JP2003112840A - Paper type determination device and method, storage medium, and image forming apparatus having the paper type determination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper type discriminating device and an image forming device equipped with the same capable of discriminating paper such as rough paper and bond paper having different surface smoothness from plain paper. SOLUTION: This paper type discriminating device 70 is provided with a weight detector 1, a paper thickness detector 2, an arithmetic part 64, a CPU 50 having a paper type discriminating part 67 and an image forming condition control part 68. The arithmetic part 64 calculates density based on the weight of a recording paper P detected by the weight detector 1 and the paper thickness of the recording paper P detected by the paper thickness detector 2. The image forming condition control part 68 carries out the change of an image forming condition in accordance with the paper type discriminated based on the weight and density by the paper type discriminating part 67.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper type discriminating apparatus and method, a storage medium, and an image forming apparatus having the paper type discriminating apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus using electrophotographic technology, optimum process conditions such as transfer conditions, fixing conditions, transport conditions and the like differ depending on the paper type and have a great influence on the image quality. In particular, rough paper and bond paper, which have low surface smoothness (there are many irregularities on the surface of the paper), are better than coated paper, which has high surface smoothness (there are few irregularities on the surface of the paper) (hereinafter referred to as “plain paper”). Since the specific heat is low due to the low density of the internal fibers, the heat transfer amount at the time of toner fixing is reduced, and the toner fixability is reduced. Cannot be fixed in. Therefore, the conventional image forming apparatus detects the paper thickness of the recording paper and changes the process condition according to the detected paper thickness.

[0003]

However, if only the paper thickness is used, whether the recording paper is rough paper having low surface smoothness or thick plain paper having high surface smoothness, and further, thin rough paper or bond is used. I can't even tell if it's paper. Therefore, it is not possible to set the process conditions according to the surface smoothness of the recording paper. For example, NEENHA Bond (trade name) 64 g paper and Xerox
The same process condition was given to 75g paper of 4024 (trade name), which caused a problem that the process condition was not optimal.

Further, a paper type discriminating apparatus capable of discriminating a paper type such as a rough paper by detecting the surface smoothness (concavity and convexity of the surface) of the recording paper is strict in optical installation conditions. Therefore, it is expensive and almost never installed in a normal image forming apparatus.

An object of the present invention is to provide a paper type discriminating apparatus capable of discriminating a recording sheet having a surface smoothness different from that of plain paper such as rough paper and bond paper, and an image forming apparatus having the apparatus. .

[0006]

In order to achieve the above object, a paper type discriminating apparatus according to claim 1 is a paper type discriminating apparatus provided with a paper thickness detecting means for detecting the paper thickness of a recording sheet. A weight detection unit that detects the weight of the paper, a calculation unit that calculates the density of the recording paper based on the detected paper thickness and the detected weight, the detected paper thickness and the calculated density And a discriminating means for discriminating the paper type of the recording paper based on the above.

A paper type discriminating apparatus according to a second aspect of the present invention is the first aspect.
In the paper type discriminating apparatus described above, the weighing detection means is an irradiation means for irradiating the recording paper with a constant amount of light, and a transmitted light amount measurement for measuring a transmitted light amount of the irradiated light that has passed through the recording paper. Means for calculating the ratio of the transmitted light amount when the recording paper is present to the transmitted light amount when the recording paper is not present, and calculating the weighing amount of the recording paper based on the ratio of the transmitted light amount. Characterize.

A paper type discriminating apparatus according to a third aspect of the present invention is the first aspect.
Alternatively, in the paper type discriminating apparatus according to the second aspect, the paper thickness detecting unit measures a displacement between another irradiating unit that irradiates the recording paper with a constant light amount of light and a barycentric position of the reflected light of the irradiated light. And a displacement measuring means for calculating a difference between the displacement when the recording paper is not present and the displacement when the recording paper is present, and calculating a paper thickness of the recording paper based on the difference in the displacement. Is characterized by.

According to a fourth aspect of the present invention, there is provided a paper type discriminating apparatus.
Alternatively, in the paper type discriminating apparatus according to the second aspect, the paper thickness detecting means includes a nipping means for nipping the recording paper and a displacement measuring means for measuring a displacement of the nipping means, and the displacement in the absence of the recording paper. And a difference between the displacement when the recording paper is present and the displacement, and the paper thickness of the recording paper is calculated based on the difference between the displacements.

According to a fifth aspect of the present invention, there is provided a paper type discriminating apparatus.
Alternatively, in the paper type discriminating apparatus according to the second aspect, the paper thickness detecting means includes a charge accumulating means for accumulating electric charges and a charge amount measuring means for measuring an amount of the accumulated electric charges, The paper thickness of the recording paper is calculated based on the amount.

An image forming apparatus according to a sixth aspect of the present invention is an image forming apparatus including: a reading unit that reads a document and an image forming unit that forms an image of the read document on a recording sheet. It is characterized by comprising the paper type discriminating apparatus according to any one of the items.

An image forming apparatus according to a seventh aspect is the image forming apparatus according to the sixth aspect.
The image forming apparatus described above is characterized by comprising control means for controlling so as to change the image forming condition of the image forming means in accordance with the judged paper type.

According to a eighth aspect of the present invention, there is provided a paper type determining method including a paper thickness detecting step of detecting a paper thickness of the recording paper, and a weight detecting step of detecting a weight of the recording paper and the detected weight. Calculating step for calculating the density of the recording sheet based on the detected sheet thickness and the detected weight, and determining step for determining the recording sheet type based on the detected sheet thickness and the calculated density And is provided.

According to a ninth aspect of the present invention, there is provided a paper type identification method according to the eighth aspect.
In the paper type determination method described above, the weighing detection step is an irradiation step of irradiating the recording paper with a constant amount of light, and a transmitted light amount measurement step of measuring the amount of light of the irradiated light that has passed through the recording paper. And calculating a ratio of the transmitted light amount when the recording paper is present to the transmitted light amount when the recording paper is not present, and calculating a weighing amount of the recording paper based on the ratio of the transmitted light amount. And

According to a tenth aspect of the present invention, there is provided a paper type determination method according to the eighth or ninth aspect, wherein the paper thickness detecting step includes another irradiation step of irradiating the recording paper with a constant amount of light. A displacement measuring step of measuring a displacement of the irradiated light from a barycentric position of reflected light, and calculating a difference between the displacement when the recording paper is not present and the displacement when the recording paper is present. The paper thickness of the recording paper is calculated based on the difference in the displacement.

The paper type determining method according to claim 11 is the paper type determining method according to claim 8 or 9, wherein the recording paper is pinched by a pinching means, and the paper thickness detecting step detects displacement of the pinching means. A displacement measuring step of measuring is provided, and a difference between the displacement when the recording paper is not present and the displacement when the recording paper is present is calculated, and a paper thickness of the recording paper is calculated based on the difference of the displacement. It is characterized by

According to a twelfth aspect of the present invention, there is provided a paper type discrimination method according to the eighth or ninth aspect, wherein the paper thickness detecting step includes an accumulation step of accumulating charges and an amount of the accumulated charges. And a step of measuring a charge amount to be measured, wherein the thickness of the recording paper is detected based on the measured amount of charge.

A storage medium according to claim 13 is a computer-readable storage medium which stores a program for executing a paper type determination method, wherein the program includes a weighing detection module for detecting a weighing of the recording paper, and the detection. An arithmetic module that calculates the density of the recording paper based on the detected paper thickness and the detected weight, and a judgment that determines the paper type of the recording paper based on the detected paper thickness and the calculated density And a module.

[0019]

DETAILED DESCRIPTION OF THE INVENTION An image forming apparatus having a paper type discriminating apparatus according to an embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus having a paper type discriminating apparatus according to an embodiment of the present invention.

In FIG. 1, a laser beam printer 60 as an image forming apparatus forms a toner image on a photosensitive drum 31 based on a laser scanner section 40 for performing a laser scanner and a laser beam from the laser scanner section 40. A printer controller (hereinafter referred to as "CPU") 5 that controls the operation of the cartridge 30 and the laser printer 60.
With 0 and. The laser scanner unit 40 includes a polygon mirror 42 for scanning the photosensitive drum 31 with laser light modulated based on an image signal sent from an external device.
The scanner motor 43, the imaging lens group 44, and the folding mirror are provided. In addition, the process cartridge 30
Is a photosensitive drum 31 required for a known electrophotographic process.
The laser printer 60 is provided with a charging roller 32 for charging the photosensitive drum, a developing blade 34 for developing image data, and a toner storage container 35 for storing toner. Further, the CPU 50 is
M52, ROM 53, timer 54, digital input / output port (hereinafter "I / O port") 55, analog input / output port (hereinafter "A / D port") 56
It is composed of an MPU (microcomputer) 51 having a and an input / output control circuit (not shown).

In the laser beam printer 60, the recording paper P stored in the paper feed cassette 10 is
The pickup roller 13 feeds the paper feed cassette 10 and the paper feed roller 14 feeds the paper feed path. At this time, the paper feed roller 14 and the retard roller 15 forming a pair with the paper feed roller 14 prevent double feeding of the recording paper P.
The recording paper P that has passed the paper feed sensor 16 that is provided downstream of the paper feed roller 14 and detects the paper feed conveyance state is sent by the paper feed conveyance roller 17 to the pre-registration sensor 18 further downstream. The sheet feeding / conveying roller 17 includes the sheet feeding cassette 1
In addition to the recording paper P from 0, the recording paper P from the cassette deck 61 or the manual paper feed tray 62 that sends the manually inserted recording paper P to the transport path is also sent.

The recording paper P conveyed downstream by the pre-registration sensor 18 is detected by a weighing amount detecting device 1 (weighing amount detecting means) shown in FIG. 2 and a sheet thickness detecting device 2 (paper thickness detecting means) shown in FIG. The weight of the recording paper and the paper thickness are detected. The weighing amount detection device 1 and the paper thickness detection device 2 constitute a paper type determination device of FIG. 6 described later.

Then, the recording paper P, which has been weighed and the paper thickness is detected, is sent to the photosensitive drum 31 with timing adjusted by the registration roller pair 19. With this photosensitive drum 31,
The process cartridge 30 forms a toner image necessary for the photographic process on the photosensitive drum 31 based on the laser light from the laser scanner unit 40, and the roller member 33 forms the toner image formed on the photosensitive drum 31 on the recording paper P. To form an image. The recording paper P on which the image has been transferred at the scanner transfer position is subjected to thermal fixing of the toner image by a fixing roller 21 having a halogen heater 20 therein for heating and a pressure roller 22 paired with the fixing roller 21. The sheet is conveyed to the fixing paper discharge sensor 23 which detects the conveying state from the fixing section. The recording paper P that has passed through the fixing paper ejection sensor 23 and is sent to the paper ejection unit passes through a paper ejection sensor 24 that detects the paper conveyance state of the paper ejection unit, and a pair of paper ejection rollers 25 of the laser beam printer 60. It is discharged to the outside.

FIG. 2 is a diagram showing a schematic configuration of the weighing detection device 1 in FIG.

In FIG. 2, the recording paper P is conveyed by the conveyance guide 10.
It is conveyed to a predetermined detection position by 3-106. The transport guides 105 and 106 are respectively the transport guides 10 on the lower side.
The recording paper P is pressed against the 3, 104.

The weighing detection device 1 includes an LED 101 (irradiation means) for irradiating the surface of the recording paper P with a constant amount of light, and an LE.
The phototransistor 102 (transmitted light amount measuring means) for measuring the amount of light transmitted through the recording paper P among the light emitted by the D 101 is provided. The measurement result is stored in the memory 72 connected to the calculation unit 64 described later (FIG. 5). Computing unit 64
The (weighing detecting means) is provided in the CPU 50, and the recording paper P
Based on the amount of transmitted light before and after being conveyed, the ratio of the amount of transmitted light when the recording paper P is present to the amount of transmitted light when the recording paper P is not present (hereinafter referred to as “light transmittance”) is calculated, and the calculation unit 64 The weight of the recording paper P is detected using the graph of FIG.

FIG. 3 is a graph showing the relationship between the light transmittance and the weight of the recording paper P used when the weight detection device 1 in FIG. 2 calculates the weight of the recording paper P.

In FIG. 3, a plot of plain paper (in the figure,
Since the plots (diamonds) and rough paper (triangles in the figure) are on the same curve, it can be seen that the light transmittance is a value that does not depend on the density or the paper thickness. Since the weighed amount is the weight of the recording paper P having a certain area, it corresponds to the amount of fibers existing in the certain area. Here, the amount of light that passes through the recording paper P when the recording paper P is irradiated with light depends on the amount of blocking objects (fibers) existing in the transmission path. Generally, paper with low surface smoothness such as rough paper has a low density of internal fibers, but the amount of transmitted light when irradiating the paper is a value that depends only on the amount of fibers on the transmission path.
The light transmittance is represented by a curve that depends on the weight and does not depend on the density, paper thickness, or the like.

FIG. 4A is a diagram showing a schematic configuration of the paper thickness detecting device 2 in FIG.

In FIG. 4A, the paper thickness detecting device 2 is
Optical reflection type displacement sensor 11 for measuring a length L described later.
0 (displacement measuring means) is provided. The measurement result is stored in the memory 72 connected to the calculation unit 64 described later (FIG. 5).
The calculation unit 64 (paper thickness detecting means) is provided in the CPU 50 (FIG. 5) and calculates a “displacement difference” described later. The optical reflective displacement sensor 110 is an LE that irradiates a detection area with light.
D112 (another irradiation means), a lens 113 that collects the reflected light from the detection area, and a position detection element 114 that detects the position of the center of gravity of the collected reflected light. Arithmetic unit 6
4 is the length L (FIG. 4B) from the center of the position detecting element 114 to the center of gravity of the reflected light is L
By utilizing the change corresponding to the distance from the ED 111 to the reflection position, the difference between the length L without the recording paper P and the length L with the recording paper P (hereinafter referred to as “difference in displacement”).
Is calculated, and the recording paper P is calculated based on the calculation result.
Detects the paper thickness of.

FIG. 5 is a block diagram of a paper type discriminating apparatus composed of the weighing amount detecting apparatus 1 of FIG. 2 and the paper thickness detecting apparatus 2 of FIG.

In FIG. 5, the paper type discriminating device 70 comprises a weighing detecting device 1, a paper thickness detecting device 2 and a CPU 50. The CPU 50 includes an I / O port 55, an A / D port 56, a calculation unit 64, and a paper type determination unit 67 that determines the paper type.
With. The calculation unit 64 includes a memory 72 and a ROM 5
3 is connected, and an image forming condition control unit 68 that sets image forming conditions is connected to the paper type determination device. The CPU 50 is also connected to the motor controller 65 and the heater drive circuit 66. The I / O port 55 sends a signal for executing the weighing and paper thickness detection sequence to the weighing detector 1 and the paper thickness detector 2, and the A / D port 56 detects from the weighing detector 1 and the paper thickness detector 2. Receive the resulting signal.

The computing section 64 independently computes the weighing amount and the sheet thickness of the recording paper P, and then computes the density based on the computation result (computing means). The paper type discriminating unit 67 discriminates the paper type from the weighing and the paper thickness using the graph of FIG. 6 described later, or discriminates the paper type from the paper thickness and the density using the graph of FIG. Means), and transmits the determination result to the image formation control circuit 68. The image formation control circuit 68 sets image formation conditions based on the transmitted determination result, and sends a control signal to the motor control unit 65 and the heater drive circuit 66 (control means).

FIG. 6 is a graph showing the relationship between the weight of the recording paper P and the paper thickness.

In FIG. 6, frame A is a plain paper plot, and frame B is a rough paper plot. These rough and plain paper plots can be separated by a straight line C,
The slope of the straight line C depends on the value obtained by dividing the weight by the paper thickness, that is, the density.

From the graph of FIG. 6, a plot of plain paper A having high surface smoothness and rough paper / bond paper B having low surface smoothness
It can be seen that the plot of can be divided by density.

FIG. 7 is a graph showing the relationship between the paper thickness and the density of the recording paper P.

In FIG. 7, an image forming condition table for a predetermined matrix indicated by a dotted line and a control program for changing the image forming condition according to the paper thickness and density of the recording paper P are stored in the ROM 53 connected to the arithmetic unit 64. By storing in advance, control is performed to change to the optimum image forming condition. For example, as shown by the arrow in FIG.
The lower the density or the thicker the paper thickness, the more the amount of heat for fixing the toner needs to be increased, and the control for changing the toner fixing temperature and the conveyance speed to the optimum conditions according to the density and the paper thickness of the recording paper P. I do.

FIG. 8 is a flow chart of the paper type discriminating process executed by the paper type discriminating apparatus 70 of FIG.

In FIG. 8, first, the amount of transmitted light and the length L (FIG. 4) when the recording paper P is not present at the weighing and paper thickness detection position.
(B) is stored in the memory 72 (step S1), and the recording paper P is conveyed to a predetermined detection position (step S2).

Next, the weighing amount detecting device 1 measures the amount of transmitted light when the recording paper P is present (step S3), and calculates the light transmittance based on the amount of transmitted light measured by the weighing amount detecting device 1 (step S4). ), The weight of the recording paper P is detected (step S5).

On the other hand, the paper thickness detecting device 2 measures the length L when the recording paper P is present (step S6), and calculates the difference in displacement based on the length L measured by the paper thickness detecting device 2. Then, the thickness of the recording paper P is detected (step S7) (step S8).

Further, the density is calculated from the detected paper thickness and the weight (step S9), and the optimum process conditions are calculated according to the matrix shown by the dotted line in FIG. 7 from the two elements of the calculated density and paper thickness. Select (step S1
0).

Next, it is judged whether or not the normal process conditions (fixing temperature, conveyance speed) need to be changed (step S
11) If it is necessary to change the normal process conditions, after changing the process conditions (step S12), on the other hand, if the normal process conditions need not be changed, this process is performed without changing the process conditions. finish.

According to the processing of FIG. 8, the weighing amount and the paper thickness are detected independently (steps S5 and S8), and the density of the recording paper P is calculated based on the detected weighing amount and the paper thickness (step S9). Therefore, it is possible to discriminate a paper (rough paper or bond paper) having a low fixing property and a low surface smoothness. Also,
The image forming apparatus equipped with the above-mentioned paper type discriminating apparatus is operated when it is necessary to change the normal process condition (Y in step S11).
ES) and the process conditions are changed (step S12), so that it is possible to prevent the output of a defective image even when the recording paper P having a low fixing property is conveyed.

FIG. 9 is a flow chart of a modified example of the paper type discrimination processing executed by the paper type discrimination device 70 of FIG.

In FIG. 9, first, the amount of transmitted light and the length L when there is no recording paper P at the weighing and paper thickness detection position are stored in the memory 72 (step S31), and the recording paper P is set at a predetermined detection position. It is conveyed (step S32).

Next, the weighing detection device 1 measures the amount of transmitted light when the recording paper P is present (step S33), and calculates the light transmittance based on the amount of transmitted light measured by the weighing device 1 (step S34). ), It is determined whether or not the recording paper P is thick paper based on the calculated light transmittance (step S).
35). In this determination, for example, when the light transmittance is 15% or less, it is determined to be thick paper.

If the result of the determination in step S35 is that the recording paper P is thick paper, the process conditions are changed to the optimum process conditions for thick paper (step S36), and this processing ends, while if the recording paper P is not thick paper Determines whether or not the recording paper P is an OHT based on the calculated light transmittance (step S3).
7). This determination is performed as OHT when the light transmittance is 60% or more.

If the result of the determination in step S37 is that the recording paper P is OHT, the process conditions are changed to the optimum process conditions for thick paper (step S38), and this processing ends, while if the recording paper P is not OHT. First detects the weight of the recording paper P based on the calculated light transmittance (step S3).
9) Then, the rough paper discriminating process of subsequent steps S39 to S44 is executed.

Next, the paper thickness detecting device 2 measures the length L when the recording paper P is present (step S40), and based on the measurement result regarding the length L received from the paper thickness detecting device 2, the displacement difference is detected. Is calculated (step S41), and the paper thickness of the recording paper P is detected (step S42).

Next, the density is calculated based on the detected weight and the paper thickness (step S43), and it is determined whether or not the recording paper P is a rough paper based on the detected weight and the calculated density. (Step S44). In this determination, for example, when the density is 7.0 × 10 ⁵ g / m ³ or less, it is determined to be rough paper.

As a result of the determination in step S44, when the recording paper P is rough paper, the optimum process conditions for rough paper are changed (step S45), while when it is not rough paper (plain paper). , This process ends without changing the process conditions.

According to the processing of FIG. 9, it is possible to discriminate the paper type of the recording paper P as one of plain paper, rough paper, thick paper, and OHT. When the recording paper P is thick paper or OHT, steps S39- Since the S44 rough paper discriminating process is not executed, the process can be simplified.

FIG. 10 is a diagram showing a schematic configuration of a modification of the paper thickness detecting device 2 of FIG.

In FIG. 10, the paper thickness detecting device 2 includes an upper roller 114 and a lower roller 115 (sandwiching means) for nipping the recording paper P, and a spring 116 for urging the upper roller 114 toward the lower roller 115. Optical reflection type displacement sensor 110a as a paper thickness sensor for detecting the displacement of the upper roller 114.
(Displacement measuring means). The measurement result is stored in the memory 72 connected to the calculation unit 64 (FIG. 5). CPU5
0 has a calculation unit 64 (FIG. 5), and the calculation unit 64 calculates the difference in displacement and detects the paper thickness of the recording paper P based on the difference in displacement. The optical reflective displacement sensor 110a has basically the same configuration as the optical reflective displacement sensor 110.

FIG. 11 is a perspective view of another modification of the paper thickness detecting device 2 of FIG.

In FIG. 11, the paper thickness detecting device 2 is provided with conveying guides 125 and 126 made of an insulating material, which are opposed to each other via spacers 123 and 124. Transport guides 125, 12
At the center of the inner surface of 6, two conductor plates 121 and 122 are provided.
(Charge storage means) is attached to form an air condenser. The area of each of the conductor plates 121 and 122 is 400 mm ² (2
0 mm × 20 mm) and the gap d is 0.5 mm. A voltage V of, for example, 5 volts is applied between the conductor plates 121 and 122 from a constant voltage power source.

At the front and rear ends of the transport guides 125 and 126, roller pairs 127 and 127 and roller pair 12 are provided, respectively.
8,128 are provided. The recording paper P is conveyed by these roller pairs 127, 128, and the conductor plate 121,
Pass between 122.

The thickness of the recording paper P is such that the recording paper P is the conductor plate 12
It can be calculated as follows from the change in the electrostatic capacitance of the air capacitor when passing between 1,122. First, when there is no recording paper P between the conductor plates 121 and 122,
The amount of charge Q ₀ accumulated between the conductor plates 121 and 122 is expressed by the following equation (1).

Q ₀ = C ₀ · V (1) Here, C ₀ is the electrostatic capacitance of the air condenser and is represented by the following equation (2).

C ₀ = ε ₀ · S / d (2) In the equation, ε ₀ is the permittivity of air (= 8.85 × 10 ⁻¹² F /
m).

Then, the recording paper P is printed on the conductor plates 121 and 122.
A charge amount Q accumulated between the conductor plates 121 and 122 when inserted between them is represented by the following equation (3).

Q = C · V (3) Here, C is the capacitance of the air condenser, and is represented by the following equation (4).

C = S / {(t / ε) + (d−t) / ε ₀ } (4) In the formula, t is the thickness of the recording paper P, and ε is the dielectric constant of the recording paper P. This dielectric constant ε shows a substantially constant value (= 2.6 × 10 ⁻¹¹ F / m) regardless of the thickness of the recording paper P.

The above formulas (1) to (4) are applied to the recording paper P.
When the thickness t is rearranged, the following equation is obtained.

[0068]       t = (d / ε₀) / {(S ・ V / d ・ ΔQ) ・ (1-ε₀/ Ε) + (1 / ε ₀ −1 / ε)} (5) In the formula, ΔQ = Q−Q₀Is.

Therefore, for the thickness t of the recording paper P, the charge amount ΔQ accumulated between the conductor plates 121 and 122 is measured by using a measuring means (charge amount measuring means), and the measured charge amount ΔQ is calculated. It can be calculated by using the above equation (5). This calculation is performed by the calculation unit 64.

The paper thickness detection device 2 shown in FIGS. 10 and 11 above.
2 can independently detect the paper thickness as in the paper thickness detection device 2 of FIG. 2. Therefore, the density is calculated from the detected paper thickness, and the optimum image formation according to the matrix based on the paper thickness and the density is performed. By retrieving the condition from the image forming condition table stored in the ROM 53 in FIG. 5, it is possible to control the image forming condition and prevent the defective image output on the recording paper P having a small toner fixing property.

In the present embodiment, the image forming apparatus is a laser beam printer, but the present invention is not limited to this.

The weighing detector 1 using the phototransistor 102 of FIG. 3 has the same structure as that used as a conventional detector for discriminating OHT. Therefore, as in the paper type determination process of FIG. 9, after the weighing detection sequence by the photo sensor is finished, the thick paper and the OHT are determined by the light transmittance, and then the rough paper and the plain paper are used for the other paper types. The control may be performed so as to detect the paper thickness for making the above determination.

Further, it goes without saying that the present invention can be applied to the case where a storage medium storing a program module of software for implementing the above-described embodiment is achieved by supplying a program to a system or an apparatus. Absent. In this case, the program module itself read from the storage medium realizes the novel function of the present invention, and the storage medium storing the program constitutes the present invention.

In the above embodiment, the program module is stored in the ROM 53 in the paper type discriminating apparatus 70, but the storage medium for supplying the program module is a floppy (registered trademark) disk, a hard disk, an optical disk, an optical disk. Magnetic disk, CD-ROM, M
Various types such as O, CD-R, DVD, magnetic tape, and non-volatile memory card are conceivable, but it is not limited to a specific type, and any program capable of storing the above program may be used.

[0075]

As described in detail above, according to the paper type discriminating apparatus of claim 1, the paper type discriminating method of claim 8 and the storage medium of claim 13, the paper thickness of the recording paper and The density is calculated based on the weight, and the paper type is determined based on the detected paper thickness and the calculated density.Therefore, it is necessary to distinguish between rough paper and bond paper that have a different surface smoothness from plain paper. You can

According to the paper type identification device of the second aspect and the paper type identification method of the ninth aspect, the amount of light transmitted through the recording paper out of the constant amount of light applied to the recording paper is measured and measured. Since the light transmittance is calculated based on the amount of transmitted light and the weighing of the recording paper is calculated based on the calculated light transmittance, the weighing of the recording paper can be accurately detected.

A paper type discriminating apparatus according to claim 3,
According to the described paper type determination method, the displacement of the barycentric position of the reflected light of a constant amount of light applied to the recording paper is measured, and the displacement difference is calculated based on the measured displacement of the barycentric position of the reflected light. Since the paper thickness of the recording paper is calculated based on the calculated difference in displacement, the paper thickness of the recording paper can be accurately detected.

A paper type discriminating apparatus according to claim 4,
According to the paper type determination method described, the displacement of the nip portion is measured,
Calculate the difference in displacement based on the measured displacement of the clamping part,
Since the paper thickness of the recording paper is calculated based on the calculated difference in displacement, it is possible to obtain the same effect as the effect of the paper type identification device of claim 3.

A paper type identification device according to claim 5,
According to the paper type determination method described, the amount of accumulated charge is measured, and the paper thickness of the recording paper is calculated based on the measured amount of charge. The same effect can be obtained.

According to the image forming apparatus of the seventh aspect, since the image forming condition is controlled so as to be changed according to the discriminating paper type, even when the recording paper having a low fixing property is conveyed, it is optimal. Image forming conditions can be given.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus having a paper type discriminating apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a weighing detection device 1 in FIG.

3 is a graph showing the relationship between the light transmittance of the recording paper P and the weight used when the weight detection device 1 in FIG. 2 calculates the weight of the recording paper P. FIG.

4A is a diagram showing a schematic configuration of the paper thickness detection device 2 in FIG. 1, and FIG. 4B is a diagram showing a length L measured by the optical reflective displacement sensor 110.

5 is a block diagram of a paper type determination device 70 including the weighing amount detection device 1 of FIG. 2 and the paper thickness detection device of FIG.

FIG. 6 is a graph showing the relationship between the weight of recording paper P and paper thickness.

FIG. 7 is a graph showing the relationship between the paper thickness and the density of recording paper P.

8 is a flowchart of an operation process of the paper type determination device 70 of FIG.

9 is a flowchart of a modified example of the operation process of the paper type determination device 70 of FIG.

10 is a diagram showing a schematic configuration of a modified example of the paper thickness detection device 2 of FIG.

11 is a perspective view of a second modification of the paper thickness detection device 2 of FIG.

[Explanation of symbols]

1 Weighing detection device 2 Paper thickness detector 50 CPU 55 I / O port 56 A / D port 64 arithmetic unit 67 Paper Type Discrimination Section 68 Image forming condition control unit 70 Paper type identification device

Claims (13)

[Claims] 1. A paper type discriminating apparatus comprising a paper thickness detecting means for detecting a paper thickness of a recording paper, a weight detecting means for detecting a weight of the recording paper, the detected paper thickness and the detected weight. A paper calculating means for calculating the density of the recording paper based on the above, and a judging means for judging the paper type of the recording paper based on the detected paper thickness and the calculated density. Species discrimination device. 2. The weighing amount detecting means includes an irradiating means for irradiating the recording paper with a constant amount of light and a transmitted light amount measuring means for measuring a transmitted light amount of the irradiated light which has passed through the recording paper. A ratio of the transmitted light amount when the recording paper is present to the transmitted light amount when the recording paper is not present, and a basis weight of the recording paper is calculated based on the ratio of the transmitted light amount. The paper type determination device according to claim 1. 3. The paper thickness detecting means includes another irradiating means for irradiating the recording paper with a constant amount of light and a displacement measuring means for measuring the displacement of the center of gravity of the reflected light of the irradiated light. The method further comprises calculating a difference between the displacement when the recording sheet is not present and the displacement when the recording sheet is present, and calculating a sheet thickness of the recording sheet based on the difference in the displacement. The paper type identification device described in 1 or 2. 4. The paper thickness detecting means includes a nipping means for nipping the recording paper and a displacement measuring means for measuring the displacement of the nipping means, and the displacement and the recording paper when the recording paper is absent. The paper type discriminating apparatus according to claim 1 or 2, wherein a difference from the displacement at a certain time is calculated, and a paper thickness of the recording paper is calculated based on the difference between the displacements. 5. The paper thickness detecting means includes a charge accumulating means for accumulating electric charges, and a charge amount measuring means for measuring an amount of the accumulated charges, and the paper thickness detecting means includes the charge amount measuring means for measuring the amount of the accumulated charges. 3. The paper type discriminating apparatus according to claim 1, wherein the paper thickness of the recording paper is calculated. 6. An image forming apparatus, comprising: a reading unit for reading a document; and an image forming unit for forming an image of the read document on a recording sheet, wherein the paper according to claim 1. An image forming apparatus comprising a type discriminating device. 7. The image forming apparatus according to claim 6, further comprising a control unit that controls to change the image forming condition of the image forming unit according to the determined paper type. 8. A paper type determining method comprising a paper thickness detecting step of detecting a paper thickness of a recording paper, a weight detecting step of detecting a weight of the recording paper, the detected paper thickness and the detected weight. A recording step of calculating the density of the recording sheet based on the above, and a determination step of determining the type of the recording sheet based on the detected sheet thickness and the calculated density. Species discrimination method. 9. The weighing detection step includes an irradiation step of irradiating the recording paper with a constant amount of light, and a transmitted light amount measurement step of measuring a light amount of the irradiated light that has passed through the recording paper. Wherein the ratio of the transmitted light amount when the recording paper is present to the transmitted light amount when the recording paper is not present is calculated, and the basis weight of the recording paper is calculated based on the ratio of the transmitted light amount. Item 8. The paper type determination method according to item 8. 10. The paper thickness detecting step includes another irradiation step of irradiating the recording paper with a constant amount of light, and a displacement measuring step of measuring a displacement between a center of gravity of reflected light of the irradiated light. And calculating a difference between the displacement when the recording sheet is absent and the displacement when the recording sheet is present,
The paper type determination method according to claim 8 or 9, wherein the paper thickness of the recording paper is calculated based on the difference in the displacement. 11. The recording paper is sandwiched by a sandwiching means, and the paper thickness detecting step includes a displacement measuring step of measuring a displacement of the sandwiching means, and the displacement and the recording paper when the recording paper is absent. 10. The paper type determination method according to claim 8, wherein a difference from the displacement at a certain time is calculated, and the paper thickness of the recording paper is calculated based on the difference between the displacements. 12. The paper thickness detecting step includes an accumulating step of accumulating electric charges and a charge amount measuring step of measuring an amount of the accumulated electric charges, and the recording based on the measured amount of the electric charges. 9. The thickness of paper is detected.
Alternatively, the paper type identification method described in item 9. 13. A computer-readable storage medium storing a program for executing a paper type determination method,
The program is a weight detection module that detects the weight of the recording paper, an arithmetic module that calculates the density of the recording paper based on the detected paper thickness and the detected weight, and the detected paper thickness. And a discrimination module that discriminates the paper type of the recording paper based on the calculated density.