JPS639765A - Feed screw - Google Patents

Abstract

PURPOSE:To improve the feeding accuracy, when driving a carrier in a print head, by forming a synthetic resin layer integrally onto the outer circumference of a metallic center shaft then forming a thread groove in said synthetic resin layer. CONSTITUTION:A feed screw 11 comprises a center shaft 13 made of a steel rod, a fine ceramic rod, etc. and covered with a synthetic resin layer 14 through powder painting. A thread groove 15 is turned in said synthetic resin layer 14. A carrier body 12 being fitted to the feed screw 11 is formed of metal or synthetic resin fine ceramic. Since the thread groove can be turned easily and accurately, the feeding accuracy can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a feed screw used for driving a print head carrier, etc.

[Conventional technology]

As shown in FIGS. 1 and 2, the feed screw mechanism used to drive the carrier of the print head in a printer has a carrier body 2 fitted to a feed screw 1 and provided on the inner periphery of the carrier body 2. The guide protrusion 3 is brought into sliding contact with the screw groove 4.

In this case, the feed screw 1 is made by cutting a thread groove 4 into a steel bar such as stainless steel, and the carrier body 2 is made of synthetic resin such as nylon or polyacetal.

[Problem that the invention seeks to solve]

The above-mentioned thread feeding mechanism has a simple structure and is easy to assemble, so it is widely used in printing mechanisms of printers and the like. However, since the thread groove 4 is formed by cutting, it is difficult to increase the feed accuracy, and the surface roughness of the thread groove 4 also becomes rough. There is a problem that the protrusions 3 of the carrier body 2 that are in contact with the carrier body 2 are easily worn out and have poor durability.

If lubricating oil or grease is applied to the surface of the feed screw 1 in order to reduce driving torque and improve durability, it will tend to attract foreign matter such as dust, and may also cause changes in the viscosity of the lubricating oil and solidification of the grease. This has drawbacks such as malfunctions caused by this. Further, if a seal structure is adopted to prevent attachment of foreign matter, the cost will be high and the driving torque will increase due to friction between the seal member and the feed screw.

Furthermore, if the thread grooves 4 are formed by grinding, the feed accuracy will be improved and the surface roughness of the thread grooves 4 will also be improved, but the processing cost will be very high. Furthermore, if the number of protrusions 3 is increased in order to improve durability, high-precision machining will be required and driving torque will also increase.

Further, if the feed screw 1 is made of synthetic resin, the bending strength is insufficient, and since synthetic resin generally has a larger coefficient of thermal expansion than metal, there is a problem that accuracy is greatly affected by changes in ambient temperature.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art and to provide a feed screw that has high feed accuracy, maintains stable drive torque, and has excellent durability.

[Means for solving problems]

In order to solve the above problems, this invention integrally forms a synthetic resin layer around the outer periphery of a central axis made of metal, fine ceramics, etc., which have high bending strength and a small coefficient of thermal expansion, and thread grooves are formed in the synthetic resin layer. It was formed.

The configuration of the present invention will be explained in more detail below.

FIG. 3 shows a screw feeding mechanism that combines the feed screw 11 and carrier body 12 of the present invention. The feed screw 11 is constructed by coating a synthetic resin layer 14 on the outer periphery of a central shaft 13 made of a steel rod, rod-shaped fine ceramics, etc. by powder coating, and turning a thread groove 15 into the synthetic resin layer 14.

The material forming the synthetic resin layer 14 may be a thermosetting resin or a thermoplastic resin, as long as a relatively thick resin layer can be obtained and can be welded to the outer periphery of the central shaft 13, and preferably powder. Something that can be painted is best.

Examples include polyimide resin, polyphenylene sulfide resin, molten fluororesin, epoxy resin, polyethylene resin, polyacetal resin, polyamide resin, tetrafluoroethylene/ethylene copolymer resin (ETFE), and the like. Further, the thickness of the zero layer may be mixed with various fillers, oils, etc. as long as the effects of the present invention are not impaired. It is about on.

The carrier main body 12 fitted to the above-mentioned feed screw 11 is
Made of metal, synthetic resin, and fine ceramics. If metal is used, a separately formed pin 16 is inserted into the carrier body 12 with a radial hole 17 as shown.
It is press-fitted and fixed, and is made to protrude from the inner circumferential surface.

In addition, when the carrier body 12 is made of synthetic resin or fine ceramics, the resin material that forms protrusions integral with the carrier body 12 instead of the pins 16 is 0. It is necessary to have the mechanical strength and dimensional stability required when the head etc. are assembled, and to have good wear resistance. For example, polyimide resin, polyamideimide resin, polyetherimide resin, polyphenylene sulfide resin,
Examples include epoxy resin, polyetherketone resin, and polyethersulfone resin.

In the case of FIG. 4, the feed screw 11 has the same structure as above, and a steel ball 18 is fitted into the inner surface of the carrier body 12. The steel ball 18 is held by a recess provided at the tip of the adjustment screw 19, and the baraclavage can be adjusted by operating the adjustment screw 19.Instead of the 0W4 ball 18, a ball made of high hardness material such as ceramics is used. A ball can also be used.

Further, as the material of the carrier body 12, metal, synthetic resin, fine ceramics, etc. are used as in the above-mentioned material.

Note that the steel balls 18 may be directly held in the recesses 20 of the carrier body 12, as shown in FIGS. 5 and 6. In this case, there is no adjustment mechanism for the baraclavusi.

FIG. 7 shows an example in which the feed screw 11 is rotatably supported by the printer main body 21, and the print head 22, guide member 23, etc. are assembled to the carrier main body 12, and the guide member 23 is attached to the carrier main body 12. The printer body 21
The carrier body 12 is brought into contact with the guide rail 24 of the carrier body 12 to prevent rotation of the carrier body 12.

[Example 1] Example 1 has the configuration shown in Fig. 3, in which a steel bar with a diameter of 4.5 mm was used for the central shaft 13, and after melting and adhering polyamide resin, the steel bar was heated at 210 to 230°C. The synthetic resin layer 14 having a thickness of 0.8 to 1°Ofi was formed by baking for 5 minutes.

The outer diameter including the synthetic resin layer 14 was turned to 6 mm, and then the thread groove 15 was formed by turning. The thread groove 15 is
Single right-handed thread, lead 6fi, groove depth 0.
It was a rectangle with a length of 6 m and a width of 1 m.

The carrier body 12 is made of aluminum, and the feed screw 11
The gap between the outer periphery and the
It had a cylindrical shape with an axial length of 20 days and an outer diameter of 15 m.

The pin 16 is made of bearing steel (SUJ2) and has a HRC of 60 to 6.
4 is quenched and hardened to have an outer diameter of 0.9 mm and a length of 4 nm, and a hole 17 is drilled at one location in the center of the carrier body 12.
It was fixed to the correct size. The protrusion amount of the pin 16 was set to 0.5fi.

The carrier body 12 processed as described above is attached to the feed screw 11.
While sliding the tip of the pin 16 into the threaded groove 15 from one end, the two were assembled by rotating them relative to each other.

[Example 2] Example 2 has the configuration shown in FIG. 4, and the feed screw 11 has the same structure as Example 1 except for the shape of the thread groove 15. The thread groove 15 in this case was an arcuate groove with a depth of 0.5 fi and a radius of 0.15 m in its right-angled cross section.

The carrier body 12 also has the same structure as in Example 1, but in this case, in addition to the pin 16, a steel ball 18 with a diameter of 1.5 fins made of quench-hardened SUJ 2 was used.

[Example 3] As a material for forming the synthetic resin layer 14 of the feed screw 11,
A material in which 75% by weight of polyamide resin was filled with 15% by weight of potassium titanate voice car and 21% by weight of Keranatsu 9F was used. Other than this point, the second embodiment is the same as the second embodiment.

[Example 4] As a material for forming the synthetic resin layer 14 of the feed screw 11,
ETFE filled with 20% by weight of carbon fiber was used. Other than this point, it was the same as Example 2. [Comparative Example] As a comparative example, a screw feeding mechanism having the structure shown in FIG. 1 was manufactured. The feed screw 11 had an outer diameter of 6 fi, was made of polished steel bar, and had a thread groove 4 machined on its outer periphery. Thread groove 1 is a single right-handed thread, with a lead of 6 mm and a depth of 0 in the cross section at right angles to the groove.
．． It was made into a rectangle with a width of 6 nm and a width of 2 squares. The carrier body 2 is made of polyacetal (Duracon M90 manufactured by Polyplastics)
), and injection molded into a shape having the protrusion 3 integrally. The clearance with the feed screw 1 should be 30 to 50μ, and the outer diameter should be 15
The protrusion 3 had a width of 1.9 fi in the direction perpendicular to the thread groove 4, a length of 3 fi in the direction parallel to the thread groove 4, and a protrusion of 10.5 nm. Feed screw 1
Lubricating oil was applied between the carrier body 2 and the carrier body 2.

[Continuous operation test and its results]

Continuous operation was performed for the above-mentioned Examples 1 to 4 and Comparative Example, and the axial clearance (puff clearance) between the feed screw and the carrier body and the driving torque were measured before the start of the continuous operation and after the end of the same. The results are shown in Table 1.

In addition, after the operation is finished, visually confirm the adhesion of foreign substances such as dust to the outer periphery of the feed screw. The amount is small (○ mark), a large amount is attached (x mark)
The results of the three-level evaluation are also shown in Table 1.

As is clear from Table 1, Examples 1 to 4 show an extremely small increase in axial clearance due to continuous operation compared to the comparative example, and exhibit excellent durability.

In addition, the change in drive torque due to continuous operation is extremely small.
It also has excellent drive torque stability.

In addition, in Examples 3 and 4, the amount of foreign matter adhering was very small compared to the others, but this was due to the synthesis of the feed screw and the filling of the resin layer with a conductive filler. This is because the generation of static electricity due to sliding was prevented.

〔effect〕

As described above, the feed screw of the present invention has a synthetic resin layer integrally formed around the outer periphery of a metal central shaft, and a thread groove is formed in the synthetic resin layer, so the thread groove can be easily formed. And it can be cut with high precision. Furthermore, due to the self-lubricating property of the resin of the synthetic resin layer itself, there is less wear on the protrusions of the carrier body that slide into the thread grooves, resulting in improved durability. Furthermore, since no lubricant is used, the driving torque is stable over a long period of time, and foreign matter such as chips is less likely to adhere. Furthermore, since the central shaft is made of metal, it has high bending rigidity, and since thermal expansion of the synthetic resin layer is restricted, the feeding accuracy is not significantly affected by temperature changes.

[Brief explanation of drawings]

Figure 1 is a sectional view of a conventional screw feed mechanism, and Figure 2 is a cross-sectional view of a conventional screw feed mechanism.
3 is a sectional view of the embodiment, FIG. 4 is a sectional view of another embodiment, FIGS. 5 and 6 are sectional views of the steel ball holding part in other embodiments, and FIG. The figure is a perspective view showing a part of the printer. 11...Feed screw, 12...Carrier body, 13...Center shaft, 14...Synthetic resin layer, 15...Thread groove , 16... Pin, 18... Steel ball, 19... Bend adjustment screw. Patent applicant: Western Bear Rulon Industrial Co., Ltd. Agent: Kama 1) Text 2 Figure 1 Figure 2 Figure 5 Figure 3 Figure 4 Figure 6

Claims (1)

[Claims] A feed screw made of metal, fine ceramics, etc., which has a high bending strength and a small coefficient of thermal expansion, and a synthetic resin layer is integrally formed around the outer periphery of the central shaft, and a thread groove is formed in the synthetic resin layer.