JP2010026279A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which prevents developer from blocking in a conveyance pipe. <P>SOLUTION: The image forming apparatus 10 includes: a conveyance screw 5s which conveys developer T; and a developer conveyance path 5 which has the conveyance pipe 5p incorporating the conveyance screw 5s. The apparatus 10 conveys the developer T to a developing unit 1 from a developer storage section 6 storing the developer T. The friction coefficient μ1 of a conveyance pipe internal wall 5p1 in the axial direction P of the conveyance pipe 5p is set smaller than the friction coefficient μ2 of the conveyance pipe internal wall 5p1 in the circumferential direction Q of the conveying pipe 5p. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer.

  Conventionally, in an electrophotographic image forming apparatus or an electrostatic recording image forming apparatus, when the developer is consumed by image formation, the consumed amount is generally supplied from the developer storage unit to the developing device through the developer transport path. It is. Further, as disclosed in Patent Document 1, the developer transport path is mainly composed of a transport screw that transports the developer and a transport pipe that includes the transport screw.

JP 2006-30526 A

  However, during continuous operation of the image forming apparatus in a high temperature environment, there are cases where the temperature in the image forming apparatus rises to nearly 50 ° C. Further, within the developer transport path, the toner that is “developer” is also subjected to the feed pressure of the transport screw. Under such conditions where both heat and pressure are applied, the degree of aggregation of the toner increases rapidly. Then, the toner having a high degree of aggregation is likely to stick to the conveying screw of the developer conveying path. Therefore, there is a risk of clogging in the developer conveyance path, and the number of maintenance for this clogging increases.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus in which clogging of a developer is suppressed inside a conveyance pipe.

  In order to achieve the above object, an image forming apparatus of the present invention includes a developer conveying path having a conveying screw that conveys a developer and a conveying pipe that encloses the conveying screw, and stores the developer. In the image forming apparatus that transports the developer from the storage unit to the developing device, the axial coefficient of friction of the transport pipe included in the transport pipe inner wall formed inside the transport pipe is greater than that of the transport pipe inner wall. It is set to be smaller than the friction coefficient in the circumferential direction of the transport pipe.

  As described above, according to the present invention, the friction coefficient in the axial direction of the transport pipe is set to be smaller than the friction coefficient in the circumferential direction of the transport pipe on the inner wall surface of the transport pipe. As a result, the slippage in the axial direction of the transport pipe included in the inner wall surface of the transport pipe is increased, and the slipperiness in the circumferential direction of the transport pipe included in the inner wall surface of the transport pipe is reduced. Therefore, the efficiency of developer movement increases in the axial direction of the transport pipe, and the rotation of the developer decreases in the circumferential direction of the transport pipe. As a result, clogging of the developer is suppressed inside the transport pipe.

(First Embodiment)
FIG. 1 is a block diagram showing an image forming apparatus 10 according to the first embodiment of the present invention. As shown in FIG. 1, the image forming apparatus 10 includes a photosensitive drum 28. Around the photosensitive drum 28, a developing rotary 8 that is rotatably supported is disposed. The developing rotary 8 includes developing devices 1LM, 1LC, 1Y, 1M, 1C, and 1K for six colors. The developing device contains a two-component developer composed of a non-magnetic toner and a magnetic carrier as a “developer”. The magnetic carrier is a magnetic powder. The number of colors and the color order are not limited to these. Further, the developing devices 1LM, 1LC, 1Y, 1M, 1C, and 1K are collectively referred to as the developing device 1 in the following description.

  An electrostatic latent image is formed on the photosensitive drum 28 by exposing the surface of the photosensitive drum 28 charged by the charger 21 with a laser 22, and the developing rotary 8 is rotated in the direction of the arrow in the vicinity of the electrostatic latent image. The predetermined developing device 1LM is moved to the developing unit on the photosensitive drum 28. Then, the developing device 1LM is operated and developed by the developing device 1LM to form a toner image on the photosensitive drum 28.

  Thereafter, the toner image formed on the photosensitive drum 28 is transferred and superimposed on the intermediate transfer belt 24 by a transfer bias by the primary transfer roller 23 which is a “primary transfer unit”. As a result, the respective toner images are sequentially superimposed on the intermediate transfer belt 24 to form a full color toner image.

  The six-color toner images formed on the intermediate transfer belt 24 are transferred to the sheet 27 by the secondary transfer charger 23Z, and then pressed and heated by the fixing device 25 to obtain a permanent image. Further, the residual toner remaining on the photosensitive drum 28 after the transfer is removed by the cleaner 26.

  FIG. 2A is a schematic view of the vicinity of the developer storage unit 6 of the image forming apparatus 10 as viewed from the front. FIG. 2B is a schematic view of the vicinity of the developer storage unit 6 of the image forming apparatus 10 as viewed from the back side. As shown in FIGS. 2A and 2B, the developer storage unit 6 and the developer transport path 5 are connected, and when the developer is consumed by image formation, the developer is stored in the developer storage unit 6. To the developing device 1 through the transport pipe 5p of the developer transport path 5. The developer T replenished from the developer storage unit 6 is a mixture of the nonmagnetic toner and the magnetic carrier as described above. The nonmagnetic toner consumed by the image formation is replenished, and the magnetic carrier is replenished at the same time. Note that the amount of developer increases inside the developing device 1 by the amount of new magnetic carrier supplied to the developing device 1, and the increased amount is a developer discharge port (not shown) formed on the wall surface of the developing device 1. ).

  The position of the developer discharge port (not shown) is adjusted so that the two-component developer becomes 330 g within the developing device 1 and is stabilized. The discharged developer is collected on a collecting screw (not shown) provided at the center of the developing rotary 8 and collected on a waste toner box (not shown). In this embodiment, the weight ratio (referred to as CD ratio) of the nonmagnetic toner and the magnetic carrier filled in the developer storage unit 6 is set to 15%, but the CD ratio is not limited to that value.

  3A is an end view showing the developer transport path 5, and FIG. 3B is a cross-sectional view taken along the line AA in FIG. 3A. 3A and 3B, the developer transport path 5 includes a transport screw 5s that transports the developer T and a transport pipe 5p that encloses the transport screw 5s. The conveying screw 5s includes a shaft 5s1 and a blade 5s2.

  FIG. 3C is an explanatory view showing a transport mechanism of the developer T, and FIG. 3D is a cross-sectional view taken along the line BB in FIG. 3C. As shown in FIGS. 3C and 3D, the developer T moves inside the transport pipe 5p. In this case, the transport pipe 5p and the transport screw 5s do not move in the transport direction of the developer T. However, when the shaft 5s1 of the conveying screw 5s rotates, the point A on the blade 5s2 of the conveying screw 5s moves to the point A '. At this time, the developer T tends to continue to exist below the vertical direction inside the transport pipe 5p due to gravity. While the developer T remains at a fixed position in the circumferential direction of the transport pipe 5p, the blade 5s2 protrudes in the axial direction P along the shaft 5s1 of the transport screw 5s by the rotation of the shaft 5s1 of the transport screw 5s. Based on this force, the developer T is transported as the transport screw 5s rotates.

  FIG. 3E is an explanatory diagram that dynamically shows the developer transport mechanism. As shown in FIG. 3E, rotation of the blade 5s2 of the conveying screw 5s causes the developer T to generate an axial first component X1 in the axial direction P and a first circumferential component Y1 in the circumferential direction Q. To do. Since the circumferential first component Y1 is canceled by the gravity of the developer T itself, only the first axial component X1 remains, and the developer T is transported as the transport screw 5s rotates.

  However, when the degree of aggregation of the developer T increases due to factors such as temperature and the developer T starts to stick to the transport screw 5s, the transport mechanism described above is broken. Then, the transportability of the developer T is reduced or the developer T is clogged. This collapse of the transport mechanism will be described later.

  FIG. 4 is a graph showing a temperature rise transition in a place where the temperature is highest in the developer transport path 5 when the image forming apparatus 10 is continuously operated. Considering the actual use temperature when the user uses the image forming apparatus 10, the relationship between the numerical values of the temperature and time is graphed for each of the environmental temperature 25 ° C, the environmental temperature 30 ° C, and the environmental temperature 35 ° C. . As shown in FIG. 1, since the developing rotary 8 is disposed in the vicinity of the fixing device 25, the developer transport path 5 inside the developing rotary 8 is the hottest place.

  This temperature rise in the hottest place is based on the amount of heat received from the fixing device 25 and is not greatly affected by the outside air temperature of the image forming apparatus 10. Therefore, the temperature rise in the developer conveyance path 5 is saturated at about 46 ° C. to 48 ° C. without being greatly affected by the outside air environment. Therefore, it is important to ensure the conveying ability of the developer T around 48 ° C. in order to prevent clogging.

FIG. 5 is a graph showing a change in the degree of aggregation with respect to the temperature of the nonmagnetic toner in the developer T. The graph is created under multiple pressure conditions. Based on the increase in temperature and pressure, the cohesion tends to increase. In particular, with respect to temperature, the degree of aggregation increases rapidly from around 45 ° C. In this embodiment, the change in the degree of aggregation in the developer conveyance path 5 is substantially the same as the plot of the load of about 0.15 g / mm ^{2. In} the developer conveyance path 5, the load of toner is about 0.15 g / mm ² . It is speculated that it has received.

  Therefore, as shown in FIGS. 4 and 5, even if the toner in the developer T rises in temperature and the degree of aggregation is 60%, if there is no problem in the transportability, the developer transport path 5 develops at 48 ° C. It is considered that the conveying ability of the agent T can be guaranteed. Then, the image forming apparatus 10 can be provided with robustness that can sufficiently withstand continuous use by the user.

  By the way, when the aggregation degree of the toner in the developer T increases, as shown in [Table 1], clogging in the developer conveyance path 5 occurs as the aggregation degree increases. In particular, when the degree of aggregation is 60%, the number of occurrences of clogging is 80k. If the degree of aggregation is lower than 60%, there is no clogging even with 500k sheets. If the degree of aggregation is higher than 60%, clogging occurs with a smaller number of sheets.

FIG. 6A is an end view of the developer conveying path 5 showing the operation of the conveying screw 5s when the developer aggregate G adheres to the conveying screw 5s, and FIG. It is sectional drawing which follows the CC line of (a). FIG. 6C shows the developer transport path 5 showing the operation of the transport screw 5s when the developer T is brought into contact with the aggregate G after the developer aggregate G is adhered to the transport screw 5s. FIG. 6D is an end view, and FIG. 6D is a cross-sectional view taken along the line DD in FIG. 6C. FIG. 6E is an explanatory diagram that dynamically shows the force applied to the developer aggregate G attached to the conveying screw 5s.

  As described above, when the aggregation degree of the toner of the developer T increases, a part of the toner T is lightly adhered to the blade 5s2 of the conveying screw 5s as the aggregate G. As shown in FIGS. 6A and 6B, the aggregate G attached to the conveying screw 5s does not advance in the axial direction P of the conveying screw 5s, but only rotates in the circumferential direction Q of the conveying pipe 5p. As shown in FIGS. 6C and 6D, the developer T on the downstream side of the adhered aggregate G receives a reaction force from the aggregate G adhered to the conveying screw 5s.

The reaction force of the aggregate G cancels the force in the axial direction P, and the developer T does not move in the axial direction P. Instead, the force in the circumferential direction Q increases, and the gravity of the developer T itself cannot overcome this, and the developer T moves in the circumferential direction of the transport pipe 5p. Hereinafter, this is referred to as “spinning” of the developer T (especially because the specific gravity of the developer T is relatively light in the vicinity of 1 g / mm ³ ). Further, in the state where the developer T is swung around, the aggregate G only rotates at a fixed position in the axial direction P, and the subsequent developer T cannot move in the axial direction P. Finally, the developer T is clogged. It will lead to.

  The clogging of the developer T is caused by the toner in the developer T having a high degree of aggregation due to a temperature factor sticking lightly to the conveying screw 5s, and becomes an obstacle to the force component in the axial direction P. It begins by running away in the direction of rotation of the conveying screw 5s. The axial direction P is also the transport direction of the developer T.

  Fig.7 (a) is a schematic diagram explaining the idea of the countermeasure when the aggregate G sticks to the conveyance screw 5s, and FIG.7 (b) is a cross section along the EE line of Fig.7 (a). FIG. FIGS. 7C and 7D are schematic views for dynamically explaining an idea of countermeasures when the aggregate G adheres to the conveying screw 5s.

  As shown in FIGS. 7A and 7B, in order to prevent the developer T from escaping in the circumferential direction Q of the transport pipe 5p, the slipping property in the circumferential direction of the transport pipe 5p is reduced. It is effective to apply a resistance against the rotation of the developer T. In other words, it is considered effective to form an obstacle for preventing the stagnation from the transport pipe 5p toward the developer T.

  As shown in FIG. 7C, a reaction force from the conveying screw 5s is applied to the developer T, and this reaction force is an axial first component X1 directed in the positive direction of the axial direction P of the conveying pipe 5p. To the circumferential first component Y1 in the positive direction of the circumferential direction Q of the transport pipe 5p. In addition, the + direction of the axial direction P of the transport pipe 5p means “the transport direction of the developer T”. Further, the + direction of the circumferential direction Q of the transport pipe 5p means “the rotation direction of the developer T”.

  Further, the reaction force from the aggregate G is applied to the developer T, and this reaction force is the second axial component X2 in the negative direction of the axial direction P of the transport pipe 5p and the circumferential direction of the transport pipe 5p. It is component-divided by the circumferential second component Y2 in the + direction of Q.

  Further, the third component Y3 in the circumferential direction is applied to the developer T as “a resistance against the dragging from the conveying pipe 5p”.

  When the developer T receives the third circumferential component Y3 as a drag against the entrainment, the reaction force from the conveying screw 5s against the developer T is again canceled. Therefore, when the developer T receives the third circumferential component Y3 as a drag against the rotation, the rotational component applied to the developer T is reduced.

  As shown in FIG. 7D, the rotational torque of the conveying screw 5s is increased to counter the circumferential third component Y3, and the reaction force from the conveying screw 5s is increased. When the reaction force of the conveying screw 5s is disassembled, both the axial first component X1 and the circumferential first component Y1 increase. In particular, since the first axial component X1 applied to the developer T increases, the developer T that has been stuck to the transport screw 5s is transported, so that the clogging of the developer T is eliminated.

  If the sliding property of the transport pipe 5p is simply lowered, the share of the developer T with respect to the toner is increased, and the increase in the share causes a problem that the degree of aggregation of the developer T is further increased. However, as in this embodiment, considering the separation of the functions of the transport pipe 5p in the axial direction P and the circumferential direction Q, the slippage in the circumferential direction Q of the transport pipe 5p is reduced, and the axial direction P of the transport pipe 5p is reduced. The problem is solved by increasing the slipperiness. That is, the adverse effect of increasing the cohesion degree of the developer T while preventing the developer T from being dragged is avoided. As a result, the transport efficiency of the developer T increases and clogging of the developer transport path 5 is suppressed.

  FIG. 8A is an end view showing the developer transport path 5, and FIG. 8B is a cross-sectional view taken along line FF in FIG. 8A. As shown in FIGS. 8A and 8B, fine concave portions 5p3 and convex portions 5p2 are formed on the inner surface 5p1 of the transport pipe formed inside the transport pipe 5p. The concave portion 5p3 and the convex portion 5p2 extend in the axial direction P of the transport pipe 5p. Further, the concave portions 5p3 and the convex portions 5p2 are alternately arranged in the circumferential direction Q of the transport pipe 5p. Note that the widths of the concave portion 5p3 and the convex portion 5p2 can be formed in opposite sizes.

  Here, when the transport pipe inner wall surface 5p1 is tilted from the horizontal direction, 0.01 g of developer T placed on the transport pipe inner wall surface 5p1 slides out, and with respect to the transport pipe 5p. The relationship of developer slipperiness at which developer T slides is defined by the following equation (1).

According to this equation, when the slipperiness is good, the inner surface 5p1 of the transport pipe on which the developer T is placed slides from an angle close to the horizontal, so that the developer slipperiness increases. On the other hand, when the slipperiness is poor, the developer T cannot slide out unless the inner wall surface 5p1 of the transport pipe on which the developer T is placed has a substantially vertical angle. Become.

  In this case, the slipping property in the axial direction P of the transport pipe 5p included in the transport pipe inner wall surface 5p1 is set larger than the slip property in the circumferential direction Q of the transport pipe 5p included in the transport pipe inner wall surface 5p1. That is, the following equation (2) is set.

When this equation (2) is established, with respect to the friction coefficient μ of the conveyance pipe inner wall surface 5p1 of the conveyance pipe 5p, the friction coefficient μ1 in the axial direction P of the conveyance pipe 5p is larger than the friction coefficient μ2 in the circumferential direction Q of the conveyance pipe 5p. It will be set smaller. Moreover, in this embodiment, although the height difference of the mountain valley regarding the unevenness | corrugation of the cross section which cut the circumferential direction Q of the conveyance pipe 5p is formed at 100 micrometers, it is not limited to this.

  The lower limit of the coefficient of friction μ2 in the circumferential direction Q is preferably μ2 = 0.25 or more. This is because if the friction coefficient μ2 is further reduced, the drag that stops the rotation of the developer T becomes difficult in the first place. Accordingly, the higher the friction coefficient μ2 in the circumferential direction Q is, the higher the resistance from the side of the conveying pipe 5p to the surroundings of the developer T, which is preferable, but the practical upper limit is about μ2 = 1.3. This is because if the friction coefficient μ2 in the circumferential direction Q is increased too much, the developer T tends to adhere to the transport pipe 5p, and the motor torque for turning the transport screw 5s in the transport pipe 5p becomes insufficient. Considering this, the practical upper limit is about μ2 = 1.3.

  On the other hand, the friction coefficient μ1 in the axial direction P is preferably as low as possible, but the cost for material selection and surface processing (smooth) increases, so the practical lower limit is about μ1 = 0.04. The upper limit is preferably about μ1 = 0.5. This is because the friction generated during the conveyance of the developer T and the conveyance pipe 5p is suppressed as much as possible so that the developer T is not loaded and the toner contained in the developer T is prevented from being deteriorated. is there.

  Furthermore, as described above, the difference μ2−μ1 between the friction coefficients in the circumferential direction Q and the axial direction P is important in terms of transportability, and the difference μ2−μ1 is preferably set to 0.05 to 1.5. When the difference [mu] 2- [mu] 1 is set as large as possible, the effect related to the transportability is increased, but if the lower limit value 0.05 is exceeded, the superiority difference related to the transportability is not exhibited. In addition, the upper limit of the difference μ2−μ1 is about 1.2 due to the motor relationship and the cost relationship described above.

  The friction coefficient was measured using a Muse TYPE: 94i-II measuring instrument manufactured by Shinto Kagaku Co., Ltd. In the measurement, the coefficient of static friction between the contact (slider) on the measuring instrument side and the pipe (test object) is automatically calculated and displayed digitally. The friction coefficients μ1 and μ2 described in the present specification are expressed by the above-mentioned static friction coefficient values, and are used for quantifying the slipperiness of the conveying pipe. Further, since the measurement is performed inside the transport pipe 5p, the transport pipe 5p is cut into an appropriate small piece that can be measured with a contactor.

  The developer slipping property of the developer T inside the transport pipe 5p is measured in the axial direction P and the circumferential direction Q of the transport pipe 5p. In the axial direction P, when the developer sliding angle of the developer T is 45 °, the developer slipping property is 90 ° −45 ° = 45 °. In the circumferential direction Q, when the developer sliding angle of the developer T is 15 °, the developer slipping property is 90 ° −75 ° = 15 °. Therefore, it is confirmed that the sliding property in the axial direction P is set to be larger than the sliding property in the circumferential direction Q on the inner wall surface 5p1 of the transport pipe.

Further, as a result of measuring the feeding pressure of the developer T in the transport pipe, it is 0.58 g / mm ² when nothing is applied to the conventional transport pipe 5p. It was confirmed that the transport pipe 5p was increased to 0.76 g / mm ² which is about 1.3 times. The feeding pressure of the developer T is calculated by attaching a rubber curtain whose elongation with respect to force is previously known to the end of the transport pipe 5p and converting the elongation amount of the rubber curtain into pressure.

  As a result, in the above-described conventional example, when the aggregation degree of the toner in the developer T is 60%, the number of occurrences of clogging is 80k sheets, but in this embodiment, when the aggregation degree is 60%, 120k sheets. It was confirmed that clogging of the developer transport path 5 did not occur.

As described above, the cohesion degree of 60% is a state of the developer which is an index under severe use conditions such as high ambient temperature and continuous use. However, in the configuration of the first embodiment, about 60 k sheets are blocked. This means that the maintenance interval can be expanded.

(Second Embodiment)
FIG. 9A is an end view showing the developer transport path 35 according to the second embodiment, and FIG. 9B is a cross-sectional view taken along the line HH of FIG. 9A. The basic configuration of the image forming apparatus according to the second embodiment of the present invention is substantially the same as the basic configuration of the image forming apparatus 10 according to the first embodiment of the present invention. However, the conveyance pipe 35p of the image forming apparatus according to the second embodiment is different from the conveyance pipe 5p of the image forming apparatus 10 according to the first embodiment. In addition, about the structure same as the structure of 1st Embodiment of this invention, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIGS. 9A and 9B, a plurality of rib portions 36 extend in the axial direction on the inner surface 35p1 of the transport pipe. A single rib portion 36 may extend in the axial direction on the inner surface 35p1 of the transport pipe. Thereby, the slipping property in the axial direction P of the transport pipe 35p is set to be larger than the slipping property in the circumferential direction of the transport pipe 35p. In the present embodiment, for example, the difference between the top and valley of the rib portion 36 on the inner wall surface 35p1 of the transport pipe is set to 750 μm, and the width of the rib portion 36 is set to 1 mm. However, the shape of the rib part 36 is not limited to this.

  A gap is provided between the rib portion 36 and the conveying screw 5s. The inner diameter of the transport pipe 35p is set to a minimum at the rib portion 36, and the rib portion 36 is prevented from touching the transport screw 5s. When the toner in the developer is sandwiched between portions where two objects, for example, the rib portion 36 and the conveying screw 5s are rubbed and receive excessive pressure, an aggregate G is generated by the stress. This agglomerate G appears as a defective image in the image during development. That is, it is preferable that the object inside the developer conveyance path 5 is not rubbed as much as possible.

  The developer slipping property of the developer T inside the transport pipe 35p is measured in the axial direction P and the circumferential direction Q of the transport pipe 35p. In the axial direction P, when the developer sliding angle of the developer T is 45 °, the developer slipping property is 90 ° −45 ° = 45 °. In the circumferential direction Q, when the developer sliding angle is 83 °, the developer slipping property is 90 ° −83 ° = 7 °. Therefore, it is confirmed that the sliding property in the axial direction P is set to be larger than the sliding property in the circumferential direction Q on the inner wall surface 35p1 of the transport pipe.

Further, as a result of measuring the feeding pressure of the developer T in the transport pipe 35p, the value is 0.58 g / mm ² when nothing is applied to the conventional transport pipe, whereas in the present embodiment, In the conveyance pipe 35p, it was confirmed that it was increased to 0.88 g / mm ² which is about 1.5 times.

  As a result, in the above-described conventional example, when the aggregation degree of the toner in the developer T is 60%, the number of occurrences of clogging is 80k, but in this embodiment, when the aggregation degree is 60%, 160k sheets. It was confirmed that no clogging of the developer transport path 35 occurred.

As described above, the cohesion degree of 60% is a state of the developer that serves as an index under severe use conditions such that the environmental temperature is high and continuous use is performed. In the configuration of the second embodiment, the maintenance interval for clogging of about 80k sheets can be expanded without the adverse effect of the occurrence of aggregate G of developer T.

(Third embodiment)
FIG. 10A is an end view showing a developer transport path 45 according to the third embodiment, and FIG. 10B is a cross-sectional view taken along the line II of FIG. 10A. The basic configuration of the image forming apparatus according to the third embodiment of the present invention is substantially the same as the basic configuration of the image forming apparatus 10 according to the first embodiment of the present invention. However, the conveyance pipe 45p of the image forming apparatus according to the third embodiment is different from the conveyance pipe 5p of the image forming apparatus 10 according to the first embodiment. In addition, about the structure same as the structure of 1st Embodiment of this invention, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIGS. 10A and 10B, a magnet 46 is attached to the outer surface 45p2 of the transport pipe in the axial direction of the transport pipe 45p. When such a magnet 46 is attached, when the developer T passes through the inside of the transport pipe 45p, a carrier spike 47 is formed on the transport pipe inner wall surface 45p1 in parallel with the axial direction P of the transport pipe 45p. The magnet 46 may be attached not to the outer surface 45p2 of the transport pipe but to the inner surface 45p1 of the transport pipe.

  When the carrier spike 47 is formed on the inner wall surface 45p1 of the transport pipe, the developer slip in the axial direction P of the transport pipe 45p is set larger than the developer slip in the circumferential direction Q of the transport pipe 45p. The

  In this embodiment, the carrier head 47 extending parallel to the axial direction P of the developer T inside the transport pipe 45p is configured to come into contact with a part of the transport screw 5s. Since the carrier spike 47 hits the conveying screw 5s, the aggregate G of the developer T due to the pressure stress concerned in the second embodiment is not generated. Therefore, since the carrier spike 47 is reliably brought into contact with the conveying screw 5s, the slipping property in the circumferential direction Q of the conveying pipe 45p can be reliably suppressed.

  In particular, also in the third embodiment, as in the first embodiment, the developer T contains a carrier that is a magnetic powder together with the toner. As a result, even if the carrier forming the spikes is peeled off from the inner surface 45p1 of the transport pipe of the developer transport path 45, the carriers are compensated directly and the carrier spikes 47 can be kept constant.

  The developer slip of the developer T inside the transport pipe 45p is measured in the axial direction P and the circumferential direction Q of the transport pipe 45p. In the axial direction P, when the developer sliding angle of the developer T is 45 °, the developer slipping property is 90 ° −45 ° = 45 °. In the circumferential direction Q, when the developer sliding angle is 90 °, the developer slipping property is 90 ° −90 ° = 0 °. Therefore, it is confirmed that the slipping property in the axial direction P is set to be larger than the slipping property in the circumferential direction Q on the inner wall surface 45p1 of the transport pipe.

Further, as a result of measuring the feeding pressure of the developer T in the transport pipe, the transport pressure of the present embodiment is 0.58 g / mm ² when nothing is applied to the conventional transport pipe. It was confirmed that the pipe 45p was increased to 1.00 g / mm ² which is about 1.72 times.

  As a result, in the above-described conventional example, when the aggregation degree of the toner in the developer T is 60%, the number of occurrences of clogging is 80k sheets, but in this embodiment, when the aggregation degree is 60%, 500k sheets. It was confirmed that no clogging of the developer conveyance path 45 occurred.

As described above, the cohesion degree of 60% is a state of the developer that serves as an index under severe use conditions such that the environmental temperature is high and continuous use is performed. In the configuration of the third embodiment, maintenance for clogging becomes unnecessary even if the life of the main body is exceeded, without the adverse effect of the occurrence of aggregate G of developer T.

  As described above, according to the first and second embodiments of the present invention, the friction coefficient in the axial direction P of the transport pipes 5p, 35p, 45p is the transport pipes 5p, 35p in the transport pipe inner wall surfaces 5p1, 35p1, 45p1. , 45p is set smaller than the friction coefficient in the circumferential direction Q. For this reason, the slipping property in the axial direction P of the transport pipes 5p, 35p, and 45p included in the transport pipe inner wall surfaces 5p1, 35p1, and 45p1 is increased. At the same time, the slipperiness in the circumferential direction Q of the transfer pipes 5p, 35p, and 45p included in the transfer pipe inner wall surfaces 5p1, 35p1, and 45p1 is reduced. Therefore, in the axial direction P of the transport pipes 5p, 35p, 45p, the efficiency of movement of the developer T increases. At the same time, the accompanying rotation of the developer T is reduced in the circumferential direction Q of the transport pipe 5p. As a result, clogging of the developer T is suppressed inside the transport pipes 5p, 35p, and 45p.

  Further, since it is not necessary to increase the share of the transport pipe 5p in the axial direction P, the developer T can be transported with increased transport efficiency without increasing the degree of aggregation of the toner in the developer T. Therefore, when the temperature in the apparatus rises due to continuous use of the image forming apparatus 10, the toner that is the developer T increases in the degree of aggregation, and the stuck toner can be transported. Maintenance interval can be increased and maintenance-free can be expected.

  If the friction coefficient in the axial direction P of the transport pipes 5p, 35p, 45p included in the inner wall surfaces 5p1, 35p1, 45p1 of the transport pipe is small, the slipping property in the axial direction P of the transport pipes 5p, 35p, 45p is high. At the same time, if the friction coefficient in the circumferential direction Q of the conveying pipes 5p, 35p, 45p included in the inner wall surfaces 5p1, 35p1, 45p1 of the conveying pipe is large, the slipping property in the circumferential direction Q of the conveying pipes 5p, 35p, 45p is low.

  In the first embodiment of the present invention, since the concave portion 5p3 and the convex portion 5p2 extend in the axial direction P of the transport pipe 5p, there is no object to be caught by the developer T in the axial direction P of the transport pipe 5p. Therefore, the developer T easily moves in the axial direction P of the transport pipe 5p. Further, when the concave portions 5p3 and the convex portions 5p2 are alternately arranged in the circumferential direction Q of the transport pipe 5p, the developer T is caught by the concave portions 5p3 and the convex portions 5p2 in the circumferential direction Q of the transport pipe 5p. Therefore, the developer T is difficult to move in the circumferential direction Q of the transport pipe 5p.

  In the second embodiment of the present invention, since the rib portion 36 extends in the axial direction P of the transport pipe 35p, there is no object to be caught by the developer T in the axial direction P of the transport pipe 35p. Therefore, the developer T easily moves in the axial direction P of the transport pipe 35p. Further, the rib portion 36 suppresses the movement of the developer T in the circumferential direction Q of the transport pipe 35p. Therefore, the developer T hardly moves in the circumferential direction Q of the transport pipe 35p.

  When a gap is secured between the rib portion 36 and the conveying screw 5s, the rib portion 36 and the conveying screw 5s are not squeezed into a portion where they are rubbed and receive excessive pressure, and the stress agglomerates. The product G is not generated. As a result, a defective image based on the aggregate G is hardly formed.

  In the third embodiment of the present invention, the magnet 46 attached to the transport pipe 45p in the axial direction of the transport pipe 45p forms a carrier spike 47 extending in parallel with the axial direction P of the transport pipe 45p inside the transport pipe 45p. To do. Therefore, the developer T is easy to move in the axial direction P of the transport pipe 45p. Further, the carrier spike 47 suppresses the movement of the developer T in the circumferential direction Q of the transport pipe 45p. Therefore, the developer T is unlikely to move in the circumferential direction Q of the transport pipe 45p. In addition, when the magnet 46 is comprised with an electromagnet, the carrier head 47 can also be attached or detached.

  The carrier spike 47 does not get caught between the rib part and the part where the conveying screw 5s is rubbed and receives excessive pressure, and the aggregate G is not generated by the stress. As a result, a defective image based on the aggregate G is hardly formed.

  Even if the carrier forming the carrier spike 47 is peeled off from the transport flow of the developer T, the carrier is supplemented directly, and the amount of the carrier spike 47 is kept constant.

1 is a configuration diagram illustrating an image forming apparatus according to a first embodiment of the present invention. (A) is the schematic diagram which looked at the vicinity of the developer storage part of an image forming apparatus from the front, (b) is the schematic diagram which looked at the vicinity of the developer storage part of an image forming apparatus from the back surface. (A) is an end view which shows a developer conveyance path | route, (b) is sectional drawing which follows the AA line of (a). (C) is explanatory drawing which shows the conveyance mechanism of a developer, (d) is sectional drawing which follows the BB line of (c). (E) is explanatory drawing which shows dynamically the conveyance mechanism of a developer. 6 is a graph showing a temperature rise transition in a place where the temperature is highest in the developer conveyance path when the image forming apparatus is operated continuously. It is a graph which shows the change of the aggregation degree with respect to the temperature of the nonmagnetic toner in a developing agent. (A) is an end view of the developer conveying path showing the operation of the conveying screw when the developer aggregates adhere to the conveying screw, and (b) is along the CC line of (a). It is sectional drawing. (C) is an end view of the developer conveying path showing the operation of the conveying screw when the developer T comes into contact with the aggregate G after the developer aggregate has adhered to the conveying screw; ) Is a cross-sectional view taken along line DD in (c). (E) is explanatory drawing which shows dynamically the force concerning the aggregate of the developer stuck on the conveyance screw. (A) is a schematic diagram explaining the idea of a countermeasure when an aggregate adheres to a conveyance screw, (b) is sectional drawing which follows the (a) EE line. (C), (d) is a schematic diagram which explains dynamically the idea of the countermeasure when an aggregate adheres to a conveyance screw. (A) is an end view which shows a developer conveyance path | route, (b) is sectional drawing which follows the FF line of (a). (A) is an end view showing a developer conveyance path of the image forming apparatus according to the second embodiment, and (b) is a cross-sectional view taken along line HH in (a). (A) is an end view showing a developer conveyance path of an image forming apparatus according to a third embodiment, and (b) is a cross-sectional view taken along line II of (a).

Explanation of symbols

1LM, 1LC, 1Y, 1M, 1C, 1K ... Developer 5, 35, 45 ... Developer transport path 6 ... Developer storage 5p, 35p, 45p Transport Pipe 5s ················ Conveying screw 5p1, 35p1, 45p1 ······························································· ······································· Developer G

Claims (7)

In an image forming apparatus that includes a developer conveying path having a conveying screw that conveys a developer and a conveying pipe that encloses the conveying screw, and conveys the developer from a developer storage unit that stores the developer to a developing device.
The friction coefficient in the axial direction of the transport pipe that the inner wall surface of the transport pipe formed inside the transport pipe has a smaller friction coefficient in the circumferential direction of the transport pipe that the inner wall surface of the transport pipe has. An image forming apparatus.   The recesses and projections extend in the axial direction of the transport pipe on the inner wall surface of the transport pipe, and the recesses and the projections are alternately arranged in the circumferential direction of the transport pipe. The image forming apparatus described in 1. In an image forming apparatus that includes a developer conveying path having a conveying screw that conveys a developer and a conveying pipe that encloses the conveying screw, and conveys the developer from a developer storage unit that stores the developer to a developing device.
An image forming apparatus, wherein a rib portion extending in an axial direction of the transport pipe is provided on an inner wall surface of the transport pipe formed inside the transport pipe.   The image forming apparatus according to claim 3, wherein a gap is secured between the rib portion and the conveying screw. In an image forming apparatus that includes a developer conveying path having a conveying screw that conveys a developer and a conveying pipe that encloses the conveying screw, and conveys the developer from a developer storage unit that stores the developer to a developing device.
An image forming apparatus comprising: a carrier attached to the transport pipe in an axial direction of the transport pipe to form an ear of a carrier extending parallel to the axial direction of the transport pipe inside the transport pipe.   6. The image forming apparatus according to claim 5, wherein the rising of the carrier contacts a part of the conveying screw.   The image forming apparatus according to claim 5, wherein the developer contains toner and a carrier that is magnetic powder.