JPH0410439Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a double gear device for eliminating meshing imbalance between gears in a paper feeding device of a printer or the like.

[Prior art and its problems] Paper feeding devices for printers generally transmit the rotation of the paper feeding motor to the platen via a gear transmission mechanism, and the gear transmission mechanism is configured to transmit the rotation of the paper feeding motor to the platen in multiple stages using a plurality of gears. configured to slow down.

However, in the meshing between gears,
In order to enable smooth engagement and rotation without interference between the tooth tips, a slight bump is created, and this bump causes a problem in that an error occurs in the amount of paper feed.

This is not so much of a problem if the recording paper is always fed in a fixed direction, but when performing high-resolution printing or graphic printing, the paper feeding described above may be necessary if the recording paper is fed by half dots or in forward and reverse directions. The problem of errors becomes apparent and the desired print quality cannot be obtained.

To solve this backlash problem, a dual gear system is used. This double gear device basically has two gears facing each other and a biasing spring provided between the two gears, and the biasing spring biases both gears in opposite directions. For example, Japanese Unexamined Patent Publication No. 125977/1982 and Japanese Utility Model Application No. 115455/1983 are known. However, the conventional double gear system is very difficult to assemble into a gear train.

For example, in the structure of JP-A-52-125977,
The two gears are rotated relative to each other, maintained in that state and meshed with another gear (for example, a pinion), and then a biasing spring is applied to the two gears. This spring loading is done in a narrow space, so it is very difficult to work with. Depending on the gear train arrangement, it may not be possible to apply the biasing spring later. In that case, first apply the biasing spring to the two gears, and then set the biasing spring in the direction in which it will be charged. The two gears are rotated relative to each other, held in a charged state by pinching the two gears with fingertips, and meshed with other gears. If your fingertips leave the double gear during this process, the biasing spring that has been so eagerly charging will release, and you will have to start the process again. In addition, since the spring force of the biasing spring changes depending on the relative relationship (amount of misalignment) between the two gears in the meshing state with other gears, the backlash may occur depending on the relative relationship between the two gears. In some cases, it was not possible to ensure the removal of Furthermore, in order to urge the two gears in opposite directions, there is an engagement piece that protrudes from the back of one gear, and an engagement piece that protrudes from the other gear and opens on one gear. A linear spring is hooked between the engagement piece and the engagement piece that passes through the long window, and this linear spring is bent in a substantially ``H'' shape. According to such a spring force biasing structure, the force stored in the spring acts diagonally outward on the engagement piece, and the relative rotation between both gears is effectively controlled by the spring force. There was a problem in producing it smoothly.

On the other hand, in Japanese Utility Model Application Publication No. 57-115455, in order to facilitate the assembly of double gears, one of the two gears is provided with an elastic projecting piece and its locking part, and the other gear is provided with an elastic projecting piece and its locking part. A stopper is formed which comes into contact with the elastic protruding piece that is locked in the locking portion, so that the relative relationship between the two gears can be kept constant. According to this structure, it is possible to engage the stopper with the elastic protruding piece that is locked in the locking part, and to install it into the wheel train with the biasing spring attached at the front. In order to release the elastic projecting piece from the locking portion after being assembled into the wheel train, the work must be done in a narrow and limited space, and therefore the workability of assembling is not improved much. Moreover, the two gears have a complicated shape, which makes it difficult to mold them. Also,
Both gears each have a long window into which a coil spring is inserted, and the coil spring is installed in a compressed state between projections protruding from the ends of each long window. However, with this structure, it is difficult to make the length of the coil spring sufficiently long, so the spring force fluctuates greatly due to fluctuations in the length of the spring, and as a result, there is the problem that stable operation is difficult to obtain. was.

[Purpose of the invention] Therefore, the present invention allows the coil spring to be used as a biasing spring to be easily engaged with other gears even if it is installed from the beginning, and also allows the length of the coil spring to be sufficiently long, while also increasing the spring force. It is an object of the present invention to provide a double gear device that does not cause the above-mentioned disadvantages by acting on both gears as closely as possible in the circumferential direction.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a first gear 13 integrally formed with the rotating shaft 12 and a cylinder coaxially fitted with the rotating shaft 12. A second gear 15 integrally formed with the body 14 is located opposite to each other and meshes with the same pinion 3, and the cylindrical body 14
There is a pinion 2 that transmits rotational force to the lower gear.
2 are integrally formed, and one of the two gears 13 has a groove that engages with a peripheral edge 17a of a long groove 17 formed in the other gear 15, so that the two gears can be moved relative to each other in the circumferential direction. The following structure is adopted in a double gear device in which an engaging piece 16 that is held in an axial direction so as not to be detachable protrudes from the engaging piece 16.

That is, the first hooking portion 20 protruding from the surface of the second gear 15 on the cylinder body 14 side and the first gear 13
A coil spring 21 is attached to the outer circumferential surface of the cylinder body 14 between the coil spring 21 and the second hook part 18 that protrudes from the surface facing the second gear 15 and passes through the long window 19 formed in the first gear 13. It is stretched out in a roughly ``he'' shape.
Then, due to the spring force of the coil spring 21, the second
When the hook 18 is in contact with one end of the long window 19, the teeth of both gears 13 and 15 are shifted by a certain amount.

[Example] Hereinafter, details of the present invention will be explained along with an example shown in the accompanying drawings.

In FIG. 1, a paper feed motor 2 is attached to the left side of a printer frame 1, and its rotation is transmitted to a shaft 7a of a platen 7 via a motor pinion 3 and double gears 4, 5, and 6. A printhead 8, opposite the platen 7, is secured on a carriage 10 which is slidably received on a guide shaft 9. A recording paper (not shown) is passed between the print head 8 and the platen 7, and dot matrix characters and the like are formed on the recording paper by the print head 8 while the carriage 10 moves back and forth. As the paper feed motor 2 rotates, the platen 7 rotates via the motor pinion 3 and the double gears 4, 5, and 6, so that the recording paper is line-feeded. Note that 11 is a pinch roller that presses the recording paper against the platen 7.

By the way, since the double gears 4, 5, and 6 have substantially the same configuration, the details of the double gear 4 will be explained with reference to FIGS. 2 to 4.

The rotating shaft 12 has a gear 13 integral therewith, and a gear 15 is integrally formed on a cylindrical body 14 coaxially fitted to the rotating shaft 12. Gears 13, 15
are opposed to each other and mesh with the same gear (in the case of the double gear 4, the pinion 3). Approximately L-shaped engaging pieces 16, 16 are protruded from the gear 13 at a height less than or equal to the thickness of the gear 15. The gear 15 has long grooves 17, 17 formed therein, and the inner walls of the long grooves 17, 17 have peripheral edges 17a, 17a projecting in the radial direction. The engaging pieces 16, 16 are engaged with the peripheral edges 17a, 17a within the long grooves 17, 17, respectively, and do not protrude from the upper surface of the gear 15. One end of the peripheral edge 17a is cut off, and the engagement piece 16 can be inserted into the long groove 17 at this position. When the gear 15 is turned counterclockwise in this state, the engagement piece 16 engages with the peripheral edge 17a of the long groove 17, thereby causing the gears 13 and 15 to rotate at a fixed angle relative to each other in the circumferential direction. It is connected freely but cannot be separated in the axial direction.

Also, a hooking portion 18 formed protrudingly on the gear 13
The coil spring 21 loosely passes through a long window 19 bored in the gear 15, and a coil spring 21 is inserted between the hook 18 and the hook 20 protruding from the gear 15. It is stretched along the surface in a roughly ``he'' shape.
This arrangement of the springs allows the coil spring 21 to have a sufficiently long length.
The acting direction of the spring force of No. 1 is close to the tangential direction (circumferential direction) with respect to the hook portions 18 and 19. Therefore, the influence of fluctuations in the spring force is reduced, and relative rotation in opposite directions to the gears 13 and 15 can be smoothly produced. As shown in FIG. 2, the spring force of the coil spring 21 causes the teeth of the gears 13 and 15 to shift by a certain amount while the hook 18 is in contact with one end of the long window 19. It's becoming like that. Note that a pinion 22 is formed on the outer circumferential surface of the cylindrical body 14, with which the next-stage double gear 5 meshes.

The latching part 18 functions not only as a latching member for simply latching the coil spring 21, but also as a stopper, and comes into contact with one end of the long window 19 to regulate the amount of deviation of each tooth of the two gears. This structure simplifies the construction and makes it very easy to incorporate the double gear into the gear train. The amount of deviation between the teeth of the gear 13 and the gear 15 is set within a range that allows the teeth of the pinion 3 to be engaged to enter between the teeth of the gear 13 and the gear 15. Of course. With this configuration, it is possible to incorporate the double gear into the wheel train with the coil spring attached to the front.

When this double gear is pushed in so that it meshes with the pinion 3, the gear 13 rotates slightly counterclockwise relative to the state shown in FIG. 2 against the spring force of the coil spring 21, and then meshes with the pinion 3. It will be done.
As a result, in this meshed state, as shown in FIG.
This results in elastic contact via the spring force of 1.

When feeding the recording paper sequentially, pinion 3 is the fifth
The gear 15 rotates in the direction of the solid line arrow 23 in the figure.
is pushed by the tooth surface 3a of the pinion 3 and the solid line arrow 24
Rotate in the direction. This progressive meshing transmission is substantially the same as the meshing transmission of ordinary gears.

When the recording paper is to be fed backwards, the pinion 3 is turned in the direction of the dashed arrow 25. In the case of normal gear meshing, the pinion 3 idles by the backlash amount, causing the driven side gear (corresponding to gear 15) to be out of phase by that amount, but in the case of double gears, the pinion 3 is rotated by the broken line arrow 2 When the gear 13 rotates in the direction shown in FIG. , rotates following the rotation of the pinion 3 without causing any phase deviation.

Therefore, even when the recording paper is reversely fed by a half dot, the minute rotation of the pinion 3 is accurately transmitted to the gear 15. Accurate transmission by this double gear is possible because double gears 4, 5, and 6 are provided in each gear of all the reduction stages that transmit the rotation of the paper feed motor 2 to the platen 7. It is accurately transmitted to the platen 7 both during forward and reverse feeding, and the quality of required printing, such as graphic printing or high resolution printing by two passes of the print head 8, can be further improved.

[Effects of the invention] According to the double gear device according to the invention described in detail above, when the two gears facing each other are urged in opposite directions by the springs, the gear 15
A hooking portion 20 protrudes from the surface of the cylindrical body 14 side of the gear 13 , and a hook portion 20 protrudes from the surface facing the gear 15 of the gear 13 .
A coil spring 21 is stretched along the outer peripheral surface of the cylindrical body 14 in a substantially "H" shape between the coil spring 21 and the hook part 18 passing through the long window 19 of the cylinder body 14.
When the locking part 18 is in contact with one end of the long window 19 due to the spring force of 1, each tooth of both gears 13 and 15 is shifted by a certain amount, so that the coil spring 21 is attached with the front. It can be installed into the gear train in the same state as it is, and there is no need to make any changes after it is installed into the gear train. Moreover, the length of the coil spring 21 can be made sufficiently long, and the direction in which the spring force of the coil spring 21 acts is close to the tangential direction (circumferential direction) with respect to the hooking parts 18 and 19. Therefore, the influence of fluctuations in the spring force is reduced, and relative rotation in the opposite direction to the gears 13 and 15 can be smoothly generated without increasing the spring force unnecessarily, thereby impairing operation or quality. A stable double gear system can be provided.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional plan view showing a part of a printer to which a double gear device according to the present invention is applied;
FIG. 2 is a front view of the double gear device, FIG. 3 is a sectional view taken along the line of FIG. 2, FIG. 4 is a sectional view taken along the line of FIG. 2, and FIG. 5 is an enlarged view showing the meshing state. 12...Rotating shaft, 13...Gear, 14...Cylinder, 15...Gear, 16...Engaging piece, 17...Long groove, 17a...Periphery of the long groove, 18...Latching part,
19...Long window, 20...Latching part, 21...Coil spring.

Claims (1)

[Claims for Utility Model Registration] A first gear 13 integrally formed on the rotating shaft 12 and a cylindrical body 1 coaxially fitted to the rotating shaft 12.
A second gear 15 formed integrally with the cylindrical body 14 is located opposite to each other and meshes with the same pinion 3, and a pinion 22 that transmits rotational force to the gear on the lower stage side is integrated with the cylindrical body 14. One of the two gears 13 has a shaft that engages with a peripheral edge 17a of a long groove 17 formed in the other gear 15, so that the two gears can be moved relatively circumferentially and axially. An engaging piece 16 is provided that protrudes to hold the second gear 15 irremovably in the direction, and a first hook 20 that protrudes from the surface of the second gear 15 on the cylindrical body 14 side, and gear 1
A coil spring 21 is connected to the cylindrical body between the coil spring 21 and a second hook 18 that protrudes from the surface facing the second gear 15 of No. 3 and passes through a long window 19 formed in the first gear 13. The coil spring 21 is stretched along the outer circumferential surface of the window 14 in an approximately "he" shape, and the second hook part 18 comes into contact with one end of the long window 19 due to the spring force of the coil spring 21. A double gear device characterized in that the teeth of both gears 13 and 15 are shifted by a certain amount when