JP2002350108A - Thickness detecting sensor, thickness detector, and image forming device using the detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device that can be improved in accuracy by stabilizing the ground contact areas of a magnetic roller and wheel rollers. SOLUTION: The representative constitution of a thickness detecting sensor is provided with the magnetic roller 36a or planar magnetic body 36b and wheel- shaped wheel rollers 37 which are arranged to face each other so that the roller 37 may come into contact with the magnetic roller 36a or magnetic body 36b and respectively fixed to both end sections of an axle wound with a coil. The longitudinal dimension of the magnetic roller 36a or magnetic body 36b is made larger than those of the wheel-shaped wheel rollers 37.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in an image forming apparatus such as a copying machine and an LBP, and relates to a thickness sensor for detecting the thickness of a sheet, a thickness detecting apparatus, and an image forming apparatus using the same.

[0002]

2. Description of the Related Art As shown in FIG. 5, a conventional thickness sensor uses a magnetic roller 10 made of a magnetic material such as ferrite.
1, a wheel roller 102 formed of a magnetic material such as a ferrite having a wheel shape disposed opposite to the magnetic roller, a bobbin 103 supporting the wheel roller and winding a coil, a bearing 104 for receiving the magnetic roller 101, The basic configuration includes a spring 105 for urging the body roller 101 against the wheel roller, a support member 107 for supporting the magnetic roller, and a coil 110.

[0005] The support member 107 is attached to the image forming apparatus main body. The magnetic roller 101 is urged against the wheel roller 102 by a spring 105, and when there is no sheet P, the magnetic roller 101 and the wheel roller 102 are in contact. Wheel roller 10
Numeral 2 forms a magnetic path with the magnetic roller 101. When the sheet P enters the press contact portion between the rollers, the magnetic roller 101 is displaced upward according to the thickness of the sheet, and the magnetic roller 101
Is slightly away from the wheel rollers 102. When the two rollers are separated by the thickness of the sheet, an air gap is generated in the magnetic path formed by the two rollers, and the inductance value of the coil decreases. The inductance value generated in the coil is inversely proportional to the displacement amount of the magnetic roller 101.

As described above, the thickness of the sheet P is directly reflected on the air gap of the magnetic path.

[0005]

However, in the above-described conventional image forming apparatus, the magnetic roller 136 and the wheel roller 137 have the same length in the longitudinal direction. If the deviation occurs due to mechanical variations, the contact area of both rollers decreases, and the variations occur in the closed magnetic loop. As a result, the inductance value becomes unstable and the detection accuracy decreases.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of achieving high precision by stabilizing the contact area between the magnetic roller and the wheel roller.

[0007]

In order to achieve the above object, a typical configuration of a thickness detecting sensor according to the present invention comprises a magnetic member and a coil mounted on an axle portion opposed to the magnetic member. , And a longitudinal dimension of the magnetic body is longer than the axle-shaped magnetic body.

[0008]

[First Embodiment] A first embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of an image forming apparatus according to the present embodiment,
FIG. 2 is a schematic diagram of the thickness sensor, and FIG. 3 is a control block diagram of the image forming apparatus.

Here, a thickness detecting device provided in the image forming apparatus will be described. As shown in FIG. 1, a controller unit 1 develops an electric signal, which is code data input from a host computer (not shown), into a dot image by a video controller unit 3 and stores it in a memory inside the video controller. It is returned to the section 2 as a video signal.

Each element of the engine unit 2 is controlled by an engine controller 5, and exchange of video signals with the controller unit 1 is also performed via the engine controller 5. A video signal input to a video interface unit (not shown) of the engine controller 5 is sent to a laser driver 6 where the semiconductor laser 7 is turned on / off.
The FF is controlled. The laser light 10 emitted from the semiconductor laser 7 is deflected by the polygon mirror 8 to become scanning light in the longitudinal direction of the photosensitive drum 12, and is projected on the photosensitive drum 12 via the mirror 9.

The photosensitive drum 12 rotates in the direction of the arrow, and is temporarily charged by the primary charger 11 and then turned on / off of the laser beam.
Upon receiving exposure corresponding to the FF, an electrostatic latent image is formed on the surface of the photosensitive drum. Then, the colored charged particles (hereinafter, referred to as toner) are applied by the developing device 13 to obtain a visible image. The sheet P is taken out of the feeding cassette 20 by the feeding roller 21, and is conveyed by the conveying rollers 34a and 34b.

The sheet P reaches the photosensitive drum through the thickness detecting device 23 (see FIG. 3). When the sheet P reaches between the photosensitive drum and the transfer roller, the visible image is transferred. The transfer residual toner is cleaned from the surface of the photosensitive drum 12 with a cleaning device.
The photosensitive drum 12 is wiped off by 15 and is ready for the next image forming step.

On the other hand, the sheet on which the unfixed toner image is placed
After the sheet is inserted into the fixing unit 16 and a permanent fixed image is obtained, the sheet is discharged out of the apparatus as a final print in the direction of the arrow in the figure. The arrows in the drawing indicate the feeding trajectory of the sheet taken out of the feeding cassette 20 and conveyed.

The fixing device 16 includes a hollow fixing roller 17 and a heater 19.
(Fixing heater), the heater 19 is energized, and the fixing roller 17 is overheated. The output of a sensor (not shown) for detecting the surface temperature of the fixing roller 17 is input to a temperature controller (not shown). The heater 19 is turned on / off to maintain a predetermined surface temperature.

The pressing roller 18 is pressed against the fixing roller 17 by an urging means (not shown), and the unfixed toner on the sheet is heated together with the sheet in a nip formed by the fixing roller 17 and the pressing roller 18. It is pressed and permanently fixed. Then, the sheet P is discharged out of the apparatus (LS direction).

In the above process, the information on the sheet thickness detected by the thickness detecting device 23 is sent to the engine controller 5, and the engine controller uses this information to control the image forming control conditions of the primary charger, the developing device, the transfer roller and the like. change. Further, the engine controller 5 also changes the temperature of the fixing roller.

Thus, the image forming apparatus can record an optimum image even if the thickness of the sheet changes.

As shown in FIG. 2, the thickness sensor 22 includes a magnetic roller 36a formed of a magnetic material such as ferrite, and a coil wound around an axle (rotating shaft) disposed opposite to and in contact with the magnetic roller 36a. A wheel roller 37 formed of a magnetic material such as a wheel-shaped ferrite having disc-shaped rotating bodies provided at both ends of an axle portion, a bobbin 38 supporting the wheel roller 37 and winding a coil, and a bearing for receiving the magnetic roller 36a Three
9. It has a basic structure including a spring 40 as a means for urging the magnetic roller 36a against the wheel roller 37 to press the magnetic roller 36a, a support member 42 for supporting the magnetic roller, and a coil 45. Here, the length of the magnetic roller 36a in the longitudinal direction is a wheel roller.
It is longer than 37.

The support member 42 is attached to the image forming apparatus main body. The magnetic roller 36a is urged against the wheel roller 37 by a spring 40. When there is no sheet P, the magnetic roller 36a is
36a and the wheel roller 37 are in contact. The wheel roller 37 forms a magnetic path with the magnetic roller 36a.

When the sheet P enters between the rollers, the magnetic roller 36a is displaced upward according to the thickness of the sheet, and the magnetic roller 36a is slightly separated from the wheel roller 37. When the two rollers are separated by the thickness of the sheet, an air gap is generated in the magnetic path formed by the two rollers, and the inductance value of the coil 45 decreases. Coil 45
Is inversely proportional to the displacement of the magnetic roller 36a.

As described above, since the thickness of the sheet P is directly reflected on the air gap of the magnetic path, that is, on the inductance value of the coil 45, the thickness of the sheet P can be detected with high accuracy. . Furthermore, the magnetic roller 36
Since the longitudinal direction of a is longer than the wheel roller 37, the closed magnetic path is constant even if the longitudinal axis of the magnetic roller 36a and the wheel roller 37 is displaced due to mechanical variation, and the closed magnetic loop is stable. Since the inductance value is stabilized, the detection accuracy is further improved.

As shown in FIG. 3, the thickness detecting device 23
It comprises a thickness sensor 22 whose inductance value changes according to the thickness of the sheet P, and an LC oscillation circuit 43 which is an oscillator as inductance detecting means. Thickness sensor 22
Is connected to the LC oscillation circuit 43, and the LC oscillation circuit 43 oscillates at a frequency corresponding to the inductance value of the thickness sensor 22. That is, oscillation is performed at a frequency corresponding to the thickness of the sheet P. The signal of the oscillation circuit 43 is divided by the frequency divider 44 and sent to the engine controller 5.

The engine controller 5 detects this frequency and recognizes the thickness of the sheet P, and controls the image formation of a primary electric device, a developing device, a transfer roller and the like (not shown) and changes the temperature of the fixing roller. This makes it possible to record an image that is optimal for the thickness of the sheet P.

Although the LC oscillation circuit 43 has been described using the LC Colpitts oscillation circuit, the invention is not limited to this. Also, the frequency divider has been described as being inserted between the oscillation circuit and the engine controller. However, it is not always necessary to insert the frequency divider.

As described above, the length of the magnetic roller 36a in the longitudinal direction is longer than that of the wheel roller 37.
It is possible to increase the accuracy of the thickness detecting device 23, and it is possible to record an optimum image according to the thickness of the sheet.

[Second Embodiment] Next, a second embodiment of the image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 4 is a schematic diagram of the thickness sensor according to the present embodiment. The same parts as those in the first embodiment will be denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, a flat magnetic body 36b having a flat detection surface is used instead of the magnetic roller 36a of the first embodiment.

In the first embodiment, the magnetic roller 36a is
Was biased to the wheel roller 37, but in the second embodiment,
By replacing a with a planar magnetic body 36b, and rotating the wheel roller 37 only without rotating the planar magnetic body 36b,
It is working. Here, the longitudinal length of the planar magnetic body 36b is configured to be longer than the longitudinal length of the wheel roller 37.

Thus, the plane magnetic body 36b, the wheel roller
Even if the longitudinal axis of the 37 is displaced due to mechanical variation, the closed magnetic path is constant, the closed magnetic loop is stabilized, and the inductance value is stabilized, so that the detection accuracy is further improved.

Also, by replacing the magnetic roller 36a with a fixed flat magnetic body 36b, the dynamic range of the closed magnetic loop is increased, and the accuracy of the thickness detecting device can be further improved.

[0031]

As described above, by making the longitudinal length of the magnetic roller longer than that of the wheel roller, the accuracy of the thickness detecting device can be improved even if a mechanical displacement occurs in the longitudinal direction of both rollers. It becomes possible.

Further, by replacing the magnetic material roller with a magnetic material having a fixed flat surface, the dynamic range of the closed magnetic loop is increased, and the accuracy of the thickness detecting device can be further improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of an image forming apparatus according to a first embodiment.

FIG. 2 is a schematic diagram of a thickness sensor.

FIG. 3 is a control block diagram of the image forming apparatus.

FIG. 4 is a schematic diagram of a thickness sensor according to a second embodiment.

FIG. 5 is a sectional view of a conventional image forming apparatus.

[Explanation of symbols] [Explanation of symbols]

 P ... sheet 1 ... controller section 2 ... engine section 3 ... video controller section 5 ... engine controller 6 ... laser driver 7 ... semiconductor laser 8 ... polygon mirror 9 ... mirror 10 ... laser beam 11 ... primary charger 12 ... photosensitive drum 13 ... Developing device 15… Cleaner 16… Fixing device 17… Fixing roller 18… Pressure roller 19… Heater 20… Feeding cassette 21… Feeding roller 22… Thickness sensor 23… Thickness detecting devices 34a, 34b… Conveying roller 36a… Magnetic material Roller (magnetic material) 36b… Planar magnetic material (magnetic material) 37… Wheel roller 38… Bobbin 40… Spring 42… Support member 43… Oscillator circuit 44… Divider 45… Coil

Claims (10)

[Claims] 1. A wheel-shaped magnetic body having a coil wound around an axle disposed opposite to and in contact with the magnetic body, wherein a longitudinal dimension of the magnetic body is greater than that of the wheel-shaped magnetic body. Thickness detection sensor characterized by a long length. 2. The thickness detecting sensor according to claim 1, further comprising means for pressing the magnetic body against the wheel-shaped magnetic body. 3. A thickness detection sensor according to the thickness of the sheet by forming a magnetic path between the magnetic material and the wheel-shaped magnetic material and passing the sheet through a pressure contact portion between the magnetic material and the wheel-shaped magnetic material. 4. The thickness detecting sensor according to claim 3, wherein said inductance is changed. 4. A thickness detecting sensor according to claim 1, wherein said magnetic body is a magnetic roller or a flat fixed magnetic body. 5. A thickness detecting device comprising: the thickness detecting sensor according to claim 4; and an oscillator using an inductance of the thickness detecting sensor, wherein an oscillation frequency of the oscillator is changed according to a thickness of a sheet. . 6. A magnetic body in the form of a rotating body rotatably supported, a rotating body having magnetism capable of sandwiching a sheet in cooperation with the magnetic body, and being wound around a shaft of the rotating body. A coil, and inductance detecting means for detecting an inductance of the coil, which varies according to a distance between the magnetic body and the rotating body, which varies according to a thickness of the sandwiched sheet. Detection device. 7. A thickness detecting device, wherein a longitudinal dimension of the magnetic body is longer than the rotating body. 8. The thickness detecting device according to claim 6, wherein the rotating body has a rotating shaft and a disk-shaped rotating body provided at both ends thereof, and the coil is wound around the rotating shaft. 9. The thickness detecting device according to claim 6, wherein said inductance detecting means has an oscillator for changing an oscillation frequency in accordance with an inductance of said coil. 10. An image forming apparatus comprising the thickness detecting device according to claim 5. Description: