JP2006112467A - Drive transmission mechanism and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive transmission mechanism with small stress value and stress amplitude and with long service life, and to provide an image forming apparatus provided with the drive transmission mechanism. <P>SOLUTION: The drive transmission mechanism is constituted of a shaft member 1 and a gear 10. A shaft end part 2 of the shaft member 1 has a cut face 3 formed to have a D-shaped cross section, and an engagement groove part 4. The gear 10 has a center hole 11 including an engagement face 12 engaged with the cut face 3, a snap-fit part 15 including a claw part , and a cutout 17. The shaft end part 2 is fit into the control hole 11 of the gear 10, and the groove part 4 is engaged with the claw part of the snap-fit part 15, so as to prevent slipping off of the gear 10. The snap-fit part 15 is arranged within a range of 135° to 270° with respect to a rotational direction B from a reference position A of an edge 11a. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a drive transmission mechanism and an image forming apparatus, and in particular, a drive transmission mechanism including a shaft member and a rotation transmission ring member such as a gear fitted to the shaft member for transmitting a rotational force, and the drive The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile provided with a transmission mechanism.

  In general, it is well known that a rotational force transmission mechanism is configured by integrally assembling a shaft member and a gear. Conventionally, the rotational force is transmitted between the shaft and the gear via a parallel pin or a D-cut surface, and the E-ring is used together to prevent the gear from coming off. However, the omission prevention structure by the E-ring is not preferable because it not only increases the cost due to an increase in the number of parts, but also requires assembling and disassembling during recycling.

  Therefore, in this type of transmission mechanism, as shown in FIG. 6, a cut surface 31 having a D-shaped section and an engaging groove portion 32 are formed in the shaft end portion of the shaft member 30, and the center hole 42 of the gear 41 is connected to the shaft 41. A configuration in which the engagement surface 43 is formed as the same as the cross-sectional shape of the end portion and the snap fit portion 44 is formed has been adopted. The engagement surface 43 engages with the cut surface 31 to rotate both together, and the snap fit portion 44 engages with the engagement groove portion 32 to prevent the gear 41 from coming off. Reference numeral 46 denotes a drive source side gear. Forming the snap-fit portion 44 integrally with the resin gear 41 is advantageous in terms of cost and has been frequently used in recent years.

  For example, Patent Documents 1 and 2 disclose several drive measures, but basically disclose a drive transmission mechanism similar to that shown in FIG.

  By the way, in this type of drive transmission mechanism, as shown in FIG. 7, since notches 45 are formed on both sides of the snap fit portion 44 of the gear 41, stress is applied in the tearing direction during drive transmission. It has a problem of occurring.

  That is, assuming a case where there is one notch 45 as a model case, the arrangement change of the notch 45 and the change of stress when the gear 41 rotates once will be described. Here, the position where the gear 41 and the drive source side gear 46 mesh with each other on the extended line of the straight line L connecting the edge 42a of the center hole 42 from the drive center O is defined as a reference position A.

  FIG. 8 shows a change in the arrangement of the notch 45 from the reference position A to the arrow B direction, and FIG.

  As is apparent from the graph of FIG. 9, even if a constant torque is transmitted from the gear 46 to the reference position A, the arrangement of the notches 45 is in the range of 0 ° to 135 ° and in the range of 270 ° to 360 °. In this case, since the stress is large and stress concentration occurs at the root portion of the snap fit portion 44 from the viewpoint of the strength characteristics of the gear 41, measures against plastic deformation and fatigue failure at the root portion are required.

  In addition, when the stress is increased, that is, when the snap fit portion is arranged in a range of 45 ° to 90 ° (see case 1, FIG. 7A), and in a case of being arranged in a range of 90 ° to 135 ° ( For each of Case 2 and FIG. 7 (B)), FIG. 10 shows the stress fluctuations when one rotation is performed with a constant driving torque. In FIG. 10, the curve Y <b> 1 indicates Case 1 and the curve Y <b> 2 indicates Case 2.

In detail, the variation amount of such stress is about 20 MPa at the maximum in case 1. In particular, when used in a drive transmission period with a heavy load such as a developer stirring blade of an image forming apparatus, the absolute value of stress and the fluctuation amplitude of the stress increase, and the gear may be damaged in a period shorter than the life of the apparatus. is there.
Japanese Patent Laid-Open No. 9-43966 JP-A-10-226439

  Accordingly, an object of the present invention is to provide a drive transmission mechanism having a small stress value and stress amplitude at the time of drive transmission and having a long durability life, and an image forming apparatus including the drive transmission mechanism.

  In order to achieve the above object, a drive transmission mechanism according to the present invention includes a shaft member having a cut surface and an engagement groove formed on the shaft end portion so as to have a substantially D-shaped cross section, and an engagement with the engagement groove. In a drive transmission mechanism comprising a snap fit portion that rotates and an annular member for rotation transmission having a center hole that engages with the cut surface, an edge portion of the center hole on which the driving force acts is used as a reference position with respect to the rotation center. The snap fit portion is arranged in a range of 135 ° to 270 ° with respect to the rotation direction of the member.

  In the drive transmission mechanism according to the present invention, with the edge portion of the center hole as a reference position with respect to the rotation center, the rotation direction of the shaft member is within the range of more than 0 ° and less than 135 ° and more than 270 ° and 360 °. The snap fit portion may not be disposed within the range below.

  In addition, an image forming apparatus according to the present invention includes the drive transmission mechanism.

  In the drive transmission mechanism according to the present invention, according to the knowledge of the present inventors, the snap fit portion provided in the rotation transmission ring member is in the range of 0 ° to 135 ° from the edge portion of the center hole, and 270 ° to 360 °. In the range of °, the stress value is large and the amplitude is also large. Therefore, by disposing the snap fit portion in the range of 135 ° to 270 ° without arranging the snap fit portion in the range where the stress increases, the strength of the ring member for rotation transmission with respect to the driving force is improved. The stress value and amplitude during drive transmission are small, and the durability life is improved.

  Embodiments of a drive transmission mechanism and an image forming apparatus according to the present invention will be described below with reference to the accompanying drawings.

  The first embodiment of the present invention includes a shaft member 1 and a gear 10 as shown in FIG. The shaft member 1 is formed with a cut surface 3 and an annular engagement groove portion 4 formed in the shaft end portion 2 so as to have a D-shaped cross section.

  As shown in FIG. 2, the gear 10 has a center hole 11 in which an engagement surface 12 that engages with the cut surface 3 is formed, and a snap fit portion 15 having a claw portion 16 is formed around the center hole 11. In addition, notches 17 and 17 are formed on both sides of the snap fit portion 15.

  The gear 10 press-fits the center hole 11 into the shaft end portion 2 of the shaft member 1 so that the claw portion 16 of the snap fit portion 15 engages with the groove portion 4 (see FIG. 3). In this state, the cut surface 3 and the engagement surface 12 are engaged, whereby the rotational force from the gear 10 is transmitted to the shaft member 1, and the claw portion 16 prevents the gear 10 from coming off.

  The gear 10 is formed by integrally forming a center hole 11, a snap fit portion 15, a claw portion 16 and a notch 17. As the material, a thermoplastic resin having elasticity represented by ABS, PS, PC and the like is most suitable. Of course, other materials (metal materials and composite materials) can be used as long as they satisfy characteristics such as elasticity, manufacturability, and mechanical strength. The shaft member 1 may be any of resin, metal, or composite material.

  In the first embodiment, the snap fit portion 15 formed on the gear 10 is disposed within a range of 180 ° to 225 ° with respect to the rotation direction B of the shaft member 1 with the edge portion 11a as a reference position A with respect to the rotation center. .

  In the second embodiment of the present invention, as shown in FIG. 4, the snap fit portion 15 formed on the gear 10 is 225 ° to 270 with respect to the rotation direction B of the shaft member 1 with the edge portion 11 a as a reference position A with respect to the rotation center. It is arranged within the range of °. The other configuration is the same as that of the first embodiment shown in FIGS. 1 to 3. In FIG. 4, the same members and portions as those in FIGS.

  In Examples 1 and 2, the stress fluctuation when the gear 10 is rotationally driven from the reference position A with a constant driving torque is shown in FIG. In FIG. 5, a curve X1 indicates the first embodiment, and a curve X2 indicates the second embodiment. As is clear from comparison between the curves X1 and X2 (example of the present invention) shown in FIG. 5 and the curves Y1 and Y2 (conventional example) shown in FIG. 10, the example of the invention has a smaller stress value and stress amplitude. Thereby, the durable life of the gear 10 is improved.

  Incidentally, the stress shown in FIG. 5 is calculated using a finite element method. In the configurations of Examples 1 and 2, the diameter of the gear 10 is 15 mm, the material is POM (M90S) manufactured by Polyplastics, The diameter of the shaft member 1 was 5 mm, the material was HIPS, and the driving torque was 30 N · mm. A similar model was adopted for the stress shown in FIG.

  The drive transmission mechanism shown in the first and second embodiments is used as a stirring blade for the developer installed in the developing unit of the image forming apparatus by forming the screw 9 on the shaft member 1. In addition, it can be used as a toner agitating / conveying blade or a roller shaft of a paper conveying system, and can be applied to a wide range of applications.

  The image forming apparatus may be a monochrome / color copying machine, a printer, a facsimile, or a complex machine of these.

(Other examples)
The drive transmission mechanism and the image forming apparatus according to the present invention are not limited to the above-described embodiments, and can be variously modified within the scope of the gist.

  For example, the detailed shape of the snap fit part, its notch, and the claw part in the ring member for rotation transmission is arbitrary. Further, the rotation transmitting annular member may be a pulley or the like in addition to the gear, and in the case of the gear, a flat tooth or a helical tooth is formed on the outer peripheral surface thereof.

It is a disassembled perspective view which shows Example 1 of the drive transmission mechanism which concerns on this invention. It is a perspective view which shows the gearwheel in the said Example 1. FIG. It is sectional drawing of the said Example 1. FIG. It is a perspective view which shows the gearwheel in Example 2 of the drive transmission mechanism which concerns on this invention. It is a graph which shows the stress fluctuation with respect to the rotation angle from the reference position of the gear in Examples 1 and 2. It is a disassembled perspective view which shows the conventional drive transmission mechanism. (A), (B) is a perspective view which shows the gearwheel of the drive transmission mechanism shown in FIG. It is explanatory drawing which shows the change of the arrangement | positioning angle of a notch in the gearwheel of a drive transmission mechanism. It is a graph which shows the stress fluctuation | variation with respect to the arrangement angle of a notch. It is a graph which shows the stress fluctuation | variation with respect to the rotation angle from the reference | standard position of the conventional gearwheel shown to FIG. 7 (A), (B).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Shaft member 2 ... Shaft end part 3 ... Cut surface 4 ... Engagement groove part 9 ... Screw 10 ... Gear 11 ... Center hole 11a ... Edge part 15 ... Snap fitting part 16 ... Claw part 17 ... Notch

Claims (3)

A shaft member having a cut surface and an engagement groove formed so as to have a substantially D-shaped cross section at the shaft end portion, a snap fit portion that engages with the engagement groove, and a center hole that engages with the cut surface In the drive transmission mechanism provided with an annular member for transmission,
The snap fit portion is disposed within a range of 135 ° to 270 ° with respect to the rotation direction of the shaft member, with the edge portion of the center hole on which the driving force acts as a reference position with respect to the rotation center,
A drive transmission mechanism characterized by this.   With the edge portion of the center hole as a reference position with respect to the rotation center, the snap is within a range of more than 0 ° and less than 135 ° and more than 270 ° and less than 360 ° with respect to the rotation direction of the shaft member. The drive transmission mechanism according to claim 1, wherein no fit portion is disposed. An image forming apparatus comprising the drive transmission mechanism according to claim 1.

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