JPH0990686A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of accurately forming an image and increasing image forming processing speed. SOLUTION: In the case where a sheet 27 is supplied from a sheet cassette nearest to a photoreceptor drum, a sensor 26 detects the end position of the sheet 27 in the width direction without moving from a standby position. Based on a detection signal from the sensor 26, an image forming position adjusting means G adjusts the relative positions of the sheet 27 and the photoreceptor drum. In the case where the sheet is supplied from the sheet cassette which is not the sheet cassette nearest to the photoreceptor drum, the sensor 26 moves from the standby position by a specified amount and detects the end position of the sheet 27 in the width direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile, a laser beam printer and the like.

[0002]

2. Description of the Related Art Generally, an image forming apparatus is provided with various sheet cassettes (sheet stacking means) for each sheet size in order to form an image on sheets of a plurality of sizes. Are sent to the image forming means side one by one. In such an image forming apparatus, since a conveyed sheet may cause skew due to an unbalanced frictional resistance received from the transport rollers and the like, the skew feeding correction means such as a registration roller corrects the skew of the sheet. After that, the sheet is sent to the image forming means. However, when the skew of the sheet is prevented, the sheet shifts in a direction orthogonal to the sheet conveying direction (generally referred to as lateral registration shift), and the relative position between the image forming unit and the sheet shifts.

Further, due to rattling of a member that regulates the width direction of the sheet in the sheet cassette (direction orthogonal to the sheet conveying direction) and variation in the size of the sheet itself in the width direction, the sheet is skewed. Even without doing so, lateral registration misalignment may occur.

When an image is formed on a sheet in the state where such lateral registration shift occurs, the image forming position shifts with respect to the sheet, as shown in FIG.

Therefore, in order to prevent such a deviation of the image forming position with respect to the sheet, a method of adjusting the image writing position (the position of the image forming means) according to the sheet position is adopted.

That is, as shown in FIG.
By moving the sensor 26, the position of the end portion in the width direction of the sheet is detected, and the position of the image forming unit with respect to the sheet is adjusted or the position of the sheet with respect to the image forming unit is adjusted based on the detection information. It was

[0007]

However, the above-mentioned conventional example has the following drawbacks.

Normally, the type of sheet to be conveyed is rarely limited to one type, and the operator can easily change the sheet size by selecting the sheet cassette to be used. , A4 sheets of various sizes need to be conveyed.

When the reference position of the conveyed sheet is at the center of the sheet (when the sheet is conveyed with the center being the center), as shown in FIG. Will result in a difference of S. At this time, the sensor 26 receives the image forming signal and at the same time,
It is determined in the vicinity of the end position of the sheet conveyed from the home position (that is, the position R which is out of the sheet conveying area so as not to hinder the conveyance of sheets of any size) or for each sheet size. Also, the sheet is moved to a predetermined position to detect the position of the edge of the sheet.

However, as described above, since the types of sheets conveyed are diverse, the sensor 26 is used when the distance from the home position to the sheet end is large.
However, the time required to move the image is increased, which is an obstacle to speeding up the image forming process. That is, the first print time (the time from the input of the image formation start signal to the image formation of the first sheet) is long.

In particular, when the sheet is fed from the uppermost sheet cassette closest to the image forming portion, the time required from the start of feeding to image formation is short because the length of the sheet conveying path is short. Therefore, in the image forming apparatus, the uppermost sheet cassette is generally used frequently, and the adverse effect on the speeding up of the image forming process due to the decrease in the speed of the first print is remarkable.

Further, in the conventional image forming apparatus, although the movement distance from the home position to the end position of the sheet is large, the resolution of the sensor 26 required for detecting the end of the sheet is 0. Since the accuracy is as high as about 1 mm, the rigidity of the support portion of the sensor 26 must be strengthened if the moving speed of the sensor 26 is to be increased (to speed up the first printing). As a result, the size of the image forming apparatus itself is increased. In addition, there is a problem in that the operation sound of the sensor 26 and the like becomes louder as the size of the image forming apparatus increases.

Therefore, the present invention has an object to solve such a problem of the conventional example.

[0014]

An image forming apparatus of the present invention comprises a plurality of sheet stacking means for stacking sheets, and a feeding means for feeding the sheets one by one from the sheet stacking means.
Detecting means for detecting an end position in the width direction of the sheet sent out by the feeding means, conveying means for conveying the sheet sent out by the feeding means, and an image formed on the sheet conveyed by the conveying means And an image forming position adjusting unit that adjusts a relative position of the sheet based on a detection signal from the detecting unit, the image forming apparatus being closest to the image forming unit. The detecting means is made to stand by at the widthwise end position of the sheet on the sheet stacking means arranged at.

Further, the image forming apparatus of the present invention is characterized in that the image forming position adjusting means moves the image forming means with respect to the sheet based on a detection signal from the detecting means.

Further, the image forming apparatus of the present invention is characterized in that the image forming position adjusting means moves the conveying means in a direction orthogonal to the sheet conveying direction based on a detection signal from the detecting means.

Further, the image forming apparatus of the present invention includes a plurality of sheet stacking means for stacking sheets, a feeding means for feeding the sheets one by one from the sheet stacking means, and a sheet fed by the feeding means. From the detecting means, a detecting means for detecting the end position in the width direction, a conveying means for conveying the sheet sent out by the feeding means, an image forming means for forming an image on the sheet conveyed by the conveying means, and the detecting means. An image forming position adjusting means for adjusting the relative position of the sheet on the basis of the detection signal of the image forming means, the image forming apparatus on the specified sheet stacking means among the plurality of sheet stacking means. It is characterized in that the detecting means is made to stand by at the end position in the width direction of the sheet.

(Operation) When the sheet is supplied from the sheet stacking means closest to the image forming means, the detecting means detects the widthwise end position of the sheet without moving from the standby position. Based on this detection signal, the image forming position adjusting means adjusts the relative position of the sheet and the image forming means. When a sheet is supplied from a sheet stacking unit that is not the sheet stacking unit closest to the image forming unit, the detecting unit moves a predetermined amount from the standby position and detects the widthwise end position of the sheet.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) A first embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a perspective view of an essential part of an image forming apparatus showing this embodiment. FIG. 4 is a schematic configuration diagram showing the overall structure of the image forming apparatus.

<Overall Structure and Operating State of Image Forming Apparatus>
A schematic configuration of the image forming apparatus 100 will be described with reference to FIG.

First, a signal is sent from the controller (CPU 101) to a laser oscillator (not shown), and laser light is emitted. Next, this laser light is reflected by a rotating mirror 9 (generally called a polygon mirror), and is reflected again by a reflection mirror 10 to be irradiated onto a photosensitive drum (image forming means) 12. A so-called latent image is formed on the photosensitive drum by such a series of operations. The latent image on the photosensitive drum is developed by the developing device 11 and then transferred as a toner image on the sheet.

Sheets are fed one by one from a sheet cassette (sheet stacking means 51 or 52) by a pickup roller (feeding means) 13 and pass below the photosensitive drum 12 in the figure. At this time, the toner image is transferred to the sheet by the process described above. After that, the sheet is guided to the pair of fixing rollers 1 and 2, the sheets are pressed against each other by the pair of fixing rollers 1 and 2, and heated by the heat of the heater provided inside the fixing rollers 1 and 2 to form a toner image. Is fixed on the sheet. The fixing roller pair 1 and 2 includes a fixing upper separation claw 3
And the lower fixing claw 4 are disposed adjacent to each other, and the separation claws 3 and 4 separate the sheet from the fixing roller pair 1 and 2. The separated sheet is conveyed to the outside of the apparatus main body by the pair of discharge rollers 5 and 6, and a series of image forming processes is completed.

Sheets for image formation are stored in the sheet cassettes 51 and 52. Sheets of desired size are set (stacked / loaded) in the respective sheet cassettes 51 and 52.
It can be stored). Then, the operator can select a sheet to be used for image formation on an operation panel (not shown) of the image forming apparatus.

The sheet is a sheet cassette (51 or 5).
From 2), the pick-up roller 13 feeds the sheets one by one to the photosensitive drum 12. While the sheet is being fed to the photosensitive drum 12, the difference in the outer diameter of the roller that conveys the sheet, the variation in the sheet conveyance speed due to the abrasion of the roller that conveys the sheet, the alignment of the roller pair, and the like.
Influenced by sliding resistance from the guide plate that guides the sheet, it is not necessarily the traveling direction (sheet conveying direction)
On the other hand, it may not be conveyed straight, but may be conveyed in an inclined state (skew). When the toner image on the photosensitive drum 12 is transferred to the sheet in the skewed state, the image is transferred to the sheet with an inclination.

In order to prevent the skew of the sheet, a pair of registration rollers 14 and 15 are arranged on the upstream side of the photosensitive drum 12 in the sheet conveying direction. This registration roller pair 1
The controllers 4 and 15 are controlled by the controller (CPU 101) so as to be in a stopped state when the leading edge of the sheet fed from the sheet cassette (51 or 52) reaches the pair of registration rollers 14 and 15. Then, with the leading edge of the sheet still abutting on the pair of registration rollers 14 and 15, the pair of pre-registration rollers 16 and 17 continue to rotate for a predetermined time to convey the sheet forward. Therefore, the sheet bends (loops) between the pair of registration rollers 14 and 15 that are stopped and the pair of pre-registration rollers 16 and 17.
I do. The sheet in which the loop is generated tries to return straight due to the elastic force of the sheet (strength of the sheet), and hits the nip of the pair of registration rollers 14 and 15 whose ends are stopped. By this abutting action, the leading end of the sheet follows the nip portion of the pair of registration rollers 14 and 15, and the skew feeding is corrected.
The pair of registration rollers 14 and 15 and the pre-registration roller 1
Conveying means is composed of 6, 17.

However, the image forming apparatus corrects the skew of the sheet by abutting the leading edge of the sheet against the pair of registration rollers 14 and 15 as described above, and therefore, is orthogonal to the sheet conveying direction (traveling direction). There is a case where a sheet position shift (generally referred to as a lateral registration shift) occurs in the direction in which the sheet is moved. As a result, the relative position between the sheet and the photosensitive drum 12 is displaced, and it becomes impossible to accurately form an image on the sheet.

Therefore, the first embodiment of the present invention adopts the configuration shown in FIG. 1 in order to solve the above-mentioned problems.

<Structure and Operating State of Image Forming Position Adjusting Means> FIG. 1 shows the registration roller pair 1 of the image forming apparatus shown in FIG.
FIG. 4 is an enlarged perspective view of a part of the upstream side of the sheet conveyance direction of sheets 4 and 15, showing the details of the image forming position adjusting means G.

In this figure, a sensor (detection means) 26 for detecting the widthwise end portion of the sheet has a light receiving portion 26a provided in parallel with the sheet advancing direction (arrow A in the figure), and the sensor arm 23. It is attached to the tip of. The sensor arm 23 has a rack gear 23 at a part thereof.
a is provided, and the rack gear 23 a meshes with the pinion gear 24 of the stepping motor 22.
Therefore, when the stepping motor 22 rotates, the sensor 26 and the sensor arm 23 move integrally in the directions of arrows B and C in the figure. As the sensor 26 moves in the directions of the arrows B and C, the end position of the sheet 27 is detected by the light receiving section 26a. Then, the detection signal of the sensor 26 is input to the CPU 101 as a controller. The CPU 101 outputs a control signal to the stepping motor 22 and the motor 102 that moves the photosensitive drum 12 based on the detection signal. In this figure, 20,
Reference numeral 21 is a guide plate for guiding the sheet 27.

The sensor 26, the sensor arm 23, the stepping motor 22, the motor 102 and the like constitute an image forming position adjusting means G.

Next, the operating state of the image forming position adjusting means G will be described with reference to the flow chart shown in FIG.

First, when the power of the apparatus is turned on (S1),
The sheet size set in the sheet cassette 51 closest to the photosensitive drum 12 as the image forming means, out of the sheet cassettes 51 and 52 mounted on the apparatus main body, is detected by the size detecting means (not shown) (S2). Then, the CPU 101 recognizes the home position of the sensor 26 according to the size information. That is, the sheet end portion of the detected sheet size is set as the home position of the sensor 26.

Next, the stepping motor 22 starts rotating in the direction of arrow D in the figure. As the motor 22 rotates, the sensor arm 23 moves in the direction of arrow C in the figure, and its rear end 23b eventually abuts against the abutting member 25 of the apparatus body and stops. At this time, the sensor 26 is located at a position apart from the sheet passing area by a predetermined distance (Q). As a result, the CPU 101 of the apparatus body has recognized the absolute position of the sensor 26. Then, the stepping motor 22 moves the sensor 26 from the state (position Q) to the home position H.
Rotates in the direction of arrow E until the sensor moves, and stops when the sensor 26 reaches the home position H (h in the figure) (S).
3). Then, the CPU 101 of the apparatus main body is in a standby state waiting for the start signal to be input by the operator (S4).

Next, when the operator presses a start button (not shown), a start signal is input to the CPU 101 and sheet conveyance is started (S5). At this time, if the selected sheet is the uppermost sheet cassette 51, the position where the sensor 26 should be is the same as the standby position H.
It is not necessary to move the sensor 26, and the moving time of the sensor 26 does not affect the image forming time.

On the other hand, when the designated sheet is not the topmost sheet (that is, in the case of the sheet cassette 52 shown in FIG. 4), the sensor 26 is moved to a position corresponding to the sheet edge of the designated size, and then the image is displayed. Start the forming operation (S6 ~
S7).

The sheet 27 conveyed from the sheet cassette (51, 52) hits the registration roller pairs 14, 15 which are stopped, forms a loop to correct skew, and then the registration roller pair 14, 15. After being conveyed by a predetermined amount at 15, it stops. Then, the sensor arm 23 moves in the direction of arrow B with respect to the stopped seat 27, and the sensor 2
The light receiving portion 26a provided at 6 detects the widthwise end portion of the sheet 27 (S8). In addition, the sheet end portion is the light receiving portion 26.
The position where a is blocked is detected by the sensor 26 as the sheet end (when the sheet end has already blocked the sensor 26, the same detection can be performed by moving the sensor 26 in the direction of arrow C). is there).

This detection signal is input to the CPU 101,
The CPU 101 calculates the sheet shift amount (S9).
As a result, the actual position of the sheet being conveyed can be known.

The CPU 101, based on the calculation result,
A control signal is output to the motor 102, the photosensitive drum 12 and the sheet position are adjusted (S10), and the image forming operation is started (S11). As a result, it is possible to write an image and form an image in accordance with the position detected by the sensor 26 and to match the relative positions of the sheet and the image.
Then, when an image formation end signal is input to the CPU 101, a series of image formation work ends (S12).

As described above, in the image forming apparatus 100 according to the present embodiment, the image forming position adjusting means G moves the photosensitive drum 12 to the sheet even if the sheet is laterally misregistered to prevent skewing. In addition to being able to perform the position alignment and form an accurate image on the sheet, the home position of the sensor 26 for detecting the widthwise end position of the sheet is housed in the sheet cassette 51 closest to the photosensitive drum 12. By setting the sheet edge position, it is possible to significantly reduce the time required for adjusting the image forming position, and thus the time required for image forming,
It is possible to speed up image processing.

[0041]

[Other Embodiments] In the above embodiment, the writing position is moved to align the image and the sheet.
That is, although the position of the photosensitive drum 12 is moved by the motor 102, the present invention is not limited to this, and the sheet conveying roller is moved back and forth (in the direction orthogonal to the sheet conveying direction) to move the sheet relative to the photosensitive drum 12. Even if the positions are adjusted, the same effect as that of the first embodiment can be obtained.

Further, in the above embodiment, the sensor 26 detects the amount of deviation with respect to the temporarily stopped sheet. However, if there is a margin for the timing for moving the image, the sensor 26 detects it while conveying the sheet. It is also possible to do so.

Further, in the above-described embodiment, the home position (standby position) is determined from the sheet size set in the uppermost sheet cassette 51 (closest to the image forming means), but the operator specifically specifies. Accordingly, it is possible to set the home position from a specific sheet size and a specific sheet cassette. This makes it possible to obtain the same effect as that of the first embodiment even for an operator who frequently uses other cassettes, manual paper feed, and the like.

[0044]

As described above, in the image forming apparatus of the present invention, even if the sheet is laterally misregistered to prevent skewing, the image forming position adjusting means aligns the sheet and the image forming means. By doing so, accurate image formation can be performed on the sheet.

Further, by adjusting the home position of the detecting means for detecting the end position of the sheet in the width direction to the end position of the sheet accommodated in the sheet cassette closest to the image forming means, the image forming position can be adjusted. The time required, and eventually the time required for image formation, can be significantly reduced, and the speed of image processing can be increased.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an operating state of the image forming apparatus.

FIG. 3 is an explanatory diagram showing a defective feeding state at the time of sheet feeding.

FIG. 4 is a schematic configuration diagram of an image forming apparatus showing an embodiment of the invention.

FIG. 5 is a plan view of a main part of a conventional image forming apparatus.

[Explanation of symbols]

 12 Photosensitive Drum (Image Forming Means) 13 Pickup Rollers (Feeding Means) 14, 15 Registration Roller Pairs (Conveying Means) 16, 17 Pre-Registration Rollers (Conveying Means) 26 Sensors (Detecting Means) 27 Sheets 51, 52 Sheet Cassettes ( Sheet stacking means) 100 Image forming means G Image forming position adjusting means

Claims (4)

[Claims] 1. A plurality of sheet stacking means for stacking sheets, a feeding means for feeding the sheets one by one from the sheet stacking means, and a position in the width direction of the sheet fed by the feeding means is detected. A detecting unit, a conveying unit that conveys the sheet sent by the feeding unit, an image forming unit that forms an image on the sheet conveyed by the conveying unit, and an image of the sheet based on a detection signal from the detecting unit. In an image forming apparatus including image forming position adjusting means for adjusting the relative position of the forming means, the detecting means is provided at the widthwise end position of the sheet on the sheet stacking means arranged closest to the image forming means. An image forming apparatus characterized by making it stand by. 2. The image forming apparatus according to claim 1, wherein the image forming position adjusting means moves the image forming means with respect to a sheet based on a detection signal from the detecting means. 3. The image forming apparatus according to claim 1, wherein the image forming position adjusting means moves the conveying means in a direction orthogonal to a sheet conveying direction based on a detection signal from the detecting means. 4. A plurality of sheet stacking means for stacking sheets, a feeding means for feeding the sheets one by one from the sheet stacking means, and a position in the width direction of the sheet fed by the feeding means is detected. A detecting unit, a conveying unit that conveys the sheet sent by the feeding unit, an image forming unit that forms an image on the sheet conveyed by the conveying unit, and an image of the sheet based on a detection signal from the detecting unit. An image forming apparatus including image forming position adjusting means for adjusting the relative position of the forming means, wherein the detection is performed at a widthwise end position of a sheet on a specified sheet stacking means among the plurality of sheet stacking means. An image forming apparatus for causing a means to stand by.