Image forming apparatus capable of controlling toner supply

An image forming apparatus, including a toner supplying unit to supply toner, a toner transporting unit to transport the toner supplied from the toner supplying unit, a sensor to sense a density of the toner transported by the toner transporting unit, a compensating signal generating unit to compensate for amounts of the toner pre-supplied by the toner supplying unit, and a control unit to generate a control signal to control the toner supplying unit by receiving a sensing signal of the sensor as an input signal and a compensating signal of the compensating signal generating unit as a feedback signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Application No. 2005-82807, filed Sep. 6, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

An aspect of the present invention relates to an image forming apparatus capable of controlling toner supply, and, more particularly, to an image forming apparatus capable of controlling toner supply by compensating amounts of toner pre-supplied.

2. Description of the Related Art

Generally, an image forming apparatus includes a recording medium supplying unit to supply a recording medium, an image forming unit to form an image on the supplied recording medium, and a paper discharging unit to discharge the recording on which the image is formed.FIG. 1is a schematic diagram that shows the image forming unit.

The image forming unit100comprises a photosensitive drum110and a transition roller120that rotate in correspondence with each other, a developer130to provide toner1to the photosensitive drum110, and a toner supplying unit140to supply the toner1to the developer130. Further, the developer130comprises a toner transporting unit131to transport the toner1provided from the toner supplying unit140, a developing roller132to transport the toner1which is transported by the toner transporting unit131into the photosensitive drum110, and a sensor133to sense a density of the toner1transported by the toner transporting unit131.

Therefore, the toner supplied from the toner supplying unit140to the developer130is sensed by the sensor133and if the toner is sensed as having reached a proper density, controlling amounts of the toner supplied by the toner supplying unit140is possible by controlling driving of a supply motor150by a control unit (not shown) equipped in the image forming apparatus.

FIG. 2shows a location relation between the toner transporting unit131and the sensor133. In the drawing, the toner supply is provided in a right end of the toner transporting unit131and the supplied toner is transported to a left side of the toner transporting unit130by a rotation of the toner transporting unit131. The sensor133is separated from a supply position P of the toner by a predetermined distance D and detects the density of the transported toner.

However, according to the above-described toner supplying and transporting method, a desired time for the supplied toner to reach the sensor133is required since the supply position P of the toner and a position of the sensor133are separated from each other, and consequently a delay time occurs in a controlling of the toner supplying unit140based on the sensing signal of the sensor133. Therefore, since the toner supply in the toner supplying unit140is controlled in a condition of being delayed for a prescribed time, the toner may be excessively supplied during that time. If the toner is excessively supplied from the developer130, the printing image on the recording medium deteriorates due to an excessive supply of the toner (i.e., an over-toner state).

SUMMARY OF THE INVENTION

Accordingly, it is an aspect of the present invention to provide an image forming apparatus capable of preventing excessive supply of toner by controlling toner supply.

The foregoing and/or other aspects of the present invention can be achieved by providing an image forming apparatus comprising a toner supplying unit to supply toner, a toner transporting unit to transport the toner supplied from the toner supplying unit, a sensor to sense a density of the toner transported by the toner transporting unit, a compensating signal generating unit to compensate amounts of the toner pre-supplied by the toner supplying unit, and a control unit to generate a control signal to control the toner supplying unit by receiving a sensing signal of the sensor as an input signal and a compensating signal of the compensating signal generating unit as a feedback signal.

According to an aspect of the present invention, the compensating signal generating unit comprises a plurality of shift registers to update consecutively the control signal of the control unit at a prescribed period and to store it; and a summing counter to sum the signal stored in the plurality of shift registers at the prescribed period to generate the compensating signal.

According to an aspect of the present invention, the period is defined by dividing a time which it takes the toner supplied from the toner supplying unit to be transported to the sensor by the number of the shift registers.

According to an aspect of the present invention, the control unit sets the control signal by changing the control signal to 0 if the control signal has a negative value through feedback of the compensating signal.

DETAILED DESCRIPTION OF THE EMBODIMENTS

An image forming apparatus, according to an embodiment of the present invention, comprises a toner supplying system200, as shown inFIG. 3. As shown inFIG. 3, a control unit210controls a driver230by generating a control signal, Vc, using a sensing signal S received from a sensor220, and the driver230controls toner supply of a toner supplying unit250by driving a supply motor240. Meanwhile, the toner supplying system200includes a compensating signal generating unit260to compensate for amounts of toner which are pre-supplied by the toner supplying unit250upon a generation of the control signal, Vc, of the control unit210.

The compensating signal generating unit260includes a plurality of shift registers261,262,263to receive the control signal, Vc, of the control unit210at a predetermined period to consecutively store the control signal, Vc, and a summing counter264to read out values stored in each of the shift registers261,262,263to sum them. A time period used for receiving and storing in the shift register261,262,264and summing in the summing counter264is transferred through a clock line270that simultaneously occurs between the control unit210and the shift registers261,262,263.

The value summed by the summing counter264is fed back to the control unit210as the compensating signal, Vb, of the compensating signal generating unit.

A process of operating the toner supplying system200with such structure will now be described.

First, the toner supplied from the toner supplying unit250is transported from the right to the left of the drawing by the toner transporting unit280to be sensed by the sensor220. The density of the toner sensed by the sensor220is inputted to the control unit210as a sensing signal S.

The control unit210converts the density of the toner corresponding to the sensing signal, S, into an input signal, Vin, and outputs the control signal, Vc, which reflects the difference, (ΔV=Vin−Vo), of a pre-stored target signal, Vo, from the input signal thereby transmitting the control signal, Vc, to the driver230. The driver230controls the toner supplying unit250by driving the supply motor240based on the control signal, Vc.

Meanwhile, the control signal, Vc, generated in the control unit210, is consecutively stored in the plurality of shift registers261,262,263at a prescribed period, T.

Herein, according to an embodiment of the invention, the number of the shift registers is 3. And the operating period, T, in the shift registers261,262,263and summing counter264is a value obtained by dividing a time t which the toner supplied from the toner supplying unit250to the toner transporting unit280takes to reach the sensor220by the number of shift registers261,262,263, that is, T=t/3.

Consequently, each of the shift registers261,262,263receives the control signal, Vc, 3 times to consecutively store the control signal, Vc, until the toner supplied from the toner supplying unit250reaches the sensor220. Further, the summing counter264receives values stored in the respective shift registers261,262,263every period, T, and sums them to generate the compensating signal, Vb. Further, the control unit210receives the compensating signal, Vb, from the summing counter264as a feedback signal every period, T.

As a result, the control unit210generates the control signal, Vc, by receiving the compensating signal, Vb, from the summing counter264while computing the input signal, Vin, for the present density of the toner using the sensing signal, S, received from the sensor220every period, T.

FIG. 4is a table to illustrate a process in which various signals are inputted/outputted and stored in the control unit210and the compensating signal generating unit260in processes of supplying the toner.

In the table ofFIG. 4, Vin, represents the input signal converted by the control unit210upon an inputting of the sensing signal, S, of the sensor220. S1, S2, and S3represent data stored in corresponding shift registers261,262,263respectively. Lastly, Vbrepresents the compensating signal generated by computation of the summing counter264. Herein, S1has the same value as the control signal, Vc, generated by the control unit210(SeeFIG. 3).

FIG. 5is a graph representing values after the sensing signal, S, inputted from the sensor220, is converted into the input signal, Vin, by the control unit210.

With reference toFIG. 4andFIG. 5, the processes of supplying the toner will be described. As shown inFIGS. 4 and 5, in a initial operation, a value of 0 is stored in each of the shift registers261,262,263and the input signal of V1is received in the control unit210after time corresponding to the period, T=t/3, is elapsed. Consequently, the control unit210generates the control signal, Vc, of difference, ΔV1=V1−V0, of a target signal, V0, indicating a proper toner density from the input signal, V1, to transmit it into the driver230. The driver230drives the supply motor240based on the control signal, Vc, to operate the toner supplying unit250so that the toner is allowed to be supplied.

On the other hand, the control signal, Vc=ΔV1, is inputted and stored in a first shift register261in this process, and the summing counter264stores results (i.e., ΔV1) obtained by summing values (i.e., ΔV1, 0, 0) stored in the respective shift registers261,252,263as the compensating signal, Vb.

Therefore, since the compensating signal generating unit260does not operate until a passage of time corresponding to the first period T after the initial operation, the toner supplying system200performs a control of amounts of the toner in a similar manner as in the related art until a first item of data is stored in the summing counter264.

Further, during a time from T to 2T, the control signal, Vc, corresponding to the value (that is, ΔV−ΔV1) obtained by subtracting the compensating signal, ΔV1, from ΔV=Vin−Vois transmitted into the driver230.

Next, upon a passing of a time of 2T after the initial operation, the input signal, Vin, in the control unit210is V2, therefore the difference, ΔV2=V2−Vo, of the target signal Vofrom the input signal, V2, is computed by the control unit210. Further, the control unit210receives the compensating signal, ΔV1, stored in the summing counter264as the feedback signal to generate a control signal, Vc=ΔV2−ΔV1, by reflecting the compensating signal, ΔV1, on the computed value, ΔV2.

Furthermore, at the point in time of 2T, the control signal, Vc=ΔV2−ΔV1, is stored in the first shift register261while being transmitted into the driver230, and the value, ΔV1, that is pre-stored in the first shift register261is transmitted into a second shift register262. Further, the summing counter264updates result obtained by summing the values (ΔV2−ΔV1, ΔV1, 0) stored in the respective shift registers261,262,263as the compensating signal (Vb=(ΔV2−ΔV1)+ΔV1+0=ΔV2) to store the compensating signal.

Therefore, during a time from 2T to 3T, the control signal, Vc, corresponding to a value obtained by subtracting the compensating signal, ΔV2, from ΔV=Vin−Vois transmitted into the driver230.

As such processes are repeatedly performed, the control signal, Vc, of ΔV−ΔV3is generated during a time from 3T to 4T, the control signal, Vc, of ΔV−ΔV4+ΔV1is generated during a time from 4T to 5T, and the control signal, Vc, of ΔV−ΔV5−ΔV1+ΔV2is generated during a time from 5T to 6T.

Herein, the control unit210changes the control signal, Vc, to 0 to transmit the changed control signal, Vc, into the driver230and the first shift register261, if the control signal, Vc, generated as a result of a reflection of the compensating signal, Vb, as a feedback signal has a negative value. The driver230to which the value of 0 is inputted then stops operating the supply motor240so that the toner supplying unit250is not allowed to supply the toner.

FIG. 6is a graph showing a change of the input signal, Vin, computed through the sensor220and the control unit210in control of the processes mentioned above. As a time point, t1, passes, the input signal, Vin, becomes higher than a target signal, Vo. Therefore, the toner supplying system (200inFIG. 3) begins to operate from that point in time. A time point, t2, represents a time when the toner that begins to be supplied from the time point, t1, reaches the sensor220through the toner transporting unit280.

On the other hand, it is appreciated that the toner supply signal, Vs, which is transported from the control signal, Vc, of the control unit210to the supply motor240through the driver230, is gradually changed to lower signals as time passes as a result of a performing of the summing process as shown in the table ofFIG. 4.

FIG. 7is a graph illustrating the processes in which the toner supply is controlled through the toner supplying system200without the compensating signal generating unit260of the related art.

That is, although the toner is supplied from the time point, t1, where the input signal, Vin, becomes higher than the target signal, Vo, feedback control cannot be made until the toner supplied from the toner supplying unit250reaches the sensor220(that is, time t2), since there is no feedback device such as the compensating signal generating unit260, according to this invention. However, since the toner that is pre-supplied from the time point, t1,to the time point, t2, is not reflected on the control signal, Vc, it may be found that there is an abrupt change in the input signal, Vin, since the time point, t2, that is, an overflow in toner supply.

However, as shown inFIG. 6, it may be appreciated that the embodiment of the present invention to which the compensating signal generating unit260is applied shows the input signal, Vin, that is comparatively close to the target signal, Vo, without the overflow such as shown inFIG. 7. Meanwhile, though the image forming apparatus, according to aspects of the present invention, may be suitably applied to 2-component toner including toner and a carrier, it is not limited thereto and may be widely applied to devices to control toner supply.

As described above, aspects of the present invention provide an image forming apparatus capable of preventing an excessive supply of toner by controlling toner supply.