JPH11349160A - Sheet feeding device and picture image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable device capable of carrying out stable sheet carriage in high precision and capable of controlling small amount of paper. SOLUTION: This device has a sheet surface detection sensor 4 to detect a difference of a sheet surface state, a feeding means consisting of a paper feeding roller to feed this sheet and a separation roller pair and a control circuit (controller) 1 to control driving of this paper feeding means in accordance with a detection result of this sheet surface detection sensor 4, and the control circuit 1 discriminates a paper kind of the sheet in accordance with the detection result of the sheet surface detection sensor 4 and controls driving of the feeding means consisting of this feeding roller and the separation roller pair in accordance with this paper kind.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding apparatus for sequentially feeding sheets, and more particularly to a sheet feeding apparatus used for an image forming apparatus such as a copying machine.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a sheet such as a transfer sheet loaded in a cassette or the like is fed by a feeding means including a feeding roller or the like. Regardless of the state, the feeding roller is controlled uniformly according to the sheet size. More specifically,
Although a sheet of the same size has a different slippage from a feeding roller for feeding the sheet due to a difference in the surface condition, the sheet feeding amount by the feeding roller is adjusted to a sheet having a relatively large slippage. The size of the sheet is larger than that of the sheet.

[0003]

However, in the above-described conventional apparatus, the amount of sheet feeding by the feed roller is made larger than the size of the sheet in accordance with the sheet in which the slip between the feed roller and the sheet is relatively large. Therefore, when feeding a sheet with less slippage between the feed roller and the sheet, the feeding of the first sheet of the stacked sheets is finished, and then the feeding of the second sheet is started. However, the accuracy of the sheet interval (inter-sheet distance) during continuous feeding of sheets has been reduced. For this reason, in the sheet conveyance control of the image forming apparatus, the sheet cannot be stably conveyed, which causes a conveyance failure.

Further, in recent years, in order to further improve the processing speed, for example, in the sheet conveyance control at the time of continuous copying, it is necessary to reduce the space between the previous sheet and the next sheet. However, in the conventional apparatus, it is necessary to consider a decrease in the accuracy of the sheet interval during the continuous feeding of the sheets, so that it is difficult to perform a desired small sheet interval control.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly reliable apparatus capable of performing more accurate and stable sheet conveyance and capable of controlling a short interval between sheets.

[0006]

A typical configuration of the present invention for achieving the above object is a sheet surface detecting means for detecting a difference in the surface state of a sheet, and a feeding means for feeding the sheet. Control means for controlling the driving of the feeding means in accordance with the detection result of the sheet surface detection means, wherein the control means determines the paper type of the sheet based on the detection result of the sheet surface detection means The driving of the feeding means is controlled according to the paper type.

Specifically, for example, the control means changes the drive stop timing of the feeding means in accordance with the detection result of the sheet surface detection means, or changes the drive stop timing of the sheet feeding means in accordance with the detection result of the sheet surface detection means. The driving time of the feeding means is changed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, with reference to the drawings, embodiments of a sheet feeding apparatus to which the present invention is applied and an image forming apparatus having the same will be described in detail.

First Embodiment A sheet feeding apparatus according to a first embodiment and an image forming apparatus having the same will be described in detail with reference to the drawings. In this embodiment, a case where the present invention is applied to a sheet feeding device in an electrophotographic image forming apparatus will be described as an example.

First, the configuration of a control system of the image forming apparatus will be described with reference to FIG. FIG. 1 is a block diagram illustrating an example of a control system of the image forming apparatus.

In FIG. 1, reference numeral 1 denotes a control circuit (controller) which comprises a CPU 1a, a ROM 1b, a RAM 1c, and the like, and controls the copy sequence on the basis of a program stored in the ROM 1b.

As will be described in detail later, the control system shown in FIG. 1 controls the driving of the feed roller in accordance with the type of the sheet and controls the conveyance of the sheet.
“a” performs correction control, the ROM 1b stores the contents of the control, and the RAM 1c reads and writes data.

The thermistor 2 detects the surface temperature of (the fixing roller of) a fixing device 71 described later, and the value converted by the A / D 3 is input to the controller 1. Controller 1
The surface temperature of the fixing roller is controlled to a predetermined value based on the detection value of the thermistor 2.

Reference numeral 4 denotes a sheet surface detecting sensor, which comprises an S-polarized light receiving element 4a and a P-polarized light receiving element 4b. The value converted by the A / D 3 is input to the controller 1. The controller 1 calculates based on the detection values of the S-polarized light receiving element 4a and the P-polarized light receiving element 4b, and detects the detection of the sheet surface state (that is, the type of paper). The detection of the paper type will be described later in detail.

Reference numeral 5 denotes a light reflection type sheet edge detection sensor, and the value converted by the A / D 3 is input to the controller 1. The controller 1 calculates the detection value of the sheet edge detection sensor 5 and the correction value corresponding to the paper type detected by the sheet surface detection sensor 4, and detects the edge of the sheet. A description of this correction operation will be described later in detail.

The high voltage controller 6 includes a primary charger 58, which will be described later,
The charging system such as the transfer charger 62 and the high-voltage unit 7 for applying a predetermined potential to the developing device 61 and the like are controlled.

The motor control unit 8 controls driving of a motor 9 such as various stepping motors and a main drive motor.

The DC load control unit 10 includes a feeding roller described later.
It controls driving of a solenoid for 67, a clutch for the pair of registration rollers 69, a fan, and the like.

Reference numeral 11 denotes sensors for detecting a sheet jam (paper jam). Detection information from the sensors 11 is input to the controller 1.

The AC driver 12 controls the supply of AC power to an AC load 13 such as a document illumination lamp 53 and a fixing heater 14, which will be described later. Further, an abnormality of the document illumination lamp 53, the fixing heater 14, and the like is detected, and the main switch (MSW) 15 with a shut-off function is turned off.

The power supply 16 supplies DC power to the controller 1 and the like, and a commercial power supply through a main switch 15 and a door switch (DSW) 18 is input to the power supply 16 from an input power plug (PULG) 17.

A deck 90 is a feeding device for increasing the number of stacked sheets, a feeder 30 is an automatic document feeding device for automatically setting a plurality of documents, and a sorter 40 is for sorting sheets to be discharged. It is a sorting device.

The operation unit 100 includes a touch panel 123, an LCD
The unit 121 includes a backlight 122 and the like, and is connected to the control circuit 1.

Next, a schematic configuration of the image forming apparatus will be described with reference to FIG. FIG. 2 is a schematic cross-sectional configuration diagram illustrating an example of the present image forming apparatus.

In FIG. 2, reference numeral 50 denotes an image forming apparatus main body;
Is a recirculating automatic document feeder (hereinafter referred to as a feeder) for automatically feeding documents, and 40 is a sorter (hereinafter referred to as a sorter).
It is designed to be freely combined for use.

In FIG. 2, reference numeral 51 denotes an original table glass as an original table. Reference numeral 52 denotes an optical system as a document reading means, which includes a document illumination lamp (exposure lamp) 53, a plurality of mirrors 54, a lens 55, a motor 56, and the like. Illuminates the original while scanning, etc., and mirrors the reflected light (image light) from the original
Irradiate the photosensitive drum 57 via the lens 54 and the lens 55.

Around the photosensitive drum 57, a primary charger 58, a blank exposure unit 59, a potential sensor 60, a developing device
61, transfer charger 62, separation charger 63, cleaning device 64
The photosensitive drum 57 and the like constitute an image forming means.

The photosensitive drum 57 is rotated in the direction of the arrow shown in FIG. 2 by the main motor 65, is corona-charged by the primary charger 58, and is irradiated with the reflected light of the original from the optical system 52. Then, an electrostatic latent image is formed. This electrostatic latent image is developed by the developing device 61 and is visualized as a toner image.

On the other hand, the sheets stored in the upper or lower cassette 66 are selectively sent out by a feed roller 67 and separated one by one by a pair of separation rollers 68.
Sent within 50. In addition, a feeding unit that feeds the sheet by the feeding roller 67 and the separation roller pair 68 is configured.
As described above, the sheet selectively fed from the upper or lower cassette 66 into the apparatus main body 50 by the separation roller pair 68 via the feed roller 67 is fed to the registration roller pair 69 by the leading edge of the toner image and the leading edge of the sheet. Is fed to the photosensitive drum 57 after the timing is set so that
The toner image is transferred by 62. The surface of the photosensitive drum 57 after the transfer is cleaned by the cleaning device 64.

After the transfer, the sheet is separated from the photosensitive drum 57 by the separation charger 63, guided to the fixing device 71 by the conveyor belt 70, and the transferred image is fixed by pressing and heating. Thereafter, the sheet is discharged out of the apparatus main body 50 by the discharge roller pair 72.

The apparatus main body 50 is provided with a deck 90 capable of storing, for example, 4000 sheets. Deck 90
The lifter 91 rises according to the amount of the sheet so that the sheet always contacts the feeding roller 92.

In FIG. 2, reference numeral 73 denotes a discharge flapper, which is a double-side recording side or a multiple recording side and a discharge side (sorter 4).
0) Switch the route. That is, the sheet fed from the discharge roller pair 72 is switched by the discharge flapper 73 to the double-sided recording side or the multiple recording side. Reference numeral 74 denotes a lower conveyance path, which reverses the sheet sent from the discharge roller pair 72 through a reversing path 75 and re-feeds the sheet.
Lead to 76. Reference numeral 77 denotes a multiplex flapper for switching the path between the double-side recording side and the multiplex recording side. The flapper is tilted leftward in the drawing to directly lead the sheet to the lower transport path 74 without passing through the reversing path 75. Reference numeral 78 denotes a feeding roller for feeding a sheet to the photosensitive drum 57 through a path 79. A discharge roller pair 80 is disposed near the discharge flapper 73 and discharges the sheet switched to the discharge side by the discharge flapper 73 to the outside of the apparatus.

At the time of double-sided recording (double-sided copying) or multiple recording (multiple copying), the discharge flapper 73 is raised upward in the drawing, and the copied sheet is re-supplied in a state of being turned over via the transport paths 74 and 75. Store in tray 76. At this time, the multiplex flapper 77 is tilted to the right in the figure during double-sided recording, and the multiplex flapper 77 is tilted to the left in the figure during multiplex recording. At the time of next double-sided recording or multiplex recording, the sheets stored in the re-feed tray 76 are fed out one by one from below by the feed roller 78, and guided to the registration roller pair 69 of the main body via the path 79. I will

When a sheet is inverted and discharged from the main body, the discharge flapper 73 is raised upward in the drawing, the multiple flapper 77 is tilted rightward in the drawing, and the copied sheet is transported in the conveying path.
75, and after the trailing edge of the sheet has passed through the first feed roller 81, the second feed roller 82
Conveyed to the side, and the sheet (front and back) of the discharge roller pair 80
Turn over and discharge outside the machine.

A plurality of sensors (not shown) for detecting a sheet are provided in the sheet conveying path. Each of the sensors detects that the sheet does not arrive by a predetermined timing (delay jam detection), and detects a predetermined timing. Paper jam detection (jam detection), such as detection that the sheet does not fall out of the sensor (retention jam detection), is performed. If a paper jam is detected, the apparatus is stopped after a predetermined operation, and the specified paper is stopped. A jam display (jam display) is performed.

Reference numeral 4 denotes a sheet surface detection sensor, which is composed of an S-polarized light receiving element and a P-polarized light receiving element. To detect the paper type.

Reference numeral 5 denotes a light reflection type sheet edge detection sensor, which calculates the correction value based on the detection value of the sheet edge detection sensor 5 and the paper type detected by the sheet surface detection sensor 4 to detect the leading edge of the sheet. .

Here, the arrangement of the operation unit 100 provided on the apparatus main body 50 will be described with reference to FIG. FIG. 3 is an explanatory diagram showing an example of an arrangement configuration of the operation unit 100 provided in the apparatus main body 50.

In FIG. 3, reference numeral 101 denotes a reset key which is used to set the copy mode to the standard mode.
A stop key 102 is used to stop copying. A start key 103 is used to start copying. Numeral 104 is used for setting the number of copies and for inputting other numerical values. A clear key 105 is used to set the number of copies to “1”.
Used to clear the numeric input from. Reference numeral 106 denotes a password key which is used when the password mode is set. 107 is a preheating key, which is used when setting / releasing the preheating mode.
When the preheating mode is set, power consumption can be reduced by lowering the temperature of the fixing unit 71 or the like. An interrupt key 108 is used for interrupt copying.
A user mode key 109 is used to set / cancel a user mode such as specification setting and timer setting. 110
Is a guide key, which is used to display a description of the mode.

Reference numeral 120 denotes a message display, which comprises, for example, a transmissive LCD (liquid crystal) unit 121 of 320 × 240 dots and a backlight 122 composed of a cold cathode tube, and has a 15 × 20 key matrix on the surface. A touch panel 123 is provided, and various setting mode displays, various status displays, and key displays corresponding to key inputs of the touch panel 123 are performed.

FIG. 4 shows an example of the display of the message display 120 and the key arrangement. FIG.
FIG. 4B is an example of a jam processing screen, and FIG. 4C is an example of a screen indicating that the door after the jam processing is closed.

In FIG. 4A, reference numeral 130 denotes a display section for displaying a magnification, a selected paper cassette, the number of copies, and the like. Reference numeral 131 denotes a reduction / enlargement key, which is used at the time of reduction / enlargement of fixed magnification. Reference numeral 132 denotes an equal-magnification key, which is used to return the magnification to equal-magnification (100%). Reference numeral 133 denotes a paper selection key, which is used for selecting an automatic paper, and selecting the upper cassette 66, the lower cassette 66, the deck 90, and the multi-bypass tray 93. Reference numeral 134 denotes a zoom key which is used when setting a zoom mode. 135 is a slightly smaller key, which is used to copy the original image slightly reduced (93%). 136
Is a copy density key, which is used when manually adjusting the copy density. An AE key 137 is used to set / cancel the AE mode (automatic density adjustment). 138
A sorter key is used when a sort mode, a staple sort mode, or a group mode is selected. A double-sided key 139 is used to set / cancel the double-sided mode. 14
0 is an application mode key, which is used to select an application mode not displayed on the basic screen.

Next, the detection principle of the sheet surface detection sensor 4 will be described with reference to FIG. The sheet surface detection sensor 4 includes an LED 4d that is a light emitting element that irradiates light at a predetermined incident angle to a sheet that is a detection object, a polarization beam splitter 4c that separates a polarization component of reflected light from the sheet, and And an S-polarized light receiving element 4a and a P-polarized light receiving element 4b that receive the polarized light components split by the polarizing beam splitter 4c.

In the sheet surface detection sensor 4, light is first incident on a sheet to be detected at a predetermined incident angle. At this time, the reflectance of the P-polarized light component and the reflectance of the S-polarized light component are different due to the difference in the surface state of the sheet to be detected.
By utilizing the difference in the reflectance, the ratio of the amount of the P-polarized light component to the amount of the S-polarized light component of the reflected light is compared to determine the paper type of the sheet to be detected.

In the configuration shown in FIG. 5, the output signal of the S-polarized light receiving element 4a is PD2 and the output signal of the P-polarized light receiving element 4b is P
D1 and each output signal is calculated (difference / sum) by the following equation (1), and the output calculation value Px of the sheet surface detection sensor is calculated.
Ask for.

Px = (PD2-PD1) / (PD2 + PD1) (1)

FIG. 9 shows the result calculated by the above equation (1). The horizontal axis in the figure indicates the distance d1 from the sensor. The vertical axis is the value Px calculated based on the above equation (1). In this embodiment, glossy paper, recycled paper, plain paper, OH
The P sheet is illustrated. As shown in FIG. 6, when the distance d1 between the sheet to be detected and the sheet surface detection sensor 4 is the median of 5 mm, the calculated value Px of each sheet is 0.06 for glossy paper with a reflectance of 90%, and the reflectance is 0.06. 0.14 on 80% plain paper,
The value is 0.22 for recycled paper with a reflectance of 70%, and 0.63 for OHP sheets.

Next, the flow of the sheets when the sheets are fed one by one from the cassette 66 storing the sheets will be described with reference to FIG. 6A to 6D, the sheet is conveyed from the cassette 66 on the path. Here, the sheet fed by the feed roller 67 separates the sheets multi-fed by the feed roller 68a and the retard roller 68b constituting the separation roller pair 68 into one sheet at a time. At this time, the feed amount of the sheet is different due to the difference in the frictional force between the feed roller 67 and the sheet, and the gap between the sheets (interval between the sheets) at the time of continuous feeding is varied. Conventionally, this variation has been taken into consideration, so that there is a limit to a small amount of paper (to reduce the interval between sheets).

Further, the separation roller pair 68 including the feed roller 68a and the retard roller 68b will be described below with reference to FIG. In FIG. 7, the opposing feed roller 68a and the retard roller 68b rotate in the directions indicated by arrows, respectively, and feed (rotate forward) the feed roller 68a to feed the top sheet, and rotate (reverse rotation) the retard roller 68b. ) Dams and separates lower sheets and the like that are multi-fed with the uppermost sheet. That is, if the friction of the sheet increases, the overrun amount of the sheet decreases, and it becomes difficult to perform double feeding. Conversely, if the friction of the sheet is small, the overrun amount of the sheet becomes large, and double feeding becomes easy.

FIG. 8 shows the relationship between the calculated value Px representing the difference in the surface state (friction) of the sheet and the overrun amount Sx. As can be seen from the figure, for example, the overrun amount is large for a sheet having a large friction amount such as recycled paper, and the overrun amount is small for a sheet having a small friction amount such as glossy paper. . Here, the relationship between the paper type Px detected by the sheet surface detection sensor 4 and the overrun amount of the sheet can be expressed by the following equation (2).

Sx = (So × Px) / Po (2)

In the above equation (2), So is 9.0 mm which is an overrun amount for plain paper, and Po is 0.14 which is an output calculation value of the sheet surface detection sensor 4 for plain paper.
And

Based on the above relationship, the paper transport control for controlling the feed roller according to the sheet according to the flowchart of FIG. 10 will be described below.

In this embodiment, the sheet surface detection sensor 4
The paper type of the sheet is determined according to the detection result of
The driving of the feed roller 67 is controlled in accordance with the type of sheet of the sheet so that the amount of sheet feeding by the sheet 67 is constant regardless of the difference in the surface state of the sheet.

As shown in FIG. 10, first, it is determined whether or not the area is a correction calculation area (S11). If it is within the correction calculation area, the overrun amount Sx [mm] is calculated by the above-described calculation equation (2).
Is calculated (S12).

Then, in consideration of the obtained overrun amount Sx, the sheet feed amount of the feed roller 67, that is, the rotation time Tr [sec] is calculated by the following equation (3) (S20).

Tr = Px (Ls + Sx) (3)

The feed roller 67 is operated for the time Tr of the calculation result.
Is driven to perform feed roller control according to the sheet type of the sheet.

Next, it is determined whether the sheet is an OHP sheet (S
13). When the output calculation value Px of the sheet surface detection sensor 4 satisfies 0.6 ≦ Px ≦ 0.7, it is determined that the sheet is an OHP sheet, and the overrun amount is set to 11 mm.
(S14).

If the output calculation value Px of the sheet surface detection sensor 4 is 0.3 <Px <0.6, it is determined that the correction upper limit is in the fixed upper limit area (S15), and the output calculation value Px of the sheet surface detection sensor 4 exceeds 0.3 hours. The run amount, that is, 12 mm is set as a fixed value (S16).

If the output calculation value Px of the sheet surface detection sensor 4 is 0 <Px <0.08, it is determined that the correction lower limit is a fixed value area (S17), and the output calculation value P of the sheet surface detection sensor 4 is determined.
The overrun amount when x is 0.08, that is, 6 mm is set as a fixed value (S18).

If the output calculated value Px of the sheet surface detection sensor 4 is 0.7 <Px, Px ≦ 0, it is out of the range of the design allowable value (the sheet type of the sheet cannot be determined), and thus a correction error is determined. (S19). Then, the operator is notified to that effect. For example, a message indicating a paper type discrimination error is displayed on the display unit 130 of the operation unit 100, or a warning sound is generated by a warning sound generation unit such as a buzzer.

As described above, the sheet surface detection sensor 4
The paper type of the sheet is determined according to the detection result of
By controlling the driving of the feed roller 67 according to the sheet type of the sheet so that the amount of sheet feeding by the sheet 67 becomes constant regardless of the difference in the surface state of the sheet, stable sheet conveyance control is possible. , And the control for a small amount of paper can be performed, and the transfer speed can be further improved.

Further, when it is determined that the sheet type is out of the range of the design permissible value, a determination error is made and the operator is notified of the determination error. Jams can be prevented from occurring.

In the present embodiment, the control for changing the rotation time of the feed roller according to the paper type has been exemplified as the drive control of the feed roller according to the paper type. However, the present invention is not limited to this. However, the same effect can be obtained by controlling to change the drive stop timing of the feeding roller according to the type of paper, for example.

[Second Embodiment] A sheet feeding apparatus according to a second embodiment and an image forming apparatus having the same will be described in detail with reference to the drawings. Since the schematic configuration of the entire apparatus is substantially the same as that of the above-described embodiment, members having the same functions are denoted by the same reference numerals, and detailed description thereof will be omitted.
Hereinafter, the sheet feeding control, which is a characteristic part of the present embodiment, will be described in detail with reference to the drawings.

In the first embodiment described above, the sheet detection point (distance) of the sheet edge detection sensor 5 is corrected according to the type of paper, whereas in the present embodiment, the sheet edge detection sensor 5 is corrected according to the type of paper. The correction is performed by changing the sheet detection threshold level.

FIG. 11 shows characteristics of the sheet edge detection sensor 5 (differences in detection points due to differences in reflectance). In the figure, the horizontal axis represents the leading end of the sheet to be moved and the sensor 5.
And the distance d2 from the end of the sensor 5, which indicates the distance at which the sensor 5 starts to detect a sheet as a detection target. In the figure, the vertical axis represents the relative photocurrent I based on the output value of the sensor 5.
L [%], the light emitting element in the sheet edge detection sensor 5 is irradiated on a sheet as a detection target, and the light reflected by the sheet is converted into light received by the light receiving element into an electric signal, which is converted into a current value. It is a representation. Also, the relative photocurrent IL [%] on the vertical axis in the figure indicates the detection level of a detection target having a reflectance of 100%.
Relative photocurrent when 100%.

As can be seen from the figure, the threshold level 20
%, In the case of an OHP sheet, the OHP sheet to be detected is a detection point for detecting the sheet when a point advanced 3.8 mm from the end of the sheet end detection sensor 5 (upstream in the sheet conveying direction). Become. To achieve the same point as this OHP sheet, glossy paper with a reflectance of 90% has a threshold level of 90%, similarly, plain paper with a reflectance of 80% has a threshold level of 70%, and recycled paper with a reflectance of 70% has Threshold level 50%.

The paper type is determined from the output of the sheet surface detection sensor 4 shown in FIG. 9 described in the first embodiment, and the detection of the sheet edge detection sensor 5 is corrected according to the detected paper type. Hereinafter, the correction control will be described.

FIG. 12 is a diagram showing the relationship between the paper type detected by the sheet surface detection sensor 4 and the threshold level correction value. With reference to the relationship shown in FIG. 12, correction control by changing the threshold level correction value according to the type of paper will be described with reference to the flowchart of FIG.

First, it is determined whether it is within the correction calculation area (S31). If it is within the correction calculation area, the threshold value correction value S1 is calculated by the calculation shown in the following equation (4) (S32). However, Px = (PD2-PD1) / (P
D2 + PD1).

S1 = (− Px + 0.57) /0.007 (4)

The correction calculation area is the sheet edge detection sensor 5
Since the detection accuracy is high, high-speed sheet conveyance control is performed, and the sheet conveyance speed is controlled to be 416 mm / sec.

Next, it is determined whether the sheet is an OHP sheet (S3).
3). When the output calculation value Px of the sheet surface detection sensor 4 satisfies 0.6 ≦ Px ≦ 0.7, it is determined that the sheet is an OHP sheet, and the threshold level correction value S1 is determined.
Is set to a fixed value of 20 (S34).

When it is determined that the sheet is an OHP sheet, since the detection accuracy of the sheet end detection sensor 5 is low, low-speed sheet conveyance control is performed, and the sheet conveyance speed is controlled to be 277 mm / sec.

If the output calculation value Px of the sheet surface detection sensor 4 is 0.3 <Px <0.6, it is determined that the correction upper limit is a fixed value region (S35), and the output calculation value Px of the sheet surface detection sensor 4 is 0.3. The threshold level correction value, that is, 50 is set as a fixed value (S36).

When it is determined that the correction upper limit is in the fixed upper limit area, since the detection accuracy of the sheet end detection sensor 5 is low, low-speed sheet conveyance control is performed, and the sheet conveyance speed is controlled to be 277 mm / sec.

Output calculated value Px of sheet surface detection sensor 4
If 0 <Px <0.08, it is determined that the correction lower limit is a fixed value area (S37), and the output calculation value Px of the sheet surface detection sensor 4 is
The threshold level correction value at 0.08, that is, 90, is set as a fixed value (S38).

When it is determined that the correction lower limit is in the fixed lower limit area, the detection accuracy of the sheet edge detection sensor 5 is low, so that low-speed sheet conveyance control is performed, and the sheet conveyance speed is controlled to be 277 mm / sec.

When the output calculation value Px of the sheet surface detection sensor 4 is 0.7 <Px, Px ≦ 0, it is out of the range of the design allowable value (the paper type of the sheet cannot be determined), and thus a correction error is determined. (S39). Then, the operator is notified to that effect. For example, a message indicating a paper type discrimination error is displayed on the display unit 130 of the operation unit 100, or a warning sound is generated by a warning sound generation unit such as a buzzer.

As described above, in the present embodiment, the sheet conveyance is controlled so that the detection point of the sheet end detection sensor 5 is constant (3.8 mm in this embodiment) regardless of the paper type. For example, when the predetermined loop amount L1 of the sheet performed by the pair of registration rollers is 10 mm, the correction amount Lx may be 3.8 mm. That is, a fixed amount (3.8 mm in this embodiment) from the end of the sheet end detection sensor 5 (upstream in the sheet conveyance direction).
Since the point where the sheet is advanced is used as a detection point for detecting the sheet, a predetermined sheet loop amount L1 is set.
6.2mm, which is 3.8mm minus 10mm, is the corrected loop amount.

According to this embodiment, similarly to the above-described embodiment, stable sheet conveyance control can be performed, small-sheet interval control can be performed, and transfer speed can be further improved.

Further, when it is determined that the type of the sheet is out of the range of the design allowable value, a determination error is made and the operator is notified of the determination error. Jams can be prevented from occurring.

[Other Embodiments] In the above-described embodiment, the correction control in registration has been described. However, the present invention is not limited to this, and a sheet sensor used for paper handling of a deck, a feeder, or a sorter may be used. It is needless to say that the sheet can be stably conveyed by using the reflection type sensor according to the present invention and making correction according to the paper type.

In the above-described embodiment, a copying machine is exemplified as an image forming apparatus. However, the present invention is not limited to this. For example, other image forming apparatuses such as a scanner, a printer, and a facsimile apparatus may be used. The same effects can be obtained by applying the present invention to a sheet feeding device used in the image forming apparatus.

Further, in the above-described embodiment, the electrophotographic method is exemplified as the recording method. However, the present invention is not limited to this, and another recording method such as an ink jet method may be used.

[0088]

As described above, according to the present invention,
In order to improve the detection accuracy of the sheet detecting means, the sheet type of the sheet is determined according to the detection result of the sheet surface detecting means, and the sheet feeding amount by the feeding means is kept constant regardless of the difference in the surface state of the sheet. Since the driving of the feeding unit is controlled in accordance with the type of sheet of the sheet, stable sheet conveyance control can be performed, small-sheet interval control can be performed, and transfer speed can be further improved. Become.

Further, when it is determined that the sheet type is out of the range of the design permissible value, a determination error is generated and the operator is notified of the determination error. Jams can be prevented from occurring.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a control system of the image forming apparatus.

FIG. 2 is a schematic cross-sectional configuration diagram illustrating an example of the present image forming apparatus.

FIG. 3 is an explanatory diagram illustrating an example of an arrangement configuration of an operation unit provided in an image forming apparatus main body.

FIG. 4 is an explanatory diagram showing an example of a display of a message display and an arrangement of keys on an operation unit.

FIG. 5 is an explanatory diagram of a detection principle of a sheet surface detection sensor.

FIG. 6 is an explanatory diagram showing the flow of sheets when sheets are fed one by one from a cassette.

FIG. 7 is an explanatory diagram of a separation roller pair including a feed roller and a retard roller.

FIG. 8 is an explanatory diagram showing a relationship between a calculated value Px representing a difference in a surface state (friction) of a sheet and an overrun amount Sx.

FIG. 9 is an explanatory diagram showing a relationship between a distance d1 from a sensor and a calculated value Px.

FIG. 10 is a flowchart illustrating sheet conveyance control according to a difference in paper type.

FIG. 11 is an explanatory diagram showing characteristics of a sheet edge detection sensor (differences in detection points due to differences in reflectance).

FIG. 12 is an explanatory diagram showing a relationship between a paper type detected by a sheet surface detection sensor and a threshold level correction value.

FIG. 13 is a flowchart illustrating correction control by changing a threshold level correction value according to a difference in paper type.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Control circuit (controller) 1a ... CPU 1b ... ROM 1c ... RAM2 ... Thermistor 3 ... A / D4 ... Sheet surface detection sensor 4a ... S polarized light receiving element 4b ... P polarized light receiving element 4c ... Polarized beam splitter 4d ... LED 5 ... Sheet end detection sensor 6 ... High voltage control unit 7 ... High voltage unit 8 ... Motor control unit 9 ... Motor 10 ... DC load control unit 11 ... Sensors 12 ... AC driver 13 ... AC load 14 ... Fusing heater 15 ... Main switch ( MSW) 16 Power supply 17 Input power plug (PULG) 18 Door switch (DSW) 30 Feeder 40 Sorter 50 Machine body 51 Platen glass 52 Optical system 53 Document illumination lamp 54 Mirror 55 Lens 56… Motor 57… Photoconductor drum 58… Primary charger 59… Blank exposure unit 60… Potential sensor 61… Developer 62… Transfer charging Unit 63: Separating charger 64: Cleaning device 65: Main motor 66: Cassette 67: Feeding roller 68: Separating roller pair 68a: Feed roller 68b: Retard roller 69: Registration roller pair 70: Conveying belt 71: Fixing unit 72: Discharge rollers 73… Discharge flapper 74… Lower transport path 75… Reverse path 76… Refeed tray 77… Multiple flapper 78… Feed rollers 79… Path 80… Discharge rollers 81… Feed rollers 82… Feed rollers 83… Reversing roller 90… Deck 91… Lifter 92… Feed roller 93… Multi-bypass tray 100… Operation unit 101… Reset key 102… Stop key 103… Start key 104… Numeric key 105… Clear key 106… Security key 107… Preheat key 108 … Interrupt key 109… User mode key 110… Guide key 120… Message display 121… Unit 122… Backlight 123… Touch panel Le 130 ... display unit 131 ... reduction / enlargement key 132 ... magnification key 133 ... sheet selection key 134 ... zoom key 135 ... slightly smaller keys 136 ... copy density key 137 ... AE key 138 ... sorter key 139 ... double-sided key 140 ... application mode key

Claims (7)

[Claims] 1. A sheet surface detecting means for detecting a difference in the surface state of a sheet, a feeding means for feeding the sheet, and a drive of the feeding means controlled in accordance with a detection result of the sheet surface detecting means. Control means for determining the paper type of the sheet based on the detection result of the sheet surface detection means, and controlling the driving of the feeding means according to the paper type. Characteristic sheet feeding device. 2. The sheet feeding device according to claim 1, wherein the control unit changes a drive stop timing of the feeding unit in accordance with a detection result of the sheet surface detection unit. 3. The sheet feeding device according to claim 1, wherein the control unit changes a driving time of the feeding unit according to a detection result of the sheet surface detecting unit. 4. When the detection result of the sheet surface detection means is out of a predetermined set value range, the control means determines that the error is a paper type determination error and displays an error on a display means. The sheet feeding device according to claim 1, wherein: 5. The control means, if the detection result of the sheet surface detection means is out of a predetermined set value range, determines that a paper type determination error has occurred, and generates a warning sound by a warning sound generation means. The sheet feeding device according to claim 1, wherein the sheet is emitted. 6. The sheet surface detecting means is a light reflection type sensor that detects a difference in surface state of the sheet by using a difference in reflectance of light irradiated on the sheet. The sheet feeding device according to any one of claims 1 to 5. 7. A sheet feeding apparatus according to claim 1, further comprising: an image forming unit configured to record and form an image on the fed sheet. Image forming apparatus.