LUBRICANT APPLICATION DEVICE FOR REMOVABLE LUBRICANT UNIT BACKGROUND [0001] An image forming system may include a lubricant application device that applies a lubricant to an image carrier to inhibit a cleaning blade from causing abrasion of the image carrier. In such a lubricant application device, a solid lubricant may be biased against an application roller that may apply the lubricant to the image carrier. BRIEF DESCRIPTION OF DRAWINGS [0002] FIG.1 is a schematic view of an image forming device according to an example. FIG. 2 is a schematic vertical cross-sectional view of an example lubricant application device, taken along a vertical transversal plane of the lubricant application device. FIG. 3 is a schematic horizontal cross-sectional view of the example lubricant application device illustrated in FIG. 2, taken along a horizontal longitudinal plane of the lubricant application device. FIG.4 is a partial perspective view of the example lubricant application device, illustrating a state in which a lubricant unit is positioned outside a housing of the lubricant application device. FIG. 5 is a schematic horizontal cross-sectional view illustrating the housing of the example lubricant application device. FIG. 6 is an exploded perspective view of the lubricant unit of the example lubricant application device. FIG. 7 is a schematic horizontal cross-sectional view of the example lubricant application device of FIG. 2, illustrating a state in which the solid lubricant is consumed. FIG. 8 is a schematic horizontal cross-sectional view of the example lubricant application device of FIG. 7, illustrating a state in which the lubricant unit is being drawn out of the housing of the lubricant application device. FIG. 9 is another schematic horizontal cross-sectional view illustrating a state in which the lubricant unit is being further drawn out of the housing of the lubricant application device. FIG.10 is another schematic horizontal cross-sectional view illustrating a state in which the lubricant unit is being further drawn out of the housing of the lubricant application device. FIG.11 is another schematic horizontal cross-sectional view illustrating a state in which a new lubricant unit is being inserted into the housing of the lubricant application device. FIG.12 is another schematic horizontal cross-sectional view illustrating a state in which the new lubricant unit is being further inserted into the housing of the lubricant application device. FIG.13 is another schematic horizontal cross-sectional view illustrating a state in which the new lubricant unit is further inserted into the lubricant application device. FIG. 14 is a perspective view of an external container device of an example. FIG. 15 is a cross-sectional view of the example external container device illustrated in FIG.14, taken along line XV-XV. FIG. 16 is a perspective view illustrating a drawing handle of the example external container device. FIG. 17 is a partial perspective view illustrating the external container device positioned adjacent the example lubricant unit in the lubricant application device illustrated in FIG.2. FIG. 18 is a partial perspective view illustrating a state in which the external container device is positioned to engage the lubricant unit of the lubricant application device. FIG. 19 is a perspective view illustrating a state in which the drawing handle of the external container device is engaged with the lubricant unit of the example lubricant application device. DETAILED DESCRIPTION [0003] In a lubricant application device, a solid lubricant may be replaced after it is consumed. However, when the lubricant application device and an image carrier are unitized as an image carrier unit, replacing the solid lubricant involves removing the image carrier unit from an image forming system (or an image forming device) and disassembling the image carrier unit. In such a case, the man-hour of an operator is increased, thereby increasing the cost for replacing the solid lubricant. In addition, a significant amount of a toner may adhere to the periphery of the image carrier, such that when the image carrier unit is disassembled, the significant amount of the toner may scatter. With a lubricant application device, according to the examples described below, the cost for replacing the solid lubricant can be reduced, and the scattering of the toner is suppressed. [0004] According to an example, a lubricant application device includes an application roller that extends in a longitudinal direction and that is disposed to apply a lubricant to an image carrier, and a housing that accommodates a lubricant unit which holds a solid lubricant, and the application roller. The housing is configured such that the lubricant unit is insertable (mountable) and removable in the longitudinal direction. [0005] In addition, an image forming system (or image forming device) of an example includes an image carrier on a surface of which an electrostatic latent image is to be formed, a developing device that develops the electrostatic latent image into a toner image, a transfer device that transfers the toner image, which has been developed, onto a paper (e.g., a sheet of paper), a fixing device that fixes the toner image to the paper, and a lubricant application device that applies a lubricant to the image carrier. The lubricant application device includes an application roller that extends in a longitudinal direction and that is disposed to apply the lubricant to the image carrier, and a housing that accommodates a lubricant unit which holds a solid lubricant, and the application roller. The housing is configured such that the lubricant unit is movable with respect to the housing, in the longitudinal direction, so as to be insertable (mountable) and removable in the longitudinal direction. [0006] Hereinafter, an image forming system of an example will be described with reference to the drawings. The image forming system may be an image forming device such as a printer or may be a device used in the image forming device or the like. In the following description, with reference to the drawings, the same reference numbers are assigned to the same components or to similar components having the same function, and overlapping description is omitted. [0007] With reference to FIG. 1, an example of the image forming device will be described. The example image forming device 1 illustrated in FIG. 1 is an apparatus that may use four colors such as magenta, yellow, cyan, and black (represented by the characters "M", "Y", "C", "K" in the reference symbols) to form a color image. The image forming device 1 includes a conveying device 10 that conveys a recording medium such as a paper (or sheet of paper) 3, image carriers 20M, 20Y, 20C, and 20K having respective surfaces (peripheral surfaces) that form electrostatic latent images, developing devices 30M, 30Y, 30C, and 30K that develop the electrostatic latent images to form toner images; a transfer device 40 that transfers the toner images onto the paper 3; a fixing device 50 that fixes the toner images to the paper 3, an output device 60 that outputs the paper 3, and a control unit 70. [0008] The conveying device 10 conveys the paper 3, which is a recording medium on which an image is to be formed, along a conveyance path 11. The papers 3 are stacked and contained in a cassette 12, and are picked up from the cassette 12 and conveyed by a paper feeding roller 13 to the conveyance path 11. [0009] Each of the image carriers 20M, 20Y, 20C, and 20K may also be referred to as an electrostatic latent image carrier, a photoconductor drum, or the like. The image carrier 20M forms an electrostatic latent image to generate a magenta toner image. The image carrier 20Y forms an electrostatic latent image to generate a yellow toner image. The image carrier 20C forms an electrostatic latent image to generate a cyan toner image. The image carrier 20K forms an electrostatic latent image to generate a black toner image. The image carriers 20M, 20Y, 20C, and 20K have similar configurations. Accordingly, the image carrier 20M will be described as a representative one of the image carriers 20M, 20Y, 20C, and 20K, unless otherwise described. [0010] The developing device 30M, a charging roller 22M, an exposure unit 23, and a cleaning unit 24M are provided adjacent the image carrier 20M. The image carrier 20M, the developing device 30M, the charging roller 22M, the exposure unit 23, and the cleaning unit 24M may be unitized as an image carrier unit. Similarly to the image carrier 20M, the respective developing devices 30Y, 30C, and 30K, respective charging rollers, the exposure unit 23, and respective cleaning units are also provided adjacent the respective image carriers 20Y, 20C, and 20K, and may form respective image carrier units. [0011] The charging roller 22M charges the surface of the image carrier 20M to a predetermined potential. The charging roller 22M rotates to follow a rotation of the image carrier 20M. The exposure unit 23 exposes the surface of the image carrier 20M to light according to the image to be formed on the paper 3, after the surface has been charged by the charging roller 22M. Accordingly, the potential of a portion of the surface of the image carrier 20M that is exposed to the light by the exposure unit 23, is changed, so that an electrostatic latent image is formed. The cleaning unit 24M recovers a toner remaining on the image carrier 20M. The cleaning unit 24M includes a cleaning blade 25 and a lubricant application device 80 (cf. FIG.2). [0012] The developing device 30M develops the electrostatic latent image with a toner supplied from a toner tank 21M filled with a magenta toner, to form a magenta toner image based on the electrostatic latent image formed on the image carrier 20M. The developing device 30Y develops an electrostatic latent image with a toner supplied from a toner tank 21Y filled with a yellow toner, to form a yellow toner image based on the electrostatic latent image formed on the image carrier 20Y. The developing device 30C develops an electrostatic latent image with a toner supplied from a toner tank 21C filled with a cyan toner, to form a cyan toner image based on the electrostatic latent image formed on the image carrier 20C. The developing device 30K develops an electrostatic latent image with a toner supplied from a toner tank 21K filled with a black toner, to form a black toner image based on the electrostatic latent image formed on the image carrier 20K. The developing devices 30M, 30Y, 30C, and 30K have similar configurations. Accordingly, the developing device 30M will be described as a representative one of the developing devices 30M, 30Y, 30C, and 30K, unless otherwise described. [0013] The developing device 30M includes a developing roller 31M that carries the toner to the image carrier 20M. The developing device 30M uses a two-component developer containing a toner and a carrier, as a developer. Namely, in the developing device 30M, the toner and the carrier are adjusted to achieve a targeted mixing ratio and are further mixed and stirred to disperse the toner, so as to adjust the developer to have an optimal charge amount. In the developing device 30M, the developer is carried on the developing roller 31M. Then, when the developer is conveyed to a region facing the image carrier 20M by the rotation of the developing roller 31M, the toner of the developer carried on the developing roller 31M transfers to the electrostatic latent image formed on a peripheral surface of the image carrier 20M, so that the electrostatic latent image is developed, thereby forming the toner image. [0014] The transfer device 40 conveys the toner images which have been formed by the developing devices 30M, 30Y, 30C, and 30K, and transfers the toner images onto the paper 3. The transfer device 40 includes a transfer belt 41 onto which the respective toner images are primarily transferred from the image carriers 20M, 20Y, 20C, and 20K in a layered manner so as to form a single composite toner image on the transfer belt 41, suspension rollers 44, 45, 46, and 47 that support (or suspend) the transfer belt 41, primary transfer rollers 42M, 42Y, 42C, and 42K that are positioned to interpose the transfer belt 41 between the primary transfer rollers 42M, 42Y, 42C, and 42K and the image carriers 20M, 20Y, 20C, and 20K in order to primarily transfer the respective toner images from the image carriers 20M, 20Y, 20C, and 20K onto the transfer belt 41, and a secondary transfer roller 43 that is positioned to interpose the transfer belt 41 between the secondary transfer roller 43 and the suspension roller 47 in order to secondarily transfer the composite toner image from the transfer belt 41 onto the paper 3. [0015] The transfer belt 41 is an endless belt which is rotated by the suspension rollers 44, 45, 46, and 47. The primary transfer rollers 42M, 42Y, 42C, and 42K are pressed against the image carriers 20M, 20Y, 20C, and 20K, respectively, from an inner peripheral side of the transfer belt 41. The secondary transfer roller 43 is disposed parallel to the suspension roller 47 with the transfer belt 41 interposed between the secondary transfer roller 43 and the suspension roller 47, and is pressed against the suspension roller 47 from an outer peripheral side of the transfer belt 41. Accordingly, a transfer nip region 14 where the toner images may be transferred from the transfer belt 41 onto the paper 3, is formed between the secondary transfer roller 43 and the transfer belt 41. [0016] The fixing device 50 is positioned to convey the paper 3 on which the composite toner image has been transferred, to pass through a fixing nip region where the paper 3 is subjected to heat and pressure, so as to attach and fixes the composite toner image to the paper 3. The fixing device 50 includes a heating roller 52 that heats the paper 3, and a pressure roller 54 that is pressed against the heating roller 52 to drive the heating roller 52 to rotate. The heating roller 52 and the pressure roller 54 are formed in a cylindrical shape, and the heating roller 52 includes a heat source such as a halogen lamp thereinside. The fixing nip region which is a contact region is provided between the heating roller 52 and the pressure roller 54, and when the paper 3 passes through the fixing nip region, the composite toner image is melted to be fixed to the paper 3. [0017] The output device 60 includes output rollers 62 and 64 that output the paper 3, to which the composite toner image has been fixed, to the outside of the apparatus. [0018] The control unit (or controller) 70 is an electronic control unit including a central processing unit (CPU), a read-only memory (ROM), a random-access memory (RAM), and the like. In the control unit 70, a program which is stored in the ROM in the form of data and instructions, may be loaded onto the RAM to be executed by the CPU to execute various control operations. The control unit 70 may include a plurality of electronic control units (electronic control devices) or may include a single electronic control unit (electronic control unit). The control unit 70 performs various control operations in the image forming device 1. [0019] With reference to FIGS.2 to 4, the lubricant application device 80 of an example is a device that applies a lubricant to the image carrier 20M to suppress the cleaning blade 25 from causing abrasion of the image carrier 20M. The lubricant application device 80 includes an application roller 81, a housing 82, and a lubricant unit 83. [0020] The application roller 81 has a central axis A1 that extends along a longitudinal direction D1, and is disposed to apply the lubricant to the image carrier 20M. The application roller 81 extends parallel to the image carrier 20M. Namely, the longitudinal direction D1 of the application roller 81 is disposed parallel to an axis direction of the image carrier 20M. In addition, the application roller 81 is adjacent to and in contact with the image carrier 20M. The application roller 81 is supported so as to be rotatable around the central axis A1 of the application roller 81. The central axis A1 of the application roller 81 defines the longitudinal direction D1 of the application roller 81. The application roller 81 includes a shaft portion 81a that is driven to rotate around the central axis A1, and an application portion 81b that is disposed around the shaft portion 81a to contact the image carrier 20M. Accordingly, when the shaft portion 81a is driven to rotate, the application roller 81 applies the lubricant to the image carrier 20M with the application portion 81b. [0021] With reference to FIGS. 2 to 5, the housing 82 accommodates the application roller 81, and removably accommodates the lubricant unit 83. An application roller chamber 84, an application opening 85, a lubricant chamber 86, an opening 87, a longitudinal guide 88, and a separation guide 89 are formed in the housing 82. [0022] The application roller chamber 84 forms a space that accommodates the application roller 81, and is positioned adjacent the image carrier 20M. The application opening 85 is formed on an image carrier 20M side of the application roller chamber 84, such that the application roller chamber 84 is open to the image carrier 20M side, through the application opening 85. The application roller 81 protrudes from the application opening 85 to be in contact with the image carrier 20M. The lubricant chamber 86 forms a space that removably accommodates the lubricant unit 83, and positioned adjacent the application roller chamber 84 and the application roller 81 accommodated in the application roller chamber 84. The opening 87 is located at an end portion of the housing 82 in the longitudinal direction D1, so as to insert (mount) and remove the lubricant unit 83 into and out from the housing 82 through the opening 87. The opening 87 is formed at an end (one side in the longitudinal direction D1) of the lubricant chamber 86 (e.g., right side in FIG. 3), and the lubricant chamber 86 is open to the outside of the housing 82, through the opening 87. Accordingly, the housing extends in a longitudinal direction and includes a first end 82a and a second end 82b opposite the first end in the longitudinal direction. The second end 82b corresponds to the end portion that forms the opening 87 and may also be referred to as a distal end. [0023] The longitudinal guide 88 is a guide to slide the lubricant unit 83 in the longitudinal direction D1 such that the lubricant unit 83 may be inserted (mounted) in and removed from the housing 82. The longitudinal guide 88 has a longitudinal guide surface 91 that extends in the longitudinal direction D1 and faces an application roller 81 side. The longitudinal guide surface 91 extends linearly along the longitudinal direction D1. [0024] The separation guide 89 is a guide that separates the lubricant unit 83 from the application roller 81 when the lubricant unit 83 slides along the longitudinal guide 88. The separation guide 89 has a separation guide surface 92 that faces away from the application roller 81. The separation guide surface 92 has a proximal end side longitudinal sliding surface portion 92a, a first slope surface portion 92b, a longitudinal sliding surface portion 92c, a second slope surface portion 92d, and a distal end side longitudinal sliding surface portion 92e. [0025] The proximal end side longitudinal sliding surface portion 92a is located a first end (e.g., an end portion) of the separation guide surface 92 that is opposite from the opening 87 of the housing, in the longitudinal direction D1. The first slope surface portion 92b is adjacent the proximal end side longitudinal sliding surface portion 92a. The longitudinal sliding surface portion 92c is adjacent the first slope surface portion 92b. The second slope surface portion 92d is adjacent the longitudinal sliding surface portion 92c. The distal end side longitudinal sliding surface portion 92e is adjacent the second slope surface portion 92d. Namely, the proximal end side longitudinal sliding surface portion 92a, the first slope surface portion 92b, the longitudinal sliding surface portion 92c, the second slope surface portion 92d, and the distal end side longitudinal sliding surface portion 92e are formed in this order, from the first end (or a proximal end, e.g., at an opposite side) of the separation guide surface 92 which is opposite to the opening 87 in the longitudinal direction D1, toward a second end (or distal end, e.g., an opening 87 side) of the separation guide surface 92 that is adjacent the opening 87. Accordingly, the distal end side longitudinal sliding surface portion 92e is located at a distal end portion (at the second end) in the longitudinal direction D1 of the separation guide surface 92 to be positioned adjacent the opening 87. [0026] The proximal end side longitudinal sliding surface portion 92a extends linearly along the longitudinal direction D1. The first slope surface portion 92b extends in a direction away from the application roller 81 and toward the distal end (adjacent the opening 87). Accordingly, a transverse distance between the longitudinal guide surface 91 and the first slope surface portion 92b narrows toward the distal end of the separation guide surface 92. The longitudinal sliding surface portion 92c extends linearly along the longitudinal direction D1. The second slope surface portion 92d extends in a direction toward the application roller 81 and toward the distal end (adjacent the opening 87). Accordingly, a transverse distance between the longitudinal guide surface 91 and the second slope surface portion 92d widens toward the distal end of the separation guide surface 92. The distal end side longitudinal sliding surface portion 92e extends linearly along the longitudinal direction D1. [0027] The first slope surface portion 92b is located closer to the proximal end of the separation guide surface 92 than the application portion 81b of the application roller 81, in the longitudinal direction D1. The second slope surface portion 92d is located closer to the distal end than the application portion 81b of the application roller 81 in the longitudinal direction D1. [0028] The first slope surface portion 92b may extend linearly, curvedly, or in a bending manner in the direction away from the application roller 81 and toward the distal end. In addition, the first slope surface portion 92b may be connected, in a bending manner or curvedly, to the proximal end side longitudinal sliding surface portion 92a and the longitudinal sliding surface portion 92c. Similarly, the second slope surface portion 92d may extend linearly, curvedly, or in a bending manner in the direction toward the application roller 81 and toward the distal end. In addition, the second slope surface portion 92d may be connected, in a bending manner or curvedly, to the longitudinal sliding surface portion 92c and the distal end side longitudinal sliding surface portion 92e. [0029] The longitudinal guide surface 91 of the longitudinal guide 88 and the separation guide surface 92 of the separation guide 89 may be formed to face each other via the lubricant chamber 86, or may be formed, in some examples, to face each other with a partition formed therebetween in the housing 82. When the longitudinal guide surface 91 and the separation guide surface 92 are formed to face each other via the lubricant chamber 86, for example, an application roller 81 side of the longitudinal guide surface 91 and a side (an opposite side) of the separation guide surface 92 that faces away from the application roller 81 may form the lubricant chamber 86. When the longitudinal guide surface 91 and the separation guide surface 92 are formed to face each other via the partition formed in the housing 82, for example, each of the application roller 81 side of the longitudinal guide surface 91 and the opposite side of the separation guide surface 92 forms a groove in the housing 82. [0030] A seal member 90 is attached to a distal end surface (an opening 87 side end surface) at the distal end (at the opening 87 side) of the housing 82. The seal member 90 forms a seal between the housing 82 and an external container device 100 which will be described further below, when the external container device 100 comes into contact with the seal member 90. The seal member 90 is attached to the distal end surface of the housing 82 so as not to block the opening 87. For example, a foam obtained by forming urethane, ethylene propylene diene monomer (EPDM) rubber, or the like, in the form of a sponge can be provided as the seal member 90. [0031] With reference to FIGS. 2 to 4 and 6, the lubricant unit 83 includes a casing 93, a solid lubricant 94, and a biasing device 95. Hereinafter, unless described otherwise, the lubricant unit 83 will be described as being accommodated within the housing 82, in a state of being set (or inserted, or mounted) in the housing 82. [0032] The casing 93 is a member that is slidable with respect to the housing 82 of the lubricant application device 80 in the longitudinal direction D1. The casing 93 includes a base plate portion 93a that extends in the longitudinal direction D1 so as to face the application roller 81, a pair of side plate portions 93b that extend toward the application roller 81 from opposite edges of the base plate portion 93a, in a contact-and-separation direction D2 with respect to the application roller 81, a proximal end side plate portion 93c that extends toward the application roller 81 from a proximal end (or first end) of the base plate portion 93a (e.g., an end portion of the base plate portion 93a on an opposite side from the opening 87 in the longitudinal direction D1), and a distal end side plate portion 93d that extends toward the application roller 81 from a distal end (or second end) of the base plate portion 93a (e.g., an opening 87 side end portion in the longitudinal direction D1 of the base plate portion 93a). The contact-and-separation direction D2 with respect to the application roller 81 is a direction orthogonal to the longitudinal direction D1. [0033] The two edges (end portions of the base plate portion 93a in a short-dimension direction (width direction) D3 orthogonal to the longitudinal direction D1) and the contact-and-separation direction D2 are provided with a pair of longitudinal projections 93f that project from the pair of side plate portions 93b in the short-dimension direction D3, respectively. The pair of longitudinal projections 93f engage with (come into contact with) the longitudinal guide surface 91 from the application roller 81 side. Namely, the longitudinal guide surface 91 is formed in a position corresponding to the pair of longitudinal projections 93f, and when the lubricant unit 83 is inserted (mounted) in or removed from the housing 82, the pair of longitudinal projections 93f slide along the longitudinal guide surface 91 of the longitudinal guide 88. [0034] Slits 93e are formed in the two end portions of the pair of side plate portions 93b. Each of the slits 93e extends in the contact-and-separation direction D2 to be open to the application roller 81 side. [0035] A projection portion 93g projects out from the distal end side plate portion 93d, to engage with the external container device 100 which will be described further below. The projection portion 93g may be formed in a substantially cylindrical shape extending in the longitudinal direction D1. A cutout 93h to engage with the external container device 100 is formed in the projection portion 93g. [0036] The solid lubricant 94 is a supply source of the lubricant, and a solid body of the lubricant is formed as the solid lubricant 94. The solid lubricant 94 extends in the longitudinal direction D1 similarly to the application roller 81 such that the lubricant is supplied to the application roller 81. The lubricant forming the solid lubricant 94 is made of, for example, a material containing zinc stearate. [0037] The biasing device 95 is a device that biases the solid lubricant 94 against the application roller 81. The biasing device 95 includes a holding member 96, a biasing member 97, and a separation projection arrangement 98. [0038] The holding member 96 holds the solid lubricant 94. The holding member 96 extends in the longitudinal direction D1 similarly to the solid lubricant 94. The holding member 96 is longer than the solid lubricant 94 in the longitudinal direction D1, and projects from both ends of the solid lubricant 94. For example, a central portion of the holding member 96 in the short-dimension direction D3 is formed in a flat plate shape, so that the central portion holds the solid lubricant 94, and both edges (end portions in the short-dimension direction D3) of the holding member 96 are formed in a gutter shape (C-shaped cross section) which is bent opposite the solid lubricant 94. The holding of the solid lubricant 94 by the holding member 96 can be achieved, for example, by bonding with an adhesive. [0039] The holding member 96 has a first end (an end portion of the holding member 96 on an opposite side from the opening 87 in the longitudinal direction D1) that forms a receiving portion 96a that contacts the biasing member 97. A pair of neck portions 96c project at opposite sides of the receiving portion 96a in the short-dimension direction D3. The holding member 96 has a second end (an opening 87 side end portion in the longitudinal direction D1 of the holding member 96) that forms a receiving portion 96b that contacts the biasing member 97. A pair of neck portions 96d project from opposite sides of the receiving portion 96b in the short-dimension direction D3. The pair of neck portions 96c and the pair of neck portions 96d are formed in positions corresponding to the slits 93e formed in the pair of side plate portions 93b, and are slidably insertable into the slits 93e in the contact-and-separation direction D2. Accordingly, the holding member 96 is guided by the slits 93e to be movable in the contact-and-separation direction D2. In addition, the pair of neck portions 96c and the pair of neck portions 96d are insertable into and removable (or extractable) from the slits 93e, so that the holding member 96 is mountable to and removable from the casing 93. [0040] The biasing members 97 are disposed between the base plate portion 93a and the receiving portion 96a, and between the base plate portion 93a and the receiving portion 96b, respectively, to urge (or bias) the holding member 96 to the application roller 81 side. The biasing member 97 urges the holding member 96 toward the application roller 81 side, in order to urge the solid lubricant 94 against the application roller 81. The biasing member 97 may be formed of, for example, a coil spring. [0041] A separation projection arrangement 98 includes a pair of separation projections 98a and a pair of separation projections 98b. The pair of separation projections 98a are connected to the receiving portion 96a via the neck portions 96c. The pair of separation projections 98b are connected to the receiving portion 96b via the neck portions 96d. The pair of separation projections 98a are disposed outside the pair of side plate portions 93b in the short-dimension direction D3, and are formed to be thicker than the gap formed by the corresponding slit 93e, so as to prevent the neck portions 96c from disengaging from the slits 93e in the short-dimension direction D3. Similarly, the pair of separation projections 98b are disposed outside the pair of side plate portions 93b in the short-dimension direction D3, and are formed to be thicker than the gap formed by the corresponding slit 93e, so as to prevent the neck portions 96d from disengaging from the slits 93e in the short-dimension direction D3. The pair of separation projections 98a are located closer to the first end of the holding member 96 (side opposite the opening 87) than the application portion 81b of the application roller 81, in the longitudinal direction D1. In addition, the pair of separation projections 98b are located closer to the second end of the holding member 96 (opening 87 side) than the application portion 81b of the application roller 81, in the longitudinal direction D1. [0042] The separation guide surface 92 is formed in a position corresponding to the pair of separation projections 98a and the pair of separation projections 98b, so that the pair of separation projections 98a can engage with (come into contact with) the separation guide surface 92 from the side opposite the application roller 81. The pair of separation projections 98b can also engage with (come into contact with) the separation guide surface 92 from the side opposite the application roller 81. Accordingly, when the casing 93 slides in the longitudinal direction D1 such that the lubricant unit 83 is mounted in and removed from the housing 82, the pair of separation projections 98a are slidable along the separation guide surface 92. [0043] A mounting and removal operation of the lubricant unit 83 with respect to the housing 82 of the lubricant application device 80 will be described with reference to FIGS.3 and 7 to 13. [0044] When the lubricant unit 83 which is a new one is set in the housing 82, with reference to FIG. 3, the distal end side plate portion 93d of the lubricant unit 83 is in contact with the second end (or the distal end, e.g., the opening 87 side end surface) of the housing 82, in the longitudinal direction D1. In addition, the pair of separation projections 98a of the lubricant unit 83 are disposed to be aligned with the proximal end side longitudinal sliding surface portion 92a of the housing 82, and the pair of separation projections 98b of the lubricant unit 83 are disposed to be aligned with the distal end side longitudinal sliding surface portion 92e of the housing 82. In addition, the solid lubricant 94 is pressed against the application portion 81b of the application roller 81, the longitudinal projection 93f of the lubricant unit 83 is in contact with the longitudinal guide surface 91 of the housing 82, and the pair of separation projections 98a and the pair of separation projections 98b of the lubricant unit 83 are separated (spaced apart) from the proximal end side longitudinal sliding surface portion 92a and the distal end side longitudinal sliding surface portion 92e of the housing 82, respectively. [0045] With reference to FIG. 7, as the solid lubricant 94 is consumed, the holding member 96 approaches the application roller 81, and the pair of separation projections 98a and the pair of separation projections 98b approach the proximal end side longitudinal sliding surface portion 92a and the distal end side longitudinal sliding surface portion 92e, respectively. In some examples, the lubricant application device 80 may be configured such that, when the solid lubricant 94 is consumed, the pair of separation projections 98a and the pair of separation projections 98b come into contact with the proximal end side longitudinal sliding surface portion 92a and the distal end side longitudinal sliding surface portion 92e, respectively. In other examples, the lubricant application device 80 may be configured such that, when the solid lubricant 94 is consumed, the pair of separation projections 98a and the pair of separation projections 98b do not contact the proximal end side longitudinal sliding surface portion 92a nor the distal end side longitudinal sliding surface portion 92e. [0046] With reference to FIG. 8, when the lubricant unit 83 is removed or drawn out (extracted) from the housing 82 in order to replace the lubricant unit 83, the lubricant unit 83 is pulled out from the opening 87 side (e.g., right side in FIG. 8) in the longitudinal direction D1. Consequently, the longitudinal projection 93f slides along the longitudinal guide surface 91 in the longitudinal direction D1, and the pair of separation projections 98a come into contact with the first slope surface portion 92b. [0047] With reference to FIG. 9, the pair of separation projections 98a which have come into contact with the first slope surface portion 92b, slide along the first slope surface portion 92b in the direction away from the application roller 81 as the pair of separation projections 98a slide toward the second end (toward the opening 87 side) of the separation guide surface 92, until the pair of separation projections 98a reach the longitudinal sliding surface portion 92c. Since the distance between the longitudinal guide surface 91 and the first slope surface portion 92b narrows toward the second end, when the pair of separation projections 98a slide along the first slope surface portion 92b toward the second end, the holding member 96 connected to the pair of separation projections 98a and the solid lubricant 94 which remains on the solid (not illustrated in FIG. 9 for simplification) move against the biasing force of the biasing member 97 in the direction away from the application roller 81. Accordingly, when the pair of separation projections 98a slide along the separation guide 89, the biasing device 95 retracts the holding member 96 and the solid lubricant 94, which has remained, in the direction away from the application roller 81. [0048] With reference to FIG.10, the pair of separation projections 98a which have reached the longitudinal sliding surface portion 92c, slide along the longitudinal sliding surface portion 92c in the longitudinal direction D1 until the pair of separation projections 98a reach the second slope surface portion 92d. Since the holding member 96 and the remaining solid lubricant 94 are retracted away from the application roller 81, the holding member 96 and the remaining solid lubricant 94 (not illustrated in FIG. 10 for simplification) slide in the longitudinal direction D1 without interfering with (without contacting) the application roller 81. [0049] Subsequently, the pair of separation projections 98a slide along the second slope surface portion 92d in the direction toward the application roller 81 as the pair of separation projections 98a slide toward the second end (toward the opening 87 side) of the separation guide surface 92. Since the distance between the longitudinal guide surface 91 and the second slope surface portion 92d toward the second end, when the pair of separation projections 98a slide along the second slope surface portion 92d toward the second end, the holding member 96 connected to the pair of separation projections 98a and the remaining solid lubricant 94 move toward the application roller 81 due to the biasing force of the biasing member 97. Then, the lubricant unit 83 may be removed (extracted) from the housing 82 in the same state as when the lubricant unit 83 is set to be inserted into the housing 82. [0050] For ease of understanding, the holding member 96 is illustrated in the drawings, as extending parallel to the application roller 81 when the pair of separation projections 98a slide along the first slope surface portion 92b, the longitudinal sliding surface portion 92c, and the second slope surface portion 92d. However, as the pair of separation projections 98a slide along the first slope surface portion 92b, the longitudinal sliding surface portion 92c, and the second slope surface portion 92d, a portion of the holding member extends outside the housing 82 through the opening 87, and accordingly, the holding member 96 may be inclined with respect to the application roller 81. [0051] With reference to FIG. 11, when the lubricant unit 83 which is a new one (e.g., a replacement lubricant unit 83) is inserted to be attached (or mounted) to the housing 82, the lubricant unit 83 is pushed into the lubricant chamber 86 from the opening 87. The longitudinal projection 93f slides along the longitudinal guide surface 91 in the longitudinal direction D1, and the pair of separation projections 98a come into contact with the second slope surface portion 92d. Then, the pair of separation projections 98a slide along the second slope surface portion 92d in the direction away from the application roller 81 and toward the first end of the separation guide surface 92 (e.g., end opposite the opening 87), until the pair of separation projections 98a reach the longitudinal sliding surface portion 92c. Since the distance between the longitudinal guide surface 91 and the second slope surface portion 92d narrows toward the first end, when the pair of separation projections 98a slide toward the first end along the second slope surface portion 92d, the holding member 96 connected to the pair of separation projections 98a and the solid lubricant 94 move against the biasing force of the biasing member 97 in the direction away from the application roller 81. Accordingly, when the pair of separation projections 98a slide along the separation guide 89, the holding member 96 and the solid lubricant 94 are retracted away from the application roller 81. [0052] With reference to FIG.12, the pair of separation projections 98a which have reached the longitudinal sliding surface portion 92c, slide along the longitudinal sliding surface portion 92c in the longitudinal direction D1 until the pair of separation projections 98a reach the first slope surface portion 92b. Since the holding member 96 and the solid lubricant 94 are retracted away from the application roller 81, the holding member 96 and the solid lubricant 94 slide in the longitudinal direction D1 without interfering with (without contacting) the application roller 81. [0053] The pair of separation projections 98a which have reached the first slope surface portion 92b, slide along the first slope surface portion 92b in the direction toward the application roller 81 and toward the first end of the separation guide surface 92. Since the distance between the longitudinal guide surface 91 and the first slope surface portion 92b widens toward the first end, when the pair of separation projections 98a slide opposite the opening 87 along the first slope surface portion 92b, the holding member 96 connected to the pair of separation projections 98a and the solid lubricant 94 held on the holding member 96 move toward the application roller 81 due to the biasing force of the biasing member 97. [0054] With reference to FIG. 13, the distal end side plate portion 93d of the lubricant unit 83 comes into contact with a surface at the second end 82b (the opening 87 side end surface in the longitudinal direction D1) of the housing 82. In addition, the pair of separation projections 98a of the lubricant unit 83 are disposed to be aligned with the proximal end side longitudinal sliding surface portion 92a of the housing 82 at the first end 82a of the housing 82, and the pair of separation projections 98b of the lubricant unit 83 are disposed to be aligned with the distal end side longitudinal sliding surface portion 92e of the housing 82. In addition, the solid lubricant 94 is pressed against the application portion 81b of the application roller 81, the longitudinal projection 93f of the lubricant unit 83 is in contact with the longitudinal guide surface 91 of the housing 82, and the pair of separation projections 98a and the pair of separation projections 98b of the lubricant unit 83 are respectively spaced apart from the proximal end side longitudinal sliding surface portion 92a and the distal end side longitudinal sliding surface portion 92e of the housing 82. [0055] In the example lubricant application device 80 described above, the lubricant unit 83 may be inserted (mounted) into and removed from the housing 82 through the opening 87, in order to replace the lubricant unit 83 without removing the image carrier unit from the image forming device 1 or disassembling the image carrier unit. Consequently, the scattering of the toner caused by disassembling of the image carrier unit can be suppressed, and the cost for replacing the solid lubricant can be reduced. [0056] In addition, the longitudinal guide 88 is provided so that the lubricant unit 83 can slide smoothly in the longitudinal direction D1. Further the separation guide 89 is provided so that when the lubricant unit 83 slides along the longitudinal guide 88, the lubricant unit 83 can be separated from the application roller 81. Accordingly, when the lubricant unit 83 is inserted (mounted) into and removed from the housing 82, the holding member 96 and the solid lubricant 94 can be prevented from coming into contact with the application roller 81. [0057] FIGS. 14 and 15 illustrate the external container device 100 of an example. The external container device 100 illustrated in FIGS. 14 and 15 is a device used to draw out the lubricant unit 83 from the housing 82. The external container device 100 includes a container body 101 and a drawing handle 102. [0058] The container body 101 extends in a longitudinal direction D4 and accommodates the lubricant unit 83. An accommodation space 103 which can accommodate the lubricant unit 83 is formed inside the container body 101. The container body 101 includes a longitudinal end portion 104 which is open in order to receive the lubricant unit 83 in the accommodation space 103. The longitudinal end portion 104 is an end portion in the longitudinal direction D4 of the container body 101. A slit 105 extending in the longitudinal direction D4 is formed in a side surface portion of the container body 101. The slit 105 penetrates through the container body 101 from the accommodation space 103, to reach the outside of the container body 101. According to examples, the length in the longitudinal direction D4 of the slit 105 is substantially the same as or longer than a length (in the longitudinal direction D1) of the lubricant unit 83 from the first end of the housing 82 (distal end opposite the opening 87) to the distal end side plate portion 93d. [0059] With reference to FIGS.14 to 16, the drawing handle 102 is a member that is slidably coupled to the container body 101 via the slit 105 to draw the lubricant unit 83 into the accommodation space 103 from the longitudinal end portion 104. The drawing handle 102 includes an attachment portion 102a, a handle portion 102b, and a hooking portion 102c. [0060] The attachment portion 102a is disposed in the accommodation space 103, and is configured to be coupled (attachable) to the lubricant unit 83. The attachment portion 102a includes, for example, a cylindrical portion 102d that extends in a columnar or cylindrical shape along the longitudinal direction D4, and a projection portion 102e that projects from the cylindrical portion 102d. The cylindrical portion 102d is inserted into the projection portion 93g which has a cylindrical shape and is formed in the distal end side plate portion 93d of the lubricant unit 83. The projection portion 102e is inserted into the cutout 93h to be hooked on the projection portion 93g when the cylindrical portion 102d is inserted into the projection portion 93g. [0061] The handle portion 102b is a portion that is operated from outside the container body 101 to cause the attachment portion 102a to slide along the slit 105 in the longitudinal direction D4. The handle portion 102b extends from the attachment portion 102a in a direction orthogonal to the longitudinal direction D4, and extends to the outside of the container body 101 through the slit 105. The drawing handle 102 extends longitudinally so that a first end of the drawing handle 102 is positioned closer to the longitudinal end portion 104 of the container body 101 than a second end of the drawing handle, in the longitudinal direction D4. The handle portion 102b extends laterally from the cylindrical portion 102d, and further extends in the longitudinal direction D4 from the second end of the drawing handle 102 toward the first end, so as to be recessed in the longitudinal direction relative to the first end of the drawing handle 102, such that cylindrical portion 102d protrudes at the first end, relative to the handle portion 102b. Accordingly, the handle portion 102b is connected to the cylindrical portion 102d at the second end of the drawing handle 102, but not connected to the cylindrical portion 102d at the first end of the drawing handle 102. Accordingly, a distal end portion of the columnar portion 102d of the attachment portion 102a, that forms the first end of the drawing handle 102, can be inserted into the projection portion 93g of the lubricant unit 83. [0062] The hooking portion 102c positions the attachment portion 102a. The hooking portion 102c is disposed in the accommodation space 103 to come into contact with an inner wall surface of the container body 101, and is wider than the slit 105. When the hooking portion 102c comes into contact with the inner wall surface of the container body 101, the attachment portion 102a is disposed in a predetermined position in the accommodation space in a cross section orthogonal to the longitudinal direction D4 (cf. FIG.15). [0063] An example method for drawing out the lubricant unit 83 from the housing 82 using the external container device 100 will be described with reference to FIGS.17 to 19. [0064] With reference to FIGS. 17 and 18, the longitudinal end portion 104 of the external container device 100 is brought into contact with the seal member 90 attached to the housing 82 of the lubricant application device 80. At this time, the container body 101 is pressed against the housing 82, so that a gap between the housing 82 and the container body 101 is sealed with the seal member 90. [0065] In this state, with reference to FIGS. 18 and 19, the drawing handle 102 is pushed toward the housing 82, so that the cylindrical portion 102d is inserted into the projection portion 93g and the projection portion 102e is inserted into the cutout 93h to be hooked on the projection portion 93g. Accordingly, the drawing handle 102 is attached to the lubricant unit 83. [0066] Subsequently, the drawing handle 102 is slid along the slit 105, toward an end opposite the longitudinal end portion 104 in the longitudinal direction D4. Then, the lubricant unit 83 attached to the drawing handle 102 is drawn into the accommodation space 103 from the longitudinal end portion 104. Accordingly, the lubricant unit 83 is accommodated in the accommodation space 103. [0067] In the example external container device 100 described above, when the drawing handle 102 is attached to the lubricant unit 83 and the drawing handle 102 is slid along the slit 105, the lubricant unit 83 can be drawn into the accommodation space 103 of the container body 101. Moreover, since the gap between the housing 82 and the container body 101 is sealed with the seal member 90 due to a pressure of container body 101 against the housing 82, the container body 101 can be drawn out from the housing 82 without exposing the lubricant unit 83 to the outside. Accordingly, the toner can be suppressed from scattering from the lubricant unit 83 to the outside. [0068] It should be appreciated that all the aspects, advantages, and features described in the specification are not necessarily achieved by or included in any one specific example. In effect, various examples have been described in the specification, and it is apparent that the arrangements and details can be also changed depending on examples. [0069] For example, the separation guide may not be formed of the separation guide surface, but may be formed of a contact-and-separation mechanism that mechanically separates the lubricant unit from the application roller. [0070] In addition, the opening which is formed in the end portion of the housing and through which the lubricant unit is mounted and removed may be openable and closable by an opening and closing mechanism such as a shutter or a door. For example, when the lubricant unit is set, the opening may be configured to be closed, and when the lubricant unit is replaced, the opening may be configured to be opened. [0071] In addition, the drawing handle of the external container device may be attached to the lubricant unit with any structure. For example, hook-shaped projections may be formed in both the drawing handle and the lubricant unit and the hooks may be latched on each other, so that the drawing handle is attached to the lubricant unit. [0072] It is to be understood that not all aspects, advantages and features described herein may necessarily be achieved by, or included in, any one particular example. Indeed, having described and illustrated various examples herein, it should be apparent that other examples may be modified in arrangement and detail is omitted.