JP5465093B2 - Loosening prevention screw - Google Patents

Description

  The present invention relates to a loosening prevention screw that does not loosen after fastening of the screw.

  Normally, in the process of fastening the male screw to the female screw, as shown in FIG. 1 (1), the screw is screwed in the fastening direction 3 with the advance side flank 11 of the male screw 10 and the flank 2 of the female screw 1 in contact with each other at the time of fastening rotation. . At the time of fastening and fixing, as shown in FIG. 1 (2), the pressure side flank 12 of the male screw 10 and the flank 2 of the female screw 1 interfere in the pressure direction 4 and are fastened and fixed by the frictional force.

  Usually, a flat washer and a spring washer are interposed between an object to be fixed and a seat surface (not shown) in order to maintain the frictional force caused by the interference between the pressure side flank 12 of the male screw 10 and the flank 2 of the female screw 1 at the time of fastening and fixing. However, there is a case where the function of the spring washer is lowered and the screw is loosened due to vibration or the like.

  For such situations, various screws have been proposed for the purpose of preventing loosening of the screws. As these, for example, as a loosening prevention screw mainly used for precision instruments, a screw thread coated with a resin such as nylon has been proposed. In this case, the frictional force of the male screw flank and the female screw flank is increased by the flexibility of a material such as nylon coated on the screw thread to make it difficult to loosen the screw.

  In addition, a screw that prevents the loosening by disposing a microcapsule containing a fixing agent in the thread valley portion of the male screw and crushing the microcapsule when the screw is tightened to exude the fixing agent from the inside. Has also been proposed.

  However, since the screws intended to prevent these slacks are not used on the assumption that the screws are removed, there is a problem that once the screws are removed, the slack prevention effect is extremely lowered.

  In addition to the above proposals, tightening screws have been proposed in which the thread shape is made special to increase the frictional force between the male thread side flank and the female thread side flank, or to prevent loosening by biting action (for example, patents) Reference 1). According to this proposal, by making the inclination of the tip of the male screw pressure side flank larger than the inclination of the female screw flank facing the male screw pressure side flank in the fastening state, the screw thread tip of the male screw becomes the female screw flank and the female screw at the time of fastening. By causing the flank base end portion to bite into the male screw flank, a strong anti-loosening effect is exhibited.

  However, in this proposal, the male and female screw flank bite the tip of the mutual thread and damage each other, and the friction prevents the loosening effect. There is a possibility that the original anti-sagging effect cannot be exhibited at the time of re-engaging in the case of slackening.

  Further, a tapping screw having a loosening prevention effect in which a thread flank has a specific shape has been proposed (see, for example, Patent Document 2). This tapping screw has a thread shape in which a first flank surface and a second flank surface having different flank angles are formed and arranged symmetrically.

  The purpose of this flank shape is to reduce the first flank angle at the tip of the screw thread to improve the shearing force when screwed into resin or the like, and to prevent the internal thread from breaking, and the first flank surface and the second flank shape. In the boundary portion of the flank surface, a contact resistance in a direction perpendicular to the screw axis is applied to prevent the screw from loosening naturally.

  In this proposal, since the target of the screw is a tapping screw and the female screw is formed by screwing the male screw, it is difficult to consider the use of multiple screws in the same place. The effect of preventing slack is not expected. Furthermore, there is a problem that it cannot be applied to a nut or the like in which a female screw is formed in advance.

JP 2006-57801 A JP-A-7-269542

  The present invention has been made in view of the circumstances as described above, and by providing the advance side flank shape and the pressure side flank shape in the screw thread as a specific shape, and imparting spring properties to the tip of the screw thread, It has a reliable anti-slack function and an initial anti-slack effect when the screw is removed and re-fastened. In addition, a protrusion with a height that interferes with the top of the female thread is formed at the root of the screw. It is an object of the present invention to provide a slack prevention screw having a sure slack prevention effect.

  The present invention is characterized by the following in order to solve the above problems.

First, a loosening-preventing screw comprising a male screw that is screwed into the female screw in the fastening direction, and that causes the male screw to be fastened to the female screw by frictional force caused by interference between the pressure-side flank of the male screw and the corresponding female screw flank. The flank angle on the pressure side flank is set smaller than the flank angle on the trough side, and the flank angle on the thread side on the advancing flank is set smaller than the flank angle on the pressure side flank. The displacement point is positioned closer to the top of the screw thread than the flank angle displacement point of the advancing flank. During fastening rotation, the leading end of the advancing flank of the male screw is screwed in contact with the female screw flank, and is fastened securely. Sometimes when the pressure side flank of the male thread interferes with the female thread flank, the screw on the pressure side flank of the male thread The top side uses the flank angle displacement point on the leading side as a fulcrum and gives the spring end to the thread end of the male thread with the flank angle displacement point on the pressure side as the working point, and applies a return force to the female thread flank. A loosening prevention screw characterized by exhibiting a prevention effect .

Second, in the slack prevention screw according to the first aspect of the present invention, when the valley flank angle θ ₂ of the pressure side flank is made equal to the flank angle of the internal thread, when the external flank interferes with the external thread flank, the external thread It is preferable that the screw thread top part side flank of the pressure side flank and the screw thread valley part side flank of the pressure side flank are linear.

Third, in the first or slack limiting screw of the second invention, the stabbing flank shape as the pressure flank shape is an asymmetrical shape, the top side flank angle theta ₁ of the pressure flanks is 18 to 22 °, the pressure The side flank valley flank angle θ ₂ is in the range of 29 to 31 °, the leading flank apex flank angle θ ₃ is in the range of 5 to 10 °, and the leading flank valley flank angle θ ₄ is in the range of 38 to 42 °. It is preferable to do so.
Fourthly, in the slack prevention screw of the first to third inventions, it is preferable that at least one protrusion having a height to be in contact with the top of the screw thread is formed in the thread valley.

According to the first to third aspects of the present invention, in the thread advance side flank and pressure side flank, the flank angle at the top of the thread is smaller than the valley flank angle, and the flank angle displacement point of the pressure side flank is By making the shape closer to the top of the thread than the flank angle displacement point of the advancing side flank, it is possible to give springiness to the thread tip, and when the female thread flank and male thread pressure side flank interfere during fastening The flank at the tip of the thread can press the female thread flank and exhibit a slack prevention effect.

According to the fourth aspect of the present invention, at least one protrusion having a height that contacts the top of the female screw thread is formed in the thread valley of the male screw so that the rattling between the male screw and the female screw occurs during fastening rotation. In the case of fastening and fixing, the loosening prevention effect can be exhibited by contact between the female screw thread crest and the male screw protrusion.

It is sectional drawing which shows the fastening process of the external thread with respect to a general internal thread, (1) is a thread sectional view which shows the time of fastening rotation, (2) is a thread sectional view at the time of fastening fixation. It is a screw thread sectional view showing the screw thread shape of the present invention. It is a screw thread sectional view showing the state of the shape change of the screw thread of the present invention, (1) is a thread thread cross sectional view during fastening rotation, (2) is a thread cross sectional view during fastening fixation. (1) is a screw provided with protrusions in the thread valley portion of the present invention, and (2) is a schematic cross-sectional view of the screw portion AA. (1)-(3) is a thread part section schematic diagram of a screw provided with 1-4 projections of the present invention. It is a screw thread sectional view at the time of fastening fixation of a screw provided with a projection of the present invention.

  Hereinafter, the present invention will be described in more detail with reference to the best mode for carrying out the present invention.

  The slack prevention screw according to the present invention is provided with a spring property at the top of the thread of the male screw. The male screw is screwed into the female screw, and at the interference surface between the male screw pressure side flank and the female screw flank when fastened, The loosening prevention effect is obtained by amplifying the frictional force with the female thread flank by the spring property of the thread tip.

  The spring property of the thread tip is such that, at the flank angle of the thread, the flank angle at the valley and the flank angle at the top are different, and the pressure flank shape and the advancing flank shape are asymmetrical. Can be obtained.

As shown in FIG. 2, the above flank shape is such that the apex flank angle θ ₁ of the pressure flank is smaller than the trough flank angle θ ₂ , and the apex flank angle θ ₃ of the advancing flank is smaller than the side flank angle theta _4.

The angle of each flank angle is not particularly limited as long as the above conditions are satisfied. From the viewpoint of imparting appropriate springiness, the flank angle θ ₁ : 18 to 22 ° and the flank angle θ ₂ : 29 to 31 °. The flank angle θ ₃ is preferably 5 to 10 °, and the flank angle θ ₄ is preferably 38 to 42 °.

Specific flank angles within the above ranges can be, for example, flank angle θ ₁ = 20 °, flank angle θ ₂ = 30 °, flank angle θ ₃ = 8 °, and flank angle θ ₄ = 40 °. .

Further, the above flank angles have the following ratios: flank angle θ ₁ / flank angle θ ₂ = 20/30, flank angle θ ₃ / flank angle θ ₄ = 8/40, flank angle θ ₁ / flank angle θ ₃ = It is preferable that 20/8 and flank angle θ ₂ / flank angle θ ₄ = 30/40.

Furthermore, it is preferable that the flank angle θ ₂ of the flank 22 of the pressure side flank is equal to the flank angle of the female screw.

  By setting each flank angle as the above condition, it is possible to give a desired spring strength to the thread tip, and to set the spring property of the thread tip according to the characteristics and material of the applied screw. It becomes possible.

  Further, the flank angle displacement point 25 of the flank 21 and the flank 22 of the pressure side flank is positioned closer to the top of the thread than the flank angle displacement point 26 of the flank 23 of the advance side flank and the flank 24. The positional relationship between the flank angle displacement point 25 of the pressure side flank and the flank angle displacement point 26 of the advance side flank is not particularly limited as long as the above-described conditions are satisfied. When the pressure side flank angle displacement point 25 is set at the position of the thread height / 2, the advance side flank angle displacement point 26 is preferably set at the position of the thread height / 3.

  By setting the positional relationship between the flank angle displacement points as described above, it is possible to set a desired fulcrum and action point, thereby enabling optimum interference of the male screw flank with the female screw flank.

  Hereinafter, the operation at the time of fastening and fixing the slack prevention screw of the present invention in which the thread having the spring property is formed will be described in detail with reference to FIG.

  FIG. 3A is a cross-sectional view showing the state of the thread of the female screw 1 and the thread of the male screw 20 during fastening rotation. The leading end portion of the male screw advance side flank 23 is screwed in a state of being in contact with the female screw flank 2. At the time of fastening and fixing, as shown in FIG. 3 (2), when the pressure side flank 21 of the male screw interferes with the female screw flank 2, the flank 21 deforms with the flank angle displacement point 26 on the advance side as a fulcrum, The flank 21 and the flank 22 are linear and are in close contact with the female thread flank 2.

  At this time, a force that the male screw flank 21 tries to return to the original is applied to the female screw flank 2, and this force causes a slack prevention effect.

  In the present invention, the reason why the positional relationship between the pressure side flank angle displacement point 25 and the advance side flank angle displacement point 26 is specified in the above condition is that the pressure side flank 25 serving as the action point and the advance side as a fulcrum. This is because the screw thread is deformed without stress from the positional relationship of the flank angle displacement point 26, and the male screw flank 21 interferes with the female screw flank 2 with a uniform and balanced force.

  The slack prevention screw of the present invention has the above-described shape and operation, and with the appropriate springiness imparted to the tip of the screw thread, the female screw flank 2, the male screw flank 21, and the flank 22 interfere with each other when the screw is fastened. The pressing effect of the flank 21 can amplify the friction and make it difficult to loosen.

  Furthermore, the slack prevention screw of the present invention is provided with a protrusion having a height that interferes with the top of the thread of the female screw at the valley of the male screw. As shown in FIG. 4 (1), the protrusion 40 is formed in the axial direction on the circumference of the thread valley portion, and is formed as shown in the AA sectional view of the screw portion 41 in FIG. 4 (2). Has been. As shown in FIGS. 5 (1) to (3), one or more, preferably 1 to 4, of the protrusions 40 can be provided.

  The cross-sectional shape of the protrusion 40 is not particularly limited, and may be various shapes such as a triangular cross-section, a trapezoidal cross-sectional shape, and a semicircular cross-sectional shape. Further, the tip of the protrusion that contacts the top of the female thread at the time of tightening can be processed for the purpose of amplifying friction, or the surface of the protrusion can be coated with nylon or the like.

  FIG. 6 shows a cross section of a screw having a protrusion provided on the thread valley portion at the time of fastening.

  The screw thread crest of the female screw interferes with the protrusion 40 provided in the screw thread valley of the male screw, and at the time of fastening rotation, a stable screwing property without rattling can be obtained and a function of preventing looseness can be expressed. .

  Further, by forming the protrusion 40, even if vibration is applied after fastening and fixing, the backlash of the male screw and the female screw is less likely to occur due to less rattling, and for this reason as well. A sagging prevention effect is expressed.

  The above-described configuration in which the protrusion is provided in the thread valley portion of the male screw of the present invention can be applied to a screw thread having a thread shape such as a triangular thread, a square thread, a trapezoidal thread, and a bulb screw.

  Further, by applying the above-described configuration in which the protrusions are provided in the thread valley portion of the male screw of the present invention to the above-described thread-shaped slack prevention screw of the present invention, it is possible to make the screw more difficult to loosen. .

The configuration of the loosening prevention screw of the present invention can be applied without selecting the type of screw, and can also be applied to generally used screws, bolts, fine screws and the like .

  Moreover, the material of the screw is not particularly limited, and can be applied to a resin screw in addition to a metal usually used for a screw.

DESCRIPTION OF SYMBOLS 1 Female thread 2 Female thread flank 3 Fastening direction 4 Pressure direction 10 Male thread thread 11 Leading side flank 12 Pressure side flank 13 Male thread seating surface 20 Male thread thread 21 to 24 Male thread flank 25 Pressure side flank angle displacement point 26 Leading side flank angle Displacement point 40 Protrusion 41 Thread part

Claims (4)

In the loosening prevention screw consisting of a male screw that is screwed into the female screw in the fastening direction and the male screw is fastened to the female screw by frictional force caused by interference between the pressure side flank of the male screw and the corresponding female screw flank.
The screw-side flank angle in the pressure-side flank is made smaller than the valley-side flank angle, and the screw-top side flank angle in the advancing flank is set smaller than the valley-side flank angle.
The flank angle displacement point of the pressure side flank is positioned closer to the top of the thread than the flank angle displacement point of the advance side flank,
During fastening rotation, the leading end of the leading flank of the male screw is screwed in contact with the female screw flank,
During fastening, when the male thread pressure side flank interferes with the female thread flank, the male thread pressure side flank thread peak side uses the advancing flank angle displacement point as a fulcrum and the pressure flank angle displacement point as the operating point. An anti-slack screw characterized in that a spring property is imparted to the tip of the thread of the male screw and a return force is applied to the female thread flank, thereby exhibiting an anti-slack effect . The pressure-side flank valley flank angle θ ₂ is made equal to the flank angle of the female thread, and when the pressure-side flank of the male thread interferes with the female thread flank, the thread-top flank of the pressure-side flank of the male thread and the pressure-side flank The screw thread valley part side flank of this becomes a linear form, The slack prevention screw of Claim 1 characterized by the above-mentioned . The pressure side flank shape and the advancing flank shape are asymmetrical, the pressure side flank apex flank angle θ ₁ is 18 to 22 °, the pressure side flank trough flank angle θ ₂ is 29 to 31 °, and the advancing flank loosening of claim 1 or 2 top side flank angle theta ₃ is 5 to 10 °, valley flank angle theta ₄ of stabbing flank is characterized in that as the range of 38 to 42 ° of Prevention screw. The slack prevention screw according to any one of claims 1 to 3, wherein at least one protrusion having a height that abuts on the top of the thread of the male screw is formed in the thread valley.

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