Patent Application
20100158557
This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2008-328734, filed Dec. 24, 2008.
(i) Technical Field
The present invention relates to a cooling device and an image forming apparatus.
(ii) Related Art
Image forming apparatuses such as mainly a printer and a copying machine have been conventionally widely used. In most image forming apparatuses, a fan for cooling the inside of an image forming apparatus is provided to avoid an increase in temperature inside of the image forming apparatus and the fan cools the inside of the image forming apparatus during image formation.
According to an aspect of the invention, there is provided a cooling device that cools the inside of an image forming apparatus provided with a developer carrier that carries an image developed with a developer while being rotated, the cooling device including:
a counting unit that counts an accumulative number of rotation of the developer carrier;
a fan that cools the inside of the image forming apparatus;
a calculating unit that calculates the abrasion amount of the developer carrier in which the accumulative number of rotation counted by the counting unit is used as at least one variable; and
a controlling unit that actuates the fan with cooling efficiency according to the abrasion amount calculated by the calculating unit.
Exemplary embodiment of the present invention will be described in detail based on the following figures, wherein:
An exemplary embodiment according to the present invention is described below with reference to the attached drawings.
The image forming apparatus in the present exemplary embodiment is a double-sided outputting color printer.
The image forming apparatus 10 is provided with image forming units 1K, 1C, 1M, and 1Y for forming images of black (K), cyan (C), magenta (M), and yellow (Y) colors. The image forming units 1K, 1C, 1M, and 1Y include laminated-type developer carriers 11K, 11C, 11M, and 11Y of an electrophotographic system, respectively, which are rotated in directions indicated by arrows Bk, Bc, Bm, and By in
An image forming unit 1 shown in
The developer carrier 11 shown in
The developer carrier 11 is rotated in the direction indicated by the arrow B in
The configuration of the image forming unit is as described above. Returning to
The image forming apparatus 10 shown in
Moreover, the image forming apparatus 10 includes a power source board 6 for supplying electric power to each of the constituent elements such as the fixing device 4 and the four image forming units in the image forming apparatus 10, a temperature sensor 8 for measuring a temperature inside of the image forming apparatus 10, and three cooling fans, that is, a first fan 101, a second fan 102, and a third fan 103. Among the constituent elements which receive the electric power from the power source board 6, the charger disposed inside of each of the image forming units needs a high voltage for electric charging. Therefore, a great quantity of electric power is supplied to the charger. The power source board 6 is liable to generate heat in supplying the electric power. The first fan 101 out of the three fans is responsible for cooling mainly the power source board 6. The residual second and third fans 102 and 103 are responsible for cooling the entire inside of the image forming apparatus 10. The three fans also are rotated upon receipt of the electric power from the power source board 6. As the received voltage is higher, the fans are rotated at a higher speed to exhibit a more excellent cooling efficiency. The image forming apparatus 10 is provided with a control board, although not shown in
Next, explanation is made below on an image forming operation in the image forming apparatus 10.
First of all, the developer carriers 11K, 11C, 11M, and 11Y inside of the four image forming units are electrically charged by the chargers inside of the image forming units, respectively. Subsequently, the electrically charged developer carriers are irradiated with the laser beams by the exposing unit 100, so that the electrostatic latent images of the colors are formed on the developer carriers inside of the image forming units, respectively. The formed electrostatic latent images are developed with the developers containing the toners of the colors corresponding to the image forming units by the developing devices inside of the image forming units, thereby forming the respective development images of the colors. The development images of the colors formed in the image forming units, respectively, are (primarily) transferred in sequence in superimposition in the order of yellow (Y), magenta (M), cyan (C), and black (K) colors on the intermediate transfer belt 2 at positions of primary transfer rolls 110K, 110C, 110M, and 110Y corresponding to the developer carriers, respectively, resulting in a multi-color primary transfer image. The multi-color primary transfer image is conveyed to the secondary transfer roll pair 3 by the intermediate transfer belt 2. In the meantime, the sheet 7 stacked in the tray 70 is taken out in line with the formation of the multi-color primary transfer image, and then, is fed by a first feeding roll pair 41a, and further, the sheet 7 is registered by a registering roll pair 40. The multi-color primary transfer image is (secondarily) transferred onto the fed sheet 7 by the secondary transfer roll pair 3, and further, the resultant secondary transfer image formed on the sheet 7 is subjected to fixing by the fixing device 4. In
In the case of single-sided image formation of the sheet 7, the sheet 7 passes the sheet feed path only once, to be fixed with the secondary transfer image in the fixing device 4, and then, is discharged onto a discharge tray 10a as it is through a second feeding roll pair 41b and a discharging roll pair 40a, as indicated by a rightward dotted arrow in
In contrast, in the case of double-sided image formation of the sheet 7, the secondary transfer image is transferred and fixed to one surface of the sheet 7 through the sheet feed path indicated by the upward arrow, and then, the sheet 7 is not discharged onto the discharge tray 10a but returns back and passes through a first double-sided feeding roll pair 40b to be fed downward on a path indicated by a downward dotted arrow. Thereafter, the sheet 7 passes a second double-sided feeding roll pair 40c, and then, is turned upward in a third double-sided feeding roll pair 40d to pass again toward the secondary transfer roll pair 3. During a period after the sheet 7 is subjected to the transfer by the secondary transfer roll pair 3 at the first time till this sheet 7 reaches the secondary transfer roll pair 3 again, another multi-color primary transfer image is formed on the intermediate transfer belt 2 by the above-described way. When the sheet 7 reaches the secondary transfer roll pair 3 at the second time, the multi-color primary transfer image is secondarily transferred onto a side reverse to the side subjected to the secondary transfer at the first time. The resultant secondary transfer image formed on the reverse side is fixed by the fixing device 4, and then, the sheet 7 having the images fixed on both sides thereof is discharged onto the discharge tray 10a.
The image forming operation in the image forming apparatus 10 has been described above.
In the image forming apparatus 10 shown in
Although explanation is made below on the assumption that the three fans are controlled according to the maximum one of the abrasion amounts of the four developer carriers, other ways of control may be adopted by changing a control program on the control board in the image forming apparatus 10. For example, a control program may be changed to that of a way of control in which the three fans are controlled according to an average of the abrasion amounts of the four developer carriers, or of a way of control in which the three fans are controlled according to the abrasion amount of the developer carrier 11K for the black color which is most frequently used.
Here, a description is given of the first fan 101, the second fan 102, and the third fan 103 shown in
Here, the control board 9 serves the functions of counting the accumulative numbers of rotation of the developer carriers, calculating the abrasion amounts of the developer carriers based on the accumulative number of rotation, and determining the maximum abrasion amount. In the present exemplary embodiment, the control board 9 represents a member serving as all of a counter, a calculator, and a controller. The control board 9 and the three fans exemplify the cooling device according to the present invention.
A detailed description is given below of the operation of the control board 9 for cooling the inside of the image forming apparatus 10.
During a period when the power source is turned on in the image forming apparatus 10, the control board 9 acquires information on the temperature inside of the image forming apparatus 10 from the temperature sensor shown in
The control board 9 individually counts the accumulative numbers of rotation in the electrically charged state and in the stopped state of the electric charging in the above-described manner because a larger frictional coefficient between the developer carrier and the charger in the state in which the developer carrier is electrically charged than that in the state in which the electric charging is stopped is liable to induce the advance in the abrasion, and therefore, attribution to the abrasion amount needs to be individually considered in the above-described two electrically charged states. The consideration of the attribution to the abrasion amounts by individually counting the accumulative numbers of rotation in the two electrically charged states enhances the calculative accuracy of the abrasion amount more than in the way in which the accumulative numbers of rotation are counted irrelevantly to the two electrically charged states and the abrasion amount is calculated based on the accumulative numbers of rotation. Incidentally, the change in frictional coefficient according to the above-described electrically charged state is induced by a change on the developer carrier (i.e., a sputtering effect) according to adhesion of a discharged product or a toner particle onto the developer carrier.
The control board 9 calculates an abrasion amount W (unit: pm, or picometer) of each of the four developer carriers by an equation below based on the temperature inside of the image forming apparatus 10, the accumulative number of rotation of each of the developer carriers in the electrically charged state, and the accumulative number of rotation of each of the developer carriers in the stopped state of the electric charging.
W=(r1×w1+r2×w2)×k (1)
The abrasion amount W determined by the equation (1) indicates an estimate of the degree of the abrasion at the surface of the developer carrier. In the equation, r1 is the accumulative number of rotation of the developer carrier in the state in which the developer carrier is electrically charged; and r2 is the accumulative number of rotation of the developer carrier in the state in which the electric charging is stopped. In addition, w1 and w2 are constants representing the abrasion amount of the developer carrier when the developer carrier is rotated once; and k is a value determined according to the temperature inside of the image forming apparatus 10. Here, w1, w2 and k are obtained from an experiment in which the degree of the abrasion is actually measured by rotating the developer carrier. As described above, the abrasion of the developer carrier is liable to advance in the electrically charged state of the developer carrier more than in the stopped state of the electric charging. In consideration of this, w1 is larger than w2.
The control board 9 compares a maximum one out of the abrasion amounts W of the four developer carriers calculated in accordance with the equation (1) with a predetermined threshold. As described above, the electrically charging power for the developer carrier, to be supplied to the charger by the power source board 6 for electrically charging the developer carrier is increased according to the abrasion of the developer carrier. The predetermined threshold is equal to an abrasion amount of the developer carrier when a heat generation amount of the power source board becomes a dangerous level from the viewpoint of a high temperature inside of the image forming apparatus 10 due to the electrically charging power reaching a predetermined value. The control board 9 controls the cooling efficiency of the three fans 101, 102, and 103 by a way shown in Table 1 below according to whether or not the maximum abrasion amount W exceeds the threshold.
In Table 1 above, the control contents when the abrasion amount W is the threshold or smaller are written in a column of “small abrasion amount:” in contrast, the control contents when the abrasion amount W exceeds the threshold is written in a column of “large abrasion amount.”
Here, a load exerted on the power source board 6 is particularly large when a user designates a job of double-sided outputting in the image forming apparatus 10. Therefore, the heat generation amount of the power source board 6 is liable to become the dangerous level from the viewpoint of the high temperature inside of the image forming apparatus 10 even in a situation in which the abrasion of the developer carrier does not advances so much. In view of this, the control board 9 and the entire inside of the image forming apparatus 10 are cooled in the way in which the three fans 101, 102, and 103 are used to the maximum irrespective of the abrasion of the developer carrier in the case of the double-sided outputting in the image forming apparatus 10. That is to say, the control board 9 controls the power source board 6 to allow the first fan 101 to be rotated at a high speed at the second predetermined voltage whereas the second fan 102 and the third fan 103 to be rotated at the third predetermined voltage and the fourth predetermined voltage, respectively, in the case of the double-sided outputting, as shown in Table 1.
In contrast, a load exerted on the power source board 6 is not large very much when the user designates a job of a single-sided outputting as long as the maximum abrasion amount W is the threshold or smaller. As a consequence, the control board 9 controls the first fan 101 to be rotated at a low speed at the first predetermined voltage whereas maintains the second fan 102 and the third fan 103 in a non-rotational state, as shown in Table 1. Even in the case of the single-sided outputting, when the maximum abrasion amount W exceeds the threshold, the heat generation amount of the power source board is liable to reach the dangerous level from the viewpoint of the high temperature inside of the image forming apparatus 10. In view of this, even in the case of the job of the single-sided outputting, the control board 9 controls the first fan 101 to be rotated at the high speed at the second predetermined voltage whereas the second fan 102 to be rotated at the third predetermined voltage when the maximum abrasion amount W exceeds the threshold, as shown in Table 1. In other words, both the number of fans to be used in cooling and the rotational speed of the fan are increased in the image forming apparatus 10 when the maximum abrasion amount W exceeds the threshold in the case of the job of the single-sided outputting.
In this manner, the cooling operation is performed with the more excellent cooling efficiency as the abrasion amount of the developer carrier is larger in the image forming apparatus 10.
In the present exemplary embodiment, when the user designates the job of the double-sided outputting, the electric power board 6 and the entire inside of the image forming apparatus 10 are cooled with the maximum cooling efficiency obtained by using all of the three fans 101, 102, and 103 irrespective of the abrasion of the developer carrier. However, this is a safety reflecting that the load exerted on the electric power board 6 is generally large in the case of the double-sided outputting. According to the present invention, when the load exerted on the electric power board 6 is not always large even in the case of the double-sided outputting for the reason such as the small number of output sheets required by the job, another cooling efficiency control for the double-sided outputting may be adopted as follows: the electric power board 6 and the entire inside of the image forming apparatus 10 are cooled with a low cooling efficiency by the three fans 101, 102, and 103 when the maximum abrasion amount W does not exceed the threshold whereas the electric power board 6 and the entire inside of the image forming apparatus 10 are cooled with the maximum cooling efficiency obtained by using all of the three fans 101, 102, and 103 when the maximum abrasion amount W exceeds the threshold.
An effect of the control of the cooling efficiency of the fan according to the abrasion amount of the developer carrier is explained below based on a specific experiment.
In the experiment, color images, each having image density in which each of the colors of black (K), cyan (C), magenta (M), and yellow (Y) is 5%, are output for five days in 10,000 sheets per day by using a double-sided outputting color printer (i.e., outputting 50,000 sheets in total). Here, 10,000 sheets per day are output by alternately a job for outputting 1,000 sheets by single-sided outputting and a job for outputting 1,000 sheets by double-sided outputting in high-temperature and high-humidity environment in which the temperature is 30° C. and the humidity is 65%. The double-sided outputting color printer used in the experiment is explained in Example and Comparative Example below.
The color printer used in Example has the same configuration as that of the image forming apparatus 10 shown in
In the color printer used in Example, the size (i.e., the area) of each of the first fan 101, the second fan 102, and the third fan 103 is about 60 cm2. To the first fan 101 is applied a first predetermined voltage of 20V during the low-speed rotation; in contrast, a second predetermined voltage of 24V during the high-speed rotation. In the case of the rotations of the second fan 102 and the third fan 103, the third and fourth predetermined voltages of 24V are applied to the second fan 102 and the third fan 103, respectively. Moreover, in the color printer used in Example, the constants w1 and w2 in the equation (1) above are set to 50 pm and 20 pm, respectively. In addition, k in the equation (1) above, which depends upon the temperature inside of the apparatus, is “1” in the case where the temperature is lower than 12° C. where as “0.8” in the case where the temperature is 12° C. or higher.
In the color printer used in Example, the accumulative number of rotation r1 in the electrically charged state and the accumulative number of rotation r2 in the stopped state of the electric charging are determined according to the number of jobs, the output mode (double-sided outputting or single-sided outputting) in each of the jobs, and the output number of sheets in each of the jobs. In the color printer incorporating four new developer carriers used in Example, when the color images are formed by alternately repeating a job of outputting 1,000 sheets by single-sided outputting and a job of outputting 1,000 sheets by double-sided outputting in the environment of a temperature of 30° C., like in the experiment, the abrasion amount W in Equation (1) above reaches the threshold in the number of output sheets of about 75,000.
In the experiment above, there is prepared the color printer which incorporates the four new developer carriers for the colors, and then, outputs 50,000 sheets, like the experiment. The experiment is carried out by using the color printer. In this manner, abrasion occurs in each of the developer carriers when the number of output sheets reaches about 25,000 which is half of the number of output sheets of 50,000 in the experiment. Thus, the effect of the cooling efficiency control of the fan according to the abrasion amount in the experiment may be confirmed.
A color printer in Comparative Example has the same configuration of that of the image forming apparatus 10 shown in
For the easy comparison with Table 1 showing the way of control by the color printer in Example, Table 2 shows the contents of controls in which the abrasion amounts of the developer carrier are “small” and “large.” As is obvious from Table 2, the contents of the controls of the three fans in the column of “small” are identical to the contents of the controls of the three fans in the column of “large”. Furthermore, the contents of the controls are identical to the contents of the controls of the three fans in the column of “small” in Table 1 in the color printer in Example.
The above-described experiment is carried out in the color printer in Example and the color printer in Comparative Example. In the color printer in Comparative Example, the image density is degraded in the fifth day, so that the image becomes poor in quality. Upon examination of the inside state of the color printer in Comparative Example, the toner is fixed near the auger inside of the developing device for each of the colors. In view of this, the poor quality of the image is construed to be caused by clogging of the toner due to the fixture of the toner.
In contrast, no deficient image is formed for five days in the color printer in Example. Upon examination of the inside state of the color printer in Example after the output of 50,000 sheets, it is revealed that no toner is fixed inside of any of the developing devices and the toner may be excellently supplied by the auger.
From the above-described experiment, the cooling efficiency of the fan is controlled according to the abrasion amount, it is concluded that the toner may be avoided from being fixed so that the image of a good quality may be formed.
The description is given above of the exemplary embodiment according to the present invention.
Although the double-sided outputting color printer is exemplified above, the image forming apparatus according to the present invention may be applied to a single-sided outputting color printer. Otherwise, the present invention may be applied to a monochromatic single-sided outputting printer or monochromatic double-sided outputting printer. Alternatively, the present invention may be applied to a copying machine or a facsimile, besides the printer.
The foregoing description of the exemplary embodiment of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The exemplary embodiment was chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-328734 | Dec 2008 | JP | national |
