JP2000159357A - Sheet feeder and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a decrease in conveying force related to the durability of a conveying rotor and a separating rotor that cooperate to separate sheets from one another, thus reporting the replacement time of the conveying rotor and/or the separating roller before jams occur frequently. SOLUTION: A CPU serving as a wear detection means recognizes the wear of a feed roller and/or a retard roller on detecting that the actual feed time Ta from the time of transmission to a motor driver of a feed signal from the CPU for feeding sheets to the time of detection of the sheets by a photosensor has delayed from normal feed time Ts. Then a report means reports replacement time to the user.

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 provided in an image forming apparatus such as a printer, a copying machine, and a facsimile.

[0002]

2. Description of the Related Art In recent years, the processing speed of image forming apparatuses such as printers, copiers, and facsimile machines has been rapidly increasing. Therefore, as a mechanism for separating sheets, a retard separation system using a high-speed separation and highly reliable pickup roller, a feed roller, and a retard roller is widely used.

A conventional retard separating mechanism will be described with reference to FIG. The sheet S is stacked on the sheet stacking plate 51, and the driving source (not shown) stops when the sheet stacking plate 51 is raised by the drive source (not shown) and the elevating means until the upper end detecting means 52 detects the uppermost sheet S. Sheet detection means
When the sheet 53 is detected by the sheet 53, the apparatus enters a ready state, and receives a feed signal from an image forming apparatus (not shown) and drives a not-shown drive motor for driving a retard separating mechanism, thereby causing a pickup roller shaft 54a, a feed roller shaft 55a, a retard The roller shafts 56a all rotate counterclockwise in FIG.

Further, since the pickup roller 54 and the feed roller 55 are respectively mounted on the pickup roller shaft 54a and the feed roller shaft 55a, they also rotate counterclockwise in FIG.

The retard roller 56 is attached to a retard roller shaft 56a via a torque limiter (not shown), and the retard roller shaft 56a is rotatably held by a holding member 57 that can rotate about a rotation shaft 57a. ing. The holding member 57 is rotated by a spring 58 around a rotation shaft 57a as shown in FIG.
, Whereby the retard roller 56 contacts the feed roller 55 with a constant contact force F.

Due to the friction coefficient μ1 with the feed roller 55, a force μ1 × F for rotating clockwise in FIG. 6 is applied to the retard roller 56, which exceeds the set value T of the torque limiter. Although the retard roller shaft 56a rotates in the counterclockwise direction in FIG. 6, the retard roller shaft 56a rotates in the clockwise direction in FIG.

A pickup roller 54 rotatably supported by a holding member 59 rotatable about a feed roller shaft 55a rotates counterclockwise in FIG. 6 about the pickup roller shaft 54a and a cam (not shown). Abuts on the holding member 59, and the holding member 59 rotates counterclockwise in FIG. 6 around the feed roller shaft 55a, and the sheet stacking plate 51
The sheet S placed on top is picked up.

At this time, when the number of sheets S sent out by the pickup roller 54 is one, the following relationship is established, and the retard roller 56 rotates clockwise in FIG. 6 to feed the sheet S. .

[0009]

(Equation 1)

When the pickup roller 54 feeds two sheets S, the retard roller 56 rotates counterclockwise in FIG. 6 because of the following relationship. The lower sheet S is conveyed back by the retard roller 56 and returns to a position just before the nip portion between the feed roller 55 and the retard roller 56.

[0011]

(Equation 2)

As a result, the sheet S is separated and fed into only the upper sheet, and the sheet detecting mechanism 60 and the photo sensor 61 arranged on the downstream side of the sheet S in the feeding direction (hereinafter, simply referred to as “downstream side”). To detect that the sheet S has been fed, and a conveying roller 62 and a conveying roller 63 disposed further downstream.
To an image forming unit (not shown).

[0013]

However, in the above-described conventional example, as the number of sheets S passing through the retard separation mechanism is increased, the friction coefficient due to wear of the feed roller 55 and the retard roller 56 (the above μ1, μ2 Etc.) and the contact force F due to the reduction of the roller diameter, the conveyance force for conveying the separated sheet S decreases.

As a result, the feed roller 55 cannot convey the sheet S to the sheet detecting mechanism 60 within a predetermined time, so that the sheet S frequently jams (paper jam), and the user frequently jams. At present, the feed roller 55 and the retard roller 56 are replaced at a suitable time, and it was not possible to know a decrease in the conveying force due to the durability of the feed roller 55 or the retard roller 56 before the occurrence of jams.

The present invention has been made to solve the above problems, and
The purpose is to detect a decrease in the conveying force due to the durability of the conveying rotating body and the separating rotating body that cooperate to separate the sheet, and replace the conveying rotating body and / or the separating rotating body before the occurrence of many jams. It is an object of the present invention to provide a sheet feeding device capable of notifying a timing and an image forming apparatus provided with the sheet feeding device.

[0016]

According to another aspect of the present invention, there is provided a sheet feeding apparatus, comprising: a sheet feeding means for feeding a sheet; and a sheet feeding direction downstream of the sheet feeding means. And a conveying rotator for conveying the sheet fed by the sheet feeding means, and a separating rotator arranged to face the conveying rotator and separating the sheet in cooperation with the conveying rotator A sheet detecting unit disposed downstream of the transport rotating body in the sheet feeding direction to detect a sheet; and a sheet detecting unit that detects a sheet from a point in time at which a sheet feeding signal for feeding the sheet is transmitted to the sheet feeding unit. A wear detecting means for detecting that the time until the sheet is detected by the means is later than a regular time and determining that the transport rotary member and / or the separation rotary member have worn out. When That.

According to the above construction, the time from when the feed signal for feeding the sheet by the wear detecting means is transmitted to the sheet feeding means to when the sheet is detected by the sheet detecting means is longer than the regular time. By detecting that the transport rotator and / or the separation rotator have worn out by detecting the delay, it is possible to detect a decrease in the transport force due to the durability of the transport rotator and / or the separation rotator before jams occur frequently. You can do it.

Further, another configuration of the sheet feeding apparatus according to the present invention includes a sheet feeding means for feeding a sheet, and a sheet feeding means disposed downstream of the sheet feeding means in the sheet feeding direction. A transport rotator that transports the sheet fed by the feeding unit, a separation rotator that is arranged to face the transport rotator and separates the sheet in cooperation with the transport rotator, and A sheet detecting unit that detects a sheet, and a sheet is detected by the sheet detecting unit from a point in time when a feed signal for feeding the sheet is transmitted to the sheet feeding unit. The average feed time of the feed time is obtained by dividing a plurality of sheets into sheets, and it is detected that the average feed time is later than the regular time, and the transport rotating body and / Or the separation rotating body And having a wear detecting means for determining that worn.

According to the above configuration, the feeding time from when the feed signal for feeding the sheet by the wear detecting means is transmitted to the sheet feeding means to when the sheet is detected by the sheet detecting means is stored. The average feeding time of the feeding time is calculated for a plurality of sheets, and it is detected that the conveying rotating body and / or the separating rotating body has worn out by detecting that the average feeding time is later than the regular time. , It is possible to detect a decrease in the conveying force due to the durability of the conveying rotator and / or the separating rotator before jams occur frequently, and compare the average feeding time of a plurality of sheets with a regular time. As a result, the reliability of detecting a decrease in the conveying force due to the durability of the conveying rotating body and / or the separating rotating body is improved.

In addition, there is provided a notifying means for notifying the replacement time of the transport rotating body and / or the separating rotary body when the wear detecting means determines that the transport rotating body and / or the separating rotary body has worn out. In this case, it is possible to notify the user of the replacement time of the transport rotating body and / or the separation rotating body before the jam occurs frequently by the notification means.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, an embodiment in which the present invention is applied to an electrophotographic printer as an example of a sheet feeding apparatus according to the present invention and an image forming apparatus having the same will be specifically described. FIG. 1 is a schematic cross-sectional explanatory view showing a configuration of an image forming apparatus provided with a sheet feeding apparatus according to the present invention, FIG. 2 is a schematic cross-sectional explanatory view showing a configuration of a sheet feeding apparatus according to the present invention, and FIG. FIG. 4 is a block diagram showing the configuration of a control unit serving as a detection unit. FIG. FIG.

First, a first embodiment of a sheet feeding apparatus according to the present invention and an image forming apparatus having the same will be described with reference to FIGS. In FIG. 1, reference numeral 1 denotes an electrophotographic photosensitive drum which is an electrostatic image carrier serving as an image forming means; 2, a semiconductor laser as a light source; 3, a rotating polygon mirror rotated by a scanner motor 4; 2
Is a laser beam that is emitted from the photosensitive drum 1 and scans the surface of the photosensitive drum 1.

Reference numeral 6 denotes a charging roller for uniformly charging the surface of the photosensitive drum 1, and reference numeral 7 denotes a developing roller for developing an electrostatic latent image formed on the surface of the photosensitive drum 1 with toner. Machine. Reference numeral 8 denotes a transfer roller for transferring the toner image developed by the developing device 7 onto a sheet S made of paper, synthetic resin, or the like. Reference numeral 9 denotes a heating and pressing process for the toner image transferred onto the sheet S. And a fixing roller pair for fusing and fixing.

Reference numeral 10 denotes a sheet cassette serving as sheet placing means having a function of identifying the size of the sheet S. The sheets S placed and accommodated in the sheet cassette 10 are pick-up rollers serving as sheet feeding means. It is fed by one rotation of 11.

In FIG. 2, a sheet S made of paper, synthetic resin, or the like is stacked on a sheet stacking plate 10a provided in a sheet cassette 10, and an upper end detecting means 10b is moved to the uppermost position by a driving source (not shown) and an elevating means. When the sheet S is detected, the driving source (not shown) stops, and at that time,
When the sheet 10c detects the sheet S, the ready state is established. In detail, a drive motor (not shown) that drives a retard separation mechanism in response to a feed signal sent from a CPU 23a of a control unit 23 of the image forming apparatus described later drives the pickup, and Roller shaft 11
a, the feed roller shaft 12a, and the retard roller shaft 13a all rotate counterclockwise in FIG.

The pickup roller 11 and the feed roller 12, which is a transport rotating member disposed downstream of the pickup roller 11, are mounted on the pickup roller shaft 11a and the feed roller shaft 12a, respectively.
Rotates counterclockwise.

A retard roller 13 which is disposed opposite to the feed roller 12 and serves as a separation rotating body for separating the sheet S in cooperation with the feed roller 12 is attached to a retard roller shaft 13a via a torque limiter (not shown). The retard roller shaft 13a is rotatably held by a holding member 14 that is rotatable about a rotation shaft 14a.

The holding member 14 is rotated by a spring 15
2, and the retard roller 13 is in contact with the feed roller 12 with a constant contact force F.

A force μ1 × F for rotating clockwise in FIG. 2 is applied to the retard roller 13 due to a friction coefficient μ1 with the feed roller 12, which exceeds the set value T of the torque limiter. Although the retard roller shaft 13a rotates in the counterclockwise direction in FIG. 2, it rotates in the clockwise direction in FIG.

The pickup roller 11 rotatably supported by a holding member 16 rotatable about a feed roller shaft 12a rotates counterclockwise in FIG. 2 about the pickup roller shaft 11a and a cam (not shown). Abuts on the holding member 16 so that the holding member 16 rotates counterclockwise in FIG. 2 around the feed roller shaft 12a, and the sheet stacking plate 10
Pick up the sheet S placed on a.

The operation of separating and feeding the sheet S sent out by the pickup roller 11 is the same as that described in the above-mentioned conventional example. Only the upper sheet S is separated and fed.
The sheet S is fed by a sheet detecting mechanism 17 serving as a sheet detecting means and a photo sensor 18 disposed further downstream, and a conveying roller pair 19 disposed further downstream is detected.
To the roller pair 20 before transfer.

Reference numeral 21 denotes a manual feed roller for guiding the sheet S from the manual feed port having no function of identifying the size of the sheet S to the pair of pre-transfer rollers 20, and reference numeral 22 denotes a sheet S on which an image is fixed. It is a discharge roller pair that discharges outside the machine.

FIG. 3 shows a state where the feed signal for feeding the sheet S is transmitted to the pickup roller 11 and the photo sensor 18 is turned on.
Is used to measure the feeding time until the sheet S is detected, and to detect that the feeding time is later than the regular time to determine that the feed roller 12 and / or the retard roller 13 has worn. 3 shows a configuration of a control unit 23 serving as a detection unit.

The control unit 23 includes a CPU (central processing unit) 23
a, a ROM (read only memory) 23b, and a RAM (read / write memory) 23c. The CPU 23a reads programs and various data from an external device such as a ROM 23b and an input device to be described later, and makes necessary calculations and determinations. It performs various controls, and sends a feed signal to a motor driver 25 that controls a drive motor 24 that drives the pickup roller 11.

The CPU 23a is provided with a counter, which counts the time from when the CPU 23a sends a feed signal to when the sheet S is detected by the photo sensor 18.

The ROM 23b stores various programs required for the operation of the CPU 23a, various types of data required for recording character codes, dot patterns, and the like.
When the retard roller 13 is in the endurance initial state, the CPU 23
The normal feeding time Ts at which the sheet S is detected by the photo sensor 18 from the time when the feeding signal is transmitted from the position a is stored.

The RAM 23c includes a working area for temporarily storing data and an operation result instructed by the CPU 23a, a buffer area for storing various data input from an external device or the like, a text area for storing documents and the like. The actual feeding time Ta at which the sheet S is detected by the photo sensor 18 from the time when the feeding signal is sent from the CPU 23a counted by the counter provided in the CPU 23a is stored at any time.

Then, the CPU 23a compares the normal feed time Ts stored in the ROM 23b with the actual feed time Ta stored in the RAM 23c at any time, and determines that the actual feed time Ta is a regular feed time. If the time Ts is delayed, it is determined that the feed roller 12 and / or the retard roller 13 has worn, and a notification signal is transmitted to the notifying means 26, and the notifying means 26 sends the feed roller 12 and / or the retard roller 13 to the user. Notify when to replace.

[0039] Figure 4 is a sheet S from the start t ₀ feed that was sent (signal to start rotation of the pickup roller 11) feeding signal from the CPU23a is picked up by the pickup roller 11, feed roller 12 and the retard roller 13 After the photo sensor 18 is separated by the
FIG. 5 is a diagram showing a time required to reach the ON state after the detection of the state.

The roller wear limit time Tb is a fixed time after the design regular feeding time Ts calculated from the conveyance speed of the sheet S by the feed roller 12 and the conveyance path distance from the pickup roller 11 to the sheet detection mechanism 17. And after a certain time, the jam limit time Tj
Is set as

Here, the actual feeding time Ta for the sheet S to reach the sheet detecting mechanism 17 is the regular feeding time of the feed roller 12 and the retard roller 13 in the initial endurance state shown in FIG. However, as the endurance progresses from the middle state of endurance shown in FIG. 4B to the end state of endurance shown in FIG. 4C, the conveyance speed decreases due to the reduction in the diameter of the feed roller 12 and the friction increases. Due to factors such as a decrease in the conveying force due to a decrease in the coefficient and the nip pressure, the design value is gradually delayed from the regular feed time Ts, and finally the jam limit time Tj as in the jam occurrence state shown by D in FIG. Conventionally, the image forming apparatus determines that the sheet S has jammed somewhere in the conveyance path, and stops the apparatus.

However, in this embodiment, the roller wear limit time Tb is provided, and the actual feeding time Ta, which is the time required for the sheet S to reach the sheet detection mechanism 17, is determined by the roller wear limit time Tb and the jam limit time. When the time reaches Tj, a message notifying the replacement time of the feed roller 12 and / or the retard roller 13 is displayed on a screen of a personal computer (hereinafter referred to as a "PC") through an operation panel (not shown) or a printer driver (not shown) of the printer. The user is notified by the notification means 26 such as display.

According to the above configuration, the feed signal for feeding the sheet S is supplied from the CPU 23a by the control unit 23 serving as the wear detecting means.
The actual feed time Ta from the time when the sheet S is detected by the photo sensor 18 to the time when the sheet S is detected by the photo sensor 18 is delayed from the time when the sheet S is transmitted to the motor driver 25 of the drive motor 24 that drives the pickup roller 11. Regular feed time Ts
When the feed roller 12 and / or the retard roller 13 is worn by detecting that the roller wear limit time Tb has reached a certain time later than the predetermined time, the feed roller 12 and / or the retard roller 13 can be replaced before jam occurs frequently. Alternatively, it is possible to detect a decrease in the conveying force due to the durability of the retard roller 13, and to notify the user of the replacement time of the feed roller 12 and / or the retard roller 13 before the occurrence of jam by the notifying means 26. I can do it.

Next, a second embodiment of the sheet feeding apparatus according to the present invention will be described with reference to FIG. FIG. 5 is a diagram showing the durability change of the probability distribution of the time from when the sheet feeding signal for feeding the sheet is transmitted to the sheet feeding means to when the sheet is detected by the sheet detecting means. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In the present embodiment, the feed signal for feeding the sheet S sent from the CPU 23a of the control unit 23 shown in FIG. Are stored in the RAM 23c from the time of transmission to the sheet S to the time when the sheet S is detected by the photo sensor 18, and the average of the plurality of actual sheet feeding times Ta is divided into a plurality of sheets S. The feeding time Tm is obtained, and it is determined that the feed roller 12 and / or the retard roller 13 has worn out by detecting that the average feeding time Tm is later than the regular feeding time Ts. .

FIG. 5 shows a state in which the sheet S is picked up by the pickup roller 11 from a feeding start time t ₀ at which a feeding signal (a signal for starting the rotation of the pickup roller 11) is sent from the CPU 23 a, and the feed roller 12 and the retard roller 13. After the photo sensor 18 is separated by the
FIG. 6 is a diagram showing a probability distribution of an actual feeding time Ta, which is an arrival time until the power is turned on after the detection is made.

In the endurance initial state shown by A in FIG.
The sheet S arrives at the sheet detecting mechanism 17 near the regular feeding time Ts which is a substantially designed value, or the regular feeding time Ts
One of them reaches the sheet detection mechanism 17 slightly earlier than the other.

When two or more sheets S are fed by the pickup roller 11, the second and subsequent sheets are separated by the cooperation of the feed roller 12 and the retard roller 13, so that the feed roller 12 and the retard roller 13 This is because the sheet is stopped just before the nip portion, and in this case, the position where the pickup roller 11 starts picking up the sheet S by the next feed signal has advanced downstream from the normal position.

As the endurance of the feed roller 12 and the retard roller 13 progresses, the probability distribution of the actual feeding time Ta gradually delays as shown in FIGS. 5B and 5C. The RAM 23c stores the actual feed from when the feed signal for feeding the sheet S sent from the CPU 23a to the motor driver 25 of the drive motor 24 rotating the pickup roller 11 until the photo sensor 18 detects the sheet S. The CPU 23 stores ten transmission times Ta.
As for a, the average value is calculated by replacing the data of the newest actual feeding time Ta and the data of the oldest actual feeding time Ta every time the sheet S is fed.

If the average value exceeds the preset roller wear limit time Tb, the CPU 23a determines that the feed roller 12 and / or the retard roller 13 has reached the end of its life, and notifies the notification means as in the first embodiment. A message for notifying the user of the replacement time of the feed roller 12 and / or the retard roller 13 is given by 26.

According to the above configuration, by comparing the average feeding time Tm of the plurality of sheets S with the regular feeding time Ts, it is possible to reliably detect the decrease in the conveying force due to the durability of the feed roller 12 and / or the retard roller 13. The performance is improved. Other configurations are the same as those of the first embodiment, and the same effects can be obtained.

[0052]

According to the present invention, the feed signal for feeding a sheet by the wear detecting means is transmitted to the sheet feeding means. It is detected that the time from when the sheet is detected by the sheet detecting means to when the sheet is detected by the sheet detecting means is later than the regular time, and it is determined that the conveying rotating body and / or the separating rotating body has worn, so that the jam is reduced. Before the occurrence of many occurrences, it is possible to detect a decrease in the conveying force due to the durability of the conveying rotating body and / or the separating rotating body.

According to the second aspect of the present invention,
The feeding time from when the feed signal for feeding the sheet by the abrasion detecting means to the sheet feeding means to when the sheet is detected by the sheet detecting means is stored, and the feeding time is divided into a plurality of sheets. The average feeding time of the time is obtained, and when the average feeding time is later than the regular time, the jam occurs frequently by judging that the transport rotating body and / or the separation rotating body has worn out. Before the transport rotating body and / or
Alternatively, it is possible to detect a decrease in the conveying force due to the durability of the separation rotating body, and compare the average feeding time of a plurality of sheets with a regular time to reduce the conveyance force due to the durability of the conveying rotating body and / or the separation rotating body. The reliability of detection is improved.

If the wear detecting means determines that the transport rotating body and / or the separating rotary body has worn out, and if there is a notifying means for notifying the replacement time of the transport rotating body and / or the separating rotating body, the warning means may be used. The notification unit can notify the user of the replacement time of the transport rotating body and / or the separation rotating body before a jam occurs frequently.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional explanatory view showing a configuration of an image forming apparatus including a sheet feeding device according to the present invention.

FIG. 2 is a schematic sectional view illustrating a configuration of a sheet feeding apparatus according to the present invention.

FIG. 3 is a block diagram illustrating a configuration of a control unit serving as a wear detecting unit.

FIG. 4 is a diagram illustrating a change in durability of a time period from when a sheet feeding signal for feeding a sheet is transmitted to a sheet feeding unit to when a sheet is detected by a sheet detecting unit in the first embodiment.

FIG. 5 is a diagram illustrating a durability change of a probability distribution of a time from when a sheet feeding signal for feeding a sheet is transmitted to a sheet feeding unit to when a sheet is detected by a sheet detecting unit in the second embodiment. is there.

FIG. 6 is a diagram illustrating a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum, 2 ... Semiconductor laser, 3 ... Rotating polygon mirror, 4 ... Scanner motor, 5 ... Laser beam, 6 ... Charging roller, 7 ... Developing machine, 8 ... Transfer roller, 9 ... Fixing roller pair, 10 ... Sheet cassette, 10a ... Sheet loading plate, 10b ...
Upper end detecting means, 10c: sheet presence detecting means, 11: pickup roller, 11a: pickup roller shaft, 12: feed roller, 12a: feed roller shaft, 13: retard roller, 13a: retard roller shaft, 14: holding member, 14a …
Rotating shaft, 15 spring, 16 holding member, 17 sheet detection mechanism, 18 photosensor, 19 transport roller pair, 20 pre-transfer roller pair, 21 manual feed roller, 22 discharge roller pair,
23 ... control unit, 23a ... CPU, 23b ... ROM, 23c ... RA
M, 24: drive motor, 25: motor driver, 26: notification means, S: sheet, Ta: actual feeding time, Tb: roller wear limit time, Tj: jam limit time, Tm ...
The average feeding time, Ts ... feeding time of regular, t ₀ ... feeding the starting point

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuzo Isoda 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Inc. (72) Inventor Takashi Kuwata 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside (72) Inventor Judge Sekiya 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroaki Namiki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Makoto Izumi 3-30-2 Shimomaruko, Ota-ku, Tokyo F term in Canon Inc. (reference) 2H027 DA38 DA46 DA50 EC06 EC09 EC10 EC20 ED17 EE02 EE07 EF09 GA32 HB01 HB02 HB16 3F343 FA02 FB02 FB03 FB04 FC01 FC22 GA01 GB01 GC01 GD01 HA12 HA33 HB04 HD16 JA01 JD03 JD09 JD33 KA04 KA13 KA16 LA04 LA16 LC19 LD10 MA03 MA15 MA44 MA54 9A001 BZ05 GG05 JJ35 KK31 KK37 KK42

Claims (4)

[Claims] A sheet feeder configured to feed a sheet, and a transport rotator disposed downstream of the sheet feeder in a sheet feeding direction and configured to transport the sheet fed by the sheet feeder. A separating rotator that is disposed to face the transport rotator and separates a sheet in cooperation with the transport rotator; and is disposed downstream of the transport rotator in the sheet feeding direction to detect a sheet. A sheet detecting means for detecting that a time from when a sheet feeding signal for feeding a sheet is transmitted to the sheet feeding means to when a sheet is detected by the sheet detecting means is later than a regular time. And a wear detecting means for determining whether the transport rotating body and / or the separating rotating body have worn out. 2. A sheet feeding means for feeding a sheet, and a transport rotator disposed downstream of the sheet feeding means in a sheet feeding direction and transporting the sheet fed by the sheet feeding means. A separating rotator that is disposed to face the transport rotator and separates a sheet in cooperation with the transport rotator; and is disposed downstream of the transport rotator in the sheet feeding direction to detect a sheet. A sheet detecting means for storing a sheet feeding time from when a sheet feeding signal for feeding a sheet is transmitted to the sheet feeding means to when a sheet is detected by the sheet detecting means; The average feed time of the feed time is obtained, and it is detected that the average feed time is later than the regular time to determine that the transport rotator and / or the separation rotator has worn. Detection means and Sheet feeding apparatus which is characterized in that. 3. A notifying means for notifying a replacement time of the transport rotator and / or the separation rotator when the wear detecting means determines that the transport rotator and / or the separation rotator has worn. The sheet feeding device according to claim 1 or 2, wherein 4. An image forming apparatus comprising: the sheet feeding device according to claim 1; and an image forming unit that forms an image on a sheet.