JPH0967037A - Cut sheet feeding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cut sheet feeding device that can prolong the service life of a feed roller and reduce stress applied to cut sheets. SOLUTION: A cut sheet feeding device having overlap feed preventing mechanism 102, 103 has a means 110 for detecting a friction coefficient between sheets, a means 113 for detecting the frequency of overlap feed of cut sheets, means 114, 115 for detecting cut sheet conveying speed in a feeding process, and a control part. On the basis of the combination of the detected result of the respective detecting means, the control part performs the change control of the grade of sheet separating force of the overlap feed preventing mechanism.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cut sheet feeding device used in a copying machine, a printer or the like, and more particularly to a cut sheet feeding device provided with a control device for preventing double feeding.

[0002]

2. Description of the Related Art A printing apparatus such as a copying machine or a printer requires a sheet feeding apparatus that feeds cut sheets one by one at high speed and reliably. That is, even if the sheets are fed at high speed, it is necessary to avoid feeding two or more cut sheets in an overlapping state (hereinafter, this phenomenon is referred to as “double feeding”). As one method for preventing such double feeding of cut sheets, there is a method called a separation roller separating method with a torque limiter. Hereinafter, a conventional technique in this system will be described.

FIG. 13 is a side view of a conventional sheet feeding device using a separation roller separating method with a torque limiter. The cut sheet 106 stacked on the push-up plate 107 urged by the push-up spring 108 is the pickup roller 101.
After feeding one or several sheets by the
The sheets are separated and separated one by one by the separation roller 103 and the separation roller 103, and fed to the outside of the apparatus by the conveyance rollers 104 and 105.

By the way, the following conditions must be satisfied in order for the cut sheet to be separated so that only the topmost sheet is reliably separated. μ1> TS / (NS × R) ≧ μ2> μ0 where μ0 is the coefficient of friction between sheets and μ1 is the forward rotation roller 10
2 to cut sheet friction coefficient (maximum 2), μ2 is separation roller 103 to cut sheet friction coefficient, NS is pressure contact force between forward rotation roller 102 and separation roller 103, TS is separation roller 103 counterclockwise direction A torque value (hereinafter, referred to as “limit torque value”) that becomes a threshold value at which the rotation starts at
R is the radius of the separation roller 103.

By the way, the inter-sheet friction coefficient μ0 takes different values depending on the type of cut sheet and the like. For example, cut sheets used in copiers generally have a particularly wide range of coefficient of friction compared to cut sheets used in other applications. Therefore, when reliably determining the limiting torque value TS that satisfies the above conditions, the limiting torque is assumed by assuming an inter-sheet friction coefficient μ0 that is somewhat higher than the average inter-sheet friction coefficient μ0 (0.4 to 0.7). It is necessary to choose the value TS.

For this reason, conventionally, by setting a limit torque value TS that can cope with a certain degree of variation in the inter-sheet friction coefficient μ0, that is, a large limit torque value TS, a large sheet separating force is applied to the sheet feeding device. Occurred, and the double feeding of cut sheets was prevented.

[0007]

However, increasing the limiting torque value TS, that is, increasing the sheet separating force is unnecessary for the driven resistance at the moment when the separation roller 103 is not separating the cut sheet. And the rollers 102, 103 and the cut sheet are excessively stressed. The friction coefficients μ1 and μ2 inevitably decrease due to roller wear, but such excessive stress on the roller causes friction coefficients μ1 and μ2.
Accelerate the decline of. Therefore, the inter-sheet friction coefficient μ0 that satisfies the above conditional expression, that is, the upper limit of the inter-sheet friction coefficient μ0 in which cut sheets are not double-fed, is limited, resulting in a decrease in sheet feeding reliability. It was the cause.

In order to avoid such unnecessary stress on the roller, the limit torque value T is calculated based on the paper information (thickness of cut sheet, air permeability, etc.) input by the operator in advance.
A method of deciding a sheet feeding condition such as S has been proposed (for example, Japanese Patent Laid-Open No. 1-117139). However, in such a method, the input work by the operator is required every time a new type of cut sheet is used, and even if it is possible to handle an average cut sheet having the input paper information. There is a problem that it is not possible to cope with a large inter-sheet friction coefficient μ0 that rarely occurs, and further it is not possible to cope with a decrease in the friction coefficients μ1 and μ2 due to abrasion of the rollers 102 and 103.

Therefore, the present invention has been made in view of the above problems, and the cut sheet is reliably separated and fed without the input work by the operator and without depending on the type of the cut sheet. A first object of the present invention is to provide a cut sheet feeding device for paper. A second object of the present invention is to wear the rollers and to reduce the coefficient of friction between sheets μ
By providing a highly reliable cut sheet feeding device in which even if a variation of 0 occurs, the feeding conditions are automatically changed according to those situations and the cut sheets are not double-fed. is there.

Further, a third object of the present invention is to avoid the generation of an unnecessarily large sheet separating force in the sheet feeding process, thereby extending the life of the sheet feeding roller and reducing the stress applied to the cut sheet. A cut sheet feeding device capable of achieving the above.

[0011]

In order to achieve the above-mentioned object, a cut sheet feeding device according to a first aspect of the present invention has a feeding means for feeding the cut sheet and a cut sheet which comes into contact with the upper surface of the fed cut sheet. On the other hand, it has a forward rotation roller that feeds in the feeding direction, a separation roller that is provided to face the forward rotation roller, and a torque limiter that transmits drive to the separation roller, and is positive until the torque limiter exceeds a threshold value. In a cut sheet feeding device that rotates a separation roller in a direction opposite to the rotation of a transfer roller and rotates the separation roller in response to rotation of a forward rotation roller in the conveyance direction when a torque limiter exceeds a threshold value. A coefficient of friction detecting means for detecting a coefficient of friction between sheets in cut sheets stacked in the apparatus; Carry detecting means for detecting whether or not there is another cut sheet carried along with the cut sheet, carrying speed detecting means for detecting a carrying speed of the cut sheet carried from the forward rotation roller, and the three detecting means. Control means for controlling the threshold value of the torque limiter based on the detection result by

A cut sheet feeding device according to claim 2 is
The cut sheet feeding device according to claim 1, further comprising a drive torque switching unit that switches a threshold value of the torque limiter, and the control unit determines that the inter-sheet friction coefficient is larger than a predetermined reference friction coefficient. In this case, when the drive torque switching means is operated to increase the threshold value of the torque limiter by a predetermined amount, and it is determined that the frequency of the accompanying feeding is higher than the predetermined frequency,
When the drive torque switching means is operated to increase the threshold value of the torque limiter by a predetermined amount and it is determined that the transport speed is lower than the predetermined reference speed, the threshold value of the torque limiter is decreased by a predetermined amount. The drive torque switching means is operated so as to

A cut sheet feeding device according to claim 3 is
3. The cut sheet feeding device according to claim 2, wherein the feeding means has a feeding roller that comes into contact with an uppermost surface of the cut sheets stacked in the apparatus and exerts a feeding force on the cut sheet, and the feeding roller as an axis. The friction coefficient detecting means includes a swinging lever that supports the swinging lever and a spring that biases the swinging lever in a direction that cancels a reaction force that the feeding roller receives from the cut sheet at the time of feeding. A photo switch that detects whether or not a predetermined amount is rocked against the urging force of the spring, and the feed detection means is, on the upstream side of the forward rotation roller, whether or not a cut sheet exists at a predetermined time. And a conveying speed detecting means, which is located at a predetermined interval in the cut sheet conveying direction on the downstream side of the forward rotation roller. Two second and third reflective photosensors provided separately from each other, and the time required for the leading edge of the cut sheet conveyed from the forward rotation roller to pass through the two points provided with these sensors. And a timer that measures the signal from those sensors, the control means,
Information from the photo switch, the first reflection type photo sensor, and the timer is accumulated for a predetermined number of cut sheets, and the drive torque switching means is operated based on the accumulated information.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the cut sheet feeding device according to the present embodiment. The apparatus is roughly divided into a sheet feeding mechanism section 100 and a control section 200 that controls the sheet feeding mechanism section 100. Control unit 200
Reads the sensor signal from the paper feed mechanism unit 100 and sends a clutch drive signal to the paper feed mechanism unit 100 based on the result. Hereinafter, these internal configurations and operations will be sequentially described. (Structure of Paper Feed Mechanism Unit 100) FIG. 2 shows a paper feed mechanism unit 1 according to the present invention, which uses a separation roller separating method with a torque limiter.
FIG. The paper feed mechanism unit 100 includes
The conventional paper feeding device shown in FIG.
12, a spring 109, a photo switch 110, and reflection type photo sensors 113 to 115 are added.
The same components as those of the conventional paper feeding unit are designated by the same reference numerals, and the description thereof will be omitted. Further, the support shaft 112, one end of the spring 109, the photo switch 110, the reflection type photo sensors 113 to 115, and the like are fixed to a frame of the present apparatus (not shown).

The pickup roller 101 includes a lever 11
1 is supported by a support shaft 112, and is normally urged by a spring 109 to the position shown in FIG. 2 (downstream side of stacked cut sheets). A photo switch 110 is provided near the upper portion of the lever 111, and detects the horizontal movement of the protrusion of the upper portion of the lever 111. Here, the “downstream side” means the direction in which the cut sheet is conveyed (to the right in FIG. 2), while
"Upstream" means in the opposite direction.

On the upstream side of the separation roller 103, a reflection type photo sensor 113 for detecting the presence or absence of the cut sheet fed from the pickup roller 101 is provided. Similarly, reflective photosensors 114 and 115 that detect the presence or absence of cut sheets at two points aligned in the transport direction are also provided on the upstream side of the transport rollers 104 and 105. The signals from the photo switch 110 and the reflective photo sensors 113 to 114 are sent to the control unit 200 as sensor signals.

The torque limiter 116 is a separation roller 103.
Determines the torque value that starts rotating in the counterclockwise direction, that is, the limiting torque value TS that acts on the separation roller 103. The torque limiter switching means shown in the perspective view of FIG. 3 and the schematic view of FIG. I am configuring. Torque limiter 1
When 16 is used, the forward rotation roller 102 and the separation roller 103
When one sheet is interposed in the nip portion between the separation roller 103 and the sheet, the separation roller 103 is normally rotated by the sheet conveying force of the forward rotation roller 102, and when there are two or more sheets, the separation roller 103 is rotated in the reverse direction. It acts to return the second and subsequent sheets to the upstream side.

As can be seen from FIGS. 3 and 4, the torque limiter 116 is specifically made up of three different types of different torque limiters 310, 320 and 330. The torque limiter 310 and the torque limiter 320 are normally closed electromagnetic clutches 314 and 324. Connected to each
On the other hand, the torque limiter 330 is directly connected to the drive without an electromagnetic clutch. Torque limiters 310, 320, 3
30 are gears 312, 313, 322, 323, 332, and 33 on the upstream side and the downstream side of the drive, respectively.
3 are connected. Electromagnetic clutch 314, 32
4 is intermittent (ON / OFF) by the clutch drive signal from the control unit 200, and the sum of the torques obtained as a result is
The limit torque value TS that acts on the separation roller 103 is obtained.
A combination of on and off of the electromagnetic clutches 314 and 324,
The limit torque value TS determined by the combination is shown in FIG.
The electromagnetic clutch control table shown in FIG. The size of each limiting torque value TS has four levels, namely, 0.6 times the standard value, the standard value, 1.3 times the standard value, and 1.7 of the standard value.
And double. In addition, the standard value is 400 g of pressure contact force NS.
In the case of, about 300 × R (g · cm) is appropriate. (Operation of Paper Feed Mechanism Unit 100) Next, the operation of each sensor in the paper feed mechanism unit 100 configured as described above will be described. In the paper feed mechanism unit 100, the pickup roller 101
For each cut sheet fed out from the sheet, three items of information, that is, the magnitude of the inter-sheet friction coefficient μ0 (Sa), the variation of the inter-sheet friction coefficient μ0 (Sb), and the sheet feeding force (Sc), are detected. The detection principle of these three items Sa, Sb, Sc will be described. [Large or small (Sa) of inter-sheet friction coefficient μ0] Sa is performed by detecting the mechanical reaction force of the pickup roller 101 when the cut sheet is fed. That is, the pickup roller 101 is at the position shown in FIG. 2 when a cut sheet having a relatively small inter-sheet friction coefficient μ0 is fed, but when the cut sheet having a relatively large inter-sheet friction coefficient μ0 is fed, a spring 109 is attached. The power is overcome and the stacked sheets 106 are turned to the upstream side to turn on the photo switch 110. This latter state is as shown in the side view of FIG. Then, when the drive for feeding the cut sheet is cut off, the rotated pickup roller 101 is moved to its original position (the position shown in FIG. 2) by the biasing force of the spring 109 and the driven resistance of the fed cut sheet. ) Automatically returns to. Therefore, by detecting the state (ON / OFF) of the photo switch 110, Sa is detected as a binary value.

The threshold of the inter-sheet friction coefficient μ0 for reversing the state of the photo switch 110 is the spring 109.
Although it can be determined according to the characteristics of the above, the position of the photo switch 110, and the like, here, it is set to 0.7. [Variation of inter-sheet friction coefficient μ0 (Sb)] Sb is
The reflection type photo sensor 113 installed close to the upstream side of the separation roller 103 detects the presence or absence of residual paper before and after the uppermost paper is separated by binary detection. That is, since the frequency with which the pickup roller 101 feeds the cut sheet is counted by counting the case where the residual paper is detected, this frequency is set to Sb. [Sheet feeding force (Sc)] Sc is on the downstream side of the separation roller 103 and on the upstream side of the conveyance rollers 104 and 105.
1 installed at a specified interval in the cut sheet conveyance direction
This is performed by measuring the time taken for the leading edge of the uppermost paper to pass between the pair of reflective photosensors 114 and 115, and comparing this passing time with a predetermined reference passing time (reference time). In this device, the transit time is 1.3 times the reference time.
The case of exceeding the double is discriminated by binary value, and the case of exceeding the double is regarded as the occurrence of the feeding slip of the uppermost paper in the handling process due to the reduction of the sheet feeding force of this apparatus, and the frequency is set as Sc.
This feeding slip occurs when the friction coefficient μ1, μ2 decreases or the inter-sheet friction coefficient μ0 is large.
2, closely related to the μ0 balance. (Structure of Control Unit 200) FIG. 7 shows the control unit 200 of the present apparatus.
FIG. 3 is a block diagram showing the configuration of FIG. The control unit 200 includes a detection circuit 201, a timer 202, a CPU 203, and a memory 20.
4 and a driver circuit 205.

The detection circuit 201 receives a sensor signal from the reflection type photo sensor 113 provided in the paper feed mechanism section 100, converts it into a binary value, and outputs it. This binary value corresponds to the presence or absence of a cut sheet at the position where this sensor 113 is provided. The timer 202 uses the paper feed mechanism unit 10.
0 receives signals from the reflective photosensors 114 and 115, and the tip of the cut sheet passes the position where the reflective photosensor 114 is provided, and then the reflective photosensor 115 is provided. The elapsed time to reach the position is measured and the time is output.

The CPU 203 operates in accordance with a control program stored in the memory 204, reads data from the photo switch 110, the detection circuit 201 and the timer 202 provided in the paper feed mechanism section 100, performs arithmetic processing, and outputs the result. Based on this, the driver circuit 205 is instructed. The memory 204 is composed of a ROM for storing a control program and a RAM as a temporary storage area for the above arithmetic processing.

The driver circuit 205 engages and disengages the electromagnetic clutches 314 and 324 provided in the torque limiter 116 according to an instruction from the CPU 203. (Operation of Control Unit 200) Next, the operation of the control unit 200 configured as described above will be described. FIG. 8 shows the control unit 200.
6 is a flowchart showing the operation of the above, and shows the processing repeated by the control unit 200 for each sheet fed.

First, the control unit 200 first determines the paper feeding mechanism unit 100.
Sa, Sb, Sc and the current sheet feed number n are detected by reading the signals from the respective sensors 110, 113 to 115 provided in the above directly or through the detection circuit 201 and the timer 202 (step S801). It should be noted that the current number of fed sheets n refers to the number of cut sheets fed from the time when the cut sheets 106 are set on the push-up plate 107 by mounting a sheet cassette (LCC) or the like, to the sheet. Until a new cut sheet 106 is set on the push-up plate 107 due to the attachment / detachment of the cassette (LCC) or the like, it is accumulated and counted.

Next, the limiting torque value TS that is uniquely determined from the combination of these values (Sa, Sb, Sc, n) is determined (step S802). Finally, according to the electromagnetic clutch control table shown in FIG. 5, step S8 is actually executed.
The limit torque value TS determined in 02 is the separation roller 103.
The electromagnetic clutches 314 and 324 are turned ON / OFF through the driver circuit 205 so that the electromagnetic force acts on (step S
803).

As described above, the control unit 200 reads the signals from the sensors 110 and 113 to 115 in the paper feed mechanism unit 100 every time one cut sheet is fed, and each time it reads the signal as necessary. The control of changing the limit torque value TS is repeated (steps S801 to 803). FIG.
8 is a sub-flow describing in detail the procedure of step S802 in FIG.

First, it is determined what range the value of the current sheet feed number n is in (step S901). As a result, when the current number of fed sheets n is equal to or smaller than the predetermined number of initially fed sheets n0 (n≤n0), the limit torque value TS is set to the standard value (1.0) (step S902). This is because the first to n0th cut sheets after setting the paper cassette (LCC) or the like are fed with the constant torque value TS kept constant.

On the other hand, the current sheet feed number n is larger than the initial sheet feed number n0 and is equal to or less than the predetermined reference information unit sheet number N (n0
When <n ≦ N), the current sheet feed number n is set as the information unit sheet number Nf (step S903), and the current sheet feed number n
Is larger than the reference information unit number N (N <n),
The reference information unit number N is set as the information unit number Nf (step S904). In this way, the information unit number Nf is set in the next step by calculating the cumulative information Na, Nb, Nc regarding Sa, Sb, Sc in the cut sheet of the latest predetermined number Nf already fed (step). This is because S905). Here, the cumulative information Na, Nb,
When the latest Nf cut sheets are fed, Nc is the number of cut sheets fed with the photo switch 110 turned on, and the reflection type photo sensor 113 detects that “remaining sheets are present”. The number of cut sheets printed, the cut sheet is a reflection type photo sensor 11
This corresponds to the number of cut sheets that have been fed after the time required to pass 4, 115 exceeds 1.3 times the reference time.

In this apparatus, the initial number of fed sheets n0 is 5, and the number of reference information unit N is 20. Therefore, the limit torque value TS becomes the standard value (1.0) up to the fifth sheet after the start of feeding, the sixth sheet is based on the accumulated information of the first to fifth sheets, and the seventh sheet is the first to sixth sheets. Based on the cumulative information of
.., 21 for the 20th sheet based on the accumulated information for 1 to 19 sheets
The sheet number is determined based on the accumulated information of 1 to 20 sheets, the 22nd sheet is determined based on the accumulated information of 2 to 21 sheets, and so on.

As described above, Nf, Na, Nb, Nc
Is calculated, the limit torque value TS that is uniquely determined from the combination of these four values is determined according to the control torque value determination table shown in FIG. 10 (step S90).
6). The processing procedure in step S906 is as shown in the flowchart in FIG. Here, the three ratios Na / Nf, Nb / Nf, Nc / Nf are
The limit torque value TS is determined depending on whether the predetermined reference values are 0.7, 0.3, 0.7 or more.

The content itself of the control torque value determination table shown in FIG. 10 is determined based on the experiment of this device, but basically it is based on the following principle. (1) When Na / Nf is large, the coefficient of friction between sheets μ
Since 0 (Sa) is large, the limit torque value TS is increased in order to generate a large sheet separating force. (2) If Nb / Nf is large, the coefficient of friction between sheets μ
This means that the variation (Sb) of 0 is large, and therefore the limit torque value TS is increased in order to increase the sheet separating force and to wait. (3) When Nc / Nf is large, the sheet feeding force (S
Since c) has decreased, the limit torque value TS is reduced in order to reduce the sheet separating force.

As described above, in this apparatus, each time one cut sheet is fed, three items of the coefficient of friction between sheets μ0, variation, and sheet feeding force (balance of μ1, μ2, μ0) are set. Is detected, and the minimum necessary sheet separating force, that is, the limiting torque value TS is determined based on these. The operation of the detection principle and control method of each sensor in the cut sheet feeding apparatus according to the present invention described above is shown in FIG.
Organize in the table shown in 2.

Although the cut sheet feeding device according to the present invention has been described above based on the embodiment, it goes without saying that the present invention is not limited to this embodiment. That is, (1) the apparatus has one sheet feeding mechanism section 100,
The number of stages is not limited. In the case of a cut sheet feeding device having a plurality of sheet feeding mechanisms, the present invention may be applied to each sheet feeding mechanism. (2) Five rollers 101 constituting the paper feeding mechanism section 100
Nos. 105 to 105 are provided at positions for conveying the cut sheet in the linear direction, but the positional relationship is not limited to this. The paper feed mechanism unit 100 may include a guide device or the like for conveying the cut sheet in a curved line, and these rollers may be provided at positions aligned on a certain curved line.

[0033]

As is apparent from the above description, according to the present invention, information regarding the friction coefficient of the cut sheet that is actually fed is automatically detected, and control is performed to prevent double feeding based on the information. Be seen. Therefore, when using a new cut sheet, it is not necessary for the operator to input information about the cut sheet in advance. Further, the cut sheet is reliably separated and fed without depending on the type of cut sheet and the size and variation of the coefficient of friction.

Further, according to the present invention, the number of cut sheets is 1.
Every time a sheet is fed, information about the coefficient of friction is detected,
It is controlled to generate an appropriate sheet handling force. Therefore, it is possible to avoid the generation of an unnecessarily large sheet separating force in the sheet feeding process, and it is possible to extend the life of the sheet feeding roller and reduce the stress applied to the cut sheet. Furthermore, according to the present invention, control is performed in consideration of not only the coefficient of friction between cut sheets but also the coefficient of friction between the rollers that cut the cut sheets and the cut sheets, so that double feed due to wear of the rollers is avoided. Therefore, it is possible to provide a more reliable cut sheet feeding device.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a cut sheet feeding device according to the present invention.

FIG. 2 is a side view of the sheet feeding mechanism section 100 of the cut sheet feeding apparatus according to the present invention.

FIG. 3 is a perspective view of a torque limiter 116 of the cut sheet feeding device according to the present invention.

FIG. 4 is a schematic view of the torque limiter 116.

FIG. 5 is an electromagnetic clutch control table showing a relationship between control of an electromagnetic clutch provided in the torque limiter and a limit torque value obtained as a result.

FIG. 6 shows a cut sheet feeding device according to the present invention.
The pickup roller 101 rotates to rotate the photo switch 11
FIG. 6 is a side view of the paper feed mechanism unit 100 when 0 is turned on.

FIG. 7 is a control unit 2 of the cut sheet feeding device according to the present invention.
It is a block diagram which shows the structure of 00.

FIG. 8 is a control unit 2 of the cut sheet feeding device according to the present invention.
It is a flowchart which shows operation | movement of 00.

9 is a step S80 in the flowchart of FIG.
It is a subflow which shows the process procedure in 2.

FIG. 10 is a step S9 in the flowchart of FIG.
It is a control torque value determination table used for the process of 06.

FIG. 11 is a step S9 in the flowchart of FIG.
It is a sub-flow showing the processing procedure in 06.

FIG. 12 is a table summarizing the operations such as the detection principle and control method of each sensor in the cut sheet feeding apparatus according to the present invention.

FIG. 13 is a side view of a mechanical section in a conventional cut sheet feeding device.

[Explanation of symbols]

 100 Paper Feed Mechanism Unit 101 Pickup Roller 102 Forward Roller 103 Separation Roller 104, 105 Conveyor Roller 106 Cut Sheet 107 Push Up Plate 108 Push Up Spring 109 Spring 110 Photo Switch 111 Lever 112 Spindle 113-115 Reflective Photo Sensor 116 Torque Limiter 200 control unit 201 detection circuit 202 timer 203 CPU 204 memory 205 driver circuit

Claims (3)

[Claims] 1. A feeding means for feeding a cut sheet, a forward rotation roller that comes into contact with the upper surface of the fed cut sheet and conveys the cut sheet in the feeding direction, and a separation provided opposite to the forward rotation roller. It has a roller and a torque limiter that transmits drive to the separation roller.The torque limiter exceeds the threshold while rotating the separation roller in the direction opposite to the rotation of the forward rotation roller in the conveying direction until the torque limiter exceeds the threshold. In the cut sheet feeding device that rotates the separation roller by following the rotation of the forward rotation roller in the conveying direction, a friction coefficient detection unit that detects the inter-sheet friction coefficient of the cut sheets stacked in the device, Carrying detection for detecting whether or not there is another cut sheet carried in the cut sheet fed by the feeding means A step, a conveying speed detecting means for detecting a conveying speed of the cut sheet conveyed from the forward rotation roller, and a controlling means for controlling a threshold value of the torque limiter based on a detection result of the three detecting means. A cut sheet feeding device characterized in that 2. The cut sheet feeding device further comprises drive torque switching means for switching a threshold value of the torque limiter, and the control means determines that the inter-sheet friction coefficient is larger than a predetermined reference friction coefficient. In this case, the drive torque switching means is operated so as to increase the threshold value of the torque limiter by a predetermined amount, and when it is determined that the frequency of the feeding is greater than the predetermined frequency, the threshold value of the torque limiter is increased. Is increased by a predetermined amount, and when it is determined that the transport speed is smaller than a predetermined reference speed, the drive torque switching is performed so that the threshold value of the torque limiter is decreased by a predetermined amount. The cut sheet feeding apparatus according to claim 1, wherein the means is operated. 3. The feeding means comprises a feeding roller which comes into contact with the uppermost surface of the cut sheets stacked in the apparatus and exerts a feeding force on the cut sheets, and a swing lever which pivotally supports the feeding rollers. The friction coefficient detecting means includes a spring for urging the swing lever in a direction in which a reaction force received by the feeding roller from the cut sheet at the time of feeding is canceled. A first switch for detecting whether a cut sheet exists at a predetermined time on the upstream side of the forward rotation roller. A photo sensor, and the conveying speed detecting means is provided with two second conveying rollers which are provided at a downstream side of the forward rotation roller and are separated from each other by a predetermined distance in the cut sheet conveying direction. And a third reflective photosensor, and a timer for measuring the time required for the leading edge of the cut sheet conveyed from the forward rotation roller to pass through the two points where the sensors are provided, by a signal from the sensors. The control means accumulates information from the photoswitch, the first reflective photosensor, and the timer for a predetermined number of cut sheets, and controls the drive torque switching means based on the accumulated information. The cut sheet feeding device according to claim 2, wherein the cut sheet feeding device is operated.