JPH05133891A - Toner concentration sensor - Google Patents

Abstract

PURPOSE:To eliminate immersion of an electric wire and others in a developing solution and thereby to increase safety by disposing a light-emitting element and a light-sensing element to be higher than the liquid level of a developing solution tank and by forming a flow passage which starts from the developing solution tank, passes through the light-emitting element and the light-sensing element and returns to the developing solution tank. CONSTITUTION:A concentration sensor 24 is provided with a tubular guide member 31 so that a developing solution be concentrated positively between a light-emitting element 25 and a light-sensing element 26. The sensor 24 is so, disposed outside a developing solution tank 10 as not to be immersed in the developing solution. In this case, an entrance guide pipe 39 and an exit guide pipe 40 are so provided in the tank as to be raised in a state of being exposed partially outside the tank 10, and the guide member 31 of the sensor 24 is fixed to the end parts of the pipes 39 and 40. The developing solution sent out by a developing solution pump 11 is sent into the pipe 39 through a tube 41, passed through the guide member 31 and returned into the tank 10 by the pipe 40.

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 receives the light passing through the developer flowing therebetween.

Conventionally, in order to prevent the toner existing in the light emitting element 25 and the light receiving element 26 constituting the toner concentration sensor 24 and the minute gap between the light emitting element and the light receiving element from being dried and fixed, the toner concentration sensor Is always placed in the liquid. Therefore, toner and paper powder in the liquid around the light emitting element and the light receiving element may adhere not only when the machine is operating but also when the machine is stopped.

Since such a conventional toner concentration sensor is arranged in the liquid, the electric conductor and the like are immersed in the liquid, which is a problem in safety.

Further, in the wet copying machine, as described above, Cd
Since the gap between the S cell and the light emitting lamp is narrow, frictional charging is caused by the flow of the developer and toner adheres to cause clogging, and the developer in the developing tank 10 is supplied to both the developing device 5 and the cleaning unit 8. Since the circulation system for collecting is used, the developer collected in the cleaning unit 8 is transferred to the peripheral surface of the photoconductor 1 from the transfer paper during the transfer of the toner image, which is generated in the process of conveying the transfer paper. Paper dust, lint, and the like are mixed, and the developer collected from the developing device 5 contains metal powder and toner agglomerates due to poor redispersion. When it is caught in the gap with the surface, the toner adheres to it, gradually grows on the light emitting surface and finally fills the gap, and the developer does not flow through the gap. As a result, the toner concentration sensor 24 erroneously detects, The inspection When performing the toner replenishment by the signal, the toner concentration is lower than a predetermined value, as a result,
This causes a problem that the density of the developed image becomes low.

In the toner concentration sensor having the structure shown in FIG. 2, the position of the nozzle is set so as to feed the liquid to the sensor gap portion, but since it is not actively guided, the liquid flows over a wide range and the light emitting element side Liquid also flows into the lamp case, the case on the light receiving element side, and the like. However, since the flow of the liquid is gentle in the portion other than the sensor gap, there is a problem that paper dust or the like is easily attached.

[0011]

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 with high safety without electric conductors or the like being immersed in a developing solution.

[0012]

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-transmitting 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 facing each other with a small gap therebetween, wherein the light-emitting element and the light-receiving element are The toner concentration sensor is characterized in that it is arranged at a position higher than the liquid surface in the developing tank, and a flow path is formed from the developing tank to the light emitting element and the light receiving element and back to the developing tank.

[0013]

According to the present invention, the light emitting element and the light receiving element are arranged at a position higher than the liquid surface of the developing tank, and the developing solution can be sent from the developing tank to the light emitting element and the light receiving element by the flow path. Only a part of the element was in contact with the developing solution, and the electrical wiring part could be provided outside, preventing contact with the developing solution, and a highly safe toner concentration sensor was obtained.

[0014]

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

As shown in FIG. 3, the toner concentration sensor 2
Reference numeral 4 has a light emitting element 25 and a light receiving element 26 supported by a bracket 27. Mounting substrate 25a for the light emitting element 25,
The mounting substrate 26a of the light receiving element 26 is connected to an electric circuit by a lead wire. A pipe (cylindrical) guide member 31 is provided so that the developer is positively concentrated in the sensor gap (gap) between the light emitting element 25 and the light receiving element 26.

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.

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 triboelectric charging. A light emitting element 25 of the toner concentration sensor 24, for example, a light emitting lamp 25
Then, at least a portion of the light receiving element 26, for example, the CdS cell 26, which comes into contact with the developer flow is formed of a substance having the same charging polarity as the toner of the developer or is covered. Further, the light emitting lamp 25 and the CdS cell 26 have Pd, In, S
It is possible to form a transparent conductive film layer which is a metal such as n or a thin film of these oxides or CuI and has a transmittance of 70% or more at 10 ⁶ Ω · cm or less. In either case, ground the part of the machine to a part of the machine with a lead wire or the like.

In the example shown in FIG. 3, the tubular portions of the light-emitting element 25 and the light-receiving element 26 are electrically grounded to the main body, and the tubular guide member 31 is made of a conductive member such as conductive plastic or conductive rubber. Can be easily enabled at. 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. 4, a transparent plate member 33 is provided as a guide member on the front surface of the condenser lamp as the light emitting element 25 so that the flow of the developing solution at 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 the time when the liquid is sent to No. 4 (for example, during the mechanical operation), but since the toner adhesion does not proceed rapidly, the effect is obtained at any timing and at any time. There is. However, in this arbitrary case, it is expected to be greatly influenced by the conditions such as the charging characteristics of the toner.

5 and 6 show a modification of the example shown in FIG. 4, which has a guide member 36 which is made of a transparent member and is integrally formed of a resin having a little elasticity, for example, vinyl chloride.

The portion of the guide member 36 that faces the light emitting element 25 and the light receiving element 26 and seals is formed thin.

Holes for inserting the light emitting element 25 and holes for inserting the light receiving element 26 are formed in the leg portions 27a, 27b on both sides of the U-shaped portion of the bracket 27, and the light emitting element 25 is inserted in the hole. In the state, the mounting substrate 25a is the leg 27.
It is fixed to a by a screw 38, and the mounting substrate 26a is fixed to the leg portion 27b by a screw 38 with the light receiving element 26 inserted in the hole. A first spacer ring 34 surrounds the light emitting element 25 between the leg portion 27a and the guide member 36, and a second spacer ring 35 holds the light receiving element 26 between the leg portion 27b and the guide member 36. It is placed in a surrounding state.

The free ends of the legs 27a and 27b are connected by an adjusting screw 37, and the distance between the legs 27a and 27b is changed from the state shown by the solid line to the state shown by the chain line by adjusting the screwing amount of the adjusting screw 37. Be done. Both legs 27
The spacer rings 34, 35 are adjusted by adjusting the distance between a and 27b.
The gap of the guide member 36 is adjusted from the position shown by the solid line in FIG. The surface of the light emitting element 25 is deformed following the adjustment of the gap of the guide member 36 at this time, that is, the sensor gap.
This is prevented by maintaining the gap of the guide member 36 in a substantially parallel plane by the numerals 4, 35.

The gap adjusting mechanism and the spacer ring are shown in FIG.
It can also be applied to the example of FIG.

By forming or covering the guide member 36 with a conductive member and grounding it, the toner adhesion to the flow path surface of the developer can be reduced.

The toner concentration sensor according to each of the above configurations can be arranged outside the developer tank 10 as shown in FIG. 7, instead of being immersed in the developer and left alone. In this case, the developing tank 10 is provided with an inlet guide pipe 39 and an outlet guide pipe 40 so as to stand up with a part thereof exposed to the outside of the developing tank 10, and the guide member 31 or 32 or 36 of the toner concentration sensor 24 is introduced. It is fixed to the ends of the guide pipe 39 and the outlet guide pipe 40.

The developing solution sent out by the developing pump 11 is sent to the inlet guide pipe 39 through the tube 41, and further returned to the inside of the developing tank 10 through the guide member and the outlet guide pipe 40.

The developing substrate 42 provided on the developing tank 10.
A float switch 43 is attached to.

The float switch 43 has a liquid level upper limit detection level A, a normal liquid level B, and a lower limit detection level C, and the developing pump 11 is installed below the liquid level of the lower limit detection level C.

The toner concentration sensor 24 is a bracket 27.
It is fixed to the developing substrate 42 by. Inlet guide pipe 3
Both the inlet end of 9 and the outlet end of the outlet guide pipe 40 are arranged so as to be submerged in the developer. This is because the developing solution remains in the liquid flow path of the toner concentration sensor 24 even when the machine is stopped, which prevents the sensor from drying and prevents the toner and the like from sticking dry. The toner concentration sensor 24 is provided slightly below the upper limit position of the liquid flow path by the inlet guide pipe 39 so that even if air is mixed in the developing solution and bubbles are generated, it is not affected. This is because

The reason why the vicinity of the outlet end of the outlet guide pipe 43 is formed to be curved is to prevent the generation of bubbles because bubbles are generated when the developer is directly returned to the developing tank 10.

The example of FIG. 7 can be modified as shown in FIG. In the figure, parts that are the same as or correspond to those in FIG.

The toner concentration sensor 24 is replaced by the tube 41 instead of the inlet guide pipe 39, and is directly connected to the developing pump 1.
Can be connected with. In this case, in order to enhance the sealing effect at the insertion end of the tube 41, the structure shown in FIG. 9 is used. In FIG. 9A, the O-ring 45 is attached to the end of the guide member 36 of the toner concentration sensor 24, and the tube 41 is elastically fitted to obtain a sealing effect. FIG. 9B may be configured so as to be closely fitted to the end portion of the guide member 36 by the elastic effect of the tube 41. Similarly, the outlet guide pipe 40 may be formed of a tube and attached to the guide member 36 in a liquid-sealed manner.

In the example of FIG. 8, the developer falling directly from the outlet guide pipe 40 is received by the stagnation prevention plate 44 and can be smoothly diffused in the developer tank 10 without generating bubbles.

[0037]

According to the present invention, the light emitting element and the light receiving element are arranged at a high position, and the mounting substrate of the light emitting element and the mounting substrate of the light receiving element are located outside the liquid, so that the safety is improved. Since the light-emitting element and the light-receiving element are located at the raised position, they are not affected by the toner or paper dust in the liquid other than the liquid that is applied to the sensor gap. Only the inside of the guide member is contaminated and it is clean and easy to handle.

According to the present invention, by setting the mounting position of the toner concentration sensor to a position slightly lower than the highest position of the flow passage, even if air is accumulated at the highest position of the flow passage when the machine is stopped, the toner concentration sensor is Was prevented from being affected by air and air bubbles.

According to the present invention, since both ends of the flow path of the toner concentration sensor are submerged in the developing solution, the solution in the flow path can be retained even when the machine is stopped, and the sensor gap and the flow path are dried. The toner is prevented from adhering to the surface.

According to the present invention, a stagnation preventing member is provided near the outlet end of the flow path to prevent the generation of bubbles when the developer is collected in the developing tank.

According to the present invention, by constructing the guide member by the transparent elastic pipe member, it is possible to prevent the developer from leaking to the outside toward the light emitting element and the light receiving element, and the conductive solution is applied to the inner wall. It has become possible to reduce toner adhesion. The sealing property of the guide member with respect to the light emitting element and the light receiving element was improved, and the deformation during the gap adjustment could be prevented.

According to the present invention, the flow path can be easily removed from the toner concentration sensor, and cleaning of the sensor gap and maintenance of the flow path can be easily performed. The place where the toner and paper dust are most likely to be clogged can be prevented from being attached by applying a conductive treatment, and it is expensive to process, but the stick part can be made smaller and the cost can be reduced. ..

[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 cross-sectional view of a toner concentration sensor according to the present invention.

FIG. 4 is an explanatory cross-sectional view of another example of the toner concentration sensor according to the present invention.

FIG. 5 is an explanatory cross-sectional view of another example of the toner concentration sensor according to the present invention.

FIG. 6 is an exploded perspective view of the example of FIG.

FIG. 7 is a sectional view of a developing tank provided with a toner concentration sensor according to the present invention.

8 is a cross-sectional view showing a modified example of FIG.

FIG. 9 is a cross-sectional view showing a connecting portion between a tube forming a flow path and a toner concentration sensor, and A and B are cross-sectional views showing different structures.

[Explanation of symbols]

 10 developing tank 24 toner concentration sensor 25 light emitting element 26 light receiving element 31 guide member 32 guide member 36 guide member 39 flow path 40 flow path

Claims (8)

[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 transmissive 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, the light emitting element and the light receiving element are arranged at a position higher than the liquid level in the developing tank. A toner concentration sensor, characterized in that a flow path is formed from the developing tank to the light emitting element and the light receiving element and returns to the developing tank. 2. The toner concentration sensor according to claim 1, wherein the light emitting element and the light receiving element are arranged slightly below the upper limit of the flow path and above the liquid level. 3. The inflow port and outflow port of the flow path are always submerged in the liquid in the developing tank.
Alternatively, the toner concentration sensor described in 2. 4. The toner concentration sensor according to claim 3, wherein a stagnation preventing member is provided at an outlet of the flow path in the developing tank or in the vicinity of the outlet. 5. A guide member for guiding the developing solution is provided in the flow path in a gap between the light emitting element and the light receiving element, the guide member is made of a pipe member, and the pipe member is transparently formed. 5. The toner concentration sensor according to claim 1, wherein at least the inner surface is treated to be conductive. 6. The toner concentration sensor according to claim 5, wherein the guide member is formed of a member facing the light emitting element and the light receiving element and having a sealing portion having elasticity. 7. The toner concentration sensor according to claim 6, wherein a sealing portion of the guide member with respect to the light emitting element and the light receiving element is formed thin. 8. The flow path is formed by an elastic tube on at least one of an inflow side and an outflow side of the guide member,
The toner concentration sensor according to any one of claims 5 to 7, wherein a connecting portion of the elastic tube with the guide member is elastically and closely fitted through a seal member.