JP3176398B2 - Toner density sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner density sensor for a wet image forming apparatus such as a copying machine, a printer, a facsimile and the like.

[0002]

2. Description of the Related Art Conventionally, for example, a wet copying machine as shown in FIG. 1 is known. Around the photoreceptor drum 1, a charger 2, an exposure unit 3, an eraser 4, a wet developing device 5, a transfer charger 6, a separation roller 7, a cleaning unit 8, and a discharging lamp 9 are arranged in the rotation direction indicated by an arrow. It is arranged. A developing solution containing toner is supplied to a developing device 5 from a developing tank 10 provided below the developing device 5 by a pump 11 through a supply pipe 12.
The latent image formed on the photosensitive drum 1 by the second developing rollers 13 and 14 in a predetermined process is developed with a developing solution to form a toner image. The developer returns to the developing tank 10 by its own weight via the recovery pipe 15 and circulates.

[0003] The toner image formed on the photoreceptor is transferred to a transfer sheet fed from a sheet feeding unit, and the transferred transfer sheet is separated by a separation roller 7 and then fixed to complete copying. After the transfer, the toner and paper dust remaining on the photoconductor drum 1 are cleaned by the cleaning unit 8, and the photoconductor is erased from the charge removing potential to prepare for the next image formation.

The cleaning unit 8 includes the photosensitive drum 1
A sponge-like foam roller 16 and a cleaning blade 17 made of an elastic material such as rubber, and a supply pipe 22 from a developing tank 10 through a liquid supply nozzle 18 provided above the cleaning unit 8. Is supplied, and is spread over the entire width of the foam roller 16 by a diffusion plate 19 provided thereunder. The residual toner and paper dust that have been cleaned are squeezed out by a squeeze roller 20 together with the liquid, The cleaning unit 8 is returned to the developing tank 10 from the lowermost hole 21 through the recovery pipe 23.

[0005] As the number of developments increases, the toner concentration in the developing solution decreases. Therefore, the toner concentration in the circulating developing solution is constantly detected, and when the toner concentration falls below a predetermined concentration, the toner is added to the developing solution. The replenishment is performed so that the toner density is always maintained within a predetermined range.

In this conventional apparatus, a toner concentration sensor 24 for detecting the toner concentration is provided in a part of the toner flow path discharged from the pump 11 in the developing tank 10, and as shown in FIG. Lamp 25 and C as
A light transmitting sensor is used in which a light receiving element 26 such as a dS cell is opposed to the light receiving element 26 with a small gap of 1 mm or less, and the light receiving element receives light passing through a developing solution flowing therebetween. In general, a light transmission type toner concentration sensor is mainly used in a wet copying machine, and a CdS cell and a light emitting lamp are opposed to each other. The gap is less than 1 mm. In such cases, the gap may be further reduced because the toner density increases. For example, according to JP-A-51-11454,
A problem that occurs because the cell and the light emitting lamp of the CdS light receiving section are made of glass, that is, such a CdS cell and the light emitting lamp are immersed in the developer, and the toner is adsorbed by immersion in the liquid for a long time. When the developer adheres to the CdS cell and the light-emitting lamp, the light transmittance is reduced, and even if the developer becomes lower than the appropriate concentration, the developer is determined to be the appropriate concentration by optical detection. As a result, Since the supply of toner is not performed, the problem that the developer remains in a low-density state and is developed and formed with this developer, and the obtained copy has low image density and low quality is solved. Therefore, the mixture of a siloxane polymer and a compound having a Si—N bond is used to cover the CdS cell and the glass of the light-emitting lamp. However, with regard to physical adsorption, a siloxane polymer-coated polymer is superior to glass alone, but it is hardly sufficient for electrostatic adhesion such as charging. There is a problem that the problem of adhesion is not sufficiently solved.

However, in a wet copying machine, as described above, C
Since the gap between the dS cell and the light-emitting lamp is narrow, frictional charging is caused by the flow of the developing solution, so that the toner adheres and clogs, and the developing solution in the developing tank 10 is supplied to both the developing device 5 and the cleaning unit 8. Since the circulating method of recovering the toner is adopted, the developer recovered by the cleaning unit 8 is generated during the transfer of the transfer paper and is transferred from the transfer paper to the peripheral surface of the photosensitive member 1 when transferring the toner image. Paper dust, lint, etc. are mixed, and metal powder and toner agglomerates due to poor re-dispersion are present in the developer recovered from the developing device 5, and these are present on the light emitting surface of the toner density sensor 24 and receive light. When the toner is caught in the gap with the surface, the toner adheres to the gap, gradually grows on the light emitting surface, and finally fills the gap, so that the developer does not flow through the gap.
Is detected incorrectly and toner is supplied in accordance with the detection signal, the toner density becomes lower than a predetermined value, and as a result, a problem occurs that the developed image density becomes lower.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide a toner density sensor which does not cause clogging in a gap between a light emitting element and a light receiving element.

[0009]

SUMMARY OF THE INVENTION According to the present invention, there is provided a wet copying machine in which a developer circulates between a developing tank and a developing unit and a cleaning unit. A light-transmitting toner density sensor having a light-emitting element and a light-receiving element provided, wherein a light-emitting surface of the light-emitting element and a light-receiving surface of the light-receiving element are opposed to each other with a small gap therebetween; The problem is solved by a toner density sensor in which a portion of the light receiving element through which the developer passes and contacts is formed of a substance having the same charge polarity as the toner of the developer.

[0010]

According to the present invention, the light-emitting element and the light-receiving element of the toner concentration sensor are formed of a substance having the same charge polarity as the toner of the developing solution because the developing solution passes through and contacts the developing solution. This prevents the clogging of the gap between the sensors.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described based on an embodiment shown in the drawings.

In FIG. 3, the light emitting element 25 of the toner concentration sensor 24 having the structure shown in FIG. 2, for example, the light emitting lamp 25 and the light receiving element 26, for example, the CdS cell 26 are brought into contact with at least the developer flow according to the present invention. The part is formed of a substance having the same charge polarity as the toner of the developer,
Coated. The light emitting lamp 25 and the CdS cell 26 are formed of a metal such as Pd, In, Sn or the like, or a thin film of these oxides or CuI on the outer periphery, and a transparent conductive film having a transmittance of 10 ⁶ Ω · cm or less and a transmittance of 70% or more. The layers can be coated. In either case, a part of the covering is grounded to a part of the machine by a lead wire or the like.

As shown in FIGS. 4 to 7, the toner density sensor 24 is a light emitting element 25 supported by a bracket 27.
And a light receiving element 26. Mounting board 25 for light emitting element 25
a, the mounting substrate 26a of the light receiving element 26 is connected to an electric circuit by a lead wire. As a guide member, for example, a light-emitting side guide plate 28 and a light-receiving side guide plate 29 are provided with a bracket so that the developing solution flowing through the nozzle 30 is actively concentrated in a sensor gap (gap) between the light-emitting element 25 and the light-receiving element 26. 27.

The light emitting side guide plate 28 provided on the side of the light emitting element 25 has a cut-out hole formed in a part of its tapered shape, and only the light-emitting element 25, for example, the condensing lens part at the lamp end, is notched. The developer is exposed through the hole to the flow path of the developer. The light-receiving side guide plate 29 on the light-receiving side 26 has a tapered entrance similarly to the light-emitting side guide plate 28, and the end surface of the light-receiving side guide plate 29 has almost the same height as the element surface of the light-receiving element 26. It forms so that it may become. With this configuration, an unnecessary exposed portion when the developer passes is minimized. Since the developer is sprayed onto the sensor gap of the toner density sensor 24 by the light emitting side guide plate 28 and the light receiving side guide plate 29, clogging of foreign matters can be effectively prevented.

A method of spraying a nozzle for directly spraying the developing solution from a plurality of locations near the Cds cell 26 or the light-emitting lamp 25 is also possible.

If the liquid flow blown to the sensor gap of the toner density sensor 24 is increased so that foreign matter does not clog, the toner tends to adhere electrostatically to the toner density sensor due to frictional charging. As shown in FIG. 3, the light emitting side guide plate 28 and the light receiving side guide plate 29 are covered with a bracket 27
The problem can be solved by reducing the electrostatic adhesion of the toner by grounding the main body of the machine via the.

As a modification of the embodiment shown in FIG. 4, as shown in FIGS.
The structure can be simplified by forming a single cylindrical guide member 31 for 8, 29. Since the cylindrical guide member 31 can be easily formed into an arbitrary shape, the distal end portion of the nozzle 30 can be formed to fit into a part of the guide member 31. This makes it possible to actively guide the developer supplied by the nozzle 30 to the sensor gap.

The portion of the cylindrical guide member 31 facing the light emitting element 25 is formed so that only the condenser lens of the light emitting element 25 can be reliably exposed to the developing solution flow by an arbitrary amount. it can. Light receiving element 26 of cylindrical guide member 31
Is formed so that the light collecting surface of the light receiving element 26 can be exposed to the developing solution flow.

In FIGS. 8 to 11, the same members as those in FIGS. 4 to 7 or corresponding members are denoted by the same reference numerals, and description thereof is omitted.

In the examples shown in FIG. 8 to FIG.
The grounding of the conductive coating portion of the light receiving element 26 to the main body can be easily made possible by forming the cylindrical guide member 31 with a conductive member such as conductive plastic or conductive rubber. Further, since the cylindrical guide member 31 is conductive, it is possible to prevent toner from adhering to the wall surface of the cylindrical guide member 31.

In the above embodiment, since the condenser lens portion of the light emitting element 25 is exposed to the liquid passage, toner adhesion can be prevented by the conductive coating, but the condenser lens portion is exposed to the flow path. Therefore, adhesion of paper powder cannot be prevented.

Therefore, in the embodiment shown in FIG. 12, a transparent plate 33 is provided in a portion located in front of the condenser lamp as the light emitting element 25 as a guide member, and the flow of the developer in the portion of the density sensor 24 is smoothly performed. A cylindrical or plate-shaped guide member 32 is provided. Although only the light emitting element side may be used, the effect can be enhanced by adopting the same configuration on the light receiving element 26 side. The transparent member is made of glass, methacrylic resin, or the like, and is integrated with the flow path of the guide member 32 and is made flush with the flow path surface to prevent toner and paper powder from adhering. Further, by covering the transparent member with a conductive material and forming the guide member 32 with the conductive member as described above, the adhesion of toner and paper powder can be more effectively prevented.

Applying a bias voltage to the conductive guide member is more effective in preventing electrostatic adhesion. The application timing for turning ON / OFF the bias voltage is determined by the density sensor 2
It is most effective to set the time for discharging the liquid from the nozzle (for example, during the mechanical operation) to No. 4; however, since the adhesion of the toner does not proceed rapidly, any time and any time are possible. There is an effect. However, in this arbitrary case, it is expected that the condition is greatly affected by conditions such as the charging characteristics of the toner.

[0024]

According to the present invention, the light emitting element 25 and the light receiving element 26 are coated with a conductive material, and the coating is grounded.
Alternatively, by applying a bias voltage, toner adhesion was prevented, and clogging of the sensor gap with foreign matter was prevented.

[Brief description of the drawings]

FIG. 1 is an overall schematic view of a conventional wet copying machine.

FIG. 2 is an explanatory perspective view of a conventional toner density sensor.

FIG. 3 is an explanatory front view of the toner density sensor according to the present invention.

FIG. 4 is an explanatory perspective view of a toner density sensor according to the present invention.

FIG. 5 is a plan sectional view of the toner density sensor according to FIG. 4;

FIG. 6 is a sectional view taken along line VI-VI of FIG. 5;

FIG. 7 is a sectional view taken along line VII-VII of FIG. 5;

FIG. 8 is an explanatory perspective view of another embodiment of the toner density sensor according to the present invention.

9 is a plan sectional view of the toner density sensor according to FIG.

FIG. 10 is a sectional view taken along line XX of FIG. 9;

11 is a sectional view taken along the line XI-XI in FIG. 9;

FIG. 12 is a sectional view of a modified example of FIG.

[Explanation of symbols]

 24 toner concentration sensor 25 light emitting element 26 light receiving element 28 guide member 29 guide member 30 nozzle 31 guide member 32 guide member 33 transparent plate

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-53-119054 (JP, A) JP-A-49-66350 (JP, A) JP-A-48-80047 (JP, A) JP-A-10-108 142923 (JP, A) Japanese Utility Model Showa 61-102951 (JP, U) Japanese Utility Model Showa 53-68245 (JP, U) Japanese Patent Publication No. 52-10010 (JP, B1) Japanese Patent Publication No. 51-4793 (JP, B1) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 21/00-21/61 G03G 15/11 JICST file (JOIS)

Claims (1)

(57) [Claims] 1. A wet copying machine in which a developer circulates between a developing tank and a developing device and a cleaning unit, the device includes a light emitting element and a light receiving element provided in the developing solution flowing in the developing tank. In a light-transmitting toner density sensor in which a light-emitting surface of a light-emitting element and a light-receiving surface of a light-receiving element are opposed to each other with a small gap, a portion where the developer of the light-emitting element and the light-receiving element of the toner density sensor passes and comes into contact with each other. A toner concentration sensor formed of a substance having the same charge polarity as the toner of the developer.