阅读说明：本技术 螺钉 (Screw nail ) 是由 森茂人 松野真弓 堀内直树 于 2020-02-03 设计创作，主要内容包括：本发明提供能够在确保涂膜等的剥离性的同时谋求螺入转矩的进一步减小、使通电性稳定的螺钉。螺钉在设置于螺杆轴主体(5)的螺纹牙的螺纹面(131)局部地设有凹部(7),所述螺钉的特征在于,形成有所述凹部(7)的部分的螺纹牙(13)比标准的螺纹牙(3)小,且螺入方向的前端部处的齿高(H12)比螺入方向(W)的后端部(H11)的齿高低。(The invention provides a screw which can ensure the stripping performance of a coating film and the like, simultaneously achieve the further reduction of screwing torque and stabilize the electrical conduction performance. A screw is provided with a recess (7) locally on a thread surface (131) of a thread provided on a screw shaft body (5), and is characterized in that a thread (13) of a portion where the recess (7) is formed is smaller than a standard thread (3), and a tooth height (H12) at a front end portion in a screwing direction is lower than a tooth height of a rear end portion (H11) in the screwing direction (W).)

1. A screw having a recessed portion provided locally on a thread surface of a thread provided on a screw shaft body,

the thread of the portion where the recess is formed is smaller than a standard thread, and the tooth height at the front end in the screwing direction is lower than the tooth height at the rear end in the screwing direction,

a step portion is provided on the thread ridge of the portion where the recessed portion is formed, the step portion projecting to a side of the thread surface of the standard thread ridge and coming into contact with or close to the inner diameter end portion of the female thread at the time of the female thread fitting,

the recessed portions are provided on the opposite thread surfaces at the same phase of the mutually adjacent threads, and the root width between the step portions of the adjacent portions where the recessed portions are formed is narrower than the root width of the standard thread, and the root width between the step portions at the leading end in the threading direction is narrower than the root width between the step portions at the trailing end in the threading direction.

2. The screw of claim 1,

the diameter of the step part is 85% -110% of the inner diameter end part of the internal thread.

3. The screw of claim 2,

the height of the step portion varies regularly or irregularly in the circumferential direction, and comes into contact with the inner diameter end of the internal thread at some point within 1 pitch.

4. The screw according to any one of claims 1 to 3,

a thread-surface bulging ridge portion is provided at a portion of the standard thread adjacent to the recessed portion, and the thread-surface bulging ridge portion includes a bulging portion that protrudes toward the thread surface of the standard thread.

5. The screw of claim 4,

the recessed portion, the crest bulging portion, and the normal thread portion are present in 2 or more in 1 lead.

Technical Field

The present invention relates to a screw having a function of peeling off a coating film in order to have electrical conductivity with a nut when the screw is fastened to the nut after coating.

Background

Conventionally, in fastening using a combination of a screw and a weld nut (hereinafter, referred to as a nut) in an automobile assembly line, as a general process, the nut is attached to a vehicle body or the like by welding, and after coating is performed, each part is fastened using the screw.

In this case, in order to perform grounding using, for example, a screw, when there is electrical conduction between the screw and the nut, it is necessary to take out paint that has entered the nut through a secondary drilling (retap) or to provide a mask so that the paint does not enter the nut at the time of painting.

In order to omit such an extra process and improve workability, screws that are electrically energized by fastening the screws in a state where paint is inserted into the nuts have been used.

As such a screw having electrical conductivity, the applicant of the present invention has proposed the screw of patent document 1.

In this screw, a 1 st recessed portion is provided on a pressure side thread surface of a thread provided on a screw shaft main body, a coating film on the female thread side can be peeled off by an edge portion of the 1 st recessed portion, the peeled coating material is retained in the 1 st recessed portion, and a pressure side thread surface other than the 1 st recessed portion of the thread is brought into pressure contact with an outer layer of the female thread from which the coating film is peeled off to enable electrical conduction. In addition, the angle of the non-load-side thread surface of the thread ridge is made smaller than the angle of the pressure-side thread surface, and a gap is formed between the internal thread and the non-load-side thread surface in which the release coating is retained.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 3389331

Disclosure of Invention

Problems to be solved by the invention

According to the screw of patent document 1, since the coating is peeled off from the edge portion of the 1 st recess and the peeled coating is accumulated in the 1 st recess, the screwing torque is reduced, which contributes to improvement of workability of the screw fastening work.

However, in recent years, the corrosion resistance of fastening members has been expected to increase, the coating film thickness has become thicker, and the thickness of the coating film adhering to the bottom of the female thread valley is about 100 μm. Even under such circumstances, higher coating film releasability and stable energization performance have been demanded while ensuring the workability up to now.

However, in the screw of patent document 1, the pressure side thread surface of the thread provided in the screw shaft main body and the pressure side thread surface of the female screw whose coating is peeled off and the metal surface is exposed are brought into pressure contact with each other to be electrically conducted, but if only the recess is simply provided to change the thread shape, it is difficult to ensure coating film peeling property, electrical conductivity, and screwing workability for coating the female screw having a thicker film thickness.

The invention provides a screw which ensures the stripping performance of a coating film and improves the screwing operation performance and has stable current-carrying performance even for a female screw part which is coated with a thick film.

Means for solving the problems

In order to achieve the above object, a screw according to the present invention is a screw in which a recessed portion is partially provided on a thread surface of a thread provided on a screw shaft body, wherein the thread of a portion in which the recessed portion is formed is smaller than a standard thread, and a tooth height at a leading end portion in a screwing direction is lower than a tooth height at a trailing end portion in the screwing direction,

a step portion is provided on the thread ridge of the portion where the recessed portion is formed, the step portion projecting to a side of the thread surface of the standard thread ridge and coming into contact with or close to the inner diameter end portion of the female thread at the time of the female thread fitting,

the recessed portion is provided on a thread surface facing each other at the same phase of the adjacent threads, a root width between the step portions between the threads of the adjacent portions where the recessed portion is formed is narrower than a root width of the standard thread, and a root width between the step portions at a front end portion in the threading direction is narrower than a root width between the step portions at a rear end portion in the threading direction.

In this way, by changing the tooth height in the lead direction in the recessed portion provided locally on the thread surface of the thread, it is possible to suppress a rise in the screwing torque while securing a larger volume of the coating film to be accumulated and peeled.

Further, by providing the step portion, it is possible to suppress rotational vibration of the male screw shaft at the time of fastening, suppress the thickness of the coating film near the valley bottom where the thickness of the female screw is the thickest and bite into the crest of the thread due to the thread biting in a state where the crest of the thread has a variation at the time of entry of the female screw, and reduce the screwing torque.

Further, by compressing and pressing the peeled coating film into the valley bottom portion having the narrowest width together with the rotation at the time of screwing, it is possible to prevent the excessive peeled coating film from moving to the thread surface of the thread which becomes the current-carrying portion, and to avoid the side current-carrying surface interposed between the male thread and the female thread of the current-carrying portion, thereby greatly stabilizing the current-carrying performance.

The step portion may have a diameter of 85% to 110% of the inner diameter end portion of the internal thread.

When the diameter of the stepped portion is set larger than the inner diameter of the inner diameter end portion of the female screw in this way, the stepped portion can be brought into contact with the inner diameter end portion of the female screw, and the electrical conductivity can be improved by the contact portion.

The height of the step portion may be changed regularly or irregularly in the circumferential direction, and may be configured to contact the inner diameter end of the female screw at a certain point within 1 pitch (one circumference on the circumference).

In addition, a thread-surface bulging ridge portion having a bulging portion protruding toward the thread surface of the standard thread may be provided at a portion of the standard thread adjacent to the recessed portion.

By providing the thread-surface bulging ridge portion locally, the convex portion formed by the bulging portion can exert a peeling function against not only the concave portion but also the ridge shape of the standard normal thread, and the peeling performance of the thick film coating film can be further improved.

At the same time, the bulge portion having a mountain-shaped thread surface bulges toward the pressure-side thread surface of the female thread compared to the thread surface of the standard thread, so that the contact surface pressure between the thread surfaces of the male thread and the female thread is locally increased in a state where the axial force at the time of fastening is low, and the resistance value of the contact energizing portion is stably decreased.

Further, by providing at least 2 or more of the above-described standard thread ridges in 1 lead, the ridge shape of the portion provided with the recessed portion, and the 3 types of thread ridge shapes of the thread surface bulging ridge shape, it is possible to suppress the screwing torque even in the thick film coated female thread, and to stably exhibit excellent electrical conduction performance while securing the film peelability.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a screw that can stably exhibit excellent electrical conduction performance even at low axial force while ensuring the peelability of a coating film even for a female screw to be thick-film coated and further reducing the screwing torque.

Drawings

Fig. 1 (a) is a conceptual diagram illustrating an overall configuration of a screw according to an embodiment of the present invention, and fig. 1 (B) is a diagram illustrating a more specific configuration of (a), and fig. 1 (C) is a partially enlarged cross-sectional view of a concave portion of (B) taken along a plane passing through a central axis of a screw shaft.

FIG. 2A is a view of the vicinity of the recess in FIG. 1 as viewed in the center axis direction, (B) is a sectional view taken along line B-B of (A), and (C) is a sectional view taken along line C-C of (A).

Fig. 3 (a) is a sectional view of a conventional screw inserted into a female screw member, (B) is an enlarged view of a portion B of (a), (C) is a sectional view of a state of the screw inserted into the female screw member of the present invention, and (D) is an enlarged view of a portion D of (C).

Fig. 4 is a partially cut-away perspective view of the screw of fig. 1.

Fig. 5 is a view showing a screw according to another embodiment of the present invention.

Detailed Description

The following describes the illustrated embodiments based on the present invention.

First, the overall structure of the screw according to the embodiment of the present invention will be described with reference to (a) and (B) of fig. 1. Fig. 1 (a) is a conceptual diagram showing the entire structure of the screw, and (B) is a diagram showing a more specific structure.

In the figure, a screw 1 includes a head portion 2 and a screw shaft portion 4 provided with a thread 3. The screw shaft portion 4 includes a screw shaft main body 5 and a tip tapered portion 6 extending from a tip end of the screw shaft main body, and the screw thread 3 is continuously formed in a range from the screw shaft main body 5 to the tip tapered portion 6.

As shown in fig. 1 (B), the screw thread 3 of the screw shaft body 5 has recesses 7 arranged at regular intervals at a plurality of locations in the circumferential direction per one turn, in this example, 6 locations, and is formed continuously from the boundary with the distal tapered portion 6 toward the head 2 side by about 8 turns in the example shown in the drawing. The recesses 7 of the respective threads 3 of 8 turns are provided at the same phase in the circumferential direction.

Next, the structure of the concave portion, which is a feature of the present invention, will be described with reference to fig. 1 (C) and 2. Fig. 1 (C) is a partially enlarged cross-sectional view of the recess 7 taken along a plane passing through the center axis N of the screw shaft, fig. 2 (a) is a view of the vicinity of the recess in fig. 1 as viewed in the center axis direction, (B) is a cross-sectional view taken along line B-B of (a), and (C) is a cross-sectional view taken along line C-C of (a).

When the thread ridge of the portion where the recessed portion 7 is formed is the recessed portion thread ridge 13, the tooth height of the recessed portion thread ridge 13 is smaller than the standard thread ridge 3, and both sides of the pressure side thread surface 31 and the non-load side thread surface 32 of the standard thread ridge 3 are recessed by a predetermined dimension. The thread angle β of the non-load-side thread surface 32 of the standard thread 3 is smaller than the thread angle α of the pressure-side thread surface, so that the clearance of the non-load-side thread surface of the female thread 100 is formed larger than the standard thread, and the contact pressure with the thick film coating film adhering to the thread on the female thread side is reduced. In this embodiment, the angle of the pressure side thread surface 31 is set to 30 °, and the angle of the non-load side thread surface 32 is set to 25 °. Of course, the angle is not limited to this, and can be appropriately selected according to the load condition and the like.

The pressure side thread surface 131 and the non-load side thread surface 132 of the recessed thread ridge 13 also have the same flank angle as the pressure side thread surface 31 and the non-load side thread surface 32 of the standard thread ridge 3, and the release coating material is retained in the space of the portions.

Stepped portions 134 and 135 are provided on the pressure side thread surface 131 and the trough portion side of the non-receiving side thread surface 132 of the recessed portion thread ridge 13, and have a stepped shape in which the stepped portions 134 and 135 project further to the side (in the central axis direction of the screw shaft) than the pressure side thread surface 31 and the non-receiving side thread surface 32 of the standard thread ridge 3, and the clearance with the inner diameter end portion 101 of the female thread 100 at the time of internal thread fitting is extremely small. The step portions 134 and 135 are located at a predetermined height h33 from the valley portion 34.

The diameter d10 of the step 134, 135 of the recessed portion thread 13 is set to be larger than the valley diameter d of the standard thread 3 and slightly larger than the inner diameter of the inner diameter end 101 of the female thread or equal to or smaller than the inner diameter of the inner diameter end 101 of the female thread. Specifically, the diameter d10 of the stepped portions 134 and 135 is set to 85% to 110% of the inner diameter end 101 of the female screw 100.

By adopting the mode, when the external thread is screwed into the internal thread, the eccentricity of the external thread rotating shaft relative to the thread axis of the screw can be restrained to be small, the crest of the external thread is prevented from being forcibly bitten into the thick film coating part attached to the bottom of the internal thread valley, and the screwing-in torque is restrained from being increased.

Fig. 3 (a) and (B) show the state of screwing the conventional screw 200 into the female screw 100, and fig. 3 (C) and (D) show the state of screwing the screw 1 of the present invention into the female screw 100. In fig. 3, the thread profile is shown as a triangular screw formed with a crest. The coating T adhering to the inner periphery of the female screw 100 is a thick coating portion T1 at the valley bottom.

In the case of the conventional screw 200, the amount of eccentricity Δ 1 from the female screw 100 (see fig. 3 a) is large, and the crest portion 203a of the thread 203 is screwed in with displacement when entering the female screw 100 due to rotational vibration of the screw shaft at the time of fastening, and the thick film coating portion T1 (the amount of penetration α 1 in fig. 3B) near the valley bottom is bitten, and the screwing torque increases. In particular, in the case of a cationic paint, the thick-film coating portion T which is forcibly engaged and pressed at the time of screwing becomes very hard, and there is a problem that workability is deteriorated due to an increase in torque.

In contrast, in the present invention, the stepped portions 134 and 135 of the recessed portion thread 13 contact the inner diameter end 101 of the female thread 100, and the eccentricity is suppressed to be very small. Therefore, the rotational vibration of the screw shaft at the time of fastening is small, the biting amount α 2 of the crest 3a of the thread 3 into the thick film coating portion T1 is small, and the increase in screwing torque can be suppressed. That is, the thick film coating portion T1 is a portion that does not require peeling, and only a necessary portion between the thread surfaces can be reliably peeled off according to the invention of the present application, in response to the problem that excessive torque is conventionally generated.

Further, the stepped portions 134 and 135 of the recess thread 13 contact the female thread inner diameter end portion 101, so that the contact portion area increases, which contributes to the improvement of the electrical conductivity.

The cross-sectional shape of the upper surface of the stepped portions 134 and 135 taken along a plane passing through the central axis N of the screw shaft shows a straight line orthogonal to the center line of the recessed portion thread 13 (a line orthogonal to the central axis N and connecting the apexes of the vertex angles of the recessed portion thread 13), but may be inclined in a direction in which the height decreases or increases as it goes toward the bottom of the valley, or may be a curved line such as an arc instead of a straight line, instead of being orthogonal to the center line of the recessed portion thread 13. The height of the upper surface of the step portions 134 and 135 from the valley portion 34 is constant in the circumferential direction, but the height may be changed regularly or irregularly, and may be configured to interfere with the inner diameter end portion of the female screw 100 at a certain position within 1 pitch (1 circumference on the circumference). The diameters of the stepped portions 134 and 135 are dimensions of the stepped portions 134 and 135 and the base portions of the pressure side threaded surface 31 and the non-load side threaded surface 32, which are restrained by the mold.

(thread height of concave thread)

Next, the thread height of the recess thread 13 will be described with reference to fig. 2.

As shown in fig. 2 (a), the diameter of the crest 133 of the concave thread 13 is further reduced at the rear end portion in the threading direction W with respect to the crest 33 of the standard thread 3, and the crest height becomes smaller as it goes toward the threading direction tip end portion, and becomes the minimum diameter at the threading direction tip end position. That is, as shown in fig. 2 (B) and (C), the tooth height H12 at the leading end in the screwing direction W of the recessed thread 13 is lower than the tooth height H11 at the trailing end in the screwing direction. The tooth height is a height dimension from the trough portion to the top portion in a perpendicular direction perpendicular to the central axis N of the screw shaft.

With such a configuration, a clearance for retaining foreign matter such as a coating film to be peeled can be secured in a larger area than in the case where the tooth height of the recessed thread 13 is constant, and the screwing torque can be reduced while improving the performance of peeling the coating film.

Further, the difference in the outer diameter from the recess 7 to the standard thread 3 can be reduced, and the increase in the screwing torque due to the rapid change in the tooth height can be suppressed.

When the tooth height of the crest 33 of the standard screw thread 3 is H0, the tooth height H12 at the tip is preferably set to about 60 to 98% of the tooth height H0 of the standard screw thread 3. The tooth height H11 at the rear end portion is preferably less than about 65% to 100% of the tooth height H0 of the standard screw thread 3.

(root width of concave thread)

Next, the root width between the recessed portion threads 13 will be described with reference to fig. 2 (B) and (C).

When viewed in the circumferential direction of the screw shank, the recessed thread ridges 13, 13 provided on the adjacent standard thread ridges 3, 3 are located at the same phase, and the root width W11 or W12 between the stepped portions 134, 135 of the recessed thread ridges 13, 13 is narrower than the root width W0 of the standard thread ridge 3 over the entire circumferential length. The root width W12 at the leading end in the screwing direction is narrower than the root width W11 between the stepped portions 134, 135 at the trailing end in the screwing direction. The tooth root width is widest at the rear end in the screwing direction, gradually becomes narrower toward the front end, and becomes narrowest at the front end in the screwing direction.

By forming in this manner, the tooth height of the recessed thread 13 increases at the rear end portion in the screwing direction, and the portion where the retention space of the coating film or the like at the crest 133 and the thread surfaces 131 and 132 is reduced can be compensated by the portion where the root width of the valley bottom is wide.

The coating film peeled off from the rear end portion of the recessed portion 7 is fed to the valley portion formed by the step portions 134 and 135 as the screwing amount in the screwing direction increases, and further is pushed into the valley portion of the tooth root width W12 at the front end portion in the screwing direction where the tooth root width becomes narrower. Further, the internal thread 100 is compressed by the inner diameter end 101 and is enclosed between the inner diameter end 101 and the stepped portion 134, whereby the excessive peeling coating can be prevented from moving to the pressure side thread surface 31 of the standard thread 3 which is the current passing portion. In this way, by avoiding the contact portion which becomes the current carrying surface where the peeling coating film is interposed between the male screw and the female screw of the current carrying portion, the contact portion becomes the metal-to-metal contact, and the current carrying performance can be greatly stabilized.

(the screw thread surface bulges out the mountain shape)

Next, a thread surface bulging ridge shape 23 existing in a portion which is a boundary between the standard thread ridge 3 and the recessed portion 7 will be described with reference to fig. 1 (C), 2, and 4.

The thread-surface bulging ridges 23 are located at the front end portion and the rear end portion in the screwing direction W, respectively, and are portions that are boundaries between the standard thread 3 and the recessed portion 7, and each of the portions has a ridge shape having bulging portions 231 and 232 that bulge slightly more than the thread surfaces 31 and 32 on the pressure side and the non-load side with respect to the standard thread portion 3.

The bulge parts 231 and 232 are located within the range of the thread surface contact line between the normal thread ridge 3 and the female thread ridge so as to extend from the 1/2-1/3 parts of the normal thread ridge 3 in the crest direction. The bulging heights of the bulging portions 231 and 232 (the heights in the orthogonal direction orthogonal to the thread surfaces 32 and 32) are exaggeratedly shown in the drawings, and have a slightly bulged structure, and are within a range of 0.1 mm. The range is not limited to this, and can be appropriately selected according to the size of the screw, the load condition, and the like.

By the presence of the thread surface bulging ridge 23, not only the recessed shape of the recessed portion 7 but also the projecting shape portions of the bulging portions 231 and 232 are arranged in the circumferential direction with respect to the ridge recess of the normal thread 3, and the peeling performance of the thick film coating film is further improved. The bulging portions 231 and 232 protrude from the thread surfaces 31 and 32 of the normal thread 3 and partially contact the pressure-side thread surface of the female thread, and even in a state where the axial force at the time of fastening is low, the bulging portions can contact the pressure-side thread surface of the female thread in a state where a high surface pressure is generated, thereby reliably bringing the male thread into metal contact with the female thread and stably reducing the resistance value of the contact energization portion.

Next, the operation of the above embodiment will be described.

The screw 1 is screwed into a female screw 100 of a coated weld nut or the like, for example. As shown in fig. 1 (C), foreign matter such as a coating film on the inner periphery of the female screw 100 is peeled off at the mountain-shaped boundary surface between the screw-in direction rear end portion of the recessed portion 7 and the normal thread ridge 3, and the peeled off powder remains in the valley portion between the recessed portion 7 and the step portions 134 and 135. In the present invention, since the tooth height of the recessed thread 13 on the rear end side in the screwing direction is high and the tooth height on the tip side is low, a sufficient clearance for retaining foreign matter such as a peeled coating film can be secured, and increase in screwing torque can be suppressed.

Further, although the crest portion 33 of the normal thread 3 is present with a clearance, the stepped portions of the valley bottoms 134 and 135 provided in the recessed portion 7 are close to the female thread inner diameter portion and the clearance is very small, so that the amount of eccentricity between the male thread axis and the female thread inner diameter axis during screwing can be suppressed, and the crest portion 33 of the normal thread 3 is prevented from being pressed into the female thread valley bottom portion which becomes the thickest and passing through the nut, so that screwing torque is suppressed, and workability is improved.

When the axial force is generated, the bulging portions 231 and 232 of the thread crest bulging ridges 23 existing in the portions that are the boundaries between the standard thread ridges 3 and the recessed portions 7 come into contact with the pressure side thread surfaces of the thread ridges of the female thread 100 first and locally, the surface pressure rises with the increase in the axial force, the metal contact is established, the energization is started, and thereafter the standard thread ridges 3 engage with the pressure side thread surfaces of the thread ridges of the female thread 100, and the metal contact surfaces are increased by friction, thereby constituting the final energization portion.

According to the present invention, it is possible to provide a screw that can stably exhibit excellent electrical conduction performance even at low axial force while ensuring the peeling property of a coating film even for a female screw portion to be thick-film coated and further reducing the screwing torque.

As described above, according to the present embodiment, it is possible to stably exhibit excellent electrical conduction performance even at low axial force while further reducing screwing torque while ensuring the peeling property of the coating film even for the female screw portion to be thick-film coated.

In the above embodiment, the screw having the distal end tapered portion was described, but the distal end tapered portion may not be provided as shown in fig. 5 (a). In the above-described embodiment, the example having the thread-land-bulging ridge 23 was described, but as shown in fig. 5 (B), the thread-land-bulging ridge 23 may not be provided.

Description of the reference numerals

1 screw

2 head part

3 thread ridge

31 pressure side thread surface

32 non-load side thread surface

33 top of

34 valley part

4 screw shaft part

5 screw shaft body

6 tip taper

7 concave part

8 nd 2 nd recess

13 concave part screw thread

131 pressure side thread surface

132 non-load side thread face

133 top part

134 step part

135 step part

100 internal screw thread

101 inner diameter end

T thick film coating part