JP2003246493A - Sheet thickness detector, sheet conveying device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet thickness detector capable of improving accuracy in measuring sheet thickness at a low cost by suppressing a lowering of accuracy in measuring the sheet thickness caused by dust or the like scattered in a conveying path. <P>SOLUTION: On end part of a lever member 51 projected into the conveying path comes in contact with the sheet P conveyed in the conveying path, and the quantity of displacement of the other end part of the lever member 51 is detected by a detecting means to measure the thickness of the sheet. The detecting means is kept away from the conveying path where dust or the like is scattered, to restrain the dust or the like from sticking to the detecting means. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet thickness detecting device for detecting the thickness of a sheet, and a sheet conveying device and an image forming apparatus having the same.

[0002]

2. Description of the Related Art In image forming apparatuses such as printers and copying machines in recent years, there is a high demand for a color / monochrome bi-functional machine capable of obtaining a color image as compared with a single monochromatic machine. However, in a color image forming apparatus, toner of three colors of three primary colors of cyan, magenta, and yellow (that is, toner more than twice that of monochrome) is deposited on the sheet, and therefore the type of sheet (that is, , The surface properties of the sheet) and the thickness thereof cause a difference in how pressure is applied to the toner formed on the sheet and how heat is transferred, which affects the fixability of the color image. Therefore, if fixing is performed on a thick sheet with fixing conditions set on a thin sheet, the toner image may not be fixed on the sheet, while if fixing is performed on a thin sheet with fixing conditions set on a thick sheet. This may cause adverse effects such as offset to the roller and increase in toner gloss. As described above, it is very difficult to apply the same fixing condition to sheets of various types and thicknesses.

Therefore, in order to secure a stable fixing property for each of various sheets as described above, the fixing speed is changed based on the type and thickness of the sheet, so that the pressure and heat to the toner on the sheet are changed. I try to communicate in the same way. The fixing speed can be changed by operating the mode from the operation panel and selecting the sheet type (for example, OH
By specifying the T paper mode, etc.), providing an OHT detection means to automatically discriminate between OHT and plain paper, and providing a sheet thickness detection device to automatically discriminate the thickness.
The type and thickness of the sheet are determined, and the determination is performed based on the information of the determined sheet.

[0004]

As shown in FIG. 5, since the sheet thickness detecting device 50 is intended to measure the sheet thickness, the sheet is conveyed, for example, a sheet guide guide 55 or a registration roller. It was commonly placed on the side of pair 24. The sheet thickness detecting device 50 includes a movable core 52 that is vertically movable as shown in FIG.
The magnetic sensor 53 has a magnetic quantity sensor 53 for detecting a change in magnetic flux density due to the movement of the movable core 52. In a device equipped with such a sheet thickness detecting device, as the number of passing sheets increases, toner, sheet powder, etc. scattered in the conveyance path between the magnetic sensor 53 and the movable core 52 (hereinafter, Movable core 52
The distance between the magnetic field sensor 53 and the surface of the magnetic field sensor 53 was changed, and the output value of the magnetic field sensor 53 was changed. From the reading error detection due to the change of this output value, for example, even if the sheets with the same thickness are judged to be different sheet thickness, the fixing operation is performed based on the output value including this error, so that it is originally appropriate for that sheet thickness. It may be fixed at a non-fixing speed, and it is difficult to secure stable fixing properties for sheets of various types and thicknesses.

Furthermore, since the sheet thickness of the sheet detected by the sheet thickness detection device is about 100 μm to 300 μm, the output value (or the difference from the initial output value) from the sheet thickness detection device is a very small value. Although it is effective to increase the detection capability of electric parts in order to improve the accuracy of the output value of the magnetic sensor, the cost is increased.

The present invention has been made in view of the above problems, and suppresses a decrease in the measurement accuracy of the sheet thickness due to dust or the like scattered in the conveyance path, and at the same time, the measurement accuracy of the sheet thickness can be reduced at low cost. An object of the present invention is to realize a sheet thickness detecting device, a sheet conveying device, and an image forming apparatus that can be improved.

[0007]

In order to achieve the above object, according to the present invention, one end portion projects into a sheet conveyance path and is conveyed between the one end portion and a reference surface in the conveyance path. It is configured to have a lever member that sandwiches the sheet and whose amount of rotation changes according to the sheet thickness, and detection means for detecting the amount of displacement of the other end of the lever member.

With this structure, one end of the lever member protruding into the conveying path contacts the sheet conveyed in the conveying path, and the displacement amount of the other end of the lever member is detected by the detecting means. By doing so, since the sheet thickness is measured, the detecting means can be moved away from the conveyance path in which dust and the like are scattered, and the adhesion of dust and the like to the detecting means can be suppressed.

Further, the position of the rotating shaft of the lever member can be adjusted within an intermediate region in the longitudinal direction of the lever member, so that the displacement amount of the other end portion with respect to the displacement amount of the one end portion of the lever member. The ratio of can be changed arbitrarily. That is, it becomes possible to adjust the sensitivity (measurement accuracy) of the sheet thickness measurement by the detection means as necessary.

At this time, by making the distance from the other end of the lever member to the rotating shaft longer than the distance from one end to the rotating shaft, the sensitivity of the sheet thickness measurement by the detecting means can be made with a simple structure. It becomes possible to improve.

A roller contacting the sheet may be arranged at one end of the lever member, and by doing so, sheet powder is generated by rubbing between the conveyed sheet and one end of the lever member. Can be suppressed.
At the same time, it is possible to suppress wear of one end of the lever member.

Of course, the sheet thickness detecting device as described above, the image forming unit for forming an image on the sheet, and the upstream side of the image forming unit in the conveying direction are arranged. The sheet thickness detection device has a registration unit that corrects the skew of the sheet and a fixing unit that performs the fixing operation of the image formed on the sheet by the image forming unit. An image forming apparatus that controls the fixing operation according to the detection result of the sheet thickness detecting apparatus may be configured. With such a configuration, the image forming apparatus after the image formation on the sheet is performed according to the sheet thickness. It is possible to adjust the fixing operation (for example, the fixing speed and the sheet conveying speed) to be optimum, which can contribute to the improvement of the fixing property during image formation.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 shows the overall configuration of an image forming apparatus 1 equipped with a sheet thickness detecting device 50 according to a first embodiment of the present invention, and FIGS. It is a figure for explaining sheet thickness detection device 50 in a forming device.

The image forming apparatus 1 in this embodiment is a laser printer capable of forming a color image. In the image forming apparatus 1 shown in FIG. 1, a plurality of recording sheets P are stacked and stored in a cassette 20 that is detachably attached to the apparatus, and the stacked recording sheets P are stored.
Are fed by the feeding roller 21. The recording sheets P thus fed are separated one by one by the retard roller pair 22, and are conveyed to the registration roller pair 24 by the conveying roller 23. When the recording sheet P is conveyed, the registration roller pair 24 has stopped rotating, and the skew of the recording sheet P is corrected by abutting the leading end of the recording sheet P against the nip portion of the registration roller pair 24. After that, the recording sheet P, in which the skew is corrected, is conveyed to the image forming portion G for transferring the image onto the recording sheet P.

In the case of the four-drum full color system, the image forming section G includes process cartridges 26Y, 26M, 26C and 26Bk which are parallel to each other and which include image carriers corresponding to four colors of cyan, magenta, yellow and black as shown in the drawing. It is arranged, for each process cartridge,
Scanning optical systems 28Y, 28M, 28C, 28Bk
Are arranged.

In the image forming section G, after the toner image is formed on the image carrier for each color based on the image signal,
Each toner is transferred onto the intermediate transfer belt 30. After that, the recording sheet P is sent to the secondary transfer roller 27 at a predetermined timing, the toner image on the intermediate transfer belt 30 is transferred onto the recording sheet P, and is fixed by the fixing device 25, and then the discharge roller pair 29a. , 29b are discharged and loaded.

Next, a sheet thickness detecting device 5 for detecting the thickness of the recording sheet P conveyed in the image forming apparatus 1.
0 will be described. First, the function of the magnetic quantity sensor 53, which will be described later, will be described with reference to FIG. First, as can be seen from FIG. 2A, magnetic flux is oscillated from the lower coil 53b to which the oscillation circuit H is connected,
The magnetic flux density of the magnetic flux passing through the inside of the upper coil 53a is detected by the detection circuit K connected to the upper coil 53a. The movable core 52 is arranged so as to be movable in the axial direction of the upper coil 53a and the lower coil 53b.

When the movable core 52 moves as shown in FIG. 2B, the magnetic flux spreads in a direction substantially orthogonal to the axial direction of the upper coil 53a and the lower coil 53b, and the magnetic flux density in the upper coil 53a is increased. Decrease. The change of the output value by the detection circuit K accompanying this, that is, the upper coil 53
The change in the magnetic flux density in a is detected as the sheet thickness.

As shown in FIG. 3B, in the sheet thickness detecting device 50, one end of the sheet thickness detecting device 50 projects upstream of the registration roller pair 24 in the sheet conveying path in the conveying direction, and the one end and the conveying path are provided. A lever member 51 arranged so as to sandwich the conveyed sheet P between it and an upper guide 56 as a reference surface, and the amount of rotation changes according to the sheet thickness, and the other end portion of this lever member. And a detection means for detecting the displacement amount of the.

The detecting means here has a ferrite having a high magnetic permeability and is a movable core 52 as a movable body which is connected so as to interlock with the other end of the lever member 51, and the displacement of the movable core 52. Magnetic quantity sensor 53 for detecting quantity
It consists of and.

When the conveyed sheet P is sandwiched between one end of the lever member 51 and the guide upper guide 56, the movable core 52, which is linked to the other end of the lever member 51, interlocks with the lever. It moves with the rotation of the member 51,
A change in the magnetic flux density due to the movement of the movable core 52 is detected by the magnetic quantity sensor 53, and the sheet thickness is detected based on the change in the magnetic flux density. In FIG. 1, the sheet thickness detection device 50 is attached to the support base 40, and is arranged on the upstream side of the registration roller pair 24 in the transport path via the support base 40.

Specifically, as shown in FIG. 3B, when the conveyed sheet P is sandwiched between one end of the lever member 51 and the guide upper guide 56, the lever member 51 moves in the direction of the arrow shown in the figure. It rotates, and the movable core 52 moves in conjunction with the rotation of the lever member 51. The magnetic flux density is changed by the movement of the movable core 52, and the output value A is obtained from the magnetic amount sensor 53. Then, the output value B obtained from the magnetic quantity sensor 53 in a state where one end of the lever member 51 abuts on the guide upper guide 56 (that is, a state where the sheet P is not sandwiched) is set as an initial value, and the output value A described above is used. From
The sheet thickness is detected based on the value obtained by subtracting the output value B as the initial value.

Further, the position of the rotation shaft of the lever member 51 is adjustable within an intermediate region in the longitudinal direction of the lever member 51, and the other end portion of the lever member 51 with respect to the displacement amount of the one end portion is adjusted. The ratio of displacement amounts can be changed arbitrarily. That is, the sensitivity (measurement accuracy) of sheet thickness measurement can be adjusted as necessary.

For example, if the distance from the other end of the lever member 51 to the rotary shaft is N and the distance from the one end to the rotary shaft is 1 as shown in the figure, the ratio is 1: N. The swing width of the other end is N times the swing width of the one end. That is, by setting the distance from the other end of the lever member to the rotating shaft to be longer than the distance from the one end to the rotating shaft, the sensitivity of the sheet thickness measurement by the detecting means can be made with a simple configuration. It is possible to improve the measurement accuracy and the measurement accuracy.

According to this structure, one end of the lever member protruding into the conveying path contacts the sheet conveyed in the conveying path, and the detecting means detects the displacement amount of the other end of the lever member. By doing so, since the sheet thickness is measured, the detecting means can be moved away from the conveyance path in which dust and the like are scattered, and the adhesion of dust and the like to the detecting means can be suppressed. There is no reading error or erroneous detection due to dirt such as dust scattered in the conveyance path, it is possible to suppress a decrease in the measurement accuracy of the sheet thickness, and it is possible to improve the measurement accuracy of the sheet thickness at low cost.

(Second Embodiment) In addition to this, the movable core 52 as a moving body connected to the other end of the lever member 51 in the above-described first embodiment is replaced with a magnet, and one end of the lever member 51 is replaced. It is also possible to use a magnetic quantity sensor configured to detect the amount of movement of the magnet corresponding to the sheet thickness of the sheet P sandwiched between the upper portion and the guide upper guide 56 from the change in the amount of magnetic flux oscillated from the magnet itself. The same effect as the first embodiment described above can be obtained.

(Third Embodiment) The above-mentioned first and second embodiments
In the embodiment, one end portion of the lever member 51 is configured to directly contact the sheet P, but a roller 54 that contacts the sheet may be disposed at one end portion of the lever member. In addition to the effects of the first and second embodiments, it is possible to suppress generation of sheet powder due to rubbing between the conveyed sheet and one end of the lever member regardless of the number of sheets of the sheet P passing through. At the same time, it becomes possible to suppress the wear of one end of the lever member.

In the image forming apparatus provided with the sheet thickness detecting device as described above, the fixing speed is determined to a speed suitable for the sheet having the sheet thickness based on the sheet thickness detected by the sheet thickness detecting device ( For example, in the case of a thick sheet, the speed can be reduced to 1/4 of the normal speed, etc.), and thus the fixing property to the sheet can be improved.

Although a full-color printer has been described as an example of the image forming apparatus here, the present invention is not limited to this, and it is needless to say that the same effect can be exhibited in a monochrome printer.

Further, in each of the above-described embodiments, an example in which the sheet thickness detecting device according to the present invention is applied to an image forming apparatus is given, but the invention is not limited to this, and the sheet thickness needs to be measured. Any device can be applied. For example, applying this sheet thickness detection device to a sheet conveying device,
It is also possible to control the sheet conveying operation according to the detection result of the sheet thickness detecting device.

As the sheet whose sheet thickness can be detected by the sheet thickness detecting device according to each of the above-mentioned embodiments,
For example, ordinary copy paper, printer paper, inkjet paper (including glossy paper, etc.), OHT sheet, etc. can be applied.

[0032]

As described above, according to the present invention, it is possible to suppress the deterioration of the measurement accuracy of the sheet thickness due to the dust scattered in the conveying path and to improve the measurement accuracy of the sheet thickness at low cost. It is possible to realize a sheet thickness detecting device, a sheet conveying device, and an image forming apparatus that can be operated.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the overall configuration of an image forming apparatus including a sheet thickness detecting device according to a first embodiment of the present invention.

FIG. 2 is a detailed view for explaining a sheet thickness detecting device in the image forming apparatus.

FIG. 3 is a detailed view for explaining a sheet thickness detecting device in the image forming apparatus.

FIG. 4 is a detailed view for explaining a sheet thickness detecting device that is a third embodiment of the present invention.

FIG. 5 is a detailed view for explaining the configuration of a conventional sheet thickness detecting device.

[Explanation of symbols]

1 Image forming device 30 Intermediate transfer belt 40 support 50 Sheet thickness detector 51 lever 52 Movable core 53 Magnetic sensor 54 Roll 55 Guide 56 Guide top guide

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Claims (8)

[Claims] 1. An end portion projects into a sheet conveying path,
A lever member for sandwiching a sheet to be conveyed between the one end portion and a reference surface in the conveyance path, the amount of rotation of which changes according to the sheet thickness, and a displacement amount of the other end portion of the lever member for detecting the displacement amount. A sheet thickness detecting device comprising: a detecting unit. 2. The sheet thickness detecting device according to claim 1, wherein the position of the rotating shaft of the lever member is adjustable within an intermediate region in the longitudinal direction of the lever member. 3. The sheet thickness according to claim 2, wherein the distance from the other end of the lever member to the rotating shaft is longer than the distance from the one end to the rotating shaft. Detection device. 4. The moving means, which is connected to the other end of the lever member and has a high magnetic permeability material that interlocks with the movement of the other end, and the moving amount of the moving body, The sheet thickness detection device according to claim 1, further comprising a sensor that detects a change. 5. The moving means, which is connected to the other end of the lever member and has a magnet that is interlocked with the movement of the other end, detects the moving amount of the moving body based on a change in magnetic flux density. 4. The sheet thickness detecting device according to claim 1, further comprising a sensor. 6. The sheet thickness detecting device according to claim 1, wherein a roller that comes into contact with the sheet is arranged at one end of the lever member. 7. A sheet conveying device having the sheet thickness detecting device according to claim 1, wherein the sheet conveying operation is controlled according to a detection result of the sheet thickness detecting device. . 8. The sheet thickness detection device according to claim 1, an image forming unit that forms an image on a sheet, and an image forming unit that is arranged upstream of the image forming unit in the conveyance direction, and is connected to the image forming unit. The sheet thickness detection device includes a registration unit that corrects a sheet supply timing and a skew of the sheet, and a fixing unit that performs a fixing operation of an image formed on the sheet by the image forming unit. Also, the image forming apparatus is arranged on the upstream side in the conveying direction, and controls the fixing operation according to the detection result of the sheet thickness detecting device.