KR20230012336A - cam device with reduction ratio profile corresponding to load torque profile of cam - Google Patents

Abstract

Disclosed is a cam driving device which comprises: a rotary cam moving an object to be moved; a load application member applying load between the object to be moved and the rotary cam; a driving motor; and a reduction unit interposed between the driving motor and the rotary cam. The reduction unit has a reduction ratio profile having the same phase with a load profile of the rotary cam.

Description

Cam drive device having a reduction ratio profile corresponding to the load torque profile of the cam {cam device with reduction ratio profile corresponding to load torque profile of cam}

A cam structure is used to change the operation mode of the device or to change the position, phase, etc. of parts in the device. A load is applied to the moving object in a direction maintained at a certain position. The load may be provided by, for example, an elastic member such as a spring. The load varies in proportion to the amount of deformation of the elastic member. In this structure, the load profile of the cam is synchronized with the change profile of the elastic force of the elastic member. The load of the drive motor that drives the cam also fluctuates in sync with the load profile of the cam. A change in the load of the driving motor may cause noise and vibration.

1 to 3 are schematic configuration diagrams of an example of a cam driving device, each showing a state in which a moving object is located at an upper position, an intermediate position, and a lower position.
FIG. 4 shows an example of a load torque profile applied to a rotating cam, a first gear, a second gear, a drive motor, and a reduction ratio profile in an example of the cam driving device shown in FIGS. 1 to 3 .
5 is a schematic configuration diagram of an example of a cam driving device.
FIG. 6 shows an example of a load torque profile applied to a rotary cam, a first gear, a second gear, and a driving motor in an example of the cam driving device shown in FIG. 5 .
7 is a schematic configuration diagram of an example of a cam driving device.
8 is a schematic configuration diagram of an example of an image forming apparatus.
9 and 10 are schematic configuration diagrams of an example of a fixing device. FIG. 9 shows a state in which a fixation nip is formed, and FIG. 10 shows a state in which the fixation nip is released.
11 and 12 are diagrams showing an example of a structure for moving an intermediate transfer roller. FIG. 11 shows a state in which the intermediate transfer roller is located in a pressing position, and FIG. 12 shows a state in which the intermediate transfer roller is located in a releasing position. show

A structure in which a moving object is moved using a cam is employed in various devices. Cams are generally rotated. The moving object may be moved from an initial position to a target position, for example. For example, a load may be applied to the moving object in a direction maintained at an initial position. The load may be provided by, for example, an elastic force of an elastic member. While the moving object is returned to the initial position from the initial position through the target position by the cam, the magnitude of the elastic force is changed. The load torque applied to the cam also changes in sync with the change in magnitude of the elastic force. A driving motor that drives the cam is selected in consideration of the maximum value of the load torque applied to the cam. For example, the driving motor is selected to produce a rated torque obtained by adding a predetermined margin to the maximum value of the load torque applied to the cam. While the drive motor is rotating, the load torque applied to the drive motor changes. If the change in load torque is large, vibration and noise may occur.

The cam driving device of this example includes a moving object, a rotating cam that moves the moving object, a load applying member that applies a load between the moving object and the rotating cam, a driving motor, and a reduction unit interposed between the rotating cam and the driving motor. While the rotary cam rotates, the load applied to the rotary cam periodically changes. The reduction unit has a structure capable of reducing fluctuations in load torque applied to the drive motor. The reduction unit has a structure in which the reduction ratio is periodically changed. The phase of the reduction ratio profile of the reduction unit may be the same as the phase of the load profile of the rotation cam. For example, the phase of the maximum value of the load applied to the rotation cam may be the same as the phase of the maximum value of the reduction ratio of the reduction unit. Additionally, the phase of the minimum value of the load applied to the rotary cam may be the same as the phase of the minimum value of the gear ratio. The fact that the phase of the reduction ratio profile of the reduction unit is identical to the phase of the load profile of the rotation cam does not mean that the two phases are exactly the same, and the phase of the maximum and minimum values of the load applied to the rotation cam is the maximum value of the reduction ratio of the reduction unit. It may include a case in which the phase of the minimum value and the same within the error range, and a case in which the two phases do not deviate to the extent that they cannot be regarded as the same case. According to this configuration, the difference between the maximum value and the minimum value of the load torque applied to the drive motor is reduced. In other words, the fluctuation range of the load torque of the driving motor may be reduced, so that vibration and noise of the driving motor may be reduced. In addition, when a DC motor is used as the drive motor, the rotational speed change of the drive motor is reduced so that the rotation cam can be stably rotated.

The configuration of the deceleration unit may vary. As an example, the reduction unit may be implemented by employing a gear whose radius of the pitch circle changes according to each phase. The deceleration unit may be implemented by a first gear having a first pitch circle profile corresponding to the load profile of the rotating cam and a second gear having a second pitch circle profile having an opposite phase to the first pitch circle profile. The first gear may be a driven gear connected to the rotating cam, and the second gear may be a driving gear connected to the driving motor. The first gear and the second gear may be eccentric gears. The first gear and the second gear may be elliptical gears.

The cam driving device described above can be variously applied to image forming apparatuses. As an example, the cam driving device may be employed as a structure for forming/disengaging a fixing nip between a heating member and a pressing member in a fixing unit. As an example, a cam driving device may be employed as a structure for moving an intermediate transfer roller to form/release an intermediate transfer nip between a photoconductor and an intermediate transfer belt. Hereinafter, embodiments of an image forming apparatus including a cam driving device, a fixing device, and an intermediate transfer belt assembly will be described in detail with reference to the accompanying drawings. In addition, components having substantially the same functional configuration in this specification and drawings are assigned the same reference numerals, thereby omitting redundant description.

1 to 3 are schematic configuration diagrams of an example of a cam driving device, each showing a state in which a moving object is positioned at an upper position, an intermediate position, and a lower position. 1 to 3 , the cam driving device 1000 includes a moving object 10, a rotating cam 20 that moves the moving object 10 according to a rotational phase, a moving object 10 and a rotating cam ( 20), the load application member 30 for applying a load between the drive motor 50, and the gear ratio interposed between the drive motor 50 and the rotation cam 20 and having the same phase as the load profile of the rotation cam 20 It may include a deceleration part 40 having a profile.

The rotation cam 20 may include a cam portion 22 whose distance from the central axis 21 changes according to the rotation phase. The cam part 22 may come into contact with the moving object 10 . The moving object 10 may be moved to a superior position (FIG. 1) and a lower inferior position (FIG. 3) according to the rotational phase of the rotation cam 20. The load applying member 30 may apply force to the moving object 10 so that the moving object 10 and the cam portion 22 come into contact with each other. The load applying member 30 may apply force to the moving object 10 in a direction in which it moves to any one of the upper and lower positions. For example, the load applying member 30 may be implemented by a spring that applies an elastic force to the moving object 10 in a direction positioned at a lower body position.

The rotation cam 20 is rotated by the drive motor 50 . A deceleration unit 40 is interposed between the rotation cam 20 and the drive motor 50 . The driving motor 50 may be directly connected to the reduction unit 40 or may be connected to the reduction unit 40 by a power transmission member such as a gear or a belt. Although not shown in the drawing, a deceleration structure with a fixed deceleration ratio may be interposed between the driving motor 50 and the deceleration unit 40 . As a result, the value of the load torque applied to the drive motor 50 can be lowered as a whole. The rotation cam 20 may be directly connected to the reduction unit 40 or may be connected to the reduction unit 40 by a power transmission member such as a gear or a belt.

The load torque applied to the rotating cam 20 is the cam radius of the cam portion 22, the force applied to the moving object 10 by the load applying member 30, and the distance between the cam portion 22 and the moving object 10. depends on the coefficient of friction. Here, assuming that the cam radius is r, the force applied to the moving object 10 by the load applying member 30 is f, and the friction coefficient is μ, the load torque τ = μ×f×r. The cam radii are r1, r2, and r3 at the upper, middle, and lower positions, respectively, and r1 > r2 > r3. The force applied to the moving object 10 by the load applying member 30 is proportional to the amount of deformation of the load applying member 30 . If the free field of the load applying member 30 is d, the deformation amounts of the load applying member 30 are d-d1, d-d2, and d-d3 at the upper position, the middle position, and the lower position, respectively, (d- d1)>(d-d2)>(d-d3). Accordingly, if the forces applied to the moving object 10 by the load application member 30 are f1, f2, and f3 at the upper position, the middle position, and the lower position, respectively, f1>f2>f3. Since the load torque of the rotary cam 20 is τ = μ×f×r, τ1 = μ×f1×r1, τ2 = μ×f2×r2, τ3 = μ×f3 at the upper position, middle position, and lower position, respectively ×r3, and τ1>τ2>τ3. While the rotary cam 20 is rotated one time, the moving object 10 is always moved to the position-lower position-upper position, and the load torque applied to the rotary cam 20 becomes the maximum value-minimum value-maximum value. The load torque profile of the rotary cam 20 gradually decreases between the maximum and minimum values and gradually increases between the minimum and maximum values.

The load torque of the rotary cam 20 is reduced by the reduction unit 40 and applied to the drive motor 50 . The reduction unit 40 has a structure capable of reducing the variation range of motor load torque acting on the driving motor 50 . For example, the deceleration unit 40 may have a load profile of the rotary cam 20, that is, a load torque profile and a gear ratio profile of the same phase. For example, when the load torque of the rotary cam 20 is maximum, the reduction unit 40 may have the maximum reduction ratio, and when the load torque of the rotation cam 20 is minimum, the reduction unit 40 may have the minimum You can have a reduction ratio. The reduction ratio may gradually decrease between the maximum value and the minimum value, and may gradually increase between the minimum value and the maximum value. The reduction ratio profile of the reduction unit 40 may not have the same phase as the load profile of the rotary cam 20, and there may be a slight phase difference between the reduction ratio profile and the load profile. Here, the phase difference is that when the load torque of the rotation cam 20 is maximum, the reduction ratio of the reduction unit 40 is almost maximum, and when the load torque of the rotation cam 20 is minimum, the reduction ratio of the reduction unit 40 is almost It can mean the extent to which it becomes a minimum.

The reduction part 40 may include a first gear 41 and a second gear 42 . The central axis 411 of the first gear 41 may be coaxial with the central axis 21 of the rotation cam 20 . The first gear 41 may be connected to the rotation cam 20 by a power transmission member such as a gear or a belt. The rotation phase of the first gear 41 may be the same as that of the rotation cam 20 . The central axis 421 of the second gear 42 may be a rotational axis of the driving motor 50 . The second gear 42 may be connected to the driving motor 50 by a power transmission member such as a gear or a belt.

The first gear 41 has a first pitch circle 412 . The first gear 41 has a first pitch circle profile corresponding to the load profile of the rotary cam 20 . Having a first pitch circle profile corresponding to the load profile of the rotating cam 20 means that when the cam radius of the cam portion 22 of the rotating cam 20 facing the moving object 10 is maximum, the second gear ( 42) means that the radius of the pitch circle of the first gear 41 meshed with is the largest. In other words, when the load torque of the rotary cam 20 is maximum, the radius of the first pitch circle 412 of the first gear 41 is maximized at the position engaged with the second gear 42, and the rotary cam ( 20), the radius of the first pitch circle 412 of the first gear 41 at a position meshing with the second gear 42 may be minimized. The second gear 42 meshes with the first gear 41 . The second gear 42 has a second pitch circle 422 . The second gear 42 has a second pitch circle profile having an opposite phase to the first pitch circle profile. Having a second pitch circle profile having an opposite phase to the first pitch circle profile means that the radius of the first pitch circle 412 is the maximum or When it is minimum, it means that the radius of the corresponding second pitch circle 422 becomes minimum or maximum.

As an example, the first gear 41 and the second gear 42 may be eccentric gears. The first pitch circle 412 and the second pitch circle 422 may be circular and may have the same diameter. The central axis 411 of the first gear 41 may be eccentric by a first distance from the center of the first pitch circle 412 . Similarly, the central axis 421 of the second gear 42 may be eccentric by a second distance from the center of the second pitch circle 422 . The first distance and the second distance are the same. The distance between the axes of the first gear 41 and the second gear 42, for example, the distance between the central axis 411 of the first gear 41 and the central axis 421 of the second gear 42 (AX ) is constant. The radius of the first pitch circle 412 of the first gear 41 and the second pitch circle 422 of the second gear 42 at the point where the first gear 41 and the second gear 42 mesh with each other The sum of the radii of is equal to the distance AX between the central axis 411 of the first gear 41 and the central axis 421 of the second gear 42 . Therefore, the first gear 41 and the second gear 42 may be engaged with each other and rotated. At the point where the first gear 41 and the second gear 42 mesh with each other, the radius of the first pitch circle 412 of the first gear 41 is P1 and the second pitch circle of the second gear 42 ( When the radius of 422) is P2, the reduction ratio of the reduction unit 40 is defined as P1/P2. For example, assuming that the reduction ratio of the reduction unit 40 is RD1 = P11/P21, RD2 = P12/P22, and RD3 = P13/P23 at the top position, the middle position, and the bottom position, respectively, RD1 > RD2 > RD3. The phases of the maximum value τ1 and the minimum value τ2 of the load torque profile of the rotary cam 20 may correspond to the phases of the maximum value RD1 and minimum value RD3 of the reduction ratio of the reduction unit 40, respectively. Of course, the phases of the maximum value τ1 and the minimum value τ3 of the load torque profile of the rotary cam 20 must completely coincide with the phases of the maximum value RD1 and minimum value RD3 of the reduction ratio of the reduction unit 40, respectively. They can be almost identical or similar, if not completely identical.

4 is an example of the cam driving device 1000 shown in FIGS. 1 to 3, which is applied to the rotary cam 20, the first gear 41, the second gear 42, and the driving motor 50. An example of the load torque profile and the reduction ratio profile of the reduction unit 40 is shown. In FIG. 4, ①, ②, and ③ denote a superior position, an intermediate position, and a lower inferior position, respectively. Referring to FIG. 4 , the load torque profiles of the rotating cam 20 and the first gear 41 are in the same phase. The load torque profile of the second gear 42 has a phase opposite to that of the first gear 41 . The load torque of the second gear 42 is smaller than the load torque of the first gear 41 by the reduction unit 40 . The load torque profiles of the second gear 42 and the driving motor 50 are in the same phase. In FIG. 4, the load torque profiles of the rotary cam 20 and the first gear 41 are shown to have completely identical phases, but the two phases may be out of alignment within a certain error range, and it can be considered that the two phases are the same. In the case where there is no misalignment, the two phases can also be regarded as the same.

Referring to FIG. 4 , while the rotation cam 20 rotates one time, the load torque of the rotation cam 20 is not constant. When a reduction unit having a fixed reduction ratio is employed, the load torque transmitted to the drive motor 50 has the same phase as the load torque of the rotary cam 20, and only the magnitude of the load torque is reduced. The difference in load torque between the upper and middle positions (LTV201) is greater than the difference in load torque between the middle and lower positions (LTV202). While the rotation cam 20 rotates once, the maximum variation range of the load torque becomes LTV201+LTV202. In this case, when the moving object 10 is moved from the middle position to the upper position, a high load is applied to the driving motor 50, and when the moving object 10 is moved from the middle position to the lower position, the load torque is small. As a result, the difference between the maximum load torque and the minimum load torque across the drive motor 50, that is, the torque variation is large. In addition, in order to ensure stable operation of the cam driving device 1000, the drive motor 50 is selected to have a rated torque that is about 10% to 30% greater than the maximum load torque. Accordingly, the price of the driving motor 50 may be high. In addition, while the driving motor 50 rotates, a large amount of torque variation may generate vibration and driving noise. Also, when a DC motor is used as the driving motor 50, the rotational speed of the motor may become non-uniform.

According to this example, since the reduction unit 40 having a reduction ratio in phase with the load torque profile of the rotation cam 20 is employed, the amount of change in the load torque applied to the drive motor 50 while the drive motor 50 rotates. this is very small That is, as shown in FIG. 4 , the deceleration unit 40 has a profile in which the reduction ratio is large in the section corresponding to the middle position and the top position, and the reduction ratio is small in the section corresponding to the middle position and the bottom position. Accordingly, the fluctuation range (LTV50) of the load torque acting on the drive motor 50 is reduced, so that the vibration of the drive motor 50 and the resulting noise can be reduced. Also, since the driving motor 50 can be rotated at an almost uniform speed, a relatively low-cost DC motor can be employed as the driving motor 50 . The DC motor has a simple driving circuit, and thus the cost of the cam driving device 1000 can be reduced.

5 is a schematic configuration diagram of an example of a cam driving device. 6 is a load torque profile applied to the rotary cam 20-1, the first gear 41, the second gear 42, and the driving motor 50 in one example of the cam driving device shown in FIG. show an example In FIG. 6, ①, ②, and ③ denote a superior position, an intermediate position, and a lower inferior position, respectively. In the cam driving device 1000-1 of this example, the profile of the cam portion 22-1 of the rotating cam 20-1 is the first and second pitch sources of the first gear 41 and the second gear 42 ( It is different from the cam driving device 1000 shown in FIGS. 1 to 3 in that the profiles 421 and 422 are almost the same. According to this configuration, as shown in FIG. 6 , the load torque applied to the driving motor 50 can be substantially constant while the driving motor 50 is rotating. Also, when a DC motor is employed as the drive motor 50, the drive motor 50 can be rotated at a substantially uniform speed. Of course, the load torque applied to the drive motor 50 may vary as indicated by a dotted line due to errors in component manufacturing, assembly errors, and the like.

7 is a schematic configuration diagram of an example of a cam driving device. The cam driving device 1000-2 of this example includes a rotating cam 20-2 having an elliptical cam portion 22-2, a first pitch circle 412-2 and a second pitch circle 422-2 having an elliptical shape. 2) the cam driving device shown in Figs. There is a difference from (1000). The rotary cam 20-2 has an elliptical cam portion 22-2. While the rotating cam 20-2 rotates once, the moving object 10 moves between the upper and lower positions twice. The first elliptical gear 41-2 has a first pitch circle 412-2 having an elliptical shape. The profile of the first pitch circle 412-2 corresponds to the load profile of the rotary cam 20-2. The second elliptical gear 42-2 meshes with the first elliptical gear 41-2. The second elliptical gear 42-2 has a second pitch circle 422-2 having an elliptical shape. The first pitch circle 412-2 and the second pitch circle 422-2 have the same form factor. The second elliptical gear 42-2 has a second pitch circle profile having an opposite phase to the first pitch circle profile. Having a first pitch circle profile corresponding to the load profile of the rotary cam 20-2 means that when the cam radius of the cam portion 22 of the rotary cam 20-2 is maximum, the second elliptical gear 42-2 ) means that the radius of the pitch circle of the first elliptical gear 41-2 meshed with is the maximum. Having a second pitch circle profile having an opposite phase to the first pitch circle profile means that the first pitch circle 412 is located at the position where the first elliptical gear 41-2 and the second elliptical gear 42-2 mesh. When the radius of -2) is the maximum or minimum, it means that the radius of the corresponding second pitch circle 422-2 becomes the minimum or maximum. According to this configuration, the load torque applied to the drive motor 50 can be substantially constant. In addition, when a DC motor is employed as the drive motor 50, the drive motor 50 can be rotated at a substantially uniform speed.

Hereinafter, examples of structures to which the aforementioned cam driving device is applied will be described. 8 is a schematic configuration diagram of an example of an image forming apparatus. The image forming apparatus of this example prints a color image on a print medium P by an electrophotographic method. Referring to FIG. 8 , a plurality of developing devices 210 , an exposure device 250 , an intermediate transfer belt 260 , a transfer roller 270 , and a fixing device 280 are illustrated.

The plurality of developing devices 210 includes four developing devices 210 for forming toner images of yellow (Y), magenta (M), cyan (C), and black (K) colors. can do. Each of the four developing devices 210 may accommodate cyan (C), magenta (M), yellow (Y), and black (K) color developers. Yellow (Y), magenta (M), cyan (C), and black (Y), magenta (M), cyan (C), and black from four developer cartridges 220 containing yellow (Y), magenta (M), cyan (C), and black (K) color developers, respectively. (K) color developers may be supplied to the four developing devices 210 .

The developing device 210 may include a photosensitive drum 212 on which an electrostatic latent image is formed, and a developing roller 211 that develops a visible toner image by supplying a developer to the electrostatic latent image. The photosensitive drum 212 is an example of a photoconductor on which an electrostatic latent image is formed, and may include a conductive metal pipe and a photosensitive layer formed on the outer circumference thereof. The charging roller 215 is an example of a charger that charges the photosensitive drum 212 to have a uniform surface potential. Instead of the charging roller 215, a charging brush, a corona charger, or the like may be employed.

Although not shown in the drawings, the developing unit 210 is a charging roller cleaner that removes foreign substances such as developer or dust attached to the charging roller 215 and a developing area where the photosensitive drum 212 and the developing roller 211 face each other. A regulating member or the like for regulating the amount of developer supplied may be further provided. The cleaning member 217 removes the developer remaining on the surface of the photosensitive drum 212 after an intermediate transfer process described later. The cleaning member 217 may be, for example, a cleaning blade that comes into contact with the surface of the photosensitive drum 212 to scrape off the developer. Although not shown in the drawings, the cleaning member 217 may be a cleaning brush that scrapes off the developer by coming into contact with the surface of the photosensitive drum 212 while being rotated.

The exposure unit 250 irradiates the photosensitive drum 212 with light modulated corresponding to image information to form an electrostatic latent image on the photosensitive drum 212 . Examples of the exposure device 250 include a laser scanning unit (LSU) using a laser diode as a light source or an LED exposure device using a light emitting diode (LED) as a light source.

The developer may include, for example, a toner, or a toner and a carrier. The developing roller 211 may be spaced apart from the photosensitive drum 212 . The distance between the outer circumferential surface of the developing roller 211 and the outer circumferential surface of the photosensitive drum 212 may be, for example, several tens to hundreds of microns. The developing roller 211 may be a magnetic roller. Also, the developing roller 211 may have a shape in which a magnet is disposed in a rotating developing sleeve. In the developing unit 210, the toner is mixed with the carrier, and the toner is adhered to the surface of the magnetic carrier. The magnetic carrier is attached to the surface of the developing roller 211 and transported to the developing area where the photosensitive drum 212 and the developing roller 211 are opposed to each other. A regulating member (not shown) regulates the amount of developer delivered to the developing area. Only toner is supplied to the photosensitive drum 212 by the developing bias voltage applied between the developing roller 211 and the photosensitive drum 212 to develop an electrostatic latent image formed on the surface of the photosensitive drum 212 into a visible toner image. .

The intermediate transfer belt 260 temporarily accommodates toner images developed on the photosensitive drums 212 of the four developing units 210. The intermediate transfer belt 260 is supported by a plurality of support rollers 262 , 263 , 264 , and 265 and is circulated. Four intermediate transfer rollers 261 are disposed facing the photosensitive drums 212 of the four developing devices 210 with the intermediate transfer belt 260 interposed therebetween. The intermediate transfer roller 261 presses the intermediate transfer belt 260 against the photosensitive drum 212 to form an intermediate transfer nip. An intermediate transfer bias voltage for intermediate transfer of the developed toner image on the photosensitive drum 212 to the intermediate transfer belt 260 is applied to the intermediate transfer roller 261 . The transfer roller 270 is positioned to face the intermediate transfer belt 260. The transfer roller 270 is positioned opposite to the support roller 262, for example, and is pressed against the intermediate transfer belt 260 to form a transfer nip. The print medium P is taken out from the paper feed unit 290 and supplied to the transfer nip along the supply path 291 . A transfer bias voltage for transferring the toner image transferred on the intermediate transfer belt 260 to the print medium P is applied to the transfer roller 270 . The fixing unit 280 applies heat and/or pressure to the toner image transferred to the print medium P to fix it to the print medium P. The print media P on which printing is completed is discharged by the discharge roller 292 .

Various members for changing positions may exist in the image forming apparatus, and for this purpose, the cam driving device described in FIGS. 1 to 7 may be applied. As an example, the cam driving device may be applied to the fixing unit 280 to form/disengage the fixing nip. As an example, a cam drive device may be applied to form/release an intermediate transfer nip. Hereinafter, examples of cam driving devices applied to image forming apparatuses will be described.

9 and 10 are schematic configuration diagrams of an example of a fixing device. FIG. 9 shows a state in which a fixation nip is formed, and FIG. 10 shows a state in which the fixation nip is released. Referring to FIGS. 9 and 10 , a heating member and a backup member of the fixing unit are provided. The heating member and the backup member are pressed together to form the fixing nip 101 . The heating element in this example may be a flexible endless belt 120 . The backup member may be a backup roller 110 . The heater 130 is located inside the endless belt 120 to heat the endless belt 120. The backup roller 110 is positioned outside the endless belt 120 facing the heater 130 . The elastic member 170 provides a pressing force for forming the fixation nip 101 to the endless belt 120 . In this example, the elastic member 170 provides a pressing force to the heater 130 . The heater 130 and the backup roller 110 are pressed toward each other with the endless belt 120 interposed therebetween by the pressing force of the elastic member 170 to form the fixing nip 101 . The heater 130 heats the endless belt 120 in the fixing nip 101. When a print medium P having a toner image formed thereon passes through the fixing nip 101, the toner image is fixed on the print medium P by heat and pressure.

The pressing force provided to the endless belt 120 by the elastic member 170 can be varied. For example, while fixing is performed, sufficient pressing force is provided to the endless belt 120 to improve fixation, and while fixing is not performed, in order to reduce stress applied to the endless belt 120 and the backup roller 110 The pressing force can be reduced or released. To this end, a cam driving device 1000-3 may be employed. In this example, the cam driving device 1000 shown in FIGS. 1 to 3 can be applied as the cam driving device 100-3.

Referring to FIGS. 9 and 10 , a pressure lever 160 rotatable about a hinge 161 is shown. The pressing lever 160 corresponds to the moving object 10 . The elastic member 170 corresponds to the load application member 30 and may be, for example, a compression coil spring that applies an elastic force to the pressure lever 160 . The heater 130 is supported by the support member 140 . The pressure bracket 150 is supported on the support member 140 and protrudes outward from the edge of the endless belt 120 in the width direction. The pressure lever 160 may form the fixation nip 101 by pressing the pressure bracket 150 . The pressure lever 160 is driven by the rotary cam 20 . The cam portion 22 of the rotation cam 20 may face the cam contact portion 162 of the pressing lever 160 . As described in FIGS. 1 to 3 , the rotation cam 20 is connected to the drive motor 50 via the deceleration part 40 .

9, when the maximum cam radius portion 22a of the cam portion 22 contacts the cam contact portion 162 of the pressing lever 160, the pressing lever 160 rotates around the hinge 161 The similar position (second position) is reached. In this state, since the elastic force of the elastic member 170 does not act on the endless belt 120, the anchoring nip 101 is released. In a state in which the fixing nip 101 is released, the jam of the printing medium P generated in the fixing nip 101 can be removed.

In the state shown in FIG. 9, when the rotation cam 20 is rotated 180 degrees, as shown in FIG. 10, the minimum cam radius portion 22b of the cam portion 22 faces the cam contact portion 162 of the pressing lever 160. . At this time, the minimum cam radius portion 22b of the cam portion 22 may be spaced apart from the cam contact portion 162 of the pressure lever 160 . The pressing lever 160 is rotated around the hinge 161 by the elastic force of the elastic member 170 to reach the lower lowering position (first position). The pressure lever 160 presses the heater 130 via the pressure bracket 150 and the support member 140, and the fixing nip 101 is formed between the endless belt 120 and the backup roller 110.

Although not shown in the drawing, when the rotary cam 20 is rotated 90 degrees in the state shown in FIG. 9, the pressing lever 160 may be located in an intermediate position, and the pressing force of the elastic member 170 is reduced. In this state, a print job for the print medium P such as an envelope can be performed. Accordingly, it is possible to prevent wrinkles from being generated in the envelope during the fixing process. The cam driving devices 1000-1 and 1000-2 shown in FIG. 5 or 7 may be applied as the cam driving devices 1000-3 that move the pressure lever 160 to the upper, middle, and lower positions. there is.

Referring to FIG. 8 , the intermediate transfer roller 261 may be positioned at a pressing position where the intermediate transfer belt 260 is pressed and brought into contact with the photosensitive drum 212 to form an intermediate transfer nip during printing. If a long period of time elapses in the state where the intermediate transfer nip is formed, the intermediate transfer roller 261 is deformed, the surface of the photosensitive drum 212 and the surface of the intermediate transfer belt 260 are damaged due to friction, and the photosensitive drum 212 due to static electricity ) may cause damage to the photosensitive layer. Considering this point, when printing is not performed, the intermediate transfer roller 261 may be moved from a pressing position to a releasing position where the intermediate transfer nip is released by releasing the pressing force applied to the intermediate transfer belt 260. A cam driving device 1000-4 may be applied to move the intermediate transfer roller 261 to the pressing position and the releasing position. 11 and 12 are examples of a structure for moving the intermediate transfer roller 261. FIG. 11 shows a state in which the intermediate transfer roller 261 is positioned at a pressing position, and FIG. 12 shows a state in which the intermediate transfer roller 261 is released. Shows the status of the location.

11 and 12, an intermediate transfer belt 260, an intermediate transfer roller 261, a holder 310, an elastic member 320, and a slider 330 are shown. The intermediate transfer roller 261 is located inside the intermediate transfer belt 260. The holder 310 rotatably supports the intermediate transfer roller 261 and is movable to a press position where the intermediate transfer roller 261 presses the intermediate transfer belt 260 outward and a release position where the press force is released. The intermediate transfer roller 261 is rotatably supported on the holder 310 . The holder 310 includes a hinge 311 and a first arm 312 and a second arm 313 extending from the hinge 311 in different directions. The holder 310 is supported on a first side frame (not shown) so as to pivot about a hinge 311 . One end of the intermediate transfer roller 261 is rotatably supported by the first arm 312 of the holder 310 . The holder 310 may be rotated around the hinge 311 to move the intermediate transfer roller 261 to a pressing position and a releasing position. The holder 310 is elastically biased by the elastic member 320 so as to be rotated in the direction of placing the intermediate transfer roller 261 in the pressing position. Although not shown in the drawings, the other end of the intermediate transfer roller 261 can be moved to a pressing position and a release position on a second side frame (not shown) facing the first side frame by the same structure as described above. supported A protrusion 314 protruding in the axial direction is provided on the second arm 313 of the holder 310 .

The slider 330 is connected to the holder 310 to be slid to a first position (FIG. 11) for placing the holder 310 in a pressing position and a second position (FIG. 12) for placing the holder 310 in a release position. can For example, a pair of sliders 330 are supported on the first side frame and the second side frame to be slid to the first and second positions, respectively. An interference protrusion 331 interfering with the protrusion 314 of the holder 310 is provided on the slider 330 . Although not shown in the drawings, the four intermediate transfer rollers 261 are supported by the holder 310 in the moving directions D1 and D2 of the slider 330 and are arranged so as to be able to rotate to a pressing position and a release position. 330 is provided with four interference protrusions 331 corresponding to each of the protrusions 314 of the four holders 310 .

As shown in FIG. 11 , when the slider 330 slides in the D1 direction and is positioned at the first position, the interference protrusion 331 is spaced apart from the protrusion 314 of the holder 310 . Accordingly, the holder 310 rotates in the B1 direction around the hinge 311 by the elastic force of the elastic member 320, and the intermediate transfer roller 261 is positioned at the pressing position. The intermediate transfer roller 261 presses the intermediate transfer belt 260 against the photosensitive drum 212 to form an intermediate transfer nip. As shown in FIG. 12 , when the slider 330 slides in the direction D2 and is positioned at the second position, the interference protrusion 331 pushes the protrusion 314 of the holder 310 in the direction D2. Then, the holder 310 is rotated around the hinge 311 in a direction opposite to the elastic force of the elastic member 320, that is, in the B2 direction, and the intermediate transfer roller 261 is positioned at the released position. The pressing force applied to the intermediate transfer belt 260 by the intermediate transfer roller 261 is released, and the intermediate transfer nip between the intermediate transfer belt 60 and the photosensitive drum 212 is released.

A cam driving device 1000-4 is applied to move the slider 330 to the first and second positions. As the cam driving device 1000-4, the cam driving device 1000 shown in Figs. 1 to 3 can be employed. In this case, the slider 330 corresponds to the moving object 10 and the elastic member 320 corresponds to the load applying member 30 . The rotating cam 340 contacts the slider 330 and slides the slider 330 between the first position and the second position while being rotated. The rotation cam 340 is rotatably supported by the first and second side frames about the central axis 341 . The rotation cam 340 includes a cam portion 342 . The rotation cam 340 corresponds to the rotation cam 20 of the cam driving device 1000 . The slider 330 includes first and second contact portions 332 and 333 that selectively contact the cam portion 342 according to the rotational phase of the rotation cam 340 .

Referring to FIG. 11 , the cam portion 342 of the rotating cam 340 is in contact with the first contact portion 332 . The slider 330 is located at the first position. Since the interference protrusion 331 is spaced apart from the protrusion 314 of the holder 310, the elastic force of the elastic member 320 does not act on the slider 330. The load torque applied to the rotary cam 340 is minimized. The state in which the slider 330 is located at the first position corresponds to the state in which the moving object 10 shown in FIG. 3 is located in the lower position. The first gear 41 and the second gear 42 are meshed with each other so that the reduction ratio is minimized.

When the rotary cam 340 rotates in the state shown in FIG. 11 , the cam part 342 starts to come into contact with the second contact part 333 and the slider 330 starts to slide in the direction D2. When the slider 330 is further slid in the direction D2 after the interference protrusion 331 of the slider 330 comes into contact with the protrusion 314 of the holder 310, the interference protrusion 331 moves to the protrusion 314 of the holder 310. ) in the direction of D2. The holder 310 is rotated around the hinge 311 in a direction opposite to the elastic force of the elastic member 320, that is, in the B2 direction. A force that hinders sliding in the D2 direction is applied to the slider 330 by the elastic force of the elastic member 320, and a load torque is applied to the rotation cam 340 by this force. The load torque is gradually increased until the rotary cam 340 is rotated by, for example, 180 degrees. When the rotary cam 340 is rotated 180 degrees, the slider 330 reaches the second position and the intermediate transfer roller 261 reaches the release position to release the intermediate transfer nip, as shown in FIG. 12 . When the slider 330 is positioned at the second position, the load torque applied to the rotary cam 340 is maximized. The state in which the slider 330 is located at the second position corresponds to the state in which the moving object 10 shown in FIG. 1 is located in the similar position. The first gear 41 and the second gear 42 are meshed with each other so that the reduction ratio is maximized. As the cam driving device 1000-4 for moving the slider 330 to the first position, the cam driving devices 1000-1 and 1000-2 shown in FIG. 5 or 7 may be applied.

Although the present disclosure has been described with reference to the embodiments shown in the drawings, this is only exemplary, and those skilled in the art can make various modifications and equivalent other embodiments therefrom. will understand Therefore, the true technical protection scope of the present disclosure should be determined by the claims below.

Claims (15)

moving object;
a rotating cam that moves the moving object;
a load applying member for applying a load between the moving object and the rotating cam;
drive motor;
and a reduction unit interposed between the drive motor and the rotation cam and having a gear ratio profile of the same phase as a load profile of the rotation cam. According to claim 1,
The cam driving device of claim 1 , wherein phases of the maximum and minimum values of the load profile correspond to phases of the maximum and minimum values of the reduction ratio, respectively. According to claim 1,
The deceleration part,
a first gear having a first pitch circle profile corresponding to the load profile of the rotating cam;
and a second gear meshing with the first gear and having a second pitch circle profile opposite to the first pitch circle profile. According to claim 3,
The first gear and the second gear are eccentric gears. According to claim 3,
The first gear and the second gear are elliptical gears. no heating;
a backup member facing the heating member;
a pressing lever movable to a first position for forming a fixing nip by pressing the heating member against the backup member and a second position for releasing the fixing nip;
an elastic member for applying an elastic force to the pressing lever in a direction positioned at the first position;
a rotating cam for moving the pressing lever to the first position and the second position according to the rotational phase;
drive motor;
and a deceleration unit interposed between the drive motor and the rotation cam and having a gear ratio profile opposite to a load profile of the rotation cam. According to claim 6,
The phases of the maximum and minimum values of the load profile correspond to the phases of the maximum and minimum values of the reduction ratio, respectively. According to claim 6,
The deceleration part,
a first gear having a first pitch circle profile corresponding to the load profile of the rotating cam;
and a second gear meshed with the first gear and having a second pitch circle profile opposite to the first pitch circle profile. According to claim 8,
The first gear and the second gear are eccentric gears. According to claim 8,
The first gear and the second gear are elliptical gears. an intermediate transfer belt to which toner images are temporarily transferred;
an intermediate transfer roller positioned inside the intermediate transfer belt;
a holder rotatably supporting the intermediate transfer roller and movable to a press position where the intermediate transfer roller presses the intermediate transfer belt outwardly and a release position where the press force is released;
an elastic member for applying an elastic force to the holder so as to be moved in a direction positioned at the pressing position;
a slider sliding into a first position for placing the holder in the pressing position and a second position for positioning the holder in the release position;
a rotating cam that contacts and rotates the slider and slides the slider between the first position and the second position;
drive motor;
and a deceleration unit interposed between the drive motor and the rotation cam and having a gear ratio profile opposite to a load profile of the rotation cam. According to claim 11,
Phases of the maximum and minimum values of the load profile correspond to phases of the maximum and minimum values of the reduction ratio, respectively. According to claim 11,
The deceleration part,
a first gear having a first pitch circle profile corresponding to the load profile of the rotating cam;
and a second gear meshed with the first gear and having a second pitch circle profile opposite to the first pitch circle profile. According to claim 13,
The first gear and the second gear are eccentric gears. According to claim 13,
The first gear and the second gear are elliptical gears.

Images