JPH0693941B2 - Cloth feeder for sewing machine - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a cloth feeding device for a sewing machine capable of continuously feeding a work cloth.

[Prior art]

Conventionally, there is known an automatic sewing machine in which a work cloth can be moved in XY directions which are relatively perpendicular to each other on a plane with respect to a sewing needle. One cycle W of the vertical movement of the needle of the automatic sewing machine is
As shown in FIG. 7A, the needle is divided into a needle up period in which the needle is above the predetermined position A above the needle plate and a needle down period in which the needle is below the predetermined position A. The detection that the vertical position of the needle has reached the predetermined position A is performed by detecting that the rotational phase of the upper shaft driven by the sewing machine motor that moves the needle vertically reaches a predetermined phase by a sensor. . Then, the relative movement of the needle of the work cloth with respect to the horizontal position (hereinafter, simply referred to as “cloth feed”) is as shown in FIG. (This period during which instantaneous feed is performed is called the "instantaneous feed period")
Done in. Further, the cloth feeding is stopped during a period other than the instantaneous feeding period in one cycle W of the vertical movement of the needle (hereinafter, this period in which the instantaneous feeding of the work cloth is stopped is referred to as "instant stop period"). B for needle up period, C for needle down period, TM for instantaneous feed period, TS for instantaneous stop period
Then, cycle W = needle up period B + needle down period C (1) cycle W = instantaneous feed period TM + instantaneous stop period TS ... (2) instantaneous feed period TM ≤ needle up period B ... (3) instantaneous stop period TS ≧ needle down period C (4) Thus, the cloth feed is an intermittent feed having the instantaneous stop period TS and the instantaneous feed period TM which are synchronized with the vertical movement of the needle. In this cloth feed control, the average cloth feed speed V in the instantaneous feed period TM (hereinafter referred to as "instantaneous feed speed") V is expressed by the following equation, where L (length) is the feed amount for each stitch. It V = 1 feed amount per stitch L / instantaneous feed period TM (5) Then, this instantaneous feed speed V is the rotation speed of the motor for driving the feed shaft, which is the cycle T ₀ (frequency F ₀ (= 1 /
T ₀ ), and the feed amount L of the work cloth for each stitch is controlled by giving the number P of command pulses for each stitch. Therefore, if the unit feed amount per command pulse is k, the feed amount per needle L = k × P (6) Instant feed period TM = cycle T ₀ × P (7) Instant feed speed V = L / (T ₀ × P) (8) = k / T ₀ (9) = k × frequency F ₀ (10)

[Problems to be Solved by the Invention]

However, in the conventional feed axis drive method, the frequency F ₀ (= 1 / T ₀ ) of the command pulse is 1 stitch when the sewing machine motor rotates at the maximum speed N ₀ regardless of the rotation speed N of the sewing machine motor. The feed of the maximum feed amount L ₀ per hit is fixed at a frequency such that it is completed at least within the above needle up period B. Therefore, as is apparent from the equation (10), the instantaneous feed speed V is a constant value that is determined only by the frequency F _{0 of the} command pulse, regardless of the rotation speed N of the sewing machine motor and the feed amount L for each stitch. Take Therefore, when the sewing machine motor is rotating at a constant speed, as is clear from the equations (6) and (7), the smaller the feed amount L per stitch is as shown in FIG. 4 (c). The command pulse number P per stitch decreases and the instantaneous feed period TM shortens. As shown in FIG. 4 (b), the feed amount L per stitch L
The larger the number, the larger the command pulse number P per stitch and the longer the instantaneous feed period TM. That is, if the ratio of the rotation speed of the upper shaft to the rotation speed of the sewing machine motor is q with respect to the rotation speed N (rps) of the sewing machine motor, then the rotation speed of the upper shaft is qN. W is expressed as W = 1 / qN (11). Therefore, when the rotation speed N of the sewing machine motor is constant, one cycle W of vertical movement of the needle is constant, and
The ratio R (= TM / W) of the instantaneous feed period TM to one cycle W of vertical movement of the needle varies depending on the feed amount L of each needle. On the other hand, when the feed amount L for each stitch is constant, the command pulse number P for each stitch is constant from equation (6). Therefore, even if the rotation speed N of the sewing machine motor decreases in relation to the sewing speed and the cycle W of one stitch becomes long as shown in FIG. 4 (d), conversely, the rotation speed N of the sewing machine motor becomes Rise to 4th
As shown in FIG. 7B, even if the cycle W of one needle is shortened, the cycle T _{0 of the} command pulse is constant, and as is apparent from the equation (7), the instantaneous feed period TM does not change. For this reason,
The ratio (TM / W) of the instantaneous feed period TM to the cycle W of one stitch changes according to the rotation speed N of the sewing machine motor. As described above, when the feed amount L per stitch or the rotation speed N of the sewing machine motor changes, the ratio R (= TM / W) of the instantaneous feed period TM to the cycle W of one stitch fluctuates greatly, resulting in intermittent cloth Since the feeding is emphasized, there is a problem that noise is generated and the quality of the sewn product is deteriorated due to damping at the stop position and mechanical vibration.

[Object of the Invention]

The present invention has been made to solve the above problems, and an object of the present invention is to continuously feed cloth regardless of the feed amount per stitch or the rotation speed of the sewing machine motor. To reduce noise and improve the quality of sewn products.

[Means for solving problems]

The configuration of the invention for solving the above problems is a cloth feeding device for a sewing machine having a motor that controls relative feed of a work cloth with respect to the needle, and a drive circuit that drives the motor in response to a command pulse signal, Reference signal generating means for outputting a reference pulse signal of a constant frequency, frequency dividing means for dividing the reference pulse signal according to a set division ratio, and outputting a command pulse signal to the motor drive circuit, and for each stitch Based on the product of the ratio of the command value of cloth feed amount to the maximum cloth feed amount per needle and the product of the ratio of the command value of the needle up / down movement frequency and its maximum frequency, the cloth feed amount per needle And a frequency division ratio that sets the frequency division ratio so that the number of command pulse signals corresponding to the cloth feed amount for each needle is evenly distributed to approximately one vertical cycle of the needle regardless of the frequency of the vertical movement of the needle. The ratio setting means is provided.

The command pulse output from the frequency dividing means of the present invention is approximately equal to one cycle W of the vertical movement of the needle, as shown in FIG. 3 (b).
The number of pulses P (= L / k) corresponding to the commanded feed amount L for each stitch is distributed to GW (1≈G ≦ 1). Here, the frequency of the reference pulse signal is F ₀ , its period is T ₀ ,
The maximum rotation speed of the sewing machine motor is N ₀ , the maximum frequency of vertical movement of the needle is qN ₀ , the minimum cycle of vertical movement of the needle is W ₀ , the maximum feed amount of the needle is L ₀ , and the maximum feed amount is 1 The maximum command pulse number per needle is P ₀ . Then, as described above, the frequency F of the command pulse for evenly distributing the command pulse number P within the period GW is obtained by the following equation. F = P / GW (12) = F ₀ · γ / G (15) However, α = P / P ₀ = L / L ₀ … (16) β ＝ W ₀ / W ＝ N / N ₀ … (17) γ ＝ α ・ β… ( 18), where α is the feed division ratio, β is the speed division ratio, and γ is the total division ratio. The present invention, as described above, the reference pulse signal of frequency F ₀ ,
When the speed is constant, the frequency is divided by the feed frequency dividing ratio α, when the feed amount for each stitch is constant, the frequency is divided by the speed frequency dividing ratio β, and when both are changed, the feed frequency dividing ratio α is changed. And the frequency division ratio β. Since the frequency is divided as described above, the frequency of the command pulse can be changed to change the instantaneous feed speed V in accordance with the feed amount L per needle or the vertical movement cycle W of the needle. Then, since the command pulse is divided substantially evenly within the approximately 1 vertical movement cycle of the needle, the macroscopic average feed speed of the work cloth becomes substantially equal to the instantaneous feed speed V. Then, the ratio R (= TM / W) of the instantaneous feed period TM to the cycle W of one stitch can be made equal to approximately 1 regardless of the feed amount per needle or the frequency of vertical movement of the needle. It is possible to continuously feed the work cloth even if the amount or the frequency of the vertical movement of the needle changes. Therefore, it is possible to reduce noise and improve the quality of sewn products.

【Example】

Hereinafter, the present invention will be described based on specific examples. FIG. 1 is a block diagram showing an electrical configuration of a cloth feeding apparatus according to a specific embodiment of the present invention. A ROM 2 storing a control program, a RAM 3 storing sewing data, output interfaces 21, 22, 23, and an input interface 25 are bus-connected to the CPU 1. The output interface 21 has an X-axis reference pulse generator 4 and a Y-axis.
The axis reference pulse generator 5 and the Z axis reference pulse generator 6 are connected, and the output interface 22 is connected to the X axis frequency divider 7
And a Y-axis frequency divider 8 are connected. Further, an X feed counter 26 and a Y feed counter 27 are connected to the output interface 23. The input interface 25 is connected to an external storage device 18 for loading sewing data into the RAM 3, an operation unit 19 for performing various operation inputs, and a needle position sensor 24 for detecting the vertical position of the needle. There is. The X-axis frequency divider 7 is connected to the X-axis servo amplifier 9 via the AND gate 28, and the Y-axis frequency divider 8 is connected to the Y-axis via the AND gate 29.
It is connected to the axis servo amplifier 10. A Z-axis servo amplifier 11 is connected to the Z-axis reference pulse generator 6. The output signal of the X feed counter 26 is input to one input terminal of the AND gate 28, and the output signal of the Y feed counter 27 is input to one input terminal of the AND gate 29. In the X feed counter 26, the feed amount Lx for each stitch in the X axis direction from the CPU 1 is set by the command pulse number Px, and the Y feed counter 27
, The feed amount Ly for each stitch in the Y-axis direction from the CPU 1 is set by the command pulse number Py. The set value of the X feed counter 26 is subtracted by the command pulse signal output from the X-axis frequency divider 7, and the set value of the Y feed counter 27 is subtracted by the command pulse signal output from the Y-axis frequency divider 8. . The X feed counter 26 outputs a high level signal to the AND gate 28 while the set value is a positive value, and the set value is 0.
A low-level signal is output to the AND gate 28 while it is a value or a negative value. Therefore, the AND gate 28 passes the command pulse output from the X-axis frequency divider 7 to the X-axis servomotor 9 until the pulse number becomes equal to the command pulse number Px per needle set in the X-feed counter 26. Let As a result, the X-axis motor 12 is rotated by the rotation angle corresponding to the commanded pulse number Px for each stitch. Similarly, the Y-feed counter 27 outputs a high level signal to the AND gate 29 while the set value is a positive value, and outputs a low level signal while the set value is a zero value or a negative value. Output to gate 29. Therefore, the AND gate 29 outputs the command pulse output from the Y-axis frequency divider 8 when the pulse number is Y.
Number of command pulses per needle set in the feed counter 27
The Y-axis servomotor 10 is passed until it becomes equal to Py.
As a result, the number of pulses commanded by the Y-axis motor 14 for each stitch
Rotate by the rotation angle corresponding to Py. Further, the X-axis servo amplifier 9 is connected to an X-axis motor 12 that drives the X-axis feed axis of the work cloth, and the Y-axis servo amplifier 10 is connected to the Y-axis that drives the Y-axis feed axis of the work cloth. A motor 14 is connected, and a sewing machine motor 16 for moving the needle up and down is connected to the Z-axis servo amplifier 11. In addition, the X-axis motor 12, the Y-axis motor 14, and the sewing machine motor 16 respectively have encoders 13, 15 for detecting the rotation angle of each motor,
17 is connected, and the pulse signals output from the encoders 13, 15, 17 are negatively fed back to the X-axis servo amplifier 9, the Y-axis servo amplifier 10 and the Z-axis servo amplifier 11, respectively. In addition, the upper shaft 30 operatively connected to the rotary shaft of the sewing machine motor 16
A needle position sensor 24 is provided to detect the rotation phase of the needle, and a timing signal is input to the input interface 25 when the needle reaches a predetermined position A above the needle plate. X-axis reference pulse generator 4, Y-axis reference pulse generator 5 and Z
The axis reference pulse generator 6 generates a reference pulse having a frequency set by the CPU 1. Further, the CPU 1 sets the feed division ratios αx and αy in the X-axis frequency divider 7 and the Y-axis frequency divider 8, and divides the reference pulse in accordance with the selected feed frequency division ratios to obtain it. Command pulse X
Output to the axis servo amplifier 9 and the Y axis servo amplifier 10. Next, the processing procedure of the CPU 1 will be described based on the flowchart of FIG. When the work cloth is set in the automatic sewing machine and the start switch of the operation unit 19 is operated, this program is executed in a cycle of one stitch. In step 100, the rotation speed N of the sewing machine motor 16 set by the speed dial of the operation unit 19 is read and compared with the rotation speed stored in the predetermined area of the RAM 3 in the next step 102, and the sewing machine motor 16 It is determined whether or not the set rotation speed has changed. At the time of initial setting when the power of the automatic sewing machine is turned on, the rotation speed stored in the predetermined area of RAM3 is cleared. Therefore, when this step is executed for the first time after the start switch is operated, the rotation speed N is always set. It is determined that it has changed, and the process proceeds to step 104. In step 104, the speed division ratio β, which is represented by the ratio N / N ₀ of the newly set rotation speed N to the maximum rotation speed N _0, is calculated. Then, in the next step 106, the speed division ratio β is set in the X-axis reference pulse generator 4, the Y-axis reference pulse generator 5, and the Z-axis reference pulse generator 6, and those reference pulse generators The reference pulse of the frequency of the reference frequency Fs (= β × F ₀ ) determined by the speed division ratio β is output. When it is determined in step 102 that the rotation speed N input from the speed dial has not changed, the process proceeds to step 108 without changing the setting of the reference frequency Fs. At step 108, it is judged whether or not the sewing data stored in the RAM 2 shown in FIG. 5 has been read and the sewing data has ended.
If it is determined that the sewing data has not ended, the X code and the Y code are read in step 110, and X is read in step 112.
The X-axis command pulse number Px corresponding to the feed amount Lx per needle in the axial direction and the Y-axis command pulse number Py corresponding to the feed amount Ly per needle in the Y-axis direction are read. Then, in step 114, it is determined whether or not the X-axis command pulse number Px is 0, and if it is determined that it is not 0, step
After shifting to 116, the feed division ratio of the X axis αx (= Px / P ₀ = Lx
/ L ₀ ) is calculated. If it is determined in step 118 that the Y-axis command pulse number Py is similar and not 0, the process proceeds to step 120 and in the same manner as step 116, the Y-axis feed frequency division ratio αy.
(= Py / P ₀ = Ly / L ₀ ) is calculated. Also, in step 114 and step 118, the X-axis command pulse number Px
Alternatively, when the Y-axis command pulse number Py is determined to be 0, the feed division ratio αx or αy is not set. Then, the routine proceeds to step 122, where it is determined whether or not a timing signal is detected from the needle position sensor 24. If a timing signal is detected, then the routine proceeds to step 124, where the X axis feed frequency division ratio αx and The Y-axis feed frequency division ratio αy is set in the X-axis frequency divider 7 and the Y-axis frequency divider 8, and in the next step 126, the X-feed counter 2
The command pulse numbers Px and Py corresponding to the feed amount per needle are set in the 6 and Y feed counters 27, respectively. On the other hand, if it is determined in step 108 that the sewing data has ended, the process moves to step 128, after thread cutting is executed, the operation is stopped, and in the next step 130, the sewing position is returned to the initial position. In the above embodiment, the frequency division of the pulse signal by the speed division ratio β according to the rotation speed of the sewing machine motor is performed by the frequency of the reference pulse signal output from the X-axis reference pulse generator and the Y-axis reference pulse generator. Is performed by changing the speed division ratio β according to the speed division ratio β.
Frequency of reference pulse signal output from axis reference pulse generator
With F ₀ fixed, with only the X-axis divider and the Y-axis divider,
You may make it divide. That is, in step 116 and step 120, the feed division ratios αx, αy and the speed division ratios βx, βy
The total frequency division ratios γx, γy may be set in consideration of both of the above. The feed amount is stored in the RAM 3 as sewing data for each stitch, but the feed amount per stitch may be set by a dial for setting the feed amount.

【The invention's effect】

The present invention includes a reference signal generating means for outputting a reference pulse signal having a constant frequency, and a frequency dividing means for dividing a reference pulse signal according to a set division ratio and outputting a command pulse signal to a motor drive circuit. Based on the product of the ratio between the command value of the cloth feed amount per needle and the maximum cloth feed amount per needle, and the product of the ratio between the command value of the vertical movement frequency of the needle and its maximum frequency Irrespective of the cloth feed amount and the vertical movement frequency of the needle, the number of command pulse signals corresponding to the cloth feed amount for each stitch is approximately 1
Since the frequency division ratio setting means for setting the frequency division ratio is provided so as to be evenly distributed in the upper and lower cycles, the frequency of the command pulse is changed to change the instantaneous feed speed by the feed amount or needle by needle. It can be changed according to the cycle of vertical movement of.
Since the command pulse is distributed substantially evenly within about one vertical movement cycle of the needle, the macroscopic average feed speed of the work cloth is
Since it is almost equal to the instantaneous feed speed, the ratio R (= TM / W) of the instantaneous feed period TM to the cycle W of one stitch can be made substantially equal to 1 regardless of the feed amount per needle or the frequency of needle vertical movement. It is possible to continuously feed the work cloth even if the feed amount for each needle or the frequency of vertical movement of the needle changes. Therefore, it is possible to reduce noise and improve the quality of sewn products.

[Brief description of drawings]

FIG. 1 is a block diagram showing the structure of a cloth feeding device of a sewing machine according to a specific embodiment of the present invention. FIG. 2 is a flow chart showing the processing procedure of the CPU of the cloth feeding device. FIG. 3 is a timing chart showing distribution of cloth feed command pulses in this embodiment. FIG. 4 is a timing chart showing distribution of command pulses in the conventional cloth feeding apparatus. FIG. 5 is an explanatory view showing the format of sewing data. 1 ... CPU, 4 ... X-axis reference pulse signal generator, 5 ...
Y-axis reference pulse signal generator, 6 ... Z-axis reference pulse signal generator, 7 ... X-axis divider, 8 ... Y-axis divider, 26 ...
… X feed counter, 27 …… Y feed counter

Claims (1)

[Claims] 1. A cloth feeding device for a sewing machine, comprising: a motor for controlling relative feed of a work cloth to a needle; and a drive circuit for driving the motor in response to a command pulse signal. Reference signal generating means for outputting, frequency dividing means for dividing the reference pulse signal according to a set division ratio, and outputting the command pulse signal to the moke drive circuit, and cloth feed amount for each stitch Based on the product of the ratio of the command value of the above and the maximum cloth feed amount per needle and the ratio of the command value of the vertical movement frequency of the needle and its maximum frequency, The frequency division ratio setting for setting the frequency division ratio so that the number of command pulse signals corresponding to the cloth feed amount for each stitch is evenly distributed to approximately one vertical cycle of the needle regardless of the vertical movement frequency. And a means for providing cloth for a sewing machine Equipment.