DE19643611B4 - Method for determining a degree of coloration of areas of concrete produced in printing and copying devices - Google Patents

Abstract

mit UDiff = UT- UTo wobei
U_Diff ein Differenzpotential ist,
U_T Messwerte der Spannung sind, die mittels des Sensors über die Zeit entlang der Spur mit Tonermarke gemessen wird,
U_To Messwerte der Spannung sind, die mittels des Sensors über die Zeit entlang der Spur ohne Tonermarke gemessen wird,
K eine geometrie- und ladungsabhängigeSensorkonstante ist,
ε_T die Dielektrizitätskonstante der Tonermarke ist, und
ε_M die Dielektrizitätskonstante des Mediums der Umgebung ist.Method for measuring the thickness of a toner layer as a measure of the degree of coloration of areas which are made of concrete in printing and copying devices, in which a fixed capacitive sensor (S1) is mounted in such a way that it also detects the influence of the flare of the surface of a carrier medium In a first step, this sensor (S1) measures against the carrier medium along a track which does not contain a toner mark,
in a second step, the same sensor is used to measure against the carrier medium along the same track provided with a toner mark (4),
the multiplicity of measured values U _T and U _To determined during one revolution of the carrier medium are each stored in a memory in the same circulation position, and
to determine the degree of coloring from the measured values U _T and U _{To obtained,} a layer-thick _{T is determined} according to the following equation:

With U Diff = U T - U to in which
U _{Diff is} a differential _potential
U _{T are} measured values of the voltage measured by means of the sensor over time along the track with the toner mark,
U _{To are} measured values of the voltage measured by means of the sensor over time along the track without a toner mark,
K is a geometry and charge dependent sensor constant,
ε _{T is} the dielectric constant of the toner mark, and
ε _{M is} the dielectric constant of the medium in the environment.

Description

The invention relates to a method to determine a degree of coloration of concrete areas produced in printing and copying facilities.

In non-impact printing and copying machines to create a visible image dye or toner on a transfer medium applied and optionally fixed on this. Here will between direct and indirect working, non-impact printing and photocopiers distinguished. For direct working printing and copying facilities, such as inkjet printers, the image is directly on a record carrier generated. With indirectly working printing and copying equipment, like most electrophotographic printing and copying devices, a toner image is first on an image forming medium, such as a photoconductor, then on transfer a record carrier and fixed on it.

Achievable print quality depends in particular on the degree of coloring a print or toner image, and thus the amount of one Record carriers transferred Dye or toner. Furthermore, for example in the case of solid surfaces, must be screened halftone, Lines, characters, etc. the degree of coloration of the printed image can be kept within certain limits. Therefore must first the degree of coloration a print or toner image measured and then with With the help of a control system according to the measurement result the one to be applied The amount of dye or toner can be set. According to the Print quality requirements the control process can also be repeated at certain time intervals become.

For determining or measuring the degree of coloring from Druckbzw. For example, toner images become areas deliberately colored, which are referred to as print or toner marks.

A determination or measurement of the degree of coloring of print or toner marks can be placed directly on a recording medium and / or an imaging medium, such as a photoconductor drum, be made.

With electrophotographic printing and copying equipment, for example, by a two-component developer, i.e. a developer mixture of carrier and toner, the toner from transferred from a developer station to the photoconductor. Here, in dependence from the process used by the two-component developer the toner from exposed or unexposed areas on the Photoconductor tightened. The amount of toner that is attracted to the photoconductor is, among other things, the mixing ratio of two components from the two-component developer and one the bias voltage applied to the photoconductor.

To achieve the required print quality, the the amount of toner applied to the photoconductor and thus the coloring of a Print or toner image can be kept within specified limits, because for example, a surface to be colored black only appears deep black, if enough toner is applied. On the other hand, for example with thin, Do not apply too much toner close to each other otherwise the lines run into each other.

Furthermore, it is economic as well as ecological establish even with one to be colored Area not reasonable or justifiable, more toner on the photoconductor than absolutely necessary to apply or in other words, it should be as possible only as much toner is applied as for the desired degree of coloring needed becomes.

For measuring the degree of coloring print or toner images in the form of toner marks are optoelectric working sensor systems known. When using such sensor systems becomes a toner mark with test light, for example with a visible one or infrared light. Due to different reflection and absorption characteristics of toner marks, which depend on the amount of toner depend on the toner tag, or a medium carrying toner is by means of an optoelectric Sensor system the intensity of the reflected or transmitted light measured and from it the coloring degree certainly.

That reflected or transmitted Light is turned on with the help of a photo receiver, for example one Photo resistor, a photo diode or a photo transistor in one electrical signal implemented. With the help of this electrical measurement signal will be the one to be transferred to the photoconductor Amount of toner, for example, by changing the mixing ratio of the two components of a developer mix.

Optoelectrically operating sensor systems, those for determining a degree of coloring used by toner brands have the particular disadvantage on that through the optical properties of the medium carrying the toner reflect the intensity of the reflected Light and thus that generated by the optoelectric sensor system electrical signal affected becomes. For example, the degree of coloring is directly on a record carrier measured, so can Already when using different types of paper misalignments occur. Similar Print image mismatches can for example, due to fluctuations in the photoconductor batches.

Another disadvantage is that with increasing emphasis of full-face toner brands the amount of reflected or transmitted light only decreases as long see you all surface elements the toner mark once without gaps are covered with toner. A multi-layered material that continues to grow Allocation of the toner mark leads at complete absorbent toner material no longer changes the amount of reflected / absorbed light and thus the electrical signal and can therefore be used with optoelectric Sensors are not recognized.

With the help of an optoelectrically working Sensor system can be therefore do not determine how many toner layers or layers on a toner mark on top of each other lie. Because a black area is already achieved with an average of 1.5 to 2 toner layers, everyone leads additionally applied toner too unnecessary high toner consumption; this can be however, can no longer be determined by means of an optoelectric sensor system.

Another disadvantage of optoelectric Sensor systems consist of different brands of toner or different colored toners also different reflection and have absorption properties. Therefore is an optoelectric Sensor to the toner used or each colored toner specially adapt, which can be very expensive. In extreme cases can optoelectric sensor systems with certain color toners at all not be used.

With electrophotographic printing and copying devices in which light is used for image formation the use of optoelectrically operating sensor systems to detect toner marks on undesired interactions of the test light used with the light-sensitive imaging medium to lead. Such interactions can, on the one hand, affect print quality and on the other hand, the life of the photosensitive imaging medium shortened become.

From Xerox Disclosure Journal, Vol. 13, No. 4, p. 201, is a method for determining the degree of coloration known from areas of a photoconductor provided with toner. Two capacitive sensors are in rolling contact with external sections the photoconductive surface. A sensor measures the capacity which is due to the air layer and the toner layer on the photoconductive surface results. The other sensor determines the background capacitance of the photoconductor. From the difference in the measurement results of the two sensors it is possible to the layer thickness of the toner are closed, taking a measurement with known layer thicknesses. The height of the photoconductor drum is not recorded.

From the DE 39 39 835 C2 it is known to determine the layer thickness of a toner material with the aid of a photo sensor, the information about the layer thickness being contained in the different reflectivities of the photoconductor and the toner surface. In order to increase the accuracy and to reduce the influence of an eccentricity of the photoconductor drum, measurements are carried out at a large number of locations along the circumference of the photoconductor drum, and the mean value is calculated from the resulting initial values. The measurement results of the photo sensor are then related to this mean.

Furthermore, from the DE 38 07 121 A1 known an electrophotographic printing device with a controlled electrophotographic process. The degree of coloring of the background area of an image can be detected with the aid of a scanning device. For this purpose, a raster mark is printed with toner and scanned. The degree of coloring can be inferred from the scanning result.

The object of the invention is therefore determining a degree of coloration of concrete areas produced in printing and copying facilities to improve in such a way that the application of toner is regulated is that the degree of coloring of a Toner image kept in a predetermined narrow tolerance range is to reduce the image quality to improve and at the same time optimize the toner consumption.

According to the invention, this object is solved by the features in claim 1. Advantageous further training are the subject of further claims.

In the method according to the invention to determine a degree of coloration of concrete areas produced in printing and copying facilities by means of a sensor, against one on a carrier medium applied toner mark as well as against an unstressed carrier medium measured. In order to obtain these measured values, according to the invention preferably capacitive sensors are used as sensors, which are usually are referred to as distance sensors.

In the method according to the invention is based on the knowledge that the degree of coloration one evenly stressed or evenly rasterized concrete area in a fixed, predetermined dependence on the middle integral Toner layer thickness stands. The means of a capacitive according to the invention Sensor-measured toner layer thickness is therefore a measure of the degree of coloration of the concrete areas.

The use of such distance sensors according to the invention is particularly advantageous since no test light is required with capacitive sensors; thus on the one hand there are no interactions with the photosensitive imaging medium, and on the other hand, it is not necessary to adapt the sensor to different toner colors or types of paper. Rather, with the aid of a capacitive sensor according to the invention, the layer thickness of the toner can be determined independently of the type or color of toner or also independently of a medium carrying a toner, such as a photoconductor or a type of paper.

When using a capacitive sensor in the method according to the invention in electrophotographic printing and copying equipment is preferred the conductive Under the surface of a photoconductor under its photosensitive layer used as one of the two capacitor plates.

In the method according to the invention for determining a degree of coloration of areas which are stressed and produced in printing and copying devices, a capacitive sensor is preferably used to measure against a toner mark provided on a carrier medium and a layer thickness d _{T is determined in} accordance with the following equation (1) in order to determine the degree of coloration

Here, U _{T is} a voltage measured by the sensor against the toner mark, K is a geometry and charge-dependent sensor constant, d _{P is} the thickness of a photoelectric layer, d is the distance between the sensor and the photosensitive layer, and ε _T denotes the dielectric constant of the toner mark, ε _M denotes the dielectric constant of the medium in the environment, and ε _P denotes the dielectric constant of the photosensitive layer.

According to the invention, the comparison of the two measured values obtained is specified in such a way that, in order to determine the degree of coloration, the layer thickness d _{T of} the toner mark by means of a difference potential U _Diff , which is the difference between a voltage U _T during measurements against a toner mark and a voltage U _oT against measurements is an unstressed area of a carrier medium, using the following Eq. (2) is determined:

K denotes a geometry and charge-dependent sensor constant, ε _T the dielectric constant of the toner mark and ε _M the dielectric constant of the medium.

If the voltages U _T and U _oT are measured in succession with only one sensor, the sensor is brought into positions such that the voltage U _oT against the unstressed area of the carrier medium is measured in a first position, while in a second position the Voltage U _{T is} measured against the toner mark applied to a carrier medium. If the two voltages U _T and Uo _T are measured in succession by means of the same sensor, the voltage value measured against the non-stressed carrier medium at appropriate time intervals is preferably stored in a memory and called up from the latter to form the differential potential U _Diff .

According to the invention, starting from a starting position (for example with the aid of a light barrier) of an unstressed carrier medium, the respective voltages U _oT against the unstressed carrier medium are measured at a plurality of measuring points by means of a sensor; the voltage values obtained in this way are stored in a memory. Then, with respect to the same starting position, the respective stresses against areas with areas of concrete (for example in the form of toner marks) are measured at a part of the plurality of measuring points on the area which is not emphasized. Finally, analogously to the method steps described above for determining the degree of coloration, a layer thickness d _T according to Eq. (2) determined.

Depending on what is to be generated Print image are in connection with the implementation of the inventive method preferably full-surface or halftone toner marks. Furthermore, with the method according to the invention both the maximum, minimum or integral layer thickness can be determined.

In the method according to the invention the measurements are not based on the type or color of the toner still influenced by optical properties of the medium carrying the toner or falsified. Since the layer thickness and from this also roughly the number of layers can be determined, the layer thickness, for example, for coloring a black surface 1.5 to 2 layers should be optimized accordingly. This can reduce toner consumption while at the same time optimizing print quality, which both under economic as well as ecological Point of view is very advantageous.

When using the method according to the invention let yourself also the quality improve significantly in full-color printing, for example, as required Toner layer thickness depending on color can be adjusted.

Below are preferred embodiments the invention with reference to the accompanying drawings in individual explained. Show it:

1a a basic structure of a preferred embodiment of an inventive device for use in the inventive method;

1b an equivalent circuit diagram of the in 1a illustrated construction;

2a and 2 B in each case graphs of voltage profiles when using a further preferred embodiment of the device according to the invention in a photoconductor drum with a pitch, namely 2a a voltage curve during measurements against an unstressed area and 2 B a voltage curve during measurements

1a shows a basic structure of a preferred embodiment of a device according to the invention, in which a sensor S with a holder 1 is firmly connected. The sensor S is at a distance d from the surface of a photosensitive layer 2 arranged, which is provided for example on a photoconductor drum. Below the photoconductive layer 2 there is a conductive, preferably metallic, surface 3 , for example the photoconductor drum.

How 1a can be seen, the photosensitive layer has a thickness d _P. Furthermore, in 1a opposite the sensor S on the photosensitive layer 2 a toner brand 4 provided with a thickness d _T.

The following is based on 1b which is an equivalent circuit diagram of the in 1a shown construction shows, the determination of the thickness d _{T of} the toner mark 4 explained. The top capacitor in the equivalent circuit diagram with a capacitance C _M corresponds to in 1a the area between the sensor S and the toner mark 4 , The light gray middle capacitor with a capacitance C _T corresponds to the toner mark 4 and the dark gray capacitor with a capacitance C _P corresponds to the photosensitive layer 2 ,

The total capacitance C of the equivalent circuit diagram or in 1a arrangement shown can thus be according to equation Eq. Calculate 1a.

By inserting the distances d, d _T and d _P defined above and the corresponding dielectric constants ε _M , ε _t and ε _P , namely ε _{M of} the medium between the sensor S and the toner mark 4 , ε _{T of} the toner mark 4 and ε _{P of} the photosensitive layer, and by introducing a geometry and charge-dependent sensor constant K, the voltage U _T against the toner mark can be measured by means of the sensor 4 by Eq. 1b represent as:

Correspondingly, the voltage U _oT measured by the sensor can be _applied to a non-concrete surface, ie a surface without toner (oT) by Eq. 1c represent as:

By reshaping Eq. 1b and insertion in Eq. 1c is the layer thickness d _{T of} the toner mark 4 by Eq. Represent (1) as follows:

If the two voltage _values U _T and U _{oT are} present _{when the device according to the invention is} used, then with the aid of the differential potential U _Diff from the two voltages U _T and U _oT, ie U _Diff = U _T - U _oT from the G1 's. lb and lc the layer thickness U _{T of} the toner mark 4 after the considerably simpler Eq. 2 calculate as:

2a and 2 B show schematic voltage curves that are measured with the use of a capacitive sensor or capacitive sensors with respect to a photoconductor drum with a pitch. Here are in the graphs 2a and 2 B a voltage U is plotted on the ordinate and time is plotted on the abscissa.

The sinusoidal line in 2a shows a voltage curve U _oT , which a sensor measures when the measurement is made directly against an unstressed photoconductor drum. On the other hand shows 2 B additionally a voltage curve U _oT which corresponds to that in 2a is shown superimposed. The voltage curve in 2 B is obtained when the measurement is against a concreted area of the photoconductor drum, preferably against a toner mark 4 (please refer 1a ) he follows.

Since the height of the photoconductor drum causes a cyclical, repetitive change in distance between the sensor and the photoconductor drum, electronic measurement value storage can be carried out. The layer thickness dr of the toner mark can then be measured using the measured voltages U _oT and U _T 4 clearly determine.

Claims (3)

Method for measuring the thickness of a toner layer as a measure of the degree of coloration of areas which are made of concrete in printing and copying devices, in which a fixed capacitive sensor (S1) is mounted in such a way that it also detects the influence of the flare of the surface of a carrier medium , wherein in a first step this sensor (S1) measures against the carrier medium along a track which does not contain a toner mark, with the aid of the same sensor in a second step against the carrier medium along the same with a toner mark ( 4 ) provided track is measured, the plurality of measured values U _T and U _To determined during one revolution of the carrier medium are stored in a memory in each case, and a layer thickness d _T according to the following is determined to determine the degree of coloration from the obtained measured values U _T and U _To Equation is determined:

With U Diff = U T - U to where U _{Diff is} a differential potential, U _{T are} measured values of the voltage which is measured by means of the sensor over the time along the track with the toner mark, U _{To are} measured values of the voltage which is measured by means of the sensor over the time along the track without the toner mark , K is a geometry and charge-dependent sensor constant, ε _{T is} the dielectric constant of the toner mark, and ε _{M is} the dielectric constant of the medium in the environment. A method according to claim 1, characterized in that as Toner brand a full-surface toner brand is provided. A method according to claim 1, characterized in that a raster toner mark as the toner mark is provided.