JP2003065994A - Paper quality detecting circuit and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small and inexpensive paper quality detecting circuit, and an imaging apparatus comprising it, in which the weight, moisture content and rough fiber density of a recording medium being carried can be detected in a short time. SOLUTION: The paper quality detecting circuit for detecting the quality of a recording medium being used in an imaging apparatus comprises a first conductor, a second conductor, a third conductor disposed oppositely to the first and second conductors, an oscillation circuit connecting the first and second conductors, and an oscillation frequency detecting circuit for detecting the output from the oscillation circuit, wherein the first and second conductors and the third conductor are arranged fixedly at such a specified interval as the recording medium can be passed continuously.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, particularly a laser beam printer (hereinafter, simply referred to as LBP).
In regard to the paper quality detection circuit which is effective in (1).

[0002]

2. Description of the Related Art A conventional LBP will be described with reference to the drawings. FIG. 26 is a schematic configuration diagram of the overall configuration of a conventional LBP. The recording medium 3 is conveyed in the direction of the arrow along the conveying path indicated by the dotted line in the figure. First, the recording medium 3 fed from a feeding unit (not shown) is fed directly below the photoconductor drum 5 via the transport roller 4. The photosensitive drum 5 is uniformly charged by the primary charger 6 and then irradiated with the scanning laser scanning light 7 to form an electrostatic latent image, and the toner supply unit 8 develops the toner by adhering the toner. . The developed toner image is transferred to the recording medium 3 by the transfer charger 9 provided on the back side of the recording medium 3, and is heated by the heating roller.
The recording medium 3 in the fixing portion including the fixing roller 10 and the fixing roller 11.
It is fixed on and discharged outside the machine. The heating roller 10 is driven by the drive circuit 12 so that the heat energy is appropriately generated.

In recent years, the LBP has been widely spread as an image forming apparatus for obtaining a high-definition, high-speed and stable image.
There is a demand for printing on a wider variety of recording media.

[0004]

However, the conventional L
The BP has a problem in a fixing process, that is, a configuration in which a toner in a particle state is heated and pressed to change into a gel state, and is entangled with fibers of a recording medium to fix the toner. This is because the optimum value of the fixing condition represented by thermal energy and pressure is different for each recording medium, and it is difficult to automatically detect the supplied recording medium and set the fixing condition appropriately. .

Generally related to the fixing process are the weight of the recording medium, the coarse density of the fibers and the water content. This is because all of these factors are major conditions for supplying heat energy to make the toner particles in a gel state. However, the above problem is caused by the fact that there is no sensor that integrates the weight of the recording medium, the coarse density of the fibers, and the amount of water content to detect them properly. Conventionally, the recording medium is irradiated with an appropriate light such as infrared light, and the reflected light in an appropriate range is C
Although the type of the recording medium was determined by detecting it with a CD sensor, a photodiode, or the like, it was difficult to detect the weight of the recording medium and the amount of water contained only by this.

Further, it is possible that the coarse density of the fiber can be detected by using a contact type sensor for detecting the contact pressure or the like. However, this method has a problem in stability, and it is difficult to detect the weight of the recording medium and the water content. In addition, it is cheap and small that can be mounted on the LBP,
Moreover, there is no sensor that can detect rapidly (1 to 0.1 seconds).

For this reason, the conventional LBP has set the fixing conditions to a certain extent for various recording media. This means that the optimum fixing conditions have not been set for the target recording medium, which is an obstacle in improving the image quality.

Therefore, the present invention provides a small and inexpensive paper quality detection circuit capable of detecting the weight of the recording medium conveyed, the water content, and the fiber coarse density in a short time, and an image forming apparatus having the same. It is intended to be provided.

[0009]

In order to solve the above-mentioned problems, a typical structure of a paper quality detection circuit according to the present invention is a paper quality detection circuit for detecting the quality of a recording medium used in an image forming apparatus. A first conductor, a second conductor, and the first conductor
A third conductor arranged to face both the conductor and the second conductor, an oscillation circuit connecting the first conductor and the second conductor, and an oscillation frequency detection for detecting the output of the oscillation circuit A first conductor and a second conductor,
The third conductor is characterized in that the recording medium is fixedly arranged with a predetermined interval through which the recording medium can continuously pass.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] A first embodiment of the paper quality detection circuit and the image forming apparatus according to the present invention will be described.
It will be described with reference to the drawings. 1 is a conceptual diagram of a paper quality sensor, FIG.
Is a cross-sectional view of the paper quality sensor when there is no recording medium, FIG. 3 is a cross-sectional view of the paper quality sensor when the recording medium passes, and FIG. 4 is a cross-sectional view of the paper quality sensor when the recording medium is deformed and conveyed. 5 is a block diagram illustrating a paper quality detection circuit, FIG. 6 is a diagram illustrating a paper quality sensor and an oscillation circuit, FIG. 7 is a diagram illustrating a circuit configuration of a differential input / output buffer included in the oscillation circuit, and FIG. 9 is an explanatory diagram of a paper quality sensor using a layer oscillation circuit, FIG. 9 is a diagram illustrating the relationship between the weight of a recording medium and a fixing energy factor, FIG. 10 is an overall configuration diagram of the image forming apparatus according to the present embodiment, and FIGS. It is a figure which shows the test result example of the paper quality sensor which used this invention, and its detection circuit.

(Image Forming Apparatus) The image forming apparatus shown in FIG. 10 is a laser beam printer (hereinafter referred to as LBP) adopting an electrophotographic system, and the entire structure of the LBP will be described first. The recording medium 3 is conveyed in the direction of the arrow along the conveying path indicated by the dotted line in the figure. First, the recording medium 3 fed from a feeding unit (not shown) is fed directly below the photoconductor drum 5 via the transport roller 4. The photosensitive drum 5 is first charged to a negative potential by the primary charger 6.
Then, the scanning laser scanning light 7 is applied to the photosensitive drum 5. The scanning laser scanning light 7 generally controls turning on and off of a laser diode according to image data, converts the generated laser light into an appropriate parallel light (beam) while narrowing it with a collimator lens, and a rotating mirror such as a polygon mirror. To generate scanning laser light, and
The .theta. lens is formed so as to scan the photosensitive drum 5 at a constant speed.

The surface potential of the portion of the photosensitive drum 5 irradiated with the laser beam rises above the negative potential charged by the primary charger 6, and an electrostatic latent image is formed. Next, a place where the laser light is irradiated by the toner supply unit 8 that generates toner particles charged to a negative potential (electrostatic latent image)
Toner is adhered only to to form a toner image. The transfer charger 9 provided on the back side of the conveyed recording medium 3 is charged to a positive potential, and the toner image attached to the photosensitive drum 5 is transferred to the recording medium 3. Finally, the recording medium 3 to which the toner adheres is passed through a fixing portion including a heating roller 10 and a fixing roller 11 for generating an appropriate pressure. As a result, the toner attached to the recording medium 3 changes from a particle state to a gel state, is entangled with the fibers of the recording medium 3 and is firmly fixed, and after the stable image is formed on the recording medium 3, the recording medium 3 is out of the machine. Is discharged to. The heating roller 10
Is driven by the drive circuit 12 so as to obtain appropriate heat energy.

Further, in the present embodiment, a paper quality detection circuit 1 and a fixing energy calculation unit 2 which will be described in detail below are provided on the conveyance path on the supply side of the photosensitive drum 5. The transmission frequency data 16 output from the oscillation circuit 13 of the paper quality detection circuit 1 is input to the fixing energy calculation unit 2 and outputs a fixing energy control signal to the driving circuit 12, and the driving circuit 12 controls the fixing energy based on this. To do.

(Paper Quality Detection Circuit) As shown in FIG. 1, the paper quality detection circuit 1 has conductors 1a and 1b having an area S and an area of 2 × S or more arranged so as to face the conductors 1a and 1b. And the conductor 1c. The conductors 1a, 1b and the conductor 1c have a fixed gap G larger than the thickness of the recording medium.
It is arranged with. Terminals A and B are connected to the conductors 1a and 1b, respectively, and are connected to the oscillation circuit 13 (see FIG. 5). In the figure, the conductor 1c is connected to the terminal C.
However, this is not essential in the present embodiment as will be described later.

As shown in FIG. 2, the recording medium 3 passes through the gap G. The preceding recording medium is 3a and the succeeding recording medium is 3b. The gap G is, for example, 1.6 mm,
Insertion openings 1d and 1e for smooth conveyance of the recording medium
Is made of an insulator and has a tapered shape. Insertion slot 1
The entrances of d and 1e are larger than the gap G between the conductors 1a and 1b and the conductor 1c, for example, about 5 mm, so that the deformation of the recording medium 3 can be dealt with. Also,
On the surfaces of the conductors 1a, 1b, 1c, the insulating treatment film 1f,
It is advisable to provide 1g and 1h.

As shown in FIG. 5, the terminal A of the conductor 1a,
The terminal B of the conductor 1b is connected to the oscillation circuit 13.
The output of the oscillation circuit 13 is input to the frequency detection circuit 15, and the frequency detection circuit 15 outputs the transmission frequency data 16 every time the detection control pulse signal 14 is input.

The oscillator circuit 13 can be constructed, for example, as shown in FIG. Differential input / output buffer 2 in FIG.
1 and 22: the positive output of the differential input / output buffer 21 is input to the positive input of the differential input / output buffer 22, and the negative output of the differential input / output buffer 21 is input to the negative input of the differential input / output buffer 22. The positive output of the output buffer 22 is connected to the negative input of the differential input / output buffer 21, and the negative output of the differential input / output buffer 22 is connected to the positive input of the differential input / output buffer 21, and the terminal A of the paper quality sensor 1 of the present invention is connected. Is connected to the negative input of the differential input / output buffer 22, and the terminal B is connected to the positive input of the differential input / output buffer 22.

The positive output of the differential input / output buffer 22 is connected to the positive input of the comparator 23, and the negative output of the differential input / output buffer 22 is connected to the negative input of the comparator 23.
The output of 23 becomes the output of the oscillation circuit 13. Although the terminal C of the conductor 1c is not connected in FIG. 5, when the oscillator circuit shown in FIG. 6 is used, the terminal C can be regarded as a virtual GND. Of course, you may actually connect it to GND.

The differential input / output buffers 21 and 22 shown in FIG. 6 can be constructed as shown in FIG. 7, for example. nMOS transistor MN
The sources of 1 and MN2 are both connected to GND, and the voltage VB is input to both gates. The drain of the nMOS transistor MN1 is the gate of the pMOS transistors MP1 to MP3 and the pMOS
It is connected to the drain of the transistor MP1. The sources of the pMOS transistors MP1 to MP3 are all connected to VCC. The drain of the nMOS transistor MN2 is connected to the sources of the nMOS transistors MN3 and MN4. The gate of the nMOS transistor MN3 becomes the positive input terminal PI, and the gate of the nMOS transistor MN4 becomes the negative input terminal NI. The drain of the nMOS transistor MN3 is connected to the drain of the pMOS transistor MP2 to serve as the negative output terminal NO, and the nMOS transistor MN4
The drain of is connected to the drain of the pMOS transistor MP3 and serves as the positive output terminal PO. In addition, the source of the nMOS transistor MN5 is connected to the terminal NO and the source of the nMOS transistor MN6 is connected to the terminal PO for stable circuit operation. The drains and gates of the nMOS transistors MN5 and MN6 are all connected to VCC.

(Description of Operation of Paper Quality Detection Circuit) Next, the operation of the paper quality detection circuit 1 shown in FIG. 5 will be described. First, FIG. 2 shows a state in which the preceding recording medium 3a and the succeeding recording medium 3b are being passed. At this time, the detection control pulse signal 14 is input to the frequency detection circuit 15 to obtain the oscillation frequency data Fo (first information). The detection of the oscillation frequency data Fo must be started and ended without fail between the conductors 1a and 1c and the period in which the recording media 3a and 3b do not exist between the conductors 1b and 1c.

Next, FIG. 3 shows the succeeding recording medium 3b.
Is completely inserted between the conductors 1a and 1c and between the conductors 1b and 1c. At this time, the detection control pulse signal 14 is input again to the frequency detection circuit 15 to obtain the oscillation frequency data Fx (second information). The oscillation frequency data Fx must be detected with the recording medium 3b completely inserted between the conductors 1a and 1c and between the conductors 1b and 1c.

Since the LBP described with reference to FIG. 10 is provided with a detection means (not shown) for detecting the leading end of the recording medium in order to accurately form an image on the recording medium 3, FIGS. It is easy to surely measure the oscillation frequencies of the Fo and Fx in the above state. If possible, the oscillation frequency data Fx should be as short as possible from the detection of the oscillation frequency data Fo.
Is desirable to detect.

In the fixing energy calculation unit 2, the fixing energy factor Ex is calculated according to the presence / absence of the recording medium 3 in the paper quality detection circuit 1 by the calculation shown in Formula 1 obtained by subtracting 1 from the ratio of the oscillation frequency data Fo and F1, for example. .

Ex = (Fo / Fx) -1 (Formula 1) Conductors 1a to 1c are capacitors (Cac and Cbc shown in FIG. 5).
When modeled as, the oscillation frequency detection is to detect the capacitance value change. In other words, it means that the change in the dielectric constant of the gap G is detected.

When the paper quality detection circuit 1 according to this embodiment and the oscillation circuit 13 having the differential circuit structure as shown in FIG. 6 are used, only one side 1ac (see FIG. 1) of the paper quality sensor as shown in FIG. Although the detection sensitivity (Fo / Fx value) will be smaller than when using an oscillation circuit with a single-layer circuit structure that has the structure and inverter INV1 and resistor R1, the effect on disturbance noise such as electromagnetic waves Can be reduced. Further, in the single-layer oscillation circuit system as shown in FIG. 8, the conductors serving as the sensor portions are arranged on both sides (front and back) of the recording medium. Therefore, when actually mounted on the LBP, the conductor and the oscillator are oscillated. The wiring to the circuit becomes very long, and the structure is very susceptible to disturbance noise, which is not practical. On the other hand, the use of the paper quality detection circuit 1 according to the present embodiment has a great effect that the recording medium can be mounted on only one side of the front and back sides of the recording medium, which is very practical. Further, even if disturbance noise is introduced into the conductor 1c, the oscillation circuit 13 has a differential structure, which is not easily affected.

The required fixing heat energy is the above-mentioned three fixing condition factors (weight of recording medium, coarse density of fiber,
Table 1 shows a conceptual summary of the relationship between the required thermal energy and the dielectric constant when the other two factors are individually fixed with respect to the water content).

[0027]

[Table 1] ↑ in Table 1 means that, for example, as the weight of the recording medium increases, the required heat energy also increases and the dielectric constant also increases. Similarly, the same applies to the coarse density and the water content of the fiber.

As shown in Table 1, the paper quality detection circuit 1 cannot inherently detect the coarse density of the fiber. But,
Since a pressure is applied to the recording medium in the LBP fixing process, the factor due to the coarse density of the fibers is reduced if the water content is constant. The water content also increases with respect to the fiber coarse density, and the effect of humidity increases with the fiber coarse density.

The present inventor actually created the detection circuit of FIG. 8 including only the above-mentioned paper quality sensor 1ac, and conducted an experiment on 10 types of recording media. Under the test conditions shown in Table 2, the thickness of the paper is shown by the weight (g / m ² ) per unit area that is generally adopted. The weight of each sample recording medium is a value at room temperature / normal humidity.

[0030]

[Table 2]

FIG. 11 shows an example of the test results. Y axis
(Fo / Fx−1) × 10 ⁶ , which shows the change in oscillation frequency (dielectric constant) in ppm by the presence or absence of the recording medium. The X axis indicates the sample number of the recording medium. This result almost expresses the tendency of the magnitude relationship of the fixing heat energy required for each sample paper.

FIG. 12 shows the oscillation frequency depending on the presence or absence of the recording medium.
In this graph, the change in (dielectric constant) is taken as the Y axis, and the X axis is plotted as the weight of each recording medium. It can be seen that the paper quality detection circuit 1 detects the weight of the recording medium extremely appropriately as indicated by the first-order approximation formula (y = a0x + b0) indicated by the dotted line. The slope a0 and the intercept b0 of the first-order approximation formula are generally determined by the area S of the paper quality sensor, the interval G, and the delay time of the INV circuit in the oscillation circuit 13. That is, when the configuration of the paper quality sensor 1ac and the detection circuit of FIG. 8 including the same is set, the recording medium can be absolutely detected with respect to the fixing condition. Since the paper quality sensor 1ac does not destroy the detection principle described above even if the recording medium 3b is deformed and conveyed as shown in FIG.
Suitable as a BP.

Furthermore, since the oscillation frequency is several tens of MHz under the experimental conditions, the time required to measure the oscillation frequencies Fo and Fx once with an accuracy of about 100 ppm is 1 msec or less, and the averaging (division) is performed. Even if you measure it, you can get the data in about 10msec.
Is also available.

From the above experiment, when the paper quality sensor (1ac and 1bc) according to the present embodiment and the paper quality detection circuit 1 having the oscillation circuit 13 of FIG. 6 are used, the relationship between the fixing energy factor Ex and the weight M of the recording medium is used. As shown in FIG. 9, the slope a1 of the first-order approximation formula is smaller than the slope a0 of the oscillation circuit having the single-layer structure. In actual operation, the fixing energy calculation unit 2 calculates the weight M = kx (g) of the recording medium from the relational expression Ex = f (M) of the fixing energy factor Ex to the weight M of the recording medium given in advance. It is calculated and used as one of the factors that determine the fixing energy.

As described above, in the configuration of the paper quality detection circuit according to this embodiment, the weight of the recording medium (fiber amount +
It becomes possible to detect the paper quality indicated by (content of water content) with one sensor comprehensively in a short time, and it is possible to detect the required heat energy in the fixing process from the detected paper quality, and the LBP system can be used for various recording media. On the other hand, it is possible to perform appropriate image formation that has not been considered in the past. Furthermore, the paper quality detection circuit according to the present embodiment has an effect that it is sufficient to provide wiring only on one side of the conveyance path of the recording medium, and it is difficult to be affected by disturbance noise. Further, since it is basically insensitive to the color of the recording medium, it is convenient when used for the LBP engine. In addition, the paper quality detection circuit can be easily realized with a small size and an inexpensive structure, so that the application range is wide.

Second Embodiment A second embodiment of the paper quality detection circuit and the image forming apparatus according to the present invention will be described with reference to the drawings. 13 is a conceptual diagram of the paper quality sensor according to the present embodiment, FIG. 14 is a cross-sectional view of the first conductor pair when the recording medium does not exist, and FIG. 15 is a cross-section of the first conductor pair when the recording medium passes. FIG. 16 is a sectional view of the first conductor pair when the recording medium is deformed and conveyed, FIG. 17 is a sectional view of the second conductor pair when the recording medium is not present, and FIG. 18 is a sectional view of the recording medium. FIG. 19 and FIG. 20 are enlarged sectional views for explaining the deformation of the recording medium due to pressure when passing through the second conductor pair, FIG. 21 is a block diagram for explaining the paper quality detection circuit, and FIG. FIG. 23 is an explanatory diagram of a paper quality sensor using a layer oscillation circuit, FIG. 23 is a diagram showing the relationship between the coarse density and the fixing energy factor with the weight of the recording medium as a parameter, and FIG. 24 is a diagram showing the relationship between the weight of the recording medium and the fixing energy factor. Fig. 25 shows the relationship between the roughness density and the fixing energy factor with the weight of the recording medium as a parameter. A to figure the overlapping portions of the description and the first embodiment will be omitted with the same reference numerals.

(Paper Quality Detection Circuit) As shown in FIG. 13, the paper quality detection circuit 1 according to this embodiment has a first conductor pair 25 composed of two parallel flat conductors 25a and 25b having an area S, and an area The second conductor pair 26 is composed of two parallel plate conductors 26a and 26b of S. The first conductor pair 25 is installed at a fixed interval G larger than the thickness of the recording medium, and the second conductor pair 26 is installed so as to press the recording medium with an appropriate pressure F. Terminals A and B are connected to the conductors 25a and 25b, respectively, and terminals C and D are connected to the conductors 26a and 26b, respectively.

FIG. 2 shows a first conductor pair 25 having terminals A and B.
FIG. The gap G between the conductors 25a and 25b is, for example, 1.6 mm, as in the first embodiment, and the insertion ports 25c and 25d are made of an insulator and have a tapered shape in order to facilitate the transport of the recording medium. . The inlets of the insertion ports 25c and 25d are larger than the gap G between the conductors 25a and 25b, and are, for example, 5
By setting it to about mm, it is possible to cope with the deformation of the recording medium 3. Insulating films 25e and 25f are preferably provided on the surfaces of the conductors 25a and 25b.

FIG. 17 shows a second conductor pair 26 having terminals C and D.
FIG. The pressure F applied to the conductors 26a and 26b is
For example, the pressure is set to an appropriate pressure that does not hinder the smooth conveyance of the recording medium and allows the recording medium and the conductor to be sufficiently adhered. Furthermore, it is preferable that the insertion openings 26c and 26d have a shape with a certain curvature as shown in the drawing so that the deformed recording medium can be smoothly conveyed. It should be noted that a tapered shape may be used as shown in FIG. The surfaces of the conductors 26a and 26b have insulating treatment films 26e and 26f with a thickness of d0.
Is provided to take measures against insulation.

As shown in FIG. 21, the terminals A and B of the first conductor pair 25 are connected to the first oscillator circuit 13a, and the second conductor pair 25 is connected to the second oscillator pair 13a.
The terminals C and D of 26 are connected to the second oscillation circuit 13b. The first oscillator circuits 13a and 13b are, for example, as shown in FIGS.
It can be configured as shown in. Oscillator circuit 13a,
The output of 13b is input to the frequency detection circuits 15a and 15b, and the transmission frequency data 16a and 16b are output. Detection control pulse signals 14a and 14b are input to the frequency detection circuits 15a and 15b, and the transmission frequency data 16a and 16b are input each time the detection control pulse signals 14a and 14b are input.
b is output.

(Description of Operation of Paper Quality Detection Circuit) Next, the operation of the paper quality detection circuit 1 shown in FIG. 21 will be described. First, the operation of the detection circuit using the first conductor pair 25 will be described. FIG. 14 shows a state where the preceding recording medium 3a and the succeeding recording medium 3b are passing. At this time, the detection control pulse signal 14a is generated to obtain the transmission frequency data Fo1 (third information).
The transmission frequency data Fo1 must be detected with conductors 25a and 25b.
Started within a period when the recording media 3a, 3b do not exist between
I have to finish.

FIG. 15 shows a state in which the succeeding recording medium 3b is completely inserted between the conductors 25a and 25b. At this time, the detection control pulse signal 14a is input again to the frequency detection circuit 15a to obtain the transmission frequency data Fx1 (fourth information). The transmission frequency data Fx1 must be detected with the recording medium 3b completely inserted between the conductors 25a and 25b.

Since the LBP described with reference to FIG. 10 is provided with detection means (not shown) for detecting the leading end of the recording medium in order to accurately form an image on the recording medium 3, FIGS. It is easy to reliably measure the oscillation frequencies of Fo1 and Fx1 in the above state. If possible, it is desirable to detect the oscillation frequency data Fx1 within as short a period as possible after the detection of the oscillation frequency data Fo1. Further, in the detection of Fx1, it is not necessary to perform measurement while the recording medium 3b is inserted between the conductors 25a and 25b, and the short time set by the user while the detection condition of Fx1 is established. (Several 10 msec or less)
Only the measurement may be performed.

Next, the operation of the detection circuit using the second conductor pair 26 will be described. FIG. 17 shows the preceding recording medium 3a.
And the following recording medium 3b is being passed. This time,
Generates the detection control pulse signal 14b to generate the transmission frequency data.
Obtain Fo2 (6th information). Be sure to detect the transmission frequency data Fo2 between the recording mediums 3a and 3b between the conductors 26a and 26b.
It must start and end within the period when b does not exist.

FIG. 18 shows a state in which the succeeding recording medium 3b is completely inserted between the conductors 26a and 26b. At this time, the detection control pulse signal 14b is input to the frequency detection circuit 15b again to obtain the transmission frequency data Fx2. The detection of the transmission frequency data Fx2 must always be performed with the recording medium 3b completely inserted between the conductors 26a and 26b. The frequency measurement of Fo2 and Fx2 can be easily performed reliably for the same reason as Fo1 and Fx1.

Since the second conductor pair 26 is greatly affected by the surface condition of the recording medium 3, if the bent recording medium 3 is inserted during the short measuring period, an erroneous detection is made. , Unable to determine the correct fixing energy. Therefore, in order to solve this problem, it is desirable to measure the transmission frequency data Fx2 as long as possible.

The fixing energy calculation unit 2 calculates the fixing energy factors Ex1 and Ex2 according to the presence or absence of the recording medium 3 in the paper quality detection circuit 1, for example, by the calculation shown in the following formulas 2 and 3.

Ex1 = (Fo1 / Fx1) -1 (Equation 2) Ex2 = 1- (Fo2 / Fx2) (Equation 3) The first conductor pair 25 and the second conductor pair 26 are capacitors (Cx shown in FIG. 21). , Cy), the oscillation frequency detection is the detection of the capacitance value change.

Here, the first conductor pair 25 and the second conductor pair 26
The operating principle of is explained. First, the first conductor pair 25 will be described. Since the first conductor pair 25 has a fixed gap G, the conductor 25 can be used when the recording medium is not inserted.
The permittivity between a and 25b is the permittivity εa of air. When the recording medium is completely inserted, the conductor 25
The permittivity between a and 25b is a function f (εa, εp) of the permittivity εa of air and the permittivity εp of the recording medium. At this time,
It is clear that εa <f (εa, εp), and the capacitance of the capacitor changes due to this change in the dielectric constant, resulting in a difference in the transmission frequency. Furthermore, as the weight of the recording medium increases (the amount of fibers increases), the dielectric constant given by the function f also increases, and the capacitance of the capacitor increases. Therefore, the fixing energy factor Ex1 has a small value when the weight of the recording medium is light (when the fiber amount is small), and has a large value when the weight of the recording medium is heavy (when the fiber amount is large). Even if the recording medium 3b is deformed and conveyed as shown in FIG. 16, the detection principle described above is not broken.

By the way, regarding the first conductor pair 25, the necessary heat energy for fixing is different from the above-mentioned three fixing condition factors (weight of recording medium, coarse density of fibers, moisture content) separately for the other two. A conceptual summary of the relationship between the required thermal energy and the permittivity when the two factors are fixed is shown in Table 1 above. Then, regarding the block of the paper quality detection circuit including the first conductor pair 25, the first oscillation circuit 13a, and the frequency detection circuit 15a, as in the case of Table 2 above, for 10 types of recording media, under normal temperature / normal humidity environment. As a result of the experiment, the same result as shown in FIGS. 11 and 12 was obtained.

However, the first conductor pair 25 cannot detect the coarse density of the fiber as described above. Therefore, it is desirable to detect the coarse density γ of the fiber in order to calculate the appropriate fixing energy for the conveyed recording medium, and the second conductor pair 26 detects this.

Next, the operating principle of the second conductor pair 26 will be described. Since the second conductor pair 26 is configured to press the recording medium with an appropriate pressure F, when the recording medium is not inserted, the conductors 26a and 26b have a thickness of 2 ×, as shown in FIG. They are in contact with each other via the insulating films 26e and 26f of d0. The unit area capacitance at this time is determined by the thickness and dielectric constant of the insulating films 26e and 26f. Also, the figure
As shown in 18, when the recording medium is completely inserted, the distance between the conductors 26a and 26b is increased by the thickness of the recording medium, and the unit area capacity is reduced accordingly.

At this time, since the pressure F is applied between the conductors 26a and 26b, the recording medium 3b is deformed in the portion suppressed by the conductors 26a and 26b. 19 and 20 are enlarged views of this situation.

The recording medium 3C shown in FIG. 19 and the recording medium 3d shown in FIG. 20 have the same fiber amount, the recording medium 3c has a smooth surface and a high fiber coarse density, and the recording medium 3d has a rough surface and a fiber coarse density. Is small. In both cases, the same pressure F is applied to the conductors 26a and 26b, but the distance between the conductors varies depending on the nature of the recording medium. That is, the recording medium 3c shown in FIG. 19 having a high fiber coarse density has a small amount of deformation of the recording medium caused by the pressure F, and the distance between the conductors at that time is d1. Also,
For a recording medium 3d having a small fiber coarse density like the recording medium 3d shown in FIG. 20, the amount of deformation of the recording medium caused by the pressure F is large, and the distance between the conductors at that time is d2, and d1 is

Here, the permittivity between the conductors 26a and 26b depends on the permittivity ε of air due to the voids due to the conductors 26a and 26b and the irregularities on the surface of the recording medium and the voids existing inside the recording medium.
a and a function f (εa, εp) of the permittivity εp of the recording medium, the recording medium is predominantly present between the conductors 26a and 26b. In the state of 19, the capacitance Cy1 of the second conductor pair 26 is Cy1 = εp / d1, and in the state of FIG. 20, the capacitance Cy2 = εa / d2. It is also clear that C0>Cy1> Cy2, where C0 is the capacitance generated in the second conductor pair 26 when the recording medium is not inserted, and that the fixing energy increases as the coarse density γ of the recording medium increases. The factor Ex2 becomes large as shown in FIG.

By the way, with respect to the second conductor pair 26, the necessary fixing energy is the required heat energy and the conductor when the factors such as the weight of the recording medium and the water content are fixed with respect to the coarse density γ of the fiber. Table 3 shows a conceptual summary of the relationship with the distance.

[0057]

[Table 3] ↑ in Table 3 means that as the fiber coarse density increases, the required heat energy increases and the distance between the conductors increases.

Further, with the weight M (fifth information) of the recording medium calculated using Ex1 as in the first embodiment as a parameter, the horizontal axis represents the coarse density γ of the recording medium (eighth information). ), And the vertical axis is the fixing energy factor Ex2, it becomes as shown in FIG. That is, the weight M of the recording medium is calculated using the detection result of the first conductor pair 25, and the fiber coarse density γ is calculated using this and the detection result of the second conductor pair 26. The fixation factor allows the calculation of the appropriate heat energy required for the fixation process.

In actual operation, the fixing energy calculation unit 2 (see FIG. 10) is provided with a calculation unit having a calculation function,
First, the oscillation frequency data sent from the first conductor pair 25
The fixing energy factor Ex1 is calculated from Fo1 and Fx1, and the weight M of the recording medium is determined as shown in FIG.

Next, the fixing energy factor Ex2 is calculated from the oscillation frequency data Fo2 and Fx2 sent from the second conductor pair 26 to determine the coarse density γ of the fiber. At this time, based on the weight M of the recording medium determined by the fixing energy factor Ex1, the weight M of the recording medium included in the fixing energy calculation unit 2
The rough density γ of the fiber is calculated from the table data showing the relationship between the fixing energy factor Ex2 and the rough density γ of the fiber with the parameter. If the weight M of the recording medium determined by the fixing energy factor Ex1 is not in the table data,
As shown in FIG. 25, the coarse density γ of the fiber can be calculated by complementing the two data close to the weight.

The heat energy required for the final fixing process can be determined by the weight M of the recording medium, which is the fixing factor, and the fiber coarse density γ thus obtained.

As described above, in the configuration of the paper quality detection circuit according to this embodiment, the weight of the recording medium (fiber amount +
It becomes possible to detect the paper quality indicated by (content of water content) with two sensors in a short time, and it is possible to detect the required heat energy in the fixing process from the detected paper quality.
The P system can perform appropriate image formation on various recording media, which has never been considered before. Further, since the paper quality detection circuit according to the present embodiment can detect the coarse density of the recording medium, it is possible to more appropriately determine the necessary thermal energy.

[0063]

As described above, in the paper quality detection circuit according to the present invention, the first conductor, the second conductor, and both the first conductor and the second conductor are arranged so as to face each other. By including a third conductor, an oscillation circuit that connects the first conductor and the second conductor, and an oscillation frequency detection circuit that detects the output of the oscillation circuit, the weight of the recording medium (fiber amount) + It is possible to detect the paper quality indicated by (content of water content) with one sensor comprehensively in a short time, and it is possible to detect the required heat energy in the fixing process from the detected paper quality, and the LBP system can use various recording media. On the other hand, it is possible to perform appropriate image formation which has not been considered in the past. Further, it is sufficient to provide the wiring only on one side of the conveyance path of the recording medium, and there is an effect that it is difficult to be affected by the disturbance noise.

Further, the first conductor pair fixedly arranged at an interval allowing the recording medium to pass therethrough, the second conductor pair closely arranged so as to be able to pass the recording medium, and each conductor pair were connected. By having the first and second oscillating circuits, it is possible to detect the paper quality indicated by the weight (fiber amount + water content) of the recording medium with two sensors in a short time, and further detect the coarse density of the recording medium. Therefore, it is possible to more appropriately determine the required heat energy.

Since the paper quality detection circuit according to the present invention is basically insensitive to the color of the recording medium, it is particularly convenient when used in an electrophotographic image forming apparatus. In addition, because the paper quality detection circuit can be easily realized with a small and inexpensive configuration,
Wide range of applications.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a paper quality sensor according to a first embodiment.

FIG. 2 is a cross-sectional view of a paper quality sensor when there is no recording medium.

FIG. 3 is a cross-sectional view of a paper quality sensor when a recording medium passes.

FIG. 4 is a cross-sectional view of a paper quality sensor when a recording medium is deformed and conveyed.

FIG. 5 is a block diagram illustrating a paper quality detection circuit.

FIG. 6 is a diagram illustrating a paper quality sensor and an oscillation circuit.

FIG. 7 is a diagram illustrating a circuit configuration of a differential input / output buffer included in an oscillation circuit.

FIG. 8 is an explanatory diagram of a paper quality sensor using a single-layer oscillation circuit.

FIG. 9 is a diagram illustrating a relationship between the weight of a recording medium and a fixing energy factor.

FIG. 10 is an overall configuration diagram of an image forming apparatus.

FIG. 11 is a diagram showing an example of test results of a paper quality sensor and its detection circuit.

FIG. 12 is a diagram showing an example of test results of a paper quality sensor and its detection circuit.

FIG. 13 is a conceptual diagram of a paper quality sensor according to a second embodiment.

FIG. 14 is a cross-sectional view of the first conductor pair when no recording medium is present.

FIG. 15 is a cross-sectional view of a first conductor pair when a recording medium passes through it.

FIG. 16 is a cross-sectional view of a first conductor pair when a recording medium is deformed and conveyed.

FIG. 17 is a cross-sectional view of a second conductor pair when no recording medium is present.

FIG. 18 is a cross-sectional view of a second conductor pair when a recording medium passes through it.

FIG. 19 is an enlarged cross-sectional view illustrating deformation of the recording medium due to pressure.

FIG. 20 is an enlarged cross-sectional view illustrating deformation of the recording medium due to pressure.

FIG. 21 is a block diagram illustrating a paper quality detection circuit.

FIG. 22 is an explanatory diagram of a paper quality sensor using a single-layer oscillation circuit.

FIG. 23 is a diagram showing the relationship between the coarse density and the fixing energy factor with the weight of the recording medium as a parameter.

FIG. 24 is a diagram showing the relationship between the weight of the recording medium and the fixing energy factor.

FIG. 25 is a diagram showing the relationship between the coarse density and the fixing energy factor with the weight of the recording medium as a parameter.

FIG. 26 is a schematic configuration diagram of an overall configuration of a conventional LBP.

[Explanation of symbols]

MN1 to MN6 ... nMOS transistors MP1 to MP3… pMOS transistors 1… Paper quality detection circuit 1a to 1c ... Conductor 1d, 1e ... insertion slot 1f to 1h ... Insulating film 2… Fixing energy calculator 3 ... Recording medium 4 ... Conveyor roller 5 ... Photosensitive drum 6 ... Primary charger 7 ... Scanning laser scanning light 8 ... Toner supply unit 9 ... Transfer charger 10… Heating roller 11… Fixing roller 12 ... Drive circuit 13 ... Oscillation circuit 13a ... First oscillator circuit 13b ... second oscillator circuit 14… Detection control pulse signal 15… Frequency detection circuit 16… Transmission frequency data 21, 22… Differential I / O buffer 23… Comparator 25 ... 1st conductor pair 25a, 25b ... Conductor 25c, 25d ... insertion slot 25e, 25f ... Insulation film 26… Second conductor pair 26a, 26b ... Conductor 26c, 26d ... insertion slot 26e, 26f ... Insulating film

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2G060 AA08 AA20 AE40 AF11 AG08                       AG11 HA03 HC10 KA09                 2H027 DC02 DE04 DE07 EA12 EC06                 2H033 CA16 CA30

Claims (10)

[Claims] 1. A paper quality detection circuit for detecting the quality of a recording medium used in an image forming apparatus, wherein a first conductor, a second conductor, and both of the first conductor and the second conductor are opposed to each other. A first conductor and an oscillation circuit that connects the first conductor and the second conductor to each other, and an oscillation frequency detection circuit that detects an output of the oscillation circuit. The paper quality detection circuit is characterized in that the second conductor and the third conductor are fixedly arranged with a predetermined interval through which the recording medium can pass continuously. 2. The paper quality detection circuit according to claim 1, wherein the oscillation circuit has a differential circuit structure, and the first conductor and the second conductor are respectively connected to the oscillation circuit. . 3. The oscillation frequency detection circuit is obtained from the oscillation circuit when the recording medium is not completely present between the first conductor or the second conductor and the third conductor. And the second information acquired from the oscillation circuit when the recording medium is completely contained between the first conductor or the second conductor and the third conductor, 2. The paper quality detection circuit according to claim 1, wherein the ratio of the first information and the second information is detected. 4. An insertion port into which the recording medium is inserted is made of an insulator, and a gap between the first conductor and the second conductor and a third conductor is larger than the predetermined gap. 2. The paper quality detection circuit according to claim 1, wherein the paper quality detection circuit is arranged in. 5. The first conductor, the second conductor, and the third conductor
The surface of the conductor is covered with an insulating film.
The paper quality detection circuit described. 6. A paper quality detection circuit for detecting the quality of a recording medium used in an image forming apparatus, comprising: a first conductor pair fixedly arranged at an interval through which the recording medium can pass; and a first conductor pair. A first oscillation circuit connected to at least one terminal of the first conductor pair, a second conductor pair closely arranged so that the recording medium can pass therethrough, and A terminal provided on each of the two conductor pairs, a second oscillator circuit connected to at least one terminal of the second conductor pair, and an oscillator for detecting outputs of the first oscillator circuit and the second oscillator circuit. A paper quality detection circuit having a frequency detection circuit. 7. The paper quality detection circuit has an arithmetic unit, and the oscillation frequency detection circuit is a third oscillation circuit obtained from the first oscillation circuit when the recording medium is not present in the first conductor pair. Information and fourth information obtained from the first oscillation circuit when the recording medium is included in the first conductor pair in a predetermined positional relationship, and the third information and the fourth information are obtained. 7. The ratio of the information of 1. is detected, and the arithmetic unit determines the fifth information by using the ratio detected by the transmission frequency detection circuit.
The paper quality detection circuit described. 8. The oscillation frequency detection circuit includes sixth information obtained from the second oscillation circuit when the recording medium is not present in the second conductor pair, and the sixth information in the second conductor pair. Acquiring the seventh information acquired from the second oscillation circuit when the recording medium is included in a predetermined positional relationship, detecting the ratio of the sixth information to the seventh information, 8. The paper quality detection circuit according to claim 7, wherein the eighth information is determined using the ratio detected by the transmission frequency detection circuit and the fifth information. 9. An insertion port into which the recording medium is inserted is made of an insulator, and the insulators on both sides of the insertion port are arranged at intervals larger than an interval at which the recording medium of the first conductor pair can pass. The paper quality detection circuit according to claim 6, wherein the paper quality detection circuit is arranged. 10. An image forming apparatus comprising: an image forming unit that forms an image on a sheet; a sheet conveying apparatus that conveys the sheet; and the paper quality detection circuit according to claim 1. .