JP2002214855A - Surface condition detecting method, toner quantitative measurement method, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface condition detecting method, whereby a surface condition of a beltlike image carrier, such as a transfer belt or a photoreceptor belt, can be detected accurately, to provide a toner quantitative measurement method whereby a quantity of toner attached to the beltlike image carrier can be measured accurately by the detection method, and to provide an image forming apparatus using the detection method. SOLUTION: After eccentricity components of rollers are obtained from sampling data, the eccentricity components are removed from the sampling output, in order to obtain a cycle profile (step S7). The cycle profile which indicates a surface condition of the intermediate transfer belt, will not include eccentricity components of the rollers and the surface condition of the intermediate transfer belt can be indicted accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface state detecting method for detecting a surface state of a belt-shaped image carrier stretched over a plurality of rollers, and to a method of detecting a surface condition of the belt-shaped image carrier using the detection method. The present invention relates to a method for measuring the amount of toner to be measured, and an image forming apparatus using the method.

[0002]

2. Description of the Related Art Some electrophotographic image forming apparatuses such as printers, copiers and facsimile machines form a toner image on a belt-shaped image carrier. For example, in an apparatus described in Japanese Patent Application Laid-Open No. H11-258872,
Four process units are arranged along a transfer belt (belt-shaped image carrier) stretched over two rollers. Each process unit forms a latent image on the photoreceptor and develops the latent image with toner to form a toner image. The toner images formed by these process units have different toner colors (yellow, cyan, magenta, and black), and the toner images are transferred to the transfer belt so as to overlap each other. Thus, a color image is formed on the transfer belt.

In this apparatus, in order to adjust the image density of a toner image, a toner image (patch image) having a predetermined pattern is formed on a transfer belt, and the density is measured by a density sensor. This density sensor includes a light emitting element that irradiates light to the transfer belt and a light receiving element that receives light reflected from the transfer belt, and calculates the amount of toner adhering to the transfer belt based on the output from the light receiving element. Thus, the image density of the toner image is measured.

[0004]

Incidentally, the amount of light reflected by the transfer belt is affected not only by the toner image formed on the transfer belt but also by the surface condition of the transfer belt. In particular, when the surface state of the transfer belt, for example, the reflectance and the surface roughness are not uniform, the influence of the surface state cannot be ignored. Therefore, a period profile indicating the surface state of the transfer belt may be detected prior to the actual measurement of the toner amount. Specifically, in a state where the toner image is not formed on the transfer belt, the output signal from the light receiving element is sampled while the transfer belt makes one rotation to determine the cycle profile. Then, in the actual toner amount measurement, the output from the light receiving element is corrected based on the periodic profile.
By doing so, the effect of the surface condition of the transfer belt is eliminated, and the accuracy of measuring the toner amount is improved.

However, since the transfer belt is stretched over a plurality of rollers, and some of the rollers have a certain degree of eccentricity, there are the following problems. That is,
In this type of apparatus, the sensor output becomes unstable due to the rotation of the eccentric roller, and the periodic profile obtained as described above is affected by the eccentric component of the roller. No consideration was given to the influence of the transfer belt, and the periodic profile could not be said to accurately indicate the surface condition of the transfer belt. for that reason,
When actually measuring the toner amount, it is difficult to accurately measure the toner amount even if the output from the light receiving element is corrected using the periodic profile.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a surface state detecting method capable of accurately detecting the surface state of a belt-shaped image carrier such as a transfer belt or a photosensitive belt. It is an object of the present invention to provide a toner amount measuring method capable of accurately measuring the amount of toner adhering on a belt-shaped image carrier, and an image forming apparatus using the detecting method.

[0007]

A surface state detecting method according to the present invention is a surface state detecting method for detecting a surface state of a belt-shaped image carrier stretched over a plurality of rollers, and achieves the above object. In order to emit light from the light emitting element to the belt-shaped image carrier that is rotating,
A first step of sampling an output signal from a light receiving element that receives light reflected from the belt-shaped image carrier to obtain a sampling output; a second step of obtaining an eccentric component of the roller from the sampling output; Removing the eccentric component from the sampling output to obtain a periodic profile indicating the surface state of the belt-shaped image carrier.

Further, according to the toner amount measuring method of the present invention, prior to the actual toner amount measurement, the eccentricity component of the roller and the periodic profile indicating the surface state of the belt-shaped image carrier are determined by using the above surface state detecting method. When the image density of the toner image is actually obtained, light is emitted from the light emitting element to the belt-shaped image carrier on which the toner image is formed, and the light reflected from the belt-shaped image carrier is obtained. After sampling the output signal from the light receiving element that receives light, the sampled output is obtained, and the sampled output is corrected by the eccentric component and the cycle profile, and the image density of the toner image is obtained based on the correction value.

Further, the image forming apparatus according to the present invention irradiates light from a light emitting element to a belt-shaped image carrier wrapped around a plurality of rollers, and receives light reflected from the belt-shaped image carrier. An image forming apparatus, comprising: a sensor for receiving a light at the sensor and outputting a signal corresponding to the amount of the received light; and control means for calculating an amount of toner adhering to the belt-shaped image carrier based on an output from the sensor. The amount of toner is determined using an amount measurement method. That is, the control means samples the output signal from the light receiving element while rotating and moving the belt-shaped image carrier, obtains the eccentric component of the roller based on the sampled output, and further removes the eccentric component from the sampled output to remove the belt. A periodic profile indicating the surface state of the belt-shaped image carrier is obtained, and when the image density of the toner image on the belt-shaped image carrier is obtained, a light-receiving element that receives light reflected by the belt-shaped image carrier is used. The output is corrected by the eccentric component and the cycle profile, and the image density of the toner image is obtained based on the correction value.

In the invention having the above-described configuration (surface state detecting method, toner amount measuring method, and image forming apparatus), light is emitted from the light emitting element to the rotating belt-shaped image carrier, and the belt-shaped image carrier is illuminated. Although the light reflected from the carrier is received by the light receiving element, a sampling output can be obtained.
After determining the eccentric component of the roller from the sampling output, the periodic profile is determined by removing the eccentric component from the sampling output. Therefore, this periodic profile accurately indicates the surface state of the belt-shaped image carrier without including the eccentric component of the roller.

The sampling output obtained for actually measuring the toner amount is corrected using the cycle profile accurately obtained in this way, and the toner amount is measured based on the corrected value. Measurement accuracy can be further improved.

Here, a light emitting element is arranged opposite to one of the plurality of rollers so as to sandwich the belt-shaped image carrier, and is wound around the sensor facing roller in the surface area of the belt-shaped image carrier. If it is configured to irradiate the hung winding area with light, fluctuations in the distance (sensing distance) between the sensor and the belt-shaped image carrier are effectively suppressed, and the detection accuracy of the periodic profile is further improved. Further, by using this periodic profile, the accuracy of measuring the amount of toner can be further improved.

[0013]

FIG. 1 is a diagram showing an embodiment of an image forming apparatus according to the present invention. This image forming apparatus includes yellow (Y), cyan (C), magenta (M),
This device forms a full-color image by superimposing four color toners of black (K). When an image signal is given to a control unit (reference numeral 1 in FIG. 2) from an external device such as a host computer, the control unit Thus, each part of the engine unit E is controlled, and an image corresponding to an image signal is formed on a sheet S such as transfer paper, copy paper, or an OHP sheet.

In the engine section E, a toner image can be formed on the photosensitive member 21 of the process unit 2. That is, the process unit 2 includes a photoconductor 21 rotatable in the direction of the arrow in FIG. 1, and further includes a charging roller 22 as a charging unit and a developing roller as a developing unit around the photoconductor 21 along the rotation direction. Developing units 23Y, 23C, 23
M, 23K, and a photoreceptor cleaner blade 24 are arranged, respectively.

In this apparatus, the charging roller 22 is connected to the photosensitive member 2
After the outer peripheral surface of the photoreceptor 21 is uniformly charged by contacting the outer peripheral surface of the photoconductor 1, the exposure unit 3 irradiates the outer peripheral surface of the photoconductor 21 with laser light L. As shown in FIG. 1, the exposure unit 3 includes a light emitting element 31 such as a semiconductor laser that is modulated and driven in accordance with an image signal, and a laser beam L from the light emitting element 31 is rotated by a high-speed motor 32. Incident on a polygon mirror 33 to be formed. The laser beam L reflected by the polygon mirror 33 is transmitted to the lens 34 and the mirror 3
5, the photosensitive drum 21 is scanned in the main scanning direction (a direction perpendicular to the plane of the paper of FIG. 1) to form an electrostatic latent image corresponding to an image signal. Reference numeral 36 denotes a horizontal synchronization reading sensor for obtaining a synchronization signal in the main scanning direction.

The electrostatic latent image thus formed is developed
Is developed with toner. That is, in this embodiment, as the developing unit 23, a developing unit 23Y for yellow, a developing unit 23C for cyan, a developing unit 23M for magenta, and a developing unit 23K for black are arranged along the photoconductor 21 in this order. Have been. These developing units 23Y and 23
C, 23M, and 23K are configured to be freely movable toward and away from the photoreceptor 21, and the four developing units 23Y, 23M, 23C, and 2 according to a command from the control unit 1.
3K selectively contacts the photoconductor 21, and applies a high voltage to apply a toner of a selected color to the surface of the photoconductor 21, thereby causing an electrostatic latent on the photoconductor 21. Reveals an image.

The toner image developed by the developing unit 23 is transferred to the intermediate transfer belt 41 (belt-shaped image carrier) of the transfer unit 4 in a primary transfer area located between the black developing device 23K and the photosensitive member cleaner blade 24. ) Is primarily transferred onto. Also, from the primary transfer area in the circumferential direction (the direction of the arrow in FIG. 1)
A cleaner blade 24 for a photoconductor is disposed at a position where the toner is transferred to the above, and scrapes off toner remaining on the outer peripheral surface of the photoconductor 21 after the primary transfer.

The transfer unit 4 has seven rollers 42 to
The endless intermediate transfer belt 41 is stretched around six rollers 42 to 47 excluding the secondary transfer roller 48. When the color image is transferred to the sheet S, the toner image of each color formed on the photoreceptor 21 is superimposed on the intermediate transfer belt 41 to form a color image, and is taken out from a cassette or a manual feed tray. The sheet S passes through the space between the upper guide member 5U and the lower guide member 5D, is conveyed to the secondary transfer area, and the color image is secondarily transferred to the sheet S to obtain a color image (color printing process). ). When a monochrome image is transferred to the sheet S, only the black toner image on the photoreceptor 21 is formed on the intermediate transfer belt 41, and is conveyed to the secondary transfer area in the same manner as in the case of a color image. The image is transferred to the sheet S to obtain a monochrome image (monochrome printing process).

A belt cleaner 49 is provided to face the roller 46. This belt cleaner 49 is
The cleaning unit removes residual toner remaining on the intermediate transfer belt 41 after the secondary transfer, and has the following configuration. That is, in this belt cleaner 49, the cleaner blade 492 is attached to the cleaner case 491, and the intermediate transfer belt 41 in the cleaner cover 493.
, And driven by a belt cleaner drive unit (not shown).
Reference numeral 494 in FIG. 1 denotes a cleaner rake sheet.

A sensor 40 for detecting a reference position of the intermediate transfer belt 41 is disposed below the roller 43, and a synchronization signal in a sub-scanning direction substantially orthogonal to the main scanning direction, that is, a vertical synchronizing signal. It functions as a vertical synchronization reading sensor for obtaining a signal. Also, the roller 43
A sensor 6 for detecting the amount of toner adhering on the intermediate transfer belt 41 stretched across the intermediate transfer belt 41 is disposed opposite to the roller 43 with the intermediate transfer belt 41 interposed therebetween. Thus, in this embodiment, the roller 43 is the “sensor facing roller” of the present invention.

FIG. 2 is a diagram showing the structure of a sensor for detecting the amount of toner on the intermediate transfer belt. The sensor 6 has a light emitting element 601 such as an LED that irradiates light to a winding area 41 a wound around the roller 43 in the surface area of the intermediate transfer belt 41. The sensor 6 includes a polarizing beam splitter 603 and a light-receiving unit 60 for monitoring the amount of irradiation light in order to adjust the amount of irradiation light.
4 and an irradiation light amount adjustment unit 605 are provided.

The polarization beam splitter 603 includes a light emitting element 601 and an intermediate transfer belt 41 as shown in FIG.
And a p-polarized light having a polarization direction parallel to the incident surface of the irradiation light on the intermediate transfer belt 41,
And s-polarized light having a perpendicular polarization direction. Then, while the p-polarized light is incident on the intermediate transfer belt 41 as it is, the s-polarized light is extracted from the polarization beam splitter 603, and then is incident on the light receiving unit 604 for monitoring the irradiation light amount. The proportional signal is the irradiation light amount adjustment unit 605
Is output to

The irradiation light amount adjusting unit 605 performs feedback control of the light emitting element 601 based on a signal from the light receiving unit 604 and a light amount control signal Slc from the control unit 1 which includes the CPU 11 and the memory 12 and controls the entire apparatus. From the light emitting element 601 to the intermediate transfer belt 41
Is adjusted to a value corresponding to the light amount control signal Slc. Thus, in this embodiment, the irradiation light amount can be changed and adjusted appropriately over a wide range.

In this embodiment, the input offset voltage 641 is applied to the output side of the light receiving element 642 provided in the irradiation light quantity monitoring light receiving unit 604, so long as the light quantity control signal Slc does not exceed a certain signal level. , And the light emitting element 601 is configured to be kept off. The specific electrical configuration is as shown in FIG.
FIG. 3 shows a light receiving unit 60 employed in the apparatus of FIG.
4 is a diagram illustrating an electrical configuration of FIG. This light receiving unit 60
In No. 4, the anode terminal of the light receiving element PS such as a photodiode is connected to the non-inverting input terminal of the operational amplifier OP constituting the current-voltage (I / V) conversion circuit, and is connected to the ground potential via the offset voltage 641. Have been. Further, the cathode terminal of the light receiving element PS is connected to an inverting input terminal of the operational amplifier OP and is connected to an output terminal of the operational amplifier OP via a resistor R. Therefore, when light is incident on the light receiving element PS and a photocurrent i flows, the output voltage V0 from the output terminal of the operational amplifier OP becomes V0 = iR + Voff (where Voff is an offset voltage value),
A signal corresponding to the amount of reflected light is output from the light receiving unit 604. The reason for this configuration will be described below.

When the input offset voltage 651 is not applied, a light quantity characteristic as shown by a broken line in FIG. 4 is exhibited. That is, when the light amount control signal Slc (0) is supplied from the control unit 1 to the irradiation light amount adjusting unit 605, the light emitting element 601 is turned off, and when the signal level of the light amount control signal Slc is increased, the light emitting element 601 is turned on. The irradiation light amount on the transfer belt 41 also increases almost in proportion to the signal level. However, the light amount characteristic may be shifted in parallel as shown by a one-dot chain line or a two-dot chain line shown in FIG. 4 depending on the influence of the ambient temperature, the configuration of the irradiation light amount adjustment unit 605, and the like. In this case, the light-emitting element 601 may be lit even though the control unit 1 gives the light-off instruction, that is, the light amount control signal Slc (0).

On the other hand, as in the present embodiment, when the input offset voltage 651 is applied and shifted in advance to the right hand side in the figure to provide a dead zone (signal levels Slc (0) to Slc (1)). The light emission command from the control unit 1, that is, the light amount control signal Slc (0) can be surely turned off by giving a light-off instruction from the control unit 1 (solid line in the figure), and malfunction of the device can be prevented beforehand. Can be.

On the other hand, when a light amount control signal Slc exceeding the signal level Slc (1) is given from the control unit 1 to the irradiation light amount adjustment unit 605, the light emitting element 601 is turned on, and p-polarized light is applied to the intermediate transfer belt 41 as irradiation light. Irradiated. Then, the p-polarized light is reflected by the intermediate transfer belt 41, the reflected light amount detection unit 607 detects the amount of p-polarized light and the amount of s-polarized light among the light components of the reflected light, and a signal corresponding to each light amount is transmitted to the control unit. 1 is output.

This reflected light amount detection unit 607 is the same as that shown in FIG.
As shown in the figure, a polarization beam splitter 671 disposed on the optical path of the reflected light, and a polarization beam splitter 671
And a light-receiving unit 670p that receives p-polarized light passing through and outputs a signal corresponding to the amount of p-polarized light, receives s-polarized light split by the polarization beam splitter 671, and outputs a signal corresponding to the amount of s-polarized light. Output light receiving unit 6
70s. In the light receiving unit 670p, the light receiving element 672p includes a polarization beam splitter 671
After receiving the p-polarized light from the light-receiving element 672p and amplifying the output from the light-receiving element 672p by the amplifier circuit 673p, the amplified signal is converted into a signal corresponding to the amount of p-polarized light.
Output from p. The light receiving unit 670s has a light receiving element 672s and an amplifier circuit 673s, like the light receiving unit 670p. For this reason, the light amounts of two component lights (p-polarized light and s-polarized light) different from each other among the light components of the reflected light can be obtained independently.

In this embodiment, the light receiving element 672
The output offset voltage 674p,
674 s is applied to each of the amplifier circuits 673 s
The output voltages Vp and Vs of the signals supplied from p and 73s to the control unit 1 are offset to the positive side as shown in FIG. The specific electrical configuration of each of the light receiving units 670p and 70s is the same as that of the light receiving unit 604, and a description thereof is omitted here. In the light receiving units 670p and 670s configured as described above,
Similarly to the light receiving unit 604, even when the amount of reflected light is zero, each of the output voltages Vp and Vs has a value of zero or more, and further, the output voltages Vp and Vs are proportional to the increase in the amount of reflected light.
Also increase. Thus, the output offset voltage 674p,
By applying 674 s, the influence of the dead zone in FIG. 4 can be reliably eliminated, and an output voltage corresponding to the amount of reflected light can be output.

The signals of the output voltages Vp and Vs are inputted to the control unit 1 and, after A / D conversion, the amount of toner adhering on the intermediate transfer belt 41 is obtained by the control unit 1. In this embodiment, prior to the measurement of the actual toner amount, the eccentric component of the roller 43 and the cycle profile of the intermediate transfer belt 41 are obtained in advance as follows.
It is stored in the memory 12. Hereinafter, the procedure for deriving the eccentric component and the periodic profile and the procedure for measuring the actual amount of toner will be described separately.

FIG. 6 is a flow chart showing a procedure for deriving the eccentric component and the cycle profile performed prior to the actual measurement of the toner amount. In this device, the control unit 1 outputs a light amount control signal Slc (0) corresponding to a light-off instruction to the irradiation light amount adjusting unit 605 to turn off the light-emitting element 601 (step S1). In particular, in this embodiment, as described above, the dead zone (the signal levels Slc (0) to Slc (1) in FIG. 4) is set by applying the input offset voltage 651, so that the light amount control signal Slc (0) ), The light emitting element 601 is surely turned off.

Then, the output voltage Vp0 indicating the amount of received p-polarized light and the output voltage Vs0 indicating the amount of received s-polarized light in the unlit state are detected and stored in the memory 12 of the control unit 1 (step S2). That is, the sensor output in the unlit state, that is, the dark output voltage is detected and stored.

Next, a signal Slc (2) having a signal level exceeding the dead zone is set as the light amount control signal Slc, and the light amount control signal Slc (2) is given to the irradiation light amount adjusting unit 605 to turn on the light emitting element 601 ( Step S3). Then
The light from the light emitting element 601 is applied to the intermediate transfer belt 41, and the light reflected by the intermediate transfer belt 41 has a light intensity p.
The amount of polarized light and the amount of s-polarized light are reflected light amount detection unit 607
Output voltage V corresponding to each received light amount
p and Vs are input to the control unit 1 (step S
4).

Therefore, the control unit 1 obtains the light amount signal SigP representing the light amount of the p-polarized light corresponding to the toner amount by subtracting the dark output voltage Vp0 from the output voltage Vp for the p-polarized light (step S5). As for the s-polarized light, similarly to the p-polarized light, a light amount signal S representing the light amount of the s-polarized light corresponding to the toner amount by subtracting the dark output voltage Vs0 from the output voltage Vs.
igS is determined (step S5). Further, the ratio between the light quantity signals SigP and SigS corrected in this way is obtained as sampling data (step S5). As described above, in this embodiment, the dark output voltages Vp0 and Vs0 are removed from the measured output voltages Vp and Vs, respectively, so that the amount of light corresponding to the toner amount can be obtained with high accuracy. Even if the dark output fluctuates due to the surrounding environment of the device or a change over time of the components of the apparatus, the index of the toner amount can be obtained without being affected.

More specifically, the sampling data is obtained as follows. In the image forming apparatus according to this embodiment, the circumferential length of the intermediate transfer belt 41 corresponding to the “belt-shaped image carrier” of the present invention is a non-integer multiple of the circumferential length of the sensor facing roller 43. The intermediate transfer belt 41 makes one turn every time the turn 43 makes about 5.2 turns. It takes 3120 ms for the intermediate transfer belt 41 to make one rotation, and the amount of reflected light from the intermediate transfer belt 41 is sampled at intervals of 10 ms, and from the output voltage Vp at each sampling position x to the output voltage Vp at the time of turning off.
By subtracting 0, the light amount signal SigP (= Vp−Vp0) is obtained, and the output voltage Vs at each sampling position x is obtained.
Is subtracted from the output voltage Vs0 at the time of turning off, and the light amount signal S
After obtaining igS (= Vs−Vs0), these light amount signal ratios (= SigP / SigS) are stored in the memory 12 as sampling data D (x) at each sampling position x (FIG. 7). In this embodiment, 312 pieces of sampling data D (x) are obtained while the intermediate transfer belt 41 makes one rotation. However, in this embodiment, since a small memory capacity and efficient computation processing are performed. The sampling number is set to 256. That is, the sampling data D (0), D (1),... D (255) are stored in the memory 12.

In the next step S6, the eccentricity component of the roller is obtained from the sampling data D (0), D (1),..., D (255) and stored in the memory 12. The details will be described with reference to FIG. In this embodiment, the intermediate transfer belt 41 makes one revolution every 5.2 revolutions of the roller 43, and therefore, the continuous 60 from the sampling data D (x).
When (= 312 ÷ 5.2) pieces of sampling data are taken out, the roller 4 is included in the 60 pieces of sampling data.
That is, the component for one round of No. 3 is included. here,
Focusing on the eccentric component of the roller 43, if the average value of one rotation of the sensor facing roller 43 is taken, it is not necessary to consider the eccentric component. This is because the sensor facing roller 43 is 1
During the lap, both the case where the sensing distance becomes longer and the case where the sensing distance becomes closer due to eccentricity are included. Because it can be considered.

Accordingly, for example, three sections (1) to (3) are defined as 60 sections of continuous sampling data from the sampling data D (x) shown in FIG. x (x = 30, 31,...,
210) Average value AV for one round of roller 43 centered on
Find (x). AV (30) = (D (0) + ... + D (30) + ... + D (59)) / 60 AV (31) = (D (1) + ... + D (31) + ... + D (60)) / 60 AV (32) = (D (2) + ... + D (32) + ... + D (61)) / 60 ... AV (210) = (D (180) + ... + D (210) + ... + D (239) ) / 60. In the above equation, the sampling positions “0” to “5”
The center of the 60 pieces of sampling data of "9" is 30. Strictly, the center is between "29" and "30", and the above equation gives AV (29) = (D (0) +... + D (30 ) +... + D (59)) / 60 (the same applies hereinafter).

The average value AV (x) thus obtained
Is the eccentric component of the roller 43 canceled.
The eccentric component E (x) of the roller 43 at each sampling position x can be obtained by subtracting the average value AV (x) from the sampling data D (x). That is, the eccentric component E (x) of the roller 43 can be obtained by E (x) = D (x) -AV (x). However, in this case, the eccentric components for three rotations of the roller 43 while the intermediate transfer belt 41 makes one rotation are obtained.

Here, the sections (1) to (3) are all rollers 4
3 corresponds to one round, so if the phase is the same, the eccentric component E
(x) should show the same value. Therefore, section (1)-(3)
The average value Eav (a) of the eccentric component in each in-phase is given by the following equation: Eav (a) = ｛D (30 + a) −AV (30 + a)｝ + ｛D (90 + a) −A
V (90 + a)｝ + {D (120 + a) -AV (120 + a)} / 3
(1) (where a = 0, 1,..., 59) Thus, in this embodiment, the intermediate transfer belt 4
Since three eccentric components are obtained during one rotation of 1 and the average value thereof is obtained, the eccentric component of the roller 43 can be obtained with high accuracy. Of course, the number of rotations of the roller 43 per one rotation of the intermediate transfer belt 41 is not limited to “5.2”, and the eccentric component of the roller 43 can be obtained in the same manner as described above if the number of rotations is two or more. it can.

In this manner, the eccentric component Eav (a) of the roller 43 at each phase is obtained according to the equation (1) (step S).
6), the eccentricity component is subtracted from the sampling data D (x), and a periodic profile F (x) reflecting the surface state of the intermediate transfer belt 41 is detected (FIG. 8). That is, the period profile F (x) is expressed as follows: F (0) = D (0) -Eav (30) F (1) = D (1) -Eav (31) ... F (29) = D (29) -Eav (59) F (30) = D (30) −Eav (0) F (31) = D (31) −Eav (1) Then, the periodic profile F (x) is stored in the memory 12.
And prepare for the actual toner amount measurement (step S
7).

Next, the procedure for measuring the actual amount of toner will be described with reference to FIG. FIG. 9 is a flowchart showing a toner amount measuring operation in the image forming apparatus of FIG. In this device, the control unit 1 performs the steps S1 to S1 in the derivation operation of the eccentric component and the periodic profile.
By executing the same procedure as in S5, the light amount signal ratio (= SigP / SigS) serving as an index of the toner amount is calculated as sampling data D (x), and stored in the memory 12.

In the next step S8, the light amount signal ratio obtained as described above is corrected by the eccentric component Eav (a) and the periodic profile F (x). The procedure for this correction is as follows.

First, in this embodiment, every time the sensor facing roller 43 makes about 5.2 rotations, the intermediate transfer belt 4
1 goes around once. Therefore, the phase of the sensor facing roller 43 differs between when the eccentric component and the cycle profile are obtained and when the detection is performed to obtain the toner amount thereafter. However, the circumferential length ratio between the sensor facing roller 43 and the intermediate transfer belt 41 is known by design. Therefore, the phase of the eccentric component is shifted based on the number of rotations of the intermediate transfer belt 41 from the time when the eccentric component and the cycle profile are obtained to the time when the toner amount is detected, so that the roller facing the sensor at the time of the toner amount detection is shifted. 43. Then, the cycle profile and the eccentric component are combined, and the light amount signal ratio is corrected.

By the above-described processing, the influence of the eccentric component of the roller and the surface condition of the intermediate transfer belt 41 can be corrected. Thereafter, the toner amount is measured based on the correction result (step S9).

As described above, according to this embodiment, the eccentric component Eav of the roller 43 is obtained from the sampling data D (x).
After obtaining (a), the eccentricity component Eav (a) is removed from the sampling data D (x) to obtain the periodic profile F (x) (step S7). The profile F (x) accurately indicates the surface state of the intermediate transfer belt 41 without including the eccentric component of the roller.

The sampling data D (x) obtained for actually measuring the toner amount is corrected by using the cycle profile F (x) thus accurately obtained (step S8), and the correction value (Step S9), the accuracy of toner amount measurement can be improved.

Further, in this embodiment, not only the surface condition of the intermediate transfer belt 41 but also a variation in the distance (sensing distance) between the sensor 6 and the intermediate transfer belt 41 is suppressed. Since the distance variation is corrected, the measurement accuracy can be further improved. Specifically, the following two effects are further provided.

The conventional apparatus described above, that is, Japanese Patent Application Laid-Open No. 11-2
In the apparatus described in Japanese Patent No. 58872, a sensor is disposed at a position distant from the roller, and the intermediate transfer belt 41 flaps in a direction substantially orthogonal to the belt moving direction. Therefore, the sensing distance from the sensor 6 to the intermediate transfer belt 41 fluctuates randomly or unstablely,
The sensor output becomes unstable due to the distance variation. On the other hand, according to this embodiment, the surface area of the intermediate transfer belt wound around the roller 43, that is, the winding area 41a is irradiated with light, and the light reflected on the winding area 41a is received by the light receiving element. 672p, 672
The amount of toner is measured based on the signal received from the sensor 6 and output from the sensor 6. In the winding area 41a, unstable fluttering of the intermediate transfer belt 41 in a direction substantially perpendicular to the belt moving direction can be prevented.

In this embodiment, the eccentricity component Eav (a) of the roller is obtained (step S6), and the fluctuation of the sensing distance between the sensor 6 and the intermediate transfer belt 41 due to the eccentricity of the roller is corrected (step S6). Since S8), the influence of the roller eccentricity can be suppressed, and the measurement accuracy can be further improved.

When the amount of toner on the intermediate transfer belt 41 is measured, the toner may fall off the intermediate transfer belt 41 and adhere to the sensor 6. Since the sensor is disposed at the opposing position, the sensing surface is vertical, so that the toner that floats and falls can be effectively prevented from adhering to the sensing surface, and the measurement accuracy can be improved. This effect is the same or more when the sensor 6 is arranged above the horizontal opposing position of the roller 43 (FIG. 2) and at a position opposing the roller 43.

In this embodiment, the light amount signal SigP representing the amount of p-polarized light and the light amount signal Sig representing the amount of s-polarized light among the light components of the reflected light from the intermediate transfer belt 41.
S are obtained independently, and their light signal ratios (= SigP / S
Since the amount of toner adhering to the intermediate transfer belt 41 is measured based on igS), the measurement of the amount of toner can be performed with high accuracy without being affected by the influence of noise or the fluctuation of the amount of light applied to the intermediate transfer belt 41. Become.

Further, when obtaining the dark output, it is necessary to surely turn off the light emitting element 601. According to this embodiment, the light emitting element 601 is applied by applying the input offset voltage 651 as described above. The light can be reliably turned off.

The present invention is not limited to the above-described embodiment, and various changes other than those described above can be made without departing from the gist of the present invention. For example, in the above-described embodiment, since the peripheral length of the intermediate transfer belt 41 and the sensor facing roller 43 is a non-integer multiple, the intermediate position of the sensor facing roller 43 between the time when the eccentric component and the cycle profile are obtained and the time when the toner amount is detected. Although the phase shift with respect to the transfer belt 41 is corrected, the phase shift may be eliminated by setting the circumference of the intermediate transfer belt 41 and the sensor facing roller 43 to an integer. In this case, since the calculation for correcting the phase shift is not required, the same effect can be obtained with fewer processing steps, and the detection error due to the calculation accuracy can be prevented beforehand.

In the above embodiment, the sensor 6 is disposed so as to face the roller 43. However, the arrangement of the sensor 6 facing the roller itself accurately detects the surface condition of the intermediate transfer belt 41. Although not a required component above,
In consideration of the above-described effects, it is desirable that the sensor 6 is disposed to face the roller 43. Instead of disposing the sensor 6 so as to face the roller 43, the sensor 6 may be arranged to face the other rollers 42, 44 to 47 around which the intermediate transfer belt 41 is stretched. However, in the above embodiment, since the roller 44 among the plurality of rollers 42 to 47 is a tension roller, one of the other rollers which is fixed to the apparatus main body in advance and is rotatable at the fixed position is used. Is desirably provided with a sensor 6. This is because, when the sensor 6 is arranged to face a roller rotatably fixed at a predetermined position, the distance between the roller and the sensor 6 is constant.

On the other hand, since the tension roller 44 is configured to move forward and backward with respect to the intermediate transfer belt 41, the distance between the sensor 6 fixed in advance and the tension roller 44 tends to fluctuate. 4
This is because the distance between the belt region and the sensor 6 spanned by the sensor 4 fluctuates, which causes a reduction in measurement accuracy. In order to prevent this, for example, the tension roller 44 and the sensor 6 may be mechanically connected, and the sensor 6 may be configured to interlock with the fluctuation of the tension roller 44.

In the above embodiment, the light amount signal ratio (= SigP / SigS) is used as the index value of the toner amount. A signal sum (= SigP + SigS), a light amount signal difference (= SigP−SigS), or the like can be used.

Further, in the above embodiment, as shown in FIG. 2, the light emitting element 601 is such that the incident surface (the paper surface in FIG. 2) including the irradiation light and the reflected light is substantially perpendicular to the rotation axis of the sensor facing roller 43. And the light receiving elements 672p and 672s are arranged, but the arrangement relationship is not limited to this. For example, the sensor 6 may be configured such that the incident surface is substantially parallel to the roller rotation axis. . If the incident surface and the roller rotation axis are not parallel, not only does the sensing distance fluctuate due to the eccentricity of the roller, but also changes in the amount of reflected light due to changes in the angle of the roller surface (reflection surface). By making the axes parallel, the angle of the reflecting surface can be further stabilized. Further, for the same reason, in order to stabilize the angle of the reflection surface, the entrance surface and the roller rotation axis may be configured to be on the same plane.

In the above-described embodiment, the present invention is applied to the image forming apparatus in which the intermediate transfer belt 41 is a belt-shaped image carrier, but the present invention is not limited to this. The present invention is also applicable to an image forming apparatus that forms a toner image on a photoreceptor belt, and the present invention can be applied to all image forming apparatuses including a belt-shaped image carrier that is stretched over a plurality of rollers.

Further, in the above-described embodiment, the image forming apparatus is capable of forming a color image using four color toners. However, the present invention is not limited to this. Naturally, the present invention can also be applied to an image forming apparatus that forms only the image forming apparatus. The image forming apparatus according to the above embodiment is a printer that forms an image given from an external device such as a host computer on a sheet S such as copy paper, transfer paper, paper, and a transparent sheet for OHP. The present invention can be applied to all electrophotographic image forming apparatuses such as copying machines and facsimile machines.

[0060]

As described above, according to the present invention, after the eccentric component of the roller is obtained from the sampling output, the eccentric component is further removed from the sampling output to obtain the periodic profile. , A periodic profile accurately indicating the surface state of the belt-shaped image carrier can be obtained. That is, the surface condition of the belt-shaped image carrier can be accurately detected.

Further, the sampling output obtained for actually measuring the toner amount is corrected by using the cycle profile thus accurately obtained, and the toner amount is measured based on the corrected value. Thereby, the measurement accuracy of the toner amount can be further improved.

Further, a light-emitting element is disposed opposite one of the plurality of rollers so as to sandwich the belt-shaped image carrier, and is wound around the sensor facing roller in the surface area of the belt-shaped image carrier. By irradiating the wound area with the light, the fluctuation of the distance (sensing distance) between the sensor and the belt-shaped image carrier can be effectively suppressed, and the detection accuracy of the periodic profile can be improved. This further improves the accuracy of measuring the amount of toner.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a diagram illustrating a configuration of a sensor that detects an amount of toner on an intermediate transfer belt.

FIG. 3 is a diagram showing an electrical configuration of a light receiving unit employed in the apparatus of FIG.

FIG. 4 is a diagram showing a light amount control characteristic in the toner amount measuring device of FIG. 1;

FIG. 5 is a graph showing how the output voltage changes with respect to the amount of reflected light in the toner amount measuring device of FIG.

FIG. 6 is a flowchart showing a procedure for deriving an eccentric component and a cycle profile performed prior to actual measurement of the toner amount.

FIG. 7 is a graph showing an example of sampling data output from a sensor.

8 is a graph showing a period profile of an intermediate transfer belt obtained by removing an eccentric component of a driving roller from the sampling data of FIG. 7;

FIG. 9 is a flowchart illustrating a toner amount measurement operation in the image forming apparatus of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Control unit (control means) 6 ... Sensor 11 ... CPU (control means) 12 ... Memory 41 ... Intermediate transfer belt (belt-shaped image carrier) 41a ... Wrapping area 42-47 ... Roller 43 ... Sensor facing roller 601 ... Light emitting elements 642, 672p, 672s, PS: light receiving element 670p, 670s: light receiving unit

Continued on front page F term (reference) 2G059 AA05 BB09 DD12 EE02 GG02 JJ22 KK01 MM01 MM02 MM09 MM10 MM15 NN02 NN07 NN10 2H027 DA09 DE02 DE07 DE10 EC06 EC11 HA14 2H032 AA15 BA09 CA14 CA15 2H035 CA05 CB

Claims (5)

[Claims] 1. A light emitting element irradiates light to a belt-shaped image carrier that is stretched over a plurality of rollers, and light reflected by the belt-shaped image carrier is received by a light-receiving element. An image forming apparatus comprising: a sensor for outputting a corresponding signal; and control means for calculating an amount of toner adhering to the belt-shaped image carrier based on an output from the sensor. While rotating the body, the output signal from the light receiving element is sampled, and the eccentric component of the roller is obtained based on the sampled output. A periodic profile indicating the surface state is determined, and when determining the image density of the toner image on the belt-shaped image carrier, the belt-shaped image carrier is used. In the output from the light receiving element for receiving reflected light, corrected by said eccentric components and said periodic profile, the image forming apparatus characterized by determining the image density of the toner image based on the correction value. 2. The sensor according to claim 1, wherein the light emitting element is disposed opposite to one of the plurality of rollers so as to sandwich the belt-shaped image carrier, and the sensor is provided in a surface area of the belt-shaped image carrier. The image forming apparatus according to claim 1, wherein light is applied to a winding area wound around the opposing roller. 3. A surface state detecting method for detecting a surface state of a belt-shaped image carrier stretched over a plurality of rollers, wherein light is emitted from a light emitting element to the rotating belt-shaped image carrier. A first step of obtaining a sampling output by sampling an output signal from a light receiving element that receives light reflected from the belt-shaped image carrier; and a second step of obtaining an eccentric component of the roller from the sampling output. And a third step of removing the eccentric component from the sampling output to obtain a periodic profile indicating a surface state of the belt-shaped image carrier. 4. In the first step, the belt-shaped image carrier is sandwiched by the light-emitting elements arranged to face one of the plurality of rollers so as to sandwich the belt-shaped image carrier. 4. The surface state detection method according to claim 3, wherein light is applied to a winding area of the surface area that is wound around the sensor facing roller. 5. A toner amount measuring method for determining an amount of toner adhering to a belt-shaped image carrier stretched over a plurality of rollers, wherein the toner image is not formed before forming the toner image. 5. A pre-process for obtaining an eccentric component of the roller and a periodic profile indicating a surface state of the belt-shaped image carrier by using the surface state detection method according to claim 3 or 4, wherein the surface state of the carrier is determined. A light emitting element irradiating the belt-shaped image carrier on which light is formed with light, and a sampling step of sampling an output signal from a light-receiving element for receiving light reflected from the belt-shaped image carrier to obtain a sampling output And the sampling output obtained in the sampling step is corrected by the eccentric component and the periodic profile, and based on the correction value, A measuring step of obtaining an image density of the toner image.