JPH11167316A - Image printing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent malfunction of an electrophotographic system image forming device due to the step-out of a stepping motor. SOLUTION: A voltage value equivalent to the average value of an exciting current flowing to the stepping motor 202 is detected by a current detector resistor 205 and a low-pass filter 208, and compared with the specified voltage value of a constant-voltage source 210 by a comparator 209. When the detected voltage value exceeds the specified voltage value, a control part 201 restores a developing means to a hole position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus.

[0002]

2. Description of the Related Art In a conventional electrophotographic image printing apparatus, a stepping motor is often used as a drive source for a developing unit, a transfer drum and the like. The gap between the developing device and the transfer drum and the photosensitive drum can be set arbitrarily. For example, the interval between the developing device and the transfer drum and the photosensitive drum is set during standby or when the power is turned off. . The attaching and detaching operations of the developing device and the transfer drum are performed by driving an eccentric cam by a stepping motor.

[0003]

However, in the above-described conventional image forming apparatus, the stepping motor is driven by open loop control. There is a problem that the attaching / detaching operation cannot be performed and an operation failure occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an image forming apparatus capable of preventing a malfunction of the apparatus due to a step out of a stepping motor.

[0005]

The image printing apparatus according to the present invention is configured as follows.

(1) In an electrophotographic image printing apparatus, a stepping motor for driving a detachable load used for image printing, and an overcurrent for detecting that an exciting current flowing through the stepping motor is an overcurrent. Detecting means; and returning means for returning the preload to a predetermined position in a detached state when the overcurrent detecting means detects that an exciting current flowing through the stepping motor is an overcurrent.

(2) The image printing apparatus according to the above (1), further comprising a position detecting means for detecting that the load is at a predetermined position in the detached state, and the return means based on a signal from the position detecting means. Is returned to the predetermined position in the detached state.

(3) The image printing apparatus according to the above (1) or (2), further comprising an effective current detecting means for detecting an effective value of a current flowing through each phase of the exciting winding of the stepping motor, wherein the overcurrent detecting means is provided. The effective value of the current detected by the effective current detecting means is compared with a predetermined value, and when the current value exceeds the predetermined value, it is detected that the exciting current flowing through the stepping motor is an overcurrent.

(4) The image printing apparatus according to the above (1) or (2), further comprising an average current detecting means for detecting an average value of a current flowing through each phase of the exciting winding of the stepping motor, wherein the overcurrent detecting means comprises: The average value of the current detected by the effective current detecting means is compared with a predetermined value, and when the average value exceeds the predetermined value, it is detected that the excitation current flowing through the stepping motor is an overcurrent.

(5) In an electrophotographic image printing apparatus, a stepping motor for driving a detachable load used for image printing, step-out detecting means for detecting that the stepping motor has stepped out, and a step-out detecting means. And a return means for returning the load to a predetermined position in a detached state when the step-out detecting means detects that the stepping motor has stepped out.

(6) The image printing apparatus according to the above (5), further comprising a position detecting means for detecting that the load is at a predetermined position in a detached state, and the return means based on a signal from the position detecting means. Is returned to the predetermined position in the detached state.

(7) In the image printing apparatus of (5) or (6), an effective current detecting means for detecting an effective value of a current flowing through each phase of the exciting winding of the stepping motor;
Differential detection means for detecting a differential value of the effective value of the detected current, wherein the step-out detecting means compares the differential value of the effective value of the detected current with a predetermined value, and exceeds the predetermined value. Sometimes, it is detected that the stepping motor has stepped out.

(8) In the image printing apparatus of the above (5) or (6), an average current detecting means for detecting an average value of a current flowing in each phase of the exciting winding of the stepping motor;
Differential detection means for detecting a differential value of the average value of the detected current, wherein the step-out detecting means compares the differential value of the average value of the detected current with a predetermined value, and exceeds the predetermined value. Sometimes, it is detected that the stepping motor has stepped out.

(9) In the image printing apparatus of any one of the above (1) to (8), the load is a developing means detachable from the photosensitive drum.

(10) In the image printing apparatus of any one of the above (1) to (9), the load is a transfer drum detachable from the photosensitive drum.

(11) In the image printing apparatus according to any one of the above (1) to (10), the load is a transfer cleaner which is detachable from the transfer drum.

(12) In the image printing apparatus according to any one of the above (1) to (11), the load is a transfer current supply unit which is detachable from the transfer drum.

(13) The image printing apparatus according to any one of the above (1) to (12), further comprising a display means for displaying an operation state or a setting state of the apparatus, and an overcurrent detection signal from the overcurrent detection means or a detachment detection. When the step-out detection signal is output from the means, an error is displayed on the display means.

[0019]

(First Embodiment) FIG. 1 is a sectional view showing a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. The image forming apparatus of the present embodiment has a configuration in which a digital color image reader unit is provided at the upper part and a digital color image printer unit is provided at the lower part.

In the reader section, the original 30 is placed on an original platen glass 31 and is exposed and scanned by an exposure lamp 32 so that a reflected light image from the original 30 is condensed on a full-color sensor 34 by a lens 33 to form a color image. Obtain a decomposed image signal. The color-separated image signal is processed by a video processing unit (not shown) through an amplifier circuit (not shown) and sent to a printer unit.

In the printer section, a photosensitive drum 1 serving as an image carrier is rotatably supported in the direction of an arrow. Around the photosensitive drum 1, a pre-exposure lamp 11, a corona charger 2, a laser exposure optical system 3, and a potential sensor 12 are provided. , Four developing units 4y, 4c, 4m, and 4bk of different colors, and a drum light amount detecting unit 1
3, a transfer device 5, and a cleaning device 6 are arranged.

In the laser exposure optical system 3, an image signal from a reader section is converted into an optical signal by a laser output section (not shown), and the converted laser light is reflected by a polygon mirror 3a, and a lens 3b and a mirror 3c, and is projected on the surface of the photosensitive drum 1.

At the time of image formation in the printer section, the photosensitive drum 1
Is rotated in the direction of the arrow to uniformly charge the photosensitive drum 1 after charging by the pre-exposure lamp 11 by the charger 2, and irradiate the light image E for each separation color to form a latent image.

Next, by operating a predetermined developing device, the latent image on the photosensitive drum 1 is developed, and a toner image is formed on the photosensitive drum 1 using a resin as a base material. The developing device has an eccentric cam 24.
By the operations of y, 24c, 24m, and 24bk, the photosensitive drum 1 is selectively approached in accordance with each separation color.

Further, the toner image on the photosensitive drum 1 is
The image is transferred from a recording material cassette 7 to a recording material supplied to a position facing the photosensitive drum 1 via a transfer system and a transfer device 5. In the present embodiment, the transfer device 5 includes a transfer drum 5a, a transfer brush 5b, a suction roller 5g opposed to a suction brush 5c for electrostatically sucking a recording material, an inner charger 5d, and an outer charger 5e. A transfer sheet 5f made of a dielectric material and carrying a recording material is laminated on a connecting plate 5i and integrally stretched in a cylindrical shape in the peripheral opening area of the transfer drum 5a which is rotatably supported. doing. The transfer sheet 5f uses a dielectric sheet such as a polycarbonate film.

As the drum-shaped transfer device 5, that is, the transfer drum 5a is rotated, the toner image on the photosensitive drum 1 is transferred onto a recording material carried on a transfer sheet 5f by a transfer brush 5b.

As described above, a desired number of color images are transferred to the recording material sucked and conveyed to the transfer sheet 5f to form a full-color image.

In the case of forming a full-color image, when the transfer of the toner images of four colors is completed in this way, the recording material is separated from the transfer drum 5a by the action of the separating claw 8a, the separating push-up roller 8b and the separating charger 5h, and the heat is removed. The sheet is discharged to the tray 10 via the roller fixing device 9.

On the other hand, after the transfer, the photosensitive drum 1 is subjected to the image forming process again after the residual toner on the surface is cleaned by the cleaning device 6.

When images are formed on both sides of a recording material,
Immediately after the fixing device 9 is ejected, the conveyance path switching guide 19 is driven, and once guided to the reversing path 21a via the conveyance vertical path 20, the rear end of the reversing roller 21b is moved forward by the reverse rotation of the reversing roller 21b. And is retracted in the direction opposite to the direction in which the sheet is fed, and stored in the intermediate tray 22. Thereafter, an image is formed on the other surface again by the above-described image forming step.

Further, in order to prevent scattering of powder on the transfer sheet 5f of the transfer drum 5a and adhesion of oil on the recording material, the brush 14 faces the brush 14 via the fur brush 14 and the transfer roller 5f. Cleaning is performed by the action of the backup brush 15 and the backup brush 17 facing the roller 16 via the oil removing roller 16 and the transfer sheet 5f. Such cleaning is performed before or after image formation, and is performed at any time when a jam (paper jam) occurs.

In this embodiment, the eccentric cam 25 is operated at a desired timing, and the cam follower 5j integrated with the transfer drum 5f is operated.
The gap between the transfer sheet 5a and the photosensitive drum 1 can be set arbitrarily. For example, during standby or when the power is off, the interval between the transfer drum and the photosensitive drum is increased.

Here, the developing units 4y, 4c, 4m, 4b
k, the transfer drum 5a is operated by driving the eccentric cam with a stepping motor. These are positioned by using a sensor for detecting each home position so that the state separated from the photosensitive drum 1 when the power is turned on is stopped as a home position, and the operation of pressing the photosensitive drum 1 is performed by a predetermined number of pulses. Just go by rotating.

FIG. 2 is a circuit diagram showing a control configuration according to the first embodiment of the present invention. As shown in FIG. 2, a stepping motor 202 for attaching / detaching the developing device 2 includes a driving circuit 203,
A control unit (Process Controller) that is controlled by the constant current chopper by the current detection resistor 205, the reference voltage source 207, and the comparator 206 and controls the entire device.
driven by a motor drive phase signal from the eccentric cam (not shown). When the power is turned on, the control unit (return means) 201 responds to a signal from the developing device home position sensor (position detection means) 204,
The developing device is stopped at a predetermined home position. When the image forming operation is started, the stepping motor 202 is rotated by a predetermined number of pulses to a desired developing device according to the content of the printing operation, and the developing device is pressed,
When the developing operation for the color is completed, the image is rotated in the opposite direction by the same number of pulses, and as a result, returns to the initial home position.

At this time, since the stepping motor 202 is driven by a constant current chopper, the current detecting resistor 205
The peak value of the exciting current (A in FIG. 2) of the motor detected by the equation (1) is constant, but the average value increases as the load on the motor increases. Therefore, a voltage value corresponding to the average value of the detected current values (hereinafter simply referred to as an average value of the current values)
(B in FIG. 2) is compared with a constant voltage source 210 having a predetermined voltage value by a comparator 209 through a low-pass filter 208.

As shown in FIG. 4, when the motor load becomes heavy, the average value B of the excitation dragon of the motor increases, and when the voltage exceeds a predetermined voltage value, the motor is overloaded, and an error signal (overcurrent detection signal) C Occurs. In the above configuration, the current detecting resistor 205 and the low-pass filter 208 are average current detecting means for detecting the average value of the exciting current of the stepping motor 202, the comparator 209, and the voltage source 210 are the average of the detected exciting current of the stepping motor 202. The overcurrent detecting means detects that the average value of the current detected by comparing the value with the predetermined value exceeds a predetermined value.

Further, it is determined that there is a possibility that the stepping motor 202 in which the error signal C is generated is out of synchronization (abnormal), the image forming operation is interrupted, and a user such as an operation panel (display means) confirms. An error is displayed where possible, and a home poisoning operation is performed when the power is turned on, and even if a step-out occurs, the home position is returned to the normal home position.

As described above, in this embodiment, the average value or the effective value of the exciting current flowing through the stepping motor 202 controlled by the constant current chopper is monitored, and if this exceeds a predetermined value, an overload of the stepping motor 202 occurs. It is determined that there is a possibility of step-out, so that the image forming operation is interrupted and an initialization operation performed when the power of the apparatus is turned on, that is, a home position search operation is performed to return the developing device and the transfer drum to predetermined home positions. Accordingly, it is possible to prevent the device from malfunctioning due to the step-out of the stepping motor.

In this embodiment, the average value of the exciting current of the stepping motor 202 is detected, but the effective value of the exciting current may be detected.

The present invention is not limited to the developing device, and can be widely applied to a portion where a detaching operation is performed using a stepping motor, such as a transfer drum, a cleaner for the transfer drum, a transfer drum in the transfer drum, a blade, and a roller.

(Second Embodiment) FIG. 3 is a circuit diagram showing a control configuration of a second embodiment.

As shown in FIG. 3, the stepping motor 302 for attaching and detaching the developing device is controlled by a driving circuit 303, a current detecting resistor 305, a reference voltage source 307, and a comparator 306 to control the entire apparatus. The eccentric cam (not shown) is driven by a motor drive phase signal from the section (return means) 301 to operate. When the power is turned on, the control unit 301 stops the developing device at a predetermined home position in response to a signal from the developing device home position sensor (position detecting means) 304. When the image forming operation starts, the stepping motor 302 is rotated by a preset number of pulses to a desired developing device according to the content of the printing operation, and the developing device is pressed. Upon completion, the motor rotates in the opposite direction by the same number of pulses, and eventually returns to the initial home position.

At this time, since the stepping motor is driven at a constant current, the peak value of the motor exciting current (A in FIG. 3) detected by the current detecting resistor 305 is constant, but the average value is the stepping motor. The larger the load of the motor 302, the larger the load. When the load of the stepping motor 302 increases beyond the driving capability, the stepping motor 302 loses synchronism, and the voltage value (B in FIG. 3) corresponding to the average value of the exciting current sharply decreases. That is,
The differential value (C in FIG. 3) of the effective value of the exciting current shows a large negative value. Therefore, the average value of the detected current values is passed through a low-pass filter 308, passed through a differentiating circuit 311, and compared with a predetermined value 310 by a comparator 309.

In the above configuration, the current detecting resistor 30
5. The low-pass filter 308 is a stepping motor 3
Effective current detecting means for detecting the effective value of the exciting current 02.
A differentiating circuit 311 is a differential detecting means for detecting a differential value of the detected effective value of the exciting current, a comparator 309, and a voltage source 310 are detected by comparing the differential value of the detected effective value of the exciting current with a predetermined value. The step-out detecting means detects that the differential value of the current value exceeds a predetermined value and detects that the stepping motor 302 has stepped out.

As shown in FIG. 5, when the motor load becomes heavy, the average value B of the exciting current of the stepping motor 302 increases, and when the motor loses synchronism, the average value B sharply decreases. Accordingly, the differential value D of the average value greatly swings in the negative direction.
In step 02, it is determined that step-out has occurred, the image forming operation is interrupted, the home position operation performed when the power is turned on is performed, and even if step-out occurs, the home position is returned to the normal home position.

As described above, in this embodiment, the differential value of the average value of the exciting current of the stepping motor 302 is monitored, and when the differential value suddenly changes to a negative value, it is detected that the stepping motor 302 has stepped out. Since the home position search operation is performed in the same manner as in the first embodiment, the developing device is returned to the predetermined home position.
The operation failure of the developing device due to the step-out of the stepping motor can be prevented.

Although the average value of the exciting current of the stepping motor 302 is detected in the present embodiment, the effective value of the exciting current may be detected.

The present invention is not limited to the developing device, and can be widely applied to a portion where a detaching operation is performed using a stepping motor, such as a transfer drum, a cleaner for the transfer drum, a transfer brush, a blade, and a roller in the transfer drum.

[0049]

As described above, according to the present invention,
In an electrophotographic image printing apparatus, a stepping motor for driving a detachable load used for image printing, an overcurrent detecting means for detecting that an exciting current flowing through the stepping motor is an overcurrent, A return means for returning the preload to a predetermined position in a detached state when the exciting current flowing through the stepping motor is detected as an overcurrent by the current detecting means, so that the stepping motor can be prevented from stepping out. In addition, there is an effect that malfunction of the device due to step-out of the stepping motor can be prevented.

A stepping motor for driving a detachable load used for image printing, step-out detecting means for detecting that the stepping motor has stepped out,
A return means for returning the load to a predetermined position in a detached state when the step-out detecting means detects that the stepping motor has stepped-out, to prevent a malfunction of the device due to step-out of the stepping motor. There is an effect that can be.

Also, display means for displaying the operation state or setting state of the apparatus is provided. When an overcurrent detection signal is output from the overcurrent detection means or a step-out detection signal is output from the desorption detection means, an error is displayed on the display means. Because it was displayed,
There is an effect that the user can be notified of an overcurrent or a step-out state of the stepping motor.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of an image forming apparatus according to a first embodiment of the present invention;

FIG. 2 is a circuit diagram showing a control configuration of the first embodiment.

FIG. 3 is a circuit diagram showing a control configuration according to a second embodiment.

FIG. 4 is a timing chart showing waveforms at various points in the first embodiment.

FIG. 5 is a timing chart showing waveforms of respective parts according to the second embodiment.

[Explanation of symbols]

 Reference Signs List 201 control unit (return means) 202 stepping motor 204 home position sensor (position detection means) 205 current detection resistor (average current detection means) 208 low-pass filter (average current detection means) 209 comparator (overcurrent detection means) 210 constant voltage Source (overcurrent detection means)

Claims (13)

[Claims] 1. An electrophotographic image printing apparatus, comprising:
A stepping motor for driving a detachable load used for image printing, overcurrent detecting means for detecting that an exciting current flowing in the stepping motor is an overcurrent, and flowing to the stepping motor by the overcurrent detecting means An image printing apparatus comprising: a return unit that returns a preload to a predetermined position in a detached state when an excitation current is detected as an overcurrent. 2. The apparatus according to claim 1, further comprising: position detecting means for detecting that the load is at a predetermined position in the detached state, wherein the return means returns the load to the predetermined position in the detached state based on a signal from the position detecting means. The image printing apparatus according to claim 1, wherein: 3. An effective current detecting means for detecting an effective value of a current flowing through each phase of an exciting winding of the stepping motor, wherein the overcurrent detecting means determines an effective value of the current detected by the effective current detecting means. 2. The method according to claim 1, wherein a value of the excitation current flowing through the stepping motor is detected as an overcurrent when the value exceeds the predetermined value.
Or the image printing apparatus according to 2. 4. An average current detecting means for detecting an average value of a current flowing in each phase of an exciting winding of the stepping motor, wherein the overcurrent detecting means determines an average value of the current detected by the effective current detecting means. 2. The method according to claim 1, wherein a value of the excitation current flowing through the stepping motor is detected as an overcurrent when the value exceeds the predetermined value.
Or the image printing apparatus according to 2. 5. An electrophotographic image printing apparatus, comprising:
A stepping motor for driving a detachable load used for image printing, step-out detecting means for detecting that the stepping motor has stepped out, and step-out detecting means detecting that the stepping motor has stepped-out. And a return unit for returning the load to a predetermined position in a detached state when the load is released. 6. A position detecting means for detecting that a load is at a predetermined position in a detached state, and a return means for returning the load to a predetermined position in the detached state based on a signal from the position detecting means. The image printing apparatus according to claim 5, wherein: 7. An effective current detecting means for detecting an effective value of a current flowing through each phase of an exciting winding of a stepping motor;
Differential detection means for detecting a differential value of the effective value of the detected current, wherein the step-out detecting means compares the differential value of the effective value of the detected current with a predetermined value, and exceeds the predetermined value. 7. The image printing apparatus according to claim 5, wherein when the stepping motor loses synchronism, it is detected. 8. An average current detecting means for detecting an average value of a current flowing through each phase of an exciting winding of a stepping motor;
Differential detection means for detecting a differential value of the average value of the detected current, wherein the step-out detecting means compares the differential value of the average value of the detected current with a predetermined value, and exceeds the predetermined value. 7. The image printing apparatus according to claim 5, wherein when the stepping motor loses synchronism, it is detected. 9. The image printing apparatus according to claim 1, wherein the load is a developing unit detachable from the photosensitive drum. 10. The image printing apparatus according to claim 1, wherein the load is a transfer drum detachable from the photosensitive drum. 11. The image printing apparatus according to claim 10, wherein the load is a transfer cleaner detachable from the transfer drum. 12. The image printing apparatus according to claim 1, wherein the load is a transfer current supply unit detachable from the transfer drum. 13. An apparatus for displaying an operation state or a setting state of an apparatus, wherein when an overcurrent detection signal is output from the overcurrent detection means or a step-out detection signal is output from the desorption detection means, an error is displayed on the display means. The image printing apparatus according to claim 1, wherein the image is displayed.