Method for detecting the status of toner using a photosensor

BACKGROUND OF THE INVENTION

The present invention relates generally to a method for detecting the level of toner an image reproduction apparatus, such as a laser printer.

In general, printers are frequently concerned with detecting the current level of printing material that is left in the printer. In particular, laser printers are provided with toner sensing apparatus for detecting the status of toner powder in those printers. Among examples of current practice, Tachihara et al. (US Patent 5,617,121 <i>Ink Jet Recording With Ink Detection,</i> April 1, 1997) discusses a recording head includes discharge ports for discharging ink. An ink detection element is provided in the liquid chamber for detecting the presence of ink. Murray et al (US Patent 5,610,635, <i>Printer Ink Cartridge With Memory Storage Capacity,</i> March 11, 1997) discusses a printer ink cartridge including a memory storage element. The memory storage element is capable of storing information regarding amount of ink remaining in the cartridge. The memory storage element is connected to the control and driver circuit to enable information to be retrieved and stored from the memory storage element. The control and driver circuit may also include a counter for counting the number of times the heating elements on the cartridge are energised. The approximate number of times the heating elements have been energised indicates the approximate number of drops of ink that have been applied by the cartridge.

Stapleton (US Patent 5,596,484 <i>Ink Level Sensing On A Pen Carriage In A Pen Plotter,</i> January 21 1997) discusses an apparatus for sensing whether a liquid with a turbulent surface and contained within a vessel has fallen to a level where the liquid is substantially expended. Cowger (US Patent 5,574,484 <i>Level Detection For Ink Cartridges of Ink-Jet Printers,</i> November 12 1996) discusses a sensor that detects the level of ink present in an ink-supply cartridge of an ink-jet type printer. The sensor moves with the reciprocating pen carriage of the printer. Ogiri et al. (US Patent 5,508,786, <i>Image Forming Apparatus,</i> April 16, 1996) discusses determining the number of copies which can be outputted corresponding to the defined capacity of the developer.

Takayanagi et al (US Patent 5,488,395, <i>Liquid Jet Recording Apparatus,</i> January 30, 1996) discusses a liquid jet recording apparatus having a pair of electrodes provided to be immersed in the ink in the container. By applying a voltage between the electrodes, the remainder of the ink is detected by a change in the electric resistance between the electrodes. Gu (US Patent 5,485, 191 <i>Image Forming Apparatus Having Tone Correction Function,</i> January 16, 1996) discusses an image forming apparatus including an electrophotographic photosensitive member. For tone controls, a detector detects a state of the tone control image, and the controller controls the electrostatic latent image forming device on the basis of a datum from the detector and predetermined tone correcting information.

Accatino et al (US Patent 5,414, 452, <i>Recognition Of Ink Expiry In An Ink Jet Printing Head,</i> May 9 1995) discusses ink jet printers in which the print head is connected to an ink reservoir, such as may be used in teleprinter or facsimile apparatuses. A logic circuit is used to count the number of drops gradually expelled, and with any necessary correction, compares this number with the maximum number of drops equivalent to a known volume of ink contained on average in the reservoir. Expiry of the ink is indicated as in dependence upon the result of the comparison. Gatten (US Patent 5,068, 806, <i>Method of Determining Useful Life of Cartridge For An Ink Jet Printer,</i> November 26, 1991) discusses a computer program in the microcontroller of an ink jet printer-plotter that counts the ink dots fired by the carriage of the printer.

El Hatem et al (US Patent 4,853, 718, <i>On Chip Conductive Fluid Sensing Circuit,</i> August 1 1989) discusses a situation in which the ink in an ink jet is sensed by a capacitor, one plate of which is coupled to the ground through the ink. From a study of these examples of contemporary practice and art, it has been found that there is a need for an effective and improved device for accurate toner detection that does not require an overly accurate (and hence extensive) photosensor.

An object of the present invention is to provide an improved method for detecting the level of toner in a printer.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a method of detecting toner status in an image reproduction apparatus having a photosensor adapted to detect toner in a toner receptacle comprising: <ul id="ul0001" list-style="none" compact="compact"><li>periodically sampling the output of the photosensor;</li><li>changing the value of a counter in accordance with either a first or a second algorithm depending upon whether the output of the photosensor is characteristic of a toner level below a predetermined level or above a predetermined level respectively;</li><li>comparing the value of the counter with a predetermined reference value; and</li><li>displaying the toner status in dependence upon the outcome of the comparison.</li></ul>

If the value of the counter is larger than the predetermined reference value, a toner status message may be displayed on a display device of the image reproduction apparatus signifying that the toner is empty and a refill is required. Similarly, if the value of the counter is smaller than the predetermined reference value, a toner status message may be displayed on a display device of the image reproduction apparatus signifying that the toner is not empty and a refill is not required.

Alternatively, if the value of the counter is smaller than the predetermined reference value, the method may further comprise comparing the value of the counter with a second predetermined reference value.

If the value of the counter is larger than the second predetermined reference value, a toner status message may be displayed on a display device of the image reproduction apparatus signifying that the toner is low and a refill is required. Similarly, if the value of the counter is larger than the second predetermined reference value, a toner status message may be displayed on a display device of the image reproduction apparatus signifying that the toner is not low and a refill is not required.

Preferably, the second algorithm is the inverse of the first algorithm. For example, the first algorithm may increment the value of the counter and the second algorithm may decrement the value of the counter.

The present invention also provides an image reproduction apparatus including: <ul id="ul0002" list-style="none" compact="compact"><li>a toner receptacle;</li><li>a photosensor adapted to detect toner in the toner receptacle;</li><li>a display device; and</li><li>control means for: <ul id="ul0003" list-style="none" compact="compact"><li>periodically sampling the output of the photosensor;</li><li>changing the value of a counter in accordance with either a first or a second algorithm depending upon whether the output of the photosensor is characteristic of a toner level below a predetermined level or above a predetermined level respectively;</li><li>comparing the value of the counter with a predetermined reference value; and</li><li>displaying the toner status on the display device in dependence upon the outcome of the comparison.</li></ul></li></ul>

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of example with reference to the accompanying drawings in which: <ul id="ul0004" list-style="none" compact="compact"><li>Fig. 1 is a schematic block diagram of a contemporary toner;</li><li>Fig. 2A shows a circuitry of another contemporary toner sensing apparatus employ a photosensor;</li><li>Fig. 2B depicts how the toner sensing apparatus of Fig. 2A is mounted in the developing device;</li><li>Fig. 2C shows a waveform of an output terminal B of the toner sensing device of Fig. 2A when the toner is properly enough or full in the developing device;</li><li>Fig. 2D shows a waveform of an output terminal B of the toner sensing device of Fig. 2A when the toner is short or empty in the developing device;</li><li>Fig. 3 is a flowchart illustrating a series of steps for detecting the status of toner using a photosensor according to one embodiment of the present invention;</li><li>Fig. 4 is a flowchart illustrating a series of steps for detecting the status of toner using a photosensor according to another embodiment of the present invention;</li><li>Fig. 5A shows a waveform obtained by sampling the signal of the output terminal B of the toner sensing apparatus of Fig. 2A in accordance with the flowchart of Fig. 3;</li><li>Fig. 5B shows a waveform obtained by filtering the waveform of Fig. 5A using a reference value for a specified duration of time;</li><li>Fig. 6A is a waveform obtained by sampling the signal of the output terminal B of the toner sensing apparatus of Fig. 2A in accordance with the flowchart of Fig. 4;</li><li>Fig. 6B is a waveform obtained by filtering the waveform of Fig. 6A using a first and second reference value for a specified duration of time; and</li><li>Fig. 6C is a waveform obtained by filtering the waveform of Fig. 6A using a first and second reference value for a specified duration of time.</li></ul>

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning now to the drawings, specifically to Fig. 1, a contemporary toner sensing apparatus is schematically illustrated, wherein a piezoelectric detector 10 measures the weight of the toner powder in a developing device not shown and outputs the measured value as digital data. A data decoder 11 reads the digital data received from the piezoelectric detector 10. A CPU or controller 12 determines whether of the status of the toner in the developing device on the basis of the data received from the data decoder 11 and outputs the resultant of determination to a display device not shown.

Fig. 2A illustrates a circuitry of another toner sensing apparatus employing a photosensor 25. An anode of a photodiode is connected to a power source Vcc via a resistance R1 and its cathode is connected to ground. Another component of the photosensor may be a phototransistor 21 of which a base receives light from the photodiode 20, a collector termination A is connected to the power source Vcc via a resistance R2 and an emitter is connected to ground. The photosensor may also include a transistor 22 of which a base is connected to the collector terminal A of the phototransistor 21 via a resistance R3, a collector terminal B is connected to the power source Vcc via a resistance R4 and an emitter is connected to ground. In this configuration, the photosensor 25 is composed of the photodiode 20 for emitting light and the phototransistor 21 for receiving the light from the photodiode 20 as shown in the dotted line in that view.

Fig. 2B shows how the toner sensing apparatus of Fig. 2A is mounted in the developing device. In arrangement, the photodiode 20 and the phototransistor 21 are opposite with each other, having the developer such as toner powder between them, two light transmitting films 22 made of transparent insulating material are provided to make isolation of the photodiode 20 and the phototransistor 21 from the toner having conductivity so as to prevent the two elements from being short-circuited by such toner. A toner removing blade 23 is fixed to a rotational shaft 24 and scrapes the toner powder adhered to the surfaces of the light transmitting films 22 as it rotates, so that the light from the photodiode 20 can be transmitted to the phototransistor 21 without interruption.

Hereinafter, such a toner sensing apparatus in more detail with reference to Figs. 2A and 2B. In the developing device, the toner powder is provided between the photodiode 20 and the phototransistor 21 by a specified height, both being arranged to face with each other as mentioned before. The photodiode 20 can emit light since it is connected to the power source Vcc in forward direction and thus current flows through it all the time.

In such a set of devices, at least two situations may arise one is when the toner is properly enough in the developing device and the other is when the toner is short or empty.

First, in case of the former (enough toner), the toner existing in the developing device by a specified height may block the light from the photodiode 20 to be transmitted to the base of the phototransistor 21. In this case, the phototransistor 21 is turned off and the collector terminal A outputs the signal of high level. This signal is then transmitted to the base of the transistor 22 through the resistance R3, so that the transistor 22 is turned on. Next, the signal is inverted and amplified at the last output terminal B of the toner sensing apparatus 3, resulting in low level.

In contrast, when the toner is nearly short or empty like the latter (low/empty toner), it is possible that the light from the photodiode 20 is transmitted to the base of the phototransistor 21 with no problem, whereby the phototransistor 21 is turned on and the collector terminal A outputs the signal of low level. This signal is then transmitted to the base of the transistor 22 through the resistance R3 and the transistor 22 is turned on. As a result, the signal at the terminal B becomes high level.

Thus, it is possible to judge the status of the toner in the developing device by means of the output signal of the terminal B in a manner that the low signal signifies that the toner is properly enough or full and the high signal signifies that the toner is short or empty. Nevertheless, this contemporary apparatus is disadvantageous in various aspects. The piezoelectric detector is very expensive and since replacement is limited to the same model of any specific manufacturer for the reliable operation, to buy such replacement may be not easy. For these reasons, the relatively cheaper photosensors have often been used instead of the piezoelectric detector. This can often bring problems in reliability because the toner removing blade or the like may make noise as shown in Figs. 2C and 2D and filtering of such noise is also not easy.

The flowchart of Fig. 3 explains how to detect the status of the toner in the developing device. As shown in this flowchart, the printer is initialised when a printer engine is on, an upper and lower limit values of a toner empty counter and a reference value are determined. These values give standard points in judging the presence or absence of the toner in the developing device (S1). After the initialisation step, the next step (S2) is followed by judging whether the signal of the last output terminal B of this toner sensing apparatus is low or high. Based on the result of judgment, the next step is performed by counting up the counter values by ones if the output signal is high (S3) and counting down the counting values by ones if low (S4). Then, the status of the toner is displayed on any display device as a series of characters "TONER EMPTY" (S6) when the counter value is equal to a larger than the reference value, or as a series of characters "TONER FULL" (S7) when the counter value is smaller than the reference values.

The flow chart of Fig. 4 explains another method according to this invention, wherein the printer is initialised when a printer engine is on. Then, there exists the steps of determining an upper and lower limit values of a toner empty counter and a first reference value and a second reference value which function as standard points in judging the amount of the remaining toner in the developing device. After the initialisation, the next step is implemented by judging whether the signal of the last output terminal B of this toner sensing apparatus is low or high. Based on the result of judgment, the next step is performed by counting up the counter value by ones if the output signal is high and counting down the counter value by ones if low. Then, comparison of the counter value and the first reference value is implemented and the resultant is displayed on any display device as a series of characters "TONER EMPTY" when the counter value is equal to or larger than the first reference value. However, if the counter value is small than the first reference value, an additional comparison is implemented between the counter value and the second reference value and the resultant is displayed on any display device as a series of characters "TONER LOW" when the counter value is equal to or larger than the second reference value, or as a series of characters "TONER FULL" (S7) when the counter value is smaller than the reference value.

The flow chart of Fig. 4 explains another method according to this invention, wherein the printer is initialised when a printer engine is on. Then, there exists the steps of determining an upper and lower limit values of a toner empty counter and a first reference value and a second reference value which function as standard points in judging the amount of the remaining toner in the developing device. After the initialisation, the next step is implemented by judging whether the signal of the last output terminal B of this toner sensing apparatus is low or high. Based on the result of judgment, the next step is performed by counting up the counter value by ones if the output signal is high and counting down the counter values by ones if low. Then, comparison of the counter value and the first reference value is implemented and the resultant is displayed on any display device as a series of characters "TONER EMPTY" when the counter value is equal to or later than the first reference value. However, if the counter value is smaller than the first reference value, an additional comparison is implemented between the counter value and the second reference value and the resultant is displayed on any display device as a series of characters "TONER LOW" when the counter value is equal to or later than the second reference value, or as a series of characters "TONER FULL" when the counter value is smaller than the second reference value.

The two preceding embodiments of this invention can also be as follows. At first, as in Fig. 3, the printer is initialised (S1) immediately when a printer engine is on, and at the same time the photodiode 20 emits light since it is connected to the power source Vcc in the forward direction as shown in Figs. 2A and 2B to allow the current to flow through it all the time. Simultaneously, the toner empty counter is programmed to have the upper limit value and the lower limit value, which is designed to be operated in response to the output from the photosensor, and the reference value which functions as a standard point for judging the presence or absence of the toner in the developing device.

In the absence of the toner, the light from the photodiode 20 is applied to the base of the phototransistor 21 so that the phototransistor 21 is turned off and the last output terminal B of this toner sensing apparatus outputs the signal of high level as shown in Fig. 2D. In contract, if the toner is properly enough or full, the light transmission from the photodiode 20 to the phototransistor 21 is blocked by the existence of toner, so that the phototransistor 21 is turned on and the last output terminal B of this toner sensing apparatus outputs the signal of low level as shown in Fig. 2C.

Next, the CPU (not shown) judges whether the output signal of the terminal B is high or low (S2). Based upon the result of judgment, the next step is selected in either of two ways (low or high signal). The high signal signifies what the toner is short or empty, so that the toner empty counter not shown increases the counting value by 1 (S3). The low signal signifies what the toner is properly enough or full, so that the counter decrease the counting value by 1 (S4). In the steps of S2 to S4, the waveform of Fig. 5A can be obtained by sampling the counter during a specified time T.

After the increase or decrease of the counter value, the resultant value is compared with the reference value (S5). As a result, if the counter value is equal to or larger than the reference value, the high signal is outputted from the terminal B as shown in Fig. 5B and a series of characters "TONER EMPTY" is displayed on the not shown display device to indicate what the toner must be refilled to the user (S6), and however if the counter value is smaller than the reference value, the low signal is outputted from the terminal B as shown in Fig. 5B and a series of characters "TONER FULL" is displayed on the not shown display device to confirm what the toner is properly enough in the developing device to the user (S7).

Another embodiment of this invention is described below with reference to Fig. 4. In the same manner with the preceding embodiment, the printing system is initialised (S1) immediately when the printer engine is turned on, and at the same time the photodiode 20 emits light since it is connected to the power source Vcc in forward direction as shown in Figs. 2A and 2B to allow the current to flow through it all the time. The toner empty counter which is designed to perform the counting operation in accordance to the output signal of the photosensor, is programmed to have the upper limit value and lower limit value, the first reference value and the second reference value which both will be standard points in judging the presence or absence of the toner in the developing device.

The light from the photodiode 20 is applied to the base of the phototransistor 21 in the absence of the toner, so that the phototransistor 21 is tuned off and the last output terminal B of this toner sensing apparatus outputs the signal of high level as shown in Fig. 2D. However if the toner is properly enough or full, the light transmission from the photodiode 20 to the phototransistor 21 is blocked by the existence of toner, so that the phototransistor 21 is tuned on and the last output terminal B of this toner sensing apparatus outputs the signal of low level as shown in Fig. 2C.

Then, the CPU (not shown) judges whether the output signal of the terminal B is high or low (S2). Based upon the result of judgment, the next step is selected in either of two ways. That is, the high signal signifies what the toner is short or empty, so that the toner empty counter not shown increases the counting value by 1 (S3) and the low signal signifies what the toner is properly enough or full, so that the counter decreases the counting value by 1 (S4). In the steps of S2 to S4, the waveform of Fig. 6A can be obtained by sampling the counter during a specified time.

After such a step (S3 or S4), the counter value is compared with the first reference value (S5). As a result, if the counter value is equal to or larger than the first reference value, a first signal of high level is outputted from the terminal B as shown in Fig. 6B and a series of characters "TONER EMPTY" is displayed on the not shown display device to indicate what the toner must be refilled to the user (S6), and however if the counter value is smaller than the first reference value, that value is again compared with the second reference value (S7). After the comparison of S7, if the counter value is equal to or larger than the second reference value, a first signal of high level and a second signal of low level are outputted from the terminal B as shown in Figs. 6B and 6C and a series of characters "TONER LOW" is displayed on the not shown display device to indicate what the toner must be refilled before long to the user (S8).

However, if the counter value is smaller than the second reference value, a first signal and a second signal of low level are outputted from the terminal B as shown in Figs. 6B and a series of characters "TONER FULL" is displayed on the not shown display device to confirm what the toner is properly enough in the developing device (S9).

As mentioned above, this invention detects the status of the toner in the developing device by means of using a photosensor that can be obtained relatively cheaply. The noise generated from such a photosensor is sampled in accordance with the integral algorithm and is filtered, bringing an improvement in reliability.

It will be recognised by those skilled in the art that changes or modifications can be made to the above described embodiments without department from the board inventive concept of the invention. It should therefore be understood that this invention is not only applicable to the LASER printers described herein but the page printers.