Image forming apparatus and data communication method

Data comprising a pulse signal is divided into predetermined data segments. The number of pulse-signal fluctuations in the data segment is counted. A transmitter transmits the unchanged data to a receiving portion in a case where the number of pulse-signal fluctuations does not exceed a predetermined number. On the other hand, in a case where the number of pulse-signal fluctuations exceeds the predetermined number, the pulse signal is converted so as to be unchanged at the fluctuation of the pulse signal but to be fluctuated when the pulse signal does not fluctuate. Then, the transmitter transmits the converted pulse signal to the receiving portion wherein only the converted pulse signal is converted to the original pulse signal.

RELATED APPLICATION

This application is based on application No. 57379/2007 filed in Japan, the contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image forming apparatus such as copiers and printers, as well as to a data communication method. Particularly in an image forming apparatus including a transmitter for sequentially transmitting data, such as image data, which comprises a variety of pulse signals, and a receiving portion for receiving the data comprising the pulse signal transmitted from the transmitter, a feature of the invention resides in a data communication method which is effective to prevent the occurrence of high-level irradiation noise when the transmitter transmits the data, such as the image data, which contains a high-frequency pulse signal having a large number of On/Off shifts.

2. Description of the Related Art

The image forming apparatus such as the copiers and printers conventionally perform a variety of operations such as image formation, as follows. The transmitter transmits the data, such as the image data, comprising a variety of pulse signals. The receiving portion receives the data comprising the pulse signal and transmitted from the transmitter. The operations such as the image formation are performed based on the data comprising the pulse signal and received by the receiving portion.

Unfortunately, the image data or the like often contains the high-frequency pulse signal having a large number of On/Off shifts. In a case where the transmitter transmits such a high-frequency pulse sign a to the receiving portion via a relatively long transmission member such as a harness, the high-level radiation noise occurs so that peripheral devices are adversely affected.

As disclosed in Japanese Unexamined Patent Publication No. 2001-309174, the following image processing apparatus and method have been proposed in the art.

The apparatus and method comprises: means for generating a flag signal which is invertible between On position and Off position in junction with each multivalued image data piece;

converting means for converting the multivalued image data to density data based on the multivalued image data and the flag signal; and

means for converting the resultant density data to serial video signals.

According to the image forming apparatus and the image processing method, out of the signals comprising plural bits representing respectively generated density data pieces, on-bits are collectively raised in a timewise forward or rearward direction according to the flags whereby the number of On/Off shifts is reduced for suppressing the radiation noises.

However, the following problem is encountered in the case where out of the signals comprising the plural bits representing the respectively generated density data pieces, the on-bits are collectively raised in the timewise forward or rearward direction according to the flags. Although the general density of the image may be controlled, it is impossible to achieve a proper density control based on an image binarization method such as dither method because On/Off positions are shifted from those of the original image data. In addition, the formed images suffer feathering at edges thereof. Hence, the apparatus and method fail to provide favorable images.

SUMMARY OF THE INVENTION

In an image forming apparatus including a transmitter for sequentially transmitting data, such as image data, comprising a variety of pulse signal; and a receiving portion for receiving the data comprising the pulse signals and transmitted from the transmitter, an object of the invention is to effectively prevent a high-level radiation noise in a case where the transmitter transmits to the receiving portion the data, such as the image data, which includes a high-frequency pulse signal having a large number of On/Off shifts.

An image forming apparatus according to the invention comprises:

a transmitter for transmitting data comprising a pulse signal;

a receiving portion for receiving the data comprising the pulse signal and transmitted from the transmitter;

a data segmenting portion for segmenting the data comprising the pulse signal into predetermined segments;

a fluctuations number counting portion for counting the number of pulse-signal fluctuations in the data segment segmented by the data segmenting portion;

a determining portion for determining whether the number of pulse-signal fluctuations counted by the fluctuations number counting portion exceeds a predetermined number or not;

a transmission data controller which causes the transmitter to transmit the unchanged data comprising the pulse signal if the determining portion determines that the number of pulse-signal fluctuations does not exceed the predetermined number, but which converts the pulse signal and causes the transmitter to transmit the resultant data if the determining portion determines that the number of pulse-signal fluctuations exceeds the predetermined number, the converted pulse signal which is unchanged at the fluctuation of the pulse signal but is fluctuated when the pulse signal does not fluctuate; and

a converting portion for converting the converted pulse signal received by the receiving portion to the original pulse signal.

A data communication method according to the invention comprises the steps of:

segmenting data comprising a pulse signal into predetermined segments;

counting the number of pulse-signal fluctuations in the data segment;

determining whether the count of pulse-signal fluctuations exceeds a predetermined number or not;

transmitting the unchanged data comprising the pulse signal in a case where it is determined that the number of pulse-signal fluctuations does not exceed the predetermined number;

converting the pulse signal and transmitting the converted pulse signal in a case where it is determined that the number of pulse-signal fluctuations exceeds the predetermined number, the converted pulse signal which is unchanged at the fluctuation of the pulse signal but is fluctuated when the pulse signal does not fluctuate; and

receiving the converted pulse signal transmitted to a receiving portion and converting the converted pulse signal to the original pulse signal.

These and other objects, advantages and features of the invention will become apparent from the following description thereof taken in conjunction with the accompanying drawings which illustrate specific embodiments of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Next, an image forming apparatus and data communication method according to an embodiment of the invention will be specifically described with reference to the accompanying drawings. It is to be noted that the image forming apparatus and data communication method according to the embodiment are not particularly limited to those illustrated by the following embodiments and modifications or changes may be made thereto as needed so long as such modifications or changes do not deviated from the scope of the invention.

In this image forming apparatus, as shown inFIG. 1, four imaging cartridges10A to10D as process cartridges for use in image forming apparatus are mounted in an apparatus body1.

Each of the above imaging cartridges10A to10D includes: a photosensitive member11; a charger12for electrically charging a surface of the photosensitive member11; an exposure device13for irradiating light on the charged surface of the photosensitive member11according to image information thereby forming an electrostatic latent image on the surface of the photosensitive member11; a developing device14for forming a toner image by supplying a toner to the electrostatic latent image formed on the surface of the photosensitive member11; and a cleaner15for removing residual toner from the surface of the photosensitive member11after the toner image formed on the surface of the photosensitive member11is transferred to an intermediate transfer belt2.

The image forming apparatus of the embodiment forms a full color image as follows. The developing devices14of the imaging cartridges10A to10D contain therein toners of mutually different colors of black, yellow, magenta and cyan, respectively. The individual imaging cartridges10A to10D form the toner images of the respective colors on the respective photosensitive members11thereof.

Subsequently, the toner images of the respective colors formed on the surfaces of the photosensitive members11of the imaging cartridges10A to10D are sequentially transferred to the intermediate transfer belt2, whereby a full-colored toner image is formed on the intermediate transfer belt2.

On the other hand, a sheet feeding roller3feeds a recording medium S, which is introduced into space between the intermediate transfer belt2and a transfer roller5in a proper timing by means of timing rollers4. Thus, the full-colored toner image formed on the intermediate transfer belt2is transferred to the recording medium S.

The recording medium S having the full-colored toner image so transferred thereto is led into space between a pair of fixing rollers7so that the full-colored toner image is fixed to the recording medium S. Subsequently, the recording medium S is discharged by means of discharge rollers8.

The toner not transferred to the recording medium S and remaining on the transfer belt2is removed therefrom by means of a second cleaner6.

In this image forming apparatus, as shown inFIG. 2, an image signal processor20disposed in the apparatus body1is connected with each of the imaging cartridges10A to10D via first and second signal lines31,32.

Data communications are carried out between the image signal processor20and each of the imaging cartridges10A to10D via the respective pair of signal lines31,32, so that the exposure device13of each of the imaging cartridges10A to10D may be controlled.

The above image signal processor20includes:

a transmitter21for transmitting data comprising a pulse signal to each of the imaging cartridges10A to10D;

a data segmenting portion22for dividing the data comprising the pulse signal into predetermined segments;

a fluctuations number counting portion23for counting the number of pulse-signal fluctuations in the data segment segmented by the data segmenting portion22;

a determining portion24for determining whether the number of pulse-signal fluctuations counted by the fluctuations number counting portion23exceeds a predetermined number or not;

a transmission data controller25which causes the transmitter21to transmit the unchanged data comprising the pulse signal if the determining portion24determines that the number of pulse-signal fluctuations does not exceed the predetermined number, but which converts the pulse signal and causes the transmitter21to transmit the resultant data if the determining portion24determines that the number of pulse-signal fluctuations exceeds the predetermined number, the converted pulse signal which is unchanged at the fluctuation of the above pulse signal but is fluctuated when the above pulse signal does not fluctuate; and

an identifier signal transmitter26which transmits an identifier signal to the individual imaging cartridges10A to10D on a per-data-segment basis, the identifier signal discriminating the signal transmitted from the transmitter21between the unconverted pulse signal and the converted pulse signal.

Each of the imaging cartridges10A to10D includes: a receiving portion41for receiving the data comprising the pulse signal and transmitted from the transmitter21via each first signal line31and the identifier signal transmitted from the identifier signal transmitter26via each second signal line32; and a converting portion42for converting the above converted pulse signal to the original pulse signal.

In the image forming apparatus of this embodiment, the image data comprising various pulse signals is transmitted from the above transmitter21to the receiving portion41of each of the imaging cartridges10A to10D via the first signal line41as follows. The data segmenting portion22divides the image data comprising the pulse signal into predetermined segments. The number of pulse-signal fluctuations in the data segment is counted by the fluctuations number counting portion23.

The determining portion24determines whether the count of pulse-signal fluctuations exceeds the predetermined number or not. If the number of pulse-signal fluctuations does not exceed the predetermined number, the transmission data controller25causes the transmitter21to transmit the unchanged image data comprising the above pulse signal. On the other hand, if it is determined that the number of pulse-signal fluctuations exceeds the predetermined number, the transmission data controller25converts the above pulse signal and causes the transmitter21to transmit the converted pulse signal, which is unchanged at the fluctuation of the pulse signal but is fluctuated when the pulse signal does not fluctuate. The transmission data controller25also causes the identifier signal transmitter26to transmit the identifier signal on a per-data-segment basis, the identifier signal discriminating the signal from the transmitter21between the unconverted pulse signal and the converted pulse signal.

This constitution reduces the number of fluctuations of the pulse signal transmitted from the transmitter21from the number of fluctuations of the pulse signal of the original image data, so that the radiation noises may be suppressed.

In the image forming apparatus of the embodiment, the pulse signal transmitted from the transmitter21and the identifier signal transmitted from the identifier signal transmitter26are received by the receiving portion41of each of the imaging cartridges10A to10D. Based on the identifier signal transmitted from the identifier signal transmitter26, only the pulse signal converted by the transmission data controller25is converted to the original pulse signal by means of the above converting portion42.

This permits the receiving portion41of each of the imaging cartridges10A to10D to correctly reproduce the image data comprising the original pulse signal, so that the exposure device13is controlled properly. Hence, a proper density control based on an image binarization method such as dither method may be provided. Further, favorable images free from feathering at edges may be formed.

Next, a specific description is made on a case where the image data comprising a pulse signal shown inFIG. 3Ais divided into each segment of eight data pieces by means of the data segmenting portion22, each data segment is subjected to the aforementioned data processing, and the resultant data segment is transmitted by the transmitter21. In this embodiment, the determining portion24determines whether the number of fluctuations of the pulse signal in the data segment exceeds five or not.

In the image data shown inFIG. 3A, the pulse signal in the first segment fluctuates between High level (abbreviated as “H”) and Low level (abbreviated as “L”) in the order of L, H, L, H, L, H, L, H. That is, the pulse signal undergoes seven level fluctuations. The pulse signal in the second segment has the signal level fluctuated in the order of H, H, H, L, H, H, H, H, undergoing two level fluctuations. The pulse signal in the third segment has the signal level fluctuated in the order of H, L, H, L, H, L, L, L, undergoing five level fluctuations. The term “the number of fluctuations”, as used herein, means the number of fluctuations between the two signal levels or the number of times the signal level fluctuates from H to L or L to H.

The transmission data controller25takes the following procedure to process the above image data before transmitting the processed data from the transmitter21. As shown inFIG. 3B, the pulse signal in the first segment undergoes the seven level fluctuations, which exceeds five times. Therefore, the pulse signal is so converted as to be unchanged at the fluctuation of the pulse signal but to be fluctuated when the pulse signal does not fluctuate. That is, the converted pulse signal has the level fluctuated in the order of L, L, L, L, L, L, L, L. The pulse signal in the second segment undergoes the two level fluctuations, which is less than five times. Therefore, the pulse signal is not converted, keeping the levels in the order of H, H, H, L, H, H, H, H. The pulse signal in the third segment undergoes the five level fluctuations, which exceeds five times. Therefore, the pulse signal is converted the same way as that of the first segment. The converted pulse signal has the level fluctuated in the order of H, H, H, H, H, H, L, H.

Transmission data comprising the pulse signal thus processed is transmitted from the transmitter21to the receiving portion41of each of the imaging cartridges10A to10D via the respective first signal line31.

As shown inFIG. 3C, the identifier signal transmitter26transmits an H-identifier signal, as the identifier signal, from a position somewhat delayed from a heading signal of the first segment. The H-identifier signal indicates that the first signal segment transmitted from the transmitter21comprises the converted pulse signal. The identifier signal transmitter26transmits an L-identifier signal from a position somewhat delayed from a heading signal of the second signal segment. The L-identifier signal indicates that the second signal segment comprises the unconverted pulse signal. The identifier signal transmitter26transmits an H-identifier signal from a position somewhat delayed from a heading signal of the third signal segment. The H-identifier signal indicates that the third signal segment comprises the converted pulse signal. The identifier signal is transmitted to the receiving portion41of each of the imaging cartridges10A to10D via the respective second signal line32.

In each of the imaging cartridges10A to10D, on the other hand, the converting portion42obtains restored data, as shown inFIG. 3D, by converting only the converted pulse signal of the transmission data to the original pulse signal based on the transmission data transmitted from the transmitter21to the receiving portion41and the identifier signal transmitted from the identifier signal transmitter26to the receiving portion41.

As shown inFIG. 3D, the first signal segment of the above transmission data has the H-identifier signal and hence, the converting portion42converts the converted pulse signal having the levels in the order of L, L, L, L, L, L, L, L to the original pulse signal having the levels in the order of L, H, L, H, L, H, L, H. The second signal segment has the L-identifier signal indicating that the pulse signal is unconverted. Hence, the converting portion42does not convert the received pulse signal which keeps the levels in the order of H, H, H, L, H, H, H, H. The third signal segment has the H-identifier signal. Hence, the converting portion42converts the converted pulse signal having the levels in the order of H, H, H, H, H, H, L, H to the original pulse signal having the levels in the order of H, L, H, L, H, L, L, L.

As a result, the restored image data comprising the same pulse signal that composes the original image data is restored correctly in each of the imaging cartridges10A to10D.

Next, an exemplary operation of converting the image data to the transmission data by segmenting the image data is described with reference to a flow chart ofFIG. 4, the operation performed by the image forming apparatus according to the above embodiment.

First, in Step S1, the image data is divided into data segments each including a predetermined number of data pieces d, say eight data pieces in the above embodiment.

In the subsequent Step S2, the number of signal fluctuations n in one data segment is counted. The operation proceeds to Step S3where the image data segment is converted to the transmission data. The conversion of the image data of one segment is carried out according to a subroutine shown inFIG. 5, which will be described herein later.

After the image data segment is converted, the operation proceeds to Step S4to determine whether the conversion of all the image data segments is completed or not. If the conversion of all the image data segments is completed, the operation ends. On the other hand, if the conversion of all the image data segments is not completed, the operation proceeds to Step S5where the conversion operation proceeds to the subsequent segment. Then, the operation returns to Step S2to repeat the aforementioned operations till the image data of all the segments is converted. The operation ends when the conversion of all the image data segments is completed.

Next, the operation of converting the image data of one segment in Step S3is described with reference to a flow chart shown inFIG. 5.

First, in Step S11, determination is made as to whether or not the number of signal fluctuations in the segment, as counted in Step S2, exceeds a predetermined number m requiring the execution of the conversion process. According to the above embodiment, for example, whether or not the number of signal fluctuations exceeds five is determined.

If the number of signal fluctuations n exceeds the predetermined number m, the operation proceeds to Step S12to set the H-identifier signal. Subsequently, the operation proceeds to Step S13to set a data process number i to 1.

Next, the operation proceeds to step S14to determine whether the signal is fluctuated or not. If the signal is fluctuated, the operation proceeds to Step S15where the signal is not converted and maintained as it is. If the signal is not fluctuated, the operation proceeds to Step S16where the signal is converted.

Next, the operation proceeds to S17to determine whether or not the data process number i reaches the predetermined number of data pieces d. If the data process number I reaches the predetermined number of data pieces d, the conversion of the image data segment ends. Subsequently, the operation returns to the flow chart shown inFIG. 4. On the other hand, if the data process number i does not reach the predetermined number of data pieces d, the operation proceeds to Step S18to increment the data process number i by 1. Then, the operation returns to Step S14so as to repeat the above operations till the data process number i reaches the predetermined number of data pieces d. Thus, the conversion of the image data segment is completed. Subsequently, the operation returns to the flow chart shown inFIG. 4.

In a case where it is determined in above step S11that the number of signal fluctuations n in the data segment, as counted in the above step S2, is less than the predetermined number m requiring the execution of the conversion process, the operation proceeds to Step S19to set the above identifier signal to L. In the subsequent step S20, all the signals of the data segment are not converted and maintained as they are. Thus, the conversion of the image data segment is completed. The operation returns to the flow chart shown inFIG. 4.

Referring to a flow chart shown inFIG. 6, description is made on an exemplary operation of restoring the above transmission data to the original data, the operation performed after the receiving portion receives the transmission data thus converted.

First, in Step S31, the received transmission data is divided into each set of the predetermined number of data pieces d. According to the above embodiment, for example, the transmission data is divided into each set of eight data pieces.

In the subsequent Step S32, each transmission data segment is subjected to a conversion process, which is carried out according to a subroutine shown inFIG. 7to be specifically described herein later.

After the transmission data segment is converted, the operation proceeds to Step S33to determine whether the conversion of all the transmission data segments is completed or not. The operation ends if the conversion of all the transmission data segments is completed. On the other hand, if the conversion of all the transmission data segments is not completed, the operation proceeds to Step S34where the conversion proceeds to the subsequent segment. That is, the operation returns to the above Step S32to repeat the aforementioned operations till the conversion of all the transmission data segments is completed. The operation ends when the conversion of all the transmission data segments is completed.

The operation of converting the transmission data segment in Step S32is described with reference to a flow chart shown inFIG. 7.

First, in Step S41, determination is made as to whether the identifier signal indicates H or not.

In the case of the H-identifier signal, the operation proceeds to Step S42to set the data process number i to 1.

Subsequently, the operation proceeds to Step S43to determine whether the signal is fluctuated or not. If the signal is fluctuated, the operation proceeds to Step S44where the signal is not converted and maintained as it is. On the other hand, if the signal is not fluctuated, the operation proceeds to Step S45to convert the signal.

Subsequently, the operation proceeds to Step S46to determine whether or not the data process number i reaches the above predetermined number of data pieces d. If the data process number reaches the predetermined number of data pieces d, the conversion of the transmission data segment is completed. The operation returns to the flow chart shown inFIG. 6. On the other hand, if the data process number i does not reach the predetermined number of data pieces d, the operation proceeds to Step S47to increment the data process number I by 1. Then, the operation returns to the above Step S43to increment the data process number i by 1. The operation returns to Step S43so as to repeat the aforementioned operations till the data process number i reaches the predetermined number of data pieces d. Thus is completed the conversion of the transmission data segment. The operation returns to the flow chart shown inFIG. 6.

On the other hand, if it is determined in Step S41that the identifier signal does not indicate H, thus indicating L, the operation proceeds to Step S48where all the signals of the data segment are not converted and maintained as they are. The conversion of the transmission data segment is completed and the operation returns to the flow chart shown inFIG. 6.

In the image forming apparatus according to the embodiment, the identifier signal transmitter26for transmitting the identifier signal is provided in addition to the transmitter21, such that the identifier signal transmitter26may transmit the above identifier signal to the receiving portion41of each of the imaging cartridges10A to10D via the respective second signal line. However, an alternative arrangement may also be made. As shown inFIG. 8, the identifier signal transmitter26and the respective second signal lines32shown inFIG. 2may be omitted and the identifier signal may be added to the transmission data transmitted from the transmitter21.

The following method may be used for adding the identifier signal to the transmission data transmitted from the transmitter21as described above. As shown inFIG. 9A, for example, when the same image data as that shown inFIG. 3Ais converted to the transmission data, the H-identifier signal comprising a nibble may be inserted in the first transmission data segment shown inFIG. 3Bat place subsequent to the initial L-signal as shown inFIG. 9B. Further, the L-identifier signal comprising a nibble may be inserted in the second transmission data segment at place subsequent to the initial H-signal. The H-identifier signal comprising a nibble may be inserted in the third transmission data segment at place subsequent to the initial H-signal.

In each of the imaging cartridges10A to10D, the converting portion42converts only the converted pulse signal in the transmission data to the original pulse signal based on the transmission data having the identifier signal inserted therein and transmitted from the transmitter21to the receiving portion41, as described above. Thus, the converting portion42obtains the restored data as shown inFIG. 9C.

More specifically, the first signal segment of the transmission data has the H-identifier signal inserted therein and hence, the converting portion42converts the converted pulse signal to the original pulse signal having the levels in the order of L, H, L, H, L, H, L, H, as shown inFIG. 9C. The second signal segment has the L-identifier signal inserted therein so that the pulse signal is not converted. Therefore, the converting portion42does not convert the received pulse signal, the levels of which remain in the order of H, H, H, L, H, H, H, H. The third signal segment has the H-identifier signal inserted therein and hence, the converting portion42converts the converted pulse signal to the original pulse signal having the levels in the order of H, L, H, L, H, L, L, L.

As a result, the image data comprising the same pulse signal as that of the original image data is correctly reproduced as the restored data in each of the imaging cartridges10A to10D.

While the foregoing embodiments illustrate so-called tandem full-color image forming apparatuses employing the plural imaging cartridges10A to10D, the application of the invention is not limited to the above image forming apparatuses. The invention is also applicable to, for example, a full-color image forming apparatus adapted to form a full-color image by rotating a rotary-type developing unit retaining plural developing devices for sequentially positioning the respective developing devices at the photosensitive member. The invention is also applicable to an image forming apparatus adapted for monochromatic image formation.

The image forming apparatuses of the embodiments are described by way of the examples where the image signal processor20disposed in the apparatus body1transmits the data comprising the pulse signal to each of the imaging cartridges10A to10D which, in turn, process the received data. However, the aforementioned data processing is not limited to this. The above data processing of the invention may be applied to any case where the data comprising the high-frequency pulse signal, such as the image data, is transmitted via the signal line and is processed. In a copier equipped with a scanner, for example, the above data processing of the invention may be applied to a case where a reading portion of the scanner reads data and transmits the read data to the image processor for data processing.

According to the invention, the data segmenting portion divides the data comprising the pulse signal into the predetermined segments. The fluctuations number counting portion counts the number of pulse-signal fluctuations in the data segment. The determining portion determines whether the count of pulse-signal fluctuations exceeds the predetermined number or not. If it is determined that the number of pulse-signal fluctuations does not exceed the predetermined number, the transmission data controller causes the transmitter to transmit the unchanged data comprising the above pulse signal. On the other hand, if it is determined that the number of pulse-signal fluctuations exceeds the predetermined number, the transmission data controller converts the above pulse signal, the converted pulse signal unchanged at fluctuation of the above pulse signal but fluctuated when the above pulse signal fluctuates. Then, the transmission data controller causes the transmitter to transmit the resultant data. Therefore, the pulse signal transmitted from the transmitter to the receiving portion is reduced in the number of fluctuations so that the occurrence of radiation noises is suppressed.

The invention is constituted such that the converted pulse signal received by the receiving portion is converted to the original pulse signal by means of the converting portion. This permits the receiving portion to reproduce the original data correctly.

As a result, a variety of operations such as image formation may be performed properly. Therefore, the proper density control based on the image binarization method such as dither method may be provided in a case where the data comprising the above pulse signal is the image data. Furthermore, the formed image does not suffer feathering at the edge thereof. Thus is ensured the favorable image formation.

Although the present invention has been fully described by way of examples, it is to be noted that various changes and modifications will be apparent to those skilled in the art.

Therefore, unless otherwise such changes and modifications depart from the scope of the present invention, they should be construed as being included therein.