JP2000356507A - Device for detecting kind-of-sheet and image-forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a kind-of-sheet detecting device which can detect the type of a sheet with high sensitivity without receiving any influence from vibrations in the device and an image forming device. SOLUTION: A kind-of-paper sensor 30 is composed of a thin negative electrode plate 33 having a sliding section on which a sheet is slid at its front end (33a), a thin film positive electrode 32A, and a piezoelectric ceramic 31 interposed between the electrodes 33 and 32A. Therefore, the sensitivity of the sensor 30 can be improved, because the sensor 30 can efficiently convert vibrations into electric energy by suppressing the attenuation of the vibrations.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet type detecting device for detecting the type of a sheet-like medium (hereinafter, referred to as a sheet) such as paper, for example, an ink jet printer, a thermal head printer, a dot impact printer, and a silver type. The present invention is applied to an image forming apparatus that forms an image using a sheet as a recording medium, such as a salt photographic printer and a laser printer, and is particularly used for an image forming apparatus using an electrophotographic process such as a copying machine, a laser printer, and a facsimile. .

[0002]

2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus has
For example, it is configured as shown in FIG.

In FIG. 8, reference numeral 1 denotes a photosensitive drum, 2 denotes a charging roller, 3 denotes a laser exposure device, 4 denotes a reflection mirror, 5 denotes a developing sleeve, 6 denotes toner, 7 denotes a toner container, 8 denotes a transfer roller, and 9 denotes a receiving roller. Paper as a recording medium sheet, 10 a cleaning blade, 11 a waste toner container, 12 a fixing device, 13 a paper cassette, 14 a paper feed roller, 1
5 is a separation pad, 16 is a high voltage power supply, and 17 is a guide before transfer.

The photosensitive drum 1 rotates in the direction of the arrow, and is uniformly charged by a charging roller 2 supplied with power from a high-voltage power supply 16. The laser light emitted from the laser exposure device 3 is reflected by the reflection mirror 4 and irradiates the photosensitive drum 1 to form an electrostatic latent image on the photosensitive drum 1.

A toner container 7 is filled with toner 6, and an appropriate amount of toner 6 is
Are supplied onto the photosensitive drum 1 after receiving an appropriate charge. The toner 6 on the developing sleeve 5 adheres to the electrostatic latent image on the photosensitive drum 1, and the latent image is developed and visualized as a toner image.

On the other hand, the paper feed roller 14 feeds the paper 9 one by one from the paper cassette 13 at a certain timing. The separation pad 15 is disposed in contact with the paper feed roller 14, and the coefficient of friction, the contact angle, and the shape of the surface of the separation pad 15 are adjusted so that only one sheet of paper 9 is fed per sheet feeding. I have.

The paper 9 sent from the paper feed roller 14 is guided by a pre-transfer guide 17 to a contact portion between the photosensitive drum 1 and the transfer roller 8. The pre-transfer guide 17 is arranged at a position that is always in contact with the paper 9 in order to stabilize the behavior of the paper 9. Then, the visualized toner image on the photosensitive drum 1 is transferred onto the paper 9 by the transfer roller 8.

The untransferred toner remaining on the photosensitive drum 1 without being transferred is scraped off by a cleaning blade 10 and stored in a waste toner container 11, and the photosensitive drum 1 whose surface has been cleaned is repeatedly subjected to the next image formation. Enter the process.

Then, the paper 9 on which the toner image is placed is heated and pressed by the fixing device 12, and the toner image is permanently fixed on the paper 9. At this time, since the electric power supplied to the fixing device 12 is set based on the standard that the sheet such as the thickest paper 9 to be passed can be sufficiently fixed, excessive electric power is required for plain paper which requires less electric power than thick paper. Power was consumed.

As a method for coping with this problem, for example, the stiffness of a sheet such as paper is detected by a strain gauge disclosed in JP-A-59-111170, the type of the sheet is identified, and fixing is performed according to the type of the sheet. For example, there is a method of changing the fixing control of the device 12.

[0011]

In an image forming apparatus such as a printer that forms an image on a sheet of paper or the like, an image forming apparatus such as a printer is inexpensive in order to form an optimal image on each sheet because of diversification of sheets as recording media. There is a need for a simple sheet type detection device.

As described above, in the method for detecting the stiffness of a sheet, the sheet type detection device and the sheet abut against each other on the surface, and a small pressure of the sheet bending is used. It was a disturbance and it was difficult to increase the detection accuracy.

[0013] In addition, in the heat fixing of a toner image in a conventional electrophotographic image forming apparatus, the surface property has a greater influence on the fixing property than the sheet thickness. On the other hand, since the fixing control is adjusted, the plain paper is given more heat energy than necessary and consumes useless electric power.

In order to prevent the wasteful consumption of electric power and achieve energy saving, it is effective to detect the surface property of the sheet.

What is problematic when detecting the surface properties of a sheet is the detection accuracy. In particular, when vibration in the image forming apparatus greatly affects detection accuracy,
An important issue is how to increase the sensitivity of the sheet type detection device.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. It is an object of the present invention to provide a sheet type detecting apparatus and a sheet type detecting apparatus capable of performing high-sensitivity detection without being affected by vibrations inside the apparatus. An object of the present invention is to provide an image forming apparatus.

[0017]

In order to achieve the above object, a sheet type detecting apparatus according to the present invention has a rubbing portion for rubbing a sheet surface of a sheet to be conveyed. Rubbing means that vibrates by rubbing, and a piezoelectric element having two electrodes and outputting a voltage according to the vibration of the rubbing means between the two electrodes, In a sheet type detecting apparatus for detecting a sheet type of a sheet by a voltage output, the rubbing means is provided by a thin plate serving also as one of the two electrodes.

Accordingly, since the rubbing means also serves as the electrode of the piezoelectric element, it is possible to efficiently convert the energy into electric energy while suppressing the attenuation of the vibration, and it is possible to increase the sensitivity of the sheet type detecting device.

Preferably, the thin plate has one end fixed and the other end provided with the rubbing portion at the other end.

Thus, since the other end of the thin plate, which is the free end, slides on the sheet, the contact pressure increases, and the detected vibration energy can be increased.

It is preferable that the thin plate also serves as an electrode opposite to an electrode fixed to one of the two electrodes.

Thus, the vibration amplitude of the thin plate can be increased, and the sensitivity of the sheet type detecting device can be increased.

It is preferable that the rubbing means is provided at a position where the conveying direction of the sheet in contact with the rubbing portion is bent by approximately 5 °.

An image forming apparatus according to the present invention includes the above-described sheet type detecting device and image forming means for forming an image on a sheet after detecting the sheet type with the sheet type detecting device. Features.

Accordingly, there is provided image forming means for forming an image which can be visualized on a sheet such as paper, which is used in an image forming apparatus such as an ink jet printer, a thermal head printer, a dot impact printer, a silver halide photographic printer, a laser printer, etc. A sheet transporting means for transporting the sheet and a sheet type detecting device in the sheet transport path are used. Then, based on the detection result of the sheet type detection device, it is possible to perform image formation control according to the sheet type.

The image forming means includes fixing means for fixing the toner image onto the sheet by heating and pressing the toner image transferred onto the sheet, and the fixing means detects the detection result of the sheet type detecting device. It is preferable to change the fixing control for the sheet accordingly.

In particular, when the rubbing portion is brought into contact with the image forming surface of the sheet, the margin for identifying the type of sheet is increased, and the fixing unit can reliably suppress wasteful power consumption according to the type of sheet.

It is preferable that the fixing control to be changed is temperature control or power control of the fixing unit.

[0029]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The materials, shapes, relative arrangements, and the like are not intended to limit the scope of the present invention only to them unless otherwise specified.

(First Embodiment) A first embodiment will be described with reference to FIGS. FIG. 1 shows a paper type sensor 3 as a sheet type detection device according to the first embodiment.
0 is shown. FIG. 1A is a cross-sectional view of the paper type sensor 30, and FIG. 1B is a top view of the paper type sensor 30.

Reference numeral 33 also serves as a rubbing means, for example, brass,
It is a thin plate made of metal such as copper, iron, and stainless steel, and has a thickness of about 0.1 mm. 31 is a piezoelectric ceramic,
For example, it is made of a ceramic having a piezoelectric effect such as barium titanate, lead zirconate titanate, lead cobalt niobate zirconate, and bismuth lead niobate lead titanate.

Reference numeral 32A denotes a thin film electrode provided by applying a paste material such as AgPd. Reference numeral 33a denotes a tip end of the thin plate 33, and a contact end portion, which is a free end portion, serves as a rubbing portion with a sheet of paper as a recording medium. Reference numeral 34 denotes a mounting hole, which is a screw hole.

The thin plate 33 is a negative electrode and the thin film electrode 32
A is a positive electrode, and has a piezoelectric ceramic 31 therebetween to constitute a piezoelectric element. The thin film electrode 32A and the thin plate 33 are connected to a signal processing circuit (not shown).

FIG. 2 shows a use mode in which the paper type sensor 30 of the present embodiment is installed in an electrophotographic image forming apparatus.
1 is a photosensitive drum, 8 is a transfer roller, P is paper, and 35 is a mounting frame of the apparatus main body. The electrophotographic image forming apparatus is the same as the related art, and the description is omitted here.

The paper type sensor 30 includes a thin film electrode 32A and a thin plate 33, and a piezoelectric ceramic 31 therebetween.

The paper type sensor 30 is fixed to the frame 35 at a position on one end side where the mounting hole 34 of the thin plate 33 is provided by a screw passed through the mounting hole 34.
The contact area between the thin plate 33 and the frame 35 is adjusted so as not to impair the elastic deformation of the thin film electrode 32A while maintaining the mounting strength of the paper type sensor 30.

The paper P is transported to a contact nip between the photosensitive drum 1 and the transfer roller 8 by a paper feed roller and transport rollers (not shown).

In the configuration shown in FIG. 2, while the paper P is being conveyed,
The leading end 33a of the thin plate 33 of the paper type sensor 30 was always arranged at a position where the leading end 33a rubs against the paper P, and the angle formed by the paper P before and after the contact portion between the leading end 33a and the paper P was 175 °. That is,
At a position where the angle of the transport direction of the transported paper P is bent by 5 °,
The tip 33a of the thin plate 33 of the paper type sensor 30 is arranged.

The tip 33a is provided at a free end opposite to the fixed end of the thin-film electrode 32A, so that the thin plate 33 can vibrate greatly by sliding against the paper P.
A voltage corresponding to the vibration is output between the two electrodes of the thin film electrode 32A and the thin plate 33.

The weak voltage output from between the two electrodes of the piezoelectric element is amplified about 300 times by an operational amplifier, and only the AC component representing the vibration is extracted from the waveform. FIG. 3A shows the results of measuring the AC power for nine types of paper P.

Rough paper is paper having a rough surface.
It is paper that is rough to the touch. The unit of the vibration energy is an arbitrary unit “AU”.

In general, if the paper surface is poor, the paper type sensor 3
When the paper is rubbed to zero, the vibration of the paper type sensor 30 increases, so that the vibration energy is measured to be large.
Also, when the basis weight of the paper is large, the thickness generally increases, and the rigidity of the paper increases.

When the rigidity of the paper is high, the paper type sensor 30
As a result, the paper conveyance direction is bent by 5 °, the contact pressure between the paper type sensor 30 and the paper increases, and the vibration increases.

When the fixing temperature of the fixing means in the electrophotographic image forming apparatus is set to the same constant temperature,
Paper having poor surface properties, that is, paper having a rough surface, has poor fixability, and a paper having a large basis weight tends to have poor fixability.

Therefore, it is possible to measure the ease of fixing of the paper by vibrating the paper type sensor 30.

The detection results shown in FIG. 3A having good surface properties are plain paper, recycled paper A, recycled paper B, and glossy paper. Those having poor surface properties are rough papers A to D and envelopes.

Those which sufficiently fix even when the fixing temperature is lowered are plain paper, recycled paper A and recycled paper B. Although the rough paper A has a low basis weight, the vibration energy is large and the surface property is poor, so that the fixing temperature cannot be lowered.

FIG. 3B is a graph of this table. From this graph, the threshold value A is set to 9.6A. U. When the threshold value A or less is a paper type having good fixability, and when the threshold value A or more is a normal paper type, it is possible to identify both types.

Further, another threshold value B is set to 11.5
A. U. By setting to, it is also possible to identify paper having a particularly high fixing property that is equal to or higher than the threshold value B.

FIG. 4 shows a configuration of a sensor 40 for detecting vibration caused by sliding between the pre-transfer guide 17 and a sheet as a comparative example compared with the present embodiment. 4, 1 is a photosensitive drum, 8 is a transfer roller, 17 is a pre-transfer guide, 35 is a mounting frame, 32 'and 33' are electrodes, and 31 is piezoelectric ceramics.

Although it is possible to detect the paper type with the configuration of the sensor 40 of the comparative example, it is the pre-transfer guide 17 that transmits the vibration due to the rubbing to the sensor 40, and the moment of inertia is relatively large. Therefore, the amplitude of the vibration does not increase so much. Further, similarly to the above, the moment of inertia of the pre-transfer guide 17 is easily affected by the internal vibration transmitted from the frame 35.

When the ratio of the vibration energy when the paper was passed and the vibration energy when the paper was not passed, that is, the S / N ratio, was 11.3 dB in the sensor 40 of the comparative example. In the paper type sensor 30 of the embodiment, the probability is 21.7 dB, and the possibility of erroneous detection is reduced even when used in an environment with a lot of vibration.

This effect largely depends on the shape of the paper type sensor 30, and the thin plate 33 to be rubbed and the electrode for directly transmitting the vibration to the piezoelectric ceramic 31 are integrated, The end of the farthest position is the fixed end, and the piezoelectric ceramic 31
It is important that the thin plate 33 on which is disposed is easily vibrated.

Although the present embodiment has been described with reference to the example of discrimination between plain paper and rough paper in an electrophotographic image forming apparatus, special paper such as a transparency sheet or a label sheet can also be discriminated. In addition to the determination of the ease of fixing of paper, the detection of special paper can be performed using the same paper type sensor 30 in the same manner.

The paper type sensor 30 is not limited to the application to the electrophotographic image forming apparatus according to the present embodiment, but may be a special paper and a plain paper or an O paper in an ink jet printer.
The present invention is also applicable to image formation control such as changing the sublimation amount of ink between plain paper and OHT in a thermal head printer, such as changing the discharge amount of the fixing liquid by determining the HP paper.

(Second Embodiment) FIGS. 5 to 7 show a second embodiment.
An embodiment will be described. The shape of the paper type sensor 30 is different from that of the first embodiment. Other configurations and operations are the same as those of the first embodiment, so that the same components are denoted by the same reference numerals and description thereof will be omitted.

Reference numeral 1 denotes a photosensitive drum, 8 denotes a transfer roller, 30 denotes a paper type sensor, 32B denotes an electrode plate, 33 denotes a thin plate having a polarity different from that of the electrode plate 32B, 31 denotes a piezoelectric ceramic, and 35 denotes a mounting frame. FIG. 5 shows a sectional view (a) and a top view (b) of the paper type sensor 30 used in the present embodiment.

The thin plate 33 rubs against the sheet surface of the sheet at the leading end 33a, and the vibration generated by the rub transmits the thin plate 33, the piezoelectric ceramic 31 and the electrode plate 32B, and attenuates at the fixed position 34.

As described above, since the thin plate 33 to be rubbed is not fixed to the apparatus main body but is fixed to the electrode plate 32B separately, the amount of vibration transmitted to the piezoelectric ceramic 31 is increased as compared with the first embodiment. Further, the sensitivity of the paper type sensor 30 was improved, and the S / N ratio was improved, and the value was 23.4 dB.

In addition to the sensitivity, the thin plate 33 abuts on the opposite side of the sheet from the image forming surface in the first embodiment. In changing the control, a configuration in which the sliding portion of the leading end 33a of the thin plate 33 abuts on the image forming surface side of the paper is more preferable from the viewpoint of detection accuracy.

In general, one side of the paper is referred to as a wire side and the other side is referred to as a felt side at the time of manufacture. In the case of plain paper having a basis weight of 60 to 80 g / m ² , the felt surface is the surface and often the image forming surface. On plain paper, the felt surface is smoother on the felt surface than on the wire surface, so the toner is more easily fixed on the paper surface than on the back surface of the paper.

However, rough paper called rough paper is premised on the use of a fountain pen, and there are some papers whose surface is intentionally roughened to give a sense of quality. In such a paper, the surface on the image forming surface side is worse than the surface on the non-image forming surface side, and it is a paper type in which the toner is hardly fixed. FIG.
FIG. 6A shows the results of measuring the vibration energy in the form of FIG. 6 for the image forming surface and the anti-image forming surface of plain paper and rough paper.

From these results, it is clear that plain paper has good surface properties on the image forming surface side and smooth surface roughness.
The vibration when the paper rubs against the rubbing part 3a is reduced. On the other hand, rough paper has the opposite tendency, and the surface energy on the image forming surface side is poor, so that the vibration energy is large. FIG. 7B shows a graph of the result of FIG. 7A.

When the rubbing portion of the leading end 33a is brought into contact with the opposite side of the image forming surface, a margin A for discriminating plain paper and rough paper is provided.
Is 1.41, whereas the tip 3 is closer to the image forming surface side.
When the rubbing portion 3a is brought into contact, the margin is 2.
24, the possibility of erroneous detection due to the paper type sensor 30, paper variation, etc. is reduced.

This effect is particularly important in an image forming apparatus using a heat fixing unit as a fixing unit described below.

In a conventional electrophotographic image forming apparatus,
Since the fixing temperature was set so as to satisfy the fixing property on the image forming surface side of the rough paper D, heat energy was applied more than necessary to plain paper.

That is, in the conventional fixing device, the cold start temperature control temperature is set to 190 ° C. irrespective of the type of paper in order to obtain sufficient fixability on rough paper.

However, in the present embodiment, the paper type is identified from the surface properties of the image forming surface side, and when it is determined that the paper is plain paper, the cold start temperature control temperature is set to 170 ° C. It has become possible to reduce the average power consumption from the cold start to the target temperature control temperature by 12% while securing sufficient fixing performance.

Also, by lowering the temperature regulation temperature when the fixing unit is sufficiently warmed, the average power consumption is increased from 160 W to 14 W.
The power consumption has been reduced to 0 W, and it has become possible to achieve 20 W of energy saving. At this time, since the target temperature needs to be changed before the paper enters the fixing device, it is necessary to arrange the paper type sensor 30 in the transport path before the entry of the fixing device.

Changing the fixing control has a similar effect not only in changing the temperature control of the temperature control temperature but also in changing the power control.

[0071]

As described above, according to the present invention, since the end of the thin plate is rubbed against the sheet, the contact pressure increases, the vibration energy increases, and the thin plate also functions as an electrode. It is possible to efficiently convert the electric energy into electric energy by suppressing the attenuation of the sheet type, and it is possible to provide a highly sensitive sheet type detecting device.

Further, by separating the thin plate to be rubbed from the electrode for fixing the sheet type detecting device, the vibration amplitude of the thin plate to be rubbed with the sheet can be increased, and the sheet type detecting device with higher sensitivity can be obtained. Can be provided.

In an image forming apparatus using such a sheet type detecting apparatus, efficient control can be performed by detecting the sheet type, for example, to surely suppress wasteful power consumption.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a paper type sensor according to a first embodiment.

FIG. 2 is a diagram illustrating a paper type detection method according to the first embodiment.

FIG. 3 is a diagram illustrating characteristics of a paper type detection method according to the first embodiment.

FIG. 4 is a diagram illustrating a paper type detection method in a comparative example.

FIG. 5 is a diagram illustrating a paper type sensor according to a second embodiment.

FIG. 6 is a diagram illustrating a paper type detection method according to a second embodiment.

FIG. 7 is a diagram illustrating characteristics of a paper type detection method according to the second embodiment.

FIG. 8 is a diagram illustrating an electrophotographic image forming apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 8 transfer roller 17 pre-transfer guide 30 paper type sensor 31 piezoelectric ceramic 32A thin film electrode 32B electrode plate 33 thin plate 33a tip 34 paper type sensor mounting hole 35 mounting frame P paper

Claims (7)

[Claims] A rubbing means for rubbing the sheet surface of a sheet to be conveyed, rubbing means oscillating by rubbing of the rubbing means, and two electrodes; A piezoelectric element that outputs a voltage corresponding to the vibration of the rubbing means from between the electrodes, a sheet type detection device that detects a sheet type of a sheet by a voltage output of the piezoelectric element, wherein the rubbing means includes: A sheet type detection device provided with a thin plate that also serves as one of the two electrodes. 2. The sheet type detection device according to claim 1, wherein the thin plate has one end fixed and the other end provided with the rubbing portion at the other end. apparatus. 3. The sheet type according to claim 1, wherein the thin plate also serves as an electrode opposite to an electrode fixed to one of the two electrodes. Detection device. 4. The sheet according to claim 1, wherein the rubbing means is provided at a position where the conveying direction of the sheet abutting on the rubbing portion is bent by approximately 5 °. Species detection device. 5. A sheet type detecting device according to claim 1, 2, 3 or 4, and an image forming means for forming an image on a sheet after detecting the sheet type with the sheet type detecting device. An image forming apparatus comprising: 6. The image forming means includes fixing means for fixing the toner image onto the sheet by heating and pressing the toner image transferred onto the sheet, wherein the fixing means detects the sheet type detecting device. 6. The image forming apparatus according to claim 5, wherein fixing control for the sheet is changed according to a result. 7. The image forming apparatus according to claim 6, wherein the fixing control to be changed is temperature control or power control of the fixing unit.