CN110453345B - Weft insertion control method for air jet loom - Google Patents

Abstract

The invention provides a weft insertion control method for an air jet loom, which can sufficiently suppress weft insertion errors caused by yarn breakage. A weft insertion control method for an air jet loom for injecting air from a weft insertion nozzle to insert a weft yarn, comprising the steps of: detecting the state of the weft yarn before weft insertion (S1); predicting a weft arrival time at which the weft arrives at a predetermined position when the weft is inserted under a predetermined weft insertion condition based on the detected state of the weft (S2); an advance limit value is set in advance for irregularity in the weft arrival time, and when the predicted weft arrival time is earlier than the advance limit value, weft insertion conditions are changed so that the actual weft arrival time is later than the advance limit value (S3, S4); and injecting air from the weft insertion nozzle according to the changed weft insertion condition to insert the weft (S5).

Description

Weft insertion control method for air jet loom

Technical Field

The invention relates to a weft insertion control method of an air jet loom.

Background

With regard to an air jet loom that inserts a weft yarn by compressed air, patent document 1, for example, describes a technique of preventing a weft insertion error due to a yarn break by using a smaller jet pressure when inserting a weft yarn that is finer than usual. In addition, this document describes that when the weft yarn is thinner than usual, the injection time of the main nozzle or/and the auxiliary nozzle is shortened.

Patent document 1: japanese examined patent publication No. 61-25817

In the technique described in patent document 1, the jet pressure and the like are changed with attention paid to only the thickness of the weft yarn used for weft insertion. However, the ease of yarn breakage is not only in consideration of the thickness of the intended weft yarn, but also in consideration of other important factors such as the number of twists of the yarn. Therefore, the technique described in patent document 1 may not sufficiently suppress a weft insertion error caused by a broken yarn.

Disclosure of Invention

The present invention has been made to solve the above-described problems, and an object thereof is to provide a weft insertion control method for an air jet loom capable of sufficiently suppressing a weft insertion error caused by a yarn break.

The invention is a weft insertion control method of an air jet loom, the air jet loom injects air from a nozzle for weft insertion to carry out weft insertion on weft yarns, the weft insertion control method comprises the following steps: detecting the state of weft yarn before weft insertion; predicting a weft arrival time at which the weft arrives at a predetermined position when the weft is inserted under a predetermined weft insertion condition based on the detected state of the weft; setting an advance limit value in advance for irregularity in the weft arrival time, and changing the weft insertion condition so that the actual weft arrival time is later than the advance limit value when the predicted weft arrival time is earlier than the advance limit value; and ejecting air from the weft insertion nozzle according to the changed weft insertion condition to insert the weft.

In the weft insertion control method of an air jet loom according to the present invention, the advance limit value may be changed in accordance with the detected state of the weft yarn.

In the weft insertion control method of an air jet loom according to the present invention, the nozzle for weft insertion may include a main nozzle, and the air injection opening degree of the main nozzle as the weft insertion condition may be changed when the predicted arrival time of the weft yarn is earlier than the advance limit value.

In the weft insertion control method of an air jet loom according to the present invention, the weft insertion nozzle may include a tandem nozzle, and the air injection start timing of the tandem nozzle as the weft insertion condition may be changed when the predicted weft arrival timing is earlier than the advance limit value.

According to the present invention, when weft is inserted by an air jet loom, weft insertion errors caused by yarn breakage can be sufficiently suppressed.

Drawings

Fig. 1 is a schematic diagram showing an example of the configuration of a weft insertion device of an air jet loom according to an embodiment of the present invention.

Fig. 2 is a flowchart showing a weft insertion control method of an air jet loom according to an embodiment of the present invention.

Fig. 3 is a diagram illustrating irregularity of weft arrival time in the case where the present invention is not applied.

Fig. 4 is a diagram illustrating irregularity in weft arrival time in the case where the present invention is applied.

Description of reference numerals

1 … weft insertion device; 3 … weft yarn state detecting device; 6 … primary nozzle; 7 … series nozzle; 8 … secondary nozzle; 11 … weft yarns; 31 … control device; twf … advances the limit.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Weft insertion device for air-jet loom

Fig. 1 is a schematic diagram showing an example of the configuration of a weft insertion device of an air jet loom according to an embodiment of the present invention.

The weft insertion device 1 includes: a weft bobbin 2, a weft state detecting device 3, a weft accumulating device 4, a weft tension correcting device 5, a main nozzle 6, a tandem nozzle 7, an auxiliary nozzle 8, a reed 9 for beating-up, and a weft feeler 10. Further, the weft insertion device 1 includes: a main valve 12, a tandem valve 14, a main tank 16, a regulator 18, a secondary valve 22, a secondary tank 23, a regulator 24, a control device 31, and a function panel 32.

The weft bobbin 2 functions as a yarn feeder that feeds a weft yarn 11 used for weft insertion to the weft yarn accumulating device 4. The weft state detector 3 detects the state of the weft yarn 11 supplied from the weft bobbin 2. The state of the weft yarn 11 as a result of detection by the weft yarn state detecting device 3 is notified to the control device 31.

The weft state detector 3 is disposed between the weft bobbin 2 and the weft accumulating device 4 in the weft conveying direction. Weft insertion is performed downstream of the weft storage device 4 in the weft conveying direction. In contrast, the weft state detector 3 is disposed upstream of the weft accumulator 4. Therefore, the weft state detector 3 detects the state of the weft yarn 11 before weft insertion.

The state of the weft yarn 11 detected by the weft yarn state detection device 3 includes at least the mass per unit length of the weft yarn (hereinafter referred to as "weft yarn mass"). This yarn state affects the flight of the weft yarn when the weft yarn is inserted by flying the weft yarn by the jet of air. The weft state detection device 3 can be exemplified by the devices disclosed in japanese patent application laid-open No. 2014-500914.

The weft yarn accumulating device 4 accumulates weft yarns before weft insertion. The weft yarn accumulating device 4 has a length measuring roller 15 and a locking pin 17. The weft yarn accumulating device 4 winds the weft yarn 11 supplied from the weft yarn bobbin 2 to the weft yarn accumulating device 4 and accumulates the same in the length measuring drum 15.

The locking pin 17 is a pin capable of locking the weft yarn 11 used for weft insertion. The locking pin 17 is operated in a direction to approach or separate from the outer peripheral surface of the length measuring cylinder 15 by driving the electromagnetic solenoid 19. The driving of the electromagnetic solenoid 19 is controlled by the control device 31. The engagement pin 17 is operated in a direction approaching the outer peripheral surface of the length measuring drum 15, and thereby engages the weft yarn 11 with the outer peripheral surface of the length measuring drum 15. Further, the engagement pin 17 is operated in a direction away from the outer peripheral surface of the length measuring drum 15, thereby releasing the engagement of the weft yarn 11. A balloon sensor 20 is disposed near the length measuring cylinder 15. The balloon sensor 20 is a sensor that detects a balloon of the weft yarn 11 drawn out from the length measuring drum 15 by the release of the locking pin 17 and outputs the detection result to the control device 31 as an electric signal.

The weft tension correcting device 5 is a device that corrects tension applied to the weft yarn 11 without applying excessive tension to the weft yarn 11.

The main nozzle 6, the tandem nozzle 7, and the sub-nozzle 8 are provided as weft insertion nozzles, respectively. The main nozzle 6 is disposed downstream of the tandem nozzle 7 in the weft yarn conveying direction, and the sub-nozzle 8 is disposed downstream of the main nozzle 6 in the weft yarn conveying direction. The main nozzle 6 and the serial nozzle 7 are provided one by one, and the sub-nozzles 8 are provided in plurality.

The main nozzle 6 is connected to a main tank 16 via a main valve 12, and the tandem nozzle 7 is connected to the main tank 16 via a tandem valve 14. Further, a regulator 18 is connected to the main tank 16. The regulator 18 adjusts the pressure of compressed air generated by an air compressor, not shown. The main tank 16 stores compressed air whose pressure is adjusted by the regulator 18. The compressed air stored in the main tank 16 is supplied to the main nozzle 6 via the main valve 12, and is supplied to the tandem nozzle 7 via the tandem valve 14.

The main nozzle 6 injects air or stops injection in accordance with the open/close state of the main valve 12. The tandem nozzle 7 injects air or stops injecting in accordance with the open/close state of the tandem valve 14. Specifically, the main nozzle 6 injects air when the main valve 12 is in the open state, and stops injecting air when the main valve 12 is in the closed state. Similarly, the tandem nozzle 7 injects air when the tandem valve 14 is in the open state, and stops injecting air when the tandem valve 14 is in the closed state. The main valve 12 and the series valve 14 are electrically connected to the control device 31. The control device 31 individually controls the open/close state of the main valve 12 and the open/close state of the serial valve 14.

The plurality of sub-nozzles 8 are arranged at predetermined intervals in the weft yarn conveying direction. Each sub-nozzle 8 transports the weft yarn 11, which is ejected by the air from the main nozzle 6 and the tandem nozzle 7, in the longitudinal direction of the reed 9. When each pair of weft yarns 11 is subjected to 1 picking, the reed 9 performs one beating-up operation. A cutter 21 is disposed between the main nozzle 6 and the reed 9. The cutter 21 cuts the weft yarn 11 when the weft insertion is performed for each pair of 1 weft yarn 11, i.e., 1 pick is performed. The driving of the tool 21 is controlled by a control device 31.

The plurality of sub-nozzles 8 are provided in a total of 6 groups, with 4 sub-nozzles 8 adjacent in the longitudinal direction of the reed 9 as one group. The number of sets of the sub-nozzles 8 varies depending on the knitting width. The sub-nozzles 8 of each group are connected to a sub-tank 23 via a corresponding one of the sub-valves 22. Further, a regulator 24 is connected to the sub-tank 23. The regulator 24 adjusts the pressure of compressed air generated by an air compressor, not shown. The sub-tank 23 stores compressed air whose pressure is adjusted by the regulator 24. The compressed air stored in the sub-tank 23 is distributed and supplied to the sub-nozzles 8 of each group via the sub-valves 22.

The sub-nozzles 8 of each group inject air or stop injecting in accordance with the open/close state of the corresponding sub-valve 22. Specifically, the sub-nozzles 8 of each group inject air when the corresponding sub-valve 22 is in the open state, and stop injecting air when the sub-valve 22 is in the closed state.

When the weft yarn 11 is inserted by injecting air from each of the main nozzle 6, the tandem nozzle 7, and the sub-nozzle 8, the weft detector 10 detects whether or not the weft yarn 11 reaches a predetermined position set in advance. The predetermined position is set on the weft insertion terminal side which is a side away from the main nozzle 6 in the longitudinal direction of the reed 9 in accordance with the weaving width of the fabric.

The weft detector 10 is constituted by an optical sensor, for example. The weft feeler 10 outputs a detection signal when the tip end portion of the weft yarn 11, which is ejected in the longitudinal direction of the reed 9 by the air from the weft insertion nozzles 6, 7, and 8, reaches a predetermined position. Therefore, the weft arrival time at which the weft 11 arrives at the predetermined position is the time at which the weft finder 10 outputs the detection signal.

The control device 31 controls the operation of the weft insertion device 1. The controller 31 is configured by, for example, a central processing unit, a ROM (Read-Only Memory), a ram (random Access Memory), and the like. The control device 31 performs weft insertion of the weft yarn 11 by feed-forward control. The feedforward control performed by the controller 31 will be described in detail later.

The function panel 32 is connected to the control device 31 and serves as an input/output device for various data necessary for weft insertion. The function panel 32 includes, for example, a display device and input keys, which are not shown. A setting screen for the controller 31 to perform weft insertion of the weft yarn 11 by the feed-forward control is displayed on the display device. The type of weft yarn 11 used for weft insertion is input by a key operation of an operator in a state where a setting screen is displayed on a display device. The data input using the function panel 32 is not limited to the type of the weft yarn 11, and may include other data, such as data specifying weft insertion setting values, such as the weaving width of the fabric and the arrival time of the target weft yarn.

Weft insertion control method for air-jet loom

Next, a weft insertion control method of an air jet loom according to an embodiment of the present invention will be described with reference to the flowchart of fig. 2. In addition, the weft insertion control method shown in fig. 2 is repeatedly applied every 1 picking.

(step 1)

First, in step S1, the state of the weft yarn 11 before weft insertion is detected.

The weft yarn 11 used for weft insertion is supplied from the weft bobbin 2 to the weft yarn accumulating device 4, and the weft yarn state detecting device 3 detects the state of the weft yarn 11 in the middle of the supply path. The state of the weft yarn 11 detected by the weft yarn state detecting device 3 is notified to the control device 31. Thereby, the control device 31 can recognize the state of the weft yarn 11 before weft insertion. In the present embodiment, the weft state detector 3 detects the weft quality, and outputs the detection result to the controller 31.

(step S2)

Next, in step S2, based on the state of the weft yarn 11 detected in the previous step S1, when the weft yarn 11 is inserted under the predetermined insertion condition, the weft arrival time at which the weft yarn 11 arrives at the predetermined position is predicted. The controller 31 predicts the weft arrival time.

Predetermined weft insertion conditions are registered in advance in the memory of the control device 31 in accordance with the type of the weft yarn 11 determined by the material, count, and the like of the weft yarn 11. Therefore, the central processing unit of the control device 31 reads the weft insertion condition registered in the memory in accordance with the type of the weft yarn 11 used for weft insertion, and predicts the weft arrival time by applying the weft insertion condition. The weft insertion conditions include the pressure of the main tank 16, the pressure of the sub tank 23, the air injection opening degrees of the main nozzle 6 and the sub nozzle 8, the air injection opening degree of the serial nozzle 7, the air injection start timing of the main nozzle 6 and the sub nozzle 8, the air injection start timing of the serial nozzle 7, and the like.

Here, assuming that the weft arrival time predicted by the control device 31 is TWp, the control device 31 predicts a weft arrival time TWp based on the state of the weft 11 detected by the weft state detecting device 3. In the present embodiment, the weft state detector 3 detects the weft quality. In this case, the control device 31 predicts the weft arrival time TWp in accordance with the weft quality. Specific examples will be described below.

When the weft quality detected by the weft state detection device 3 is greater than the reference quality, the control device 31 predicts that the weft arrival time TWp is later than the reference weft arrival time TWr. When the weft quality detected by the weft state detecting device 3 is smaller than the reference quality, the control device 31 predicts that the weft arrival time TWp is earlier than the reference weft arrival time TWr. At this time, the difference between the reference weft arrival time TWr and the weft arrival time TWp predicted by the control device 31 is determined by the difference between the reference quality and the detected weft quality. In other words, the larger the difference between the reference quality and the detected weft quality, the larger the difference between the reference weft arrival time TWr and the predicted weft arrival time TWp.

The reference mass of the weft yarn is set in advance in accordance with the type of the weft yarn 11, and is stored in advance as data in a memory (e.g., RAM) of the control device 31. Then, when the predicted weft arrival time TWp is reached, the central processing unit of the control device 31 reads the weft arrival time from the memory and uses the weft arrival time.

(step S3)

Next, in step S3, it is determined whether or not the weft arrival time TWp predicted in the previous step S2 is earlier than a preset advance limit value TWf. This determination is made by the control device 31. The advance limit value TWf is a limit value that is preset for irregularities in the weft yarn arrival time.

Here, how the advance limit value TWf is set for an irregularity in the weft yarn arrival time will be described.

First, when weft insertion is performed under weft insertion conditions in which the type of weft yarn 11 specified using the function panel 32 is registered in the memory of the control device 31 in association with the type, even if weft insertion is performed on the same type of weft yarn 11 under the same weft insertion conditions, an advance or delay occurs in the flight of the weft yarn 11. Therefore, for example, when the same kind of weft yarns 11 are inserted under the same weft insertion condition in several thousands of picks, the weft arrival times actually detected by the weft feeler 10 have irregularities approaching a normal distribution centered around the reference weft arrival time TWr as shown in fig. 3.

In fig. 3, the vertical axis represents the longitudinal position of the reed, the horizontal axis represents the machine angle, and the movement characteristic line L represents the movement of the tip end of the weft. As is clear from fig. 3, weft insertion of weft yarns is performed at a machine angle in the range of 90 ° to 240 °. The weft arrival time is not regular around the time when the machine angle becomes 240 °. The time at which the bed angle becomes 240 ° corresponds to a target weft arrival time when a weft is inserted under a predetermined weft insertion condition, that is, a reference weft arrival time TWr.

In the embodiment of the present invention, the advance limit value TWf is set for an irregularity earlier than the weft arrival time TWr corresponding to the machine angle of 240 ° among the irregularities of the weft arrival times shown in fig. 3. The advance limit value TWf is set in accordance with the occurrence situation of a weft insertion error that may occur when the weft reaches a predetermined position at a time earlier than the reference weft arrival time TWr.

The generation state of the weft insertion error indicates how proportional the weft insertion error is actually generated. The occurrence of the weft insertion error can be confirmed in advance by an experiment or the like according to the type of the weft yarn 11. Therefore, based on data obtained by an experiment or the like, for example, in an irregular normal distribution indicating the arrival time of a weft, a distribution region E in which a weft insertion error is likely to occur due to a broken yarn is specified. Then, the timing corresponding to the minimum table angle excluding the distribution area E or the table angle obtained by adding a predetermined amount of safety angle (for example, about 2 °) to the minimum table angle is set as the advance limit value TWf. In this case, the advance limit value TWf is not simply set in accordance with the thickness of the weft yarn 11 used for weft insertion, but is set by referring to other important factors that affect the ease of yarn breakage, such as the number of twists of the weft yarn 11.

The occurrence state of a weft insertion error that may occur when a weft reaches a predetermined position at a time earlier than the reference weft arrival time TWr largely depends on the type of the weft 11, but may slightly vary depending on the state of the weft 11. Therefore, the control device 31 may change the advance limit value TWf in accordance with the state of the weft yarn 11 detected in step S1. The advance limit value TWf may be changed every 1-time picking according to the state of the weft yarn 11, or may be changed every multiple picks. By changing the advance limit value TWf in accordance with the state of the weft yarn 11 in this way, the process of step S3 can be performed using the advance limit value TWf suitable for the state of the weft yarn 11 at each time.

In step S3, the control device 31 determines whether the weft arrival time TWp is earlier than the advance limit value TWf by comparing the advance limit value TWf thus set with the weft arrival time TWp predicted in the previous step S2. If yes in step S3, the control device 31 proceeds to step S4, and if no, the control device 31 proceeds to step S5.

(step S4)

Next, in step S4, the weft insertion condition is changed so that the actual weft arrival time is delayed from the advance limit value TWf. The weft insertion condition is changed by the control device 31. There are a plurality of weft insertion conditions that can be changed by the control device 31. However, in the feed forward control, when the weft insertion condition is changed, high responsiveness is required to enable weft insertion under the changed condition immediately. In contrast, the pressure of the main tank 16 and the pressure of the sub-tank 23 require time until the actual tank pressure stabilizes at the changed pressures because the responsiveness of the actuator of the pressure regulating valve is slow even if the pressure set values are changed. Therefore, the weft insertion condition to be changed in step S4 does not apply to the pressure of the main tank 16 and the pressure of the sub tank 23. In the present embodiment, a preferable example of the weft insertion condition to be changed in step S4 includes the air injection opening degree of the main nozzle 6 and the air injection start timing of the tandem nozzle 7. The air injection opening degree of the main nozzle 6 and the air injection start timing of the tandem nozzle 7 may be changed by either one or both of them. A specific modification method will be described below.

First, a case of changing the air injection opening degree of the main nozzle 6 will be described.

The air injection opening degree of the main nozzle 6 is defined by the period from the start of air injection by the main nozzle 6 to the end of air injection by the main nozzle 6 at the time of 1-time picking, and the longer the period is, the larger the air injection opening degree is. The air injection opening degree of the main nozzle 6 is adjusted by controlling the open/close state of the main valve 12 by the control device 31. Therefore, when the weft arrival time TWp predicted in the previous step S2 is earlier than the advance limit value TWf, the control device 31 changes the air injection opening degree of the main nozzle 6 such that the air injection opening degree of the main nozzle 6 is smaller than before the weft insertion condition is changed.

When the air injection opening degree of the main nozzle 6 is small, the transport speed when transporting the weft yarn 11 in the longitudinal direction of the reed 9 is slow. Therefore, in the control device 31, the air injection opening degree of the main nozzle 6 is reduced by a predetermined ratio so that the actual weft yarn arrival time is later than the advance limit value TWf. The air injection opening degree of the main nozzle 6 may be reduced to what degree, and may be determined by confirming the relationship between the air injection opening degree of the main nozzle 6 and the weft arrival time in advance through experiments or the like and using data obtained thereby. When the air injection opening degree of the main nozzle 6 is changed, it is preferable to change the actual weft arrival time so as to match the reference weft arrival time TWr.

Next, a case of changing the air ejection start timing of the serial nozzle 7 will be described.

When the weft yarn 11 is inserted by air injection from the main nozzle 6 and the tandem nozzle 7, the air is injected from the main nozzle 6 and then the air is injected from the tandem nozzle 7, thereby accelerating the weft yarn 11. In this case, the air injection start timing of the serial nozzle 7 is set with reference to the air injection start timing of the main nozzle 6. For example, assuming that the air injection start timing of the main nozzle 6 is a timing corresponding to the stage angle θ m, the air injection start timing of the serial nozzle 7 is set to a timing corresponding to the stage angle θ m + α.

The timing of starting the air injection from the tandem nozzle 7 is adjusted by controlling the timing of switching the tandem valve 14 from the closed state to the open state by the control device 31. Therefore, when the weft arrival time TWp predicted in step S2 is earlier than the advance limit value TWf, the control device 31 changes the air injection start time of the tandem nozzle 7 so that the air injection start time of the tandem nozzle 7 becomes later than before the weft insertion condition is changed.

When the air ejection start timing of the tandem nozzle 7 becomes slow, the transport speed when transporting the weft yarn 11 in the longitudinal direction of the reed 9 becomes slow. Therefore, in the control device 31, the air ejection start timing of the tandem nozzle 7 is retarded by a predetermined amount so that the actual weft yarn arrival timing is delayed from the advance limit value TWf. The timing of starting the air injection from the tandem nozzle 7 may be delayed to what extent, and may be determined by using data obtained by confirming the relationship between the timing of starting the air injection from the tandem nozzle 7 and the weft arrival timing in advance through experiments or the like. When the air ejection start timing of the tandem nozzle 7 is changed, it is preferable to change the actual weft arrival timing so as to match the reference weft arrival timing TWr.

(step S5)

Next, in step S5, the control device 31 performs weft insertion of the weft yarn 11 by air injection from the main nozzle 6, the tandem nozzle 7, and the sub-nozzle 8 by controlling the open/close states of the main valve 12, the tandem valve 14, and the sub-valve 22, respectively. At this time, if it is determined yes in the previous step S3, the control device 31 controls the open/close states of the valves 12, 14, and 22 based on the weft insertion condition changed in step S4, and inserts the weft yarn 11. When the determination in step S3 is no, the control device 31 controls the open/close states of the valves 12, 14, and 22 according to the weft insertion condition before the change in step S4, and inserts the weft yarn 11.

< effects of the embodiment >

In the weft insertion control method of the air jet loom according to the embodiment of the present invention, the weft arrival time of the weft 11 actually inserted becomes irregular distribution including the distribution region E (see fig. 3) in which a weft insertion error is likely to occur due to yarn breakage, as shown in fig. 4. Thereby, the weft feeler 10 detects the arrival of the weft thread 11, i.e. the actual weft arrival time is not earlier than the advance limit value TWf. Therefore, when the weft yarn 11 is inserted in the air jet loom, the weft insertion error due to the yarn breakage can be sufficiently suppressed.

< modification example et al >

The technical scope of the present invention is not limited to the above-described embodiments, and various modifications and improvements are possible within the scope of deriving the specific effects obtained by the technical features and combinations thereof of the present invention.

For example, in the above-described embodiment, the weft yarn quality is described as the state of the weft yarn 11 detected by the weft yarn state detecting device 3, but the present invention is not limited thereto. For example, if there are other yarn states that may affect the flight of the weft yarn, such as the thickness and fuzzing of the weft yarn, the state may be detected by the weft yarn state detection device 3 and applied to the feedback control of the weft insertion by the control device 31.

Claims (5)

1. A weft insertion control method for an air jet loom for inserting a weft yarn by ejecting air from a nozzle for weft insertion,

the weft insertion control method of the air jet loom comprises the following steps:

detecting the state of weft yarn before weft insertion;

predicting a weft arrival time at which the weft arrives at a predetermined position when the weft is inserted under a predetermined weft insertion condition based on the detected state of the weft;

setting an advance limit value in advance for irregularity in the weft arrival time, and changing the weft insertion condition so that the actual weft arrival time is later than the advance limit value when the predicted weft arrival time is earlier than the advance limit value, the advance limit value being a time corresponding to a minimum machine angle not including a distribution area in which a weft insertion error is likely to occur due to yarn breakage or a machine angle obtained by adding a predetermined amount of safety angle to the minimum machine angle; and

and injecting air from the weft insertion nozzle according to the changed weft insertion condition to insert the weft.

2. The weft insertion control method of an air jet loom according to claim 1,

the advance limit value is changed according to the detected state of the weft yarn.

3. The weft insertion control method of an air jet loom according to claim 1 or 2,

the nozzle for weft insertion comprises a main nozzle,

changing an air injection opening degree of the main nozzle as the weft insertion condition in a case where the predicted weft arrival time is earlier than the advance limit value.

4. The weft insertion control method of an air jet loom according to claim 1 or 2,

the weft insertion nozzle comprises a series nozzle,

and changing the air injection start timing of the tandem nozzle as the weft insertion condition when the predicted weft arrival timing is earlier than the advance limit value.

5. The weft insertion control method of an air jet loom according to claim 3,

the weft insertion nozzle comprises a series nozzle,

and changing the air injection start timing of the tandem nozzle as the weft insertion condition when the predicted weft arrival timing is earlier than the advance limit value.

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