Drive mechanism and selvage forming device for loom

Abstract

This invention provides a drive mechanism that can improve operating efficiency by suppressing the temperature rise associated with the repeated operation of an electric motor. [Solution] The selvage forming device 1 for weaving machines has a drive mechanism 10 equipped with an electric motor 2, an inverter 7, and a control unit 9. The control unit 9 controls the electric motor 2 to alternately rotate in the forward direction and in the reverse direction, and makes the dwell period T2 when the electric motor 2 reverses direction greater than the dwell period T1 when it rotates in the same direction.

Description

Technical Field

[0001] The present invention relates to a drive mechanism and a leno selvage forming apparatus for a loom.

Background Art

[0002] Conventionally, technologies related to control of electric motors are known (Patent Document 1: Japanese Unexamined Patent Publication No. 2007-037299). Further, as a configuration example in which an electric motor frequently repeats acceleration, deceleration and reversal, a leno selvage forming apparatus is known (Patent Document 2: Japanese Unexamined Patent Publication No. 11-107129).

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problem to be Solved by the Invention

[0004] The frequent repetition of acceleration, deceleration and reversal by the electric motor causes a problem that the temperature of the body rises and the operation rate decreases.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a drive mechanism capable of improving the operation rate by suppressing temperature rise accompanying repeated operations of an electric motor, and a leno selvage forming apparatus for a loom including the drive mechanism.

Means for Solving the Problem

[0006] As one embodiment, the above problem is solved by the solution disclosed below.

[0007] The drive mechanism according to the present invention comprises an electric motor, an inverter that drives the electric motor, and a control unit that controls the inverter, and is configured to alternately repeat the operation of forward rotation and reverse rotation, wherein the control unit is characterized in that it makes the retention period when the electric motor reverses direction longer than the retention period when the electric motor rotates in the same direction. With this configuration, it is possible to reduce power consumption while suppressing the temperature rise associated with the repeated operation of the electric motor. Therefore, it is possible to improve the operating rate.

[0008] As an example, the control unit sets the minimum speed during the dwell period when rotating in the same direction to 0.1 to 0.9 times the maximum speed during the dwell period when reversing. With this configuration, the speed during the dwell period when rotating in the same direction does not cross zero. Therefore, both high speed and power saving can be achieved. By setting the minimum speed during the dwell period when rotating in the same direction to 0.1 times or more the maximum speed during the dwell period when reversing, inertial force can be effectively utilized. By setting the minimum speed during the dwell period when rotating in the same direction to 0.9 times or less the maximum speed during the dwell period when reversing, regular repetitive operation can be easily performed.

[0009] As an example, the control unit makes the second proportional gain during the dwell period when reversing greater than the first proportional gain during the dwell period when rotating in the same direction. This configuration makes it easy to perform high-speed and regular repetitive operations.

[0010] As an example, the electric motor includes a casing, three or more rollers arranged at predetermined intervals in the casing, a rotor supported by the rollers, a plurality of rotor magnets built into the rotor, a stator core built into the casing, and a magnetic encoder for detecting the rotor magnetic poles of the rotor magnets. The control unit controls the speed of the electric motor using the rotor magnet position signal detected by the magnetic encoder. This configuration makes it easy to perform highly accurate and regular repetitive operations.

[0011] As an example, a home magnet is provided on the rotor, a magnetic sensor for detecting the home magnetic pole of the home magnet is provided on the casing, and the control unit controls the rotation period of the electric motor using the home magnet position signal detected by the magnetic sensor. With this configuration, highly accurate and regular rotational operation can be easily achieved.

[0012] The selvedge forming apparatus for a loom according to the present invention comprises a drive mechanism having an electric motor, an inverter that drives the electric motor, and a control unit that controls the inverter, wherein the electric motor alternately rotates in the forward direction and in the reverse direction, and the control unit is characterized in that it makes the retention period when the electric motor reverses direction longer than the retention period when the electric motor rotates in the same direction. With this configuration, it is possible to reduce power consumption while suppressing the temperature rise associated with the repeated operation of the electric motor in the selvedge forming apparatus for a loom. [Effects of the Invention]

[0013] According to the present invention, a drive mechanism capable of suppressing the temperature rise associated with the repeated operation of an electric motor and improving the operating rate, as well as a selvedge forming apparatus for a loom equipped with the drive mechanism, can be realized. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a schematic diagram showing an example of a drive mechanism according to this embodiment. [Figure 2] Figure 2 is a schematic structural diagram showing an example of a selvedge forming device for a loom equipped with the drive mechanism shown in Figure 1. [Figure 3] Figure 3 is a schematic structural diagram showing an example of an electric motor related to the selvage forming device for a loom shown in Figure 2. [Figure 4] Figure 4 is a schematic cross-sectional view of the electric motor shown in Figure 3 in the Y direction. [Figure 5] Figure 5 is a schematic cross-sectional view of the electric motor shown in Figure 3 in the X direction. [Figure 6]FIG. 6A is a schematic plan view of the sensor unit according to the present embodiment. FIG. 6B is a schematic diagram showing the origin signal detection position during clockwise rotation. FIG. 6C is a schematic diagram showing the origin signal detection position during counterclockwise rotation. [Figure 7] FIG. 7 is a schematic diagram showing the moving region and the stagnation region of the electric motor according to the present embodiment. [Figure 8] FIG. 8 is a schematic developed structural view of a rotor and a stator core of the electric motor according to the present embodiment. [Figure 9] FIG. 9 is a schematic waveform diagram showing an example of a control system signal according to the present embodiment. [Figure 10] FIG. 10 is a schematic waveform diagram showing an example of a control system signal according to the prior art. [Figure 11] FIG. 11 is a schematic waveform diagram showing an example of a control system signal according to the present embodiment. [Figure 12] FIG. 12 is a schematic waveform diagram showing an example of a control system signal according to the present embodiment. [Figure 13] FIG. 13 is a schematic graph diagram showing a setting example of the current limiting table according to the present embodiment. [Figure 14] FIG. 14 is a schematic graph diagram showing a setting example of the speed profile according to the present embodiment. DESCRIPTION OF EMBODIMENTS

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. As shown in Fig. 1, the drive mechanism 10 of the present embodiment includes an electric motor 2, an inverter 7 that drives the electric motor 2, and a control unit 9 that controls the inverter 7. The electric motor 2 of the present embodiment is a permanent magnet synchronous motor, and the inverter 7 is a PWM inverter. The control unit 9 independently controls the d-axis current and the q-axis current, performs coordinate conversion, and controls the magnitude, frequency and phase of the output current of the inverter 7. Then, an origin magnet M1 disposed at the origin position of the electric motor 2 is detected by a magnetic sensor Ho incorporated in a magnetic encoder He, and the magnetic encoder He feeds back a speed signal and a position signal corresponding to the detection timing of the origin position to the control unit 9. The control unit 9 performs current vector control.

[0016] Fig. 2 is a schematic structural diagram showing an example of a leno selvedge forming apparatus 1 for a loom including the drive mechanism 10. The leno selvedge forming apparatus 1 for a loom (hereinafter abbreviated as the selvedge forming apparatus 1) includes a casing 15 formed by combining a base and a cover. A signal line and a power supply line are led out to the outside through a vent of the casing 15 and connected to the inverter 7 and the control unit 9. The selvedge forming apparatus 1 is attached to a loom main body by an attachment through fixing members such as bolts inserted into a plurality of through holes formed in the casing 15 (not shown). Two selvedge yarns N1 are respectively supplied from the loom main body to a pair of guide portions 11, and rotating the electric motor 2 moves the selvedge yarns N1 up and down, so that the weft of the fabric is woven while being twisted to prevent unraveling. The selvedge yarns N1 need to be synchronized with the movement of the warp. Therefore, the electric motor 2 repeats acceleration and deceleration every 180° of mechanical angle, reverses every predetermined number of rotations, and repeats the same operation. In all the drawings for describing the embodiments, members having the same function are denoted by the same reference numerals, and repeated description thereof may be omitted.

[0017] Figure 3 is a schematic structural diagram of the electric motor 2 according to this embodiment. Figure 4 is a schematic cross-sectional view of the electric motor 2 in the Y direction. Figure 5 is a schematic cross-sectional view of the electric motor 2 in the X direction. The inner rotor type electric motor 2 comprises a rotor 5, a plurality of rotor magnets M2 built into the rotor 5, a stator core 6, windings 8 wound around the salient pole portion 6a of the stator core 6, and a sensor unit 4 capable of detecting the magnetic poles of the rotor magnets M2. The rotor 5 rotates when current is supplied to the windings 8. Here, to make it easier to explain the positional relationship of each part of the electric motor 2, the directions are indicated by X, Y, and Z arrows in the figures. The electric motor 2 operates normally in any direction. The axis P1 is the center line when the rotor 5 rotates.

[0018] As shown in Figures 3 to 5, the electric motor 2 is equipped with a casing 15, which is made up of a base 15a and a cover 15b. The stator core 6 is mounted and fixed to the base 15a and is housed within the casing 15. The casing 15 has three or more rollers 3 arranged at first intervals in the circumferential direction. The rotor 5 is supported by the three or more rollers 3 to allow for easy rotation. Multiple rotor magnets M2 are arranged in a circumferentially aligned manner on the ring-shaped rotor 5.

[0019] Roller 3 is formed by fitting a ring-shaped sleeve 3a onto the outer ring of a radial bearing. The collar 19a is attached and fixed to the base 15a. Roller 3 is attached to the collar 19a, and the inner ring of the radial bearing is fixed to the base 15a via the collar 19a by a screw 19. As a result, the rotor 5 is supported by the roller 3 with the sleeve 3a in contact with the rotor 5, allowing it to rotate easily.

[0020] Figure 6A is a schematic plan view of the sensor unit 4. As an example, the sensor unit 4 has a magnetic sensor Ho and a magnetic encoder He mounted on the substrate 4a. Also, magnetic sensors Hu, Hv, and Hw are mounted on the substrate 4a. Magnetic sensor Ho is an origin sensor mounted in a position opposite the origin magnet M1. The magnetic encoder He has multiple Hall element chips embedded in its package. Magnetic sensor Hu is the first Hall element, magnetic sensor Hv is the second Hall element, and magnetic sensor Hw is the third Hall element. In the sensor unit 4, the rotor magnet M2 and the substrate 4a are arranged opposite each other in the circumferential direction of the rotor 5. Magnetic sensors Hu, Hv, and Hw are mounted on the substrate 4a at an electrical angle of 60 degrees pitch, and the control unit 9 uses the detection signals from these Hall elements to control the three-phase drive. Note that the above configuration is an example, and magnetic sensors Hu, Hv, and Hw may be omitted.

[0021] The magnetic encoder He outputs encoder signal A, which is output 4096 times per rotation of the rotor 5, and encoder signal B, based on the change in the magnetic field of the rotor magnet M2, which is magnetized in 32 poles. There is a 90° phase difference between the A and B phases of the encoder signal. Therefore, 16384 encoder signals are obtained per rotation of the rotor 5, which is four times the A phase. In other words, the position of the rotor magnet M2 is determined from the change in the magnetic field using the magnetic encoder He, and accurate position control, speed control, and discrimination between forward and reverse rotation are possible even if there are mounting errors in the Hall element.

[0022] Figure 6B is a schematic diagram showing the origin signal detection position of the sensor unit 4 when rotating to the right. Figure 6C is a schematic diagram showing the origin signal detection position of the sensor unit 4 when rotating to the left. Since the origin magnet M1 has a predetermined size, the origin signal detection position differs between right and left rotation. Also, the center position of the origin magnet M1 and the origin signal detection position are different. In contrast, by using a magnetic encoder He, the control unit 9 can store as a pattern the shift in the origin detection position due to the influence of the rotation direction and calculate the origin position through computational correction. Therefore, a more accurate origin position can be obtained.

[0023] Figure 7 is a schematic diagram showing the movement and stagnation regions of the electric motor 2. The stagnation region consists of the left and right regions with the origin magnet M1 as the top dead center, and the left and right regions centered on the bottom dead center 180° opposite the origin magnet M1. As an example, the stagnation region is within ±24° of the top dead center, and the stagnation region is within ±24° of the bottom dead center.

[0024] Figure 8 is a schematic exploded view of the rotor 5 and stator core 6 of the electric motor 2. The rotor 5 has an origin magnet M1 that indicates the origin position, and a ring-shaped rotor magnet M2 divided into 32 poles and magnetized is fixed to it by adhesive or the like. The stator core 6 has salient pole sections 6a in multiples of the number of drive phases, a first notch, a second notch for housing the rollers 3, and a third notch. Here, 18 salient pole sections 6a are formed. A sensor section 4 capable of detecting each magnetic pole of the origin magnet M1 and the rotor magnet M2 is housed in the first notch. An insulator is provided in each salient pole section 6a, and a winding 8 is wound around the insulator. The area where the winding 8 is wound is then resin-molded to form a molded section. For the sake of explanation, some parts of the winding 8, molded sections, and other parts are omitted in each figure.

[0025] Figure 9 is a schematic waveform diagram showing an example of a control system signal according to this embodiment. Winding 8 consists of winding 8u corresponding to the U phase, winding 8v corresponding to the V phase, and winding 8w corresponding to the W phase. Sensor unit 4 has a Hall element Hu that detects the magnetic pole when winding 8u is energized, a Hall element Hv that detects the magnetic pole when winding 8v is energized, and a Hall element Hw that detects the magnetic pole when winding 8w is energized. The Hall elements Hu, Hv, and Hw are mounted on the substrate 4a at an electrical angle K1 of 60 degrees, and three-phase drive is performed using the detection signals from each Hall element.

[0026] The control unit 9 makes the dwell period T2 when the electric motor 2 reverses direction longer than the dwell period T1 when it rotates in the same direction. This makes it possible to reduce power consumption while suppressing temperature rise. As an example, the control unit 9 sets the minimum speed during the dwell period T1 when rotating in the same direction to 0.1 to 0.9 times the maximum speed during the dwell period T2 when reversing. This makes it possible to achieve both high speed and power saving. As an example, the control unit 9 sets the control range of the speed during the dwell period T1 when rotating in the same direction to a range of 0.1 to 0.9 times the maximum speed during the dwell period T2 when reversing.

[0027] Figure 10 is a schematic waveform diagram showing an example of a control system signal according to the conventional technology. The dwell time when the electric motor reverses direction is the same as the dwell time when it rotates in the same direction. Furthermore, the current limit value when the electric motor rotates is either the maximum value or a constant value in absolute terms. In this case, the current consumption increases, and the pulsation of the actual current when rotating at a constant speed becomes large.

[0028] Figure 11 is a schematic waveform diagram showing an example of a control system signal according to this embodiment. The control unit 9 sets the second current limit value U2 when the electric motor 2 reverses direction to be larger than the first current limit value U1 when it rotates in the same direction. As a result, even if there is an overrun near zero speed when reversing, sufficient acceleration and deceleration can be used to achieve a dwell angle within a predetermined time. Therefore, responsiveness can be improved while ensuring the time required for repeated operation.

[0029] The electric motor 2 operates at a constant speed after accelerating and decelerating. When operating at a constant speed, the third current value U3 is reached. The control unit 9 reduces the third current value U3 to less than the first current limit value U1. By reducing the third current value U3, the pulsation of the actual current can be reduced. By setting the third current value U3 to the minimum value that allows operation at a constant speed, the pulsation of the actual current can be minimized.

[0030] For example, this configuration is particularly useful in a setup where both the acceleration torque and deceleration torque of the electric motor 2 are 1.5 times or more the load torque, and the load torque fluctuation is within plus or minus 50%. In other words, this configuration is suitable for direct drive systems.

[0031] As an example, the control unit 9 makes the second proportional gain greater when the electric motor 2 reverses direction than the first proportional gain when it rotates in the same direction. With this configuration, high-speed and regular repetitive operation can be easily achieved.

[0032] Figure 12 is a schematic waveform diagram showing an example of a control system signal according to this embodiment. The control unit 9 makes the second current limit value U2 when the electric motor 2 reverses direction greater than the first current limit value U1 when it rotates in the same direction. It then sets the third current value U3 to the minimum value that allows operation at a constant speed. In addition, the control unit 9 makes the dwell period T2 when the electric motor 2 reverses direction greater than the dwell period T1 when it rotates in the same direction.

[0033] Figure 12 shows an example of the speed profile of this embodiment. Here, the acceleration time of the electric motor 2 at startup is the first time r1, the travel time of the electric motor 2 during the first high-speed movement is the second time r2, the initial deceleration time of the electric motor 2 when rotating in the same direction is the third time r3, the initial acceleration time of the electric motor 2 when rotating in the same direction is the third time r3, the travel time of the electric motor 2 when moving at a constant speed is the fourth time r4, the deceleration time of the electric motor 2 when rotating in the same direction is the third time r3, ..., the acceleration time of the electric motor 2 when rotating in the same direction is the third time r3, the travel time of the electric motor 2 during high-speed movement is the second time r2, the deceleration time of the electric motor 2 to zero speed when reversing is the first time r1, the deceleration time of the electric motor 2 from zero speed when reversing is the first time r1, the travel time of the electric motor 2 during the first high-speed movement when reversing is the second time r2, and the deceleration time of the electric motor 2 when rotating in the same direction is the third time r3.

[0034] The velocity profile in Figure 12 is r1 + r2 + r3 = 2 × r3 + r4, and r1 > r3. This reduces the acceleration during reversal and thus the current value. Furthermore, by adding a current limit corresponding to the acceleration, current pulsation can be reduced. In addition, by not letting the speed become zero during repeated rotation in the same direction, the acceleration required for the next rotation can be suppressed, thereby reducing the current consumption of the electric motor 2.

[0035] (Examples) The selvage forming apparatus 1 of this embodiment uses a three-phase driven permanent magnet synchronous motor as the electric motor 2, and is used for forming selvages on a loom. When the electric motor 2 is rotated at a constant speed in the same direction, the average rotational speed is 0.5 times the loom speed. On a loom, the surface temperature is specified to be 67°C or less to prevent burns. For example, when the upper limit of the operating environment temperature is 40°C, the temperature rise of the selvage forming apparatus 1 must be kept below 27°C. The average power output of the selvage forming apparatus 1 can be approximated by the temperature rise.

[0036] Simplified equations of motion for a rotating system show that acceleration is proportional to torque (torque is proportional to current). In this case, the average power required for acceleration is proportional to torque and inversely proportional to acceleration time. Therefore, the average power of the electric motor in a loom has a positive correlation with the square of the current value and the temperature rise value. Furthermore, the average power is proportional to the square of the loom speed in the loom equipped with the selvage forming device 1, and also proportional to the square of the residence time ratio in the rotation period of the electric motor 2. The number of repetitions of rotation in the same direction has little effect on the average power. From these facts, by reducing the residence time ratio in the rotation period of the electric motor 2, the average power can be kept within a desired range. In other words, by reducing the residence time ratio in the rotation period of the electric motor 2, the temperature rise value can be kept within a desired range. With this configuration, the loom speed can be increased compared to conventional machines, and it can be applied to looms with a maximum speed of 2000 rpm.

[0037] (Current limiting table) When the dwell time ratio is constant and only the dwell period is changed in accordance with the loom speed, for example, when the loom speed doubles and the dwell period becomes 0.5 times, the initial current limit table sets the current limit value to 4 times the square of the loom speed. In practice, an offset is made to take into account the effect of the friction load rate. In addition, by increasing the current limit value to 1.05 to 1.2 times during reversal, the reversal operation can be completed within the desired time even if the electric motor 2 overruns.

[0038] By setting the residence time ratio to 50% or less, it is possible to reduce the current value during movement while ensuring sufficient movement time in the loom. By setting the residence time ratio to 25-50%, it is possible to prevent temperature rise associated with high current during movement. More preferably, the residence time ratio should be set to 25-40%.

[0039] Figure 13 is a schematic graph showing an example of setting the current limit table according to this embodiment. A reference example is given when the dwell time ratio in the rotation cycle of the electric motor 2 is 57%. Example 1 is when the dwell time ratio is 33%. Example 2 is when the dwell time ratio is 40%. Example 3 is when the dwell time ratio is 50%. Figure 13 shows the relationship between the loom speed and the current limit value in these cases. By adopting the current limit value according to the current limit table provided for each dwell cycle in accordance with the loom speed, it is possible to reduce the current value during movement while ensuring sufficient movement time in the loom.

[0040] (Speed ​​profile) As described above, the control unit 9 prefers that the residence time in the ear-forming device 1 during rotation in the same direction be greater than 25% and less than 50% of the rotation period. Figure 14 is a schematic graph showing an example of setting the speed profile according to this embodiment when the loom speed is 1250 rpm. A comparative example is when the residence time ratio in the rotation period of the electric motor 2 is 33% and reversal is not considered. Example 5 is when the residence time ratio is 33% and reversal is considered. Example 6 is when the residence time ratio is 26% and reversal is considered. By using a speed profile like that of Example 5 or Example 6, it is easy to suppress the temperature rise. By using a speed profile like that of Example 6, it is easy to repeatedly accelerate, then decelerate, then reverse the direction and repeat the same acceleration, constant speed, and deceleration operation, and then repeat this forward rotation and reversal operation, while suppressing the temperature rise and the amount of work.

[0041] According to the above embodiment, the operation of repeatedly accelerating, maintaining a constant speed, and decelerating, then reversing direction and repeating the same acceleration, constant speed, and deceleration operation, and further repeating this forward rotation and reversal operation, can be performed with high precision and high speed. The drive mechanism of this embodiment is suitable for applications that require moving objects with small load torque, such as threads and RGB filters, at high speeds. Note that the above drive mechanism may be modified as appropriate depending on the application. [Explanation of symbols]

[0042] 1. Selvedge forming device for looms 2 Electric motor 3 Laura, 3a Sleeve 4 Sensor unit, 4a Circuit board 5 rotors 6 Stator core, 6a Salient pole section 7 Inverter 8, 8u, 8v, 8w winding 9. Control Unit 10 Drive mechanism 15 Casing, 15a Base, 15b Cover 19 screws, 19a collar Ho Magnetic Sensor (Origin Sensor) He magnetic encoder Hu Magnetic Sensor (First Hall Element) Hv magnetic sensor (second Hall element) Hw Magnetic Sensor (Third Hall Element) K1 Electric Angle K2 mechanical angle M1 Origin Magnet M2 Rotor Magnet N1 selvage thread P1 axis T1 Dwelling period during rotation in the same direction T2 Reversal Period U1 First current limit value U2 Second current limit value U3 Third current limit value

Claims

1. The system comprises an electric motor, an inverter that drives the electric motor, and a control unit that controls the inverter, wherein the electric motor alternately rotates in the forward direction and in the reverse direction, and the control unit makes the dwell time when the electric motor reverses direction greater than the dwell time when the electric motor rotates in the same direction. A drive mechanism characterized by the following.

2. The control unit sets the minimum speed during the dwell period when rotating in the same direction to 0.1 to 0.9 times the maximum speed during the dwell period when reversing direction. The drive mechanism according to claim 1, characterized by the following:

3. The control unit makes the second proportional gain during the dwell time in the reversal phase greater than the first proportional gain during the dwell time in the same direction rotation phase. The drive mechanism according to claim 1, characterized by the following:

4. The electric motor comprises a casing, three or more rollers arranged at predetermined intervals in the casing, a rotor supported by the rollers, a plurality of rotor magnets built into the rotor, a stator core built into the casing, and a magnetic encoder for detecting the rotor magnetic poles of the rotor magnets. The control unit controls the speed of the electric motor using the rotor magnet position signals detected by the magnetic encoder. The drive mechanism according to claim 1, characterized by the following:

5. An origin magnet is provided on the rotor, a magnetic sensor for detecting the origin magnetic pole of the origin magnet is provided on the casing, and the control unit controls the rotation period of the electric motor using the origin magnet position signal detected by the magnetic sensor. The drive mechanism according to claim 4, characterized by the following:

6. A selvedge forming apparatus for a loom, comprising the drive mechanism described in any one of claims 1 to 5.

7. The drive mechanism comprises an electric motor, an inverter for driving the electric motor, and a control unit for controlling the inverter, and is configured to alternately repeat the operation of forward rotation and reverse rotation, and the control unit makes the dwell time when the electric motor reverses direction longer than the dwell time when the electric motor rotates in the same direction. A selvedge forming device for looms, characterized by the following features.

Images