JP2002369588A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus in which consumed powers of respective stepping motors, driving respective mechanical components which constitute the imaging apparatus, are reduced and long-term operations of the respective stepping motors are stabilized. SOLUTION: In an imaging forming apparatus, which forms a toner image, and finally, transfers and fixes the toner image onto a conveyed recording medium to form an image comprising the fixed toner image on the recording medium, stepping motors which drive some of mechanical elements of the imaging apparatus and a switching means, which switches drive currents of the stepping motors, according to the load torques of some of the mechanical elements are provided.

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 used for a copying machine, a printer and the like.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus used in a copying machine, a printer or the like forms an electrostatic latent image by irradiating a photosensitive drum rotating uniformly in a predetermined direction with exposure light. Forming, developing the electrostatic latent image on the rotating photosensitive drum with a developing roll rotating in the same direction at a position close to the photosensitive drum to form a toner image, and forming the toner image on the photosensitive drum. The image is transferred directly or once via an intermediate transfer member to a recording medium sent out one by one from a paper supply cassette by a paper supply roll, and the unfixed toner image on the recording medium is heated by a fixing device including a pair of rotating rolls. A method of forming an image by fixing under pressure is widely used.

[0003] The mechanical elements of these image forming apparatuses are driven by a drive motor. As the drive motor, a stepping motor, a DC brushless motor, or the like is used.

[0004] DC brushless motors provide high output, but are difficult to position control and are expensive. On the other hand, a stepping motor is easy to perform position control and is relatively inexpensive, but has a feature that it has a lower output than a DC brushless motor. To increase the output of this stepping motor as much as possible, it is necessary to increase the current supplied to the stepping motor.However, if the supply current is increased, the motor temperature will increase and power consumption will increase. Or increase the power supply capacity. Since these countermeasures can increase costs, it is common practice to set the current level of the stepping motor to a relatively large value from the beginning in anticipation of the maximum load taking into account load fluctuations, environmental changes, aging, and variations. It is.

For this reason, in a section where the load is small,
Since more current than necessary is supplied, wasteful power is consumed, and the temperature of the motor is raised more than necessary.

As a method for improving this, Japanese Patent Laid-Open No. 3-2
Japanese Patent No. 15192 discloses a technique including a temperature sensor and switching a drive current according to a temperature.

According to this technique, a temperature sensor is provided in a mechanical element, an actual temperature is detected from the temperature sensor, and a driving current switching set temperature of a stepping motor set in advance is compared with the actual temperature. When the actual temperature becomes equal to or higher than the set temperature, the drive current is switched, so that there is an advantage that overheating of the stepping motor and power labor can be avoided.

[0008]

However, in the technique disclosed in Japanese Patent Application Laid-Open No. 3-215192, a current corresponding to a load due to a temperature change is supplied, but the motor includes a load fluctuation at that temperature. There is a problem that a current corresponding to the maximum load is always supplied.

In general, the load torque of a motor for driving a mechanical element of an image forming apparatus such as a printer fluctuates regularly in accordance with the position of a recording medium conveyed for forming an image. By supplying a drive current according to a typical load torque fluctuation, overheating of the stepping motor and labor costs of electric power can be avoided.

The present invention has been made in view of the above circumstances, and provides an image forming apparatus which stabilizes operation of a stepping motor for driving a mechanical element constituting a part of the image forming apparatus for a long time and reduces power consumption. The purpose is to do.

[0011]

An image forming apparatus according to the present invention for achieving the above object forms a toner image, and finally transfers and fixes the toner image on a conveyed recording medium. An image forming apparatus for forming an image composed of a fixed toner image on the recording medium by using a stepping motor for driving some mechanical elements of the image forming apparatus, and a stepping motor according to a load torque of the some mechanical elements. Switching means for switching the drive current of the stepping motor.

The stepping motor drives a roll or a belt that conveys a recording medium, and the switching means drives the stepping motor before and after the recording medium enters the roll or the belt. Preferably, it switches the current.

Further, the roll or belt is a fixing device for forming an image fixed on the recording medium by heating and pressing the toner image transferred onto the recording medium. It is preferable that the drive current of the stepping motor is switched before and after the recording medium enters the fixing device.

Further, the roll or belt is a transfer device for finally transferring the toner image onto a conveyed recording medium, and the switching means transfers the recording medium to the transfer device. It is preferable that the drive current of the stepping motor be switched between before and after the entry.

Further, the roll or belt is a paper feeding device for feeding the recording media one by one from a cassette containing the recording media, and the switching means is provided before and after the paper feeding device feeds the recording media. It is preferable to switch the drive current of the stepping motor.

The stepping motor drives the roll or belt with a clutch interposed therebetween, and the switching means switches the drive current of the stepping motor in accordance with the on / off of the clutch. It is preferred that

Further, the roll is a registration roll having a clutch for adjusting a leading end position of a recording medium, and the switching means switches a drive current of the stepping motor in accordance with ON / OFF of the clutch. This is also a preferred embodiment.

[0018]

Embodiments of the present invention will be described below.

FIG. 1 is a schematic diagram showing a first embodiment of the image forming apparatus of the present invention.

In the center of the image forming apparatus shown in FIG. 1, a photosensitive drum 1Y on which a Y (yellow) toner image rotating in a predetermined direction is formed, and a photosensitive drum on which an M (magenta) color toner image is formed There is a photosensitive drum 1C on which 1M and C (cyan) color toner images are formed, and a photosensitive drum 1K on which a K (black) color toner image is formed. The four photosensitive drums 1Y, 1M, 1C and 1K On the right side, there is an exposure device 3 for irradiating each of the photosensitive drums 1Y, 1M, 1C and 1K with exposure light. Each photoconductor drum 1Y, 1M, 1C,
1K, each photoconductor drum 1Y, 1M, 1C, 1
Chargers 2Y, 2M, 2C, 2 for charging K respectively
K, developing units 4Y and 4 for developing electrostatic latent images formed by irradiating exposure light with Y, M, C, and K developers, respectively.
M, 4C, 4K, and cleaners 5Y, 5M, 5C, 5C for removing toner remaining on each photosensitive drum after transfer.
K is deployed. At a position close to the two photosensitive drums 1Y and 1M, a first-stage intermediate transfer body 6-1 to which the Y and M color toner images are transferred is disposed. A first-stage intermediate transfer body 6-2 to which the C and K color toner images are transferred is arranged at a close position. Close to both the first stage intermediate transfer body 6-1 to which the Y and M color toner images are transferred and the first stage intermediate transfer body 6-2 to which the C and K color toner images are transferred A second-stage intermediate transfer body 7 to which the respective toner images on the first-stage intermediate transfer bodies 6-1 and 6-2 are transferred is disposed at the position where the toner image is transferred. The second-stage intermediate transfer body 7 is in contact with a transfer roll 8 that transfers the Y, M, C, and K color toner images formed on the second-stage intermediate transfer body 7 to a recording medium with the recording medium interposed therebetween. I do. A transfer cleaner 10 for cleaning excess toner is provided around the transfer roll 8. Below the exposure device 3, there is a paper feed cassette 11 for storing a recording medium. The recording media contained in the paper feed cassette 11 are fed out one by one by a paper feed roll 12, guided upward by a pinch roll 13, and aligned with the leading end position of the recording medium via a transport roll 14-1. , And temporarily waits on the resist roll 15 having the clutch. Registration roll 1 for adjusting the leading end position of the recording medium
A registration sensor 21 that detects the presence or absence of a recording medium before
Has been deployed. Transfer roll 8 in the transport direction of the recording medium
A fixing device 17 for heating and pressing the unfixed toner image is provided downstream of the fixing device 17. The fixing device 17 includes a heating roll 17 a for heating the unfixed toner image and a pressing roll 17 b for pressing the unfixed toner image. ing. Downstream of the fixing device 17, there are a fuser exit roll pair 19 that conveys the recording medium on which fixing has been completed, and an exit sensor 20 that detects that the recording medium is discharged.
There are a transport roll 14-2 and a discharge roll 18 for discharging the recording medium to the outside. Transport roll 14-2, discharge roll 1
Upstream of the fixing device 17, there is a route for forming an image on both sides, which is different from the route passing through the fixing device. The route includes a transport roll 14-3 for reversely feeding the recording medium passing through the fixing device 17. , 14-4. The recording medium that has been fed back through the route for forming the two-sided image waits again on the registration roll 15 to align the leading end position. Further, the recording medium for forming an image includes, in addition to a route automatically fed out from the paper feed cassette 11, a route from which the recording medium is manually supplied from the left side of the drawing. There is a manual paper feed unit 23 for manual feeding, and the recording medium supplied manually from the manual paper feed unit 23 passes through the manual feed roll 16 and the transport roll 14-4, and waits on the registration roll 15 to adjust the leading end position. . The image forming apparatus is housed in a housing 30 configured to be able to open a predetermined location, and has a concave portion 31 at the top of the housing 30 for stacking the recording medium discharged from the discharge roll 18. .

In the image forming apparatus, the photosensitive drums 1Y, 1M, 1C, 1K, developing units 4Y, 4M, 4C,
4K, the first-stage intermediate transfer bodies 6-1 and 6-2, the second-stage intermediate transfer body 7, the transfer roll 8, the fixing device 17, the paper feed roll 12, the pinch roll 13, and the leading end positions of the recording medium are aligned. And rotating mechanical elements such as a registration roll 15 with a clutch, transport rolls 14-1 to 14-4, and a discharge roll 18, and these are driven by a motor, and among these, the photosensitive drums 1Y, 1M, and 1C , 1K, the first-stage intermediate transfer bodies 6-1 and 6-2, the second-stage intermediate transfer body 7, and the like are driven by the main motor 24.

In this embodiment, a motor 25 for driving the fixing device 17 and a motor 26 for driving the transfer roll
As the motor 27 for driving the registration roll 15 and the motor 28 for driving the paper feed roll 12, a stepping motor whose position can be easily controlled is used.

In the image forming apparatus, the exposing device 3 emits exposure light pulse-modulated for each color of Y (yellow), M (magenta), C (cyan), and K (black) based on image data. Exposure light is applied to the photosensitive drums 1Y, 1Y for each color.
An electrostatic latent image is formed on M, 1C, and 1K. The electrostatic latent images on the photosensitive drums 1Y, 1M, 1C and 1K are respectively
Each of the developing devices 4Y, 4M, 4C, and 4K is developed with a developer to form a color toner image, and the Y and M color toner images and the C and K color toner images are each intermediate between two first-stage toner images. The toner images for two colors on the transfer members 6-1 and 6-2 and on the two first-stage intermediate transfer members 6-1 and 6-2 are transferred to the second-stage intermediate transfer member 7, A four-color toner image is formed on the intermediate transfer body 7 in the second stage. The recording recording medium sent out from the paper feed cassette 11 by the feed roll 12 and waiting on the registration roll 15 is moved to the registration roll at the timing when the four-color toner image on the intermediate transfer body 7 at the second stage reaches a predetermined transfer position. The clutch 15 is turned on, carried to the transfer position, and the four-color toner image is transferred by the transfer roll 8.
The unfixed toner image on the recording medium to which the four-color toner image has been transferred is heated and pressed by the fixing device 27 to form a fixed image. The recording medium on which the image has been formed is ejected by the discharge roll 28 to the concave portion 3 provided above the cover 31.
Stacked in two.

In general, a stepping motor is driven by pulsed power, and the torque depends on the driving current. However, the rated output of the stepping motor is naturally limited, so that there is a limit. Further, the generated torque of the motor and the load torque are irrelevant, and the drive current is not reduced even if the load torque is reduced. Therefore, in the present invention, the switching means 29 is provided for switching the drive current supplied to the stepping motor to a predetermined level in accordance with the load torque for driving each mechanical element by each stepping motor.

In the present embodiment, the switching means 29 sets the timing at which a predetermined time has elapsed since the clutch of the registration roll 15 was turned on as the timing at which the recording medium enters the fixing device, and the registration sensor 21 detects the timing of the recording medium. The timing at which a predetermined time has passed after the detection of the passage of the rear end is the timing at which the recording medium passes through the fixing device, and the driving current supplied to the stepping motor 25 for driving the fixing device is switched to a predetermined level. A detailed flow in which the drive current is switched by the switching means 29 will be described later.

By switching the drive current in this manner, the power consumption is reduced, and the stepping motor 25 for driving the fixing device is not overheated even after a long operation.

FIG. 2 is a diagram showing the load torque of a stepping motor for driving the fixing device used in the present embodiment.

In FIG. 2, the vertical axis represents the magnitude of the load torque, the horizontal axis represents the passage of time, and the solid line in the figure represents the measured value of the load torque of the stepping motor for driving the fixing device.

As is apparent from the figure, the load torque of the stepping motor for driving the fixing device is 10.2 times.
A relatively small steady torque is applied from S to 11.0S, and the maximum load torque is applied from 11.1S to 11.2S at the moment when the recording medium enters the nip portion of the fixing device. When the medium is in the nip portion of the fixing device, a small steady load torque is applied again from 11.2S to 12.0S or later. Therefore, the driving current supplied to the stepping motor for driving the fixing device is switched to a driving current corresponding to the maximum load torque immediately before the recording medium enters the nip portion of the fixing device, and the recording recording medium changes the nip portion of the fixing device. It can be seen that it is only necessary to return the drive current to a value corresponding to the above-mentioned small load torque when passing completely.

Although the load torque of the stepping motor for driving the fixing device has been described here, the load torque of the stepping motor has the same tendency for the other rolls that convey the recording medium.

FIG. 3 is a diagram showing a flow in which the switching means switches the drive current of the stepping motor for driving the fixing device to a predetermined level.

In FIG. 3, when the main motor for driving the photosensitive drum and the developing device is rotated by the print command, the switching means changes the drive current of the stepping motor to a drive current corresponding to a relatively low load excluding the vicinity of the maximum load. Switch to I1 (S-1). Next, the timing at which the clutch of the registration roll with the clutch that matches the leading end position of the recording medium is turned on is detected (S-2). When the time T1 has elapsed since the clutch of the registration roll was turned on (S-3), and at the timing when the recording medium enters the fixing device, the switching means checks the drive current of the stepping motor for driving the fixing device from the load history. The drive current is switched to the drive current I2 corresponding to the maximum torque (S-4). Next, when the registration sensor that detects the presence or absence of the recording medium immediately before the registration roll detects the passage of the rear end of the recording medium (S-5), the time T1 has elapsed from that point (S-6), and the recording medium is fixed. At the timing of passing through the apparatus, the drive current of the stepping motor for driving the fixing device is returned to the drive current I1 suitable for a low load (S-1).

FIG. 4 is a sequence chart showing the operation of the mechanical elements or the motor of the image forming apparatus according to the first embodiment.

In FIG. 4, the first row is a chart showing the operation of the main motor for driving the photosensitive drum, the intermediate transfer member, the developing device, and the like, and the second row is a paper feed for sending the recording medium from the cassette. Chart showing the action of the roll, third
The fourth row is a chart showing the operation of the registration sensor, the fourth row is a chart showing the operation of the registration roll, the fifth row is a chart showing the drive current supplied to the stepping motor for driving the fixing device, and the sixth row. The second row is a chart showing the operation of the exit sensor for detecting that the recording medium is discharged.

In the figure, when the main motor starts rotating (first stage), a drive current suitable for a relatively low-load torque is supplied to the stepping motor for driving the fixing device (fifth stage). When the paper feed roll rotates and sends the recording medium to the position of the registration roll, the registration sensor detects the leading end of the sent recording medium (third stage). When the toner image is transferred to the intermediate transfer body in the second stage to form a toner image of each color, the clutch of the registration roll is turned on, and the recording medium is sent to the transfer roll (fourth stage). Thereafter, the registration sensor detects that the rear end of the recording medium has passed (third stage). The registration sensor detects the passage of the rear end of the recording medium, and when the recording medium has passed through the registration roll, the clutch of the registration roll is turned off (fourth stage). Approximately T1 time after the clutch of the registration roll has been turned on, the leading end of the recording medium on which the toner images of each color have been transferred onto the recording medium by the transfer roll enters the fixing device. The drive current of the stepping motor to be driven is switched to the drive current I2 corresponding to the maximum load torque (fifth stage). Then, approximately T2 after the registration sensor detects that the rear end of the recording medium has passed, the rear end of the recording medium passes through the fixing device. The drive current is returned to a drive current suitable for a low load (fifth stage). The exit sensor located downstream of the fixing device detects that the rear end of the recording medium passes through the fixing device, and the driving current of the stepping motor is returned to a driving current suitable for a low load, and then the rear end of the recording medium passes. Is detected (the sixth
Stage). Next, a second embodiment of the image forming apparatus of the present invention will be described.

The second embodiment is different from the first embodiment in that the switching means switches the drive current of the stepping motor for driving the transfer roll, but is otherwise the same. A configuration diagram, a diagram showing a switching flow of the switching means, and a description thereof will be omitted, and description will be made based on a sequence chart.

FIG. 5 is a sequence chart showing the operation of the mechanical elements or the motor of the image forming apparatus according to the second embodiment.

In FIG. 5, the first row is a chart showing the operation of the main motor for driving the photosensitive drum, the intermediate transfer member, the developing device, and the like, and the second row is a paper feed for sending the recording medium from the cassette. Chart showing the action of the roll, third
The tier is a chart showing the operation of the registration sensor, the fourth tier is a chart showing the operation of the registration roll, and the fifth tier is a chart showing the drive current supplied to the stepping motor that drives the transfer roll.

In the figure, when the main motor starts rotating (first stage), a drive current I1 corresponding to a low load is supplied to the stepping motor for driving the transfer roll (fifth stage). When the paper feed roll rotates and sends the recording medium to the position of the registration roll (second stage), the registration sensor detects the leading end of the sent recording medium (third stage). Second
When the toner image is transferred to the intermediate transfer member at the stage to form a toner image of each color, the clutch of the registration roll is turned on (fourth stage), and the recording medium is sent to the transfer roll. At this time, the registration sensor detects that the rear end of the recording medium has passed (third stage). The registration sensor detects the passage of the rear end of the recording medium, and when the recording medium has passed through the registration roll, the clutch of the registration roll is turned off (fourth stage). After a lapse of approximately T1 time since the clutch of the registration roll has been turned on, the leading end of the recording medium enters the transfer roll. Therefore, the switching unit sets the drive current of the stepping motor that drives the fixing device to a drive corresponding to the maximum load torque. Switch to current I2 (fifth stage). Then, approximately T2 time after the registration sensor detects that the rear end of the recording medium has passed, the rear end of the recording medium passes through the transfer roll. The drive current is returned to a drive current suitable for a low load (fifth stage).

Next, a third embodiment of the image forming apparatus of the present invention will be described.

The third embodiment is different from the first embodiment in that the switching means switches the drive current of the stepping motor for driving the sheet feed roll, but is otherwise the same. A schematic configuration diagram, a diagram showing a switching flow of the switching means, and a description thereof will be omitted, and description will be made based on a sequence chart.

FIG. 6 is a sequence chart showing the operation of the mechanical elements or the motor of the image forming apparatus according to the third embodiment.

In FIG. 6, the first row shows the operation of the main motor for driving the photosensitive drum, the intermediate transfer member, the developing device and the like, and the second row sends out the recording medium from the paper feed cassette. A chart showing the operation of the paper feed roll,
The third row is a chart showing the operation of the registration sensor.
The top row is a chart showing the operation of the resist roll.
The second row is a chart showing the drive current supplied to the stepping motor that drives the paper feed roll.

In the figure, when the main motor starts rotating (first stage), a drive current corresponding to a low load is supplied to the stepping motor for driving the paper feed roll (fifth stage). Since the paper feed roll sends out one recording medium from the paper supply cassette approximately T1 after the start of rotation of the main motor, the switching means switches to the drive current I2 that matches the maximum load torque (fifth stage). ). Then, approximately T2 after the start of rotation of the main motor, 1
Since the sending of the recording media is completed, the driving current is returned to a value corresponding to the low load again (fifth stage).

Next, a fourth embodiment of the image forming apparatus of the present invention will be described.

The fourth embodiment is different from the first embodiment in that the switching means switches the drive current of the stepping motor for driving the registration roll, but is otherwise the same. A configuration diagram, a diagram showing a switching flow of the switching means, and a description thereof will be omitted, and description will be made based on a sequence chart.

FIG. 7 is a sequence chart showing the operation of the mechanical elements or the motor of the image forming apparatus according to the fourth embodiment.

In FIG. 7, the first row is a chart showing the operation of the main motor for driving the photosensitive drum, the intermediate transfer member, the developing device and the like, and the second row is a paper feed for sending the recording medium from the cassette. Chart showing the action of the roll, third
The tier is a chart showing the operation of the registration sensor, the fourth tier is a chart showing the operation of the registration roll, and the fifth tier is a chart showing the drive current supplied to the stepping motor that drives the registration roll.

In the figure, when the main motor starts rotating (first stage), a drive current suitable for a low load is supplied to the stepping motor for driving the registration roll (fifth stage). The paper feed roll rotates to send the recording medium to the position of the registration roll (second stage). The registration sensor detects the leading end of the sent recording medium (third stage). When the toner image is transferred to the intermediate transfer body in the second stage to form a toner image of each color, the clutch of the registration roll is turned on (fourth stage), and the recording medium is sent to the transfer roll. Thereafter, the registration sensor detects that the rear end of the recording medium has passed (third stage). The registration sensor detects the passage of the rear end of the recording medium, and when the recording medium has passed through the registration roll, the clutch of the registration roll is turned off (fourth stage). The switching means controls the drive current of the stepping motor for driving the registration roll by using the clutch of the registration roll as an O.
Immediately before reaching N, the drive current is switched to the drive current I2 corresponding to the maximum load torque (fifth stage). When the recording medium has passed through the registration roll, the registration roll clutch
Immediately after the FF, the drive current of the stepping motor for driving the registration roll is returned to the drive current I1 suitable for a low load (fifth stage).

[0050]

As described above, according to the image forming apparatus of the present invention, the temperature of the stepping motor rises by switching the driving current of the stepping motor in accordance with the load torque of the mechanical element driven by the stepping motor. Therefore, stable operation for a long time can be achieved. Further, power consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a first embodiment of an image forming apparatus of the present invention.

FIG. 2 is a diagram illustrating a load torque of a stepping motor that drives a fixing device used in the embodiment.

FIG. 3 is a diagram illustrating a flow in which a switching unit switches a drive current of a stepping motor that drives a fixing device to a predetermined level.

FIG. 4 is a sequence chart showing an operation of a mechanical element or a motor of the image forming apparatus according to the first embodiment.

FIG. 5 is a sequence chart showing an operation of a mechanical element or a motor of the image forming apparatus according to the second embodiment.

FIG. 6 is a sequence chart showing an operation of a mechanical element or a motor of the image forming apparatus according to the third embodiment.

FIG. 7 is a sequence chart showing an operation of a mechanical element or a motor of the image forming apparatus according to the fourth embodiment.

[Explanation of symbols]

 1Y, 1M, 1C, 1K Photoconductor drum 2Y, 2M, 2C, 2K Charger 3 Exposure device 4Y, 4M, 4C, 4K Developing device 5Y, 5M, 5C, 5K Cleaner 6-1, 6-2 First stage Intermediate transfer member 7 Intermediate transfer member of second stage 8 Transfer roll 10 Transfer cleaner 11 Paper feed cassette 12 Paper feed roll 13 Pinch roll 14-1 to 14-4 Transport roll 15 Registration roll 16 Manual feed roll 17 Fixing device 17a Heating roll 17b Pressure roll 18 Discharge roll 19 Fuser outlet roll pair 20 Exit sensor 21 Registration sensor 23 Manual feed unit 24 Main motor 25 Stepping motor for driving the fixing device 26 Stepping motor for driving the transfer roll 27 Stepping motor 28 for driving the registration roll 28 Switch that drives the paper feed roll Stepping motor 29 Switching means 30 Housing 31 Recess

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B65H 5/06 B65H 5/06 L 3F102 9/14 3F343 9/14 G03G 15/00 518 5H580 G03G 15/00 518 15 / 16 15/16 15/20 102 15/20 102 21/00 370 21/00 370 H02P 8/00 B (72) Inventor Takayuki Yazawa 3-7-1, Funai, Iwatsuki City, Saitama Prefecture Fuji Xerox Co., Ltd. Iwatsuki Business In-house F term (reference) 2H027 DA32 DA39 DC04 DC05 DC11 ED02 ED16 ED24 ED25 EE02 EE04 EF09 2H033 AA32 BA08 BA10 BA11 BB01 BB28 BB37 CA22 CA40 2H072 CA01 CA05 JA02 JA03 JA08 2H200 FA15 GA16 GB10 GA23 GB23 GA23 HA02 HA28 HB12 JA02 JB20 JC02 JC09 JC19 LA27 PA02 PB12 PB35 3F049 AA10 EA01 EA21 LA02 LA07 LB03 3F102 AA02 AA11 AB01 BA02 BB02 DA08 EA03 EC02 3F343 FA02 FB02 GA01 GB01 GC01 GD01 JA04 MB21 LC04 MB01 LC04 FA22 FA23 HH31 HH33 JJ 05

Claims (7)

[Claims] An image forming method for forming a toner image on a recording medium by forming a toner image, and finally transferring and fixing the toner image on a conveyed recording medium. An image forming apparatus comprising: a stepping motor for driving some mechanical elements of the image forming apparatus; and switching means for switching a driving current of the stepping motor according to a load torque of the some mechanical elements. Image forming apparatus. 2. The method according to claim 1, wherein the stepping motor drives a roll or a belt that conveys a recording medium, and the switching unit controls a driving current of the stepping motor before and after the recording medium enters the roll or the belt. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus switches the image forming apparatus. 3. The fixing device according to claim 1, wherein the roll or the belt is a fixing device that forms an image fixed on the recording medium by heating and pressing the toner image transferred on the recording medium. 3. The image forming apparatus according to claim 2, wherein the drive current of the stepping motor is switched before and after the recording medium enters the fixing device. 4. A transfer device for transferring the toner image onto a conveyed recording medium, wherein the roll or the belt transfers the toner image onto the conveyed recording medium. 3. The image forming apparatus according to claim 2, wherein the driving current of the stepping motor is switched. 5. A paper feeder comprising a cassette for storing a recording medium, wherein said roll or belt feeds said recording medium one by one from said cassette, said switching means comprising: 3. The image forming apparatus according to claim 2, wherein the drive current of the stepping motor is switched before and after the recording medium is sent from the cassette. 6. The stepping motor drives the roll or belt with a clutch interposed therebetween, and the switching means switches a drive current of the stepping motor according to ON / OFF of the clutch. The image forming apparatus according to claim 2, wherein 7. A registration roll having a clutch for adjusting a leading end position of a recording medium, wherein said switching means switches a drive current of said stepping motor in accordance with ON / OFF of said clutch. The image forming apparatus according to claim 6, wherein: