JPH0714649Y2 - Screw fastening structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a screw fastening structure using a tapping screw.

[Conventional technology]

Conventionally, when using a screw fastening structure that fastens members with tapping screws, the operating force at the time of screwing,
The diameter of the screw hole is set appropriately in consideration of the balance with the fastening strength after screwing.

[Problems to be solved by the device]

However, especially when the screw holes are made of plastic, tapping may occur due to heat after fastening.
There was a problem that the screw was likely to come loose.

As a countermeasure against this point, it is conceivable to make the diameter of the pilot hole small in anticipation of loosening later so that the tapping screw bites deeply into the peripheral wall of the pilot hole.

However, in this case, it is actually extremely difficult to set the pilot hole diameter to the optimum size, and the screw hole resistance is excessively reduced by making the hole diameter too small, which makes screwing difficult and also causes cracks in the pilot hole peripheral wall. There are cases.

Therefore, the present invention provides a screw fastening structure in which the screwing resistance does not become excessive and a stable fastening state in which loosening does not occur later can be obtained.

[Means for Solving the Problems]

According to the present invention, an axial projection is provided on the outer peripheral surface of a tubular member, and the tubular member is press-fitted into a mounting hole of a member to be fastened. With the bulge corresponding to the protrusion pushed out on the peripheral surface,
A tapping screw is screwed into this tubular member.

Further, the bulging portion may be provided in advance on the inner peripheral surface of the tubular member.

[Action]

With this configuration, the bulging portion on the inner circumference of the tubular member deepens the biting of the tapping screw in the circumferential direction,
At this portion, the constraint force applied to the tapping screw from the outer peripheral side becomes large, so that the screwing resistance does not become excessive, and a stable fastening state in which loosening does not occur later can be obtained.

In addition, since the tubular member can be fixed in the mounting hole by forming the bulging portion as the inner peripheral side pushing portion by the press-fitting reaction force of the outer peripheral protrusion, the tubular member can be fixed when the tapping screw is screwed in. It is not necessary to press it from the back side, and the screwing work becomes easy.

Furthermore, since the tubular member is made of a soft synthetic resin, it has flexibility, and even if there is some variation in the hole diameter of the mounting hole, the above variation can be absorbed by expansion and contraction of the protrusion in the radial direction. is there. In addition, the expansion and contraction of the protrusion in the radial direction also expands and contracts in the radial direction.Therefore, the expansion and contraction of the protrusion expands the applicable range of the hole diameter of the mounting hole and the size of the tapping screw, and also causes the fluctuation. However, the tubular member can be securely fixed to the member to be fastened via the tapping screw.

〔Example〕

 An embodiment of the present invention will be described with reference to the drawings.

In this embodiment, a case where the P range switch 2 is attached to the guide plate 1 of the selector lever in a vehicle with an automatic transmission is applied as an example.

The P range switch 2 detects that the selector lever is in the P range in a safety device that allows lever operation on condition that the selector lever is in the P range (parking range) as a part of measures against sudden start. It is for doing.

As a mounting means of the P range switch 2 to the guide plate (fastened member) 1, as shown in FIGS.
The switch mounting holes 3 and 3 corresponding to the switch mounting holes 3 and 3 are provided, and with the cylindrical stopper plugs 4 and 4 as the tubular member pressed into the switch mounting holes 3 and 3 from the back side, tapping to these stopper plugs 4 and 4 is performed.・ The screws 5 and 5 are screwed in from the front side.

Both stopper plugs 4 and 4 are made of a plastic such as nylon that is relatively soft and easily deformed by a mechanical external force, and are integrally formed on a common substrate 41.
The diameter of 4a (see Fig. 3) is tapping screw 5.
It is set to be smaller than the outer diameter (thread diameter) dimension of.

On the outer peripheral surfaces of the both stopper plugs 4, 4, projections 42 having a substantially semicircular cross section are integrally provided at three locations at regular intervals in the circumferential direction over the entire axial length.

As shown in FIG. 4, the diameter D ₁ of the switch mounting hole 3 is slightly larger than the outer diameter D _{2 of the} portion of the stopper plug 4 excluding the protrusions 42, and the diameter of the circle passing through the tips of the protrusions 42 ( hereinafter referred protrusions outside diameter) than D ₃ is set smaller, the projection outside diameter D ₃
And the switch mounting hole diameter D ₁ cause the stop plug 4 to be pressed into the switch mounting hole 3. In order to facilitate this press-fitting operation, it is desirable to form the tip outer peripheral surfaces of the stopper plugs 4, 4 in a tapered shape.

When the stopper plug 4 is press-fitted into the switch mounting hole 3, the press-fitting reaction force, that is, the protrusions 42 are pressed from the outer periphery by the peripheral wall of the mounting hole, so that the state shown in FIG. At the inner peripheral surface of the stopper plug (the peripheral wall of the lower hole 4a), the portions corresponding to the protrusions 42 are extruded inward to form bulging portions 43. In FIG. 5, 42a ... Remains of the protrusions 42.

In this manner, with the bulging portions 43 ... Formed on the peripheral wall of the lower hole 4a of the stopper plug 4, the tapping screw 5 (in FIG. 5, the broken line a in FIG. 5 indicates the thread crest of the tapping screw 5, When the solid line mouths indicate the valley bottoms), the biting of the tapping screw 5 to the peripheral wall of the pilot hole becomes deeper than the other parts at the bulging part 43 ..., and the tapping screw at the deep part of this biting 5 is strongly pressed from the outer peripheral side toward the center side, and the restraining force is increased locally in the circumferential direction. That is, as shown in FIG. 6, the tapping screw 5 is screwed into the pilot hole 4a, and the meat portion of the circumferential wall of the pilot hole corresponding to the biting amount of the tapping screw 5 (the portion surrounded by the thick chain line in the figure) is The bulge 43 when chasing chips, including chips, into the root of the screw
Since the flesh to be driven in is increased and the valley is almost full, the binding force applied from the outer peripheral side to the tapping screw 5 is increased at this portion. In FIG. 6, an imaginary line C shows the original inner peripheral surface of the prepared hole 4a excluding the bulging portion 43.

As a result, the fastening strength is increased, and a stable fastening state in which loosening does not occur even if the stop plug 4 is thermally expanded later is obtained.

Further, since the large restraining force on the tapping screw 5 acts only on the bulging portion 43, an excessive screwing resistance does not act when the tapping screw 5 is screwed in. For example, the diameter of the pilot hole 4a is expanded. There is no danger that the screwing operation itself will become difficult or that the stopper plug 4 will be broken due to excessive screwing resistance, as in the case where the dimensions are set with reference to the tips of the protruding portions 43.

Further, according to the structure of this embodiment in which the stopper plug 4 is press-fitted into the switch mounting hole 3 to form the bulging portion 43 ... Corresponding to the protrusion 42 on the inner peripheral side, the stopper plug 4 is screwed when the tapping screw 5 is screwed in. Since it is not necessary to hold it from the back side, the screwing operation becomes easy.

By the way, in the above embodiment, the two stopper plugs 4 and 4 are integrally formed with the substrate 41 being common.
The 4,4 may be formed separately. Further, the bulging portions 43, 44 of the stopper plug 4 are not limited to the above-mentioned three locations in the circumferential direction, but may be formed in two locations or four or more locations.

On the other hand, the present invention can be widely applied not only to the mounting portion of the P range switch to the guide plate of the selector lever in the vehicle with the automatic transmission described above, but also to the mounting portion of various members by tapping screws in various fields. it can.

[Effect of device]

As described above, according to the present invention, an axial bulge is formed on the inner peripheral surface of the tubular member into which the tapping screw is screwed, and the bulge allows the tapping screw to bite partially in the circumferential direction. Since the structure is deep, that is, the binding force of the tapping screw is increased, it is possible to obtain a stable fastening state in which the screwing resistance does not become excessive and the loosening does not occur later.

In addition, the bulging portion is formed as the inner peripheral side pushing portion by the press-fitting reaction force of the outer peripheral projection, and the bulging portion is formed.
Since the tubular member can be fixed in the mounting hole, it is not necessary to press the tubular member from the back side when the tapping screw is screwed in, and the screwing operation becomes easy. in addition,
As compared with the case where the bulging portion is provided on the inner circumference of the tubular member from the beginning, the tubular member can be processed more easily.

Furthermore, since the tubular member is made of a soft synthetic resin, it has flexibility, and even if there is some variation in the hole diameter of the mounting hole, the above variation can be absorbed by expansion and contraction of the protrusion in the radial direction. is there. Further, since the bulging portion also expands and contracts in the radial direction due to the radial expansion and contraction of the protrusion, the expansion and contraction of the bulging portion can correspond to the tapping screw size set in proportion to the hole diameter of the mounting hole. In addition, the applicable range of the diameter of the mounting hole and the size of the tapping screw is expanded, and even if there is the above fluctuation, it is possible to securely fix the tubular member to the fastened member via the tapping screw, which is convenient. is there.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a first embodiment of the present invention, FIG. 2 is a sectional view of the same fastening state, and FIG. 3 is an enlarged perspective view of a stopper plug as a tubular member in the same embodiment. The figure is an enlarged front view of the stopper plug, and Fig. 5 is a diagram corresponding to Fig. 4 in which the tapping screw is screwed into the stopper plug.
The drawing is an enlarged sectional view taken along line VI-VI in FIG. 3 ... Mounting hole, 4 ... Stop plug as a tubular member, 42 ... Outer peripheral projection of the same stop plug, 43 ... Swelling portion extruded toward the inner peripheral side by the same projection, 44 ... Preliminarily provided on the inner peripheral surface of the stop plug Bulged part, 5 ... Tapping screw.

Claims (1)

[Scope of utility model registration request] 1. A cylindrical member made of soft synthetic resin is provided with an axial projection on an outer peripheral surface thereof, and the cylindrical member is press-fitted into a mounting hole of a member to be fastened, and the press-fitting presses the projection from the outer circumference. The tapping screw is screwed into the tubular member in a state where the bulging portion corresponding to the protrusion is pushed out to the inner peripheral surface of the tubular member, and the tapping screw is screwed into the tubular member.