JPH04157251A - Gear device - Google Patents

Abstract

PURPOSE:To prevent a driven shaft from uneven rotation by parting drive gears into a main gear and sub-gear and making both gears engage with each other through a frictional force. CONSTITUTION:A driven gear 42 provided on a driven shaft 54 meshes with a drive gear 18 to transmit a rotational florce thereto. Then, a friction engaging means 60 is secured fixedly to the driven shaft 54. A main gear 32 meshing wit the drive gear 18 and a sub-gear having the number of teeth less than that of the main gear and supported by the driven shaft 54 coaxially with the main gear 32 to mesh with the drive gear 18 engage each other with a frictional force so that the main gear 32 and sub-gear 34 can be relatively rotated by an external force having at least a predetermined value. Thus, the driven shaft 54 can be prevented from uneven rotation when the rotational speed of the drive gear 18 is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gear device that transmits rotational force through meshing of gears.

[Conventional technology]

A gear device transmits the rotational force of a drive shaft to a driven shaft by meshing and rotating gears.

In order to ensure smooth rotation of this gear, backlash is provided in the meshing portion of the gear.

However, when the rotational speed of the drive shaft changes, this backlash causes uneven rotation of the driven shaft, making it difficult to rotate the driven shaft in accordance with the rotational force and amount of rotation of the drive shaft.

Conventionally, in order to prevent this uneven rotation, methods have been devised to substantially reduce the backlash of gear devices.

(Japanese Patent Application Laid-Open Nos. 58-74916 and 62-63268).

According to this, one gear is composed of a main gear fixed to a rotating shaft and a sub gear coaxially supported on the rotating shaft with the main gear, and the main gear and the sub gear can rotate relative to each other. Furthermore, a biasing means is provided between the main gear and the secondary gear to bias the secondary gear in the relative rotation direction, and this biasing force causes the teeth of the main gear and the teeth of the secondary gear to move between the teeth of the other gear. The backlash of the gear device is substantially reduced by putting the two in a pinched state.

[Problem to be solved by the invention]

However, in order to provide the biasing means between the main gear and the auxiliary gear, processing must be performed to engage the biasing means with both the main gear and the auxiliary gear. Therefore, the number of parts constituting the gear increases, the structure becomes complicated, and furthermore, the assembly becomes complicated.

The present invention takes the above facts into consideration, and aims to provide a gear device that can substantially reduce the backlash provided at the meshing portion of the gears in order to eliminate uneven rotation of the gears, and that has a small number of parts and a simple structure. purpose.

[Means to solve the problem]

The gear device according to claim (1) of the present invention is a gear device that transmits rotational force by meshing a driven gear provided on a driven shaft with a driving gear, and is fixed to the driven shaft. a main gear that meshes with the driving gear; a auxiliary gear that has fewer teeth than the main gear and is coaxially supported on a driven shaft with the main gear and meshes with the driving gear; and the main gear and the auxiliary gear. The main gear and the auxiliary gear can be rotated relative to each other by an external force of a predetermined value or more by engaging the gears by frictional force.

The gear device according to claim (2) of the present invention is the gear device according to claim (1).
The gear device according to the invention, wherein the frictional engagement means includes:
The frictional force is generated by an elastic force of a frictional engagement means provided on the auxiliary gear.

The gear device according to claim (3) of the present invention is a gear device that transmits rotational force by meshing a driven gear provided on a driven shaft with a driving gear, and □ is fixed to the driven shaft. a main gear that meshes with the driving gear; a secondary gear that has fewer teeth than the main gear and is coaxially supported on a driven shaft with the main gear and meshes with the driving gear; and the main gear and the secondary gear. and magnetic force engagement means for engaging the main gear and the auxiliary gear with magnetic force so that the main gear and the auxiliary gear can rotate relative to each other by an external force of a predetermined value or more.

[Effect]

According to the gear device according to claim (1) of the present invention, the driven gear is composed of a main gear and a auxiliary gear, and the rotational force of the driving gear is transmitted to the driven shaft by the main gear.

Further, the drive gear meshes with a sub gear which is coaxial with the main gear and engages with the drive gear by frictional force.

The auxiliary gear has fewer teeth than the main gear, so the tooth pitch is wider.

The rotation of the driving gear causes the main gear and the secondary gear to rotate together, but in the portion where the teeth begin to mesh with each other, the secondary gear contacts the driving gear first, so the driving gear uses the secondary gear as a frictional engagement means. It resists and rotates faster than the main gear. For this reason,
At the portion where the main gear and the drive gear mesh, the teeth of the auxiliary gear fill the gap between the teeth of the main gear and the teeth of the drive gear.

Therefore, the teeth of the main gear and the teeth of the auxiliary gear fill the tooth gap of the drive gear, and the backlash between the drive gear and the main gear is substantially reduced, resulting in a change in the rotational speed of the drive gear. It is possible to prevent uneven rotation of the drive shaft.

In the gear device according to claim (2) of the present invention, claim (1)
), the frictional force between the main gear and the auxiliary gear is generated by the elasticity of the frictional engagement means formed on the auxiliary gear, and the same effects as in claim (1) can be obtained.

In the gear device according to claim (3) of the present invention, claim (1)
), the main gear and the auxiliary gear are engaged by magnetic force. This magnetic engagement means also makes it possible to
The same effect as 1) can be obtained.

〔Example〕

First Embodiment FIG. 2 shows a roll paper conveying device 12 of a thermal printer 10 to which the present invention is applied.

The thermal printer 10 is provided with a storage section 38 that accommodates a roll of thermal paper 36, and both longitudinal ends of a core 40 of the roll of thermal paper 36 are pivotally supported (not shown).

From the outer peripheral edge of this roll-shaped thermal paper 36, the thermal paper 36
One longitudinal end of the paper is pulled out, bent by a paper guide 44, and wound around a platen roller 46.

A print head 48 is in contact with the platen roller 46 , and a longitudinally intermediate portion of the thermal paper 36 is sandwiched between the platen roller 46 and the print head 48 .

The print head 48 is supported by an arm 52 and is movable in the width direction of the thermal paper 36 (main scanning direction). Heat generating elements (not shown) are arranged in the print head 48, and a recording processing device (not shown) built in the thermal printer 10
The heating element generates heat due to the pulsed current sent from the heating element, thereby heating the thermal paper 36.

The platen roller 46 is fixed to the middle part of the platen shaft 54 in the axial direction.
Both ends of the thermal printer 10 are pivotally supported by a frame (not shown) of the thermal printer 10 . Further, a conveyance roller (not shown) is arranged on the side of the print head 480 and the rolled thermal paper 36, and the thermal printer 10 is further provided with a paper discharge port 50 downstream of the platen roller 46.

The thermal paper 36 is held between the conveyance roller and the platen roller 46, and when the platen roller 46 rotates in the direction of arrow C in FIG. 2, it is pulled out from the storage section 38 by the platen roller 46 and the conveyance roller. At approximately the same time, the leading end of the thermal paper 36 is sent out from the paper outlet 50 of the thermal printer 50 in the direction of the arrow (sub-scanning direction).

On the other hand, the platen roller 4 around which the thermal paper 36 is wound
The platen shaft 54 of No. 6 has a driven gear 4 which will be described later.
2 is provided. This driven gear 42 is meshed with an intermediate gear 30 provided on the shaft 22,
Further, an intermediate gear 28 provided on the shaft 22 is meshed with an intermediate gear 26 provided on the shaft 20. Further, the shaft 20 is provided with an intermediate gear 24, which is meshed with the drive gear 18 which is a drive gear.

The drive gear 18 is fixed to a drive shaft 16 of a stepping motor 14 which is a drive source for the roll paper conveyance device 12. The rotation of the stepping motor 14 is controlled by the drive gear 18 and intermediate gears 24. 2
6.28.30, and the platen roller 46 is rotated via the driven gear 42.

That is, the rotation of the stepping motor 14 in the direction of arrow C in FIG. 2 is transmitted to the intermediate gear 30 of the shaft 22, the intermediate gear 30 of the shaft 22 is rotated in the direction of arrow C in FIG. It is rotated in the direction of arrow C in the figure.

As shown in FIG. 1, the platen shaft 54 is provided with a stepped portion 56 that is outside the platen roller 46 and whose diameter is reduced toward one tip. Furthermore, a notch 58 is formed in the outer circumferential surface of the platen shaft 54 whose diameter has been reduced, extending from the intermediate portion in the axial direction toward the distal end portion.

In this case, a roughening process such as knurling or satin finishing may be performed from the axially intermediate portion of the outer circumferential surface of the platen shaft 54 having a reduced diameter to the stepped portion 56 .

The driven gear 42 is inserted into the reduced diameter portion of the platen shaft 54.

The driven gear 42 has a configuration in which a driven gear 32 as a main gear and a friction gear 34 as a auxiliary gear are coaxially combined.

As shown in FIG. 1, the driven gear 32 has 20 teeth 7.
0, and a substantially circular through hole 64 is bored in the axial center portion of the driven gear 32 along the axial direction. A projection 64A is provided on the outer periphery of the through hole 64 so as to protrude in the radial direction toward the axis.

The friction gear 34 is an integrally molded product made of resin and has 19 teeth 72 formed therein. In this case, resins such as polyacetal, nylon, ABS, and polyurethane can be used. Friction gear 34
A substantially cylindrical boss 60 is provided protruding to one side along the axis, and this boss 60 and the friction gear 34 are
A through hole 66 is bored along the axis of the friction gear 34.

The diameter of this boss 60 is reduced at the tip, and a plurality of notches 62 are formed along the axis from the tip. boss 6
The tip portion of the 0 is made elastically deformable in the radial direction by this notch 62. Further, the inner surface of the through hole 66 may be given a satin finish.

Although the friction gear 34 and the driven gear 32 have the same tip circle diameter, the number of teeth of the friction gear 34 is one less than the number of teeth of the driven gear 32. This changes the pitch between the driven gear 32 and the friction gear 34, so that the tooth space K of the friction gear 34 is made wider than the tooth space of the driven gear 32, as shown in FIG. 3A.

As shown in FIG. 4, the driven gear 42 is inserted from the boss 60 of the friction gear 34 into the reduced diameter portion of the platen shaft 54, after which the driven gear 32 is inserted. Projection 6 of through hole 66 of driven gear 32
6A is in contact with the notch 58 of the platen shaft 54. Friction gear 3 of this driven gear 32
An E-ring (not shown) is provided on the side opposite to 4, and prevents the driven gear 32 from moving in the axial direction on the side opposite to the friction gear 34.

The friction gear 34 is inserted into the platen shaft 54 until the diameter of the tip of the boss 60 is expanded and the tip of the boss 60 comes into contact with the stepped portion 56 of the platen shaft 54 . The platen shaft 54 is held by the boss 60 of the friction gear 34 as the boss 60 restores its shape.

When the platen shaft 54 is held between the bosses 60, a frictional force is generated between the platen shaft 54 and the boss 600, and this frictional force allows the platen shaft 54 and the friction gear 34 to rotate together. Further, by applying a predetermined force or more to the friction gear 34, the friction gear 34 and the platen shaft 54 can rotate relative to each other.

Further, the friction gear 34 is connected to the platen shaft 54.
It is sandwiched between the zero step portion 56 and the driven gear 32, and the platen shaft 54 is prevented from moving in the axial direction.

The driven gear 32 is configured to rotate integrally with the platen shaft 54 through a notch 58 in the platen shaft 54.

The driven gear 32 and the friction gear 34 are engaged through a platen shaft 54, and are enabled to rotate together due to the frictional force between the boss 60 of the friction gear 34 and the platen shaft 54. . However, when an external force of a predetermined value or more is applied to the friction gear 34, the friction gear 34 is allowed to rotate relative to the driven gear 32 against this frictional force.

The driven gear 32 and the friction gear 34 are engaged with the intermediate gear 30 of the shaft 22 as a driven gear 42.

3A and 3B show the engagement of the intermediate gear 30 with teeth 68, the driven gear 32, and the friction gear 34, and FIG. 3A shows the part where each gear starts to mesh, FIG. 3B shows a state in which the intermediate gear 30 has rotated slightly in the direction of arrow B from FIG. 3A.

As shown in FIG. 3A, when the intermediate gear 30 rotates in the direction of arrow B, the teeth 72 of the friction gear 34 are closer to the teeth 70 of the driven gear 32 at the portion where the intermediate gear 30, the driven gear 32, and the friction gear 34 begin to mesh with each other. It is in a state where it is shifted in the direction opposite to the direction of arrow C. This allows the teeth 72 of the friction gear 34 to come into contact with the teeth 68 of the intermediate gear 30 before the teeth 70 of the driven gear 32.

The teeth 72 of the friction gear 34 are the teeth 68 of the intermediate gear 30.
By coming into contact with , the friction gear 34 is rotated relative to the driven gear 32 in the direction of arrow C against the frictional force between the boss 60 and the platen shaft 54 . As a result, as shown in FIG. 3B, the teeth 68 of the intermediate gear 30
At the portion where the teeth 70 of the driven gear 32 and the intermediate gear 30 mesh, the gap between the plow 68 of the intermediate gear 30 and the teeth 70 of the driven gear 32 is filled by the teeth 72 of the friction gear 34.

The intermediate gear 30, the driven gear 32, and the friction gear 34 sequentially repeat this engagement and rotate, and as the driven gear 32 rotates, the platen shaft 54 and the platen roller 46 are rotated.

The operation of this embodiment will be explained below.

In FIG. 2, the thermal printer 100 and the roll paper conveying device 12 are shown.

In the roll paper conveyance device 12, the stepping motor 14 rotates in the six directions of arrows, thereby rotating the platen roller 46 in the direction of arrow C, thereby drawing out the thermal paper 36.

The print head 48 prints a portion of characters or images onto the thermal paper 36 which is sandwiched between the platen roller 46 and the print head 48 . Furthermore, the stepping motor 14 rotates in the six directions of the arrows to feed the thermal paper 36 in the direction of the paper discharge port 50 and pull out the thermal paper 36 from the storage section 38.
The operation of printing characters or images onto the thermal paper 36 by the print head 48 is successively repeated.

As a result, characters or images are printed onto the thermal paper 36, but if there is unevenness in the amount of rotation of the platen roller 46 rotated by the stepping motor 14, sub-scanning unevenness (a degree unevenness) may occur on the thermal paper 36. become.

In the roll paper conveying device 12, the drive gear 18 transmits the rotation of the stepping motor 14 to the intermediate gear 30 of the shaft 22 via intermediate gears 24, 26, and 28. The intermediate gear 30 of the shaft 22 meshes with the driven gear 32 and the friction gear 34 of the platen shaft 54 to transmit the rotation of the stepping motor 14 to the platen roller 46.

As shown in FIGS. 3A and 3B, the intermediate gear 30 of the shaft 22, the driven gear 32, and the friction gear 34 rotate as shown in FIGS. 3A and 3B. It rotates while meshing with the intermediate gear 30 of the shaft 22.

As shown in FIG. 3A, at the portion where the driven gear 32 and the friction gear 34 begin to mesh with the intermediate gear 30, the friction gear 34 starts to mesh with the intermediate gear 30 before the driven gear 32, so the driven gear resists the frictional force. Rotates faster than 32.

As a result, as shown in FIG. 3B, the teeth 72 of the friction gear 34 fill the gap between the teeth 68 of the intermediate gear 30 and the teeth 70 of the trike gear 32 at the portion where the intermediate gear 30 and the driven gear 32 mesh. .

The intermediate gear 30, the driven gear 32, and the friction gear 34 are rotating by repeating this state one after another, and the platen shaft 54 is rotating together with the driven gear 32.

When the stepping motor 14 stops rotating after a certain amount of rotation, the opening gear 30 of the shaft 22 also stops rotating. As shown in FIGS. 3A and 3B, the gap between the teeth 68 of the intermediate gear 30 and the teeth 70 of the driven gear 32 is filled with the teeth 72 of the friction gear 34. In addition, since the driven gear 32 and the friction gear 34 are engaged by frictional force, there is no rattling between the teeth 68 of the intermediate gear 30, and the driven gear 32 and the friction gear 34 are substantially integrated to control the rotation of the intermediate gear 30. It will stop when it stops.

Therefore, the driven gear 32 can be rotated in accordance with a certain amount of rotation of the stepping motor 14, and uneven rotation of the platen roller 46 caused by backlash can be prevented. Thereby, the thermal paper 36 can be accurately moved by a certain amount, and no sub-scanning unevenness will occur on the thermal paper 36.

In this embodiment, a stepped portion 56 is provided in the platen shaft 54 to prevent the friction gear 34 from moving in the axial direction of the platen shaft 54, but as shown in FIG. 5A, a groove is provided in the platen shaft 54. It is also possible to form That is, the groove 74 is formed radially inward and along the outer circumference of the platen shaft 540. Further, a ring-shaped protrusion 76 may be formed at the tip of the boss 60 of the friction gear 34 radially inward and inserted into the groove 74 .

Further, in this embodiment, the platen shaft 54 and the friction gear 34 are engaged by frictional force, but as shown in FIG. 5B, a structure may be adopted in which the driven gear 32 and the friction gear 34 are directly engaged by frictional force. .

That is, a boss 78 is provided at a narrow portion of the driven gear 32 so as to protrude toward the platen roller 46. The friction gear 34 is inserted into the boss 78 of the driven gear 32, and the driven gear 32 is inserted and fixed onto the platen shaft 54. In this case, a configuration may be adopted in which frictional force is generated between the outer peripheral surface of the boss 78 of the driven gear 32 and the inner surface of the boss 60 of the friction gear 34.

Note that since the boss 60 of the friction gear 34 can be insert-molded, the materials of the friction gear 34 body and the boss 60 may be different. Thereby, noise during driving can be suppressed and wear of the boss 60 can be reduced.

For example, the boss 60 may be made of a resin such as the aforementioned polyacetal nylon to which glass fiber, carbon fiber, or other additives are added. Furthermore, the boss 60 may be formed by insert molding of an elastic metal such as stainless steel, phosphorus, bronze, or beryllium copper.

Second example Next, a second embodiment of the present invention will be described.

Note that parts that are basically the same as those in the first embodiment are given the same reference numerals as in the first embodiment, and their explanations are omitted.

FIG. 6 shows a driven gear 32 and a friction gear 34 according to a second embodiment.

The driven gear 32 is magnetized as magnetic engagement means. Further, the friction gear 34 is made of a paramagnetic material, and the stepped portion 5 between the driven gear 32 and the platen shaft 54
6, and movement in the axial direction is prevented.

The friction gear 34 is attracted by the magnetic force of the driven gear 32 and engaged with the driven gear 32.

Therefore, the driven gear 32 and the 7th traction gear 34 are
Although it is possible to rotate integrally by magnetic force, it is configured to rotate relatively against the magnetic force of the drive gear 32 by an external force of a predetermined amount or more.

Further, the intermediate gear 30 of the shaft 22 is made of resin and is not affected by the magnetic force of the driven gear 32.

The other configurations are the same as in the first embodiment.

Also in the second embodiment with the above configuration, the roll paper conveying device 12 can obtain the same effect as the first embodiment by using the driven gear 32 and the friction gear 34 that are engaged with each other by magnetic force.

In this manner, the gear devices according to the first and second embodiments are capable of accurately transmitting changes in the rotational speed and amount of rotation of the driving gear to the driven shaft.

In the first and second embodiments, the rotation direction of the driven gear 32 and the friction gear 34 is in the direction of arrow C, but the frictional force and magnetic force are Friction gear 34
Since the same force is exerted between the drive gear 32 and the driven gear 32, it can also be used in a gear device in which the direction of rotation changes.

Incidentally, the friction gear 34, the driven gear 32, and the drive gear 1 in the first embodiment and the second embodiment of the present invention
The gear specifications of No. 8 can be arbitrarily selected except for the distance between the shafts.

〔Effect of the invention〕

As explained above, the gear device according to claim (1) of the present invention divides the driving gear into the main gear and the auxiliary gear and engages the two gears by frictional force, so that the gear device can be easily manufactured without increasing the number of parts. The backlash of the gear device can be substantially reduced, and the rotation of the driving gear can be transmitted to the driven shaft without uneven rotation, which has an excellent effect.

The gear device according to claim (2) of the present invention is also provided by the frictional engagement means having elasticity provided on the auxiliary gear as claimed in claim (2).
The same effect as 1) can be obtained.

The gear device according to claim (3) of the present invention is the gear device according to claim (1).
) by engaging the main gear and secondary gear with magnetic force,
The same effects as the gear device according to claim (1) can be obtained.

Furthermore, when the gear device according to the present invention is made of resin, it is possible to obtain an effect that noise during driving is lower than that of a metal gear device.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of essential parts of a gear device to which the present invention is applied, FIG. 2 is a sectional view of essential parts according to an embodiment, and FIGS.
Figure B is an enlarged plan view of the main parts showing the meshing of the gears in Figure 2, Figure 3A is an enlarged plan view of the main parts in a state where the secondary gears begin to mesh, and Figure 3B is an enlarged plan view of the main parts showing the state where the secondary gears are meshed. FIG. 4 is a cross-sectional view of the main part taken along the line 4-4 in FIG. 1, and FIGS. 5A to 6 show a drive gear similar to FIG. FIGS. 5A and 5B are sectional views of essential parts showing a modification of the frictional engagement means, and FIG. 6 is a sectional view of essential parts showing a magnetic engagement means. DESCRIPTION OF SYMBOLS 10... Thermal printer, 12... Roll paper conveyance device, 18... Drive gear (driving gear), 32... Driven gear (main gear), 34... Friction gear (auxiliary gear), 36... ...Thermal paper, 54...Platen shaft (driven shaft), 60...
Boss (frictional engagement means).

Claims (3)

[Claims] (1) A gear device that transmits rotational force by meshing a driven gear provided on a driven shaft with a driving gear, and includes a main gear fixed to the driven shaft and meshing with the driving gear, and a main gear fixed to the driven shaft and meshing with the driving gear. A auxiliary gear has a smaller number of teeth than the gear, is coaxially supported by the driven shaft with the main gear, and meshes with the drive gear; A gear device comprising: frictional engagement means that allows relative rotation of the main gear and the auxiliary gear by external force. (2) The gear device according to claim 1, wherein in the frictional engagement means, the frictional force is generated by an elastic force of the frictional engagement means provided on the auxiliary gear. (3) A gear device that transmits rotational force by meshing a driven gear provided on a driven shaft with a driving gear, the main gear being fixed to the driven shaft and meshing with the driving gear; A auxiliary gear that has a smaller number of teeth than a gear, is coaxially supported on a driven shaft with the main gear, and meshes with the drive gear, and the main gear and the auxiliary gear are engaged by magnetic force to generate an external force of a predetermined value or more. 1. A gear device comprising: a magnetic engagement means that enables relative rotation between the main gear and the auxiliary gear.