JPH07222885A - Sewing machine - Google Patents

Abstract

PURPOSE:To provide a sewing machine which can suppresses inertial force caused by the vertical movement of a needle bar, and concurrently lower vibration and noise. CONSTITUTION:When an upper shaft 48 is rotated with a motor 40 started based on a sewing speed set by a sewing speed setting means 10, the rotation angle of the upper shaft 48 is detected by an upper shaft rotation angle detecting means 12. A speed command signal operated, by an arithmetic device 14 makes the rotating speed of the upper shaft 48 lower than that of other phase section at a phase section where the needle bar 50 is reversed from descending to ascending in the moving direction based on the set value of the sewing speed setting means 10 and a detected signal by the upper shaft rotation angle detecting means 12, in accordance with the speed command signal, and the rotation speed of the motor 40 is controlled by a motor speed control means 16. Therefore, at the phase section where the needle bar 50 is reversed in moving direction from descending to ascending, the rotating speed of the upper shaft is lowered, and the speed of the needle bar 50 reversing from descending to ascending is sufficiently lowered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sewing machine capable of reducing the vibration generated by the vertical movement of a needle bar.

[0002]

2. Description of the Related Art Conventionally, in a frame of a sewing machine, a pedestal portion is erected from a right end of a bed portion, an arm portion projects from an upper end of the pedestal portion to a position above the bed portion, and a head portion is left end of the arm portion. It is formed downward from the section toward the bed section. The bed portion, the pillar portion, the arm portion and the head portion are continuously formed.

At the joint between the bed and the pedestal,
As shown in FIG. 4, a motor 40 is provided and a belt 44
Is suspended inside the pedestal portion between a motor pulley (not shown) of the motor 40 and the upper shaft pulley 46. The upper shaft pulley 46 is fixed to the right end of the upper shaft 48, and
8 is rotatably supported by the arm portion. The rotation speed of the motor 40 and the rotation speed of the upper shaft 48 are set to be directly proportional to the gear ratio between the upper shaft pulley 46 and the motor pulley.

As shown in FIG. 5, a needle bar 50 is supported on the head portion by a needle bar holder 52, and is vertically moved by a needle bar crank rod 54 and a needle bar crank 56. ing. The needle bar crank rod 54 and the needle bar crank 56 are configured to rotate by the upper shaft 48. Further, a balance 60 is supported on the head portion by a balance support 62, and is configured to move up and down by rotation of a balance crank 64. This balance crank 64 also has an upper shaft 48
It is configured to rotate by.

Further, an upper shaft crank 70 is fixed to a portion of the upper shaft 48 corresponding to a joint portion between the arm portion and the pedestal portion so as to contact an upper end portion of a crank rod 72. The lower end of the crank rod 72 extends downward to the bed and is connected to the lower shaft crank 74. The lower shaft crank 74 rotates the lower shaft 76 in the bed. The lower shaft 76 is the lower shaft gear 7
It is configured to rotate the shuttle 79 via 8.

Further, the upper shaft cam 80 is fixed to the upper shaft 48 adjacent to the upper shaft crank 70, and the feed rod 84 is rocked based on the position of the feed adjuster 82. A horizontal feed arm 86 is fixed to the lower end of the feed rod 84 so as to rotate a horizontal feed shaft 88. The rotation of the horizontal feed shaft 88 is transmitted via the upper and lower feed plates 90, and the feed dog 93 fixed to the horizontal feed base 92 is configured to perform the known four feed movement.

The sewing mechanism of the sewing machine is constructed as described above, and includes the needle bar 50, the balance 60, the shuttle 79 and the feed dog 9.
3 moves in synchronization with the rotation of the upper shaft 48, and sewing is performed. During sewing, the motor 40 is constantly rotated at a constant speed to move the needle bar 50 up and down.

[0008]

However, since the moving direction of the needle bar 50 is reversed at the lowest point or the highest point with the vertical movement, the moving speed of the needle bar 50 temporarily becomes zero. Become. Therefore, immediately before the reversal of the needle bar 50, the needle bar 5
The moving speed of 0 sharply decreases, and the needle bar 50
Since the moving speed of the robot rapidly increases, there is a problem that vibration and noise occur due to the inertial force due to the acceleration at that time.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a sewing machine which suppresses inertial force and has less vibration and noise.

[0010]

In order to achieve this object, a sewing machine of the present invention has a sewing speed which is controlled by rotating a motor to reciprocally move a needle bar up and down through an upper shaft for sewing. Sewing speed setting means for setting, upper shaft rotation angle detecting means for detecting a rotation angle of the upper shaft, set values set by the sewing speed setting means, and a detection signal of the upper shaft rotation angle detecting means. And a calculating means for calculating a speed command signal for making the rotation speed of the upper shaft smaller in the phase portion in which the movement direction of the needle bar reverses from descending to ascending than in the other phase portions. Motor speed control means for controlling the rotation speed of the motor according to the speed command signal calculated by

The calculating means may be configured to calculate the speed command signal in consideration of a correction signal relating to a delay in control time such as the calculation time and the detection time of the upper shaft rotation angle detecting means. Good.

Further, the calculating means may be configured to calculate the speed command signal in consideration of a control parameter relating to an inertial force generated by the rotation of the upper shaft.

[0013]

In the sewing machine of the present invention having the above construction, when the upper shaft is rotated by starting the motor based on the sewing speed set by the sewing speed setting means, the upper shaft rotation angle detecting means causes the upper shaft rotation angle detecting means to rotate. To detect the rotation angle of. Then, the calculation means, the set value of the sewing speed setting means,
Based on the detection signal of the upper shaft rotation angle detecting means, a speed command signal for decreasing the rotation speed of the upper shaft at a phase portion where the movement direction of the needle bar is reversed from descending to ascending than other phase portions The motor speed control means controls the rotational speed of the motor according to the calculated speed command signal. Therefore, the rotational speed of the upper shaft becomes small in the phase portion in which the direction of movement of the needle bar reverses from upward to downward, and the speed at which the needle bar reverses from upward to upward is sufficiently reduced, causing vertical movement of the needle bar. It is possible to suppress the inertial force due to.

Further, the calculating means can calculate the speed command signal in consideration of a correction signal relating to the delay of the control time and a control parameter relating to the inertial force,
This enables more precise and precise motor speed control.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the drawings. The same parts as those of the conventional sewing machine described at the beginning are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 shows a block diagram for controlling the speed of the motor 40 together with the main components of the sewing machine.
In the figure, the sewing speed setting means 10 is for setting the sewing speed, and can be adjusted and set in advance by a manual adjusting knob or the like. The upper shaft rotation angle detection means 12 detects the rotation angle of the upper shaft 48 driven by the motor 40, and is composed of, for example, a slit disk and a photoelectric sensor. The calculation device 14 constituting the calculation means changes the moving direction of the needle bar 50 from downward to upward based on the set value set by the sewing speed setting means 10 and the detection signal of the upper shaft rotation angle detection means 12. A speed command signal is calculated so that the rotation speed of the upper shaft 48 is smaller in the inverted phase portion than in the other phase portions. The motor speed control means 16 controls the rotation speed of the motor 40 according to the speed command signal calculated by the calculation device 14.

In this embodiment having the above-mentioned structure, the upper shaft rotation angle detecting means 12 detects the upper shaft rotation angle, and the arithmetic unit 14 is operated.
Calculates the speed command value ω _M given to the motor 40 by the set value ω ₀ of the sewing speed setting means 10 and the detection signal θ _{T of the} upper shaft rotation angle detection means 12, and the motor speed control means 16 causes the motor speed control means 16 to operate according to the speed command. The rotation speed ω _{1 of} 40 is feedback-controlled.

Next, the rotation speed of the upper shaft 48 will be described.

Assuming that the diameter of the motor pulley 42 is D ₁ and the diameter of the upper shaft pulley 46 is D ₂ , when the above-described motor 40 rotates at a constant speed ω ₁ , the upper shaft 48 rotates at a speed of the following formula 1. To rotate.

[0020]

[Equation 1]

Further, with respect to the sewing speed ω ₀ set by the sewing speed setting means, the rotation speed ω expressed by the following _equation 2
It is assumed that the rotation speed of the motor 40 is controlled so that the upper shaft rotates at ₂ . Note that θ is the rotation angle of the upper shaft 48.

[0022]

[Equation 2]

Next, the displacement amount generated by the needle bar mechanism including the needle bar 50 and the needle bar crank rod 54 will be described with reference to FIG.

From the axis of the upper shaft 48 to the needle bar crank rod 5
4 is R, the distance between the support points of the needle bar crank rod 54 is L, and the crank ratio is λ (= R / L), the vertical displacement amount y of the needle bar 50 is λ. If neglecting a minute amount of 2nd order or higher, the following equation 3 is given.

[0025]

[Equation 3]

Then, the vertical acceleration a of the needle bar 50
Can be obtained by the second-order differentiation of the displacement amount y with respect to the time t as shown in the following Expression 4.

[0027]

[Equation 4]

The vertical inertial force F generated by the movement of the needle bar mechanism, if the mass of the needle bar crank rod 54 is ignored, is the inertial force F ₁ generated by the acceleration motion of the needle bar 50 and the balance. Crank 64 and needle bar crank 5
The sum of the centrifugal force of 6 and the vertical component F ₂ is expressed by the following equation 5.

[0029]

[Equation 5]

Here, M is the mass of the needle bar, m is the mass of the balance crank and the needle bar crank, and r is the distance from the axial center of the upper shaft to the combined center of gravity of the balance crank and the needle bar crank.

The vertical inertial force F at an arbitrary upper shaft rotation angle can be calculated from the above equations (2), (3) and (4).

Next, the control parameters A ₁ = A ₂ = A ₃ =
A ₄ = 0 (upper axis rotating at constant velocity) and A ₁ = 0.
31, A ₂ = 0.048, A ₃ = 0.036, A ₄ =
With respect to the case of 0.031, the upper shaft rotation speed and the inertial force will be described with reference to FIG. In addition, λ = 0.5, mr / MR
= 0.2, the upper shaft rotation speed is ω ₀ , and the inertial force is MR ω
It is displayed dimensionless with ₀ .

When A ₁ = A ₂ = A ₃ = A ₄ = 0, that is, when the motor 40 is rotated at a constant speed like a conventional sewing machine,
Inertial force is generated like the dotted line. On the other hand, A ₁ = 0.31,
A ₂ = 0.048, A ₃ = 0.036, A ₄ = 0.031
In the case of, that is, when the rotation speed of the motor 40 is controlled like the sewing machine of the present invention, an inertial force is generated as shown by the solid line. Therefore, in the case of the sewing machine of the present invention, the maximum value of the inertia force F can be reduced by 46% as compared with the case of the conventional sewing machine.

Next, the arithmetic algorithm in the arithmetic unit 14 will be described.

The arithmetic unit 14 determines the rotational speed of the upper shaft 48 to a value obtained by the equation 2 based on the set value ω ₀ of the sewing speed setting means 10 and the detection signal θ _{T of the} upper shaft rotation angle detecting means 12. It is necessary to calculate the speed command value ω _M of the motor 40 such that _Assuming that the correction angle considering the detection time of the upper shaft rotation angle detection means 12, the calculation time of the arithmetic device 14, the control delay of the motor speed control means 16 and the like is δ, the speed command ω _M output from the arithmetic device 14 is as follows. Equation 6 is obtained by Equation 7. The correction angle δ is a function of the set value ω ₀ of the sewing speed setting means 10.

[0036]

[Equation 6]

[0037]

[Equation 7]

In this embodiment, in the sewing machine in which the constants determined by the parts of the sewing machine are λ = 0.5 and mr / MR = 0.2, the control parameters A ₁ , A ₂ , A ₃ and A ₄ are The above values are the best, but if the constants λ and mr / MR are changed according to the sewing machine, the inertia force is reduced so that A
The values of ₁ , A ₂ , A ₃ , and A ₄ may be changed appropriately. Further, the function of Expression 2 is not limited to this, and any other function may be used as long as it satisfies Expression 8 below.

[0039]

[Equation 8]

[0040]

As is apparent from the above description, according to the sewing machine of the present invention, the rotational speed of the upper shaft is higher in the phase portion in which the direction of movement of the needle bar is reversed from downward to upward than in other phase portions. Since the speed command signal for reducing the speed is given to the motor speed control means, the inertial force generated especially at the time of reversing the vertical movement of the needle bar can be sufficiently reduced and the vibration of the sewing machine can be prevented. You can Along with this, it is possible to perform accurate sewing on the workpiece and reduce noise due to vibration. Further, when the speed command signal is calculated by the calculation means, a more accurate and precise motor speed control can be performed by considering the correction signal regarding the control time delay, the control parameter regarding the inertial force, and the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical control configuration of a sewing machine of the present invention.

FIG. 2 is an explanatory diagram of inertial force of a needle bar mechanism of a sewing machine.

FIG. 3 is a diagram showing calculation results of upper shaft rotation speed and inertial force.

FIG. 4 is a perspective view of a lower shaft mechanism and a feed mechanism of a conventional sewing machine.

FIG. 5 is a perspective view of a needle bar mechanism and a balance mechanism of a conventional sewing machine.

[Explanation of symbols]

 10 sewing speed setting means 12 upper shaft rotation angle detecting means 14 arithmetic unit 16 motor speed control means 40 motor 48 upper shaft 50 needle bar

Claims (3)

[Claims] 1. In a sewing machine for sewing by reciprocating a needle bar up and down through an upper shaft by rotation of a motor, a sewing speed setting means for setting a sewing speed and a rotation angle of the upper shaft are detected. The upper shaft rotation angle detecting means, a phase in which the moving direction of the needle bar reverses from descending to ascending based on the set value set by the sewing speed setting means and the detection signal of the upper shaft rotating angle detecting means. In accordance with the speed command signal calculated by the calculating means for calculating the speed command signal that makes the rotation speed of the upper shaft smaller than the other phase parts in the part,
A sewing machine, comprising: a motor speed control unit that controls a rotation speed of the motor. 2. The calculation means is configured to calculate the speed command signal in consideration of a correction signal relating to a delay in control time such as the calculation time and the detection time of the upper shaft rotation angle detection means. The sewing machine according to claim 1, wherein: 3. The calculation means is configured to calculate the speed command signal in consideration of a control parameter relating to an inertial force generated with the rotation of the upper shaft. Sewing machine described in.