JP2001201897A - Image-forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that the actuation of a developing device is hindered, because temperature at the inside of the developing device rises abnormally by the actuation of the developing device. SOLUTION: The developing device is intermittently actuated by lowering image forming speed, when the temperature at the inside of the developing device rises while detecting the temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus for forming an image by an electrophotographic method, and more particularly to an improvement of a developing device in the image forming apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus for forming an image by an electrophotographic method, a magnetic brush development using a dry developer, particularly a developing apparatus using a two-component developer is widely used.

In the two-component magnetic brush development, a carrier and a toner are uniformly mixed in a developing device, and a developer is agitated to give a necessary charge to the toner. The developer which supplies the developer is conveyed. A rotating member such as a screw is used for stirring and transporting the developer.

[0004]

However, when the operation of the rotating stirring / conveying member is continued for a long time or when the rotation speed of the stirring / conveying member is high, the temperature in the developing device rises, which is desirable. No phenomena were found to occur. That is, it has been found that the developer becomes a lump due to a rise in the temperature in the developing device, which hinders the agitation and conveyance and impairs the developing performance.

An object of the present invention is to solve such a problem caused by a rise in the temperature inside the developing device.

[0006]

The object of the present invention is achieved by the following invention.

(1) An electrostatic latent image carrier, a developing device for developing an electrostatic latent image on the electrostatic latent image carrier, temperature detecting means for detecting the temperature in the developing device, and the temperature detecting means An image forming apparatus comprising: a control unit that changes an image forming speed based on temperature information from a printer.

(2) The control means changes the image forming speed by changing an interval between toner images on the electrostatic latent image carrier. Image forming device.

(3) The control means (1) or (2), wherein when the temperature in the developing device exceeds a first predetermined value, the control means performs control to reduce the image forming speed. Item 10. The image forming apparatus according to item 1.

(4) When the temperature in the developing device falls below a second predetermined value lower than the first predetermined value, the control means performs control to return the lowered image forming speed to the original value. The image forming apparatus according to the above mode (3), wherein

(5) The image forming apparatus includes a plurality of the developing devices, and the control unit reduces the image forming speed when a temperature in at least one of the plurality of the developing devices exceeds the first predetermined value. (1) to (4) characterized in that control is performed.
The image forming apparatus according to any one of (4).

(6) The temperature detecting means has time measuring means for measuring the operation time and the stop time of the developing device, and the temperature in the developing device is measured based on the time measured by the time measuring means. Wherein the temperature in the developing device is detected by estimating the temperature.
The image forming apparatus according to any one of (5).

(7) When the operating time is ta and the stop time is tb, the temperature Tmp in the developing device is estimated by the following equation: Image forming device.

Tmp = Σα × ta−Σβ × tb + T0 where α, β and T0 are constants.

(8) When the estimated temperature Tmp falls below a third predetermined value lower than the first predetermined value and the second predetermined value, the estimated temperature Tmp is set to a predetermined value. (6) or (7) above,
Item 10. The image forming apparatus according to item 1.

(9) The image forming apparatus according to the above (7) or (8), wherein the constant T0 is changed according to the temperature of the fixing device at the time when the power is turned on.

(10) At the time of turning off the power, the temperature Tmp is initialized to the constant T0, and the time measuring means measures the power-off time during which the power is off, and corresponds to the length of the power-off time. The image forming apparatus according to any one of (7) to (9), wherein the value of the constant T0 is changed.

(11) There is provided an environmental temperature detecting means for detecting the environmental temperature, and the constant T0 can be changed according to the detected environmental temperature. Item 10. The image forming apparatus according to item 1.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure and operation of a color image forming apparatus according to an embodiment of the present invention will be described with reference to FIG.

FIG. 1 is a diagram showing a configuration of a color printer which is an image forming apparatus according to the present embodiment.

In this color printer, a flexible, endless belt-shaped photosensitive member (hereinafter, referred to as a photosensitive member) 1 as an electrostatic latent image carrier for carrying an electrostatic latent image developed by a developing device. , Four sets of scorotron chargers (hereinafter, referred to as chargers) 2Y, 2M, 2C, 2K, and four sets of image exposure devices (scanning optical devices) for forming electrostatic latent images by scanning exposure with a light beam 3Y, 3M, 3C, 3K, four sets of developing devices 4
The image forming units (Y, 4M, 4C, and 4K) (four sets in the drawing) are arranged in tandem. In addition,
The illustrated image exposure apparatuses 3Y, 3M, 3C, and 3K each include a semiconductor laser that generates a light beam according to image data and a rotary polygon mirror that deflects the light beam and performs scanning exposure.

The photosensitive member 1 is stretched around a driving roller 11, a lower roller 12, and an upper roller 13, and a tension roller 14
And the backup member 15 provided on the inner peripheral surface locally regulates a predetermined position and rotates clockwise in the drawing. That is, the backup member 15 is locally brought into contact with the back surface of the photoconductor 1, and the developer carrying members (hereinafter, referred to as developing sleeves) 41Y, 41M, 41C, 41K of the developing devices 4Y, 4M, 4C, 4K. And image exposure devices 3Y, 3M, 3
The photosensitive member 1 is regulated at an image forming position formed by C and 3K.

The two-component developer contains a toner and a carrier as main components. The toner contains a binder resin and a colorant,
If necessary, a release agent, a charge control agent and the like are also contained. The toner of the two-component developer used in the color image forming apparatus contains, as the colorant, a colorant composed of a pigment or dye such as yellow, magenta, and cyan, and a black pigment such as carbon black. The particle size of the toner is 4 to 10 μm. As the carrier, ferromagnetic particles such as ferrite, magnetite, and iron powder are used. Desirably, the surface of the ferromagnetic particles is coated with a resin such as a fluorine-based or silicone-based resin. The particle size of the carrier is 10 to 80 μm. The mixing ratio of the toner and the carrier is 3 to 20 for the toner.
% By mass is preferred.

At the start of image recording, a drive motor (not shown) is rotated to rotate the photosensitive member 1 in a clockwise direction as shown by a drive roller 11, and the photosensitive member 1 is charged by a charging device 2Y. The application of the potential to is started. Photoconductor 1
After the potential is applied, the image exposure device 3Y starts exposure based on the first color image data, that is, the image data of yellow (Y), and the rotation of the photoconductor 1 (sub-scan) causes the surface of the photoconductor 1 to be exposed. An electrostatic latent image corresponding to the yellow (Y) image is formed on the layer. This latent image is reversely developed by the developing device 4Y in a non-contact state in the developing area, and a yellow (Y) toner image is formed on the photoreceptor 1.

Next, the photoreceptor 1 carrying the yellow toner image further includes a charger 2M on the yellow (Y) toner image.
Of the second color image data, that is, magenta (M) image data, and the non-contact and reversal development is performed by the developing device 4M. Thus, a magenta (M) toner image is formed on the yellow (Y) toner image in a superimposed manner.

By the same process, a cyan (C) toner image is further formed by the charger 2C, the image exposing device 3C and the developing device 4C based on the third color image data. Further, a black (K) toner image based on the fourth color image data is superimposed and formed by the charger 2K, the image exposure device 3K, and the developing device 4K, and a full-color image is formed on the peripheral surface within one rotation of the photoconductor 1. A toner image is formed.

In the developing operation by the developing devices 4Y, 4M, 4C, and 4K, the developing sleeves 41Y, 41
A DC bias having the same polarity as the charging of the photoconductor 1 or a developing bias obtained by adding an AC to the DC bias is applied to M, 41C and 41K, and the developing sleeves 41Y and 41K are applied.
Non-contact reversal development is performed by the two-component developer adhered to M, 41C, and 41K, and toner adheres to the electrostatic latent image forming portion on the photoconductor 1 with the conductive layer grounded.

The full-color toner image formed on the peripheral surface of the photoreceptor 1 in this manner is constituted by a transfer roller at a transfer section after the potential of the toner forming the toner image is adjusted by the charger 2F. The image is transferred to a transfer sheet by the transferred transfer device 7. The transfer paper is sent out from paper feed cassettes 20A and 20B or a manual paper feed unit 20C by paper feed means 21A, 21B and 21C, respectively, is conveyed to a pair of registration rollers 23, and is exposed by the pair of registration rollers 23. The toner is supplied to the transfer position in synchronization with the toner image area on the body 1.

The transfer paper on which the toner image has been transferred is separated from the peripheral surface of the photoconductor 1 which is strongly bent at the position of the drive roller 11 by the rigidity of the transfer paper, and then conveyed to the fixing device 24. The fixing device 24 melts the toner image and fixes it on the transfer paper. After completion of the fixing process, the transfer sheet is conveyed by a pair of discharge rollers 25A, 25B, and 25C, and is discharged to a discharge tray 26 provided at an upper portion with the toner image surface on the transfer sheet facing downward.

On the other hand, the photoreceptor 1 that has passed the separation position is cleaned by rubbing with the cleaning blade 81 of the cleaning device 8 to remove residual toner. When the formation of the toner image of the next original image is subsequently performed, the pre-charging static eliminator 9 uniformly exposes the photoconductor surface of the photoconductor 1 to remove the history.

FIG. 2 is a sectional view of the developing device of the present invention.
Since the plurality of developing devices 4Y, 4M, 4C, and 4K have substantially the same configuration, these developing devices will be generically referred to as the developing device 4.

In FIG. 2, reference numeral 40 denotes a frame which forms the outer shape of a developing device for accommodating a two-component developer comprising a toner and a carrier; 41, a developing sleeve which is a developer carrying member for transporting the developer to a developing position; , 42 are disposed inside the developing sleeve 41 and fixed magnetic field generating means (magnet roll) for attaching the developer to the developing sleeve 41 by magnetic force;
Reference numeral 43 denotes a developer layer thickness regulating member that regulates the thickness of the developer layer on the developing sleeve 41 to a predetermined amount, and reference numeral 44 denotes a paddle-shaped developer conveying member (hereinafter, referred to as a paddle wheel) that supplies the developer to the developing sleeve 41. Reference numerals 45A and 45B denote developer stirring and conveying members having a screw shape (hereinafter, referred to as stirring screws). The paddle wheel 44 has a plurality of blades 44a erected on the rotating shaft 44b. However, the developer conveying member is not limited to the paddle wheel, but may be any other member for efficiently conveying the developer. Shape may be sufficient. The stirring screws 45A and 45 also serve as stirring and conveying members.
The present invention is not limited to B, and may take another form in which the toner supplied to the developing device 4 is mixed with the developer and the developer is supplied to the paddle wheel 44. The illustrated arrows indicate the rotation direction of each rotating member (41, 44, 45A, 45B), and the outlined arrows indicate the flow of the developer. E
1 and E2 are AC power supplies for forming a developing bias, respectively.
DC power supply.

The developing sleeve 41 of the developing device 4 has five magnetic poles S1, S2, N1 to N as shown in FIG.
3 are arranged. Of these magnetic poles, adjacent magnetic poles N2 and N3 of the same polarity form a repulsive magnetic field, peel off the developer after the developing process on the developing sleeve 41, and erase the image history on the developing sleeve 41.

The paddle wheel 44 includes a developing sleeve 41
The developer peeled off from above is transported and the stirring screw 4
Transfer to 5A side.

Stirring screw 45A and stirring screw 4
5B is a partition wall 40a standing upright from the bottom of the frame body 40.
The first transfer chamber 40b and the second transfer chamber 40b formed on both sides of
Are arranged in parallel in the transfer chambers 40c, and are driven and rotated in the same direction. The upper portions of the first transfer chamber 40b and the second transfer chamber 40c are closed by a top plate 46.

The toner cartridges 5Y and 5 shown in FIG.
The toner supplied from M, 5C, and 5K is supplied to the developing device 4
(Y, M, C, K) from the toner supply port (not shown) formed in each top plate 46 (see FIG. 2).
It is thrown in and supplied in b.

Reference numeral 47 denotes a sensor as a temperature detecting means for detecting the temperature in the developing device 4, which is constituted by a thermistor and is disposed in close contact with the bottom plate of the developing device 4.
The temperature in the developing device 4 is detected.

This embodiment has a control system for controlling the temperature in the developing device 4 as shown in FIG. It has been found that the temperature inside the developing device 4 rises due to frictional heat generated by the stirring action of the developing sleeve 41, the paddle wheel 44 and the stirring screws 45A and 45B. The temperature rise in the developing device 4 may affect the properties of the developer, particularly, the toner. The control system described above is for avoiding such a temperature influence on the toner.

As shown in FIG. 3, the developing sleeve 41, the paddle wheel 44 and the stirring screws 45A and 45B are driven by a motor M. The motor M is a control means CPU
The control means CPU controls the motor M based on the temperature information from the sensor 47.

The control means CPU controls the motor M as described below. For control, an upper limit temperature T1 as a first predetermined value and a lower limit temperature T2 as a second predetermined value are used.
When the temperature inside the developing device 4 detected by the sensor 47 is equal to or lower than the upper limit temperature T1, image formation is performed at a normal image forming speed. Normally, the image forming speed is represented by the number of image forming sheets per minute. For example, an image is formed on A4 size transfer paper at an image forming speed of 24 sheets. FIG.
As shown in (a), images P1, P2 to P
In the continuous image forming process for forming the photoconductor 5, both the photoconductor 1 and the motor M operate continuously.

When the temperature in the developing device exceeds the upper limit temperature T1, the image interval is doubled, as shown in FIG.
D, and the image forming speed is reduced to one half, that is, one minute per minute.
As two sheets, images P1, P2, and P3 are formed. In the continuous image forming process shown in FIG. 4B, the photosensitive member 1 operates continuously without changing its moving speed, but the motor M operates intermittently as indicated by m1, m2, and m3.
The operation is stopped during n1 and n2, that is, during a period in which development is not performed.
In this way, by providing an interval between images or increasing the interval between images, in continuous image formation, the stirring effect of the developer is reduced, and the temperature in the developing device 4 is reduced. Ascent is avoided. As the upper limit temperature T1, a value of about 50 to 60 ° C. is used.

The control means CPU determines the upper limit temperature T of the temperature.
Control using the lower limit temperature T2 in addition to 1 is performed. That is, when the temperature in the developing device 4 falls below the lower limit temperature T2 due to the stop of the image formation or the continuous image formation shown in FIG. ), The image forming speed is increased, and the image is formed. 40-50 ° C as lower limit temperature
A degree value is used.

In the above-described embodiment, the developing sleeve 41, the paddle wheel 44, and the stirring screws 45A and 45B rotate and stop together, but the developing sleeve 41, the paddle wheel 44, and the stirring screw 45A and 45B are separately driven to continuously rotate the developing sleeve 41 in the continuous image forming process, while the paddle wheel 44 and the stirring screws 45A and 45A are rotated.
It is also possible to adopt a configuration in which 5B is intermittently operated to stop at the interval between images.

The temperature in the developing device 4 can be indirectly detected without installing the sensor 47. As described above, the temperature in the developing device 4 is controlled by the developing sleeve 41,
Paddle wheel 44 and stirring screws 45A, 45B
Rises in response to the operation of the member for stirring and transporting the developer, that is, the operation of the developing device 4. Therefore, by measuring the operation time of the developing device 4, the temperature inside the developing device 4 can be estimated.

As described above, by detecting the temperature in the developing device 4 without providing the temperature sensor, the cost increase and the problem of the arrangement of the temperature sensor due to the provision of the temperature sensor are eliminated. In particular, in a color image forming apparatus provided with four developing devices, when a sensor is provided, a sensor is provided in each of the four developing devices. Remarkable.

Hereinafter, the estimation of the temperature in the developing device 4 and the control of the image forming speed based on the estimated temperature in the developing device 4 will be described.

In FIG. 3, the control means CPU is a motor M
The operation time ta and the stop time tb of the motor M are monitored based on a control signal for turning on / off the motor M. When the estimated temperature in the developing device 4 reaches a predetermined value, the motor M
Is controlled by changing the ratio of the operation time ta to the stop time tb.

The temperature Tmp in the developing device 4 is given by the following equation (1).
Is estimated by Tmp = Σα × ta−Σβ × tb + T0 (1) ta is the operation time of the motor M, that is, the developing sleeve 41,
Paddle wheel 44 and stirring screws 45A, 45B
Tb is the stop time of the motor M, that is,
This is the stop time of the developing sleeve 41, the paddle wheel 44, and the stirring screws 45A and 45B. α and β are multipliers of the operation time ta and the stop time tb, respectively, and T0 is a constant serving as an initial value.

As is apparent from the equation (1), the temperature Tmp in the developing device is estimated from the sum of the operation time and the stop time of the developing device 4. Then, this total is calculated as the total time during which the power of the image forming apparatus is turned on and the main switch is on. When the main switch of the image forming apparatus is turned off, the operation time ta and the stop time tb
Is initialized, and the temperature Tmp becomes the initial value T0.

The fixing device 24 as a heat source in the image forming apparatus
The temperature inside the developing device 4 is affected by the temperature. Therefore, when estimating the temperature inside the developing device 4, it is desirable to take the temperature of the fixing device 24 into consideration. For this reason, it is desirable to set the initial value T0, that is, the temperature T0 in the developing device 4 estimated when the power is turned on, according to the temperature of the fixing device 24. Further, the temperature inside the developing device 4 is affected by the environmental temperature. Therefore, an environmental temperature detecting means for detecting the temperature outside the image forming apparatus, that is, the environmental temperature of the image forming apparatus is provided, and the output thereof is used to determine the initial value T.
It is desirable to set 0. Further, the temperature inside the developing device 4 also depends on the time during which the main power supply of the image forming apparatus is turned off. Therefore, the image forming apparatus is provided with a time measuring means for measuring the stop time of the image forming apparatus, that is, the length of time the main switch is turned off, and sets the initial value T0 according to the output of the time measuring means. It is desirable to do.

Further, when the stop time of the image forming apparatus is long, the temperature estimated by the above equation (1) may fall to a value distant from the actual temperature value. When the temperature value estimated by the above becomes equal to or lower than a third predetermined value lower than the upper limit temperature T1 and the lower limit temperature T2, it is desirable to set a predetermined constant temperature value as the estimated value.

In the illustrated color printer, the properties of the developers for forming the toner images of the respective colors are different, and there is also a difference in the cohesion with respect to an increase in temperature. Alternatively, the operation time of the black developing device 4K tends to be longer than other developing devices. Therefore, the temperature inside the developing device during continuous image formation may be different between 4Y, 4M, 4C, and 4K, and the cohesiveness of the developer at the same temperature is not uniform. Therefore, the developing devices 4Y, 4M, 4C, 4
It is desirable to perform temperature detection for each of K and use it for controlling the image forming speed. In this case, the developing device 4
When the temperature in any one of Y, 4M, 4C, and 4K exceeds the first predetermined value, it is desirable to change the image forming speed, and the first predetermined value and the second predetermined value are set to each developing device 4Y. , 4M, 4C, and 4K.

When estimating the temperature in the developing device 4 by the above equation (1), it is desirable to set the multipliers α, β and T0 to different values for each developing device.

[0054]

According to the first aspect of the present invention, it is possible to prevent the temperature inside the developing device from rising due to continuous image formation or the like. The malfunction of the stirring / transporting member is prevented.

According to the second aspect of the present invention, the image forming speed is changed without changing the moving speed of the electrostatic latent image carrier.
A complicated control change and a change in image quality due to a change in image forming speed can be avoided.

According to the third aspect of the present invention, an abnormal rise in the temperature in the developing device can be reliably prevented by a simple control.

According to the fourth aspect of the present invention, when the temperature in the developing device returns to normal, the image forming speed is increased to a normal one, so that a high image forming speed is secured.

According to the fifth aspect of the present invention, when a plurality of developing devices are provided as in a color image forming apparatus, an abnormal rise in the temperature in each developing device is reliably prevented.

According to the sixth or seventh aspect of the present invention, the temperature in the developing device is detected without installing a temperature sensor, so that the temperature in the developing device can be reduced without increasing the size of the device. Can be prevented from rising abnormally. In particular, in an image forming apparatus such as a color image forming apparatus in which a plurality of developing devices are provided, a great effect of avoiding an increase in cost and an increase in the size of the device due to the provision of the temperature sensor can be obtained.

According to the present invention, factors such as the operation time of the image forming apparatus, the operation time of the fixing device, and the environmental temperature are considered when estimating the temperature in the developing device.
A reliable temperature estimate is obtained.

[Brief description of the drawings]

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

FIG. 2 is a sectional view of a developing device.

FIG. 3 is a block diagram of a control system for controlling a temperature in the developing device.

FIG. 4 is a time chart for explaining a change in image forming speed.

[Explanation of symbols]

 4, 4Y, 4M, 4C, 4K Developing device 41, 41Y, 41M, 41C, 41K Developing sleeve 44 Paddle wheel 45A, 45B Stirring screw 47 Sensor CPU control means D, 2D Image interval m1, m2, m3 Operating time n1, n2 Stop time M Motor

Claims (11)

[Claims] An electrostatic latent image carrier, a developing device for developing an electrostatic latent image on the electrostatic latent image carrier, a temperature detecting unit for detecting a temperature in the developing device, and a temperature detecting unit. An image forming apparatus having a control unit for changing an image forming speed based on the temperature information. 2. The image forming apparatus according to claim 1, wherein the control unit changes the image forming speed by changing an interval between toner images on the electrostatic latent image carrier. . 3. The image forming apparatus according to claim 1, wherein the control unit performs control to reduce the image forming speed when the temperature in the developing device exceeds a first predetermined value.
An image forming apparatus according to claim 1. 4. The control device according to claim 1, wherein when the temperature in the developing device falls below a second predetermined value lower than the first predetermined value, the controller returns the lowered image forming speed to the original value. The image forming apparatus according to claim 3, wherein: 5. A control device comprising: a plurality of the developing devices; wherein the control unit controls the image forming speed to decrease when a temperature in at least one of the plurality of the developing devices exceeds the first predetermined value. The image forming apparatus according to claim 1, wherein: 6. The temperature detecting means has a time measuring means for measuring an operation time and a stop time of the developing device, and detects a temperature in the developing device based on the time measured by the time measuring means. The image forming apparatus according to claim 1, wherein the temperature in the developing device is detected by estimating the temperature. 7. The operation time is ta, and the stop time is t.
7. The image forming apparatus according to claim 6, wherein the temperature Tmp in the developing device is estimated by the following equation when b is set. Tmp = Σα × ta−Σβ × tb + T0 (where α, β, and T0 are constants) 8. When the estimated temperature Tmp falls below a third predetermined value lower than the first predetermined value and the second predetermined value, the estimated temperature Tmp is set to a predetermined value. The image forming apparatus according to claim 6, wherein the image forming apparatus performs the operation. 9. The image forming apparatus according to claim 7, wherein the constant T0 is changed according to a temperature of the fixing device at the time of power-on. 10. When the power is turned off, the temperature Tmp is initialized to the constant T0, and the time measuring means measures a power-off time during which the power is off, and corresponds to the length of the power-off time. 10. The image forming apparatus according to claim 7, wherein the value of the constant T0 is changed by changing the value of the constant T0. 11. The apparatus according to claim 7, further comprising an environmental temperature detecting means for detecting an environmental temperature, wherein said constant T0 can be changed according to the detected environmental temperature.
Item 10. The image forming apparatus according to item 1.