JPH11125325A - Resinous gear and transmission device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the stiffness of a resinous gear by arranging a rib, and beside, prevent occurrence of speed fluctuation by the rib. SOLUTION: This gear 14 is provided with a hub part 25 positioned in a center, a ringlike part 27 which is positioned on the outer side of the radial direction of the hub part 25 and of which a plurality of teeth 26 is formed on the peripheral surface, a web 28 by which the ringlike part 27 and the hub part 25 and integrally connected to ech other, and a rib 29 extended from the hub part 25 toward the ringlike part 27. In this case, the height H of the rib 29 projected from the surface of the web 28 to the axial line direction of the gear 14 is set higher in a rib part provided in vicinity of the hub part 25 and the ringlike part 27, and is set lower in an intermediate part 30 therebetween.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin gear and a transmission using the resin gear.

[0002]

2. Description of the Related Art It is well known in the art to employ a transmission having at least one resin gear to transmit the rotation of a drive motor to a driven body. For example, in an image forming apparatus configured as a copier, a printer, a facsimile, or a multifunction peripheral having at least two functions thereof, the rotation of a drive motor is transmitted to a driven body configured as an image carrier, A toner image is formed on the surface of the image carrier. In addition, a printing machine, a camera, a video deck, a CD player, and various other mechanical devices also use a resin gear to drive a predetermined driven body.

[0003] Such a resin gear is provided with a hub located at the center, a ring located radially outward of the hub, and substantially concentric with the hub, and formed on the outer peripheral surface. It is composed of a ring-shaped part having a plurality of teeth formed thereon, and a web for integrally connecting the ring-shaped part and the hub part, and the whole is integrally formed by, for example, injection molding.

[0004] In recent years, in particular, with the speeding up of various types of mechanical devices using such gears, the gears are rotated at a high speed, and a large external force tends to be applied to the gears. Rigidity has been required. For this reason, it has become difficult to satisfy the rigidity required for the resin gear only by connecting the hub portion and the ring-shaped portion with a web. It is possible to increase the rigidity of the gear by setting the size and thickness of the gear to be large, but this increases the cost of the gear and avoids the disadvantage that the transmission using such a gear becomes large. Absent.

[0005] In view of this, a method has been considered in which ribs extending from the resin gear toward the ring-shaped portion are formed integrally with the web to increase the rigidity of the gear. The resin gear having such ribs has high rigidity and strength, and can have a long life.

However, according to studies made by the present inventor, the resin gear having ribs has a non-uniform outer diameter due to the "sink" phenomenon at the time of molding.
As a result, it has become clear that when the gear rotates, a periodic fluctuation occurs in the speed, and this may appear as uneven rotation speed of the driven body.

[0007]

SUMMARY OF THE INVENTION The present invention has been made based on the above-described novel recognition, and an object of the present invention is to minimize the adverse effects of providing ribs for increasing rigidity. It is an object of the present invention to provide a resin gear that can be suppressed to a minimum, and a transmission having the resin gear.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a hub located at a center and an annular ring located radially outward of the hub and substantially concentric with the hub. And a resin gear having a ring-shaped portion having a plurality of teeth formed on an outer peripheral surface thereof, and a web for integrally connecting the ring-shaped portion and the hub portion. And at least one rib integrally formed with the web, and a height of a rib protruding from a surface of the web in an axial direction of the gear is adjacent to the hub portion and the ring-shaped portion. A gear is proposed which is set high in a rib portion and low in an intermediate portion therebetween (Claim 1).

In this case, in the above structure, the height of the rib is zero at the intermediate portion of the rib, and the rib is divided into a hub portion-side portion and a ring-shaped portion-side portion. Advantageously (claim 2).

In order to achieve the above object, the present invention has at least one resin gear for transmitting rotation of a drive motor to a driven body, and the resin gear is located at the center. A hub portion, located radially outward of the hub portion,
A ring-shaped portion formed in a substantially concentric annular shape with respect to the hub portion and having a plurality of teeth formed on an outer peripheral surface thereof; and a web for integrally connecting the ring-shaped portion and the hub portion. Transmission, wherein at least one of the resin gears
One has a plurality of ribs extending from the hub portion toward the ring-shaped portion, and has a plurality of ribs integrally formed on the web, and the speed fluctuation frequency of the gear generated by the rib when the gear having the rib rotates is represented by: To be higher than the speed fluctuation frequency of the gear caused by the rotation of the drive motor,
A transmission is proposed wherein the number of the ribs is set (claim 3).

In this case, in the transmission according to claim 3, the height of the rib protruding in the axial direction of the gear from the surface of the web of the gear provided with the rib is equal to the height of the hub portion and the ring-shaped portion. It is particularly advantageous if the height is set high in the rib portion adjacent to the first portion and low in the middle portion therebetween.

5. The transmission according to claim 4, wherein the height of the rib is zero at the intermediate portion of the rib, and the rib is connected to the hub-side portion and the ring-shaped portion. It is even more advantageous if it is bisected into a side part (claim 5).

Further, in the transmission according to any one of claims 3 to 5, the driven body is an image carrier that is rotatably supported by an image forming apparatus main body and has a toner image formed on a surface thereof. It is advantageous if present (claim 6).

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, if a rib is simply provided on a resin gear, periodic speed fluctuation may occur in a driven body. Will be clarified more specifically with reference to the drawings.

FIG. 1 is a schematic sectional view showing an example of an image forming apparatus employing a transmission having a resin gear according to the present invention. The image forming apparatus shown here is configured as a laser printer, and a drum-shaped photoconductor 1 as an example of an image carrier is rotatably supported on a frame of the image forming apparatus main body. The photoconductor 1 will be described later. It is rotationally driven clockwise in FIG. 1 by the transmission. At this time, the surface of the photoreceptor is uniformly charged to a predetermined polarity by the charging device 2, and the charged surface is irradiated with the modulated laser light L emitted from the optical writing device 3, whereby the surface of the photoreceptor is irradiated. A predetermined electrostatic latent image is formed. The electrostatic latent image is visualized by toner as it passes through the developing device 4.

On the other hand, a recording sheet P is fed from a sheet feeding device (not shown), and the recording sheet P is sent to a transfer position 6 by a pair of registration rollers 5 at a predetermined timing. Is transferred onto the recording paper.

The recording paper P on which the toner image has been transferred is sent to a fixing device (not shown) by the conveyor belt 7, where the toner image is fixed on the recording paper. After the toner image is fixed, the recording paper is discharged outside the apparatus and stacked on a discharge tray (not shown).

After the transfer of the toner image, the transfer residual toner adhering to the surface of the photoreceptor is removed by the cleaning device 8, and the surface of the photoreceptor is cleaned. Thereafter, the surface of the photoreceptor is subjected to a charge removing operation by light from the charge removing lamp 9.

FIG. 2 is a partial sectional plan view showing an example of a drive motor 10 for rotating the above-mentioned photosensitive member 1 and a transmission device for transmitting the rotation to the photosensitive member 1. FIG. It is a front view explaining the arrangement state of an element.

The drive motor 10 is fixedly supported by a bracket 12 fixed to a frame 11 of the image forming apparatus main body, and an output gear 13 is meshed with a first resin gear 14 made of resin. The gear 14 is rotatably supported by a shaft 15 fixed to the bracket 12 and meshes with a second gear 16 made of resin. The second gear 16 is a shaft 1 rotatably supported on the bracket 12 via a bearing.
7, a timing pulley 18 concentric with the second gear 16 is fixed to one end of the shaft 17. An endless timing belt 21 is wound around the timing pulley 18 and another timing pulley 19, and the other timing pulley 19 is
Is fixed to a support shaft 22 for fixing and supporting the photoconductor 1, and the photoconductor 1, its support shaft 22 and the timing pulley 19 are arranged concentrically with each other. One end of the support shaft 22 is rotatably supported by a photoconductor holder 24 via two bearings 23, and the holder 24 is fixed to the frame 11 of the image forming apparatus main body. The other end (not shown) of the support shaft 22 is also rotatably supported by the frame 11 via a bearing (not shown).

The drive motor 10 is operated and its output gear 1
3 rotates, the rotation of the first and second gears 14,
The rotation is transmitted to the photoreceptor 1 via the timing belt 21, the timing pulley 19 and the support shaft 22, and the photoreceptor 1 rotates clockwise in FIG. 1. I do.

The output gear 13 is made of a metal such as S45C, for example.
Reference numeral 16 is made of a resin molded product as described above. Photoconductor 1
Constitutes an example of a driven body that is rotationally driven via these gears 14 and 16. In the transmission shown in FIG. 2, two gears 14 and 16 made of resin are provided.
The transmission can also be configured using one or three or more resin gears. Thus, the transmission has at least one resin gear 14 and 16 for transmitting the rotation of the drive motor 10 to the driven body.

As shown in FIGS. 4 and 5, the resin gears 14, 16 are located at the center of the gears 14, 16 and are cylindrically supported by a shaft 15 (FIG. 2). And a hub portion 25 located radially outside of the hub portion 25,
A ring-shaped portion 27 formed substantially in an annular shape concentric with the hub portion 25 and having a plurality of teeth 26 formed on an outer peripheral surface thereof;
And a plate-shaped web 28 for integrally connecting the ring-shaped portion 27 and the hub portion 25, and these are configured as an integrated resin gear 14. The gear 14 is formed by molding a resin material using, for example, an injection molding machine (not shown).

The second gear 16 is also the first gear 14 described above.
And a molded product formed by, for example, an injection molding machine.

The gears 14, 16 are provided with ribs 29, which will be described later in detail.

By the way, as described above, the image forming apparatus as shown in FIGS.
The gears 14 and 16 are rotated at a high speed, and a large external force is applied to the gears. To deal with this, each gear 1
It is sufficient to increase the size and thickness of the 4, 4 and 16 to increase their rigidity and strength. However, this increases the cost and the overall structure of the transmission, and thus the structure of the image forming apparatus. I can't escape the shortcomings.

Therefore, as shown in FIGS. 11 and 12,
An appropriate number of ribs 29 radially extending radially from the hub portion 25 of the resin gear 14 toward the ring-shaped portion 27;
It is conceivable to increase the overall rigidity. Each rib 29
Is formed integrally with the ring-shaped portion 27, the hub portion 25, and the web 28 of the gear 14, and the height H of the gear 14 projecting in the axial direction from the surface of the web 28 is constant. By configuring the gear 14 in this manner, the overall rigidity can be increased without unnecessarily increasing the size and thickness of the gear. However, if only such a rib 29 is provided, the following problem occurs.

The gear 14 shown in FIGS. 11 and 12 is manufactured by molding a resin material using, for example, an injection molding machine, similarly to the gear 14 shown in FIG. that time,
Due to the non-uniform internal shrinkage of the material during the cooling process during molding, the outer diameter of the gear at the portion where each rib 29 is formed becomes very small, but slightly smaller than the other portions. This is a phenomenon called "hike".

FIG. 13 is a sectional view of the rib 2 shown in FIG.
The results of a meshing test are shown in which the horizontal axis represents the circumference S of the resin gear 14 in which six 9s are formed, and the eccentric state (μm) of the addendum circle of the gear 14 is represented by the vertical axis. As can be seen from the uneven state in this figure, the outer diameter of the gear 14 changes in correspondence with the number of the ribs 29. In this example, 6
Individual irregularities appear. As described above, when the molding accuracy of the gear 14 is reduced, when the gear 14 rotates, a speed variation, that is, uneven rotation occurs in the gear 14. Although the cause of this speed fluctuation is not always clear, it can be estimated as follows.

FIG. 14 is an explanatory view schematically showing the ring-shaped portion 27 of the resin gear 14 shown in FIGS. 11 and 12, and the teeth 26A, 26B, 26C formed on the outer peripheral surface thereof. Ring-shaped portion 27 between two teeth 26B, 26C
It is assumed that one end of one rib 29 is integrally connected. In FIG. 14, the teeth 26 are shown for easy understanding.
The area between B and 26C is shown in an enlarged scale. The resin gear 14 is used as a "shade" at the time of molding.
Due to this phenomenon, the portion of the ring-shaped portion 27 to which the rib 29 is connected sinks toward the center of the gear. Therefore, the teeth 26B located on the left side of the rib 29 fall rightward, and the teeth 26C located on the right side fall leftward.

Numeral 26D in FIG. 14 indicates the teeth of the mating gear meshing with the gear 14. If the normal pressure angle at the meshing portion is α ₀ , the tooth 2 that has fallen to the right
The pressure angle in the case of 6B is α ₁ (> α ₀ ), and is the pressure angle α ₂ (> α ₀ ) in the case of the tooth 26C that has fallen to the left. The angular velocity at each pressure angle is ω ₀ (when α ₀ ), ω ₁ (when α ₁ ),
Assuming that ω ₂ (when α ₂ ), the angular velocity decreases as the pressure angle increases, and the angular velocity increases as the pressure angle decreases. Therefore, the relationship of ω ₁ <ω ₀ <ω ₂ around the rib 29. Assuming that the ribs 29 extend radially from the center side of the gear 14 and are arranged at equal intervals, the speed fluctuation of the gear 14 (increase / decrease in angular velocity) appears periodically.
However, the speed fluctuation itself is not so large.

However, the drive motor 1 shown in FIG.
0 usually causes one speed change per revolution,
When the frequency of the speed fluctuation at this time matches the frequency of the above-described speed fluctuation of the resin gear 14, and the peaks and the peaks of the vibration waveform coincide with each other, the vibration is transmitted to the photoconductor 1. The speed fluctuation becomes large, and the speed of the photoconductor 1 fluctuates violently. When the speed of the photosensitive member 1 fluctuates in this manner, unevenness in density (jitter) occurs in a toner image formed on the surface of the photosensitive member, and the image quality is significantly deteriorated.

For example, assuming that the drive motor 10 rotates at 1800 rpm, the frequency of the speed fluctuation that occurs once per rotation is 1800 rpm ÷ 60 seconds = 30 Hz. On the other hand, if the number of teeth of the output gear 13 of the drive motor 10 is 1
0, assuming that the number of teeth of the resin gear 14 meshing with this is 70, and assuming that seven ribs 29 as shown in FIG. The frequency of the speed fluctuation of the gear 14 is 1800 rp
m × (10/70) × (1/60 sec) × 7 = 30 Hz. When the peaks and valleys and the valleys and valleys of these speed fluctuations coincide with each other, the speed fluctuation generated in the photoconductor is obtained by adding the speed fluctuation generated by the rib 29 of the gear 14 to the speed fluctuation of the drive motor 10. In this case, extremely large speed fluctuations occur in the photoconductor.

Therefore, the resin gears 14 and 16 used in the transmission of the present embodiment are arranged such that one of the gears 14 has a radius from the hub 25 to the ring 27 as shown in FIGS. A rib 29 extending radially in the direction
Each of the ribs 29 is formed integrally with the web 28, the hub portion 25, and the ring-shaped portion 27, and protrudes from the surface of the web 28 in the axial direction of the gear 14. The height H of the rib 29 protruding from the surface of the web 28 in the axial direction of the gear 14 is set high at the rib portion adjacent to the hub portion 25 and the ring-shaped portion 27 and set low at the intermediate portion 30. In the example shown in FIGS. 4 and 5, the height of the rib is zero in the intermediate portion 30 of the rib 29, and the rib 29 is connected to the portion 31 on the hub portion side and the side of the ring-shaped portion 27. And a portion 32 of FIG. In the intermediate portion 30, the rib 29 does not exist, and the central portion of the rib 29 is trapezoidally lightened. The second gear 16 made of resin is similarly configured.

If the ribs 29 are formed as described above, the occurrence of the "sink" phenomenon can be effectively suppressed when the resin gear 14 is manufactured by injection molding, as shown in FIG. The portion of the ring-shaped portion 27 to which the rib 29 is connected can be prevented from largely sinking toward the center of the gear.

As described above, the gear 14 of the present embodiment is provided with the ribs 29 shown in FIGS. 4 and 5 so that its rigidity can be increased and the gear 14 can be used without trouble in an image forming apparatus which operates at high speed. The speed fluctuation of the photoconductor 1 due to the rib 29 can be suppressed. The same applies to the second gear 16.

In the example shown in FIGS. 4 and 5, a plurality of ribs 29 extending in the radial direction of the gear 14 are provided, more precisely six ribs, each of which is arranged at equal intervals in the circumferential direction of the gear 14. The number of the ribs 29 need not be plural, and if at least one rib is provided, the intended object of the present invention can be achieved.

FIG. 6 shows the results of a meshing test of the gear 14 shown in FIGS. When this gear 14 is used, it is possible to minimize the sinking of the ring-shaped portion 27 due to “sink” at the time of molding, so that as shown in FIG. Outer diameter change,
That is, only the speed fluctuation is observed. Such a speed fluctuation is usually observed in manufacturing a resin gear, and is not caused by the rib 29.

The above is the configuration example of the resin gear according to the first and second aspects.

As described above, the transmission shown in FIG. 2 includes at least one resin gear 14 or 16 for transmitting the rotation of the drive motor 10 to the driven member composed of the photosensitive member 1. The resin gears 14 and 16 are formed in a hub portion 25 located at the center and an annular shape which is located radially outside the hub portion 25 and substantially concentric with the hub portion 25. Further, it has a ring-shaped portion 27 having a plurality of teeth 26 formed on the outer peripheral surface, and a web 28 for integrally connecting the ring-shaped portion 27 and the hub portion. The resin gears 14 and 16 have a plurality of ribs 29 extending from the hub portion 25 toward the ring-shaped portion 27 and formed integrally with the web 28. When the gears 14, 16 having the ribs 29 rotate, the speed fluctuation frequency of the gears 14, 16 caused by the ribs 29 becomes
The gears 14 and 1 generated by the rotation of the drive motor 10
6 so as to be higher than the speed fluctuation frequency of
When the number is set, even if a gear having a rib with a constant height H is used as the resin gear, the speed fluctuation occurring in the driven body, in this example, the photosensitive member 1 can be effectively suppressed. .

The resin gears 14 and 1 constituting the transmission device
When a plurality of 6 are provided as shown in FIG.
By configuring the at least one resin gear as described above, an effect of suppressing the occurrence of speed fluctuation of the photoconductor can be obtained. This is a configuration example corresponding to claim 3.

Next, an experimental example conducted by the present inventor in connection with the above-described configuration will be described to clarify the reason why the above-mentioned effects can be obtained.

As the resin gear 14 shown in FIG. 2, the helical gear 14 having the rib 29 shown in FIGS. 11 and 12 was used. As described above, the height H of the rib 29 of the gear from the web portion 28 is constant from the hub portion 25 to the ring-shaped portion 27. The module of the gear 14 was 1, the number of teeth was 36, and the twist angle of the teeth 26 was 16 °. There are six ribs 29 extending in the radial direction of the gear 14, and the ribs 29 are arranged at equal intervals in the circumferential direction of the gear.

FIG. 7 shows the results of the meshing test of the gear 14, and since the gear 14 has six ribs 29, the result of the test is the same as that of FIG. , And one rotation of the gear 14 causes six speed fluctuations.

Assuming that the gear 14 rotates at 300 rpm, the frequency of the speed fluctuation is 300 rpm × (1
/ 60 seconds) × 6 = 30 Hz.

Next, as the gear 14 shown in FIG. 2, a resin gear having the same specifications as described above and having 12 ribs 29 provided at equal intervals in the circumferential direction of the gear, The same experiment was attempted using 17 devices. At this time, the frequency of the speed fluctuation of each gear due to each rib 29 is
They are 60 Hz and 85 Hz, respectively. The results of these meshing tests are as shown in FIGS. 8 and 9, respectively.

The number of the ribs 29 is 6, 12 and 17, respectively.
The total meshing error of each gear 14, ie, each gear 1
When the difference (μm) between the maximum radius and the minimum radius of the tip circle (or pitch circle) of No. 4 was calculated, they were 85 μm each.
m, 43 μm and 31 μm.

The results are summarized in a table as shown in Table 1 below.

[0049]

[Table 1]

As can be seen from Table 1, as the number of the ribs 29 increases, the frequency of the speed fluctuation of the gear 14 caused by the ribs 29 increases, and the total meshing error decreases. In the test results shown in FIG. 7, the number of ribs 29 is six.
Since the number of ribs is small, the speed fluctuation appears remarkably. However, as the number of ribs increases to 12 or 17, the change in the outer diameter of the gear 14 due to each rib, that is, the unevenness in FIGS. Thus, the speed fluctuation amount of each gear is reduced. By increasing the number of the ribs 29 in this manner, the speed fluctuation frequency of the gear increases, and the speed fluctuation amount can be reduced.

On the other hand, FIG. 10 shows a state in which the rotation of the drive motor 10 shown in FIG. 2 is transmitted to the photosensitive member 1 via the transmission shown in FIG. FIG. 5 is a result of analyzing the speed fluctuation frequency of the photoconductor 1 when the gears 14 and 16 made of the same are used. That is, the drive motor 1
FIG. 6 is a diagram illustrating an example of how the photoconductor 1 undergoes speed fluctuations only with a speed fluctuation of 0. With the output gear 13 made of metal, a large speed fluctuation does not occur originally.

In the example of FIG. 10, a large speed fluctuation occurs at a frequency of 30 Hz in the photosensitive member 1 due to the speed fluctuation that occurs once per rotation of the drive motor 10.

If the gear 14 having the six ribs 29 described above is used to drive the photosensitive member 1, the speed fluctuation of 30 Hz caused by the rib 29 causes
The speed fluctuation by the drive motor 10 shown in FIG. 10 overlaps, and a large speed fluctuation occurs in the photoconductor 1.

However, the number of the ribs 29 of the gear 14 is 12
If the number is set to 17 or 17, the frequency of the speed fluctuation caused by each rib 29 is 60 Hz and 85H, respectively.
Since they are z, they do not coincide with the frequency of the speed fluctuation of the drive motor 10, and the speed fluctuation of the photoconductor 1 can be suppressed to be small.

Even if the number of the ribs 29 of the gear 14 is made smaller than six, for example, set to three, the frequency of the speed fluctuation due to this and the frequency of the speed fluctuation of the drive motor 10 are inconsistent. But the gear 14
When the number of the ribs 29 is reduced, the total meshing error of the gear 14 is further increased as compared with the case of six ribs.
As a result, there is a possibility that the photoconductor 1 may cause a large speed fluctuation.

For this reason, as described above, the rib 2
The number of the ribs 29 is set such that the speed fluctuation frequency of the gear caused by the rib 29 when the resin gear having the number 9 rotates is higher than the speed fluctuation frequency of the gear caused by the rotation of the drive motor 10. It is. According to the above experimental example, the number of ribs 29 is not 6
They increase as many as seventeen or seventeen.

If the above-described configuration is adopted, the rib 29 may have the same height H from the hub portion 25 to the ring-shaped portion 27 as shown in FIGS. In this case, the speed fluctuation of the photosensitive member 1 as a driven body can be suppressed to be small.

However, also in the case of the configuration example corresponding to the third aspect, as illustrated in FIGS. 4 and 5, the gears 14, 16 provided with the ribs 29 are removed from the surfaces of the webs 28 of the gears 14, 16. Height H of the rib 29 protruding in the axial direction of
Is set high in the rib portion adjacent to the hub portion 25 and the ring-shaped portion 27 and low in the intermediate portion 30 between them, it is possible to more effectively suppress the speed fluctuation of the driven body, that is, the photoconductor 1. it can. This is a configuration example corresponding to claim 4.

Further, in the configuration example corresponding to the third aspect, in the intermediate portion 30 of the rib 29, the rib 29
Height H is zero, and the rib 29 is divided into a portion 31 on the hub portion side and a portion 32 on the ring-shaped portion 27 side. It is possible to suppress. This is a configuration example corresponding to claim 5.

In each of the above embodiments, the driven member is an image carrier which is rotatably supported by the main body of the image forming apparatus and is formed as the photosensitive member 1 on which a toner image is formed. This is a configuration example corresponding to claim 6, whereby a high-quality toner image without density unevenness can be formed on the surface of the image carrier. However, the present invention is applicable to various types of mechanical devices other than the image forming apparatus exemplified above. It can be widely applied to resin gears and transmissions.

[0061]

According to the first aspect of the present invention, the rigidity can be increased by the ribs, and the outer diameter of the gear becomes uneven due to the "sink" phenomenon at the time of forming the gear. It is possible to effectively suppress the speed fluctuation when the gear rotates.

According to the gear of the second aspect, the above effect can be further ensured.

According to the transmission device of the third aspect, the rigidity of the gear can be increased by the rib, and furthermore, the effect that the influence of the speed fluctuation of the gear by the rib appears on the driven body can be effectively suppressed. it can.

According to the transmission of the fourth aspect, the operation and effect of the configuration of the third aspect can be more reliably achieved.

According to the transmission of the fifth aspect, the above effect can be further ensured.

According to the sixth aspect of the present invention, the rigidity of the gear can be increased, and the quality of the toner image formed on the surface of the image carrier can be prevented from being deteriorated.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view illustrating an example of an image forming apparatus.

FIG. 2 is a partial cross-sectional plan view showing a transmission used in the image forming apparatus shown in FIG.

FIG. 3 is a diagram illustrating an arrangement state of each element of the transmission illustrated in FIG. 2;

FIG. 4 is a perspective view showing an example of a resin gear.

FIG. 5 is a sectional view of the gear shown in FIG. 4;

FIG. 6 is a diagram illustrating an example of a result of a meshing test of the gears illustrated in FIGS. 4 and 5;

FIG. 7 is a diagram showing a meshing test result of the gears shown in FIGS. 11 and 12;

FIG. 8 is a diagram showing a meshing test result of a resin gear when the number of ribs is twelve.

FIG. 9 is a diagram showing a meshing test result of a resin gear when the number of ribs is 17.

FIG. 10 is a diagram illustrating a result of analyzing a speed fluctuation frequency of a photoconductor due to a speed fluctuation of a drive motor.

FIG. 11 is a front view of a gear in which the height of a rib is formed to be constant.

FIG. 12 is a sectional view of the gear shown in FIG. 11;

FIG. 13 is a diagram showing an example of a meshing test result of a gear having only six ribs.

FIG. 14 is a view for explaining a defect of the gear shown in FIGS. 11 and 12;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Drive motor 14 Gear 16 Gear 25 Hub part 26 Teeth 27 Ring part 28 Webb 30 Intermediate part 31 Part 32 Part H Height

Claims (6)

[Claims] 1. A hub located at a center, a ring located radially outside of the hub and formed substantially concentric with the hub, and a plurality of teeth formed on an outer peripheral surface. In a resin gear having a ring-shaped portion and a web that integrally connects the ring-shaped portion and the hub portion, at least one extending from the hub portion toward the ring-shaped portion, and integrally formed with the web. The height of the rib having one rib and projecting in the axial direction of the gear from the surface of the web,
A gear which is set high in a rib portion adjacent to the hub portion and the ring-shaped portion, and low in a middle portion therebetween. 2. In the intermediate portion of the rib, the height of the rib is zero, and the rib is divided into a hub portion-side portion and a ring-shaped portion-side portion. 2. The gear according to 1. 3. At least one resin gear for transmitting the rotation of the drive motor to the driven body is provided. The resin gear is provided at a centrally located hub portion and at a radially outer side of the hub portion. A ring-shaped portion that is located, is formed in a substantially concentric annular shape with respect to the hub portion, and has a plurality of teeth formed on an outer peripheral surface thereof;
In a transmission having the ring-shaped portion and a web that integrally connects the hub portion, at least one of the resin gears extends from the hub portion toward the ring-shaped portion, and is connected to the web. It has a plurality of ribs formed integrally, and the speed fluctuation frequency of the gear caused by the rib when the gear having the rib rotates is higher than the speed fluctuation frequency of the gear caused by the rotation of the drive motor. And a number of the ribs set. 4. The height of a rib projecting in the axial direction of the gear from the surface of the web of the gear provided with the rib,
The transmission according to claim 3, wherein the transmission is set to be high at a rib portion adjacent to the hub portion and the ring-shaped portion, and to be low at an intermediate portion therebetween. 5. The intermediate portion of the rib, wherein the height of the rib is zero, and the rib is divided into a hub portion-side portion and a ring-shaped portion-side portion. 5. The transmission according to 4. 6. The transmission according to claim 3, wherein the driven body is an image carrier that is rotatably supported by an image forming apparatus main body and has a surface on which a toner image is formed.