JP2015086476A - Pressure control device for compressed air in air jet loom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress variations in weft insertion pressure of compressed air in an air jet loom using an electropneumatic regulator.SOLUTION: A target pressure PT of a weft insertion pressure is preset. A lower limit pressure PL for determining the timing of starting the actuation of an air supply electromagnetic valve is set to a pressure lower than a weft insertion pressure P1 upon the completion of the first weft insertion and higher than a weft insertion pressure P2 upon the completion of the second weft insertion after an air jet loom is started. The weft insertion pressure lowered by the first weft insertion intersects the lower limit pressure PL upon the second weft insertion. A control device always compares the detection data of the weft insertion pressure with the lower limit pressure PL and sends a valve opening command to the air supply electromagnetic valve when the weft insertion pressure coincides with the lower limit pressure PL. When the air supply electromagnetic valve is opened, high-pressure compressed air is supplied to a primary-side space of an air spring pressure adjustment part, thereby displacing a diaphragm to open a pilot-type on-off valve. As a result, the high-pressure compressed air on an air supply source side is supplied to a main air tank side to increase the weft insertion pressure.

Description

  The present invention relates to a compressed air pressure control device in an air jet loom for controlling the weft insertion pressure of compressed air supplied to a main nozzle and a sub nozzle.

  In an air jet loom, high-pressure compressed air supplied from an air supply source is reduced to a weft insertion pressure suitable for weft insertion by a regulator and supplied to a main nozzle and a sub nozzle. In recent air jet looms, for example, high speed operation of 1000 revolutions per minute or more is performed, so that a regulator for controlling the weft insertion pressure can cope with high speed operation, from a conventional manual type or motor type regulator, for example, The electropneumatic regulator disclosed in Patent Document 1 has been adopted.

  In patent document 1, the electropneumatic regulator is disclosed as follows. In the fluid jet loom, a pressure regulating valve is provided on the fluid pressure supply side in order to set the optimum fluid pressure for the weft conveyance during weft insertion. As the pressure regulating valve, an electric pressure regulating valve with a built-in pressure sensor is often used in order to perform pressure control during loom operation by automatic control and to always bring the optimum weft conveyance state. The electric pressure regulating valve detects the output side pressure with a pressure sensor and feeds it back to the back pressure chamber on the input side, and uses the difference between the input side pressure and the output side pressure to open the opening of the regulating valve via the diaphragm. Is adjusted to realize the output side pressure according to the set pressure value.

JP-A-6-73640

  In the air jet loom, since the compressed air is consumed by weft insertion, the weft insertion pressure decreases with each weft insertion. When a decrease in weft insertion pressure is detected by the pressure sensor, the back pressure chamber feedback control of the electropneumatic regulator is activated to quickly supply the compressed air on the input side to the output side. For this reason, the electropneumatic regulator disclosed in Patent Document 1 simply calculates and activates the back pressure chamber feedback control 1000 times per minute. Therefore, since the electropneumatic regulator executes the back pressure chamber feedback control for every weft insertion, the weft insertion pressure easily repeats overshoot, and it becomes difficult to converge to a set pressure suitable for weft insertion.

  The fluctuation of the weft insertion pressure causes variations in the weft arrival timing at which the weft reaches a predetermined position on the side opposite to the main nozzle, and causes a weft insertion failure. Generation | occurrence | production of the weft insertion defect resulting from the dispersion | variation in the weft arrival timing will reduce the operating quality of an air jet loom while lowering textile quality. Further, in the air jet loom, the number of times of operation of the electropneumatic regulator is extremely increased, and there is a problem that the life of the electropneumatic regulator is significantly reduced.

  An object of the present invention is to suppress fluctuations in the weft insertion pressure of compressed air in an air jet loom using an electropneumatic regulator.

  Claim 1 has a diaphragm, a solenoid valve for supplying compressed air to a primary side space formed on one side of the diaphragm, and a solenoid valve for exhausting exhausted compressed air in the primary side space, An air spring pressure adjusting unit that controls the air supply solenoid valve and the exhaust solenoid valve based on the pressure on the output side, a pilot type on-off valve that is operated by the diaphragm and connects the output side and the input side, and Compression supplied from the air supply source to the weft insertion nozzle by an electropneumatic regulator that is operated by the diaphragm and includes an exhaust valve that is formed on the other side of the diaphragm and communicates with the output side and communicates with the output side. In the compressed air pressure control apparatus of an air jet loom for controlling the weft insertion pressure of air to a target pressure, the weft insertion pressure for determining the operation start timing of the air supply solenoid valve The lower limit pressure, after activation of the air jet loom, characterized by being set from the first of the weft insertion pressure during the weft insertion ends low.

  According to the first aspect, by appropriately setting the lower limit pressure that determines the operation timing of the air supply solenoid valve of the electropneumatic regulator, overshoot of the weft insertion pressure is prevented and fluctuation of the weft insertion pressure is suppressed. be able to. Stable weft flying can be realized by reducing fluctuations in weft insertion pressure, reducing the occurrence of weft insertion due to variations in weft arrival timing, and improving fabric quality and air jet loom availability. Can do. In addition, since the number of operations of the supply solenoid valve and the exhaust solenoid valve of the electropneumatic regulator is reduced, the life of the electropneumatic regulator can be increased.

  According to a second aspect of the present invention, the lower limit pressure is set higher than the weft insertion pressure at the end of the second weft insertion after the start of the air jet loom. According to the second aspect of the present invention, it is possible to prevent the pressure control that occurs every time the weft insertion is performed by the air supply solenoid valve of the electropneumatic regulator and the start delay of the pressure control, and obtain the optimum pressure control timing and the number of times of pressure control.

  According to a third aspect of the present invention, the upper limit pressure of the weft insertion pressure that determines the operation start timing of the exhaust solenoid valve is set to a pressure obtained by adding a difference between the target pressure and the lower limit pressure to the target pressure. And According to claim 3, the fluctuation range of the weft insertion pressure accompanying the weft insertion can be kept between the lower limit pressure and the upper limit pressure except for the first and second weft insertions at the time of starting the air jet loom. Can be inserted.

  The present invention can suppress fluctuations in the weft insertion pressure in an air jet loom using an electropneumatic regulator.

It is a schematic explanatory drawing which shows the piping system of the compressed air in an air jet loom. It is a schematic explanatory drawing of an electropneumatic regulator. It is a diagram which shows the change of the weft insertion pressure controlled by the electropneumatic regulator. It is a schematic explanatory drawing of the electropneumatic regulator which shows the pressure adjustment at the time of the non-operation of the air supply solenoid valve. It is a schematic explanatory drawing of the electropneumatic regulator which shows the pressure adjustment at the time of the action | operation of the solenoid valve for air supply.

  An embodiment of a compressed air pressure control device according to the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a compressed air piping system 2 in a weft insertion device of an air jet loom 1. The air supply source 3 installed in the weaving factory is composed of related devices (not shown) such as an air compressor and a dryer, and supplies compressed air to the air jet loom 1 through a pipe 4. The pipe 4 is connected to the pipe 6 of the air jet loom 1 through a source pressure opening / closing valve 5 provided in the air jet loom 1. The source pressure on-off valve 5 can supply or stop the compressed air to the air jet loom 1.

  The pipe 6 is connected to the pressure gauge 8 through the filter 7. The pressure gauge 8 measures the original pressure of the compressed air supplied from the air supply source 3. The original pressure is set to be supplied at a pressure higher than the weft insertion pressure used for the weft insertion of the air jet loom 1. The pipe 6 connected to the pressure gauge 8 is connected to the main air tank 10 via the electropneumatic regulator 9. A pressure gauge 11 is provided in the pipe 6 connecting the electropneumatic regulator 9 and the main air tank 10.

  The electropneumatic regulator 9 controls the original pressure of the compressed air to a preset weft insertion pressure suitable for the weft insertion. The compressed air controlled to the weft insertion pressure is supplied to the main air tank 10 and stored. The weft insertion pressure is set to be lower than the original pressure. The pressure gauge 11 measures the pressure of the compressed air stored in the main air tank 10, that is, the main nozzle pressure (weft insertion pressure), and checks whether the main nozzle pressure is controlled to the set pressure. it can. The main air tank 10 is connected to a main nozzle 13 (weft insertion nozzle) through a main air valve 12 by a pipe 6. The main air valve 12 supplies compressed air to the main nozzle 13 by a valve opening operation, and stops supplying compressed air to the main nozzle 13 by a valve closing operation.

  A pipe 14 branched from a pipe 6 that connects the pressure gauge 8 and the electropneumatic regulator 9 is connected to a pipe 6 that connects the main air valve 12 and the main nozzle 13 via a throttle valve 15 to form a light wind circuit 16. doing. Therefore, a small amount of compressed air adjusted by the throttle valve 15 is always supplied to the main nozzle 13 while the weft insertion is stopped. The main nozzle 13 keeps the tip of the weft yarn after weft insertion in a stable state by always injecting a slight wind while weft insertion is stopped.

  On the other hand, a pipe 17 further branched from the pipe 6 connecting the pressure gauge 8 and the electropneumatic regulator 9 is connected to the sub air tank 19 via an electropneumatic regulator 18 having the same structure and function as the electropneumatic regulator 9. . A pressure gauge 20 is provided in the pipe 17 that connects the electropneumatic regulator 18 and the sub air tank 19. The electropneumatic regulator 18 controls the original pressure of the compressed air supplied from the air supply source 3 to a sub nozzle pressure (weft insertion pressure) suitable for weft insertion. For this reason, the sub air tank 19 stores compressed air controlled to the sub nozzle pressure. The sub nozzle pressure is set to be the same as the main nozzle pressure.

  The sub air tank 19 is connected to each of four sub air valves 21 arranged along the weft insertion direction by pipes 17. Each of the sub nozzle groups 22 divided into four groups in the weft insertion direction includes a plurality of sub nozzles (weft insertion nozzles), and each sub air valve 21 is connected to each sub nozzle of each sub nozzle group 22 by a pipe 17. Therefore, each sub nozzle group 22 is supplied with compressed air at a sub nozzle pressure set from the sub air tank 19 by the operation of each sub air valve 21 to perform weft insertion.

  The pressure gauges 8, 11, and 20 are electrically connected to a control device 24 having a function panel 23, and transmit measured compressed air original pressure, main nozzle pressure, and sub nozzle pressure data to the control device 24. The control device 24 performs various calculations based on the data transmitted from the pressure gauges 8, 11, 20, the set value, etc., and the data of the original pressure, the main nozzle pressure, and the sub nozzle pressure. An operation unit (not shown) is provided.

  The control device 24 stores a program (not shown) for controlling power supply to the electropneumatic regulator 9 and the electropneumatic regulator 18 and a program (not shown) for instructing pressure control. The control device 24 includes various programs necessary for operating the air jet loom 1 and transmits signals to the main air valve 12 and the sub air valve 21 at the time of weft insertion to control the start and stop of the weft insertion operation.

  The electropneumatic regulator 9 and the electropneumatic regulator 18 have the same structure. Therefore, this embodiment demonstrates the structure of the electropneumatic regulator 9 in detail based on FIG. The electropneumatic regulator 9 includes an air spring pressure adjusting unit 25, a pilot type on-off valve 26, an exhaust valve 27, an air supply electromagnetic valve 28, and an exhaust electromagnetic valve 29. The air spring pressure adjustment unit 25 includes a diaphragm 30 disposed in the housing, a primary space 31 formed in one of the diaphragms 30, and a secondary space 32 formed in the other. The diaphragm 30 is displaced toward the primary side space 31 or the secondary side space 32 due to the difference between the pressure in the primary side space 31 and the pressure in the secondary side space 32.

  The primary side space 31 is connected to the supply solenoid valve 28 and the exhaust solenoid valve 29 via a conduit 33. The supply solenoid valve 28 and the exhaust solenoid valve 29 are each electrically connected to the control device 24, and perform an opening / closing operation according to a command from the control device 24. The air supply solenoid valve 28 is connected to a pipe 6 connected to the air supply source 3 through a pipe line 34. Accordingly, when the air supply solenoid valve 28 is opened, the compressed air having the original pressure is supplied to the primary side space 31 via the pipe 33. The exhaust solenoid valve 29 includes an exhaust port 35 opened to the outside. When the exhaust solenoid valve 29 is opened, the compressed air in the primary space 31 is released from the exhaust port 35 to the outside.

  The pilot type on-off valve 26 includes an inlet 36 connected to the pipe 6 on the air supply source 3 side and an outlet 37 connected to the pipe 6 on the main air tank 10 side. Further, since the pilot type on-off valve 26 is connected to the diaphragm 30 of the air spring pressure adjusting unit 25, the pilot-type on-off valve 26 opens and closes by the displacement of the diaphragm 30. For example, the pilot-type on-off valve 26 opens when the primary side space 31 becomes higher in pressure than the secondary side space 32, and closes when the secondary side space 32 is in balance with the primary side space 31 or becomes high pressure. To do. When the pilot type on-off valve 26 is opened, high-pressure compressed air on the air supply source 3 side is supplied to the main air tank 10 side. The pipe 6 connected to the outlet 37 of the pilot type on-off valve 26 communicates with the secondary space 32 through a pipe line 38.

  The exhaust valve 27 includes a pipe line 39 communicating with the secondary side space 32 and an exhaust port 40 communicating with the atmosphere side, and performs an opening / closing operation by the displacement of the diaphragm 30 as in the pilot type on-off valve 26. For example, the exhaust valve 27 is closed when the primary side space 31 is in a balanced state with the secondary side space 32 or is in a high pressure state. When the secondary side space 32 becomes higher in pressure than the primary side space 31, the exhaust valve 27 is opened by the displacement of the diaphragm 30. Accordingly, the compressed air in the secondary side space 32, that is, the compressed air on the outlet 37 side of the pilot type on-off valve 26 is released from the exhaust port 40 through the pipe line 38, the secondary side space 32 and the pipe line 39. The

  With reference to FIG. 3, the set values relating to pressure control of the electropneumatic regulator 9 will be described. A target pressure PT of the main nozzle pressure of the compressed air stored in the main air tank 10 is set in advance and stored in the control device 24. Therefore, the electropneumatic regulator 9 performs pressure control so that the main nozzle pressure becomes the target pressure PT. Further, a lower limit pressure PL for determining the operation start timing of the supply solenoid valve 28 and an upper limit pressure PU for determining the operation start timing of the exhaust solenoid valve 29 are set for the main nozzle pressure and stored in the control device 24. Has been.

  The lower limit pressure PL is lower than the main nozzle pressure P1 at the end of the first weft insertion after the start of the air jet loom 1, and is higher than the main nozzle pressure P2 at the end of the second weft insertion. Is set. In the present embodiment, the lower limit pressure PL is set to a pressure that is intermediate between the weft insertion pressure P1 and the weft insertion pressure P2. The upper limit pressure PU is set to a pressure obtained by adding the difference between the target pressure PT and the lower limit pressure PL to the target pressure PT.

  For example, when the lower limit pressure PL is set to a pressure higher than the main nozzle pressure P1 at the end of the first weft insertion after the start of the air jet loom 1, the air supply is performed while the main nozzle pressure at the time of weft insertion is decreasing. Since the solenoid valve for exhaust 28 and the solenoid valve for exhaust 29 operate, pressure control is frequently performed, which is not preferable. That is, the air supply solenoid valve 28 operates every time weft insertion, and the exhaust electromagnetic valve 29 operates every time weft insertion due to overshoot accompanying the pressure control of the air supply electromagnetic valve 28. For this reason, as a result of frequent pressure control, the main nozzle pressure may not converge to the target pressure PT. The supply solenoid valve 28 and the exhaust solenoid valve 29 may be frequently operated to cause component damage.

  Further, when the lower limit pressure PL is set to a pressure lower than the main nozzle pressure P2 at the end of the second weft insertion after the air jet loom 1, for example, the main nozzle by the third or third and subsequent weft insertions The supply solenoid valve 28 is activated by the pressure drop. For this reason, the start of the pressure control is delayed, the main nozzle pressure is greatly reduced after the air jet loom 1 is started, and there is a possibility that a weft insertion failure may occur.

  Hereinafter, the control of the main nozzle pressure by the electropneumatic regulator 9 will be described with reference to FIGS. When the air jet loom 1 is started, the pressure gauge 11 detects the pressure of compressed air (main nozzle pressure) downstream from the electropneumatic regulator 9 and transmits the detected pressure data to the control device 24. As shown in FIG. 3, after the air jet loom 1 is started, the first weft insertion is started and the main nozzle pressure decreases, but the main nozzle pressure P1 at the end of the weft insertion decreases to the lower limit pressure PL. Therefore, the control device 24 does not transmit an operation command for valve opening control of the air supply solenoid valve 28 in the electropneumatic regulator 9.

  Therefore, in the electropneumatic regulator 9, as shown in FIG. 4, the supply solenoid valve 28 and the exhaust solenoid valve 29 are maintained in the closed state, but in the secondary side space 32 of the air spring pressure adjustment unit 25. The pressure of the nozzle decreases due to fluctuations in the main nozzle pressure. For this reason, the diaphragm 30 is displaced from the imaginary line position to the solid line position toward the secondary side space 32 by the pressure in the primary side space 31, and opens the pilot type on-off valve 26. By opening the pilot type on-off valve 26, high-pressure compressed air on the air supply source 3 side is supplied from the outlet 37 to the pipe 6 on the main air tank 10 side to increase the main nozzle pressure. However, when the air jet loom 1 is started, the pressure in the primary space 31 is not sufficiently high, and the diaphragm 30 is not greatly displaced. Therefore, the main nozzle pressure cannot be increased to the target pressure PT.

  As shown in FIG. 3, the second weft insertion is started in a state where the main nozzle pressure decreased by the first weft insertion has not been increased to the target pressure PT. Therefore, the main nozzle pressure decreases again. During the second weft insertion, the pressure falls below the lower limit pressure PL at the position of point A and is further lowered at the end of the weft insertion. In the control device 24, the detection data of the main nozzle pressure transmitted from the pressure gauge 11 is constantly compared with the stored lower limit pressure PL. When recognizing that the detected main nozzle pressure is lower than the lower limit pressure PL, the control device 24 transmits an operation command to the supply solenoid valve 28 of the electropneumatic regulator 9.

  As shown in FIG. 5, the solenoid valve for air supply 28 opens in response to a command from the control device 24 when the solenoid is excited and operates downward. The high-pressure compressed air on the air supply source 3 side is supplied into the primary space 31 of the air spring pressure adjusting unit 25 through the pipe 34, the air supply solenoid valve 28, and the pipe 33. The pressure in the primary space 31 is increased by the inflow of high-pressure compressed air, the diaphragm 30 is displaced from the phantom line position to the solid line position, and the pilot on-off valve 26 is opened.

  For this reason, high-pressure compressed air on the air supply source 3 side is supplied to the pipe 6 on the main air tank 10 side via the inlet 36 and outlet 37 of the pilot on-off valve 26 to increase the main nozzle pressure. The operation of the air supply solenoid valve 28 is determined in advance according to a command from the control device 24. The main nozzle pressure once decreases to the main nozzle pressure P2 at the end of the second weft insertion, but is then rapidly increased by the operation of the air supply solenoid valve 28. However, the main nozzle pressure is not increased enough to reach the upper limit pressure PU, and the next third weft insertion is started.

  Since the main nozzle pressure at the end of the third weft insertion is after the pressure is increased by the operation of the air supply solenoid valve 28, the main nozzle pressure does not fall below the lower limit pressure PL. Do not send an operation command signal. In the electropneumatic regulator 9, as shown in FIG. 5, the supply solenoid valve 28 and the exhaust solenoid valve 29 are closed, but due to the decrease in the main nozzle pressure at the end of the third weft insertion, The pressure in the side space 32 decreases. For this reason, the diaphragm 30 is displaced from the imaginary line position to the position on the secondary side space 32 side indicated by the solid line by the pressure of the primary side space 31.

  Due to the displacement of the diaphragm 30, the pilot type on-off valve 26 is opened, high pressure compressed air on the air supply source 3 side is supplied to the main air tank 10 side, and the main nozzle pressure is increased. At the end of the third weft insertion, the pressure in the primary space 31 is sufficiently increased because the air supply solenoid valve 28 is actuated. For this reason, the diaphragm 30 is greatly displaced, the supply amount of high-pressure compressed air becomes sufficient, and the main nozzle pressure is increased to such an extent that it reaches the target pressure PT. Therefore, the decrease in the main nozzle pressure due to the end of the third and subsequent weft insertions is controlled by the displacement of the diaphragm 30 due to the fluctuation of the main nozzle pressure, and the fluctuation of the main nozzle pressure in the state of convergence near the target pressure PT is maintained. Can do.

  In the present embodiment, the upper limit pressure PU is set to have the same pressure difference from the target pressure PT as the lower limit pressure PL, but the pressure difference need not be the same. For example, it is sufficient that the upper limit pressure PU is set to a pressure higher than the pressure increase value of the main nozzle pressure that is controlled during normal operation of the air jet loom 1 (after the start of the third weft insertion). Further, in the present embodiment, during operation of the air jet loom 1, the main nozzle pressure is converged near the target pressure PT, and therefore the upper limit pressure PU does not have to be set. In the present embodiment, the electropneumatic regulator 9 has been described. However, the electropneumatic regulator 18 connected to the sub air tank 19 also controls the sub nozzle pressure as in the electropneumatic regulator 9.

  In the present embodiment, since the lower limit pressure PL is set so as to be lower than the weft insertion pressure at the end of the first weft insertion after the air jet loom 1 is started, the electropneumatic regulators 9 and 18 are supplied with electromagnetic waves. The number of operations of the valve 28 and the exhaust electromagnetic valve 29 can be minimized. Further, during the operation of the air jet loom 1, the diaphragm 30 is displaced by utilizing the decrease in the weft insertion pressure due to the weft insertion, and the weft insertion pressure is controlled. Does not require operation. For this reason, the present embodiment can suppress a large fluctuation of the weft insertion pressure, converge the weft insertion pressure in the vicinity of the target pressure PT, and stabilize it, and can also control the supply solenoid valve 28 and the exhaust solenoid valve 29. The number of operations can be reduced, and the life of the electropneumatic regulators 9 and 18 can be increased.

  The present invention is not limited to the configuration of the above-described embodiment, and various modifications are possible within the scope of the gist of the present invention, and can be implemented as follows.

(1) In this embodiment, the lower limit pressure PL is intermediate between the weft insertion pressure P1 at the end of the first weft insertion and the weft insertion pressure P2 at the end of the second weft insertion after the air jet loom 1 is started. Although the pressure is set, any pressure between the weft insertion pressure P1 and the weft insertion pressure P2 can be set freely.
(2) The present invention can be implemented in an air jet loom having a tandem nozzle that pulls the weft yarn upstream of the main nozzle 13 or a multi-color air jet loom having a plurality of main nozzles 13.

DESCRIPTION OF SYMBOLS 1 Air jet loom 3 Air supply source 9, 18 Electropneumatic regulator 10 Main air tank 11, 20 Pressure gauge 13 Main nozzle (weft insertion nozzle)
19 Sub air tank 22 Sub nozzle group (nozzle for weft insertion)
23 Function panel 24 Control device 25 Air spring pressure adjustment unit 26 Pilot type on-off valve 27 Exhaust valve 28 Supply solenoid valve 29 Exhaust solenoid valve 30 Diaphragm 31 Primary side space 32 Secondary side space PT Target pressure PL Lower limit pressure PU Upper limit Pressure P1 Main nozzle pressure at the end of the first weft insertion (weft insertion pressure)
P2 Main nozzle pressure at the end of the second weft insertion (weft insertion pressure)

Claims (3)

A diaphragm, a supply solenoid valve for supplying compressed air to a primary space formed in one of the diaphragms, and an exhaust solenoid valve for exhausting compressed air in the primary space, the pressure on the output side An air spring pressure adjusting unit that controls the air supply solenoid valve and the exhaust solenoid valve, a pilot type on-off valve that is operated by the diaphragm and connects the output side and the input side, and operated by the diaphragm Weft insertion pressure of compressed air supplied from the air supply source to the weft insertion nozzle by an electropneumatic regulator formed on the other side of the diaphragm and having an exhaust valve communicating with the secondary side space communicating with the output side to the atmosphere side In the compressed air pressure control device of the air jet loom that controls the pressure to the target pressure,
The lower limit pressure of the weft insertion pressure for determining the operation start timing of the air supply solenoid valve is set lower than the weft insertion pressure at the end of the first weft insertion after the start of the air jet loom. Compressed air pressure control device for air jet looms.   The compressed air pressure control apparatus for an air jet loom according to claim 1, wherein the lower limit pressure is set higher than the weft insertion pressure at the end of the second weft insertion after the air jet loom is started.   The upper limit pressure of the weft insertion pressure that determines the operation start timing of the exhaust solenoid valve is set to a pressure obtained by adding a difference between the target pressure and the lower limit pressure to the target pressure. Or the compressed air pressure control apparatus in the air-jet loom of Claim 2.

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