JPH0529583Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a flexible boot that covers the joints of mechanical elements that are relatively displaced to prevent the intrusion of dust, water, etc., and that can freely expand, contract, and bend.

PRIOR ART Such flexible boots are used, for example, in automobile steering devices, power transmission systems, etc., and the main body portion thereof is usually formed as a bellows-shaped body having a plurality of peaks and troughs. Here, an example of a flexible boot applied to a rack and pinion type steering device of an automobile will be described (see FIG. 6). The rack and pinion steering system is
This type of steering is performed by immediately converting the rotational movement of the handle into linear movement using a rack. Figure 6 shows the structure of the main part. A pinion that engages with a rack (see rack shaft 3) is attached to the tip of the pinion shaft 1, and the rack moves left and right inside the steering housing 2 according to the rotation of the pinion. move in a straight line. A tie rod 4 is connected to both ends of the rack shaft 3, and the movement of the rack shaft 3 is controlled by the tie rod 4.
The signal is transmitted to the knuckle arms of both the left and right wheels through the steering wheel, and the wheels are steered.

A flexible boot 8 made of elastomer such as rubber or resin is connected to the rack shaft 3 and the tie rod 4.
It is fitted and fixed to the tie rod 4 and steering housing 2 by means of fastening bands 6 and 7, covering the ball joint 5, which is the connecting part of the rack shaft 3, and the end of the rack shaft 3. The flexible boot 8 is formed as a bellows-shaped body consisting of a plurality of series of peaks 10 and troughs 11. One end of the main body 9 is open as a large-diameter opening, and the other end is open as a small-diameter opening. There is.

The flexible boot 8 defines a sealed space in the attached state, and the space is filled with air.

Problems to be solved by the invention However, the materials forming the flexible boot, such as rubber and resin, have gas permeability, and the amount of gas permeation increases as the pressure difference between the inner and outer surfaces of the flexible boot increases and the temperature rises. increases. Therefore, when the air inside the flexible boot expands and the internal pressure increases due to a rise in ambient temperature, etc., the air in the sealed space passes through the wall of the flexible boot and escapes to the outside, and then due to the temperature drop, the air in the sealed space increases. When the air inside contracts, the sealed space becomes negative pressure,
A phenomenon occurs in which outside air penetrates the wall of the flexible boot and enters the sealed space. In this phenomenon of air entering and exiting, the rate of gas permeation that enters when the temperature drops is extremely small compared to the rate of gas permeation that is released when the temperature rises, so the amount of air inside the flexible boot returns to the amount at the initial low temperature. It takes a significantly longer time. Therefore, when the temperature rises and falls repeatedly, the pressure within the flexible boot gradually decreases, and the wall of the main body of the flexible boot gradually recesses inward in the radial direction. If a flexible boot is used in such a concave state, the flexible boot will frequently come into contact with internal mechanical elements and wear out prematurely, or it will get caught between the mechanical elements and break. There is a risk. Further, as the dent progresses, the flexible boot may become abnormally deformed, causing localized stress concentration, which may lead to breakage.

The present invention was devised against this technical background, and is designed to provide a highly rigid flexible boot that is unlikely to cause concave deformation of the main trunk even if a negative pressure phenomenon occurs in the sealed space inside the flexible boot due to temperature changes, etc. Its purpose is to provide.

Means for Solving the Problems and Their Effects This object is to provide a flexible boot made of an elastomer such as rubber or resin and whose main body portion is formed as a bellows-shaped body having a plurality of peaks and troughs. For a small number of arbitrary peaks and valleys, the wall thickness of at least one of the peak part and the valley bottom part is formed to be thicker than the remaining part over a relatively short circumferential length range at at least one place along the circumferential direction, thereby making the wall thickness flexible. This is achieved by shifting the circumferential phase of the one or a small number of adjacent peaks and valleys and the similar thickened portions of the adjacent peaks and valleys and the former thickened portion in the axial direction of the boot.

The principle of the present invention will be explained with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional view of an arbitrary mountain part of the flexible boot as shown in FIG. In other words, the wall thickness of the opposing walls 20a, 20a at the position intersecting the x-axis is small, and the opposing wall 2 at the position intersecting the y-axis
The wall thickness of 0b and 20b is increased. FIG. 2 is a cross-sectional view of the mountain adjacent to the mountain shown in FIG. 1, taken along the top portion 21 of the mountain.
The wall thicknesses of the walls a and 21a are large, and the wall thicknesses of the opposing walls 21b and 21b at positions intersecting the y-axis are small.

In this way, when the wall thickness of the mountain top part changes in the circumferential direction, if the pressure inside the sealed space A of the flexible boot attached to the machine element becomes reduced due to temperature changes, for example, the mountain top part in FIG. 20
However, due to the difference in rigidity in the circumferential direction, it tries to deform into an elliptical shape with the major axis in the y-axis direction, as indicated by arrows B and C. However, the mountain top portion 21 of the adjacent mountain portion is different from the mountain top portion 20 in the size relationship of wall thickness in the circumferential direction, and thick walls 21a, 21
Walls 20b, 20 whose phase in the circumferential direction of a is thick
Since the central angle (θ) is shifted by 90 degrees from b, the pressure inside the sealed space A becomes reduced, resulting in an elliptical shape with the major axis in the x-axis direction, as indicated by arrows D and E. trying to transform into Therefore,
Against the force indicated by arrow B that attempts to dent the thin walls 20a, 20a of the mountain top portion 20 inward,
The force indicated by arrow E which attempts to bulge the thick walls 21a, 21a of the mountain top portion 21 outward opposes the force indicated by arrow D, and similarly the force indicated by arrow D is opposed by arrow C.
The forces directed by will oppose. This means that the low rigidity of the thin wall 20a of the peak portion 20 can be compensated for by the high rigidity of the thick wall 21a of the adjacent peak portion 21. Thus, by mutually shifting the circumferential phase of the thick wall at the top of all the adjacent peaks, the main trunk wall of the flexible boot when the sealed space A is in a reduced pressure state is The phenomenon of inward depression can be effectively prevented. What should be noted here is that compared to the case where the wall thickness at the top of the mountain is increased over the entire circumference, when the structure of the present invention is adopted, the deformation resistance during depressurization can be increased, and the material saving effect is also reduced. That's what you get. The above-mentioned effects can be obtained even if the phase difference between the thick walls at the adjacent peak parts is less than 90 degrees at the center angle, and the number of thick walls (thick parts) is reduced to one pair (two). However, the number may be one or three or more. However, if the number is increased too much, there will be no difference from the case where the wall thickness at the top of the mountain is increased over the entire circumference.

Several different configurations of the present invention are possible, some examples of which are shown below.

As shown in FIGS. 1 and 2, the circumferential phase of each large wall thick portion of adjacent mountain top portions is shifted.

In addition to the configuration described in the previous section, the wall thickness of the local range (relatively short circumferential length range) along the circumferential direction of the valley bottom portion is increased, and the circumferential phase of each large wall thickness location of adjacent valley bottom portions is shifted.

In the configuration described above, the circumferential phase difference between the thick-wall positions of the peak and bottom portions of each pair is set to a central angle (θ) of 0°.

In the configuration described in the previous section, the circumferential phases of the respective thick wall positions of the paired mountain top portion and valley bottom portion are shifted from each other.

The above configuration is omitted from the configuration in the previous section. That is, without adopting the configuration described in the previous section, the wall thickness is increased in a local range along the circumferential direction (relatively short circumferential length range) in the valley bottom part, and the circumferential phase of each large wall thickness point in the adjacent valley bottom part is changed. shift.

Matching the circumferential phase of each large wall thickness point of multiple (preferably two) adjacent mountain top portions,
The circumferential phases of other adjacent mountain top portions having similar large wall thicknesses are shifted from each other.

Match the circumferential phase of each large wall thickness point of a plurality of adjacent valley bottom portions (preferably two),
The circumferential phases of other adjacent valley bottom portions having similar large wall thicknesses are shifted from each other.

In addition to the configuration described in the previous section, the wall thickness in a local area along the circumferential direction is also increased for the valley bottom portion, and the wall thickness is increased in the circumferential direction at each large wall thickness point of each of the plurality of mountain top portions and the valley bottom portion that is paired with the mountain top portion. Set the phase difference to zero.

In addition to the configuration described in the previous section, the wall thickness in a local area along the circumferential direction is also increased for the valley bottom portion, and the wall thickness is increased in the circumferential direction at each large wall thickness point of each of the plurality of mountain top portions and the valley bottom portion that is paired with the mountain top portion. shift the phases from each other.

Embodiment An embodiment shown in FIGS. 3 to 5 will be described below.

3 is an end view of the flexible boot 30 viewed from the direction along the axis L thereof, and FIG. 4 is a sectional view taken along the line -- in FIG. 3. The main body portion 31 of the flexible boot 30 is formed as a cylindrical bellows-shaped body in which a large number of peaks 32 and valleys 34 are connected. In the figure, if we pay attention to specific mountain parts 32A and 32B, in a short circumferential range where the wall thickness of the mountain top part 33 intersects with the y-axis, thick wall 33b,
33b, and the remaining wall thickness including the portion intersecting the x-axis is formed as a relatively thin wall 33a having a normally adopted wall thickness dimension. Further, the wall thickness of the valley bottom portions 35 of the valley portions 34A, 34B that are paired with the mountain portions 32A, 32B is different from the thick wall thickness of the mountain top portion 33.
3b in the same phase in the circumferential direction (thick walls 35b, 35b).

Mountain parts 32A, 32B, mountain parts 32C, 32D adjacent to valley parts 34A, 34B, valley parts 34C, 34D
In this case, the wall thickness of the mountain top portion and the valley bottom portion are both formed as thick walls in a short circumferential length range intersecting the x-axis.

And the mountain parts 32C, 32D, the valley parts 34C, 3
Peaks 32E, 32F and valleys 34 adjacent to 4D
In the case of E, 34F, the wall thickness of the mountain top part and the valley bottom part are both formed as a thick wall in a short circumferential range that intersects the y-axis, and the following successively applies to other adjacent peaks and valley parts. The thick wall is formed with a similar circumferential phase difference relationship.

Here, the outer diameter of the flexible boot 30 measured at the relatively thin wall portion of the mountain top portion 33 is D ₁ , the inner diameter of the flexible boot 30 measured at the relatively thin wall portion of the valley bottom portion 35 is D 2 , and the inner diameter of the flexible boot 30 measured at the relatively thin wall portion of the valley bottom portion 35 is D ₂ . When the wall thickness of the thick wall is t ₁ , the wall thickness of the thin wall is t ₂ , and the pitch that is equal among all the peak portions 33 is P, it is preferable to adopt, for example, the following dimensions.

D ₁ = 60Φmm, D ₂ = 45Φmm t ₁ = 2.0mm, t ₂ = 1.5mm P = 8mm The flexible boot 30 is formed as described above, and the flexible boot 30 is attached to a mechanical element in the manner shown in FIG. When the internal space of the flexible boot 30, which is a sealed space, becomes depressurized due to a temperature change, the mutually adjacent peaks 32A, 32B and valleys 34A, 34
Since the circumferential phase of the thick wall is shifted by the central angle (θ) = 90 degrees between B, the peaks 32C, 32D, and the valleys 34C, 34D, an attempt is made to deform one of the peaks and valleys. The force and the force that attempts to deform the other peak and trough cancel each other out, making it difficult for any part to undergo concave deformation. This characteristic is the same between all adjacent peaks and valleys, and the negative pressure resistance of the flexible boot 30 is achieved by making the wall thickness of all the peaks and valleys as large as the thick walls. Better than that in case. This also means that
This means that the rigidity (negative pressure resistance characteristics) of the flexible boot 30 can be improved while saving materials.

Effects of the Invention As is clear from the above explanation, in the flexible boot of the present invention in which the main trunk portion is formed as a bellows-shaped body having a plurality of peaks and valleys, for one or a small number of adjacent peaks and valleys, The wall thickness of at least one of the mountain top portion and the valley bottom portion is formed to be thicker in at least one portion along the circumferential direction than the remaining portion over a relatively short circumferential length range, and the wall thickness of at least one of the mountain top portion and the valley bottom portion is formed to be thicker than the remaining portion over a relatively short circumferential length range. Because the circumferential phase of a small number of adjacent peaks and valleys and the similar thick walled portions of the adjacent peaks and valleys and the thick walled portion of the former are shifted, the flexible boot is sealed while being attached to a machine element and used. When the internal space of the flexible boot is in a depressurized state, the decompression characteristics (deformation direction) of adjacent mountain top portions or valley bottom portions having thick walls with different circumferential phases are different, and the deformation characteristics (deformation direction) are different due to the characteristic difference. Therefore, concave deformation of the main body wall is effectively suppressed, and excellent negative pressure resistance can be expected. Further, in the flexible boot of the present invention, since the wall thickness is not increased over the entire circumference of the mountain top portion or the valley bottom portion, a material saving effect can be obtained in a relative sense.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an arbitrary peak of a flexible boot according to an example of the present invention, cut into circles along the peak, and FIG. 2 is a sectional view of the peak of the flexible boot shown in FIG. 1 (peak). FIG. 3 is an end view of a flexible boot according to an embodiment as viewed from the direction along its axis L, and FIG. 3 is a sectional view taken along the - line in FIG. 3, FIG. 5 is a sectional view taken along the - line in FIG. 3 (enlarged view of the main part), and FIG. It is a sectional view showing the whole shape of the flexible boot concerning this. 20...Mountain top part, 20a...Thin wall, 20b
...Thick wall, 21... Mountain top portion, 21a... Thick wall, 21b... Thin wall, 30... Flexible boot, 31... Main trunk, 32... Mountain part, 33...
Mountain top portion, 33a... Thin wall, 33b... Thick wall, 34... Valley portion, 35... Valley bottom portion, 35b...
...thick walls.

Claims (1)

[Claims for Utility Model Registration] A flexible boot made of an elastomer such as rubber or resin and whose main body portion is formed as a bellows-shaped body having a plurality of peaks and valleys, one or a small number of adjacent peaks and valleys. For each part, at least one wall thickness of the peak part and the valley bottom part is formed to be thicker in at least one part along the circumferential direction than the remaining part over a relatively short circumferential length range, and in the axial direction of the flexible boot. A flexible boot characterized in that the circumferential phase of one or a small number of adjacent peaks and valleys and a similar thick walled portion of an adjacent peak and valley are different from that of the former thick walled portion.