JP2916221B2 - Drive transmission mechanism - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive transmission mechanism for transmitting a driving force by driving a drive source to rotate forward and reverse.

<Prior Art> Conventionally, in an image forming apparatus such as a copying machine or a laser beam printer, for example, a driving source is driven forward and reverse to a conveying unit for selectively conveying a sheet material from a plurality of cassettes to an image forming unit. A drive transmission mechanism that switches the transmission of the driving force by using the drive transmission mechanism is employed. When a pulse motor is used as the drive source, tooth flanking of gears occurs based on the detent torque at the time of starting or driving the motor,
Vibration noise may be generated.

In order to prevent this, for example, as shown in FIGS. 5 (a) and 5 (b), a drive pulley 53 attached to a drive shaft 52a of a pulse motor 52 and a first stage as a drive transmission mechanism for the transport rollers 50 and 51 are provided. Belt 55 between pulley gear 54
To transmit the driving force.

As shown in FIGS. 6A and 6B, a motor gear 56 attached to a drive shaft 52a of the pulse motor 52 includes:
A mechanism for transmitting a driving force by meshing a so-called scissor gear 57 constituted by a pair of a driven gear and a backlash gear has been proposed.

<Problems to be Solved by the Invention> However, in the configuration shown in FIGS. 5 (a) and 5 (b), the tension of the belt 55 generated by the load torque of the transport rollers 50 and 51 causes the tension of the belt 55 with respect to the drive shaft 52a. Since it acts as a radial load, the bearing of the pulse motor 52 may be worn and its life may be shortened.

In the configuration shown in FIGS. 6 (a) and 6 (b),
When the pulse motor 52 rotates forward and backward, vibration cannot be suppressed. For example, when the pulse motor 52 is switched to drive the upper transport roller 50 during forward rotation drive, and to drive the lower transport roller 51 during reverse rotation drive, respectively.
In a general scissors gear 57, when the pulse motor 52 is driven to rotate in the reverse direction, the driving force is transmitted to the backlash gear, which is not originally transmitted, so that the backlash cannot be eliminated and vibration occurs.

Further, when the pulse motor 52 is generally excited from the non-excited state, the rotation direction of the first one pulse is not determined, and may be momentarily rotated in a direction opposite to the rotation direction.
For this reason, at the moment when the pulse motor 52 is started, there is a possibility that rattling due to a long gear train and loud impact noise due to backlash or the like may occur.

The present invention solves the above-mentioned problems of the prior art,
A drive transmission mechanism that prevents the occurrence of backlash by transmitting the driving force from the second pair of rotating bodies to the third rotating body via a gap even when the driving source is driven in the forward or reverse direction. Is to provide.

<Means for Solving the Problems> A typical means according to the present invention for solving the problems is an upper feed roller and a lower feed roller for feeding sheet materials from upper and lower cassettes, and a driving source. A first rotator that rotates in the forward and reverse directions, a pair of second rotators that mesh with the first rotator to transmit driving force, and a pair of the second rotators that are relatively rotated in the rotation direction. A spring for urging the first rotator therebetween, and a third rotator mounted coaxially with the pair of second rotators and selectively locked to one of the pair of second rotators. One of the pair of second rotators is a drive gear by the biasing force of the spring, the other has a role of a backlash gear, and the role is switched by the rotation direction of the first rotator, The first
When the rotating body rotates in either the forward or reverse direction, the third rotating body is engaged with the driving force transmitting side of the pair of second rotating bodies and the driving force is transmitted, and When the drive source rotates in the forward direction, the drive of the third rotating body is transmitted to the upper feed roller, and when the drive source rotates in the reverse direction, the drive of the third rotary body is transmitted to the lower feed roller. The driving of the third rotating body is transmitted to the upper and lower feed rollers via two one-way clutches whose idling directions are opposite to each other.

<Operation> According to the above means, when the drive source is driven to rotate, the first rotating body attached to the drive shaft rotates, and then the first
Of the second pair of rotating bodies meshing with the rotating body,
The driving force can be selectively transmitted to the third rotating body via the rotating body.

Further, since the driving force is transmitted from the second rotating body pair to the coaxial third rotating body via the gap, the transmission of the reverse driving force can be prevented by the gap when the drive source is started.

Further, even if the rotation direction of the drive source is switched, it is possible to prevent backlash from occurring due to the second rotating body of the second rotating body pair to which the driving force is not transmitted.

<Embodiment> Hereinafter, an embodiment of a drive transmission mechanism to which the present invention is applied will be described with reference to the drawings. In this embodiment, a case will be described in which the drive transmission mechanism is applied to a feed roller of a laser beam printer.

1 is a perspective explanatory view showing a drive transmission mechanism, FIGS. 2 (a) and 3 (a) are explanatory views showing a drive force transmission system, and FIGS. 2 (b) and 3 (b). FIG. 4 is a partially enlarged explanatory view, and FIG. 4 is a sectional explanatory view showing a schematic configuration of a laser beam printer.

First, a schematic configuration of the laser beam printer will be described with reference to FIG.

Reference numeral 1 denotes a laser beam printer capable of recording on both sides of a sheet material 2. The laser beam printer 1 is provided with a scanner unit 3 for irradiating and scanning a laser beam according to recording information, a process cartridge 4, and the like. In the process cartridge 4, image forming means such as a photosensitive drum 5 serving as an image carrier, a primary charger (not shown) serving as a corona discharger, a developing device 6 containing a toner, and a cleaner 7 are incorporated. I have.

The laser light emitted from the scanner unit 3 is reflected by the process mirror 4 via the return mirror 8.
The light is irradiated onto the photosensitive drum 5 inside. The photosensitive drum 5
Is charged in advance by a primary charger, and is irradiated with a laser beam to form an electrostatic latent image, and then a developing device 6 forms a toner image to be visualized.

On the right side of the printer 1, cassettes 9, 10 on which sheet materials 2 are loaded are mounted vertically. The above cassette
From 9 and 10, the sheet material 2 fed by the corresponding feed rollers 11 and 12 is conveyed to the temporarily stopped registration roller pair 13 to correct the skew. Then, the sheet material 2 is conveyed by the registration roller pair 13 in synchronization with the leading end of the toner image formed on the photosensitive drum 5,
The image is transferred to the first surface of the sheet material 2, and the unfixed transferred image is fixed by the fixing device 14.

When the conveyance path is selected by the flapper 15 and recording is performed only on one side of the sheet material 2, the sheet is guided to the upper conveyance path as shown in FIG. The paper is discharged to the discharge tray 17.

When recording on both sides of the sheet material 2, the flapper 15 is rotated to be guided to the lower re-conveying path,
The sheet is conveyed to a sheet conveying apparatus on the downstream side via the conveying guide 18.

Reference numeral 19 denotes a pair of curl removing rollers for correcting the curl of the sheet material, and reference numeral 20 denotes a pair of transport rollers. The curl removing roller pair 19 and the transport roller pair
Guide members 21a and 21b, which are guide means, are provided in the vertical direction between the guide members 21 and 20.

The sheet material 2 is conveyed between the reversing guide members 23a and 23b via the curl removing roller pair 19, the guide members 21a and 21b, the conveying roller pair 20, and the flapper 22, and the forward rotation of the half-moon reversing roller 24 ( It is conveyed to the right side of the drawing by the (left rotation) operation. Thereafter, the sheet material 2 is transported upward by the reverse rotation (right rotation) operation of the reversing roller 24 and the switching operation of the flapper 22, and is again transported to the register roller pair 13 by the re-transport roller 25.

The sheet material 2 is conveyed by the registration roller pair 13 in synchronization with the leading end of the toner image formed on the photosensitive drum 5, and the image is transferred to the second surface of the sheet material 2, and the fixing device is used.
The unfixed transfer image is fixed by 14.

Then, it is guided to the upper transport path shown in FIG. 1 by the flapper 15 and is discharged by the discharge roller 16 to the discharge tray 17 provided on the upper surface of the apparatus.

Next, a drive transmission mechanism applied to the feed rollers 11 and 12 of the printer 1 configured as described above will be described with reference to FIGS. 1 to 3A and 3B.

In FIG. 1, M is a pulse motor that is a drive source that can be driven forward and reverse. The drive shaft M ₁ of the pulse motor M, the motor gear 26 is attached is a first rotating body.

The motor gear 26 meshes with scissor gears 27a and 27b as a second rotating body pair. These scissor gears 27a, 27b
Are constituted by a pair of a driven gear and a backlash gear, and their roles are exchanged according to the rotation direction. A transmission gear 28, which is a third rotating body, is coaxially mounted on the scissor gears 27a, 27b.

Holes 29a and 29b are formed in the side surfaces of the scissor gears 27a and 27b so as to be displaced from each other, and a projection 28a protruding from the side surface of the transmission gear 28 is inserted into the holes 29a and 29b. . The gap between the projection 28a and the holes 29a, 29b is formed by the transmission gear 28 after the rotation direction of the pulse motor M is switched.
Projections 28a are holes 29a, 29b of any of the scissor gears 27a, 27b.
Until it locks at a half pulse angle or more. That is, an appropriate amount of play is formed between the protrusion 28a and the holes 29a and 29b.

A spring 30 is attached to each of the above-mentioned third gears 27a and 27b, and a rotational moment acts on each spring. As shown in FIG. 2 (b), the motor gear 26 meshes with the scissor gears 27a and 27b by the above moment.

The transmission gear 28 is an intermediate gear via an idler gear 31.
32 meshed. The drive shaft 32a of the intermediate gear 32 has
Clutch gears 33 and 34 are mounted coaxially. The clutch gear 33 is a rotating shaft 11 of the upper feed roller 11.
The driving force is transmitted to the feed roller gear 35 attached to the a, and the clutch gear 34 is rotated by the rotation shaft 12 of the lower feed roller 12.
This is for transmitting the driving force to the feed roller gear 36 attached to a. A one-way clutch is attached to each of the clutch gears 33 and 34 so that their idling directions are opposite to each other, and each transmits torque only in one direction.

Next, the operation of transmitting the driving force to the feed rollers 11 and 12 will be described with reference to FIGS.
This will be described with reference to FIG.

First, the case where the upper feed roller 11 is driven will be described with reference to FIGS. 2 (a) and 2 (b).

Fig. 1 and Fig. 2
In FIG. 9A, when the pulse motor M rotates in the counterclockwise direction (forward direction), the scissor gear 27a meshing with the motor gear 26 and the transmission gear 28 coaxially mounted with the scissor gear 27a move in the clockwise direction (reverse direction). The drive is rotated to rotate the idler gear 31 in the forward direction. The idler gear 31
The intermediate gear 32 that meshes with the gear rotates in the reverse direction, and only the clutch gear 33 coaxially mounted rotates in the reverse direction. The driving force is transmitted from the clutch gear 33 to the feed roller gear 35 to rotate the feed roller 11 in the forward direction.

The operation of transmitting the driving force from the motor gear 26 to the scissors gears 27a and 27b will be described with reference to FIG.

The scissor gears 27a and 27b are each given a rotational moment by the spring 30 as described above, and mesh with each other so as to sandwich the tooth surface of the motor gear 26 back and forth.

Holes 29a, 29b are provided on the side surfaces of the scissor gears 27a, 27b.
The transmission gear 28 is formed with holes that are shifted from each other, and a projection 28a protruding from a side surface of the transmission gear 28 is inserted into the hole. The driving force from the scissor gears 27a, 27b is transmitted to the transmission gear 28 via the projection 28a.

When the motor gear 26 rotates in the counterclockwise direction (forward direction) as shown in FIG. 2 (b), the scissor gear 27a on the back side of the drawing rotates in the clockwise direction (reverse direction), and the hole 29a is rotated.
The driving force is transmitted to the transmission gear 28 via the projection 28a locked to the transmission gear 28. At this time, the scissor gear 27b does not contribute to the transmission of the driving force at all, and has only the function of preventing backlash. Further, the gap between the protrusion 28a and the hole 29 becomes the protrusion 28a after the rotation direction of the pulse motor M is switched.
Has a gap of at least a half-pulse angle until it locks into the hole 29a, so that even if the motor gear 26 rotates instantaneously by a half-pulse angle at the time of startup, the reverse driving force is absorbed by the gap. The transmission gear 28 does not rotate in the reverse direction. That is, when driving the upper feed roller 11, the lower feed roller
12 can be prevented from rotating.

Next, a case where the lower feed roller 12 is driven will be described with reference to FIGS. 3 (a) and 3 (b).

The transmission system of the driving force will be described with reference to FIGS.
In FIG. 7A, when the pulse motor M rotates in the clockwise direction (reverse direction), the scissor gear 27b meshing with the motor gear 26 and the transmission gear 28 coaxially mounted with the scissor gear 27b move in the counterclockwise direction (forward direction). The drive is rotated to rotate the idler gear 31 in the opposite direction. Also the above idler gear
The intermediate gear 32 meshing with 31 rotates in the forward direction, and only the clutch gear 32 coaxially mounted rotates in the forward direction.
The driving force is transmitted from the clutch gear 34 to the feed roller gear 36 to rotate the feed roller 12 in the forward direction.

The operation of transmitting the driving force from the motor gear 26 to the scissor gears 27a and 27b will be described with reference to FIG.

When the motor gear 26 rotates in the reverse direction as shown in FIG. 3 (b), the scissor gear 27b on the front side of the drawing rotates in the forward direction, and the scissor gear 27b is transferred to the transmission gear 28 via the projection 28a locked in the hole 29b. Driving force is transmitted. At this time, the scissor gear 27a
Does not contribute to driving force transmission at all, and has only the effect of preventing backlash. Further, the gap between the projection 28a and the hole 29 has a gap of a half pulse angle or more after the rotation direction of the pulse motor M is switched and the projection 28a is locked in the hole 29b. Even if the motor 26 is momentarily reversely rotated by a half-pulse angle at the time of start-up, the reverse driving force is absorbed by the gap and the transmission gear 28 does not reversely rotate. That is, when driving the lower feed roller 12, the upper feed roller 11 can be prevented from rotating.

In the embodiment, the projection 28a protruding from the transmission gear 28 is used.
Are inserted into the holes 29a and 29b of the scissor gears 27a and 27b with a gap provided therebetween. Alternatively, the protrusions may be inserted through the transmission gear 28 from the scissor gears 27a and 27b side.

Further, the drive transmission mechanism is not limited to the feed roller,
It can be applied to a general transport roller.

<Effect of the Invention> As described above, in the drive transmission mechanism according to the present invention, when the rotation direction is switched, the driving force is selectively applied to the third rotating body from one of the pair of second rotating bodies. Can be transmitted. At this time, the rotating body that does not transmit the driving force among the second two rotating bodies operates as a backlash gear, so that a configuration in which backlash does not occur even when driven to rotate in either the forward or reverse direction can be achieved.

In addition, a third hole is provided in the second rotating body,
By inserting the projection of the rotating body, even if the step motor rotates reversely at the time of startup, the operation can be absorbed, and transmission of the reverse driving force can be prevented. As a result, it is possible to prevent an impulsive sound due to rattling or backlash of the gear train at the time of starting.

Further, by connecting the third rotating body to the feeding roller via a one-way clutch, it is possible to select a feeding roller that transmits a driving force according to the rotation direction of the third rotating body.

[Brief description of the drawings]

FIG. 1 is an explanatory perspective view showing a drive transmission mechanism, and FIG. 2 (a).
FIG. 3 (a) is an explanatory view showing a driving force transmission system, and FIG.
FIG. 3 (b) and FIG. 3 (b) are partially enlarged explanatory views of FIG.
The drawings are cross-sectional explanatory views showing the schematic configuration of a laser beam printer, and FIGS. 5 (a) and (b) and FIGS. 6 (a) and (b) are explanatory views of a conventional example. M is a pulse motor, 1 is a laser beam printer,
2 is a sheet material, 3 is a scanner unit, 4 is a process cartridge, 5 is a photosensitive drum, 6 is a developing device, 7 is a cleaner, 8 is a folding mirror, 9 and 10 are cassettes, 11 and 12 are feed rollers, 13 is Registration roller pair, 14 is a fuser, 15,2
2 is a flapper, 16 is a discharge roller, 17 is a discharge tray, 1
8 is a conveyance guide, 19 is a curling roller pair, 20 is a conveyance roller pair, 21a and 21b are guide members, 23a and 23b are reversing guide members, 24 is a reversing roller, 25 is a re-conveying roller, 26 is a motor gear, and 27a. , 27b are scissor gears, 28 is a transmission gear, 28a is a protrusion, 29a and 29b are holes, 30 is a spring, 31 is an idler gear, 32 is an intermediate gear, 33 and 34 are clutch gears, and 35 and 36 are feed roller gears. .

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F16H 1/20 B65H 3/06

Claims (3)

(57) [Claims] An upper feed roller and a lower feed roller for feeding a sheet material from upper and lower cassettes, a first rotating body that rotates in a forward and reverse direction by a driving source, and a first rotating body. A pair of second rotating bodies that mesh with each other to transmit a driving force, a spring that relatively urges the pair of second rotating bodies in a rotating direction to sandwich the first rotating body, and the pair of second rotating bodies. A third rotating body attached coaxially with the two rotating bodies and selectively locked to one of the pair of second rotating bodies; and a third rotating body of the pair of second rotating bodies by a biasing force of the spring. One has a role of a drive gear and the other has a role of a backlash gear, and the roles are switched according to the rotation direction of the first rotating body. The third rotating body receives a driving force transmitted from the pair of second rotating bodies. When the driving source rotates in the forward direction, the driving of the third rotating body is transmitted to the upper feed roller, and when the driving source rotates in the reverse direction, the third rotating body rotates. The driving of the body is transmitted to the lower feeding roller, and the driving of the third rotating body is transmitted to the upper and lower feeding rollers via two one-way clutches whose idling directions are opposite to each other. A drive transmission mechanism comprising: 2. The pair of second rotating bodies are formed by piercing holes in respective side surfaces by displacing holes, and projecting the third rotating body with projections, and inserting the projections into the holes. When the first rotating body rotates in the forward direction, the hole of one of the pair of second rotating bodies is engaged with the projection to drive the first rotating body. 4. A power transmission device, wherein when the first rotating body rotates in the opposite direction, a hole of the other rotating body is engaged with the projection to transmit a driving force. The drive transmission mechanism described in the above. 3. The driving source is a pulse motor, and the gap is driven by a hole of one of the pair of second rotating bodies being locked with a projection of the third rotating body. From the state in which the force is being transmitted to the state in which the rotation direction of the driving source is switched to the state in which the hole of the other rotator is engaged with the projection of the third rotator to transmit the driving force, The drive transmission mechanism according to claim 1 or 2, wherein the pulse motor is configured to be able to spin more than a half pulse angle.