JP3505949B2 - Mechanism to prevent helical gear from falling - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a helical gear forming a gear train for transmitting a driving force, and more particularly to a mechanism for preventing the helical gear from collapsing used in a driving force transmission system of an image forming apparatus.

[0002]

2. Description of the Related Art A drive mechanism of an image forming apparatus is made of a plastic molded by a mold as shown in FIGS. 8 and 9 for reasons such as low cost, low noise, and no rattling of meshing portions. A helical gear 92 is used.

Since the tooth surface of the helical gear 92 is tilted in the thrust direction and the tooth lines are spirally wound, if the space between the bearing boss 94 and the tooth portion 96 is lightened, FIG.
As shown in FIG. 6, the tooth portion 96 falls toward the bearing boss 94 due to the load applied to the meshing portion. For this reason, the meshing of the helical gears 92 and 98 becomes poor, and uneven rotation and image deterioration called banding occur.

In response to this, there have been adopted methods of using expensive metal helical gears, forming the helical gears without cutting lightening, and molding the helical gears with a high-strength plastic material that is difficult to obtain accuracy. However, it does not solve the essential problem.

As described above, it has been difficult to achieve both rigidity and precision in the conventional gear having a lightening structure formed by molding.

[0006]

SUMMARY OF THE INVENTION In consideration of the above facts, the present invention uses a usual plastic material and has a thinned structure helical gear formed by a mold.
It is an object of the present invention to prevent the teeth from inclining and causing a defective meshing when a load is applied to the meshing portion.

[0007]

According to the first aspect of the invention, a helical gear having a thinned portion between the bearing portion and the tooth portion is formed by molding. Around the bearing portion of the helical gear, a cylindrical reinforcing rib that reinforces the tooth bottom of the tooth portion is formed. Falling prevention means is provided on the side plate that axially supports the helical gear so as to face the reinforcing rib.

Therefore, even if the tooth portion of the helical gear is inclined toward the bearing portion side, the reinforcing rib is in sliding contact with the inclination preventing means, so that the tooth portion is not inclined. Therefore, the engagement failure does not occur.

According to the second aspect of the present invention, the side plate is provided with the roller rotatably supported, and the roller is in sliding contact with the reinforcing rib. Therefore, unnecessary rotation load is not applied to the helical gear.

According to the third aspect of the invention, the plastic block is fixed to the side plate and is in sliding contact with the reinforcing rib. In this way, by forming the falling prevention means using the same material as the helical gear, the reinforcing ribs are less likely to wear.

According to the fourth aspect of the invention, the plate piece formed by punching out the side plate comes into sliding contact with the reinforcing rib. As a result, the number of parts and the manufacturing cost can be reduced.

According to the fifth aspect of the invention, the gear train is formed by using a helical gear having a cylindrical reinforcing rib for supporting the tooth bottom of the tooth portion formed around the bearing portion. The reinforcing ribs of the adjacent helical gears forming this gear train are in contact with each other.

That is, since the adjacent helical gears receive a reaction force on the opposite side to the falling direction due to the reinforcing ribs, the teeth do not fall and no defective meshing occurs. Further, the combination of the helical gears can prevent the teeth from falling, so that it is not necessary to provide the side plate with a falling prevention member.

According to the sixth aspect of the invention, the ring for supporting the tooth bottom of the tooth portion is mounted on the bearing portion. The ring prevents the teeth from falling in the bearing direction. Further, it can be applied to a helical gear having a conventional structure formed by molding.

In the invention according to claim 7, the tooth bottom of the tooth portion of the helical gear is filled with the shaft. Since it is supported by this shaft, the meshing portion of the helical gear does not fall down.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 to 3 show a gear train of an image forming apparatus using a tilting prevention mechanism for a helical gear according to the first and second embodiments.

In this gear train, the deceleration helical gear 10 meshes with the driving helical gear 14 of the driving motor 12, and transmits the driving force to the rotary gear 22 for rotating the photoconductor 20 via the reduction gears 16 and 18. ing.

Next, a description will be given of a fall prevention mechanism for the helical gear of the first embodiment which constitutes this gear train. Deceleration helical gear 1
0 is the drive helical gear 1 centered on the bearing boss 24.
4 and the large tooth portion 30 of the reduction gear 16
A small tooth portion 28 that meshes with the bearing boss 24, and the large tooth portion 26, the small tooth portion 28, and the bearing boss 24 are lightened, and is molded by molding using a plastic material.

The center portion of the tooth bottom 26A of the large tooth portion 26 in the tooth width direction is connected to the bearing boss 24 by a circular rib 32, and the rib 32 reinforces the tooth bottom 26A. From the side surface of the rib 32, a cylindrical reinforcing rib 34 is provided so as to center around the bearing boss 24, and the outer edge portion projects outward from the end portion of the large tooth portion 26.

On the other hand, the side plate 38 supporting the shaft 36 inserted into the bearing boss 24 has a cylindrical plastic block 4 formed of the same material as that of the reduction helical gear 10.
0 is provided. A collar plate 40A projects from the plastic block 40. This collar plate 40A is
Hole 4 with plastic block 40 formed in side plate 38
It is fixed to the side plate 38 with a pin 44 in a state where it is inserted into 2. Further, the front end portion of the plastic block 40 is R-processed, and the large tooth portion 26 is located at a portion meshing with the drive helical gear 14 and is in sliding contact with the reinforcing rib 34.

Further, the small tooth portion 28 is provided so as to project from the side surface of the rib 32 (the side opposite to the reinforcing rib 34), and the tooth bottom 28A and the bearing boss 24 are reinforced by a triangular auxiliary rib 46. Has been done.

In such a structure, even if a large load is applied to the meshing portion of the large tooth portion 26 and the driving helical gear 14 and the large tooth portion 26 tends to fall in the direction of arrow A, the reinforcing rib 3
Since 4 is in sliding contact with the plastic block 40, the large tooth portion 26 does not fall down, and no defective meshing occurs. Further, by forming the fall prevention means with the same material as that of the reduction helical gear 10, the reinforcing ribs 34 are less likely to wear.

Next, a description will be given of the second embodiment of the helical gear fall prevention mechanism (the meshing portion between the reduction gear 16 and the gear 18).

The reduction gear 16 has the same structure as that of the reduction helical gear 10, and the gear 18 differs from the reduction gear 16 in that it does not include the small gear 28.

The bearing boss 48 of the reduction gear 16 is rotatably supported by the shaft 50 supported by the side plate 38.
Further, the bearing boss 52 of the gear 18 is axially supported by the shaft 54 supported by the side plate 38, and the respective reinforcing ribs 56,
58 are in contact with each other at the meshing portion between the reduction gear 16 and the gear 18.

With such a structure, even if a load is applied to the meshing portions, the reinforcing ribs 56 and 58 can provide a reaction force on the side opposite to the tilting direction, so that the tooth portions 60 and 62 do not fall down and the meshing failure occurs. Does not occur. Further, the combination of the helical gears can prevent the teeth from falling, so that it is not necessary to provide the side plate 38 with a member for preventing the falling.

Next, a mechanism for preventing the helical gears from collapsing according to the third embodiment will be described. As shown in FIG. 4, the reinforcing rib 34 of the reduction helical gear 10 to which the driving force is transmitted from the driving helical gear 14 is in sliding contact with the roller 66. This roller 66
Are rotatably supported by the shaft member 68. This shaft material 6
Both ends of 8 are supported by a channel-shaped shaft plate 70 fixed to the side plate 38.

As described above, by making the rotatable roller 66 slidably contact the reinforcing rib 34, an unnecessary rotational load is not applied to the reduction helical gear 10.

Next, a description will be given of the mechanism for preventing the helical gears from collapsing according to the fourth embodiment. As shown in FIG. 5, in the fourth mode,
The plate piece 7 that punches out the side plate 38 and is in sliding contact with the reinforcing rib 34.
Forming 2. As a result, it is possible to reduce the number of parts and the manufacturing cost.

Next, a description will be given of the mechanism for preventing the helical gear from collapsing according to the fifth embodiment. As shown in FIG. 6, in the fifth mode,
A ring 78 is fitted between the bottom 74A of the small tooth portion 74 of the helical gear 72 and the bearing boss 76. The tooth bottom 74A is supported by the ring 78, and the small tooth portion 74 does not fall toward the bearing boss 76 side. The invention of this embodiment can be applied to a helical gear having a conventional structure formed by molding.

Further, in the present embodiment, the ring 78 is fitted only on the small tooth portion 74 side, but it goes without saying that the ring can be fitted on the large tooth portion 80 side.

Next, a mechanism for preventing the helical gear from falling down according to the sixth embodiment will be described. As shown in FIG. 7, in the helical gear 82 of the sixth embodiment, the shaft portion including the bearing boss is a two-step cylindrical body in which the entire shaft is thinned, and the large tooth portion 84 and the small tooth portion 86 are provided on the outer peripheral surface thereof. Has been formed. The shaft portion is filled with the shaft 90, and both ends of the shaft 90 are supported by the side plates 38.

As described above, by filling the thinned portion of the molded helical gear 82 with the shaft 90, the meshing portion of the large tooth portion 84 and the small tooth portion 86 does not fall in the axial direction.

[0034]

EFFECTS OF THE INVENTION Since the present invention has the above-described structure, even in a helical gear having a lightening structure which is molded from a usual plastic material by molding, when the gear meshing portion is loaded, the teeth are inclined. Does not cause poor meshing.

Therefore, when used in the drive mechanism of the image forming apparatus, uneven rotation and banding do not occur.

[Brief description of drawings]

FIG. 1 is a perspective view of a gear train that uses a fall prevention mechanism for a helical gear according to first and second embodiments.

FIG. 2 is a plan view of a gear train using the tilt-prevention mechanism for the helical gears according to the first and second embodiments.

FIG. 3 is a cross-sectional view of a gear train using the tilt-preventing mechanism for the helical gears according to the first and second embodiments.

FIG. 4 is a cross-sectional view showing a tilting prevention mechanism for a helical gear according to a third embodiment.

FIG. 5 is a cross-sectional view showing a fourth mechanism for preventing the helical gear from collapsing.

FIG. 6 is a cross-sectional view showing a fifth mechanism for preventing the helical gear from collapsing.

FIG. 7 is a cross-sectional view showing a fall prevention mechanism for a helical gear according to a sixth embodiment.

FIG. 8 is a front view showing a conventional helical gear.

FIG. 9 is a sectional view showing a conventional helical gear.

FIG. 10 is a sectional view showing a meshed state of a conventional helical gear.

[Explanation of symbols]

34 Reinforcing rib 40 plastic block (falling prevention means) 56 Reinforcing rib 58 Reinforcing rib 66 Rolls (Means to prevent falls) 72 Plate piece (falling prevention means) 78 ring 90 shaft

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Claims (7)

(57) [Claims] 1. A cylindrical shape, which is formed by molding and has a space between a bearing portion and a tooth portion thinned, is formed around a bearing portion of the helical gear and reinforces a tooth bottom of the tooth portion. A fall prevention mechanism for a helical gear, comprising: a reinforcement rib; and a fall prevention unit that is provided on a side plate that axially supports the helical gear and is in sliding contact with the reinforcement rib. 2. The fall prevention mechanism for a helical gear according to claim 1, wherein the fall prevention unit is a roller rotatably supported by the side plate. 3. The fall prevention mechanism for a helical gear according to claim 1, wherein the fall prevention means is a plastic block fixed to the side plate. 4. The fall prevention mechanism for a helical gear according to claim 1, wherein the fall prevention means is a plate piece formed by punching out the side plate. 5. A cylindrical reinforcing rib, which is used for a helical gear formed by molding and has a thinned portion between the bearing and the tooth, and which reinforces the bottom of the tooth, is formed around the bearing. A fall prevention mechanism for a helical gear, wherein a gear train is formed by using helical gears, and the reinforcing ribs are in contact with each other. 6. A ring used for a helical gear formed by molding and having a thinned space between a bearing portion and a tooth portion, wherein a ring for supporting a root of the tooth portion is attached to the bearing portion. A mechanism that prevents the helical gear from falling. 7. A fall prevention mechanism for a helical gear, which is used in a helical gear having teeth formed by molding, and in which a tooth bottom side of the tooth is filled with a shaft.