JPH0485224A - Drive transmission mechanism - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a drive transmission mechanism that transmits driving force by driving a drive source in forward and reverse rotation.

<Prior Art> Conventionally, in image forming apparatuses such as copying machines and laser beam printers, a drive source is driven in forward and reverse rotation for a conveying means that selectively conveys sheet materials from a plurality of cassettes to an image forming means. A drive transmission mechanism is adopted that switches the transmission of driving force.

When a pulse motor is used as the drive source, the teeth of the gears may strike against each other due to detent torque when the motor is started or is being driven, and vibration noise may be generated.

In order to prevent this, for example, as a drive transmission mechanism for the conveyance roller 5051, as shown in FIG. There is a mechanism for transmitting driving force by passing a belt 55 between the two.

In addition, as shown in FIGS. 6(a) and (b), the pulse motor
Motor gear 56 attached to drive shaft 52a of 52
In addition, a mechanism has been proposed in which driving force is transmitted by meshing so-called scissor gears 57 constituted by a pair of driven gears and backlash gears.

<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 conveyance rollers 50, 51 is applied to the drive shaft 52a. Since it acts as a radial load, there is a risk that the bearing of the pulse motor 52 will wear out and its life will be shortened.

Furthermore, in the configuration shown in FIGS. 6(a) and 6(b),
When the pulse motor 52 rotates in forward and reverse directions, vibration cannot be suppressed. For example, when the pulse motor 52 is switched to drive the upper transport roller 50 during forward rotation and to drive the lower transport roller 51 during reverse rotation, the pulse motor is
When 52 is driven in reverse, the driving force is transmitted to a backlash gear to which no drive is originally transmitted, so backlash cannot be eliminated and vibrations occur.

Furthermore, when the pulse motor 52 is generally energized from a non-energized state, the rotation direction is not determined for the first pulse, and the pulse motor 52 may rotate momentarily in the opposite direction to the rotation direction.

Therefore, at the moment when the pulse motor 52 is activated, there is a risk that rattling due to the long gear train or a loud impact noise due to hacklanche or the like may be generated.

The present invention solves the problems of the prior art described above, and its purpose is to transmit driving force from the second rotating body pair to the third rotating body through a gap even if the drive source rotates in forward and reverse directions. It is an object of the present invention to provide a drive transmission mechanism that prevents the occurrence of backlash by transmitting the power.

<Means for Solving the Problems> A typical means according to the present invention for solving the above problems includes a drive source, a first rotating body attached to a drive shaft of the drive source and driven to rotate in forward and reverse directions. , a second rotating body pair that meshes with the first rotating body to selectively transmit driving force; and
It is characterized in that it has a third rotating body attached coaxially to which the driving force is transmitted from the pair of rotating bodies through a gap.

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

Furthermore, since the driving force is transmitted from the second rotating body pair to the coaxial third rotating body through the gap, it is possible to prevent the transmission of reverse driving force by the gap when the drive source is activated.

Furthermore, even if the rotational 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> An embodiment of a drive transmission mechanism to which the present invention is applied will be described below with reference to the drawings. In this embodiment, a case will be described in which the above drive transmission mechanism is applied to a feeding roller of a laser beam printer.

Fig. 1 is a perspective explanatory view showing the drive transmission mechanism, Fig. 2119
(a) and Fig. 3 (a) are explanatory diagrams showing the driving force transmission system, Fig. 2 (b) and Fig. 3 (b) are partially enlarged explanatory diagrams, and Fig. 4 is an illustration of the laser beam printer. FIG. 2 is a cross-sectional explanatory diagram showing a schematic configuration.

First, the schematic structure of the laser beam printer will be explained with reference to FIG.

1 is a laser beam printer capable of recording on both sides of a sheet material 2. Inside the laser beam printer 1 is a scanner unit 3 that irradiates and scans laser light according to recorded information. Equipped with process cartridge 4 etc. The process cartridge 4 includes a photosensitive drum 5 which is an image carrier, a primary charger (not shown) which is a corona discharger, and a developing device 6 which stores toner. It has a built-in image forming means such as a cleaner 7.

Further, the laser beam emitted from the scanner unit 3 is irradiated onto the photosensitive drum 5 in the process cartridge 4 via the folding mirror 8.

The photosensitive drum 5 is charged in advance by a primary charger, and is irradiated with laser light to form an electrostatic latent image, and then a toner image is formed by the developer 6 and visualized.

On the right side of the printer 1, stacks 9 and 10 loaded with sheet materials 2 are mounted above and below.

From the above force roller) 9.10, the corresponding feeding roller 11
, 12, the sheet material 2 is conveyed to a pair of registration rollers 13, which are temporarily stopped, and the skew is corrected. Next, the sheet material 2 is conveyed by the pair of registration rollers 13 in synchronization with the leading edge of the toner image formed on the photosensitive drum 5, and the image is transferred to the first surface of the sheet material 2. The transferred image is fixed.

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

In addition, when recording on both sides of the sheet material 20, the flapper 15 is rotated and guided to the lower re-conveying path.
The sheet material is transported via the transport guide 18 to a sheet material transport device on the downstream side.

Reference numeral 19 designates a pair of curl removal rollers for correcting the curl of the sheet material, and reference numeral 20 designates a pair of conveyance rollers. Further, a guide member 21 serving as a guide means is provided between the pair of curl removal rollers 19 and the pair of conveyance rollers 20.
a and 21b are provided in the vertical direction.

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

The sheet material 2 is conveyed by the pair of registration rollers 13 in synchronization with the leading edge 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 unfixed image is transferred by the fixing device 14. The image is fixed.

Then, the paper is guided by the flapper 15 to the upper conveyance path shown in FIG. 1, and is discharged by the discharge rollers 16 to a discharge tray 17 provided on the top surface of the apparatus.

Next, a drive transmission mechanism used in the feed rollers 11, 12 of the printer 1 configured as described above will be explained with reference to FIGS. 1 to 3(a) and (b).

In FIG. 1, M is a pulse motor which is a drive source capable of forward and reverse rotation. A motor gear 26, which is a first rotating body, is attached to the drive shaft M1 of the pulse motor M.

The motor gear 26 meshes with scissor gears 27a and 27b, which are a second pair of rotating bodies. The scissor gears 27a and 27b are configured as a pair of a driven gear and a backlash gear, and their roles change depending on the direction of rotation.

Further, a transmission gear 28, which is a third rotating body, is coaxially attached to the scissor gears 27a and 27b.

Holes 29a are provided on the sides of the scissor gears 27a and 27b.
, 29b are bored at positions shifted from each other, and a protrusion 28a protruding from the side surface of the transmission gear 28 is inserted into these holes 29a, 29b. The protrusion 28a and hole 29a
, 29b, after the rotation direction of the pulse motor M is switched, the protrusion 28a of the transmission gear 28 is connected to the holes 29a, 29b of either of the scissor gears 27a, 27b.
There is a gap of more than half a pulse angle until it is locked. That is, an appropriate amount of backlash is formed between the projection 28a and the holes 29a and 29b.

Further, blades 30 are attached to the scissor gears 27a and 27b, and rotational moment acts on each of them. Due to the above moment, as shown in Figure 2, etc.
The motor gear 26 is a scissor gear 27a.

27b, so as to sandwich and mesh with each other.

The transmission gear 28 meshes with an intermediate gear 32 via an idler gear 31. The drive shaft 32 of this intermediate gear 32
Clutch gears 33 and 34 are coaxially attached to a. Of these, the clutch gear 33 transmits driving force to the feed roller gear 35 attached to the rotation shaft 11a of the upper feed roller 11, and the clutch gear 34 is attached to the rotation shaft 12a of the lower feed roller 12. It transmits driving force to the feed roller gear 36. One-way flanches are attached to the clutch gears 33 and 34 so that their idling directions are opposite to each other, and each of the clutch gears 33 and 34 transmits rotational force in only one direction.

Next, FIGS. 2(a)(b) and 3(a)(b) show the operation of transmitting the driving force to the feeding roller 11.12.
).

First, the case of driving the upper feeding roller 11 will be described with reference to FIGS. 2(a) and 2(b).

To explain the driving force transmission system, Figs. 1 and 21
In N(a), when the pulse motor M rotates counterclockwise (positive direction), the scissor gear 27a meshing with the motor gear 26 and the transmission gear 28 coaxially attached thereto rotate clockwise (reverse direction). The idler gear 31 is rotated in the forward direction. Further, the intermediate gear 32 meshing with the idler gear 31 rotates in the opposite direction, and only the clutch gear 33 attached coaxially rotates in the opposite direction. A 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.

From the motor gear 26 to the scissor gears 27a and 27b
The driving force transmission operation will be explained with reference to FIG. 2(b).

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

Further, there are holes 2 on the sides of the scissor gears 27a and 27b.
Holes 9a and 29b are bored at different positions, and a protrusion 28a protruding from the side surface of the transmission gear 2B is inserted into these holes. The driving force from the scissor gears 27a, 27b is transmitted to the transmission gear 28 via the protrusion 28a.

When the motor gear 26 rotates counterclockwise (positive direction) as shown in FIG. The driving force is transmitted to the transmission gear 28 via the stopped protrusion 28a. At this time, the scissor gear 27b does not contribute to the transmission of driving force at all, and has only the function of preventing backlash. Further, the gap between the protrusion 28a and the hole 29a is longer than half a pulse angle after the rotation direction of the pulse motor M is switched until the protrusion 28a is locked in the hole 29a. Even if the gear 26 instantaneously rotates backward by half a pulse angle at startup, the reverse driving force is absorbed by the gap, and the transmission gear 28 will not rotate backwards. That is, when driving the upper feed roller 11, it is possible to prevent the lower feed roller 12 from rotating.

Next, the case of driving the lower feeding roller 12 will be described with reference to FIGS. 3(a) and 3(b).

To explain the driving force transmission system, in FIGS. 1 and 3(a), when the pulse motor M rotates clockwise (in the opposite direction), the scissor gear 27b meshes with the motor gear 26 and the scissor gear 27b coaxially engages with the motor gear 26. The attached transmission gear 28 is driven to rotate in a counterclockwise direction (forward direction), causing the idler gear 31 to rotate in the opposite direction. Further, the intermediate gear 32 meshing with the idler gear 31 rotates in the forward direction,
Only the coaxially attached clutch gear 34 rotates in the forward direction. A 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.

From the motor gear 26 to the scissor gears 27a and 27b
The driving force transmission operation will be explained with reference to FIG. 3(b).

When the motor gear 26 rotates in the opposite direction as shown in FIG. 3(b), the scissor gear 27b on the near side of the drawing rotates in the forward direction and is connected to the transmission gear 28 via the protrusion 28a locked in the hole 29b. Driving force is transmitted. At this time, the scissor gear 27a does not contribute to the transmission of driving force at all, and has only the function of preventing hacklash. In addition, the protrusion 28
The gap between a and the hole 29b is more than half a pulse angle after the rotation direction of the pulse motor M is switched until the protrusion 28a is locked in the hole 29b. Even if the transmission gear 28 instantaneously rotates backward by half a pulse angle at startup, the reverse driving force is absorbed by the gap, and the transmission gear 28 will not rotate backwards. That is, when driving the lower feed roller 12, it is possible to prevent the upper feed roller 11 from rotating.

In the above embodiment, the protrusion 28 protruding from the transmission gear 28
a to the holes 29a and 29b of the scissor gears 27a and 27b.
Although the scissor gear 27 is inserted with a gap, the scissor gear 27
It is also possible to configure the projection to be inserted into the transmission gear 28 from the sides a and 27b.

Further, the drive transmission mechanism described above can be applied not only to the feeding roller but also to general conveyance rollers.

<Effects of the Invention> As described above, the present invention transmits the driving force from the second rotating body pair to the coaxial third rotating body through the gap, so that when the drive source is started, the gap causes reverse drive. Force transmission can be prevented.

For example, if a hole is drilled in the side surface of the second rotating body pair and a protrusion protruding from the side surface of the third rotating body is inserted into the hole with a gap formed, the size of the gap is determined by the rotation of the drive source. If it takes more than half a pulse angle after the direction is switched until the protrusion of the third rotary body is locked in one of the holes of the second rotary body pair, the instantaneous reverse when the drive source is activated By absorbing the rotation by the gap, it is possible to prevent reverse driving force from being transmitted to the third rotating body.

Further, even if the rotational 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.

Therefore, generation of vibration noise due to the detent torque of the drive source can be prevented.

[Brief explanation of the drawing]

Figure 1 is a perspective explanatory diagram showing the drive transmission jII structure, Figure 2 (
a) and FIG. 3(a) are explanatory diagrams showing the driving force transmission system,
2(b) and 3~) are partially enlarged explanatory views, FIG. 4 is a cross-sectional explanatory view showing the schematic structure of the laser beam printer, and FIG. 5(a) et al.) and 6(a) )(b) is an explanatory diagram 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. 10 is a cassette, 11.
12 is a feed roller, 13 is a pair of registration rollers, 14 is a fixing device, 15.22 is a flapper, 16 is an ejection roller, 17 is an ejection tray, 18 is a conveyance guide, 19 is a pair of curl removal rollers, and 20 is a pair of conveyance rollers. , 21a, 21
b is a guide member 23a; 23b is a reversing guide member, 24 is a reversing roller, 25 is a re-conveying roller, 26 is a motor gear, 27a, 27b
is a scissor gear, 28 is a transmission gear, 28a is a protrusion, 29
a, 29b are holes, 30 is a spring, 31 is an idler gear, 3
2 is intermediate gear, 33.34 is clutch gear, 35.36
is the feed roller gear. (a) Figure 3 (b) (b) (a) (b) (a) (b) 2a

Claims (4)

[Claims] (1) A drive source, a first rotating body that is attached to the drive shaft of the drive source and driven to rotate in forward and reverse directions, and a second rotating body that meshes with the first rotating body and selectively transmits driving force. and a third rotating body coaxially attached to which a driving force is transmitted from the second pair of rotating bodies through a gap. (2) The drive transmission mechanism according to claim (1), wherein the second rotating body pair is a scissor gear that is a pair of a driven gear and a backlash gear. (3) The drive transmission mechanism according to claim (1), wherein a hole is bored in the side surface of the second rotating body pair, and a protrusion protruding from the side surface of the third rotating body is inserted into the hole with a gap formed therein. (4) Claim (3) wherein there is a gap of at least half a pulse angle after the rotational direction of the drive source is switched until the protrusion of the third rotating body is locked in one of the holes of the second rotating body pair. The drive transmission mechanism described.