JP4824440B2 - Density measuring apparatus and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a density measuring device for measuring a toner particle concentration of a liquid developer containing toner particles, and an image forming apparatus including the density measuring device.

There is an image forming apparatus including a liquid developing device that develops an electrostatic latent image formed by an electrophotographic method with a liquid developer in which toner particles are dispersed in an insulating carrier liquid. In this type of image forming apparatus, for example, the liquid developer that has not contributed to the development of the electrostatic latent image is collected, adjusted to an appropriate toner particle concentration, and used again for the development of the electrostatic latent image.
As a configuration for measuring the toner particle concentration of the collected liquid developer, as described in Patent Document 1, a storage unit that stores the liquid developer, and a moving body that has a facing surface facing the inner surface of the storage unit, Some have a light-emitting element and a light-receiving element provided with the inner surface and the opposing surface interposed therebetween. The recovered liquid developer is made into a thin film between the inner surface and the opposing surface by the proximity of the opposing surface to the inner surface of the reservoir. Then, light is transmitted through the thin liquid developer, and the toner particle concentration of the liquid developer is measured based on the amount of transmitted light. Further, the liquid developer between the inner surface and the opposing surface of the storage portion is replaced with the opposing surface being separated from the inner surface.
JP 2005-315948 A

The recovered liquid developer usually has a reduced carrier liquid ratio and a high toner particle concentration. Therefore, the fluidity of the liquid developer is deteriorated. Therefore, in the concentration measuring apparatus described in Patent Document 1, it is difficult to replace the liquid developer between the inner surface and the opposed surface, and the toner particle concentration of the collected liquid developer cannot be accurately measured.
Further, in the concentration measuring device, when measuring the toner particle concentration, the opposing surface must be brought close to and away from the inner surface of the storage portion, and the toner particle concentration cannot be measured immediately.

An object of the present invention is to provide a density measuring apparatus capable of accurately measuring the toner particle density of a liquid developer and an image forming apparatus including the density measuring apparatus.
Another object of the present invention is to provide a density measuring device that can immediately measure the toner particle concentration of a liquid developer and an image forming apparatus including the same.

  In order to achieve the above object, the invention according to claim 1 is a concentration measuring device for measuring a toner particle concentration in a liquid developer containing toner particles, and a storage unit (17) for storing the liquid developer; In the reservoir, a gap (34) formed by the outer peripheral surface (30) of the roller (27) having a hollow elliptical cross-section and the opposing surface (33) facing the outer peripheral surface, and the roller By rotating in the circumferential direction, the liquid developer intervening in the gap is replaced and the roller rotation driving means (37) capable of expanding and contracting the gap, and the first member disposed inside the roller (28) and a second member (29) opposed to the first member across the gap, and a concentration test for detecting the toner particle concentration based on the amount of light transmitted between the first and second members. And means (28, 29), a concentration measuring device (18).

In addition, the alphanumeric characters in parentheses represent corresponding components in the embodiments described later. The same applies hereinafter.
According to this configuration, it is possible to measure the toner particle concentration by allowing the first and second members to transmit light to the liquid developer interposed between the outer peripheral surface and the opposing surface of the roller. In addition, since the transmission of light between the first and second members is performed continuously, the toner particle concentration can be measured immediately.

Further, by rotating the roller by the roller rotation driving means, the liquid developer interposed between the outer peripheral surface and the opposing surface of the roller can be forcibly replaced. Since the roller has an elliptical cross section, the liquid developer can be effectively replaced.
The invention according to claim 2 is the concentration measuring apparatus according to claim 1, wherein a cleaning member (31) for cleaning the outer peripheral surface is in contact with the outer peripheral surface of the roller. .

According to this configuration, it is possible to clean the toner particles adhering to the outer peripheral surface of the roller and the foreign matters mixed in the liquid developer by the cleaning member. As a result, the light transmitted between the first and second members is not blocked by foreign matter or the like, so that the toner particle concentration can be accurately measured.
The invention according to claim 3 is characterized in that the density detecting means detects the toner particle density based on the amount of transmitted light between the first and second members when the gap is minimum. Or it is a density | concentration measuring apparatus of 2 description.

According to this configuration, the outer peripheral surface in the major axis direction in the cross section of the roller is opposed to the opposing surface, and light is transmitted through the thin film-like liquid developer formed when the gap is minimized. Measure the concentration. Thereby, the toner particle concentration of the liquid developer can be accurately measured.
According to a fourth aspect of the present invention, one of the first and second members includes a light emitting element (28) for emitting light, and the other is for receiving light emitted from the light emitting element. 4. The concentration measuring device according to claim 1, further comprising a light receiving element (29).

According to this configuration, the toner particle concentration can be measured by receiving the light emitted from one of the first and second members.
According to a fifth aspect of the present invention, either one of the first and second members includes a reflecting member for reflecting light, and the other is a light emitting element for emitting light to the reflecting member. 4. The concentration measuring apparatus according to claim 1, further comprising a light receiving element for receiving the light reflected by the reflecting member. 5.

According to this configuration, the light emitted from the light emitting element is reflected by the reflecting member, and the reflected light is received by the light receiving element, whereby the toner particle concentration can be measured.
The invention according to claim 6 is the density measuring apparatus according to any one of claims 1 to 5, wherein the storage part includes a flow path of the liquid developer.
According to this configuration, it is possible to measure the toner particle concentration by transmitting light to the liquid developer flowing through the flow path. Further, the liquid developer intervening in the gap can be efficiently replaced by the flow in the distribution path.

The invention according to claim 7 is a liquid developing device (6) for developing an electrostatic latent image formed by electrophotography with a liquid developer, and a density measuring device according to any one of claims 1 to 6. An image forming apparatus (1).
According to this configuration, the toner particle concentration of the collected liquid developer can be accurately measured, and the liquid developer adjusted to an appropriate toner particle concentration can be circulated to the liquid developing device.

Embodiments of the present invention will be specifically described below with reference to the drawings.
FIG. 1 is a schematic diagram illustrating a main configuration of a printer 1 as an image forming apparatus according to an embodiment of the present invention.
Referring to FIG. 1, a printer 1 is a wet image forming apparatus using a liquid developer in which toner particles are dispersed in an insulating carrier liquid, and an image forming mechanism for forming a toner image by electrophotography. 2 is provided.

  The image forming mechanism 2 includes a photoconductive drum 3, and a charging device 4 for charging the peripheral surface of the photoconductive drum 3 around the photoconductive drum 3, and a peripheral surface of the charged photoconductive drum 3. An exposure device 5 for exposing and forming an electrostatic latent image based on image data, a liquid developing device 6 for developing the electrostatic latent image with a liquid developer to form a toner image, and a toner image on a sheet 7 A transfer roller 8 for transferring, and a cleaner 9 for removing residual toner remaining on the peripheral surface of the photosensitive drum 3 after the toner image is transferred are provided in the rotational direction of the photosensitive drum 3 (indicated by an arrow 38). (In the direction shown).

A sheet 7 as a recording material is conveyed along a line indicated by a horizontal left-pointing arrow in FIG. 1, and a toner image is formed on the surface (lower surface) of the sheet 7 when passing between the photosensitive drum 3 and the transfer roller 8. Is transcribed.
The liquid developing device 6 for developing the electrostatic latent image includes a storage tank 10 for storing the liquid developer, and a plurality of liquid developers for supplying the liquid developer in the storage tank 10 to the peripheral surface of the photosensitive drum 3. The rollers 11 to 13 are provided. In the present embodiment, the plurality of rollers 11 to 13 include a pickup roller 11 that draws the liquid developer from the storage tank 10, a developing roller 12 that supplies the liquid developer to the peripheral surface of the photosensitive drum 3, and the pickup roller 11. And an application roller 13 that applies the liquid developer thus pumped onto the peripheral surface of the developing roller 12.

  The liquid developer pumped from the storage tank 10 by the pickup roller 11 is supplied to the peripheral surface of the application roller 13. Then, the liquid developer supplied to the peripheral surface of the application roller 13 is regulated to a predetermined amount by, for example, a liquid amount regulating blade (not shown) in contact with the peripheral surface of the application roller 13. A predetermined amount of liquid developer is applied from the application roller 13 to the developing roller 12, and a thin film of liquid developer having a uniform thickness is formed on the peripheral surface of the developing roller 12. Thereby, the developing roller 12 can supply the liquid developer to the peripheral surface of the photosensitive drum 3.

A collecting blade 14 for collecting the liquid developer remaining on the peripheral surface of the developing roller 12 without contributing to the development of the electrostatic latent image is in contact with the peripheral surface of the developing roller 12. The liquid developer remaining on the peripheral surface of the developing roller 12 is collected by the collecting blade 14 and guided to the density adjusting unit 16 through the collecting channel 15.
The density adjusting unit 16 is used to adjust the collected liquid developer to an appropriate toner particle concentration so that it can be used again for developing the electrostatic latent image. The density adjusting unit 16 stores the collected liquid developer. Unit 17, a concentration measuring device 18 for measuring the toner particle concentration of the collected liquid developer, a carrier liquid tank 21 communicated with the storage unit 17 through the flow channel 19, and the flow channel 20. And a liquid developer tank 22 communicated with the storage unit 17. Valves 23 and 24 are interposed in the flow paths 19 and 20, respectively, and the supply of new carrier liquid and new liquid developer to the storage unit 17 is controlled by opening and closing the valves 23 and 24, respectively. be able to.

  The toner particle concentration measured by the concentration measuring device 18 is input to the control device 25. Then, the control device 25 opens and closes the valves 23 and 24 based on the input toner particle concentration, and supplies a new carrier liquid or a new liquid developer to the storage unit 17. Thereby, the liquid developer in the reservoir 17 is adjusted to an appropriate toner particle concentration. Further, the liquid developer in the storage unit 17 is stirred by a stirring device (not shown), and the toner particles are uniformly dispersed in the carrier liquid.

In this way, the collected liquid developer is adjusted to an appropriate toner particle concentration. Then, the adjusted liquid developer is circulated to the storage tank 10 of the liquid developing device 6 through the circulation channel 26. Thereby, the collected liquid developer is used again for developing the electrostatic latent image.
FIG. 2 is a schematic cross-sectional view of the concentration measuring device 18, and FIG. 3 is a perspective view of the concentration measuring device 18. In FIG. 3, only a part of the storage unit 17 is illustrated.

Referring to FIGS. 2 and 3, concentration measuring apparatus 18 includes a rotating roller 27 having a hollow cross-sectional shape, a light emitting element 28 that emits light, and a light receiving element that receives light emitted from light emitting element 28. 29 and a cleaning blade 31 for cleaning the outer peripheral surface 30 of the rotating roller 27.
The rotating roller 27 is disposed in the storage unit 17, and at least a part of the rotating roller 27 is immersed in the liquid developer. The rotating roller 27 is disposed in the vicinity of the outer wall 32 of the storage unit 17, and the outer peripheral surface 30 of the rotating roller 27 faces the inner surface 33 of the outer wall 32. A gap 34 is always formed between the outer peripheral surface 30 of the rotating roller 27 and the inner surface 33 of the outer wall 32.

  As shown in FIG. 3, rotary shafts 35 and 36 arranged coaxially with the rotary roller 27 are connected to both ends of the rotary roller 27, respectively. A roller rotation drive source 37 that rotates the rotation roller 27 and the rotation shafts 35 and 36 integrally is connected to the rotation shaft 35. The rotary roller 27 and the rotary shafts 35 and 36 are rotated at a constant rotational speed around the central axis C1 by a roller rotary drive source 37, and the rotary drive force of the roller rotary drive source 37 is applied during startup of the printer 1. Is always communicated. As a result, the gap 34 is enlarged and reduced at regular intervals. Further, the liquid developer interposed in the gap 34 is forcibly replaced by the rotation of the rotating roller 27. The replacement of the liquid developer is effectively performed because the sectional shape of the rotary roller 27 is elliptical.

The light emitting element 28 is disposed inside the rotating roller 27, and the rotating roller 27 and the rotating shafts 35 and 36 are fixed to the storage unit 17 independently. Therefore, even if the rotating roller 27 and the rotating shafts 35 and 36 rotate, the light emitting element 28 is held at a fixed position in the rotating roller 27.
The light receiving element 29 is disposed outside the storage unit 17 with the gap 34 interposed therebetween, and is opposed to the light emitting element 28. The light receiving element 29 is fixed outside the storage unit 17, and the distance between the light emitting element 28 and the light receiving element 29 is always constant.

  The light emitting element 28 always emits light while the rotary roller 27 is rotating. The light emitted from the light emitting element 28 is received by the light receiving element 29 through the light transmitting portion of the rotating roller 27, the liquid developer interposed in the gap 34 and the light transmitting portion of the outer wall 32 in order. Therefore, the light receiving element 29 always receives the light emitted from the light emitting element 28 while the rotating roller 27 is rotating. Thereby, the concentration measuring device 18 can continuously measure the toner particle concentration based on the amount of light received by the light receiving element 29.

  Moreover, the light transmission part of the rotation roller 27 and the light transmission part of the outer wall 32 are formed of a transparent member. The cleaning blade 31 is in contact with a position corresponding to the light transmitting portion on the outer peripheral surface 30 of the rotating roller 27. As a result, the cleaning blade 31 is slidably contacted with the outer peripheral surface 30 of the rotating roller 27 by the rotation of the rotating roller 27 and is mixed into the toner particles and liquid developer adhering to the outer peripheral surface 30 of the rotating roller 27. Foreign matter that has been removed can be cleaned.

FIG. 4 is a schematic cross-sectional view of the concentration measuring device 18 showing a state in which the gap 34 is minimum, and FIG.
Referring to FIG. 5, the amount of light received by light receiving element 29 with respect to the measurement time is represented as a sine curve. That is, the amount of light received by the light receiving element 29 changes according to the thickness of the liquid developer interposed in the gap 34, and the smaller the thickness, the larger the amount of received light. Therefore, as shown in FIG. 4, in the cross section of the rotating roller 27, the pair of outer peripheral surfaces 39 corresponding to the long axis direction X <b> 1 respectively opposes the inner surface 33 of the outer wall 32, and the gap 34 is minimum (in this embodiment, 0.1mm), the peak value P1 of the received light amount is obtained. The density measuring device measures the toner particle concentration based on the difference between the light emission amount of the light emitting element 28 and the peak value P1 of the light reception amount obtained periodically.

  As described above, the concentration measuring apparatus measures the toner particle concentration based on the transmitted light amount when the thickness of the liquid developer interposed in the gap 34 is the thinnest. Thereby, the toner particle concentration can be accurately measured. Further, since the peak value P1 of the amount of light received by the light receiving element 29 can be obtained every half cycle of rotation of the rotating roller 27, the toner particle concentration can be measured immediately. Further, since the liquid developer interposed in the gap 34 is continuously replaced by the rotation of the rotating roller 27, the toner particle concentration of the collected liquid developer can be accurately measured.

  The present invention is not limited to the contents of the above embodiments, and various modifications can be made within the scope of the claims. For example, in the above-described embodiment, an example in which the light emitting element 28 is provided inside the rotating roller 27 and the light receiving element 29 is provided outside the storage unit 17 has been described, but the light receiving element 29 is disposed inside the rotating roller 27. The light emitting element 28 may be disposed outside the storage unit 17.

In addition, a reflection member that reflects light emitted from the light emitting element 28 may be disposed on either the inside of the rotating roller 27 or the exterior of the storage unit 17, and the light emitting element 28 and the light receiving element 29 may be disposed on the other side. . In this case, the light emitted from the light emitting element 28 is reflected by the reflecting member, and the reflected light is received by the light receiving element 29 disposed in the vicinity of the light emitting element 28.
In the above-described embodiment, the example in which the concentration measuring device 18 is disposed in the concentration adjusting unit 16 has been described. However, the concentration measuring device 18 is provided in a flow path such as the recovery flow path 15 or the circulation flow path 26. It may be done. In this case, the liquid developer interposed in the gap 34 is more efficiently replaced by the flow of the liquid developer in the flow path.

  In the above-described embodiment, an example in which the image forming apparatus is a printer has been described. However, the image forming apparatus may be a copying machine or a facsimile. Further, the image forming apparatus may be a multifunction peripheral having two or more functions of a printer, a copier, or a facsimile.

1 is a schematic diagram illustrating a main configuration of a printer as an image forming apparatus according to an embodiment of the present invention. It is a schematic sectional drawing of a concentration measuring device. It is a perspective view of a concentration measuring device. It is a schematic sectional view of a concentration measuring device showing a state where the gap is minimum. It is a figure which shows the light reception amount of the light receiving element with respect to measurement time.

Explanation of symbols

1 Printer (image forming device)
6 Liquid Developing Device 17 Storage Unit 18 Concentration Measuring Device 27 Rotating Roller (Roller)
28 Light-emitting element (first member, concentration detection means)
29 Light receiving element (second member, density detecting means)
30 Outer peripheral surface 31 Cleaning blade (cleaning member)
33 Inner surface (opposite surface)
34 Clearance 37 Roller rotation drive source (roller rotation drive means)

Claims (7)

In a concentration measuring device for measuring the concentration of toner particles in a liquid developer containing toner particles,
A reservoir for storing the liquid developer;
In the storage section, a gap formed by an outer peripheral surface of a roller having a hollow elliptical cross-sectional shape, and an opposing surface facing the outer peripheral surface;
Roller rotation driving means capable of replacing the liquid developer interposed in the gap by rotating the roller in the circumferential direction, and capable of expanding and contracting the gap;
A toner particle concentration based on the amount of light transmitted between the first and second members, including a first member disposed inside the roller and a second member facing the first member across the gap A concentration measuring device comprising a concentration detecting means for detecting   The concentration measuring apparatus according to claim 1, wherein a cleaning member for cleaning the outer peripheral surface is in contact with the outer peripheral surface of the roller.   The density measuring apparatus according to claim 1, wherein the density detecting unit detects the toner particle density based on a transmitted light amount between the first and second members when the gap is minimum.   One of the first and second members includes a light emitting element for emitting light, and the other includes a light receiving element for receiving light emitted from the light emitting element. Item 4. The concentration measuring apparatus according to any one of Items 1 to 3.   One of the first and second members includes a reflecting member for reflecting light, and the other includes a light emitting element for emitting light to the reflecting member and light reflected by the reflecting member. The density | concentration measuring apparatus of any one of Claims 1-3 characterized by including the light receiving element for light-receiving.   The density measuring apparatus according to claim 1, wherein the storage unit includes a flow path of the liquid developer. A liquid developing device for developing an electrostatic latent image formed by an electrophotographic method with a liquid developer;
An image forming apparatus comprising the density measuring device according to claim 1.

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