JP2005234605A - Toner, toner conveying device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of suppressing clogging of toner in a suction pipe even when a toner conveyance method using both toner suction and air supply to a toner container is employed.
An image forming apparatus is configured to use toner having any of the properties listed below.
(1) A toner having a maximum shear stress τmax of 30 G [N / m 2] or less when a normal stress of 16 G [N / m 2] is applied in the shear tester 100.
(2) A toner having a uniaxial collapse stress fc of 50 G [N / m 2] or less measured by a uniaxial collapse stress measurement method using the shear tester 100.
[Selection] Figure 8

Description

  The present invention relates to a toner for developing a latent image, and a toner conveying device and an image forming apparatus using the toner.

  2. Description of the Related Art Conventionally, in an image forming apparatus using toner, one that conveys toner from a toner container to a predetermined position in the main body of the image forming apparatus is known. For example, an electrophotographic image forming apparatus includes a replenishing toner container that contains replenishing toner, and conveys the toner from here to developing means. The toner conveyed into the developing means is used to develop an electrostatic latent image formed on a latent image carrier such as a drum-shaped photoconductor. Further, for example, there is a recovery toner container that stores toner recovered by the cleaning unit from the latent image carrier after the toner image is transferred, and transports the toner from here to a waste toner container or a developing unit.

  In such an image forming apparatus, there are various methods for conveying toner. For example, there is an apparatus that transports toner by moving a coil screw disposed in a transport pipe connecting a transport source and a transport destination. Further, for example, there is a type in which a transport destination is positioned directly below a transport source and toner is transported by gravity drop. In addition, for example, there is a type in which toner in a toner container is conveyed while being sucked by a suction pump.

  Among these, in the case where the toner is transported by the rotation of the coil screw, the transport pipe containing the coil screw has a linear shape, so the toner transport path must be configured in a straight line, and the degree of layout freedom is low. There is a drawback. In addition, even in the case where toner is transported by gravity drop, it is necessary to position the transport destination immediately below the transport source, which causes a drawback that the degree of freedom in layout becomes low.

  On the other hand, in a case where toner is transported by a suction pump, a transport member such as a coil screw is connected to a suction tube connecting the suction port of the suction pump and the toner container, or a discharge tube connecting the discharge port of the suction pump and the transport destination. Need not be built in. For this reason, it is possible to freely design the toner conveyance path by using a flexible pipe having high flexibility as the suction pipe and the discharge pipe.

  However, depending on the shape of the toner container, the toner adhering to the inner surface of the container may coalesce with the surrounding toner and become solidified, causing a phenomenon of so-called toner blocking and not flowing toward the suction tube.

  In view of this, a system in which toner suction by a suction pump and air feeding into a toner container by an air pump are used together has appeared. In this system, the toner in the toner container can be agitated by the air pressure or the airflow by the air supply and the toner blocking can be broken, so that the toner in the toner container can reach the suction pipe without waste.

  By the way, when the present inventors made a prototype of a toner conveying device that uses both toner suction and air feeding, it was found that the toner in the suction tube is likely to be clogged as compared with the case of only toner suction. Therefore, as a result of earnest research on the toner clogging, the cause was found as follows. That is, in the combined system of toner suction and air feeding, if both are performed simultaneously, the air feeding from the air pump is sucked into the suction pump without being sufficiently retained in the toner container. As a result, the toner stirring efficiency in the toner container is significantly reduced. For this reason, toner suction and air supply are generally performed at different timings. However, when only the air pump is driven for single air supply, the internal pressure of the suction pipe is increased by the influence of the air supply to promote toner aggregation, resulting in toner clogging in the suction pipe.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a toner as described below, and a toner conveying device and an image forming apparatus using the toner. That is, a toner that can suppress toner clogging in the suction tube even when a toner conveyance method that uses both toner suction and air supply to the toner container is employed, and a toner conveyance device and an image forming apparatus that use the toner.

  The present inventors investigated the air pump air supply pressure and the air supply frequency that can suppress toner clogging in the suction pipe by experiments. However, it has been found that the occurrence of toner clogging differs depending on the type of toner even with the same air pump air supply pressure and air supply frequency. Therefore, attention was paid to the properties of the toner. We have conducted extensive research on the occurrence of toner clogging using toners of various properties. Then, it was found that toner clogging in the suction tube is closely related to toner fluidity.

  FIG. 1 is a schematic diagram showing a shear tester used for measuring the maximum shear stress and uniaxial collapse stress of toner. This shear tester is conventionally known as an apparatus for measuring the maximum shear stress and the uniaxial collapse stress, which are indicators of powder fluidity. In FIG. 1, the shear tester 100 is moved by a fixed plate 101 having a sawtooth uniform unevenness on the upper surface, a movable plate 102 having a sawtooth uniform unevenness on the lower surface, a weight 103, and four wheels. A possible load cell 104 is included. In addition, a drive motor 105 for driving the load cell 104, a reel 106 fixed to the drive shaft thereof, a conducting wire 107 wound around the drive motor 105, a connection line 108 for connecting the load cell 104 and the movable plate 102, and the like are also provided. Yes. On the fixed plate 101 fixed with the saw blade-shaped surface facing upward, a powder 109 as an object is placed, and on the powder 109, the movable plate 102 has its saw blade-shaped surface down. It is put on. The powder 109 is sandwiched between the saw blade-shaped upper surface of the fixed plate 101 and the saw blade-shaped lower surface of the movable plate 102. A weight 103 is further placed on the movable plate 101. Due to the weight between the weight 103 and the movable plate 101, a predetermined vertical stress is applied to the powder 109. One end of a connection line 108 is connected to the movable plate 102, and the other end is connected to the rear part of the load cell 104. The load cell 104 is configured to be movable by four wheels, and an end portion of a conducting wire 107 wound around a reel 106 is connected to a front portion thereof. When the drive motor 105 is driven to rotate, the lead wire 107 is wound around the reel 106 along with this, and the load cell 104 is pulled to move forward. Further, as the load cell 104 moves, the movable plate 102 also moves forward, so that shear stress is applied to the powder 109.

The present inventors measured the uniaxial collapse stress for various types of toner by the uniaxial collapse stress measurement method using the shear tester 100 having such a configuration. Details of this uniaxial collapse stress measurement method are as follows. That is, a powder layer of about 50 mm × 70 mm × 6 mm is placed on the fixed plate 101, and about 700 G [N / m ² ] (70 g / cm ² or less) due to the weight of the movable plate 102 and the weight 103. ) Is applied for about 5 minutes. Then, the weight 103 is replaced with a lighter one, and a normal stress σ of 200 G [N / m ² ] (20 g / cm ² ) or less is applied to the powder layer (the toner layer in this example). Next, as shown in FIG. 2, while applying the vertical stress σ, the load cell 104 is gradually moved in the horizontal direction to apply a shear stress to the powder layer. Then, the characteristics shown in FIG. 3 appear in the displacement amount δ of the load cell 104 and the shear stress τ applied to the powder layer. Specifically, the shear stress τ applied to the toner increases as the displacement amount δ of the load cell 104 increases, and the toner layer collapses at the displacement amount δ1 and the maximum shear stress τmax1 (when the vertical stress σ1 is applied). Value). And the shear stress τ after the powder layer collapse shows a constant value τs. In the uniaxial collapse stress measurement method, the maximum shear stress τmax is measured for each of two or more different vertical stresses σ, and an approximate linear equation that is a relational expression between the vertical stress σ and the maximum shear stress τmax is obtained based on the measurement result. Then, the origin (0 point) of the approximate line in the σ-τ axis coordinates and the diameter of the circle in contact with the approximate line are obtained as the uniaxial collapse stress fc.

  FIG. 4 is a graph showing the relationship between the normal stress σ and the maximum shear stress τmax. This figure shows an example in which an approximate straight line L1 is obtained by obtaining maximum shear stresses τmax1, τmax2, and τmax3 for three different vertical stresses σ1, σ2, and σ3, respectively. Strictly speaking, when many points are measured with more normal stress σ, the relationship between the normal stress σ and the maximum shear stress τmax becomes a fracture envelope curve L2, but in the uniaxial collapse stress measurement method, instead of the fracture envelope curve L2, An approximate straight line L1 is used. Then, the diameter (σ axis intercept) of the contact circle C that is in contact with the origin P1 of the approximate straight line L1 on the σ-τ axis coordinates and the contact point P2 with the approximate straight line L1 is obtained as the uniaxial collapse stress fc. As can be seen from FIG. 4, the uniaxial collapse stress fc having substantially the same value is obtained for the approximate straight line L1 and the fracture envelope curve L2 in the normal stress σ near the contact point P2 between the contact circle C and the approximate straight line L1.

For the nine types of toners A to I having the same average particle diameter and different fluidity, the present inventors have determined whether there is uniaxial collapse stress fc by the uniaxial collapse stress measurement method and toner clogging in the suction tube. I tried to test the relationship. Toner clogging was investigated with an electrophotographic printer tester equipped with a toner transport device (together with toner suction and air feed) that transports toner from a toner cartridge containing toner for replenishment to a developing device. . This tester has the conditions listed below, all of which are values applicable to most printers and copiers.
-Length and lift of toner conveyance path (rear end of suction pipe to front end of discharge pipe): 0.3 to 1.0 [m]
・ Suction tube length: 0.5 [m]
・ Suction tube inner diameter: φ6 [mm]
-Suction pump suction pressure: 10-30 [kPa]
・ Maximum pressure in the suction pipe when supplying air: 30 [kPa]
・ Air supply frequency: Once every 30 seconds (1 second)
・ Air flow rate: 2 [liter / min]
The results of the test are shown in Table 1 below.

From Table 1, toner clogging does not occur with toner having a uniaxial collapse stress fc of 4.8 [g / cm ² ] or less, whereas toner clogging occurs with toner of 5.2 [g / cm ² ] or more. I understand that. When the uniaxial collapse stress fc near the boundary of the presence or absence of toner clogging was examined in detail, it was found that the critical point of “no toner clogging” was generally 5.0 [g / cm ² ]. Conventionally, the value of the uniaxial collapse stress fc has been used as an index indicating the fluidity of the powder. However, this research result may be useful as an index indicating the ease of clogging of toner in the suction tube. It turns out. Note that 5.0 [g / cm ² ] corresponds to 50 G [N / m ² ] (where G is gravitational acceleration: about 9.80665).

表２より、１．６［ｇ／ｃｍ^２］の垂直応力σを付与したときの最大せん断応力τｍａｘが２．９［ｇ／ｃｍ^２］以下のトナーではトナー詰まりを生じていない。これに対し、３．１［ｇ／ｃｍ^２］以上のトナーではトナー詰まりを生じている。トナー詰まり有無の境界付近における最大せん断応力τｍａｘをより詳細に調べたところ、トナー詰まり「無し」の臨界点はおおむね３．０［ｇ／ｃｍ^２］であることがわかった。よって、１．６［ｇ／ｃｍ^２］の垂直応力σを付与したときの最大せん断応力τｍａｘは、上記吸引管内におけるトナーの詰まり易さを示す指標として有用であると言える。なお、１．６［ｇ／ｃｍ^２］、３．０［ｇ／ｃｍ^２］は、それぞれ１６Ｇ［Ｎ／ｍ^２］、３０Ｇ［Ｎ／ｍ^２］に相当する。 The present inventors found an interesting phenomenon as described below while collecting the measurement results by such a uniaxial collapse stress measurement method. That is, in the uniaxial collapse stress measurement method, the maximum shear stress τmax must be measured with respect to one specimen (powder) with at least two normal stresses σ. If a certain degree of correlation is obtained between the maximum shear stress τmax and the uniaxial collapse stress FC, the maximum shear stress τmax may be measured only for a specific value of the normal stress σ, but a good correlation cannot be obtained. It is. 5 and 6 show the relationship between the maximum shear stress τmax and the uniaxial collapse stress FC when a normal stress σ of 4.5 [g / cm ² ] and 7.4 [g / cm ² ] is applied, respectively. It is a graph to show. It can be seen that the respective plot coordinates are widely separated from the approximate straight line L1. A good correlation coefficient is not obtained between the maximum shear stress τmax and the uniaxial collapse stress FC. However, when a similar graph was created for a normal stress σ of 1.6 [g / cm ² ], it was surprisingly found that a very good correlation was shown as shown in FIG. Therefore, attention was focused on the relationship between the maximum shear stress τmax when a normal stress σ of 1.6 [g / cm ² ] was applied and the presence or absence of toner clogging. The relationship between the two is shown in Table 2 below.

From Table 2, toner clogging does not occur in the toner having a maximum shear stress τmax of 2.9 [g / cm ² ] or less when a normal stress σ of 1.6 [g / cm ² ] is applied. On the other hand, toner clogging occurs in the toner of 3.1 [g / cm ² ] or more. When the maximum shear stress τmax in the vicinity of the boundary of the presence or absence of toner clogging was examined in more detail, it was found that the critical point of “no toner clogging” was approximately 3.0 [g / cm ² ]. Therefore, it can be said that the maximum shear stress τmax when the normal stress σ of 1.6 [g / cm ² ] is applied is useful as an index indicating the ease of toner clogging in the suction pipe. In addition, 1.6 [g / cm ² ] and 3.0 [g / cm ² ] correspond to 16 G [N / m ² ] and 30 G [N / m ² ], respectively.

In order to achieve the above object, the invention of claim 1 is a toner which forms a toner image by adhering to an image forming body, and is a maximum shear stress test used for a uniaxial collapse stress measurement method. (However, G is the gravitational acceleration) is characterized in that the maximum shear stress when a vertical stress of [N / m ^2] is assigned is equal to or less than 30G [N / m ^2].
The invention of claim 2 is a toner which forms a toner image by adhering to an image forming body, and has a uniaxial collapse stress of 50 G (G is gravitational acceleration) determined by a uniaxial collapse stress measurement method. [N / m ² ] or less.
According to a third aspect of the present invention, there is provided a blower for blowing air into a toner container for containing toner, a suction pipe connected to the toner container, and a negative pressure in the suction pipe to generate the toner container. And a suction pump that sucks the toner in the toner container and sucks the toner with the suction pump to transport the toner from the toner container to a transport destination. It is characterized by this.
According to a fourth aspect of the present invention, there is provided a toner container that contains toner and a toner conveying device that conveys the toner in the toner container to a conveyance destination, and the toner is attached to the image forming body to form an image. An image forming apparatus to be formed, wherein the toner according to claim 1 or 2 is used as a toner.
According to a fifth aspect of the present invention, there is provided the image forming apparatus according to the fourth aspect, comprising: a latent image carrier that carries a latent image; and a developing unit that develops the latent image on the latent image carrier with toner. The transport destination is the developing means.
The invention according to claim 6 is the image forming apparatus according to claim 4 or 5, wherein a head between the toner container and the transport destination and a total length of the suction tube are both 1 [m] or less. In addition, the negative pressure by the suction pump is 10 [kPa] or more.
Of these inventions, as in those with the configuration of the invention of claim 1, keep the maximum shear stress when a vertical stress of 16G [N / m ^2] is applied to the following 30G [N / m ^2] The toner exhibiting good fluidity suppresses toner clogging in the suction tube of the toner conveying device. Therefore, even if a toner conveyance method using both toner suction and air supply to the toner container is employed, toner clogging in the suction tube can be suppressed.
Further, in the toner having the configuration of the invention of claim 2, a toner exhibiting good fluidity that keeps the uniaxial collapse stress obtained by the uniaxial collapse stress measurement method to 50 G [N / m ² ] or less, Toner clogging in the suction tube of the toner conveying device is suppressed. Therefore, even if a toner conveyance method using both toner suction and air supply to the toner container is employed, toner clogging in the suction tube can be suppressed.

  According to the first, second, third, fourth, fifth, and sixth aspects of the present invention, even when the toner conveyance method using both the toner suction and the air supply to the toner container is employed, the toner clogging in the suction tube can be suppressed. There is an excellent effect of being able to.

Hereinafter, an embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter simply referred to as a copying machine) as an image forming apparatus will be described.
First, a basic configuration of the copying machine according to the present embodiment will be described. FIG. 8 is a schematic diagram showing the main part of the copying machine. In the figure, the copying machine includes a document reading unit 1, an automatic document supply unit 2, a printer unit 3, and a paper feeding unit 4.

The automatic document feeder 2 automatically supplies a document (not shown) placed on the upper surface thereof onto a contact glass 5 described later.
The document reading unit 1 is for reading an image of a document (not shown). When a start switch (not shown) is operated while the original is placed on the contact glass 5 fixed on the upper part of the original reading unit 1 by a user's manual operation, the original reading by the original reading unit 1 starts immediately. Is done. Further, when the start switch is operated with the document placed on the automatic document feeder 2, the document is automatically fed onto the contact glass 5, and then the document reading by the document reading unit 1 is started. The When reading is started, the document placed on the contact glass 5 is illuminated with a light source 6 that moves in the right direction in the figure. The reflected light image from the document is sequentially reflected by the first mirror 7 and the second mirror 8. Then, after passing through the imaging lens 9, it is detected by the image sensor 10 comprising a CCD or the like for reading the reflected light image, and the image information is read.

  The printer unit 3 is for forming a toner image as an image on a transfer paper P as an image forming body, and includes an optical writing unit 11 and a drum-shaped photoconductor 12. Further, a charging device 13, a developing device 40 as a developing means, a transfer conveyance unit 14, a drum cleaning device 15, a static eliminator 16 and the like are provided around the drum-shaped photoconductor 12 as a latent image carrier. Further, a fixing device 17, a reverse paper discharge unit 18, a registration roller pair 19 and the like are also provided. When the start switch is operated, the drum-shaped photosensitive member 12 starts to be rotated by driving means (not shown).

  The optical writing unit 11 optically modulates the laser light L based on the image signal read by the document reading unit 1 to expose the drum-shaped photosensitive member 12 as a latent image carrier. Specifically, the laser light L is emitted from the light source 20 made of a laser diode or the like. The laser beam L is deflected in the main scanning direction (axial direction of the drum-shaped photosensitive member 12) on the rotary polygon mirror 22 that is rotationally driven by the polygon motor 21, and is a lens for scanning imaging composed of an fθ lens. Pass through system 23. Then, it passes through the mirror 24 and the lens 25 and reaches the drum-like photoconductor 12 that is rotationally driven, and scans the surface of the electrostatic latent image.

  The transfer / conveying unit 14 forms a transfer nip by contacting the peripheral surface of the drum-like photoconductor 12 while moving the transfer / conveying belt endlessly while tensioning with a plurality of stretching rollers. Further, a transfer bias roller (not shown) is brought into contact with the back surface (the inner peripheral surface of the hoop) of the transfer conveyance belt in the transfer nip. A transfer bias is applied to the transfer bias roller by a power source (not shown), and a transfer electric field is formed in the transfer nip by this application.

  The electrostatic latent image formed on the drum-shaped photoconductor 12 by exposure by the optical writing unit 11 is developed by the developing device 40 to become a toner image, and then enters the transfer nip. On the other hand, the registration roller pair 19 sandwiches a transfer sheet P sent from a sheet feeding unit 4 (described later) between the rollers based on the operation of the start switch. Then, the transfer paper P is sent out at a timing at which the transfer paper P can be superimposed on the toner image on the drum-shaped photoconductor 12 at the transfer nip. By this feeding, the toner image on the drum-shaped photoconductor 12 is brought into close contact with the transfer paper P at the transfer nip. Then, it is transferred from the drum surface to the transfer paper surface under the influence of the transfer electric field and nip pressure. The transfer paper P that has passed through the transfer nip is fed into the fixing device 17 by the transfer conveyance belt of the transfer conveyance unit 14. The fixing device 17 sandwiches the transferred transfer paper P between the heating roller 17a and the pressure roller 17b. Then, the toner image is discharged toward the reverse discharge unit 18 while being fixed on the transfer paper P by the influence of heat and pressure.

  The reverse paper discharge unit 18 passes the transferred transfer paper P through a discharge path 18a and discharges it to a paper discharge tray (not shown) outside the apparatus. However, when the double-sided copy mode is selected by the user, the transfer paper P is passed through the reversing unit 18b and turned upside down, and then conveyed toward the registration roller pair 19. As a result, the transfer paper P is fed again from the registration roller pair 19 toward the transfer nip, and a new toner image is transferred to the surface opposite to the surface on which the toner image has been previously transferred.

  The drum cleaning device 15 cleans the transfer residual toner adhering to the surface of the drum-shaped photoconductor 12 after passing through the transfer nip, and stores it in a collection tank (not shown) as a toner container. The surface of the drum-shaped photoreceptor 12 after cleaning is discharged by the charge eliminator 16 and then uniformly charged by the charging device 13 to prepare for the next image formation.

  The paper feed unit 4 includes three paper feed cassettes 26, 27, and 28 arranged in multiple stages, each of which accommodates a plurality of transfer papers P. A paper feed path 33 having a plurality of pairs of transport rollers 32 is also provided. The paper feed cassettes 26, 27, 28 press the paper feed rollers 26 a, 27 a, 28 a against the uppermost paper of the transfer paper P accommodated therein, and the uppermost paper is directed toward the paper feed path 33 by its rotational drive. And send it out. When the start switch is operated, the transfer paper is sent out from any one of the paper feed cassettes to the paper feed path 33. The paper feed path 33 feeds the received transfer paper P toward the registration rollers 19 of the printer unit by a plurality of pairs of transport rollers 32.

  A developing device 40 disposed on the side of the drum-shaped photoconductor 12 is equipped with a toner transport device 50 that transports toner to the developing device 40. In the developing device 40, a two-component developer (not shown) containing toner and a magnetic carrier is accommodated. The toner replenished into the developing device 40 by the toner conveying device 50 is mixed and stirred with the internal two-component developer and used for development. A T sensor (not shown) is disposed on the bottom surface of the developing device 40. The T sensor outputs a signal corresponding to the magnetic permeability of the two-component developer in the developing device 40 to a control unit (not shown). Since the toner concentration of the two-component developer correlates with the magnetic permeability, the T sensor detects the toner concentration of the two-component developer. The control unit appropriately operates the toner conveying device 50 so that the output signal from the T sensor approaches a predetermined target value, thereby reducing the toner concentration of the two-component developer whose toner concentration has been reduced with development. Let me recover. However, since the magnetic permeability of the two-component developer fluctuates due to an environmental change such as humidity or a bulk change of the two-component developer, the control unit appropriately corrects the target value. Specifically, the target value is corrected according to the image density of the reference toner image formed on the drum-shaped photoconductor 12 at a predetermined timing. The image density is grasped by, for example, an output from a reflection type photosensor (hereinafter referred to as P sensor) that detects the light reflectance of the reference toner image.

  Untransferred toner that has not been transferred onto the transfer paper adheres to the surface of the drum-shaped photoconductor 12 that has passed through the transfer nip. The transfer residual toner is scraped off by the drum cleaning device 15 and collected in a collection tank (not shown).

  FIG. 9 is a detailed configuration diagram showing the toner conveying device 50. The toner conveying device 50 includes a suction pump 60, a cartridge holder 70, an air pump unit 80, and the like. The suction pump 60 is of a type referred to as a uniaxial eccentric screw pump or a Mono pump, and generates a negative pressure in the suction port 64 by rotating a rotor 62 in the stator 61 by a suction motor 63. The tip of a flexible suction tube 51 is connected to the suction port 64.

  The cartridge holder 70 includes a holder portion 71 whose upper side is opened in the drawing, a nozzle 72 inserted in the bottom surface thereof, and the like. The holder portion 71 is for holding a toner cartridge 90 as a toner container. In the toner cartridge 90, the protective case 91 is made of a material such as paper, cardboard, or plastic that exhibits a certain degree of rigidity, and includes a toner containing bag 92. The toner containing bag 92 is composed of a bag portion 93 in which a sheet material having a thickness of 80 to 200 [μm] is formed into a single layer or multiple layers into a bag shape, and a base portion 94 fixed to the toner discharge side. It has a sealed structure that does not allow air to enter and exit. As the sheet material, a resin sheet such as polyethylene or nylon, or a paper sheet is used. A toner for replenishment is stored inside the toner storage bag 92. The base portion 94 of the toner containing bag 92 includes an engaging portion 94b made of a rigid material such as resin or paper and an opening seal portion 94a made of an elastic material such as sponge so as to be engaged in the opening of the bag portion 93. Have. The toner cartridge 90 having such a configuration is mounted on the holder portion 71 of the cartridge holder 70 with the base portion 94 side vertically downward. At this time, the tip of the nozzle 72 inserted in the bottom surface of the holder portion 71 penetrates through the opening seal portion 94 a of the base portion 94 of the toner cartridge 90 and enters the bag portion 93. Since the opening seal portion 94a is in close contact with the periphery of the nozzle 74, toner leakage from the inside of the toner cartridge 90 to the outside is prevented. A toner suction port 73 is formed on the tip side of the nozzle 72. A T-shaped path is formed on the rear end side so as to be divided into a toner path 74 and an air receiving path 75. Among these, the rear end of the suction tube 51 is connected to the toner passage 74.

  The air pump unit 80 includes an air pump 81, a relay tube 82, an electromagnetic valve 83 connected thereto, an air supply tube 84, and the like. The air pump 81 is driven in a state where the electromagnetic valve 83 is opened, so that air is supplied into the air receiving path 75 of the nozzle 72 via the relay tube 82, the electromagnetic valve 83, and the air supply tube 84. send. The suction pump 60 has a structure that does not receive fluid from the suction port 64 in a non-operating state. For this reason, the air sent from the air pump 81 into the air receiving path 75 of the nozzle 72 does not flow into the toner passage 74 and reaches the bag portion 93 through the toner suction port 73 of the nozzle 72. Then, the toner in the bag portion 96 is agitated and loosened to suppress the occurrence of toner blocking (toner cross-linking phenomenon) in the bag portion 93. Further, even if toner blocking occurs due to long-term standing, it is broken by an air current or the like. As a result, the toner in the bag portion 93 can flow smoothly toward the toner suction port 73 of the nozzle 72 by its own weight, and the amount of toner remaining in the toner cartridge 90 is reduced.

  FIG. 10 is a perspective view showing the toner containing bag 92. As shown in the figure, a ventilation filter 95 is provided at the bottom (on the side opposite to the toner discharge side) of the bag portion 93 of the toner containing bag 92. The air sent from the air pump into the bag portion 93 is finally discharged to the outside through the ventilation filter 95, but the mesh of the ventilation filter 95 is fine enough to prevent the toner particles from passing therethrough. . For this reason, it passes through the ventilation filter 95 over a certain period of time, and the air pressure in the bag portion 93 temporarily rises when the air pump is driven.

  In FIG. 9 described above, in a state where the electromagnetic valve 83 of the air pump unit 80 is closed, the toner cartridge 90 extends from the bag unit 93 to the nozzle 72, the suction tube 51, and the suction pump 60. The space up to is a sealed environment. For this reason, when the suction pump 60 is operated and a negative pressure is generated in the suction tube 51, a suction force is generated in the toner suction port 73 of the nozzle 72. Then, the toner in the bag portion 93 is sucked from the toner suction port 73 and sequentially passes through the toner passage 74 of the nozzle 72, the suction tube 51, and the suction pump 60, and is connected to the discharge side of the suction pump 60. The vessel 40 is replenished.

  The suction tube 51 connecting the suction pump 60 and the nozzle 72 is formed with an inner diameter of 3 to 7 [mm], and a rubber material or plastic material having excellent flexibility and toner resistance is used. Yes. Examples of such a rubber material include polyurethane rubber, nitrile rubber, EPDM rubber, silicon rubber and the like. Examples of the plastic material include polyethylene and nylon. By using the flexible suction tube 51 having excellent flexibility, it is possible to freely arrange the toner transfer path inside the copying machine, and the layout flexibility inside the apparatus is very good. Further, in the toner replenishing device 50, even when the toner cartridge 90 is positioned below the developing device 40 in the gravity direction, the toner pumping-up conveyance of the toner can be performed by using a suction pump 60 having a relatively high suction force. It becomes possible. This also improves the degree of freedom of layout inside the apparatus, and the toner cartridge 90 can be disposed at a position where the replacement operation is easiest.

  FIG. 11 is an exploded perspective view showing a pump portion of the suction pump 60. In the figure, the pump portion of the suction pump 60 includes a stator 61, a rotor 62, a holder 65 that contains these, and the like. The stator 61 has a female screw shape in which a double pitch spiral groove is formed in an elastic member such as rubber. The rotor 62 is formed of a material such as metal or resin in the shape of an external thread, and is inserted into the spiral groove of the stator 61 so as to be rotatable. A drive shaft 67 fixed by a spring pin 66 is connected to the rear end of the rotor 62. The holder 65 including the stator 61 supports the stator 61 so as to be swingable in the direction of arrow A in the figure by bringing a flange portion provided at an end of the stator 61 into contact with an inner peripheral surface thereof. For this swing, a gap G is formed between the inner surface of the holder 65 and the outer surface of the stator 61. A motor (not shown) is connected to the tip of the drive shaft 67, and the rotor 62 rotates in the stator 61 as the motor rotates. At this time, the rotor 62 rotates eccentrically due to its complicated shape. This is why the suction pump (60) is referred to as a uniaxial eccentric screw pump. When the rotor 62 rotates eccentrically, the stator 61 swings in the direction of arrow A in the figure. When the suction force P <b> 2 is generated at the suction port 64 by the rotation of the rotor 62, the toner is sucked from the suction port 64. The sucked toner passes through the inside of the pump unit and is then discharged from a discharge port (not shown) provided on the lower side of the drive shaft 67.

  FIG. 12A is a longitudinal sectional view showing the stator 61 in which the rotor 62 is inserted. In this figure, D2 indicates the amount of biting of the spiral outer diameter of the rotor 62 with respect to the inner diameter of the stator 61. FIG. 12B is a cross-sectional view showing a state where the rotor 62 is stopped at a position deviated toward one end side of the inner diameter of the stator 61. In this figure, D3 indicates the amount of biting of the rotor 62 in the vicinity of its end with respect to the stator 61. FIG. 12C is a cross-sectional view showing a state in which the rotor 62 is substantially at the center position of the inner diameter of the stator 61. In this figure, D 1 indicates the amount of biting of the rotor 62 with respect to the minimum inner diameter portion of the stator 61. The present inventors have found through experiments that it is important to set the three biting amounts D1, D2, and D3 in order to cause the suction pump 60 to exhibit the desired discharge pressure and suction pressure. In FIG. 12A described above, gaps g <b> 1 to g <b> 3 are formed between the rotor 62 and the stator 61 in the pump portion of the suction pump 60. These gaps are in a state of being partitioned from each other and sealed by the rotor 62 biting into the stator 61 with the above-described three biting amounts. When the rotor 62 is rotationally driven in this state, the three sealed gaps g1 to g3 rotate to convey the toner inside to the discharge side. On the discharge side, when the rotor 62 comes to a predetermined rotational position, the sealed gap g1 is opened and the toner is discharged. On the other hand, on the suction side, when the rotor 62 comes to a predetermined rotational position, the sealed gap g3 is opened, and then the sealed state is again made while surrounding air and toner are involved. As a result, a discharge pressure and a suction pressure are generated on the discharge side and the suction side of the suction pump 60, respectively.

  In order to increase the discharge pressure and the suction pressure, the sealing degree of the gaps g1 to g3 may be increased. Specifically, the amount of biting of D1 to D3 is increased. Then, the torque of the suction pump 60 can be increased. However, if the amount of biting is increased, the internal temperature rises and the toner is easily aggregated inside the suction pump 60. On the other hand, if the amount of biting is reduced, the toner suction force and toner conveyance force of the suction pump 60 are reduced by the torque reduction, but toner aggregation due to temperature rise is less likely to occur. In the copying machine according to the present embodiment, three biting amounts D1, D2, and D3 are set to appropriate values found by the inventors' research. This appropriate value is a value that does not change the degree of toner aggregation between before and after passing through the suction pump 60 and that can exhibit a desired toner conveying force. Therefore, the suction pump 60 can reliably convey the toner and suppress the occurrence of abnormal images due to toner aggregation.

  FIG. 13 is a block diagram showing a part of an electric circuit of the copying machine according to the present embodiment. In the figure, a micro processing unit (hereinafter referred to as MPU) 150 is a control means of the copying machine main body. Connected to the MPU 150 are a P sensor 151 for detecting the density of a reference toner image formed on the drum-shaped photoconductor, a T sensor 41 provided in the developing device (40), and the like. Further, a suction motor 63, an air pump 81, an electromagnetic valve 83 and the like provided in the toner conveying device (50) are also connected. The MPU 150 replenishes toner in the developing device (40) by drivingly controlling the suction motor 63 in accordance with the output value of the signal sent from the P sensor 151. The MPU 150 also has a timer function, and accumulates and counts the toner replenishment operation time (suction motor drive operation time). Further, the air pump 81 is driven and controlled at a predetermined timing to stir the toner in the toner cartridge 90 by supplying air. Even if the main power supply of the copying machine (not shown) is turned off, the power is supplied to the MPU 150, so the accumulated count value of the toner replenishment operation time stored therein is held.

  FIG. 14 is a timing chart showing operation timings of the suction motor 63, the air pump 81, and the electromagnetic valve 83. In the figure, the suction motor 63 is appropriately turned on and off based on the output of the P sensor (151). When the cumulative count value of the toner replenishment operation time of the suction motor 63 reaches a predetermined value, the air pump 81 and the electromagnetic valve 83 are driven and controlled for a predetermined time after the suction motor 63 is stopped. Thereby, the toner is agitated in the toner cartridge (90). In FIG. 9 described above, if the air from the air pump 81 is sucked into the suction pump 60, the toner cartridge 90 cannot be sufficiently convected, and the toner stirring performance is significantly reduced. Therefore, the air pump 81 and the solenoid valve (opening when energized) 83 are always driven when the suction motor 63 (suction pump 60) is stopped.

  FIG. 15 is a flowchart illustrating an example of toner supply control performed by the MPU (150). In the toner replenishment control, the MPU (150) first reads an output value from the P sensor (151) (step 1: step is hereinafter referred to as S), and then reads an image area ratio of an image to be output (step S1). S2). Then, after calculating the toner consumption based on the output value from the P sensor and the image area ratio (S3), the driving time of the suction motor 63 is calculated based on the calculation result (S4). Next, after adding this drive time to the cumulative count value C1 of the toner replenishment operation time so far (S5), the suction motor 63 is driven for that drive time (S6, S7). Then, it is determined whether or not the accumulated count value C1 has exceeded N seconds (S8). If N seconds have been exceeded (Y in S8), the air pump 81 and the electromagnetic valve 83 are driven for a predetermined time (S9), and then the cumulative count value C1 is reset to zero (S10). ), The toner supply control is terminated. If N seconds have not been exceeded (N in S8), the toner supply control is terminated as it is.

Next, a characteristic configuration of the copying machine according to the present embodiment will be described.
FIG. 16 shows a side view and a sectional view of the nozzle 72 of the toner replenishing device (50) side by side. In the figure, the dotted arrow indicates the moving direction of the air supplied from the air pump 81, and the solid line arrow indicates the moving direction of the toner. Most of the air sent from an air pump (81) (not shown) first moves along a dotted arrow C and a dotted arrow A in the figure. Specifically, after passing through the air receiving path 75 of the nozzle 72, the toner enters the toner storage bag (not shown) via the toner suction port 73 and stirs the internal toner. Thus, the air that has entered the toner storage bag is eventually discharged from the ventilation filter 95 (see FIG. 10) to the outside of the bag. Since this discharge takes a certain amount of time, the air pressure in the bag temporarily changes. To rise. Then, a part of the air after passing through the air receiving path 75 of the nozzle 72 moves not in the direction of the toner suction port 73 but in the direction of the toner passage 74 (in the direction of the dotted arrow B) and moves inside the suction tube 51. Press the toner. When this pressure is repeatedly generated by periodically driving the air pump 81, the toner in the suction tube 51 will eventually aggregate (portion F in the figure). And there exists a possibility that it may become a strong agglomerate which cannot be conveyed with the suction pressure of the suction pump 60.

  FIG. 17 shows a side view and a sectional view of a modified example of the nozzle 72 side by side. The nozzle 72A of this modification is of a so-called “double tube nozzle system”. In the double tube nozzle method, a T-shaped fork is not formed in the nozzle. Air sent from an air pump (81) (not shown) always enters a toner storage bag (not shown) through a gap between the outer tube and the inner tube. The inner tube is formed longer than the outer tube and protrudes from the tip of the outer tube, and a toner suction port 73 is formed in the protruding portion. The toner in the toner storage bag is sucked from the toner suction port 73 and conveyed through the suction tube 51 by driving a suction pump (60) (not shown). Even in the nozzle 72A having such a configuration, when the internal pressure in the toner storage bag is increased by air supplied from an air pump (81) (not shown), the internal air eventually enters the suction tube 51 from the toner suction port 73 and enters the inside of the tube. Press the toner. This pressing causes toner aggregation.

Therefore, this copying machine is configured to use any of the properties listed below as the toner. The user is instructed to use toner having such properties. This designation is performed, for example, by specifying information (at least one of property, type, product name, and product number) of toner to be used in an instruction manual or a pamphlet of the copying machine main body. Further, for example, this information is specified on the copying machine main body, or a sticker describing the information is attached to the copying machine main body. In addition, for example, this is performed by the manufacturer or distributor of the copying machine main body transmitting this information to the user by document, electronic data, or verbally.
(1) A toner having a maximum shear stress τmax of 30 G [N / m ² ] or less when a normal stress of 16 G [N / m ² ] is applied in the shear tester 100.
(2) A toner having a uniaxial collapse stress fc of 50 G [N / m ² ] or less measured by a uniaxial collapse stress measurement method using the shear tester 100.

In the copying machine having such a configuration, the maximum shear stress τmax when a normal stress of 16 G [N / m ² ] is applied is 30 G [N / m ² ] or less, or the uniaxial collapse stress fc is 50 G [N / M ² ] or less, a toner that exhibits good fluidity is used. As a result, toner aggregation in the suction tube 51 serving as a suction tube is suppressed even when toner suction and air supply to the toner cartridge 90 (strictly, the toner storage bag 92) serving as a toner container are used in combination. Therefore, toner clogging in the suction tube 51 due to such aggregation can be suppressed. Furthermore, by suppressing the toner clogging, it is possible to suppress the overload of the suction pump 60 due to the toner clogging, so that the damage due to the overload of the suction pump 60 can also be suppressed.

In addition, as an index indicating the ease of clogging of the toner, the fluidity test method is used by using 16τmax which is the maximum shear stress when a normal stress of 16 G [N / m ² ] is applied instead of the uniaxial collapse stress fc. It is possible to simplify and manage the toner more easily. This is because at the maximum shear stress of 16τmax, it is possible to know the ease of clogging of the toner only by measuring the maximum shear stress of the toner once. On the other hand, when the uniaxial collapse stress fc is used, it is possible to know the ease of clogging of toner more accurately than when the maximum shear stress 16τmax is used.

  In the above, a two-component development type copying machine using a two-component developer containing toner and a magnetic carrier has been described. However, the present invention is also applied to a one-component development method using a one-component developer not containing a magnetic carrier. Can be applied. Further, the image forming apparatus is not limited to a copying machine, and may be another image forming apparatus such as a printer or a facsimile. In addition, a method of forming an electrostatic latent image by exposure using an LED or ion application may be used instead of the method of performing exposure using a laser beam. The present invention can also be applied to an image forming method that does not use an electrophotographic process. As such a method, for example, there is a direct recording method such as an image forming apparatus described in JP-A-11-301014. Furthermore, the present invention can be applied not only to the image forming apparatus but also to the toner conveying apparatus. Needless to say, the configuration of the toner conveying device is not limited to that shown in FIG.

FIG. 18 is a detailed configuration diagram illustrating a modified example of the toner conveying device 50.
A discharge tube 68 is connected to the discharge side of the suction pump 60 in this modified apparatus, and a discharge hopper 69 is connected to the tip thereof. The toner discharged to the discharge hopper 69 through the discharge tube 68 is supplied to the developing device 40. The relay tube 82 connected to the discharge port of the air pump 81 is connected to a branch pipe 88 that is divided into two branches, and a first electromagnetic valve 85 and a second electromagnetic valve 86 are connected to the respective ends. The tip of the first electromagnetic valve 85 is connected to the air receiving path 75 of the nozzle 72 via the air supply tube 84. On the other hand, the tip of the second electromagnetic valve 86 is connected to the discharge side of the suction pump 60 via a flow dividing tube 89. Since the toner transfer path from the discharge side of the suction pump 60 to the tip of the discharge tube 68 is sealed, the toner discharged from the discharge side is pumped through the discharge tube 68 and reaches the discharge hopper 69. At this time, the toner positioned near the rear end of the discharge tube 68 is pressed by receiving the weight of the toner positioned near the front end. However, since the toner having the properties as described above is also used in this modified apparatus, toner clogging in the discharge tube 68 can be suppressed. In addition, when the air pump 60 is ON, the first solenoid valve 85 is OFF (closed), and the second solenoid valve is ON (open), the air supply from the air pump 60 is directed to the discharge side of the suction pump 60. Led. The toner discharged from the discharge side of the suction pump 60 is conveyed through the discharge tube 68 while being fluidized. This also suppresses toner clogging in the discharge tube 68. When the air pump 60 is ON, the first electromagnetic valve 85 is ON (open), and the second electromagnetic valve is OFF (closed), the air supply from the air pump 60 is guided into the toner containing bag 92. Then, the toner in the bag is agitated.

  FIG. 19 is a timing chart showing operation timings of the suction motor 63, the air pump 81, the first electromagnetic valve 85, and the second electromagnetic valve 86. When the cumulative count value C1 of the toner replenishment operation time exceeds N seconds, after the suction motor 63 is stopped, the air pump 60 is turned on, the first solenoid valve 85 is turned on (opened), and the second solenoid valve is turned off. The condition (closed) occurs. Then, the air supply from the air pump 60 is guided into the toner storage bag 92, and the toner in the bag is agitated and fluidized to break the toner blocking in the toner storage bag (92). As a result, the toner in the toner storage bag is sucked without any excess, so that the remaining amount of toner at the time of cartridge replacement is almost eliminated.

As described above, the toner conveying device 50 of the copying machine according to the present embodiment includes the air pump unit 80 serving as a blowing unit that blows air into the toner cartridge 90 serving as a toner container. In addition, a suction tube 51 as a suction tube and a suction pump 60 that sucks by generating a negative pressure in the suction tube 51 are provided, and toner having the above-described properties is used. In such a configuration, even when toner suction and air supply for the toner cartridge 90 are used in combination, the toner can be conveyed while suppressing clogging of the toner in the suction tube 51.
Further, in the copying machine according to the embodiment, by using the toner having the above-described properties, toner clogging in the suction tube 51 of the toner transport device 50 is suppressed, and stable toner transport control is performed. Can do.
Further, toner is replenished from the toner cartridge 90 into the developing device 40 while forming a toner image by an electrophotographic process using the drum-shaped photosensitive member 12 as a latent image carrier and the developing device 40 as a developing means. Control can be performed stably. As a result, the toner density in the developing device 40 can be stably maintained.
Further, the head of the toner cartridge 90 and the developing device 40 as the transport destination and the total length of the suction tube 51 as the suction tube are both 1 [m] or less, and the negative pressure by the suction pump 60 is 10 [kPa] or more. It is. Such a configuration is under the same conditions as the prototype used in the tests of the present inventors. Therefore, the toner clogging in the suction tube 51 can be suppressed more reliably than those under different conditions.

FIG. 3 is a schematic diagram showing a shear tester used for measuring the maximum shear stress and uniaxial collapse stress of toner. The graph which shows the characteristic of the toner to which a shear force is provided by the shear tester. The graph which shows the relationship between displacement amount (delta) of the load cell of the same shear tester, and the shear stress (tau) provided to a powder layer. The graph which shows the relationship between the normal stress (sigma) with respect to the toner set to the same shear testing machine, and the largest shear stress (tau) max. The graph which shows the relationship between the maximum shear stress (tau) max of the toner to which the normal stress (sigma) of 4.5 [g / cm < ² >] is provided with the same shear tester, and the uniaxial collapse stress FC. The graph which shows the relationship between the maximum shear stress (tau) max of the toner to which the normal stress (sigma) of 7.4 [g / cm < ² >] is provided with the shear tester, and the uniaxial collapse stress FC. The graph which shows the relationship between the maximum shear stress (tau) max of the toner to which the normal stress (sigma) of 1.6 [g / cm < ² >] is provided with the shear tester, and the uniaxial collapse stress FC. 1 is a schematic configuration diagram showing a copier according to an embodiment. 2 is a detailed configuration diagram illustrating a toner conveying device of the copier. FIG. FIG. 3 is a perspective view showing a toner storage bag of a toner cartridge set in the toner conveying device. FIG. 3 is an exploded perspective view showing a pump portion of a suction pump of the toner conveying device. (A) is a longitudinal cross-sectional view which shows the same pump part by which the rotor was inserted by the stator. (B) is a cross-sectional view showing a state where the rotor is stopped at a position deviated toward one end of the inner diameter of the stator. (C) is a cross-sectional view showing a state in which the rotor is substantially at the center position of the inner diameter of the stator. FIG. 2 is a block diagram showing a part of an electric circuit of the copier. 6 is a timing chart showing operation timings of a suction motor, an air pump, and a solenoid valve in the toner conveying device. 6 is a flowchart illustrating an example of toner supply control performed by the MPU of the copier. The side view and sectional drawing of the nozzle of the toner replenishing device. The side view and sectional drawing of a nozzle of a double nozzle system. FIG. 6 is a detailed configuration diagram illustrating a modified example of the toner conveying device. The timing chart which shows the operation | movement timing of a suction motor, an air pump, a 1st solenoid valve, and a 2nd solenoid valve in the modification apparatus.

Explanation of symbols

12 Drum-shaped photoconductor (latent image carrier)
40 Developer (Developer)
50 Toner conveying device 51 Suction tube (suction tube)
60 Suction pump 81 Air pump (air supply means)
90 Toner cartridge (toner container)
P Transfer paper (image forming body)
σ Normal stress τ Shear stress τmax Maximum shear stress 16τmax 16G [N / m ² ] Maximum shear stress fc Uniaxial collapse stress

Claims (6)

A toner that forms a toner image by adhering to an image forming body,
Maximum shear stress when normal stress of 16G (G is acceleration of gravity) [N / m ² ] is applied in the maximum shear stress test used for the uniaxial collapse stress measurement method is 30G [N / m ² ] or less Toner characterized by being. A toner that forms a toner image by adhering to an image forming body,
A toner having a uniaxial collapse stress obtained by a uniaxial collapse stress measurement method of 50 G (where G is a gravitational acceleration) [N / m ² ] or less. A blowing means for blowing air into a toner container for containing toner, a suction pipe connected to the toner container, and a suction pump for sucking the toner in the toner container by generating a negative pressure in the suction pipe; A toner transport device that sucks toner with the suction pump and transports the toner from the toner container to a transport destination,
A toner conveying apparatus using the toner according to claim 1 or 2 as the toner. An image forming apparatus comprising: a toner container that contains toner; and a toner conveyance device that conveys toner in the toner container to a conveyance destination, and forms an image by attaching the toner to an image forming body.
An image forming apparatus using the toner according to claim 1 or 2 as a toner. The image forming apparatus according to claim 4,
An image forming apparatus comprising: a latent image carrier that carries a latent image; and a developing unit that develops the latent image on the latent image carrier with toner, and the transport destination is the developing unit. The image forming apparatus according to claim 4, wherein:
The lift between the toner container and the transport destination and the total length of the suction pipe are both 1 [m] or less, and the negative pressure by the suction pump is 10 [kPa] or more. Image forming apparatus.

Images