JPH08198477A - Electrophotographic device - Google Patents

Abstract

PURPOSE: To provide an electrophotographic device, which can prevent the feeding of a paper sheet curled more than the regulation in a paper carrying passage so as to previously prevent the generation of paper jam in the paper carrying passage and which is coupled with a paper sheet curl correcting mechanism so as to perform the stabilized carrying of the paper sheet. CONSTITUTION: A paper sheet 11 is carried in a paper carrying passage by a carrying roller 12 and a pressure roller 13 in the condition that it is curled upward or downward. At this stage, an optical distance sensor 14 provided in the paper carrying passage detects direction and quantity of curl of the paper sheet 11. In the case where the tip of the paper sheet 11 is curled upward, when the tip of the paper sheet 11 passes under the sensor 14, the paper sheet 11 comes closest to the sensor 14 surface, and separated from the sensor 14 surface, as it is carried away. In the case where the tip of the paper sheet 11 is curled downward, the paper sheet 11 is passed in the opposite condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus, and more particularly to a sheet conveying mechanism for an electrophotographic apparatus.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic apparatus using a cut sheet, a sheet position detecting sensor is arranged in the middle of a sheet conveying path, and the arrival time, passing time, etc. of the sheet are measured by this sensor, and a predetermined time period is measured. When the paper is not conveyed inside or when the paper does not pass within a predetermined time, the paper is stopped on the spot, or the paper is sent to a position where the operator can easily take it and stopped.

[0003]

By the way, one of the factors that change the arrival time and the passage time of the paper is the warp (curl) of the paper itself. On the other hand, the conventional electrophotographic apparatus that uses a cut sheet does not have a device that detects the curl of the paper, so if there is more than a predetermined amount of curl, the edge of the paper interferes with the paper transport path, causing the paper to The phenomenon of being able to use occurs.

An object of the present invention is to detect the curl direction and the size of the curl of the paper, which changes depending on the type of paper, the continuous amount, and the printing mode, and the paper curled more than a specified amount is sent into the paper transport path. It is an object of the present invention to provide an electrophotographic apparatus capable of preventing a sheet from being caught in the sheet conveying path and preventing the sheet from being jammed, or performing stable sheet conveyance by interlocking with a sheet curl correcting mechanism.

[0005]

The above object is to provide an electrophotographic apparatus having a sheet position detecting sensor in the middle of a sheet conveying path for conveying a cut sheet, and a mechanism for detecting the arrival time, the passage time, etc. of the sheet. At least one of the paper transport paths
This is achieved by providing a paper curl detection mechanism at the above-mentioned parts.

[0006]

According to the present invention, by arranging the paper curl detection mechanism at the entrance portion of the paper transport path immediately after the paper feed section, it is possible to prevent the paper curled beyond the specified level from being fed into the paper transport path. As a result, it is possible to prevent the paper from being caught in the paper transport path. Further, by interlocking the paper curl detection mechanism and the paper curl correction mechanism, stable paper conveyance can be performed.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of a sheet conveying system of an electrophotographic apparatus using a cut sheet. Paper 1 is paper feed unit 2
The sheets 1 picked up one by one are conveyed to the stacker section 8 through the resist section 3, the transfer section 4, the fixing section 5, the reverse path section 6, and the switchback section 7. During single-sided printing, the sheet is conveyed along the path indicated by arrow A, and when double-sided printing is conveyed along the path indicated by arrow B. Further, a paper position detection sensor 9 is arranged in the middle of the paper conveyance path to measure the arrival time and passage time of the paper. In the figure, the curl detection device 10 is arranged at the entrance portion of the paper conveyance path immediately after the paper feed section.

FIG. 2 is a diagram showing a specific example of the paper curl detecting mechanism. 3 is a diagram showing the relationship between the output value of the optical distance sensor 14 and the time axis based on the curl direction (upward) of the leading edge of the paper 11 in the paper curl detection mechanism shown in FIG. 2, and FIG. 4 is the same as FIG. FIG. 5 is a diagram showing a relationship between an output value of the optical distance sensor 14 based on the curl direction (downward) of the leading end of the paper 11 and a time axis.

The sheet 11 is conveyed in the sheet conveying path by the conveying roller 12 and the pressure roller 13 while curling upward or downward. At this time, the curl direction and curl amount of the paper 11 are detected by the optical distance sensor 14 provided in the paper transport path. Let V _{0 be} the sensor output when the front end of the sheet 11 has passed the sensor 14, and V _{1 be} the sensor output when the sheet 11 is conveyed for a certain distance. When the leading edge of the sheet 11 is directed upward, the leading edge of the sheet 11 is closest to the sensor 14 surface when it passes under the sensor 14, and as the sheet 11 is conveyed, the distance from the sensor 14 surface is increased. Since they are separated, the relationship between the output of the sensor 14 and the passage time of the paper 11 is as shown in FIG.

When the leading edge of the sheet 11 is downward, the leading edge of the sheet 11 passes the lower part of the sensor 14 and is most distant from the surface of the sensor 14, and as the sheet 11 is conveyed. Since the distance from the surface of the sensor 14 becomes shorter, the relationship between the output of the sensor 14 and the passage time of the paper 11 is as shown in FIG.

Therefore, the relationship between the output of the sensor 14 and the curl direction of the paper 11 is V ₀ -V ₁ > 0 → upward curl, V
_0- V ₁ <0 → downward curl relationship holds. Further, the relationship of | dV / dt | = large → curl amount is large and | dV / dt | = small → curl amount is small from the change rate of the output of the sensor 14.

As described above, it is possible to prevent the paper curled to a value greater than the specified value from being fed into the paper transport path to prevent the paper from being caught in the paper transport path, or to interlock with the paper curl correction mechanism. By doing so, stable sheet conveyance can be performed. In the illustrated embodiment, the case where the optical distance sensor is used as the paper curl detection mechanism has been described as an example, but instead of this, another type of sensor capable of performing the same function may be used. .

[0013]

As described above, according to the present invention, the curl direction and the curl size of the paper, which change depending on the type of the paper, the continuous amount, and the printing mode, are detected, and the paper curled more than the specified value is detected in the paper transport path. It is possible to perform stable sheet conveyance by preventing the sheet from being caught in the sheet conveying path by being prevented from being sent to the sheet, or by interlocking with the sheet curl correcting mechanism.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a sheet transport system of an electrophotographic apparatus that uses a cut sheet.

FIG. 2 is a diagram showing a specific example of a paper curl detection mechanism.

FIG. 3 is a diagram showing a relationship between an output value of an optical distance sensor 14 and a time axis based on a curl direction (upward) of the leading end of the paper 11 in the paper curl detection mechanism shown in FIG.

FIG. 4 is a diagram showing the relationship between the output value of the optical distance sensor 14 based on the curl direction (downward) of the leading end of the sheet 11 and the time axis, similar to FIG.

[Explanation of symbols]

11 ... Paper, 12 ... Conveying roller, 13 ... Pressure roller, 14 ... Optical distance sensor.

Claims (2)

[Claims] 1. An electrophotographic apparatus comprising a paper position detection sensor in the middle of a paper transport path for transporting cut sheets, and a mechanism for detecting the arrival time, transit time, etc. of the paper, in at least one or more locations of the paper transport path. An electrophotographic apparatus, which is provided with a paper curl detection mechanism at the part. 2. A paper curl detection mechanism for detecting the curl direction and the size of the curl of the paper from the output value of the optical distance sensor, the time axis, and the rate of change of the sensor output value.
The described electrophotographic apparatus.