Draft device of spinning machine and draft method in draft device of spinning machine

Abstract

To provide a draft device of a spinning machine and a draft method in the draft device of the spinning machine, capable of reducing yarn unevenness in a fiber bundle by a discontinuous fiber-like carbon fiber.SOLUTION: The draft device 10 includes three or more roller pairs 11. The three or more roller pairs 11 send the fiber bundle 20 composed of discontinuous carbon fibers to the downstream side while stretching the fiber bundle 20. The three or more roller pairs 11 are rotated in accordance with the draft ratio between the roller pair 11 and the adjacent roller pair 11 located downstream of the roller pair 11. A value obtained by multiplying all the draft ratios is defined as a total draft ratio. A draft ratio between the roller pair 11 around which the apron pair 16 is wound and the roller pair 11 adjacent to the roller pair 11 on the downstream side of the roller pair 11 and having a value equal to or more than a draft ratio other than the draft ratio is defined as a main draft ratio. The proportion of the main draft ratio in the total draft ratio is 75% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a drafting device for a spinning machine and a drafting method for the drafting device for a spinning machine. [Background technology]

[0002] The draft device of the spinning machine includes a plurality of roller pairs. The draft device stretches the fiber bundle using the plurality of roller pairs. The draft device has a plurality of draft ratios. The draft device stretches the fiber bundle according to the draft ratio between each roller pair and an adjacent roller pair downstream of the roller pair.

[0003] For example, Patent Document 1 discloses a spinning method in which a spun yarn is obtained from a carbon fiber mat through carding, drawing, and spinning processes. In the spinning process, a sliver is stretched 12.0 times using a spinning frame. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-179809 Summary of the Invention [Problem to be solved by the invention]

[0005] When drafting a sliver, it is known to perform apron drafting, in which the sliver is drafted while being held by a pair of aprons. Patent Document 1 also discloses, as an example of a spinning machine, in Fig. 3, that an apron is wrapped around a middle roller. Since apron drafting can suppress yarn unevenness compared to drafting without an apron, it is common for the majority of drafting by all roller pairs to be performed by apron drafting, and the draft ratio in apron drafting is generally referred to as the main draft ratio.

[0006] However, when a fiber bundle made of discontinuous carbon fiber is stretched using a drafting device, carbon fiber is less likely to stretch than, for example, cotton, and therefore increasing the main draft ratio may actually increase yarn unevenness in the fiber bundle. [Means for solving the problem]

[0007] The draft device of a spinning machine for solving the above-mentioned problems comprises three or more pairs of rollers that stretch and send a fiber bundle made of discontinuous carbon fiber downstream, the three or more pairs of rollers rotating according to the draft ratio between the pair of rollers and an adjacent pair of rollers downstream of the pair of rollers, and an apron pair wrapped around at least one of the pairs of rollers, and when the total draft ratio is the product of all the multiple draft ratios, and the main draft ratio is the draft ratio between the pair of rollers around which the apron pair is wrapped and the adjacent pair of rollers downstream of the pair of rollers that is equal to or greater than any other draft ratio, the proportion of the main draft ratio in the total draft ratio is 75% or less.

[0008] According to this, by lowering the proportion of the main draft ratio in the total draft ratio compared to the conventional method, it is possible to reduce yarn unevenness in the fiber bundle. In other words, the draft device can reduce yarn unevenness in the fiber bundle made of discontinuous carbon fiber.

[0009] In the draft device of the spinning machine, all of the draft ratios are preferably uniform. According to this, the draft device can minimize the proportion of the main draft ratio in the total draft ratio by making all draft ratios uniform. Since the larger the main draft ratio, the greater the tendency for yarn unevenness in a fiber bundle made of carbon fiber, the draft device configured as above can achieve the smallest yarn unevenness for the total draft ratio. As described above, the draft device can minimize yarn unevenness in a fiber bundle made of discontinuous carbon fiber.

[0010] To solve the above-mentioned problems, a drafting method in a drafting device of a spinning machine includes three or more roller pairs that stretch and send a fiber bundle made of discontinuous carbon fiber downstream, and an apron pair wrapped around at least one of the three or more roller pairs, and includes stretching the fiber bundle for each roller pair in accordance with a draft ratio between the roller pair and an adjacent roller pair downstream of the roller pair, and when a value obtained by multiplying all of the draft ratios is defined as a total draft ratio, and a main draft ratio is defined as a draft ratio between the roller pair around which the apron pair is wrapped and an adjacent roller pair downstream of the roller pair that is equal to or greater than a draft ratio other than the main draft ratio, the proportion of the main draft ratio in the total draft ratio is 75% or less.

[0011] In the drafting method for the drafting device of the spinning machine, it is preferable that all of the draft ratios are uniform. [Effects of the Invention]

[0012] According to the present invention, yarn irregularities can be reduced in a fiber bundle made of discontinuous carbon fibers. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing a draft device. [Figure 2] FIG. 2 is a table showing comparative examples and examples when the total draft ratio is 4.70, and comparative examples and examples when the total draft ratio is 12.00. [Figure 3] FIG. 3 is a schematic diagram showing a modified draft device. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, a specific embodiment of a drafting device for a spinning machine and a drafting method for the drafting device for a spinning machine will be described with reference to FIGS. <Overall view of the draft device> As shown in Fig. 1, the draft device 10 of the spinning machine includes four roller pairs 11. That is, the draft device 10 includes three or more roller pairs 11. The four roller pairs 11 stretch the fiber bundle 20 and send it downstream. In the following description, "downstream" means downstream in the direction in which the fiber bundle 20 is sent out by the four roller pairs 11, and "upstream" means upstream in the direction in which the fiber bundle 20 is sent out by the four roller pairs 11.

[0015] The fiber bundle 20 is made of discontinuous carbon fibers. More specifically, the fiber bundle 20 is made of a collection of multiple discontinuous carbon fibers that are shorter than the length of the fiber bundle 20. The cross section of the fiber bundle 20 that is perpendicular to the main yarn axis contains multiple carbon fibers.

[0016] In the fiber bundle 20, yarn unevenness due to the distribution of carbon fibers occurs as a result of drafting by the draft device 10. The yarn unevenness of the fiber bundle 20 is evaluated by the magnitude of variation in yarn diameter along the main yarn axis. For example, the yarn unevenness of the fiber bundle 20 is evaluated by the CV value of the yarn diameter. Here, the CV value is calculated by dividing the standard deviation of the yarn diameter in the fiber bundle 20 by the average value of the yarn diameter in the fiber bundle 20. The standard deviation and average value of the yarn diameter are calculated, for example, from multiple yarn diameters obtained by measuring at regular intervals in the direction in which the main yarn axis extends. The smaller the yarn unevenness of the fiber bundle 20, the smaller the CV value. The greater the yarn unevenness of the fiber bundle 20, the greater the CV value.

[0017] <Laura vs.> The four roller pairs 11 include, in order from the upstream side, a back roller pair 12, a first downstream roller pair 13, a second downstream roller pair 14, and a front roller pair 15. In other words, the back roller pair 12 is the roller pair 11 located most upstream. Also, the front roller pair 15 is the roller pair 11 located most downstream. The draft device 10 of this embodiment has a four-wire configuration including a back bottom roller 12a, a first downstream bottom roller 13a, a second downstream bottom roller 14a, and a front bottom roller 15a.

[0018] The back roller pair 12 includes a back bottom roller 12a and a back top roller 12b. The back top roller 12b is pressed against the back bottom roller 12a.

[0019] The first downstream roller pair 13 is located downstream of the back roller pair 12. The first downstream roller pair 13 has a first downstream bottom roller 13a and a first downstream top roller 13b. The first downstream bottom roller 13a is adjacent to the back bottom roller 12a on the downstream side of the back bottom roller 12a. The first downstream top roller 13b is adjacent to the back top roller 12b on the downstream side of the back top roller 12b. The first downstream top roller 13b is pressed against the first downstream bottom roller 13a.

[0020] The second downstream roller pair 14 is located downstream of the first downstream roller pair 13. The second downstream roller pair 14 has a second downstream bottom roller 14a and a second downstream top roller 14b. The second downstream bottom roller 14a is adjacent to the first downstream bottom roller 13a on the downstream side of the first downstream bottom roller 13a. The second downstream top roller 14b is adjacent to the first downstream top roller 13b on the downstream side of the first downstream top roller 13b. The second downstream top roller 14b is pressed against the second downstream bottom roller 14a.

[0021] The front roller pair 15 is located downstream of the second downstream roller pair 14. The front roller pair 15 has a front bottom roller 15a and a front top roller 15b. The front bottom roller 15a is adjacent to the second downstream bottom roller 14a on the downstream side of the second downstream bottom roller 14a. The front top roller 15b is adjacent to the second downstream top roller 14b on the downstream side of the second downstream top roller 14b. The front top roller 15b is pressed against the front bottom roller 15a.

[0022] The draft device 10 includes a back roller drive motor 31, a first downstream roller drive motor 32, a second downstream roller drive motor 33, and a front roller drive motor 34. The back roller drive motor 31 drives to rotate the back bottom roller 12a. The first downstream roller drive motor 32 drives to rotate the first downstream bottom roller 13a. The second downstream roller drive motor 33 drives to rotate the second downstream bottom roller 14a. The front roller drive motor 34 drives to rotate the front bottom roller 15a.

[0023] When the back bottom roller 12a is rotated by the back roller drive motor 31, the back top roller 12b rotates in synchronization with the rotation of the back bottom roller 12a. The back top roller 12b rotates by being pressed against the back bottom roller 12a. When the first downstream bottom roller 13a is rotated by the first downstream roller drive motor 32, the first downstream top roller 13b rotates in synchronization with the rotation of the first downstream bottom roller 13a. The first downstream top roller 13b rotates by being pressed against the first downstream bottom roller 13a. When the second downstream roller drive motor 33 is driven to rotate the second downstream bottom roller 14a, the second downstream top roller 14b rotates in synchronization with the rotation of the second downstream bottom roller 14a. The second downstream top roller 14b rotates by being pressed against the second downstream bottom roller 14a. When the front bottom roller 15a is rotated by the front roller drive motor 34, the front top roller 15b rotates in synchronization with the rotation of the front bottom roller 15a. The front top roller 15b rotates by being pressed against the front bottom roller 15a.

[0024] The draft device 10 includes a pair of aprons 16. The pair of aprons 16 includes a bottom apron 16a and a top apron 16b. The bottom apron 16a is wrapped around a tension bar 17 and the first downstream bottom roller 13a. The top apron 16b is wrapped around an apron cradle 18 and the first downstream top roller 13b. The top apron 16b is pressed against the bottom apron 16a. The bottom apron 16a rotates in conjunction with the rotation of the first downstream bottom roller 13a. The top apron 16b rotates in synchronization with the rotation of the bottom apron 16a. By wrapping the pair of aprons 16 around the first pair of downstream rollers 13, the distance between the first pair of downstream rollers 13 and the second pair of downstream rollers 14 is shortened. More specifically, the distance by which the first downstream roller pair 13 pinches the fiber bundle 20 increases downstream due to the apron pair 16 .

[0025] <Control device> The drafting device 10 is equipped with a control device 30. The control device 30 is equipped with a central processing control device (not shown). The central processing control device is composed of a CPU. The control device 30 also has a memory (not shown) composed of a read-only memory in which various programs, maps, etc. are pre-stored, and a random access memory (not shown) for temporarily storing the results of CPU calculations, etc. The read-only memory is composed of a ROM. The control device 30 also has a timer counter, an input interface, an output interface, etc. (not shown).

[0026] The control device 30 is electrically connected to each of the back roller drive motor 31, the first downstream roller drive motor 32, the second downstream roller drive motor 33, and the front roller drive motor 34. The control device 30 controls the driving of each of the back roller drive motor 31, the first downstream roller drive motor 32, the second downstream roller drive motor 33, and the front roller drive motor 34.

[0027] The control device 30 controls the rotation of the back bottom roller 12a by controlling the drive of the back roller drive motor 31. That is, the control device 30 controls the rotation of the back roller pair 12.

[0028] The control device 30 controls the drive of the first downstream roller drive motor 32, thereby controlling the rotation of the first downstream bottom roller 13a. In other words, the control device 30 controls the rotation of the first downstream roller pair 13. The control device 30 rotates the first downstream roller pair 13 faster than the back roller pair 12.

[0029] The control device 30 controls the drive of the second downstream roller drive motor 33, thereby controlling the rotation of the second downstream bottom roller 14a. That is, the control device 30 controls the rotation of the second downstream roller pair 14. The control device 30 rotates the second downstream roller pair 14 faster than the first downstream roller pair 13.

[0030] The control device 30 controls the drive of the front roller drive motor 34, thereby controlling the rotation of the front bottom roller 15a. That is, the control device 30 controls the rotation of the front roller pair 15. The control device 30 rotates the front roller pair 15 faster than the second downstream roller pair 14.

[0031] <Draft ratio> A first draft ratio, a second draft ratio, and a third draft ratio are set as the draft ratios in the control device 30. That is, in this embodiment, there are three draft ratios set in the draft device 10.

[0032] The first draft ratio is the ratio of the tangential velocity of the back bottom roller 12a to the tangential velocity of the first downstream bottom roller 13a. In other words, the tangential velocity of the first downstream bottom roller 13a is equal to the product of the first draft ratio and the tangential velocity of the back bottom roller 12a. The tangential velocity is the product of the rotational speed and the radius of the roller.

[0033] The second draft ratio is the ratio of the tangential velocity of the first downstream bottom roller 13a to the tangential velocity of the second downstream bottom roller 14a. In other words, the tangential velocity of the second downstream bottom roller 14a is equal to the product of the second draft ratio and the tangential velocity of the first downstream bottom roller 13a.

[0034] The third draft ratio is the ratio of the tangential velocity of the second downstream bottom roller 14a to the tangential velocity of the front bottom roller 15a. In other words, the tangential velocity of the front bottom roller 15a is equal to the product of the third draft ratio and the tangential velocity of the second downstream bottom roller 14a.

[0035] Of the four roller pairs 11, the more downstream the roller pair 11 rotates, the faster it rotates. That is, each of the first draft ratio, the second draft ratio, and the third draft ratio is 1 or greater. After being introduced into the draft device 10, the fiber bundle 20 delivered from the draft device 10 is stretched by the ratio between the tangential velocity of the back bottom roller 12a and the tangential velocity of the front bottom roller 15a. This ratio is referred to as the total draft ratio. In other words, the total draft ratio is the ratio between the tangential velocity of the back bottom roller 12a and the tangential velocity of the front bottom roller 15a. The total draft ratio is also the product of the first draft ratio, the second draft ratio, and the third draft ratio. In other words, the total draft ratio is a value obtained by multiplying all of the multiple draft ratios. The total draft ratio can also be said to be the ratio of the length of the fiber bundle 20 delivered by the back roller pair 12 per unit time to the length of the fiber bundle 20 delivered by the front roller pair 15 per unit time. In other words, the fiber bundle 20 is stretched by the draft device 10 by the total draft ratio.

[0036] The second draft ratio is set to be equal to or greater than the first draft ratio and the third draft ratio. Hereinafter, the second draft ratio will also be referred to as the main draft ratio. In other words, the main draft ratio is the draft ratio between the roller pair 11 around which the apron pair 16 is wrapped and the adjacent roller pair 11 downstream of the roller pair 11, and is equal to or greater than the draft ratios other than the main draft ratio. The total draft ratio is set to be equal to or less than 75% of the main draft ratio. In other words, the proportion of the main draft ratio in the total draft ratio is equal to or less than 75%.

[0037] The control device 30 controls the tangential speed of each roller pair 11 so that the first draft ratio, the second draft ratio, and the third draft ratio each become a preset value. The first draft ratio, second draft ratio, third draft ratio, and total draft ratio are each rounded off to two decimal places. The number of decimal places that are valid is determined depending on the precision with which the roller pairs 11 can be controlled in the draft device 10. In this embodiment, the number of decimal places is determined depending on the precision with which the back roller drive motor 31, the first downstream roller drive motor 32, the second downstream roller drive motor 33, and the front roller drive motor 34 can be controlled.

[0038] As mentioned above, the values ​​of the first to third draft ratios and the total draft are referenced to two decimal places. Therefore, even if the first to third draft ratios and the total draft differ in the third decimal place and beyond, they will be treated as uniform if the values ​​obtained by rounding to the third decimal place are the same.

[0039] The percentage of the main draft ratio to the total draft ratio is rounded to the first decimal place. <Draft device operation> The operation of the draft device 10 will now be described.

[0040] The draft device 10 rotates each of the back bottom roller 12a, the first downstream bottom roller 13a, the second downstream bottom roller 14a, and the front bottom roller 15a. As a result, the draft device 10 rotates each of the back roller pair 12, the first downstream roller pair 13, the second downstream roller pair 14, and the front roller pair 15. In other words, the draft device 10 rotates three or more roller pairs 11.

[0041] The control device 30 controls the tangential speed of each roller pair 11, thereby controlling the speed at which the fiber bundle 20 is sent from upstream to downstream at each roller pair 11. The back roller pair 12 and the first downstream roller pair 13 each rotate at a tangential speed determined according to the first draft ratio. The first downstream roller pair 13 and the second downstream roller pair 14 each rotate at a tangential speed determined according to the second draft ratio. The second downstream roller pair 14 and the front roller pair 15 each rotate at a tangential speed determined according to the third draft ratio. The front roller pair 15 and the back roller pair 12 each rotate at a tangential speed determined according to the total draft ratio.

[0042] As described above, the three or more roller pairs 11 rotate according to the draft ratio between each roller pair 11 and the adjacent roller pair 11 downstream of the roller pair 11. The fiber bundle 20 is sent from upstream to downstream by three or more rotating roller pairs 11. More specifically, the fiber bundle 20 is sent from upstream to downstream while being sandwiched between a back bottom roller 12a and a back top roller 12b in the back roller pair 12. The fiber bundle 20 is sent from upstream to downstream while being sandwiched between a first downstream bottom roller 13a and a first downstream top roller 13b in the first downstream roller pair 13.

[0043] At this time, the fiber bundle 20 is sent from upstream to downstream while being sandwiched between the top apron 16b and the bottom apron 16a. That is, the distance over which the first downstream roller pair 13 sandwiches the fiber bundle 20 is increased by the length of the apron pair 16. The apron pair 16 is used, for example, to prevent the fiber bundle 20 from being cut and to reduce floating fibers between the first downstream roller pair 13 and the second downstream roller pair 14.

[0044] The fiber bundle 20 is fed from upstream to downstream while being sandwiched between the second downstream bottom roller 14a and the second downstream top roller 14b in the second downstream roller pair 14. The fiber bundle 20 is fed from upstream to downstream while being sandwiched between the front bottom roller 15a and the front top roller 15b in the front roller pair 15.

[0045] <Drafting method of the draft device> The drafting method of the drafting device 10 will be described together with the operation of this embodiment. In the drafting method of the drafting device 10, a first drafting step, a second drafting step, and a third drafting step are performed.

[0046] The draft device 10 first stretches the fiber bundle 20 in a first draft step. In the first draft step, the draft device 10 stretches the fiber bundle 20 with the back roller pair 12 and the first downstream roller pair 13. Specifically, the draft device 10 sends the fiber bundle 20 downstream with the back roller pair 12, and then sends it further downstream with the first downstream roller pair 13, which has a tangential velocity higher by the first draft ratio. As a result, in the first draft step, the fiber bundle 20 is stretched by the first draft ratio.

[0047] After the first draft step, the draft device 10 stretches the fiber bundle 20 in a second draft step. In the second draft step, the draft device 10 stretches the fiber bundle 20 with a first downstream roller pair 13 and a second downstream roller pair 14. Specifically, the draft device 10 sends the fiber bundle 20 downstream with the first downstream roller pair 13, and then sends it further downstream with the second downstream roller pair 14, which has a tangential velocity higher by the second draft ratio. As a result, in the second draft step, the fiber bundle 20 is stretched by the second draft ratio.

[0048] After the second draft step, the draft device 10 stretches the fiber bundle 20 in a third draft step. In the third draft step, the draft device 10 stretches the fiber bundle 20 with the second downstream roller pair 14 and the front roller pair 15. Specifically, the draft device 10 sends the fiber bundle 20 downstream with the second downstream roller pair 14, and also sends it further downstream with the front roller pair 15, which has a tangential velocity that is higher by the third draft ratio. As a result, in the third draft step, the fiber bundle 20 is stretched by the third draft ratio.

[0049] Thus, the drafting method of the drafting device 10 includes stretching the fiber bundle 20 for each roller pair 11 according to the draft ratio between the roller pair 11 and the adjacent roller pair 11 downstream of the roller pair 11.

[0050] <Relationship between the first draft ratio, second draft ratio, and third draft ratio and the CV value> Fig. 2 shows examples of combinations of the first draft ratio, the second draft ratio, the third draft ratio, and the total draft ratio set in the draft device 10. Fig. 2 also shows the CV values ​​of the fiber bundle 20 drawn by the draft device 10 set with each combination.

[0051] 2 shows examples of combinations of first to third draft ratios set in the draft device 10 when the total draft ratio is 4.70, as Comparative Example 1, Example 1-1, Example 1-2, and Example 1-3. Comparative Example 1, Example 1-1, Example 1-2, and Example 1-3 have the same total draft ratio, but different combinations of the first draft ratio, second draft ratio, and third draft ratio. Different main draft ratios are set in Comparative Example 1, Example 1-1, Example 1-2, and Example 1-3. The main draft ratios decrease in the order of Comparative Example 1, Example 1-1, Example 1-2, and Example 1-3.

[0052] In each of Comparative Example 1, Example 1-1, Example 1-2, and Example 1-3, the ratio of the main draft ratio to the total draft ratio is shown as main draft ratio / total draft ratio. In each of Examples 1-1, 1-2, and 1-3, the ratio of the main draft ratio to the total draft ratio is 75% or less. In Comparative Example 1, the ratio of the main draft ratio to the total draft ratio is greater than 75%.

[0053] In Examples 1-3, the first draft ratio, the second draft ratio, and the third draft ratio are equal. That is, the control device 30 in Examples 1-3 rotates each of the first downstream roller pair 13 and the second downstream roller pair 14 so that the first draft ratio, the second draft ratio, and the third draft ratio are equal. In other words, in the draft device 10 in Examples 1-3, all draft ratios are equal.

[0054] Furthermore, in the drafting method of the draft device 10 in Examples 1-3, the fiber bundle 20 is uniformly stretched by the first drafting step, the second drafting step, and the third drafting step. That is, in the drafting method of the draft device 10 in Examples 1-3, all the draft ratios are uniform. When all the draft ratios are uniform, each of the first draft ratio, the second draft ratio, and the third draft ratio is the cube root of the total draft ratio.

[0055] 2 shows examples of combinations of first to third draft ratios set in the draft device 10 when the total draft ratio is 12.00, as Comparative Example 2, Example 2-1, Example 2-2, and Example 2-3. Comparative Example 2, Example 2-1, Example 2-2, and Example 2-3 share the same total draft ratio, but have different combinations of the first, second, and third draft ratios. Different main draft ratios are set in Comparative Example 2, Example 2-1, Example 2-2, and Example 2-3. The main draft ratios decrease in the order of Comparative Example 2, Example 2-1, Example 2-2, and Example 2-3.

[0056] In each of Comparative Example 2, Example 2-1, Example 2-2, and Example 2-3, the ratio of the main draft ratio to the total draft ratio is shown as main draft ratio / total draft ratio. In each of Examples 2-1, 2-2, and 2-3, the ratio of the main draft ratio to the total draft ratio is 75% or less. In Comparative Example 2, the ratio of the main draft ratio to the total draft ratio is greater than 75%.

[0057] In Example 2-3, the first draft ratio, the second draft ratio, and the third draft ratio are equal. That is, the control device 30 in Example 2-3 rotates each of the first downstream roller pair 13 and the second downstream roller pair 14 so that the first draft ratio, the second draft ratio, and the third draft ratio are equal. In other words, in the draft device 10 in Example 2-3, all draft ratios are equal. In this case, similar to Examples 1-3, it can also be said that in the draft method of the draft device 10 in Example 2-3, all draft ratios are equal. Also, similar to Examples 1-3, in Example 2-3, each of the first draft ratio, the second draft ratio, and the third draft ratio is the cube root of the total draft ratio.

[0058] When the total draft ratio is 4.70, each of Examples 1-1, 1-2, and 1-3 shows a smaller CV value than Comparative Example 1. Furthermore, when the total draft ratio is 12.00, each of Examples 2-1, 2-2, and 2-3 shows a smaller CV value than Comparative Example 2. These results show that by setting the proportion of the main draft ratio in the total draft ratio to 75% or less, the CV value can be made smaller than when the proportion is greater than 75%.

[0059] Furthermore, when the total draft ratio is 4.70, the smaller the proportion of the main draft ratio in the total draft ratio, the smaller the CV value, and the smallest CV value was obtained in Example 1-3, where this proportion was the smallest. Similarly, when the total draft ratio is 12.00, the smallest CV value was obtained in Example 2-3, where this proportion was the smallest. The situation where the proportion of the main draft ratio in the total draft ratio is the smallest corresponds to a situation where the first to third draft ratios are uniform. From the above, it was shown that the CV value becomes smaller as the first to third draft ratios become more uniform.

[0060] A comparison is made between a total draft ratio of 4.70 and a total draft ratio of 12.00. For example, even when the proportion of the main draft ratio in the total draft ratio is approximately the same, as in Example 1-1 and Example 2-1, the CV value is smaller when the total draft ratio is smaller. This result shows that the smaller the total draft ratio, the smaller the CV value.

[0061] [Effects of this embodiment] The effects of this embodiment will be described. (1) By setting the ratio of the main draft ratio to the total draft ratio to 75% or less, the draft device 10 can reduce yarn unevenness in the fiber bundle 20 compared to when the ratio is greater than 75%.

[0062] (2) The draft device 10 can reduce the CV value of the drafted fiber bundle 20 by reducing the proportion of the main draft ratio in the total draft ratio. Here, the draft device 10 can minimize the proportion of the main draft ratio in the total draft ratio when the first to third draft ratios are all uniform, regardless of the total draft ratio. Therefore, by uniforming the first to third draft ratios, the draft device 10 can reduce yarn unevenness in the fiber bundle 20 compared to when the first to third draft ratios are different from one another.

[0063] (3) As a method for increasing the total draft ratio, for example, one method is to increase one of the first, second, and third draft ratios while keeping two of them fixed. Compared to this method, when the first, second, and third draft ratios are uniform as in Examples 1-3 and 2-3, even if the total draft ratio is increased, the increase in the value of each draft ratio can be reduced. In other words, the draft device 10 can set the total draft ratio to be large while suppressing the increase in each draft ratio.

[0064] (4) The control device 30 is configured to be able to individually control the rotation of the three roller pairs 11. As a result, the draft device 10 can more accurately equalize the three draft ratios than, for example, when the three roller pairs 11 are synchronized by gears and the control device 30 controls the gears.

[0065] [Example of change] The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0066] In the draft device 10, the apron pair 16 may be wrapped around each of two or more roller pairs 11. In short, it is sufficient that the apron pair 16 is wrapped around at least one of the roller pairs 11.

[0067] The draft device 10 is not limited to a four-wire type. For example, the draft device 10 may be a three-wire type having three roller pairs 11. Alternatively, the draft device 10 may be a five-wire type having five roller pairs 11.

[0068] The draft device 10 does not necessarily have to control each roller pair 11 with the control device 30. For example, as shown in FIG. 3, the control device 30 of the draft device 10 may control the roller pairs 11 via a drive source M1, one drive shaft M2, and a gear mechanism G. More specifically, the draft device 10 rotates the drive shaft M2 by driving the drive source M1 with the control device 30. The drive shaft M2 rotates one of multiple gears (not shown) included in the gear mechanism G. The rotation of this gear induces the rotation of the other gears included in the gear mechanism G. Each roller pair 11 is connected to a gear included in the gear mechanism G and rotates due to the rotation of the gear.

[0069] In this case, each roller pair 11 is rotated by the control device 30 via the drive shaft M2 and the gear mechanism G. When the driving method of each roller pair 11 in the draft device 10 is changed from that of the embodiment, the precision in controlling each roller pair 11 also changes. In other words, the decimal places referenced for determining whether the draft ratio values ​​are uniform are also changed appropriately depending on the control method of each roller pair 11.

[0070] The drafting steps performed by the drafting method in the drafting device 10 are not limited to the first drafting step, the second drafting step, and the third drafting step. For example, if the drafting device 10 is a three-line type, the drafting step may consist of two drafting steps. Also, if the drafting device 10 is a five-line type, the drafting step may consist of four drafting steps.

[0071] When all draft ratios are uniform, the control device 30 may set the total draft ratio but may not set the first, second, and third draft ratios. In this case, the control device 30 may calculate the cube root of the set total draft ratio and use the calculated value as the first, second, and third draft ratios. This eliminates the need to calculate each draft ratio from the total draft ratio and set each draft ratio in the control device 30 when a desired total draft ratio is determined in advance.

[0072] [Note] The technical ideas that can be understood from the above-described embodiment and modifications will be described below. (i) A drafting device for a spinning machine including a control device configured to be able to control the rotation of each of the roller pairs.

[0073] (b) A draft device for a spinning machine in which, when all draft ratios are uniform, a total draft ratio is set, the draft ratio for each pair of rollers is calculated from the total draft ratio, and the draft device is equipped with a control device that controls the rotation of the pair of rollers in accordance with the draft ratio.

[0074] (c) A drafting method for a drafting device of a spinning machine, comprising: setting a total draft ratio when all draft ratios are uniform; and calculating the draft ratios from the total draft ratios. [Explanation of symbols]

[0075] 10...draft device, 11...roller pair, 16...apron pair, 20...fiber bundle.

Claims

1. three or more roller pairs that stretch and send a fiber bundle made of discontinuous carbon fiber downstream, a draft device for a spinning machine, wherein the three or more roller pairs rotate in accordance with a draft ratio between the roller pair and an adjacent roller pair downstream of the roller pair, and an apron pair is wrapped around at least one of the roller pairs, a total draft ratio being a value obtained by multiplying all of the plurality of draft ratios; and a main draft ratio being a draft ratio between the pair of rollers around which the pair of aprons are wrapped and the adjacent pair of rollers downstream of the pair of rollers, the main draft ratio being equal to or greater than any other draft ratio; wherein the proportion of the main draft ratio to the total draft ratio is 75% or less.

2. 2. The drafting device for a spinning machine according to claim 1, wherein all of said draft ratios are uniform.

3. three or more roller pairs that stretch and send a fiber bundle made of discontinuous carbon fiber downstream, A drafting method for a drafting device of a spinning machine, in which an apron pair is wrapped around at least one of the three or more roller pairs, comprising: stretching the fiber bundle for each roller pair in accordance with a draft ratio between the roller pair and an adjacent roller pair downstream of the roller pair, a total draft ratio being a value obtained by multiplying all of the plurality of draft ratios; a main draft ratio being a draft ratio between the pair of rollers around which the pair of aprons are wrapped and the adjacent pair of rollers downstream of the pair of rollers, the main draft ratio having a value equal to or greater than any other draft ratio; and a draft method for a draft device of a spinning machine, characterized in that the proportion of the main draft ratio in the total draft ratio is 75% or less.

4. 4. A drafting method for a drafting device of a spinning machine according to claim 3, wherein all of said draft ratios are uniform.

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