rotational speed of the stepping motor, the greater the advance angle, that is, the timing of voltage application is advanced with respect to the electrical angle of the rotor. However, when setting the advance angle according to the rotational speed of the motor, the advance angle may vary due to fluctuations in the rotational speed caused by uneven rotation of the motor, further deteriorating the uneven rotation of the motor. Also, although it is desirable to set the advance angle according to the magnitude of the load torque, it is set to an advance angle that has little effect on the assumed maximum load torque. For this reason, when the load torque is different from the assumed maximum load torque, there may be problems such as a decrease in efficiency due to the flow of wasteful current that does not contribute to the generation of driving torque, or a shortage of driving torque due to insufficient current flow.

[0006] The present invention has been made under such circumstances, and an object thereof is to suppress a decrease in efficiency and a shortage of driving torque when controlling a motor.

Means for Solving the Problems

[0007] In order to solve the above-described problems, the present invention comprises the following configuration.

[0008] (1) An image forming apparatus that forms an image on a recording material, comprising a stepping motor having a coil and a rotor, first detection means for detecting the orientation of the rotor, excitation means for exciting the coil, setting means for setting an advance angle which is the timing for exciting the coil with respect to the orientation of the rotor detected by the first detection means, second detection means for detecting the rotational speed of the rotor, and control means for controlling the stepping motor, wherein the control means rotates the stepping motor at a predetermined rotational speed, obtains a load torque value based on an operation amount and the advance angle set by the setting means, the setting means updates the advance angle based on the load torque value obtained by the control means and a rotational speed value based on a target rotational speed of the stepping motor or the rotational speed detected by the second detection means, and the control means controls the excitation means according to the orientation of the rotor detected by the first detection means and the advance angle updated by the setting means.

Effect of the Invention

[0009] According to the present invention, it is possible to suppress a decrease in efficiency and a shortage of drive torque when controlling the motor.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Best Mode for Carrying Out the Invention

[0011] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments are merely examples, and the present invention is not limited to the content of the embodiments. Also, in the following figures, components that are not necessary for the description of the embodiments are omitted from the figures.

Examples

[0012] <Image Forming Apparatus> FIG. 1(a) is a configuration diagram of an image forming apparatus 100 according to Example 1. The image forming apparatus 100 can be, for example, any one of a printing apparatus, a printer, a copier, a multifunction machine, and a facsimile machine. A sheet P as a recording material stored in a paper feed cassette 25 of the image forming apparatus 100 is conveyed along a conveyance path by a paper feed roller 26 and a conveyance roller 27. The image forming unit 1 forms toner images of yellow, magenta, cyan, and black, and transfers these toner images to the sheet P conveyed through the conveyance path. The fixing device 24 has a heating roller and a pressure roller, heats and pressurizes the sheet P to which an unfixed toner image has been transferred, and fixes the toner image to the sheet P. The sheet P on which the fixing process of the toner image has been performed is discharged outside the image forming apparatus 100. The motor 15F is a drive source that rotates a pair of rollers of the fixing device 24, a paper conveyance roller downstream of the fixing device 24 in the conveyance direction of the sheet P, and a duplex conveyance roller group 28 that conveys the sheet P when performing duplex printing on the sheet P.

[0013] Figure 1(b) shows the control configuration of the image forming apparatus 100. When the printer control unit 11 receives image data of an image to be formed from the host computer 22 via the communication controller 21, it controls the image forming unit 1 to form a toner image on the sheet P, and controls the fixing unit 24 to fix the toner image on the sheet P. At this time, the printer control unit 11 also controls the motor control unit 14 to control the motors 15 including the motor 15F, and performs conveyance control of the sheet P and the like. Further, the printer control unit 11 displays the state of the image forming apparatus 100 on the display unit 20. Note that the printer control unit 11 includes a microcomputer and a memory. The memory holds various control programs and data, and the microcomputer controls each part of the image forming apparatus 100 based on the various control programs and data stored in the memory.

[0014] <Motor control unit> Figure 2 shows a configuration example of the motor control unit 14. The motor control unit 14 as control means includes a microcomputer 51 and a motor driver IC 60 as excitation means. The microcomputer 51 is connected to the printer control unit 11 via a communication port 52 by a serial communication line and communicates with each other. The microcomputer 51 outputs a control signal from the GPIO port 58 to the motor driver IC 60 to control the motor driver IC 60. Further, an analog voltage is output from the DAC port 59 to serve as a reference voltage for current control of the motor driver IC 60. The microcomputer 51 is provided with a timer / counter 53, and counts the number of pulses and measures the period of the pulse signal output by a rotary encoder 61 described later.

[0015] The motor driver IC60 incorporates two sets of H-bridge circuits for the A-phase coil and the B-phase coil, and drives the motor 15F, which is a stepping motor, according to the control signal and analog voltage output from the microcomputer 51. The control signal output from the GPIO port 58 will be described. The PHA signal controls the H-bridge circuit for the A-phase, and the PHB signal controls the H-bridge circuit for the B-phase. The IA_0 and IA_1 signals switch the set value of the A-phase coil current to 100%, 67%, 33%, and 0% of the maximum current value. The IB_0 and IB_1 signals also switch the set value of the B-phase coil current in the same way. By setting the above signals, the microcomputer 51 can drive the motor 15F, such as full-step drive and half-step drive, via the motor driver IC60.

[0016] The voltage input from the microcomputer 51 to the Vref terminal of the motor driver IC60 sets the maximum current value of the coil. The output torque of the motor is approximately proportional to the maximum current value of the coil. The microcomputer 51 can change the output torque by changing the voltage input to the Vref terminal of the motor driver IC60. Here, the larger the voltage input to the Vref terminal, the larger the output torque.

[0017] Note that in the first embodiment, an analog voltage is input to the Vref terminal to change (set) the output torque, but it is not limited to this. For example, a pulse signal may be output from the microcomputer 51, converted into an analog voltage by a low-pass filter, and input to the Vref terminal. In this case, the output torque can be changed by changing the duty (on-duty) of the pulse signal. The larger the duty (on-duty) of the pulse signal, the larger the output torque. The analog voltage or the duty of the pulse signal input to the Vref terminal to determine the output torque corresponds to the operation amount.

[0018] In addition, the motor driver IC60 has a constant current control function as follows. The motor driver IC60 determines the current value flowing through the coil based on the voltage input to the Vref terminal and the current reference voltage determined by the ratio set by the IA_0, IA_1 signals and the IB_0, IB_1 signals. That is, the motor driver IC60 compares the voltage Vr generated by a current detection resistor (not shown) with the current reference voltage. As a result of the comparison, when Vr ≥ current reference voltage, the motor driver IC60 turns off the switching elements constituting the H-bridge circuit built in the motor driver IC60 once. Then, after a predetermined period has elapsed, the motor driver IC60 turns on the switching elements of the H-bridge circuit again to allow current to flow through the coil. Thereafter, the motor driver IC60 repeats this operation to control the current flowing through the coil so that it does not exceed a predetermined value. In addition, the microcomputer 51 has a non-volatile memory 55 and a memory 57.

[0019] <Configuration of the motor> FIG. 3(a) is a configuration diagram of the motor 15F. The motor 15F has a coil, a rotor, and a shaft 64, and is a two-phase bipolar stepping motor that mechanically rotates once (360-degree rotation) in, for example, 48 steps. A two-phase bipolar stepping motor has advantages such as good utilization efficiency of the winding by flowing current in both directions, being able to perform precise control, and obtaining a high output torque. Note that electrically, it rotates once (360-degree rotation) in 4 mechanical steps. Also, the electrical angle is the angle expressed by setting one cycle of the rotor's magnetic field as 360 degrees. The motor 15F has two coils, a phase A coil and a phase B coil, and uses the H-bridge circuit of the motor driver IC60 to flow the exciting current in two directions, positive or negative. Here, The state in which the phase A coil is excited in the positive direction is denoted as A, The state in which the phase A coil is excited in the negative direction is denoted as / A, The state in which the phase B coil is excited in the positive direction is denoted as B, The state in which the phase B coil is excited in the negative direction is denoted as / B and described as such.

[0020] The motor driver IC60 A, B → A, / B → / A, / B → / A, B (in the case of forward full step) By switching the excitation phase, the electrical angle rotates once (mechanical 4 steps). By repeating the above operation 12 times (switching the excitation phase 48 steps), it rotates mechanically once. Note that A, B → / A, B → / A, / B → A, / B ··· When excited, the motor 15F rotates in the reverse direction (counterclockwise). Thereafter, for example, when the rotor of the motor 15F faces the electrical angle excited by A, B, it may be described as "the position of the A, B phase".

[0021] A gear 65 is attached to one side of the shaft 64 of the motor 15F, and a rotary encoder 61 is attached to the other side. The rotary encoder 61 is composed of a code wheel 62 provided with slits and a photosensor 63 that detects the slits. The rotary encoder 61 outputs two pulses with different phases (pulse A, pulse B). The rotary encoder 61 functions as a first detection means for detecting the direction of the roller of the motor 15F.

[0022] The number of counts per mechanical rotation of pulses A and B output from the rotary encoder 61 is made an integer multiple (48 × n; n is a positive integer) of the number of steps (48 steps) required to mechanically rotate the motor 15F once. In the first embodiment, in full-step drive, the motor 15F mechanically rotates once in 48 steps, so there are 480 pulses each for pulses A and B. Then, by counting the rising edges and falling edges of pulses A and B output from the rotary encoder 61, the count becomes 1920, which is 40 times the number of 48 steps. Therefore, in the case of full-step drive, the excitation phase is switched every 40 counts of pulses A and B output from the rotary encoder 61. On the other hand, in the case of half-step drive, the excitation phase is switched every 20 counts of pulses A and B output from the rotary encoder 61. Note that as the motor driver IC 60, a motor driver IC capable of microstep drive may be used, for example, switching the excitation phase every 5 counts to perform 1 / 8 step drive or the like.

[0023] As described above, by making the number of counts per mechanical rotation an integer multiple of the number of times the excitation phase is switched required for one mechanical rotation of the motor 15F, the switching timing of the excitation phase coincides with the counted timing. This simplifies the management of the excitation phase switching timing. In addition, it is possible to suppress the deterioration of rotational unevenness caused by a slight deviation between the switching timing and the counting timing, such as switching the excitation phase every 2.5 counts. Also, the forward / reverse rotation of the motor 15F can be determined from the phases of pulses A and B of the rotary encoder 61.

[0024] <Motor Drive Control> The motor drive control by the motor control unit 14 will be described. The motor drive control includes excitation phase switching control and speed control, and each control includes an excitation phase switching loop and a speed control loop.

[0025] (Excitation Phase Switching Control) First, the excitation phase switching control will be described. Basically, the excitation phase switching control counts the number of pulses of pulses A and B of the rotary encoder 61, and performs an operation of switching the excitation phase according to the value obtained by offsetting the count value. This offset value is the so-called advance angle. In the first embodiment, the motor control unit 14 adjusts the advance angle, which is the offset value, according to the driving conditions (rotation speed, load torque).

[0026] FIG. 3(b) is a diagram for explaining the advance angle. The upper graph shows the time change of the direction of the rotor of the motor 15F (rotor direction, 0° to 360°) detected by the rotary encoder 61. When the motor control unit 14 performs control to pass a current based on the detection result of the rotary encoder 61, there may be a delay in the rise of the current due to the influence of the inductance of the coil or the like. Therefore, as shown in the lower graph of FIG. 3(b), the advance angle An is set so that the voltage application timing is earlier than the direction of the rotor indicated by the broken line detected by the rotary encoder 61 (with respect to the electrical angle of the rotor). The motor control unit 14 determines the current passing timing based on the direction of the virtual rotor indicated by the solid line advanced by the amount of the advance angle An. Hereinafter, the value after offsetting the count value counted by the rotary encoder 61 (the value taking into account the advance angle) will be described as the excitation phase instruction value, and the adjustment of the offset value will be described as the advance angle adjustment. In the lower graph of FIG. 3(b), the excitation phase instruction value corresponds to the solid line advanced by the amount of the advance angle An.

[0027] The motor control unit 14 (microcomputer 51) resets the count values of pulses A and B of the rotary encoder 61 to 0 in a state where the electrical angle of the rotor is determined. Further, the motor control unit 14 adds or subtracts to the count value according to the movement of the rotor (output status of pulses A and B). Here, as described above, the count value of the pulses for one mechanical rotation is set to 1920 counts (0 to 1919). Then, when the motor control unit 14 adds 1 to 1919 (1919 + 1), it sets it to 0, and when it subtracts 1 from 0 (0 - 1), it sets it to 1919, and performs count value processing such as this. By this processing, the range of the count value can be set to 0 to 1919. Note that similar count value processing may be performed, and the count may be in the range of 0 to 159 (160 = 1920 / 12) for one rotation of the electrical angle.

[0028] For example, when the motor 15F is rotated forward in full step, first, the rotor is drawn into the positions of phases A and B, and the pulse count value is reset to 0. The drawing in of the rotor is performed, for example, by performing / A, B phase excitation for 500 ms, and then performing A, B phase excitation for 500 ms. Thereby, the direction of the rotor can be drawn into the electrical angles of phases A and B. In the first embodiment, the range of the count value is set to the count in the range of 0 to 159 for one rotation of the electrical angle.

[0029] Subsequently, as the offset value (advance angle), for example, a value obtained by adding 40 is used as the excitation phase instruction value. The reason for setting the advance angle to 40 will be described with reference to FIG. 4(a) described later. The excitation phase instruction value also performs the count value processing as described above. Therefore, the range of the excitation phase instruction value also becomes 0 to 159. When the motor control unit 14 rotates the motor 15F forward in full step, for example, when the excitation phase instruction value is 0 to 39, A, B 40 to 79, A, / B 80 to 119, / A, / B 120 to 159, / A, B According to the excitation phase indication value, it outputs PHA and PHB signals and switches the excitation phase. Therefore, when the rotor of the motor 15F is at the A and B positions, the excitation phase indication value becomes 40, so A and / B are excited, and torque is generated to rotate the rotor one step forward. Next, speed control will be described.

[0030] (Speed Control) In speed control, the motor control unit 14 (microcomputer 51) measures the periods of the pulses A and B of the rotary encoder 61, obtains the current rotational speed, and calculates the difference between the current rotational speed and the target rotational speed (hereinafter referred to as the rotational speed error). The motor control unit 14 functions as a second detection means for detecting the current rotational speed of the motor 15F. Then, the motor control unit 14 performs, for example, PID calculation on the calculated rotational speed error and outputs the Vref voltage as a current value command to the motor driver IC60.

[0031] <Regarding the Vref Voltage, Load, and Advance Angle> FIG. 4 is a diagram showing the relationship among the load torque, the advance angle, and the voltage Vref for a predetermined rotational speed of the motor 15F, and is a diagram for explaining the determination (setting) of the advance angle based on the rotational speed and the load torque of the motor 15F. FIG. 4(a) shows the case where the rotational speed of the motor 15F is 500 rpm, FIG. 4(b) shows the case where the rotational speed of the motor 15F is 1500 rpm, and FIG. 4(c) shows the case where the rotational speed of the motor 15F is 2500 rpm. In all of them, the horizontal axis represents the advance angle and the vertical axis represents the voltage Vref. Also, in FIG. 4(a), Ld11 is a graph for a predetermined load torque, Ld12 shows the case where the load torque is smaller than Ld11, and Ld13 shows the case where the load torque is smaller than Ld12 (Ld11 > Ld12 > Ld13). Similarly, in FIG. 4(b), Ld21 is a graph for a predetermined load torque, Ld22 shows the case where the load torque is smaller than Ld21, and Ld23 shows the case where the load torque is smaller than Ld22 (Ld21 > Ld22 > Ld23). Further, in FIG. 4(c), Ld31 is a graph for a predetermined load torque, Ld32 shows the case where the load torque is smaller than Ld31, and Ld33 shows the case where the load torque is smaller than Ld32 (Ld31 > Ld32 > Ld33).

[0032] As shown in Fig. 4, when the rotational speed of motor 15F is a certain predetermined rotational speed, even with the same load torque, if the advance angle is changed, the Vref voltage required to obtain that load torque also changes. In Example 1, the advance angle at which the Vref voltage becomes the lowest is selected (set). For example, as shown in Fig. 4(a), when the rotational speed of motor 15F is 500 rmp, for load torque Ld11, the advance angle corresponding to Vref voltage Vref11 is selected. Similarly, for load torque Ld12, the advance angle corresponding to Vref voltage Vref12 is selected, and for load torque Ld13, the advance angle corresponding to Vref voltage Vref13 is selected (set). Note that when the rotational speed of motor 15F is as low as 500 rpm, since the Vref voltage becomes low within the allowable range of the advance angle (hereinafter referred to as the advance angle allowable range) α1, the degree of freedom in selecting the advance angle is high. For example, the same advance angle A11 can be selected for any load torque. In Example 1, when the rotational speed of motor 15F is 500 rpm, regardless of the load torque, for example, the advance angle A11 can be set to 40.

[0033] When the rotational speed of motor 15F shown in Fig. 4(b) is 1500 rpm, in the case of load torque Ld21, since the Vref voltage becomes the lowest Vref21 at advance angle A21, advance angle A21 is selected. Similarly, in the case of load torque Ld22, since the Vref voltage becomes the lowest Vref22 at advance angle A22, advance angle A22 is selected, and in the case of load torque Ld23, since the Vref voltage becomes the lowest Vref23 at advance angle A23, advance angle A23 is selected respectively. In order to provide a range for selecting the advance angle, the following method may be used. For example, in the case of load torque Ld21, when the Vref voltage is acceptable in the range from Vref21 to Vref21a, the advance angle may also be selectable within the advance angle allowable range α21. Similarly, in the case of load torque Ld22, it may be selectable within the advance angle allowable range α22 corresponding to the range from Vref22 to Vref22a, and in the case of load torque Ld23, it may be selectable within the advance angle allowable range α23 corresponding to the range from Vref23 to Vref23a.

[0034] When the rotational speed of the motor 15F shown in Fig. 4(c) is 2500 rpm, in the case of the load torque Ld31, the advance angle A31 is selected because the Vref voltage becomes the lowest Vref31 at the advance angle A31. Similarly, in the case of the load torque Ld32, the advance angle A32 is selected because the Vref voltage becomes the lowest Vref32 at the advance angle A32, and in the case of the load torque Ld33, the advance angle A33 is selected because the Vref voltage becomes the lowest Vref33 at the advance angle A33. In order to provide a range for the selection of the advance angle, the following method may be adopted. For example, in the case of the load torque Ld31, when the Vref voltage is acceptable in the range from Vref31 to Vref31a, the advance angle may also be selectable within the advance angle tolerance range α31. Similarly, in the case of the load torque Ld32, it may be selectable within the advance angle tolerance range α32 corresponding to the range from Vref32 to Vref32a, and in the case of the load torque Ld33, it may be selectable within the advance angle tolerance range α33 corresponding to the range from Vref33 to Vref33a.

[0035] As described above, the advance angle is associated with the rotational speed and load torque of the motor 15F. Specifically, when the rotational speed of the motor 15F is 500 rpm, the advance angle A11 (e.g., 40) is set regardless of the load torque. Also, when the rotational speed of the motor 15F is 1500 rpm, the advance angle A21 is set for the load torque Ld21, the advance angle A22 is set for the load torque Ld22, and the advance angle A23 is set for the load torque Ld23. Further, when the rotational speed of the motor 15F is 2500 rpm, the advance angle A31 is set for the load torque Ld31, the advance angle A32 is set for the load torque Ld32, and the advance angle A33 is set for the load torque Ld33. The information associating the rotational speed, load torque, and advance angle is stored in advance in the non-volatile memory 55. In addition, when the operation amount is the duty of the PWM signal, the vertical axis in Fig. 4 may be read as the duty of the PWM signal.

[0036] <Advance Angle Adjustment> In the first embodiment, the motor rotation speed value SPD and the load torque value TRQ are used for the advance angle adjustment. Here, the motor control unit 14 functions as a setting means for setting the advance angle, which is the timing for exciting the coil with respect to the direction of the rotor detected by the rotary encoder 61. The motor rotation speed value SPD is determined by the motor rotation speed command value (target speed) or the actual rotation speed of the motor 15F. In the first embodiment, the motor rotation speed command value is used as the motor rotation speed value SPD. However, when the deviation between the actual motor rotation speed and the motor rotation speed command value exceeds a predetermined value, the actual motor rotation speed is used as the motor rotation speed value SPD. The load torque value TRQ is generated by the load torque detected by the load torque detection described later.

[0037] Here, the advance angle varies in conjunction with the variation in the rotation speed of the motor 15F (see FIG. 4), and the rotation speed of the motor 15F varies in conjunction with the advance angle. That is, the rotation speed of the motor 15F and the advance angle vary in conjunction with each other's variations. For this reason, if the actual rotation speed of the motor 15F that varies is always used as the motor rotation speed value SPD for the advance angle adjustment, the efficiency of the motor 15F may decrease due to the variation in the rotation speed. Therefore, when the deviation between the actual motor rotation speed and the motor rotation speed command value is equal to or less than a predetermined value, in order to avoid a decrease in the efficiency of the motor 15F due to the rotation speed variation, the motor rotation speed command value, which is a fixed value, is used as the motor rotation speed value SPD. On the other hand, for example, there may be a case where the load torque is large at the timing when the motor 15F starts and it takes time to reach the motor rotation command value. In such a case, the deviation between the actual motor rotation speed and the motor rotation speed command value exceeds a predetermined value. In this case, in order to enable the rotation speed of the motor 15F to quickly return to the motor rotation speed command value, the actual motor rotation speed is used as the motor rotation speed value SPD.

[0038] FIG. 5(a) is a graph showing the advance angle set as described in FIG. 4. The horizontal axis represents the motor rotation speed value SPD, and the vertical axis represents the advance angle value. FIG. 5(a) shows examples of four different load torque values TRQ. As described in FIG. 4, the optimal advance angle value for each driving condition is obtained in advance and stored in the non-volatile memory 55. In the first embodiment, it is assumed that the advance angle values when the load torque value TRQ is 30 mN·m, 40 mN·m, 50 mN·m, 60 mN·m, and the motor rotation speed value SPD is 500 rpm, 1000 rpm, 1500 rpm, 2000 rpm are stored in the non-volatile memory 55.

[0039] Note that in order to reduce the capacity of the non-volatile memory 55, when the number of data is reduced, an advance angle value interpolated from the stored data may be obtained for the actual load torque and motor rotation speed. Also, the combination of the load torque value TRQ and the motor rotation speed value SPD may be increased, and an advance angle value close to the actual load torque and motor rotation speed may be used. Hereinafter, a data group of advance angle values with respect to the motor rotation speed value SPD for each load torque value TRQ will be described as an advance angle curve.

[0040] An example of advance angle adjustment is shown in FIG. 5(b). First, an advance angle curve corresponding to the load torque value TRQ is set. When there is no advance angle curve with the same value as the generated load torque value TRQ, an advance angle curve with a value larger than the load torque value TRQ may be selected, or an advance angle curve interpolated from the advance angle curves before and after the stored load torque value TRQ may be generated. In FIG. 5(b), it is assumed that the generated load torque value TRQ is 38 mN·m, and the advance angle adjustment is performed using the advance angle curve of 40 mN·m which is larger than this value.

[0041] The motor control unit 14 uses the advance angle value of 500 rpm when the motor rotation speed value SPD is between 0 and 500 rpm from the advance angle curve of 40 mN·m. Also, when the motor rotation speed value SPD is between 500 rpm and 1000 rpm, the motor control unit 14 uses the advance angle value interpolated from the advance angle values of 500 rpm and 1000 rpm. Even when the motor rotation speed is 1000 rpm or more, the motor control unit 14 similarly interpolates and uses the advance angle value. In addition, in the advance angle adjustment, although the advance angle curve for each load torque value TRQ is used, it is not limited to this. A calculation formula for obtaining the advance angle value from the motor rotation speed value SPD and the load torque value TRQ may be stored in the non-volatile memory 55, and the advance angle value may be obtained using the calculation formula during the advance angle adjustment.

[0042] <Load torque detection method> Next, a load torque detection method for generating the load torque value TRQ will be described. In the first embodiment, the motor control unit 14 rotates the motor 15F at a constant speed in the low rotation speed (second rotation speed) region where the influence of the advance angle is small, for example, at 500 rpm, and detects the magnitude of the load torque from the magnitude of the Vref voltage (operation amount) at that time, and sets it as the load torque value TRQ.

[0043] Here, the reason for detecting the magnitude of the load torque at 500 rpm, which is the low rotation speed region, is that as shown in FIG. 4(a), the load torque is uniquely determined from the Vref voltage. Specifically, when the rotation speed is 500 rmp, for the advance angle A11, it can be detected that when the Vref voltage is Vref11, the load torque is Ld11, when the Vref voltage is Vref12, the load torque is Ld12, and when the Vref voltage is Vref13, the load torque is Ld13. Note that the rotation speed of the motor 15F when detecting the load torque is not limited to 500 rpm, and other rotation speeds may be used as long as the load torque can be detected from the Vref voltage when a predetermined advance angle is set. The same applies when the operation amount is the duty of the PWM signal.

[0044] When the motor 15F is driven to rotate at a constant speed by speed control, the power input to the motor 15F changes according to the load torque. In the first embodiment, since the power input to the motor 15F changes according to the Vref voltage, as described above, the motor control unit 14 can detect the magnitude of the load torque based on the Vref voltage when the motor is rotating at a constant speed. The relationship between the Vref voltage, the advance angle, and the load torque is obtained in advance and stored in the non-volatile memory 55.

[0045] The load torque detection can be performed during the initial operation after the power-on of the image forming apparatus 100 or the like. Alternatively, when the motor 15F is started, the motor control unit 14 once rotates the motor 15F at, for example, 500 rpm, and detects the magnitude of the load torque from the magnitude of the Vref voltage at that time. Thereafter, the motor control unit 14 may accelerate to a desired target rotational speed (the first rotational speed > the second rotational speed).

[0046] Further, the motor control unit 14 may associate the Vref voltage with the detected load torque value TRQ and store them in the non-volatile memory 55 (storage unit). Thereby, the motor control unit 14 can obtain the load torque value TRQ based on the information stored in the non-volatile memory 55 and the Vref voltage without performing the load torque detection from the next time.

[0047] (Regarding the difference from the load torque during the printing operation) In the above load torque detection, the load torque may change compared to the actual printing operation. In the first embodiment, the sheet P is not conveyed during the load torque detection, and the sheet P is conveyed during the printing operation. For this reason, during the printing operation, the load torque increases by the amount of the conveyance of the sheet P. Therefore, in the first embodiment, the tendency of the torque increase due to the presence or absence of the conveyance of the sheet P is obtained in advance, and the value obtained by adding the torque increase amount to the detected load torque is used as the load torque.

[0048] In addition, in the first embodiment, the actual load torque is obtained from the Vref voltage, and the obtained load torque is used as the load torque value TRQ, but it is not limited to this. For example, when the relationship between the Vref voltage and the actual load torque is constant, such as when the advance angle at the time of load torque detection is fixed, the Vref voltage may be directly used as the load torque value TRQ.

[0049] <Motor drive process> Next, the motor drive process executed by the motor control unit 14 will be described. FIG. 6 is a flowchart of a motor startup sequence executed by the motor control unit 14. In step (hereinafter referred to as S) 101, the motor control unit 14 pulls in the rotor of the motor 15F and pulls in the rotor to the electrical angles of phases A and B. In S102, the motor control unit 14 resets the count value of the rotary encoder 61 to 0. In S103, the motor control unit 14 sets the motor rotation speed command value to 500 rpm and starts driving the motor 15F at a low speed. Note that the motor control unit 14 executes the generation of the excitation phase instruction value, the excitation phase switching control, and the speed control as described above during the motor drive. When the motor rotation speed reaches, for example, 500 rpm ± 3%, the motor control unit 14 proceeds to the process of S104.

[0050] In S104, the motor control unit 14 samples the currently output Vref voltage for a predetermined period so as to obtain a predetermined number of data. For example, the motor control unit 14 samples 200 data every 1 ms. After the sampling is completed, the motor control unit 14 averages the sampled data. In S105, the motor control unit 14 generates a load torque value TRQ from the data (Vref average value) averaged in S104 (load torque detection). Note that the relationship between the Vref voltage, the advance angle, and the load torque is obtained in advance as described above and stored in the non-volatile memory 55.

[0051] In S106, as described with reference to FIG. 5(b), the motor control unit 14 sets an ignition advance curve according to the load torque value TRQ generated in S105. Next, the motor control unit 14 starts accelerating the motor 15F up to the final target rotational speed. In S107, the motor control unit 14 updates the motor rotation speed command value. Here, the motor control unit 14 adds a predetermined value to the motor rotation speed command value so as to accelerate at a predetermined acceleration.

[0052] In S108, the motor control unit 14 calculates the rotational speed error between the motor rotation speed command value updated in S107 and the actual rotational speed. In S109, the motor control unit 14 determines whether the rotational speed error calculated in S108 is greater than a predetermined value. If, in S109, the motor control unit 14 determines that the rotational speed error is less than or equal to the predetermined value, the process proceeds to S110. In S110, the motor control unit 14 updates the ignition advance based on the ignition advance curve set in S106 using the motor rotation speed command value updated in S107 as the motor rotation speed value SPD, and the process proceeds to S112.

[0053] If, in S109, the motor control unit 14 determines that the rotational speed error exceeds the predetermined value, the process proceeds to S111. In S111, the motor control unit 14 updates the ignition advance based on the ignition advance curve set in S106 using the actual rotational speed as the motor rotation speed value SPD, and the process proceeds to S112. For example, if the load torque value TRQ generated in S105 is 38 mN·m, the motor control unit 14 sets an ignition advance curve as shown in FIG. 5(b). Then, if the motor rotation speed value SPD in S110 or S111 is, for example, between 500 rpm and 1000 rpm, the motor control unit 14 updates the ignition advance value based on the ignition advance value at 500 rpm and the ignition advance value at 1000 rpm. In S112, the motor control unit 14 determines whether the motor rotation speed command value has reached the final target rotational speed. If it determines that the final target rotational speed has not been reached, the process returns to S107, and if it determines that it has reached, the startup sequence ends.

[0054] In this way, the motor control unit 14 rotates the motor 15F at a predetermined rotational speed (500 rpm) and acquires the load torque value TRQ based on the operation amount and the set advance angle (for example, 40). The motor control unit 14 updates the advance angle based on the acquired load torque value TRQ and the motor rotational speed value SPD based on the motor rotational speed command value (target rotational speed) or the current rotational speed of the motor 15F. The motor control unit 14 controls the motor driver IC60 according to the direction of the rotor detected by the rotary encoder 61 and the updated advance angle. Here, the operation amount includes the Vref voltage which is an analog voltage or the duty of the PWM signal. When the motor rotational speed command value (target rotational speed) is the first rotational speed, the predetermined rotational speed is a low rotational speed (for example, 500 rpm) which is slower than the first rotational speed or has a smaller influence of the advance angle than the first rotational speed. The motor control unit 14 updates the advance angle with the motor rotational speed command value as the motor rotational speed value SPD when the difference between the motor rotational speed command value (target rotational speed) and the current rotational speed is within a predetermined range. On the other hand, the motor control unit 14 updates the advance angle with the current rotational speed as the motor rotational speed value SPD when the difference exceeds the predetermined range. Further, in the non-volatile memory 55, information associating the motor rotational speed value SPD, the load torque value TRQ, and the advance angle, or a calculation formula for calculating the advance angle from the rotational speed value SPD and the load torque value TRQ is stored. The motor control unit 14 updates the advance angle based on the information or the calculation formula stored in the non-volatile memory 55. Note that the motor control unit 14 may store the acquired load torque value TRQ in the non-volatile memory 55 (storage unit). In this case, the motor control unit 14 may read out the load torque value TRQ stored in the non-volatile memory 55 and update the advance angle. Also, the rotary encoder 61 is set such that the count value of the number of pulses output per rotation of the motor 15F is a multiple of the number of times of switching of the excitation phase of the coil required per rotation of the motor 15F.

[0055] As described above, according to Embodiment 1, since the load torque is detected and the advance angle is set according to the motor rotation speed (motor rotation speed) and the load torque, it is possible to suppress a decrease in the efficiency of the motor and the occurrence of rotation failure due to insufficient output torque. Further, since the advance angle is set based on the motor rotation speed command value, the advance angle does not fluctuate due to rotation unevenness, and the rotation unevenness is not further deteriorated. When the deviation between the motor rotation speed command value and the actual rotation speed becomes large (when it becomes larger than a predetermined value), since the advance angle is set based on the actual rotation speed, it is possible to suppress a decrease in the efficiency of the motor and the occurrence of rotation failure due to insufficient output torque.

[0056] As described above, according to Embodiment 1, it is possible to suppress a decrease in efficiency and insufficient drive torque when controlling the motor.

Embodiment

[0057] Subsequently, Embodiment 2 will be described focusing on the differences from Embodiment 1. In Embodiment 2, the processing related to the rotation speed and the advance angle setting is different from that in Embodiment 1. In Embodiment 2, the motor rotation speed value SPD used for advance angle adjustment uses a value obtained by performing a low-pass filter process on the actual rotation speed of the motor. For the low-pass filter process, various methods such as the moving average method and the method using a first-order lag system can be used. Further, during acceleration or deceleration of the motor 15F, the acceleration or deceleration and the characteristics of the low-pass filter process are also reflected in the advance angle adjustment.

[0058] <Low-pass filter process> FIG. 7 shows the rotation speed of the motor 15F during acceleration / deceleration, the value obtained by performing a low-pass filter process on the rotation speed, and the value obtained by adding or subtracting a correction value to the value obtained by the low-pass filter process. FIG. 7 shows time on the horizontal axis and the rotation speed [rpm] of the motor 15F on the vertical axis. The solid line represents the actual rotation speed of the motor 15F, the dotted line represents the rotation speed after the low-pass filter process (low-pass filter process value), and the dashed line represents the rotation speed obtained by adding or subtracting a correction value to the low-pass filter process value.

[0059] In the second embodiment, the motor control unit 14 performs low-pass filter processing on the rotational speed based on the detection result of the rotary encoder 61 in order to smooth the speed variation of the rotational speed of the motor 15F. As shown in FIG. 7, during the acceleration or deceleration of the motor 15F, a difference occurs between the actual rotational speed and the value obtained by the low-pass filter processing according to the acceleration or deceleration and the delay of the low-pass filter processing. The delay of the low-pass filter processing is caused by the time constant of the low-pass filter. The greater the effect of the low-pass filter processing, the greater the delay, and the greater the difference between the actual rotational speed and the value after the low-pass filter processing.

[0060] Therefore, the motor control unit 14 calculates a correction value according to the low-pass filter characteristics, the acceleration or deceleration, the motor rotational speed command value, the rotational speed information, or the value obtained by the low-pass filter processing. As shown in FIG. 7, during the acceleration of the rotational speed of the motor 15F, a delay occurs in the rotational speed after the low-pass filter processing (dotted line) compared to the actual rotational speed (solid line). For this reason, the motor control unit 14 corrects the delay caused by performing the low-pass filter processing. In the second embodiment, during the acceleration of the motor 15F, the motor control unit 14 uses, as the motor rotational speed value SPD, a value obtained by adding a predetermined correction value to the value obtained by performing low-pass filter processing on the rotational speed. For example, as shown in FIG. 7, the control unit 14 adds the correction value β1 to the value obtained by performing low-pass filter processing on the rotational speed at the timing t1. The motor control unit 14 sets the correction value according to the acceleration, the delay of the low-pass filter processing, and the motor rotational speed command value. When the motor rotational speed value SPD obtained by adding the correction value exceeds the motor rotational speed command value, the motor control unit 14 reduces the correction value by the excess amount. That is, the motor rotational speed value SPD becomes the same value as the motor rotational speed command value.

[0061] Also, during the deceleration of the motor 15F, the motor control unit 14 advances the rotation speed after the low-pass filter processing compared to the actual rotation speed (solid line). Therefore, the motor control unit 14 corrects the advance caused by performing the low-pass filter processing. In the second embodiment, during the deceleration of the motor 15F, the motor control unit 14 uses, as the motor rotation speed value SPD, a value obtained by subtracting a correction value from the value obtained by performing low-pass filter processing on the rotation speed. For example, as shown in FIG. 7, at timing t2, the control unit 14 subtracts the correction value β2 from the value obtained by performing low-pass filter processing on the rotation speed. The motor control unit 14 sets the correction value according to the deceleration speed, the advance of the low-pass filter processing, and the motor rotation speed command value. When the motor rotation speed value SPD obtained by subtracting the correction value is lower than the motor rotation speed command value, the motor control unit 14 increases the correction value by the amount of the shortfall. That is, the motor rotation speed value SPD becomes the same value as the motor rotation speed command.

[0062] Note that in the constant rotation speed region from the end of the acceleration of the motor 15F until the deceleration starts after reaching the predetermined rotation speed, the delay and advance caused by the low-pass filter processing during acceleration and deceleration as described above do not occur. Therefore, the value obtained by performing low-pass filter processing is used as the motor rotation speed value SPD. Other controls according to the second embodiment are the same as those in the first embodiment, and thus the description thereof is omitted.

[0063] In this way, when the motor 15F is rotating at a constant speed, the motor control unit 14 sets the advance angle using the value obtained by subjecting the current rotational speed to low-pass filter processing as the motor rotational speed value SPD. When the motor 15F is accelerating or decelerating, the motor control unit 14 sets the advance angle using the value obtained by correcting the value obtained by low-pass filter processing according to the time constant, the acceleration or deceleration, the motor rotational speed command value, the current rotational speed, and the value obtained by low-pass filter processing as the motor rotational speed value SPD. Specifically, when the motor 15F is accelerating, the motor control unit 14 calculates a correction value according to the time constant of the low-pass filter, the acceleration, the motor rotational speed command value, the current rotational speed, and the value obtained by low-pass filter processing for the value obtained by low-pass filter processing. The motor control unit 14 adds the correction value to the value obtained by low-pass filter processing, and sets the corrected value as the motor rotational speed value SPD to set the advance angle. On the other hand, when the motor 15F is decelerating, the motor control unit 14 calculates a correction value according to the time constant of the low-pass filter, the deceleration, the motor rotational speed command value, the current rotational speed, and the value obtained by low-pass filter processing for the value obtained by low-pass filter processing. The motor control unit 14 subtracts the correction value from the value obtained by low-pass filter processing, and sets the corrected value as the motor rotational speed value SPD to set the advance angle.

[0064] As described above, according to the second embodiment, since the advance angle is set after subjecting the actual rotational speed to low-pass filter processing and reducing the variation in rotational speed due to rotational unevenness, it is possible to suppress the variation in the advance angle due to the speed variation caused by rotational unevenness and further deterioration of rotational unevenness. As described above, according to the second embodiment, it is possible to suppress a decrease in efficiency and a shortage of drive torque when controlling the motor.

Embodiment

[0065] Next, Example 3 will be described focusing on the differences from Examples 1 and 2. In Example 3, the processing regarding the advance angle setting when the load torque changes during the rotation of the motor 15F is different from that in Example 1. When the image forming apparatus 100 performs double-sided printing, the motor 15F drives the double-sided conveyance roller group 28 as well, so the load torque changes between when the double-sided conveyance roller is driven and when it is not driven. Also, not limited to single-sided printing and double-sided printing, the load torque also changes at the timing when the sheet feeding roller 26 feeds the sheet P from the sheet feeding cassette 25 and at the timing when the trailing edge of the sheet P passes through the sheet feeding roller 26. In Example 3, the advance angle is set in accordance with the change in the load torque of the motor 15F caused by the image forming operation of the image forming apparatus 100.

[0066] <Relationship between Load Torque and Advance Angle> Fig. 8 shows the change in load torque and the state of advance angle change. Fig. 8(i) is a graph showing the time change of the load torque, and (ii) is a graph showing the time change of the advance angle. t11 to t14 indicate timings, and T1 to T3 indicate intervals. Interval T1 indicates, for example, the interval from the start to the stop of the drive of the double-sided conveyance roller group 28. Interval T2 indicates, for example, the interval in which the advance angle is gradually increased in accordance with the start of the drive of the double-sided conveyance roller group 28. Interval T3 indicates, for example, the interval in which the advance angle is gradually decreased in accordance with the stop of the drive of the double-sided conveyance roller group 28.

[0067] The motor control unit 14 switches the advance angle curve to an advance angle curve corresponding to the load torque increment in accordance with the timings t11 and t13 when the motor 15F drives the double-sided conveyance roller group 28 as well. Then, the motor control unit 14 returns the advance angle curve to the original advance angle curve in accordance with the timings t12 and t14 when the drive of the double-sided conveyance roller group 28 is stopped. At this time, the motor control unit 14 gradually changes the advance angle (intervals T2 and T3) so that the advance angle does not change abruptly.

[0068] When the double-sided conveyance roller group 28 is driven, the increase in the load torque can be detected and obtained by detecting the load torques in two states, namely, when there is driving of the double-sided conveyance roller group 28 and when there is no driving, during the initial operation after the power-on of the image forming apparatus 100. The method for detecting the load torque is the same as that in the first embodiment. Since other controls in the third embodiment are the same as those in the first embodiment, the description thereof is omitted. As described above, in the third embodiment, even when the load torque changes during the rotation of the motor 15F, the advance angle can be appropriately set. Thus, when the load torque changes during the driving of the motor 15F, the motor control unit 14 may give a load torque value TRQ in accordance with the change in the load torque, select an advance angle curve corresponding to the load torque value TRQ, and adjust the advance angle. As described above, according to the third embodiment, it is possible to suppress a decrease in efficiency and a shortage of driving torque when controlling the motor.

[0069] [Other Embodiments] Note that the motor control unit 14 can be implemented as a motor control device. Further, the part related to the motor control of the motor control unit 14 and the printer control unit 11 can be implemented as a motor control device. Furthermore, in the present embodiment, the control of the motor 15F that drives the fixing unit 24 has been described as an example, but the present invention can be similarly applied to a motor that drives each roller related to sheet conveyance in an image forming apparatus, for example. Similarly, the present invention can be similarly applied to a motor that drives a member in the image forming unit 1 of the image forming apparatus 100.

[0070] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and causing one or more processors in a computer of the system or device to read and execute the program. Further, the present invention can also be realized by a circuit (for example, an ASIC) that realizes one or more functions.

[0071] The disclosure of the present embodiment includes the following configurations. (Configuration 1) An image forming apparatus that forms an image on a recording material, A stepping motor having a coil and a rotor, first detecting means for detecting the direction of the rotor, excitation means for exciting the coil, setting means for setting an advance angle which is a timing for exciting the coil with respect to the direction of the rotor detected by the first detecting means, second detecting means for detecting the rotational speed of the rotor, control means for controlling the stepping motor, comprising, the control means rotates the stepping motor at a predetermined rotational speed, acquires a load torque value based on an operation amount and the advance angle set by the setting means, the setting means updates the advance angle based on the load torque value acquired by the control means and a rotational speed value based on a target rotational speed of the stepping motor or the rotational speed detected by the second detecting means, the control means controls the excitation means according to the direction of the rotor detected by the first detecting means and the advance angle updated by the setting means, and an image forming apparatus characterized by this. (Configuration 2) The operation amount includes an analog voltage output from the control means to the excitation means or a duty of a PWM signal, and the image forming apparatus according to Configuration 1, characterized by this. (Configuration 3) When the target rotational speed is a first rotational speed, the predetermined rotational speed is a second rotational speed slower than the first rotational speed or having less influence of the advance angle than the first rotational speed, and the image forming apparatus according to Configuration 1 or Configuration 2, characterized by this. (Configuration 4) When the difference between the target rotational speed and the rotational speed detected by the second detecting means is within a predetermined range, the setting means updates the advance angle using the target rotational speed as the rotational speed value, and when the difference exceeds the predetermined range, the setting means updates the advance angle using the rotational speed detected by the second detecting means as the rotational speed value, and the image forming apparatus according to any one of Configurations 1 to 3, characterized by this. (Configuration 5) The setting means updates the phase advance angle using, as the rotational speed value, a value obtained by subjecting the rotational speed detected by the second detection means to low-pass filter processing, in any one of Configurations 1 to 4. The image forming apparatus according to any one of Configurations 1 to 4, characterized in that the phase advance angle is updated using, as the rotational speed value, a value obtained by subjecting the rotational speed detected by the second detection means to low-pass filter processing. (Configuration 6) During acceleration or deceleration of the stepping motor, the setting means updates the phase advance angle using, as the rotational speed value, a value corrected according to the characteristics of the low-pass filter, the acceleration or deceleration, the target rotational speed, the rotational speed detected by the second detection means, and the value obtained by subjecting the rotational speed detected by the second detection means to low-pass filter processing, in the image forming apparatus according to Configuration 5. The image forming apparatus according to Configuration 5, characterized in that during acceleration or deceleration of the stepping motor, the setting means updates the phase advance angle using, as the rotational speed value, a value corrected according to the characteristics of the low-pass filter, the acceleration or deceleration, the target rotational speed, the rotational speed detected by the second detection means, and the value obtained by subjecting the rotational speed detected by the second detection means to low-pass filter processing. (Configuration 7) During acceleration of the stepping motor, the setting means calculates a correction value according to the characteristics of the low-pass filter, the acceleration, the target rotational speed, the rotational speed detected by the second detection means, and the value obtained by subjecting the rotational speed detected by the second detection means to low-pass filter processing, adds the correction value to the value obtained by subjecting the rotational speed detected by the second detection means to low-pass filter processing to correct the value, and updates the phase advance angle using the corrected value as the rotational speed value, in the image forming apparatus according to Configuration 6. The image forming apparatus according to Configuration 6, characterized in that during acceleration of the stepping motor, the setting means calculates a correction value according to the characteristics of the low-pass filter, the acceleration, the target rotational speed, the rotational speed detected by the second detection means, and the value obtained by subjecting the rotational speed detected by the second detection means to low-pass filter processing, adds the correction value to the value obtained by subjecting the rotational speed detected by the second detection means to low-pass filter processing to correct the value, and updates the phase advance angle using the corrected value as the rotational speed value. (Configuration 8) During deceleration of the stepping motor, the setting means calculates a correction value according to the characteristics of the low-pass filter, the deceleration, the target rotational speed, the rotational speed detected by the second detection means, and the value obtained by subjecting the rotational speed detected by the second detection means to low-pass filter processing, subtracts the correction value from the value obtained by subjecting the rotational speed detected by the second detection means to low-pass filter processing to correct the value, and updates the phase advance angle using the corrected value as the rotational speed value, in the image forming apparatus according to Configuration 6. The image forming apparatus according to Configuration 6, characterized in that during deceleration of the stepping motor, the setting means calculates a correction value according to the characteristics of the low-pass filter, the deceleration, the target rotational speed, the rotational speed detected by the second detection means, and the value obtained by subjecting the rotational speed detected by the second detection means to low-pass filter processing, subtracts the correction value from the value obtained by subjecting the rotational speed detected by the second detection means to low-pass filter processing to correct the value, and updates the phase advance angle using the corrected value as the rotational speed value. (Configuration 9) The characteristics of the low-pass filter include the time constant of the low-pass filter, in any one of Configurations 6 to 8. The image forming apparatus according to any one of Configurations 6 to 8, characterized in that the characteristics of the low-pass filter include the time constant of the low-pass filter. (Configuration 10) The image forming apparatus includes a non-volatile memory in which information associating the rotational speed value, the load torque value, and the phase advance angle, or a calculation formula for calculating the phase advance angle from the rotational speed value and the load torque value is stored. The image forming apparatus according to any one of Configurations 1 to 9, wherein the setting means updates the advance angle based on the information stored in the nonvolatile memory or the calculation formula. (Configuration 11) The control means stores the acquired load torque value in a storage unit, The image forming apparatus according to any one of Configurations 1 to 10, wherein the setting means reads the load torque value stored in the storage unit and updates the advance angle. (Configuration 12) When the load torque changes during driving of the stepping motor, the control means supplies the setting means with the load torque value corresponding to the change in the load torque, The image forming apparatus according to any one of Configurations 1 to 11, wherein the setting means updates the advance angle according to the load torque value supplied from the control means. (Configuration 13) The first detection means is a rotary encoder that outputs a pulse signal in response to rotation of the stepping motor, The image forming apparatus according to any one of Configurations 1 to 12, wherein the rotary encoder is set such that a count value of the number of pulses based on the pulse signal output per rotation of the stepping motor is an integer multiple of the number of switching times of the exciting phases of the coils required per rotation of the stepping motor.

Explanation of Signs

[0072] 14 Motor control unit 15F Motor 60 Motor driver IC 61 Rotary encoder

Claims

1. An image forming apparatus that forms an image on a recording material, A stepping motor having a coil and a rotor, First detection means for detecting the direction of the rotor, Excitation means for exciting the coil, Setting means for setting an advance angle that is the timing for exciting the coil with respect to the direction of the rotor detected by the first detection means, Second detection means for detecting the rotation speed of the rotor, Control means for controlling the stepping motor, comprising The control means rotates the stepping motor at a predetermined rotation speed, obtains a load torque value based on an operation amount and the advance angle set by the setting means, The setting means updates the advance angle based on the load torque value obtained by the control means and a rotation speed value based on the target rotation speed of the stepping motor or the rotation speed detected by the second detection means, The control means controls the excitation means according to the direction of the rotor detected by the first detection means and the advance angle updated by the setting means. An image forming apparatus characterized by that.

2. The image forming apparatus according to claim 1, wherein the operation amount includes an analog voltage output from the control means to the excitation means or a duty of a PWM signal.

3. When the target rotation speed is a first rotation speed, The image forming apparatus according to claim 1, wherein the predetermined rotation speed is a second rotation speed that is slower than the first rotation speed or has a smaller influence of the advance angle than the first rotation speed.

4. When the difference between the target rotation speed and the rotation speed detected by the second detection means is within a predetermined range, the setting means updates the advance angle with the target rotation speed as the rotation speed value. When the difference exceeds the predetermined range, the setting means updates the advance angle with the rotation speed detected by the second detection means as the rotation speed value. The image forming apparatus according to claim 1, characterized in that.

5. The setting means updates the advance angle with a value obtained by subjecting the rotation speed detected by the second detection means to low-pass filter processing as the rotation speed value. The image forming apparatus according to claim 1, characterized in that.

6. During acceleration or deceleration of the stepping motor, the setting means corrects the value obtained by the low-pass filter processing according to the characteristics of the low-pass filter, the acceleration or deceleration, the target rotation speed, the rotation speed detected by the second detection means, and the value obtained by the low-pass filter processing. The image forming apparatus according to claim 5, characterized in that the advance angle is updated with the corrected value as the rotation speed value.

7. During acceleration of the stepping motor, the setting means calculates a correction value according to the characteristics of the low-pass filter, the acceleration, the target rotation speed, the rotation speed detected by the second detection means, and the value obtained by the low-pass filter processing. The image forming apparatus according to claim 6, characterized in that the advance angle is updated with a value obtained by adding the correction value to the value obtained by the low-pass filter processing and correcting the result as the rotation speed value.

8. During deceleration of the stepping motor, the setting means calculates a correction value according to the characteristics of the low-pass filter, the deceleration, the target rotation speed, the rotation speed detected by the second detection means, and the value obtained by the low-pass filter processing. The image forming apparatus according to claim 6, characterized in that the advance angle is updated with a value obtained by subtracting the correction value from the value obtained by the low-pass filter processing and correcting the result as the rotation speed value.

9. The image forming apparatus according to any one of claims 6 to 8, wherein the characteristics of the low-pass filter include the time constant of the low-pass filter.

10. The apparatus comprises a non-volatile memory in which information associating the rotational speed value, the load torque value and the advance angle, or a calculation formula for calculating the advance angle from the rotational speed value and the load torque value is stored. The image forming apparatus according to claim 1, wherein the setting means updates the advance angle based on the information or the calculation formula stored in the non-volatile memory.

11. The control means stores the acquired load torque value in a storage unit. The image forming apparatus according to claim 1, wherein the setting means reads the load torque value stored in the storage unit and updates the advance angle.

12. When the load torque changes during driving of the stepping motor, the control means supplies the setting means with the load torque value corresponding to the change in the load torque. The image forming apparatus according to claim 1, wherein the setting means updates the advance angle according to the load torque value supplied from the control means.

13. The first detection means is a rotary encoder that outputs a pulse signal in response to rotation of the stepping motor. The image forming apparatus according to claim 1, wherein the rotary encoder is set such that a count value of the number of pulses based on the pulse signal output per rotation of the stepping motor is an integer multiple of the number of times of switching of the exciting phases of the coils required per rotation of the stepping motor.

Images