JP2873757B2 - Image forming device - Google Patents

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 multicolor copying machine and a laser beam printer.

[0002]

2. Description of the Related Art An image forming apparatus of this type includes an image carrier,
The image forming apparatus includes a developing unit that forms an image on the image carrier using a developer, and a transfer unit that transfers the formed image to a transfer material.

In Japanese Patent Application Laid-Open No. 63-43169, the image density on the transfer material is detected, and the transfer current value of the transfer means is corrected based on the detection result.

[0004]

However, in the above-mentioned conventional example, a difference in which two densities, for example, 25% and 100%, are fixed, is not proportional to the transferred image, is determined as the transfer efficiency. , Or the effect of density change due to a decrease in developing ability could not be taken into account.

An object of the present invention is to solve the above-mentioned problem, and an object of the present invention is to provide an image forming apparatus capable of setting a transfer current in response to a change in environment.

[0006]

In order to achieve the above object, the present invention provides an image carrier and a latent image formed on the image carrier.
Developing means for developing with an image agent, and a transfer material for developing the developed developer image
Forming a developer for detection
The transfer condition is set by detecting the concentration of the detection developer.
Image forming apparatus, the image is not transferred onto the image carrier.
A first detecting means for detecting the concentration of the detection developer that, Zo担
Detects the concentration of developer transferred from the carrier
The second detection means, the first detection means and the second detection means
A method for determining the transfer efficiency by the transfer means based on the detection result
Environmental conditions are classified into multiple categories based on steps, temperature and humidity.
Stores the correlation between transfer current and transfer efficiency for each classification
Built-in table held by the detection means
The transfer current is set according to the transfer efficiency obtained and the table.
A constant control means, and a environment detecting means, said environmental test
Measured environmental conditions detected by intellectual means and transfer efficiency
The transfer current at the time is compared with the table.
And setting the transfer current .

[0007]

[0008]

[0009]

[0010]

[0011]

[0012]

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

According to the present invention based on the above configuration, the transfer current is set by comparing the environmental conditions detected by the environment detecting means, the transfer current when the transfer efficiency is measured, and the table.

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

【Example】

Embodiment 1 FIG. 1 shows an example of an image forming apparatus which can embody the present invention. This image forming apparatus includes four photosensitive drums (image carriers) 1K, 1Y, and 1 as an example of a laser beam printer having a light traveling unit using a plurality of laser beams.
This is a laser beam printer having C and 1M. This printer is provided around the photosensitive drums 1K, 1Y, 1C and 1M.
Each of the developing means 4K, 4Y, 4C, and 4M for a plurality of colors has 4
The transfer material is provided so that the images on the photosensitive drums 1K, 1Y, 1C, 1M formed by the respective developing means 4K, 4Y, 4C, 4M move in opposition to the photosensitive drums 1K, 1Y, 1C, 1M. The recording is performed on a transfer member P, that is, a transfer material conveyed by a belt 6a.

Each photosensitive drum 1M, 1C, 1Y, 1K
, Primary chargers 2M, 2C, 2Y, 2K are provided, and scanning optical devices 3M, 3 as light traveling means are provided.
C, 3Y, and 3K are provided. Further, the developing devices 4M, 4M
C, 4Y, 4K, and cleaners 5M, 5C, 5Y, 5
K is arranged.

Further, the transfer section 6 constituting one of the image forming means includes a transfer belt 6a commonly used for the photosensitive drums 1K, 1Y, 1C and 1M and a transfer charger (transfer means) for each drum. ) 6M, 6C, 6Y, 6K. The formation of a full-color image is achieved by sequentially transferring each color toner image formed on the photosensitive drum onto a transfer material P supported on a transfer belt 6a. The transfer material P is supplied from a sheet cassette (not shown), and the transfer material P having completed the transfer process is separated and discharged out of the apparatus via a fixing device (not shown).

The scanning optical devices 3M, 3C, 3Y, 3K
Denotes a laser light source (not shown), a rotating polygon mirror for scanning laser light from the laser light source, an fθ lens for condensing a scanning beam on a generatrix on the surface of the photosensitive drum, a reflection mirror for deflecting a light beam, And a beam detector for detecting a specific position of the beam.

FIG. 2 is an enlarged view of the arrangement around the photosensitive drum of each image forming station typified by the final black station. 11K is a surface potential sensor,
The surface state of the photosensitive drum 1K is detected based on the surface potential of the photosensitive drum. Reference numeral 14 denotes an electrometer, and the surface potential sensor 1
The value detected at 1 is sent to the controller (control means) 15. Further, 13K is a developer concentration sensor, and the developing device 4
A developer concentration sensor 13 for keeping the developer concentration in K constant
And a light reflection type or an inductance type.

As another method for detecting the developer density, there is a method of forming a specific density image on the photosensitive drum 1K and detecting the density by the light receiving element 19a or 19b. In this embodiment, this is adopted. Information on the developer concentration sensor 13 or the light receiving elements 19a and 19b is also sent to the controller 15.

Reference numeral 22 denotes a test patch (developer), which is a visible image transferred on the transfer belt 6a. 12a is L
The light is an ED, and the reflected light of the test patch 22 with respect to the irradiating light is received by the light receiving element 12b, and the signal whose density has been converted is sent to the controller 15.

Here, the image transferred onto the transfer belt 6a may be a step patch having a step density of 8 steps or 16 steps from the lowest density to the highest density or a specific single density patch. These test patches are generated by a test pattern generator (not shown).

Next, a method for measuring the transfer efficiency according to the present invention will be described with reference to FIG. A test patch is generated by a test pattern generator (not shown) and the optical scanning device 3
A latent image is formed on the photosensitive drum 1K by the K laser beam, and the latent image is visualized by the developing unit 4K. Visible image read by the light receiving element 19a, is density converted by the controller 15 is stored as a density D _1.

Thereafter, the visible image is transferred onto the transfer belt 6a by the transfer charger 6K to form a test patch 22, and the light-emitting and light-receiving elements 12 provided above the transfer belt 6a.
a, further read again by 12b, is density converted by the controller 15 is stored as a density D _2. The controller compares D ₁ and D ₂ , and sets D ₂ / D ₁ as the transfer efficiency.

Next, means for correcting the transfer efficiency obtained above will be described. FIG. 3 shows a range in which the same transfer effect can be obtained with the same transfer current due to changes in the temperature and relative humidity at the place where the image forming apparatus is installed. Areas 1 to 7 demarcated by dotted lines are areas where the same transfer efficiency can be obtained with the same transfer current, and section 8 indicates a boundary where good image transfer efficiency can be obtained. The above-mentioned temperature and relative humidity are detected by an environment sensor attached to the image forming apparatus.

FIG. 4A is a diagram showing the transfer current and the transfer efficiency in each environmental region. Region 2 corresponds to solid line A, region 4 corresponds to B, and region 7 corresponds to C. In the regions 6, 5, 3, and 1, they fall between the solid lines A to C, respectively. For example, if the transfer efficiency of the transfer charger 6K at a transfer current of 300 μA is 75% and the environment at this time is in the area 2, the transfer current is corrected in a direction to increase by a table in the controller 15.

Similarly, if the transfer efficiency at a transfer current of 300 μA is 75% and the environment at this time is 7, the transfer current is corrected by the table in the controller 15 to decrease. In this way, the correction direction can be uniquely determined by combining with the environmental characteristics.

FIG. 4B shows the use of the transfer system used in the experiment. The toner has a particle diameter of 800 μm and a charge amount of −30 μc /
g, the photosensitive drum uses an OPC photoreceptor of 80φ, CT
The layer has a characteristic of 20 μm and a dielectric constant ε = 2.7. The volume resistivity of the transfer belt 6a is 10 ⁻¹⁴ to 10 ⁻¹⁵ Ω · cm, and the film thickness is 150 μm.

The shield width SW and the shield height SH of the transfer charger are both 20 mm, and the distance WH between the wire transfer belts is
Is 10 mm, the distance between the rear surfaces of the wire shield is 15 mm, and the wire is a 60 μm tungsten wire.

Since the relationship between the transfer current and the transfer efficiency changes depending on the above-described conditions, the characteristic shown in FIG. 3 is also an example, and the transfer current may be determined according to the specifications of each image forming apparatus.
A stable image can always be obtained by using the appropriate transfer current obtained by the above method. Embodiment 2 Next, an example in which an image is transferred onto a transfer material P conveyed by a transfer belt 6a and the density of the image is detected will be described.

When a test patch is formed on the transfer material 6a, the total current flowing through the transfer chargers 6M to 6K is, for example, 100
Six types of test patches were prepared in which the test patches were changed every 100 μA from 600 μA to 600 μA.
The density is converted by the controller 15 and is plotted on a graph in a memory in the controller 15 so that an optimum transfer current can be determined from a peak value of the transfer efficiency.

FIG. 4A shows an example of a graph on a memory in the controller 15. C is temperature 30 ℃, relative humidity 8
0%, B is temperature 23 ° C, relative humidity 60%, A is temperature 20
° C and a relative humidity of 10%.

According to an experiment showing the relationship between the total current to the transfer charger and the transfer efficiency, the transfer efficiency changes depending on the environment. In this embodiment, a change in the transfer current of 100 μA to 60 μA is suitable for all environments. The transfer current can be determined. [Embodiment 3] In the above embodiment, the sensor 19a for reading the test patch on the photosensitive drum 1K has not been transferred yet. In this embodiment, the light receiving element 19b is provided downstream of the transfer charger 6K. Arranging the light receiving element 19b downstream of the transfer charger 6K is advantageous in that the influence of the scattered toner is smaller than that of the upstream side.

However, at this time, the light receiving elements 12a, 12b
The detected concentration D ₂ in transfer efficiency obtained from the detected concentration D ₃ of the light receiving element 19b is given by D ₂ / D ₂ + D _3. Fourth Embodiment In FIGS. 5 and 9, reference numerals 9 and 10 denote cross-shaped or well-shaped 11M, 11C, 1
The registration pattern formed on 6a when transferred by each color of 1Y and 11K. 18a, 18b
Is a reading element capable of detecting the patterns 9 and 10 of 9, 10, 17a and 17b are light sources, and 14a and 14b are optical systems.

In the present embodiment, in the system in which the test pattern is read in the previous embodiment, the above-mentioned 11M, 11C, 11Y,
By reading the registration pattern of each color of 11K, detecting each deviation in the main scanning direction K and the sub-scanning direction L of each color, and controlling a scanning optical system (not shown), the accuracy of registration is also improved. This control method is known from Japanese Patent Application Laid-Open No. 63-271275. The patterns 9 and 10 may be formed on the transfer material P. [Embodiment 5] In Embodiment 4, two sets of light receiving elements 18a and 18b as pattern detection means are provided at the same position in the main scanning direction K. In this embodiment, the reading accuracy can be improved by causing the controller 15 to calculate the density of the test patch detected by the two light receiving elements as an average value of the two sets. [Embodiment 6] In this embodiment, each patch is transferred to the same position on the transfer belt 6a in order to prevent the test patches or the registration patterns 9, 10 from being affected by the flaws of the transfer belt 6a. [Embodiment 7] For example, if the black toner contains carbon black or the like, the carbon black is
The wavelengths in the sensitivity regions a, 19b, 12a, 12b, 18a, and 18b are absorbed, so that reading may not be possible. Therefore, when the toner having the above-described characteristics is used in combination with another readable toner, the complete solid patch of the readable toner is first transferred onto the transfer belt 6a, and the toner is not read by being superimposed thereon. Transfer possible toner patches.

Then, the absorption characteristics are read by each light receiving element, and as a result, the density of all toners can be read.
In this case, however, one more table for density conversion of the controller 15 must be prepared. [Embodiment 8] In this embodiment, the timing for performing the transfer current review control according to the present invention will be described. The control is preferably performed after a specific operation such as when the main power is turned off / on, or when a reset switch is operated or a front door is opened or closed due to a paper jam or the like.

Further, specific conditions, that is, the temperature and humidity of the place where the main body is installed are detected by the detecting means attached to the main body of the image forming apparatus, and the control is performed based on the result. [Embodiment 9] According to the structure of the present invention, when a test patch of a magenta image is formed in the first station, there is a concern that the test patches come into contact with the photosensitive drums 1Y, 1C and 1K of cyan, yellow and black, and the toner image is disturbed. There is. In this case, when the test patch formed in the upstream station passes through the downstream station, for example, release of a pressing member (not shown) that maintains the contact pressure between the transfer belt 6a and the photosensitive drum, or transfer of the transfer unit 6 is performed. It is desirable to provide a distance between the transfer belt 6a and the photosensitive drum, for example, by lowering it.

[0055]

As described above, according to the environment detecting means.
Environmental conditions detected and transfer when transfer efficiency is measured
By determining the optimal transfer current by comparing the current with the table , high image quality can be maintained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus to which the present invention is applied.

FIG. 2 is a partially enlarged view of FIG. 1;

FIG. 3 is an environment table showing regions of the same transfer efficiency used in the present embodiment.

FIG. 4A is a graph showing the transfer efficiency according to the environmental difference of the present embodiment, and FIG. 4B is a diagram showing the vicinity of the photosensitive drum and the transfer charger of the present embodiment.

FIG. 5 is a conceptual diagram of a registration servo unit according to the present invention.

[Explanation of symbols]

1K, 1Y, 1C, 1M Photosensitive drum 4K, 4Y, 4C, 4M Developing device 6a Transfer belt 15 Controller P Transfer material 22 Test patch 19a, 19b, 12a, 12b, 18a, 18b Light receiving element 6K Transfer charger

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 15/16

Claims (1)

(57) [Claims] An image bearing member and a latent image formed on the image bearing member
Developing means for developing the developer with the developer, and transferring the developed developer image
Transfer means for transferring to a copying material, and forming a developer for detection.
The transfer conditions by detecting the concentration of the developer for detection.
In the image forming apparatus, the density of the detection developer on the image carrier without being transferred is detected.
First detecting means for detecting the density of the developer transferred from the image carrier
A second detecting means for, based on a detection result of the above-described first detection means and second detection means
Environmental conditions into two or more categories based on the means for determining the transfer efficiency by the transfer means and the temperature and humidity.
Correlation between transfer current and transfer efficiency is stored in storage means
With a built-in table.
Transfer current is set according to the transfer efficiency and the table
And control means, and a environment detecting unit, and the environmental conditions detected by the environment detection unit, a transfer efficiency
Is compared with the transfer current when measuring
An image forming apparatus for setting a transfer current .