JPH10310276A - Paper feeding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent nonconformity of lowering of carrier force due to extension of a belt, entrainment, etc., by providing an elastic member to support a driven roller on a driving roller free to advance and retreat and to constantly energize the driven roller in a direction to be separated from the driving roller. SOLUTION: A driven roller 3 is elastically energized in a direction to be separated from a driving roller 2 by supporting a shaft 8 free to rotate by a bearing member 21 and arranging a spring 20 between the bearing member 21 and a duct 6. Such a tension giving mechanism constantly applies elastic energizing force to the shaft 8 of the driven roller 3 in the tension direction so as to absorb (tension application to prevent sagging is carried out) extension of a belt 4 caused by heat, etc. Consequently, it is possible to eliminate extension and sagging by applying tension immediately in correspondence with extension and sagging caused by temperature rise of the belt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a paper feeding apparatus using a vacuum belt, and more particularly, to feeding of a transfer paper in an image forming apparatus such as an electrophotographic copying machine, a printer, a facsimile apparatus, and a printing apparatus. The present invention relates to an elongation of a conveying belt with a vacuum suction device used for conveying and a paper feeding device capable of solving various problems caused by the elongation.

[0002]

2. Description of the Related Art In an image forming apparatus as described above,
The transfer paper stacked in the paper feed unit is taken out one sheet at a time, then fed to the image forming unit and transported to form an image (transfer, fix,
Or printing). As a paper feeding device that takes out the stacked transfer paper and then feeds and conveys it,
Some paper feeders are equipped with a conveyor belt with a vacuum suction device.In this type of paper feeder, there is a sliding resistance due to the rotation of the belt and a rise in the temperature of the belt portion due to the single-sided copied transfer paper during double-sided copying. The belt is likely to elongate, and if the elongation occurs, the conveying force is reduced, the slip is increased, a delay in sheet feeding timing or a non-sending state occurs, and in some cases, a jam occurs. Also, when the belt is stretched, the possibility that the belt is caught in the gap between the roller supporting the belt and the vacuum suction device is increased. It can be lost. A conventional conveyor belt with a vacuum suction device will be described in more detail with reference to FIG. FIG. 5A is a front view, and FIG.
Is a plan view. Under the transfer paper 1 stacked in a tray (not shown), a belt 4 (3 in this example) stretched endlessly by a driving roller 2 and a driven roller 3.
Book) is arranged, and in front of the stacked transfer papers 1, air is jetted to the front of the transfer paper bundle to separate the lowermost transfer paper 1 a from other upper transfer paper bundles. An air knife device 5 for promoting separation is provided.
A duct 6 for introducing a negative pressure from a suction fan (not shown) is disposed inside the belt 4, and the lowermost transfer paper 1 a is attracted to the upper surface of the belt by a negative pressure from a suction hole 4 a formed in the belt 4. It is transported to the left of the drawing. The belt 4 is a drive roller 2 (three in this example) integrated with a drive shaft 7.
Driven by The drive shaft 7 is driven by a motor 10 via gears 11 and 12. The belt 4 is stretched between the driving roller 2 and the driven roller 3 to apply a constant tension. When the belt 4 feeds the transfer paper 1a while sucking the transfer paper 1a, the belt 4 moves while being in contact with the upper surface of the duct 6, so that heat due to friction is generated, and the belt 4 extends in the longitudinal direction due to the heat. Further, in the double-sided copy, the transfer paper stacked on the double-sided tray in the single-sided copy is in a state immediately after being heated to a high temperature in the fixing unit, and thus its temperature is high. For this reason,
The temperature of the belt 4 is further increased when the transfer paper having been copied on one side in the double-sided tray is fed for re-feeding, and the amount of extension of the belt 4 further increases. The amount of elongation of the belt 4 is generally determined as follows. l = l ₀ (1 + α △ t) (l: total length before thermal expansion, l ₀ : total length before thermal expansion, α: linear expansion coefficient, Δt: rising temperature) The tension of the belt 4 stretched on the belt 3 is reduced, and the belt 4 and the driving roller 2
, The transporting force becomes smaller, and transport failures such as slippage increase. As a result, the sheet feeding timing shifts, jams, and the like occur. In addition, when the belt 4 has a large elongation, since the belt is easily bent, a part of the belt 4 enters the gap between the drive roller 2 and the duct 6 as shown by an arrow a in FIG. Locking causes the motor 10 to lose synchronism, or in the worst case, the belt 4 is cut off, making it very difficult to replace.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and the invention of claim 1 operates by following the belt tension fluctuation caused by a temperature rise or the like, thereby reducing the belt tension. The purpose is to always keep it constant. Another object of the present invention is to measure the current temperature of the belt and correct the belt tension by an amount corresponding to the amount of elongation based on the amount of elongation of the belt determined based on the current temperature. A third object of the present invention is to prevent the belt from being entangled even when the belt tension is reduced due to the elongation of the belt. A fourth object of the present invention is to reduce the belt temperature in order to prevent the belt itself from stretching. By preventing the belt from elongating and the belt tension from decreasing as described above, it is possible to prevent a decrease in the conveying force and maintain good conveying performance.

[0004]

To achieve the above object, a first aspect of the present invention is a belt transport mechanism which is stretched endlessly between a driving roller and a driven roller and transports paper sheets on a belt upper surface. And a resilient member for constantly supporting the driven roller so as to be able to advance and retreat with respect to the driving roller, and for urging the driven roller away from the driving roller. According to a second aspect of the present invention, there is provided a paper feeder provided with a belt transport mechanism for transporting paper sheets on an upper surface of a belt, which is stretched endlessly between a drive roller and a driven roller, and detects a temperature of the belt. And a tension applying mechanism for calculating the amount of belt elongation based on data on the temperature of the belt detected by the temperature sensor to keep the belt tension constant. According to a third aspect of the present invention, there is provided a belt conveying mechanism which is stretched endlessly between a driving roller and a driven roller, and conveys paper sheets on a belt upper surface, and a vacuum suction duct disposed inside the belt. In the paper feeder, a belt is prevented from being entangled by providing a closing mechanism for closing a gap between the driving roller and the duct. According to a fourth aspect of the present invention, in the paper feeder provided with a belt transport mechanism that stretches endlessly between a driving roller and a driven roller and that transports paper sheets on the upper surface of the belt, the driven roller is configured by a heat pipe. It is characterized by having done.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a configuration diagram of an example of a main part of a sheet feeding device according to an embodiment of the present invention, that is, an example of a tension imparting mechanism of a transport belt with a vacuum suction device.
Referring also to FIG. 5, the same parts will be described with the same reference numerals. The air knife device 5, transfer paper (sheets) and the like shown in FIG. 5 are not shown in FIG. 1, but their configurations are exactly the same. The tension applying mechanism is configured such that a shaft 8 of the driven roller 3 is supported by a support mechanism (not shown) in a direction indicated by an arrow (approaching from the driving roller).
A characteristic feature is that the spring (elastic member) 20 constantly elastically urges in the direction away from the drive roller 2 while supporting the movable roller in the direction in which the drive roller 2 moves away. Specifically, the shaft 8 is rotatably supported by the bearing member 21 as shown in the drawing, while the spring 20 is disposed between the bearing member 21 and the duct 6, thereby separating the driven roller 3 from the driving roller. It is elastically biased in the direction. As described above, the tension applying mechanism of the present embodiment absorbs the elongation of the belt 4 due to heat or the like (performs the application of tension to prevent slack) in the tension direction with respect to the shaft 8 of the driven roller 3. Since the elastic urging force is constantly applied to the belt, tension can be immediately applied to the elongation and slack of the belt caused by the temperature rise of the belt, and the elongation and slack can be eliminated. As a result, it is possible to effectively prevent a conveyance failure due to a belt slip or the like and a problem such as a bite of the belt at a position A or the like. When the belt shrinks due to a decrease in temperature, the shaft 8 is moved in a direction in which the shaft 8 approaches the drive roller by following the action of the spring. The configuration of the tension applying mechanism using such elastic urging means is not limited to the illustrated one, and various modifications are possible. For example, one end of the spring may be held at a position other than the duct 6, or a tension spring may be used as the spring instead of the compression spring as shown in FIG.

FIGS. 2 (a), 2 (b) and 2 (c) are front views of a main part (temperature detecting section) showing another configuration of the tension applying mechanism of the present invention, and front views of a driven roller moving mechanism section. And a plan view. A characteristic configuration of the embodiment of FIG. 2 is that, after detecting the temperature of the belt 4 in real time, the control unit operates a tension applying mechanism including a motor, a gear, and the like based on the detection information. Exist. First, FIG. 2A shows an arrangement example of a temperature sensor 25 for detecting the temperature of the belt 4. In this example, the temperature sensor 25 is arranged in the duct 6, and the detection piece contacts the belt 4. I try to make it. As the temperature sensor, a thermistor or other various sensors can be used, and the control unit (CPU, ROM, RAM, I / O port, etc.)
6 The memory of the control unit 26 includes the temperature sensor 2
5 to correct data on the amount of elongation (elongation rate) or shrinkage of the belt corresponding to the belt temperature (increase or decrease in temperature) detected by step 5 and to correct the amount of elongation or contraction. The control information required to move the driven roller shaft 8 is stored.

The tension applying mechanism shown in FIGS. 2B and 2C includes a motor 30 for driving the tension applying mechanism, a gear 31 provided on an output shaft of the motor 30, a gear 32 meshing with the gear 31, and the like. Have. The gear 32 has its axis fixed by a shaft 34 pivotally supported by a bracket 33. The shaft 34 has a part formed as a screw part 34a, and the screw part 34a has a female screw provided on a slide member 35. The part is screwed.
Therefore, when the shaft 34 rotates forward and backward, the slide member 35 to be screwed also advances and retreats in the axial direction. Further, by fitting the projection 35a provided on the upper end of the slide member 35 into the elongated hole guide hole 33a provided in the bracket 33, the slide member 35 can be stably advanced and retracted in the axial direction of the shaft 34. I have. The slide member 35 is integrated with the shaft 8 of the driven roller, and the shaft 8 also moves integrally with the drive roller 2 by moving the slide member.
Since the driven roller 3 is configured to be rotatable relative to the shaft 8 via the bearing 40, the driven roller 3 can be stably driven and rotated regardless of the movement of the shaft 8. The tension applying mechanism (driven shaft moving mechanism) is preferably disposed at both ends of the driven shaft 8 in the axial direction. In this case, only one motor is sufficient. When the correction is performed by calculating the belt elongation amount from the detected temperature, the relationship between the temperature and the belt elongation can be calculated by the following equation. l = l ₀ (1 + αΔt) l: elongation at the time of temperature rise (total length), l ₀ : Δt = 0
Belt length at the time (initial length), α: coefficient of thermal expansion
If the temperature of the belt means a temperature change that causes the belt to expand and contract with respect to the current length of the belt, the control unit determines the length of the belt that would be expanded or contracted by this temperature change. In order to correct and maintain the belt tension constant, the motor 30 is driven to rotate the shaft 34 in the forward or reverse direction by a required amount (number of times or angle). As a result, the driven shaft 8 supported by the slide member 35 is
The belt 4 is moved in a direction away from, or approaching, to correct the tension of the belt 4 to an ideal state. That is, when the belt is likely to be stretched due to a rise in temperature, the driven shaft 8 is moved in the separating direction by a required amount corresponding to the rise in the temperature to maintain the tension of the belt. If the belt is likely to shrink due to the drop, the driven shaft 8 is moved in the approaching direction by a required amount corresponding to the temperature drop to lower the belt tension. By performing such control, it is possible to eliminate problems such as poor conveyance due to the slack of the belt, biting of the belt, and pain of the belt and the like due to excessive belt tension.

Next, FIGS. 3 (a) and 3 (b) show that the belt 4 is prevented from being caught in the gap between the drive roller 2 and the duct 6 (the position indicated by the arrow A in FIG. 1) due to the stretching. In this embodiment, a protrusion (protruding member) 6a is projected from the duct toward the gap to close the gap, and at the same time, a groove (step) 2a is formed in the center of the drive roller 2 in the axial direction. And the tip of the projection member 6a is
a. Therefore, even if the belt is stretched and sagged, there is no possibility that a part of the belt may enter the gap. The closing mechanism of this embodiment may be used in combination with a tension applying mechanism, or may be applied to a sheet feeding device having no tension applying mechanism. In addition, without providing the groove 2a in the drive roller 2, the protrusion member 6
The structure of a closing mechanism that only closes the gap by protruding a may be used. In this case, it is a matter of course that the projecting length of the projecting member is made short so that the projecting member 6a does not interfere with the driving roller 2. Also, there are places where entrainment is likely to occur,
If there is a gap other than the illustrated gap, it is effective to provide a similar projection or the like at this location.

FIG. 4 is a plan view of a belt portion of a sheet feeding device according to another embodiment of the present invention. In this embodiment, the belt 4 is cooled so as not to be stretched by heat. In this embodiment, the driven roller 3 itself or the heat pipe 50 is used as the driven shaft 8,
The fan 5 is attached to the fin 51 provided at one end of the heat pipe 50.
Cooling air is blown from 2 to cool. For this reason, since the driven roller 3 itself is cooled at all times or as needed, each belt 4 wound around the driven roller can be effectively cooled to prevent elongation. In the above-described embodiment, the transfer paper is separated and floated by the air from the air knife device, and the transfer paper is fed from the lower side. However, the air knife device is not necessarily required, and the lower paper feeder using a belt is not always necessary. The method can be generally applied. Further, the present invention can be applied to a belt conveyance device that does not perform suction by vacuum.

[0010]

As described above, according to the first aspect of the present invention,
The driven roller is supported so as to be able to be separated and approached from the drive roller, and is always urged in the separating direction by the elastic member. Therefore, it is possible to prevent a problem such as a decrease in the conveying force due to the elongation of the belt and a tangling. According to the second aspect of the present invention, the amount of elongation of the belt is determined by detecting the temperature of the belt, and the position of the driven roller is appropriately moved based on the determination result, thereby always maintaining good tension. This can reduce the conveyance force and prevent entanglement. Claim 3
According to the invention, the device is devised so as to block a portion where the belt is likely to be entangled. Therefore, even if the belt is elongated, the entanglement does not occur, and even if the conveying force is reduced, the belt is cut and the motor is locked. The occurrence of a situation can be prevented. According to the fourth aspect of the present invention, the belt can be cooled to prevent the belt from being stretched, and the temperature of each belt can be kept constant by using a heat pipe as the cooling means.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of a sheet feeding device according to an embodiment of the present invention, that is, an example of a tension applying mechanism of a transport belt with a vacuum suction device.

FIGS. 2 (a), (b) and (c) are a front view of a main part (temperature detecting section) and a front view and a plan view of a driven roller moving mechanism section showing a configuration of another tension applying mechanism of the present invention.

3 (a) and 3 (b) are a front view and a plan view showing a main part configuration of another embodiment of the present invention.

FIG. 4 is a plan view showing the configuration of another embodiment of the present invention.

FIG. 5A is a front view of a conventional sheet feeding device, and FIG. 5B is a plan view thereof.

[Explanation of symbols]

1 transfer paper (sheets), 2 drive rollers, 3 driven rollers, 4 belts, 5 air knives, 6 ducts, 7
Drive shaft, 8 driven shafts, 10 motors, 11, 12 gears,
Reference Signs List 20 spring (elastic member), 21 bearing member, 25
Temperature sensor, 26 control unit, 30 motor, 31 gear, 32 gear, 33 bracket, 34 shaft, 34a
Screw part, 35 slide member, 35a projection,

Claims (4)

[Claims] 1. A paper feeding device having a belt transport mechanism for transporting paper sheets on an upper surface of a belt, wherein the driven roller is capable of moving forward and backward with respect to the drive roller. And a resilient member that constantly urges the driven roller in a direction to separate the driven roller from the driving roller. 2. A sheet feeder, which is provided between a drive roller and a driven roller endlessly and has a belt transport mechanism for transporting paper sheets on an upper surface of the belt, a temperature sensor for detecting a temperature of the belt, A sheet feeding device comprising a tension applying mechanism that calculates a belt elongation amount based on data on a belt temperature detected by the temperature sensor and keeps a belt tension constant. 3. A feeder, which is provided between a driving roller and a driven roller endlessly and has a belt transport mechanism for transporting paper sheets on the upper surface of the belt, and a vacuum suction duct disposed inside the belt. A paper feeding device, wherein a belt is prevented from being entangled by providing a closing mechanism for closing a gap between the drive roller and the duct. 4. A paper feeder provided with a belt transport mechanism for transporting paper sheets on an upper surface of a belt, which is stretched endlessly between a drive roller and a driven roller, wherein the driven roller is constituted by a heat pipe. A sheet feeding device characterized by the above-mentioned.