JP2024083715A - Driving device and image forming apparatus - Google Patents

Abstract

The present invention aims to suppress the rotational fluctuation of a rotating body even when the load torque of the rotating body is small.
[Solution] The device comprises a drive motor, a gear for transmitting the driving force of the drive motor, a gear shaft 29 for rotatably supporting the gear, a rear side plate supporting one end of the gear shaft 29 in the axial direction, and a drive frame 37 supporting the other end of the gear shaft 29 opposite the one end in the axial direction, and the drive frame 37 has a leaf spring 37a that urges the other end in a direction in which a reaction force against the driving force acts (arrow 24c), and an abutment surface 44a against which the side surface 29a of the other end abuts as the other end is urged by the leaf spring 37a.
[Selected figure] Figure 8

Description

The present invention relates to a drive device and an image forming apparatus, and more particularly to a rotating body drive device that transmits driving force via gears to a rotating body such as an image carrier used in, for example, a printer, a copier, or a facsimile machine, and an image forming apparatus using the same.

Image forming devices such as printers, copiers, and facsimile machines have a photosensitive layer capable of generating an electrostatic latent image through exposure by an exposure means, and a photosensitive drum that carries a toner image formed through development by a development means. The photosensitive drum rotates when a driving force is transmitted from a drive means, and after toner is attached to the electrostatic latent image by a developer, the toner is transferred onto a recording medium by a transfer device. However, since there is a fair amount of toner that is not transferred to the recording medium by the transfer device and remains on the photosensitive drum (hereinafter referred to as residual toner), a removal means is also provided to remove this residual toner from the photosensitive drum.

There are two main types of removal means. The first type has a cleaning blade, which is brought into strong contact with the rotating photosensitive drum from the counter direction to remove the toner from the photosensitive drum. The second type is generally called a cleanerless type. In the cleanerless type, the residual toner is stirred up and uniformly dispersed by a memory removal member such as a conductive brush arranged to face the outer circumferential surface of the photosensitive drum, and then the toner is collected by the developing unit by electrostatic attraction while the developing unit adheres the toner to the photosensitive drum. Here, there are the following differences between the two removal means in terms of the load torque when rotating the photosensitive drum. First, in the case of a means having a cleaning blade, the load torque is large because the frictional force at the contact point with the blade is large. On the other hand, in the case of a cleanerless means, the load torque is small because almost no frictional force is applied. The cleanerless type has the advantages of being able to reuse the residual toner, not requiring space to collect and store the residual toner, and requiring a small driving torque, which reduces resources, makes the device compact, and saves energy.

Here, if a sudden load fluctuation occurs, the rotation of the photosensitive drum becomes unstable momentarily, and problems such as "blurring" that causes stripes to appear on parts of the image can occur. This problem is generally more pronounced in areas where the load torque is small. That is, compared to means having a cleaning blade, the cleanerless method has the advantage of using less resources, being more compact, and saving energy, but it has the problem that the rotation is more likely to become unstable due to load fluctuations, and image defects such as blurring that causes stripes to appear can easily occur. One cause of this problem is the movement of the support shaft due to play at the tip of the gear support shaft (hereinafter also referred to as the gear shaft tip or support shaft tip). One method for suppressing the play at the gear shaft tip is to insert a mylar sheet or the like into the fitting portion between the tip of the support shaft and the drive frame (see, for example, Patent Document 1).

JP 2010-059998 A

However, the above-mentioned configuration in which a Mylar sheet or similar is inserted into the fitting between the tip of the support shaft and the drive frame has the following problem. In other words, in order to eliminate backlash by inserting it between rigid bodies, the insert member must be made of a material with a certain degree of elasticity, such as resin, and it is not possible to eliminate shaft movement when load fluctuations occur. However, even a slight movement of the shaft can change the rotation of the photosensitive drum.

The present invention was made under these circumstances, and aims to suppress the rotational fluctuation of a rotating body even when the load torque of the rotating body is small.

To solve the above problems, the present invention has the following configuration.

(1) A drive device comprising: a drive source; a gear for transmitting the drive force of the drive source; a gear shaft for rotatably supporting the gear; a first frame for supporting one end of the gear shaft in the axial direction; and a second frame for supporting the other end of the gear shaft opposite the one end in the axial direction, the second frame having a biasing portion for biasing the other end in a direction in which a reaction force against the drive force acts, and an abutment portion against which a side surface of the other end abuts as the other end is biased by the biasing portion.

(2) An image forming apparatus comprising an image carrier on which an electrostatic latent image is formed, a developing means for developing the electrostatic latent image with toner to form a toner image, a transfer means for transferring the toner image to a recording material, a removing means for removing the toner remaining on the image carrier after transfer by the transfer means, and the drive device described in (1) for driving the image carrier.

According to the present invention, it is possible to suppress the rotational fluctuation of the rotating body even when the load torque of the rotating body is small.

1 is a schematic diagram of an image forming apparatus according to a first embodiment of the present invention; FIG. 1 is a top view showing a drive device according to a first embodiment of the present invention; 1 is a rear view of the drive device according to the first embodiment; 1 is a rear view of the gear of the driving device according to the first embodiment; FIG. 13 is a diagram showing the posture of the gear shaft and the fitting state of the tip for comparison with the first embodiment. FIG. 13 is a diagram showing the posture of the gear shaft and the fitting state of the tip for comparison with the first embodiment. FIG. 13 is a diagram showing how each gear transmits drive force for comparison with the first embodiment. FIG. 1 is a diagram showing the shape of a biasing portion of a gear shaft according to a first embodiment; FIG. 13 is a diagram showing the shape of a biasing portion of a gear shaft according to a second embodiment; FIG. 13 is a diagram showing the shape of a biasing portion of a gear shaft according to a third embodiment; FIG. 13 is a diagram showing a drive train according to a fourth embodiment; FIG. 14 is a diagram showing the shape of a biasing portion of a gear shaft;

The following describes in detail the embodiments of the present invention with reference to the drawings.

<Image forming apparatus>
The image forming apparatus of the first embodiment will be described in detail with reference to Fig. 1. Fig. 1 is a schematic diagram of the image forming apparatus 1 of the first embodiment as viewed from the front. In Fig. 1, a photosensitive drum 2, which is an image carrier, is rotatably supported at both ends by a process cartridge 3 containing a black developer (toner). The photosensitive drum 2 receives driving force from the end on the rear side by a driving motor 20, a pinion gear 22, transmission gears 23, 24, 25, and a drum gear 26 shown in Fig. 2, and is driven to rotate in the counterclockwise direction indicated by the arrow in Fig. 1.

The surface of the photosensitive drum 2, which has an organic photoconductor layer applied to it, is uniformly charged by applying a charging voltage to the charging roller 4. The photosensitive drum 2 is selectively exposed to laser light 6 emitted from the laser scanner unit 5, which serves as an exposure means, and an electrostatic latent image is formed. Toner is attached to this electrostatic latent image by the developing roller 7, which serves as a developing means, and the image is developed into a toner image.

The recording paper P, which is a recording material, is loaded in the paper feed cassette 8, and the recording paper P is fed by a feed roller 9 driven at a predetermined timing by a drive motor, which is a drive source and a transmission mechanism, which is a drive transmission means, not shown in FIG. 1. At the same time, the recording paper P is separated by the frictional force of a separation pad 10, and only one sheet of recording paper P is fed. The recording paper P is then transported through a pair of registration rollers (hereinafter referred to as the registration roller pair) 11 to a transfer position where the photosensitive drum 2 and a transfer roller 12, which is a transfer means, come into contact with each other. At the transfer position, the toner image on the photosensitive drum 2 (on the image carrier) is transferred to the recording paper P by the transfer roller 12, to which a predetermined voltage has been applied.

The recording paper P with the unfixed toner image transferred is transported to the fixing roller pair 13, where the toner image is fused and fixed onto the recording paper P by heat and pressure, resulting in an image. The recording paper P transported by the fixing roller pair 13 passes through the discharge roller pair 14 and is discharged and stacked on the discharge tray 15.

The image forming apparatus 1 of the first embodiment is equipped with a brush 19, which is a removal means called a cleanerless system. The brush 19 is a conductive memory removal member arranged to face the outer circumferential surface of the photosensitive drum 2. The brush 19 stirs up and uniformly disperses the toner (hereinafter referred to as residual toner) remaining on the photosensitive drum 2 after transfer. After that, at the contact point with the developing roller 7, the developing roller 7 adheres the toner to the photosensitive drum 2 and the developing roller 7 collects the residual toner by electrostatic attraction.

The image forming device 1 includes a control unit 200, which is a control means. The control unit 200 includes a CPU 200a, a ROM 200b, a RAM 200c, and a timer 200d. The control unit 200 performs various controls of the image forming device 1 described above, in accordance with various programs prestored in the ROM 200b, while using the RAM 200c as a temporary work area. When performing the various controls described above, the control unit 200 controls various timings while referring to the timer 200d. Note that the image forming device to which the present invention described below can be applied is not limited to the configuration of the image forming device 1 shown in FIG. 1.

<Drive unit>
2 is a top view of the image forming apparatus 1 in FIG. 1 for explaining a driving device 100 that drives and rotates the photosensitive drum 2, and also shows arrows indicating the front and rear. The image forming apparatus 1 has a rear plate 27 and a front plate 45. The rear plate 27 and the front plate 45 are made of metal.

The drive motor 20, which is the drive source, is fastened to the rear plate 27 of the image forming apparatus 1 main body (hereinafter also simply referred to as the main body) with screws (not shown) and is controlled by the control unit 200. A pinion gear 22 is press-fitted and fixed to the motor shaft 21, which is the output of the drive motor 20. Gear shafts 28, 29, and 30 are attached to the rear plate 27 by crimping means (crimping fastening), and transmission gears 23, 24, and 25 for transmitting the driving force of the drive motor 20 are rotatably held on the gear shafts 28, 29, and 30. Here, when focusing on the transmission gear 24, the transmission gear 23 close to the drive motor 20 is also referred to as the input side gear or upstream side gear, and the transmission gear 25 far from the drive motor 20 is also referred to as the output side gear or downstream side gear. The same applies when focusing on other gears.

The ends of the gear shafts 28, 29, 30 that are crimped to the rear plate 27 are also referred to as the roots (one end), and the other ends are also referred to as the tips (the other end). In the first embodiment, the roots of the gear shafts 28, 29, 30 are fixed to the rear plate 27 by crimping, but this is not limiting. For example, the gear shafts 28, 29, 30 may be formed integrally with the rear plate 27. The rear plate 27 functions as a first frame that supports one end of the gear shafts 28, 29, 30 in the axial direction.

The photosensitive drum 2 has a hollow structure, and resin flanges 31 and 32 are press-fitted and fixed to both ends. The drum shaft 33 passes through the inside of the photosensitive drum 2 and is fixed and held by the flanges 31 and 32. In other words, the drum shaft 33 and the photosensitive drum 2 can rotate together.

The process cartridge container 34 is positioned by fitting into holes provided in the front side plate 45 and the rear side plate 27, and is held by a pressing means (not shown). The drum shaft 33 is rotatably held in the process cartridge container 34, and the drum gear 26 is attached to the tip of the rear side of the drum shaft 33 by a parallel pin (not shown). Therefore, when the drum gear 26 rotates, the photosensitive drum 2 rotates via the drum shaft 33.

The drive frame 37 supports the transmission gears 23, 24, 25 and the drum gear 26, and is used to attach the drive unit 100 to the main body. The drive frame 37 functions as a second frame that supports the other end of the gear shafts 28, 29, 30 opposite to one end in the axial direction. The drive frame 37 has grounding parts 37b, 37c having a surface to be installed on the rear plate 27. The drive frame 37 is made of metal. Note that the material of the rear plate 27 is not limited to metal. For example, the rear plate 27 may be made of resin. Therefore, combinations such as a combination of a metal rear plate 27 and a metal drive frame 37, or a combination of a resin rear plate 27 and a metal drive frame 37 may be used depending on the situation.

<Drive unit installation status>
FIG. 3 is a view from the rear side (arrow R direction in FIG. 2) of the image forming apparatus 1 in FIG. 1 to explain the mounting state of the drive unit 100 shown in FIG. 2 to the drive frame 37. The rear plate 27 is provided with positioning bosses 27a and 27b. The drive frame 37 is made by bending a single sheet metal, and has grounding parts 37b and 37c having a grounding surface that is grounded on the rear plate 27 as shown in FIG. 2. The grounding part 37b is provided with a positioning hole 35a, and the grounding part 37c is provided with a rotation stop hole 35b. The positioning hole 35a is fitted with the positioning boss 27a and is restrained in the planar direction. The positioning boss 27b is fitted with the rotation stop hole 35b only in the vertical direction and is restrained only in the vertical direction. In this way, the drive frame 37 is fastened to the rear plate 27 by screws 46, 47, 48, and 49 in a state where it is positioned relative to the rear plate 27. The drive frame 37 is also provided with insertion holes 40, 41, 42, which are holes for supporting shafts, and the tips of the gear shafts 28, 29, 30, in other words the ends on the side that are not fixed, are inserted therethrough.

<Driving reaction force and gear shaft displacement>
Fig. 4 is a view from the rear side (the direction of arrow R in Fig. 2) of the image forming apparatus 1 in Fig. 1, similarly to Fig. 3, and shows the drive transmission from the pinion gear 22 to the drum gear 26. When a drive signal is sent from the control unit 200 of the image forming apparatus 1 to the drive motor 20, the pinion gear 22 is driven in the direction of arrow A. Then, the transmission gear 23 meshing with this pinion gear 22 transmits rotation in the direction of arrow B (hereinafter referred to as rotation transmission). Then, the transmission gears 24, 25 and the drum gear 26 which mesh with each other in turn transmit rotation in the directions of arrows C, D and E, respectively.

Here, we will explain the direction of the reaction force (hereinafter also referred to as the drive reaction force) against the drive force when the drive force of the drive motor 20 is transmitted. The position where the two gears mesh is called the meshing portion. Furthermore, with regard to the force received at the meshing portion, a force in the same direction as the rotation direction in the tangential direction is called the drive transmission force, and a force in the opposite direction to the rotation direction in the tangential direction is called the drive transmission reaction force. Furthermore, the resultant force of the drive transmission force and the reaction force due to drive transmission is called the drive reaction force.

The transmission gear 23 receives the driving force in the direction of the arrow 23a at the meshing portion with the pinion gear 22. Also, at the meshing portion with the transmission gear 24, it receives a reaction force due to the driving force transmission in the direction of the arrow 23b. Therefore, the transmission gear 23 receives the driving reaction force in the direction of the arrow 23c as a resultant force of these forces added together. Similarly, the transmission gear 24 receives the driving force in the direction of the arrow 24a at the meshing portion with the transmission gear 23, and receives a reaction force in the direction of the arrow 24b at the meshing portion with the transmission gear 25. Therefore, the transmission gear 24 receives the driving reaction force in the direction of the arrow 24c as a resultant force of these forces added together. Similarly, the transmission gear 25 receives the driving force in the direction of the arrow 25a at the meshing portion with the transmission gear 24, and receives a reaction force in the direction of the arrow 25b at the meshing portion with the drum gear 26. Therefore, the transmission gear 25 receives the driving reaction force in the direction of the arrow 25c as a resultant force of these forces added together.

Here, attention is focused on the gear shaft 29 that supports the transmission gear 24. Figures 5 and 6 are intended to explain what the posture of the gear shaft 29 would be if there were no biasing portion of the first embodiment described later, in other words, in the case of a conventional configuration. Here, Figure 5 shows the posture of the gear shaft 29 and the engagement state of the tip when the load torque is particularly small, for example, when the load torque of the photosensitive drum 2 is 0.5 kgf-cm. Also, Figure 6 shows the posture of the gear shaft 29 and the engagement state of the tip when the load torque is slightly increased from the state shown in Figure 5, for example, when the load torque of the photosensitive drum 2 is 1.0 kgf-cm. In each figure, (a) is a view of the gear shaft 29 and the insertion hole 41 provided in the drive frame 37 from the tip side of the gear shaft 29, and (b) is a cross-sectional view of (a) as viewed from the direction of the arrow F.

The base side of the gear shaft 29 is crimped to the rear plate 27, and the tip side protrudes from the insertion hole 41. The gear shaft 29 and the insertion hole 41 are fitted together, but due to dimensional tolerances of the parts, a certain amount of play exists. In FIG. 5(b), the gear shaft 29 is subjected to a small driving reaction force in the direction of arrow 24c. Here, because the gear shaft 29 and the rear plate 27 have a certain amount of rigidity, the amount of deformation caused by the small driving reaction force is very small, and the gear shaft 29 does not hit the insertion hole 41.

Next, as shown in FIG. 6(b), when the driving reaction force (arrow 24c) becomes slightly larger, the rear plate 27 deforms near the base of the gear shaft 29, causing the gear shaft 29 to tilt and come into contact with the insertion hole 41 at the contact surface 41a. The contact state includes cases where the gear shaft 29 (more specifically, the side surface 29a of the gear shaft 29) and the contact surface 41a are in point contact, line contact, or surface contact. As described above, when there is a load fluctuation, particularly in the region where the load torque is small (for example, the load torque is 0.5 to 1.0 kgf cm) (low load region), the attitude of the gear shaft 29 changes and a displacement occurs in the gear shaft 29.

<Changes in gear shaft displacement and photosensitive drum rotation speed>
7 is a schematic diagram showing a state in which the teeth of the transmission gear 24 in FIG. 4 mesh with the teeth of the input side transmission gear 23 and the output side transmission gear 25, respectively, to transmit the drive force. Here, FIG. 7(a) corresponds to the load torque state in FIG. 5, and is a case in which the photosensitive drum 2 is driven to rotate in a constant load torque of, for example, 0.5 kgf cm. At this time, the teeth of the transmission gears 23 and 24 come into contact with each other at the meshing portion 72, so that the rotation of the transmission gear 23 is reliably transmitted to the transmission gear 24. Furthermore, the teeth of the transmission gears 24 and 25 come into contact with each other at the meshing portion 73, so that the rotation of the transmission gear 24 is reliably transmitted to the transmission gear 25, and the rotation of the transmission gear 24 is reliably transmitted to the transmission gear 25. Thus, in this drive train, the drive force is transmitted at a stable rotation speed.

Figure 7(b) shows the moment when the load torque state of Figure 6, for example the load torque of the photosensitive drum 2, changes from the state of Figure 7(a) to 1.0 kgf-cm. At this time, the arrows 23c, 24c, and 25c representing the driving reaction force received by each gear become larger, and as described in Figure 6, displacement occurs in each gear shaft 28, 29, and 30. Accordingly, each transmission gear 23, 24, and 25 also displace in the direction of the arrows 23c, 24c, and 25c, respectively. This means that at the moment when the load torque changes, the teeth of the meshing portion 72 and the meshing portion 73 move to separate from each other. Due to this movement, a delay occurs in the rotation transmission from the transmission gear 23 to the transmission gear 24, and also a delay occurs in the rotation transmission from the transmission gear 24 to the transmission gear 25. In this way, when displacement occurs in each gear shaft 28, 29, and 30 when the load torque changes, a change occurs in the rotation transmission at that moment, and the rotation speed also changes.

As mentioned above, without the biasing section, fluctuations in the load torque would cause the gear shaft to change position, which would then displace the gear, resulting in a transmission error in the rotational speed.

<Using portion of embodiment 1>
8 shows a method of supporting the tip of the gear shaft 29 when the leaf spring 37a, which is a biasing portion characteristic of the first embodiment, is included. Fig. 8(a) is a view of the gear shaft 29 and the through hole 44 provided in the drive frame 37 as viewed from the tip side of the gear shaft 29, and Fig. 8(b) is a cross-sectional view as viewed from the direction of the arrow F in Fig. 8(a). Note that the gear shafts 28 and 30 are supported in the same manner, so their explanation will be omitted.

In the first embodiment, the drive frame 37, which is the second frame, has a leaf spring 37a that biases the other end of the gear shaft 29 (28, 30) in the direction in which a reaction force against the drive force acts. The drive frame 37 also has an abutment surface 44a that is an abutment portion against which the side surface 29a (28a, 30a) of the other end of the gear shaft 29 (28, 30) abuts as the other end of the gear shaft 29 (28, 30) is biased by the leaf spring 37a.

The drive frame 37 has an insertion hole 44 through which the other end of the gear shaft 29 (28, 30) is inserted, and the tip of the gear shaft 29 is inserted. A leaf spring 37a is also formed integrally with the drive frame 37. More specifically, the leaf spring 37a is a leaf spring formed integrally with the drive frame 37, and the leaf spring 37a protrudes from a part of the drive frame 37 that forms the insertion hole 44 toward the inside of the insertion hole 44. The drive frame 37 that forms the insertion hole 44 also has an abutment surface 44a, which is a surface that faces the direction of the arrow 24c, which is the direction in which the driving reaction force acts. More specifically, the abutment surface 44a is provided in a part of the drive frame 37 that forms the insertion hole 44 in the direction in which the leaf spring 37a protrudes. The tip of the leaf spring 37a abuts against the gear shaft 29, biasing the gear shaft 29 in the direction in which the driving reaction force acts (arrow 24c), so that the gear shaft 29 always abuts against the abutment surface 44a regardless of the presence or absence of load torque.

As described above, in the first embodiment, the tip of the gear shaft is biased by a leaf spring in the direction in which the driving reaction force acts, so that the tip of the gear shaft is always in contact with a predetermined abutment surface formed on the drive frame. Therefore, even if the load torque fluctuates, the attitude of the gear shaft does not change, and thus the gear displacement can be suppressed, resulting in a drive device that maintains good transmission of rotational speed. By using this drive device, it is possible to obtain an image forming device that suppresses image defects such as blurring that appear when the load torque fluctuates.

As described above, according to the first embodiment, it is possible to suppress the rotational fluctuation of the rotating body even when the load torque of the rotating body is small.

The image forming apparatus of the second embodiment will be described in detail with reference to the drawings. The general configuration of the image forming apparatus 1 is the same as that of the first embodiment described above, and therefore the description will be omitted. The same members as those of the first embodiment will be given the same reference numerals, and the description thereof will be omitted. In the second embodiment, the rear plate 27 functions as the first frame, and the drive frame 37 functions as the second frame. In the second embodiment, the rear plate 27 and the drive frame 37 may be formed of metal or resin.

<Using portion of embodiment 2>
9A is a schematic diagram showing the main part as viewed from the same direction (rear side) as in FIG. 3, and FIG. 9B is a cross-sectional view as viewed from the direction of arrow G in FIG. 9A (i.e., the bottom side). The drive frame 37 has insertion holes 40, 41, and 42 through which the other ends of the gear shafts 28, 29, and 30 are inserted.

The wire spring 50, which is the biasing part of the second embodiment, has the shape shown by the dashed line in its natural state when no force is applied. It is hooked onto the ends of the gear shafts 28, 29, 30 as shown in FIG. 9(a), and the bent parts 50a, 50b at both ends are passed through the spring holes 37d, 37e and slipped behind the drive frame 37 to prevent it from coming loose. In other words, the wire spring 50 is hooked onto the side surfaces 28a, 29a, 30a of the other ends of the gear shafts 28, 29, 30 opposite the abutment surfaces 40a, 41a, 42a, which are the abutment parts.

When a drive signal is sent from the control unit 200 to the drive motor 20 and the pinion gear 22, the transmission gears 23, 24, 25, and the drum gear 26 are rotated, a drive reaction force is applied to the gear shafts 28, 29, 30 in the directions of the arrows 23c, 24c, and 25c, respectively. In addition, the gear shafts 28, 29, 30 are constantly biased by the wire spring 50 in the same direction as the drive reaction force indicated by the arrows 23c, 24c, and 25c, and are constantly abutting against a part of the insertion holes 40, 41, and 42 regardless of the presence or absence of a load torque.

In the second embodiment, the transmission gear 23 functions as a first gear supported by the gear shaft 28, which is the first gear shaft. The transmission gear 24 functions as a second gear supported by the gear shaft 29, which is the second gear shaft. The transmission gear 25 functions as a third gear supported by the gear shaft 30, which is the third gear shaft. At this time, the drive frame 37 includes an abutment surface 40a, which is a first abutment portion against which the gear shaft 28 abuts, an abutment surface 41a, which is a second abutment portion against which the gear shaft 29 abuts, and an abutment surface 42a, which is a third abutment portion against which the gear shaft 30 abuts. The wire spring 50 is hooked to the side surface 28a of the tip of the gear shaft 28 opposite the abutment surface 40a, hooked to the side surface 29a of the tip of the gear shaft 29 opposite the abutment surface 41a, and hooked to the side surface 30a of the tip of the gear shaft 30 opposite the abutment surface 42a.

As described above, by biasing the tip of the gear shaft with a wire spring in the direction in which the driving reaction force acts, in the second embodiment as well, the tip of the gear shaft can be kept in constant contact with a predetermined portion of the hole formed in the drive frame, as in the first embodiment. Therefore, even if the load torque fluctuates, the gear shaft's posture does not change, and thus gear displacement can be suppressed, resulting in a drive device that maintains good rotation transmission. By using this drive device, an image forming device can be obtained that suppresses image defects such as blurring that occur when the load torque fluctuates. Note that it is also possible to use wire springs for some gear shafts and leaf springs as in the first embodiment for other gear shafts.

As described above, according to the second embodiment, it is possible to suppress the rotational fluctuation of the rotating body even when the load torque of the rotating body is small.

The image forming apparatus of the third embodiment will be described in detail with reference to the drawings. The schematic configuration of the image forming apparatus 1 is the same as that of the first embodiment described above, and therefore the description will be omitted. The same members as those of the first embodiment are given the same reference numerals, and the description thereof will be omitted. In the third embodiment, the drive frame 61 functions as the first frame, and the rear plate 62 functions as the second frame. In the third embodiment, the rear plate 62, which is the second frame, is made of resin. In the third embodiment, the gear shaft supporting the transmission gear is described as the gear shaft 60, but it may be applied to a plurality of transmission gears and gear shafts, such as the transmission gears 23, 24, and 25 and the gear shafts 28, 29, and 30 of the first embodiment.

<Using portion of embodiment 3>
8 of the first embodiment, Fig. 10 shows a method of supporting the tip of the gear shaft 60 by a rear side plate 62 having a biasing portion, which is a feature of the third embodiment. One end of the gear shaft 60 is attached to a drive frame 61 by crimping means. The rear side plate 62, which is the second frame of the third embodiment, is made of a molded material, and is integrally formed with a circular rib 62a into which the other end (the tip) of the gear shaft 60 fits.

Two protrusions 62b are formed on the inside of the circular rib 62a. The tip of the gear shaft 60 enters the inside of the circular rib 62a with the tip of the protrusion 62b, which is the biasing part, slightly crushed. The protrusion 62b biases the gear shaft 60 in the direction of the arrow 24c where the driving reaction force acts, and the tip of the gear shaft 60 always abuts against the part 62c on the side opposite the protrusion 62b regardless of the presence or absence of load torque. In this way, the protrusion 62b protrudes toward the inside of the circular rib 62a and is a protrusion formed integrally with the circular rib 62a. The protrusion 62b biases the tip of the gear shaft 60 against the part 62c by being crushed when it comes into contact with the tip of the gear shaft 60.

Note that, although two protrusions 62b are shown in FIG. 10, this is not limiting. As long as the protrusions 62b bias the gear shaft 60 in the direction of the arrow 24c, which is the direction in which the driving reaction force acts, and the tip of the gear shaft 60 abuts against the portion 62c, the number of protrusions 62b may be one, or three or more.

As described above, by biasing the tip of the gear shaft in the direction in which the driving reaction force acts, in the third embodiment, as in the first embodiment, the tip of the gear shaft can be kept in constant contact with a predetermined portion of the circular rib formed on the rear plate. Therefore, even if the load torque fluctuates, the gear shaft does not change its position, and the gear displacement can be suppressed, resulting in a drive device that maintains good rotation transmission. By using this drive device, an image forming device can be obtained that suppresses image defects such as blurring that occur when the load torque fluctuates. In addition, if the drive frame can be made of resin, the base of the gear shaft can be crimped to the rear plate, and the drive frame can be provided with a circular rib 62a and a protrusion 62b to support the tip of the gear shaft.

As described above, according to the third embodiment, it is possible to suppress the rotational fluctuation of the rotating body even when the load torque of the rotating body is small.

The image forming apparatus of the fourth embodiment will be described in detail with reference to the drawings. The general configuration of the image forming apparatus 1 is the same as that of the first embodiment described above, and therefore the description will be omitted. The same reference numerals will be used to designate the same members as those of the first embodiment, and the description thereof will be omitted.

<Driving reaction force and gear shaft displacement>
11A is a view seen from the rear side of the image forming apparatus 1, similar to FIG. 4, and shows the drive transmission from the pinion gear 22 to the drum gear 26, and also shows how the paper feed drive train for driving the feed roller 9 to rotate branches off from the transmission gear 25. The paper feed transmission gear 70 is the first gear in the paper feed drive train, and the gears downstream of it are not shown.

As described in the first embodiment, the transmission gear 25 receives forces in the directions of arrows 25a and 25b at the meshing portions with the transmission gear 24 and the drum gear 26, respectively, and receives a driving reaction force in the direction of arrow 25c as a resultant force of these forces. In addition, when the transmission gear 25 drives the paper feed transmission gear 70 to rotate in the direction of arrow H, the transmission gear 25 receives a reaction force in the direction of arrow 25d at the meshing portion with the paper feed transmission gear 70. At this time, the transmission gear 25 receives a driving reaction force in the direction of arrow 25e as a resultant force of the three reaction forces of arrows 25a, 25b, and 25d. In other words, the direction of the driving reaction force changes in the transmission gear 25.

Here, the feed drive train is only loaded when the feed roller 9 feeds out the recording paper P, so the transmission gear 25 receives a reaction force (arrow 25d) only at that time. Therefore, the direction of the drive reaction force received by the transmission gear 25 changes from arrow 25c to arrow 25e when the feed roller 9 rotates, and changes from arrow 25e to arrow 25c when the feed roller 9 stops rotating.

<Using portion of embodiment 4>
11(b) shows a method of supporting the tip of the gear shaft 30 by a drive frame 37 having a biasing portion according to the fourth embodiment. The drive frame 37 has an insertion hole 80 through which the tip of the gear shaft 30 is inserted. The drive frame 37 is also integrally formed with a leaf spring 37f which serves as a biasing portion. The insertion hole 80 has two abutment surfaces 80a and 80b. The abutment surfaces 80a and 80b are arranged to form a V-shape.

Here, the perpendicular line drawn from the center O of the gear shaft 30 to the abutment surface 80a is taken as imaginary line L1, and the perpendicular line drawn from the center O of the gear shaft 30 to the abutment surface 80b is taken as imaginary line L2. Then, the direction in which the driving reaction force acts (arrows 25c and 25e) is within the range between imaginary lines L1 and L2. The leaf spring 37f biases the gear shaft 30 by abutting its tip against the gear shaft 30, and the gear shaft 30 always abuts against the abutment surfaces 80a and 80b regardless of the presence or absence of load torque.

In the fourth embodiment, the transmission mechanism is branched. Here, the path through which the driving force of the drive motor 20 is transmitted from the pinion gear 22, the transmission gear 23, the transmission gear 24, the transmission gear 25, and the drum gear 26 is the first transmission path. The pinion gear 22, the transmission gear 23, the transmission gear 24, the transmission gear 25, and the drum gear 26 function as the first gear group. The path through which the driving force of the drive motor 20 is transmitted from the pinion gear 22, the transmission gear 23, the transmission gear 24, the transmission gear 25, and the paper feed transmission gear 70 is the second transmission path. A part of the second transmission path overlaps with the first transmission path. The pinion gear 22, the transmission gear 23, the transmission gear 24, the transmission gear 25, and the paper feed transmission gear 70 function as the second gear group. The transmission gear 25 is a gear located at the part where the first transmission path and the second transmission path branch off. The contact portion 80c against which the side surface 30a of the gear shaft 30 of the transmission gear 25 contacts has a first contact surface 80a and a second contact surface 80b that form a V-shape.

When viewed from the direction of the rotation axis of the gear shaft 30 with the gear shaft 30 in contact with the V-shaped contact portion 80c, the first perpendicular line extending from the center O of the gear shaft 30 to the contact surface 80a is the imaginary line L1. Also, the second perpendicular line extending from the center O of the gear shaft 30 to the contact surface 80b is the imaginary line L1. At this time, the V-shaped contact portion 80c is formed so that the direction of the reaction force to the driving force is between the imaginary lines L1 and L2.

As described above, even if the direction of the driving reaction force fluctuates, the tip of the gear shaft can be biased against the two abutment surfaces by the leaf spring, so that the tip of the gear shaft can be constantly in abutment against these two abutment surfaces. Therefore, even if the direction of the driving reaction force fluctuates, the attitude of the gear shaft does not change at all, and thus the gear displacement can be suppressed, and a driving device that maintains good rotation transmission can be obtained. By using this driving device, an image forming device can be obtained that suppresses image defects such as blurring that appear when load torque fluctuation occurs. Note that, when the direction of the driving reaction force fluctuates, it is sufficient that the driving frame has a V-shaped abutment portion, and the biasing portion is not limited to the leaf spring 37f, and may be a wire spring as in Example 2, or a circular rib and protrusion as in Example 3.

As described above, according to the fourth embodiment, it is possible to suppress the rotational fluctuation of the rotating body even when the load torque of the rotating body is small.

20 Drive motor 23, 24, 25 Transmission gear 27 Rear plate 28, 29, 30 Gear shaft 37 Drive frame 37a Leaf spring 44a Abutment surface

Claims (12)

A driving source;
A gear for transmitting a driving force of the driving source;
a gear shaft that rotatably supports the gear;
a first frame supporting one end of the gear shaft in an axial direction;
a second frame supporting the other end of the gear shaft opposite to the one end in the axial direction;
Equipped with
a drive device characterized in that the second frame has a biasing portion that biases the other end in a direction in which a reaction force against the driving force acts, and an abutment portion with which a side surface of the other end abuts when the other end is biased by the biasing portion. the second frame has a hole through which the other end is inserted,
the biasing portion is a leaf spring integrally formed with the second frame,
the leaf spring protrudes from a portion of the second frame that defines the hole toward an inside of the hole,
2. The drive device according to claim 1, wherein the contact portion is provided on a part of the second frame that defines the hole in the direction in which the leaf spring protrudes. The drive device according to claim 2, characterized in that the second frame is made of metal. The drive device according to claim 1, characterized in that the biasing portion is a wire spring hooked onto the side surface of the other end opposite the abutment portion. the gears include a first gear supported on a first gear shaft, a second gear supported on a second gear shaft, and a third gear supported on a third gear shaft;
The abutment portion includes a first abutment portion against which the first gear shaft abuts, a second abutment portion against which the second gear shaft abuts, and a third abutment portion against which the third gear shaft abuts,
5. The drive device according to claim 4, wherein the wire spring is hooked onto a side surface of the other end of the first gear shaft opposite the first contact portion, hooked onto a side surface of the other end of the second gear shaft opposite the second contact portion, and hooked onto a side surface of the other end of the third gear shaft opposite the third contact portion. The drive device according to claim 5, characterized in that the first frame and/or the second frame are made of metal and/or resin. the second frame has a rib into which the other end is fitted,
the biasing portion is a protrusion that protrudes toward the inside of the rib and is integrally formed with the rib,
2. The drive device according to claim 1, wherein the protrusion is crushed when it comes into contact with the other end of the gear shaft, thereby urging the other end of the gear shaft against the contact portion. The drive device according to claim 7, characterized in that the second frame is made of resin. the gears include a first gear group that transmits the driving force through a first transmission path, and a second gear group that transmits the driving force through a second transmission path that partially overlaps with the first transmission path,
a contact portion with which a side surface of a gear shaft of a gear located at a portion where the first transmission path and the second transmission path branch off contacts has a first surface and a second surface that form a V shape,
When the gear shaft is in contact with the abutment portion of the V-shape and viewed from the rotation axis direction of the gear shaft, a perpendicular line extending from the center of the gear shaft to the first surface is defined as a first perpendicular line, and a perpendicular line extending from the center of the gear shaft to the second surface is defined as a second perpendicular line,
The drive device according to claim 1, characterized in that the V-shaped abutment portion is formed so that the direction of the reaction force is between the first perpendicular line and the second perpendicular line when viewed from the rotation axis direction. The drive device according to claim 9, characterized in that the second frame is made of metal. an image carrier on which an electrostatic latent image is formed;
a developing means for developing the electrostatic latent image with a toner to form a toner image;
a transfer means for transferring the toner image onto a recording material;
a removing unit for removing toner remaining on the image carrier after the transfer by the transfer unit;
A driving device according to any one of claims 1 to 10, which drives the image carrier;
An image forming apparatus comprising: The image forming apparatus according to claim 11, characterized in that the removing means is a cleanerless removing means having a brush, dispersing the toner remaining on the image carrier with the brush and collecting it with the developing means.

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