JP3784983B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus using a stepping motor.
[0002]
[Prior art]
In this type of image forming apparatus, a stepping motor is usually used for driving for feeding paper. In general, this stepping motor is often used outside the self-starting area from the viewpoint of cost, etc., so at the start of motor driving (starting up), through-up control is performed to switch excitation in time series. It has been broken. FIG. 7 is a characteristic diagram showing normal through-up control, where the vertical axis indicates “stepping motor speed (rad / s)” and the horizontal axis indicates “time (sec)”. That is, as shown in FIG. 7, normally, the number of rotations is gradually increased from the start of the stepping motor, and the stepping motor is stepped after a predetermined time (after t1 time) by increasing the number of pulse rotations in time series. The motor rotation is allowed to reach steady rotation. Also, as a conventional technique for such a through-up control, Japanese Patent Laid-Open No. 10-120237 discloses that when a paper feed failure occurs after the through-up operation, the paper is fed again and the through-up time is made longer than the previous time. Thus, there is described a control technique capable of preventing a paper feed failure and using an inexpensive motor.
[0003]
[Problems to be solved by the invention]
However, the following problems may occur in the case of the conventional image forming apparatus. That is, when the through-up control is started, the number of rotations of the stepping motor changes, and the inertial force is the largest influence, which increases the load on the stepping motor. For this reason, conventionally, in order to drive the stepping motor with certainty, it is necessary to consider a considerable margin in the motor capacity, which makes it impossible to use a small and inexpensive motor. As a result, there is a problem in that the image forming apparatus itself is also increased in size and causes an increase in cost.
[0004]
In the case of the technology described in the conventional publication, for example, when feeding a relatively heavy paper type such as an envelope, there is a high possibility that a paper feeding failure due to a motor step-out or the like still occurs. In order to prevent this, it is necessary to use a large and expensive motor, which is problematic from the viewpoint of cost.
[0005]
Accordingly, an object of the present invention is to solve the problems of the conventional image forming apparatus as described above, to surely drive the stepping motor, and to use a small and inexpensive stepping motor, thereby reducing the cost. An object of the present invention is to provide an image forming apparatus.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is used to feed a sheet for forming an image and to drive the sheet feeding unit. an image forming apparatus having a stepping motor, and a size of the paper the feeding means is to feed paper sheet size detecting unit that determines whether a particular size heavy load to the stepping motor, the paper Control means is provided for controlling so that the through-up time of the stepping motor becomes longer when the size detection means determines that the size is a specific size .
[0007]
According to a second aspect of the present invention, in the first aspect, the paper feeding unit has at least a member that contacts the paper and transmits a driving force from the stepping motor to feed the paper. It is characterized by.
According to a third aspect of the present invention, in the second aspect of the present invention, the paper feeding member is a paper feeding roller that is in contact with the uppermost paper of the stacked and accommodated paper .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a configuration diagram showing an outline of an image forming apparatus according to the present invention. As shown in FIG. 1, the image forming apparatus 1 includes a photosensitive drum 2 for forming an image. The photosensitive drum 2 is driven to rotate by a main motor (not shown), and is also charged by a charging roller 3. The surface is uniformly charged, and the charged photosensitive drum 2 is irradiated with a laser beam from the optical unit 8 to form an electrostatic latent image. This electrostatic latent image is visualized by developing processing by the developing roller 11. On the other hand, a sheet is placed in the sheet feeding tray 9, and the sheet is fed by the sheet feeding roller 10 and conveyed to the registration roller 6. The registration roller 6 aligns the leading edge of the image. The visible image on the photosensitive drum 2 is transferred onto a sheet conveyed by the transfer roller 5 via the registration roller 6, fixed by heating and pressing by the fixing unit 7, and discharged. The manual paper feeding is performed by the manual tray 12.
[0010]
FIG. 2 is a block diagram of a control system applied to the image forming apparatus of the present invention. As shown in FIG. 2, the overall control of the image forming apparatus 1 is performed by the main control unit 13. The main control unit 13 includes a controller 14 for sending an image formation instruction, various types of sensors 15 for detecting the “paper type” and “paper size” and detecting the fixing temperature, a writing unit 16, a high-pressure unit 17, and a fixing unit. Part 18 is connected. The stepping motor 20 is connected via a driver 19.
[0011]
FIG. 3 is a flowchart showing the first embodiment of the present invention. That is, first, it is determined whether or not “There is a paper feed request?” (Step 1). If “There is a paper feed request” (YES), “Paper” using the following various sensors 15 (FIG. 2) is used. Based on the determination of “What type?”, “Determination of paper type” is performed (Step 2). When the determination result is “plain paper”, the control (Step 3) by “through-up control 1” is performed. When this paper is “special paper” other than “plain paper”, “through-up control 2” is performed. Control (Step 4) is performed by switching each. Here, “through-up control 1” and “through-up control 2” are paper feeding operations by two types of through-up control methods prepared in advance. On the other hand, if there is no paper feed request, the sequence is terminated as it is (RET).
[0012]
FIG. 4 is a flowchart showing a second embodiment of the present invention. In this second embodiment, the “through-up control 1” is set to “normal through-up control”, and the “through-up control 2” is set to “gradual through-up”. Control "is set. Specifically, the “normal through-up control” performed in the case of “plain paper” means that after a predetermined time has elapsed (after t1 time), the pulse rotation speed is increased in time series as in the conventional case. Control is performed to set the rotation speed of the stepping motor to a steady rotation (see FIG. 7). In the case of “special paper”, the control method is switched to reach the rotation speed of the stepping motor as shown in FIG. The control to increase the time until (after t2 hours) is performed. For this reason, as shown in FIG. 5, when the control method is switched to “gradual slew-up control”, the increase in the number of pulse rotations becomes gradual, and the time to reach steady rotation is also the time of “normal slew-up control”. Longer (t1 <t2).
[0013]
FIG. 6 is a flowchart showing a third embodiment of the present invention. In the third embodiment, a sheet size detecting means capable of determining a sheet type having a large load on the stepping motor as a “specific size” is provided. The feature is that the through-up control of the stepping motor is switched in accordance with the paper size between the “specific size” and the “normal size”. That is, as shown in FIG. 6, “determination of paper size type” is performed based on the determination of “what is the paper size” (Step 2), and when the determination result is “normal” paper size, “ “Normal through-up control” is performed (Step 3), and control is switched to “gradual through-up control” (Step 4) shown in FIG. Done. As a result, when the paper is a specific size paper such as an envelope, a slow motor control (paper feeding operation) accompanied by a gradual increase in the number of pulse rotations is performed, thereby effectively preventing the motor from stepping out and feeding failure. Can be prevented.
[0014]
【The invention's effect】
The present invention is as described above, and the invention according to claim 1 is characterized in that a sheet feeding unit that feeds a sheet for forming an image, a stepping motor used to drive the sheet feeding unit, an image forming apparatus size of the paper the feeding means is to feed paper and a sheet size detecting unit that determines whether a particular size heavy load to the stepping motor, by the paper size detecting means When it is determined that the size is a specific size, it is equipped with control means for controlling the step-up motor so that the slew-up time is increased. Therefore, the stepping motor can be driven reliably, and the stepping motor is small and inexpensive. Can be used, and the cost can be reduced.
[0015]
According to the second aspect of the present invention , the sheet feeding means has at least a member that contacts the sheet and transmits the driving force from the stepping motor to feed the sheet, so that the stepping motor can be driven more reliably. In addition to being able to be performed, a small and inexpensive stepping motor can be used, and the cost can be reduced. That is, when feeding a specific size paper with a heavy load on the stepping motor, the drive source of the member in contact with the specific size paper at the time when the transmission of the driving force is started based on the above determination. Since the step-up motor has a long slew-up time, it accelerates the paper smoothly without increasing the motor drive load and without causing slippage between the member and the paper. Thus, the paper can be fed by reaching a predetermined paper conveyance speed, and high driving efficiency can be obtained with high certainty regarding driving for feeding paper of a specific size. For this reason, a small and inexpensive motor can be used, and cost reduction can be achieved.
In addition, according to the third aspect of the present invention, the sheet feeding member included in the sheet feeding means is a sheet feeding roller that is in contact with the uppermost sheet of the stacked and stored sheets. The paper rollers are always in contact with the uppermost paper as the paper when the motor drive is started, and not only the load fluctuation caused by the characteristics of the single paper but also the paper with the characteristics stacked and accommodated with each other. Load fluctuation caused by the frictional resistance inherent in the paper surface of the characteristic between the papers can also be determined as a specific size with a large load on the motor, and this can be dealt with. High driving efficiency can be obtained.
[Brief description of the drawings]
FIG. 1 is a configuration diagram schematically showing an image forming apparatus according to the present invention.
FIG. 2 is a block diagram showing a configuration of the control system.
FIG. 3 is a flowchart showing the first embodiment.
FIG. 4 is a flowchart showing the second embodiment.
FIG. 5 is a diagram showing characteristics of the through-up control.
FIG. 6 is a flowchart showing the third embodiment.
FIG. 7 is a diagram showing characteristics of conventional through-up control.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Photosensitive drum 3 Charging roller 4 Cleaning blade 5 Transfer roller 6 Registration roller 7 Fixing unit 8 Optical unit 9 Paper feed tray
10 Feed roller
11 Developing roller
13 Main controller
14 Controller
15 Various sensors
16 Writing section
17 High pressure section
18 Fixing part
19 Drivers
20 Stepping motor

Claims (3)

Paper feeding means for feeding paper for forming an image, a stepping motor used to drive the paper feeding means, and the size of the paper to be fed by the paper feeding means is a load on the stepping motor an image forming apparatus having a sheet size detecting unit that determines whether a large specific size,
An image forming apparatus, comprising: a control unit configured to control so that a through-up time of a stepping motor is increased when the paper size detection unit determines that the size is a specific size . The image forming apparatus according to claim 1 , wherein the sheet feeding unit includes at least a member that contacts the sheet and transmits a driving force from the stepping motor to feed the sheet . The image forming apparatus according to claim 2, wherein the sheet feeding member is a sheet feeding roller that is in contact with an uppermost sheet of stacked sheets .

Images