JPH05133892A - Toner concentration sensor - Google Patents

Abstract

PURPOSE:To obtain a sensor wherein no clogging occurs in a gap between a light-emitting element and a light-sensing element, by providing a guide member in the vicinity of the light-emitting element and the light-sensing element and by constructing the guide member so that the velocity of the flow of a developing solution be increased. CONSTITUTION:A concentration sensor has a light-emitting element 25 and a light-sensing element 26 which are supported by a bracket 27. Fitting bases 25a and 26a of the elements 25 and 26 are connected to an electric circuit by lead wires respectively. A light-emitting-side guide plate 28 and a light-sensing- side guide plate 29, for instance, are provided for the bracket 27, as guide members, so that a developing solution made to flow by a nozzle 30 be concentrated positively in a sensor gap between the elements 25 and 26. A cut hole is formed in a tapered part of the guide plate 28 so that only a condenser lens in the fore end of the element 25 is exposed in a flow passage of the developing solution through the cut hole. Besides, the guide plate 29 is formed so that the face of the end part is at the same height substantially as the element face of the element 26. In this way, an exposed part being unnecessary in relation to passing of the developing solution is made small as much as possible.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a wet copying machine as shown in FIG. 1 has been known. Around the photosensitive 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 charge eliminating lamp 9 are arranged in this order in the rotation direction indicated by the arrow. It is arranged. A developing solution containing toner is supplied to the developing device 5 from a developing tank 10 provided below the developing device 5 through a supply pipe 12 by a pump 11, and a first developing device provided in the developing device is provided.
The second developing rollers 13 and 14 develop the latent image formed on the photosensitive drum 1 in a predetermined process with a developing solution to form a toner image. The developer passes through the recovery pipe 15 and returns to the developer tank 10 by its own weight and circulates.

The toner image formed on the photosensitive member is transferred onto a transfer paper fed from a paper feeding section, and the transferred transfer paper is separated by a separation roller 7 and then fixed, whereby the copying is completed. After the transfer, the toner and the paper dust remaining on the photoconductor drum 1 are cleaned by the cleaning unit 8, and the charge removal potential of the photoconductor is erased to prepare for the next image formation.

The cleaning unit 8 is a photosensitive drum 1.
A sponge-like foam roller 16 and a cleaning blade 17 made of an elastic material such as rubber. The sponge-like foam roller 16 and the cleaning blade 17 are made of an elastic material such as rubber. The developing solution supplied through the above is supplied, and the residual toner and the paper dust which are cleaned by being diffused to the entire width of the foam roller 16 by the diffusion plate 19 provided thereunder are squeezed by the squeezing roller 20 together with the liquid, The cleaning unit 8 is returned to the developing tank 10 through the lowermost hole 21 and the recovery pipe 23.

Since the toner concentration in the developing solution decreases as the number of times of development increases, the toner concentration in the circulating developing solution is constantly detected, and when the toner concentration falls below a predetermined level, the toner becomes the developing solution. Replenishment is performed to constantly maintain the toner density 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. 25 and C as
A light transmissive sensor is used which is opposed to a light receiving element 26 such as a dS cell with a slight gap of 1 mm or less, and the light receiving element receives the light passing through the developer flowing between them. The toner concentration sensor of the wet type copier is generally of the light transmission type, and the CdS cell and the light emitting lamp face each other. The gap is 1 mm or less, but the copy speed is high. In such cases, the toner density becomes high, and therefore the gap may be made smaller. For example, according to Japanese Patent Laid-Open No. 51-11454,
A problem that occurs because the cell of the CdS light receiving part and the light emitting lamp are made of glass, that is, such a CdS cell and the light emitting lamp are immersed in the developing solution, and the toner is adsorbed by the immersion in the solution for a long time. Even if the developer adheres to the CdS cell and the light-emitting lamp due to the action and the light transmittance decreases, and the concentration of the developing solution becomes lower than the proper concentration, it is judged to be the proper concentration by optical detection. However, since the toner is not supplied, the developing solution is kept in a low concentration state and developed and image-formed with this developing solution, and the obtained copy has a low image density and a low quality, which solves the problem. Therefore, the CdS cell and the glass of the light emitting lamp are coated with a mixture of a siloxane polymer and a compound having a Si—N bond to eliminate the problem. However, with regard to physical adsorption, those coated with siloxane polymers are superior to glass alone, but it is difficult to say that they are sufficiently attached to electrostatic charges such as charges, and toner is attached to the sensor by triboelectrification due to developer flow. There is a problem that the problem of adhesion is not solved sufficiently.

As described above, in the wet type copying machine, since the gap between the CdS cell and the light emitting lamp is narrow, frictional charging is caused by the flow of the developing solution and the toner adheres to cause clogging, and the developing solution in the developing tank 10 is clogged. Since the circulation system for supplying and recovering the toner to both the developing device 5 and the cleaning unit 8 is adopted, the developer collected in the cleaning unit 8 contains a toner image that is generated in the process of transporting the transfer paper. At this time, paper powder, lint, etc. transferred from the transfer paper to the peripheral surface of the photoconductor 1 are mixed, and the developer collected from the developing device 5 contains metal powder and toner agglomerates due to poor redispersion. When they are caught in the gap between the light emitting surface and the light receiving surface of the toner concentration sensor 24, the toner adheres to the light emitting surface and gradually grows on the light emitting surface to finally fill the gap, so that the developer does not flow through the gap. That conclusion Detects the toner concentration sensor 24 is erroneous, in the case of performing the toner replenishment by the detection signal, the toner concentration is lower than a predetermined value, as a result, a problem that the developed image density is lowered occurs.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems of the prior art and to provide a toner concentration sensor which does not cause clogging in the gap between the light emitting element and the light receiving element.

[0009]

SUMMARY OF THE INVENTION The present invention addresses the above problems in a developer flowing in the developing tank of a wet copying machine in which the developer circulates between the developing tank and the developing unit and the cleaning unit. A light transmissive toner concentration sensor having a light emitting element and a light receiving element provided, and the light emitting surface of the light emitting element and the light receiving surface of the light receiving element are opposed to each other with a small gap therebetween. The toner concentration sensor is characterized in that a guide member is provided in the vicinity and the guide member is configured to increase the liquid flow velocity of the developer.

[0010]

According to the present invention, a guide member is provided in the vicinity of the light emitting element and the light receiving element to form a flow path for increasing the liquid flow rate of the developing solution, and foreign matter such as paper dust adheres to the flow path to cause clogging. Is prevented. Furthermore, by forming the guide member with a conductive member and grounding it, it is possible to prevent frictional electrification due to a fast liquid flow, to reliably prevent toner from adhering, and to prevent clogging of the sensor gap. It

[0011]

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

In FIG. 3, the light emitting element 25, for example, the light emitting lamp 25 and the light receiving element 26, for example, the CdS cell 26, of the toner concentration sensor 24 having the structure shown in FIG. The part is formed of a substance having the same charge polarity as the toner of the developer,
It is coated. Further, the light-emitting lamp 25 and the CdS cell 26 are thin films of Pd, In, Sn or the like metal, or oxides thereof or CuI or the like on the outer periphery, and a transparent conductive film having a transmittance of 70% or more at 10 ⁶ Ω · cm or less. The layers can be coated. In either case, ground the part of the machine to a part of the machine with a lead wire or the like.

As shown in FIGS. 4 to 7, the toner concentration 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 used as brackets so that the developer flown by the nozzle 30 is actively concentrated in the 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 notched hole formed in a part of its tapered shape, and only the tip of the light emitting element 25, for example, the condenser lens portion at the tip of the lamp is notched. It is exposed through the hole in the flow path of the developing solution. The light-receiving side guide plate 29 on the side of the light-receiving element 26 has a tapered entrance like the light-emitting side guide plate 28, and the end surface of the light-receiving side guide plate 29 has substantially the same height as the element surface of the light-receiving element 26. To be formed. With this configuration, an unnecessary exposed portion when the developing solution passes is made as small as possible. Since the developing solution is sprayed onto the sensor gap of the toner concentration sensor 24 by the light emitting side guide plate 28 and the light receiving side guide plate 29, clogging of foreign matter can be effectively prevented.

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

If the liquid flow blown to the sensor gap of the toner concentration sensor 24 is accelerated so as not to block foreign matter, the toner tends to electrostatically adhere to the toner concentration 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 material for preventing electrostatic adhesion, and the bracket 27 is provided.
It is possible to solve the problem by reducing the electrostatic adhesion of the toner by grounding it to the main body of the machine through.

As a modified example of FIG. 4, as shown in FIGS. 8 to 11, the guide member is replaced by the guide plate 2 of FIG.
It is possible to simplify the structure by forming one tubular guide member 31 for 8 and 29. Since the tubular guide member 31 is easy to have an arbitrary shape, the tip of the nozzle 30 can be fitted into a part of the guide member 31. This makes it possible to positively 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 may be formed so that only the condenser lens portion of the light emitting element 25 can be surely exposed to the developer flow by an arbitrary amount. it can. Light receiving element 26 of cylindrical guide member 31
The portion facing to is formed so that the light collecting surface of the light receiving element 26 can be exposed to the developer flow.

In FIGS. 8 to 11, the same members as those of FIGS. 4 to 7 or corresponding members are designated by the same reference numerals, and the description thereof will be omitted.

In the example shown in FIGS. 8 to 11, the light emitting element 25 is used.
It is possible to easily ground the conductive coating portion of the light receiving element 26 to the main body by configuring the tubular guide member 31 with a conductive member such as conductive plastic or conductive rubber. Further, since the tubular guide member 31 is conductive, it is possible to prevent toner from adhering to the wall surface of the tubular guide member 31.

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

Therefore, in the embodiment shown in FIG. 12, a transparent plate member 33 is provided as a guide member in front of the condenser lamp as the light emitting element 25 so that the flow of the developer in the concentration sensor 24 can be made smooth. The tubular or plate-shaped guide member 32 is provided. Although only the light emitting element side may be used, the same effect can be obtained by using the same configuration on the light receiving element 26 side. As the transparent member, there is glass, methacrylic resin, or the like, which is integrated with the flow path of the guide member 32 and is flush with the flow path surface to prevent toner and paper dust 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 dust can be prevented more effectively.

Applying a bias voltage to the conductive guide member is more effective in preventing electrostatic adhesion. The application timing for turning the bias voltage on and off is the concentration sensor 2
It is most effective to set 4 to the time when the liquid is ejected from the nozzle (for example, during the mechanical operation), but since the toner adhesion does not proceed rapidly, at any timing, at any time. There is an effect. However, in this arbitrary case, it is expected to be greatly influenced by the conditions such as the charging characteristics of the toner.

[0024]

According to the present invention, the guide member is provided, the flow path for blowing the developing solution to the sensor gap is positively formed, and the problem caused by the variation in the mounting position of the sensor and the nozzle can be eliminated. Naturally, only the condenser lamp portion of the light emitting element could be exposed to the liquid flow, and the adhesion area of the toner and paper powder could be reduced.

By positively collecting the liquid between the sensor gaps, the flow velocity of the developing liquid can be increased, and since the exposed portion of the sensor member is small, it is possible to prevent the paper dust from adhering.

According to the present invention, the light emitting element 25 and the light receiving element 2
No. 6 was coated with a conductive material, and the coated portion was grounded or a bias voltage was applied, whereby toner adhesion was prevented and clogging of the sensor gap due to foreign matter could be prevented. Further, by forming or covering the guide member with a conductive material, it becomes possible to reduce the adhesion of toner to the wall surface of the guide member.

By making the light emitting element and the light receiving element fit in a part of the guide member, the conductive process of the sensor can be facilitated and the nozzle position and the sensor position can be set at arbitrary positions.

Further, by providing a transparent plate in a seal-like shape on the portion of the guide member facing the light emitting element, a Venturi effect is formed, a higher flow velocity of the developer is obtained, and it is possible to prevent foreign matter from being clogged. It became a target. By applying conductive coating to the transparent plate and using a conductive material for the guide member, it is possible to effectively prevent electrostatic adhesion.

[Brief description of 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 concentration sensor.

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

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

5 is a cross-sectional plan view of the toner concentration sensor according to FIG.

6 is a sectional view taken along line VI-VI in FIG.

7 is a sectional view taken along line VII-VII in FIG.

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

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

10 is a cross-sectional view taken along line XX of FIG.

11 is a sectional view taken along line XI-XI of FIG.

FIG. 12 is a cross-sectional view of a modified example with respect to 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

Claims (9)

[Claims] 1. A light-emitting element and a light-receiving element are provided in a developer flowing in the developer tank of a wet copying machine in which the developer circulates between the developer tank and a developing unit and a cleaning unit. In a light-transmitting toner concentration sensor in which the light emitting surface of the light emitting element and the light receiving surface of the light receiving element are opposed to each other with a small gap, a guide member is provided in the vicinity of the light emitting element and the light receiving element.
A toner concentration sensor, wherein the guide member is configured to increase the liquid flow velocity of the developer. 2. The toner concentration sensor according to claim 1, wherein the guide member is formed of a conductive member and is grounded. 3. The toner according to claim 1, wherein the light-emitting surface of the light-emitting element and the light-receiving surface of the light-receiving element are exposed in the flow path of the developing solution constituted by the guide member. Concentration sensor. 4. The guide member is formed as a tubular member that forms a predetermined flow path.
The toner concentration sensor according to any one of 1. 5. The toner concentration sensor according to claim 4, wherein windows for the light receiving element and the light emitting element are formed in the guide member. 6. The toner concentration sensor according to claim 4, wherein the guide member has transparency with a transmittance of 70% or more and is subjected to a conductive treatment. 7. The light emitting element and the light receiving element of the toner concentration sensor are formed of a conductive member at a portion where the developing solution passes and contacts, and the guide member is formed to be conductive, and the light emission is performed through the guide member. 7. The toner concentration sensor according to claim 1, wherein a part of the element and the light receiving element are grounded. 8. A guide member for guiding the developing solution to a gap between the light emitting element and the light receiving element, wherein a portion of the light emitting element and the light receiving element of the toner concentration sensor where the developing solution passes and contacts is formed of a conductive member. 7. The toner concentration sensor according to claim 1, wherein the guide member is made conductive and a bias voltage having the same polarity as the toner is applied to the guide member. 9. A guide member for guiding the developing solution to the light emitting element and the light receiving element is formed by forming a portion of the light emitting element and the light receiving element of the toner concentration sensor where the developing solution passes and contacts, with a conductive member. The member is formed to be conductive, and a bias voltage having the same polarity as that of the toner is applied to the light emitting element and the light receiving element through the guide member.
Toner density sensor according to any one of.