JPH0764365A - Multicolor image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device capable of preventing the step-out or surely attaining the restarting of a stepping motor at the time of exerting the factor of load fluctuation, etc., on the rotating body driven by the stepping motor while holding the respective developing means. CONSTITUTION:The multicolor image forming device is provided with the rotary type developing means changeover mechanism 108 by which one of the plural developing means Dc, Dm, Db and Dy is rotationally moved to the position opposite to the image carrier C by the stepping motor for properly performing the selective changeover, and moreover, the device is provided with the deviation calculating means for calculating the theoretical rotating position by the motor calculating on the basis of the drive command pulse signal of the stepping motor, the actual rotating position obtained by the actual rotating position detecting means provided to the stepping motor or the developing means changeover mechanism 108 and the deviation between the actual rotating position and the logical rotating position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic multicolor image forming apparatus, for example, a plurality of developing devices are provided on a rotary carrier, and the developing devices are appropriately moved by driving a stepping motor to select the developing devices. The present invention relates to a multi-color image forming apparatus having a configuration for selectively switching.

[0002]

2. Description of the Related Art Conventionally, for example, four developing devices of different colors (three primary colors of color and black) are provided on a rotating body, and the developing device is appropriately moved by being driven by a stepping motor as a power source. 2. Description of the Related Art There is known an electrophotographic multicolor image forming apparatus having a built-in rotary developing machine switching machine for selectively switching the developing units. Since this rotary developing machine switching machine has a load fluctuation due to the consumption of the developing device, the stepping motor is driven by a specific slewing control to appropriately accelerate and decelerate the positioning drive control of each developing device. Is going.

[0003]

However, if the weight fluctuation caused by the consumption of the toner contained in each developing device carried by the rotating member becomes large as described above, the slewing control alone becomes insufficient. There is a case where the stepping motor cannot be driven for a predetermined number of pulses, so-called step-out of the stepping motor may occur.

As described above, when the stepping motor loses synchronization, the reliability of stopping accuracy of the rotating body is lost, and as a result, each developing device cannot be stopped accurately at the developing position, resulting in a defective formed image. Also, an extremely large load acts,
Once the stepping motor has stepped out, it has the property that it cannot move after that (it becomes impossible to restart). It means loss of functionality, so
It is absolutely necessary to prevent the stepping motor from being unable to restart.

Therefore, the present invention has been made in view of the above problems, and when factors such as load fluctuations act on a rotating body that carries each developing device and is driven by a stepping motor, It is an object of the present invention to provide an image forming apparatus capable of surely preventing step out of a stepping motor or restarting the stepping motor.

It is another object of the present invention to reduce drive noise due to excessive supply of drive energy for the stepping motor by appropriately maintaining the torque margin of the stepping motor.

[0007]

[Means for Solving the Problems] and

According to the present invention, a multicolor image having at least a plurality of developing devices and having a rotary developing device switching mechanism for selectively switching by selectively rotating the developing device facing the image bearing member by driving a stepping motor. In the forming apparatus, between the theoretical rotational position of the motor calculated based on the drive command pulse signal of the stepping motor and the actual rotational position obtained by the actual rotational position detecting means mounted on the stepping motor or the developing device switching mechanism. Deviation is calculated, and based on the result, adjustment is performed so as to increase the startup acceleration rate of the rotary developing device switching machine when the deviation during startup acceleration is small, and when the deviation is large, startup acceleration of the rotary developing device switching machine is performed. Make adjustments that lower the rate. Further, when the deviation at the time of stop deceleration is small, an adjustment is made to increase the stop deceleration rate of the rotary developing device changer, and when the deviation is small, an adjustment is made to decrease the stop deceleration rate of the rotary developing device changer. To do. Further, in the case where the stepping motor is driven by constant current control, the adjustment for increasing the acceleration / deceleration rate is performed, while the adjustment for decreasing the motor driving current value and the acceleration / deceleration rate is performed. The motor drive current value may be increased.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a fragmentary sectional view showing the overall construction of the embodiment. In the figure, the paper S fed from a paper feed unit 101 provided detachably below the main body of the apparatus.
The front end portion is held by the gripper 103f provided on the outer peripheral surface of the transfer drum 103 and is held on the outer peripheral surface of the transfer drum 103.

On the other hand, a latent image for each color is formed on the image carrier 1 of the drum cleaner unit C by the optical unit 107 arranged above the apparatus main body.

Continuing with further reference to the plan view of FIG. 2, a shaft body 110 provided parallel to the axis of the image carrier 1 shown in FIG. And the developing cartridges Dy, Dc, D
A stepping motor 25 that is driven in a predetermined manner to selectively move m and Db, and an encoder 2 that is provided on the output shaft of the stepping motor 25 and detects the rotation amount of the motor.
8 and between the developing cartridge holding member 108 and the stepping motor 25 to perform predetermined deceleration,
The entire rotary developing device switching mechanism is configured by the drive transmission mechanism 22 that drives the developing cartridge holding member 108 by a predetermined rotation.

Referring again to FIG. 1, the developed images formed by the selection mechanism having the above-described structure for each color are sequentially transferred onto the sheet S on the transfer drum 103 to form a multicolor image. After being separated, it is separated from the transfer drum 103 and is fixed by the fixing unit 104, and the paper discharge unit 105
The sheet is discharged from the sheet discharge tray unit 106.

Next, referring to the block diagram of FIG.
6, a power-on switch 25 of this apparatus, a motor driver circuit 27 for driving the stepping motor 25, and a deviation calculation unit 32 are connected. The encoder 28 connected to the rotary developing device changer 108 is connected to the encoder pulse number counter 30, and together with the motor drive pulse number counter 31, the deviation calculation unit 3 is connected.
Connected to 2. Further, the stepping motor 25 is connected to the motor driver circuit 27. In the above configuration, when the power switch 25 is turned on, the CPU 26
Is a stepping motor 25 via a motor driver 27.
As a result, the rotary developing device switching machine 108 is rotated. Along with this, the counter 30 counts the number of pulses of the encoder 28 fixed to the output shaft of the stepping motor 25 as follows.

That is, in the flow chart of FIG. 4, Ne: Encoder counter register pulse number Nm: Motor counter register pulse number Pe: Actual position register pulse number dem: Deviation register pulse number Th: As one step angle encoder pulse number, When the encoder counter is activated, the rotary developing device switching device 108 is rotated in step S1, the forward / reverse rotation is determined in step S1, and it is determined that the clockwise rotation direction is the CW direction. Then, the process proceeds to step S3, 1 is added to Ne, and then the process proceeds to step S4. Also,
When it is determined in step S1 that the direction is the counterclockwise rotation direction, in step S2, 1 is subtracted from Ne, and then the process proceeds to step S4. In step S4,
It is determined whether the encoder counter register pulse number Ne is equal to the encoder pulse number Th for one step angle. If they are equal, the process proceeds to step S5 and the value obtained by adding 1 to the actual position register pulse number Pe is added to the new actual position. The register pulse number Pe is set, the encoder counter register pulse number Ne is set to 0, and the process ends.

On the other hand, if it is determined in step S4 that the encoder counter register pulse number Ne is not equal to the encoder pulse number Th for one step angle,
In step S6, it is determined whether Ne is equal to -Th. If it is determined that they are equal, the process proceeds to step S7, and the value obtained by subtracting 1 from the actual position register pulse number Pe is changed to the new actual position register pulse number Pe. And the encoder counter register pulse number Ne is set to 0, and the process ends. Further, in step S6, N
When it is determined that e is not equal to -Th, the process ends. With the above flow, the number of pulses of the encoder 28 is counted.

On the other hand, the counter 31 is a motor driver 27.
The motor drive pulse generated in step (4) is logically processed and counted as follows.

That is, in the flow chart of FIG. 5, it is determined in step S10 whether the rotation direction of the stepping motor 25 is the clockwise rotation direction CW or the CCW direction. If it is determined that the rotation direction is the CW direction, step S10 is performed.
Go to 12 and add 1 to the motor counter register pulse number Nm.
Is added to the new motor counter register pulse count N
Set to m and exit. When it is determined in step S10 that the counterclockwise rotation direction is set, the value obtained by subtracting 1 from the motor counter register pulse number Nm is set as the new motor counter register pulse number Nm in step S11, and the process is ended. To do.

Next, when the rotary developing device switching unit 108 starts to rotate, the deviation calculating unit 32 performs the processing as shown in the flow chart of FIG.

First, in step S21, each counter register Ne, Nm, Pe to be used is reset.
Next, the counters 30 and 31 are controlled until the positioning operation of the rotary developing device changer 108 is completed (step S2).
2 to 28).

During the above processing, when the CPU 26 issues a data detection command by the data detection flag, the deviation is calculated as shown in the flow chart of FIG. That is, when the deviation calculation is started, in step S31, a value obtained by subtracting the actual position register pulse number Pe from the motor counter register pulse number Nm is set as a new motor counter register pulse number Nd, and then the process proceeds to step S32. A value obtained by multiplying this Nd by the encoder pulse number Th for one step angle is the encoder pulse number Ne.
The value subtracted from is set to the deviation register pulse number dem.

After this, the process proceeds to step S33, and the CPU
The flag of the data detection command from the data detection flag from 26 is turned off, and the deviation calculation is completed.

At this time, the data detection is performed within the acceleration region and the deceleration region at a constant sampling interval, and the sampling interval is set longer than the time required for acceleration and deceleration.

Further, since the stepping motor vibrates violently in the self-starting region, data detection is performed while avoiding the self-starting region. Acceleration and deceleration deviations for each sampling are obtained in independent registers, and after all the developing device positioning operations are completed, the motor acceleration rate and deceleration rate are determined based on the maximum values of acceleration deviation and deceleration deviation. Adjustment.

At this time, the deviation during acceleration has a step angle of 0% to
When it is within the -25% range or when it has a positive characteristic, the motor torque has a margin, so the acceleration rate is increased to accelerate.

On the other hand, the deviation during acceleration has a step angle of -25% to
If it is within the -50% range, the motor is operating stably and no adjustment is made. Further, when the deviation during acceleration is within the step angle range of -50% to -100%, there is not much margin in the motor torque, so the acceleration rate is lowered to accelerate.

The deviation during acceleration is the step angle -100.
If it exceeds%, the motor is out of step, so the acceleration rate is lowered and the above-mentioned processing is performed again. If step out continues, a warning is displayed and the machine is stopped.

Further, the deceleration deviation has a step angle of 0% to 25%.
When it is within the% range or when it has a negative characteristic, there is a margin in the motor torque, so the deceleration is increased by increasing the deceleration rate.

If the deviation during deceleration is within the step angle range of 25% to 50%, the motor is operating stably and no adjustment is made. When the deviation during deceleration falls within the range of the step angle of 50% to 100%, there is not much margin in the motor torque, so the deceleration rate is reduced to perform deceleration.

Deviation angle is -80% to -100% or 8
When it falls within the range of 0% to 100%, a warning is displayed to indicate the danger of step-out. When the deviation during deceleration exceeds 100% of the step angle, the motor is out of step, so the deceleration rate is reduced and the above check operation is performed again. If step out continues, a warning is displayed and the machine is stopped. The above processing is performed at the time of starting the machine and during the developing machine switching operation during printing, and the adjusted acceleration rate and deceleration rate are used from the next printing operation. Although the rotary encoder is directly provided on the motor 25 in the above embodiment, it may be provided so as to be connected to the shaft body 110 on the side of the development switching mechanism.

[Second Embodiment] Next, a second embodiment will be described. Data detection is performed for each stepping motor drive pulse, and the next drive pulse width is obtained from the deviation. The current deviation is calculated when the current drive pulse is generated. It was obtained during the generation of the current pulse. After adjusting the acceleration rate TR, the next pulse width T2 is adjusted to the current pulse width T1.
And the adjusted acceleration rate TR and the following equation.

T2 = ((T1) ⁻¹ + T1TR) ⁻¹ Equation 1 Here, the unit of the acceleration rate TR is [MHz / μs], and the unit of the pulse widths T1 and T2 is [μs]. The acceleration rate is adjusted as follows. When the acceleration deviation is within the range of the step angle of 0% to -25% or has the positive characteristic, the acceleration rate is increased.

Further, the deviation during acceleration has a step angle of -25% to
When it is within the range of -50%, the acceleration rate is not adjusted. Acceleration deviation is step angle -50
When it falls within the range of% -100%, the acceleration rate is lowered. When the deviation during acceleration is -100% or more of the step angle, the motor is out of step and the torque rate is 0.
And rotate at a constant speed. The deceleration rate is not adjusted to maintain the stopping accuracy.

[Third Embodiment] Next, referring to the block diagram of FIG. 8, a third embodiment will be described. When the deviation indicates that the torque has a margin based on the result of the deviation calculating means. That is, the deviation is 0% to 25% or 0%
When it falls within the range of -25%, the CPU
Via 26, the current setting value of the constant current control of the current control circuit 33 is lowered to lower the drive torque. Further, when the deviation indicates that the torque has no margin based on the result of the deviation calculating means, that is, the deviation is 50% to 100% in step angle.
% Or -50% to -100%, the current setting value of the constant current control of the current control circuit 33 is increased via the CPU 26 to increase the driving torque.

As described above, according to each embodiment,
In a multicolor image forming apparatus having at least a plurality of developing devices and having a rotary developing device switching mechanism for selectively switching by rotating a developing device facing the image carrier by driving a stepping motor, a stepping motor drive command The deviation between the theoretical rotational position of the motor calculated based on the pulse signal and the actual rotational position obtained by the actual rotational position detecting means mounted on the stepping motor or the developing device switching mechanism is calculated, and based on the result, When the deviation at the time of startup acceleration is small, adjustment is made to increase the startup acceleration rate of the rotary developing device switching machine, and when the deviation is large, adjustment is performed to decrease the startup acceleration rate of the rotary developing device switching machine. Also, when the deviation at the time of stop deceleration is small, adjustment is made to increase the stop deceleration rate of the rotary developing device switching machine,
When the deviation is small, adjustment is performed so as to reduce the stop deceleration rate of the rotary type developing device switching machine. On the other hand, in the case where the stepping motor is driven by constant current control, adjustment where the acceleration / deceleration rate is increased is reduced, while adjustment where the acceleration / deceleration rate is reduced is reduced. The motor drive current value may be increased. In this way, it is possible to always maintain the drive torque margin of the motor, prevent imbalance caused by toner consumption and the like, and prevent out-of-step accidents caused by increased load due to friction and dirt. It is effective in improving heat resistance, prolonging service life, improving maintainability, saving energy, and reducing noise.

[0035]

As described above, according to the present invention,
Provided is an image forming apparatus capable of reliably performing step-out prevention or restarting of a stepping motor when a load fluctuation or the like acts on a rotating body that carries each developing device and is driven by the stepping motor. can do.

Further, by properly maintaining the torque margin of the stepping motor, it is possible to reduce drive noise due to excessive supply of stepping motor drive energy.

[Brief description of drawings]

FIG. 1 is a fragmentary side view of a multicolor image forming apparatus common to each embodiment.

FIG. 2 is a plan view showing a drive unit of a rotary developing device switching machine.

FIG. 3 is a block diagram showing the overall configuration of the first embodiment.

FIG. 4 is a flowchart showing an operation of an encoder counter.

FIG. 5 is a flowchart showing the operation of a motor drive pulse counter.

FIG. 6 is a flowchart showing the operation of the deviation calculation unit.

FIG. 7 is a flowchart showing an operation of calculating a deviation.

FIG. 8 is a block diagram showing a configuration of a third embodiment.

[Explanation of symbols]

 D developing cartridge 108 rotary developing device changer 22 drive transmission mechanism Ne encoder counter register Nm motor counter register Pe actual position register dem deviation register Th 1 encoder pulse number of one step angle

Claims (15)

[Claims] 1. A multicolor image forming apparatus provided with a rotary developing device switching mechanism for selectively moving one of a plurality of developing devices to a position opposed to an image carrier by a stepping motor to appropriately select and switch. The theoretical rotational position of the motor calculated based on the drive command pulse signal of the stepping motor, and the actual rotational position obtained by the actual rotational position detecting means provided in the stepping motor or the developing device switching mechanism. And a deviation calculating means for calculating a deviation between the actual rotational position and the theoretical rotational position. 2. The multicolor image forming apparatus according to claim 1, further comprising adjusting means for adjusting a start acceleration rate and a stop deceleration rate of the stepping motor based on a result of the deviation calculating means. . 3. The adjusting means is set based on the result of the deviation calculating means so as to increase the starting acceleration rate of the rotary developing device switching machine when the deviation at the time of starting acceleration of the stepping motor is small. The multicolor image forming apparatus according to claim 2, wherein 4. When the maximum value of the deviation at the time of starting acceleration of the stepping motor falls within the range of 0% to -25% of the stepping angle based on the result of the deviation calculating means. The adjustment is performed so as to increase the acceleration rate of the stepping motor.
The multicolor image forming apparatus described in 1. 5. The adjusting means adjusts, based on the result of the deviation calculating means, to decrease the startup acceleration rate of the rotary developing device switching device when the deviation at the startup acceleration of the stepping motor is large. The multicolor image forming apparatus according to claim 2, wherein 6. The maximum value of the deviation at the time of starting acceleration of the stepping motor is -50% to -100% of the stepping angle, based on the result of the deviation calculating means.
6. The multicolor image forming apparatus according to claim 5, wherein adjustment is performed so as to reduce the acceleration rate when it is within the range. 7. The adjusting means makes an adjustment based on the result of the deviation calculating means so as to increase the stop deceleration rate of the rotary developing device changer when the deviation during stop deceleration of the stepping motor is small. The multicolor image forming apparatus according to claim 2, wherein 8. The stepping device, when the maximum value of the deviation when the stepping motor is stopped and decelerating is within the range of 0% to 25% of the stepping angle based on the result of the deviation calculating device. 8. The adjustment is performed to increase the stop deceleration rate of the motor.
The multicolor image forming apparatus described in 1. 9. The adjusting means makes an adjustment based on the result of the deviation calculating means so as to reduce the stop deceleration rate of the rotary developing device changer when the deviation at the stop deceleration of the stepping motor is large. 2. The method according to claim 2, wherein
The multicolor image forming apparatus described in 1. 10. The step of adjusting when the maximum value of the deviation when the stepping motor is stopped and decelerating is within the range of 50% to 100% of the stepping angle based on the result of the deviation calculating means. The multicolor image forming apparatus according to claim 9, wherein the adjustment is performed so as to increase the stop deceleration rate of the motor. 11. In order to drive the stepping motor by constant current control, instead of making the adjustment to decrease the acceleration / deceleration rate by the adjusting means, an adjustment is made to increase the drive current value of the stepping motor. The multicolor image forming apparatus according to claim 2. 12. The driving current value of the stepping motor is adjusted to be lowered, instead of the adjustment means to increase the acceleration / deceleration rate in order to drive the stepping motor under constant current control. The multicolor image forming apparatus according to claim 2, which is characterized in that. 13. Based on the result of the deviation calculating means,
The multicolor image forming apparatus according to claim 2, wherein step out of the stepping motor is detected. 14. Based on the result of the deviation calculating means,
The multicolor image forming apparatus according to claim 1, further comprising: a warning display that warns that there is a risk of step-out when the deviation of the stepping motor is close to the step angle. 15. Based on the result of the deviation calculating means,
The deviation of the stepping motor is a step angle of −80% or more.
The multicolor image forming apparatus according to claim 1, wherein a warning display is provided to warn that there is a risk of stepping out of the stepping motor when it is within a range of -100% or 80% to 100%.