JP2006187420A - Sewing machine component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-strength sewing machine component reducing the weight and improving the friction resistance. <P>SOLUTION: This sewing machine component receiving a driving force for sewing and executing an operation is characterized in that a base material of the sewing machine component is composed of aluminum or aluminum alloy, the surface layer part of the base material is formed of a two-layer structured hybrid plasma electrolytic oxidation film consisting of a lower layer mainly composed of crystalline substance Al<SB>2</SB>O<SB>3</SB>and an upper layer mainly composed of amorphous substance Al<SB>2</SB>O<SB>3</SB>, and the hybrid plasma electrolytic oxidation film is formed with a plurality of through-holes in the thickness direction reaching the interface with the base material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention is adapted to each part of the material (steel (specific gravity 7.86 g / cm ^3), or copper material (specific gravity 8.93g / cm ³⁾⁾ of aluminum or an aluminum alloy, (specific gravity 2.70 g / cm ³⁾ In such a case, the present invention relates to a sewing machine part in which durability (tensile strength and wear resistance) of the aluminum or aluminum alloy is improved.

  In a conventional sewing machine, a high-strength aluminum alloy is used to reduce the weight of a member that causes high-speed movement and that slides during driving during sewing, for example, a crank rod that transmits a driving force for vertical movement from the sewing machine spindle to the needle bar. Was forming. And, the end of the crank rod is provided with a metal bearing that supports a spindle provided on a needle bar holder fixed to the needle bar so as to be slidably rotatable, and the bearing is a copper-based material having a high specific gravity, Or the copper material which performed the nitriding process on the surface was used (for example, refer patent document 1).

Further, steel materials are used for the link material used as the needle bar, the upper looper hug, the upper looper guide, the swinging canister, the sliding piece such as the square piece, the hook for providing the lower thread, and the connecting part.
JP 7-217657 A

However, if the bearing material provided at the end of the crank rod is made of copper or steel, the weight of the bearing increases, and the crank rod has insufficient strength or inertial force when moving at a higher speed. There was a risk of growth.
Also, in recent sewing machines, dry parts that do not use lubricating oil are being promoted in each part of the machine frame, and in order to cope with this, conversion to copper bearings with good slidability is being attempted. After all, there was a problem that the weight of the bearing became heavy.

In addition, when trying to change the sewing machine part using the steel material described above from a steel material having a high specific gravity to an aluminum or aluminum alloy having a low specific gravity, there is a problem of strength or durability, which is quite difficult.
SUMMARY OF THE INVENTION An object of the present invention is to provide a sewing machine component that can be reduced in weight and strength and improved in slidability in a sewing machine component that performs high-speed motion.

According to the first aspect of the present invention, in any one of the sewing machine parts that perform the movement by receiving a driving force for sewing, the base material of the sewing machine parts is made of aluminum or an aluminum alloy, and the surface layer portion of the base material is a crystal. A hybrid plasma electrolytic oxide film having a two-layer structure composed of a lower layer mainly composed of porous Al ₂ O ₃ and an upper layer mainly composed of amorphous Al ₂ O _3. A plurality of through-holes reaching the interface with the base material are formed in the thickness direction.

Each component of the sewing machine performs various motions such as rotation and reciprocation according to the number of rotations of the sewing machine motor as a drive source. For parts that slide or collide with other parts due to such movement, wear resistance is required to prevent deterioration due to wear.
In particular, in parts that perform high-speed motion, the tensile load is increased due to the centrifugal force, so that durability against the tensile load is also required.

According to a second aspect of the present invention, in the sewing machine part that moves by receiving a driving force for sewing, the base material of the sewing machine part is made of aluminum or an aluminum alloy, and the sliding part with the other sewing machine part the surface portion of the base material is made from a hybrid plasma electrolytic oxide film of 2-layer structure composed of a lower layer mainly composed of the upper layer and the amorphous of Al ₂ O ₃ mainly composed of Al ₂ O ₃ crystalline, the hybrid plasma The electrolytic oxide film is characterized in that a plurality of through-holes reaching the interface with the base material are formed in the thickness direction.

Each component of the sewing machine may slide with other parts depending on the operation at the time of sewing, or may slide with the shaft at the rotary connecting portion.
The invention described in claim 3 has the same configuration as that of the invention described in claim 1 or 2, and is characterized in that the thickness of the hybrid plasma electrolytic oxide film is in the range of 1 to 150 μm.
If the thickness is 150 μm or more, the porous upper layer becomes thick, and as a result, there is a high possibility of causing a problem with initial braking, cracking of the upper layer, and generation of cracks.

The invention described in claim 4 has the same configuration as that of the invention described in claim 1, 2, or 3, and is characterized in that the surface hardness of the hybrid plasma electrolytic oxide film is 800 Hv or more.

  According to the first aspect of the present invention, in the sewing machine part that moves by receiving a driving force for sewing, the hybrid film having the two-layer structure described above is applied to the surface of the base material of aluminum or aluminum alloy by plasma electrolytic oxidation. Because it is formed, it is possible to improve the durability through wear resistance and improve the durability of the tensile load by hardening the surface of the base material and reducing the friction coefficient. For parts that perform high speed motion, sliding, collision, etc. Therefore, it is possible to avoid the use of a heavy material having durability, and it is possible to reduce the weight and improve the slidability. In such parts, the base material is made of aluminum or an aluminum alloy, and the surface thereof, particularly the surface of a part where wear is likely to occur or a part where a tensile load is likely to occur due to structure is subjected to plasma electrolytic oxidation treatment. By forming a hybrid film having a layer structure, the surface is hardened and the friction coefficient is reduced, whereby the durability is improved by wear resistance and the durability of tensile load is improved.

  According to a second aspect of the present invention, in a sewing machine component that moves by receiving a driving force for sewing, the surface of the aluminum or aluminum alloy base material is subjected to plasma electrolytic oxidation treatment on the sliding surface that causes sliding. Since the two-layered hybrid film described above is formed, the surface can be hardened and the friction coefficient can be reduced to improve the durability through wear resistance. Thus, it is possible to avoid the use of a heavy material having durability, and it is possible to reduce the weight and improve the slidability.

In the third aspect of the invention, it is not necessary to increase the thickness of the coating, the processing becomes simple, and the parts can be made lighter.
In the invention according to claim 4, the maximum hardness of the conventional hard anodized film is 450 Hv and the normal hardness is about 350 Hv. However, the two-layer hybrid film of the present invention is hard and wear-resistant. There is an effect that is superior to the conventional hard anodized film applied to the sewing machine parts.

  In addition, iron is weak in high-speed motion and has a failure factor that easily generates frictional heat, but the hybrid film of the present invention has an effect of dissipating frictional heat by the action of a through-hole formed in the thickness direction. Prevents adverse effects caused by frictional heat.

(Overall configuration of the embodiment of the present invention)
As an embodiment of the present invention, an example in which the present invention is applied to a needle bar drive mechanism 10 of a sewing machine will be described with reference to FIGS. FIG. 1 is an exploded perspective view of the needle bar drive mechanism 10.
As shown in FIG. 1, a needle bar drive mechanism 10 for a sewing machine includes a needle bar 12 that holds a sewing needle 11 at its lower end and a needle bar 12 that is fixed to a sewing machine frame (not shown) and that can move up and down at its lower end. Needle bar lower metal bearing 13 to be supported, needle bar upper metal bearing 14 which is fixed to the sewing machine frame and supports the needle bar 12 so that it can move up and down at its upper end, and a needle which is fixedly installed at an intermediate position between the needle bar 12 A bar holder 15, a needle bar crank 16 connected to the sewing machine main shaft, and a crank rod 17 that connects a support shaft provided on the needle bar holder 15 and an eccentric shaft provided on the needle bar crank 16. . Reference numerals 2 and 3 in FIG. 1 denote a balance crank and a balance rod, respectively, for applying a driving force to a balance (not shown).

With the above configuration, the needle bar 12 is supported by the sewing machine frame in a state in which only the vertical movement is possible by the upper and lower metal bearings 13 and 14.
The needle bar crank 16 includes a central axis and an eccentric shaft that is eccentric from the central axis, and the central axis is rotationally driven by a sewing machine motor. On the other hand, the eccentric shaft of the needle bar crank 16 is connected to the base end portion of the crank rod 17, and when a rotational driving force is applied from the center axis side of the needle bar crank 16, the base end portion of the crank rod 17 is moved to the eccentric distance. Around the circumference according to the movement.

The other end side of the crank rod 17 is connected to the needle bar holder 15, and when a circular motion is given by the needle bar crank 16 on one end side, only the vertical movement displacement is transmitted to the needle bar holder 15, The needle bar 12 is moved up and down via the needle bar holder 15. The vertical movement frequency of the needle bar 12 at this time coincides with the rotational speed of the sewing machine motor.
The crank rod 17 will be further described.

This crank rod 17 uses aluminum or aluminum alloy as a base material, and plasma electrolytic oxidation (PEO) treatment method is applied to the entire surface and the inner peripheral surface of the insertion hole into which the support shaft of the needle bar holder 15 is inserted. Thus, a plasma electrolytic oxide film is formed.
This plasma electrolytic oxide film is not formed by attaching to the surface of the base material from the outside, but the surface layer portion (made of aluminum or aluminum alloy) of the base material is a ceramic mainly composed of Al ₂ O ₃ It has been converted to.

Specifically, a two-layer structure composed of a relatively coarse grain layer mainly composed of relatively dense lower layer and amorphous of Al ₂ O ₃ mainly composed of Al ₂ O ₃ crystalline In the thickness direction, a plurality of through holes reaching the interface with the base material are formed. This through hole is the trace of the electric hole formed in the film during plasma electrolytic oxidation.
The two-layer hybrid film can be formed as follows.

First, for example, an electrolytic solution consisting of potassium hydroxide 1 to 3 g / L, water glass 2 to 5 g / L, sodium polyphosphate 2 to 6 g / L, adjusted to pH 8 to 12 and liquid temperature 20 to 25 ° C. is prepared. .
While bubbling the electrolyte, the crank rod (base material) is immersed in the electrolyte as an anode. The counter electrode is a stainless steel cathode electrode.
Next, a voltage of 250 V or more is applied between both electrodes to apply a pulse current, and a plasma filament is generated at the contact interface between the anode electrode (base material) and the electrolytic solution.

  The current to be energized includes a current mode (A mode) in which a plurality of positively polarized anode pulses are periodically arranged, a current mode (C mode) in which a plurality of negatively polarized cathode pulses are periodically arranged, and positive polarization. A mode in which a current mode (AC mode) in which one anodic pulse to be negatively polarized and one cathodic pulse to be negatively polarized are alternately arranged to form one mode is appropriately adopted.

In particular, when the A mode is applied first and then the AC mode is applied, it is preferable because a hybrid film having a two-layer structure can be reliably formed.
The voltage control and the above-described pulse current mode control are all performed by a computer incorporated in the power supply control device.
In addition, in the PEO process, a film is formed on all surfaces where the electrolytic solution is immersed, and therefore, of course, a hybrid film is also formed on the inner peripheral surfaces of the shaft insertion holes at both ends that are not exposed to the outside in the sewing machine assembly. Is done.

FIG. 2 is a cross-sectional photomicrograph of the hybrid film formed on the crank rod surface by PEO treatment. In the figure, reference numeral B denotes a base material, reference numeral M denotes a film of two-layer structure consisting of an upper layer mainly composed of Al ₂ O ₃ of the lower layer and the amorphous mainly composed of crystalline Al ₂ O ₃ .
(Explanation of operation of needle drive mechanism of sewing machine)
The operation of the needle drive mechanism 10 will be described. In the above configuration, when a rotational driving force is input to the central axis of the needle bar crank 16 by driving the sewing machine motor, the one end portion of the crank rod 17 is rotated around the eccentric shaft. As a result, the needle bar 12 supported by the metal bearings 13 and 14 in a state in which only the vertical movement is allowed is only displaced in the vertical direction from the other end of the crank rod 17 through the needle bar holder 15. Communicated. Accordingly, the sewing needle moves up and down appropriately, and the sewing machine executes sewing.

  At the time of sewing, the crank rod 17 generates a tensile load between the needle bar crank 16 and the needle bar holder 15 due to its vertical movement. However, since a hybrid film is formed on the surface of the connecting portion between the connecting portion of the crank rod 17 and the needle bar crank 16 and the connecting portion of the needle bar holder 15 by PEO treatment, Effective and durable. Also, since the coating is formed on the surface around the shaft insertion holes at both ends of the crank rod, the durability of the tensile load around the shaft is ensured, and breakage around the shaft insertion hole is effectively prevented. .

Furthermore, since the film formation treatment is also performed on the inner peripheral surface of the shaft insertion hole at both ends of the crank rod 17, the slidability with the inserted shaft can be ensured, and the sliding surface Since the surface is hardened, the shaft can be smoothly rotated and the wear resistance can be ensured.
(Effect of embodiment)
In the sewing machine, the crank rod 17 of the needle drive mechanism 10 has an aluminum alloy as a base material and a hybrid film formed by PEO treatment on the surface, so that the surface is hardened and wear resistance is reduced by reducing the friction coefficient. It is possible to improve durability and durability of tensile load. Accordingly, even when power is transmitted between the needle bar crank 16 and the needle bar holder 15 at a high speed during sewing, it is effectively endured against the tensile load generated around the whole or around the shaft.

In addition, since a film is also formed on the inner peripheral surface of the shaft insertion hole at both ends of the crank rod 17, the shaft rotation during sewing is facilitated while wear of the shaft insertion hole of the crank rod 17 is suppressed. To do.
Further, since the crank rod 17 is made of an aluminum alloy as a base material, the weight of the member can be reduced, and the above-described wear resistance and durability of the tensile strength can be further improved.
(Other)
In the present embodiment, the base material of the crank rod 17 is made of an aluminum alloy, and the surface thereof is formed with a hybrid film by PEO treatment. However, the other parts may be made of the same material and subjected to the same treatment. Needless to say. In that case, in particular, a component that performs high-speed movement during sewing or a component that causes sliding or collision is more desirable.

A7075 alloy was prepared as a base material, and two specimens were produced from this alloy. At this time, the surface area of one sample (sample 1) was about twice the surface area of the other sample (sample 2). Vickers hardness (Hv) was measured for 5 points on the surface of each specimen, and the average value was obtained. The results are shown in Table 1.
On the other hand, KOH, Na ₂ SiO ₃ and Na ₂ HPO ₄ are dissolved in distilled water, and an electrolyte solution having a pH of 9 mainly composed of a KOH concentration of 2 g / L, a Na ₂ SiO ₃ concentration of 4 g / L and a Na ₂ HPO ₄ concentration of 5 g / L. Was prepared.

A stainless steel plate as a counter electrode was immersed in the electrolytic solution, and the liquid temperature was adjusted to 21 ± 3 ° C. while bubbling the electrolytic solution with air.
Next, the power supply control device was operated to perform plasma electrolytic oxidation in the A + AC mode. The applied voltage was 320 V and the energization current was 3.2 A. The energization time in the A mode was 7 minutes, the energization time in the subsequent AC mode was 13 minutes, and the entire energization was completed in 20 minutes.

  Vickers hardness (Hv) was measured at five points on the surface of the two kinds of treated products obtained, and the average value was obtained. The results are shown in Table 1.

  As is apparent from Table 1, the surface hardness of each specimen before plasma electrolytic oxidation is about 130 to 140 (Hv), but the surface hardness in the case of specimen 1 treated at a low current density. Is 900 (Hv) or more, and in the case of Sample 2 processed at a high current density, the hardness is as extremely high as 1150 (Hv) or more.

For reference, in a hard anodic oxide film forming process (a film forming process of γ-AL203 by an anodic oxidation method) generally performed as a surface treatment for an aluminum alloy, the hardness is 450 (Hv) at the maximum value, It can be seen that the hardness of the hard anodized film is about 350 Hv, and in the case of the specimen of the example, the surface hardness is dramatically increased as compared with this.
From the above results, it can be seen that even when a light aluminum alloy is used, the surface hardness is dramatically improved by the formation of the hybrid film by the PEO treatment. Therefore, it can be seen that it is possible to improve the wear resistance and durability of the sewing machine component that causes movement and sliding.

Further, surface slidability was measured for Sample 1 after plasma electrolytic oxidation. The measurement was performed as follows.
While pressing a spherical indenter with a radius of 5 mm against the surface of the sample, reciprocating 1 to 100 times at a moving speed of 5 mm / sec over a distance of 20 mm and changing the pressing load of the indenter in the range of 20 to 600 g, The coefficient of friction was measured for each reciprocating motion and each pressing load.

The measurement results are shown in FIG.
As apparent from FIG. 3, the surface friction coefficient of the specimen 1 is in the range of 0.15 to 0.3, and the surface friction coefficient of the specimen 1 before plasma electrolytic oxidation is approximately 0.7. Therefore, it can be seen that by forming a hybrid film, the surface of the specimen 1 has a very low coefficient of friction, that is, the slidability is remarkably improved.

Therefore, even when a light aluminum alloy is used, it can be seen that the slidability is improved by forming a film of α-Al ₂ O ₃ by PEO treatment. Therefore, it can be seen that smooth operation can be performed without using a bearing even in the application to a part having a portion that causes high-speed sliding.

Plasma electrolytic oxidation was performed on a round bar (diameter: 12 mm) of A5052 alloy under the conditions of Example 1 to produce five tensile test pieces whose surface layer portion was converted to a hybrid film.
Next, for each test piece, the tensile strength and the elongation were measured according to JIS Z2241, and the average value was obtained.
The tensile strength was 325.4 N / mm ² and the elongation percentage was 22.7%.

That is, considering that the tensile strength of the A5052 alloy is 175 to 245 N / mm ² , it can be seen that the tensile strength is improved by 25% or more by plasma electrolytic oxidation.
In addition, it cannot be overemphasized that conditions, such as a base material material and comparative thickness in each Example mentioned above, may be applied to each member of the sewing machine of embodiment mentioned above. That is, sliding parts such as a needle bar, an upper looper hug, an upper looper guide, a swing canister, and a square piece may be used for parts that require strength such as tensile strength. Or you may make it utilize for the hook etc. which provide a bobbin thread, the link used as a connection component.

  Therefore, even when a light aluminum alloy is used, it is possible to dramatically improve the tensile strength by forming a hybrid film by PEO treatment. Therefore, it can be seen that the durability can be improved even in the application to a member that requires high-speed motion, particularly tensile strength by centrifugal force.

    The sewing machine part of the present invention is made of lightweight aluminum or aluminum alloy as a base material, and the surface layer portion is hard, has excellent frictional properties, and has a high-strength hybrid plasma electrolytic oxide film, so that it can be moved at high speed. On the other hand, its industrial value is great as a sewing machine part having excellent durability.

It is a disassembled perspective view of the needle drive mechanism of the sewing machine which is an embodiment of the present invention. It is a cross-sectional microscope picture of the hybrid membrane | film | coat formed in the crank rod surface by the PEO process. In the surface slidability measurement test, one horizontal axis is the number of reciprocations, the other horizontal axis is the load, and the vertical axis is the measured friction coefficient, showing the friction coefficient based on the measurement in each state in three dimensions It is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Needle drive mechanism of sewing machine 11 Sewing needle 12 Needle bar 13 Lower bearing 14 Upper bearing 15 Needle bar holding 16 Needle bar crank 17 Crank rod

Claims (4)

In sewing machine parts that move by receiving driving force for sewing,
Consisting of an upper layer of the base material of the sewing machine parts made of aluminum or an aluminum alloy, the surface portion of the base material is mainly composed of a lower layer and an amorphous of Al ₂ O ₃ mainly composed of Al ₂ O ₃ crystalline A hybrid plasma electrolytic oxide film having a two-layer structure, wherein the hybrid plasma electrolytic oxide film is formed with a plurality of through holes reaching the interface with the base material in the thickness direction. Sewing machine parts. In sewing machine parts that move by receiving driving force for sewing,
A base material of the sewing machine part is made of aluminum or an aluminum alloy, and a surface layer portion of the base material on a sliding surface with other sewing machine parts is an upper layer mainly composed of crystalline Al ₂ O ₃ and amorphous Al _2. A hybrid plasma electrolytic oxide film having a two-layer structure composed of a lower layer mainly composed of O ₃ , wherein the hybrid plasma electrolytic oxide film has a plurality of through holes reaching the interface with the base material in the thickness direction. Sewing machine parts characterized by being formed.   The sewing machine component according to claim 1 or 2, wherein the hybrid plasma electrolytic oxide film has a thickness of 1 to 150 µm.   4. The sewing machine component according to claim 1, wherein the hybrid plasma electrolytic oxide film has a surface hardness of 800 Hv or more.

Images