JP2611223B2 - sewing machine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sewing machine, and more particularly, to a control structure of a sewing machine motor for determining a reference position of a cloth thickness.

(Prior Art) Conventionally, a cloth thickness detector is provided in relation to a presser bar, and a work cloth support surface on which no work cloth is placed is set as a reference position, and the work cloth is placed on the reference position and the work cloth support surface. 2. Description of the Related Art A sewing machine that detects a cloth thickness based on a movement amount of a presser bar between the work cloth and an upper surface position of the work cloth is known.

(Problems to be Solved by the Invention) In this type of sewing machine, if the height of the presser bar located on the work cloth support surface is changed by replacing the work clamp, feed dog, needle plate, etc. Accordingly, it is necessary to reset the cloth thickness reference position. However, according to the conventional sewing machine, the setting of the reference position and the driving of the sewing machine are irrelevant. Therefore, when the work cloth supporting surface is changed, the sewing machine motor is operated by manually operating the foot pedal without resetting the reference position. If is activated, incorrect cloth thickness data is collected. Therefore, in particular, in a sewing machine configured to control the tension of the upper thread based on the cloth thickness data, there is a problem that an inappropriate tension is applied to the upper thread and a defective stitch is formed. . In addition, for example, the needle plate is often replaced with a needle plate having a different thickness so as to obtain an optimum amount of protrusion of the feed dog according to the properties of the work cloth.

Configuration of the Invention (Means for Solving the Problems) In order to solve the above problems, the present invention provides a sewing machine frame having a work cloth support surface, a sewing machine motor, and driving of the sewing machine motor based on manual operation. Stitch forming means for forming a stitch on a work cloth with the rotation of the sewing machine motor, and a raising and lowering position of a presser bar having a cloth presser. Detecting means for detecting, and a first value detected by the detecting means when the work clamp is disposed on the work cloth support surface in a state where the work cloth is not placed on the work cloth support surface. And a second value detected by the detection means when the work clamp is placed on the work cloth with the work cloth placed on the work cloth support surface, and the cloth thickness is calculated. Calculation means for performing the calculation and the calculated cloth And control means for controlling the tension of the upper thread in response to said up detecting means detects said first value is characterized in that the disabling the operation of said drive control means.

(Operation) According to the above solution, when the work cloth is set on the work cloth support surface, the cloth thickness is calculated, and accordingly, the upper thread tension can be controlled to an optimum value and the cloth thickness can be calculated. Since the sewing machine motor is not started until the first value is detected, there is no possibility that a stitch will be formed under the needle thread tension based on incorrect cloth thickness data.

(Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the arm portion 1a of the sewing machine frame 1
A main shaft 2 is rotatably supported inside, and a pulley 3 attached to the right end thereof is connected to a sewing machine motor 5 via a belt 4. A needle bar 7 is supported on the head 6 of the arm portion 1a so as to be able to move up and down, and a needle 8 is attached to a lower end thereof. A lower shaft 9 operatively connected to the main shaft 2 is provided in the bed 1b of the sewing machine frame 1, and a thread catcher 10 is mounted on the lower shaft 9 so as to be located below the needle 8. . With the rotation of the sewing machine motor 5 and the main shaft 2, the stitch forming means including the needle 8 and the thread catcher 10 causes
A stitch is formed on the work cloth W (see FIG. 2) placed on the work cloth support surface 11 including a needle plate (not shown) and the like on 1b.

A presser bar 12 is supported on the head 6 at the back of the needle bar 7 so as to be able to move up and down, and a cloth presser 13 is attached to a lower end thereof.
A rack 12a is formed on the presser bar 12, and the head 6
Inside, an encoder 14 as a detection means having a pinion 14a engaged with the rack 12a is installed. Then, as shown by a chain line in FIG. 2, a first value t ₁ is detected by a signal of the encoder 14 when the work clamp 13 is placed on the work cloth support surface 11 on which the work cloth W is not placed. As well as
As shown by a solid line in the figure, the encoder when the work clamp 13 is placed on the work cloth W placed on the work cloth support surface 11
The second value t ₂ is detected by the 14 signals. Then, the thickness of the workpiece cloth W is adapted to be calculated by the difference between the first value t ₁ and the second value t _2.

An operation knob 15 for setting the sewing pitch of the work cloth by operating a pitch adjusting mechanism (not shown) is provided on the pillar 1c of the sewing machine frame 1 and detects the set sewing pitch. Detector 16 is provided in connection with the pitch adjusting mechanism.

A balance 17 is provided on the front surface of the head 6 so as to be vertically movable, and a pair of left and right thread guides 18 and 19 is provided below the balance 17.
Below the right thread guide 19, there is provided a movable thread guide 20 which is lifted and lowered integrally with the presser bar 12. On the jaw 21 of the head 6 on the right side of the movable thread guide 20, an upper thread feeding device 22 for controlling the tension of the upper thread T in accordance with the cloth thickness data calculated by the CPU 42 described later is installed. The needle thread feeding device 22 has a servo motor 23 built in the jaw portion 21 and an output shaft 24 of the servo motor 23 so as to be located on the front surface of the jaw portion 21.
, And a thread take-up spring 26 located around the thread take-up body 25.

A guide piece is provided on the head 6 above the needle thread feeding device 22.
Pretensioner with 27, fixing part 28 and pressing part 29
30 is installed. The upper thread T from a thread supply source (not shown) is supplied to a pretensioner 30, a spool 25, and a thread take-up spring.
26, movable thread guide 20, right thread guide 19, balance 17, and left thread guide
The needle 18 is supplied to an eye (not shown) of the needle 8 via the pin 18.

A thread cutting device 31 for cutting the upper thread T after forming the stitch is arranged in the bed 1b. This thread cutting device 31
Is composed of a fixed blade 32 and a movable blade 33 located near the yarn wheel catcher 10, and a thread cutting solenoid 34 (see FIG. 3) for operating the movable blade 33 to perform a thread cutting operation.

A foot pedal 36 is disposed below the sewing machine frame 1 as drive control means that can be manually operated. And
When the foot pedal 36 is depressed forward, the sewing machine motor 5 is driven at a speed corresponding to the depressed amount, and when the pedal is returned to the center state after depressing the front, the rotation of the sewing machine motor 5 is stopped and the needle 8 is moved to the bottom dead center. In addition to outputting a needle stop signal for stopping the sewing machine, a thread trimming signal for exciting the thread trimming solenoid 34 is output at the time of a rear stepping operation.

A detection object 37 is provided on the pulley 3 so as to be integrally rotatable, and the arm portion 1a is opposed to the detection object 37.
A needle position detector 38 composed of a light emitting / receiving element is fixed, and the needle position detector 38 outputs a needle down signal, a needle up signal, and the like as the main shaft 2 rotates.

On the operation panel 39 provided on the front of the arm 1a,
A reference setting key 40 and an LED display unit 41 for confirming the operation state are provided. Detecting means is constituted by the reference setting key 40 and the encoder 14 and the like, and a value detected by the encoder 14 when the work clamp 13 is arranged on the work cloth support surface 11 in a state where the reference setting key 40 is operated, is a first value t _1.

As shown in FIG. 3, a central processing unit (CPU) 42 receives various signals from the encoder 14, the pitch detector 16, the foot pedal 36, the needle position detector 38, and the reference setting key 40, and Sewing machine motor 5, servo motor
23, a drive or stop signal is output to the thread cutting solenoid 34 and the LED display unit 41. CPU42 constitutes the calculation means calculates the cloth thickness from a first value t ₁ and the second value t ₂ Metropolitan detected by the encoder 14. The CPU 42 constitutes a control means together with the upper thread feeding device 22, and drives the servo motor 23 to feed out the upper thread T in a thread amount according to the cloth thickness data and the pitch data, thereby adjusting the tension of the upper thread T appropriately. It is controlled to a value.

Further, the CPU 42 invalidates the operation of the foot pedal 36 as the drive control means until the first value t ₁ is determined, and even if the foot pedal 36 is operated at this time, the sewing machine motor 5 Is controlled not to be activated. In addition, CPU4
2, a read only memory (ROM) 43 and a random access memory (RAM) 44 are connected. The ROM 43 stores a control program for the entire sewing machine. The RAM 44 stores sewing pitch data and thread amount data calculated based on the pitch data and the cloth thickness data.

 The operation of the sewing machine having the above configuration will be described.

When the power is turned on to the sewing machine, the program shown in the flowchart of FIG. 4 is started under the control of the CPU 42, and firstly waits for the operation of the reference setting key 40 (step S
1) While this is OFF, the LED display section 41 blinks (step S2), and the operation of the foot pedal 36 is invalidated (step S3). Therefore, even if the foot pedal 36 is operated in this state, the sewing machine motor 5 is not started.

When the reference setting key 40 is turned on, the LED display section 41 is lit continuously (step S4), and the operation of the foot pedal 36 is activated (step S5). Is done. Then, the work clamp 13 is
Is placed on the work cloth supporting surface 11 on which the needle is not placed (the position indicated by the dashed line in FIG. 2), and when the needle down signal from the needle position detector 38 is confirmed (step S6), the encoder 14
The first value t ₁ is detected based on the signal from
S7), the cloth thickness is stored as 0 in the RAM 44.

Workpiece cloth W is placed on workpiece cloth supporting surface 11 after detection of the first value t _1. Then, when the foot pedal 36 is operated forward and a sewing machine start signal is generated from the foot pedal 36 (step S8), the spindle 2 is rotated. In this state, a needle down signal is confirmed (step S9), and pitch detection is performed. The sewing pitch is detected based on the signal from the device 16 (step S1).
0), a second value t ₂ based on a signal from the encoder 14 is detected. The cloth thickness t is calculated by the difference between the second value t ₂ of the first value t ₁ Toko. (Step S11) The value of the cloth thickness t is compared with 0 (Step S12), and the cloth thickness t
Is zero, it is determined that the work cloth W is not placed on the work cloth support surface 11, and the servomotor 23 and the sewing machine motor 5 of the upper thread feeding device 22 are stopped, respectively (steps S13 and S14). ), And waits for the sewing machine start signal again (S8).
In this way, the operation of the sewing machine in a state where the work cloth W is not set is prevented, so that both damages caused by contact between the feed dog (not shown) and the presser foot 13 can be prevented, and the upper thread T Is not unnecessarily fed out.

If the value of the cloth thickness t is not equal to 0, the number of pulses generated by the encoder 14 corresponding to the maximum moving distance of the presser bar 12, for example, 150, and the number of pulses of the cloth thickness t are compared (step S1).
5) If the encoder 14 generates an abnormal signal exceeding 150 due to noise or the like, the LED display section 41 blinks as described above (step S2), and the operation of the foot pedal 36 is invalidated. (Step S3). In this case, by operating the standard setting key 40 (step S1), and since the sewing machine motor 5 unless you set the first value t ₁ again is not activated, the poor seam based on the erroneous fabric thickness data form Can be avoided.

If the pulse number of the cloth thickness t is 150 or less, it is determined to be normal cloth thickness data, and the thread amount of the upper thread T required for the first stitch is determined based on the cloth thickness data and the sewing pitch data. After the calculation (Step S16), the servomotor 23 is driven (Step S17), and the upper thread T of the calculated thread amount is fed out to the needle 8 side with the rotation of the bobbin 25, whereby the cloth thickness t
Is applied to the upper thread T. Therefore, there is no possibility that a defective stitch is formed on the work cloth W in the subsequent stitch formation.

By repeating the above processing, predetermined sewing is completed, and when a thread trimming signal due to the rear stepping operation of the foot pedal 36 is confirmed (step S19), the upper thread T is cut by the operation of the thread trimming device 31. After that (step S20), the series of programs ends.

In the above-described embodiment, the tension of the upper thread T is controlled by the upper thread feeding device 22 having a motor.
The same operation and effect as described above can be achieved even when the upper thread tension is controlled using a known thread tension device having a solenoid or the like.

Effects of the Invention As described in detail above, according to the present invention, when the work cloth is set on the work cloth support surface, the cloth thickness is detected, and accordingly, the upper thread tension can be controlled to an optimum value, and for up to a first value t ₁ for calculating the thickness is determined sewing machine motor is not activated, the problem that defective stitches are formed under a needle thread tension based on erroneous fabric thickness data It is possible to eliminate the stitch and always obtain a good seam with tight thread.

[Brief description of the drawings]

FIG. 1 is a front view of a sewing machine showing one embodiment of the present invention, FIG. 2 is an enlarged front view showing a configuration around a presser bar, FIG. 3 is a block diagram showing a control circuit of the sewing machine, 4th
The figure is a flowchart showing the operation. In the figure, 1 is a sewing machine frame, 5 is a sewing machine motor,
Reference numeral 8 denotes a needle, 10 denotes a thread catcher, 11 denotes a work cloth support surface, 14 denotes an encoder serving as a detecting means, 22 denotes an upper thread feeding device which constitutes a control means, 23 denotes a servomotor, and 36 denotes a drive control means. A foot pedal, 40 is a reference setting key constituting detection means together with the encoder 14, 42 is a CPU constituting calculation means and control means, T is an upper thread, and W is a work cloth.

Claims (1)

(57) [Claims] 1. A sewing machine frame (1) having a work cloth support surface (11), a sewing machine motor (5), and drive control means (36) for driving the sewing machine motor (5) based on manual operation. A stitch forming means for forming a stitch on the work cloth (W) with the rotation of the sewing machine motor (5), the stitch forming means including a needle (8) and a thread catcher (10); Detecting means (14, 40) for detecting the elevation position of a presser bar (12) having a work cloth (W) on a work cloth support surface (11) when the work cloth (W) is not placed on the work cloth support surface (11). (13) is the work cloth support surface (11)
When the work cloth (W) is placed on the work cloth support surface (11) with the first value (t ₁ ) detected by the detection means (14, 40) when the work cloth (W) is placed on the work cloth (W). The cloth foot (13)
Calculating means (42) for calculating a cloth thickness based on a difference from a _second value (t ₂ ) detected by the detecting means (14, 40) when is disposed on the work cloth (W); Control means (22, 42) for controlling the tension of the upper thread in accordance with the calculated cloth thickness, wherein the detection means (14, 40) is adapted to detect the first value (t ₁ )
The operation of the drive control means (36) is invalidated until the operation is detected.