CN104762713B - The three component similarities and differences walk the method and device of drawing-off regulation and control yarn linear density and blending ratio - Google Patents

Abstract

The invention discloses a method for regulating yarn linear density and blending ratio by three-component synchronous drafting, which specifically includes a drafting and twisting system including a first-stage drafting unit and a second-stage drafting unit arranged before and after; The drafting unit includes the combined rear roller and the middle roller; the secondary drafting unit includes the front roller and the middle roller; on the basis of the reference line speed of the reference line segment, increase or decrease the first rear roller and the second rear roller on the combined rear roller. Roller and/or the rotational speed of the third back roller, realize the online dynamic adjustment of the linear density or/and blending ratio of the i-th yarn Y. The dotted yarn, slub yarn, and belly yarn produced by the method and device of the present invention are more uniform and accurate in color mixing, and the constant setting speed rotation listed in the control ensures that the blending effect is more stable, even if different batches There will be no obvious change in yarn color difference.

Description

Method and device for regulating yarn linear density and blending ratio by three-component synchronous drafting

technical field

The invention relates to the field of spinning in textile engineering, in particular to a method and device for regulating yarn linear density and blending ratio by three-component synchronous two-stage drafting.

Background technique

Yarn is an elongated fiber assembly formed by twisting fibers in parallel orientation. When the fibers are not evenly distributed in the length direction of the yarn, its linear density (or appearance) will increase a dynamic linear density (dynamic thickness) on the basis of the reference linear density (reference thickness), resulting in the yarn line Density (or thickness) changes. According to the size of this uneven distribution, it can be classified into slub yarn, dot yarn, etc., or collectively referred to as fancy yarn with linear density change. If the blending ratio can be changed while the linear density of the yarn is changed, fancy yarns with variable linear density and color can be formed. We define this type of yarn as colorful variable density yarn, which can be divided into It is colorful slub yarn, colorful dot yarn, etc.

At present, the method for producing variable linear density yarn by ring spinning basically uses the middle and rear rollers to feed a roving sliver respectively, and performs intermittent spinning through the uneven feeding of the rear roller to produce variable linear density yarn. For example, the patent "A Discontinuous Spinning Process and Its Yarn" (Authorization No. ZL01126398.9), its principle is that an auxiliary yarn sliver B fed by the rear roller is unevenly drawn by the middle and rear rollers , and then intersect with another main yarn strand A fed from the rear point of the middle roller, and then enter the front drafting area, after being drafted by the front and middle rollers, it is output from the front nip, and enters the twisting area to be twisted together to form a yarn . Since the auxiliary yarn is fed into the main yarn by the gap feeding of the back roller, under the action of the main draft multiple in the front area, the main yarn is evenly drawn to a certain linear density, and the auxiliary yarn is attached to the main yarn. Intermittent uneven linear density distribution is formed on the yarn whiskers. By controlling the amount of fluctuation in the uneven feeding of the auxiliary yarn by the rear roller, different effects such as slubs and dots can be formed on the yarn.

The spinning process of the variable linear density yarn in the prior art has the following limitations:

① When two different raw materials (or different colors) of roving are used as the main and auxiliary yarn strands, the blending ratio (color mixing ratio) of the yarn cannot be adjusted randomly online; the blending ratio (color mixing ratio) cannot be adjusted while adjusting the thickness of the yarn The change.

② During the spinning process, the main and auxiliary yarns cannot be exchanged (the main yarn whiskers are continuously distributed in the yarn, and the auxiliary yarn whiskers are discretely distributed in the yarn), resulting in spinning yarn pattern Monotonous, with few variables.

③ The reproducibility of the pattern is poor. In the existing yarn forming method of changing the linear density of the yarn, the finally formed slub (thick and fine details) shape and the shape of the dots are related to the spindle speed of the spinning machine. The shapes of the bamboo joints (coarse details), the shape and color of the dots formed by different spindle speeds will be different.

Contents of the invention

In order to solve the above problems, the object of the present invention is to provide a method for spinning multicolored slub yarns and multicolored dotted yarns through online dynamic regulation of yarn density and blending ratio controlled by three-component synchronous drafting. This method changes the traditional synchronous drafting of the front and rear areas of three components into three-component separated asynchronous drafting (hereinafter referred to as primary asynchronous drafting) and three-component combined synchronous drafting (hereinafter referred to as secondary synchronous drafting), The mixing ratio of the three components and the dynamic change of the yarn linear density are controlled by one-stage asynchronous drafting, and the equivalent linear density (or reference linear density) of the yarn is controlled by two-stage synchronous drafting. Through the spinning device and process of three-component separation and synchronous two-stage drafting of the present invention, recombination and twisting into yarn, random on-line dynamic control of the change of spinning linear density and blending ratio can be realized, breaking through the original bamboo There are three technical bottlenecks in the process of knuckle yarn and dot yarn spinning: ① only the yarn density can be adjusted but not its blending ratio (or color change); ② the yarn pattern is single; ③ the pattern reproducibility is poor.

In order to achieve the above purpose, a method for regulating yarn linear density and blending ratio by three-component synchronous drafting disclosed by the present invention specifically includes:

1) The drafting and twisting system includes a primary drafting unit and a secondary drafting unit arranged in front and rear;

2) The primary drafting unit includes a combined rear roller and a middle roller; the combined rear roller has three rotational degrees of freedom, and it includes the first rear roller, the second rear roller and the third rear roller arranged side by side on the same rear roller shaft. Rear rollers; the first rear roller, the second rear roller and the third rear roller move at speeds V _h1 , V _h2 and V _h3 respectively; the middle roller rotates at a speed of V _z ; the secondary synchronous drafting unit includes the front Roller and described middle roller; Front roller rotates with surface linear velocity V _q ;

Suppose the linear densities of the first component roving, the second component roving and the third component roving drafted by the first back roller, the second back roller and the third back roller are ρ ₁ , ρ ₂ and ρ ₃ respectively, The linear density of the yarn Y obtained after drafting and twisting by the front roller is ρ _y ,

3) According to the set blending ratio and/or linear density, the yarn Y is divided into n sections, the linear density and blending ratio of each section of yarn Y are the same, but the linear densities or blending ratios of two adjacent sections are different; When drafting the i-th yarn Y, the linear speeds of the first back roller, the second back roller and the third back roller are V _h1i , V _h2i and V _{h3i respectively} , where i∈(1,2,…,n) ;

After the first component roving, the second component roving and the third component roving are drawn and twisted to form the i-th segment yarn Y, the blending ratios k _1i , k _2i and k _3i can be expressed as follows :

The linear density of the i-th segment yarn Y is:

in, is the secondary draft ratio;

4) Assuming that the segment with the smallest linear density among the n segments of yarn Y is defined as the reference line segment, the reference linear density of this segment is ρ ₀ , and the reference lines of the first rear roller, the second rear roller and the third rear roller of this segment The speeds are V _h10 , V _h20 and V _h30 ; the benchmark blending ratios of the first component roving, the second component roving and the third component roving in this section are k ₁₀ , k ₂₀ and k ₃₀ respectively

Keep the linear speed of the middle roller constant,

And V _z =V _h10 +V _h20 +V _h30 (6);

At the same time, let the secondary draft ratio constant;

Among them, the reference line speeds V _h10 , V _h20 and V _h30 of the first back roller, the second back roller and the third back roller are based on the material and benchmark of the first component roving, the second component roving and the third component roving The linear density ρ ₀ and the benchmark blending ratios k ₁₀ , k ₂₀ and k ₃₀ are set in advance;

5) When drafting and blending the yarn Y of the i-th segment, under the premise of knowing the set linear density ρ _yi of the i-th segment and the set blending ratios k _1i , k _2i and k _3i , according to formulas (2)-(6 ) Calculate the linear speeds V _h1i , V _h2i and V _h3i of the first rear roller, the second rear roller and the third rear roller;

6) On the basis of the reference line speeds V _h10 , V _h20 and V _h30 of the reference line segment, increase or decrease the rotational speed of the first rear roller, the second rear roller and/or the third rear roller to realize the line speed of the i-th segment yarn Y. Online dynamic adjustment of density or/and blending ratio.

Further, assuming ρ ₁ =ρ ₂ =ρ ₃ =ρ, the formula (5) is simplified as:

According to formula (2)-(4) and (6)-(7), calculate the linear velocity V _h1i , V _h2i and V _h3i of described first back roller, second back roller and the 3rd back roller; On the basis of speeds V _h10 , V _h20 and V _h30 , increase or decrease the speed of the first back roller, the second back roller and/or the third back roller to achieve the set i-th section yarn Y linear density or/and blending ratio .

Further, at the moment when the yarn Y is converted from the i-1 segment to the i segment, the linear density of the yarn Y is set to increase the dynamic increment Δρ _yi on the basis of the reference linear density, that is, the thickness change Δρ _yi ; The linear speeds of the first rear roller, the second rear roller and the third rear roller respectively increase correspondingly on the basis of the reference linear speed, namely (V _h10 +V _h20 +V _h30 )→(V _h10 +ΔV _h1i + When V _h20 +ΔV _h2i +V _h30 +ΔV _h3i ), the increment of yarn Y linear density is:

Then the linear density _ρyi of the yarn Y can be expressed as follows:

Let ΔV _i = ΔV _h1i + ΔV _h2i + ΔV _h3i , then (8) becomes:

The linear density change of the yarn Y is realized by controlling the sum ΔV _i of the linear speed increments of the first rear roller, the second rear roller and the third rear roller.

Further, let ρ ₁ =ρ ₂ =ρ ₃ =ρ, then at the moment when yarn Y switches from the i-1th segment to the i-th segment, the blending ratio of the yarn Y, that is, formulas (2)-(4) simplify for:

The adjustment of the blending ratio of the yarn Y is realized by controlling the line speed increment of the first back roller, the second back roller and the third back roller;

in,

ΔV _h1i =k _1i *(V _z +ΔV _i )-V _h10

ΔV _h2i =k _2i *(V _z +ΔV _i )-V _h20

ΔV _h3i =k _3i *(V _z +ΔV _i )−V _h30 .

Further, let V _h1i *ρ ₁ +V _h2i *ρ ₂ +V _h3i *ρ ₃ =H, and H is a constant, then ΔV _i is always 0, thereby realizing the adjustment of the blending ratio of the yarn Y while ensuring The linear density does not change.

Further, if one or two of ΔV _h1i , ΔV _h2i and ΔV _h3i are zero, and the others are not zero, then the change of one or two roving components in the yarn Y is realized, while the other roving components do not change , the adjusted blending ratio is:

Among them, k, j∈(1, 2, 3), and k≠j.

Further, if ΔV _h1i , ΔV _h2i and ΔV _h3i are not zero, the three roving components in the yarn Y can be varied.

Further, if one or two of V _h1i , V _h2i and V _h3i are zero, and the others are not zero, then the discontinuity of one or two roving components in the i-th segment yarn Y is realized.

A device for regulating yarn linear density and blending ratio by three-component synchronous drafting includes a control system and an actuator, and the actuator includes a three-component synchronous two-stage drafting mechanism, a twisting mechanism, and a winding forming mechanism. ; The secondary drafting mechanism includes a primary drafting unit and a secondary drafting unit; the primary drafting unit includes a combined rear roller and a middle roller; the combined rear roller has three rotational degrees of freedom, including the same rear The first rear roller, the second rear roller and the third rear roller arranged side by side on the roller shaft; the secondary drafting unit includes the front roller and the middle roller.

Furthermore, the control system mainly includes a PLC programmable controller, a servo driver, a servo motor, and the like.

Further, any one of the first rear roller, the second rear roller and the third rear roller is fixedly arranged on the rear roller shaft, and the other two rear rollers are independently rotatably arranged on the rear roller shaft.

Further, during the drafting process, the speed of the middle roller is fixed and not greater than the sum of the speeds of the first rear roller, the second rear roller and the third rear roller.

The dotted yarn, slub yarn, and color mixing produced by the method and device of the present invention are more uniform and accurate, and through the constant set speed rotation listed in the control, the blending effect is guaranteed to be more stable, even if the yarn color of different batches is different There will be no noticeable change. The following table is a comparison between the technical effect of the present invention and the prior art.

This shows that the technical effect of the present invention is remarkable.

Description of drawings

Fig. 1 is the schematic diagram of the principle of the secondary draft spinning device;

Fig. 2 is the schematic diagram of the structure of the combined back roller;

Fig. 3 is a structural side view of the secondary draft spinning device;

Fig. 4 is the traveling path diagram of yarn in secondary drafting in the embodiment;

Figure 5 is a schematic diagram of the structure of the control system.

Detailed ways

Specific embodiments of the present invention will be described below in conjunction with the accompanying drawings.

As shown in Figure 1-5, a method for regulating yarn linear density and blending ratio by three-component synchronous drafting specifically includes:

1) The drafting and twisting system includes a primary drafting unit and a secondary drafting unit arranged in front and rear;

2) The primary drafting unit includes a combined rear roller 11 and a middle roller 3; the combined rear roller 11 has three rotational degrees of freedom, including the first rear roller 5, the second rear roller 7 and the second rear roller arranged side by side on the same rear roller shaft. The third rear roller 9; the secondary drafting unit includes the front roller 1 and the middle roller 3. 4 is the top roller corresponding to the middle roller 3, and 6, 8, 10 are the three top rollers corresponding to the three rear rollers. 2 is the top roller corresponding to the front roller 1. 13 and 14 are winding forming mechanism and guide roller respectively, and 15 is yarn Y.

The first rear roller, the second rear roller and the third rear roller move at speeds V _h1 , V _h2 and V _h3 respectively; the middle roller rotates at a speed of V _z ; the secondary synchronous drafting unit includes front rollers and all The middle roller; the front roller rotates at the surface speed V _q ;

As shown in Figure 2, there are 3 degrees of freedom combined back rollers with triple nesting, three movable back rollers 5, 7, and 9 are looped on the same mandrel, and are driven by pulleys 16, 22, 17 respectively.

Figure 4 is a diagram of the traveling path of the first to third component rovings. The three-component roving is first separated and asynchronously drafted by the rear combination roller, then synchronously drawn by the middle roller, and finally mixed by the collector to form the yarn Y on the front roller. The one-stage asynchronous drafting can accurately control the mixing ratio of the two components and the dynamic change of the yarn linear density, while the two-stage synchronous drafting controls the equivalent linear density (or reference linear density) of the yarn. The combination of the two makes the blended yarn more uniform and has a lower end-break rate.

As shown in Figure 5, the control system mainly includes PLC programmable controller, servo driver, servo motor and so on. The programmable controller controls the motor through the servo driver to drive the rollers, the program plate, the spindle and so on.

The linear densities of the first component roving, the second component roving and the third component roving drawn by the first rear roller, the second rear roller and the third rear roller are ρ ₁ , ρ ₂ and ρ ₃ respectively, and the front The linear density of the yarn Y obtained after roller drafting and twisting is ρ _y ,

3) According to the set blending ratio and/or linear density, the yarn Y is divided into n sections, the linear density and blending ratio of each section of yarn Y are the same, but the linear densities or blending ratios of two adjacent sections are different; When drafting the i-th yarn Y, the linear speeds of the first back roller, the second back roller and the third back roller are V _h1i , V _h2i and V _{h3i respectively} , where i∈(1,2,…,n) ;

After the first component roving, the second component roving and the third component roving are drawn and twisted to form the i-th section yarn Y, the blending ratio k _1i , k _2i and k _3i can be expressed as follows:

The linear density of the i-th segment yarn Y is:

in, is the secondary draft ratio;

4) Assuming that the segment with the smallest linear density among the n segments of yarn Y is defined as the reference line segment, the reference linear density of this segment is ρ ₀ , and the reference lines of the first rear roller, the second rear roller and the third rear roller of this segment The speeds are V _h10 , V _h20 and V _h30 ; the benchmark blending ratios of the first component roving, the second component roving and the third component roving in this section are k ₁₀ , k ₂₀ and k ₃₀ respectively

Keep the linear speed of the middle roller constant,

And V _z =V _h10 +V _h20 +V _h30 (6);

At the same time, let the secondary draft ratio constant;

Among them, the reference line speeds V _h10 , V _h20 and V _h30 of the first back roller, the second back roller and the third back roller are based on the material and benchmark of the first component roving, the second component roving and the third component roving The linear density ρ ₀ and the benchmark blending ratios k ₁₀ , k ₂₀ and k ₃₀ are set in advance;

5) When drafting and blending the yarn Y of the i-th segment, under the premise of knowing the set linear density ρ _yi of the i-th segment and the set blending ratios k _1i , k _2i and k _3i , according to formulas (2)-(6 ) Calculate the linear speeds V _h1i , V _h2i and V _h3i of the first rear roller, the second rear roller and the third rear roller;

6) On the basis of the reference line speeds V _h10 , V _h20 and V _h30 of the reference line segment, increase or decrease the rotational speed of the first rear roller, the second rear roller and/or the third rear roller to realize the line speed of the i-th segment yarn Y. Online dynamic adjustment of density or/and blending ratio.

7) Suppose ρ ₁ =ρ ₂ =ρ ₃ =ρ, then formula (5) can be simplified as:

According to formula (2)-(4) and (6)-(7), calculate the linear velocity V _h1i , V _h2i and V _h3i of described first back roller, second back roller and the 3rd back roller; On the basis of the speeds V _h10 , V _h20 and V _h30 , increase or decrease the rotational speed of the first back roller and/or the second back roller to achieve the set i-th section yarn Y linear density or/and blending ratio.

8) At the moment when the yarn Y is converted from the i-1 segment to the i segment, the linear density of the yarn Y is set to increase the dynamic increment Δρ _yi on the basis of the reference linear density, that is, the thickness occurs Δρ _yi ; The linear speeds of the first rear roller, the second rear roller and the third rear roller respectively increase correspondingly on the basis of the reference linear speed, namely (V _h10 +V _h20 +V _h30 )→(V _h10 +ΔV _h1i + When V _h20 +ΔV _h2i +V _h30 +ΔV _h3i ), the increment of yarn Y linear density is:

Then the linear density _ρyi of the yarn Y can be expressed as follows:

Let ΔV _i = ΔV _h1i + ΔV _h2i + ΔV _h3i , then (8) becomes:

The linear density change of the yarn Y is realized by controlling the sum ΔV _i of the linear speed increments of the first rear roller, the second rear roller and the third rear roller.

9) Let ρ ₁ = ρ ₂ = ρ ₃ = ρ, then at the moment when the yarn Y switches from the i-1th section to the i-th section, the blending ratio of the yarn Y, that is, formulas (2) and (3) simplify for:

The adjustment of the blending ratio of the yarn Y is realized by controlling the line speed increment of the first back roller, the second back roller and the third back roller;

in,

ΔV _h1i =k _1i *(V _z +ΔV _i )-V _h10

ΔV _h2i =k _2i *(V _z +ΔV _i )-V _h20

ΔV _h3i =k _3i *(V _z +ΔV _i )−V _h30 .

10) Let V _h1i *ρ ₁ +V _h2i *ρ ₂ +V _h3i *ρ ₃ =H, H is a constant, then ΔV _i is always 0, thereby realizing the adjustment of the blending ratio of the yarn Y while ensuring The linear density does not change.

11) If one or two of ΔV _h1i , ΔV _h2i and ΔV _h3i are zero, and the others are not zero, one or two roving components in the yarn Y will be changed, while the other roving components will not change , the adjusted blending ratio is:

Among them, k, j∈(1, 2, 3), and k≠j.

12) If ΔV _h1i , ΔV _h2i and ΔV _h3i are not zero, the three roving components in the yarn Y can be varied.

13) Let one or two of V _h1i , V _h2i and V _h3i be zero, while the others are not zero, so that the discontinuity of one or two roving components in the i-th segment yarn Y is realized.

The above only describes several preferred embodiments of the present application in conjunction with the accompanying drawings, but the present application is not limited thereto, any improvement and/or deformation made by those skilled in the art without departing from the spirit of the present application shall belong to protection scope of this application.

Claims (6)

1. A method for regulating and controlling the linear density and the blending ratio of yarns by three-component asynchronous and synchronous drafting is characterized by comprising the following steps:

1) the drafting and twisting system comprises a primary drafting unit and a secondary drafting unit which are arranged in front and back;

2) the primary drafting unit comprises a combined rear roller and a middle roller; the combined back roller has three rotational degrees of freedom and comprises a first back roller, a second back roller and a third back roller which are arranged on the same back roller shaft side by side; the first back roller, the second back roller and the third back roller are respectively at a speed V_h1、V_h2And V_h3Moving; middle roller with speed V_zIs rotated at the speed of (1); the secondary drafting unit comprises a front roller and a middle roller; front roller with surface linear velocity V_qRotating; any one of the first rear roller, the second rear roller and the third rear roller is fixedly arranged on the rear roller shaft, the other two rear rollers are arranged on the rear roller shaft in a mutually independent rotating manner, and the speed of the middle roller is fixed and is not more than the sum of the speeds of the first rear roller, the second rear roller and the third rear roller in the drafting process;

respectively setting the linear densities of the first component roving, the second component roving and the third component roving drafted by the first rear roller, the second rear roller and the third rear roller as rho₁、ρ₂And ρ₃And the linear density of the yarn Y obtained after the front roller drafting twisting is rho_y，

3) Dividing the yarn Y into n sections according to a set blending ratio and/or linear density, wherein the linear density and the blending ratio of each section of yarn Y are the same, and the linear density or the blending ratio of two adjacent sections is different; when the i-th section of yarn Y is drafted, the linear speeds of the first back roller, the second back roller and the third back roller are respectively V_h1i、V_h2iAnd V_h3iWhere i ∈ (1,2, …, n);

after the i-th section of yarn Y formed by the first component roving, the second component roving and the third component roving through two-stage drafting and twisting, the blending ratio k of the first component roving, the second component roving and the third component roving is_1i、k_2iAnd k_3iCan be expressed as follows:

the linear density of the i-th section of yarn Y is as follows:

wherein,the second-stage draft ratio;

4) let a section of the n sections of yarn Y with the lowest linear density be defined as a reference line section, and the reference line density of the section be rho₀And the reference line speeds of the first back roller, the second back roller and the third back roller of the section are respectively V_h10、V_h20And V_h30(ii) a The reference blending ratio of the first component roving, the second component roving and the third component roving of the section is respectively k₁₀、k₂₀And k₃₀，

The linear velocity of the middle roller is kept constant,

and V is_z＝V_h10+V_h20+V_h30(6)；

At the same time, let the secondary draft ratioConstant;

wherein the reference linear velocity V of the first back roller, the second back roller and the third back roller_h10、V_h20And V_h30According to the material and reference line density rho of the first component roving, the second component roving and the third component roving₀And a reference blend ratio k₁₀、k₂₀And k₃₀Setting in advance;

5) when drafting and blending the i-th section yarn Y, the set linear density rho of the i-th section is known_yiAnd setting the blending ratio k_1i、k_2iAnd k_3iOn the premise of calculating the linear speed V of the first back roller, the second back roller and the third back roller according to the formulas (2) to (6)_h1i、V_h2iAnd V_h3i；

6) Reference line velocity V in reference line segment_h10、V_h20And V_h30On the basis, the rotating speeds of the first back roller, the second back roller and/or the third back roller are increased or decreased, so that the on-line dynamic adjustment of the linear density or/and the blending ratio of the i-section yarn Y is realized;

let ρ be₁＝ρ₂＝ρ₃Where ρ, equation (5) is simplified as:

calculating linear speeds V of the first back roller, the second back roller and the third back roller according to formulas (2) - (4) and (6) - (7)_h1i、V_h2iAnd V_h3i(ii) a At the reference line velocity V_h10、V_h20And V_h30On the basis of the yarn density and/or the blending ratio of the ith section of yarn Y, increasing and decreasing the rotating speed of the first back roller, the second back roller and/or the third back roller;

at the moment when the yarn Y is switched from the section i-1 to the section i, the linear density of the yarn Y is set to be increased by a dynamic increment △ rho on the basis of the reference linear density_yiI.e. thickness generation △ ρ_yi(ii) a For this purpose, the linear velocities of the first back roller, the second back roller and the third back roller are respectively increased correspondingly on the basis of the reference line velocity, namely (V)_h10+V_h20+V_h30)→(V_h10+ΔV_h1i+V_h20+ΔV_h2i+V_h30+ΔV_h3i) And the increment of the linear density of the yarn Y is as follows:

linear density rho of the yarn Y_yiCan be expressed as follows:

let Delta V_i＝ΔV_h1i+ΔV_h2i+ΔV_h3iThen (8) becomes:

by controlling the sum delta V of the linear velocity increments of the first back roller, the second back roller and the third back roller_iA linear density variation of the yarn Y is achieved.

2. A method of regulating the linear density and blend ratio of a yarn as in claim 1 wherein let ρ be₁＝ρ₂＝ρ₃At the instant when yarn Y switches from the i-1 th stage to the i-th stage, the blending ratio of yarn Y, i.e., equations (2) to (4), is reduced to ρ:

adjusting the blending ratio of the yarn Y by controlling the linear velocity increment of the first back roller, the second back roller and the third back roller;

wherein,

ΔV_h1i＝k_1i*(V_z+ΔV_i)-V_h10

ΔV_h2i＝k_2i*(V_z+ΔV_i)-V_h20

ΔV_h3i＝k_3i*(V_z+ΔV_i)-V_h30。

3. the method for regulating and controlling the linear density and blending ratio of yarns according to claim 2, wherein V is made_h1i*ρ₁+V_h2i*ρ₂+V_h3i*ρ₃H is a constant, then Δ V_iThe yarn density is constantly 0, so that the linear density is kept unchanged while the blending ratio of the yarn Y is adjusted.

4. The method for regulating and controlling the linear density and blending ratio of yarns according to claim 2, wherein Δ V is adjusted_h1i、ΔV_h2iAnd Δ V_h3iOne or two of the roving yarn components are zero, the other roving yarn components are not zero, the variation of one or two roving yarn components in the yarn Y is realized, the other roving yarn components are not varied, and the adjusted blending ratio is as follows:

wherein k, j ∈ (1,2,3), and k ≠ j.

5. The method for regulating and controlling the linear density and blending ratio of yarns according to claim 2, wherein Δ V is adjusted_h1i、ΔV_h2iAnd Δ V_h3iAnd if the components are not zero, the variation of the three roving components in the yarn Y is realized.

6. The method for regulating and controlling the linear density and blending ratio of yarns according to claim 2, wherein V is made_h1i、V_h2iAnd V_h3iOne or two of which are zero and the other of which are non-zero, a discontinuity in one or both roving components in the i-th yarn section Y is achieved.