JP2006313150A - Liquid level detection device, developer liquid container, wet imaging formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect accurately more number of stages of developer liquid levels than the number of the sensors, without immersing the sensor in the developer liquid. <P>SOLUTION: The device comprises a float part which goes up and down due to a change of a height of the developer liquid level, a plurality of the parts to be detected mounted the float part which is located outside of the developer liquid, the plurality of detection means mounting capable of each detection optically of the plurality of the parts to be detected arranged in the up and down direction of the float part, and a detection control means detecting the height of the developer liquid level from the detected result of the plurality of the detection means. The plurality of the detection means display on-signal when detected corresponding to the part to be detected, if not detected, off-signal is displayed. The plurality of the parts to be detected can be made on-signal on more than two detection means simultaneously, and corresponding to the height of the plurality of the liquid levels which have more number of the plurality of the detection means, the liquid level detection device is provided constituting so as to be capable of the different combinations of on/off-signals on the plurality of the detection means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid level detector that detects a liquid level of a developer, a developer container that includes the liquid level detector, and a wet image forming apparatus that includes the developer container.

  As an apparatus for forming an image by transferring toner to a recording paper, a wet image forming apparatus for carrying a development by carrying a developer containing toner in a carrier liquid on the surface of a developing roller and supplying the developer to a photosensitive drum. It has been known. Since the toner used in the wet image forming apparatus is finer than the toner used in the dry image forming apparatus using powdery toner, the wet image forming apparatus generally forms a higher quality image than the dry image forming apparatus. it can.

  The density of the printed image varies depending on the density of the toner in the developer. In order to maintain the printed image with high quality, it is necessary to uniformly stir the developer and to adjust the toner concentration in the developer to an appropriate value. In a developer container containing a developer, it is necessary to recognize the amount of the developer in order to adjust the concentration of the developer. For this reason, the level of the developer is detected. A measuring device for measuring the liquid level of a developing solution is described in Patent Document 1, for example.

There is also known a liquid level measuring device that measures the position of a detected portion (arranged outside the developer) fixed to a float floating on the developer surface by a photosensor.
Japanese Patent Laid-Open No. 2001-194915

  In Patent Document 1, a columnar body fixed in a tank for storing a developer, a float with a magnet that floats in the tank and moves up and down along the columnar body as the developer increases and decreases, and a vertical direction of the columnar body And a plurality of reed switches that are responsive to magnets, and a detection device that detects the level of the developer is disclosed. In the above detection device, the level of the developer is detected based on the ON / OFF results of the plurality of reed switches.

  In the detection apparatus described in Patent Document 1, since the contact portion between the columnar body and the float with magnet is immersed in the developer, the developer enters the contact portion between the columnar body and the float with magnet, and the magnet is attached. There is a problem that the movement of the float is blocked and proper operation cannot be obtained.

  Further, in an apparatus that directly measures the position of the detected portion fixed to the float, for example, five photosensors are required to detect the level of the developer in five stages. In order to detect one level of the liquid level with one photosensor, it is necessary to arrange a large number of photosensors in a narrow arrangement space when finely detecting the liquid level in a narrow range.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to accurately detect a liquid level having a number of steps larger than the number of sensors without immersing the sensor in a developer.

  In order to solve the above problems, in the present invention, a float member that moves up and down according to a change in the liquid level of the developer, and a plurality of detected portions that are provided on the float member and are located outside the developer. A plurality of detection means arranged in the up-and-down direction of the float member so as to be able to optically detect each of the plurality of detected parts, and the level of the developer from the detection results of the plurality of detection means Detection control means for detecting the height, and the plurality of detection means respectively indicate ON when detecting corresponding detection parts, and OFF when not detecting, respectively. By enabling two or more detection means to be turned on, the plurality of detection means that are different from each other are turned on and off corresponding to the heights of the plurality of liquid levels greater than the number of the plurality of detection means. Can form a combination of Providing fluid level detecting apparatus characterized by being configured a certain way.

  According to the present invention, it is possible to detect the level of the developer without immersing a detection means such as a sensor in the developer. Further, the liquid level can be detected based on a combination of whether a plurality of detection units turn on or off detection means such as a plurality of sensors. In some cases, two or more sensors can be detected. Can be turned on, so that the liquid level of the number of stages larger than the number of sensors can be detected. In addition, since the level of the multi-step can be detected rather than the number of sensors, the liquid level detection accuracy is increased.

  Further, in the liquid level detecting device according to the present invention, the plurality of detected parts have three parts, a lower detected part, a central detected part, and an upper detected part in order from the lower side in the ascending / descending direction, The plurality of detecting means includes a lower detecting means corresponding to the lower detected part, a central detecting means corresponding to the central detected part, and an upper detecting means corresponding to the upper detected part.

  In addition, the detected part is the first state in which only the lower detection part is turned on, the second state in which the lower detection part and the central detection part are turned on, the third state in which only the central detection part is turned on, the center It is possible to form five states, a fourth state in which the detection unit and the upper detection unit are turned on, and a fifth state in which only the upper detection unit is turned on, and the detection control means has five states corresponding to those states. The height of the developer surface can be detected.

  Also, the lower detection part and the central detection part are provided so as not to follow the same trajectory when moving in the lifting direction, and the upper detection part and the central detection part are the same when moving in the lifting direction. It is provided so as not to follow the trajectory. Furthermore, the center detected part protrudes a predetermined amount in the direction perpendicular to the ascending / descending direction from the lower detected part and the upper detected part.

  In addition, the position to be lifted / lowered of the float member is regulated by the central detected portion coming into contact with the lifting / lowering position regulating means for regulating the raising / lowering position of the float member. Further, the elevating position restricting means is the end face of each of the lower detecting means and the upper detecting means.

  Further, the liquid level detecting device has a guide bar arranged in parallel with the ascending / descending direction, and the float member moves up and down along the guide bar.

  Each of the plurality of detection means includes a photosensor. In the plurality of detection means, the detection means is turned on when the photosensor is shielded by the corresponding detected part, and the photosensor is shielded. When not present, the detection means indicates that it is off.

  In the present invention, a holding container that holds the developer, a stirring unit that stirs the developer, and a float member that moves up and down according to a change in the height of the liquid level of the developer held in the holding container; , A plurality of detection portions provided on the float member and positioned outside the developer, and a plurality of detections arranged in the ascending / descending direction of the float member so that each of the plurality of detection portions can be optically detected And a detection control means for detecting the level of the developer surface. Each of the plurality of detection means is on when detecting a corresponding plurality of detected parts, and off when not detecting. The detection control means includes a liquid level detecting device for detecting the height of the liquid level of the developer larger than the number of the plurality of detection means based on a combination of turning on and off the plurality of detection means. And providing a developer container characterized by having That.

  The present invention also provides a wet image forming apparatus that includes the developer container described above and that forms an image by electrophotography using the developer held in the developer container.

  According to the present invention, it is possible to accurately detect the liquid level of the number of stages larger than the number of sensors without immersing the sensor in the developer.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view showing a configuration of the wet printer 100. The wet-type printer 100 is an apparatus for forming an image by carrying a developer containing toner in a carrier liquid on the surface of a developing roller, and based on character / image information input from an external device such as a computer. It is an apparatus that prints and outputs on recording paper P1 by electrophotography using a beam.

  The wet printer 100 is formed on a photosensitive drum by laser scanning unit (Laser Scanning Unit, hereinafter abbreviated as LSU) 30 for outputting laser light modulated according to character / image information, and irradiation of the laser light. A developing unit 50 that develops the electrostatic latent image by electrophotography to generate a toner image, a transfer unit 70 that transfers the toner image developed by the developing unit 50 onto the recording paper P1 at a transfer position, and a transport mechanism A fixing unit 80 for fixing the toner image transferred onto the recording paper P1 conveyed by the recording medium P1, and a conveying unit 90 for conveying the recording paper P1.

  The developing unit 50 carries a holding roller 51, a metering roller 52 for metering the developer, a metering roller blade 52a for uniformizing the developer on the surface of the metering roller 52, and a developer supplied from the metering roller 52. An electrostatic latent image is formed by the developing roller 53, the developing roller cleaning blade 53 a that scrapes and removes the developer from the surface of the developing roller 53, the developing roller charging corona 54 that charges the developing roller 53, and the laser light from the LSU 30. The photosensitive drum 55, the photosensitive drum charging corona 57 that uniformly charges the surface of the photosensitive drum 55, the squeezed roller 58 that recovers the carrier liquid from the photosensitive drum 55, and the residual developer generated in the developing unit 50 are put into the wet printer 100. It has a screw 59 for returning it to the arranged developer container (not shown).

  The developer supplied from the developer container holding the developer via the developer pipe 49 is supplied above the rolling contact portion between the holding roller 51 and the metering roller 52. The developer measured by the measuring roller 52 is applied to the developing roller 53. On the other hand, in the photosensitive drum 55, the surface of the drum charged with a uniform potential by the charging corona 57 for the photosensitive drum is irradiated with laser light, and the irradiated portion has a potential lower than the uniform potential. The portion where the potential is reduced compared to this uniform potential is an electrostatic latent image. The toner of the developer applied to the developing roller 53 is charged and is attracted to the electrostatic latent image portion of the photosensitive drum 55. Thus, the electrostatic latent image is developed to form a toner image.

  The transfer unit 70 includes an intermediate transfer roller 71 and a secondary transfer roller 73. A voltage having a polarity opposite to that of the toner is applied to the intermediate transfer roller 71, and the toner image on the surface of the photosensitive drum 55 is primarily transferred to the surface of the intermediate transfer roller 71 at the rolling contact portion between the photosensitive drum 55 and the intermediate transfer roller 71. The The secondary transfer roller 73 is installed at a position facing the intermediate transfer roller 71 across the conveyance path of the recording paper P1, and a voltage having a reverse polarity higher than that of the intermediate transfer roller 71 is applied. Therefore, the toner image is sucked in the direction of the secondary transfer roller 73, and the toner image transferred to the surface of the intermediate transfer roller 71 is transferred to the recording paper P1 at the rolling contact portion with the secondary transfer roller 73.

  The fixing unit 80 is installed at a position opposed to the heat roller 81 that heats the recording paper P1 and the heat roller 81 across the conveyance path, and a press roller 82 that presses the recording paper P1 between itself and the heat roller 81. It consists of and. By this fixing unit 80, the toner image on the recording paper P1 is fixed on the recording paper P1 by heating and pressing.

  The transport unit 90 includes a roll shaft 91 on which a roll-shaped recording paper P1 is installed, a paper feed driving roller 93 that transports the recording paper P1, a paper feed driven roller 94 that is in rolling contact with the paper feed drive roller 93, and a paper feed drive roller 93. Drive motor 95 and paper feed sensor 97. The recording paper P1 is conveyed by the paper feed driving roller 93, and the timing at which the LSU 30 emits light is calculated by the control unit of the wet printer 100 with reference to the time when the recording paper P1 passes the paper feed sensor 97. Since the timing at which the LSU 30 emits light is controlled based on when the recording paper P1 passes the paper feed sensor 97, printing can be performed at an appropriate position on the recording paper P1.

  Next, the arrangement of the developer container holding the developer will be described. FIG. 2 is a side sectional view of the wet printer 100 observed from the back side of FIG. 1 and a diagram showing a control system. The wet printer 100 includes a developer container 3 that supplies a developer to the developing unit 50, a developer preliminary container 5 that supplies the developer to the developer container 3, and a carrier liquid preliminary container 7 that supplies the carrier liquid to the developer container 3. And a developer replenishment pump 9 used for transporting the developer from the developer preliminary container 5 to the developer container 3, and a developer circulation pump 11 for transporting the developer from the developer container 3 to the developing unit 50. The control unit 300 also has a function of controlling the developer container 3, the developer replenishment pump 9, the developer circulation pump 11, and the like.

  In the embodiment of the present invention, the amount of the developer in the developer container 3 is detected as will be described later. When the controller 300 detects that the amount of the developer in the developer container 3 has decreased below a predetermined amount, the developer is supplied to the developer container 3 with the spare developer from the developer preliminary container 5. The replenishment pump 9 is driven. During the operation of the wet printer 100, the developer in the developer container 3 is conveyed to the developing unit 50 by the developer circulation pump 11. The discharge port of the developer circulation pump 11 is connected to the developer pipe 49.

  The developer in the developer container 3 and the developer preliminary container 5 is configured so that about 30% is toner and the remaining about 70% is carrier liquid. An image to be printed becomes dark when the toner ratio is high, and light when the toner ratio is low. The preliminary developer is supplied from the developer preliminary container 5 to the developer container 3, and the spare carrier liquid is supplied from the carrier liquid preliminary container 7 to the developer container 3, and the toner concentration of the developer in the developer container 3 is The quality of the printed image is kept constant by being adjusted to be constant. In order to adjust the toner concentration of the developer, it is necessary to know the amount of the developer, and therefore the amount of the developer is detected.

  The developer container 3 includes a holding container 103, a stirring device 104, and a side opening 106. The holding container 103 has a cylindrical shape, the bottom is closed, and the top is open. The side opening 106 is provided on the peripheral surface of the holding container 103. Since the developer used in the wet printer 100 has a relatively high viscosity, if it is left as it is, it becomes a semi-solid and loses its fluidity. Accordingly, the developer is stirred by the stirring device 104 in the holding container 103. An opening is formed on the extension line of the shaft of the screw 59 (see FIG. 1) of the developing unit 50 described above, and the opening is connected to the side opening 106 through a pipe. That is, the developer conveyed by the screw 59 is configured to be returned to the holding container 103 from the side opening 106.

  In FIG. 2, the liquid level in the holding container 103 is schematically shown. The liquid level L1 to L5 each indicate a predetermined range of the liquid level. The liquid level L1 of the developer is a level indicating that the amount of the developer is small. When the liquid level is L1, the level is equal to the absence of the developer. The liquid level L2 of the developing solution is a lower limit level at which the toner concentration of the developing solution can be adjusted satisfactorily, and is a level that requires replenishment of the developing solution. The developer level L3 is an optimum developer level for adjusting the toner density of the developer, and the center thereof is a reference position for adjustment. The liquid level L4 of the developer is the upper limit amount of the developer that can satisfactorily adjust the toner concentration of the developer. The liquid level L5 of the developer is a level indicating that the amount of the developer is large. When the liquid level is higher than L5, the developer may overflow.

  Hereinafter, a liquid level detecting device according to an embodiment of the present invention will be described. FIG. 3 is a view showing the developer container 3 and the liquid level detecting device 105. The stirring device 104 includes a drive motor 119, a rotating shaft 113 that is rotated by the driving motor 119, and a stirring unit 111 that is fixed to one end of the rotating shaft 113 so that the rotating shaft 113 is the center of rotation. When the developer is stirred, the developer is also stirred while being rotated by the rotational force of the drive motor 119. The stirring device 104 is controlled by the control unit 300.

  The liquid level detection device 105 includes a float member 115, a photo sensor 121 (121a, 121b, 121c from the bottom) and a guide bar 123, respectively. The float member 115 includes a flat dog 116, a float 117, a float support member 119 that connects the dog 116 and the float 117, and a ring 125 (at least two are required) through which the guide rod 123 can be inserted. The guide rod 123 extends in a direction perpendicular to the liquid level of the developer at rest. The photo sensor 121 is controlled by the control unit 300.

  4 is a view of the float member 115 and the photosensor 121 as viewed from above in FIG. The photosensor 121 has a U-shape. When the dog 116 shields the U-shaped gap, the photo sensor 121 is turned on, and when the dog 116 is not shielded, the photo sensor 121 is turned off. The float support member 119 has a V shape. In the embodiment of the present invention, the float 117 is fixed to each of the V-shaped tips of the float support member 119. A guide rod 123 is inserted into the hole of the ring 125, and the float member 115 moves along the guide rod 123 according to the increase / decrease of the developer.

  FIG. 5A is a view for explaining the float member 115 in more detail. FIG. 5B is a diagram for explaining the photosensor 121 in more detail. FIG. 5 is a view showing the same direction as FIG. The dog 116 has a detected part 127 detected by the photosensor 121. The detected portion 127 is disposed outside the peripheral surface of the holding container 3 in the dog 116. The detected part 127 includes a lower detected part 127a, a central detected part 127b, and an upper detected part 127c. The upper detected portion 127c is a portion that occupies an area of a length A from the upper end of the detected portion 127 in the downward movement direction of the float member 115, and the lower detected portion 127a is a float member from the lower end of the detected portion 127. 115 is a portion occupying an area of length A in the upward direction of movement. The central detected portion 127b is a portion that occupies a region of length B in the middle between the upper detected portion 127c and the lower detected portion 127a, and is a float member than the lower detected portion 127a and the upper detected portion 127c. 115 has a shape protruding by a length E in a direction perpendicular to the moving direction.

  The upper photosensor 121c, the center photosensor 121b, and the lower photosensor 121a are arranged in a plane parallel to the moving direction of the float member 115, respectively. The upper photosensor 121c and the lower photosensor 121a are aligned on a straight line parallel to the moving direction of the float member 115, but the center photosensor 121b is arranged at a position shifted by a predetermined amount. The length of the photosensor 121 in the direction parallel to the moving direction of the float member 115 is D, and a slit 129 (129a, 129b, 129c) is formed at the center of the length D. The slits 129 (129a, 129b, 129c) are provided on both sides of the U-shaped inner surface of the photosensor 121, respectively. Note that the slit 129 may be provided only on one side of the U-shaped inner surface of the photosensor 121. That is, it is provided on both sides of the U shape when the light emitting element and the light receiving element face each other, and only on one side of the U shape when the light emitting element and the light receiving element are adjacent to detect reflected light. The width of the slit 129 in the direction parallel to the moving direction of the float member 115 is a very narrow width, and the width is not considered.

  It is assumed that the photo sensor 121 is turned on when the detected part 127 of the dog 116 shields between the slits 129, and is turned off when not shielded. The upper photosensor 121c and the lower photosensor 121a are disposed so as to protrude in a direction perpendicular to the moving direction of the float member 115 by a length E closer to the float member 115 than the center photosensor 121b. In other words, the central photosensor 121b is arranged at a position farther from the float member 115 in the vertical direction than the upper photosensor 121c and the lower photosensor 121a according to the protruding length E of the central detected portion 127b. Is done. The photosensor 121 has an interval between the upper slit 129c of the upper photosensor 121c and the central slit 129b of the central photosensor 121b, and an interval between the central slit 129b of the central photosensor 121b and the lower slit 129b of the lower photosensor 121a, respectively. It arrange | positions so that it may become length C.

  6 to 10 are diagrams showing the amount of the developer and the state of the liquid level detecting device 105. FIG. In FIG. 6, the upper end portion of the central detected portion 127b of the dog 116 is in a position where the slit 129b is not shielded, and the lower detected portion 127a shields the lower slit 129a. At this time, the lower photosensor 121a is on, the center photosensor 121b is off, and the upper photosensor 121c is off. The level of the developer in this state is L1.

  In FIG. 7, the center detected portion 127b of the dog 116 shields the central slit 129b, and the lower detected portion 127a shields the lower slit 129a. At this time, the lower photosensor 121a is on, the center photosensor 121b is on, and the upper photosensor 121c is off. The level of the developer in this state is L2.

  In FIG. 8, only the center detected portion 127b of the dog 116 is in a position to shield the center slit 129b. At this time, the lower photosensor 121a is turned off, the center photosensor 121b is turned on, and the upper photosensor 121c is turned off. The level of the developer in this state is L3.

  In FIG. 9, the center detected portion 127b of the dog 116 shields the central slit 129b, and the upper detected portion 127c is in a position shielding the upper slit 129c. At this time, the lower photosensor 121a is turned off, the center photosensor 121b is turned on, and the upper photosensor 121c is turned on. The level of the developer in this state is L4.

  In FIG. 10, the lower end portion of the central detected portion 127b of the dog 116 does not shield the slit 129b, and the upper detected portion 127c shields the upper slit 129c. At this time, the lower photosensor 121a is off, the center photosensor 121b is off, and the upper photosensor 121c is on. The level of the developer in this state is L5.

  FIG. 11 is a table showing the relationship between on / off of the photosensor 121 and the level of the liquid surface. The table shown in FIG. 11 is recorded in the control unit 300 of the wet-type printer 100, and the control unit performs on / off results indicated by the table, the lower photosensor 121a, the central photosensor 121b, and the upper photosensor 121c. Based on the above, the liquid level is detected. Further, the control unit 300 controls the developer replenishment pump 9, the developer circulation pump 11, and the like based on the detected liquid level. In this way, the liquid level detecting device 105 can detect five levels of liquid level with three photosensors. That is, it is possible to accurately detect the level of the developer having the number of stages larger than the number of photosensors. By accurately detecting the liquid level, it is possible to reliably adjust the concentration of the developer, and to perform stable density control of printing. In addition, the liquid level is inclined when the stirring device 104 is operated, and the liquid level is horizontal when stopped. Therefore, in order to detect an accurate liquid level, the detection of the liquid level is performed when the stirring device 104 where the liquid level is horizontal is stopped.

  Next, with reference to FIGS. 5, 12A, and 12B, conditions for detecting five levels of liquid level with three photosensors will be described. FIG. 12A shows the float 117 located at the lowest reachable position. FIG. 12B is a diagram showing the float 117 located at the highest reachable position. The lowest position at which the float 117 can reach is a position where the lower end portion of the central detected portion 127b comes into contact with the upper portion of the lower photosensor 121a and the float member 115 cannot move downward (see FIG. 12A). The highest position at which the float 117 can reach is a position where the upper end portion of the central detected portion 127b contacts the lower portion of the upper photosensor 121c and the float member 115 cannot move upward (see FIG. 12B). The distance that the float member 115 moves from the lowest reachable position to the highest reachable position is represented by 2C-BD. Therefore, the condition for securing the stroke (movement amount) of the float member 115 is 2C> B + D where 2C−B−D is greater than 0 (see FIG. 5).

  As a condition for simultaneously shielding the two photosensors 121, the interval C between the photosensors is the addition of the length A of the lower detected portion 127a or the upper detected portion 127c and the length B of the central detected portion 127b. It is necessary that the length is shorter than the length A + B, that is, A + B> C. Further, as a condition for shielding only the central photosensor 121b, it is necessary that the distance 2C between the photosensors at both ends is longer than the total length 2A + B of the detected portion, that is, 2C> 2A + B.

  Conditions for shielding only the lower photosensor 121a or the upper photosensor 121c are as follows. The distance from the center of the center photosensor 121b to the outer periphery of the lower photosensor 121a or the upper photosensor 121c is represented by CD / 2, and CD / 2 is longer than the length B of the center detected portion 127b. That is, 2C-D> 2B is required.

  If the length A of the upper detected portion 127c or the length B of the central detected portion 127b is longer than the interval C between the photosensors, there is a possibility that one detected portion shields the two photosensors. Therefore, as a basis for ensuring the operation, the interval C between the photosensors is longer than the length A of the lower detected portion 127a or the upper detected portion 127c and the length B of the central detected portion 127b, that is, C> A, B It is necessary to be.

  By setting the dimension of the detected part and the interval and dimension between the photosensors so as to satisfy the above-described conditions, it is possible to detect five levels of liquid level with three photosensors. It should be noted that liquid level of various heights can be detected by adjusting the size of the detected portion and the interval and size between the photosensors so as to satisfy the above conditions.

  Although the number of photosensors is three, the length of the U-shaped gap between the lower photosensor 121a and the upper photosensor 121c (the length in the direction perpendicular to the moving direction of the float member 115) is sufficiently long. Then, the central detected portion 127b may pass through the lower photosensor 121a and the upper photosensor 121c, and the number of photosensors may be three or more to detect five or more liquid level levels.

  In addition to the above-described configuration, various configurations are conceivable as a liquid level detecting device that detects the liquid level of a number of stages larger than the number of photosensors. FIG. 13 shows a liquid level detecting device capable of detecting the level of 2 n stages by n sensors. In FIG. 13, there are three sensors, and the number of liquid level levels that can be detected is eight. The liquid level detection device 205 includes a float member 215, a photo sensor 221, and a guide bar 223. The float member 215 includes a dog 216 and a float 217, and moves up and down along the guide rod 223 in accordance with a change in the liquid level height within a predetermined range.

  The dog 217 is divided into n equal parts so as to have a length in the ascending / descending direction corresponding to a predetermined range of the liquid level. In this example, the dog 217 is divided into an upper dog 227, a middle dog 229, and a lower dog 231. Further, each dog is equally divided into 2 to the nth power when n sensors are provided. In this example, since there are three sensors, each dog is divided into eight equal parts, and projections 233 are provided in half of the divided eight parts. Depending on the presence or absence of protrusions in the eight divided sections of the upper dog 227, the middle dog 229, and the lower dog 231, different predetermined protrusion patterns are formed on each dog. The combination method of arranging protrusions in each dog section corresponding to the same liquid level is as follows: the presence of protrusion is 1 and the absence is 0, and the presence or absence of protrusions is indicated in the order of the upper dog 227, the middle dog 229, and the lower dog 231. , (0, 0, 0), (0, 1, 0), (0, 1, 1), (0, 0, 1), (1, 0, 0), (1, 1, 0), ( 1, 1, 1) and (1, 0, 1). In the upper dog 227, the middle dog 229, and the lower dog 231 each of which is divided into eight sections, the above-mentioned combination of protrusions is arranged without overlapping.

  The photosensor 221 includes an upper photosensor 221a, a middle photosensor 221b, and a lower photosensor 221c corresponding to the upper dog 227, the middle dog 229, and the lower dog 231, so that the three photosensors 221 are equally spaced. Is arranged. When the float member 215 moves up and down according to the change in the liquid level and the protrusion 233 shields the photosensor 221, the photosensor 221 is turned on, and when the shield is removed, it is turned off.

  The liquid level in a predetermined range is divided into eight equal parts, and there is a correspondence between each liquid level divided into eight and the combination of on / off of the three photosensors 221. This correspondence relationship is stored as a table in the control unit 300 provided in the wet printer 100, and the control unit 300 calculates 2 n powers based on the detected ON / OFF combinations of the n photosensors 221. The liquid level of the number of stages can be detected. Thus, by detecting the combination of the on / off states of the three photosensors 221, it is possible to detect eight levels of liquid level. In other words, it is possible to detect the liquid level of 2 n steps by n photosensors.

  According to the present invention, it is possible to detect the level of the developer without immersing a detection means such as a sensor in the developer. In addition, since the level of the liquid level can be detected based on the combination of whether the plurality of detected parts turn on or off the detection means such as a plurality of sensors, the number of detection means such as sensors It is possible to detect the liquid level of a large number of stages. In addition, since the level of the multi-step can be detected rather than the number of sensors, the liquid level detection accuracy is increased. In addition, since a photosensor is used unlike a sensor using a magnet or the like, even if the sensor is arranged outside the developer, that is, outside the holding container, other members of the wet printer 100 are not adversely affected. In addition, the photosensor has higher position detection accuracy than a sensor that detects a magnetic field such as a magnet.

It is a sectional side view which shows the structure of a wet printer. It is the sectional side view which observed the wet printer from the back direction of FIG. It is a figure which shows a developing solution container and a liquid level detection apparatus. It is a figure which shows a float member and a photosensor. FIG. 5A shows a float member. FIG. 5B shows a photosensor. It is a figure which shows the quantity of a developing solution, and the state of a liquid level detection apparatus. It is a figure which shows the quantity of a developing solution, and the state of a liquid level detection apparatus. It is a figure which shows the quantity of a developing solution, and the state of a liquid level detection apparatus. It is a figure which shows the quantity of a developing solution, and the state of a liquid level detection apparatus. It is a figure which shows the quantity of a developing solution, and the state of a liquid level detection apparatus. It is a table which shows the relationship between ON / OFF of a photo sensor and the level of a liquid level. FIG. 12A is a diagram illustrating a float located at the lowest reachable position. FIG. 12B is a diagram showing the float located at the highest reachable position. 1 shows a liquid level detecting device capable of detecting the level of 2 n steps by n sensors.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Developer container 5 Developer preliminary container 7 Carrier liquid preliminary container 9 Developer supply pump 11 Developer circulation pump 49 Developer pipe 100 Wet printer 104 Stirrer 105 Liquid level detector 106 Side opening 115 Float member 116 Dog 117 Float 119 Float support member 121 Photo sensor 123 Guide rod 125 Ring 127 Detected part 129 Slit

Claims (11)

A float member that moves up and down in response to a change in the level of the developer surface;
A plurality of detected portions provided on the float member and positioned outside the developer;
A plurality of detection means arranged in the ascending / descending direction of the float member and provided so as to be capable of optically detecting each of the plurality of detected parts;
Detection control means for detecting the height of the developer surface from the detection results of the plurality of detection means,
The plurality of detection means respectively indicate ON when detecting the corresponding detected part, and OFF when not detecting,
The plurality of detected parts can simultaneously turn on two or more detection means, corresponding to a plurality of liquid surface heights greater than the number of the plurality of detection means, respectively. An apparatus for detecting a level of liquid level, characterized in that a combination of ON and OFF of the plurality of different detection means can be formed. The plurality of detected parts, in order from the lower side in the ascending / descending direction, have three parts, a lower detected part, a central detected part, and an upper detected part,
The plurality of detection means include lower detection means corresponding to the lower detection part, central detection means corresponding to the central detection part, and upper detection means corresponding to the upper detection part. Item 2. The liquid level detection device according to Item 1.   The detected portion includes a first state in which only the lower detection portion is turned on, a second state in which the lower detection portion and the central detection portion are turned on, and a third state in which only the central detection portion is turned on. A state, a fourth state in which the central detection unit and the upper detection unit are turned on, and a fifth state in which only the upper detection unit is turned on, and the detection control means The liquid level detecting device according to claim 2, wherein the heights of the five developer liquids corresponding to the above state can be detected.   The lower detected portion and the central detected portion are provided so as not to follow the same trajectory when moving in the ascending / descending direction, and the upper detected portion and the central detected portion also move in the ascending / descending direction. 4. The liquid level detecting device according to claim 2, wherein the liquid level detecting device is provided so as not to follow the same trajectory.   5. The liquid level detecting device according to claim 4, wherein the center detected portion protrudes by a predetermined amount in a direction perpendicular to the ascending / descending direction from the lower detected portion and the upper detected portion.   6. The lift position of the float member is regulated by contacting the lift position restricting means for restricting the lift position of the float member with the central detected portion. Liquid level detection device.   The liquid level detecting device according to claim 6, wherein the elevating position restricting means is an end face of each of the lower detecting means and the upper detecting means. The liquid level detection device has a guide bar arranged in parallel with the elevation direction,
The liquid level detecting device according to claim 1, wherein the float member moves up and down along the guide rod. Each of the plurality of detection means has a photo sensor,
The plurality of detection means are characterized in that the detection means is turned on when the photosensor is shielded by the corresponding detected part, and the detection means is turned off when the photosensor is not shielded. The liquid level detection apparatus in any one of Claim 1 to 8. A holding container for holding the developer,
A stirring means for stirring the developer;
A float member that moves up and down according to a change in the liquid level of the developer held in the holding container, a plurality of detected portions that are provided on the float member and are located outside the developer, and the float A plurality of detection means arranged in the ascending / descending direction of the member and provided so as to be able to optically detect each of the plurality of detected parts, and a detection control means for detecting the height of the developer surface. Each of the plurality of detection means indicates ON when detecting the corresponding plurality of detected parts, and indicates OFF when not detecting, and the detection control means indicates ON / OFF of the plurality of detection means. Based on the combination, a liquid level detecting device for detecting the height of the liquid level of the developer larger than the number of the plurality of detecting means,
A developer container characterized by comprising: A developer container according to claim 10,
A wet image forming apparatus that forms an image by electrophotography using a developer held in the developer container.

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