JPH086738B2 - Fatigue resistant screw structure - Google Patents

Description

Description: [Industrial application] The present invention relates to a fatigue-resistant screw structure used for accumulators and the like.

[Prior Art] As shown in FIG. 9, the accumulator is a container main body 1.
The inside of the chamber is partitioned by a bladder 2 into a gas chamber 2a and a fluid chamber 2b, both ends of which are closed by side plates 3 and 4, and the bladder 2 is expanded and contracted in response to changes in the hydraulic pressure of the liquid circuit 5 to pulsate the hydraulic circuit. It is used for absorption and shock absorbers.

Parallel screws are used as fixing means for the container body 1 and the side plates 3 and 4.

However, when the pressure inside the accumulator rises and the side plate is pushed outward, axial and circumferential loads are applied to the screw. However, this load is largely biased in the tensile force direction,
A large load is applied to the thread on the tip side of the female screw that receives the tensile load, and the load is concentrated especially on the first thread. Therefore, stress concentration occurs in the thread bottom valley at the tip of the female thread, and the thread is destroyed from there.

Therefore, in order to solve this problem, the tops of the threads of the male thread are cut off in order from the first peak, the second peak, and the third peak so that the straight line connecting the tops is tapered. It is possible to use a screw (hereinafter referred to as a taper screw). (Japanese Patent Publication No. 56-53651, U.S. Pat.
(See No.) This screw is intended to prevent the generation of concentrated stress by gradually reducing the contact area between the male and female threads in the tensile load direction so that the shared load of each thread is uniform. .

[Problems to be Solved by the Invention] In the taper screw of the conventional example, the first thread that receives a tensile load causes plastic deformation and deformation within the elastic limit with respect to the tensile load, and only the elastic limit deformation component is generated. The load is shared, and the other loads are transmitted to the next second thread ridge. Then, the thread shares the load in the same manner as the thread of the first thread, and the other load is transmitted to the next thread. In this way, if the shared load of each screw thread is regulated by the contact area, the pitch changes because the local portion of each screw thread undergoes plastic deformation as described above. Therefore, the screwed female screw and male screw may not be able to move relative to each other, which may hinder maintenance and inspection of the accumulator.

The present invention has been made in view of the above circumstances, and an object thereof is to prevent a screw thread from being plastically deformed.

[Means for Solving the Problems] The present invention relates to a screw structure in which a male thread and a female thread each having a screw thread and a thread trough are screwed together; the diameters of the thread roots of the male thread are the same. The diameters of the thread roots of the screw are the same, the threads of the both threads are formed in a plate shape in vertical cross section, and both slopes of the threads of the female thread are in surface contact with the slopes of the opposite threads of the male thread. Bias prevention rings are provided on both end surfaces of the female thread, and the outer peripheral surface of the baffle prevention ring is located outside the thread root of the female thread, and the inner peripheral surface abuts the top of the male thread. It has a screw structure that is strong against fatigue.

[Operation] When a load is applied to the male screw, the threads of the female screw receive a compressive load. The ridges of the female thread are sandwiched between the sloping surfaces on the top side by the sloping surfaces of the male thread, and both end surfaces are deformed while being sandwiched by the anti-bias rings.

[First Embodiment] A first embodiment of the present invention will be described with reference to the accompanying drawings.
The same reference numerals have the same names and functions. Male thread 10
The female screws 15 are concentrically screwed together, and the distances from the shaft center to the respective thread roots 13 of the male screw 10, that is, the diameters are equal, and the distances from the shaft center to the respective thread roots 18 of the female screw 15, that is, the diameters. Are formed equal to each other.

The threads 11 of the male screw 10 having the same pitch P are formed in a trapezoidal cross section.

In order to make the thread 16 of the female screw 15 easily deformable, the relief portions 12, 12 'are formed. Female thread 15 is the above male thread 10
Is formed of a material having the same elastic coefficient as that of P and has an equal pitch P. The thread 16 of the female thread 15 is formed in a plate shape in a longitudinal section, and the height H of the thread 16 is higher than that of a normal thread and higher than the thread height h of the male thread 10. Top of female thread 15
The width D of 15a is formed to be narrower than the width d of the top portion 10a of the thread 11 of the male thread, and the thread 16 is more easily deformed than the thread 11. An eccentricity prevention ring is fixed to both end surfaces of the female screw 15 with bolts in order to prevent eccentricity.
The prevention ring 17 is an annular body having a width in the radial direction larger than the height H of the internal thread, and its outer peripheral surface is located outside the thread root 18 of the internal thread 15. That is, the distance between the outer peripheral surface and the center of the male screw 10 is formed larger than the distance between the root of the female screw and the center of the male screw 10.

The inner peripheral surface of the ring 17 is the top of the thread 11 of the male screw 10.
It is in contact with 10a. An adjusting space 14 is provided between the top portion 15a of the female screw 15 and the screw root 13 of the male screw 10, and an adjusting space 19 is provided between the top portion 10a of the male screw 10 and the female screw root 18.
The threads 16 of the female thread are made to be easily deformed. Both slopes near the top of each thread of female thread 15 are opposite male threads 10
Is in surface contact with the slope of the thread.

As shown in FIG. 1, when a load is applied to the external thread 10 in the direction of arrow A10, the internal thread 15 receives the compressive load of arrow A15 and
As shown, the female thread 16 is deformed over its height H, ie its entire length. However, the length of this deformation, that is, the deformation span is extremely longer than that of the standard screw or the male screw, and since it is a plate shape that is easily deformed, the load per unit length of the screw thread 16 is small, and No stress concentration occurs.

Therefore, the thread 16 is deformed only within the range of the elastic limit, and is not plastically deformed.

The axial center of the female screw 15 tends to displace as the thread 16 is deformed, but the anti-bias rings 17, 1 provided at both ends of the thread
This is prevented by the 7 ', so that the screws 10, 15 are always kept concentric.

It should be noted that the thread 11 of the external thread 10 is substantially not deformed, as compared with the thread 16 of the female thread 15, because the width d of the top portion 10a thereof is wider and the height h thereof is lower.

The embodiment of the present invention is not limited to the above,
For example, as in the second embodiment shown in FIGS. 3 and 4, the threads 21 and 26 of the external thread 20 and the internal thread 25 are formed in a plate shape in longitudinal section, and the height H of both threads 21 and 26 is H. The widths D and d of the tops 21a and 26a and the adjustment spaces 24 and 29 may be formed in the same manner. In the second embodiment, when a load is applied to the male screw 20 in the direction of arrow A20, the female screw 25 is compressed in the direction of arrow A25.

Then, both threads 21, 26 are deformed as shown in FIG. The threads 21 and 26 are higher than the standard threads, have a long so-called deformation span, and are formed in a plate shape in a vertical cross section. Therefore, the threads are less weighted per unit length and stress concentration does not occur. Therefore, it is possible to prevent plastic deformation because it deforms only within the elastic limit.

FIG. 5 and FIG. 6 show the third embodiment, in which spiral grooves 33, 38 are formed in the male screw main body 30 and the female screw main body 35, respectively, and the thread-shaped thread members 31, 36 formed in a strip shape are described above. Spiral groove 33,
38, respectively, to form male thread threads 31, 36.

In the third embodiment, when the male screw 30 is loaded in the direction of arrow A30, the female screw 35 is compressed in the direction of arrow A35,
As shown in the drawing, the threads 31 and 36 are deformed to each other, but the procedure is the same as in the second embodiment.

7 and 8 are views showing a fourth embodiment, in which the container body 45 of the accumulator Acc and the screw surfaces 45a, 40a of the side plate 40 are
Threaded fitting grooves 45b, 40b are formed at equal pitches on the respective screw surfaces 45a, 40a, which are opposed to each other via the deformation space S. One plate-shaped screw thread member 50 is positioned in the deformation space S, and both end edges thereof are set in the screw thread fitting grooves 45b, 4b.
Fit in 0b and fix.

In the fourth embodiment, when the bladder 2 is compressed and the side plate 40 is weighted in the direction of arrow A40 due to the fluctuation of the hydraulic pressure in the hydraulic circuit, the container body 45 receives the force in the direction of arrow A45. At this time, the plate screw thread member 50 in the deformation space S is deformed over its width W, that is, its entire width as shown in FIG. 8, so that the deformation span is longer than that of the standard screw thread. . Therefore, the weight per unit length of the member 50 is much smaller than that of the standard screw, and the stress concentration is small.

Therefore, it can be deformed only within the elastic limit, and does not reach plastic deformation.

In addition, in the above embodiment, the screw thread having a plate shape (strip shape) and having a rectangular cross section in the width direction has been described, but the cross section in the width direction of the screw thread does not necessarily have to be a rectangular shape. Of course, for example, it may be trapezoidal or triangular.

[Effects of the Invention] Since the fatigue-resistant screw structure according to the present invention has a thread formed in a plate shape in a vertical cross section to extend the deformation span, it is more easily deformed than the conventional one, and the load per unit length is increased. Get smaller.

Therefore, it is possible to prevent the stress concentration from occurring and the threads are deformed only within the elastic limit range. Therefore, since plastic deformation does not occur, the pitch of the screw does not change unlike the conventional example.

[Brief description of drawings]

1 and 2 are views showing a first embodiment of the present invention.
The drawing is a vertical sectional view, FIG. 2 is a vertical sectional view showing another state of FIG. 1, FIG. 3 is a vertical sectional view showing a second embodiment, and FIG.
FIG. 5 is a vertical sectional view showing another state of the drawing, FIG. 5 is a vertical sectional view showing a third embodiment, FIG. 6 is a vertical sectional view showing another state of FIG. 5, and FIG. 7 is a fourth embodiment. FIG. 8 is a vertical sectional view showing
FIG. 9 is a vertical sectional view showing another state of the figure, and FIG. 9 is a vertical sectional view showing a conventional example. 10 …… Male thread 11 …… Screw thread 14 …… Adjustment space 15 …… Female thread 16 …… Screw thread 17 …… Bias prevention ring 19 …… Adjustment space 30 …… Screw body 31 …… Plate thread member 33 ...... Screw groove 35 …… Screw body 36 …… Plate thread member 38 …… Spiral groove 40b …… Screw groove 45b …… Screw groove 50 …… Plate thread member

Claims (4)

[Claims] 1. A screw structure in which a male screw and a female screw each having a screw thread and a screw trough are screwed together; the diameters of the screw roots of the male screw are the same, and the diameters of the screw roots of the female screw are the same. Are the same, and the threads of the both threads are each formed in a plate shape in a longitudinal section, and both slopes of the threads of the female thread are in surface contact with the slopes of the threads of the male thread that face each other. Bias prevention rings are provided on both end surfaces, the outer circumferential surface of the bias prevention ring is positioned outside the thread root of the female thread, and the inner circumferential surface abuts the top of the thread of the male thread. A screw structure that resists fatigue. 2. The fatigue-resistant screw according to claim 1, wherein the height of the thread of the female thread is higher than that of the male thread, and the width of the top is narrower than that of the male thread. Construction. 3. The fatigue-resistant screw structure according to claim 1, wherein the height of the thread of the female thread and the width of the top thereof are equal to those of the thread of the male thread. 4. The fatigue-resistant structure according to claim 1, wherein an adjusting space is formed between the thread crest of the female thread and the thread root of the male thread.