Drive unit, transport unit, and image forming apparatus

Abstract

To achieve an increase in the tension of a belt while improving the degree of freedom of design change and suppressing an increase in energization force of energizing member.SOLUTION: A driving force transmission mechanism 60 includes an endless belt 55, a pressing member 61 for pressing the belt 55, a first link member 62 provided rotatably around a first spindle 48 to hold the pressing member 61, a second link member 63 provided rotatably around a second spindle 49 to press the first link member 62, and an energizing member 64 for energizing the second link member 63 such that the pressing member 61 presses the belt 55. Relations of L1>L2, L3>L4 are satisfied when a distance between an energization position of the energizing member 64 and the second spindle 49 is regarded as L1, a distance between a pressing position of the second link member 63 and the second spindle 49 is regarded as L2, a distance between a pressing position of the second link member 63 and the first spindle 48 is regarded as L3, and a distance between a pressing position of the pressing member 61 and the first spindle 48 is regarded as L4.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a drive device, a conveyance device, and an image forming device.

Background Art

[0002] As a drive device mounted on an image forming device such as a printer, a fax machine, or a copier, a device including an endless belt is known.

[0003] Such a drive device includes, in addition to the belt, a drive roller that rotationally drives the belt, a driven roller that cooperates with the drive roller to stretch the belt, a tension roller that applies tension to the belt, and the like. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 8-14342) discloses a configuration in which a tension roller is biased by a spring to apply tension to the belt.

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the drive device as described above, when the torque for driving the drive object increases, a large load is applied between the belt and each roller that stretches the belt, so there is a risk of rotational displacement such as slip or tooth skipping between the belt and the roller.

[0005] As a method for preventing such rotational displacement, there is a method of increasing the biasing force of the spring that biases the tension roller to increase the pressing force of the tension roller on the belt. However, when the biasing force of the spring is increased, there is a problem that the assembly work of the components including the spring becomes difficult. Further, as another method, there is a method of changing the shape of the link member that holds the tension roller or the arrangement of the spring that biases the link member, thereby changing the positions of the force point, the fulcrum point, and the action point of the lever principle to increase the pressing force of the tension roller. However, in the case of this method, due to the constraints of the component layout, it may be difficult to change the shape of the link member or the arrangement of the spring. [Means for solving the problem]

[0006] To solve the above problems, the present invention provides a drive device equipped with a drive force transmission mechanism for transmitting the driving force of a drive source to a drive target member, wherein the drive force transmission mechanism comprises an endless belt stretched by a plurality of rotating bodies, a pressing member that presses the belt and applies tension to the belt, a first link member that is rotatably provided around a first support shaft and holds the pressing member, a second link member that is rotatably provided around a second support shaft and presses the first link member, and the pressing member presses the belt If a biasing member is provided to bias the second link member, and the distance between the biasing position where the biasing member biases the second link member and the second support shaft is L1, the distance between the pressing position where the second link member presses the first link member and the second support shaft is L2, the distance between the pressing position where the second link member presses the first link member and the first support shaft is L3, and the distance between the pressing position where the pressing member presses the belt and the first support shaft is L4, then the relationships L1 > L2 and L3 > L4 are satisfied. The first link member and the second link member each have a pair of opposing pieces facing each other and a bent portion connecting the opposing pieces, the second link member is inserted into the first link member, and the second support shaft is provided in the portion where the opposing pieces of the first link member and the opposing pieces of the second link member overlap. It is characterized by the following: [Effects of the Invention]

[0007] According to the present invention, the degree of freedom for design changes is improved, and the tension of the belt can be increased while suppressing an increase in the biasing force of the biasing member. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows one embodiment of the image forming apparatus according to the present invention. [Figure 2] This figure shows the configuration of the drive device according to this embodiment. [Figure 3] This is a perspective view showing the configuration of the tension-applying mechanism according to this embodiment. [Figure 4] This is a side view showing the configuration of the tension-applying mechanism according to this embodiment. [Figure 5] This is a perspective view illustrating the connection structure between the first link member and the second link member. [Figure 6] This diagram shows the configuration of the tension-applying mechanism according to the second embodiment of the present invention. [Figure 7] This diagram shows the configuration of the tension-applying mechanism according to the third embodiment of the present invention. [Figure 8] This figure shows the configuration of the comparative example. [Modes for carrying out the invention]

[0009] The present invention will be described below with reference to the attached drawings. In each drawing used to explain the present invention, components such as members and parts having the same function or shape will be given the same reference numerals to the extent possible so that they can be distinguished, and their description will be omitted after they have been described once.

[0010] Figure 1 shows one embodiment of the image forming apparatus according to the present invention. Here, "image forming apparatus" in this specification includes printers, copiers, facsimile machines, printing presses, or multifunction devices that combine two or more of these. In the following description, an electrophotographic image forming apparatus will be given as an example, but the image forming method may be an inkjet method or the like, in addition to the electrophotographic method. Furthermore, "image forming" in this specification means not only forming images that have meaning, such as characters and figures, but also forming images that do not have meaning, such as patterns. First, the overall configuration and operation of the image forming apparatus according to this embodiment will be described with reference to Figure 1.

[0011] As shown in Figure 1, the image forming apparatus 100 according to this embodiment includes a document transport unit 1 for transporting documents, an image reading unit 2 for reading images from documents, an image forming unit 3 for forming images on a recording medium, a fixing unit 4 for fixing images to the recording medium, a recording medium supply unit 5 for supplying recording mediums, and a recording medium discharge unit 6 for discharging recording mediums.

[0012] The document transport unit 1 is equipped with a document supply tray 25 on which documents are placed, a plurality of transport rollers 26 that transport documents from the document supply tray 25 toward the contact glass 32 of the image reading unit 2, and a document discharge tray 27 from which documents are discharged.

[0013] The image reading unit 2 is equipped with a contact glass 32 and an optical scanning unit 31 that reads the image of the document on the contact glass 32. The optical scanning unit 31 includes a light source that illuminates the document with light, as well as a CCD (charge-coupled device) that reads the image from the reflected light of the light illuminated on the document. Alternatively, other image sensors, such as a contact image sensor (CIS), may be used instead of the CCD to read the image. The optical scanning unit 31 moves in the direction of the arrow in Figure 1 (sub-scanning direction) by a carrier acting as a drive device, and captures an image of the document by forming an image on the imaging element via a lens. Furthermore, the image reading unit 2 is not mounted on the image forming apparatus 100, but may be installed in a separate location away from the image forming apparatus 100 and capable of communicating with the image forming apparatus 100 via wired or wireless means.

[0014] The image forming unit 3 is equipped with four image forming units 10Y, 10M, 10C, and 10Bk, an image writing device 7 that writes an electrostatic latent image to the photoreceptor 11 of each image forming unit 10Y, 10M, 10C, and 10Bk, and a transfer device 8 that transfers the image to a recording medium.

[0015] Each image-forming unit 10Y, 10M, 10C, and 10Bk has essentially the same configuration, except that they contain toners (developers) of different colors: yellow, magenta, cyan, and black, which correspond to the color separation components of a color image. Specifically, each image-forming unit 10Y, 10M, 10C, and 10Bk includes a photoreceptor 11 as an image carrier that carries an image on its surface, a charging member 12 that charges the surface of the photoreceptor 11, a developing device 13 that supplies toner as a developer to the surface of the photoreceptor 11 to form a toner image, and a cleaning device 14 that cleans the surface of the photoreceptor 11.

[0016] The image writing device 7 has an LD (laser diode) or the like that irradiates light (laser beam) onto the surface of the photoreceptor 11. The image writing device 7 modulates the drive signal of the LD according to image data, and writes an electrostatic latent image onto the photoreceptor 11 with the light irradiated from the LD.

[0017] The transfer device 8 has an intermediate transfer belt 15, a primary transfer roller 16, and a secondary transfer roller 17. The intermediate transfer belt 15 is constituted by an endless belt and is stretched by a plurality of rollers. Four primary transfer rollers 16 are provided inside the intermediate transfer belt 15. When each primary transfer roller 16 contacts each photoreceptor 11 via the intermediate transfer belt 15, a primary transfer portion (primary transfer nip) is formed between the intermediate transfer belt 15 and each photoreceptor 11. The secondary transfer roller 17 contacts the outer peripheral surface of the intermediate transfer belt 15 and forms a secondary transfer portion (secondary transfer nip).

[0018] The fixing unit 4 is provided with a fixing rotating body 21 heated by a heating source such as a heater, and a pressing rotating body 22 that presses against the fixing rotating body 21 to form a fixing nip.

[0019] The recording medium supply unit 5 is provided with a paper feed cassette 18 that houses paper as the recording medium, and a paper feed roller 19 that feeds out the paper from the paper feed cassette 18. Hereinafter, the "recording medium" will be described as "paper", but the "recording medium" is not limited to paper. The "recording medium" includes not only paper but also OHP sheets, cloth, metal sheets, plastic films, or prepreg sheets in which carbon fibers are impregnated with resin in advance. Also, the "paper" includes, in addition to ordinary paper, cardboard, postcards, envelopes, tissue paper, coated paper (such as coated paper and art paper), tracing paper, and the like.

[0020] The recording medium discharge unit 6 is provided with a pair of paper discharge rollers 23 that discharge the paper, and a paper discharge tray 24 on which the discharged paper is placed.

[0021] Next, with reference to FIG. 1, the printing operation of the image forming apparatus 100 according to the present embodiment will be described.

[0022] When an instruction for image formation is given, first, the image reading unit 2 reads an image on the document. This document is a document conveyed from the document supply tray 25 to the contact glass 32 or a document placed on the contact glass 32, and the image of the document passing or placed on the contact glass 32 is read by the optical scanning unit 31 of the image reading unit 2, and the read image data is sent to the image forming unit 3.

[0023] In the image forming unit 3, the photoreceptors 11 of the respective image forming units 10Y, 10M, 10C, and 10Bk start to rotate, and the surface of the photoreceptor 11 is charged to a uniform high potential by the charging member 12. Next, based on the image information of the document read by the image reading unit 2, the image writing device 7 irradiates light onto the surface (charged surface) of each photoreceptor 11. As a result, the potential of the portion irradiated with light decreases, and an electrostatic latent image is formed on the surface of each photoreceptor 11. Then, the developing device 13 supplies toner to this electrostatic latent image, and a toner image is formed on each photoreceptor 11.

[0024] When the toner images formed on each photoreceptor 11 reach the primary transfer portion (the position of the primary transfer roller 16) as the photoreceptors 11 rotate, they are transferred onto the rotating intermediate transfer belt 15 so as to sequentially overlap. Thus, a full-color toner image is formed on the intermediate transfer belt 15. Note that a monochromatic image can be formed using any one of the image forming units 10Y, 10M, 10C, and 10Bk, or a two-color or three-color image can be formed using any two or three of them. Also, after the toner image is transferred from the photoreceptor 11 to the intermediate transfer belt 15, the cleaning device 14 removes residual toner and the like on the photoreceptor 11.

[0025] The toner image on the intermediate transfer belt 15 is transported to the secondary transfer section (the position of the secondary transfer roller 17) as the intermediate transfer belt 15 rotates, and is transferred onto the paper in the secondary transfer section. This paper is supplied from the paper feed cassette 18, and the paper is fed out of the paper feed cassette 18 as the paper feed roller 19 rotates. The fed paper is temporarily stopped by a pair of timing rollers 20, and then transported by the timing rollers 20 in time with the toner image on the intermediate transfer belt 15 reaching the secondary transfer section.

[0026] The paper is then transported to the fuser unit 4, where the toner image on the paper is heated and pressurized by the fuser rotating body 21 and the pressurizing rotating body 22, fixing the toner image to the paper. After that, the paper is discharged from the device by the paper discharge roller 23 and placed on the paper discharge tray 24. This completes the series of image forming operations.

[0027] Figure 2 shows the configuration of the drive device 40 that drives the secondary transfer roller 17.

[0028] As shown in Figure 2, the drive device 40 according to this embodiment includes an electric motor 39 which is a drive source, and a drive force transmission mechanism 50 which transmits the driving force of the electric motor 39 to the secondary transfer roller 17 which is the member to be driven.

[0029] The power transmission mechanism 50 includes an input gear 51 to which the power of the electric motor 39 is input, an input shaft 52 connected to the input gear 51, a drive pulley 53 as a driving rotating body provided on the input shaft 52, a driven pulley 54 as a driven rotating body, an endless belt 55 stretched by the drive pulley 53 and the driven pulley 54, an output gear 56 provided on the rotating shaft of the driven pulley 54, a secondary transfer roller gear 57 that meshes with the output gear 56, and a tensioning mechanism 60 that applies tension to the belt 55.

[0030] As shown in Figure 2, a coupling mechanism 41 is provided at one end of the input shaft 52, and the input shaft 52 is connected to the rotating shaft of the input gear 51 via this coupling mechanism 41. A drive pulley 53 is provided at the end of the input shaft 52 opposite to the end on the coupling mechanism 41 side.

[0031] In the drive device 40 according to this embodiment, when the electric motor 39 starts rotating and the driving force of the electric motor 39 is input to the input gear 51, the input gear 51 rotates, and consequently the input shaft 52 and the drive pulley 53 rotate. Then, the rotation of the drive pulley 53 causes the belt 55 and the driven pulley 54 to rotate, and furthermore, the output gear 56 and the secondary transfer roller gear 57 that meshes with it also rotate. As a result, the secondary transfer roller 17, which has the secondary transfer roller gear 57 at one end, rotates. In this way, the driving force is transmitted from the electric motor 39 to the secondary transfer roller 17.

[0032] Next, the configuration of the tension-applying mechanism 60 will be explained based on Figures 3 to 5.

[0033] As shown in Figures 3 and 4, the tensioning mechanism 60 includes a tension roller 61 as a pressing member that presses the belt 55, a first link member 62 that holds the tension roller 61, a second link member 63 that moves the first link member 62, and a spring 64 as a biasing member that biases the second link member 63.

[0034] The tension roller 61 presses against the outer surface of the belt 55 between the drive pulley 53 and the driven pulley 54. The tension roller 61 is rotatably held by a first link member 62. The first link member 62 is rotatably supported by a first support shaft 48 provided on a side plate 58, which is a support member.

[0035] On the other hand, the second link member 63 is rotatably supported around a second support shaft 49 provided on the first link member 62. The second link member 63 also has an arm-shaped portion 63a, and one end 64a of the spring 64 is locked to a concave locking portion 63b (see Figure 5) provided at the tip of this arm-shaped portion 63a. The other end 64b of the spring 64 is locked to a pin-shaped locking portion 58a protruding from the side plate 58. As a result, the tensile force of the spring 64 is applied to the second link member 63.

[0036] As shown in Figure 5, both the first link member 62 and the second link member 63 in this embodiment are formed in a U-shape in cross-section and have opposing pieces 62e1, 62e2, 63e1, and 63e2 that are folded back via U-shaped bent portions 62f and 63f. Of the pair of opposing pieces 62e1 and 62e2 of the first link member 62, a tension roller 61 is rotatably attached to the opposing piece 62e1 closer to the side plate 58. On the other hand, of the pair of opposing pieces 63e1 and 63e2 of the second link member 63, a portion (an arm-like extension) 63a is provided on the opposing piece 63e1 closer to the side plate 58, to which a spring 64 is locked.

[0037] Furthermore, as shown in Figure 5, an opening 62a is provided in the bent portion 62f of the first link member 62, and the second link member 63 is inserted into the first link member 62 through this opening 62a. In addition, the second support shaft 49 passes through the overlapping portion of the opposing pieces 62e1, 62e2, 63e1, and 63e2 of the first link member 62 and the second link member 63 when the second link member 63 is inserted into the first link member 62, and is fixed to the opposing pieces 62e1 and 62e2 of the first link member 62. In this way, the first link member 62 and the second link member 63 are connected so as to be able to swing relative to each other via the second support shaft 49. Alternatively, the second support shaft 49 may be fixed to the opposing pieces 63e1 and 63e2 of the second link member 63 and rotatably inserted into the holes provided in the opposing pieces 62e1 and 62e2 of the first link member 62. On the other hand, the first support shaft 48 passes through a pair of opposing pieces 62e1 and 62e2 of the first link member 62 and is fixed to the side plate 58. As a result, the first link member 62 is pivotably mounted to the side plate 58. Alternatively, the first support shaft 48 may be fixed to each of the opposing pieces 62e1 and 62e2 of the first link member 62 and rotatably inserted into a hole provided in the side plate 58.

[0038] In the tensioning mechanism 60 configured as described above, when the second link member 63 is pulled by the spring 64 in the direction of the arrow shown in Figure 4, the second link member 63 rotates clockwise around the second support shaft 49 in Figure 4 due to the biasing force of the spring 64. When the second link member 63 rotates at this time, it comes into contact with the edge 62d (see Figure 5) of the opening 62a of the first link member 62 and presses against that edge 62d. As a result, the first link member 62 rotates clockwise around the first support shaft 48 in Figure 4, and the tension roller 61 held by the first link member 62 presses against the outer surface of the belt 55.

[0039] Here, as shown in Figure 4, if we define L1 as the distance between the point of force application A, which is the biasing position where the spring 64 biases the second link member 63, and the fulcrum B of the second support shaft 49, and L2 as the distance between the point of application C, which is the pressing position where the second link member 63 presses the first link member 62, and the fulcrum B of the second support shaft 49, then the positions of the point of force application A, the fulcrum B, and the point of application C are set such that the relationship L1 > L2 is satisfied. Furthermore, if we define L3 as the distance between the point of force application D, which is the pressing position where the second link member 63 presses the first link member 62, and the fulcrum E of the first support shaft 48, and L4 as the distance between the point of application F, which is the pressing position where the tension roller 61 presses the belt 55, and the fulcrum E of the first support shaft 48, then the positions of the point of force application D, the fulcrum E, and the point of application F are set such that the relationship L3 > L4 is satisfied.

[0040] Thus, in this embodiment, the positions of each point of force application, each fulcrum, and each point of application are set such that the relationships L1 > L2 and L3 > L4 are satisfied, and the biasing force of the spring 64 is increased by the lever principle and transmitted to the tension roller 61. As a result, the tension roller 61 presses against the surface of the belt 55 with the increased force, and tension is applied to the belt 55.

[0041] Furthermore, in this embodiment, two link members 62 and 63 are used to transmit the biasing force of the spring 64 to the tension roller 61. This configuration, which transmits the biasing force via two link members 62 and 63, has the following advantages compared to the configuration shown in Figure 8, which transmits the biasing force of the spring 72 using a single link member 71 that rotates around a single pivot point G.

[0042] First, in the embodiment of the present invention, the biasing force of the spring 64 is transmitted via two link members 62 and 63 with different fulcrums. Compared to the configuration shown in Figure 8, where the biasing force of the spring 72 is transmitted to the tension roller 73 via a single link member 71, this has the advantage of effectively increasing the pressing force of the tension roller. In other words, in the embodiment of the present invention, the force is increased using the principle of a two-stage lever, so a large pressing force can be obtained.

[0043] Next, the second advantage is that the embodiment of the present invention offers greater freedom in design modifications compared to the example shown in Figure 8. The pressing force of the tension roller is influenced not only by the magnitude of the spring biasing force, but also by the positional relationship and relative distance of the point of force application, the fulcrum, and the point of application. By changing these positional relationships and relative distances, the pressing force of the tension roller can be increased. However, in the example shown in Figure 8, there is only one link member 71, so there are few variations in the selectable arrangement of the point of force application, the fulcrum, and the point of application, and the component layout is easily constrained. In contrast, in the embodiment of the present invention, two link members 62 and 63 are used, so there are two points of force application, two fulcrums, and two points of application, and the variations in their arrangement are greater. For this reason, the embodiment of the present invention is less constrained by the component layout compared to the example shown in Figure 8, and it is easier to make design modifications to increase the pressing force of the tension roller.

[0044] As described above, according to the embodiment of the present invention, by using multiple link members, the pressing force of the tension roller can be increased and the belt tension increased without significantly increasing the spring biasing force compared to the example shown in Figure 8. Therefore, rotational displacement such as slippage or tooth skipping between the belt and roller can be suppressed with a relatively small spring biasing force. In addition, the problem of reduced ease of assembly of parts caused by increasing the spring biasing force can be improved.

[0045] Furthermore, according to the embodiment of the present invention, by using multiple link members, the constraints on the component layout are less significant compared to the example shown in Figure 8, making it easier to change the design to increase the pressing force of the tension roller. In other words, the options for component layout increase, and it becomes possible to increase the pressing force of the tension roller by changing the component layout. As a result, the pressing force of the tension roller can be increased without relying solely on increasing the biasing force of the spring, thus increasing the pressing force of the tension roller while suppressing an increase in the biasing force of the spring. Therefore, according to the embodiment of the present invention, it becomes possible to achieve both suppression of rotational displacement between the belt and the roller and suppression of a decrease in component assembly ease.

[0046] Furthermore, as shown in the embodiments in Figures 2 to 5, when the second link member 63 is inserted into the first link member 62, the installation space for each link member 62 and 63 can be reduced, allowing for miniaturization. In this case, the constraints on component layout become even less pronounced, making it easier to arrange components within a limited space.

[0047] Next, other embodiments of the present invention will be described. In the following description, we will mainly describe parts that differ from the above embodiments, and since other parts have basically the same configuration, we will omit their explanation as appropriate.

[0048] Figure 6 shows the configuration of the tension-applying mechanism 60 according to the second embodiment of the present invention.

[0049] In the second embodiment shown in Figure 6, a second pivot shaft 49, which serves as the pivot point for the second link member 63, is provided on the side plate 58. That is, the second pivot shaft 49 passes through the portion where the opposing pieces 62e1, 62e2, 63e1, 63e2 (see Figure 5) of the first link member 62 and the second link member 63 overlap, and is fixed to the side plate 58. In this case, unlike the above embodiment, the second pivot shaft 49 does not swing together with the first link member 62, so it is necessary to ensure that the rotational motion of the first link member 62 around the first pivot shaft 48 is not constrained by the second pivot shaft 49. For this reason, in this embodiment, a gap S is provided between the shaft insertion hole 62b of the first link member 62 through which the second pivot shaft 49 is inserted and the second pivot shaft 49, at least in the rotational direction around the first pivot shaft 48. Furthermore, since the second link member 63 only needs to be able to rotate around the second support shaft 49, the diameter of the shaft insertion hole in the second link member 63 through which the second support shaft 49 is inserted is formed to be the same size as the diameter of the second support shaft 49.

[0050] Thus, even when the second support shaft 49 is fixed to the side plate 58, the first link member 62 rotates around the first support shaft 48 and the second link member 63 rotates around the second support shaft 49, just as in the above embodiment. Therefore, the biasing force of the spring 64 can be increased through these link members 62 and 63 by the principle of leverage and applied to the tension roller 61. Accordingly, in this embodiment as well, a large belt tension can be obtained with a relatively small spring biasing force, achieving both suppression of rotational displacement between the belt and the roller and suppression of a decrease in the ease of assembly of parts.

[0051] Figure 7 shows the configuration of the tension-applying mechanism 60 according to the third embodiment of the present invention.

[0052] In the third embodiment shown in Figure 7, the tension-applying mechanism 60 includes two tension rollers 61A and 61B. Each tension roller 61A and 61B is mounted on the first link member 62 and follows the rotational motion (oscillating motion) of the first link member 62 around the first support shaft 48. Therefore, when the biasing force of the spring 64 causes the second link member 63 to press against the first link member 62, the first link member 62 rotates around the first support shaft 48, and the two tension rollers 61A and 61B press against the outer circumferential surface of the belt 55 at different positions.

[0053] Thus, in this embodiment, the biasing force of the spring 64 is increased via the two link members 62 and 63 and applied to each tension roller 61A and 61B, so that a large belt tension can be obtained with a relatively small spring biasing force. Therefore, in this embodiment as well, it is possible to achieve both the suppression of rotational displacement between the belt and rollers and the suppression of a decrease in the ease of assembly of parts.

[0054] In this embodiment, since the belt 55 is pressed by two tension rollers 61A and 61B, there are two pressing positions on the belt 55 that serve as points of application. Therefore, in this embodiment, the distance L4 (the distance between the point of application F, which is the pressing position of the belt 55, and the fulcrum E of the first support shaft 48) set to satisfy the above-mentioned relationship L3 > L4 differs for each tension roller 61A and 61B. However, in order to obtain the tension-increasing effect due to the lever principle, it is sufficient to satisfy the relationship L3 > L4 in relation to at least one of the tension rollers. Therefore, in this embodiment, the distance L4 is set to the distance between the pressing position (point of application F) of the tension roller 61A that has a shorter distance from the first support shaft 48 and the fulcrum E of the first support shaft 48. In other words, in this embodiment, the distance L4 is defined as the distance between the point of application F, which is the pressing position of the left tension roller 61A shown in Figure 7, and the fulcrum E of the first support shaft 48. The positions of the point of application D, the fulcrum E, and the point of application F are set such that this distance L4 is shorter than the distance L3 between the point of force application D, which is the pressing position of the second link member 63, and the fulcrum E of the first support shaft 48 (satisfying L3 > L4).

[0055] Note that the number of tension rollers may be three or more. In that case as well, the positions of the effort point, fulcrum, and load point are set such that the relationship L3 > L4 is satisfied, with the distance between the pressing position of the tension roller with the shortest distance from the first support shaft and the first support shaft being defined as distance L4.

[0056] Although the embodiments of the present invention have been described above using a drive device for rotating a secondary transfer roller as an example, the present invention is not limited to a drive device for rotating a secondary transfer roller, but is also applicable to drive devices or transport devices that rotate drive target members or transport members, such as the paper feed roller 19, timing roller 20, and paper discharge roller 23 that transport paper as the object to be transported, as shown in Figure 1, as well as the transport roller 26 that transports the original document, the carrier that moves the optical scanning unit 31, the fixing rotating body 21, or the pressurizing rotating body 22.

[0057] Furthermore, the present invention can be applied not only to drive devices and conveying devices mounted on image forming apparatuses, but also to drive devices that drive belt conveyors (such as drive rollers) that carry and transport goods, and to drive devices that drive rotating bodies (such as wheels) of transportation equipment such as bicycles and automobiles. [Explanation of Symbols]

[0058] 39. Electric motor (power source) 17. Secondary transfer roller (driven component) 48 First spindle 49 Second support shaft 50 Power transmission mechanism 53 Drive pulley (driving rotating body) 54. Driven pulley (driven rotating body) 55 belt 58 Side plate (support member) 61 Tension roller (pressing member) 62 First link member 62a opening 62b Shaft insertion hole 63 Second link member 64. Spring (biasing member) 100 Image forming apparatus [Prior art documents] [Patent Documents]

[0059] [Patent Document 1] Japanese Patent Application Publication No. 8-14342

Claims

1. A drive device comprising a drive force transmission mechanism that transmits the driving force of a drive source to a member to be driven, The aforementioned drive force transmission mechanism is An endless belt stretched by multiple rotating bodies, A pressing member that presses the belt to apply tension to the belt, A first link member is provided so as to be rotatable around a first support shaft and holds the pressing member, A second link member is provided so as to be rotatable around a second support shaft and presses against the first link member, The pressing member comprises a biasing member that biases the second link member so that the pressing member presses the belt, Let L1 be the distance between the biasing position where the biasing member biases the second link member and the second support shaft, L2 be the distance between the pressing position where the second link member presses the first link member and the second support shaft, L3 be the distance between the pressing position where the second link member presses the first link member and the first support shaft, and L4 be the distance between the pressing position where the pressing member presses the belt and the first support shaft. Then the relationships L1 > L2 and L3 > L4 are satisfied. The first link member and the second link member each have a pair of opposing pieces facing each other and a bent portion connecting the opposing pieces, The second link member is inserted into the first link member, The drive device is characterized in that the second support shaft is provided in the portion where the opposing piece of the first link member and the opposing piece of the second link member overlap.

2. The system includes a support member that supports the first link member, The drive device according to claim 1, wherein the first support shaft is provided on the support member.

3. The first link member has an opening into which the second link member is inserted. The drive device according to claim 1 or 2, wherein the second link member rotates relative to the first link member and presses against the opening of the first link member.

4. The drive device according to any one of claims 1 to 3, wherein the second support shaft is provided on the first link member.

5. The system includes a support member that supports the first link member, The second support shaft is provided on the support member, The first link member has a shaft insertion hole through which the second support shaft is inserted, The drive device according to any one of claims 1 to 3, wherein the shaft insertion hole has a gap with respect to the second support shaft in the rotational direction at least around the first support shaft.

6. The pressing members are provided in multiple locations. The drive device according to any one of claims 1 to 5, wherein the distance L4 is the distance from the pressing position of the plurality of pressing members to the belt that has the shortest distance from the first support shaft.

7. A conveying member that conveys the object to be conveyed, A conveying device characterized by comprising a drive device according to any one of claims 1 to 6 for driving the conveying member.

8. An image forming unit that forms an image on a recording medium, An image forming apparatus characterized by comprising a drive device according to any one of claims 1 to 6 or a transport device according to claim 7.

Images