JP2507999Y2 - Transfer paper thickness detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an image forming apparatus using an electrophotographic process, and particularly to a transfer that is likely to occur due to a difference in the thickness of transfer paper used in an image forming process. The present invention relates to a transfer paper thickness detection mechanism that can eliminate inconveniences such as image deterioration.

(Prior Art) In an image forming apparatus using an electrophotographic image forming process such as a copying machine, a printer and a facsimile machine, a reflected light on a document and other optical image information are uniformly charged on a photoconductor. A predetermined electrostatic latent image is formed by irradiating the toner onto the electrostatic latent image to form a developed image with toner adhered on the electrostatic latent image, and the developed image is transferred onto a transfer paper and then fixed to perform a series of image forming steps. It is being carried out.

By the way, the image forming apparatus as described above is often required to have adaptability not only to transfer paper having a certain thickness but also to various types of transfer paper ranging from thin paper to thick paper. For example, conditions such as the toner density on the photoconductor drum and the transfer conditions in the image forming process and the conditions in the carrying process vary depending on the thickness of the transfer paper. For example, if the voltage applied to the transfer charger is set in accordance with thin paper, insufficient transfer is likely to occur and a faint image is likely to occur when discharging thick paper. On the contrary, when the transfer is performed on the thin paper under the transfer condition suitable for the thick paper, the transfer becomes excessive this time, and the toner is easily scattered.

As described above, in the image forming apparatus, there are many units in which the required characteristics are not uniform depending on the difference in the paper thickness of the transfer paper, and until now, the user has to change the condition such as the paper thickness by operating the changeover switch. Was responding by changing the settings. However, it is difficult for the user to judge the thickness of the transfer paper each time, and to set the appropriate conditions corresponding to the paper thickness, and it is difficult to obtain an appropriate image regardless of the change of the paper thickness. Met.

Further, technically, it is difficult to accurately and quickly detect the thickness of the fed transfer paper and to reflect the detection result in the image forming conditions and the like, and a solution to this point has been desired. .

(Purpose of the Invention) The present invention has been made in view of the above, and accurately detects the paper thickness of the transfer paper to be fed in advance, and according to the detection result, various image forming conditions during the image forming process. It is an object of the present invention to provide a transfer paper thickness detection device that can properly obtain a proper image regardless of the change of the paper thickness.

(Structure of the Invention) In order to achieve the above object, the present invention is provided with a guide member for forcibly changing the direction of the transfer paper conveyance path and a paper thickness detecting means connected to the guide member, and the transfer paper is guided. The paper thickness detecting means electrically detects a reaction force generated when the paper passes through the member.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration explanatory view of an embodiment of the paper thickness detecting device of the present invention, and FIGS. 2 (a) and 2 (b) are operation principle explanatory views of the embodiment of FIG.

This detection device includes a pair of guide plates 1a and 1b forming a part of a transfer paper conveyance path, a stay 3 integrated so as to hang down from an intermediate position of the inner guide plate 1a, and a stay 3
The L-shaped frame 5 has a lower end portion 3a supported so as to be tiltable in the left-right direction indicated by an arrow, and a piezoelectric element (paper thickness detection element) 7 fixed to a support wall 5a of the frame 5.

The piezoelectric element 7 may be adhered to the stay 3, or may be configured to be always in contact with the stay 3 by means other than adhesion.

Each of the guide plates 1a and 1b is curved with a predetermined curvature, and is arranged, for example, in the middle of the conveyance path from the paper feed cassette or the like to the registration rollers. The outer guide plate 1b is fixed to the illustrated position, and the inner guide plate 1a is integrated with the upper end portion of the stay 3 so as to rotate together with the stay 3 in the arrow direction. Reference numeral 10 is a stopper that prevents the stay from tilting to the right.

When the transfer paper passes through the conveyance path formed by the guide plates 1a and 1b, the transfer paper is forcibly curved along with the guide plates, so that a reaction force for returning to the original shape is applied to each guide plate. When the paper quality is the same, the strength of this reaction force differs depending on the stiffness of the transfer paper, in other words, the thickness of the paper, so the force with which the stay 3 presses the piezoelectric element 7 via the movable guide plate 1a also differs. Come on.

As shown in FIG. 2 (a), the reaction force F1 is small when the thin paper P1 is passed, and the force f1 that presses the piezoelectric element 7 is also small, but when the thick paper P2 is passed, the reaction force F1 is small. As shown in, the reaction force F2 and the pressing force f2 increase substantially in proportion to the paper thickness.

The mechanical pressing force on the piezoelectric element 7 causes an electric charge proportional to the pressing force inside the piezoelectric element, and the value of this electric charge is detected as an electric signal to determine the thickness of the transfer paper passed between the guide plates. I can know.

When the electric charge value generated inside the piezoelectric element is A / D converted and input to the control unit (not shown), the CPU in the control unit reads the control information corresponding to this value from the ROM, and the read control information The image forming process conditions and the like are changed based on the above, and an operation command signal is output to each control target. Therefore, for example, the operating conditions of the developing device, the transfer charger, etc. can be changed to the optimum conditions according to the paper thickness of the transfer paper to be transferred, and an appropriate image can be obtained.

In the above embodiment, the piezoelectric element is illustrated as the paper thickness detecting element 7, but this is only an example. For example, the lower end of the stay 3 is fixed and a strain gauge is attached to a predetermined portion of the stay 3 to connect it. A strain gauge may detect a change in the electric resistance of the stay 3 caused by the strain generated in the stay 3 via the inner guide plate 1a when the sheet is printed. Similar to the above, the paper thickness is obtained based on the detected value and each component is controlled according to the paper thickness.

The bending angle of each guide plate, the stay attaching position and the stay inclination angle, the piezoelectric element attaching position, etc. are not limited to those shown in the drawings, and the configuration change within the range in which the above detection effect is exhibited is within the scope of the present invention. Are included in.

Although the reaction force applied to the stay via the inner guide plate is detected in the above embodiment, the stay may be provided on the outer guide plate to detect the reaction force.

Alternatively, only a part of the inner guide plate may be made movable, and the stay may be provided at this movable portion.

A piezoelectric element, strain gauge, or the like may be directly provided on one of the guide plates.

Next, FIG. 3 shows a second embodiment of the present invention in which a recording paper P stacked in a paper feed cassette or the like is picked up by a pickup roller 15,
This is a configuration example in which the paper thickness is detected immediately after being fed by the feed roller pair 16 and the like. In this embodiment, a flat movable guide plate 17 inclined upward at a predetermined angle is arranged in front of the feed roller pair 16, and a lower end 18a of a stay 18 integrally suspended from an intermediate portion of the movable guide plate 17 is provided. The frame 5 is supported so as to be tiltable in the direction of the arrow, and a paper thickness detection element 7 such as a piezoelectric element is arranged on the support wall 5a of the frame 5.

The distance between the feed roller pair 16 and the movable guide plate 17 is set shorter than that of the transfer sheet having the shortest length in the transport direction. As a result, the leading edge of the transfer paper, which is horizontally fed while being nipped by the feed roller pair 16, comes into contact with the guide plate 17 and is further forcedly turned upward and fed. At the time of bending due to this direction change, the reaction force generated by the waist of the transfer paper is transferred to the piezoelectric element 7 via the stay.
Is added to

Of course, a strain gauge may be used instead of the piezoelectric element 7. In this case, needless to say, it is necessary to make necessary changes according to the characteristics of the strain gauge as described above.

(Effect of the Invention) As described above, according to the present invention, the reaction force applied to the guide plate when the transfer paper passes through the guide plate is detected by the paper thickness detecting element, and control is performed based on the detection result. Since the control part changes the control condition for each part constituting the image forming process according to the paper pressure, it is possible to always obtain an appropriate image forming condition regardless of the change of the paper thickness.

The present invention is not limited to the image forming process, and other electrical and mechanical conditions may be set and changed by the control unit.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory view of an embodiment of the thickness detecting device of the present invention, FIGS. 2 (a) and 2 (b) are explanatory views of the operation principle of the embodiment of FIG. 1, and FIG. 3 is the present invention. It is a configuration explanatory view of the second embodiment of. 1a, 1b …… Guide plate, 3 …… Stay 7 …… Piezoelectric element (paper thickness detection element)

Claims (1)

(57) [Scope of utility model registration request] 1. A guide member for forcibly changing the direction of a transfer paper conveyance path and a paper thickness detecting means connected to the guide member are provided, and a reaction force generated when the transfer paper passes through the guide member is provided. An apparatus for detecting the thickness of a transfer sheet, which is electrically detected by a thickness detecting means.