BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to an apparatus for determining the validity of an
origin search operation in which the apparatus receives a signal from a sensor while
driving a motor dedicated to a moving member and determines a rotational position
of the dedicated motor that corresponds to a mechanical origin of the moving member
on the basis of the received signal. The validity of the origin search operation is
determined by comparing one of an output period and a no-output period of the sensor
signal received in the origin search operation with a predetermined allowance.
2. Description of the Related Art
[0003] According to the above-described publications, in the origin search operation, the
proximity sensor may output an incorrect signal due to noise or dust or an intermittent
signal due to vibration of the proximity sensor itself or vibration of the detected
object, such as the swing lever and heald frame, relative to the proximity sensor.
If the mechanical origin is determined on the basis of such an abnormal signal, the
motor dedicated to the heald frame is driven with a phase shifted from the phase of
the main shaft of the loom when the operation of the loom is started. This leads to
malfunction of the loom or defects in woven cloth.
SUMMARY OF THE INVENTION
[0004] Accordingly, an object of the present invention is to provide a control apparatus
for a moving member that is included in a loom and driven by a dedicated motor in
synchronization with a main shaft of the loom, the control apparatus determining whether
or not an origin search operation has been normally performed.
[0005] A control apparatus for a moving member of a loom and a sensor that detects the presence
of the moving member at a predetermined position are included in the loom. The moving
member is driven by a dedicated motor that is provided separately from a main motor
of the loom. The control apparatus performs an origin search operation in which the
control apparatus receives a signal from the sensor while driving the dedicated motor
and determines a rotational position of the dedicated motor that corresponds to a
mechanical origin of the moving member on the basis of the received signal. The control
apparatus determines the validity of the origin search operation by comparing one
of an output period and a no-output period of the signal from the sensor with a predetermined
allowance in the origin search operation.
[0006] The above-described period may be determined in terms of rotational angle that represents
a rotational position of the dedicated motor or in terms of time.
[0007] According to the present invention, if an abnormal signal is output from the sensor
in the origin search operation, the output period or the no-output period will be
out of an allowable range defined by the allowance and the operator can be informed
of the origin search error. Accordingly, the loom is prevented from being operated
under the condition that the phase of the dedicated motor and the phase of the main
shaft are shifted from each other.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008]
Fig. 1 is a side view illustrating the main part of an electric shedding device;
Fig. 2 is a block diagram of a control apparatus included in the electric shedding
device;
Fig. 3 is a diagram illustrating amplitudes of a swing lever, which functions as a
moving member, and the relationship between a sensor and a detected portion;
Fig. 4 is a diagram illustrating a sensor signal;
Fig. 5 is a diagram illustrating sensor signals and the relationship between the rotational
angle of a drive motor and the vertical displacement of a heald frame;
Fig. 6 is a flowchart of an origin search operation and determination of its validity
performed by the control apparatus; and
Fig. 7 is another flowchart of an origin search operation and determination of its
validity performed by the control apparatus.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0009] The present invention may be applied to devices included in a loom and having moving
members driven by dedicated motors that are provided separately from a main motor
of the loom. In a typical loom, an electric shedding device and an electric selvage
device are examples of such devices. In a first embodiment described below, the present
invention is applied to an electric shedding device according to the above-mentioned
Japanese Unexamined Patent Application Publication No. 2004-324033. In a second embodiment described below, the present invention is applied to an electric
shedding device according to the above-mentioned
Japanese Unexamined Patent Application Publication No. 9-111576.
First Embodiment
Device Structure
[0011] Fig. 1 illustrates the main part of the electric shedding device 10 included in a
loom. The electric shedding device 10 includes a plurality of heald frames 11 that
function as moving members of the loom. A drive motor 12 is provided separately from
a main motor (not shown) for driving a main shaft of the loom as a motor dedicated
to each heald frame 11. Although the electric shedding device 10 includes a plurality
of drive motors 12 for a plurality of heald frames 11 in practice, only one heald
frame 11 and one drive motor 12 are shown in Fig. 1.
[0012] An output shaft of the drive motor 12 is connected to an incremental encoder 13,
and the rotation of the output shaft of the drive motor 12 is reduced in speed by
a speed reduction device 14 and is transmitted to a disc shaft 16 of a crank disc
15 to drive the corresponding heald frame 11. According to the present embodiment,
the reduction ratio of the speed reduction device 14 is determined such that the heald
frame 11 moves up and down once when the drive motor 12 rotates five turns.
[0013] The rotation of the crank disc 15 is converted into a swinging movement of a swing
lever 21 by an eccentric shaft 17 of the crank disc 15, a crank rod 18 connected to
the eccentric shaft 17, and a connection shaft 20 of a connecting member 19. The swing
lever 21 has a triangular shape and is rotatably supported on a loom frame 23 by a
lever shaft 22 at a substantially central position thereof. An arm portion 24 of the
swing lever 21 is connected to the connecting member 19 such that the connecting position
thereof can be adjusted.
[0014] The swing lever 21 has a projecting portion that is connected to one end of the heald
frame 11 with two pins 25 and a connecting rod 26 having an adjustable length. In
addition, the swing lever 21 also has another projecting portion that is connected
to the other end of the heald frame 11 with a pin 27, a connecting bar 28, and a unit
of a swing lever, two pins, and a connecting rod (not shown) disposed at the other
end. Accordingly, the heald frame 11 and the other heald frames that are not shown
in the figure are moved vertically by the rotating force of the respective drive motors
12, thereby performing a shedding motion corresponding to a weave structure in synchronization
with the rotation of the loom main shaft (not shown) that is driven independently
of the heald frames.
[0015] The shed size of the heald frame 11 can be changed by adjusting the position at which
the connecting member 19 is attached to the arm portion 24 of the swing lever 21.
More specifically, the shed size of the heald frame 11 is increased as the arm length
is reduced by moving the position at which the connecting member 19 is attached toward
the lever shaft 22, and is reduced as the arm length is increased by moving the position
at which the connecting member 19 is attached away from the lever shaft 22.
[0016] The swing lever 21 has an arc-shaped detected portion 31 that extends along the reciprocating
direction of the swing lever 21. The swinging movement of the detected portion 31
is detected by a proximity sensor 30 as a vertical position of the heald frame 11.
The sensor 30 is attached to a shaft support 29 provided on the loom frame 23 with
a bracket 32 and faces the detected portion 31 with a predetermined gap therebetween.
[0017] Fig. 2 illustrates the structure of a control apparatus 33 of the electric shedding
device 10. An output signal from the encoder 13 is input to a counter 34, and a count
output signal from the counter 34 and a signal from the sensor 30 are input to a computing
unit 35 included in the control apparatus 33. The computing unit 35 includes a clock
pulse generator 37 as necessary. An output from the computing unit 35 is transmitted
to a drive motor controller 36 in synchronization with the operation of the loom.
The drive motor controller 36 receives the output from the computing unit 35 and controls
the rotation of the drive motor 12. The control apparatus 33 is connected to a setter
38 and a display 39. The setter 38 is used to set input data and the display 39 displays
the input data and control data so that the input data and the control data can be
checked visually.
[0018] Fig. 3 shows the relationship between the sensor 30 and the movement of the detected
portion 31. Referring to Fig. 3, although the detected portion 31 moves along the
same arc irrespective of whether the amplitude is set to a minimum value (small shedding
motion) or to a maximum value (large shedding motion) in practice, two arcs having
different radii are displayed for convenience of explanation. The detected portion
31 has a relatively long arc shape that extends along the reciprocating direction
so that the detected portion 31 can move close to the sensor 30 and be detected by
the sensor 30 irrespective of whether the amplitude of the swing lever 21 is set to
a minimum value (small shedding motion) or to a maximum value (large shedding motion).
[0019] As shown in Fig. 3, the detected portion 31 has a relatively long arc shape that
extends along the reciprocating direction of the swing lever 21. Accordingly, both
when the heald frame 11 performs a small shedding motion and a large shedding motion,
the sensor 30 is turned on and continuously outputs a signal while the heald frame
11 is at one of the maximum opening positions (limit positions) and is turned off
otherwise.
[0020] Fig. 4 shows the manner in which the signal from the sensor 30 is turned on and off
with time t. The signal is turned on during an output period in which the detected
portion 31 is being detected and is turned off otherwise.
[0021] The shed size of the heald frame 11 can be changed by adjusting the position at which
the connecting member 19 is attached to the arm portion 24 of the swing lever 21.
However, even when the shed size is changed, the output period (ON period) of the
sensor 30 can be determined with respect to one of the maximum opening positions.
[0022] Thus, the amount of movement of the swing lever 21 and the maximum opening positions
vary depending on the shed size. However, when the sensor 30 is placed at a position
with enough allowance, for example, at the midpoint between the top and bottom maximum
opening positions (so-called cross position), the signal from the sensor 30 can be
turned on at one of the maximum opening positions and off at the other irrespective
of the setting of the shed size between maximum and minimum values.
Movement of Heald Frame 11 and Sensor 30 in Origin Search Operation
[0023] Fig. 5 shows the relationship between the rotation of the drive motor 12, the shedding
motion (vertical displacement) of the heald frame 11, and the signal from the sensor
30 in a weaving process. In Fig. 5, the horizontal axis shows the rotational angle
of the drive motor 12 that represents time and the vertical axis shows the displacement
of the heald frame 11. The rotation of the drive motor 12 is expressed as a sine curve
for convenience and the vertical displacement of the heald frame 11 is determined
on the basis of the swinging movement of the swing lever 21 in practice. In the sine
curve showing the rotation of the drive motor 12, one period corresponds to one turn
of the drive motor 12. Although the horizontal axis shows the rotational angle in
Fig. 5, it may also show time, similar to Fig. 4.
[0024] As described above, since the speed reduction device 14 is provided, the heald frame
11 moves up and down once while the drive motor 12 rotates five turns. More specifically,
the heald frame 11 leaves a bottom dead center (the bottom maximum opening position),
reaches a top dead center (the top maximum opening position that corresponds to a
rotation amount P0), and returns to the bottom dead center. When the heald frame 11
moves upward and reaches an approximate midpoint of the moving range of the heald
frame 11 at a rotation amount P1, the detected portion 31 enters a detecting area
of the sensor 30. Accordingly, the signal from the sensor 30 is turned on and is continuously
output. Then, when the heald frame 11 moves downward and reaches the approximate midpoint
of the moving range at a rotation amount P2, the detected portion 31 leaves the detecting
area of the sensor 30 and the signal from the sensor 30 is turned off. The rotation
amounts P0, P1, and P2 are detected as the numbers of counts of the counter 34, as
described below.
[0025] As indicated by circled numbers 1 and 2 in Fig. 5, the ON signal output from the
sensor 30 is approximately symmetric about the rotation amount P0 along the horizontal
axis representing the rotational angle. When the rotation amount is P0, the heald
frame 11, which functions as a moving member of the loom, is at the maximum opening
position. The circled number 1 shows the ON signal obtained from the sensor 30 when
a large shedding motion is performed and the circled number 2 shows the ON signal
obtained from the sensor 30 when a small shedding motion is performed.
Calculation of Rotation Angle Corresponding to Maximum Opening
[0026] Fig. 6 is a flowchart of an origin search operation according to the first embodiment.
In the first embodiment, the top dead center of the heald frame 11, that is, the rotation
amount P0 corresponding to the maximum opening, is determined as the mechanical origin.
In this case, the origin search operation (calculation of the rotation angle corresponding
to the maximum opening) is performed as described below.
[0027] When an operator turns on a power switch (not shown) of the loom and presses a synchronization
operation button (not shown) for the origin search operation, the control apparatus
33 starts the origin search operation. First, the number of counts of the counter
34 is cleared to 0 and the counter 34 is enabled. Then, the drive motor controller
36 starts the rotation of the drive motor 12 at a low speed (inching operation) to
move the heald frame 11 in the vertical direction (step 1).
[0028] While the drive motor 12 continues to rotate, the counter 34 counts each pulse of
the pulse signal output from the incremental encoder 13 connected to the drive motor
12 (step 2). When the number of pulses that corresponds to the number of turns of
the drive motor 12 reaches five, the counter 34 resets the number of counts to 0.
[0029] When the signal from the sensor 30 is switched from OFF to ON (step 3), the computing
unit 35 receives the number of counts, i.e., the rotation amount P1 from the counter
34 (step 4). In Fig. 6, the parenthesized expressions in steps 3 and 6 correspond
to the case in which allowances are set for a no-output period, as will be described
in more detail below.
[0030] The counter 34 continuous to count the pulse signal from the encoder 13 (step 5).
Then, when the signal from the sensor 30 is switched from ON to OFF for the first
time since it has been turned from OFF to ON (step 6), the computing unit 35 receives
the number of counts, i.e., the rotation amount P2 from the counter 34 (step 7).
[0031] The computing unit 35 confirms the validity of the origin search operation (steps
8 and 9), and then calculates the middle rotation amount P0 between the rotation amounts
P1 and P2 as P0 = (P1 + P2)/2. Thus, the rotation amount P0 of the drive motor 12
corresponding to the maximum opening is determined, and this rotation amount P0 is
used as the mechanical origin for achieving synchronization with the loom main shaft
(step 10). When the origin search is normally performed, the display 39 displays that
normal origin search has been performed (step 11) and the origin search operation
is normally finished. Thus, the electric shedding device 10 and the loom main shaft
can be synchronized with each other by determining the rotation amount (rotational
position) of the drive motor 12 that corresponds to the mechanical origin of the heald
frame 11 that functions as a moving member.
Determination of Validity of Origin Search Operation
[0032] The determination of validity of the origin search operation is performed in steps
8 and 9 in the above-described process of calculating the rotation angle corresponding
to the maximum opening and in steps 13 and 14.
[0033] When the top dead center of the heald frame 11 is determined as the origin in the
origin search operation, allowances defining an allowable range for the output period
(ON period) of the signal from the sensor 30 are input by the setter 38 and set in
the control apparatus 33 (computing unit 35) in advance. The allowances serve to limit
a range of the rotation amount during the output period (ON period) and are set in
accordance with the shed size that is set mechanically. As is clear from the above,
the allowances may also be set for the no-output period (OFF period).
[0034] If, for example, one pulse is output each time the drive motor 12 is rotated by 1°
and the shed size of the heald frame 11 is 142 mm, an allowable range for the output
period (ON period) is set to 785 ± 50 pulses (see circled number 1 in Fig. 5). If
the shed size of the heald frame 11 is 64 mm, the allowable range is set to 620 ±
50 pulses (see circled number 2 in Fig. 5).
[0035] After step 7 in Fig. 6, the computing unit 35 calculates an increase in the rotation
amount as P3 = |P1 - P2| in step 8. Then, the computing unit 35 determines whether
or not the increase P3 in the rotation amount is within the allowable range, that
is, whether or not 570 ≤ P3 ≤ 670 is satisfied if the shed size of the heald frame
11 is 64 mm (step 9). If the result of determination is Y (Yes), that is, if the increase
P3 in the rotation amount is within the allowable range, it is determined that the
detection result of the sensor 30 has no errors and the origin search operation has
been normally performed. Then, the process proceeds to step 10.
[0036] When the result of determination is N (No) in step 9, that is, when the increase
P3 in the rotation amount is out of the allowable range, it is determined that the
origin search operation is abnormal. The abnormal state of the origin search operation
is displayed on the display 39 as a result of the operation. The normal state of the
origin search operation may also be displayed on the display 39 if the origin search
operation is normal.
[0037] Although two allowances are set for each shed size in the first embodiment, only
one allowance may be set for each shed size. In such a case, the validity of the origin
search operation is determined on the basis of the relationship between the increase
P3 in the rotation amount and the allowance.
[0038] In the above-described operation, it may be difficult for a typical operator to set
the allowances in terms of the number of pulses of the encoder 13. Accordingly, a
maintenance staff, for example, may input the allowances with the setter 38. Alternatively,
the maintenance staff may input reference allowances in advance and the computing
unit 35 may automatically set the allowances in accordance with the shed size set
by the operator.
First Modification of First Embodiment
[0039] In the first embodiment, when the validity of the origin search operation is determined,
the number of pulses of the encoder 13 is counted. However, if the clock pulse generator
37 is installed in or attached to the computing unit 35 as shown in Fig. 2, the number
of clock pulses may also be counted. In such a case, as shown in Fig. 7, counting
of the number of clock pulses is started from 0 when the signal from the sensor 30
is switched from OFF to ON. Then, the time C1 elapsed until the signal is switched
from ON to OFF for the first time since it has been switched from OFF to ON is determined
and the validity of the origin search operation is determined on the basis of the
time C1. In this case, the allowances are set in accordance with the rotational speed
of the drive motor 12 in the origin search operation since the above-described time
C1 varies depending on the rotational speed of the drive motor 12. The allowances
may be changed automatically when the setting of the rotational speed of the drive
motor 12 is changed. Fig. 7 shows only the steps regarding the determination of validity
of the origin search operation. In this modification, the steps of the calculation
of rotational angle corresponding to the maximum opening are similar to those in the
first embodiment.
Second Modification of First Embodiment
[0040] In the determination of validity of the origin search operation according to the
first embodiment, the output signal from the encoder 13 that is connected to the drive
motor 12 may be directly input to the computing unit 35 as a count signal of the rotational
angle. The rotation amount is counted from 0 using the count signal after the signal
from the sensor 30 is switched from OFF to ON, and the rotation amount obtained at
the time when the signal is switched from ON to OFF for the first time since it has
been switched from OFF to ON is determined as the rotation amount P3.
[0041] In the first embodiment, if the bottom dead center of the heald frame 11 is determined
as the origin in the origin search operation, allowances for the no-output period
(OFF period) of the signal from the sensor 30 are set in advance. Then, the rotation
amounts P1 and P2 of the drive motor 12 that are respectively obtained when the signal
from the sensor 30 is switched from ON to OFF and when the signal is switched from
OFF to ON for the first time since it has been switched from ON to OFF are determined.
Then, the increase P3 in the rotation amount during the no-output period is calculated
from the rotation amounts P1 and P2, and the validity of the origin search operation
is determined on the basis of the increase P3 in the rotation amount. Then, the rotation
amount (rotational position) P0 of the drive motor 12 that corresponds to the mechanical
origin is calculated. The determination of validity of the origin search operation
based on the no-output period (OFF period) and the calculation of the rotation amount
(rotational position) P0 in the no-output period (OFF period) may also be applied
to the above-described first and second modifications.
Second Embodiment
[0042] As described above, the present invention may also be applied to the electric shedding
device according to
Japanese Unexamined Patent Application Publication No. 9-111576. The electric shedding device according to this publication has mechanisms (crank
mechanism and link mechanism) similar to those of the first embodiment. In this electric
shedding device, a predetermined position (distance) of a swing lever 21, which is
similar to the swing lever 21, in the swing area thereof is detected by a distance
detection sensor (height detection sensor). Alternatively, a predetermined position
(top dead center) of a heald frame is detected by a position detection sensor disposed
at the top dead center of the heald frame. In either case, the output signal (ON signal)
is obtained from the sensor while the heald frame is placed at the predetermined position,
that is, at the top dead center. Therefore, in either case, an allowance for the output
period (ON period) of the sensor is set in advance and is compared with the detected
output period to determine the validity of the origin search operation. If the no-output
period (OFF period) of the sensor is longer than the output period (ON period) due
to the adjustment of the sensor or the like, an allowance may be set for the no-output
period (OFF period).
[0043] The present invention may be applied not only to electric shedding devices of looms
but also to other devices, such as electric selvage devices, included in looms. In
an electric selvage device, rotating members through which selvage yarns are inserted
function as moving members. The rotating members are driven in synchronization with
a main motor of the loom by dedicated motors that are provided separately from the
main motor. Accordingly, sensors are disposed near the rotating members that function
as moving members, and rotational positions of the dedicated motors (output shafts)
corresponding to the mechanical origins are determined on the basis of signals obtained
from the sensors. The validity of the origin search operation is determined in the
process of determining the rotational position (searching the origin).