JPH03172255A - Size detecting method of paper used in picture forming device - Google Patents

Abstract

PURPOSE:To form a device in a small size with a single detecting sensor in use by measuring a time, after a resist roller is started before the final end of recording paper passes, by the detecting sensor and utilizing the measured time and a conveying speed of the resist roller to detect a size of paper. CONSTITUTION:A single paper detecting sensor 10 is provided on a recording paper conveying path in the upstream side of a resist roller 3. Next, after the resist roller 3 is started, a time before the final end of recording paper passes is measured by this detecting sensor 10. By utilizing this measured time and a conveying speed of the resist roller 3, a size of paper is detected. That is, by assuming (t) for measured time, (m) for conveying speed of the resist roller 3 and D0 for a distance from the resist roller 3 to the paper detecting sensor 10, the paper size can be grasped by a value (mt+D0).

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a paper size detection method used in facsimile machines, printers, and copying machines that form images using electrophotographic technology, and particularly relates to a paper size detection method used in facsimile machines, printers, and copying machines that form images using electrophotographic technology, and particularly relates to a method for detecting paper size used in facsimile machines, printers, and copying machines that form images using electrophotographic technology. The present invention relates to a paper size detection method used in an image forming apparatus that forms a predetermined image while passing a recording paper through the road.

[Prior Art] Conventionally, for example, as shown in FIG. 4, a guide plate 1, a paper feed roller 2, . A registration roller 3, a transfer device 5 facing the photosensitive drum 4, and a fixing device 6. Paper output tray 7
While transporting the recording paper along the conveyance path from the guide plate l, the recording paper is temporarily stopped by the registration rollers 3, and the transfer position is set in synchronization with the starting edge of the latent image formed on the photoreceptor drum 4. Image forming apparatuses such as facsimile machines, printers, and copying machines are well known in which an unfixed toner image carried on a photoreceptor drum 4 is transferred, and then the image is fixed by a fixing device 6. In these types of devices, the amount of latent image formed in the circumferential direction of the photoreceptor drum 4<m latent image writing length in the scanning direction), the rotation time of the registration roller 3, etc. depend on the paper size of the recording paper. For non-standard paper whose paper size is not determined in advance by a magnetic signal from a paper feed cassette, etc., the paper size is detected by a paper size detection sensor IOA disposed upstream of the registration rollers 3.

As such paper size detection means, the detection sensor 10^ is generally arranged on the recording paper transport path immediately after the exit of the paper feed roller 2 located upstream of the registration roller 3, and the paper size detection sensor 10^ is arranged on the recording paper conveyance path immediately after the exit of the paper feed roller 2 located upstream of the registration roller 3. The time it takes for the recording paper being conveyed to pass the detection sensor IOA, in other words, the passing time from the starting edge to the ending edge of the recording paper, is detected, and the product of the passing time and the roller speed (1.S) is calculated. As a result, he knew the paper size of the recording paper.

However, since the activation timing of the registration roller 3 is uncertain, in this detection means, the registration roller 3 is not activated until the end of the recording paper passes the sensor IOA.
For this reason, for example, in an apparatus that enables image formation on long paper such as legal size paper, the distance between the sensor and the registration roller 3 is set to be longer than that of the legal size paper. This results in an increase in the size of the device.

In order to solve this problem, we focused on the fact that it is not necessary to use the same sensor to detect the leading edge and trailing edge of recording paper as long as it is transported at a constant speed by the paper feed roller 2. A detecting sensor 10B is arranged on the inlet side of the paper feed roller 2, and the detection is performed based on the time from when the starting edge of the recording paper passes through the outlet side sensor IOA until the end of the recording paper passes through the inlet side sensor and the distance MD3 between both detection sensors. (T2/S+03) A technique has been proposed in which the paper size of the recording paper is determined.

(Utility Model Application No. 64-9251) ``Technical Problems to be Solved by the Invention'' However, even in this prior art, as shown in FIG. The distance must be set longer, and even though two detection sensors are provided, the distance that can be reduced is only the inter-sensor distance D3, and the increase in size of the device cannot be solved.

Furthermore, two detection sensors are installed on the upstream conveyance path of the registration roller 3.
Providing one leads to an increase in the total failure rate and jams,
Undesirable.

The present invention makes it possible to accurately detect the paper size of recording paper even when the distance between the paper detection sensor and the registration roller is smaller than that of legal size paper or other long paper.
An object of the present invention is to provide a paper size detection method in an image forming apparatus.

Another object of the present invention is to provide a paper size detection method that can effectively downsize the apparatus and detect the paper size of the recording paper even when a single detection sensor is used. It is in.

[Technical means for solving the problem] All of the above-mentioned conventional technologies are based on the idea that the paper size is detected until the starting edge of the recording paper reaches the registration roller 3 (until the registration roller 3 starts). For this reason, there is a constraint that the distance between the paper detection sensor that detects the end of the recording paper and the registration roller 3 must be set larger than the length of the long paper.

However, the latent image writing length in the sub-scanning direction and the rotation time of the registration rollers 3, which are set depending on the paper size, do not necessarily need to be set before the registration rollers 3 are started (, Even after the start-up, the setting can be made until the latent image writing or the rotation of the registration roller 3 is completed.

In addition, since the prior art described above detects the paper size using the conveyance speed of the paper feed roller 2, while the paper feed roller 2 is rotating, in other words, the starting edge of the recording paper is not on the registration roller 3. There was a constraint that the paper size had to be detected before the paper size was reached.

However, since the registration rollers 3 are also rotating at a constant speed, the above-mentioned restrictions can be eliminated if the conveyance speed of the registration rollers 3 is utilized.

The present invention focuses on these two points, and its features include the provision of at least one paper detection sensor 10 provided on the recording paper conveyance path upstream of the registration roller 3;
After starting the registration roller 3, the detection sensor 10 measures the time until the end of the recording paper passes, and the paper size is detected using the measured time and the conveyance speed of the registration roller 3.

That is, the paper size is determined by (m t +D
o) can be understood.

By setting the distance Do to be larger than the distance 1IiL from the latent image writing position on the photosensitive drum 4 to the transfer position, the paper size can be detected at least before the end of latent image writing, which improves image formation. No problems arise as before.

[Function] According to this technical means, since the paper detection sensor 10 on the upstream side of the registration roller 3 only needs to detect the end of the recording paper, one sensor is sufficient, but if it is on the upstream side of the registration roller 3, the paper detection sensor 10 can be removed. Since the attachment is not particularly limited to the position, it can be used in common with sensors for adjusting the timing of paper feed, etc., leading to a significant reduction in the number of parts.

Also, the distance D from the registration roller 3 to the paper detection sensor IO
It is sufficient that o is greater than the distance from the latent image writing position to the transfer position on the photoreceptor drum 4. Therefore, the smaller the diameter of the photoreceptor drum 4, the smaller the distance Do can be set, and as a result, The conveyance distance on the upstream side of the registration roller 3 can be significantly reduced.

This leads to equipment downsizing.

Furthermore, in the case of a laser printer or the like, since the starting timing of the registration roller 3 is set with high accuracy based on the horizontal synchronization signal VSYNC, it also has the advantage that the paper size detection accuracy is greatly improved as a result.

"Embodiments" Hereinafter, embodiments of the present invention will be described in detail by way of example based on the drawings. However, unless otherwise specified, the dimensions, materials, shapes, and relative positions of the components described in this example are not intended to limit the scope of this invention, but are merely illustrative examples. Not too much.

FIG. 1 is a schematic diagram of a laser printer according to an embodiment of the present invention, and to explain the difference from the conventional technology described above, a cleaner is installed around the photoreceptor drum 4 along the rotational direction from the downstream side of the transfer position. 11, an eraser 12, a charger 13, a latent image writing optical system unit 14, and a developer 15 are arranged, and the photosensitive drum 4 is rotated to perform a predetermined electrophotographic process while moving the image information to the transfer position. The unfixed toner image is transported, and the toner image is transferred to the recording paper inserted into the transfer position at a certain timing by the registration rollers 3. Since this point is well known, detailed explanation thereof will be omitted.

Now, on the recording paper conveyance path upstream of the registration roller 3, a paper detection sensor 1O, which is the gist of the present invention, is arranged.

After the registration roller 3 is started, the paper feed roller 2 becomes free due to the clutch, so the sensor lO is placed on either the inlet side or the outlet side of the paper feed roller 2 if the condition Do>L is satisfied. Although it may be disposed, it is preferable to dispose it on the exit side of the paper feed roller 2 when it also functions as the paper feed sensor IO.

FIG. 2 is a block diagram showing the main part configuration of the control circuit of this embodiment, in which the CP
The arithmetic circuit 16a in the U 16 calculates (mt+Do) to detect the paper size in the case of non-standard paper such as long paper.

FIG. 3 briefly explains the timing chart of the embodiment. Note that a, b, and c, which will be described later, are b=L/α, a=(Do-L)/α, where α is the peripheral speed of the photoreceptor drum 4.

It is determined by cwDo/l+β (β: monetary time taking into account error), both of which are constants.

First, after the drive motor rotates, the paper feed roller 2 rotates and guides the recording paper to the end of the registration roller 3, and then stops rotating.

After the paper feed sensor lO detects the starting edge of the recording paper, a predetermined image forming operation is started.

First, after a period of time b has elapsed after the start of latent image writing in the optical system unit 14, a horizontal opening signal is issued, and the registration roller 3 starts to be activated in synchronization with this signal. Then, the time until the sensor lO detects the end of the recording paper after the start of the startup is counted, and the paper size is detected based on the above formula. The end of latent image writing of the optical system unit 14 and the end of rotation of the registration roller 3 are determined by χ10.

Therefore, according to this embodiment, not only paper size detection but also
Various timing controls in the electrophotographic process can be performed efficiently and accurately by using the end detection timing χ of the recording paper.
This is extremely advantageous in practical terms.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a laser printer according to an embodiment of the present invention, FIG. 2 is a block diagram showing the main configuration of a control circuit of this embodiment, FIG. 3 is a timing chart diagram of the embodiment, and FIG. The figure is a schematic diagram of an image forming apparatus according to the prior art.

Claims (1)

[Scope of Claims] 1) In an image forming apparatus that forms a predetermined image while passing a recording paper through a recording paper transport path on which registration rollers are arranged, at least one image forming apparatus is provided on the recording paper transport path upstream of the registration rollers. A paper detection sensor is prepared, and the detection sensor measures the time until the end of the recording paper passes after starting the registration roller, and the paper size is detected using the measured time and the conveyance speed of the registration roller. 2) A paper size detection method used in an image forming apparatus characterized by The paper size detection method according to claim 1), characterized in that the paper size is set as (mt+Do). 3) The distance from the registration roller to the paper detection sensor is set as Do.
The paper size detection method according to claim 1), characterized in that is set to be larger than the distance L from the latent image writing position of the photosensitive drum to the transfer position.