JP2002148876A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device to solve both nonconformity caused because the reflected light of a reference toner image is detected and nonconformity caused because a transmission type photosensor is used for the detection of the reference toner image. SOLUTION: Reflection type photosensors 69a and 69b as a light-transmissible detecting means to detect the light-transmissivity of a paper feeding belt 60 and a reflection member 70 to reflect transmitted light emitted by the light- emitting part not shown in a figure of sensors thereof and transmitted through the paper feeding belt 60 is reflected to the light-receiving part not shown in the figure of the sensors are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a facsimile, a printer, a copying machine, and the like. More specifically, the present invention relates to a method for transferring a reference toner image onto a moving body such as an intermediate transfer belt or a paper conveying belt. The present invention relates to an image forming apparatus which detects an image density and a position of a reference toner image based on light transmittance of an upper reference toner image portion and performs predetermined control.

[0002]

2. Description of the Related Art Generally, in an electrophotographic image forming apparatus, its image forming property fluctuates with time. For example, when the environment such as temperature and humidity changes, the developing property as the image forming property changes due to the change of the developer property accompanying the change. Further, for example, if a transfer member such as an intermediate transfer belt is stretched due to use, or if various members are displaced due to an impact or the like, the accuracy of an image forming position changes as an image forming property.

Therefore, while the reference toner image formed on the image carrier is transferred onto a moving body such as an intermediate transfer belt or a paper transport belt, the amount of light reflection on the surface of the moving body is detected by a reflection type photo sensor. 2. Description of the Related Art There is known an image forming apparatus that detects a position shift and an image density of a reference toner image on a moving body based on a detection result. According to this image forming apparatus, for example, the formation position of the toner image on the image carrier is corrected based on the displacement of the reference toner image, or the developing bias or the toner of the developer is corrected based on the image density of the reference toner image. By adjusting the density to correct the developing property or the like, the instability of the image forming property can be suppressed.

However, in a multi-color image forming apparatus using a so-called color toner such as yellow in addition to the black toner, the light reflection characteristics of the reference toner images of each color are different from each other. There is a problem that it is difficult to detect the shift and the image density with one reflection photosensor.

Therefore, in Japanese Patent Application Laid-Open No. 3-174560, a transparent portion is formed on a moving body such as an intermediate transfer member and an image of the reference toner image is formed based on the transmitted light amount of the transparent portion onto which the reference toner image has been transferred. 2. Description of the Related Art There has been proposed an image forming apparatus for detecting a density. According to this image forming apparatus, since the amount of transmitted light changes according to the image density regardless of the color of the toner, the image density of the reference toner image of each color can be detected by one transmission photosensor.

[0006]

However, a transmissive photosensor is different from a reflective photosensor in which a light-emitting unit and a light-receiving unit can be housed together in one housing. It is necessary to face each other via the light transmission target. In such a transmissive photosensor, it is necessary to arrange the housing for housing the light emitting unit and the housing for housing the light receiving unit at separate positions and to secure an optical path between the two housings. There is a disadvantage that the degree of freedom in layout in the device is reduced as compared with the case where the device is used. In addition, there is also a problem that the maintenance workability is reduced or the cost is increased by individually drawing electrical wiring into each housing or supporting each housing with an individual support member.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and an object thereof is to generate a reference toner image by detecting reflected light of the reference toner image. It is an object of the present invention to provide an image forming apparatus capable of solving both a problem and a problem caused by using a transmission type photosensor.

[0008]

In order to achieve the above object, the present invention provides an image carrier for carrying a toner image, a toner image forming means for forming a toner image on the image carrier, A moving body that transfers a reference toner image on the image carrier to the surface while moving in a predetermined direction; and a light transmissivity detecting unit that detects light transmissivity in a reference toner image portion on the moving body. Control means for performing predetermined control based on the detection result of the light transmissivity detecting means, wherein the light transmissivity detecting means is directed to a front surface which is a transfer surface of the endless moving body. A light-emitting member that emits light through the moving body, a light reflecting member that reflects the transmitted light transmitted through the moving body toward the front surface, and a light receiving section that receives the reflected light transmitted through the moving body again after the reflection. It is characterized by having a thing provided.

In this image forming apparatus, in order to detect a reference toner image transferred from an image carrier such as a photosensitive member to a moving body such as an intermediate transfer body, reflected light of the reference toner image is not detected. Instead, the light transmittance of the reference toner image portion on the moving body is detected. Therefore, it is possible to eliminate various problems caused by detecting the reflected light of the reference toner image. Further, in this image forming apparatus,
The transmitted light of the reference toner image portion of the moving body is not detected by the light receiving section facing the light emitting section via the moving body, but the transmitted light is reflected by the reflecting member to be reflected light, and the moving body is again reflected on the transmitted light. And then detected by the light receiving unit. In such a configuration, since both the light emitting unit and the light receiving unit can be disposed on the front surface side of the moving body, the transmission type photo sensor in which both are housed in different housings as a combination of both. Instead, it becomes possible to use a reflection type photosensor in which both are housed in one housing. Therefore, various problems caused by using the transmission type photo sensor can be solved. As described above, in this image forming apparatus, in order to detect the reference toner image, there are the problems caused by detecting the reflected light of the reference toner image and the use of the transmission type photo sensor. Both of the problems that occur can be eliminated.

When an endless belt such as an intermediate transfer belt is used as a moving body, when the endless belt vibrates up and down, light from the light emitting section hits a belt portion deviated from a normal position, or the light emitting section and the endless belt do not move. It is difficult to accurately detect the reference toner image due to a change in the relative distance between the reference toner image and the light receiving unit. Therefore, it is desirable to detect the reference toner image on the endless belt at a belt position with as little vibration as possible. As such a belt position, a belt stretching position backed up by a stretching roller can be considered. However, since the belt tension position is backed up by the tension roller and curved, the light from the photosensor does not directly hit the reference toner image on the belt, and the displacement and image density of the reference toner image can be accurately determined. There is a problem that it is difficult to detect. JP-A-6-3886 discloses an image forming apparatus capable of solving such a problem.
A publication is known. In this image forming apparatus,
Equipped with a belt supporting means for generating a negative pressure while abutting on the back surface of the transport belt as a moving body, and solving the above-described problems by restraining the transport belt on the plane of the belt supporting means by the negative pressure. In addition, erroneous detection of the photo sensor due to vertical vibration of the belt can be suppressed.
However, in this image forming apparatus, it is necessary to provide a negative pressure generating means for generating the negative pressure, which causes problems such as an increase in cost and generation of noise.

According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the movable body is provided with an endless belt that is moved endlessly while being stretched by a plurality of stretching members that contact the back surface thereof. Further, as the above-mentioned reflecting member, a reflecting member formed in a planar shape is provided which comes into contact with the back surface of the endless belt to back up the endless belt.

In this image forming apparatus, the reflecting member having a planar shape backs up the endless belt as a moving body, so that the endless belt at the abutting portion is provided in the same manner as a stretching member such as a stretching roller. The vertical vibration of The light emitting section of the light transmissivity detecting means irradiates light to the endless belt portion (hereinafter, referred to as a belt portion) in which the vertical vibration is suppressed, and the light receiving portion detects the reflected wave reflected by the reflecting member. Therefore, in this image forming apparatus, the light transmissivity detecting means can detect the light transmissivity of the belt portion whose vertical vibration has been suppressed by the reflection member, and can suppress erroneous detection due to the vertical vibration. Further, the belt portion in which the vertical vibration is suppressed is different from the belt portion backed up by the stretching roller, and has a planar shape following the plane of the reflection member to be backed up. Therefore, it is possible to suppress misregistration and erroneous detection of the image density caused by detecting the reference toner image at the curved portion of the endless belt. Further, in this image forming apparatus, unlike the image forming apparatus disclosed in JP-A-6-3886, which requires a negative pressure generating means, the light transmitting detecting means can detect the negative pressure without providing the negative pressure generating means. Since the vertical vibration of the belt portion is suppressed, it is possible to eliminate cost increase and noise generation caused by providing the negative pressure generating means. As described above, in this image forming apparatus, erroneous detection of the light transmissivity detecting unit due to vertical vibration and bending of the endless belt is suppressed, and
The cost increase and the noise generation due to the provision of the negative pressure generating means can be eliminated.

According to a third aspect of the present invention, in the image forming apparatus of the second aspect, the light emitting section and the light receiving section are arranged at positions facing the vicinity of the downstream end of the reflecting member in the direction of movement of the endless belt. It is characterized by the following.

In this image forming apparatus, erroneous detection of the light transmissivity detecting means due to vertical vibration of the endless belt can be more reliably suppressed for the following reason.
That is, on the upstream side in the belt moving direction from the belt portion backed up by the reflection member, a force mainly for feeding the endless belt to this belt portion acts.
If vertical vibration of the endless belt is generated at a position where such a force is applied, the vibration will bend the belt and easily reach the belt portion backed up by the reflection member. On the other hand, on the downstream side of the belt portion in the belt moving direction, a force mainly for pulling out the endless belt from the belt portion acts. If vertical vibration of the endless belt occurs at a position where such a force is applied, the vibration mainly becomes slack in the belt and tends to be transmitted to the belt feeding side, so that it is difficult to be transmitted to the belt portion on the belt pulling side. Therefore, in the belt portion backed up by the reflection member, the vertical vibration of the belt is more suppressed near the downstream end than near the upstream end in the belt moving direction. In the present image forming apparatus, since the light transmittance of the belt is detected near the latter end portion, erroneous detection of the light transmittance detecting means due to the vertical vibration of the endless belt can be suppressed more reliably.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first, second or third aspect, the control means performs the predetermined control as the predetermined control based on a detection result of the light transmission detecting means. The amount of displacement of the reference toner image from the normal position is calculated, and the control condition for the toner image forming means is changed based on the calculation result to correct the formation position of the toner image on the image carrier. The present invention is characterized in that misregistration correction control is performed.

In this image forming apparatus, the control condition for the toner image forming means is changed based on the position shift of the reference toner image, so that the position shift of the toner image formation on the image carrier can be suppressed.

According to a fifth aspect of the present invention, in the image forming apparatus of the fourth aspect, a plurality of the image carriers and the toner image forming means corresponding to each of the image carriers are provided, and each of the image carriers is sequentially provided. The moving body is configured to transfer the reference toner image on each image carrier while moving in a predetermined direction so as to face each other.

In this image forming apparatus, toner images of different colors are formed on the respective image carriers, and the obtained toner images of the respective colors are superimposedly transferred onto a moving body or a transfer paper conveyed to the moving body. Then, a full-color image can be formed. In addition, in the case of forming a full-color image in this manner, for the reason described below, compared with the case of providing only one image carrier and forming a full-color image, the structure of the full-color image is formed. The image forming speed can be increased. That is, as a method of configuring the image forming apparatus to form a full-color image, a method of providing only one image carrier and sequentially performing primary transfer to an intermediate transfer body or the like while sequentially forming toner images of each color on the image carrier, There is a method that employs a so-called tandem system in which a plurality of latent image carriers are provided as in the present image forming apparatus. In the former method, since only one image carrier is provided, it is necessary to repeat formation of a toner image and primary transfer for each color. On the other hand, in the latter method, since a plurality of image carriers are provided, there is no need to repeatedly form a toner image or perform primary transfer, and each color toner image is almost simultaneously placed on a dedicated image carrier. While being formed, it is possible to transfer the image by superimposing it on a transfer paper or the like. Therefore, the image forming speed of the full-color image can be increased as compared with the case where the full-color image is formed by the former method. In such a configuration, a color shift is likely to occur in the full-color image due to a relative positional shift between the image carriers and a toner image forming position shift of the toner image forming unit with respect to each image carrier.
However, in the present image forming apparatus, these misregistrations are corrected based on the misregistration of the reference toner image of each color, so that the above-described misregistration can be suppressed. In addition, since a reflection type photo sensor can be used as the light transmissivity detecting unit, the reference toner image of each color can be detected by one photo sensor.

The invention according to claim 6 is the invention according to claims 1, 2, 3, and 4.
Or the image forming apparatus according to 5, wherein the image carrier is a latent image carrier for carrying a latent image, and the toner image forming means is:
Latent image forming means for forming a latent image on the latent image carrier, a developing device for developing the latent image on the latent image carrier with a developer containing toner and carrier, and replenishing toner to the developing device A toner supply unit that controls the driving of the toner supply unit based on the detection result of the light transmittance detection unit as the predetermined control. It is assumed that.

In this image forming apparatus, the toner replenishment control is performed based on the image density of the reference toner image, so that even if the toner in the developer in the developing device is consumed during development, Can be maintained in an appropriate density range.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A tandem type color laser printer (hereinafter, referred to as "laser printer") will be described below as an embodiment of a tandem type image forming apparatus to which the present invention is applied.

First, the basic configuration of the laser printer will be described. [Overall Configuration] FIG. 1 is a schematic configuration diagram of a laser printer according to the present embodiment. This laser printer includes four sets of toner image forming units 1Y for forming images of each color of yellow (Y), magenta (M), cyan (C), and black (K).
1M, 1C, 1K (hereinafter, suffixes Y, M, C, K
Indicate the members for yellow, magenta, cyan, and black, respectively) are arranged in order from the upstream side in the moving direction of the transfer paper (not shown). The toner image forming units 1Y, 1M, 1C, and 1K include photosensitive drums 11Y, 11M, 11C, and 11K as a latent image carrier.

In addition to the toner image forming units 1Y, 1M, 1C and 1K, the laser printer according to the present invention includes an optical writing unit 2 serving as a latent image forming unit, paper feed cassettes 3 and 4, a pair of registration rollers 5, Unit 6, a belt fixing type fixing unit 7, a paper discharge tray 8, a manual feed tray (not shown),
It also has a toner supply container, a waste toner bottle, a double-sided / reversing unit, a power supply unit, and the like.

[Optical writing unit] Optical writing unit 2
Is provided with a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like.
The surface of Y, 11M, 11C, 11K is irradiated with laser light while scanning.

[Photosensitive Drum, etc.] FIG. 2 is an enlarged view showing a schematic configuration of the yellow toner image forming section 1Y among the toner image forming sections 1Y, 1M, 1C, and 1K. In addition,
The other toner image forming units 1M, 1C, and 1K have the same configuration, and a description thereof will be omitted. In FIG. 2, the toner image forming unit 1Y includes the photoconductor unit 10Y and the developing device 20Y as described above. The photoconductor unit 10Y includes a photoconductor drum 11
In addition to Y, a brush roller 12Y for applying a lubricant to the drum surface, a swingable counter blade 13Y for performing cleaning, a static elimination lamp 14Y for performing static elimination processing, and a non-contact type charging roller 15Y for performing uniform charging processing Etc. are provided. As the photoconductor drum 11Y, a photoconductor drum having an organic photoconductor (OPC) layer on its surface is used.

In the photoconductor unit 10Y, a laser beam modulated and deflected by the optical writing unit 2 scans the surface of the photoconductor drum 11Y uniformly charged by the charging roller 15Y to which an AC voltage is applied. When irradiating the drum, an electrostatic latent image is formed on the drum surface.

[Developing Device] The developing device 20Y includes a developing roller 22Y, a first transport screw 23Y, and a second
A transport screw 24Y, a developing doctor 25Y, a toner density sensor (T sensor) 26Y, a powder pump 27Y, and the like are provided.

The developing case 21Y contains a developer containing a magnetic carrier and a negatively charged Y toner. This developer is used for the first transport screw 23Y,
After being frictionally charged while being agitated and transported by the second transport screw 24Y, it is carried on the surface of a developing roller 22Y as a developer carrier. Then, after the layer thickness is regulated by the developing doctor 25Y, the developer is conveyed to a developing area opposed to the photosensitive drum 11Y, where the Y toner adheres to the electrostatic latent image on the photosensitive drum 11Y. With this attachment, a Y toner image is formed on the photosensitive drum 11Y. The developer that has consumed the Y toner during the development is transferred to the developing case 21 by the rotation of the developing roller 22Y.
Returned in Y.

A partition wall 28Y is provided between the first transport screw 23Y and the second transport screw 24Y, so that a first supply for accommodating the developing roller 22Y, the first transport screw 23Y, and the like. Part 29Y,
Second supply unit 30Y that accommodates second transport screw 24Y
Are separated in the developing case 21Y.

The Y developed on the photosensitive drum 11Y
The toner image is transferred onto a transfer sheet conveyed by a transfer / conveyance belt 60 described later.

The first transport screw 23Y is driven to rotate by driving means (not shown), and transports the developer in the first supply section 29Y from the near side to the far side in the figure along the surface of the developing roller 22Y. While supplying it to the developing roller 22Y.

FIG. 3 is a longitudinal sectional view showing the developing device 20Y. As shown in the drawing, the partition wall 28Y has two openings that respectively connect the first supply unit 29Y and the second supply unit 30Y near both ends of each transport screw.

The developer transported to the vicinity of the end of the first supply section 29Y by the first transport screw 23Y enters the second supply section 30Y through one of the openings provided in the partition wall 28Y. I do.

In the second supply section 30Y, the second transport screw 24Y is driven to rotate by a driving means (not shown), and the developer entering from the first supply section 29Y flows in a direction opposite to that of the first transport screw 23Y. Transport to The second supply unit 30 is controlled by the second transfer screw 24Y.
The developer transported to the vicinity of the end of Y is separated from the partition wall 28Y.
And returns to the inside of the first supply unit 29Y through the other opening provided in the first supply unit 29Y.

The T sensor 26Y comprising a magnetic permeability sensor
Is provided on the bottom wall near the center of the second supply unit 30Y, and outputs a voltage having a value corresponding to the magnetic permeability of the developer passing therethrough. Since the magnetic permeability of the developer shows a certain correlation with the toner concentration of the developer, the T sensor 26Y outputs a voltage having a value corresponding to the Y toner concentration. The value of the output voltage is sent to a control unit (not shown).

The control section includes a RAM, in which a Vtref for Y, which is a target value of the output voltage from the T sensor 26Y, and a T sensor 26 mounted in another developing device.
It stores data of the target values of the output voltages from M, 26C, and 26K, that is, Vtref for M, Vtref for C, and Vtref for K. For the developing device 20Y, the value of the output voltage from the T sensor 26Y is compared with the Vtref for Y,
By driving the powder pump 27Y connected to a Y toner cartridge (not shown) for a time corresponding to the comparison result,
The Y toner in the toner cartridge is supplied into the second supply unit 30Y. By controlling the driving of the powder pump 27Y (toner replenishment control) in this manner, the developer that consumes the Y toner by development and reduces the Y toner concentration becomes the second developer.
An appropriate amount of Y toner is supplied in the supply section 30Y, and the Y toner concentration of the developer supplied to the first supply section 29Y is maintained within a predetermined range. Other developing devices 20M, 20C, 20
Similar toner supply control is performed for K.

[Transfer Unit] The photosensitive drum 11
Y, 11M, 11C, and 11K form a transfer nip as a transfer position by contacting a transfer conveyance belt (described later) of the transfer unit 6 disposed below the transfer rollers.

FIG. 4 is an enlarged view showing a schematic configuration of the transfer unit 6. The transfer conveyance belt 60 used in the transfer unit 6 has a volume resistivity of 10 ⁹ to 10 ¹¹ Ω.
cm, a high-resistance endless single-layer belt made of PVDF (polyvinylidene fluoride). The transfer / conveying belt 60 as an endless moving body includes the photosensitive drums 11 of the toner image forming units 1Y, 1M, 1C, and 1K.
It is wrapped around four grounded support rollers 61 so as to pass through each transfer position in contact with Y, 11M, 11C and 11K.

Of these support rollers 61, the one on the rightmost side in the drawing is arranged so that an electrostatic attraction roller 62 to which a predetermined voltage is applied from a power supply 62a is opposed.
Between the support roller 61 and the electrostatic suction roller 62,
The transfer paper 100 is fed by the pair of registration rollers 5 and electrostatically attracted onto the transfer conveyance belt 60.

The leftmost support roller 61 in the figure is a drive roller that is rotated by drive means (not shown) to frictionally drive the transfer / conveyance belt 60.

A power supply 63a is provided on the outer peripheral surface of the transfer conveying belt 60 located between the two lower supporting rollers 61 in the figure.
And a bias roller 63 to which a predetermined cleaning bias has been applied from above.

Below each transfer nip, transfer bias applying members 65Y, 65
5M, 65C and 65K are provided. These transfer bias applying members 65Y, 65M, 65C and 65K are constituted by fixed brushes made of Mylar, and transfer biases are applied from respective transfer bias power supplies 9Y, 9M, 9C and 9K. By the transfer bias applied by the transfer bias applying member, a transfer charge is applied to the transfer conveyance belt 60, and the transfer conveyance belt 60 is transferred at each transfer position.
A transfer electric field having a predetermined strength is formed between the photosensitive drum and the surface of the photosensitive drum.

FIG. 5 is a schematic diagram showing the transfer pressure adjusting means of the transfer unit 6. As shown in FIG. In the figure, each transfer bias applying member 65Y, 65M, 65C, 65K is rotatably supported by a single support 66, and this support 66 is supported by two solenoids 67, 68. By driving these two solenoids 67 and 68, the transfer bias applying members 65Y, 65M, 65
The contact pressure (nip pressure) between the photoconductor drum 11 and the transfer conveyance belt 60 at each transfer position is adjusted by moving C and 65K up and down. At the time of superposition transfer of the toner images of the respective colors, the transfer / conveyance belt 60 is moved so that the contact pressure becomes a predetermined value.
M, 11C and 11K are pressed.

The dashed line in FIG. 1 indicates the transfer path of the transfer paper. The transfer paper (not shown) fed from the paper feed cassettes 3 and 4 is conveyed by conveyance rollers while being guided by a conveyance guide (not shown), and sent to a temporary stop position where the registration roller pair 5 is provided. The transfer paper sent at a predetermined timing by the registration roller pair 5 is carried by the transfer / conveyance belt 60 and passes through each transfer nip that can contact the toner image forming units 1Y, 1M, 1C, and 1K.

Each toner image forming section 1Y, 1M, 1C, 1K
The toner images developed on the photoreceptor drums 11Y, 11M, 11C, and 11K are superimposed on the transfer paper at the respective transfer nips, and are transferred onto the transfer paper under the action of the transfer electric field and the nip pressure. By the transfer of the superposition, a full-color toner image is formed on the transfer paper.

[Electrification Removal] In FIG. 2, the surface of the photosensitive drum 11Y after the transfer of the toner image is
After a predetermined amount of lubricant is applied in 2Y, it is cleaned by the counter blade 13Y. And the static elimination lamp 1
The charge is removed by the light emitted from the 4Y, and the preparation is made for the formation of the next electrostatic latent image.

[Fixing Unit] On the other hand, the transfer paper 100 on which the full-color toner image is formed is fixed in the fixing unit 7 (see FIG. 1) having a heating roller (see FIG. 1). Is discharged on top. Note that the fixing unit 7 includes a temperature sensor (not shown) that detects the temperature of the heating roller.

[Control Unit] FIG. 6 is a block diagram showing a part of an electric circuit of the laser printer. In the figure, a control unit 150 includes toner image forming units 1Y, 1M, 1C, and 1K electrically connected to each other, an optical writing unit 2, paper feed cassettes 3, 4, a pair of registration rollers 5, a transfer unit 6, and a reflection type. It controls the photo sensor 69 and the like. Further, the control unit 150 includes a CPU 150a for performing arithmetic processing and a RAM 150b for storing data.

The RAM 150a stores data of a Y developing bias value, an M developing bias value, a C developing bias value, a K developing bias value corresponding to the toner image forming portions 1Y, 1M, 1C and 1K, and a Y developing bias value. The data of the drum charging potential, the drum charging potential for M, the drum charging potential for C, and the data of the drum charging potential for K are stored.

In the printout process, the control unit 150 controls the charging rollers 15Y, 15M, 15
Control is performed so that charging biases of the Y drum charging potential, the M drum charging potential, the C drum charging potential, and the K drum charging potential are supplied to C and 15K. By this control, the photosensitive drums 11Y, 11M, 11C, 11K
Are charged uniformly to the Y drum charging potential, the M drum charging potential, the C drum charging potential, and the K drum charging potential. Further, the control unit 150 controls the developing roller 22Y,
Control is performed such that biases of the Y developing bias value, the M developing bias value, the C developing bias value, and the K developing bias value are supplied to 22M, 22C, and 22K.

Immediately after the main power supply (not shown) is turned on, 60
When the temperature of the heating roller is equal to or lower than [° C.] or when a printout of a predetermined number or more is performed, the controller 1
50 tests the image forming performance of each toner image forming unit 1. Specifically, first, the photosensitive drums 11Y, 11M, 11C,
Charge while rotating 11K. The potential in this charging is different from the uniform drum charging potential in the printout process, and the value is gradually increased to the negative polarity side. Then, the developing unit 20Y, 20M, 20C, 20K develops the electrostatic latent image for the reference pattern image on the photosensitive drums 11Y, 11M, 11C, 11K by scanning the laser light. With this development, the photosensitive drums 11Y, 1Y
Reference pattern image Py, reference pattern image Pm, reference pattern image Pc, reference pattern image P on 1M, 11C, 11K
k is formed. At the time of development, the control unit 150 controls the values of the developing bias applied to the developing rollers 22Y, 22M, 22C, and 22K so as to gradually increase toward the negative polarity. Further, even immediately after the main power is turned on, when a heating roller temperature exceeding 60 ° C. is detected, the image forming performance is not tested. Therefore, when the time from the OFF to the ON of the main power supply is relatively short, for example, several minutes to several tens of minutes, the test is omitted, and the user is unnecessarily waited for by the excessive test, or the power and toner are wasted. It is possible to eliminate such a situation.

FIG. 7 shows a reference pattern image P (Py, Pm,
It is a schematic diagram which shows Pc, Pk). In the figure, a reference pattern image P is composed of five reference images 101 arranged at an interval L4. In this laser printer, each reference image 101 as a reference toner image is
[Mm] × width (L3) 20 [mm], L4 =
It is formed with a gap of 10 [mm]. Therefore, the reference pattern images Py, Pm, Pc,
The length L2 of Pk is 140 [mm]. The reference pattern images Py, Pm, Pc, and Pk are transferred so as to be lined up on the transfer / transport belt 60 without being different from the toner images of the respective colors formed during the printing process. By such transfer, one pattern block PB composed of the reference pattern images Py, Pm, Pc, and Pk of each color is formed on the transfer conveyance belt 60.

FIG. 8 is a schematic diagram showing the installation pitch of the photosensitive drum 11. As shown, the photosensitive drum 11
Y, 11M, 11C, and 11K are arranged at equal intervals at a pitch of L1. In this laser printer, L
1 is set to 200 [mm]. As mentioned above,
The length L2 of each of the reference pattern images Py, Pm, Pc, Pk is 140 [mm], which is shorter than the installation pitch L1 of the photosensitive drum 11. Therefore, the reference pattern image P
y, Pm, Pc, and Pk can be independently transferred so that their ends do not overlap each other.

FIG. 9 is a schematic diagram showing the pattern block formed on the transfer / conveying belt 60. The four reference patterns Pk, Pc, P
Two pattern blocks PB composed of m and Py are formed. Specifically, the reference pattern images Pk1, Pc1, Pm
1, a pattern block PB1 composed of Py1,
A pattern block PB2 including the reference pattern images Pk2, Pc2, Pm2, and Py2 is formed.

The pattern blocks PB1, PB2 are formed as follows. That is, the control unit 150 sets the reference pattern image Pk in the first pattern block PB1.
1, Pc1, Pm1, and Py1 have been transferred to the transfer conveyance belt 60, and the reference pattern P at the most upstream side
Until y1 finishes passing through the transfer nip of the photosensitive drum 11K on the most downstream side, the solenoids 67 and 68 (see FIG. 5) of the transfer unit 6 are driven to reduce the transfer pressure to a predetermined level. Pressure). Due to this reduced pressure, the reference pattern images Pc1, Pm1, Py1
The transfer conveyance belt 60 is controlled while the reverse transfer to the photosensitive drum 11 in the transfer nip on the downstream side is suppressed.
Move with. Therefore, the pattern block PB1
Reference pattern images Pc1, Pm1, and Py1 in
Each of the density patterns has a state in which reverse transfer to the photosensitive drum 11 is suppressed.

The control unit 150 forms the respective reference pattern images Pk2, Pc2, Pm2, Py2 of the second pattern block PB2 on the photosensitive drums 11Y, 11M, 11C, 11K at a predetermined timing. . Specifically, the predetermined timing refers to the rear end of the first pattern block PB1 (the reference pattern image Py).
From the point when 1) further moves by a predetermined amount after passing through the transfer nip of the photosensitive drum 11K on the most downstream side, the reference pattern images Pk2, Pc2, Pm of the pattern block PB2.
2. The timing at which Py2 can start to be transferred onto the transfer / conveyance belt 60.

The control unit 150 sets the second pattern after the rear end (reference pattern image Py1) of the first pattern block PB1 passes through the transfer nip of the photosensitive drum 11K on the most downstream side. The solenoids 67 and 68 are driven to increase the transfer pressure to the original value before each reference pattern image P of the block PB2 starts to be transferred to the transfer conveyance belt 60. This pressurization enables good transfer of each reference pattern image P for the pattern block PB2.

Further, similarly to the first pattern block PB1, the control unit 150 controls the solenoid 67 and the second pattern block PB2 so that the reverse transfer to the photosensitive drum 11 can be suppressed. 68 is controlled.

The pattern blocks PB1 and PB2 include four reference pattern images Py, Pm, Pc and Pk, respectively. Further, since these reference pattern images each include five reference images 101, each color (Y , M, C, K)
, 5 × 2 = 10 reference images 101 are formed.

For each color, these ten reference images 10
Reference numeral 1 denotes a photosensitive drum 11 under image forming conditions shown in Table 1 below.
Formed on top. Note that the intensity of the laser beam is set to an intensity capable of attenuating the electrostatic latent image for the reference image 101 to, for example, -20 [V] regardless of the drum charging potential.

[Table 1]

In Table 1, (1), (2), (3), (4),
(5), (6), (7), (8), (9), and (10) are the first, second, third, and fourth from the leading end of the pattern block PB1 to the trailing end of the pattern block PB2. The fifth, sixth, seventh, eighth, ninth, and tenth reference images 101 are shown. Therefore, the reference image 1 of (1) to (5)
01 exists in the pattern block PB1, and the reference images 101 of (6) to (7) exist in the pattern block PB2.

As shown in Table 1, this laser printer is
In each of the toner image forming units 1Y, 1M, 1C, and 1K, the reference images 101 of (1) to (10) are formed while gradually switching the drum charging potential and the developing bias to lower values. The later the ten reference images 101 are formed, the higher the developing potential (difference between the potential of the electrostatic latent image and the developing bias), so that the image density becomes higher.

Each of the developing bias values shown in Table 1 and (1) to
The relationship between the reference image 101 and the image density of (10) is, for example, as shown in FIG.
The graph shown in FIG. That is, there is a positive correlation between the developing bias value and the image density (toner attachment amount per unit area), and a straight line graph as shown in the figure is obtained. By using the function (y = ax + b) showing the straight line graph, it is possible to calculate the developing bias value at which a desired image density (toner adhesion amount) is obtained.

FIG. 11 is a perspective view showing the transfer conveyance belt 60 together with the reflection type photosensor 69. As shown, the laser printer includes two reflection-type photosensors 69a and 69b. The two pattern blocks PB1, PB2 are respectively
Is formed near the front end in the drawing, and is detected by the reflection type photosensor 69a. The vicinity of this end is a portion corresponding to the region R2 of the developing device 20Y shown in FIG. In FIG. 3, the width W2 is a portion corresponding to the width of the transfer paper (not shown).
It is on the upstream side of the supply section 29Y in the developer transport direction. At the time of a normal printout process, the developer existing in the region R2 on the developing roller 22Y does not contribute to the development, and the developer on the developing roller 22Y and the region R2 of the first supply unit 29Y do not.
2 has a toner density maintained within a predetermined range by the toner supply control. Therefore, even when the Y toner image having a high image area ratio, such as a solid design image or a photographic image, is continuously developed during the printout process, the reference pattern image Py is developed with the developer having the normal toner density. Note that other reference pattern images P
m, Pc, and Pk are also developed by a developer having a regular toner concentration for the same reason. The role of the reflective photosensor 69b will be described later.

Next, the characteristic configuration of the laser printer will be described. [Light Transmitting Detecting Means] FIG.
It is a side view which shows a, 69b, and the structure of the periphery.
In the figure, a reflection member 70 in which a surface of a base material such as stainless steel is plated with Ni or Cr is in contact with the back surface of the transfer conveyance belt 60. This reflecting member 70
Backs up the transfer conveyance belt 60 while urging the back surface of the transfer conveyance belt 60 to move along the movement locus indicated by the alternate long and short dash line with an urging distance K of, for example, 1 to 2 [mm]. The contact surface of the reflection member 70 with the transfer / transport belt 60 is formed in a flat shape, and is subjected to a mirror finish so as to reflect light well. The light transmissivity detecting means in the present laser printer is constituted by the reflection type photo sensors 69a and 69b and the reflection member 70.

The reflection type photosensors 69a and 69b are opposed to the reflection member 70 for backing up the transfer and conveyance belt 60 with the transfer and conveyance belt 60 interposed therebetween.
Light emitted from light-emitting portions (not shown) of the reflection type photosensors 69a and 69b passes through the milky white or transparent light transmission portion of the transfer conveyance belt 60 and reaches the reflection member 70. And
The light is reflected by the surface of the reflecting member 70 to become reflected light, and is transmitted through the transfer / conveyance belt 60 again, and is reflected by the reflection type photo sensor 69.
a and 69b are detected by light receiving units (not shown). PVDF
The transfer conveyance belt 60 made of is milky white,
Even if the light emitted from the light emitting unit is transmitted through one round trip, the light transmitting unit has sufficient light transmittance to be sufficiently detected by the light receiving unit. If a sufficient amount of received light cannot be obtained, a transparent material may be used for the transfer and conveyance belt 60. Further, the transfer / conveying belt 60 may be configured so that only portions through which light is transmitted exhibit light transmittance.

In such a configuration, the photosensitive drum 11
In order to detect each reference image 101 transferred from Y, 11M, 11C, 11K to the transfer conveyance belt 60 as a moving body, instead of detecting reflected light of each reference image 101,
The transmitted light of the reference image portion on the transfer and conveyance belt 60 is detected. Therefore, various problems caused by detecting the reflected light of each reference image 101 can be solved.

As a photosensor for detecting transmitted light by reflecting light from the light emitting section by the light reflecting member 70, a reflection type photosensor in which the light receiving section and the light emitting section are housed in the same housing. Since it is possible to use the 69a and 69b, it is possible to eliminate problems such as deterioration in maintenance and layout flexibility caused by using a transmission type photosensor in which both parts are housed in separate housings. it can.

Further, as shown in the figure, the transfer / transport belt 6 in which the vertical vibration is suppressed by the backup by the reflection member 70 is provided.
By detecting the light transmittance of the zero portion (belt portion) by the reflection type photo sensors 69a and 69b, erroneous detection of the sensor due to vertical vibration can be suppressed.

Further, the belt portion in which the vertical vibration is suppressed is different from the belt portion backed up by the tension roller as shown in the drawing, and has a planar shape following the plane of the backed-up reflecting member 70. Therefore, erroneous detection due to detection of the reference image 101 at the curved portion of the transfer conveyance belt 60 can be suppressed. Further, since the vertical vibration of the transfer conveyance belt 60 is suppressed without using the negative pressure generating means, it is possible to eliminate cost increase and noise generation by the negative pressure generating means.

As shown in the figure, the position of the reflection type photosensors 69a and 69b is not the position facing the center O of the reflection member 70, but the position near the end of the reflection member 70 on the downstream side in the belt moving direction. Position is desirable. This is because the vertical vibration of the transfer conveyance belt 60 is suppressed near the end in comparison with the vicinity of the end on the upstream side in the belt moving direction.

In FIG. 9 described above, each of the reference pattern images Pk1, Pc1,
After the belt Pm1 and Py1 move with the endless movement of the belt and are detected by the reflection type photosensor 69a, they enter the contact position of the transfer unit 6 with the bias roller 63 (see FIG. 2), where the bias is applied. The toner is electrostatically transferred to the roller 63 and removed. The reflection type photo sensor 69a

Two reflective photosensors 69a and 69b
Of the reference pattern images 69a, reference pattern images Pk1, Pc1, and Pc1 extend from the front end to the rear end of the first pattern block PB1.
Each reference image 101 in Pm1 and Py1 is detected in the following order. That is, five reference images 101 of the reference pattern image Pk1, five reference images 101 of the reference pattern image Pc1,
The five reference images 101 of the reference pattern image Pm1 and the five reference images 101 of the reference pattern image Py1 are detected in this order. At this time, a voltage signal corresponding to the transmitted light amount is sequentially output to the control unit 150. The control unit 150 includes:
Based on the voltage signals sequentially sent from the reflection type photosensor 69, the image density of each reference image 101 is sequentially calculated and stored in the RAM 150a.

The reflection-type photo sensor 69a extends from the front end to the rear end of the second pattern block PB2.
The amount of reflected light from each of the reference images 101 constituting the reference pattern images Pk2, Pc2, Pm2, and Py2 is detected in the same order as in the pattern block PB1. The control unit 150
As in the case of the first pattern block PB1, the image density of each reference image 101 is sequentially calculated based on the voltage signal sequentially transmitted from the reflection type photosensor 69, and the RAM is used.
150a.

The control unit 150 performs a regression analysis for each color using each developing bias value and the image density data of the reference image 101 (1) to (10), and performs a linear graph as shown in FIG. (Regression equation) Then, an appropriate developing bias value is calculated by substituting the target value of the image density into this function, and is stored in the RAM 150a as a corrected developing bias value for Y, M, C or K.

On the other hand, the RAM 150a stores the following Table 2.
The image forming condition table shown in FIG.

[Table 2]

As shown in Table 2, in the image forming condition table, 30 types of developing bias values are associated with appropriate drum charging potentials.

The control unit 150 controls the toner image forming unit 1
For Y, 1M, 1C, and 1K, a developing bias value closest to the corrected developing bias value is selected from the image forming condition table, and a drum charging potential associated with the developing bias value is specified. Regarding the specified drum charging potential, the correction drum charging potential for Y, M, C or K is R
Store it in the AM 150a. When all the corrected developing bias values and the corrected drum charging potentials are stored in the RAM 150a, the data of the developing bias value for Y, the developing bias value for M, the developing bias value for C, and the developing bias value for K correspond respectively. The value is corrected to a value equivalent to the corrected development bias value and stored again. Also, the Y drum charging potential, the M drum charging potential, the C drum charging potential, and the K drum charging potential are corrected and stored again to values equivalent to the corresponding correction drum charging potentials. By such correction, the image forming conditions of the toner image forming units 1Y, 1M, 1C, and 1K at the time of the printout process are corrected to conditions that can form a toner image having a desired image density.

The above T sensor 2 in this laser printer
Reference numeral 6 does not actually detect the toner concentration of the developer, but detects the magnetic permeability showing a certain correlation with the toner concentration. However, the magnetic permeability of the developer varies not only with the toner density but also with the bulk density of the toner, and this bulk density varies with the temperature and humidity and the degree of stirring of the developer.
For this reason, even if the toner replenishment is performed so that the output value from the T sensor 26 becomes the target value Vtref as described above, if the bulk density of the toner changes due to a change in temperature and humidity, the toner density is changed. Is controlled higher than the goal,
It is controlled lower. When controlled to a higher level, FIG.
The slope of the straight line graph becomes larger than the state shown in the figure (the graph rises). If the control is made lower, the inclination of the straight line graph becomes smaller than that in the state of the figure (the graph falls down). Therefore, when the inclination of the straight line graph is increased or decreased as described above, the target value Vtref is not suitable for the current developer due to a change in the bulk density of the toner.

Therefore, when the inclination of the straight line graph becomes larger or smaller than a predetermined value, the control unit 150 sets the T of the corresponding developing device 20 (any of Y, M, C, and K). The target value Vtref of the sensor 26 is corrected to a value equivalent to the output value from the T sensor 26 at that time,
Try to match the current developer.

In FIG. 1 described above, the optical writing unit 2 reflects the laser beams emitted from the light sources for Y, M, C, and K to reflect the photosensitive drums 11Y, 11M, 11M.
Reflection mirrors for guiding C and 11K are individually provided. Further, the photosensitive drums 11Y, 11M, 11
Mirror tilting means (not shown) for individually tilting the reflecting mirrors arranged in parallel with C and 11K is also provided.

After completing the correction of each developing bias value and the charging potential of each drum, the control unit 150 executes a displacement correction control. In this misregistration correction control, misregistration detection reference pattern images pP1 and pP2 are formed on the transfer conveyance belt 60 as shown in FIG. The reference pattern image pP1 is formed near the lower end of the transfer conveyance belt 60 in FIG.
Is detected by The reference pattern image pP2 is
It is formed near the upper end of the transfer conveyance belt 60 in the figure and is detected by the reflection type photo sensor 69b.

The reference pattern images pP1 and pP2 are shown in FIG.
, Four reference images d101K, d101C, d101M, extending straight in the belt width direction, respectively.
d101Y, and reference images s101K, s101C, s101M, and s101Y inclined by 45 ° from the belt width direction. Within the reference pattern images pP1 and pP2, the reference images d101K, d101C, d101M, d1
01Y, s101K, s101C, s101M, s10
1Y is formed at a pitch of a distance d, and the entire length of the reference pattern is L3. Of these reference images, reference images d101K, d101C, d101M, and d101Y are:
The length A and the width W are formed. Also, the reference image s1
01K, s101C, s101M, and s101Y are formed with a length A√2 and a width W. Further, reference images d101K, d101C, d101 of the reference pattern image pP1.
M, d101Y, s101K, s101C, s101
M, s101Y, and reference image d10 of reference pattern pP2
1K, d101C, d101M, d101Y, s101
K, s101C, s101M, and s101Y are formed to face each other in the belt width direction.

Here, the photosensitive drums 11Y, 11M, 1M
1C and 11K are tilted due to an assembly error, and Y, M, C, and K reflecting mirrors in the optical writing unit 2 are tilted in the longitudinal direction.
It is assumed that the driving timing of the polygon mirrors for Y, M, C, and K and the light source does not deviate from the regular timing. Then, as shown in FIG. 13, the reference images 101 are formed so as to maintain a parallel state at equal intervals. With respect to the reference image 101 formed in this manner, both of the reflective photosensors 69a and 69b detect the reference image almost simultaneously. Further, as shown in FIG. 15, the reference images d101K, d101C, d101M, d1 by the reflection type photosensor 69a.
The detection intervals t1a, t2a, and t3a of 01Y become equal. The detection intervals t1a, t2a, and t3a are defined as a period from the time when the reference image d101K is detected to the time when the reference image d101C is detected, after the reference image d101C is detected.
This is the time from detection of the reference image d101M until detection of the d reference image 101Y until 1M is detected. Also,
The reflection type photo sensor 69b is a reflection type photo sensor 69b.
The reference images d101K, d101C,
d101M and d101Y are detected, and each detection interval t1b,
t2b and t3b become equal.

However, for example, the photosensitive drum 11
When the inclination due to the assembling error occurs in C or when the reflection mirror for C in the optical writing unit 2 is inclined in the longitudinal direction, as shown in FIG.
The two reference images d101C facing each other are displaced due to skew. When the positional shift due to the skew occurs as described above, the reflection type photosensor 69a sets the reference image d1.
01C detection timing and reflection type photosensor 6
A time lag Δt occurs between the timing at which the reference image 9b detects the reference image d101C. The skew angle θ can be obtained based on the time lag Δt and the moving speed of the transfer conveyance belt 60. Also, instead of the reference image d101C, other reference images d101K, d101M, d101
Even when skew occurs in Y, the skew angle θ can be obtained in the same manner.

Therefore, the control unit 150 sets the reference image d1 for the two reference toner images pP1 and pP2.
The detection timings of 01K, d101C, d101M, and d101Y are sequentially stored in the RAM 150a, and the detection intervals t1a, t2a, t3a, t1b, t2b, and t3b are obtained. The skew angle θ is calculated for the reference image having the time lag Δt, and the skew is suppressed by tilting the corresponding reflection mirror by the mirror tilting means based on the calculation result.

If, for example, the drive timing of the C light source in the optical writing unit 2 deviates from the regular timing, as shown in FIG.
01C is displaced by the resist in the sub-scanning direction. When the displacement occurs as described above, the detection interval t1a,
While t2a and t3a have different values,
The detection intervals t1b, t2b, and t3b also have different values. However, as shown in FIG. 16, even when the position shift due to the skew occurs, the detection interval t1a,
t2a, t3a and the detection intervals t1b, t2b, t3b have different values. Therefore, the control unit 150 determines the detection intervals t1a, t2a, t3a, t1b, t2 based on the time lag Δt generated by the skew.
After correcting b and t3b to remove the influence of skew, the amount of positional deviation due to registration in the sub-scanning direction is obtained. Then, K, C, M,
The drive timing for Y is corrected to suppress registration in the sub-scanning direction.

When the skew and the misregistration due to the registration in the sub-scanning direction are corrected in this manner,
Reference image s1 in two reference pattern images pP1 and pP2
Based on 01K, s101C, s101M, and s101Y, the positional deviation due to the registration in the main scanning direction is corrected. Specifically, as long as there is no registration shift in the main scanning direction, as described above, the detection intervals t1a, t1
2a, t3a, t1b, t2b, and t3b are all equal. However, for example, as shown in FIG. 18, when a registration shift in the main scanning direction occurs in the reference image s101C in the reference pattern image pP2 (upper side in the figure), the detection interval t1b,
t2b and t3b have different values. At this time, if the size of the reference image s101C in the main scanning direction is a regular size (the magnification in the main scanning direction is 1).
As shown in FIG. 18, the reference image s101C in the reference pattern image pP1 (lower side in the figure) is similarly registered, and the detection intervals t1a, t2a, and t3a have different values. t1b, t2b, t3b
Sync to. On the other hand, the reference image s101 in the main scanning direction
When the size of C is larger than the normal size (the magnification in the main scanning direction exceeds 1), for example, the reference image s101C in the reference pattern image pP2 is registered (in the main scanning direction) even though it is registered (main scanning direction). As shown in FIG. 19, the reference image s101C in the reference pattern image pP1 is not registered, or the amount of registration is reduced.

Therefore, the control unit 150 sets the detection interval t
1a, t2a, t3a, t1b, t2b, t3b and the reference image s101K in the two reference pattern images pP1, pP2 based on the moving speed of the transfer conveyance belt 60.
The amount of registration deviation (main scanning direction) and the magnification (main scanning direction) of s101C, s101M, and s101Y are calculated. Then, based on the calculation result, the drive timing of the corresponding polygon mirror is corrected, or the corresponding reflection mirror is tilted by the mirror tilting means to suppress such registration deviation and magnification deviation.

As described above, by suppressing the skew, the registration in the sub-scanning direction, and the registration in the main scanning direction for each color, the disturbance of the full-color toner image formed during the printing process can be suppressed.

The magnification in the sub-scanning direction is corrected by the time during which the reference images d101K, d101C, d101M, and d101Y are detected.

Table 3 below shows an example of the configuration of the reference pattern images pP1 and pP2 for detecting a positional deviation. As shown in Table 3, the reference pattern image pP for detecting the displacement is used.
1. Various variations can be considered for the configuration of pP2.

[Table 3]

In the laser printer having the above configuration, the reference image 101 of each color is not based on the reflected light amount of the reference image 101 of each color, but on the basis of the transmitted light amount of the transfer conveying belt 60 on which the reference image 101 of each color is transferred. And the image density are detected. Therefore, the reference image 101 of each color can be detected by the same reflective photosensor without providing a dedicated photosensor for detecting the reference image 101 for each color.

As described above, the laser printer that corrects the latent image forming position on the photosensitive drum 11 by correcting the conditions in the optical writing unit 2 such as the angle of inclination of the above-mentioned reflecting mirror to suppress registration deviation and skew. As described above, instead of correcting this condition, the latent image forming position is corrected by correcting the position of a latent image carrier such as a photosensitive drum or an endless moving body such as a transfer conveyance belt. Is also good.

[0095]

According to the first, second, third, fourth, fifth, or sixth aspect of the present invention, there is a problem caused by detecting reflected light of the reference toner image for detecting the reference toner image. In addition, there is an excellent effect that both problems caused by using the transmission type photosensor can be eliminated.

In particular, according to the second or third aspect of the present invention, the erroneous detection of the light transmissivity detecting means due to the vertical vibration and bending of the endless belt is suppressed, and the cost due to the provision of the negative pressure generating means is provided. There is an excellent effect that ups and noise generation can be eliminated.

In particular, according to the invention of claim 3, there is an excellent effect that the erroneous detection of the light transmissivity detecting means due to the vertical vibration of the endless belt can be suppressed more reliably.

Further, in particular, according to the invention of claim 4, there is an excellent effect that the displacement of the formation position of the toner image on the image carrier can be suppressed.

In particular, according to the invention of claim 5, there is an excellent effect that a full-color image can be formed. Further, there is an excellent effect that the image forming speed of a full-color image can be increased as compared with the case where a single image carrier is provided to form a full-color image. Further, a tandem system in which color misregistration easily occurs in a full-color image is used, but the color misregistration can be suppressed by correcting the misregistration of each color toner image based on the misregistration of the reference toner image of each color. There is an excellent effect. Further, there is an excellent effect that the reference toner image of each color can be detected by one reflection type photo sensor.

According to the present invention, even if the toner in the developer in the developing device is consumed during the development,
There is an excellent effect that the toner density of the developer can be maintained in an appropriate density range.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a laser printer according to an embodiment.

FIG. 2 is an enlarged view showing a schematic configuration of a toner image forming unit 1Y of the laser printer.

FIG. 3 is a longitudinal sectional view showing a developing device 20Y of the toner image forming unit 1Y.

FIG. 4 is an enlarged view showing a schematic configuration of a transfer unit of the laser printer.

FIG. 5 is a schematic diagram showing a transfer pressure adjusting unit of the transfer unit.

FIG. 6 is a block diagram showing a part of an electric circuit of the laser printer.

FIG. 7 is a schematic diagram showing a reference pattern image for density detection formed by the laser printer.

FIG. 8 is a schematic diagram showing an installation pitch of each photosensitive drum in the laser printer.

FIG. 9 is a schematic view showing a pattern block formed on a transfer conveyance belt of the laser printer.

FIG. 10 is a graph showing a relationship between a developing bias value and a toner adhesion amount of each reference image.

FIG. 11 is a perspective view showing the transfer conveyance belt together with a reflection type photo sensor.

FIG. 12 is a side view showing a reflection type photo sensor in the laser printer and a configuration around the reflection type photo sensor.

FIG. 13 is a schematic diagram showing reference pattern images pP1 and pP2 for detecting positional deviation formed by the laser printer together with a transfer conveyance belt.

FIG. 14 shows reference pattern images pP1 and pP for detecting displacement.
The enlarged schematic diagram which shows P2.

FIG. 15 is a schematic diagram showing the same reference pattern images pP1 and pP2 in a state where no displacement has occurred.

FIG. 16 is a schematic view showing the reference pattern images pP1 and pP2 in a state where a position shift due to skew has occurred in the reference image d101C.

FIG. 17 shows a reference image dP in which the reference image d101C is displaced by a resist in the sub-scanning direction.
1, a schematic diagram showing pP2.

FIG. 18 shows a reference pattern image pP in which a reference image d101C is displaced due to registration in the main scanning direction.
1, a schematic diagram showing pP2.

FIG. 19 is a schematic diagram showing the same reference pattern images pP1 and pP2 in a state where a reference image d101C has a positional shift due to registration in the main scanning direction and a magnification change in the main scanning direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Toner image forming part 2 Optical writing unit (latent image forming means) 3, 4 Paper feed cassette 5 Registration roller pair 6 Transfer unit 7 Fixing unit 8 Discharge tray 11 Photoconductor drum (latent image carrier) 20 Developing device 22 Developing roller (developer carrier) 27 Powder pump (toner replenishing means) 29 First supply unit 30 Second supply unit 60 Transfer / conveyance belt (endless belt) 69 Reflective photosensor 101 Reference image (reference toner image) 150 Control Department

Continued on the front page (72) Inventor Tetsuo Yamanaka 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Jun Hosokawa 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Satoshi Shinohara 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Shita Fujimori 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. Reference) 2H027 DA09 DE02 DE07 EA06 EB04 EC03 EC06 ED10 ED16 2H030 AA01 AB02 AD05 AD16 BB36 BB38 BB44 BB56 2H077 DA03 DA31 DA63 DA64 DB02 EA03 GA12

Claims (6)

[Claims] An image carrier for carrying a toner image, a toner image forming means for forming a toner image on the image carrier, and a reference toner image on the image carrier transferred to a surface while moving in a predetermined direction. And a control unit for performing predetermined control based on a detection result of the light transmission detecting unit, the light transmitting unit detecting light transmission in a reference toner image portion on the moving unit. In the image forming apparatus including: a light emitting unit that emits light toward a front surface that is a transfer surface of the endless moving body; and a light transmitting unit that transmits the transmitted light that has passed through the moving body as the light transmissivity detecting unit. An image forming apparatus comprising: a light reflecting member that reflects light toward a surface of the movable body; and a light receiving unit that receives light reflected by the moving body after reflection. 2. The image forming apparatus according to claim 1, wherein the movable body is provided with an endless belt that is endlessly moved while being stretched by a plurality of stretching members that contact the back surface thereof, and the reflecting member is An image forming apparatus, comprising: a reflecting portion formed in a planar shape, which is in contact with a back surface of the endless belt to back up the endless belt. 3. An image forming apparatus according to claim 2, wherein said light-emitting portion and said light-receiving portion are arranged at a position facing the vicinity of a downstream end of said reflecting member in the direction of endless belt movement. Forming equipment. 4. The image forming apparatus according to claim 1, wherein the control means performs the predetermined control as the predetermined control based on a detection result of the light transmission detecting means. A position shift correction control for calculating a position shift amount of the image from a normal position, and changing a control condition for the toner image forming means based on the calculation result to correct a toner image formation position on the image carrier. An image forming apparatus according to claim 1. 5. An image forming apparatus according to claim 4, further comprising a plurality of said image carriers and said toner image forming means respectively corresponding to each of said image carriers, wherein said plurality of image carriers are provided so as to sequentially face each image carrier. An image forming apparatus comprising: the moving body configured to transfer the reference toner image on each image carrier while moving in a direction. 6. An image forming apparatus according to claim 1, wherein said image carrier is a latent image carrier for carrying a latent image, and said toner image forming means is a latent image carrier. Latent image forming means for forming a latent image on the image carrier, a developing device for developing the latent image on the latent image carrier with a developer containing toner and carrier, and toner for supplying toner to the developing device Replenishing means, and the control means performs toner replenishment control for controlling the driving of the toner replenishing means based on a detection result of the light transmissivity detecting means as the predetermined control. Image forming device.