JPH1119358A - Device for controlling cloth holding pressure of sewing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent various cases of non-conformity from occurring by automatically varying a cloth holding pressure in accordance with the number of rotation and the phase of a sewing machine. SOLUTION: A cloth holding pressure is made controllable variably for example, in such a manner that the cloth holding pressure increases according to an increase in the number of rotation of a sewing machine under control by controlling a control current for regulating the torque of a holding force imparting means 1 which imparts the holding force to a cloth holder 6 in compliance with the number of rotation of the sewing machine. Thus it is possible to prevent the cloth holder 6 from increasingly jumping following the increase in the number of rotation of the sewing machine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling a presser foot pressure of a sewing machine.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. Sho 57-43785 and U.S. Pat. No. 5,551,361 disclose devices for controlling a presser pressure of a sewing machine. These presser foot pressure control devices include a sensor that detects the presser foot pressure, and a pressing force applying unit that presses the presser foot, such as a motor, an actuator such as a solenoid or a cylinder, and is detected by the sensor. The presser foot pressure is fed back, and the actuator is controlled based on the presser foot pressure so that the presser foot pressure during sewing becomes constant.

[0003] Further, a presser foot pressure control device that drives the above-described actuator by operating a manual switch by an operator to adjust the presser foot pressure, and a link mechanism that drives a solenoid by operating a knee switch by the operator. There is also known a presser foot pressure control device and the like which can adjust the presser foot pressure via the same.

[0004]

However, in the former presser foot pressure control device (in which the presser foot pressure is kept constant), the presser foot presser is controlled in accordance with, for example, the number of rotations of the sewing machine or the phase during one rotation of the main shaft of the sewing machine. The pressure cannot be changed arbitrarily, and the latter presser foot pressure control device (which can adjust the presser foot pressure) allows the operator to adjust the presser foot pressure by operating a manual switch or a knee switch. Therefore, it is practically impossible to change the presser foot pressure arbitrarily by sequentially following the rotation speed of the sewing machine and the phase during one rotation of the sewing machine spindle. There is a problem that various problems described below occur.

More specifically, jumping (jumping phenomenon) of the presser foot increases with an increase in the number of rotations of the sewing machine. As shown in FIG. 12, there is a problem that the cloth feeding force decreases with an increase in the number of rotations of the sewing machine. .

Further, as shown in FIG. 13, the feed dog and the cloth collide with each other at a phase X at which the feed dog rises and the feed tooth comes into contact with the cloth (a phase at which the feed dog starts cloth feeding). Therefore, there is a problem that the cloth presser bounces and the cloth feeding force is reduced. Further, at the phase Y in which the feed dog is lowered and the feed dog is separated from the cloth (the phase at which the feed dog ends the cloth feed), the cloth and the presser foot are both lowered to collide with the needle plate and generate an impact force. However, there is a problem that the cloth presser is bound and the cloth position is shifted from a predetermined position, so that a beautiful seam cannot be formed.

In the case of sewing a soft and bulky material such as a sweater, for example, in the cloth feed pause section, the cloth is crushed and the cloth presser pressure is reduced so that the seam does not become hard. It is desirable to increase the pressure of the presser foot so as to prevent it. However, since the pressure of the presser foot cannot be changed in accordance with the phase in this manner, FIG. If the cloth presser pressure shown is set low, the cloth cannot be fed in the cloth feed section, and if the cloth presser pressure is set high with emphasis on preventing jumping in the cloth feed section, the cloth will be crushed in the cloth feed pause section and sewing will not be performed. There is a problem that the eyes become hard.

When sewing a thin material such as a shirt, for example, when the needle is stuck in the cloth (cloth feeding pause section), the cloth pressing pressure is increased so as to prevent the cloth from sticking, while the cloth feeding section is sewn. In this case, it is desirable to reduce the pressure of the presser foot so that puckering due to displacement of the cloth does not occur. However, as described above, the pressure of the presser foot cannot be changed according to the phase. When the pressure of the presser foot shown in FIG. 13 is set high with emphasis on the prevention of sticking, puckering due to cloth displacement occurs in the cloth feed section, and the pressure of the presser foot is lowered with emphasis on prevention of puckering in the cloth feed section. If it is set, there is a problem in that the cloth sticks in the cloth feed pause section, resulting in poor feeding.

In addition, a variety of sewing patterns can be obtained by intentionally generating slips in the feed dog by lowering the pressure of the cloth presser only in the cloth feed section and obtaining various sewing patterns by reducing the feed pitch. There is also a problem that can not be.

When performing curve stitching or the like, it is necessary to form a predetermined minute gap between the cloth and the presser foot so that the cloth can be easily turned. This problem is dealt with by lowering the lifting cloth presser pressure. However, there is a problem that the operation requires skill and is troublesome.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sewing machine presser foot pressure control device capable of automatically varying the presser foot pressure in accordance with the number of rotations and phase of the sewing machine, and preventing the occurrence of the various problems described above. .

[0012]

According to a first aspect of the present invention, there is provided an apparatus for controlling a presser foot pressure of a sewing machine, wherein the presser foot pressure control means controls the presser foot pressure of the sewing machine. A control current supply circuit for supplying a control current for torque adjustment of the pressing force applying means, and a control means for controlling the control current in accordance with the rotation speed of the sewing machine and variably controlling the presser foot pressure, Was provided.

According to the pressure control device for a presser foot of a sewing machine according to the present invention, the control current for adjusting the torque of the pressing force applying means for applying a press force to the presser foot is controlled in accordance with the rotation speed of the sewing machine. Since the pressure of the presser foot is variably controlled, for example, if the pressure of the presser foot is increased in accordance with an increase in the rotation speed of the sewing machine, jumping of the presser foot which increases with an increase in the rotation speed of the sewing machine is prevented. Become like

According to a second aspect of the present invention, there is provided a sewing machine presser pressure control device for controlling a sewing machine presser pressure by a pressing force applied by a pressing force applying means. A control current supply circuit for supplying a control current for adjusting the torque of the means; and control means for controlling the control current while the main shaft of the sewing machine makes one rotation so as to variably control the pressure of the presser foot.

According to the pressure control device for a presser foot of a sewing machine according to the second aspect of the present invention, the control current for adjusting the torque of the pressing force applying means for applying the presser force to the presser foot is controlled during one rotation of the main shaft of the sewing machine. The presser foot pressure is variably controlled, that is, for example, as described in claim 3, the presser foot pressure can be variably controlled by being controlled in accordance with the movement locus of the feed dog of the sewing machine.
For example, as in claim 4, the control current is different between the phase at which the feed dog of the sewing machine starts or ends the cloth feeding and the other phase. If the pressure is controlled so as to be lower than the pressure of the cloth, the bounce of the cloth due to the collision between the feed dog and the cloth at the phase of starting the cloth feeding can be prevented, and the cloth and the cloth at the phase of ending the cloth feeding can be prevented. It is possible to prevent the fabric from bouncing due to the collision between the presser and the needle plate.

According to a fifth aspect of the present invention, there is provided a sewing machine pressure control device according to the third aspect, wherein the control current is different between a phase when the feed dog of the sewing machine feeds the cloth and a phase when the cloth is not feeding the cloth. In this case, for example, when sewing a soft and bulky material such as a sweater, the cloth presser pressure in the cloth feed pause section is low and the cloth presser pressure in the cloth feed section is high. By controlling, it is possible to prevent the cloth from being crushed in the cloth feeding pause section and to prevent jumping in the cloth feeding section. Further, when sewing a thin material such as a shirt, for example, if the cloth presser pressure is controlled to be high when the needle is stuck in the cloth (cloth feed pause section) and the cloth presser pressure in the cloth feed section is low, then the cloth This prevents the cloth from sticking in the feed pause section and prevents the cloth from shifting in the cloth feed section. Further, for example, if the cloth presser pressure is controlled to be low only in the cloth feeding section, the feed dog slips and the feed pitch is reduced.

According to another aspect of the present invention, there is provided an apparatus for controlling a presser foot pressure of a sewing machine by a pressing force applied by a pressing force applying means. A control current supply circuit for supplying a control current for adjusting torque of the means, and controlling the control current at a predetermined time during sewing to form a predetermined minute gap between the cloth and the presser foot. Control means for variably controlling the height of the presser foot.

According to the sewing machine pressure control device of the sixth aspect, the control current for adjusting the torque of the pressing force applying means for applying the pressing force to the cloth presser is controlled at a predetermined time during sewing. Since the height of the presser foot is variably controlled so that a predetermined minute gap is formed between the cloth and the presser foot, for example, the predetermined minute gap is formed when sewing a curve. If controlled, the cloth can be easily turned.

At this time, various means are conceivable as the pressing force applying means according to the first to sixth aspects. However, there are various types of the pressing force applying means which have good high-speed followability, a large stroke of the cloth presser, and high reliability in use. Since it has characteristics, it is preferable to adopt a motor as in claim 7.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a side view showing a pressure control device for a presser foot of a sewing machine according to a first embodiment of the present invention. FIG. 2 is a perspective view showing a pressure control device for the presser foot. FIG. 2 is a block diagram illustrating a control system of the apparatus.

As shown in FIGS. 1 to 3, the presser foot pressure control device for a sewing machine according to the present embodiment includes a coreless motor 1 as pressing force applying means. The coreless motor 1 is such that a torque proportional to the current value of the supplied control current is generated in a rotor inside the coreless motor 1 and the output shaft 1a rotates. The coreless motor 1 is mounted on the back of a sewing machine arm 2 via a bracket 3, and a pinion gear 4 is fixed to an output shaft 1a.

As is well known, the presser bar 5 is attached to the sewing machine arm 2 so as to be vertically movable and has a cloth presser 6 at the lower end thereof.
A rack gear 7 that meshes with the pinion gear 4 is fixed to the upper end.

Therefore, when a predetermined control current is supplied to the coreless motor 1, a torque proportional to the current value is generated, and the torque is transmitted to the rack gear 7 via the pinion gear 4.
The presser foot pressure is transmitted to the presser foot 6 via the presser bar 5.

Reference numeral 8 in FIGS. 1 and 2 denotes a needle bar having a needle 9 (see FIG. 2) attached to the lower end, reference numeral 10 in FIG. 1 denotes a needle plate, and reference numeral 11 denotes a feed dog. Are respectively shown. Although not shown, the feed dog 11 is connected to a main shaft of the sewing machine, and performs cloth feeding by a well-known four-feed motion in conjunction with the main shaft of the sewing machine.

As shown in FIG. 3, the presser foot pressure control device for a sewing machine according to the present embodiment also includes a sensor 1 such as an encoder for detecting and outputting information on the rotation speed and phase of the sewing machine.
2 and a sensor 13 for detecting and outputting presser height information of the coreless motor 1. The sensor 13 includes, for example, an encoder that detects the rotation angle of the output shaft 1a of the motor 1, and detects and outputs the rotation angle information as presser height information. The presser foot pressure control device also includes, as shown in FIGS.
A knee raising switch 15 that outputs an ON signal as knee raising switch press-up information is provided in conjunction with the pressing (on) of the knee switch 14 (known).

As shown in FIG. 3, the input side of a CPU 16 as control means (control device) is connected to the sensors 12, 13 and the knee raising switch 15. The input side of the MPU 16 also has a presser condition allowing input of a cloth presser condition (for example, refer to each embodiment described later in detail) such as a variable setting of a cloth presser pressure according to the type of cloth, the hardness and the phase of the cloth. The output side of the setting panel 17 is connected.

The input / output side of the CPU 16 is connected to a network, a LAN, a removable medium, and the like.

The coreless motor 1 is connected to the output side of the CPU 16 via a control current supply circuit (driver) 18. The control current supply circuit 18 supplies a control current for torque adjustment to the coreless motor 1, and the current value of the control current is controlled by a command from the CPU 16.

The CPU 16 includes therein a coefficient map and an evaluation function which are set through the network, the LAN, and the removable medium. There are various types of coefficient maps according to the purpose of controlling the current (the purpose of varying the pressure of the presser foot). For example, when the pressure of the presser foot is changed in accordance with the number of rotations of the sewing machine, FIG. The two-dimensional coefficient map shown is used.
When changing the presser foot pressure according to the phase during rotation and changing the presser foot pressure according to the number of rotations of the sewing machine,
The three-dimensional coefficient map shown in FIG. 4B is used.
Then, the CPU 16 sets the pressing condition setting panel 1
7 based on the input information from the sensor 1, the one corresponding to the input information is called from the coefficient map, and the sensor 1
The control current value corresponding to the input information from the knee lift switches 2 and 13 is obtained from the above-mentioned coefficient map, and a command to supply the control current value to the coreless motor 1 is given to the control current supply circuit 18. It is configured.
Further, the CPU 16 can control the current value for controlling the torque of the coreless motor 1 by using a program having predetermined procedures such as an evaluation function and an arithmetic expression, instead of the coefficient map.

Next, the operation of the thus-configured presser foot pressure control device will be described below. In the first embodiment of the present invention, the CPU 16 gives a command to the control current supply circuit 18 to increase the torque adjustment current value of the coreless motor 1 as the rotation speed of the sewing machine increases. I have.

Here, in the coreless motor 1, as described above, a torque proportional to the current value is generated, and this torque is transmitted to the work clamp 6 as the work clamp pressure, so that the rotation speed of the sewing machine increases. Accordingly, the pressure of the presser foot increases. As described above, when the pressure of the presser foot increases with an increase in the rotation speed of the sewing machine, jumping of the presser foot 6 that increases with an increase in the rotation speed of the sewing machine described in the related art is prevented, and as a result, As shown in FIG. 5, a constant cloth feeding force is obtained on the cloth by the cooperation of the cloth presser 6 and the feed dog 11 irrespective of the rotation speed of the sewing machine. For this reason, FIG.
Thus, a decrease in the cloth feeding force described with reference to FIG.

Conversely, the current value for adjusting the torque of the coreless motor 1 is intentionally controlled so as to decrease as the rotation speed of the sewing machine decreases, or the sewing machine speed is reduced to a predetermined low speed. If the sewing machine is controlled to be lower when it reaches, the cloth can be easily turned when the number of rotations of the sewing machine is reduced by a curve or the like, and a beautiful stitch can be formed.

In the second embodiment of the present invention, the CPU
16 gives to the control current supply circuit 18 a command to make the current value for adjusting the torque of the coreless motor 1 different between the phase at which the feed dog 11 starts cloth feeding and another phase. Thus, a command is issued to lower the current value of the phase at which cloth feeding is started to be lower than the current values of the other phases.

Therefore, the cloth presser pressure in the phase at which the cloth feed is started is reduced, and the cloth bounces due to the collision between the feed dog 11 and the cloth at the phase at which the cloth feed is started as described in the prior art (FIG. 13). 6 is prevented, as shown in FIG. 6, so that a decrease in the cloth feeding force in the phase at which cloth feeding is started can be prevented.

In the third embodiment of the present invention, the CPU
16 gives a command to the control current supply circuit 18 to make the current value for torque adjustment of the coreless motor 1 different between the phase at which the feed dog 11 completes the cloth feeding and the other phase. Thus, a command is given to make the current value of the phase at which the cloth feeding ends is lower than the current values of the other phases.

Therefore, the pressure of the presser foot in the phase of terminating the cloth feed is reduced, and the cloth presser 6 in the phase of terminating the cloth feed described in the related art, and the presser foot 6 due to the collision between the presser foot 6 and the needle plate 10 is pressed. Occurrence of bounce (see waveform at phase Y in FIG. 13)
However, as shown in FIG. 7, the cloth is prevented from being shifted at the phase where the cloth feeding is completed, and a beautiful stitch can be formed.

In the fourth embodiment of the present invention, when information indicating that a soft and bulky material such as a sweater is selected as a sewing object from the presser condition setting panel 17, the CPU 16 executes the coreless operation. An instruction is given to the control current supply circuit 18 to make the current value for adjusting the torque of the motor 1 different between the phase when the feed dog 11 feeds the cloth and the phase when the feed tooth 11 does not feed the cloth. As a result, a command is given to lower the current value in the cloth feed pause section and increase the current value in the cloth feed section.

Therefore, as shown in FIG. 8, the cloth pressing pressure in the cloth feed pause section is reduced, and the cloth crushing in the cloth feed pause section described in the prior art is prevented.
A soft seam can be formed, and the presser foot pressure in the cloth feed section is increased, thereby preventing the occurrence of jumping in the cloth feed section described in the related art, and reducing the cloth feed force. It can be prevented.

In the fifth embodiment of the present invention, when information indicating that a thin object such as a shirt is selected as a sewing object is input from the pressing condition setting panel 17, the CPU 16 operates the coreless motor 1. The control current supply circuit 18 issues a command to make the current value for torque adjustment different between the phase when the feed dog 11 feeds the cloth and the phase when the feed tooth 11 does not feed the cloth (especially when the needle 9 is stuck in the cloth). In particular,
As shown in FIG. 9, a command to increase the current value in the cloth feeding pause section and decrease the current value in the cloth feeding section is given.

Therefore, as shown in FIG. 9, the pressure of the cloth presser in the cloth feed pause section is increased, so that the sticking of the cloth in the cloth feed pause section described in the prior art is prevented, and In addition to preventing the deterioration of the eye quality, the pressure of the presser foot in the cloth feed section is reduced, and the cloth displacement in the cloth feed section described in the related art is prevented, thereby preventing the occurrence of puckering. I can do it.

Further, the current value for adjusting the torque of the coreless motor 1 is controlled so that the presser foot pressure is reduced only in the cloth feeding section, so that the feed dog 11 is intentionally slipped to reduce the feed pitch. Thus, the variety of sewing patterns can be achieved.

In the sixth embodiment of the present invention, as shown in FIG. 10, a known optical line sensor 19 is provided just before a needle drop. This optical line sensor 19
Is a light receiving element 19a composed of a solar cell buried in the needle plate 10 so that the surface is exposed, and this light receiving element 19a
Light emitting device 19 composed of a large number of LEDs capable of uniformly irradiating light
b, and outputs a voltage signal corresponding to the light shielding area of the light receiving element 19a covered with the cloth 20 to the CP.
It is configured to output to U16.

The CPU 16 has a known function of receiving the signal and judging whether or not the shape of the cloth edge is a curve according to a change in the voltage signal. 18 is given a rising command by a predetermined amount to raise the presser foot 6 slightly by the operation of the coreless motor 1, and a predetermined minute gap Z between the cloth 20 and the presser foot 6.
Can be formed.

That is, in the sixth embodiment, the cloth curve is determined based on the output signal of the optical line sensor 19, and when the curve is reached, the coreless motor 1 is driven by a predetermined amount, and the cloth presser 6 is moved. Since a predetermined minute gap Z is formed between the cloth 20 and the presser foot 6 and raised, the cloth can be easily turned at the time of curve sewing, so that a beautiful seam can be formed even by a non-expert. Has become.

When the worker turns on the knee switch 14 shown in FIG.
The knee-up switch 15 is turned on in conjunction with, the ON signal is input to the CPU 16, and the CPU 16
Upon receiving this ON signal, a presser lifting command is given to the control current supply circuit 18, so that the work clamp 6 is raised by the operation of the coreless motor 1 so that the cloth 20 can be easily taken out.

As a modification of the sixth embodiment, the CP
It is also possible to issue a command to form the predetermined minute gap Z when U16 detects, for example, by a stitch number counter that the number of stitches for performing a curve sewing of a preset sewing pattern has been reached. .

FIG. 11 is a side view showing a pressure control device for a presser foot of a sewing machine according to a seventh embodiment of the present invention. The seventh embodiment is different from the above-described embodiments in that the pressing force applying means is replaced with the coreless motor 1 by a voice coil motor 21, and a bobbin inside the voice coil motor 21 has an upper end of the pressing rod 5. It is the point where the parts are combined.

The voice coil motor 21 generates a thrust proportional to the current value of the supplied control current on the bobbin.

Accordingly, when a predetermined control current is supplied to the voice coil motor 21, a thrust proportional to the current value is generated, and the thrust is transmitted to the presser foot 6 via the presser bar 5 as the presser foot pressure. It has become so.

It is needless to say that the effect of each of the above-described embodiments can be obtained even if the pressing force applying means is configured as described above. In the present embodiment, the bobbin inside the voice coil motor 21 and the upper end of the holding rod 5 are directly connected. However, for example, the two may be connected by inserting a link mechanism between the two. Of course it is possible.

As described above, the coreless motor 1 is used in the first to sixth embodiments of the present invention, and the voice coil motor 21 is used in the seventh embodiment. And
In the first to sixth embodiments, the coreless motor 1
Is transmitted to the presser bar 5 provided with the cloth presser 6 at the lower end via the pinion gear 4 and the rack gear 7, while in the seventh embodiment, the change in thrust of the voice coil motor 21 is directly transmitted to the presser bar 5. It is configured to transmit. Therefore, the responsiveness of the seventh embodiment is better than that of the first to sixth embodiments. Further, in the first to sixth embodiments, by changing the gear ratio, a larger load can be converted with a smaller motor output than in the seventh embodiment.

Although the invention made by the present inventor has been specifically described based on the embodiment, the invention is not limited to the above embodiment, and can be variously modified without departing from the gist thereof. Needless to say. For example, according to the three-dimensional map of the control current, the sewing machine speed, and the phase shown in FIG. 4B, the control current is controlled in accordance with the machine speed as described in the first embodiment, and the second to the second. As described in the fifth embodiment, it is of course possible to control in accordance with the phase, that is, to combine the first embodiment with the second to fifth embodiments to variably control the pressure of the cloth presser.

In the embodiment of the present invention, the feed dog 11
Is connected to a sewing machine spindle, and performs cloth feeding by a well-known four-feeding motion in conjunction with the sewing machine spindle. Instead, a separate drive motor (feed dog drive motor) is provided for the feed dog 11.
In addition to the above, the feed dog drive motor and the main motor for driving the main shaft of the sewing machine are synchronized with each other to apply a predetermined motion to the needle bar 8, the shuttle and the feed dog 11 to form a stitch. The invention is equally applicable. That is, it is possible to detect the rotation speed and phase of at least one of the feed dog drive motor and the main motor (spindle), and control the current value of the coreless motor 1 based on the detected values.

As still another embodiment of the above-described embodiment, the curve of the cloth being sewn is detected by the optical element 19 described in the sixth embodiment, or described as a modification of the sixth embodiment. As described above, when the number of stitches is detected by the stitch number counter, the control current may be reduced to reduce the pressure of the presser foot, so that the cloth can be easily turned.

Further, whether or not the sewing machine power is turned on is determined by the CP.
It is also possible to make it easy to insert the cloth 20 between the needle plate 10 and the presser foot 6 by inputting it to U16 and applying a control current to raise the presser foot 6 when the power is turned on. .

Further, by applying a control current for raising or lowering the presser foot 6, the cloth 20 is brought into contact with the presser foot 6 and the needle plate 10.
It is also possible to detect the cloth thickness based on the output of the sensor 13 at this time. At the time of this measurement, the pressure of the presser foot was
However, it is also possible to know the hardness such as soft or hard. As a result, when it is determined that the cloth 20 is soft,
It is preferable that the control current is reduced to reduce the pressure of the presser foot, so that the presser cloth 20 can be pressed softly, except when the sheet 20 is sent. In addition, since the feed pitch tends to be small with such a soft cloth, it is desirable to give a command to the sewing machine to increase the feed pitch.

Further, in the above-described embodiment, the motors 1 and 21 are used as the pressing force applying means from the viewpoint of good high-speed followability, a large stroke of the presser foot, and high reliability in use. However, another actuator such as an electromagnetic solenoid can be used instead.

[0058]

As described above, the pressure control device for the presser foot of the sewing machine according to the first aspect of the present invention controls the control current for adjusting the torque of the pressing force applying means for applying the press force to the presser foot to the rotation speed of the sewing machine. The presser foot pressure can be variably controlled by controlling the presser foot pressure, for example, by controlling the presser foot pressure to increase in accordance with an increase in the number of rotations of the sewing machine. Therefore, it is possible to prevent a decrease in the cloth feeding force.

According to a second aspect of the present invention, there is provided a pressure control device for a presser foot of a sewing machine, which controls a control current for torque adjustment of a pressing force applying means for applying a press force to the presser foot during one rotation of a main shaft of the sewing machine. Thus, the pressure of the presser foot can be variably controlled, that is, the pressure of the presser foot can be variably controlled by controlling according to the movement trajectory of the feed dog of the sewing machine. The control current is different between the phase at which the feed dog of the sewing machine starts or ends the cloth feeding and the other phase, for example, the presser foot pressure of the phase at which the cloth feed starts or ends becomes lower than the cloth presser pressure of the other phase. Control so as to prevent the occurrence of cloth bouncing due to the collision between the feed dog and the cloth at the phase at which cloth feeding starts, and the cloth at the phase at which cloth feeding ends, the cloth presser and the like. Cloth bag due to collision with needle plate Is configured to prevent the occurrence of the cloth feed, it is possible to prevent a decrease in the cloth feeding force at the phase where the cloth feeding is started, and to prevent the cloth from shifting at the phase where the cloth feeding is ended. This makes it possible to form beautiful seams.

According to a fifth aspect of the present invention, there is provided a sewing machine presser pressure control device according to the third aspect, wherein a control current is different between a phase when the feed dog of the sewing machine feeds the cloth and a phase when the cloth is not feeding the cloth. For example, when sewing a soft and bulky material such as a sweater, for example, by controlling the cloth presser pressure in the cloth feed pause section to be lower and the cloth presser pressure in the cloth feed section to be higher, the cloth in the cloth feed pause section is controlled. Since the configuration is such that crushing and jumping in the cloth feeding section can be prevented, it is possible to form soft stitches and to prevent a reduction in cloth feeding force. In the case of sewing a thin material such as a shirt, for example, when the needle is stuck in the cloth (cloth feed pause section), the cloth presser pressure is controlled to be high and the cloth presser pressure in the cloth feed section is controlled to be low. Since the configuration is such that it is possible to prevent the sticking of the cloth in the feed pause section and the displacement of the cloth in the cloth feed section, it is possible to prevent the deterioration of the stitch quality and the occurrence of puckering. Also, for example, by controlling the fabric presser pressure to be lower only in the fabric feed section,
Since the feed dog is intentionally slipped to reduce the feed pitch, it is possible to achieve a variety of sewing patterns.

In the sewing machine presser foot pressure control device of the present invention, the control current for torque adjustment of the pressing force applying means for applying a pressing force to the cloth presser is controlled at a predetermined time during sewing. The height of the presser foot can be variably controlled so as to form a predetermined minute gap between the cloth and the presser foot, for example, by controlling such that the predetermined minute gap can be formed when sewing a curve. Since the cloth can be easily rotated, beautiful stitches can be formed even by a non-expert.

At this time, various means are conceivable as the pressing force applying means according to the first to sixth aspects. However, there are various kinds of means which have a good high-speed followability, a large stroke of the cloth presser, and a high reliability in use. Since it has characteristics, it is preferable to use a motor as in claim 7, and by adopting a motor as the pressing force applying means, it is possible to further enhance the effects of the above-described claims.

[Brief description of the drawings]

FIG. 1 is a side view illustrating a pressure control device for a presser foot of a sewing machine according to a first embodiment of the present invention.

FIG. 2 is a perspective configuration diagram showing the same presser foot pressure control device.

FIG. 3 is a block diagram showing a control system of the pressure control device of the same embodiment.

4A and 4B show an example of a coefficient map stored in a CPU of the pressure control device of the same embodiment, wherein FIG. 4A is a two-dimensional map of a control current and a rotation speed of a sewing machine, and FIG. It is a three-dimensional map of rotation speed and phase.

FIG. 5 is a characteristic diagram showing the relationship between the number of rotations of the sewing machine and the cloth feeding force when the control current is controlled by the cloth presser pressure control device, using the cloth presser pressure as a parameter;

FIG. 6 is a characteristic diagram showing a relationship between a control current controlled by a presser foot pressure control device of a sewing machine, a displacement amount of a feed dog, and a presser foot pressure according to a second embodiment of the present invention.

FIG. 7 is a characteristic diagram showing a relationship between a control current controlled by a presser foot pressure control device of a sewing machine, a displacement amount of a feed dog, and a presser foot pressure according to a third embodiment of the present invention.

FIG. 8 is a characteristic diagram showing a relationship between a control current controlled by a presser foot pressure control device of a sewing machine, a displacement amount of a feed dog, and a presser foot pressure according to a fourth embodiment of the present invention.

FIG. 9 is a characteristic diagram illustrating a relationship between a control current controlled by a presser foot pressure control device of a sewing machine, a displacement amount of a feed dog, and a presser foot pressure according to a fifth embodiment of the present invention.

FIG. 10 is an explanatory side view showing a main part of a pressure control device for a presser foot of a sewing machine according to a sixth embodiment of the present invention.

FIG. 11 is a side view illustrating a pressure control device for a presser foot of a sewing machine according to a seventh embodiment of the present invention.

FIG. 12 is a characteristic diagram showing the relationship between the rotation speed of the sewing machine and the cloth feeding force in the related art, using the pressure of the cloth presser as a parameter.

FIG. 13 is a characteristic diagram showing a relationship between a displacement amount of a feed dog and a presser foot pressure according to a conventional technique.

[Explanation of symbols]

 1, 21 pressing force applying means (motor) 6 cloth presser 11 feed dog 16 control means 18 control current supply circuit (driver) 20 cloth

Claims (7)

[Claims] 1. A device for controlling a presser pressure of a sewing machine by a pressing force applied by a pressing force applying means, comprising: a control current supply circuit for supplying a control current for torque adjustment of the pressing force applying means; Control means for controlling the control current in accordance with the number of revolutions so as to variably control the pressure of the presser foot. 2. An apparatus for controlling a presser pressure of a sewing machine by a pressing force applied by a pressing force applying means, comprising: a control current supply circuit for supplying a control current for torque adjustment of the pressing force applying means; Control means for controlling the control current during one rotation of the main shaft and variably controlling the pressure of the presser foot. 3. The presser foot pressure control device for a sewing machine according to claim 2, wherein the control means controls the control current in accordance with the movement trajectory of the feed dog of the sewing machine so as to variably control the presser foot pressure. 4. The sewing machine according to claim 3, wherein the control means is capable of variably controlling the cloth pressing pressure by making the control current different between a phase at which the feed dog of the sewing machine starts or ends the cloth feeding and another phase. Pressure control device for the presser foot. 5. The cloth presser pressure can be variably controlled by differentiating a control current between a phase when the feed dog of the sewing machine feeds the cloth and a phase when the cloth does not feed the cloth. Sewing machine pressure control device. 6. A device for controlling a presser pressure of a sewing machine by a pressing force applied by a pressing force applying means, comprising: a control current supply circuit for supplying a control current for adjusting a torque of the pressing force applying means; Control means for controlling the control current at a predetermined time, and variably controlling the height of the presser foot so as to form a predetermined minute gap between the cloth and the presser foot. Presser pressure control device. 7. The pressure control device for a presser foot of a sewing machine according to claim 1, wherein the pressing force applying means is a motor.